Science.gov

Sample records for mechanical analysis teoria

  1. Probabilistic analysis of mechanical systems

    SciTech Connect

    Priddy, T.G.; Paez, T.L.; Veers, P.S.

    1993-09-01

    This paper proposes a framework for the comprehensive analysis of complex problems in probabilistic structural mechanics. Tools that can be used to accurately estimate the probabilistic behavior of mechanical systems are discussed, and some of the techniques proposed in the paper are developed and used in the solution of a problem in nonlinear structural dynamics.

  2. Majorana Electroformed Copper Mechanical Analysis

    SciTech Connect

    Overman, Nicole R.; Overman, Cory T.; Kafentzis, Tyler A.; Edwards, Danny J.; Hoppe, Eric W.

    2012-04-30

    The MAJORANA DEMONSTRATOR is a large array of ultra-low background high-purity germanium detectors, enriched in 76Ge, designed to search for zero-neutrino double-beta decay. The DEMONSTRATOR will utilize ultra high purity electroformed copper for a variety of detector components and shielding. A preliminary mechanical evaluation was performed on the Majorana prototype electroformed copper material. Several samples were removed from a variety of positions on the mandrel. Tensile testing, optical metallography, scanning electron microscopy, and hardness testing were conducted to evaluate mechanical response. Analyses carried out on the Majorana prototype copper to this point show consistent mechanical response from a variety of test locations. Evaluation shows the copper meets or exceeds the design specifications.

  3. Mechanical analysis of eyelid morphology.

    PubMed

    Zhu, Liangliang; Chen, Xi

    2013-08-01

    From a mechanical instability perspective a double eyelid is a double-folded thin film structure on a curved substrate, caused by compression as the film "slides" on the substrate. The underlying mechanics issues, in particular the requirements for forming a double folded structure, are studied using a modeling/simulation framework. A minimalist model is employed to explore the wrinkle to fold transition. Refined and enriched models are further developed based on anatomical structures, which demonstrate three critical factors for the formation of double layer folding of the eyelid. First, a crease line in the eyelid is essential where the local bending rigidity is relatively weak. Second, the skin above the crease line should be thin and wide enough. Third, the skin below the crease line should have a relatively large effective stiffness so it can be lifted as a whole when the eyes open. When the eye is opened beyond about 40% of its initial wrinkle wavelength, the double-folded structure emerges. Various types of eyelid morphologies are discussed based on the mechanistic model. The study provides useful insights for surgery, cosmetics, and morphogenesis, as well as microfabrication. PMID:23597858

  4. Analysis of Skylab fluid mechanics science demonstrations

    NASA Technical Reports Server (NTRS)

    Tegart, J. R.; Butz, J. R.

    1975-01-01

    The results of the data reduction and analysis of the Skylab fluid mechanics demonstrations are presented. All the fluid mechanics data available from the Skylab missions were identified and surveyed. The significant fluid mechanics phenomena were identified and reduced to measurable quantities wherever possible. Data correlations were performed using existing theories. Among the phenomena analyzed were: static low-g interface shapes, oscillation frequency and damping of a liquid drop, coalescence, rotating drop, liquid films and low-g ice melting. A survey of the possible applications of the results was made and future experiments are recommended.

  5. Elucidation of wear mechanisms by ferrographic analysis

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1981-01-01

    The use of ferrographic analysis in conjunction with light and scanning electron microscopy is described for the elucidation of wear mechanisms taking place in operating equipment. Example of adhesive wear, abrasive wear, corrosive wear, rolling element fatigue, lubricant breakdown, and other wear modes are illustrated. In addition, the use of magnetic solutions to precipitate nonmagnetic debris from aqueous and nonaqueous fluids is described.

  6. An Analysis of the Auto Mechanic Occupation.

    ERIC Educational Resources Information Center

    Conner, Michael; Thoman, LeRoy

    The general purpose of the occupational analysis is to provide workable, basic information dealing with the many and varied duties performed in the auto mechanic occupation. It identifies the broad area of skills and knowledge necessary to perform various tasks involved in diagnosis, maintenance, and repair of automotive systems. Selected…

  7. Diesel Mechanics. Ohio's Competency Analysis Profile.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Vocational Instructional Materials Lab.

    This Ohio Competency Analysis Profile (OCAP), derived from a modified Developing a Curriculum (DACUM) process, is a current comprehensive and verified employer competency program list for diesel mechanics. Each unit (with or without subunits) contains competencies and competency builders that identify the occupational, academic, and employability…

  8. A mechanical energy analysis of gait initiation

    NASA Technical Reports Server (NTRS)

    Miller, C. A.; Verstraete, M. C.

    1999-01-01

    The analysis of gait initiation (the transient state between standing and walking) is an important diagnostic tool to study pathologic gait and to evaluate prosthetic devices. While past studies have quantified mechanical energy of the body during steady-state gait, to date no one has computed the mechanical energy of the body during gait initiation. In this study, gait initiation in seven normal male subjects was studied using a mechanical energy analysis to compute total body energy. The data showed three separate states: quiet standing, gait initiation, and steady-state gait. During gait initiation, the trends in the energy data for the individual segments were similar to those seen during steady-state gait (and in Winter DA, Quanbury AO, Reimer GD. Analysis of instantaneous energy of normal gait. J Biochem 1976;9:253-257), but diminished in amplitude. However, these amplitudes increased to those seen in steady-state during the gait initiation event (GIE), with the greatest increase occurring in the second step due to the push-off of the foundation leg. The baseline level of mechanical energy was due to the potential energy of the individual segments, while the cyclic nature of the data was indicative of the kinetic energy of the particular leg in swing phase during that step. The data presented showed differences in energy trends during gait initiation from those of steady state, thereby demonstrating the importance of this event in the study of locomotion.

  9. HFIR vessel probabilistic fracture mechanics analysis

    SciTech Connect

    Cheverton, R.D.; Dickson, T.L.

    1997-01-01

    The life of the High Flux Isotope Reactor (HFIR) pressure vessel is limited by a radiation induced reduction in the material`s fracture toughness. Hydrostatic proof testing and probabilistic fracture mechanics analyses are being used to meet the intent of the ASME Code, while extending the life of the vessel well beyond its original design value. The most recent probabilistic evaluation is more precise and accounts for the effects of gamma as well as neutron radiation embrittlement. This analysis confirms the earlier estimates of a permissible vessel lifetime of at least 50 EFPY (100 MW).

  10. Analysis of mechanical joint in composite cylinder

    NASA Astrophysics Data System (ADS)

    Hong, C. S.; Kim, Y. W.; Park, J. S.

    Joining techniques of composite materials are of great interest in cylindrical structures as the application of composites is widely used for weight-sensitive structures. Little information for the mechanical fastening joint of the laminated shell structure is available in the literature. In this study, a finite element program, which was based on the first order shear deformation theory, was developed for the analysis of the mechanical joint in the laminated composite structure. The failure of the mechanical fastening joint for the laminated graphite/epoxy cylinder subject to internal pressure was analyzed by using the developed program. Modeling of the bolt head in the composite cylinder was studied, and the effect of steel reinforcement outside the composite cylinder on the failure was investigated. The stress component near the bolt head was influenced by the size of the bolt head. The failure load and the failure mode were dependent on the bolt diameter, the number of bolts, and fiber orientation. The failure load was constant when the edge distance exceeds three times the bolt diameter.

  11. Obtaining railpad properties via dynamic mechanical analysis

    NASA Astrophysics Data System (ADS)

    Oregui, M.; de Man, A.; Woldekidan, M. F.; Li, Z.; Dollevoet, R.

    2016-02-01

    In this paper, we propose combining dynamic mechanical analysis (DMA) and the time-temperature superposition principle to determine various railpad dynamic properties. Having accurate information regarding the dynamic properties of a railpad is a fundamental requirement for designing tracks and understanding track deterioration. By testing three different railpad types, we demonstrate that the dynamic behavior of railpads over a wide frequency range can be successfully obtained under different preloads and temperatures if time-temperature superposition can be applied. To investigate railpad aging, worn railpads taken from a mainline in the Netherlands are tested. In this case, worn railpads are softer and possess a lower damping capacity than new railpads. In addition to performing these measurements, a Prony series material model is proposed to reproduce the dynamic behavior of railpads. The Prony series model is in good agreement with the measurements. Measured railpad dynamic properties and the corresponding Prony series numerical model provide valuable information for track design and modeling.

  12. Molecular mechanics conformational analysis of tylosin

    NASA Astrophysics Data System (ADS)

    Ivanov, Petko M.

    1998-01-01

    The conformations of the 16-membered macrolide antibiotic tylosin were studied with molecular mechanics (AMBER∗ force field) including modelling of the effect of the solvent on the conformational preferences (GB/SA). A Monte Carlo conformational search procedure was used for finding the most probable low-energy conformations. The present study provides complementary data to recently reported analysis of the conformations of tylosin based on NMR techniques. A search for the low-energy conformations of protynolide, a 16-membered lactone containing the same aglycone as tylosin, was also carried out, and the results were compared with the observed conformation in the crystal as well as with the most probable conformations of the macrocyclic ring of tylosin. The dependence of the results on force field was also studied by utilizing the MM3 force field. Some particular conformations were computed with the semiempirical molecular orbital methods AM1 and PM3.

  13. Thermal mechanical analysis of sprag clutches

    NASA Technical Reports Server (NTRS)

    Mullen, Robert L.; Zab, Ronald Joseph; Kurniawan, Antonius S.

    1992-01-01

    Work done at Case Western Reserve University on the Thermal Mechanical analysis of sprag helicopter clutches is reported. The report is presented in two parts. The first part is a description of a test rig for the measurement of the heat generated by high speed sprag clutch assemblies during cyclic torsional loading. The second part describes a finite element modeling procedure for sliding contact. The test rig provides a cyclic torsional load of 756 inch-pounds at 5000 rpm using a four-square arrangement. The sprag clutch test unit was placed between the high speed pinions of the circulating power loop. The test unit was designed to have replaceable inner ad outer races, which contain the instrumentation to monitor the sprag clutch. The torque loading device was chosen to be a water cooled magnetic clutch, which is controlled either manually or through a computer. In the second part, a Generalized Eulerian-Lagrangian formulation for non-linear dynamic problems is developed for solid materials. This formulation is derived from the basic laws and axioms of continuum mechanics. The novel aspect of this method is that we are able to investigate the physics in the spatial region of interest as material flows through it without having to follow material points. A finite element approximation to the governing equations is developed. Iterative Methods for the solution of the discrete finite element equations are explored. A FORTRAN program to implement this formulation is developed and a number of solutions to problems of sliding contact are presented.

  14. Thermal mechanical analysis of sprag clutches

    NASA Astrophysics Data System (ADS)

    Mullen, Robert L.; Zab, Ronald Joseph; Kurniawan, Antonius S.

    1992-07-01

    Work done at Case Western Reserve University on the Thermal Mechanical analysis of sprag helicopter clutches is reported. The report is presented in two parts. The first part is a description of a test rig for the measurement of the heat generated by high speed sprag clutch assemblies during cyclic torsional loading. The second part describes a finite element modeling procedure for sliding contact. The test rig provides a cyclic torsional load of 756 inch-pounds at 5000 rpm using a four-square arrangement. The sprag clutch test unit was placed between the high speed pinions of the circulating power loop. The test unit was designed to have replaceable inner ad outer races, which contain the instrumentation to monitor the sprag clutch. The torque loading device was chosen to be a water cooled magnetic clutch, which is controlled either manually or through a computer. In the second part, a Generalized Eulerian-Lagrangian formulation for non-linear dynamic problems is developed for solid materials. This formulation is derived from the basic laws and axioms of continuum mechanics. The novel aspect of this method is that we are able to investigate the physics in the spatial region of interest as material flows through it without having to follow material points. A finite element approximation to the governing equations is developed. Iterative Methods for the solution of the discrete finite element equations are explored. A FORTRAN program to implement this formulation is developed and a number of solutions to problems of sliding contact are presented.

  15. Mechanical analysis of infant carrying in hominoids

    NASA Astrophysics Data System (ADS)

    Amaral, Lia Q.

    2008-04-01

    In all higher nonhuman primates, species survival depends upon safe carrying of infants clinging to body hair of adults. In this work, measurements of mechanical properties of ape hair (gibbon, orangutan, and gorilla) are presented, focusing on constraints for safe infant carrying. Results of hair tensile properties are shown to be species-dependent. Analysis of the mechanics of the mounting position, typical of heavier infant carrying among African apes, shows that both clinging and friction are necessary to carry heavy infants. As a consequence, a required relationship between infant weight, hair-hair friction coefficient, and body angle exists. The hair-hair friction coefficient is measured using natural ape skin samples, and dependence on load and humidity is analyzed. Numerical evaluation of the equilibrium constraint is in agreement with the knuckle-walking quadruped position of African apes. Bipedality is clearly incompatible with the usual clinging and mounting pattern of infant carrying, requiring a revision of models of hominization in relation to the divergence between apes and hominins. These results suggest that safe carrying of heavy infants justify the emergence of biped form of locomotion. Ways to test this possibility are foreseen here.

  16. A Coupled Thermal-Mechanical Analysis of Ultrasonic Bonding Mechanism

    NASA Astrophysics Data System (ADS)

    Zhang, Chunbo (Sam); Li, Leijun

    2009-04-01

    A three-dimensional (3-D) finite element model has been developed to simulate the coupled thermal-mechanical fields in ultrasonic welding of aluminum foils. Transient distributions and evolution of the in-process variables, including normal stress, shear stress, slide distance, heat generation, temperature, and plastic deformation on the contact interface, and their interactions have been studied in detail. The von Mises plastic strain from the simulation has been correlated with the measured bonded area of ultrasonic joints. A possible mechanism for ultrasonic bond formation is proposed. The severe, localized, plastic deformation at the bond region is believed to be the major phenomenon causing bond formation in ultrasonic welding.

  17. PERFORMANCE ANALYSIS OF MECHANICAL DRAFT COOLING TOWER

    SciTech Connect

    Lee, S; Alfred Garrett, A; James02 Bollinger, J; Larry Koffman, L

    2009-02-10

    Industrial processes use mechanical draft cooling towers (MDCT's) to dissipate waste heat by transferring heat from water to air via evaporative cooling, which causes air humidification. The Savannah River Site (SRS) has cross-flow and counter-current MDCT's consisting of four independent compartments called cells. Each cell has its own fan to help maximize heat transfer between ambient air and circulated water. The primary objective of the work is to simulate the cooling tower performance for the counter-current cooling tower and to conduct a parametric study under different fan speeds and ambient air conditions. The Savannah River National Laboratory (SRNL) developed a computational fluid dynamics (CFD) model and performed the benchmarking analysis against the integral measurement results to accomplish the objective. The model uses three-dimensional steady-state momentum, continuity equations, air-vapor species balance equation, and two-equation turbulence as the basic governing equations. It was assumed that vapor phase is always transported by the continuous air phase with no slip velocity. In this case, water droplet component was considered as discrete phase for the interfacial heat and mass transfer via Lagrangian approach. Thus, the air-vapor mixture model with discrete water droplet phase is used for the analysis. A series of parametric calculations was performed to investigate the impact of wind speeds and ambient conditions on the thermal performance of the cooling tower when fans were operating and when they were turned off. The model was also benchmarked against the literature data and the SRS integral test results for key parameters such as air temperature and humidity at the tower exit and water temperature for given ambient conditions. Detailed results will be published here.

  18. DYNAMIC MECHANICAL ANALYSIS CHARACTERIZATION OF GLOVEBOX GLOVES

    SciTech Connect

    Korinko, P.

    2012-02-29

    As part of the characterization of various glovebox glove material from four vendors, the permeability of gas through each type as a function of temperature was determined and a discontinuity in the permeability with temperature was revealed. A series of tests to determine the viscoelastic properties of the glove materials as a function of temperature using Dynamic Mechanical Analysis (DMA) was initiated. The glass transition temperature and the elastic and viscoelastic properties as a function of temperature up to maximum use temperature were determined for each glove material. The glass transition temperatures of the gloves were -60 C for butyl, -30 C for polyurethane, -16 C Hypalon{reg_sign}, - 16 C for Viton{reg_sign}, and -24 C for polyurethane-Hypalon{reg_sign}. The glass transition was too complex for the butyl-Hypalon{reg_sign} and butyl-Viton{reg_sign} composite gloves to be characterized by a single glass transition temperature. All of the glass transition temperatures exceed the vendor projected use temperatures.

  19. Biomechanical analysis of the splenic avulsion mechanism.

    PubMed

    Chebil, Omar; Behr, Michel; Auriault, Florent; Arnoux, Pierre-Jean

    2014-08-01

    The spleen is a frequently injured abdominal organ in road accidents, with an injury frequency close to 30%. The splenic avulsion exhibit a significant ratio of morbidity. It is clinically described as the complete failure of the pancreatico-splenic ligament (PSL) which is composed of splenic vessels and connective tissues. What are the biomechanical mechanisms involved with spleen avulsion? Is it possible to quantify tolerance levels of PSL structure? The current work combines both experimental and finite element (FE) investigations to determine the splenic avulsion process. Tensile tests on 13 PSL samples were performed up to failure. The experimental results provide reference data for model validation and showed a failure process starting at a peak force of 70±34 N combined with a peak strain of 105±26%. In an attempt to identify possible vessel ruptures within the PSL, a FE model of the PSL was developed including both vessels and connective tissues. The vessel wall behaviour up to failure was reproduced using an Ogden law and calibrated by inverse analysis according to literature data. The connective tissues function was modelled by a cohesion-loss interface. Once model correlation to experimental results was achieved, numerical simulation revealed that haemorrhage could occur even before the maximum peak is reached. Indeed, the first vessel ruptures were recorded at a strain of 92% at the upper lobe vein. PMID:24944004

  20. Mechanics analysis of molar tooth splitting.

    PubMed

    Barani, Amir; Chai, Herzl; Lawn, Brian R; Bush, Mark B

    2015-03-01

    A model for the splitting of teeth from wedge loading of molar cusps from a round indenting object is presented. The model is developed in two parts: first, a simple 2D fracture mechanics configuration with the wedged tooth simulated by a compact tension specimen; second, a full 3D numerical analysis using extended finite element modeling (XFEM) with an embedded crack. The result is an explicit equation for splitting load in terms of indenter radius and key tooth dimensions. Fracture experiments on extracted human molars loaded axially with metal spheres are used to quantify the splitting forces and thence to validate the model. The XFEM calculations enable the complex crack propagation, initially in the enamel coat and subsequently in the interior dentin, to be followed incrementally with increasing load. The fracture evolution is shown to be stable prior to failure, so that dentin toughness, not strength, is the controlling material parameter. Critical conditions under which tooth splitting in biological and dental settings are likely to be met, however rare, are considered. PMID:25584989

  1. Dynamic analysis of mechanisms by finite elements

    SciTech Connect

    Botsali, F.M.; Uenuevar, A.

    1996-11-01

    The need to increase productivity in order to decrease manufacturing costs lead to an increase in the working speeds of machines and mechanical systems used in manufacturing. A method is presented for investigating the dynamics of mechanisms with elastic links. Finite element method is used in the formulation of the dynamic problem. Modal transformation is used in order to reduce the number of equations of motion. Using the presented technique, elastic and rigid body motions of mechanism links are solved simultaneously. The presented method may be applied to spatial and open loop mechanisms including robot manipulators as well.

  2. Methods of stability analysis in nonlinear mechanics

    SciTech Connect

    Warnock, R.L.; Ruth, R.D.; Gabella, W.; Ecklund, K.

    1989-01-01

    We review our recent work on methods to study stability in nonlinear mechanics, especially for the problems of particle accelerators, and compare our ideals to those of other authors. We emphasize methods that (1) show promise as practical design tools, (2) are effective when the nonlinearity is large, and (3) have a strong theoretical basis. 24 refs., 2 figs., 2 tabs.

  3. Integrated Turbopump Thermo-Mechanical Design and Analysis Tools

    NASA Astrophysics Data System (ADS)

    Platt, Mike

    2002-07-01

    This viewgraph presentation provides information on the thermo-mechanical design and analysis tools used to control the steady and transient thermo-mechanical effects which drive life, reliability, and cost. The thermo-mechanical analysis tools provide upfront design capability by effectively leveraging existing component design tools to analyze and control: fits, clearance, preload; cooling requirements; stress levels, LCF (low cycle fatigue) limits, and HCF (high cycle fatigue) margin.

  4. Thermo-mechanical analysis of polyamide biocomposites

    NASA Astrophysics Data System (ADS)

    Lattimer, Jessica Lynne

    Biobased fillers in thermoplastics have seen increased usage over the last several years. The increased usage of biobased fillers follows the ever-increasing thrust to reduce petroleum and synthetic petrochemical product consumption. Biocomposites made from polyolefin matrices have shown improved elastic moduli with moderate impact on strength. For engineering thermoplastics, the increased processing temperatures lead to degradation of the biomass, often detrimental for the mechanical performance. The goal of this work was to evaluate the effectiveness of agricultural byproducts as fillers in polyamides, while minimizing the effects of increased processing temperatures. Torrefaction has been identified as an effective means of preparing biomass for introduction into polyamide. Polyamide biocomposites were produced and shown to have comparable mechanical properties to the neat matrix. Torrefied biomass was shown to produce tensile strengths within 70% of the neat matrix, increase elastic modulus by 150%, flexural strength by 170%, and flexural modulus by 154%.

  5. On the kinematic analysis of robotic mechanisms

    SciTech Connect

    Nielsen, J.; Roth, B.

    1999-12-01

    The kinematic analyses, of manipulators and other robotic devices composed of mechanical links, usually depend on the solution of sets of nonlinear equations. There are a variety of both numerical and algebraic techniques available to solve such systems of equations and to give bounds on the number of solutions. These solution methods have also led to an understanding of how special choices of the various structural parameters of a mechanism influence the number of solutions inherent to the kinematic geometry of a given structure. In this paper, results from studying the kinematic geometry of such systems are reviewed, and the three most useful solution techniques are summarized. The solution techniques are polynomial continuation, Groebner bases, and elimination. The authors then discuss the results that have been obtained with these techniques in the solution of two basic problems, namely, the inverse kinematics for serial-chain manipulators, and the direct kinematics of in-parallel platform devices.

  6. Analysis of Stabilization Mechanisms in Lifted Flames

    NASA Astrophysics Data System (ADS)

    Navarro-Martinez, S.; Kronenburg, A.

    2009-12-01

    Flame stabilization and the mechanisms that govern the dynamics at the flame base have been subject to numerous studies in recent years. Recent results using a combined Large Eddy Simulation-Conditional Moment Closure (LES-CMC) approach to model the turbulent flow field and the turbulence-chemistry interactions has been successful in predicting flame ignition and stabilization by auto-ignition, but LES-CMCs capability of the accurate modelling of the competition between turbulent quenching and laminar and turbulent flame propagation at the anchor point has not been resolved. This paper will consolidate LES-CMC results by analysing a wide range of lifted flame geometries with different prevailing stabilization mechanisms. The simulations allow a clear distinction of the prevailing stabilization mechanisms for the different flames, LES-CMC accurately predicts the competition between turbulence and chemistry during the auto-ignition process, however, the dynamics of the extinction process and turbulent flame propagation are not well captured. The averaging process inherent in the CMC methods does not allow for an instant response of the transported conditionally averaged reactive species to the changes in the flow conditions and any response of the scalars will therefore be delayed. Stationary or quasi-stationary conditions, however, can be well predicted for all flame configurations.

  7. Mechanical and acoustic analysis in ultrasonic angioplasty

    NASA Astrophysics Data System (ADS)

    Detwiler, Paul W.; Watkins, James F.; Rose, Eric A.; Ratner, A.; Vu, Louis P.; Severinsky, J. Y.; Rosenschein, Uri

    1991-05-01

    The goal of this study was to investigate the relationship between ultrasonic tissue ablation and passive mechanical elasticity. Experience with ultrasonic angioplasty in experimental settings (in-vivo and in-vitro) together with clinical experience in peripheral vascular disease is reported. A model composed exclusively of a hydroxyproline ballistic gelatin matrix showed a negative correlation between material elasticity and the rate of ultrasonic ablation. This model provided a means of studying the effects of collagen content on ablation, exclusive of other biologic components. Ballistic gelatin ablation (mg/sec) was found to increase logarithmically with decreasing protein concentration over the range studied (20.00 to 1.25%). Ablation as a function of gelatin elasticity behaved in a similar manner. Temperature of the material ablated was also demonstrated to affect the rate of ablation. We conclude that the previously reported differences in ablation between thrombi and blood vessel are predictable based on the large difference in their mechanical elasticity, and that this difference provides a wide margin of safety.

  8. Mitophagy: mechanisms, pathophysiological roles, and analysis

    PubMed Central

    Ding, Wen-Xing; Yin, Xiao-Ming

    2013-01-01

    Mitochondria are essential organelles that regulate cellular energy homeostasis and cell death. The removal of damaged mitochondria through autophagy, a process called mitophagy, is thus critical for maintaining proper cellular functions. Indeed, mitophagy has been recently proposed to play critical roles in terminal differentiation of red blood cells, paternal mitochondrial degradation, neurodegenerative diseases, and ischemia or drug-induced tissue injury. Removal of damaged mitochondria through autophagy requires two steps: induction of general autophagy and priming of damaged mitochondria for selective autophagic recognition. Recent progress in mitophagy studies reveals that mitochondrial priming is mediated either by the Pink1-Parkin signaling pathway or the mitophagic receptors Nix and Bnip3. In this review, we summarize our current knowledge on the mechanisms of mitophagy. We also discuss the pathophysiological roles of mitophagy and current assays used to monitor mitophagy. PMID:22944659

  9. Kinematic analysis of a spatial mechanism for estimating shaking effects

    NASA Astrophysics Data System (ADS)

    Murthy, P. S. S.; Satyadevi, A.; Gopala Krishna, A.; Eswaraiah, K.

    2015-12-01

    Spatial mechanisms are the most general category of kinematic devices. They offer the greatest capability to accomplish any desired kinematic task. A mechanism exerts forces and moments on its supporting frame, which result in vibration. Besides of its effect on efficiency, reducing vibration has become inevitable in the current industrial environment where stern standards on noise and vibration prevail. Balancing of shaking forces and shaking moments in mechanisms is important in order to improve their dynamic performance and fatigue life by reducing vibration, noise and wear. The analysis and synthesis of spatial mechanisms which involves extensive vector mathematics and linear algebra is to be simplified to be taught to engineers in undergraduate education. In the present paper the kinematic analysis of a spatial four-link RSCR mechanism is done to get the velocities and accelerations of its various links which is necessary for the estimation of inertia forces in a mechanism.

  10. Acoustic analysis of a mechanical circulatory support.

    PubMed

    Hubbert, Laila; Sundbom, Per; Loebe, Matthias; Peterzén, Bengt; Granfeldt, Hans; Ahn, Henrik

    2014-07-01

    Mechanical circulatory support technology is continually improving. However, adverse complications do occur with devastating consequences, for example, pump thrombosis that may develop in several parts of the pump system. The aim of this study was to design an experimental clot/thrombosis model to register and analyze acoustic signals from the left ventricular assist device (LVAD) HeartMate II (HMII) (Thoratec Corporation, Inc., Pleasanton, CA, USA) and detect changes in sound signals correlating to clots in the inflow, outflow, and pump housing. Using modern telecom techniques, it was possible to register and analyze the HMII pump-specific acoustic fingerprint in an experimental model of LVAD support using a mock loop. Increase in pump speed significantly (P<0.005) changed the acoustic fingerprint at certain frequency (0-23,000 Hz) intervals (regions: R1-3 and peaks: P1,3-4). When the ball valves connected to the tubing were narrowed sequentially by ∼50% of the inner diameter (to mimic clot in the out- and inflow tubing), the frequency spectrum changed significantly (P<0.005) in P1 and P2 and R1 when the outflow tubing was narrowed. This change was not seen to the same extent when the lumen of the ball valve connected to the inflow tube was narrowed by ∼50%. More significant (P<0.005) acoustic changes were detected in P1 and P2 and R1 and R3, with the largest dB figs. in the lower frequency ranges in R1 and P2, when artificial clots and blood clots passed through the pump system. At higher frequencies, a significant change in dB figs. in R3 and P4 was detected when clots passed through the pump system. Acoustic monitoring of pump sounds may become a valuable tool in LVAD surveillance. PMID:24372095

  11. Airflow analysis in mechanically ventilated obstructed rooms

    NASA Astrophysics Data System (ADS)

    Priest, John Brian

    1999-11-01

    Local and mean air velocities and standard deviations were measured in realistic rooms. Obstructions represented occupants and equipment in the rooms, internal heat loads varied and supply air temperature differed from room averages. Experimental setups differed for the isothermal and nonisothermal tests. Room dimensions for isothermal tests were 2.44 m high by 4.88 x 4.88 m. Ten different obstruction ratios using three different inlet types were analyzed. Obstructions covered 0 to 30% floor area and from 0 to 75% of room height. Air was supplied at ventilation rates ranging between 0.8 and 1.1 m 3/s. Room dimensions for the nonisothermal tests were 2.44 m high by 3.66 x 7.32 m. Obstruction differences between solid versus open partitions for farrowing crates were investigated for three commercially available inlets using two ventilation loads. Ventilation rates were 0.11 to 1.18 m 3/s, simulating cold and warm weather ventilation conditions, respectively. Based on these data and theoretical calculations, a kinetic energy model that predicts average room air velocity and energy level was developed as a practical room air flow design and analysis tool. It was recommended that designers interested in using CFD as a tool should use a three dimensional laminar model for acceptable qualitative flow results. It was concluded that for typical room flowrates and inlet types the room air distribution system is obstruction ratio independent. Local velocities and standard deviations varied with each obstruction setup and inlet combination. However, average air velocities and turbulence intensities were not influenced by obstruction setups or inlet configurations. The decay rate of mean velocity kinetic energy in the bulk flow region was independent of obstructions and inlets. Room average kinetic energy was a function of the supplied kinetic energy within the supply jet plus internal kinetic energy resulting from internal heat load (convective energy).

  12. Analysis of frequency characteristics and sensitivity of compliant mechanisms

    NASA Astrophysics Data System (ADS)

    Liu, Shanzeng; Dai, Jiansheng; Li, Aimin; Sun, Zhaopeng; Feng, Shizhe; Cao, Guohua

    2016-03-01

    Based on a modified pseudo-rigid-body model, the frequency characteristics and sensitivity of the large-deformation compliant mechanism are studied. Firstly, the pseudo-rigid-body model under the static and kinetic conditions is modified to enable the modified pseudo-rigid-body model to be more suitable for the dynamic analysis of the compliant mechanism. Subsequently, based on the modified pseudo-rigid-body model, the dynamic equations of the ordinary compliant four-bar mechanism are established using the analytical mechanics. Finally, in combination with the finite element analysis software ANSYS, the frequency characteristics and sensitivity of the compliant mechanism are analyzed by taking the compliant parallel-guiding mechanism and the compliant bistable mechanism as examples. From the simulation results, the dynamic characteristics of compliant mechanism are relatively sensitive to the structure size, section parameter, and characteristic parameter of material on mechanisms. The results could provide great theoretical significance and application values for the structural optimization of compliant mechanisms, the improvement of their dynamic properties and the expansion of their application range.

  13. Kinematic analysis of a flexible six-DOF parallel mechanism.

    PubMed

    Jing, Feng-Shui; Tan, Min; Hou, Zeng-Guang; Liang, Zi-Ze; Wang, Yun-Kuan; Gupta, Madan M; Nikiforuk, Peter N

    2006-04-01

    In this paper, a new type of six-degrees of freedom (DOF) flexible parallel mechanism (FPM) is presented. This type of parallel mechanism possesses several favorable properties: (1) its number of DOFs is independent of the number of serial chains which make up the mechanism; (2) it has no kinematical singularities; (3) it is designed to move on rails, and therefore its workspace is much larger than that of a conventional parallel manipulator; and (4) without changing the number of DOFs and the kinematics of the mechanisms, the number of the serial chains can be reconfigured according to the needs of the tasks. These properties make the mechanism very preferable in practice, especially for such tasks as joining huge ship blocks, in which the manipulated objects vary dramatically both in weights and dimensions. Furthermore, the mechanism can be used as either a fully actuated system or an underactuated system. In the fully actuated case, the mechanism has six DOF motion capabilities and manipulation capabilities. However, in the underactuated case, the mechanism still has six DOF motion capabilities, but it has only five DOF manipulation capabilities. In this paper, both the inverse and forward kinematics are studied and expressed in a closed form. The workspace and singularity analysis of the mechanism are also presented. An example is presented to illustrate how to calculate the kinematics of the mechanism in both fully-actuated and underactuated cases. Finally, an application of such a mechanism to manufacturing industry is introduced. PMID:16602597

  14. Ethical challenges in home mechanical ventilation: A secondary analysis

    PubMed Central

    Dybwik, Knut; Nielsen, Erik Waage; Brinchmann, Berit Støre

    2012-01-01

    The aim of this study was to explore the ethical challenges in home mechanical ventilation based on a secondary analysis of qualitative empirical data. The data included perceptions of healthcare professionals in hospitals and community health services and family members of children and adults using home mechanical ventilation. The findings show that a number of ethical challenges, or dilemmas, arise at all levels in the course of treatment: deciding who should be offered home mechanical ventilation, respect for patient and family wishes, quality of life, dignity and equal access to home mechanical ventilation. Other challenges were the impacts home mechanical ventilation had on the patient, the family, the healthcare services and the allocation of resources. A better and broader understanding of these issues is crucial in order to improve the quality of care for both patient and family and assist healthcare professionals involved in home mechanical ventilation to make decisions for the good of the patient and his or her family. PMID:22183963

  15. Mechanics of intraply hybrid composites - Properties, analysis and design

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1979-01-01

    A mechanics theory is developed for predicting the physical thermal, hygral and mechanical properties (including various strengths) of unidirectional intraply hybrid composites (UIHC) based on unidirectional properties of the constituent composites. Procedures are described which can use this theory in conjunction with composite mechanics computer codes and general purpose structural analysis finite element programs for the analysis/design of structural components made from intraply hybrid angleplied laminates (IHAL). Comparisons with limited data show that this theory predicts mechanical properties of UIHC and flexural stiffnesses of IHAL which are in good agreement with experimental data. The theory developed herein makes it possible to design and optimize structural components from IHAL based on a large class of available constituent fibers.

  16. Dynamic mechanical analysis: A practical introduction to techniques and applications

    SciTech Connect

    Menard, K.

    1999-03-01

    This introduction provides the chemist, chemical engineer, or materials scientists with a starting point to understand the applications of dynamic mechanical analysis, its workings, and its advantages and limitations. This book serves as a systematic study of manufacturing polymeric materials and components as well as for developing new materials. Contents include: introduction to dynamic mechanical analysis; basic rheological concepts: stress, strain, and flow; rheology basic: creep-recovery and stress relaxation; dynamic testing; time-temperature scans part 1: transitions in polymers; time and temperature studies part 2: thermosets; frequency scans; DMA applications to real problems: guidelines; and appendix: sample experiments for the DMA.

  17. Acoustic emission spectral analysis of fiber composite failure mechanisms

    NASA Technical Reports Server (NTRS)

    Egan, D. M.; Williams, J. H., Jr.

    1978-01-01

    The acoustic emission of graphite fiber polyimide composite failure mechanisms was investigated with emphasis on frequency spectrum analysis. Although visual examination of spectral densities could not distinguish among fracture sources, a paired-sample t statistical analysis of mean normalized spectral densities did provide quantitative discrimination among acoustic emissions from 10 deg, 90 deg, and plus or minus 45 deg, plus or minus 45 deg sub s specimens. Comparable discrimination was not obtained for 0 deg specimens.

  18. Analysis of fluid/mechanical systems using EASY5

    NASA Technical Reports Server (NTRS)

    Clark, Robert W., Jr.; Arndt, Scott D.; Hurlbert, Eric A.

    1992-01-01

    This paper illustrates how the use of a general analysis package can simplify modeling and analyzing fluid/mechanical systems. One such package is EASY5, a Boeing Computer Services product. The basic transmission line equations for modeling piped fluid systems are presented, as well as methods of incorporating these equations into the EASY5 environment. The paper describes how this analysis tool has been used to model several fluid subsystems of the Space Shuttle Orbiter.

  19. UPDATE ON MECHANICAL ANALYSIS OF MONOLITHIC FUEL PLATES

    SciTech Connect

    D. E. Burkes; F. J. Rice; J.-F. Jue; N. P. Hallinan

    2008-03-01

    Results on the relative bond strength of the fuel-clad interface in monolithic fuel plates have been presented at previous RRFM conferences. An understanding of mechanical properties of the fuel, cladding, and fuel / cladding interface has been identified as an important area of investigation and quantification for qualification of monolithic fuel forms. Significant progress has been made in the area of mechanical analysis of the monolithic fuel plates, including mechanical property determination of fuel foils, cladding processed by both hot isostatic pressing and friction bonding, and the fuel-clad composite. In addition, mechanical analysis of fabrication induced residual stress has been initiated, along with a study to address how such stress can be relieved prior to irradiation. Results of destructive examinations and mechanical tests are presented along with analysis and supporting conclusions. A brief discussion of alternative non-destructive evaluation techniques to quantify not only bond quality, but also bond integrity and strength, will also be provided. These are all necessary steps to link out-of-pile observations as a function of fabrication with in-pile behaviours.

  20. Analysis of Links Positions in Landing Gear Mechanism

    NASA Astrophysics Data System (ADS)

    Brewczyński, D.; Tora, G.

    2014-08-01

    This article contains a kinematic analysis of an aircraft chassis mechanism in a range of positions. The mechanism of the chassis is made up of several smaller subsystems with different functions. The first mechanism is used to eject the chassis before landing (touchdown) and fold it to hatchway after the lift off. The second mechanism is designed to perform rotation of the crossover with the wheel, in order to adjust the position of the wheel to fit it in the limited space in the hold. The third mechanism allows movement of the chassis resulting from the change in length of the damper. To determine the position of the following links of the mechanism calculus of vectors was applied in which unit vectors were used to represent the angular position of the links. The aim of the analysis is to determine the angle of convergence and the angle of heel wheels as a function of the variable length of hydraulic cylinder, length of the shock absorber, length of the regulations rods

  1. An Analysis of the Waste Water Treatment Maintenance Mechanic Occupation.

    ERIC Educational Resources Information Center

    Clark, Anthony B.; And Others

    The general purpose of the occupational analysis is to provide workable, basic information dealing with the many and varied duties performed in the waste water treatment mechanics occupation. The document opens with a brief introduction followed by a job description. The bulk of the document is presented in table form. Twelve duties are broken…

  2. Computer-aided design and analysis of mechanisms

    NASA Technical Reports Server (NTRS)

    Knight, F. L.

    1982-01-01

    An introduction to the computer programs developed to assist in the design and analysis of mechanisms is presented. A survey of the various types of programs which are available is given, and the most widely used programs are compared. The way in which the programs are used is discussed, and demonstrated with an example.

  3. Computer aided analysis and optimization of mechanical system dynamics

    NASA Technical Reports Server (NTRS)

    Haug, E. J.

    1984-01-01

    The purpose is to outline a computational approach to spatial dynamics of mechanical systems that substantially enlarges the scope of consideration to include flexible bodies, feedback control, hydraulics, and related interdisciplinary effects. Design sensitivity analysis and optimization is the ultimate goal. The approach to computer generation and solution of the system dynamic equations and graphical methods for creating animations as output is outlined.

  4. An Analysis of the Diesel Truck Mechanic Occupation.

    ERIC Educational Resources Information Center

    Kilo, Joseph L.

    The general purpose of the occupational analysis is to provide workable, basic information dealing with the many and varied duties performed in the diesel truck mechanic occupation. The document opens with a brief introduction followed by a job description. The bulk of the document is presented in table form. Thirteen duties are broken down into a…

  5. Fracture mechanics analysis of composite microcracking - Experimental results in fatigue

    NASA Technical Reports Server (NTRS)

    Nairn, J. A.; Liu, S.

    1990-01-01

    The Nairn (1989) variational mechanics analysis, which yields the energy release rate of a microcrack's formation between two existing microcracks, has proven useful in the fracture mechanics interpretation of cross-ply laminates' microcracking. Attention is presently given to the application of this energy release rate analysis to a fracture mechanics-based interpretation of microcrack formation during fatigue loading, for the case of fatigue experiments on three layups of Avimid K/IM6 laminates and four layups of Fiberite 934/T300 laminates. The single master Paris-law plot onto which the data from all layups of a given material system fall is claimed to offer a complete characterization of that system's microcrack-formation resistance during fatigue loading.

  6. Independent Orbiter Assessment (IOA): Analysis of the mechanical actuation subsystem

    NASA Technical Reports Server (NTRS)

    Bacher, J. L.; Montgomery, A. D.; Bradway, M. W.; Slaughter, W. T.

    1987-01-01

    The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Mechanical Actuation System (MAS) hardware. Specifically, the MAS hardware consists of the following components: Air Data Probe (ADP); Elevon Seal Panel (ESP); External Tank Umbilical (ETU); Ku-Band Deploy (KBD); Payload Bay Doors (PBD); Payload Bay Radiators (PBR); Personnel Hatches (PH); Vent Door Mechanism (VDM); and Startracker Door Mechanism (SDM). The IOA analysis process utilized available MAS hardware drawings and schematics for defining hardware assemblies, components, and hardware items. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode.

  7. Scaling analysis for the investigation of slip mechanisms in nanofluids

    NASA Astrophysics Data System (ADS)

    Savithiri, S.; Pattamatta, Arvind; Das, Sarit K.

    2011-07-01

    The primary objective of this study is to investigate the effect of slip mechanisms in nanofluids through scaling analysis. The role of nanoparticle slip mechanisms in both water- and ethylene glycol-based nanofluids is analyzed by considering shape, size, concentration, and temperature of the nanoparticles. From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles. The magnitudes of slip mechanisms are found to be higher for particles of size between 10 and 80 nm. The Brownian force is found to dominate in smaller particles below 10 nm and also at smaller volume fraction. However, the drag force is found to dominate in smaller particles below 10 nm and at higher volume fraction. The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration. In terms of time scales, the Brownian and gravity forces act considerably over a longer duration than the other forces. For copper-water-based nanofluid, the effective contribution of slip mechanisms leads to a heat transfer augmentation which is approximately 36% over that of the base fluid. The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it.

  8. Failure analysis for micro-electrical-mechanical systems (MEMS)

    SciTech Connect

    Peterson, K.A.; Tangyunyong, P.; Barton, D.L.

    1997-10-01

    Micro-Electrical Mechanical Systems (MEMS) is an emerging technology with demonstrated potential for a wide range of applications including sensors and actuators for medical, industrial, consumer, military, automotive and instrumentation products. Failure analysis (FA) of MEMS is critically needed for the successful design, fabrication, performance analysis and reliability assurance of this new technology. Many devices have been examined using techniques developed for integrated circuit analysis, including optical inspection, scanning laser microscopy (SLM), scanning electron microscopy (SEM), focused ion beam (FIB) techniques, atomic force microscopy (AFM), infrared (IR) microscopy, light emission (LE) microscopy, acoustic microscopy and acoustic emission analysis. For example, the FIB was used to microsection microengines that developed poor performance characteristics. Subsequent SEM analysis clearly demonstrated the absence of wear on gear, hub, and pin joint bearing surfaces, contrary to expectations. Another example involved the use of infrared microscopy for thermal analysis of operating microengines. Hot spots were located, which did not involve the gear or hub, but indicated contact between comb structures which drive microengines. Voltage contrast imaging proved useful on static and operating MEMS in both the SEM and the FIB and identified electrostatic clamping as a potentially significant contributor to failure mechanisms in microengines. This work describes MEMS devices, FA techniques, failure modes, and examples of FA of MEMS.

  9. Mechanical Network in Titin Immunoglobulin from Force Distribution Analysis

    PubMed Central

    Wilmanns, Matthias; Gräter, Frauke

    2009-01-01

    The role of mechanical force in cellular processes is increasingly revealed by single molecule experiments and simulations of force-induced transitions in proteins. How the applied force propagates within proteins determines their mechanical behavior yet remains largely unknown. We present a new method based on molecular dynamics simulations to disclose the distribution of strain in protein structures, here for the newly determined high-resolution crystal structure of I27, a titin immunoglobulin (IG) domain. We obtain a sparse, spatially connected, and highly anisotropic mechanical network. This allows us to detect load-bearing motifs composed of interstrand hydrogen bonds and hydrophobic core interactions, including parts distal to the site to which force was applied. The role of the force distribution pattern for mechanical stability is tested by in silico unfolding of I27 mutants. We then compare the observed force pattern to the sparse network of coevolved residues found in this family. We find a remarkable overlap, suggesting the force distribution to reflect constraints for the evolutionary design of mechanical resistance in the IG family. The force distribution analysis provides a molecular interpretation of coevolution and opens the road to the study of the mechanism of signal propagation in proteins in general. PMID:19282960

  10. Conformational analysis of small molecules: NMR and quantum mechanics calculations.

    PubMed

    Tormena, Cláudio F

    2016-08-01

    This review deals with conformational analysis in small organic molecules, and describes the stereoelectronic interactions responsible for conformational stability. Conformational analysis is usually performed using NMR spectroscopy through measurement of coupling constants at room or low temperature in different solvents to determine the populations of conformers in solution. Quantum mechanical calculations are used to address the interactions responsible for conformer stability. The conformational analysis of a large number of small molecules is described, using coupling constant measurements in different solvents and at low temperature, as well as recent applications of through-space and through-hydrogen bond coupling constants JFH as tools for the conformational analysis of fluorinated molecules. Besides NMR parameters, stereoelectronic interactions such as conjugative, hyperconjugative, steric and intramolecular hydrogen bond interactions involved in conformational preferences are discussed. PMID:27573182

  11. Variational mechanics analysis of the stresses in microdrop debond specimens

    NASA Technical Reports Server (NTRS)

    Scheer, Robert J.; Nairn, John A.

    1991-01-01

    A recently derived variational mechanics analysis of stresses in single-fiber model composites has been applied to the analysis of the stresses in the microdrop debond specimen. The new analysis is more accurate than the commonly applied shear-lag or elastic-plastic analyses. The results from a sample stress state calculation suggest that interfacial failure between the fiber and the microdrop is by mode I or opening mode failure at the beginning of the microdrop. The opening mode failure is caused by a large tensile radial stress at the fiber/matrix interface. Previous analyses of microdrop debond data have been in terms of a shear strength. It is suggested that these analyses misrepresent microdrop debond results and recommend instead a failure analysis based on energy release rate and interfacial fracture toughness. A procedure for calculating the energy release rate for the growth of an interfacial crack is described.

  12. Behavior analysis and mechanism: One is not the other

    PubMed Central

    Morris, Edward K.

    1993-01-01

    Behavior analysts have been called mechanists, and behavior analysis is said to be mechanistic; that is, they are claimed to be aligned with the philosophy of mechanism. What this means is analyzed by (a) examining standard and specialized dictionary and encyclopedia definitions and descriptions of mechanism and its cognates and (b) reviewing contemporary representations of the mechanistic worldview in the literature on the philosophy of psychology. Although the term mechanism and its cognates are sometimes an honorific (e.g., “natural science”), their standard meanings, usages, and functions in society, science, psychology, and philosophy do not aptly characterize the discipline. These terms mischaracterize how behavior analysts conceptualize (a) the behavior of their subjects and the individuals with whom they work and (b) their own behavior as scientists. Discussion is interwoven throughout about the nature of terms and definitions in science. PMID:22478129

  13. Mechanics, analysis and geometry: 200 years after Lagrange.

    NASA Astrophysics Data System (ADS)

    Francaviglia, M.

    This volume consists of articles written on the occasion of the bicentennial of the publication by J.-Louis Lagrange of his treatise, Mechanique Analytique (1788). This book opened a floodgate of contributions to mechanics by analysis. The resulting volume provides insight and perspective on various research problems in modern topics of physics, astrophysics, mathematics and the history of science. Furthermore it presents a balanced and authoritative account of the different branches and problems of mathematical physics that Lagrange originally studied and developed.

  14. Potential of isotope analysis (C, Cl) to identify dechlorination mechanisms

    NASA Astrophysics Data System (ADS)

    Cretnik, Stefan; Thoreson, Kristen; Bernstein, Anat; Ebert, Karin; Buchner, Daniel; Laskov, Christine; Haderlein, Stefan; Shouakar-Stash, Orfan; Kliegman, Sarah; McNeill, Kristopher; Elsner, Martin

    2013-04-01

    Chloroethenes are commonly used in industrial applications, and detected as carcinogenic contaminants in the environment. Their dehalogenation is of environmental importance in remediation processes. However, a detailed understanding frequently accounted problem is the accumulation of toxic degradation products such as cis-dichloroethylene (cis-DCE) at contaminated sites. Several studies have addressed the reductive dehalogenation reactions using biotic and abiotic model systems, but a crucial question in this context has remained open: Do environmental transformations occur by the same mechanism as in their corresponding in vitro model systems? The presented study shows the potential to close this research gap using the latest developments in compound specific chlorine isotope analysis, which make it possible to routinely measure chlorine isotope fractionation of chloroethenes in environmental samples and complex reaction mixtures.1,2 In particular, such chlorine isotope analysis enables the measurement of isotope fractionation for two elements (i.e., C and Cl) in chloroethenes. When isotope values of both elements are plotted against each other, different slopes reflect different underlying mechanisms and are remarkably insensitive towards masking. Our results suggest that different microbial strains (G. lovleyi strain SZ, D. hafniense Y51) and the isolated cofactor cobalamin employ similar mechanisms of reductive dechlorination of TCE. In contrast, evidence for a different mechanism was obtained with cobaloxime cautioning its use as a model for biodegradation. The study shows the potential of the dual isotope approach as a tool to directly compare transformation mechanisms of environmental scenarios, biotic transformations, and their putative chemical lab scale systems. Furthermore, it serves as an essential reference when using the dual isotope approach to assess the fate of chlorinated compounds in the environment.

  15. Fracture mechanics analysis for various fiber/matrix interface loadings

    NASA Technical Reports Server (NTRS)

    Naik, R. A.; Crews, J. H., Jr.

    1991-01-01

    Fiber/matrix (F/M) cracking was analyzed to provide better understanding and guidance in developing F/M interface fracture toughness tests. Two configurations, corresponding to F/M cracking at a broken fiber and at the free edge, were investigated. The effects of mechanical loading, thermal cooldown, and friction were investigated. Each configuration was analyzed for two loadings: longitudinal and normal to the fiber. A nonlinear finite element analysis was performed to model friction and slip at the F/M interface. A new procedure for fitting a square-root singularity to calculated stresses was developed to determine stress intensity factors (K sub I and K sub II) for a bimaterial interface crack. For the case of F/M cracking at a broken fiber with longitudinal loading, crack tip conditions were strongly influenced by interface friction. As a result, an F/M interface toughness test based on this case was not recommended because nonlinear data analysis methods would be required. For the free edge crack configuration, both mechanical and thermal loading caused crack opening, thereby avoiding frictional effects. A F/M interface toughness test based on this configuration would provide data for K(sub I)/K(sub II) ratios of about 0.7 and 1.6 for fiber and radial normal loading, respectively. However, thermal effects must be accounted for in the data analysis.

  16. Fracture mechanics analysis for various fiber/matrix interface loadings

    NASA Technical Reports Server (NTRS)

    Naik, Rajiv A.; Crews, John H., Jr.

    1992-01-01

    Fiber/matrix (F/M) cracking was analyzed to provide better understanding and guidance in developing F/M interface fracture toughness tests. Two configurations, corresponding to F/M cracking at a broken fiber and at the free edge, were investigated. The effects of mechanical loading, thermal cooldown, and friction were investigated. Each configuration was analyzed for two loadings: longitudinal and normal to the fiber. A nonlinear finite element analysis was performed to model friction and slip at the F/M interface. A new procedure for fitting a square-root singularity to calculated stresses was developed to determine stress intensity factors (K sub I and K sub II) for a bimaterial interface crack. For the case of F/M cracking at a broken fiber with longitudinal loading, crack tip conditions were strongly influenced by interface friction. As a result, an F/M interface toughness test based on this case was not recommended because nonlinear data analysis methods would be required. For the free edge crack configuration, both mechanical and thermal loading caused crack opening, theory avoiding fractional effects. A F/M interface toughness test based on this configuration would provide data for K(sub I/K(sub II) ratios of about 0.7 and 1.6 for fiber and radial normal loading, respectively. However, thermal effects must be accounted for in the data analysis.

  17. Fracture mechanics analysis for various fiber/matrix interface loadings

    NASA Technical Reports Server (NTRS)

    Naik, R. A.; Crews, J. H., Jr.

    1991-01-01

    Fiber/matrix (F/M) cracking was analyzed to provide better understanding and guidance in developing F/M interface fracture toughness tests. Two configurations, corresponding to F/M cracking at a broken fiber and at the free edge, were investigated. The effects of mechanical loading, thermal cooldown, and friction were investigated. Each configuration was analyzed for two loadings: longitudinal and normal to the fiber. A nonlinear finite element analysis was performed to model friction and slip at the F/M interface. A new procedure for fitting a square-root singularity to calculated stresses was developed to determine stress intensity factors (K sub I and K sub II) for a bimaterial interface crack. For the case of F/M cracking at a broken fiber with longitudinal loading, crack tip conditions were strongly influenced by interface friction. As a result, an F/M interface toughness test based on this case was not recommended because nonlinear data analysis methods would be required. For the free edge crack configuration, both mechanical and thermal loading caused crack opening, thereby avoiding frictional effects. An F/M interface toughness test based on this configuration would provide data for K(sub I)/K(sub II) ratios of about 0.7 and 1.6 for fiber and radial normal loading, respectively. However, thermal effects must be accounted for in the data analysis.

  18. Statistical Mechanics Analysis of ATP Binding to a Multisubunit Enzyme

    NASA Astrophysics Data System (ADS)

    Zhang, Yun-Xin

    2014-10-01

    Due to inter-subunit communication, multisubunit enzymes usually hydrolyze ATP in a concerted fashion. However, so far the principle of this process remains poorly understood. In this study, from the viewpoint of statistical mechanics, a simple model is presented. In this model, we assume that the binding of ATP will change the potential of the corresponding enzyme subunit, and the degree of this change depends on the state of its adjacent subunits. The probability of enzyme in a given state satisfies the Boltzmann's distribution. Although it looks much simple, this model can fit the recent experimental data of chaperonin TRiC/CCT well. From this model, the dominant state of TRiC/CCT can be obtained. This study provide a new way to understand biophysical processe by statistical mechanics analysis.

  19. A Characterization of the Mechanical Behavior of Resin-Infiltrated Dentin Using Nanoscopic Dynamic Mechanical Analysis

    PubMed Central

    Ryou, Heonjune; Pashley, David H.; Tay, Franklin R.; Arola, Dwayne

    2013-01-01

    This study explored the spatial variations in mechanical behavior of resin-infiltrated dentin using nanoscopic Dynamic Mechanical Analysis (DMA). Objective The objectives were to: 1) evaluate the mechanical behavior of resin-infiltrated dentin using a scanning-based approach to nanoindentation, 2) identify contributions of the collagen matrix to time-dependent deformation of the hybrid layer, and 3) assess the importance of specimen hydration on the nanoDMA response. Methods Specimens of completely demineralized dentin infiltrated with commercial resin adhesive and control samples of resin adhesive were evaluated using a nanoindenter in scanning mode. The load and displacement responses were used to perform DMA and to estimate the complex (E*), storage (E’) and loss (E”) moduli over selected regions of evaluation. The importance of hydration on the mechanical behavior was also examined from a comparison of responses in the hydrated and dehydrated conditions. Results In the hydrated state the apparent complex, storage and loss moduli for the resin-infiltrated dentin samples were 3.5±0.3 GPa, 3.4±0.2 GPa and 0.9±0.3 GPa, respectively. Those values for the resin adhesive control were 2.7±0.3 GPa, 2.7±0.3 GPa and 0.2±0.02 GPa, respectively. Viscoelastic deformation of the resin-infiltrated collagen exceeded that occurring in regions of uniform resin adhesive. Though dehydration resulted in a significant increase in both the complex and storage moduli of the macro hybrid layer, the largest changes occurred to the resin adhesive. Significance The microstructure and hydration play critical roles on the mechanical behavior of the hybrid layer and nanoDMA provides a potent measurement tool for identifying the spatial variations. PMID:23639453

  20. Intraoral Laser Welding (ILW): ultrastructural and mechanical analysis

    NASA Astrophysics Data System (ADS)

    Fornaini, Carlo; Passaretti, Francesca; Villa, Elena; Nammour, Samir

    2010-05-01

    Nd:YAG, currently used since 1970 in dental laboratories to weld metals on dental prostheses has some limits such great dimensions, high costs and fixed delivery system. Recently it was proposed the possibility to use the Nd:YAG laser device commonly utilised in dental office, to repair broken fixed, removable and orthodontic prostheses and to weld metals directly into the mouth. The aim of this work is to value, through SEM (Scanning Electron Microscope), EDS (Energy Dispersive X-Ray Spectroscopy) and DMA (Dynamic Mechanical Analysis), quality and mechanical strength of the welding process comparing a device normally used in dental lab and a device normally used in dental office for oral surgery. Sixteen CoCrMo metal plates and twenty steel orthodontic wires were divided in four groups: one was welded without metal apposition by laboratory laser, one was welded with metal apposition by laboratory laser, one was welded without metal apposition by office laser and one was welded with metal apposition by office laser. The welding process was analysed by SEM, EDS and DMA to compare the differences between the different samples. By SEM analysis it was seen that the plates welded by office laser without apposition metal showed a greater number of fissurations compared with the other samples. By EDS analysis it was seen a homogeneous composition of the metals in all the samples. The mechanical tests showed a similar elastic behaviour of the samples, with minimal differences between the two devices. No wire broke even under the maximum strength by the Analyser. This study seems to demonstrate that the welding process by office Nd:YAG laser device and the welding process by laboratory Nd:YAG laser device, analysed by SEM, EDS and DMA, showed minimal and not significant differences even if these data will be confirmed by a greater number of samples.

  1. Nonlinear fracture mechanics-based analysis of thin wall cylinders

    NASA Technical Reports Server (NTRS)

    Brust, Frederick W.; Leis, Brian N.; Forte, Thomas P.

    1994-01-01

    This paper presents a simple analysis technique to predict the crack initiation, growth, and rupture of large-radius, R, to thickness, t, ratio (thin wall) cylinders. The method is formulated to deal both with stable tearing as well as fatigue mechanisms in applications to both surface and through-wall axial cracks, including interacting surface cracks. The method can also account for time-dependent effects. Validation of the model is provided by comparisons of predictions to more than forty full scale experiments of thin wall cylinders pressurized to failure.

  2. Surge Nozzle NDE Specimen Mechanical Stress Improvement Analysis

    SciTech Connect

    Fredette, Lee F.

    2011-07-14

    The purpose of this project was to perform a finite element analysis of a pressurized water reactor pressurizer surge nozzle mock-up to predict both the weld residual stresses created in its construction and the final stress state after the application of the Mechanical Stress Improvement Process (MSIP). Strain gages were applied to the inner diameter of the mock-up to record strain changes during the MSIP. These strain readings were used in an attempt to calculate the final stress state of the mock-up as well.

  3. Adhesive fracture mechanics. [stress analysis for bond line interface

    NASA Technical Reports Server (NTRS)

    Bennett, S. J.; Devries, K. L.; Williams, M. L.

    1974-01-01

    In studies of fracture mechanics the adhesive fracture energy is regarded as a fundamental property of the adhesive system. It is pointed out that the value of the adhesive fracture energy depends on surface preparation, curing conditions, and absorbed monolayers. A test method reported makes use of a disk whose peripheral part is bonded to a substrate material. Pressure is injected into the unbonded central part of the disk. At a certain critical pressure value adhesive failure can be observed. A numerical stress analysis involving arbitrary geometries is conducted.

  4. Cell mechanics through analysis of cell trajectories in microfluidic channel

    NASA Astrophysics Data System (ADS)

    Bowie, Samuel; Alexeev, Alexander; Sulchek, Todd

    The understanding of dynamic cell behavior can aid in research ranging from the mechanistic causes of diseases to the development of microfluidic devices for cancer detection. Through analysis of trajectories captured from video of the cells moving in a specially designed microfluidic device, insight into the dynamic viscoelastic nature of cells can be found. The microfluidic device distinguishes cells viscoelastic properties through the use of angled ridges causing a series of compressions, resulting in differences in trajectories based on cell stiffness. Trajectories of cell passing through the device are collected using image processing methods and data mining techniques are used to relate the trajectories to cell properties obtained from experiments. Furthermore, numerical simulation of the cell and microfluidic device are used to match the experimental results from the trajectory analysis. Combination of the modeling and experimental data help to uncover how changes in cellular structures result in changes in mechanical properties.

  5. Control of a mechanical aeration process via topological sensitivity analysis

    NASA Astrophysics Data System (ADS)

    Abdelwahed, M.; Hassine, M.; Masmoudi, M.

    2009-06-01

    The topological sensitivity analysis method gives the variation of a criterion with respect to the creation of a small hole in the domain. In this paper, we use this method to control the mechanical aeration process in eutrophic lakes. A simplified model based on incompressible Navier-Stokes equations is used, only considering the liquid phase, which is the dominant one. The injected air is taken into account through local boundary conditions for the velocity, on the injector holes. A 3D numerical simulation of the aeration effects is proposed using a mixed finite element method. In order to generate the best motion in the fluid for aeration purposes, the optimization of the injector location is considered. The main idea is to carry out topological sensitivity analysis with respect to the insertion of an injector. Finally, a topological optimization algorithm is proposed and some numerical results, showing the efficiency of our approach, are presented.

  6. Fracture mechanics concepts in reliability analysis of monolithic ceramics

    NASA Technical Reports Server (NTRS)

    Manderscheid, Jane M.; Gyekenyesi, John P.

    1987-01-01

    Basic design concepts for high-performance, monolithic ceramic structural components are addressed. The design of brittle ceramics differs from that of ductile metals because of the inability of ceramic materials to redistribute high local stresses caused by inherent flaws. Random flaw size and orientation requires that a probabilistic analysis be performed in order to determine component reliability. The current trend in probabilistic analysis is to combine linear elastic fracture mechanics concepts with the two parameter Weibull distribution function to predict component reliability under multiaxial stress states. Nondestructive evaluation supports this analytical effort by supplying data during verification testing. It can also help to determine statistical parameters which describe the material strength variation, in particular the material threshold strength (the third Weibull parameter), which in the past was often taken as zero for simplicity.

  7. A κ-generalized statistical mechanics approach to income analysis

    NASA Astrophysics Data System (ADS)

    Clementi, F.; Gallegati, M.; Kaniadakis, G.

    2009-02-01

    This paper proposes a statistical mechanics approach to the analysis of income distribution and inequality. A new distribution function, having its roots in the framework of κ-generalized statistics, is derived that is particularly suitable for describing the whole spectrum of incomes, from the low-middle income region up to the high income Pareto power-law regime. Analytical expressions for the shape, moments and some other basic statistical properties are given. Furthermore, several well-known econometric tools for measuring inequality, which all exist in a closed form, are considered. A method for parameter estimation is also discussed. The model is shown to fit remarkably well the data on personal income for the United States, and the analysis of inequality performed in terms of its parameters is revealed as very powerful.

  8. In vivo liver tissue mechanical properties by Transient Elastography: comparison with Dynamic Mechanical Analysis.

    PubMed

    Chatelin, Simon; Oudry, Jennifer; Périchon, Nicolas; Sandrin, Laurent; Allemann, Pierre; Soler, Luc; Willinger, Rémy

    2011-01-01

    Understanding the mechanical properties of human liver is one of the most critical aspects of its numerical modeling for medical applications or impact biomechanics. Generally, model constitutive laws come from in vitro data. However, the elastic properties of liver may change significantly after death and with time. Furthermore, in vitro liver elastic properties reported in the literature have often not been compared quantitatively with in vivo liver mechanical properties on the same organ. In this study, both steps are investigated on porcine liver. The elastic property of the porcine liver, given by the shear modulus G, was measured by both Transient Elastography (TE) and Dynamic Mechanical Analysis (DMA). Shear modulus measurements were realized on in vivo and in vitro liver to compare the TE and DMA methods and to study the influence of testing conditions on the liver viscoelastic properties. In vitro results show that elastic properties obtained by TE and DMA are in agreement. Liver tissue in the frequency range from 0.1 to 4 Hz can be modeled by a two-mode relaxation model. Furthermore, results show that the liver is homogeneous, isotropic and more elastic than viscous. Finally, it is shown in this study that viscoelastic properties obtained by TE and DMA change significantly with post mortem time and with the boundary conditions. PMID:21811013

  9. Application of dynamic mechanical analysis (DMA) to determine the mechanical properties of pellets.

    PubMed

    Bashaiwoldu, Abraham B; Podczeck, F; Newton, J M

    2004-01-28

    Pellets of a wide range of mechanical properties were produced by the process of extrusion and spheronisation using various formulation factors. A range of mechanical properties from a simple fracture load to detailed load/displacement curves obtained when pellets were subjected to diametral compression test and a bed of pellets was compacted, were used to provide measure of tensile strength, deformability, linear strain, elastic modulus, yield and shear strength. Such conventional techniques resulted in irreversible damage to the structure of the pellets and were unable to establish the viscoelastic properties of the pellets. The application of the dynamic mechanical analysis (DMA), however, allowed the determination of (1) an accurate Young's modulus of elasticity, which was found to be between 8.4 and 24-fold higher than that determined from the diametral compression test, (2) the presence of a reversible elastic deformation even after the yield point in terms of storage modulus and (3) a change in the values of the phase angle, which illustrates the increase in viscoelasticity of the pellets formed with ethanol, glyceryl monostearate (GMS) or glycerol, while a decrease in viscoelasticity with the incorporation of lactose into the microcrystalline cellulose (MCC) pellets. This work further demonstrated that the only feasible technique for determining the elastic and plastic deformability of the pellets is the one which subjects the specimen to stress/relaxation cycles and can determine the dissipated energy in terms of loss modulus or phase angle, and that is DMA. PMID:14706245

  10. Application of dynamic mechanical analysis (DMA) to the determination of the mechanical properties of coated pellets.

    PubMed

    Bashaiwoldu, Abraham B; Podczeck, F; Newton, J M

    2004-04-15

    Pellets containing a model drug, paracetamol, and microcrystalline cellulose (MCC) were designed to vary their mechanical properties by the incorporation of lactose, glyceryl monostearate (GMS), ethanol, or glycerol, and were produced by the process of extrusion and spheronization. The pellets were coated with an aqueous dispersion of ethyl cellulose (Surelease) to different levels of weight gain (5, 10, and 20%). The tensile strength, deformability, linear strain, elastic modulus, and shear strength of the coated and uncoated pellets were determined by conventional techniques, which are obtained from diametral compression test of individual pellets and compaction of a bed of pellets. Dynamic Mechanical Analysis (DMA) was performed on single pellets to determine the storage modulus and phase angle of the coated pellets. This work demonstrated that the coating film affected the mechanical properties of the pellets differently depending on the properties of the core pellets. Analysis of variance established a significant increase in the strength of the soft GMS- or glycerol-containing pellets with coating, while the effect of the coating material was not significant with respect to the elastic modulus, storage modulus, and phase angle of such pellets. The effects of the coating material on the elastic modulus, deformability, storage modulus, and phase angle of the rigid lactose-containing pellets were significant. The sinusoidal stress-relaxation cycle of the DMA illustrated the increase in the viscoelasticity of all the pellets after coating. Finally, the work demonstrate the advantages of DMA in determining the reversible or dissipated energy by means of storage modulus or phase angle when compared with the irreversible structural destruction of the pellets by conventional techniques. PMID:15072782

  11. Quantitative Financial Analysis of Alternative Energy Efficiency Shareholder Incentive Mechanisms

    SciTech Connect

    Cappers, Peter; Goldman, Charles; Chait, Michele; Edgar, George; Schlegel, Jeff; Shirley, Wayne

    2008-08-03

    Rising energy prices and climate change are central issues in the debate about our nation's energy policy. Many are demanding increased energy efficiency as a way to help reduce greenhouse gas emissions and lower the total cost of electricity and energy services for consumers and businesses. Yet, as the National Action Plan on Energy Efficiency (NAPEE) pointed out, many utilities continue to shy away from seriously expanding their energy efficiency program offerings because they claim there is insufficient profit-motivation, or even a financial disincentive, when compared to supply-side investments. With the recent introduction of Duke Energy's Save-a-Watt incentive mechanism and ongoing discussions about decoupling, regulators and policymakers are now faced with an expanded and diverse landscape of financial incentive mechanisms, Determining the 'right' way forward to promote deep and sustainable demand side resource programs is challenging. Due to the renaissance that energy efficiency is currently experiencing, many want to better understand the tradeoffs in stakeholder benefits between these alternative incentive structures before aggressively embarking on a path for which course corrections can be time-consuming and costly. Using a prototypical Southwest utility and a publicly available financial model, we show how various stakeholders (e.g. shareholders, ratepayers, etc.) are affected by these different types of shareholder incentive mechanisms under varying assumptions about program portfolios. This quantitative analysis compares the financial consequences associated with a wide range of alternative incentive structures. The results will help regulators and policymakers better understand the financial implications of DSR program incentive regulation.

  12. Dynamic mechanical analysis of hydrogen purification substrates and membranes

    NASA Astrophysics Data System (ADS)

    Steinborn, Brandon

    Porous 420 stainless steel hydrogen purification substrates were fabricated using an ExOne R2 printer and sintered at temperatures of 1075 °C and 1100 °C for times ranging from 15 minutes to 240 minutes. Coatings of 1 micron silica beads, silica sol-gel, and palladium were applied to the sintered structure. Mechanical properties/degradation of each substrate/coating combination were evaluated using a cyclic 3-point loading condition imposed by a TA Q800 dynamic mechanical analysis unit (DMA). A constant deformation procedure was used while the required drive force for deformation and the elasticity (tan delta) were recorded throughout the cycle. Findings with respect to coating additions include: drive force increases with the addition of each coating, tan delta decreases with ceramic additions and increases with palladium addition (eventually decreases when membrane fails), and tan delta values become comparable with the addition of palladium regardless of other parameters. Findings with respect to sintering time and temperature include: drive force increases with increased sintering time and temperature, tan delta increases with increased sintering time at 1075 °C, and tan delta decreases with increased sintering time at 1100 °C. Overall, the palladium layer would likely remain intact in service due to actual force oscillations not being as extreme in service, poisoning would likely be the life limiting factor. Keywords: Sintering, dynamic mechanical properties, porous stainless steel, hydrogen purification, sol-gel.

  13. a Numerical Method for Stability Analysis of Pinned Flexible Mechanisms

    NASA Astrophysics Data System (ADS)

    Beale, D. G.; Lee, S. W.

    1996-05-01

    A technique is presented to investigate the stability of mechanisms with pin-jointed flexible members. The method relies on a special floating frame from which elastic link co-ordinates are defined. Energies are easily developed for use in a Lagrange equation formulation, leading to a set of non-linear and mixed ordinary differential-algebraic equations of motion with constraints. Stability and bifurcation analysis is handled using a numerical procedure (generalized co-ordinate partitioning) that avoids the tedious and difficult task of analytically reducing the system of equations to a number equalling the system degrees of freedom. The proposed method was then applied to (1) a slider-crank mechanism with a flexible connecting rod and crank of constant rotational speed, and (2) a four-bar linkage with a flexible coupler with a constant speed crank. In both cases, a single pinned-pinned beam bending mode is employed to develop resonance curves and stability boundaries in the crank length-crank speed parameter plane. Flip and fold bifurcations are common occurrences in both mechanisms. The accuracy of the proposed method was also verified by comparison with previous experimental results [1].

  14. Critical Analysis of Wear Mechanisms in Cemented Carbide

    NASA Astrophysics Data System (ADS)

    Dewangan, Saurabh; Chattopadhyaya, Somnath

    2015-07-01

    Wear phenomena of cemented carbide (94 wt.% WC, 6 wt.% Co) tip of conical picks have been observed by field emission scanning electron microscopy, energy dispersive x-ray spectroscopy (EDS), and x-ray diffraction analysis (XRD). The conical pick is one type of the cutters which are used to excavate soft structure like coal. It has a cone-shaped abrasive part made of cemented carbide (CC). The picks, under study, have been used for coal mining in an underground mine through a continuous miner machine. During the critical analysis of four picks, wear mechanisms are categorized into four parts, such as, cracks, cavity formation in WC grains, grinding effect, and roughness of WC surface. Through a careful examination, the cracking mechanism has been further divided into three parts. They are cracks with overlapping surfaces, crack on a large surface of CC, and cracks in WC grains. In addition, the severe crushing and tearing of WC grains have also been clearly examined. The possible causes of each wear phenomenon have been explained comprehensively. Crushing and corrosion are the two wearing processes which have severely deteriorated the condition of the CC. Corrosion has been easily identified by observing a number of pores and triangular notches in the WC surface. The oxidation of WC grains due to corrosion has been established by EDS and XRD.

  15. Dynamic-Mechanical Analysis of Monodomain Nematic Liquid Crystalline Elastomers

    NASA Astrophysics Data System (ADS)

    Hotta, Atsushi; Terentjev, Eugene

    2003-03-01

    Dynamic-mechanical analysis was performed in the glassy, nematic and isotropic states of several monodomain nematic liquid crystalline elastomers (LCE) which differ in their degrees of anisotropy and internal microstructure. It was found that the type of network crosslinker makes a significant difference in the equilibrium properties of these elastomers, in particular, in their effective anisotropy. In spite of these differences, the observed dynamic-mechanical behaviour was very similar. The fact that there is a consistently high and wide loss over the whole nematic region, where storage modulus G' behaves non-monotonically, is most likely an indicator of the fact that the dynamic-mechanical response is not linear. Master curves have been built between the glassy state and the nematic-isotropic phase transition, where the modulus reaches a low-level soft plateau. Above the nematic-isotropic transition temperature Tni, the modulus rises substantially, since internal relaxation is no longer able to reduce the elastic response - and further time-temperature superposition fails. The dynamics of these elastomers are dominated by power laws, which was confirmed by the successful procedure of the master curve inversion (time-frequency inversion) to describe the static stress relaxation. Interestingly, it was found that mechanical properties characterized by power laws (in time) of stress relaxation match very well with the dynamic properties, where power laws (in frequency) were also observed in the dynamic modulus in the appropriate range of temperatures. The work demonstrates the potential for the use of nematic liquid crystalline elastomers in many acoustic and vibration damping applications.

  16. Multiple methods integration for structural mechanics analysis and design

    NASA Technical Reports Server (NTRS)

    Housner, J. M.; Aminpour, M. A.

    1991-01-01

    A new research area of multiple methods integration is proposed for joining diverse methods of structural mechanics analysis which interact with one another. Three categories of multiple methods are defined: those in which a physical interface are well defined; those in which a physical interface is not well-defined, but selected; and those in which the interface is a mathematical transformation. Two fundamental integration procedures are presented that can be extended to integrate various methods (e.g., finite elements, Rayleigh Ritz, Galerkin, and integral methods) with one another. Since the finite element method will likely be the major method to be integrated, its enhanced robustness under element distortion is also examined and a new robust shell element is demonstrated.

  17. Dynamic Mechanical Thermal Analysis of Virgin TR-55 Silicone Rubber

    SciTech Connect

    Small IV, W; Wilson, T S

    2009-10-09

    Dynamic mechanical thermal analysis (DMTA) of virgin TR-55 silicone rubber specimens was conducted. Dynamic frequency/temperature sweep tests were conducted over the ranges 0.1-100 rad/s and 30-100 C using a parallel plate test geometry. A strain of 0.2% was used, which was near the upper limit of the linear viscoelastic region of the material based on initial dynamic strain sweep tests. Master curves of G{prime} and G{double_prime} as a function of frequency were generated using time-temperature superposition (horizontal shift with initial vertical correction). The activation energy calculated from an Arrhenius fit to the horizontal shift factors was 178-355 kJ/mol. The calculated percent load retention at {approx}50 years was 61-68%.

  18. Nonlinear analysis of ubitron, orbitron, and gyroharmonitron mechanisms. Final report

    SciTech Connect

    Not Available

    1987-11-01

    The research program during the contract period consisted of the analysis of the Ubitron/FEL amplifier in three-dimensions. The principal configuration of interest consisted of the propagation of an energetic electron beam through a loss-free rectangular waveguide in the presence of a linearly polarized wiggler field with parabolically tapered pole pieces. The purpose of the tapered pole faces is to provide a mechanism for focussing the electron beam in the plane of the bulk wiggler induced oscillation. A nonlinear theory and simulation code has been developed to study this configuration which can treat a multiple mode interaction, harmonic growth, efficiency enhancement by means of a tapered wiggler, the effect of beam thermal spread on the interaction, the injection of the beam into the wiggler, and detailed facets of the particle dynamics such as Betatron oscillations and velocity shear. Comparisons of the experiment at the Lawrence Livermore National Laboratory are excellent.

  19. Analysis of loss mechanisms in polycrystalline thin film solar cells

    NASA Astrophysics Data System (ADS)

    Sites, J. R.

    1990-08-01

    Our goal for thin-film polycrystalline solar cell analysis was to increase the useful information extracted from relatively straightforward electrical measurements. The strategy was to (1) systematize measurements and reporting, (2) organize results in terms of quantitative values for individual sources of current and voltage loss, and (3) evaluate possible analytical techniques to enhance precision and avoid pitfalls, and (4) insist on a viable physical explanation of each loss mechanism. Current-voltage, quantum efficiency, and capacitance measurements on CuInSe2 and CdTe solar cells from a variety of sources have been analyzed. In many cases losses were identified that may be lessened relatively easily. However, the operating voltage loss due to excessive forward recombination current throughout the depletion region remains the primary obstacle to efficiencies competitive with single crystal cells.

  20. Development of test methodology for dynamic mechanical analysis instrumentation

    NASA Technical Reports Server (NTRS)

    Allen, V. R.

    1982-01-01

    Dynamic mechanical analysis instrumentation was used for the development of specific test methodology in the determination of engineering parameters of selected materials, esp. plastics and elastomers, over a broad range of temperature with selected environment. The methodology for routine procedures was established with specific attention given to sample geometry, sample size, and mounting techniques. The basic software of the duPont 1090 thermal analyzer was used for data reduction which simplify the theoretical interpretation. Clamps were developed which allowed 'relative' damping during the cure cycle to be measured for the fiber-glass supported resin. The correlation of fracture energy 'toughness' (or impact strength) with the low temperature (glassy) relaxation responses for a 'rubber-modified' epoxy system was negative in result because the low-temperature dispersion mode (-80 C) of the modifier coincided with that of the epoxy matrix, making quantitative comparison unrealistic.

  1. Structure-activity analysis and antiprion mechanism of isoprenoid compounds.

    PubMed

    Hamanaka, Taichi; Nishizawa, Keiko; Sakasegawa, Yuji; Teruya, Kenta; Doh-ura, Katsumi

    2015-12-01

    The prion strain-specific mechanism by which normal prion protein is converted to abnormal prion protein remains largely unknown. This study found that insect juvenile hormone III reduced abnormal prion protein levels only in cells infected with the RML prion. We conducted a structure-activity analysis using juvenile hormone III biosynthetic intermediates in the isoprenoid pathway. Both farnesol and geranylgeraniol, the most potent inhibitors of abnormal prion protein formation, behaved in an RML prion-dependent fashion. Neither of them modified cellular and cell surface prion protein levels. Events downstream of this pathway include cholesterol biosynthesis and protein prenylation. However, neither of these isoprenoid compounds modified lipid raft microdomains and cellular cholesterol levels and neither affected the representative prenylated protein expression levels of prenylation pathways. Therefore, these isoprenoid compounds are a new class of prion strain-dependent antiprion compounds. They are useful for exploring strain-specific prion biology. PMID:26402376

  2. Analysis of sponge zones for computational fluid mechanics

    SciTech Connect

    Bodony, Daniel J. . E-mail: bodony@stanford.edu

    2006-03-01

    The use of sponge regions, or sponge zones, which add the forcing term -{sigma}(q - q {sub ref}) to the right-hand-side of the governing equations in computational fluid mechanics as an ad hoc boundary treatment is widespread. They are used to absorb and minimize reflections from computational boundaries and as forcing sponges to introduce prescribed disturbances into a calculation. A less common usage is as a means of extending a calculation from a smaller domain into a larger one, such as in computing the far-field sound generated in a localized region. By analogy to the penalty method of finite elements, the method is placed on a solid foundation, complete with estimates of convergence. The analysis generalizes the work of Israeli and Orszag [M. Israeli, S.A. Orszag, Approximation of radiation boundary conditions, J. Comp. Phys. 41 (1981) 115-135] and confirms their findings when applied as a special case to one-dimensional wave propagation in an absorbing sponge. It is found that the rate of convergence of the actual solution to the target solution, with an appropriate norm, is inversely proportional to the sponge strength. A detailed analysis for acoustic wave propagation in one-dimension verifies the convergence rate given by the general theory. The exponential point-wise convergence derived by Israeli and Orszag in the high-frequency limit is recovered and found to hold over all frequencies. A weakly nonlinear analysis of the method when applied to Burgers' equation shows similar convergence properties. Three numerical examples are given to confirm the analysis: the acoustic extension of a two-dimensional time-harmonic point source, the acoustic extension of a three-dimensional initial-value problem of a sound pulse, and the introduction of unstable eigenmodes from linear stability theory into a two-dimensional shear layer.

  3. A dynamic mechanical analysis technique for porous media

    PubMed Central

    Pattison, Adam J; McGarry, Matthew; Weaver, John B; Paulsen, Keith D

    2015-01-01

    Dynamic mechanical analysis (DMA) is a common way to measure the mechanical properties of materials as functions of frequency. Traditionally, a viscoelastic mechanical model is applied and current DMA techniques fit an analytical approximation to measured dynamic motion data by neglecting inertial forces and adding empirical correction factors to account for transverse boundary displacements. Here, a finite element (FE) approach to processing DMA data was developed to estimate poroelastic material properties. Frequency-dependent inertial forces, which are significant in soft media and often neglected in DMA, were included in the FE model. The technique applies a constitutive relation to the DMA measurements and exploits a non-linear inversion to estimate the material properties in the model that best fit the model response to the DMA data. A viscoelastic version of this approach was developed to validate the approach by comparing complex modulus estimates to the direct DMA results. Both analytical and FE poroelastic models were also developed to explore their behavior in the DMA testing environment. All of the models were applied to tofu as a representative soft poroelastic material that is a common phantom in elastography imaging studies. Five samples of three different stiffnesses were tested from 1 – 14 Hz with rough platens placed on the top and bottom surfaces of the material specimen under test to restrict transverse displacements and promote fluid-solid interaction. The viscoelastic models were identical in the static case, and nearly the same at frequency with inertial forces accounting for some of the discrepancy. The poroelastic analytical method was not sufficient when the relevant physical boundary constraints were applied, whereas the poroelastic FE approach produced high quality estimates of shear modulus and hydraulic conductivity. These results illustrated appropriate shear modulus contrast between tofu samples and yielded a consistent contrast in

  4. A dynamic mechanical analysis technique for porous media.

    PubMed

    Pattison, Adam Jeffry; McGarry, Matthew; Weaver, John B; Paulsen, Keith D

    2015-02-01

    Dynamic mechanical analysis (DMA) is a common way to measure the mechanical properties of materials as functions of frequency. Traditionally, a viscoelastic mechanical model is applied and current DMA techniques fit an analytical approximation to measured dynamic motion data by neglecting inertial forces and adding empirical correction factors to account for transverse boundary displacements. Here, a finite-element (FE) approach to processing DMA data was developed to estimate poroelastic material properties. Frequency-dependent inertial forces, which are significant in soft media and often neglected in DMA, were included in the FE model. The technique applies a constitutive relation to the DMA measurements and exploits a nonlinear inversion to estimate the material properties in the model that best fit the model response to the DMA data. A viscoelastic version of this approach was developed to validate the approach by comparing complex modulus estimates to the direct DMA results. Both analytical and FE poroelastic models were also developed to explore their behavior in the DMA testing environment. All of the models were applied to tofu as a representative soft poroelastic material that is a common phantom in elastography imaging studies. Five samples of three different stiffnesses were tested from 1-14 Hz with rough platens placed on the top and bottom surfaces of the material specimen under test to restrict transverse displacements and promote fluid-solid interaction. The viscoelastic models were identical in the static case, and nearly the same at frequency with inertial forces accounting for some of the discrepancy. The poroelastic analytical method was not sufficient when the relevant physical boundary constraints were applied, whereas the poroelastic FE approach produced high quality estimates of shear modulus and hydraulic conductivity. These results illustrated appropriate shear modulus contrast between tofu samples and yielded a consistent contrast in

  5. Mechanical analysis of UMo/Al dispersion fuel

    NASA Astrophysics Data System (ADS)

    Jeong, Gwan Yoon; Kim, Yeon Soo; Sohn, Dong-Seong

    2015-11-01

    Deformation of fuel particles and mass transfer from the transverse end of fuel meat toward the meat center was observed. This caused plate thickness peaking at a location between the meat edge and the meat center. The underlying mechanism for this fuel volume transport is believed to be fission induced creep of the U-Mo/Al meat. Fuel meat swelling was measured using optical microscopy images of the cross sections of the irradiated test plates. The time-dependent meat swelling was modeled for use in numerical simulation. A distinctive discrepancy between the predicted and measured meat thickness was found at the meat ends, which was assumed to be due to creep-induced mass relocation from the meat end to the meat center region that was not considered in the meat swelling model. ABAQUS FEA simulation was performed to reproduce the observed phenomenon at the meat ends. Through the simulation, we obtained the effective creep rate constants for the interaction layers (IL) and aluminum matrix. In addition, we obtained the corresponding stress and strain analysis results that can be used to understand mechanical behavior of U-Mo/Al dispersion fuel.

  6. Biomechanical Analysis of Force Distribution in Human Finger Extensor Mechanisms

    PubMed Central

    Hu, Dan; Ren, Lei; Howard, David; Zong, Changfu

    2014-01-01

    The complexities of the function and structure of human fingers have long been recognised. The in vivo forces in the human finger tendon network during different activities are critical information for clinical diagnosis, surgical treatment, prosthetic finger design, and biomimetic hand development. In this study, we propose a novel method for in vivo force estimation for the finger tendon network by combining a three-dimensional motion analysis technique and a novel biomechanical tendon network model. The extensor mechanism of a human index finger is represented by an interconnected tendinous network moving around the phalanx's dorsum. A novel analytical approach based on the “Principle of Minimum Total Potential Energy” is used to calculate the forces and deformations throughout the tendon network of the extensor mechanism when subjected to an external load and with the finger posture defined by measurement data. The predicted deformations and forces in the tendon network are in broad agreement with the results obtained by previous experimental in vitro studies. The proposed methodology provides a promising tool for investigating the biomechanical function of complex interconnected tendon networks in vivo. PMID:25126576

  7. Silk Fiber Mechanics from Multiscale Force Distribution Analysis

    PubMed Central

    Cetinkaya, Murat; Xiao, Senbo; Markert, Bernd; Stacklies, Wolfram; Gräter, Frauke

    2011-01-01

    Here we decipher the molecular determinants for the extreme toughness of spider silk fibers. Our bottom-up computational approach incorporates molecular dynamics and finite element simulations. Therefore, the approach allows the analysis of the internal strain distribution and load-carrying motifs in silk fibers on scales of both molecular and continuum mechanics. We thereby dissect the contributions from the nanoscale building blocks, the soft amorphous and the strong crystalline subunits, to silk fiber mechanics. We identify the amorphous subunits not only to give rise to high elasticity, but to also ensure efficient stress homogenization through the friction between entangled chains, which also allows the crystals to withstand stresses as high as 2 GPa in the context of the amorphous matrix. We show that the maximal toughness of silk is achieved at 10–40% crystallinity depending on the distribution of crystals in the fiber. We also determined a serial arrangement of the crystalline and amorphous subunits in lamellae to outperform a random or a parallel arrangement, putting forward what we believe to be a new structural model for silk and other semicrystalline materials. The multiscale approach, not requiring any empirical parameters, is applicable to other partially ordered polymeric systems. Hence, it is an efficient tool for the design of artificial silk fibers. PMID:21354403

  8. Mechanical analysis of conventional and small diameter conical implant abutments

    PubMed Central

    Moris, Izabela Cristina Maurício; Faria, Adriana Cláudia Lapria; de Mattos, Maria da Gloria Chiarello; Ribeiro, Ricardo Faria

    2012-01-01

    PURPOSE The aim of the present study was to evaluate if a smaller morse taper abutment has a negative effect on the fracture resistance of implant-abutment connections under oblique compressive loads compared to a conventional abutment. MATERIALS AND METHODS Twenty morse taper conventional abutments (4.8 mm diameter) and smaller abutments (3.8 mm diameter) were tightened (20 Ncm) to their respective implants (3.5 × 11 mm) and after a 10 minute interval, implant/abutment assemblies were subjected to static compressive test, performed in a universal test machine with 1 mm/min displacement, at 45° inclination. The maximum deformation force was determined. Data were statistically analyzed by student t test. RESULTS Maximum deformation force of 4.8 mm and 3.8 mm abutments was approximately 95.33 kgf and 95.25 kgf, respectively, but no fractures were noted after mechanical test. Statistical analysis demonstrated that the evaluated abutments were statistically similar (P=.230). CONCLUSION Abutment measuring 3.8 mm in diameter (reduced) presented mechanical properties similar to 4.8 mm (conventional) abutments, enabling its clinical use as indicated. PMID:22977724

  9. Biomechanical analysis of force distribution in human finger extensor mechanisms.

    PubMed

    Hu, Dan; Ren, Lei; Howard, David; Zong, Changfu

    2014-01-01

    The complexities of the function and structure of human fingers have long been recognised. The in vivo forces in the human finger tendon network during different activities are critical information for clinical diagnosis, surgical treatment, prosthetic finger design, and biomimetic hand development. In this study, we propose a novel method for in vivo force estimation for the finger tendon network by combining a three-dimensional motion analysis technique and a novel biomechanical tendon network model. The extensor mechanism of a human index finger is represented by an interconnected tendinous network moving around the phalanx's dorsum. A novel analytical approach based on the "Principle of Minimum Total Potential Energy" is used to calculate the forces and deformations throughout the tendon network of the extensor mechanism when subjected to an external load and with the finger posture defined by measurement data. The predicted deformations and forces in the tendon network are in broad agreement with the results obtained by previous experimental in vitro studies. The proposed methodology provides a promising tool for investigating the biomechanical function of complex interconnected tendon networks in vivo. PMID:25126576

  10. Analysis of the Molecular Mechanisms of Reepithelialization in Drosophila Embryos

    PubMed Central

    Matsubayashi, Yutaka; Millard, Tom H.

    2016-01-01

    Significance: The epidermis provides the main barrier function of skin, and therefore its repair following wounding is an essential component of wound healing. Repair of the epidermis, also known as reepithelialization, occurs by collective migration of epithelial cells from around the wound edge across the wound until the advancing edges meet and fuse. Therapeutic manipulation of this process could potentially be used to accelerate wound healing. Recent Advances: It is difficult to analyze the cellular and molecular mechanisms of reepithelialization in human tissue, so a variety of model organisms have been used to improve our understanding of the process. One model system that has been especially useful is the embryo of the fruit fly Drosophila, which provides a simple, accessible model of the epidermis and can be manipulated genetically, allowing detailed analysis of reepithelialization at the molecular level. This review will highlight the key insights that have been gained from studying reepithelialization in Drosophila embryos. Critical Issues: Slow reepithelialization increases the risk of wounds becoming infected and ulcerous; therefore, the development of therapies to accelerate or enhance the process would be a great clinical advance. Improving our understanding of the molecular mechanisms that underlie reepithelialization will help in the development of such therapies. Future Directions: Research in Drosophila embryos has identified a variety of genes and proteins involved in triggering and driving reepithelialization, many of which are conserved in humans. These novel reepithelialization proteins are potential therapeutic targets and therefore findings obtained in Drosophila may ultimately lead to significant clinical advances. PMID:27274434

  11. Elucidating Polypharmacological Mechanisms of Polyphenols by Gene Module Profile Analysis

    PubMed Central

    Li, Bin; Xiong, Min; Zhang, Hong-Yu

    2014-01-01

    Due to the diverse medicinal effects, polyphenols are among the most intensively studied natural products. However, it is a great challenge to elucidate the polypharmacological mechanisms of polyphenols. To address this challenge, we establish a method for identifying multiple targets of chemical agents through analyzing the module profiles of gene expression upon chemical treatments. By using FABIA algorithm, we have performed a biclustering analysis of gene expression profiles derived from Connectivity Map (cMap), and clustered the profiles into 49 gene modules. This allowed us to define a 49 dimensional binary vector to characterize the gene module profiles, by which we can compare the expression profiles for each pair of chemical agents with Tanimoto coefficient. For the agent pairs with similar gene expression profiles, we can predict the target of one agent from the other. Drug target enrichment analysis indicated that this method is efficient to predict the multiple targets of chemical agents. By using this method, we identify 148 targets for 20 polyphenols derived from cMap. A large part of the targets are validated by experimental observations. The results show that the medicinal effects of polyphenols are far beyond their well-known antioxidant activities. This method is also applicable to dissect the polypharmacology of other natural products. PMID:24968267

  12. Elucidating polypharmacological mechanisms of polyphenols by gene module profile analysis.

    PubMed

    Li, Bin; Xiong, Min; Zhang, Hong-Yu

    2014-01-01

    Due to the diverse medicinal effects, polyphenols are among the most intensively studied natural products. However, it is a great challenge to elucidate the polypharmacological mechanisms of polyphenols. To address this challenge, we establish a method for identifying multiple targets of chemical agents through analyzing the module profiles of gene expression upon chemical treatments. By using FABIA algorithm, we have performed a biclustering analysis of gene expression profiles derived from Connectivity Map (cMap), and clustered the profiles into 49 gene modules. This allowed us to define a 49 dimensional binary vector to characterize the gene module profiles, by which we can compare the expression profiles for each pair of chemical agents with Tanimoto coefficient. For the agent pairs with similar gene expression profiles, we can predict the target of one agent from the other. Drug target enrichment analysis indicated that this method is efficient to predict the multiple targets of chemical agents. By using this method, we identify 148 targets for 20 polyphenols derived from cMap. A large part of the targets are validated by experimental observations. The results show that the medicinal effects of polyphenols are far beyond their well-known antioxidant activities. This method is also applicable to dissect the polypharmacology of other natural products. PMID:24968267

  13. In silico analysis of the molecular mechanism of postmenopausal osteoporosis.

    PubMed

    Liu, Yanqing; Wang, Yueqiu; Yang, Nailong; Wu, Suning; Lv, Yanhua; Xu, Lili

    2015-11-01

    Postmenopausal osteoporosis (PO) is a common disease in females >50 years of age worldwide and is becoming an increasing burden to society. The present study aimed to assess the molecular mechanism of PO using bioinformatic methods. The gene expression data from patients with PO and normal controls were downloaded from the ArrayExpress database provided by European Bioinformatics Institute. Following the screening of the differentially expressed genes (DEGs) using the Limma package in R language, Kyoto Encyclopedia of Genes and Genomes pathways enrichment analysis was performed using the Database for Annotation, Visualization and Integrated Discovery online tools. Sequentially, modulators of the DEGs, including transcription factors (TFs) and microRNAs, were predicted by the ChIP Enrichment Analysis databases and WEB‑based GEne SeT AnaLysis Toolkit system, respectively. In addition, the protein‑protein interaction network of DEGs was constructed via the search tool for the retrieval of interacting genes and then the functional modules were further analyzed via the clusterMaker package and The Biological Networks Gene Ontology package within the Cytoscape software. A total of 482 DEGs, including 279 upregulated and 203 downregulated DEGs, were screened out. DEGs were predominantly enriched in the pathways of fatty acid metabolism, cardiac muscle contraction and DNA replication. TFs, including SMAD4, in addition to microRNAs, including the microRNA‑125 (miR‑125) family, miR‑331 and miR‑24, may be the modulators of the DEGs in PO. In addition, the five largest modules were identified with TTN, L1G1, ACADM, UQCRC2 and TRIM63 as the hub proteins, and they were associated with the biological processes of muscle contraction, DNA replication initiation, lipid modification, generation of precursor metabolites and energy, and regulation of acetyl‑CoA biosynthetic process, respectively. SMAD4, CACNG1 and TRIM63 are suggested to be important factors in the

  14. In silico analysis of the molecular mechanism of postmenopausal osteoporosis

    PubMed Central

    LIU, YANQING; WANG, YUEQIU; YANG, NAILONG; WU, SUNING; LV, YANHUA; XU, LILI

    2015-01-01

    Postmenopausal osteoporosis (PO) is a common disease in females >50 years of age worldwide and is becoming an increasing burden to society. The present study aimed to assess the molecular mechanism of PO using bioinformatic methods. The gene expression data from patients with PO and normal controls were downloaded from the ArrayExpress database provided by European Bioinformatics Institute. Following the screening of the differentially expressed genes (DEGs) using the Limma package in R language, Kyoto Encyclopedia of Genes and Genomes pathways enrichment analysis was performed using the Database for Annotation, Visualization and Integrated Discovery online tools. Sequentially, modulators of the DEGs, including transcription factors (TFs) and microRNAs, were predicted by the ChIP Enrichment Analysis databases and WEB-based GEne SeT AnaLysis Toolkit system, respectively. In addition, the protein-protein interaction network of DEGs was constructed via the search tool for the retrieval of interacting genes and then the functional modules were further analyzed via the cluster-Maker package and The Biological Networks Gene Ontology package within the Cytoscape software. A total of 482 DEGs, including 279 upregulated and 203 downregulated DEGs, were screened out. DEGs were predominantly enriched in the pathways of fatty acid metabolism, cardiac muscle contraction and DNA replication. TFs, including SMAD4, in addition to microRNAs, including the microRNA-125 (miR-125) family, miR-331 and miR-24, may be the modulators of the DEGs in PO. In addition, the five largest modules were identified with TTN, L1G1, ACADM, UQCRC2 and TRIM63 as the hub proteins, and they were associated with the biological processes of muscle contraction, DNA replication initiation, lipid modification, generation of precursor metabolites and energy, and regulation of acetyl-CoA biosynthetic process, respectively. SMAD4, CACNG1 and TRIM63 are suggested to be important factors in the molecular

  15. Atom depth analysis delineates mechanisms of protein intermolecular interactions

    SciTech Connect

    Alocci, Davide; Bernini, Andrea; Niccolai, Neri

    2013-07-12

    Highlights: •3D atom depth analysis is proposed to identify different layers in protein structures. •Amino acid contents for each layers have been analyzed for a large protein dataset. •Charged amino acids in the most external layer are present at very different extents. •Atom depth indexes of K residues reflect their side chains flexibility. •Mobile surface charges can be responsible for long range protein–protein recognition. -- Abstract: The systematic analysis of amino acid distribution, performed inside a large set of resolved protein structures, sheds light on possible mechanisms driving non random protein–protein approaches. Protein Data Bank entries have been selected using as filters a series of restrictions ensuring that the shape of protein surface is not modified by interactions with large or small ligands. 3D atom depth has been evaluated for all the atoms of the 2,410 selected structures. The amino acid relative population in each of the structural layers formed by grouping atoms on the basis of their calculated depths, has been evaluated. We have identified seven structural layers, the inner ones reproducing the core of proteins and the outer one incorporating their most protruding moieties. Quantitative analysis of amino acid contents of structural layers identified, as expected, different behaviors. Atoms of Q, R, K, N, D residues are increasingly more abundant in going from core to surfaces. An opposite trend is observed for V, I, L, A, C, and G. An intermediate behavior is exhibited by P, S, T, M, W, H, F and Y. The outer structural layer hosts predominantly E and K residues whose charged moieties, protruding from outer regions of the protein surface, reorient free from steric hindrances, determining specific electrodynamics maps. This feature may represent a protein signature for long distance effects, driving the formation of encounter complexes and the eventual short distance approaches that are required for protein

  16. Connecting caddisworm silk structure and mechanical properties: combined infrared spectroscopy and mechanical analysis

    PubMed Central

    Ashton, Nicholas N.; Pan, Huaizhong; Stewart, Russell J.

    2016-01-01

    The underwater silk of an aquatic casemaking caddisfly larvae (Hesperophylax occidentalis) is viscoelastic, and displays distinct yield behaviour, large strain cycle hysteresis and near complete recovery of its initial strength and stiffness when unloaded. Yield followed by a stress plateau has been attributed to sequential rupture of serial Ca2+-cross-linked phosphoserine (pS) β-domains. Spontaneous recovery has been attributed to refolding of the Ca2+/pS domains powered by an elastic network. In this study, native Ca2+ ions were exchanged with other metal ions, followed by combined mechanical and FTIR analysis to probe the contribution of pS/metal ion complexes to silk mechanical properties. After exchange of Ca2+ with Na+, the fibres are soft elastomers and the infrared spectra are consistent with Cv3 symmetry of the – groups. Multivalent metal ions decreased the – symmetry and the symmetric stretching modes (vs) split in a manner characteristic of ordered phosphate compounds, such as phosphate minerals and lamellar bilayers of phosphatidic acid lipids. Integrated intensities of the vs bands, indicative of the metal ion's effect on transition dipole moment of the P–O bonds, and thereby the strength of the phosphate metal complex, increased in the order: Na+ < Mg2+ < Sr2+ < Ba2+ < Ca2+ < Eu3+ < La3+ < Zn2+ < Fe2+. With a subset of the metal ion series, the initial stiffness and yield stress of metal ion-exchanged fibres increased in the same order: establishing the link between phosphate transition dipole moments and silk fibre strength. PMID:27278649

  17. Connecting caddisworm silk structure and mechanical properties: combined infrared spectroscopy and mechanical analysis.

    PubMed

    Ashton, Nicholas N; Pan, Huaizhong; Stewart, Russell J

    2016-06-01

    The underwater silk of an aquatic casemaking caddisfly larvae (Hesperophylax occidentalis) is viscoelastic, and displays distinct yield behaviour, large strain cycle hysteresis and near complete recovery of its initial strength and stiffness when unloaded. Yield followed by a stress plateau has been attributed to sequential rupture of serial Ca(2+)-cross-linked phosphoserine (pS) β-domains. Spontaneous recovery has been attributed to refolding of the Ca(2+)/pS domains powered by an elastic network. In this study, native Ca(2+) ions were exchanged with other metal ions, followed by combined mechanical and FTIR analysis to probe the contribution of pS/metal ion complexes to silk mechanical properties. After exchange of Ca(2+) with Na(+), the fibres are soft elastomers and the infrared spectra are consistent with Cv3 symmetry of the -[Formula: see text] groups. Multivalent metal ions decreased the -[Formula: see text] symmetry and the symmetric stretching modes (vs) split in a manner characteristic of ordered phosphate compounds, such as phosphate minerals and lamellar bilayers of phosphatidic acid lipids. Integrated intensities of the vs bands, indicative of the metal ion's effect on transition dipole moment of the P-O bonds, and thereby the strength of the phosphate metal complex, increased in the order: Na(+) < Mg(2+) < Sr(2+) < Ba(2+) < Ca(2+) < Eu(3+) < La(3+) < Zn(2+) < Fe(2+) With a subset of the metal ion series, the initial stiffness and yield stress of metal ion-exchanged fibres increased in the same order: [Formula: see text] [Formula: see text] establishing the link between phosphate transition dipole moments and silk fibre strength. PMID:27278649

  18. Numerical analysis of fume formation mechanism in arc welding

    NASA Astrophysics Data System (ADS)

    Tashiro, Shinichi; Zeniya, Tasuku; Yamamoto, Kentaro; Tanaka, Manabu; Nakata, Kazuhiro; Murphy, Anthony B.; Yamamoto, Eri; Yamazaki, Kei; Suzuki, Keiichi

    2010-11-01

    In order to clarify the fume formation mechanism in arc welding, a quantitative investigation based on the knowledge of interaction among the electrode, arc and weld pool is indispensable. A fume formation model consisting of a heterogeneous condensation model, a homogeneous nucleation model and a coagulation model has been developed and coupled with the GTA or GMA welding model. A series of processes from evaporation of metal vapour to fume formation from the metal vapour was totally investigated by employing this simulation model. The aim of this paper is to visualize the fume formation process and clarify the fume formation mechanism theoretically through a numerical analysis. Furthermore, the reliability of the simulation model was also evaluated through a comparison of the simulation result with the experimental result. As a result, it was found that the size of the secondary particles consisting of small particles with a size of several tens of nanometres reached 300 nm at maximum and the secondary particle was in a U-shaped chain form in helium GTA welding. Furthermore, it was also clarified that most part of the fume was produced in the downstream region of the arc originating from the metal vapour evaporated mainly from the droplet in argon GMA welding. The fume was constituted by particles with a size of several tens of nanometres and had similar characteristics to that of GTA welding. On the other hand, if the metal transfer becomes unstable and the metal vapour near the droplet diffuses directly towards the surroundings of the arc not getting into the plasma flow, the size of the particles reaches several hundred nanometres.

  19. Analysis of toughening mechanisms in the Strombus gigas shell.

    PubMed

    DiPette, Scott; Ural, Ani; Santhanam, Sridhar

    2015-08-01

    A finite element analysis of the fracture mechanisms in the Strombus gigas conch shell is presented in this work. The S. gigas shell has a complex microarchitecture that consists of three main macroscopic layers of calcium carbonate: the inner, middle, and outer layers. Each layer is composed of lamellae of calcium carbonate, held together by a cohesive organic protein. As a result of this elaborate architecture, the S. gigas shell exhibits a much greater damage tolerance than the calcium carbonate by itself, with a work of fracture reported to be three magnitudes of order greater. The two main energy dissipating factors that contribute to this are multiple, parallel cracking along first-order interfaces in the inner and outer layers and crack bridging through the second-order interfaces of the middle layer. Finite element analysis was conducted to simulate and replicate flexural strength and work-of-fracture results obtained in the literature for both dry and wet physical bend test specimens. Several parameters were varied including protein strength and fracture toughness, initial protein damage, and the relative heights of macroscopic layers in order to create a model that predicted published, experimental results. The simulations indicate that having some initially weakened protein interfaces is key to matching the parallel cracking in the inner layer of the physical specimens. The wet models exhibit significantly higher work of fracture compared to the dry specimens in large part due to a crack growth resistance behavior in the middle layer, which was successfully modeled. The parametric studies that have been performed on the finite element models provide guidelines for manufacturing the ideal S. gigas-inspired, biomimetic composite. PMID:25955562

  20. Dynamic Analysis of Hammer Mechanism "Twin Hammer" of Impact Wrench

    NASA Astrophysics Data System (ADS)

    Konečný, M.; Slavík, J.

    This paper describes function of the hammer mechanism "Twin hammer" the impact wrench, calculation of dynamic forces exerted on the mechanism and determining the contact pressures between the parts of the mechanism. The modelling of parts was performed in system Pro ENGINEER—standard. The simulation and finding dynamic forces was performed in advanced module Pro ENGINEER—mechanism design and finding contacts pressures in modul Pro ENGENEER—mechanica.

  1. Opto-thermo-mechanical analysis for the FAME Observatory

    NASA Astrophysics Data System (ADS)

    Sokolsky, Larry; Ambrose, Jay

    2004-01-01

    The Full-Sky Astrometric Mapping Explorer (FAME) instrument was designed to be an extremely accurate star mapper. To map the entire sky, the earth-orbiting FAME satellite rotates about its spin axis every 40 minutes, and uses solar pressure to precess about the spin axis every 40 days. The instrument had two apertures, separated by 84.3 degrees, allowing a star to be imaged twice in one rotation with about a 10 minute delay. This delay enables the elimination of most measurement errors. The light enters an aperture, bounces off of a compound fold flat mirror, (2 ULE fold flats bonded together at an 84.3 degree angle), passes through a Cassegrain telescope, and is imaged by the focal plane. The requirement for the fold flat"s dimensional stability is severe - the variation in the angle between the flats (basic angle) must be held to be held to 10 μarcsec during the 10 minute period between the first and second time a star is imaged. This paper presents a transient opto-thermo-mechanical analysis of the optical system.

  2. Dissection of the Hormetic Curve: Analysis of Components and Mechanisms

    PubMed Central

    Lushchak, Volodymyr I.

    2014-01-01

    The relationship between the dose of an effector and the biological response frequently is not described by a linear function and, moreover, in some cases the dose-response relationship may change from positive/adverse to adverse/positive with increasing dose. This complicated relationship is called “hormesis”. This paper provides a short analysis of the concept along with a description of used approaches to characterize hormetic relationships. The whole hormetic curve can be divided into three zones: I – a lag-zone where no changes are observed with increasing dose; II – a zone where beneficial/adverse effects are observed, and III – a zone where the effects are opposite to those seen in zone II. Some approaches are proposed to analyze the molecular components involved in the development of the hormetic character of dose-response relationships with the use of specific genetic lines or inhibitors of regulatory pathways. The discussion is then extended to suggest a new parameter (half-width of the hormetic curve at zone II) for quantitative characterization of the hormetic curve. The problems limiting progress in the development of the hormesis concept such as low reproducibility and predictability may be solved, at least partly, by deciphering the molecular mechanisms underlying the hormetic dose-effect relationship. PMID:25249836

  3. Immunosensor with Fluid Control Mechanism for Salivary Cortisol Analysis

    PubMed Central

    Yamaguchi, Masaki; Matsuda, Yohei; Sasaki, Shohei; Sasaki, Makoto; Kadoma, Yoshihiro; Imai, Yoshikatsu; Niwa, Daisuke; Shetty, Vivek

    2012-01-01

    The purpose of this research is to demonstrate a new design for a cortisol immunosensor for the noninvasive and quantitative analysis of salivary cortisol. We propose a cortisol immunosensor with a fluid control mechanism which has both a vertical flow and a lateral flow. The detected current resulting from a competitive reaction between the sample cortisol and a glucose oxidase (GOD)-labeled cortisol conjugate was found to be inversely related to the concentration of cortisol in the sample solution. A calibration curve using the relative detected current showed an R2 = 0.98 and CV = 14% for a range of standard cortisol solutions corresponding to the concentrations of native salivary cortisol (0.1 – 10 ng/ml). The measurement could be accomplished within 35 minutes and the cortisol immunosensor could be reused. These results show promise for realizing an on-site and easy-to-use biosensor for cortisol. Used for evaluation of human salivary cortisol levels, the cortisol immunosensor measurement corresponded closely with commercially available ELISA method (R2 = 0.92). Our results indicate the promise of the new cortisol immunosensor for noninvasive, point-of care measurement of human salivary cortisol levels. PMID:22939507

  4. Morphological and mechanical analysis of electrospun shape memory polymer fibers

    NASA Astrophysics Data System (ADS)

    Budun, Sinem; İşgören, Erkan; Erdem, Ramazan; Yüksek, Metin

    2016-09-01

    Shape memory block co-polymer Polyurethane (PU) fibers were fabricated by electrospinning technique. Four different solution concentrations (5 wt.%, 10 wt.%, 15 wt.% and 20 wt.%) were prepared by using Tetrahydrofuran (THF)/N,N-dimethylformamide (DMF) (50:50, v/v) as solvents, and three different voltages (30 kV, 35 kV and 38.9 kV) were determined for the electrospinning process. Solution properties were explored in terms of viscosity and electrical conductivity. It was observed that as the polymer concentration increased in the solution, the conductivity declined. Morphological characteristics of the obtained fibers were analyzed through Scanning Electron Microscopy (SEM) measurements. Findings indicated that fiber morphology varied especially with polymer concentration and applied voltage. Obtained fiber diameter ranged from 112 ± 34 nm to 2046 ± 654 nm, respectively. DSC analysis presented that chain orientation of the polymer increased after electrospinning process. Shape fixity and shape recovery calculations were realized. The best shape fixity value (92 ± 4%) was obtained for Y10K30 and the highest shape recovery measurement (130 ± 4%) was belonged to Y15K39. Mechanical properties of the electrospun webs were also investigated in both machine and transverse directions. Tensile and elongation values were also affected from fiber diameter distribution and morphological characteristics of the electrospun webs.

  5. Analysis of barosensitive mechanisms in yeast for Pressure Regulated Fermentation

    NASA Astrophysics Data System (ADS)

    Nomura, Kazuki; Iwahashi, Hitoshi; Iguchi, Akinori; Shigematsu, Toru

    2013-06-01

    Introduction: We are intending to develop a novel food processing technology, Pressure Regulated Fermentation (PReF), using pressure sensitive (barosensitive) fermentation microorganisms. Objectives of our study are to clarify barosensitive mechanisms for application to PReF technology. We isolated Saccharomyces cerevisiae barosensitive mutant a924E1 that was derived from the parent KA31a. Methods: Gene expression levels were analyzed by DNA microarray. The altered genes of expression levels were classified according to the gene function. Mutated genes were estimated by mating and producing diploid strains and confirmed by PCR of mitochondrial DNA (mtDNA). Results and Discussion: Gene expression profiles showed that genes of `Energy' function and that of encoding protein localized in ``Mitochondria'' were significantly down regulated in the mutant. These results suggest the respiratory deficiency and relationship between barosensitivity and respiratory deficiency. Since the respiratory functions of diploids showed non Mendelian inheritance, the respiratory deficiency was indicated to be due to mtDNA mutation. PCR analysis showed that the region of COX1 locus was deleted. COX1 gene encodes the subunit 1 of cytochrome c oxidase. For this reason, barosensitivity is strongly correlated with mitochondrial functions.

  6. Mechanical Analysis of High Power Internally Cooled Annular Fuel

    SciTech Connect

    Zhao Jiyun; No, Hee Cheon; Kazimi, Mujid S.

    2004-05-15

    Annular fuel with internal flow is proposed to allow higher power density in pressurized water reactors. The structural behavior issues arising from the higher flow rate required to cool the fuel are assessed here, including buckling, vibrations, and potential wear problems. Five flow-induced vibration mechanisms are addressed: buckling instability, vortex-induced vibration, acoustic resonance, fluid-elastic instability, and turbulence-induced vibration. The structural behavior of the 17 x 17 traditional solid fuel array is compared with that of two types of annular fuels, a 15 x 15 array, and a 13 x 13 array.It is seen that the annular fuels are superior to the reference fuel in avoiding vibration-induced damage, even at a 50% increase in flow velocity above today's reactors. The higher resistance to vibration is mainly due to their relatively larger cross section area making them more rigid. The 13 x 13 annular fuel shows better structural performance than the 15 x 15 one due to its higher rigidity. Analysis of acoustic resonance of the inner channel cladding with pump blade passing frequencies showed that the acoustic frequencies are within 120% of the pulsation frequency. The annular fuel exhibits reduced impact, sliding, and fretting wear than the solid fuel, even at 150% flow rate of today's reactors.

  7. Spatiotemporal Analysis of Different Mechanisms for Interpreting Morphogen Gradients

    PubMed Central

    Richards, David M.; Saunders, Timothy E.

    2015-01-01

    During development, multicellular organisms must accurately control both temporal and spatial aspects of tissue patterning. This is often achieved using morphogens, signaling molecules that form spatially varying concentrations and so encode positional information. Typical analysis of morphogens assumes that spatial information is decoded in steady state by measuring the value of the morphogen concentration. However, recent experimental work suggests that both pre-steady-state readout and measurement of spatial and temporal derivatives of the morphogen concentration can play important roles in defining boundaries. Here, we undertake a detailed theoretical and numerical study of the accuracy of patterning—both in space and time—in models where readout is provided not by the morphogen concentration but by its spatial and temporal derivatives. In both cases we find that accurate patterning can be achieved, with sometimes even smaller errors than directly reading the morphogen concentration. We further demonstrate that such models provide other potential benefits to the system, such as the ability to switch on and off gene response with a high degree of spatiotemporal accuracy. Finally, we discuss how such derivatives might be calculated biologically and examine these models in relation to Sonic Hedgehog signaling in the vertebrate central nervous system. We show that, when coupled to a downstream transcriptional network, pre-steady-state measurement of the temporal change in the Shh morphogen is a plausible mechanism for determining precise gene boundaries in both space and time. PMID:25902445

  8. Majorana Demonstrator Bolted Joint Mechanical and Thermal Analysis

    SciTech Connect

    Aguayo Navarrete, Estanislao; Reid, Douglas J.; Fast, James E.

    2012-06-01

    The MAJORANA DEMONSTRATOR is designed to probe for neutrinoless double-beta decay, an extremely rare process with a half-life in the order of 1026 years. The experiment uses an ultra-low background, high-purity germanium detector array. The germanium crystals are both the source and the detector in this experiment. Operating these crystals as ionizing radiation detectors requires having them under cryogenic conditions (below 90 K). A liquid nitrogen thermosyphon is used to extract the heat from the detectors. The detector channels are arranged in strings and thermally coupled to the thermosyphon through a cold plate. The cold plate is joined to the thermosyphon by a bolted joint. This circular plate is housed inside the cryostat can. This document provides a detailed study of the bolted joint that connects the cold plate and the thermosyphon. An analysis of the mechanical and thermal properties of this bolted joint is presented. The force applied to the joint is derived from the torque applied to each one of the six bolts that form the joint. The thermal conductivity of the joint is measured as a function of applied force. The required heat conductivity for a successful experiment is the combination of the thermal conductivity of the detector string and this joint. The thermal behavior of the joint is experimentally implemented and analyzed in this study.

  9. Kinetic and Mechanical Analysis of Live Tube Morphogenesis

    PubMed Central

    Cheshire, Alan M.; Kerman, Bilal E.; Zipfel, Warren R.; Spector, Alexander A.; Andrew, Deborah J.

    2008-01-01

    Ribbon is a nuclear BTB-domain protein required for morphogenesis of the salivary gland and trachea. We recently showed that ribbon mutants exhibit decreased Crumbs and Rab11-coincident apical vesicles and increased apical Moesin activity and microvillar structure during tube elongation. To learn how these molecular and morphological changes affect the dynamics of tubulogenesis, we optimized an advanced two-photon microscope to enable high-resolution live imaging of the salivary gland and trachea. Live imaging revealed that ribbon mutant tissues exhibit slowed and incomplete lumenal morphogenesis, consistent with previously described apical defects. Since Moesin activity correlates with cortical stiffness, we hypothesize that ribbon mutants suffer from increased apical stiffness during morphogenesis. We develop this hypothesis through mechanical analysis, using the advantages of live imaging to construct computational elastic and analytical viscoelastic models of tube elongation, which suggest that ribbon mutant tubes exhibit three- to five-fold increased apical stiffness and two-fold increased effective apical viscosity. PMID:18816822

  10. CFD MODELING ANALYSIS OF MECHANICAL DRAFT COOLING TOWER

    SciTech Connect

    Lee, S; Alfred Garrett, A; James02 Bollinger, J; Larry Koffman, L

    2008-03-03

    Industrial processes use mechanical draft cooling towers (MDCT's) to dissipate waste heat by transferring heat from water to air via evaporative cooling, which causes air humidification. The Savannah River Site (SRS) has a MDCT consisting of four independent compartments called cells. Each cell has its own fan to help maximize heat transfer between ambient air and circulated water. The primary objective of the work is to conduct a parametric study for cooling tower performance under different fan speeds and ambient air conditions. The Savannah River National Laboratory (SRNL) developed a computational fluid dynamics (CFD) model to achieve the objective. The model uses three-dimensional steady-state momentum, continuity equations, air-vapor species balance equation, and two-equation turbulence as the basic governing equations. It was assumed that vapor phase is always transported by the continuous air phase with no slip velocity. In this case, water droplet component was considered as discrete phase for the interfacial heat and mass transfer via Lagrangian approach. Thus, the air-vapor mixture model with discrete water droplet phase is used for the analysis. A series of the modeling calculations was performed to investigate the impact of ambient and operating conditions on the thermal performance of the cooling tower when fans were operating and when they were turned off. The model was benchmarked against the literature data and the SRS test results for key parameters such as air temperature and humidity at the tower exit and water temperature for given ambient conditions. Detailed results will be presented here.

  11. Pulmonary mechanics by spectral analysis of forced random noise.

    PubMed Central

    Michaelson, E D; Grassman, E D; Peters, W R

    1975-01-01

    The magnitude (Zrs) and phase angle (thetars) of the total respiratory impedance (Zrs), from 3 to 45 Hz, were rapidly obtained by a modification of the forced oscillation method, in which a random noise pressure wave is imposed on the respiratory system at the mouth and compared to the induced random flow using Fourier and spectral analysis. No significant amplitude or phase errors were introduced by the instrumentation. 10 normals, 5 smokers, and 5 patients with chronic obstructive lung disease (COPD) were studied. Measurements of Zrs were corrected for the parallel shunt impedance of the mouth, which was independently measured during a Valsalva maneuver, and from which the mechanical properties of the mouth were derived. There were small differences in Zrs between normals and smokers but both behaved approximately like a second-order system with thetars = 0 degree in the range of 5--9 Hz, and thetars in the range of +40 degrees at 20 Hz and +60 degrees at 40 Hz. In COPD, thetars remained more negative (compared to normals and smokers) at all frequencies and crossed 0 between 15 and 29 Hz. Changes in Zrs, similar in those in COPD, were also observed at low lung volumes in normals. These changes, the effects of a bronchodilator in COPD, and deviations of Zrs from second-order behavior in normals, can best be explained by a two-compartment parallel model, in which time-constant discrepancies between the lung parenchyma and compliant airway keep compliant greater than inertial reactance, resulting in a more negative phase angle as frequency is increased. PMID:1184746

  12. Shaken baby syndrome: a biomechanics analysis of injury mechanisms.

    PubMed

    Bandak, Faris A

    2005-06-30

    Traumatic infant shaking has been associated with the shaken baby syndrome (SBS) diagnosis without verification of the operative mechanisms of injury. Intensities for SBS have been expressed only in qualitative, unsubstantiated terms usually referring to acceleration/deceleration rotational injury and relating to falls from great heights onto hard surfaces or from severe motor vehicle crashes. We conducted an injury biomechanics analysis of the reported SBS levels of rotational velocity and acceleration of the head for their injury effects on the infant head-neck. Resulting forces were compared with experimental data on the structural failure limits of the cervical spine in several animal models as well as human neonate cadaver models. We have determined that an infant head subjected to the levels of rotational velocity and acceleration called for in the SBS literature, would experience forces on the infant neck far exceeding the limits for structural failure of the cervical spine. Furthermore, shaking cervical spine injury can occur at much lower levels of head velocity and acceleration than those reported for the SBS. These findings are consistent with the physical laws of injury biomechanics as well as our collective understanding of the fragile infant cervical spine from (1) clinical obstetric experience, (2) automotive medicine and crash safety experience, and (3) common parental experience. The findings are not, however, consistent with the current clinical SBS experience and are in stark contradiction with the reported rarity of cervical spine injury in children diagnosed with SBS. In light of the implications of these findings on child protection and their social and medico-legal significance, a re-evaluation of the current diagnostic criteria for the SBS and its application is suggested. PMID:15885948

  13. Application of symbolic computation to the analysis of mechanical systems, including robot arms

    NASA Technical Reports Server (NTRS)

    Hussain, M. A.; Noble, B.

    1984-01-01

    This paper illustrates the application of symbolic computation in connection with three aspects of mechanical systems: (1) The derivation of dynamical equations by Lagrangian methods; (2) The analysis and synthesis of kinematic mechanisms; and (3) A robot manipulator arm.

  14. Transient thermal-mechanical coupling behavior analysis of mechanical seals during start-up operation

    NASA Astrophysics Data System (ADS)

    Gao, B. C.; Meng, X. K.; Shen, M. X.; Peng, X. D.

    2016-05-01

    A transient thermal-mechanical coupling model for a contacting mechanical seal during start-up has been developed. It takes into consideration the coupling relationship among thermal-mechanical deformation, film thickness, temperature and heat generation. The finite element method and multi-iteration technology are applied to solve the temperature distribution and thermal-mechanical deformation as well as their evolution behavior. Results show that the seal gap transforms from negative coning to positive coning and the contact area of the mechanical seal gradually decreases during start-up. The location of the maximum temperature and maximum contact pressure move from the outer diameter to inside diameter. The heat generation and the friction torque increase sharply at first and then decrease. Meanwhile, the contact force decreases and the fluid film force and leakage rate increase.

  15. Understanding the mechanism(s) of mosaic trisomy 21 by using DNA polymorphism analysis.

    PubMed

    Pangalos, C; Avramopoulos, D; Blouin, J L; Raoul, O; deBlois, M C; Prieur, M; Schinzel, A A; Gika, M; Abazis, D; Antonarakis, S E

    1994-03-01

    In order to investigate the mechanism(s) underlying mosaicism for trisomy 21, we genotyped 17 families with mosaic trisomy 21 probands, using 28 PCR-detectable DNA polymorphic markers that map in the pericentromeric region and long arm of chromosome 21. The percentage of cells with trisomy 21 in the probands' blood lymphocytes was 6%-94%. There were two classes of autoradiographic results: In class I, a "third allele" of lower intensity was detected in the proband's DNA for at least two chromosome 21 markers. The interpretation of this result was that the proband had inherited three chromosomes 21 after meiotic nondisjunction (NDJ) (trisomy 21 zygote) and subsequently lost one because of mitotic (somatic) error, the lost chromosome 21 being that with the lowest-intensity polymorphic allele. The parental origin and the meiotic stage of NDJ could also be determined. In class II, a "third allele" was never detected. In these cases, the mosaicism probably occurred either by a postzygotic, mitotic error in a normal zygote that followed a normal meiosis (class IIA mechanism); by premeiotic, mitotic NDJ yielding an aneusomic zygote after meiosis, and subsequent mitotic loss (class IIB mechanism); or by a meiosis II error with lack of crossover in the preceding meiosis I, followed by mitotic loss after fertilization (class IIC mechanism). Among class II mechanisms, the most likely is mechanism IIA, while IIC is the least likely. There were 10 cases of class I and 7 cases of class II results.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8116616

  16. Analysis of fouling mechanisms in anaerobic membrane bioreactors.

    PubMed

    Charfi, Amine; Ben Amar, Nihel; Harmand, Jérôme

    2012-05-15

    In this paper, we investigate the fouling mechanisms responsible for MF and UF membrane flux decline in Anaerobic Membrane Bioreactors (AnMBR). We have used the fouling mechanism models proposed by Hermia (1982), namely pore constriction, cake formation, complete blocking and intermediate blocking. Based on an optimization approach and using experimental data extracted from the literature, we propose a systematic procedure for identifying the most likely fouling mechanism in play. Short-term as well as long-term experiments are considered and discussed. It was found that short-term experiments are usually characterized by two fouling phases during which the same fouling mechanism or two different mechanisms affect the process. In contrast, in long-term experiments involving cleaning cycles, membrane fouling appears to be better ascribed to one phase only. The impact of abiotic parameters on membrane fouling mechanisms is reviewed and discussed in the light of these results. Finally, it is shown that the mechanism most responsible for membrane fouling in an AnMBR is cake formation. This main result will be useful for the future development of simple integrated models for optimization and control. PMID:22397816

  17. Reinforcement Mechanism Of Polyurethane-Urea/Clay Nanocomposites Probed By Positron Annihilation Lifetime Spectroscopy And Dynamic Mechanical Analysis

    SciTech Connect

    Rath, S. K.; Patri, M.; Sudarshan, K.; Pujari, P. K.; Khakhar, D. V.

    2010-12-01

    A basis for quantitative analysis of the reinforcement mechanism of polyurethane-urea/clay nanocomposites using two characterization methods, positron annihilation life time spectroscopy (PALS) and dynamic mechanical analysis (DMA) is provided. DMA was used to measure the constrained volume fraction of amorphous soft segments induced by nanoclay and the storage modulus of the nanocomposites. The interfacial interactions in the nanocomposites were investigated by PALS. The modulus enhancement of the organoclay nanocomposites was found to have a good correlation with the volume fraction of the constrained region and the interfacial interactions.

  18. Spartan Release Engagement Mechanism (REM) stress and fracture analysis

    NASA Technical Reports Server (NTRS)

    Marlowe, D. S.; West, E. J.

    1984-01-01

    The revised stress and fracture analysis of the Spartan REM hardware for current load conditions and mass properties is presented. The stress analysis was performed using a NASTRAN math model of the Spartan REM adapter, base, and payload. Appendix A contains the material properties, loads, and stress analysis of the hardware. The computer output and model description are in Appendix B. Factors of safety used in the stress analysis were 1.4 on tested items and 2.0 on all other items. Fracture analysis of the items considered fracture critical was accomplished using the MSFC Crack Growth Analysis code. Loads and stresses were obtaind from the stress analysis. The fracture analysis notes are located in Appendix A and the computer output in Appendix B. All items analyzed met design and fracture criteria.

  19. Security Analysis of Yeh-Tsai Security Mechanism

    NASA Astrophysics Data System (ADS)

    Yum, Dae Hyun; Shin, Jong Hoon; Lee, Pil Joong

    Yeh and Tsai recently proposed an enhanced mobile commerce security mechanism. They modified the lightweight security mechanism due to Lam, Chung, Gu, and Sun to relieve the burden of mobile clients. However, this article shows that a malicious WAP gateway can successfully obtain the mobile client's PIN by sending a fake public key of a mobile commerce server and exploiting information leakage caused by addition operation. We also present a countermeasure against the proposed attack.

  20. Understanding the mechanism(s) of mosaic trisomy 21 by using DNA polymorphism analysis.

    PubMed Central

    Pangalos, C.; Avramopoulos, D.; Blouin, J. L.; Raoul, O.; deBlois, M. C.; Prieur, M.; Schinzel, A. A.; Gika, M.; Abazis, D.; Antonarakis, S. E.

    1994-01-01

    In order to investigate the mechanism(s) underlying mosaicism for trisomy 21, we genotyped 17 families with mosaic trisomy 21 probands, using 28 PCR-detectable DNA polymorphic markers that map in the pericentromeric region and long arm of chromosome 21. The percentage of cells with trisomy 21 in the probands' blood lymphocytes was 6%-94%. There were two classes of autoradiographic results: In class I, a "third allele" of lower intensity was detected in the proband's DNA for at least two chromosome 21 markers. The interpretation of this result was that the proband had inherited three chromosomes 21 after meiotic nondisjunction (NDJ) (trisomy 21 zygote) and subsequently lost one because of mitotic (somatic) error, the lost chromosome 21 being that with the lowest-intensity polymorphic allele. The parental origin and the meiotic stage of NDJ could also be determined. In class II, a "third allele" was never detected. In these cases, the mosaicism probably occurred either by a postzygotic, mitotic error in a normal zygote that followed a normal meiosis (class IIA mechanism); by premeiotic, mitotic NDJ yielding an aneusomic zygote after meiosis, and subsequent mitotic loss (class IIB mechanism); or by a meiosis II error with lack of crossover in the preceding meiosis I, followed by mitotic loss after fertilization (class IIC mechanism). Among class II mechanisms, the most likely is mechanism IIA, while IIC is the least likely. There were 10 cases of class I and 7 cases of class II results.(ABSTRACT TRUNCATED AT 250 WORDS) Images Figure 1 PMID:8116616

  1. Understanding the mechanism(s) of mosaic trisomy 21 by using DNA polymorphism analysis

    SciTech Connect

    Pangalos, C.; Abazis, D.; Avramopoulos, D.; Blouin, J.L.; Antonaraksi, S.E. ); Raoul, O.; deBlois, M.C.; Prieur, M. ); Schinzel, A.A.

    1994-03-01

    In order to investigate the mechanism(s) underlying mosaicism for trisomy 21, the authors genotyped 17 families with mosaic trisomy 21 probands, using 28 PCR-detectable DNA polymorphic markers that map in the pericentromeric region and long arm of chromosome 21. The percentage of cells with trisomy 21 in the probands' blood lymphocytes was 6%-94%. There were two classes of autoradiographic results: In class I, a third allele' of lower intensity was detected in the proband's DNA for at least two chromosome 21 markers. The interpretation of this result was that the proband had inherited three chromosomes 21 after meiotic nondisjunction (NDJ) (trisomy 21 zygote) and subsequently lost one because of mitotic (somatic) error, the lost chromosome 21 being that with the lowest-intensity polymorphic allele. The parental origin and the meiotic stage of NDJ could also be determined. In class II, a third allele' was never detected. In these cases, the mosaicism probably occurred either by a postzygotic, mitotic error in anormal zygote that followed a normal meiosis (class IIA mechanism); by premeiotic, mitotic NDJ yielding an aneusomic zygote after meiosis, and subsequent mitotic loss (class IIB mechanism); or by a meiosis II error with lack of crossover in the preceding meiosis I, followed by mitotic loss after fertilization (class IIC mechanism). Among class II mechanisms, the most likely is mechanism IIA, while IIC is the least likely. There were 10 cases of class I and 7 cases of class II results. Within class I, there were nine cases with maternal meitoic errors (six meiosis I and three meiosis II errors, on the basis of pericentromeric markers) and one with paternal meiosis I error. The postzygotic loss of chromosome 21 was determined in eight maternal class I cases, and it was maternally derived in five cases and paternally derived in three; this suggests that the postzygotic loss of chromosome 21 is probably random. 28 refs., 1 fig., 2 tabs.

  2. Dynamic mechanical thermal analysis of hypromellose 2910 free films.

    PubMed

    Cespi, Marco; Bonacucina, Giulia; Mencarelli, Giovanna; Casettari, Luca; Palmieri, Giovanni Filippo

    2011-10-01

    It is common practice to coat oral solid dosage forms with polymeric materials for controlled release purposes or for practical and aesthetic reasons. Good knowledge of thermo-mechanical film properties or their variation as a function of polymer grade, type and amount of additives or preparation method is of prime importance in developing solid dosage forms. This work focused on the dynamic mechanical thermal characteristics of free films of hypromellose 2910 (also known as HPMC), prepared using three grades of this polymer from two different manufacturers, in order to assess whether polymer chain length or origin affects the mechanical or thermo-mechanical properties of the final films. Hypromellose free films were obtained by casting their aqueous solutions prepared at a specific concentrations in order to obtain the same viscosity for each. The films were stored at room temperature until dried and then examined using a dynamic mechanical analyser. The results of the frequency scans showed no significant differences in the mechanical moduli E' and E″ of the different samples when analysed at room temperature; however, the grade of the polymer affected material transitions during the heating process. Glass transition temperature, apparent activation energy and fragility parameters depended on polymer chain length, while the material brand showed little impact on film performance. PMID:21645616

  3. Analysis of internal crack healing mechanism under rolling deformation.

    PubMed

    Gao, Haitao; Ai, Zhengrong; Yu, Hailiang; Wu, Hongyan; Liu, Xianghua

    2014-01-01

    A new experimental method, called the 'hole filling method', is proposed to simulate the healing of internal cracks in rolled workpieces. Based on the experimental results, the evolution in the microstructure, in terms of diffusion, nucleation and recrystallisation were used to analyze the crack healing mechanism. We also validated the phenomenon of segmented healing. Internal crack healing involves plastic deformation, heat transfer and an increase in the free energy introduced by the cracks. It is proposed that internal cracks heal better under high plastic deformation followed by slow cooling after rolling. Crack healing is controlled by diffusion of atoms from the matrix to the crack surface, and also by the nucleation and growth of ferrite grain on the crack surface. The diffusion mechanism is used to explain the source of material needed for crack healing. The recrystallisation mechanism is used to explain grain nucleation and growth, accompanied by atomic migration to the crack surface. PMID:25003518

  4. Analysis of Internal Crack Healing Mechanism under Rolling Deformation

    PubMed Central

    Gao, Haitao; Ai, Zhengrong; Yu, Hailiang; Wu, Hongyan; Liu, Xianghua

    2014-01-01

    A new experimental method, called the ‘hole filling method’, is proposed to simulate the healing of internal cracks in rolled workpieces. Based on the experimental results, the evolution in the microstructure, in terms of diffusion, nucleation and recrystallisation were used to analyze the crack healing mechanism. We also validated the phenomenon of segmented healing. Internal crack healing involves plastic deformation, heat transfer and an increase in the free energy introduced by the cracks. It is proposed that internal cracks heal better under high plastic deformation followed by slow cooling after rolling. Crack healing is controlled by diffusion of atoms from the matrix to the crack surface, and also by the nucleation and growth of ferrite grain on the crack surface. The diffusion mechanism is used to explain the source of material needed for crack healing. The recrystallisation mechanism is used to explain grain nucleation and growth, accompanied by atomic migration to the crack surface. PMID:25003518

  5. Characterization of Esophageal Physiology Using Mechanical State Analysis

    PubMed Central

    Leibbrandt, Richard E.; Dinning, Phil G.; Costa, Marcello; Cock, Charles; Wiklendt, Lukasz; Wang, Guangsong; Tack, Jan; van Beckevoort, Dirk; Rommel, Nathalie; Omari, Taher I.

    2016-01-01

    The esophagus functions to transport swallowed fluids and food from the pharynx to the stomach. The esophageal muscles governing bolus transport comprise circular striated muscle of the proximal esophagus and circular smooth muscle of the distal esophagus. Longitudinal smooth muscle contraction provides a mechanical advantage to bolus transit during circular smooth muscle contraction. Esophageal striated muscle is directly controlled by neural circuits originating in the central nervous system, resulting in coordinated contractions. In contrast, the esophageal smooth muscle is controlled by enteric circuits modulated by extrinsic central neural connections resulting in neural relaxation and contraction. The esophageal muscles are modulated by sensory information arising from within the lumen. Contraction or relaxation, which changes the diameter of the lumen, alters the intraluminal pressure and ultimately inhibits or promotes flow of content. This relationship that exists between the changes in diameter and concurrent changes in intraluminal pressure has been used previously to identify the “mechanical states” of the circular muscle; that is when the muscles are passively or actively, relaxing or contracting. Detecting these changes in the mechanical state of the muscle has been difficult and as the current interpretation of esophageal motility is based largely upon pressure measurement (manometry), subtle changes in the muscle function during peristalsis can be missed. We hypothesized that quantification of mechanical states of the esophageal circular muscles and the pressure-diameter properties that define them, would allow objective characterization of the mechanisms that govern esophageal peristalsis. To achieve this we analyzed barium swallows captured by simultaneous videofluoroscopy and pressure with impedance recording. From these data we demonstrated that intraluminal impedance measurements could be used to determine changes in the internal diameter

  6. Characterization of Esophageal Physiology Using Mechanical State Analysis.

    PubMed

    Leibbrandt, Richard E; Dinning, Phil G; Costa, Marcello; Cock, Charles; Wiklendt, Lukasz; Wang, Guangsong; Tack, Jan; van Beckevoort, Dirk; Rommel, Nathalie; Omari, Taher I

    2016-01-01

    The esophagus functions to transport swallowed fluids and food from the pharynx to the stomach. The esophageal muscles governing bolus transport comprise circular striated muscle of the proximal esophagus and circular smooth muscle of the distal esophagus. Longitudinal smooth muscle contraction provides a mechanical advantage to bolus transit during circular smooth muscle contraction. Esophageal striated muscle is directly controlled by neural circuits originating in the central nervous system, resulting in coordinated contractions. In contrast, the esophageal smooth muscle is controlled by enteric circuits modulated by extrinsic central neural connections resulting in neural relaxation and contraction. The esophageal muscles are modulated by sensory information arising from within the lumen. Contraction or relaxation, which changes the diameter of the lumen, alters the intraluminal pressure and ultimately inhibits or promotes flow of content. This relationship that exists between the changes in diameter and concurrent changes in intraluminal pressure has been used previously to identify the "mechanical states" of the circular muscle; that is when the muscles are passively or actively, relaxing or contracting. Detecting these changes in the mechanical state of the muscle has been difficult and as the current interpretation of esophageal motility is based largely upon pressure measurement (manometry), subtle changes in the muscle function during peristalsis can be missed. We hypothesized that quantification of mechanical states of the esophageal circular muscles and the pressure-diameter properties that define them, would allow objective characterization of the mechanisms that govern esophageal peristalsis. To achieve this we analyzed barium swallows captured by simultaneous videofluoroscopy and pressure with impedance recording. From these data we demonstrated that intraluminal impedance measurements could be used to determine changes in the internal diameter of

  7. Progress of Stirling cycle analysis and loss mechanism characterization

    NASA Technical Reports Server (NTRS)

    Tew, R. C., Jr.

    1986-01-01

    An assessment of Stirling engine thermodynamic modeling and design codes shows a general deficiency; this deficiency is due to poor understanding of the fluid flow and heat transfer phenomena that occur in the oscillating flow and pressure level environment within the engines. Stirling engine thermodynamic loss mechanisms are listed. Several experimental and computational research efforts now underway to characterize various loss mechanisms are reviewed. The need for additional experimental rigs and rig upgrades is discussed. Recent developments and current efforts in Stirling engine thermodynamic modeling are also reviewed.

  8. Cantilever arrays for multiplexed mechanical analysis of biomolecular reactions.

    PubMed

    Yue, Min; Stachowiak, Jeanne C; Majumdar, Arunava

    2004-09-01

    Microchips containing arrays of cantilever beams have been used to mechanically detect and quantitatively analyze multiple reactions of DNA hybridization and antigen-antibody binding simultaneously. The reaction-induced deflection of a cantilever beam reflects the interplay between strain energy increase of the beam and the free energy reduction of a reaction, providing an ideal tool for investigating the connection between mechanics and chemistry of biomolecular reactions. Since free energy reduction is common for all reactions, the cantilever array forms a universal platform for label-free detection of various specific biomolecular reactions. A few such reactions and their implications in biology and biotechnology are discussed. PMID:16783934

  9. The Wayside Mechanic: An Analysis of Skill Acquisition in Ghana.

    ERIC Educational Resources Information Center

    McLaughlin, Stephen Douglas

    This study describes and analyzes the nature of skill acquisition process in one indigenous, informal training system--the apprenticeship of the wayside mechanics workshops in Koforidua, Ghana. Chapter 2 places apprenticeships training in the wider context of artisanship and training. It traces the history of the West African craft shop and its…

  10. An Analysis of Knowledge Management Mechanisms in Healthcare Portals

    ERIC Educational Resources Information Center

    Lee, Chei Sian; Goh, Dion Hoe-Lian; Chua, Alton Y. K.

    2010-01-01

    Healthcare portals are becoming increasingly popular with Internet users since they play an important role in supporting interaction between individuals and healthcare organizations with a Web presence. Additionally, many of these organizations make use of knowledge management mechanisms on their healthcare portals to manage the abundance of…

  11. The distinct element analysis of toppling failure mechanisms

    NASA Astrophysics Data System (ADS)

    Özge Dinç, Şaziye; Sinan Işık, Nihat; Karaca, Zeki

    2016-04-01

    This project investigates the toppling failure mechanisms of rock masses having different rock materials and discontinuity properties in slopes that are designed in different heights. For this purpose, PFC2D as a distinct element code was used to anticipate the post failure behaviors of rock masses. After the simulation of laboratory tests on the samples in 2 (width) *4 (height) m, macro mechanical properties of rock masses were determined to be assigned the slopes. The properties of discontinuities were set up based on the smooth-joint method in PFC. The movements in the slopes -equipped with persistent and non-persistent discontinuities- were analyzed by using gravity increase method. The results show that the post failure behaviors of all rock samples have been controlled primarily by joint location and joint length. In addition to this, an increase on the slope height has an influence on the failure mechanism such that triggers the materials to transit from the toppling to circular yielding manner in some models. It has been also worth note that all models begin to fail as soon as the wing cracks develop by tension stresses, thus the tensile strength of the relevant rock material is the most critical mechanic parameter on the failure.

  12. Women's Eating Problems: An Analysis of a Coping Mechanism.

    ERIC Educational Resources Information Center

    Hooker, Dawn; Convisser, Ellen

    1983-01-01

    Discusses clinical observations of women (N=100) with eating problems, focusing on emotional issues as well as how these women use food as a coping mechanism. Reported that therapy helped these women shed anxiety and fear about food and to see eating as something they consciously choose to do. (LLL)

  13. Mechanical analysis of a heat-shock induced developmental defect

    NASA Astrophysics Data System (ADS)

    Crews, Sarah M.; McCleery, W. Tyler; Hutson, M. Shane

    2014-03-01

    Embryonic development in Drosophila is a complex process involving coordinated movements of mechanically interacting tissues. Perturbing this system with a transient heat shock can result in a number of developmental defects. In particular, a heat shock applied during the earliest morphogenetic movements of gastrulation can lead to apparent recovery, but then subsequent morphogenetic failure 5-6 hours later during germ band retraction. The process of germ band retraction requires an intact amnioserosa - a single layered extra-embryonic epithelial tissue - and heat shock at gastrulation can induce the later opening of holes in the amnioserosa. These holes are highly correlated with failures of germ band retraction. These holes could be caused by a combination of mechanical weakness in the amnioserosa or local increases in mechanical stress. Here, we assess the role of mechanical stress using confocal imaging to compare cell and tissue morphology in the amnioserosa of normal and heat-shocked embryos and laser hole drilling to map the stress field around the times and locations at which heat-shock induced holes open.

  14. Agricultural/Industrial Mechanical Technician. Ohio's Competency Analysis Profile.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Vocational Instructional Materials Lab.

    Developed through a modified DACUM (Developing a Curriculum) process involving business, industry, labor, and community agency representatives in Ohio, this document is a comprehensive and verified employer competency profile for agricultural/industrial mechanical technician occupations. The list contains units (with and without subunits),…

  15. Comprehensive mechanisms for combustion chemistry: Experiment, modeling, and sensitivity analysis

    SciTech Connect

    Dryer, F.L.; Yetter, R.A.

    1993-12-01

    This research program is an integrated experimental/numerical effort to study pyrolysis and oxidation reactions and mechanisms for small-molecule hydrocarbon structures under conditions representative of combustion environments. The experimental aspects of the work are conducted in large diameter flow reactors, at pressures from one to twenty atmospheres, temperatures from 550 K to 1200 K, and with observed reaction times from 10{sup {minus}2} to 5 seconds. Gas sampling of stable reactant, intermediate, and product species concentrations provides not only substantial definition of the phenomenology of reaction mechanisms, but a significantly constrained set of kinetic information with negligible diffusive coupling. Analytical techniques used for detecting hydrocarbons and carbon oxides include gas chromatography (GC), and gas infrared (NDIR) and FTIR methods are utilized for continuous on-line sample detection of light absorption measurements of OH have also been performed in an atmospheric pressure flow reactor (APFR), and a variable pressure flow (VPFR) reactor is presently being instrumented to perform optical measurements of radicals and highly reactive molecular intermediates. The numerical aspects of the work utilize zero and one-dimensional pre-mixed, detailed kinetic studies, including path, elemental gradient sensitivity, and feature sensitivity analyses. The program emphasizes the use of hierarchical mechanistic construction to understand and develop detailed kinetic mechanisms. Numerical studies are utilized for guiding experimental parameter selections, for interpreting observations, for extending the predictive range of mechanism constructs, and to study the effects of diffusive transport coupling on reaction behavior in flames. Modeling using well defined and validated mechanisms for the CO/H{sub 2}/oxidant systems.

  16. Failure Analysis and Mechanisms of Failure of Fibrous Composite Structures

    NASA Technical Reports Server (NTRS)

    Noor, A. K. (Compiler); Shuart, M. J. (Compiler); Starnes, J. H., Jr. (Compiler); Williams, J. G. (Compiler)

    1983-01-01

    The state of the art of failure analysis and current design practices, especially as applied to the use of fibrous composite materials in aircraft structures is discussed. Deficiencies in these technologies are identified, as are directions for future research.

  17. Mechanical analysis of Drosophila indirect flight and jump muscles

    PubMed Central

    Swank, Douglas M.

    2011-01-01

    The genetic advantages of Drosophila make it a very appealing choice for investigating muscle development, muscle physiology and muscle protein structure and function. To take full advantage of this model organism, it has been vital to develop isolated Drosophila muscle preparations that can be mechanically evaluated. We describe techniques to isolate, prepare and mechanically analyze skinned muscle fibers from two Drosophila muscle types, the indirect flight muscle and the jump muscle. The function of the indirect flight muscle is similar to vertebrate cardiac muscle, to generate power in an oscillatory manner. The indirect flight muscle is ideal for evaluating the influence of protein mutations on muscle and cross-bridge stiffness, oscillatory power, and deriving cross-bridge rate constants. Jump muscle physiology and structure are more similar to skeletal vertebrate muscle than indirect flight muscle, and it is ideal for measuring maximum shortening velocity, force-velocity characteristics and steady-state power generation. PMID:22079350

  18. An analysis of B cell selection mechanisms in germinal centers.

    PubMed

    Meyer-Hermann, Michael E; Maini, Philip K; Iber, Dagmar

    2006-09-01

    Affinity maturation of antibodies during immune responses is achieved by multiple rounds of somatic hypermutation and subsequent preferential selection of those B cells that express B cell receptors with improved binding characteristics for the antigen. The mechanism underlying B cell selection has not yet been defined. By employing an agent-based model, we show that for physiologically reasonable parameter values affinity maturation can be driven by competition for neither binding sites nor antigen--even in the presence of competing secreted antibodies. Within the tested mechanisms, only clonal competition for T cell help or a refractory time for the interaction of centrocytes with follicular dendritic cells is found to enable affinity maturation while generating the experimentally observed germinal centre characteristics and tolerating large variations in the initial antigen density. PMID:16707510

  19. Mechanical analysis of Drosophila indirect flight and jump muscles.

    PubMed

    Swank, Douglas M

    2012-01-01

    The genetic advantages of Drosophila make it a very appealing choice for investigating muscle development, muscle physiology and muscle protein structure and function. To take full advantage of this model organism, it has been vital to develop isolated Drosophila muscle preparations that can be mechanically evaluated. We describe techniques to isolate, prepare and mechanically analyze skinned muscle fibers from two Drosophila muscle types, the indirect flight muscle and the jump muscle. The function of the indirect flight muscle is similar to vertebrate cardiac muscle, to generate power in an oscillatory manner. The indirect flight muscle is ideal for evaluating the influence of protein mutations on muscle and cross-bridge stiffness, oscillatory power, and deriving cross-bridge rate constants. Jump muscle physiology and structure are more similar to skeletal vertebrate muscle than indirect flight muscle, and it is ideal for measuring maximum shortening velocity, force-velocity characteristics and steady-state power generation. PMID:22079350

  20. Numerical analysis of biosonar beamforming mechanisms and strategies in bats.

    PubMed

    Müller, Rolf

    2010-09-01

    Beamforming is critical to the function of most sonar systems. The conspicuous noseleaf and pinna shapes in bats suggest that beamforming mechanisms based on diffraction of the outgoing and incoming ultrasonic waves play a major role in bat biosonar. Numerical methods can be used to investigate the relationships between baffle geometry, acoustic mechanisms, and resulting beampatterns. Key advantages of numerical approaches are: efficient, high-resolution estimation of beampatterns, spatially dense predictions of near-field amplitudes, and the malleability of the underlying shape representations. A numerical approach that combines near-field predictions based on a finite-element formulation for harmonic solutions to the Helmholtz equation with a free-field projection based on the Kirchhoff integral to obtain estimates of the far-field beampattern is reviewed. This method has been used to predict physical beamforming mechanisms such as frequency-dependent beamforming with half-open resonance cavities in the noseleaf of horseshoe bats and beam narrowing through extension of the pinna aperture with skin folds in false vampire bats. The fine structure of biosonar beampatterns is discussed for the case of the Chinese noctule and methods for assessing the spatial information conveyed by beampatterns are demonstrated for the brown long-eared bat. PMID:20815475

  1. Operation analysis of a Chebyshev-Pantograph leg mechanism for a single DOF biped robot

    NASA Astrophysics Data System (ADS)

    Liang, Conghui; Ceccarelli, Marco; Takeda, Yukio

    2012-12-01

    In this paper, operation analysis of a Chebyshev-Pantograph leg mechanism is presented for a single degree of freedom (DOF) biped robot. The proposed leg mechanism is composed of a Chebyshev four-bar linkage and a pantograph mechanism. In contrast to general fully actuated anthropomorphic leg mechanisms, the proposed leg mechanism has peculiar features like compactness, low-cost, and easy-operation. Kinematic equations of the proposed leg mechanism are formulated for a computer oriented simulation. Simulation results show the operation performance of the proposed leg mechanism with suitable characteristics. A parametric study has been carried out to evaluate the operation performance as function of design parameters. A prototype of a single DOF biped robot equipped with two proposed leg mechanisms has been built at LARM (Laboratory of Robotics and Mechatronics). Experimental test shows practical feasible walking ability of the prototype, as well as drawbacks are discussed for the mechanical design.

  2. Nano Scale Mechanical Analysis of Biomaterials Using Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Dutta, Diganta

    The atomic force microscope (AFM) is a probe-based microscope that uses nanoscale and structural imaging where high resolution is desired. AFM has also been used in mechanical, electrical, and thermal engineering applications. This unique technique provides vital local material properties like the modulus of elasticity, hardness, surface potential, Hamaker constant, and the surface charge density from force versus displacement curve. Therefore, AFM was used to measure both the diameter and mechanical properties of the collagen nanostraws in human costal cartilage. Human costal cartilage forms a bridge between the sternum and bony ribs. The chest wall of some humans is deformed due to defective costal cartilage. However, costal cartilage is less studied compared to load bearing cartilage. Results show that there is a difference between chemical fixation and non-chemical fixation treatments. Our findings imply that the patients' chest wall is mechanically weak and protein deposition is abnormal. This may impact the nanostraws' ability to facilitate fluid flow between the ribs and the sternum. At present, AFM is the only tool for imaging cells' ultra-structure at the nanometer scale because cells are not homogeneous. The first layer of the cell is called the cell membrane, and the layer under it is made of the cytoskeleton. Cancerous cells are different from normal cells in term of cell growth, mechanical properties, and ultra-structure. Here, force is measured with very high sensitivity and this is accomplished with highly sensitive probes such as a nano-probe. We performed experiments to determine ultra-structural differences that emerge when such cancerous cells are subject to treatments such as with drugs and electric pulses. Jurkat cells are cancerous cells. These cells were pulsed at different conditions. Pulsed and non-pulsed Jurkat cell ultra-structures were investigated at the nano meter scale using AFM. Jurkat cell mechanical properties were measured under

  3. Analysis of Mechanical Failure of Polymer Microneedles by Axial Force

    PubMed Central

    Park, Jung-Hwan; Prausnitz, Mark R.

    2010-01-01

    A polymeric microneedle has been developed for drug delivery applications. The ultimate goal of the polymeric microneedle is insertion into the specified region without failure for effective transdermal drug delivery. Mechanical failure of various geometries of microneedles by axial load was modeled using the Euler formula and the Johnson formula to predict the failure force of tapered-column microneedles. These formulas were compared with measured data to identify the mechanical behavior of microneedles by determining the critical factors including the actual length and end-fixed factor. The comparison of the two formulas with the data showed good agreement at the end-fixity (K) of 0.7. This value means that a microneedle column has one fixed end and one pinned end, and that part of the microneedle was overloaded by axial load. When the aspect ratio of length to equivalent diameter is 12:1 at 3 GPa of Young’s modulus, there is a transition from the Euler region to the Johnson region by the decreased length and increased base diameter of the microneedle. A polymer having less than 3 GPa of stiffness would follow the Euler formula. A 12:1 aspect ratio of length to equivalent diameter of the microneedle was the mechanical indicator determining the failure mode between elastic buckling and inelastic buckling at less than 3 GPa of Young’s modulus of polymer. Microneedles with below a 12:1 aspect ratio of length-to-equivalent diameter and more than 3 GPa of Young’s were recommended for reducing sudden failure by buckling and for successfully inserting the microneedle into the skin. PMID:21218133

  4. Transcriptional profiling and biochemical analysis of mechanically induced cartilaginous tissues

    PubMed Central

    Salisbury Palomares, Kristy T.; Gerstenfeld, Louis C.; Wigner, Nathan A.; Lenburg, Marc E.; Einhorn, Thomas A.; Morgan, Elise F.

    2010-01-01

    Objective In order to characterize patterns of molecular expression that lead to cartilage formation in vivo in a post-natal setting, mRNA expression profiling was carried out across the timecourse of mechanically induced chondrogenesis. Methods Retired breeder Sprague-Dawley rats underwent production of a non-critical-size, transverse femoral osteotomy. Experimental animals (n=45) were subjected to bending stimulation (60° cyclic motion in the sagittal plane for 15 minutes/day) of the osteotomy gap beginning on post-operative day (POD) 10. Control animals (n=32) experienced continuous rigid fixation. mRNA isolated on POD 10, 17, 24, and 38 was analyzed using a microarray containing 608 genes involved in skeletal development, tissue differentiation, fracture healing, and mechanotransduction. The glycosaminoglycan (GAG) content of the stimulated tissues was compared to native articular cartilage as a means of assessing the progression of chondrogenic development of the tissues. Results The majority of the 100 genes that were differentially expressed were upregulated in response to mechanical stimulation. Many of these genes are associated with articular cartilage development and maintenance, diarthroidal joint development, cell adhesion, extracellular matrix synthesis, signal transduction, and skeletal development. Quantitative real-time PCR results were consistent with the microarray findings. The GAG content of the stimulated tissues increased over time and was no different from that of articular cartilage at POD 38. Conclusions The mechanical stimulation caused upregulation of genes principally involved in joint cavity morphogenesis and critical to articular cartilage function. Further study of this type of stimulation may identify key signaling events required for post-natal, hyaline cartilage formation. PMID:20131271

  5. Analysis of Jovian decametric data: Study of radio emission mechanisms

    NASA Technical Reports Server (NTRS)

    Staelin, D. H.; Arias, T. A.; Garnavich, P. M.; Rosenkranz, P. W.

    1985-01-01

    The Voyager 1 and Voyager 2 Planetary Radio Astronomy Experiments (PRA) have produced the finest set of Jovian decametric radio emission data ever obtained. Jovian decametric L-burst and S-burst arcs were characterized and the data reconciled with models for the radio emission geometry and mechanisms. The first major results involve comparisons of the distribution of arc separations with longitudes. The identification and analyses of systematic variations in the PRA data have yielded interesting results, but only the most obvious features of the data were examined. Analyses of the PRA data were extended with the use of new 6-Sec formats that are more sensitive to the S-bursts.

  6. Analysis of beam loss mechanism in the Project X linac

    SciTech Connect

    Carneiro, J.-P.; Lebedev, V.; Nagaitsev, S.; Ostiguy, J.-F.; Solyak, N.; /Fermilab

    2011-03-01

    Minimization of the beam losses in a multi-MW H{sup -} linac such as ProjectX to a level below 1 W/m is a challenging task. The impact of different mechanism of beam stripping, including stripping in electric and magnetic fields, residual gas, blackbody radiation and intra-beam stripping, is analyzed. Other sources of beam losses are misalignements of beamline elements and errors in RF fields and phases. We present in this paper requirements for dynamic errors and correction schemes to keep beam losses under control.

  7. Analysis, scientific computing and fundamental studies in fluid mechanics

    SciTech Connect

    Keller, H.B.; Saffman, P.G.

    1991-01-01

    Progress is reported on work in the following areas: vortex dynamics and turbulence, fingers and bubbles in Hele-Shaw cells and unbounded fluid, vortex reconnection, pattern selection in solidifying systems, Richtmyer-Meshkov instability, Wavy-Taylor vortex flows, high reynolds number laminar flows, and lastly numerical analysis and dynamical systems. (GHH)

  8. ESTABLISHMENT OF A COMMUNITY MODELING AND ANALYSIS SUPPORT MECHANISM

    EPA Science Inventory

    During the fall of 2001, a Cooperative Research Agreement between the U.S. Environmental Protection Agency and MCNC began a Community Modeling and Analysis System (CMAS) center. The CMAS will foster development, distribution, and use of the Models-3/CMAQ (Community Multiscale ...

  9. Dynamic mechanical analysis: A practical introduction to techniques and applications

    SciTech Connect

    Menard, K.

    1999-01-01

    This book introduces DMA, its history, and its current position as part of thermal analysis on polymers. It discusses major types of instrumentation, including oscillatory rotational, oscillatory axial, and torsional pendulum. It also describes analytical techniques in terms of utility, quality of data, methods of calibration, and suitability for different types of materials and assesses applications for thermoplastics, thermosetting systems, and thermosets.

  10. Mapping Learning and Game Mechanics for Serious Games Analysis

    ERIC Educational Resources Information Center

    Arnab, Sylvester; Lim, Theodore; Carvalho, Maira B.; Bellotti, Francesco; de Freitas, Sara; Louchart, Sandy; Suttie, Neil; Berta, Riccardo; De Gloria, Alessandro

    2015-01-01

    Although there is a consensus on the instructional potential of Serious Games (SGs), there is still a lack of methodologies and tools not only for design but also to support analysis and assessment. Filling this gap is one of the main aims of the Games and Learning Alliance (http://www.galanoe.eu) European Network of Excellence on Serious Games,…

  11. Analysis of thermal conductivity of polymeric nanocomposites under mechanical loading

    NASA Astrophysics Data System (ADS)

    Yu, Suyoung; Yang, Seunghwa; Cho, Maenghyo

    2013-12-01

    When the plastic deformation is applied to neat polymer, the polymer chains are aligned and the thermal conductivity of neat polymer increases linearly along the loading direction. However, the thermal conductivity change of nanocomposites consisting of polymer matrix and nanofillers during plastic deformation is not simple. The volume fraction and size of nanofillers scarcely affect the structural change of polymer chains during the plastic deformation. In this study, the structural change of polymeric materials according to the mechanical loading and its effect on the thermal transport properties are investigated through a molecular dynamics simulation. To investigate the effects of nanofiller, its volume fraction, and size on the thermal transport properties, the unit cells of neat amorphous nylon 6 and nanocomposites consisting of amorphous nylon 6 matrix and spherical silica particles are prepared. The molecular unit cells are uniaxially stretched by applying constant strain along the loading directions. Then, non-equilibrium molecular dynamics (NEMD) simulations are performed to estimate the thermal conductivities during plastic deformation. The alignment of polymer chains is analyzed by tracing the orientation correlation function of each polymer molecule and the free volume change during the mechanical loading is also analyzed.

  12. Mechanical and structural property analysis of bacterial cellulose composites.

    PubMed

    Dayal, Manmeet Singh; Catchmark, Jeffrey M

    2016-06-25

    Bacterial cellulose (BC) exhibits unique properties including high mechanical strength and high crystallinity. Improvement in the mechanical properties of BC is sought for many applications ranging from food to structural composites to biomedical materials. In this study, different additives including carboxymethyl cellulose (CMC), pectin, gelatin, cornstarch, and corn steep liquor were included in the fermentation media to alter the BC produced. Three different concentrations (1%, 3% and 5%) were chosen for each of the additives, with no additive (0%) as the control. The produced BC was then analyzed to determine tensile and compression modulus. Amongst the tested additives, BC produced in media containing 3% (w/v) pectin had the maximum compressive modulus (142kPa), and BC produced in media containing 1% (w/v) gelatin exhibited the maximum tensile modulus (21MPa). Structural characteristics of BC and BC-additive composites were compared using X-Ray diffraction (XRD). The crystal size and crystallinity of BC was reduced when grown in the presence of CMC and gelatin while pectin only decreased the crystallite size. This suggested that CMC and gelatin may be incorporated into the BC fibril structure. The field emission scanning electron microscopy (FESEM) images showed the increased micro-fibril aggregation in BC pellicles grown in the presence of additives to the culture media. PMID:27083837

  13. Analysis of Europan Cycloid Morphology and Implications for Formation Mechanisms

    NASA Technical Reports Server (NTRS)

    Marshall, S. T.; Kattenhorn, S. A.

    2004-01-01

    Europa's highly fractured crust has been shown to contain features with a range of differing morphologies. Most lineaments on Europa are believed to have initiated as cracks, although the type of cracking (e.g. tensile vs. shear) remains unclear and may vary for different morphologies. Arcuate lineaments, called cycloids or flexi, have been observed in nearly all imaged regions of Europa and have been modeled as tensile fractures that were initiated in response to diurnal variations in tides. Despite this hypothesis about the formation mechanism, there have been no detailed analyses of the variable morphologies of cycloids. We have examined Galileo images of numerous locations on Europa to develop a catalog of the different morphologies of cycloids. This study focuses on variations in morphology along individual cycloid segments and differences in cusp styles between segments, while illustrating how morphologic evidence can help unravel formation mechanisms. In so doing, we present evidence for cycloid cusps forming due to secondary fracturing during strike-slip sliding on pre-existing cycloid segments.

  14. Experimental Analysis of the Mechanism of Hearing under Water

    PubMed Central

    Chordekar, Shai; Kishon-Rabin, Liat; Kriksunov, Leonid; Adelman, Cahtia; Sohmer, Haim

    2015-01-01

    The mechanism of human hearing under water is debated. Some suggest it is by air conduction (AC), others by bone conduction (BC), and others by a combination of AC and BC. A clinical bone vibrator applied to soft tissue sites on the head, neck, and thorax also elicits hearing by a mechanism called soft tissue conduction (STC) or nonosseous BC. The present study was designed to test whether underwater hearing at low intensities is by AC or by osseous BC based on bone vibrations or by nonosseous BC (STC). Thresholds of normal hearing participants to bone vibrator stimulation with their forehead in air were recorded and again when forehead and bone vibrator were under water. A vibrometer detected vibrations of a dry human skull in all similar conditions (in air and under water) but not when water was the intermediary between the sound source and the skull forehead. Therefore, the intensities required to induce vibrations of the dry skull in water were significantly higher than the underwater hearing thresholds of the participants, under conditions when hearing by AC and osseous BC is not likely. The results support the hypothesis that hearing under water at low sound intensities may be attributed to nonosseous BC (STC). PMID:26770975

  15. Analysis of femtosecond quantum control mechanisms with colored double pulses

    SciTech Connect

    Vogt, Gerhard; Nuernberger, Patrick; Selle, Reimer; Dimler, Frank; Brixner, Tobias; Gerber, Gustav

    2006-09-15

    Fitness landscapes based on a limited number of laser pulse shape parameters can elucidate reaction pathways and can help to find the underlying control mechanism of optimal pulses determined by adaptive femtosecond quantum control. In a first experiment, we employ colored double pulses and systematically scan both the temporal subpulse separation and the relative amplitude of the two subpulses to acquire fitness landscapes. Comparison with results obtained from a closed-loop experiment demonstrates the capability of fitness landscapes for the revelation of possible control mechanisms. In a second experiment, using transient absorption spectroscopy, we investigate and compare the dependence of the excitation efficiency of the solvated dye molecule 5,5{sup '}-dichloro-11-diphenylamino-3,3{sup '}-diethyl-10,12-ethylene thiatricarbocyanine perchlorate (IR140) on selected pulse shapes in two parametrizations. The results show that very different pulse profiles can be equivalently adequate to maximize a given control objective. Fitness landscapes thus provide valuable information about different pathways along which a molecular system can be controlled with shaped laser pulses.

  16. Subgrain lath martensite mechanics: A numerical-experimental analysis

    NASA Astrophysics Data System (ADS)

    Maresca, F.; Kouznetsova, V. G.; Geers, M. G. D.

    2014-12-01

    Lath martensite reveals a specific hierarchical subgrain structure, with laths, blocks and packets of particular crystallography. The presence of interlath retained austenite layers has been reported in the literature. This paper investigates the potential influence of the interlath retained austenite on the mechanical behaviour of lath martensite subgrains. To this purpose, a martensite grain substructure is modelled using a crystal plasticity framework, with a BCC lath-FCC austenite bicrystal at the fine scale. The main novel contribution of this work is the validation of the hypothesis on the role of the interlath retained austenite in lath martensite using the experimental results reported in the literature. The main features of the experimentally observed deformation behaviour (stress-strain curve, slip activity and roughness pattern) are qualitatively well reproduced by the model. It is shown that the presence of austenite interlath films has the potential to remarkably enhance the local deformation of martensite. In spite of its minor volume fraction, it plays a major role in the orientation dependent mechanical behaviour of the aggregate. It is also shown that if the presence of interlath austenite is neglected, the observed experimental flow curves are not captured.

  17. Identification of possible cytotoxicity mechanism of polyethylenimine by proteomics analysis.

    PubMed

    Khansarizadeh, M; Mokhtarzadeh, A; Rashedinia, M; Taghdisi, S M; Lari, P; Abnous, K H; Ramezani, M

    2016-04-01

    Polyethylenimine (PEI) is a polycation widely used for successful gene delivery both in vitro and in vivo experiments. However, different studies showed that PEI could be cytotoxic to transfected cells, and the mechanism of toxicity is poorly understood. Identification of PEI-interacting proteins may help in understanding the toxicity pathways. In this study, we investigated proteins that could interact with PEI in human colorectal adenocarcinoma cells (HT29). In order to identify the proteins interacting with PEI, PEI was immobilized to sepharose beads as solid matrix. The HT29 cell lysate were passed through the matrix. PEI-bound proteins were isolated, and further separation was performed by two-dimensional gel electrophoresis. After gel digestion, proteins were identified by matrix-assisted laser desorption/ionization-time-of-flight (TOF)/TOF mass spectrometry. Our data indicated that most of the identified PEI-interacting proteins such as shock proteins, glutathione-S-transferases, and protein disulfide isomerase are involved in apoptosis process in cells. Thus, although this is a preliminary experiment implicating the involvement of some proteins in PEI cytotoxicity, it could partly explain the mechanism of PEI cytotoxicity in cells. PMID:26134983

  18. Some Aspects on the Mechanical Analysis of Micro-Shutters

    NASA Technical Reports Server (NTRS)

    Fettig, Rainer K.; Kuhn, Jonathan L.; Moseley, S. Harvey; Kutyrev, Alexander S.; Orloff, Jon; Lu, Shude

    1999-01-01

    An array of individually addressable micro-shutters is being designed for spectroscopic applications. Details of the design are presented in a companion paper. The mechanical design of a single shutter element has been completed. This design consists of a shutter blade suspended on a torsion beam manufactured out of single crystal silicon membranes. During operation the shutter blade will be rotated by 90 degrees out of the array plane. Thus, the stability and durability of the beams are crucial for the reliability of the devices. Structures were fabricated using focused ion beam milling in a FEI 620 dual beam machine, and subsequent testing was completed using the same platform. This allowed for short turn around times. We performed torsion and bending experiments to determine key characteristics of the membrane material. Results of measurements on prototype shutters were compared with the predictions of the numerical models. The data from these focused studies were used in conjunction with experiments and numerical models of shutter prototypes to optimize the design. In this work, we present the results of the material studies, and assess the mechanical performance of the resulting design.

  19. Failure mechanics of fiber composite notched charpy specimens. [stress analysis

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1976-01-01

    A finite element stress analysis was performed to determine the stress variation in the vicinity of the notch and far field of fiber composites Charpy specimens (ASTM Standard). NASTRAN was used for the finite element analysis assuming linear behavior and equivalent static load. The unidirectional composites investigated ranged from Thornel 75 Epoxy to S-Glass/Epoxy with the fiber direction parallel to the long dimension of the specimen. The results indicate a biaxial stress state exists in (1) the notch vicinity which is dominated by transverse tensile and interlaminar shear and (2) near the load application point which is dominated by transverse compression and interlaminar shear. The results also lead to the postulation of hypotheses for the predominant failure modes, the fracture initiation, and the fracture process. Finally, the results indicate that the notched Charpy test specimen is not suitable for assessing the impact resistance of nonmetallic fiber composites directly.

  20. Mechanical System Analysis/Design Tool (MSAT) Quick Guide

    NASA Technical Reports Server (NTRS)

    Lee, HauHua; Kolb, Mark; Madelone, Jack

    1998-01-01

    MSAT is a unique multi-component multi-disciplinary tool that organizes design analysis tasks around object-oriented representations of configuration components, analysis programs and modules, and data transfer links between them. This creative modular architecture enables rapid generation of input stream for trade-off studies of various engine configurations. The data transfer links automatically transport output from one application as relevant input to the next application once the sequence is set up by the user. The computations are managed via constraint propagation - the constraints supplied by the user as part of any optimization module. The software can be used in the preliminary design stage as well as during the detail design of product development process.

  1. Dynamic fracture mechanics analysis for an edge delamination crack

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Doyle, James F.

    1994-01-01

    A global/local analysis is applied to the problem of a panel with an edge delamination crack subject to an impulse loading to ascertain the dynamic J integral. The approach uses the spectral element method to obtain the global dynamic response and local resultants to obtain the J integral. The variation of J integral along the crack front is shown. The crack behavior is mixed mode (Mode 2 and Mode 3), but is dominated by the Mode 2 behavior.

  2. Estudo de soluções locais e cosmológicas em teorias do tipo tensor-escalar

    NASA Astrophysics Data System (ADS)

    Silva E Costa, S.

    2003-08-01

    Teorias do tipo tensor-escalar são a mais simples extensão possí vel da Relatividade Geral. Nessas teorias, cujo modelo padrão é a teoria de Brans-Dicke, a curvatura do espaço-tempo, descrita por componentes tensoriais, aparece acoplada a um campo escalar que, de certo modo, representa uma variação na constante de acoplamento da gravitação. Tais teorias apresentam soluções locais e cosmológicas que, em determinados limites, recaem nas apresentadas pela Relatividade Geral, mas que em outros limites trazem novidades, tais como conseqüências observacionais da evolução de flutuações primordiais distintas daquelas previstas pela Relatividade Geral (ver, por ex., Nagata et al., PRD 66, p. 103510 (2002)). Graças a esta possibilidade de trazer à luz novidades em relação à gravitação, teorias do tipo tensor-escalar podem ser vistas como um interessante campo alternativo de pesquisas para soluções dos problemas de massa faltante (ou escura) e/ou energia escura. Seguindo tal linha, este trabalho, ainda em sua fase inicial, apresenta soluções gerais de teorias do tipo tensor-escalar para diversas situações, verificando-se em que consiste a divergência dessas soluções dos casos tradicionais possí veis na Relatividade Geral. Como exemplos das soluções aqui apresentadas pode-se destacar uma expressão geral para diferentes soluções cosmológicas englobando diferentes tipos de matéria (representados por diferentes equações de estado), e a expressão para uma solução local representando um buraco negro com rotação, similar à solução de Kerr da Relatividade Geral. Por fim, é importante ressaltar que, embora aqui apresentem-se poucos resultados novos, na literatura sobre o assunto a maior parte das soluções apresentadas limita-se a uns poucos casos especí ficos, tal como soluções cosmológicas apenas com curvatura nula, e que mesmo as soluções disponí veis são, em geral, pouco divulgadas e, portanto, pouco conhecidas, e

  3. Analysis of Jovian decametric data: Study of radio emission mechanisms

    NASA Technical Reports Server (NTRS)

    Staelin, D. H.; Arias, T. A.

    1985-01-01

    Data gathered by the Voyager 1 and Voyager 2 Planetary Radio Astronomy Experiments (PRA) are unique in many ways including their frequency range, time resolution, polarization information and geometric characteristics. Studies of rapidly varying phenomena have thus far been hampered by paper display techniques which require large amounts of paper to exploit the full PRA time resolution. A software package capable of effectively displaying full 6s resolution PRA dynamic spectra on a high quality video monitor while compensating for the aforementioned variations was developed. The most striking phenomena revealed by the new display techniques is called Modulated Spectral Activity (MSA) because of its appearance in dynamic spectra as a series at least two parallel emission bands which drift back and forth in frequency on time scales of tens of seconds. In an attempt to locate and understand the MSA source mechanism, a catalogue has been compiled of the start and end of all known MSA events.

  4. Compatibility conditions of structural mechanics for finite element analysis

    NASA Technical Reports Server (NTRS)

    Patnaik, Surya N.; Berke, Laszlo; Gallagher, Richard H.

    1990-01-01

    The equilibrium equations and the compatibility conditions are fundamental to the analyses of structures. However, anyone who undertakes even a cursory generic study of the compatibility conditions can discover, with little effort, that historically this facet of structural mechanics had not been adequately researched by the profession. Now the compatibility conditions (CC's) have been researched and are understood to a great extent. For finite element discretizations, the CC's are banded and can be divided into three distinct categories: (1) the interface CC's; (2) the cluster or field CC's; and (3) the external CC's. The generation of CC's requires the separating of a local region, then writing the deformation displacement relation (ddr) for the region, and finally, the eliminating of the displacements from the ddr. The procedure to generate all three types of CC's is presented and illustrated through examples of finite element models. The uniqueness of the CC's thus generated is shown.

  5. Analysis of thermal mechanical fatigue in titanium matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. Steven; Mirdamadi, Massoud

    1993-01-01

    Titanium metal matrix composites are being evaluated for structural applications on advanced hypersonic vehicles. These composites are reinforced with ceramic fibers such as silicon carbide, SCS-6. This combination of matrix and fiber results in a high stiffness, high strength composite that has good retention of properties even at elevated temperatures. However, significant thermal stresses are developed within the composite between the fiber and the matrix due to the difference in their respective coefficients of thermal expansion. In addition to the internal stresses that are generated due to thermal cycling, the overall laminate will be subjected to considerable mechanical loads during the thermal cycling. In order to develop life prediction methodology, one must be able to predict the stresses and strains that occur in the composite's constituents during the complex loading. Thus the purpose is to describe such an analytical tool, VISCOPLY.

  6. [Exploration and analysis on the mechanism of sinew acupuncture].

    PubMed

    Liu, Nongyu

    2015-12-01

    In order to explore the mechanism of sinew acupuncture (SA), related literature is reviewed and analyzed in combination with clinical practice. It is believed that the clinical indications of SA mainly include sinew injury and sinew injury related diseases. Sinew and channel tissue is similar to the superficial and deep fascia, which has a close relationship with defensive qi. The pathogenesis of sinew injury results from the deficiency of defense qi, leading to stagnation of evil qi in sinew tissue. The manipulation of SA is featured with the floating and superficial needling, transverse needling at points without arrival of qi. SA treatment can activate the defense qi, regulate sinew and channels and disperse the evil qi in sinew and channels, by which it exerts therapeutic effects. The SA will have a promotion effects on acupuncture popularization. PMID:26964184

  7. Analysis of biomaterial latex-derived flow mechanical controller.

    PubMed

    Paula, Patricia M C; Rodrigues, Suelia S R; Brasil, Lourdes M; Silva, Rita C; da Rocha, Adson F

    2010-01-01

    This paper describes the basic guidelines for developing an innovative biomedical device. It covers the issues of researching about a suitable material, developing a new device, and testing its proprieties to check its effectiveness. The goal of the device is to control food flow into the esophagus, reducing its volume and the speed of food intake to help in the treatment of obesity. This module, called Esophageal Flow Controller (EFC®), is made of latex. Three different models of prototypes were developed, and 10 units of each model had their constructive and mechanical characteristics evaluated. All of them have followed the same manufacturing cycle. The results showed that the Esophageal Flow Control module has all the essential characteristics of an effective device for flow control in the esophagus. PMID:21096751

  8. Forebrain Mechanisms of Nociception and Pain: Analysis through Imaging

    NASA Astrophysics Data System (ADS)

    Casey, Kenneth L.

    1999-07-01

    Pain is a unified experience composed of interacting discriminative, affective-motivational, and cognitive components, each of which is mediated and modulated through forebrain mechanisms acting at spinal, brainstem, and cerebral levels. The size of the human forebrain in relation to the spinal cord gives anatomical emphasis to forebrain control over nociceptive processing. Human forebrain pathology can cause pain without the activation of nociceptors. Functional imaging of the normal human brain with positron emission tomography (PET) shows synaptically induced increases in regional cerebral blood flow (rCBF) in several regions specifically during pain. We have examined the variables of gender, type of noxious stimulus, and the origin of nociceptive input as potential determinants of the pattern and intensity of rCBF responses. The structures most consistently activated across genders and during contact heat pain, cold pain, cutaneous laser pain or intramuscular pain were the contralateral insula and anterior cingulate cortex, the bilateral thalamus and premotor cortex, and the cerebellar vermis. These regions are commonly activated in PET studies of pain conducted by other investigators, and the intensity of the brain rCBF response correlates parametrically with perceived pain intensity. To complement the human studies, we developed an animal model for investigating stimulus-induced rCBF responses in the rat. In accord with behavioral measures and the results of human PET, there is a progressive and selective activation of somatosensory and limbic system structures in the brain and brainstem following the subcutaneous injection of formalin. The animal model and human PET studies should be mutually reinforcing and thus facilitate progress in understanding forebrain mechanisms of normal and pathological pain.

  9. Thermal-mechanical coupled analysis of a brake disk rotor

    NASA Astrophysics Data System (ADS)

    Belhocine, Ali; Bouchetara, Mostefa

    2013-08-01

    The main purpose of this study is to analyze the thermomechanical behavior of the dry contact between the brake disk and pads during the braking phase. The simulation strategy is based on computer code ANSYS11. The modeling of transient temperature in the disk is actually used to identify the factor of geometric design of the disk to install the ventilation system in vehicles The thermal-structural analysis is then used with coupling to determine the deformation and the Von Mises stress established in the disk, the contact pressure distribution in pads. The results are satisfactory when compared to those of the specialized literature.

  10. Improved inhomogeneous finite elements for fabric reinforced composite mechanics analysis

    NASA Technical Reports Server (NTRS)

    Foye, R. L.

    1992-01-01

    There is a need to do routine stress/failure analysis of fabric reinforced composite microstructures to provide additional confidence in critical applications and guide materials development. Conventional methods of 3-D stress analysis are time consuming to set up, run and interpret. A need exists for simpler methods of modeling these structures and analyzing the models. The principal difficulty is the discrete element mesh generation problem. Inhomogeneous finite elements are worth investigating for application to these problems because they eliminate the mesh generation problem. However, there are penalties associated with these elements. Their convergence rates can be slow compared to homogeneous elements. Also, there is no accepted method for obtaining detailed stresses in the constituent materials of each element. This paper shows that the convergence rate can be significantly improved by a simple device which substitutes homogeneous elements for the inhomogeneous ones. The device is shown to work well in simple one and two dimensional problems. However, demonstration of the application to more complex two and three dimensional problems remains to be done. Work is also progressing toward more realistic fabric microstructural geometries.

  11. Endocrine-disrupting Chemicals: Review of Toxicological Mechanisms Using Molecular Pathway Analysis

    PubMed Central

    Yang, Oneyeol; Kim, Hye Lim; Weon, Jong-Il; Seo, Young Rok

    2015-01-01

    Endocrine disruptors are known to cause harmful effects to human through various exposure routes. These chemicals mainly appear to interfere with the endocrine or hormone systems. As importantly, numerous studies have demonstrated that the accumulation of endocrine disruptors can induce fatal disorders including obesity and cancer. Using diverse biological tools, the potential molecular mechanisms related with these diseases by exposure of endocrine disruptors. Recently, pathway analysis, a bioinformatics tool, is being widely used to predict the potential mechanism or biological network of certain chemicals. In this review, we initially summarize the major molecular mechanisms involved in the induction of the above mentioned diseases by endocrine disruptors. Additionally, we provide the potential markers and signaling mechanisms discovered via pathway analysis under exposure to representative endocrine disruptors, bisphenol, diethylhexylphthalate, and nonylphenol. The review emphasizes the importance of pathway analysis using bioinformatics to finding the specific mechanisms of toxic chemicals, including endocrine disruptors. PMID:25853100

  12. Hypolipidemic effect of safflower yellow and primary mechanism analysis.

    PubMed

    Bao, L D; Wang, Y; Ren, X H; Ma, R L; Lv, H J; Agula, B

    2015-01-01

    We examined the hypolipidemic effect of safflower yellow (SY) on hyperlipidemic mice and its influence on the biological synthesis of cholesterol in cells. Over 4 weeks, the levels of total cholesterol, triglyceride, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol in serum were detected using a kit; mouse liver samples were acquired for paraffin sections, and mouse liver cells were observed under light microscope. Chinese hamster ovary cells were cultured in vitro, and an amphotericin B-cell model was adopted to observe the inhibitory effect of SY on the biological synthesis of intracellular cholesterol. An enzyme-linked immunosorbent assay was used to detect the survival rate of Chinese hamster ovary cells. The middle and high doses of SY significantly reduced the levels of total cholesterol, triglycerides, and low-density lipoprotein cholesterol in the serum of hyperlipidemic mice and low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio (P < 0.05), and the fatty liver of hyperlipidemic mice was significantly alleviated. SY had a protective effect on Chinese hamster ovary cells following amphotericin B injury (P < 0.01). SY exerts significant hypolipidemic effects and prevents fatty liver in a mechanism associated with inhibition of the biosynthesis of intracellular cholesterol. PMID:26125829

  13. Proteomic analysis of the flooding tolerance mechanism in mutant soybean.

    PubMed

    Komatsu, Setsuko; Nanjo, Yohei; Nishimura, Minoru

    2013-02-21

    Flooding stress of soybean is a serious problem because it reduces growth; however, flooding-tolerant cultivars have not been identified. To analyze the flooding tolerance mechanism of soybean, the flooding-tolerant mutant was isolated and analyzed using a proteomic technique. Flooding-tolerance tests were repeated five times using gamma-ray irradiated soybeans, whose root growth (M6 stage) was not suppressed even under flooding stress. Two-day-old wild-type and mutant plants were subjected to flooding stress for 2days, and proteins were identified using a gel-based proteomic technique. In wild-type under flooding stress, levels of proteins related to development, protein synthesis/degradation, secondary metabolism, and the cell wall changed; however, these proteins did not markedly differ in the mutant. In contrast, an increased number of fermentation-related proteins were identified in the mutant under flooding stress. The root tips of mutant plants were not affected by flooding stress, even though the wild-type plants had damaged root. Alcohol dehydrogenase activity in the mutant increased at an early stage of flooding stress compared with that of the wild-type. Taken together, these results suggest that activation of the fermentation system in the early stages of flooding may be an important factor for the acquisition of flooding tolerance in soybean. PMID:23313221

  14. Mechanical and Infrared Thermography Analysis of Shape Memory Polyurethane

    NASA Astrophysics Data System (ADS)

    Pieczyska, Elzbieta Alicja; Maj, Michal; Kowalczyk-Gajewska, Katarzyna; Staszczak, Maria; Urbanski, Leszek; Tobushi, Hisaaki; Hayashi, Shunichi; Cristea, Mariana

    2014-07-01

    Multifunctional new material—polyurethane shape memory polymer (PU-SMP)—was subjected to tension carried out at room temperature at various strain rates. The influence of effects of thermomechanical couplings on the SMP mechanical properties was studied, based on the sample temperature changes, measured by a fast and sensitive infrared camera. It was found that the polymer deformation process strongly depends on the strain rate applied. The initial reversible strain is accompanied by a small drop in temperature, called thermoelastic effect. Its maximal value is related to the SMP yield point and increases upon increase of the strain rate. At higher strains, the stress and temperature significantly increase, caused by reorientation of the polymer molecular chains, followed by the stress drop and its subsequent increase accompanying the sample rupture. The higher strain rate, the higher stress, and temperature changes were obtained, since the deformation process was more dynamic and has occurred in almost adiabatic conditions. The constitutive model of SMP valid in finite strain regime was developed. In the proposed approach, SMP is described as a two-phase material composed of hyperelastic rubbery phase and elastic-viscoplastic glassy phase, while the volume content of phases is specified by the current temperature.

  15. Systems analysis of the CO2 concentrating mechanism in cyanobacteria

    PubMed Central

    Mangan, Niall M; Brenner, Michael P

    2014-01-01

    Cyanobacteria are photosynthetic bacteria with a unique CO2 concentrating mechanism (CCM), enhancing carbon fixation. Understanding the CCM requires a systems level perspective of how molecular components work together to enhance CO2 fixation. We present a mathematical model of the cyanobacterial CCM, giving the parameter regime (expression levels, catalytic rates, permeability of carboxysome shell) for efficient carbon fixation. Efficiency requires saturating the RuBisCO reaction, staying below saturation for carbonic anhydrase, and avoiding wasteful oxygenation reactions. We find selectivity at the carboxysome shell is not necessary; there is an optimal non-specific carboxysome shell permeability. We compare the efficacy of facilitated CO2 uptake, CO2 scavenging, and HCO3− transport with varying external pH. At the optimal carboxysome permeability, contributions from CO2 scavenging at the cell membrane are small. We examine the cumulative benefits of CCM spatial organization strategies: enzyme co-localization and compartmentalization. DOI: http://dx.doi.org/10.7554/eLife.02043.001 PMID:24842993

  16. Mechanical analysis of lightweight constructions manufactured with fused deposition modeling

    NASA Astrophysics Data System (ADS)

    Bagsik, A.; Josupeit, S.; Schoeppner, V.; Klemp, E.

    2014-05-01

    Additive production techniques have the advantage of manufacturing parts without needing a forming tool. One of the most used additive manufacturing processes is "Fused Deposition Modeling" (FDM) which allows the production of prototypes and end-use parts. Due to the manufacture layer by layer, also complex part geometries can be created in one working step. Furthermore, lightweight parts with specific inner core structures can be manufactured in order to achieve good weightrelated strength properties. In this paper the mechanical behavior of lightweight parts manufactured with the 3D production system Fortus 400mc from Stratasys and the material Polyetherimide (PEI) with the trade name Ultem*9085 is analyzed. The test specimens were built up with different inner structures and building directions. Therefore, test specimens with known lightweight core geometries (e.g. corrugated and honeycomb cores) were designed. A four-point bending test was conducted to analyze the strength properties as well as the weight-related strength properties. Additionally the influence of the structure width, the structure wall thickness and the top layer thickness was analyzed using a honeycomb structure.

  17. Fracture Mechanics Analysis of LH2 Feed Line Flow Liners

    NASA Technical Reports Server (NTRS)

    James, Mark A.; Dawicke, David S.; Brzowski, Matthew B.; Raju, Ivatury S.; Elliott, Kenny B.; Harris, Charles E.

    2006-01-01

    Inspections of the Space Shuttle Main Engine revealed fatigue cracks growing from slots in the flow liner of the liquid hydrogen (LH2) feed lines. During flight, the flow liners experience complex loading induced by flow of LH2 and the resonance characteristics of the structure. The flow liners are made of Inconel 718 and had previously not been considered a fracture critical component. However, fatigue failure of a flow liner could have catastrophic effect on the Shuttle engines. A fracture mechanics study was performed to determine if a damage tolerance approach to life management was possible and to determine the sensitivity to the load spectra, material properties, and crack size. The load spectra were derived separately from ground tests and material properties were obtained from coupon tests. The stress-intensity factors for the fatigue cracks were determined from a shell-dynamics approach that simulated the dominant resonant frequencies. Life predictions were obtained using the NASGRO life prediction code. The results indicated that adequate life could not be demonstrated for initial crack lengths of the size that could be detected by traditional NDE techniques.

  18. Fracture Mechanics Analysis of Stitched Stiffener-Skin Debonding

    NASA Technical Reports Server (NTRS)

    Glaessgen, E. H.; Raju, I. S.; Poe, C. C., Jr.

    1998-01-01

    An analysis based on plate finite elements and the virtual crack closure technique has been implemented to study the effect of stitching on mode I and mode II strain energy release rates for debond configurations. The stitches were modeled as discrete nonlinear fastener elements with a compliance determined by experiment. The axial and shear behavior of the stitches was considered, however, the two compliances and failure loads were assumed to be independent. Both a double cantilever beam (mode I) and a mixed mode skin-stiffener debond configuration were studied. In the double cantilever beam configurations, G(sub I) began to decrease once the debond had grown beyond the first row of stitches and was reduced to zero for long debonds. In the mixed-mode skin-stiffener configurations, G(sub I) showed a similar behavior as in the double cantilever beam configurations, however, G(sub u), continued to increase with increasing debond length.

  19. An Historical Perspective on the Theory and Practice of Soil Mechanical Analysis.

    ERIC Educational Resources Information Center

    Miller, W. P.; And Others

    1988-01-01

    Traces the history of soil mechanical analysis. Evaluates this history in order to place current concepts in perspective, from both a research and teaching viewpoint. Alternatives to traditional separation techniques for use in soils teaching laboratories are discussed. (TW)

  20. Mechanical Analysis of Cartilage Graft Reinforced with PDS Plate

    PubMed Central

    Conderman, Christian; Kinzinger, Michael; Manuel, Cyrus; Protsenko, Dmitry; Wong, Brian J. F.

    2014-01-01

    Objectives/Hypothesis This study attempts to characterize the biomechanical properties of a PDS-cartilage composite graft for use in septorhinoplasty. Study Design Experimental Study. Methods This study used a PDS analog, porcine cartilage cut to 1 × 5 × 20 mm, and a mechanical testing platform to measure flexure of a composite graft. Samples were assessed in four groups based on variations in suture pattern and orientation. The platform measured the force required to deflect the sample 2 mm in single cantilever beam geometry before and after the polymer was affixed to the specimen. Elastic Moduli were calculated before and after application of the polydioxanone polymer. Results The average modulus of the cartilage alone was 17 ± 0.9 MPa. The modulus of the composite cartilage-polymer graft with 2 suture fixation was 21.2 ± 1.5 MPa. The 3-suture configuration produced an increase to 25.8 ± 2.23 MPa. The four-suture configuration produced 23.1 ± 3.19 MPa. The five-suture configuration produced 25.7 ± 2.6 MPa. The modulus of the analog alone was 170 ± 30 MPa. The modulus of the 0.5 mm PDS was 692 ± 37.4 MPa. The modulus of the 0.15 mm perforated PDS was 447 ± 34.8 MPa. Conclusions The study found that suturing a polymer plate to cartilage resulted in enhanced stiffness of the composite. Under the conditions of the study, there was no significant difference in elastic moduli between suture configurations, making the two-suture linear configuration optimal in the one-plane cantilever deflection model. PMID:22965809

  1. Theoretical analysis of hydrogen spillover mechanism on carbon nanotubes

    PubMed Central

    Juarez-Mosqueda, Rosalba; Mavrandonakis, Andreas; Kuc, Agnieszka B.; Pettersson, Lars G. M.; Heine, Thomas

    2015-01-01

    The spillover mechanism of molecular hydrogen on carbon nanotubes in the presence of catalytically active platinum clusters was critically and systematically investigated by using density-functional theory. Our simulation model includes a Pt4 cluster for the catalyst nanoparticle and curved and planar circumcoronene for two exemplary single-walled carbon nanotubes (CNT), the (10,10) CNT and one of large diameter, respectively. Our results show that the H2 molecule dissociates spontaneously on the Pt4 cluster. However, the dissociated H atoms have to overcome a barrier of more than 2 eV to migrate from the catalyst to the CNT, even if the Pt4 cluster is at full saturation with six adsorbed and dissociated hydrogen molecules. Previous investigations have shown that the mobility of hydrogen atoms on the CNT surface is hindered by a barrier. We find that instead the Pt4 catalyst may move along the outer surface of the CNT with activation energy of only 0.16 eV, and that this effect offers the possibility of full hydrogenation of the CNT. Thus, although we have not found a low-energy pathway to spillover onto the CNT, we suggest, based on our calculations and calculated data reported in the literature, that in the hydrogen-spillover process the observed saturation of the CNT at hydrogen background pressure occurs through mobile Pt nanoclusters, which move on the substrate more easily than the substrate-chemisorbed hydrogens, and deposit or reattach hydrogens in the process. Initial hydrogenation of the carbon substrate, however, is thermodynamically unfavoured, suggesting that defects should play a significant role. PMID:25699250

  2. A unified approach to the analysis and design of elasto-plastic structures with mechanical contact

    NASA Technical Reports Server (NTRS)

    Bendsoe, Martin P.; Olhoff, Niels; Taylor, John E.

    1990-01-01

    With structural design in mind, a new unified variational model has been developed which represents the mechanics of deformation elasto-plasticity with unilateral contact conditions. For a design problem formulated as maximization of the load carrying capacity of a structure under certain constraints, the unified model allows for a simultaneous analysis and design synthesis for a whole range of mechanical behavior.

  3. Statistical mechanical modeling: Computer simulations, analysis and applications

    NASA Astrophysics Data System (ADS)

    Subramanian, Balakrishna

    This thesis describes the applications of statistical mechanical models and tools, especially computational techniques to the study of several problems in science. We study in chapter 2, various properties of a non-equilibrium cellular automaton model, the Toom model. We obtain numerically the exponents describing the fluctuations of the interface between the two stable phases of the model. In chapter 3, we introduce a binary alloy model with three-body potentials. Unlike the usual Ising-type models with two-body interactions, this model is not symmetric in its components. We calculate the exact low temperature phase diagram using Pirogov-Sinai theory and also find the mean-field equilibrium properties of this model. We then study the kinetics of phase segregation following a quenching in this model. We find that the results are very similar to those obtained for Ising-type models with pair interactions, indicating universality. In chapter 4, we discuss the statistical properties of "Contact Maps". These maps, are used to represent three-dimensional structures of proteins in modeling problems. We find that this representation space has particular properties that make it a convenient choice. The maps representing native folds of proteins correspond to compact structures which in turn correspond to maps with low degeneracy, making it easier to translate the map into the detailed 3-dimensional structure. The early stage of formation of a river network is described in Chapter 5 using quasi-random spanning trees on a square lattice. We observe that the statistical properties generated by these models are quite similar (better than some of the earlier models) to the empirical laws and results presented by geologists for real river networks. Finally, in chapter 6 we present a brief note on our study of the problem of progression of heterogeneous breast tumors. We investigate some of the possible pathways of progression based on the traditional notions of DCIS (Ductal

  4. Price Analysis of Railway Freight Transport under Marketing Mechanism

    NASA Astrophysics Data System (ADS)

    Shi, Ying; Fang, Xiaoping; Chen, Zhiya

    Regarding the problems in the reform of the railway tariff system and the pricing of the transport, by means of assaying the influence of the price elasticity on the artifice used for price, this article proposed multiple regressive model which analyzed price elasticity quantitatively. This model conclude multi-factors which influences on the price elasticity, such as the averagely railway freight charge, the averagely freight haulage of proximate supersede transportation mode, the GDP per capita in the point of origin, and a series of dummy variable which can reflect the features of some productive and consume demesne. It can calculate the price elasticity of different classes in different domains, and predict the freight traffic volume on different rate levels. It can calculate confidence-level, and evaluate the relevance of each parameter to get rid of irrelevant or little relevant variables. It supplied a good theoretical basis for directing the pricing of transport enterprises in market economic conditions, which is suitable for railway freight, passenger traffic and other transportation manner as well. SPSS (Statistical Package for the Social Science) software was used to calculate and analysis the example. This article realized the calculation by HYFX system(Ministry of Railways fund).

  5. Phosphoproteomic analysis reveals regulatory mechanisms at the kidney filtration barrier.

    PubMed

    Rinschen, Markus M; Wu, Xiongwu; König, Tim; Pisitkun, Trairak; Hagmann, Henning; Pahmeyer, Caroline; Lamkemeyer, Tobias; Kohli, Priyanka; Schnell, Nicole; Schermer, Bernhard; Dryer, Stuart; Brooks, Bernard R; Beltrao, Pedro; Krueger, Marcus; Brinkkoetter, Paul T; Benzing, Thomas

    2014-07-01

    Diseases of the kidney filtration barrier are a leading cause of ESRD. Most disorders affect the podocytes, polarized cells with a limited capacity for self-renewal that require tightly controlled signaling to maintain their integrity, viability, and function. Here, we provide an atlas of in vivo phosphorylated, glomerulus-expressed proteins, including podocyte-specific gene products, identified in an unbiased tandem mass spectrometry-based approach. We discovered 2449 phosphorylated proteins corresponding to 4079 identified high-confidence phosphorylated residues and performed a systematic bioinformatics analysis of this dataset. We discovered 146 phosphorylation sites on proteins abundantly expressed in podocytes. The prohibitin homology domain of the slit diaphragm protein podocin contained one such site, threonine 234 (T234), located within a phosphorylation motif that is mutated in human genetic forms of proteinuria. The T234 site resides at the interface of podocin dimers. Free energy calculation through molecular dynamic simulations revealed a role for T234 in regulating podocin dimerization. We show that phosphorylation critically regulates formation of high molecular weight complexes and that this may represent a general principle for the assembly of proteins containing prohibitin homology domains. PMID:24511133

  6. Damped Mechanical Oscillator: Experiment and Detailed Energy Analysis

    NASA Astrophysics Data System (ADS)

    Corridoni, Tommaso; D'Anna, Michele; Fuchs, Hans

    2014-02-01

    The damped oscillator is discussed in every high school textbook or introductory physics course, and a large number of papers are devoted to it in physics didactics journals. Papers typically focus on kinematic and dynamic aspects and less often on energy. Among the latter, some are devoted to the peculiar decreasing behavior of energy characterized by ripples, which can easily be demonstrated by using a dynamic modeling approach.8 In this note we consider an oscillator consisting of a cart running on a horizontal track, two springs, and a damping device created with magnets and a metal plate attached to the cart (Fig. 1). Using sensors and data-acquisition software,9 we measure kinematic quantities and three forces: those of the springs on the cart and, separately, the force between magnets and the plate. A detailed analysis of the energy exchanges between the cart and the interacting parts is obtained. In particular, we show that only the energy exchanges with the magnets are affected by dissipative processes while over a suitable time interval the net energy exchanged between cart and springs equals zero.

  7. [Analysis of synaptic neurotransmitter release mechanisms using bacterial toxins].

    PubMed

    Doussau, F; Humeau, Y; Vitiello, F; Popoff, M R; Poulain, B

    1999-01-01

    Several bacterial toxins are powerful and highly specific tools for studying basic mechanisms involved in cell biology. Whereas the clostridial neurotoxins are widely used by neurobiologists, many other toxins (i.e. toxins acting on small G-proteins or actin) are still overlooked. Botulinum neurotoxins (BoNT, serotypes A-G) and tetanus neurotoxin (TeNT), known under the generic term of clostridial neurotoxins, are characterized by their unique ability to selectively block neurotransmitter release. These proteins are formed of a light (Mr approximately 50) and a heavy (Mr approximately 100) chain which are disulfide linked. The cellular action of BoNT and TeNT involves several steps: heavy chain-mediated binding to the nerve ending membrane, endocytosis, and translocation of the light chain (their catalytic moiety) into the cytosol. The light chains each cleaves one of three, highly conserved, proteins (VAMP/synaptobrevin, syntaxin, and SNAP-25 also termed SNAREs) implicated in fusion of synaptic vesicles with plasma membrane at the release site. Hence, when these neurotoxins are applied extracellularly, they can be used as specific tools to inhibit evoked and spontaneous transmitter release from certain neurones whereas, when the membrane limiting steps are bypassed by the mean of intracellular applications, BoNTs orTeNT can be used to affect regulated secretion in various cell types. Several members of the Rho GTPase family have been involved in intracellular trafficking of synaptic vesicles and secretory organelles. As they are natural targets for several bacterial exoenzymes or cytotoxins, their role in neurotransmitter release can be probed by examining the action of these toxins on neurotransmission. Such toxins include: i) the non permeant C3 exoenzymes from C. botulinum or C. limosum which ADP-ribosylate and thereby inactivate Rho, ii) exoenzyme S from Pseudomonas aeruginosa which ADP-ribosylates different members of the Ras, Rab, Ral and Rap families, iii

  8. [Present status and trend of heart fluid mechanics research based on medical image analysis].

    PubMed

    Gan, Jianhong; Yin, Lixue; Xie, Shenghua; Li, Wenhua; Lu, Jing; Luo, Anguo

    2014-06-01

    With introduction of current main methods for heart fluid mechanics researches, we studied the characteristics and weakness for three primary analysis methods based on magnetic resonance imaging, color Doppler ultrasound and grayscale ultrasound image, respectively. It is pointed out that particle image velocity (PIV), speckle tracking and block match have the same nature, and three algorithms all adopt block correlation. The further analysis shows that, with the development of information technology and sensor, the research for cardiac function and fluid mechanics will focus on energy transfer process of heart fluid, characteristics of Chamber wall related to blood fluid and Fluid-structure interaction in the future heart fluid mechanics fields. PMID:25219260

  9. Analysis and modeling of resistive switching mechanisms oriented to resistive random-access memory

    NASA Astrophysics Data System (ADS)

    Huang, Da; Wu, Jun-Jie; Tang, Yu-Hua

    2013-03-01

    With the progress of the semiconductor industry, the resistive random-access memory (RAM) has drawn increasing attention. The discovery of the memristor has brought much attention to this study. Research has focused on the resistive switching characteristics of different materials and the analysis of resistive switching mechanisms. We discuss the resistive switching mechanisms of different materials in this paper and analyze the differences of those mechanisms from the view point of circuitry to establish their respective circuit models. Finally, simulations are presented. We give the prospect of using different materials in resistive RAM on account of their resistive switching mechanisms, which are applied to explain their resistive switchings.

  10. Analysis of the Resistance Mechanism of a Benzoxaborole Inhibitor Reveals Insight into the Leucyl-tRNA Synthetase Editing Mechanism.

    PubMed

    Zhao, Hanchao; Palencia, Andres; Seiradake, Elena; Ghaemi, Zhaleh; Cusack, Stephen; Luthey-Schulten, Zaida; Martinis, Susan

    2015-10-16

    A new class of antimicrobial benzoxaborole compounds was identified as a potent inhibitor of leucyl-tRNA synthetase (LeuRS) and therefore of protein synthesis. In a novel mechanism, AN2690 (5-fluoro-1,3-dihydro-1-hydroxy-2,1-benzoxaborole) blocks fungal cytoplasmic LeuRS by covalently trapping tRNA(Leu) in the editing site of the enzyme's CP1 domain. However, some resistant mutation sites are located outside of the CP1 hydrolytic editing active site. Thus, their mode of action that undermines drug inhibition was not understood. A combination of X-ray crystallography, molecular dynamics, metadynamics, biochemical experiments, and mutational analysis of a distal benzoxaborole-resistant mutant uncovered a eukaryote-specific tyrosine "switch" that is critical to tRNA-dependent post-transfer editing. The tyrosine "switch" has three states that shift between interactions with a lysine and the 3'-hydroxyl of the tRNA terminus, to inhibit or promote post-transfer editing. The oxaborole's mechanism of action capitalizes upon one of these editing active site states. This tunable editing mechanism in eukaryotic and archaeal LeuRSs is proposed to facilitate precise quality control of aminoacylation fidelity. These mechanistic distinctions could also be capitalized upon for development of the benzoxaboroles as a broad spectrum antibacterial. PMID:26172575

  11. NASGRO(registered trademark): Fracture Mechanics and Fatigue Crack Growth Analysis Software

    NASA Technical Reports Server (NTRS)

    Forman, Royce; Shivakumar, V.; Mettu, Sambi; Beek, Joachim; Williams, Leonard; Yeh, Feng; McClung, Craig; Cardinal, Joe

    2004-01-01

    This viewgraph presentation describes NASGRO, which is a fracture mechanics and fatigue crack growth analysis software package that is used to reduce risk of fracture in Space Shuttles. The contents include: 1) Consequences of Fracture; 2) NASA Fracture Control Requirements; 3) NASGRO Reduces Risk; 4) NASGRO Use Inside NASA; 5) NASGRO Components: Crack Growth Module; 6) NASGRO Components:Material Property Module; 7) Typical NASGRO analysis: Crack growth or component life calculation; and 8) NASGRO Sample Application: Orbiter feedline flowliner crack analysis.

  12. Disentangling the ambiguity of the lagged correlation function - analysis of the Walker circulation mechanism

    NASA Astrophysics Data System (ADS)

    Runge, Jakob; Kurths, Jürgen

    2013-04-01

    A first step towards the investigation of tropical climate variability and teleconnections is the analysis of observations. Lagged correlation analysis is commonly used to gain insights into interaction mechanisms between climatological processes, in particular to determine the time delay and strength of a mechanism. In this talk, such an analysis is discussed on the mechanism of the Walker circulation. The influence of serial correlation on lagged correlation functions and regressions is investigated and it is demonstrated how this influence can lead to ambiguous and misleading conclusions about the time delay and strength of an interaction mechanism. To overcome the issues arising in interpreting the lag and strength of a correlation, we propose to use graphical models that encode the lag-specific causality between multiple processes. In this framework a certain partial correlation measure is derived that allows to very specifically measure the time delay and strength of a coupling mechanism. This approach is then shown to yield a more precise picture of the interaction mechanism of the Walker circulation. The talk is intended to serve as a guideline to interpret lagged correlations and regressions and introduces a more powerful approach to analyze time delays and strengths of interaction mechanisms.

  13. Skeletal mechanism generation for surrogate fuels using directed relation graph with error propagation and sensitivity analysis

    SciTech Connect

    Niemeyer, Kyle E.; Sung, Chih-Jen; Raju, Mandhapati P.

    2010-09-15

    A novel implementation for the skeletal reduction of large detailed reaction mechanisms using the directed relation graph with error propagation and sensitivity analysis (DRGEPSA) is developed and presented with examples for three hydrocarbon components, n-heptane, iso-octane, and n-decane, relevant to surrogate fuel development. DRGEPSA integrates two previously developed methods, directed relation graph-aided sensitivity analysis (DRGASA) and directed relation graph with error propagation (DRGEP), by first applying DRGEP to efficiently remove many unimportant species prior to sensitivity analysis to further remove unimportant species, producing an optimally small skeletal mechanism for a given error limit. It is illustrated that the combination of the DRGEP and DRGASA methods allows the DRGEPSA approach to overcome the weaknesses of each, specifically that DRGEP cannot identify all unimportant species and that DRGASA shields unimportant species from removal. Skeletal mechanisms for n-heptane and iso-octane generated using the DRGEP, DRGASA, and DRGEPSA methods are presented and compared to illustrate the improvement of DRGEPSA. From a detailed reaction mechanism for n-alkanes covering n-octane to n-hexadecane with 2115 species and 8157 reactions, two skeletal mechanisms for n-decane generated using DRGEPSA, one covering a comprehensive range of temperature, pressure, and equivalence ratio conditions for autoignition and the other limited to high temperatures, are presented and validated. The comprehensive skeletal mechanism consists of 202 species and 846 reactions and the high-temperature skeletal mechanism consists of 51 species and 256 reactions. Both mechanisms are further demonstrated to well reproduce the results of the detailed mechanism in perfectly-stirred reactor and laminar flame simulations over a wide range of conditions. The comprehensive and high-temperature n-decane skeletal mechanisms are included as supplementary material with this article

  14. A perturbation analysis of a mechanical model for stable spatial patterning in embryology

    NASA Astrophysics Data System (ADS)

    Bentil, D. E.; Murray, J. D.

    1992-12-01

    We investigate a mechanical cell-traction mechanism that generates stationary spatial patterns. A linear analysis highlights the model's potential for these heterogeneous solutions. We use multiple-scale perturbation techniques to study the evolution of these solutions and compare our solutions with numerical simulations of the model system. We discuss some potential biological applications among which are the formation of ridge patterns, dermatoglyphs, and wound healing.

  15. Mechanical thrombectomy in patients with acute ischemic stroke: a cost-utility analysis

    PubMed Central

    Xie, Xuanqian; Lambrinos, Anna; Chan, Brian; Dhalla, Irfan A.; Krings, Timo; Casaubon, Leanne K.; Lum, Cheemun; Sikich, Nancy; Bharatha, Aditya; Pereira, Vitor Mendes; Stotts, Grant; Saposnik, Gustavo; O'Callaghan, Christina; Kelloway, Linda; Hill, Michael D.

    2016-01-01

    Background: The beneficial effects of endovascular treatment with new-generation mechanical thrombectomy devices compared with intravenous thrombolysis alone to treat acute large-artery ischemic stroke have been shown in randomized controlled trials (RCTs). This study aimed to estimate the cost utility of mechanical thrombectomy compared with the established standard of care. Methods: We developed a Markov decision process analytic model to assess the cost-effectiveness of treatment with mechanical thrombectomy plus intravenous thrombolysis versus treatment with intravenous thrombolysis alone from the public payer perspective in Canada. We conducted comprehensive literature searches to populate model inputs. We estimated the efficacy of mechanical thrombectomy plus intravenous thrombolysis from a meta-analysis of 5 RCTs, and we used data from the Oxford Vascular Study to model long-term clinical outcomes. We calculated incremental cost-effectiveness ratios (ICER) using a 5-year time horizon. Results: The base case analysis showed the cost and effectiveness of treatment with mechanical thrombectomy plus intravenous thrombolysis to be $126 939 and 1.484 quality-adjusted life-years (QALYs), respectively, and the cost and effectiveness of treatment with intravenous thrombolysis alone to be $124 419 and 1.273 QALYs, respectively. The mechanical thrombectomy plus intravenous thrombolysis strategy was associated with an ICER of $11 990 per QALY gained. Probabilistic sensitivity analysis showed that the probability of treatment with mechanical thrombectomy plus intravenous thrombolysis being cost-effective was 57.5%, 89.7% and 99.6% at thresholds of $20 000, $50 000 and $100 000 per QALY gained, respectively. The main factors influencing the ICER were time horizon, extra cost of mechanical thrombectomy treatment and age of the patient. Interpretation: Mechanical thrombectomy as an adjunct therapy to intravenous thrombolysis is cost-effective compared with

  16. Investigation on design and reliability analysis of a new deployable and lockable mechanism

    NASA Astrophysics Data System (ADS)

    Lin, Qing; Nie, Hong; Ren, Jie; Chen, Jinbao

    2012-04-01

    The traditional structure of the deployable and lockable mechanism on soft-landing gear system is complicated and unreliable. To overcome the defects, a new deployable and lockable mechanism for planetary probes is developed. The compression assembly shares a set of new mechanism with the deployment assembly and locking assembly. The new mechanism shows some advantages: more steady deployment, simpler mechanism and higher reliability. This paper presents an introduction of the deployment and locking theory of the new mechanism, and constitutes the fault tree, which would contribute to qualitative and quantitative analyses. In addition, probability importance and criticality importance of the new mechanism are derived and calculated. The reliability modeling and analysis of the mechanism are accomplished from static torque margin, torque and the work by torque. In investigation results, reliability rate that the new mechanism could deploy successfully is 0.999334. The crucial problems concentrate on the insufficiency of storage force torque of high strength spring, the lubrication failure between the inner cylinder and the outer cylinder of the strut and the stuck soft-landing gear system. And then, the paper presents some improvement approaches and suggestions according to the problems discussed above.

  17. Multiscale Thermo-Mechanical Design and Analysis of High Frequency and High Power Vacuum Electron Devices

    NASA Astrophysics Data System (ADS)

    Gamzina, Diana

    Diana Gamzina March 2016 Mechanical and Aerospace Engineering Multiscale Thermo-Mechanical Design and Analysis of High Frequency and High Power Vacuum Electron Devices Abstract A methodology for performing thermo-mechanical design and analysis of high frequency and high average power vacuum electron devices is presented. This methodology results in a "first-pass" engineering design directly ready for manufacturing. The methodology includes establishment of thermal and mechanical boundary conditions, evaluation of convective film heat transfer coefficients, identification of material options, evaluation of temperature and stress field distributions, assessment of microscale effects on the stress state of the material, and fatigue analysis. The feature size of vacuum electron devices operating in the high frequency regime of 100 GHz to 1 THz is comparable to the microstructure of the materials employed for their fabrication. As a result, the thermo-mechanical performance of a device is affected by the local material microstructure. Such multiscale effects on the stress state are considered in the range of scales from about 10 microns up to a few millimeters. The design and analysis methodology is demonstrated on three separate microwave devices: a 95 GHz 10 kW cw sheet beam klystron, a 263 GHz 50 W long pulse wide-bandwidth sheet beam travelling wave tube, and a 346 GHz 1 W cw backward wave oscillator.

  18. An improved path flux analysis with multi generations method for mechanism reduction

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Gou, Xiaolong

    2016-03-01

    An improved path flux analysis with a multi generations (IMPFA) method is proposed to eliminate unimportant species and reactions, and to generate skeletal mechanisms. The production and consumption path fluxes of each species at multiple reaction paths are calculated and analysed to identify the importance of the species and of the elementary reactions. On the basis of the indexes of each reaction path of the first, second, and third generations, the improved path flux analysis with two generations (IMPFA2) and improved path flux analysis with three generations (IMPFA3) are used to generate skeletal mechanisms that contain different numbers of species. The skeletal mechanisms are validated in the case of homogeneous autoignition and perfectly stirred reactor of methane and n-decane/air mixtures. Simulation results of the skeletal mechanisms generated by IMPFA2 and IMPFA3 are compared with those obtained by path flux analysis (PFA) with two and three generations, respectively. The comparisons of ignition delay times, final temperatures, and temperature dependence on flow residence time show that the skeletal mechanisms generated by the present IMPFA method are more accurate than those obtained by the PFA method, with almost the same number of species under a range of initial conditions. By considering the accuracy and computational efficiency, when using the IMPFA (or PFA) method, three generations may be the best choice for the reduction of large-scale detailed chemistry.

  19. Analysis of cause and mechanism for injection-induced seismicityat the Geysers Geothermal Field, California

    SciTech Connect

    Rutqvist, Jonny; Oldenburg, Curtis

    2007-06-14

    We analyzed relative contributions to the cause andmechanism of injection-induced seismicity at The Geysers geothermalfield, California, using coupled thermal-hydrological-mechanicalmodeling. Our analysis shows that the most important cause forinjection-induced seismicity is injection-induced cooling and associatedthermal-elastic shrinkage that changes the stress state in such a waythat mechanical failure and seismicity can be induced. Specifically, thecooling shrinkage results in unloading and associated loss of shearstrength in critically shear-stressed fractures, which are thenreactivated. Thus, our analysis shows that cooling-induced shear slipalong fractures is the dominant mechanism of injection-induced seismicityat The Geysers.

  20. Mechanical analysis of photo-electricity measure equipment shafting in mobile-platform

    NASA Astrophysics Data System (ADS)

    Jiang, Weiwei; Hu, Hongyi; Tan, Yi; Liu, Ruzhen

    2015-02-01

    Along with the development of technology, photo-electricity measure equipment has been from ground-fixed to mobile-platform borne, So it is need to mechanical analysis of shafting for adapt movement environment of mobile-platform. First listed three kinds of shafting form, then analysis mechanical station of the foremost component bearing in vertical load, radial load, swing load station, last work out the formulas, which was the theory for the shafting design in mobile-platforms photo-electricity equipment.

  1. A mechanism-based framework for the numerical analysis of creep in zircaloy-4

    NASA Astrophysics Data System (ADS)

    Wang, H.; Hu, Z.; Lu, W.; Thouless, M. D.

    2013-02-01

    A deformation-mechanism map has been developed for unirradiated zircaloy-4 based on the creep data available from the literature of the last 35 years. These data have been analyzed to identify different creep mechanisms, based on the forms of the relationships between stress, temperature and strain rate. This identification allowed the activation energies and other associated creep parameters to be derived for each mechanism. The creep parameters were used to construct a deformation-mechanism map for zircaloy-4 that shows the conditions under which different mechanisms are dominant. This information provides an important tool for assessing the effects of stress and temperature in design, especially when extrapolating to different regimes. As an example of how this information might be used in a numerical analysis for design purposes, a novel mechanism-based creep framework was implemented within a finite-element code. Although the framework was developed specifically for zircaloy-4, it provides a general example of how mechanism-based creep laws can be implemented into finite-element analyses. This approach allows the creep of complex geometries to be analyzed rigorously, with the dominant deformation mechanisms being identified and evolving automatically in response to the local temperatures and stresses.

  2. Postmodeling Sensitivity Analysis to Detect the Effect of Missing Data Mechanisms

    ERIC Educational Resources Information Center

    Jamshidian, Mortaza; Mata, Matthew

    2008-01-01

    Incomplete or missing data is a common problem in almost all areas of empirical research. It is well known that simple and ad hoc methods such as complete case analysis or mean imputation can lead to biased and/or inefficient estimates. The method of maximum likelihood works well; however, when the missing data mechanism is not one of missing…

  3. Analysis of bipolar linear circuit response mechanisms for high and low dose rate total dose irradiations

    SciTech Connect

    Barnaby, H.; Tausch, H.J.; Turfler, R.; Cole, P.; Baker, P.; Pease, R.L.

    1996-12-01

    A methodology is presented for the identification of circuit total dose response mechanisms in bipolar linear microcircuits irradiated at high and low dose rates. This methodology includes manual circuit analysis, circuit simulations with SPICE using extracted device parameters, and selective irradiations of portions of the circuit using a scanning electron microscope.

  4. Mechanical Analysis of the Nb3Sn Dipole Magnet HD1

    SciTech Connect

    Ferracin, Paolo; Bartlett, Scott E.; Caspi, Shlomo; Dietderich, Daniel R.; Gourlay, Steve A.; Hannaford, Charles R.; Hafalia, Aurelio R.; Lietzke, Alan F.; Mattafirri, Sara; Sabbi, Gianluca

    2005-06-01

    The Superconducting Magnet Group at Lawrence Berkeley National Laboratory (LBNL) has recently fabricated and tested HD1, a Nb3Sn dipole magnet. The magnet reached a 16 T field, and exhibited training quenches in the end regions and in the straight section. After the test, HD1 was disassembled and inspected, and a detailed 3D finite element mechanical analysis was done to investigate for possible quench triggers. The study led to minor modifications to mechanical structure and assembly procedure, which were verified in a second test (HD1b). This paper presents the results of the mechanical analysis, including strain gauge measurements and coil visual inspection. The adjustments implemented in the magnet structure are reported and their effect on magnet training discussed.

  5. Mechanical analysis of the Nb3Sn dipole magnet HD1

    SciTech Connect

    Ferracin, Paolo; Bartlett, Scott E.; Caspi, Shlomo; Dietderich,Daniel R.; Gourlay, Steve A.; Hannaford, Carles R.; Hafalia, Aurelio R.; Lietzke, Alan F.; Mattafirri, Sara; Sabbi, Gianluca

    2005-04-14

    The Superconducting Magnet Group at Lawrence Berkeley National Laboratory (LBNL) has recently fabricated and tested HD1, a Nb{sub 3}Sn dipole magnet. The magnet reached a 16 T field, and exhibited training quenches in the end regions and in the straight section. After the test, HD1 was disassembled and inspected, and a detailed 3D finite element mechanical analysis was done to investigate for possible quench triggers. The study led to minor modifications to mechanical structure and assembly procedure, which were verified in a second test (HD1b). This paper presents the results of the mechanical analysis, including strain gauge measurements and coil visual inspection. The adjustments implemented in the magnet structure are reported and their effect on magnet training discussed.

  6. Layerwise mechanics and finite element for the dynamic analysis of piezoelectric composite plates

    NASA Technical Reports Server (NTRS)

    Saravanos, Dimitris A.; Heyliger, Paul R.; Hopkins, Dale A.

    1996-01-01

    Laminate and structural mechanics for the analysis of laminated composite plate structures with piezoelectric actuators and sensors are presented. The theories implement layerwise representations of displacements and electric potential, and can model both the global and local electromechanical response of smart composite laminates. Finite-element formulations are developed for the quasi-static and dynamic analysis of smart composite structures containing piezoelectric layers. Comparisons with an exact solution illustrate the accuracy, robustness and capability of the developed mechanics to capture the global and local response of thin and/or thick laminated piezoelectric plates. Additional correlations and numerical applications demonstrate the unique capabilities of the mechanics in analyzing the static and free-vibration response of composite plates with distributed piezoelectric actuators and sensors.

  7. The research Of Multilayer Thermal Insulation With Mechanical Properties Based On Model Analysis Test

    NASA Astrophysics Data System (ADS)

    Lianhua, Yin

    The heat shield of aircraft is made of the major thrusts structure with multilayer thermal insulation part. For protecting against thermo-radiation from larger thrusting force engine,the heat shield is installed around this engine nearby.The multilayer thermal insulation part with multilayer radiation/reflection structure is made of reflection layer and interval layer.At vacuum condition,these materials is higher heat insulation capability than other material,is applied for lots of pats on aircraft extensively.But because of these material is made of metal and nonmetal,it is impossible to receive it's mechanical properties of materials from mechanical tests.These paper describes a new measure of mechanical properties of materials in the heat shield based on model analysis test.At the requirement for the first order lateral frequency,these measure provide for the FEM analysis foundation on the optimization structure of the heat shield.

  8. A Massively Parallel Solver for the Mechanical Harmonic Analysis of Accelerator Cavities

    SciTech Connect

    O. Kononenko

    2015-02-17

    ACE3P is a 3D massively parallel simulation suite that developed at SLAC National Accelerator Laboratory that can perform coupled electromagnetic, thermal and mechanical study. Effectively utilizing supercomputer resources, ACE3P has become a key simulation tool for particle accelerator R and D. A new frequency domain solver to perform mechanical harmonic response analysis of accelerator components is developed within the existing parallel framework. This solver is designed to determine the frequency response of the mechanical system to external harmonic excitations for time-efficient accurate analysis of the large-scale problems. Coupled with the ACE3P electromagnetic modules, this capability complements a set of multi-physics tools for a comprehensive study of microphonics in superconducting accelerating cavities in order to understand the RF response and feedback requirements for the operational reliability of a particle accelerator. (auth)

  9. User-defined Material Model for Thermo-mechanical Progressive Failure Analysis

    NASA Technical Reports Server (NTRS)

    Knight, Norman F., Jr.

    2008-01-01

    Previously a user-defined material model for orthotropic bimodulus materials was developed for linear and nonlinear stress analysis of composite structures using either shell or solid finite elements within a nonlinear finite element analysis tool. Extensions of this user-defined material model to thermo-mechanical progressive failure analysis are described, and the required input data are documented. The extensions include providing for temperature-dependent material properties, archival of the elastic strains, and a thermal strain calculation for materials exhibiting a stress-free temperature.

  10. Workspace Analysis and Optimization of 3-PUU Parallel Mechanism in Medicine Base on Genetic Algorithm.

    PubMed

    Hou, Yongchao; Zhao, Yang

    2015-01-01

    A novel 3-PUU parallel robot was put forward, on which kinematic analysis was conducted to obtain its inverse kinematics solution, and on this basis, the limitations of the sliding pair and the Hooke joint on the workspace were analyzed. Moreover, the workspace was solved through the three dimensional limit search method, and then optimization analysis was performed on the workspace of this parallel robot, which laid the foundations for the configuration design and further analysis of the parallel mechanism, with the result indicated that this type of robot was equipped with promising application prospect. In addition that, the workspace after optimization can meet more requirements of patients. PMID:26628930

  11. Analysis of an evaporator-condenser-separated mechanical vapor compression system

    NASA Astrophysics Data System (ADS)

    Wu, Hong; Li, Yulong; Chen, Jiang

    2013-04-01

    An evaporator-condenser-separated mechanical vapor compression (MVC) system was presented. The better effect of descaling and antiscaling was obtained by the new system. This study focused on the method of thermodynamic analysis, and the energy and exergy flow diagrams were established by using the first and second law of thermodynamics analysis. The results show that the energy utilization rate is very high and the specific power consumption is low. Exergy analysis indicates that the exergy efficiency is low, and the largest exergy loss occurs within the evaporator -condenser and the compressor.

  12. Workspace Analysis and Optimization of 3-PUU Parallel Mechanism in Medicine Base on Genetic Algorithm

    PubMed Central

    Hou, Yongchao; Zhao, Yang

    2015-01-01

    A novel 3-PUU parallel robot was put forward, on which kinematic analysis was conducted to obtain its inverse kinematics solution, and on this basis, the limitations of the sliding pair and the Hooke joint on the workspace were analyzed. Moreover, the workspace was solved through the three dimensional limit search method, and then optimization analysis was performed on the workspace of this parallel robot, which laid the foundations for the configuration design and further analysis of the parallel mechanism, with the result indicated that this type of robot was equipped with promising application prospect. In addition that, the workspace after optimization can meet more requirements of patients. PMID:26628930

  13. Mechanics unloading analysis and experimentation of a new type of parallel biomimetic shoulder complex

    NASA Astrophysics Data System (ADS)

    Hou, Yulei; Li, Zhisen; Wang, Yi; Zhang, Wenwen; Zeng, Daxing; Zhou, Yulin

    2016-06-01

    The structure design for high ratio of carrying capacity to deadweight is one of the challenges for the bionic mechanism, while the problem concerning high carrying capacity has not yet be solved for the existing shoulder complex. A new type biomimetic shoulder complex, which adopts 3-PSS/S(P for prismatic pair, S for spherical pair) spherical parallel mechanism (SPM), is proposed. The static equilibrium equations of each component are established by using the vector method and the equations for constrain forces with certain load are solved. Then the constrain force on the middle limb and that on the side limbs are compared in order to verify the unloading performance of the mechanism. In addition, the prototype mechanism of the shoulder complex is developed, and the force feedback experiment is conducted to verify the static analysis, which indicates that the middle limb suffers most of the external force and the effect of mechanics unloading is achieved. The 3-PSS/S spherical parallel mechanism is presented for the shoulder complex, and the realization of mechanics unloading is benefit for the improvement of the carrying capacity of the shoulder complex.

  14. Application of nanoscopic dynamic mechanical analysis for evaluating the mechanical behavior of hard tissues and bonded interfaces

    NASA Astrophysics Data System (ADS)

    Ryou, Heonjune

    2011-12-01

    In this study Dynamic Mechanical Analysis (DMA) was applied to dentin, the macro hybrid layer and intact hybrid layers of the bonded dental restorative interface using nanoindentation. Both intertubular and peritubular dentin were evaluated by DMA using discrete and scanning mode nanoindentation. The complex (E*), loss (E"), and storage (E') moduli were quantified over a range of indentation loads and scanning frequencies. The storage modulus of the peritubular cuff (22.19 GPa0.05). A model bonded interface (i.e. the macro hybrid) was evaluated using scanning DMA. A new approach for hydrating samples using ethylene glycol solution was developed and then applied to identify the importance of hydration on the measured properties. Fully hydrated samples exhibited mean values of E*, E' and E" of 3.54 GPa, 3.42 GPa and 0.86 GPa, respectively, whereas fully dehydrated samples exhibited values of 4.01 GPa, 3.88 GPa and 0.94 GPa, respectively. There were significant differences in the complex modulus (p<0.05) and storage modulus (p<0.001) between the hydrated and dehydrated conditions. However, differences in the loss moduli with hydration were not significantly different (p>0.05). A dynamic loading frequency of 100 Hz and scanning frequency of 0.2 Hz were identified to provide the most reliable results in scanning the collagen-based systems. Lastly, the optimal testing parameters obtained from studying the macro hybrid layer were used to evaluate intact resin-dentin bonded interfaces. The property maps clearly distinguished variations in properties as a function of the constituents. It was

  15. Critical analysis on degradation mechanism of dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Mohamad Shahimin, Mukhzeer; Suhaimi, Suriati; Abd Wahid, Mohd Halim; Retnasamy, Vithyacharan; Ahmad Hambali, Nor Azura Malini; Reshak, Ali Hussain

    2015-09-01

    This paper reports on a précis of degradation mechanism for dye-sensitized solar cell (DSSCs). The review indicates progress in the understanding of degradation mechanism, in particular, the large improvement in the analysis of the materials used in DSSCs. The paper discussed on the stability issues of the dye, advancement of the photoelectrode film lifetime, changes in the electrolyte components and degradation analysis of the counter electrode. The photoelectrochemical parameters were evaluated in view of the possible degradation routes via open circuit voltage (Voc), short circuit current (Isc), fill factor (FF) and overall conversion efficiency (η) from the current-voltage curve. This analysis covers several types of materials that have paved the way for better-performing solar cells and directly influenced the stability and reliability of DSSCs. The new research trend together with the previous research has been highlighted to examine the key challenges faced in developing the ultimate DSSCs.

  16. Analysis and inverse substructuring computation on dynamic quality of mechanical assembly

    NASA Astrophysics Data System (ADS)

    Lü, Guangqing; Yi, Chuijie; Fang, Ke

    2016-05-01

    Mechanical assembly has its own dynamic quality directly affecting the dynamic quality of whole product and should be considered in quality inspection and estimation of mechanical assembly. Based on functional relations between dynamic characteristics involved in mechanical assembly, the effects of assembling process on dynamic characteristics of substructural components of an assembly system are investigated by substructuring analysis. Assembly-coupling dynamic stiffness is clarified as the dominant factor of the effects and can be used as a quantitative measure of assembly dynamic quality. Two computational schemes using frequency response functions(FRFs) to determine the stiffness are provided and discussed by inverse substructuring analysis, including their applicable conditions and implementation procedure in application. Eigenvalue analysis on matrix-ratios of FRFs before and after assembling is employed and well validates the analytical outcomes and the schemes via both a lumped-parameter model and its analogic experimental counterpart. Applying the two schemes to inspect the dynamic quality provides the message of dynamic performance of the assembly system, and therefore improves conventional quality inspection and estimation of mechanical assembly in completeness.

  17. Analysis and inverse substructuring computation on dynamic quality of mechanical assembly

    NASA Astrophysics Data System (ADS)

    Lü, Guangqing; Yi, Chuijie; Fang, Ke

    2016-04-01

    Mechanical assembly has its own dynamic quality directly affecting the dynamic quality of whole product and should be considered in quality inspection and estimation of mechanical assembly. Based on functional relations between dynamic characteristics involved in mechanical assembly, the effects of assembling process on dynamic characteristics of substructural components of an assembly system are investigated by substructuring analysis. Assembly-coupling dynamic stiffness is clarified as the dominant factor of the effects and can be used as a quantitative measure of assembly dynamic quality. Two computational schemes using frequency response functions(FRFs) to determine the stiffness are provided and discussed by inverse substructuring analysis, including their applicable conditions and implementation procedure in application. Eigenvalue analysis on matrix-ratios of FRFs before and after assembling is employed and well validates the analytical outcomes and the schemes via both a lumped-parameter model and its analogic experimental counterpart. Applying the two schemes to inspect the dynamic quality provides the message of dynamic performance of the assembly system, and therefore improves conventional quality inspection and estimation of mechanical assembly in completeness.

  18. Biomechanical analysis of the human finger extensor mechanism during isometric pressing.

    PubMed

    Hu, Dan; Howard, David; Ren, Lei

    2014-01-01

    This study investigated the effects of the finger extensor mechanism on the bone-to-bone contact forces at the interphalangeal and metacarpal joints and also on the forces in the intrinsic and extrinsic muscles during finger pressing. This was done with finger postures ranging from very flexed to fully extended. The role of the finger extensor mechanism was investigated by using two alternative finger models, one which omitted the extensor mechanism and another which included it. A six-camera three-dimensional motion analysis system was used to capture the finger posture during maximum voluntary isometric pressing. The fingertip loads were recorded simultaneously using a force plate system. Two three-dimensional biomechanical finger models, a minimal model without extensor mechanism and a full model with extensor mechanism (tendon network), were used to calculate the joint bone-to-bone contact forces and the extrinsic and intrinsic muscle forces. If the full model is assumed to be realistic, then the results suggest some useful biomechanical advantages provided by the tendon network of the extensor mechanism. It was found that the forces in the intrinsic muscles (interosseus group and lumbrical) are significantly reduced by 22% to 61% due to the action of the extensor mechanism, with the greatest reductions in more flexed postures. The bone-to-bone contact force at the MCP joint is reduced by 10% to 41%. This suggests that the extensor mechanism may help to reduce the risk of injury at the finger joints and also to moderate the forces in intrinsic muscles. These apparent biomechanical advantages may be a result of the extensor mechanism's distinctive interconnected fibrous structure, through which the contraction of the intrinsic muscles as flexors of the MCP joint can generate extensions at the DIP and PIP joints. PMID:24732789

  19. Biomechanical Analysis of the Human Finger Extensor Mechanism during Isometric Pressing

    PubMed Central

    Hu, Dan; Howard, David; Ren, Lei

    2014-01-01

    This study investigated the effects of the finger extensor mechanism on the bone-to-bone contact forces at the interphalangeal and metacarpal joints and also on the forces in the intrinsic and extrinsic muscles during finger pressing. This was done with finger postures ranging from very flexed to fully extended. The role of the finger extensor mechanism was investigated by using two alternative finger models, one which omitted the extensor mechanism and another which included it. A six-camera three-dimensional motion analysis system was used to capture the finger posture during maximum voluntary isometric pressing. The fingertip loads were recorded simultaneously using a force plate system. Two three-dimensional biomechanical finger models, a minimal model without extensor mechanism and a full model with extensor mechanism (tendon network), were used to calculate the joint bone-to-bone contact forces and the extrinsic and intrinsic muscle forces. If the full model is assumed to be realistic, then the results suggest some useful biomechanical advantages provided by the tendon network of the extensor mechanism. It was found that the forces in the intrinsic muscles (interosseus group and lumbrical) are significantly reduced by 22% to 61% due to the action of the extensor mechanism, with the greatest reductions in more flexed postures. The bone-to-bone contact force at the MCP joint is reduced by 10% to 41%. This suggests that the extensor mechanism may help to reduce the risk of injury at the finger joints and also to moderate the forces in intrinsic muscles. These apparent biomechanical advantages may be a result of the extensor mechanism's distinctive interconnected fibrous structure, through which the contraction of the intrinsic muscles as flexors of the MCP joint can generate extensions at the DIP and PIP joints. PMID:24732789

  20. Research in progress in applied mathematics, numerical analysis, fluid mechanics, and computer science

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, fluid mechanics, and computer science during the period October 1, 1993 through March 31, 1994. The major categories of the current ICASE research program are: (1) applied and numerical mathematics, including numerical analysis and algorithm development; (2) theoretical and computational research in fluid mechanics in selected areas of interest to LaRC, including acoustics and combustion; (3) experimental research in transition and turbulence and aerodynamics involving LaRC facilities and scientists; and (4) computer science.

  1. Analysis and optimal design of an underactuated finger mechanism for LARM hand

    NASA Astrophysics Data System (ADS)

    Yao, Shuangji; Ceccarelli, Marco; Carbone, Giuseppe; Zhan, Qiang; Lu, Zhen

    2011-09-01

    This paper aims to present general design considerations and optimality criteria for underactuated mechanisms in finger designs. Design issues related to grasping task of robotic fingers are discussed. Performance characteristics are outlined as referring to several aspects of finger mechanisms. Optimality criteria of the finger performances are formulated after careful analysis. A general design algorithm is summarized and formulated as a suitable multi-objective optimization problem. A numerical case of an underactuated robot finger design for Laboratory of Robotics and Mechatronics (LARM) hand is illustrated with the aim to show the practical feasibility of the proposed concepts and computations.

  2. A poroviscohyperelastic model for numerical analysis of mechanical behavior of single chondrocyte.

    PubMed

    Nguyen, Trung Dung; Oloyede, Adekunle; Gu, Yuantong

    2016-01-01

    The aim of this paper is to use a poroviscohyperelastic (PVHE) model, which is developed based on the porohyperelastic (PHE) model to explore the mechanical deformation properties of single chondrocytes. Both creep and relaxation responses are investigated by using finite element analysis models of micropipette aspiration and atomic force microscopy experiments, respectively. The newly developed PVHE model is compared thoroughly with the standard neo-Hookean solid and PHE models. It has been found that the PVHE can accurately capture both creep and stress relaxation behaviors of chondrocytes better than other two models. Hence, the PVHE is a promising model to investigate mechanical properties of single chondrocytes. PMID:25588670

  3. Acoustical analysis of mechanical heart valve sounds for early detection of malfunction.

    PubMed

    Famaey, Nele; Defever, Korijn; Bielen, Paul; Flameng, Willem; Vander Sloten, Jos; Sas, Paul; Meuris, Bart

    2010-10-01

    Mechanical heart valves carry the disadvantage of lifelong antithrombotic therapy, due to the high risk of thrombus formation on the valve surface. Current diagnostic methods are incapable of detecting thrombus formation in an early stage. This article investigates a new diagnostic method, based on the analysis of the acoustic signal produced by the valve. This method should be capable of early detection of malfunction, thus permitting targeted medication and reducing valve-related complications and mortality. A measurement setup assuring optimal signal quality was developed, and a signal analysis program was implemented and validated on an in vitro mock circulatory loop. Next, four sheep were implanted with a bileaflet mechanical valve. The signals of their valves developing thrombosis were assessed on a weekly basis before explantation. Three sheep were sacrificed shortly after detection of malfunction according to the newly developed method. In each case, thrombus or membrane formation was detected on the leaflets upon explantation. In one sheep, no malfunction was found in the analysis, which was also confirmed by the condition of the valve upon explantation. These preliminary results indicate that acoustical analysis of mechanical heart valves permits early detection of valvular malfunction. Further research with more in vitro and animal testing is required to statistically validate these findings. PMID:20573536

  4. The slider motion error analysis by positive solution method in parallel mechanism

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoqing; Zhang, Lisong; Zhu, Liang; Yang, Wenguo; Hu, Penghao

    2016-01-01

    Motion error of slider plays key role in 3-PUU parallel coordinates measuring machine (CMM) performance and influence the CMM accuracy, which attracts lots of experts eyes in the world, Generally, the analysis method is based on the view of space 6-DOF. Here, a new analysis method is provided. First, the structure relation of slider and guideway can be abstracted as a 4-bar parallel mechanism. So, the sliders can be considered as moving platform in parallel kinematic mechanism PKM. Its motion error analysis is also transferred to moving platform position analysis in PKM. Then, after establishing the positive and negative solutions, some existed theory and technology for PKM can be applied to analyze slider straightness motion error and angular motion error simultaneously. Thirdly, some experiments by autocollimator are carried out to capture the original error data about guideway its own error, the data can be described as straightness error function by fitting curvilinear equation. Finally, the Straightness error of two guideways are considered as the variation of rod length in parallel mechanism, the slider's straightness error and angular error can be obtained by putting data into the established model. The calculated result is generally consistent with experiment result. The idea will be beneficial on accuracy calibration and error correction of 3-PUU CMM and also provides a new thought to analyze kinematic error of guideway in precision machine tool and precision instrument.

  5. Deflection Analysis of the Space Shuttle External Tank Door Drive Mechanism

    NASA Technical Reports Server (NTRS)

    Tosto, Michael A.; Trieu, Bo C.; Evernden, Brent A.; Hope, Drew J.; Wong, Kenneth A.; Lindberg, Robert E.

    2008-01-01

    Upon observing an abnormal closure of the Space Shuttle s External Tank Doors (ETD), a dynamic model was created in MSC/ADAMS to conduct deflection analyses of the Door Drive Mechanism (DDM). For a similar analysis, the traditional approach would be to construct a full finite element model of the mechanism. The purpose of this paper is to describe an alternative approach that models the flexibility of the DDM using a lumped parameter approximation to capture the compliance of individual parts within the drive linkage. This approach allows for rapid construction of a dynamic model in a time-critical setting, while still retaining the appropriate equivalent stiffness of each linkage component. As a validation of these equivalent stiffnesses, finite element analysis (FEA) was used to iteratively update the model towards convergence. Following this analysis, deflections recovered from the dynamic model can be used to calculate stress and classify each component s deformation as either elastic or plastic. Based on the modeling assumptions used in this analysis and the maximum input forcing condition, two components in the DDM show a factor of safety less than or equal to 0.5. However, to accurately evaluate the induced stresses, additional mechanism rigging information would be necessary to characterize the input forcing conditions. This information would also allow for the classification of stresses as either elastic or plastic.

  6. Finite element cochlea box model - Mechanical and electrical analysis of the cochlea

    NASA Astrophysics Data System (ADS)

    Nikolic, Milica; Teal, Paul D.; Isailovic, Velibor; Filipović, Nenad

    2015-12-01

    The primary role of the cochlea is to transform external sound stimuli into mechanical vibrations and then to neural impulses which are sent to the brain. A simplified cochlea box model was developed using the finite element method. Firstly, a mechanical model of the cochlea was analyzed. The box model consists of the basilar membrane and two fluid chambers - the scala vestibuli and scala tympani. The third chamber, the scala media, was neglected in the mechanical analysis. The best agreement with currently available analytical and experimental results was obtained when behavior of the fluid in the chambers was described using the wave acoustic equation and behavior of the basilar membrane was modeled with Newtonian dynamics. The obtained results show good frequency mapping. The second approach was to use an active model of the cochlea in which the Organ of Corti was included. The operation of the Organ of Corti involves the generation of current, caused by mechanical vibration. This current in turn causes a force applied to the basilar membrane, creating in this way an active feedback mechanism. A state space representation of the electro-mechanical model from existing literature was implemented and a first comparison with the finite element method is presented.

  7. Mechanical evaluation and fem analysis of stress in fixed partial dentures zirconium-ceramic

    PubMed Central

    CARDELLI, P.L.; VERTUCCI, V.; BALESTRA, F.; MONTANI, M.; ARCURI, C.

    2013-01-01

    SUMMARY Objective. Over the last several years, the Finite Element Analysis (FEM) has been widely recognized as a reference method in different fields of study, to simulate the distribution of mechanical stress, in order to evaluate the relative distribution of loads of different nature. The aim of this study is to investigate through the FEM analysis the stress distribution in fixed prostheses that have a core in Zirconia and a ceramic veneer supported by implants. Materials and methods. In this work we investigated the mechanical flexural strength of a ceramic material (Noritake®) and a of zirconium framework (Zircodent®) and the effects of the manufacturing processes of the material commonly performed during the production of fixed prostheses with CAD/CAM technology. Specifically three point bending mechanical tests were performed (three-point-bending) (1–3), using a machine from Test Equipment Instron 5566®, on two structures in zirconium framework-ceramic (structures supported by two implant abutments with pontic elements 1 and 2). A further in-depth analysis on the mechanical behavior in flexure of the specimens was conducted carrying out FEM studies in order to compare analog and digital data. Results. The analysis of the data obtained showed that the stresses are distributed in a different way according to the intrinsic elasticity of the structure. The analysis of FPD with four elements, the stresses are mainly concentrated on the surface of the load, while, in the FPD of three elements, much more rigid, the stresses are concentrated near the inner margins of the abutments. The concentration of many stresses in this point could be correlated to chipping (4) that is found in the outer edges of the structure, as a direct result of the ceramic brittleness which opposes the resilience of the structure subjected to bending. Conclusions. The analysis of the UY linear displacement confirms previous data, showing, in a numerical way, that the presence of the

  8. Automatic generation of skeletal mechanisms for ignition combustion based on level of importance analysis

    SciTech Connect

    Loevaas, Terese

    2009-07-15

    A level of importance (LOI) selection parameter is employed in order to identify species with general low importance to the overall accuracy of a chemical model. This enables elimination of the minor reaction paths in which these species are involved. The generation of such skeletal mechanisms is performed automatically in a pre-processing step ranking species according to their level of importance. This selection criterion is a combined parameter based on a time scale and sensitivity analysis, identifying both short lived species and species with respect to which the observable of interest has low sensitivity. In this work a careful element flux analysis demonstrates that such species do not interact in major reaction paths. Employing the LOI procedure replaces the previous method of identifying redundant species through a two step procedure involving a reaction flow analysis followed by a sensitivity analysis. The flux analysis is performed using DARS {sup copyright}, a digital analysis tool modelling reactive systems. Simplified chemical models are generated based on a detailed ethylene mechanism involving 111 species and 784 reactions (1566 forward and backward reactions) proposed by Wang et al. Eliminating species from detailed mechanisms introduces errors in the predicted combustion parameters. In the present work these errors are systematically studied for a wide range of conditions, including temperature, pressure and mixtures. Results show that the accuracy of simplified models is particularly lowered when the initial temperatures are close to the transition between low- and high-temperature chemistry. A speed-up factor of 5 is observed when using a simplified model containing only 27% of the original species and 19% of the original reactions. (author)

  9. In Situ Mechanical Analysis of Myofibrillar Perturbation and Aging on Soft, Bilayered Drosophila Myocardium

    PubMed Central

    Kaushik, Gaurav; Fuhrmann, Alexander; Cammarato, Anthony; Engler, Adam J.

    2011-01-01

    Drosophila melanogaster is a genetically malleable organism with a short life span, making it a tractable system in which to study mechanical effects of genetic perturbation and aging on tissues, e.g., impaired heart function. However, Drosophila heart-tube studies can be hampered by its bilayered structure: a ventral muscle layer covers the contractile cardiomyocytes. Here we propose an atomic force microscopy-based analysis that uses a linearized-Hertz method to measure individual mechanical components of soft composite materials. The technique was verified using bilayered polydimethylsiloxane. We further demonstrated its biological utility via its ability to resolve stiffness changes due to RNA interference to reduce myofibrillar content or due to aging in Drosophila myocardial layers. This protocol provides a platform to assess the mechanics of soft biological composite systems and, to our knowledge, for the first time, permits direct measurement of how genetic perturbations, aging, and disease can impact cardiac function in situ. PMID:22261050

  10. Atypical cytostatic mechanism of N-1-sulfonylcytosine derivatives determined by in vitro screening and computational analysis.

    PubMed

    Supek, Fran; Kralj, Marijeta; Marjanović, Marko; Suman, Lidija; Smuc, Tomislav; Krizmanić, Irena; Zinić, Biserka

    2008-04-01

    We have previously shown that N-1-sulfonylpyrimidine derivatives have strong antiproliferative activity on human tumor cell lines, whereby 1-(p-toluenesulfonyl)cytosine showed good selectivity with regard to normal cells and was easily synthesized on a large scale. In the present work we have used an interdisciplinary approach to elucidate the compounds' mechanistic class. An augmented number of cell lines (11) has allowed a computational search for compounds with similar activity profiles and/or mechanistic class by integrating our data with the comprehensive DTP-NCI database. We applied supervised machine learning methodology (Random Forest classifier), which offers information complementary to unsupervised algorithms commonly used for analysis of cytostatic activity profiles, such as self-organizing maps. The computational results taken together with cell cycle perturbation and apoptosis analysis of the cell lines point to an unusual mechanism of cytostatic action, possibly a combination of nucleic acid antimetabolite activity and a novel molecular mechanism. PMID:17898928

  11. Inverse thermoelastic analysis for thermal and mechanical loads identification using FBG data

    NASA Astrophysics Data System (ADS)

    Nakamura, Toshiya; Kamimura, Yukihiro; Igawa, Hirotaka; Morino, Yoshiki

    2014-12-01

    Fiber Bragg Grating (FBG) sensors have widely been used to monitor temperature and strain distributions as a part of the structural health monitoring system. Since FBG has the sensitivity to the variations in both temperature and strain, a compensation is required to separate the strain or temperature data from the sensor output which is the shift of the grating's Bragg wavelength. The present study develops a computational inverse thermoelastic analysis method to separately identify the thermal and mechanical boundary conditions (loads) from the output of the FBG sensor. Numerical study has been made for a corrugate-core sandwich integral thermal protection system (TPS) to examine the method. The discussion is focused on the computational stability. The results reveal that the identification of the mechanical load is less stable than that of the heat flux. It is also shown that the condition number of a coefficient matrix serves as the index of the stability of the inverse analysis.

  12. Mouse tetrad analysis provides insights into recombination mechanisms and hotspot evolutionary dynamics

    PubMed Central

    Cole, Francesca; Baudat, Frédéric; Grey, Corinne; Keeney, Scott; de Massy, Bernard; Jasin, Maria

    2014-01-01

    The ability to examine all chromatids from a single meiosis in yeast tetrads has been indispensable for defining mechanisms of homologous recombination initiated by DNA double-strand breaks (DSBs). Using a broadly applicable strategy for the analysis of chromatids from a single meiosis at two recombination hotspots in mouse oocytes and spermatocytes, we demonstrate here the unidirectional transfer of information — gene conversion — in both crossovers and noncrossovers. Whereas gene conversion in crossovers is associated with reciprocal exchange, the unbroken chromatid is not altered in noncrossover gene conversions, providing strong evidence that noncrossovers arise from a distinct pathway. Gene conversion frequently spares the binding site of the hotspot-specifying protein PRDM9 with the result that erosion of the hotspot is slowed. Thus, mouse tetrad analysis demonstrates how unique aspects of mammalian recombination mechanisms shape hotspot evolutionary dynamics. PMID:25151354

  13. OTU Deubiquitinases Reveal Mechanisms of Linkage Specificity and Enable Ubiquitin Chain Restriction Analysis

    PubMed Central

    Mevissen, Tycho E.T.; Hospenthal, Manuela K.; Geurink, Paul P.; Elliott, Paul R.; Akutsu, Masato; Arnaudo, Nadia; Ekkebus, Reggy; Kulathu, Yogesh; Wauer, Tobias; El Oualid, Farid; Freund, Stefan M.V.; Ovaa, Huib; Komander, David

    2013-01-01

    Summary Sixteen ovarian tumor (OTU) family deubiquitinases (DUBs) exist in humans, and most members regulate cell-signaling cascades. Several OTU DUBs were reported to be ubiquitin (Ub) chain linkage specific, but comprehensive analyses are missing, and the underlying mechanisms of linkage specificity are unclear. Using Ub chains of all eight linkage types, we reveal that most human OTU enzymes are linkage specific, preferring one, two, or a defined subset of linkage types, including unstudied atypical Ub chains. Biochemical analysis and five crystal structures of OTU DUBs with or without Ub substrates reveal four mechanisms of linkage specificity. Additional Ub-binding domains, the ubiquitinated sequence in the substrate, and defined S1’ and S2 Ub-binding sites on the OTU domain enable OTU DUBs to distinguish linkage types. We introduce Ub chain restriction analysis, in which OTU DUBs are used as restriction enzymes to reveal linkage type and the relative abundance of Ub chains on substrates. PMID:23827681

  14. [Mass Spectrometric Methods for Colorative Mechanism Analysis of Yaozhou Porcelain Glaze].

    PubMed

    Xiao, Yuan-fang; He, Miao-hong; Zhang, Shu-di; Hang, Wei

    2015-09-01

    An in-house-built femtosecond laser ionization time-of-flight mass spectrometry (fs-LI-TOFMS) has been applied to the multi-elemental analysis of porcelain glaze from Yaozhou kiln. The samples are selected representing products of different dynasties, including Tang, Five, Song, Jin, and Ming Dynasty. For exploring the colorative mechanism of Yaozhou porcelain through the elemental analysis of the glaze, the effects of all potential coloring elements, especially transition elements, were considered. There was a speculation that the typical Co-Cr-Fe-Mn recipe was used in the fabrication of Yaozhou black glaze; the low content of Fe and high content of Ni resulted in the porcelain of white glaze; an increase content of P could lead the porcelain to be yellow-glazed. Undoubtedly, this research is an important supplement to the study of the colorative mechanism of the Yaozhou porcelain system. PMID:26669145

  15. Application of Homotopy analysis method for mechanical model of deepwater SCR installation

    NASA Astrophysics Data System (ADS)

    You, Xiangcheng; Xu, Hang

    2012-09-01

    In this paper, considering the process of deepwater SCR installation with the limitations of small deformation theory of beam and catenary theory, a mechanical model of deepwater SCR installation is given based on large deformation beam model. In the following model, getting the relation of the length of the riser, bending stiffness and the unit weight by dimensional analysis, the simple approximate analytical expressions are obtained by using Homotopy Analysis Method. In the same condition, the calculated results are compared with the proposed approximate analytical expressions, the catenary theory or the commercial software of nonlinear finite element program ORCAFLEX. Hopefully, a convenient and effective method for mechanical model of deepwater SCR installation is provided.

  16. Code System for Fracture Mechanics Analysis of Circumferential Surface Cracks in Pipes.

    SciTech Connect

    BRUST, F.

    1999-07-28

    Version 00 The NRCPIPES software is designed to perform elastic and elastic-plastic fracture mechanics analysis for a circumferential surface cracked pipe, i.e., to establish the fracture-failure condition in terms of sustainable load (or stress) or displacement. The NRCPIPES software also includes several evaluation procedures and acceptance criteria for circumferential surface flaws based on the ASME Boiler and Pressure Vessel Code, Section XI criteria, the British R6 Revision 3 Option 1 criteria, and the original Net-Section-Collapse (limit-load) analysis.

  17. Network Analysis Reveals the Recognition Mechanism for Mannose-binding Lectins

    NASA Astrophysics Data System (ADS)

    Zhao, Yunjie; Jian, Yiren; Zeng, Chen; Computational Biophysics Lab Team

    The specific carbohydrate binding of mannose-binding lectin (MBL) protein in plants makes it a very useful molecular tool for cancer cell detection and other applications. The biological states of most MBL proteins are dimeric. Using dynamics network analysis on molecular dynamics (MD) simulations on the model protein of MBL, we elucidate the short- and long-range driving forces behind the dimer formation. The results are further supported by sequence coevolution analysis. We propose a general framework for deciphering the recognition mechanism underlying protein-protein interactions that may have potential applications in signaling pathways.

  18. Code System for Fracture Mechanics Analysis of Circumferential Surface Cracks in Pipes.

    Energy Science and Technology Software Center (ESTSC)

    1999-07-28

    Version 00 The NRCPIPES software is designed to perform elastic and elastic-plastic fracture mechanics analysis for a circumferential surface cracked pipe, i.e., to establish the fracture-failure condition in terms of sustainable load (or stress) or displacement. The NRCPIPES software also includes several evaluation procedures and acceptance criteria for circumferential surface flaws based on the ASME Boiler and Pressure Vessel Code, Section XI criteria, the British R6 Revision 3 Option 1 criteria, and the original Net-Section-Collapsemore » (limit-load) analysis.« less

  19. Thermo-mechanical analysis of LWR SiC/SiC composite cladding

    NASA Astrophysics Data System (ADS)

    Ben-Belgacem, M.; Richet, V.; Terrani, K. A.; Katoh, Y.; Snead, L. L.

    2014-04-01

    A dedicated framework for thermo-mechanical analysis of the in-pile performance of SiC/SiC composite fuel cladding concepts in LWRs has been developed. This analysis framework focuses on cladding and omits any fuel-cladding interaction and fuel behavior. Since radial expansion of the cladding occurs early in life for these ceramic structures, fuel-cladding contact is expected to be delayed or eliminated and therefore it is not considered in this analysis. The analysis inputs recent out-of-pile and in-pile materials property data and phenomenological understanding of material evolution under neutron irradiation for nuclear-grade SiC/SiC composites to provide a best-estimate analysis. The analysis provides insight into the concept design and feasibility of SiC/SiC composite cladding concepts that exhibit significantly different behavior than metallic cladding structures. In particular, absence of any tangible creep (thermal or irradiation) coupled with a large and temperature-gradient-driven irradiation swelling strain gradient across the cladding, drive development of large stresses across the cladding thickness. The resulting analysis indicates that significant stresses develop after a modest neutron dose (∼1 dpa) and a pronounced variation across the cladding thickness exists and is opposite to that observed for metallic cladding structures where swelling or growth strains are either negligible (with small temperature dependence) or absent. Following this thermo-mechanical analysis, a best-estimate and parametric examination of SiC/SiC fuel rod cladding structures has been performed using appropriate Weibull statistics to prescribe basic design guidelines and to begin to define a probable design space.

  20. Failure analysis of porcupine quills under axial compression reveals their mechanical response during buckling.

    PubMed

    Torres, Fernando G; Troncoso, Omar P; Diaz, John; Arce, Diego

    2014-11-01

    Porcupine quills are natural structures formed by a thin walled conical shell and an inner foam core. Axial compression tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) were all used to compare the characteristics and mechanical properties of porcupine quills with and without core. The failure mechanisms that occur during buckling were analyzed by scanning electron microscopy (SEM), and it was found that delamination buckling is mostly responsible for the decrease in the measured buckling stress of the quills with regard to predicted theoretical values. Our analysis also confirmed that the foam core works as an energy dissipater improving the mechanical response of an empty cylindrical shell, retarding the onset of buckling as well as producing a step wise decrease in force after buckling, instead of an instantaneous decrease in force typical for specimens without core. Cell collapse and cell densification in the inner foam core were identified as the key mechanisms that allow for energy absorption during buckling. PMID:25123434

  1. BATMAN-TCM: a Bioinformatics Analysis Tool for Molecular mechANism of Traditional Chinese Medicine

    PubMed Central

    Liu, Zhongyang; Guo, Feifei; Wang, Yong; Li, Chun; Zhang, Xinlei; Li, Honglei; Diao, Lihong; Gu, Jiangyong; Wang, Wei; Li, Dong; He, Fuchu

    2016-01-01

    Traditional Chinese Medicine (TCM), with a history of thousands of years of clinical practice, is gaining more and more attention and application worldwide. And TCM-based new drug development, especially for the treatment of complex diseases is promising. However, owing to the TCM’s diverse ingredients and their complex interaction with human body, it is still quite difficult to uncover its molecular mechanism, which greatly hinders the TCM modernization and internationalization. Here we developed the first online Bioinformatics Analysis Tool for Molecular mechANism of TCM (BATMAN-TCM). Its main functions include 1) TCM ingredients’ target prediction; 2) functional analyses of targets including biological pathway, Gene Ontology functional term and disease enrichment analyses; 3) the visualization of ingredient-target-pathway/disease association network and KEGG biological pathway with highlighted targets; 4) comparison analysis of multiple TCMs. Finally, we applied BATMAN-TCM to Qishen Yiqi dripping Pill (QSYQ) and combined with subsequent experimental validation to reveal the functions of renin-angiotensin system responsible for QSYQ’s cardioprotective effects for the first time. BATMAN-TCM will contribute to the understanding of the “multi-component, multi-target and multi-pathway” combinational therapeutic mechanism of TCM, and provide valuable clues for subsequent experimental validation, accelerating the elucidation of TCM’s molecular mechanism. BATMAN-TCM is available at http://bionet.ncpsb.org/batman-tcm. PMID:26879404

  2. BATMAN-TCM: a Bioinformatics Analysis Tool for Molecular mechANism of Traditional Chinese Medicine.

    PubMed

    Liu, Zhongyang; Guo, Feifei; Wang, Yong; Li, Chun; Zhang, Xinlei; Li, Honglei; Diao, Lihong; Gu, Jiangyong; Wang, Wei; Li, Dong; He, Fuchu

    2016-01-01

    Traditional Chinese Medicine (TCM), with a history of thousands of years of clinical practice, is gaining more and more attention and application worldwide. And TCM-based new drug development, especially for the treatment of complex diseases is promising. However, owing to the TCM's diverse ingredients and their complex interaction with human body, it is still quite difficult to uncover its molecular mechanism, which greatly hinders the TCM modernization and internationalization. Here we developed the first online Bioinformatics Analysis Tool for Molecular mechANism of TCM (BATMAN-TCM). Its main functions include 1) TCM ingredients' target prediction; 2) functional analyses of targets including biological pathway, Gene Ontology functional term and disease enrichment analyses; 3) the visualization of ingredient-target-pathway/disease association network and KEGG biological pathway with highlighted targets; 4) comparison analysis of multiple TCMs. Finally, we applied BATMAN-TCM to Qishen Yiqi dripping Pill (QSYQ) and combined with subsequent experimental validation to reveal the functions of renin-angiotensin system responsible for QSYQ's cardioprotective effects for the first time. BATMAN-TCM will contribute to the understanding of the "multi-component, multi-target and multi-pathway" combinational therapeutic mechanism of TCM, and provide valuable clues for subsequent experimental validation, accelerating the elucidation of TCM's molecular mechanism. BATMAN-TCM is available at http://bionet.ncpsb.org/batman-tcm. PMID:26879404

  3. BATMAN-TCM: a Bioinformatics Analysis Tool for Molecular mechANism of Traditional Chinese Medicine

    NASA Astrophysics Data System (ADS)

    Liu, Zhongyang; Guo, Feifei; Wang, Yong; Li, Chun; Zhang, Xinlei; Li, Honglei; Diao, Lihong; Gu, Jiangyong; Wang, Wei; Li, Dong; He, Fuchu

    2016-02-01

    Traditional Chinese Medicine (TCM), with a history of thousands of years of clinical practice, is gaining more and more attention and application worldwide. And TCM-based new drug development, especially for the treatment of complex diseases is promising. However, owing to the TCM’s diverse ingredients and their complex interaction with human body, it is still quite difficult to uncover its molecular mechanism, which greatly hinders the TCM modernization and internationalization. Here we developed the first online Bioinformatics Analysis Tool for Molecular mechANism of TCM (BATMAN-TCM). Its main functions include 1) TCM ingredients’ target prediction; 2) functional analyses of targets including biological pathway, Gene Ontology functional term and disease enrichment analyses; 3) the visualization of ingredient-target-pathway/disease association network and KEGG biological pathway with highlighted targets; 4) comparison analysis of multiple TCMs. Finally, we applied BATMAN-TCM to Qishen Yiqi dripping Pill (QSYQ) and combined with subsequent experimental validation to reveal the functions of renin-angiotensin system responsible for QSYQ’s cardioprotective effects for the first time. BATMAN-TCM will contribute to the understanding of the “multi-component, multi-target and multi-pathway” combinational therapeutic mechanism of TCM, and provide valuable clues for subsequent experimental validation, accelerating the elucidation of TCM’s molecular mechanism. BATMAN-TCM is available at http://bionet.ncpsb.org/batman-tcm.

  4. Fermilab Central Computing Facility: Energy conservation report and mechanical systems design optimization and cost analysis study

    SciTech Connect

    Krstulovich, S.F.

    1986-11-12

    This report is developed as part of the Fermilab Central Computing Facility Project Title II Design Documentation Update under the provisions of DOE Document 6430.1, Chapter XIII-21, Section 14, paragraph a. As such, it concentrates primarily on HVAC mechanical systems design optimization and cost analysis and should be considered as a supplement to the Title I Design Report date March 1986 wherein energy related issues are discussed pertaining to building envelope and orientation as well as electrical systems design.

  5. Fracture mechanics analysis of a high-pressure hydrogen facility compressor

    NASA Technical Reports Server (NTRS)

    Vroman, G. A.

    1974-01-01

    The investigation and analysis of a high-pressure hydrogen facility compressor is chronicled, and a life prediction based on fracture mechanics is presented. Crack growth rates in SA 105 Gr II steel are developed for the condition of sustained loading, using a hypothesis of hydrogen embrittlement associated with plastic zone reverse yielding. The resultant formula is compared with test data obtained from laboratory specimens.

  6. An electro-mechanical periodic system with piezoelectric transducers and coupled circuitry: dynamic analysis and applications

    NASA Astrophysics Data System (ADS)

    Lu, Y.; Tang, J.

    2010-04-01

    In this paper, we integrate piezoelectric transducers and coupled circuitry, which themselves form an electrical periodic system, onto a mechanical structure to form an electro-mechanical periodic system. The overall dynamics of the electro-mechanical system can thus be altered by tuning the electrical parameters. A transfer-matrix-based modeling technique is adopted in the dynamic analysis, where each element is represented by two state vectors at its both ends with a transfer matrix relating them. As the transfer matrix has the advantage on describing harmonic motions within the element, the global analysis can be facilitated given the repetitive nature of periodic systems. Numerical simulations are conducted to demonstrate the characteristics of wave propagation and attenuation in terms of propagation constants. Effects of each tunable parameter are also discussed through detailed parametric analysis. The proposed system can be tailored to various engineering needs. One example is adaptive vibration isolation with tunable effective frequency range. Another example is vibration energy harvesting through the piezoelectric transducers and circuitry.

  7. Systems analysis of the mechanisms of cardiac diastolic function changes after microgravity exposure

    NASA Astrophysics Data System (ADS)

    Summers, Richard; Coleman, Thomas; Steven, Platts; Martin, David

    Detailed information concerning cardiac function was collected by two-dimensional and M-mode echocardiography at 10 days before flight and 3h after landing in astronauts returning from shuttle missions. A comparative analysis of this data suggests that cardiac diastolic function is reduced after microgravity exposure with little or no change in systolic function as measured by ejection fraction However, the mechanisms responsible for these adaptations have not been determined. In this study, an integrative computer model of human physiology that forms the framework for the Digital Astronaut Project (Guyton/Coleman/Summers Model) was used in a systems analysis of the echocardiographic data in the context of general cardiovascular physiologic functioning. The physiologic mechanisms involved in the observed changes were then determined by a dissection of model interrelationships. The systems analysis of possible physiologic mechanisms involved reveals that a loss of fluid from the myocardial interstitial space may lead to a stiffening of the myocardium and could potentially result in some of the cardiac diastolic dysfunction seen postflight. The cardiovascular dynamics may be different during spaceflight.

  8. Network Analysis Shows Novel Molecular Mechanisms of Action for Copper-Based Chemotherapy

    PubMed Central

    Espinal-Enríquez, Jesús; Hernández-Lemus, Enrique; Mejía, Carmen; Ruiz-Azuara, Lena

    2016-01-01

    The understanding of the mechanisms associated with the action of chemotherapeutic agents is fundamental to assess and account for possible side-effects of such treatments. Casiopeínas have demonstrated a cytotoxic effect by activation of pro-apoptotic processes in malignant cells. Such processes have been proved to activate the apoptotic intrinsic route, as well as cell cycle arrest. Despite this knowledge, the whole mechanism of action of Casiopeínas is yet to be completely understood. In this work we implement a systems biology approach based on two pathway analysis tools (Over-Representation Analysis and Causal Network Analysis) to observe changes in some hallmarks of cancer, induced by this copper-based chemotherapeutic agent in HeLa cell lines. We find that the metabolism of metal ions is exacerbated, as well as cell division processes being globally diminished. We also show that cellular migration and proliferation events are decreased. Moreover, the molecular mechanisms of liver protection are increased in the cell cultures under the actions of Casiopeínas, unlike the case in many other cytotoxic drugs. We argue that this chemotherapeutic agent may be promising, given its protective hepatic function, concomitant with its cytotoxic participation in the onset of apoptotic processes in malignant cells. PMID:26793116

  9. Continuum Damage Mechanics Models for the Analysis of Progressive Failure in Open-Hole Tension Laminates

    NASA Technical Reports Server (NTRS)

    Song, Kyonchan; Li, Yingyong; Rose, Cheryl A.

    2011-01-01

    The performance of a state-of-the-art continuum damage mechanics model for interlaminar damage, coupled with a cohesive zone model for delamination is examined for failure prediction of quasi-isotropic open-hole tension laminates. Limitations of continuum representations of intra-ply damage and the effect of mesh orientation on the analysis predictions are discussed. It is shown that accurate prediction of matrix crack paths and stress redistribution after cracking requires a mesh aligned with the fiber orientation. Based on these results, an aligned mesh is proposed for analysis of the open-hole tension specimens consisting of different meshes within the individual plies, such that the element edges are aligned with the ply fiber direction. The modeling approach is assessed by comparison of analysis predictions to experimental data for specimen configurations in which failure is dominated by complex interactions between matrix cracks and delaminations. It is shown that the different failure mechanisms observed in the tests are well predicted. In addition, the modeling approach is demonstrated to predict proper trends in the effect of scaling on strength and failure mechanisms of quasi-isotropic open-hole tension laminates.

  10. Comparative Analysis of the Tour Jete and Aerial with Detailed Analysis of Aerial Takeoff Mechanics

    NASA Astrophysics Data System (ADS)

    Pierson, Mimi; Coplin, Kim

    2006-10-01

    Whether internally as muscle tension or from external sources, forces are necessary for all motion. This research focused on athletic rotations where conditions of flight are established during takeoff. By studying reaction forces that produce torques, moments of inertia, and linear and angular differences between distinct rotations around different principle axes of the body (tour jete in ballet - longitudinal axis; aerial in gymnastics - anteroposterior axis), and by looking at the values of angular momentum in the specific mechanics of aerial takeoff, we can gain insight into possible causes of injury, flaws in technique and limitations of athletes. Results showed significant differences in the horizontal and vertical components of takeoff between the tour jete and the aerial, and a realization that torque was produced in different biomechanical planes. Both rotations showed braking forces before takeoff to counteract forward momentum and increase vertical lift, but the angle of applied force varied, and the horizontal components of velocity and force and vertical velocity as well as moment of inertia throughout flight were consistently greater for the aerial. Breakdown of aerial takeoff highlighted the relative importance of the takeoff phases, showing that completion depends fundamentally upon the rotation of the rear foot and torso twisting during takeoff rather than the last foot in contact with the ground.

  11. Studies in photochemical smog chemistry. 1. Atmospheric chemistry of toulene. 2. Analysis of chemical reaction mechanisms for photochemical smog

    SciTech Connect

    Leone, J.A.

    1985-01-01

    This study focuses on two related topics in the gas phase organic chemistry of importance in urban air pollution. An experimental effort aimed at developing a new explicit reaction mechanism for the atmospheric photooxidation of toluene is described. This mechanism is tested using experimental data from both indoor and outdoor smog chamber facilities. The predictions of the new reaction mechanism are found to be in good agreement with both sets of experimental data. Additional simulations performed with the new mechanism are used to investigate various mechanistic paths. A theoretical analysis of lumped chemical reaction mechanisms for photochemical smog is presented. Included is a description of a new counter species analysis technique which can be used to analyze any complex chemical reaction mechanism. When applied to mechanisms for photochemical smog, this analysis is shown capable of providing answers to previously inaccessible questions such as the relative contributions of individual organics to photochemical ozone formation.

  12. Evaluation of a Post-Processing Approach for Multiscale Analysis of Biphasic Mechanics of Chondrocytes

    PubMed Central

    Sibole, Scott C.; Maas, Steve; Halloran, Jason P.; Weiss, Jeffrey A.; Erdemir, Ahmet

    2014-01-01

    Understanding the mechanical behavior of chondrocytes as a result of cartilage tissue mechanics has significant implications for both evaluation of mechanobiological function and to elaborate on damage mechanisms. A common procedure for prediction of chondrocyte mechanics (and of cell mechanics in general) relies on a computational post-processing approach where tissue level deformations drive cell level models. Potential loss of information in this numerical coupling approach may cause erroneous cellular scale results, particularly during multiphysics analysis of cartilage. The goal of this study was to evaluate the capacity of 1st and 2nd order data passing to predict chondrocyte mechanics by analyzing cartilage deformations obtained for varying complexity of loading scenarios. A tissue scale model with a sub-region incorporating representation of chondron size and distribution served as control. The postprocessing approach first required solution of a homogeneous tissue level model, results of which were used to drive a separate cell level model (same characteristics as the subregion of control model). The 1st data passing appeared to be adequate for simplified loading of the cartilage and for a subset of cell deformation metrics, e.g., change in aspect ratio. The 2nd order data passing scheme was more accurate, particularly when asymmetric permeability of the tissue boundaries were considered. Yet, the method exhibited limitations for predictions of instantaneous metrics related to the fluid phase, e.g., mass exchange rate. Nonetheless, employing higher-order data exchange schemes may be necessary to understand the biphasic mechanics of cells under lifelike tissue loading states for the whole time history of the simulation. PMID:23809004

  13. Dynamic mechanical thermal analysis of maxillofacial prosthetic elastomers: the effect of different disinfecting aging procedures.

    PubMed

    Eleni, Panagiota N; Krokida, Magdalini K; Polyzois, Gregory L; Gettleman, Lawrence

    2014-05-01

    In this study, dynamic mechanical thermal analysis was used to evaluate the changes that occurred in maxillofacial elastomers subjected to different disinfecting regimens. A commercial polydimethyl siloxane (PDMS) and an experimental chlorinated polyethylene (CPE) were treated with different disinfection procedures for a period that simulates 1 year of clinical service: microwave exposure (D1), hypochlorite solution (D2), neutral soap (D3), and a commercial disinfecting solution (D4). A fifth group was kept in dark storage as control. Dynamic mechanical thermal analysis tests operated in a fixed frequency (1 Hz) over a range of temperatures (-130°C to 20°C for PDMS, -60°C to 120°C for CPE). Loss modulus (G″), storage modulus (G'), and loss factor (tanδ) were recorded as a function of temperature. The obtained glass transition temperature (Tg) values were subjected to statistical analysis. Dynamic mechanical thermal analysis revealed changes in Tg values for both materials, which reflect the possible changes in their chemical and physical structure, after different disinfection procedures. The PDMS and CPE samples seem to have less dense structure maybe because of chain scission reaction that probably occurred during the disinfection procedures. According to statistical analysis, Tg values presented significant changes from the control samples among the different materials and disinfecting procedures. Microwave exposure and hypochlorite solution affect CPE significantly, whereas PDMS exhibited significant changes after being treated with a commercial antimicrobial agent, concerning changes that occurred in Tg. In all cases, Tg values were decreased compared with the untreated samples, which were stiffer, presenting higher Tg and G' values. PMID:24799103

  14. Gas-phase Ion Isomer Analysis Reveals the Mechanism of Peptide Sequence Scrambling

    PubMed Central

    Jia, Chenxi; Wu, Zhe; Lietz, Christopher B.; Liang, Zhidan; Cui, Qiang; Li, Lingjun

    2014-01-01

    Peptide sequence scrambling during mass spectrometry-based gas-phase fragmentation analysis causes misidentification of peptides and proteins. Thus, there is a need to develop an efficient approach to probing the gas-phase fragment ion isomers related to sequence scrambling and the underlying fragmentation mechanism, which will facilitate the development of bioinformatics algorithm for proteomics research. Herein, we report on the first use of electron transfer dissociation (ETD)-produced diagnostic fragment ions to probe the components of gas-phase peptide fragment ion isomers. In combination with ion mobility spectrometry (IMS) and formaldehyde labeling, this novel strategy enables qualitative and quantitative analysis of b-type fragment ion isomers. ETD fragmentation produced diagnostic fragment ions indicative of the precursor ion isomer components, and subsequent IMS analysis of b ion isomers provided their quantitative and structural information. The isomer components of three representative b ions (b9, b10, and b33 from three different peptides) were accurately profiled by this method. IMS analysis of the b9 ion isomers exhibited dynamic conversion among these structures. Furthermore, molecular dynamics simulation predicted theoretical drift time values which were in good agreement with experimentally measured values. Our results strongly support the mechanism of peptide sequence scrambling via b ion cyclization, and provide the first experimental evidence to support that the conversion from molecular precursor ion to cyclic b ion (M→cb) pathway is less energetically (or kinetically) favored. PMID:24313304

  15. Multifractal spectrum analysis of nonlinear dynamical mechanisms in China’s agricultural futures markets

    NASA Astrophysics Data System (ADS)

    Chen, Shu-Peng; He, Ling-Yun

    2010-04-01

    Based on Partition Function and Multifractal Spectrum Analysis, we investigated the nonlinear dynamical mechanisms in China’s agricultural futures markets, namely, Dalian Commodity Exchange (DCE for short) and Zhengzhou Commodity Exchange (ZCE for short), where nearly all agricultural futures contracts are traded in the two markets. Firstly, we found nontrivial multifractal spectra, which are the empirical evidence of the existence of multifractal features, in 4 representative futures markets in China, that is, Hard Winter wheat (HW for short) and Strong Gluten wheat (SG for short) futures markets from ZCE and Soy Meal (SM for short) futures and Soy Bean No.1 (SB for short) futures markets from DCE. Secondly, by shuffling the original time series, we destroyed the underlying nonlinear temporal correlation; thus, we identified that long-range correlation mechanism constitutes major contributions in the formation in the multifractals of the markets. Thirdly, by tracking the evolution of left- and right-half spectra, we found that there exist critical points, between which there are different behaviors, in the left-half spectra for large price fluctuations; but for the right-hand spectra for small price fluctuations, the width of those increases slowly as the delay t increases in the long run. Finally, the dynamics of large fluctuations is significantly different from that of the small ones, which implies that there exist different underlying mechanisms in the formation of multifractality in the markets. Our main contributions focus on that we not only provided empirical evidence of the existence of multifractal features in China agricultural commodity futures markets; but also we pioneered in investigating the sources of the multifractality in China’s agricultural futures markets in current literature; furthermore, we investigated the nonlinear dynamical mechanisms based on spectrum analysis, which offers us insights into the underlying dynamical mechanisms in

  16. Kinematic analysis of in situ measurement during chemical mechanical planarization process

    SciTech Connect

    Li, Hongkai; Wang, Tongqing; Zhao, Qian; Meng, Yonggang; Lu, Xinchun

    2015-10-15

    Chemical mechanical planarization (CMP) is the most widely used planarization technique in semiconductor manufacturing presently. With the aid of in situ measurement technology, CMP tools can achieve good performance and stable productivity. However, the in situ measurement has remained unexplored from a kinematic standpoint. The available related resources for the kinematic analysis are very limited due to the complexity and technical secret. In this paper, a comprehensive kinematic analysis of in situ measurement is provided, including the analysis model, the measurement trajectory, and the measurement time of each zone of wafer surface during the practical CMP process. In addition, a lot of numerical calculations are performed to study the influences of main parameters on the measurement trajectory and the measurement velocity variation of the probe during the measurement process. All the efforts are expected to improve the in situ measurement system and promote the advancement in CMP control system.

  17. Nonlinear dynamic mechanism of vocal tremor from voice analysis and model simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Jiang, Jack J.

    2008-09-01

    Nonlinear dynamic analysis and model simulations are used to study the nonlinear dynamic characteristics of vocal folds with vocal tremor, which can typically be characterized by low-frequency modulation and aperiodicity. Tremor voices from patients with disorders such as paresis, Parkinson's disease, hyperfunction, and adductor spasmodic dysphonia show low-dimensional characteristics, differing from random noise. Correlation dimension analysis statistically distinguishes tremor voices from normal voices. Furthermore, a nonlinear tremor model is proposed to study the vibrations of the vocal folds with vocal tremor. Fractal dimensions and positive Lyapunov exponents demonstrate the evidence of chaos in the tremor model, where amplitude and frequency play important roles in governing vocal fold dynamics. Nonlinear dynamic voice analysis and vocal fold modeling may provide a useful set of tools for understanding the dynamic mechanism of vocal tremor in patients with laryngeal diseases.

  18. Mechanism of Xinfeng Capsule on Adjuvant-Induced Arthritis via Analysis of Urinary Metabolomic Profiles

    PubMed Central

    Jiang, Hui; Liu, Jian; Wang, Ting; Gao, Jia-rong; Sun, Yue; Huang, Chuan-bing; Meng, Mei; Qin, Xiu-juan

    2016-01-01

    We aimed to explore the potential effects of Xinfeng capsule (XFC) on urine metabolic profiling in adjuvant-induced arthritis (AA) rats by using gas chromatography time-of-flight mass spectrometry (GC-TOF/MS). GC-TOF/MS technology was combined with multivariate statistical approaches, such as principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and orthogonal projections to latent structures discriminant analysis (OPLS-DA). These methods were used to distinguish the healthy group, untreated group, and XFC treated group and elucidate potential biomarkers. Nine potential biomarkers such as hippuric acid, adenine, and L-dopa were identified as potential biomarkers, indicating that purine metabolism, fat metabolism, amino acid metabolism, and energy metabolism were disturbed in AA rats. This study demonstrated that XFC is efficacious for RA and explained its potential metabolomics mechanism. PMID:26989506

  19. The design and realisation of the IXV Mission Analysis and Flight Mechanics

    NASA Astrophysics Data System (ADS)

    Haya-Ramos, Rodrigo; Blanco, Gonzalo; Pontijas, Irene; Bonetti, Davide; Freixa, Jordi; Parigini, Cristina; Bassano, Edmondo; Carducci, Riccardo; Sudars, Martins; Denaro, Angelo; Angelini, Roberto; Mancuso, Salvatore

    2016-07-01

    The Intermediate eXperimental Vehicle (IXV) is a suborbital re-entry demonstrator successfully launched in February 2015 focusing on the in-flight demonstration of a lifting body system with active aerodynamic control surfaces. This paper presents an overview of the Mission Analysis and Flight Mechanics of the IXV vehicle, which comprises computation of the End-to-End (launch to splashdown) design trajectories, characterisation of the Entry Corridor, assessment of the Mission Performances through Monte Carlo campaigns, contribution to the aerodynamic database, analysis of the Visibility and link budget from Ground Stations and GPS, support to safety analyses (off nominal footprints), specification of the Centre of Gravity box, selection of the Angle of Attack trim line to be flown and characterisation of the Flying Qualities performances. An initial analysis and comparison with the raw flight data obtained during the flight will be discussed and first lessons learned derived.

  20. Nanoscale Structural and Mechanical Analysis of Bacillus anthracis Spores Inactivated with Rapid Dry Heating

    PubMed Central

    Felker, Daniel L.; Burggraf, Larry W.

    2014-01-01

    Effective killing of Bacillus anthracis spores is of paramount importance to antibioterrorism, food safety, environmental protection, and the medical device industry. Thus, a deeper understanding of the mechanisms of spore resistance and inactivation is highly desired for developing new strategies or improving the known methods for spore destruction. Previous studies have shown that spore inactivation mechanisms differ considerably depending upon the killing agents, such as heat (wet heat, dry heat), UV, ionizing radiation, and chemicals. It is believed that wet heat kills spores by inactivating critical enzymes, while dry heat kills spores by damaging their DNA. Many studies have focused on the biochemical aspects of spore inactivation by dry heat; few have investigated structural damages and changes in spore mechanical properties. In this study, we have inactivated Bacillus anthracis spores with rapid dry heating and performed nanoscale topographical and mechanical analysis of inactivated spores using atomic force microscopy (AFM). Our results revealed significant changes in spore morphology and nanomechanical properties after heat inactivation. In addition, we also found that these changes were different under different heating conditions that produced similar inactivation probabilities (high temperature for short exposure time versus low temperature for long exposure time). We attributed the differences to the differential thermal and mechanical stresses in the spore. The buildup of internal thermal and mechanical stresses may become prominent only in ultrafast, high-temperature heat inactivation when the experimental timescale is too short for heat-generated vapor to efficiently escape from the spore. Our results thus provide direct, visual evidences of the importance of thermal stresses and heat and mass transfer to spore inactivation by very rapid dry heating. PMID:24375142

  1. Finite element analysis of mechanics of neovessels with intraplaque hemorrhage in carotid atherosclerosis

    PubMed Central

    2015-01-01

    Background Intraplaque hemorrhage is a widely known factor facilitating plaque instability. Neovascularization of plaque can be regarded as a compensatory response to the blood supply in the deep intimal and medial areas of the artery. Due to the physiological function, the deformation of carotid atherosclerotic plaque would happen under the action of blood pressure and blood flow. Neovessels are subject to mechanical loading and likely undergo deformation. The rupture of neovessels may deteriorate the instability of plaque. This study focuses on the local mechanical environments around neovessels and investigates the relationship between the biomechanics and the morphological specificity of neovessels. Methods Stress and stretch were used to evaluate the rupture risk of the neovessels in plaque. Computational structural analysis was performed based on two human carotid plaque slice samples. Two-dimensional models containing neovessels and other components were built according to the plaque slice samples. Each component was assumed to be non-linear isotropic, piecewise homogeneous and incompressible. Different mechanical boundary conditions, i.e. static pressures, were imposed in the carotid lumen and neovessels lumen respectively. Finite element method was used to simulate the mechanical conditions in the atherosclerotic plaque. Results Those neovessels closer to the carotid lumen undergo larger stress and stretch. With the same distance to the carotid lumen, the longer the perimeter of neovessels is, the larger stress and the deformation of the neovessels will be. Under the same conditions, the neovessels with larger curvature suffer greater stress and stretch. Neovessels surrounded by red blood cells undergo a much larger stretch. Conclusions Local mechanical conditions may result in the hemorrhage of neovessels and accelerate the rupture of plaque. The mechanical environments of the neovessel are related to its shape, curvature, distance to the carotid lumen

  2. Nanoscale structural and mechanical analysis of Bacillus anthracis spores inactivated with rapid dry heating.

    PubMed

    Xing, Yun; Li, Alex; Felker, Daniel L; Burggraf, Larry W

    2014-03-01

    Effective killing of Bacillus anthracis spores is of paramount importance to antibioterrorism, food safety, environmental protection, and the medical device industry. Thus, a deeper understanding of the mechanisms of spore resistance and inactivation is highly desired for developing new strategies or improving the known methods for spore destruction. Previous studies have shown that spore inactivation mechanisms differ considerably depending upon the killing agents, such as heat (wet heat, dry heat), UV, ionizing radiation, and chemicals. It is believed that wet heat kills spores by inactivating critical enzymes, while dry heat kills spores by damaging their DNA. Many studies have focused on the biochemical aspects of spore inactivation by dry heat; few have investigated structural damages and changes in spore mechanical properties. In this study, we have inactivated Bacillus anthracis spores with rapid dry heating and performed nanoscale topographical and mechanical analysis of inactivated spores using atomic force microscopy (AFM). Our results revealed significant changes in spore morphology and nanomechanical properties after heat inactivation. In addition, we also found that these changes were different under different heating conditions that produced similar inactivation probabilities (high temperature for short exposure time versus low temperature for long exposure time). We attributed the differences to the differential thermal and mechanical stresses in the spore. The buildup of internal thermal and mechanical stresses may become prominent only in ultrafast, high-temperature heat inactivation when the experimental timescale is too short for heat-generated vapor to efficiently escape from the spore. Our results thus provide direct, visual evidences of the importance of thermal stresses and heat and mass transfer to spore inactivation by very rapid dry heating. PMID:24375142

  3. On the continuum mechanics approach for the analysis of single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chaudhry, M. S.; Czekanski, A.

    2016-04-01

    Today carbon nanotubes have found various applications in structural, thermal and almost every field of engineering. Carbon nanotubes provide great strength, stiffness resilience properties. Evaluating the structural behavior of nanoscale materials is an important task. In order to understand the materialistic behavior of nanotubes, atomistic models provide a basis for continuum mechanics modelling. Although the properties of bulk materials are consistent with the size and depends mainly on the material but the properties when we are in Nano-range, continuously change with the size. Such models start from the modelling of interatomic interaction. Modelling and simulation has advantage of cost saving when compared with the experiments. So in this project our aim is to use a continuum mechanics model of carbon nanotubes from atomistic perspective and analyses some structural behaviors of nanotubes. It is generally recognized that mechanical properties of nanotubes are dependent upon their structural details. The properties of nanotubes vary with the varying with the interatomic distance, angular orientation, radius of the tube and many such parameters. Based on such models one can analyses the variation of young's modulus, strength, deformation behavior, vibration behavior and thermal behavior. In this study some of the structural behaviors of the nanotubes are analyzed with the help of continuum mechanics models. Using the properties derived from the molecular mechanics model a Finite Element Analysis of carbon nanotubes is performed and results are verified. This study provides the insight on continuum mechanics modelling of nanotubes and hence the scope to study the effect of various parameters on some structural behavior of nanotubes.

  4. Deep-sequencing transcriptome analysis of chilling tolerance mechanisms of a subnival alpine plant, Chorispora bungeana

    PubMed Central

    2012-01-01

    Background The plant tolerance mechanisms to low temperature have been studied extensively in the model plant Arabidopsis at the transcriptional level. However, few studies were carried out in plants with strong inherited cold tolerance. Chorispora bungeana is a subnival alpine plant possessing strong cold tolerance mechanisms. To get a deeper insight into its cold tolerance mechanisms, the transcriptome profiles of chilling-treated C. bungeana seedlings were analyzed by Illumina deep-sequencing and compared with Arabidopsis. Results Two cDNA libraries constructed from mRNAs of control and chilling-treated seedlings were sequenced by Illumina technology. A total of 54,870 unigenes were obtained by de novo assembly, and 3,484 chilling up-regulated and 4,571 down-regulated unigenes were identified. The expressions of 18 out of top 20 up-regulated unigenes were confirmed by qPCR analysis. Functional network analysis of the up-regulated genes revealed some common biological processes, including cold responses, and molecular functions in C. bungeana and Arabidopsis responding to chilling. Karrikins were found as new plant growth regulators involved in chilling responses of C. bungeana and Arabidopsis. However, genes involved in cold acclimation were enriched in chilling up-regulated genes in Arabidopsis but not in C. bungeana. In addition, although transcription activations were stimulated in both C. bungeana and Arabidopsis, no CBF putative ortholog was up-regulated in C. bungeana while CBF2 and CBF3 were chilling up-regulated in Arabidopsis. On the other hand, up-regulated genes related to protein phosphorylation and auto-ubiquitination processes were over-represented in C. bungeana but not in Arabidopsis. Conclusions We conducted the first deep-sequencing transcriptome profiling and chilling stress regulatory network analysis of C. bungeana, a subnival alpine plant with inherited cold tolerance. Comparative transcriptome analysis suggests that cold acclimation is not

  5. Analysis method and principle of dual-mode electro-mechanical variable transmission program

    NASA Astrophysics Data System (ADS)

    Li, Hongcai; Yan, Qingdong; Xiang, Changle; Wang, Weida

    2012-05-01

    Automotive industry, as an important pillar of the national economy, has been rapidly developing in recent years. But proplems such as energy comsumption and environmental pollution are posed at the same time. Electro-mechanical variable transmission system is considered one of avilable workarounds. It is brought forward a kind of design methods of dual-mode electro-mechanical variable transmission system rotational speed characteristics and dual-mode drive diagrams. With the motor operating behavior of running in four quadrants and the speed characteristics of the simple internal and external meshing single planetary gear train, four kinds of dual-mode electro-mechanical transmission system scheme are designed. And the velocity, torque and power characteristics of one of the programs are analyzed. The magnitude of the electric split-flow power is an important factor which influences the system performance, so in the parameters matching design, it needs to reduce the power needs under the first mode of the motor. The motor, output rotational speed range and the position of the mode switching point have relationships with the characteristics design of the planetary gear set. The analysis method is to provide a reference for hybrid vehicles' design. As the involved rotational speed and torque relationships are the natural contact of every part of transmission system, a theory basis of system program and performance analysis is provided.

  6. The Mechanism Research of Qishen Yiqi Formula by Module-Network Analysis

    PubMed Central

    Zheng, Shichao; Zhang, Yanling; Qiao, Yanjiang

    2015-01-01

    Qishen Yiqi formula (QSYQ) has the effect of tonifying Qi and promoting blood circulation, which is widely used to treat the cardiovascular diseases with Qi deficiency and blood stasis syndrome. However, the mechanism of QSYQ to tonify Qi and promote blood circulation is rarely reported at molecular or systems level. This study aimed to elucidate the mechanism of QSYQ based on the protein interaction network (PIN) analysis. The targets' information of the active components was obtained from ChEMBL and STITCH databases and was further used to search against protein-protein interactions by String database. Next, the PINs of QSYQ were constructed by Cytoscape and were analyzed by gene ontology enrichment analysis based on Markov Cluster algorithm. Finally, based on the topological parameters, the properties of scale-free, small world, and modularity of the QSYQ's PINs were analyzed. And based on function modules, the mechanism of QSYQ was elucidated. The results indicated that Qi-tonifying efficacy of QSYQ may be partly attributed to the regulation of amino acid metabolism, carbohydrate metabolism, lipid metabolism, and cAMP metabolism, while QSYQ improves the blood stasis through the regulation of blood coagulation and cardiac muscle contraction. Meanwhile, the “synergy” of formula compatibility was also illuminated. PMID:26379745

  7. Analysis of ice-binding sites in fish type II antifreeze protein by quantum mechanics.

    PubMed Central

    Cheng, Yuhua; Yang, Zuoyin; Tan, Hongwei; Liu, Ruozhuang; Chen, Guangju; Jia, Zongchao

    2002-01-01

    Many organisms living in cold environments can survive subzero temperatures by producing antifreeze proteins (AFPs) or antifreeze glycoproteins. In this paper we investigate the ice-binding surface of type II AFP by quantum mechanical methods, which, to the best of our knowledge, represents the first time that molecular orbital computational approaches have been applied to AFPs. Molecular mechanical approaches, including molecular docking, energy minimization, and molecular dynamics simulation, were used to obtain optimal systems for subsequent quantum mechanical analysis. We selected 17 surface patches covering the entire surface of the type II AFP and evaluated the interaction energy between each of these patches and two different ice planes using semi-empirical quantum mechanical methods. We have demonstrated the weak orbital overlay phenomenon and the change of bond orders in ice. These results consistently indicate that a surface patch containing 19 residues (K37, L38, Y20, E22, Y21, I19, L57, T56, F53, M127, T128, F129, R17, C7, N6, P5, G10, Q1, and W11) is the most favorable ice-binding site for both a regular ice plane and an ice plane where water O atoms are randomly positioned. Furthermore, for the first time the computation results provide new insights into the weakening of the ice lattice upon AFP binding, which may well be a primary factor leading to AFP-induced ice growth inhibition. PMID:12324437

  8. Variability Analysis of the Mechanical Parameters in order to Determine the Forming Limit Band

    NASA Astrophysics Data System (ADS)

    Paraianu, Liana; Bichis, Ioana; Banabic, Dorel

    2011-05-01

    The variability of the so called noise factors greatly influences the results of any forming process (deep-drawing, stretching, etc.). By taking into account this variability, the number of the rejected parts and the manufacturing costs will decrease. The aim of this work is to evaluate the variability of the mechanical parameters of a DC04 steel sheet (0.85 mm thickness). The experimental data needed for evaluating the variability of the mechanical parameters has been obtained from uniaxial tensile tests. A total number of 113 experiments have been made using samples cut at 0°, 45° and 90° with respect to the rolling direction. In this way, the yield stress and the plastic anisotropy coefficient have been determined for each of the orientations mentioned above. The power hardening law offers the possibility to study the variability of the following parameters: yield stress, strength coefficient and strain-hardening exponent. Based on the dispersion of the stress-strain curves, the mechanical coefficients of the Swift hardening law have been determined using a new method. The input parameters exhibiting the most important influence on the scattering of the forming limit diagram have been also established. Finally, in order to determine the Forming Limit Band (FLB), a Monte-Carlo analysis (MCA) has been performed using values and correlations between the mechanical parameters.

  9. Physical mechanisms of phonation onset: a linear stability analysis of an aeroelastic continuum model of phonation.

    PubMed

    Zhang, Zhaoyan; Neubauer, Juergen; Berry, David A

    2007-10-01

    In an investigation of phonation onset, a linear stability analysis was performed on a two-dimensional, aeroelastic, continuum model of phonation. The model consisted of a vocal fold-shaped constriction situated in a rigid pipe coupled to a potential flow which separated at the superior edge of the vocal fold. The vocal fold constriction was modeled as a plane-strain linear elastic layer. The dominant eigenvalues and eigenmodes of the fluid-structure-interaction system were investigated as a function of glottal airflow. To investigate specific aerodynamic mechanisms of phonation onset, individual components of the glottal airflow (e.g., flow-induced stiffness, inertia, and damping) were systematically added to the driving force. The investigations suggested that flow-induced stiffness was the primary mechanism of phonation onset, involving the synchronization of two structural eigenmodes. Only under conditions of negligible structural damping and a restricted set of vocal fold geometries did flow-induced damping become the primary mechanism of phonation onset. However, for moderate to high structural damping and a more generalized set of vocal fold geometries, flow-induced stiffness remained the primary mechanism of phonation onset. PMID:17902864

  10. Grid indentation analysis of mechanical properties of composite electrodes in Li-ion batteries

    DOE PAGESBeta

    Vasconcelos, Luize Scalco de; Xu, Rong; Li, Jianlin; Zhao, Kejie

    2016-03-09

    We report that electrodes in commercial rechargeable batteries are microscopically heterogeneous materials. The constituent components, including active materials, polymeric binders, and porous conductive matrix, often have large variation in their mechanical properties, making the mechanical characterization of composite electrodes a challenging task. In a model system of LiNi0.5Mn0.3Co0.2O2 cathode, we employ the instrumented grid indentation to determine the elastic modulus and hardness of the constituent phases. The approach relies on a large array of nanoindentation experiments and statistical analysis of the resulting data provided that the maximum indentation depth is carefully chosen. The statistically extracted properties of the active particlesmore » and the surrounding medium are in good agreement with the tests of targeted indentation at selected sites. Lastly, the combinatory technique of grid indentation and statistical deconvolution represents a fast and reliable route to quantify the mechanical properties of composite electrodes that feed the parametric input for the mechanics models.« less

  11. Dynamical systems analysis of spike-adding mechanisms in transient bursts.

    PubMed

    Nowacki, Jakub; Osinga, Hinke M; Tsaneva-Atanasova, Krasimira

    2012-01-01

    Transient bursting behaviour of excitable cells, such as neurons, is a common feature observed experimentally, but theoretically, it is not well understood. We analyse a five-dimensional simplified model of after-depolarisation that exhibits transient bursting behaviour when perturbed with a short current injection. Using one-parameter continuation of the perturbed orbit segment formulated as a well-posed boundary value problem, we show that the spike-adding mechanism is a canard-like transition that has a different character from known mechanisms for periodic burst solutions. The biophysical basis of the model gives a natural time-scale separation, which allows us to explain the spike-adding mechanism using geometric singular perturbation theory, but it does not involve actual bifurcations as for periodic bursts. We show that unstable sheets of the critical manifold, formed by saddle equilibria of the system that only exist in a singular limit, are responsible for the spike-adding transition; the transition is organised by the slow flow on the critical manifold near folds of this manifold. Our analysis shows that the orbit segment during the spike-adding transition includes a fast transition between two unstable sheets of the slow manifold that are of saddle type. We also discuss a different parameter regime where the presence of additional saddle equilibria of the full system alters the spike-adding mechanism. PMID:22655748

  12. Dynamic analysis and control of lightweight manipulators with flexible parallel link mechanisms

    NASA Technical Reports Server (NTRS)

    Lee, Jeh Won

    1991-01-01

    The flexible parallel link mechanism is designed for increased rigidity to sustain the buckling when it carries a heavy payload. Compared to a one link flexible manipulator, a two link flexible manipulator, especially the flexible parallel mechanism, has more complicated characteristics in dynamics and control. The objective of this research is the theoretical analysis and the experimental verification of dynamics and control of a two link flexible manipulator with a flexible parallel link mechanism. Nonlinear equations of motion of the lightweight manipulator are derived by the Lagrangian method in symbolic form to better understand the structure of the dynamic model. A manipulator with a flexible parallel link mechanism is a constrained dynamic system whose equations are sensitive to numerical integration error. This constrained system is solved using singular value decomposition of the constraint Jacobian matrix. The discrepancies between the analytical model and the experiment are explained using a simplified and a detailed finite element model. The step response of the analytical model and the TREETOPS model match each other well. The nonlinear dynamics is studied using a sinusoidal excitation. The actuator dynamic effect on a flexible robot was investigated. The effects are explained by the root loci and the Bode plot theoretically and experimentally. For the base performance for the advanced control scheme, a simple decoupled feedback scheme is applied.

  13. Design, analysis, and applications of cellular contact-aided compliant mechanisms

    NASA Astrophysics Data System (ADS)

    Mehta, Vipul

    A new class of compliant mechanisms utilizing the benefits of cellular geometry and contact are addressed in this work. The design, analysis, fabrication and testing of such structures for high-strain and high-strength applications is the focus of the present research. Cellular structures have relatively good strength-to-weight ratios. They also have a higher strain capability than solid structures. Contact during deformation reduces failure-causing bending stresses through stress relief, thereby enabling such cellular structures to be stretched more than the corresponding structures without contact. Both analytical and numerical models are developed to represent one specific mechanism. Several candidate materials are investigated for such mechanisms. Although the allowable strain of all these materials is small, the overall strain of the contact-aided cellular mechanisms is at least an order of magnitude greater than that of the constitutive material. Application of contact to different materials yields an improvement in the global strain capacity by more than 100% relative to cellular structures without contact. Experiments are conducted to validate the models, and good agreement is found. Size optimization is carried out to maximize the stress relief and the overall strain. Two main applications are considered in the present work. One application consists of a morphing aircraft skin for adaptive structures. Different material models such as linearly elastic and multi-linear elastic are examined. For linearly elastic materials, contact-induced stress-relief is advantageous and for nonlinear elastic materials, reduction of transverse deflection due to contact is useful. The proposed contact-aided skin structure is compared with a cellular skin without contact. The contact mechanism helps to increase the morphing capacity while decreasing the structural mass. Using contact-aided cellular mechanisms, the global strain capability is increased by as much as 37%. For a

  14. Differential analysis of bifurcations and isolated singularities for robots and mechanisms

    SciTech Connect

    Kieffer, J. . Engineering Dept.)

    1994-02-01

    This article develops a general technique for differential analysis that can be applied to singularities of three related problems: path tracking for nonredundant robots, self-motion analysis for robots with one degree of redundancy, and displacement analysis of single-loop mechanisms. For each of these problems, the locus of displacement solutions generally forms a set of one-dimensional manifolds in the space of variable parameters. However, if singularities occur, the manifolds may degenerate into isolated points, or into curves that include bifurcation at the singular points. Higher-order equations, derived from Taylor series expansion of the matrix equation of closure, are solved to identify singularity type and, in the case of bifurcations, to determine the number of intersecting branches as well as a Taylor series expansion of each branch about the point of bifurcation. To avoid unbounded mathematics, branch expansions are derived in terms of an introduced curve parameter. The results are useful for identifying singularity type, for numerical curve tracking with continuation past bifurcations on any chosen branch, and for determining exact rate relations (i.e., velocity, acceleration, etc.) for each branch at a bifurcation. The noniterative solution procedure involves configuration-dependent systems of equations that are evaluated by recursive algorithm, then solved using singular value decomposition, polynomial equation solution, and linear system solution. Examples show applications to RCRCR mechanisms and the Puma manipulator.

  15. Structural and mechanical analysis of the Mont Terri Anticline (Jura, Switzerland)

    NASA Astrophysics Data System (ADS)

    Caer, Typhaine; Souloumiac, Pauline; Maillot, Bertrand; Leturmy, Pascale; Nussbaum, Christophe

    2014-05-01

    The main motivation of this study is to illustrate how geometrical constructions of geological structures can be constrained by mechanical equilibrium and the Coulomb criterion using the theory of limit analysis. In the NW deformation front of the Jura thrust belt in Switzerland, the Mont-Terri anticline is located at an interruption of the Muschelkalk décollement, due to former normal faults. It is characterised by a reversed frontal limb, a steep back limb, and a ramp cross-cutting some of the former normal faults. A borehole and a highway tunnel constrain the inner structure. Three 2D kinematics and present-day cross-sections are proposed as various combinations of fault-bend folds, fault propagation folds and detachment folds (one of them being the only previously published interpretation of Mont Terri). Each interpretation is tentatively tested with the external approach of limit analysis, leading to different compatible ranges of values of the frictional parameters and of their variation with progressive shortening. It is not possible to reject any interpretation with confidence. Furthermore, the exact evolution of the topography during shortening is largely unknown. It is shown by the mechanical analysis to play a very important role in selecting the locations and dips of the active faults because it imposes spatial variations of their loading. The merit of the present approach is therefore to provide a quantitative link between the assumed evolution of the internal structure, the topography, and the frictional parameters.

  16. Deformation and fracture of Macadamia nuts Part 2: Microstructure and fracture mechanics analysis of nutshell

    NASA Astrophysics Data System (ADS)

    Wang, Chun-Hui; Mai, Yiu-Wing

    A study of the microstructure and mechanical properties of Macadamia nutshells subjected to various heat treatments is given in Part 2 of this paper. It is found that the nutshell has a three-dimensional, close-packed, cell structure. The cells have a diameter to length ratio of about 1 to 3, and the orientation of the cells is reasonably isotropic with no apparent variation with either position or direction. The material behaves in a very brittle manner under tension and compression. Based on the elastic stress analysis of a nut under diametrical compression and the mechanical properties of the shell, it is shown that cracks that cause the final fracture are initiated from the inner surface beneath the loading point. A theoretical model is proposed and predictions of the fracture load for Macadamia nuts are in good agreement with experimental results.

  17. Coupled model analysis of the structure and nano-mechanical properties of dragonfly wings.

    PubMed

    Sun, J Y; Pan, C X; Tong, J; Zhang, J

    2010-03-01

    To establish the quantitative model of the dragonfly wing the reconfiguration and nanoindentation technique were used. The mechanical properties of wings were measured by nanoindentre. Generally, the costa undertake is mainly pressure, and its mechanical properties should be the largest. However, in the nanoindentation test, the largest value of the reduced modulus (E(r)) and hardness (H) mainly appear in the radius, except the value at 0.7L (L is the wing length). The E(r) and H of the forewing were larger than that of the hindwing, except the value at 0.7L. The reversing engineering (3-D scanner) and AutoCAD were cooperated to reconfigure the dragonfly wing. Then the material parameters and skeleton transforms to a finite element analysis. The quantitative models were discussed in static range. PMID:20170254

  18. Mechanism of transcriptional repression at a bacterial promoter by analysis of single molecules.

    PubMed

    Sanchez, Alvaro; Osborne, Melisa L; Friedman, Larry J; Kondev, Jane; Gelles, Jeff

    2011-10-01

    The molecular basis for regulation of lactose metabolism in Escherichia coli is well studied. Nonetheless, the physical mechanism by which the Lac repressor protein prevents transcription of the lactose promoter remains unresolved. Using multi-wavelength single-molecule fluorescence microscopy, we visualized individual complexes of fluorescently tagged RNA polymerase holoenzyme bound to promoter DNA. Quantitative analysis of the single-molecule observations, including use of a novel statistical partitioning approach, reveals highly kinetically stable binding of polymerase to two different sites on the DNA, only one of which leads to transcription. Addition of Lac repressor directly demonstrates that bound repressor prevents the formation of transcriptionally productive open promoter complexes; discrepancies in earlier studies may be attributable to transcriptionally inactive polymerase binding. The single-molecule statistical partitioning approach is broadly applicable to elucidating mechanisms of regulatory systems including those that are kinetically rather than thermodynamically controlled. PMID:21829165

  19. Mechanical Performance and Parameter Sensitivity Analysis of 3D Braided Composites Joints

    PubMed Central

    Wu, Yue; Nan, Bo; Chen, Liang

    2014-01-01

    3D braided composite joints are the important components in CFRP truss, which have significant influence on the reliability and lightweight of structures. To investigate the mechanical performance of 3D braided composite joints, a numerical method based on the microscopic mechanics is put forward, the modeling technologies, including the material constants selection, element type, grid size, and the boundary conditions, are discussed in detail. Secondly, a method for determination of ultimate bearing capacity is established, which can consider the strength failure. Finally, the effect of load parameters, geometric parameters, and process parameters on the ultimate bearing capacity of joints is analyzed by the global sensitivity analysis method. The results show that the main pipe diameter thickness ratio γ, the main pipe diameter D, and the braided angle α are sensitive to the ultimate bearing capacity N. PMID:25121121

  20. Analysis of mechanisms that could contribute to neutrinoless double-beta decay

    NASA Astrophysics Data System (ADS)

    Horoi, Mihai; Neacsu, Andrei

    2016-06-01

    Neutrinoless double-beta decay is a beyond the Standard Model process that would indicate that neutrinos are Majorana fermions, and the lepton number is not conserved. It could be interesting to use the neutrinoless double-beta decay observations to distinguish between several beyond Standard Model mechanisms that could contribute to this process. Accurate nuclear structure calculations of the nuclear matrix elements necessary to analyze the decay rates could be helpful to narrow down the list of contributing mechanisms. We investigate the information one can get from the angular and energy distribution of the emitted electrons and from the half-lives of several isotopes, assuming that the right-handed currents exist. For the analysis of these distributions, we calculate the necessary nuclear matrix elements using shell model techniques, and we explicitly consider interference terms.

  1. A failure modes, mechanisms, and effects analysis (FMMEA) of lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Hendricks, Christopher; Williard, Nick; Mathew, Sony; Pecht, Michael

    2015-11-01

    Lithium-ion batteries are popular energy storage devices for a wide variety of applications. As batteries have transitioned from being used in portable electronics to being used in longer lifetime and more safety-critical applications, such as electric vehicles (EVs) and aircraft, the cost of failure has become more significant both in terms of liability as well as the cost of replacement. Failure modes, mechanisms, and effects analysis (FMMEA) provides a rigorous framework to define the ways in which lithium-ion batteries can fail, how failures can be detected, what processes cause the failures, and how to model failures for failure prediction. This enables a physics-of-failure (PoF) approach to battery life prediction that takes into account life cycle conditions, multiple failure mechanisms, and their effects on battery health and safety. This paper presents an FMMEA of battery failure and describes how this process enables improved battery failure mitigation control strategies.

  2. Wind Evaluation Breadboard: mechanical design and analysis, control architecture, dynamic model, and performance simulation

    NASA Astrophysics Data System (ADS)

    Reyes García-Talavera, Marcos; Viera, Teodora; Núñez, Miguel; Zuluaga, Pablo; Ronquillo, Bernardo; Ronquillo, Mariano; Brunetto, Enzo; Quattri, Marco; Castro, Javier; Hernández, Elvio

    2008-07-01

    The Wind Evaluation Breadboard (WEB) for the European Extremely Large Telescope (ELT) is a primary mirror and telescope simulator formed by seven segments simulators, including position sensors, electromechanical support systems and support structures. The purpose of the WEB is to evaluate the performance of the control of wind buffeting disturbance on ELT segmented mirrors using an electro-mechanical set-up which simulates the real operational constrains applied to large segmented mirrors. The instrument has been designed and developed by IAC, ALTRAN, JUPASA and ESO, with FOGALE responsible of the Edge Sensors, and TNO of the Position Actuators. This paper describes the mechanical design and analysis, the control architecture, the dynamic model generated based on the Finite Element Model and the close loop performance achieved in simulations. A comparison in control performance between segments modal control and actuators local control is also presented.

  3. Mechanical performance and parameter sensitivity analysis of 3D braided composites joints.

    PubMed

    Wu, Yue; Nan, Bo; Chen, Liang

    2014-01-01

    3D braided composite joints are the important components in CFRP truss, which have significant influence on the reliability and lightweight of structures. To investigate the mechanical performance of 3D braided composite joints, a numerical method based on the microscopic mechanics is put forward, the modeling technologies, including the material constants selection, element type, grid size, and the boundary conditions, are discussed in detail. Secondly, a method for determination of ultimate bearing capacity is established, which can consider the strength failure. Finally, the effect of load parameters, geometric parameters, and process parameters on the ultimate bearing capacity of joints is analyzed by the global sensitivity analysis method. The results show that the main pipe diameter thickness ratio γ, the main pipe diameter D, and the braided angle α are sensitive to the ultimate bearing capacity N. PMID:25121121

  4. Characterization of Thin Film Polymers Through Dynamic Mechanical Analysis and Permeation

    NASA Technical Reports Server (NTRS)

    Herring, Helen

    2003-01-01

    Thin polymer films are being considered, as candidate materials to augment the permeation resistance of cryogenic hydrogen fuel tanks such as would be required for future reusable launch vehicles. To evaluate performance of candidate films after environmental exposure, an experimental study was performed to measure the thermal/mechanical and permeation performance of six, commercial-grade materials. Dynamic storage modulus, as measured by Dynamic Mechanical Analysis, was found over a range of temperatures. Permeability, as measured by helium gas diffusion, was found at room temperature. Test data was correlated with respect to film type and pre-test exposure to moisture, elevated temperature, and cryogenic temperature. Results indicated that the six films were comparable in performance and their resistance to environmental degradation.

  5. Real-time analysis of mechanical and electrical resonances with open-source sound card software

    NASA Astrophysics Data System (ADS)

    Makan, G.; Kopasz, K.; Gingl, Z.

    2014-01-01

    We present an easily reproducible, open-source, sound card based experimental set-up to support transfer function measurement. Our system is able to visualize the signals of mechanical and electrical resonances and their spectra in real time. We give a brief description of the system, and show some examples of electrical and mechanical resonance experiments that are supported by the system. The theoretical background, experimental set-up, component selection and digital signal processing are all discussed, and more detailed information (building instructions, software download) is provided on a dedicated web page (www.noise.inf.u-szeged.hu/edudev/RealTimeAnalysisOfResonances/). The experimental set-up can support the undergraduate and graduate education of students of physics, physics education and engineering by means of experimental demonstrations and laboratory exercises. The very low cost, high efficiency and transparent system provides a scalable experimental environment that can be easily built in several instances.

  6. Computer systems analysis of the cardiovascular mechanisms of reentry orthostasis in astronauts.

    PubMed

    Summers, R L; Coleman, T G

    2002-01-01

    Reentry orthostasis secondary to a prolonged exposure to microgravity is a common problem among astronauts. However, the physiologic mechanisms are poorly understood due to the many control systems involved. In this study an advanced computer model of cardiovascular functioning was employed in a systems analysis approach to clarify the relative importance of some of the adaptive physiologic processes engaged when humans return from space. After simulation of the conditions of zero gravity for one month, the model predicted that the change in capacitance of the lower extremity veins resulting from a loss of external fluid forces in the dehydrated extracellular compartment was the dominant mechanism associated with reentry orthostasis. This condition appears accentuated in women due to their inherent lower center of gravity and proportionately larger mass in the lower extremities. PMID:14686452

  7. Dynamic Analysis and Control of Lightweight Manipulators with Flexible Parallel Link Mechanisms. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Lee, Jeh Won

    1990-01-01

    The objective is the theoretical analysis and the experimental verification of dynamics and control of a two link flexible manipulator with a flexible parallel link mechanism. Nonlinear equations of motion of the lightweight manipulator are derived by the Lagrangian method in symbolic form to better understand the structure of the dynamic model. The resulting equation of motion have a structure which is useful to reduce the number of terms calculated, to check correctness, or to extend the model to higher order. A manipulator with a flexible parallel link mechanism is a constrained dynamic system whose equations are sensitive to numerical integration error. This constrained system is solved using singular value decomposition of the constraint Jacobian matrix. Elastic motion is expressed by the assumed mode method. Mode shape functions of each link are chosen using the load interfaced component mode synthesis. The discrepancies between the analytical model and the experiment are explained using a simplified and a detailed finite element model.

  8. Mechanical Behavior and Microstructural Analysis of Extruded AZ31B Magnesium Alloy Processed by Backward Extrusion

    NASA Astrophysics Data System (ADS)

    Zhou, Ping; Beeh, Elmar; Friedrich, Horst E.; Grünheid, Thomas

    2016-07-01

    This study investigates the mechanical behavior of an extruded AZ31B magnesium alloy profile at various strain rates from 0.001 to 375/s. The electron backscatter diffraction analysis revealed that the profile has \\{ { 0 0 0 1} \\}< 1 0overline{1} 0 rangle and \\{ {1 0overline{1} 0 }\\}< { 1 1overline{2} 0}rangle textures. Due to the textures, the profile exhibits pronounced anisotropy in mechanical properties. In the extrusion direction (ED), the profile shows the highest yield strength (YS) but the lowest total elongation at fracture (TE) due to a hard activation of non-basal slip and \\{ { 1 0overline{1} 1} \\}< { 1 0overline{1} overline{2} } rangle twinning; in the diagonal direction (DD), it shows the lowest ultimate tensile strength (UTS) but the highest TE due to an easy activation of basal slip; in the transverse direction (TD), it shows the lowest YS due to an easy activation of \\{ {10overline{1} 2} \\}< {10overline{1} overline{1} } rangle twinning. Moreover, the number of twins increases with the increasing strain rate. This indicates that deformation twinning becomes prevalent to accommodate high-rate deformation. Due to the different deformation mechanisms, the profile exhibits an orientation-dependent effect of strain rate on the mechanical properties. A positive effect of strain rate on the YS and UTS was found in the ED, while the effect of strain rate on the YS is negligible in the DD and TD. The TE in the ED, DD, and TD decreases in general as the strain rate increases. Fractographic analysis under a scanning electron microscope revealed that the fracture is a mixed mode of ductile and brittle fracture, and the magnesium oxide inclusions could be the origins of the fracture.

  9. Mechanical Behavior and Microstructural Analysis of Extruded AZ31B Magnesium Alloy Processed by Backward Extrusion

    NASA Astrophysics Data System (ADS)

    Zhou, Ping; Beeh, Elmar; Friedrich, Horst E.; Grünheid, Thomas

    2016-05-01

    This study investigates the mechanical behavior of an extruded AZ31B magnesium alloy profile at various strain rates from 0.001 to 375/s. The electron backscatter diffraction analysis revealed that the profile has { { 0 0 0 1} }< 1 0overline{1} 0 rangle and { {1 0overline{1} 0 }}< { 1 1overline{2} 0}rangle textures. Due to the textures, the profile exhibits pronounced anisotropy in mechanical properties. In the extrusion direction (ED), the profile shows the highest yield strength (YS) but the lowest total elongation at fracture (TE) due to a hard activation of non-basal slip and { { 1 0overline{1} 1} }< { 1 0overline{1} overline{2} } rangle twinning; in the diagonal direction (DD), it shows the lowest ultimate tensile strength (UTS) but the highest TE due to an easy activation of basal slip; in the transverse direction (TD), it shows the lowest YS due to an easy activation of { {10overline{1} 2} }< {10overline{1} overline{1} } rangle twinning. Moreover, the number of twins increases with the increasing strain rate. This indicates that deformation twinning becomes prevalent to accommodate high-rate deformation. Due to the different deformation mechanisms, the profile exhibits an orientation-dependent effect of strain rate on the mechanical properties. A positive effect of strain rate on the YS and UTS was found in the ED, while the effect of strain rate on the YS is negligible in the DD and TD. The TE in the ED, DD, and TD decreases in general as the strain rate increases. Fractographic analysis under a scanning electron microscope revealed that the fracture is a mixed mode of ductile and brittle fracture, and the magnesium oxide inclusions could be the origins of the fracture.

  10. Pressurized thermal shock probabilistic fracture mechanics sensitivity analysis for Yankee Rowe reactor pressure vessel

    SciTech Connect

    Dickson, T.L.; Cheverton, R.D.; Bryson, J.W.; Bass, B.R.; Shum, D.K.M.; Keeney, J.A.

    1993-08-01

    The Nuclear Regulatory Commission (NRC) requested Oak Ridge National Laboratory (ORNL) to perform a pressurized-thermal-shock (PTS) probabilistic fracture mechanics (PFM) sensitivity analysis for the Yankee Rowe reactor pressure vessel, for the fluences corresponding to the end of operating cycle 22, using a specific small-break-loss- of-coolant transient as the loading condition. Regions of the vessel with distinguishing features were to be treated individually -- upper axial weld, lower axial weld, circumferential weld, upper plate spot welds, upper plate regions between the spot welds, lower plate spot welds, and the lower plate regions between the spot welds. The fracture analysis methods used in the analysis of through-clad surface flaws were those contained in the established OCA-P computer code, which was developed during the Integrated Pressurized Thermal Shock (IPTS) Program. The NRC request specified that the OCA-P code be enhanced for this study to also calculate the conditional probabilities of failure for subclad flaws and embedded flaws. The results of this sensitivity analysis provide the NRC with (1) data that could be used to assess the relative influence of a number of key input parameters in the Yankee Rowe PTS analysis and (2) data that can be used for readily determining the probability of vessel failure once a more accurate indication of vessel embrittlement becomes available. This report is designated as HSST report No. 117.

  11. Analysis of Loss Mechanisms in G-M Type Pulse Tube Refrigerators

    NASA Astrophysics Data System (ADS)

    Baik, J. H.; Nellis, G. F.; Pfotenhauer, J. M.

    2004-06-01

    A one dimensional, numerical analysis that considers the heat transfer between the pulse tube walls and the internal working fluid has been performed to incorporate DC flow and shuttle heat loss mechanisms in a 5-valve G-M type pulse tube refrigerator model. All of the physical dimensions and operating conditions associated with three refrigeration systems built at UW-Madison have been used to provide input information for a 1st and 2nd order numerical analysis. The 1st order numerical analysis assumes that the pulse-tube is adiabatic and predicts the pressure, temperatures and mass flow rates at any time and location during a cycle. The gas and wall temperature profiles are subsequently modified by a 2nd order analysis that considers more realistic thermal behavior in the pulse-tube by explicitly modeling the heat transfer interaction between the fluid and the wall. Three different convective heat transfer correlations have been considered. The 2nd order analysis allows the calculation of various losses including DC flow and shuttle heat transfer in order to predict actual performances of the systems. The comparisons of the numerical model with a series of experimental results display very good agreement across significantly different system geometries and operating conditions.

  12. Mechanical models of the cellular cytoskeletal network for the analysis of intracellular mechanical properties and force distributions: a review.

    PubMed

    Chen, Ting-Jung; Wu, Chia-Ching; Su, Fong-Chin

    2012-12-01

    The cytoskeleton, which is the major mechanical component of cells, supports the cell body and regulates the cellular motility to assist the cell in performing its biological functions. Several cytoskeletal network models have been proposed to investigate the mechanical properties of cells. This review paper summarizes these models with a focus on the prestressed cable network, the semi-flexible chain network, the open-cell foam, the tensegrity, and the granular models. The components, material parameters, types of connection joints, tension conditions, and the advantages and disadvantages of each model are evaluated from a structural and biological point of view. The underlying mechanisms that are associated with the morphological changes of spreading cells are expected to be simulated using a cytoskeletal model; however, it is still paid less attention most likely due to the lack of a suitable cytoskeletal model that can accurately model the spreading process. In this review article, the established cytoskeletal models are hoped to provide useful information for the development of future cytoskeletal models with different degrees of cell attachment for the study of the mechanical mechanisms underlying the cellular behaviors in response to external stimulations. PMID:23062682

  13. Statistical mechanical analysis of the linear vector channel in digital communication

    NASA Astrophysics Data System (ADS)

    Takeda, Koujin; Hatabu, Atsushi; Kabashima, Yoshiyuki

    2007-11-01

    A statistical mechanical framework to analyze linear vector channel models in digital wireless communication is proposed for a large system. The framework is a generalization of that proposed for code-division multiple-access systems in Takeda et al (2006 Europhys. Lett. 76 1193) and enables the analysis of the system in which the elements of the channel transfer matrix are statistically correlated with each other. The significance of the proposed scheme is demonstrated by assessing the performance of an existing model of multi-input multi-output communication systems.

  14. Dynamic mechanical analysis and organization/storage of data for polymetric materials

    NASA Technical Reports Server (NTRS)

    Rosenberg, M.; Buckley, W.

    1982-01-01

    Dynamic mechanical analysis was performed on a variety of temperature resistant polymers and composite resin matrices. Data on glass transition temperatures and degree of cure attained were derived. In addition a laboratory based computer system was installed and data base set up to allow entry of composite data. The laboratory CPU termed TYCHO is based on a DEC PDP 11/44 CPU with a Datatrieve relational data base. The function of TYCHO is integration of chemical laboratory analytical instrumentation and storage of chemical structures for modeling of new polymeric structures and compounds

  15. Hermetic Narratives and False Analysis: A Unique Variant of the Mechanism of Identification With the Aggressor.

    PubMed

    Amir, Dana

    2016-08-01

    This paper focuses on a unique variant of the mechanism of identification with the aggressor. The term "hermetic narrative" refers to a condition in which the trauma victim creates a hermetically sealed narrative of witnessing, which becomes an addictive and subjugating object in itself, while obstructing natural processes of thinking. This paper examines the ways in which the hermetic narrative reconstructs victim-aggressor relations both within the individual and in the analytic relationship. It further discusses the risk of creating a "false analysis" that is based on a malignant cooperation of the analyst and patient with the internalized traumatic object. PMID:27500704

  16. Direct system parameter identification of mechanical structures with application to modal analysis

    NASA Technical Reports Server (NTRS)

    Leuridan, J. M.; Brown, D. L.; Allemang, R. J.

    1982-01-01

    In this paper a method is described to estimate mechanical structure characteristics in terms of mass, stiffness and damping matrices using measured force input and response data. The estimated matrices can be used to calculate a consistent set of damped natural frequencies and damping values, mode shapes and modal scale factors for the structure. The proposed technique is attractive as an experimental modal analysis method since the estimation of the matrices does not require previous estimation of frequency responses and since the method can be used, without any additional complications, for multiple force input structure testing.

  17. Uranium Isotopic and Quantitative Analysis Using a Mechanically-Cooled HPGe Detector

    SciTech Connect

    Solodov, Alexander A

    2008-01-01

    A new, portable high-resolution spectroscopy system based on a high-purity germanium detector cooled with a miniature Stirling-cycle cooler, ORTEC trans-SPEC, has recently become commercially available. The use of a long-life mechanical cooling system eliminates the need for liquid nitrogen. The purpose of this study was to determine the applicability of this new instrument for isotopic and quantitative analyses of uranium samples. The results of the performance of the trans-SPEC with the combination of PC-FRAM and ISOTOPIC software packages are described in this paper. An optimal set of analysis parameters for uranium measurements is proposed.

  18. Perturbation analysis of internal balancing for lightly damped mechanical systems with gyroscopic and circulatory forces

    NASA Technical Reports Server (NTRS)

    Blelloch, P. A.; Mingori, D. L.; Wei, J. D.

    1987-01-01

    Approximate expressions are developed for internally balanced singular values corresponding to the modes of mechanical systems with gyroscopic forces, light damping, and small circulatory forces. A brief overview is first given of the balanced realization model reduction method, including a discussion of recent work. The models considered are defined, and a perturbation analysis is used to show that the modal representation becomes asymptotically balanced as damping reduces to zero. The approximate balanced singular values are calculated, and a simple example of a flexible, dual-spin spacecraft is given as an illustration of the results.

  19. Nanoscopic dynamic mechanical analysis of resin-infiltrated dentine, under in vitro chewing and bruxism events.

    PubMed

    Toledano, Manuel; Osorio, Estrella; Cabello, Inmaculada; Aguilera, Fátima S; López-López, Modesto T; Toledano-Osorio, Manuel; Osorio, Raquel

    2016-02-01

    The aim of this study was to evaluate the induced changes in mechanical behavior and bonding capability of resin-infiltrated dentine interfaces, after application of mechanical stimuli. Dentine surfaces were subjected to partial demineralization through 37% phosphoric acid etching followed by the application of an etch-and-rinse dentine adhesive, Single Bond (3M/ESPE). Bonded interfaces were stored in simulated body fluid during 24h, and then tested or submitted to the mechanical loading challenge. Different loading waveforms were applied: No cycling (I), 24h cycled in sine (II) or square (III) waves, sustained loading held for 24h (IV) or sustained loading held for 72h (V). Microtensile bond strength (MTBS) was assessed for the different groups. Debonded dentine surfaces were studied by field emission scanning electron microscopy (FESEM). At the resin-dentine interface, both the hybrid layer (HL) and the bottom of the hybrid layer (BHL), and both peritubular and intertubular were evaluated using a nanoindenter in scanning mode. The load and displacement responses were used to perform the nano-Dynamic Mechanical analysis and to estimate the complex and storage modulus. Dye assisted Confocal Microscopy Evaluation was used to assess sealing ability. Load cycling increased the percentage of adhesive failures in all groups. Specimens load cycled in held 24h attained the highest complex and storage moduli at HL and BHL. The storage modulus was maximum in specimens load cycled in held 24h at peritubular dentine, and the lowest values were attained at intertubular dentine. The storage modulus increased in all mechanical tests, at peritubular dentine. An absence of micropermeability and nanoleakage after loading in sine and square waveforms were encountered. Porosity of the resin-dentine interface was observed when specimens were load cycled in held 72h. Areas of combined sealing and permeability were discovered at the interface of specimens load cycled in held 24h. Crack

  20. Thermo-mechanical buckling analysis of FGM plate using generalized plate theory

    NASA Astrophysics Data System (ADS)

    Sharma, Kanishk; Kumar, Dinesh; Gite, Anil

    2016-05-01

    This paper investigates the thermo-mechanical buckling behavior of simply-supported FGM plate under the framework of generalized plate theory (GPT), which includes classical plate theory (CPT), first order shear deformation theory (FSDT) and higher order shear deformation theory (HSDT) as special cases. The governing equations for FGM plate under thermal and mechanical loading conditions are derived from the principle of virtual displacements and Navier-type solution is assumed for simply supported boundary condition. The efficiency and applicability of presented methodology is illustrated by considering various examples of thermal and mechanical buckling of FGM plates. The closed form solutions in the form of critical thermal and mechanical buckling loads, predicted by CPT, FSDT and HSDT are compared for different side-to-thickness of FGM plate. Subsequently, the effect of material gradation profile on critical buckling parameters is examined by evaluating the buckling response for a range of power law indexes. The effect of geometrical parameters on mechanical buckling of FGM plate under uni-axial and bi-axial loading conditions are also illustrated by calculating the critical load for various values of slenderness ratios. Furthermore a comparative analysis of critical thermal buckling loads of FGM plate for different temperature profiles is also presented. It is identified that all plate theories predicted approximately same critical buckling loads and critical buckling temperatures for thin FGM plate, however for thick FGM plates, CPT overestimates the critical buckling parameters. Moreover the critical buckling loads and critical buckling temperatures of FGM plate are found to be significantly lower than the corresponding homogenous isotropic ceramic plate (n=0).

  1. Analysis of scattering mechanisms in zinc oxide films grown by the atomic layer deposition technique

    SciTech Connect

    Krajewski, Tomasz A. Dybko, Krzysztof; Luka, Grzegorz; Wachnicki, Lukasz; Kopalko, Krzysztof; Paszkowicz, Wojciech; Guziewicz, Elzbieta

    2015-07-21

    In this work, the analysis of the temperature-dependent electrical conductivity of highly crystalline zinc oxide (ZnO) thin films obtained by the Atomic Layer Deposition (ALD) method is performed. It is deduced that the most important scattering mechanisms are: scattering by ionized defects (at low temperatures) as well as by phonons (mainly optical ones) at higher temperatures. Nevertheless, the role of grain boundaries in the carrier mobility limitation ought to be included as well. These conclusions are based on theoretical analysis and temperature-dependent Hall mobility measurements. The presented results prove that existing models can explain the mobility behavior in the ALD-ZnO films, being helpful for understanding their transport properties, which are strongly related both to the crystalline quality of deposited ZnO material and defects in its lattice.

  2. Advances in explosives analysis--part I: animal, chemical, ion, and mechanical methods.

    PubMed

    Brown, Kathryn E; Greenfield, Margo T; McGrane, Shawn D; Moore, David S

    2016-01-01

    The number and capability of explosives detection and analysis methods have increased substantially since the publication of the Analytical and Bioanalytical Chemistry special issue devoted to Explosives Analysis (Moore and Goodpaster, Anal Bioanal Chem 395(2):245-246, 2009). Here we review and critically evaluate the latest (the past five years) important advances in explosives detection, with details of the improvements over previous methods, and suggest possible avenues towards further advances in, e.g., stand-off distance, detection limit, selectivity, and penetration through camouflage or packaging. The review consists of two parts. This part, Part I, reviews methods based on animals, chemicals (including colorimetry, molecularly imprinted polymers, electrochemistry, and immunochemistry), ions (both ion-mobility spectrometry and mass spectrometry), and mechanical devices. Part II will review methods based on photons, from very energetic photons including X-rays and gamma rays down to the terahertz range, and neutrons. PMID:26462922

  3. Bearing-Load Modeling and Analysis Study for Mechanically Connected Structures

    NASA Technical Reports Server (NTRS)

    Knight, Norman F., Jr.

    2006-01-01

    Bearing-load response for a pin-loaded hole is studied within the context of two-dimensional finite element analyses. Pin-loaded-hole configurations are representative of mechanically connected structures, such as a stiffener fastened to a rib of an isogrid panel, that are idealized as part of a larger structural component. Within this context, the larger structural component may be idealized as a two-dimensional shell finite element model to identify load paths and high stress regions. Finite element modeling and analysis aspects of a pin-loaded hole are considered in the present paper including the use of linear and nonlinear springs to simulate the pin-bearing contact condition. Simulating pin-connected structures within a two-dimensional finite element analysis model using nonlinear spring or gap elements provides an effective way for accurate prediction of the local effective stress state and peak forces.

  4. Postpolypectomy haemorrhage following removal of large polyps using mechanical haemostasis or epinephrine: a meta-analysis

    PubMed Central

    Burger, Daniel C; Horgan, Gareth; Bailey, Adam A; East, James E

    2014-01-01

    Background and aim Postpolypectomy haemorrhage (PPH) is a known adverse event that can occur following polypectomy, occurring in 0.3–6.1% of cases. Previous meta-analysis has included small polyps, which are less likely to bleed, and less amenable to some methods of mechanical haemostasis. No comprehensive cost–benefit analysis of this topic is available. The aim of this study was to perform a meta-analysis of randomized trials and a cost–benefit analysis of prophylactic haemostasis in PPH. Methods A total of 3092 abstracts from prospective trials conducted in human colonoscopic polypectomy were screened. Outpatients undergoing polypectomy in seven suitable studies (1426 episodes), without polyposis syndromes or bleeding diathesis, were identified. The interventions of prophylactic haemostatic measures (clips, loops, and/or adrenaline injection) to prevent PPH were assessed. The main outcome measurements were PPH measured by haematochezia or drop in haematocrit >10% or haemoglobin >1 g/dl. Risk ratio and number needed to treat (NNT) were generated using meta-analysis. Results Comparing any prophylactic haemostasis to none, the pooled risk ratio for PPH was 0.35 (0.21–0.57; p < 0.0001), NNT was 13.6, and cost to prevent one PPH was USD652. Using adrenaline alone vs. no prophylactic haemostasis revealed a pooled risk ratio of 0.37 (0.20–0.66; p = 0.001), NNT 14.0, cost to prevent one PPH USD382. Any prophylactic mechanical haemostasis compared to adrenaline produced a RR for PPH of 0.28 (0.14–0.57; p < 0.0001), NNT 12.3, and cost to prevent one PPH USD1368. Conclusions Adrenaline injection or mechanical haemostasis reduces the risk of PPH. Routine prophylactic measures to reduce PPH for polyps larger than 10 mm are potentially cost effective, although more thorough cost–benefit modelling is required. PMID:24918017

  5. Having a direct look: Analysis of DNA damage and repair mechanisms by next generation sequencing

    PubMed Central

    Meier, Bettina; Gartner, Anton

    2014-01-01

    Genetic information is under constant attack from endogenous and exogenous sources, and the use of model organisms has provided important frameworks to understand how genome stability is maintained and how various DNA lesions are repaired. The advance of high throughput next generation sequencing (NGS) provides new inroads for investigating mechanisms needed for genome maintenance. These emerging studies, which aim to link genetic toxicology and mechanistic analyses of DNA repair processes in vivo, rely on defining mutational signatures caused by faulty replication, endogenous DNA damaging metabolites, or exogenously applied genotoxins; the analysis of their nature, their frequency and distribution. In contrast to classical studies, where DNA repair deficiency is assessed by reduced cellular survival, the localization of DNA repair factors and their interdependence as well as limited analysis of single locus reporter assays, NGS based approaches reveal the direct, quantal imprint of mutagenesis genome-wide, at the DNA sequence level. As we will show, such investigations require the analysis of DNA derived from single genotoxin treated cells, or DNA from cell populations regularly passaged through single cell bottlenecks when naturally occurring mutation accumulation is investigated. We will argue that the life cycle of the nematode Caenorhabditis elegans, its genetic malleability combined with whole genome sequencing provides an exciting model system to conduct such analysis. PMID:25131498

  6. Experimental validation of the direct transmissibility approach to classical transfer path analysis on a mechanical setup

    NASA Astrophysics Data System (ADS)

    Guasch, Oriol; García, Carlos; Jové, Jordi; Artís, Pere

    2013-05-01

    Transmissibility functions have received renewed interest given the important role they play in operational modal analysis and operational transfer path analysis. However, transmissibilities can also be used in the framework of classical transmission path analysis. This avoids some of the problems associated to the latter, such as the measurement of operational loads, or the need to remove the active parts of the system to measure frequency response functions. The key of the transmissibility approach to classical transfer path analysis relies on the notion of direct or blocked transmissibilities, which can be computed from standard measurable transmissibilities. The response at any degree of freedom to a system external load can then be decomposed in terms of the remaining degrees of freedom responses and the system direct transmissibilities. Although the theory supporting this approach has been known for long, no experimental validation test has been reported to date. It is the purpose of this paper to provide such a test by applying the method to a simple mechanical system for which an analytical solution can be derived. For different configurations, it will be shown that direct transmissibilities computed from measured transmissibilities compare fairly well with analytical results. This opens the door to apply the method to more complex situations of practical interest with confidence.

  7. Application of structural analysis to the mechanical behaviour of the cornea.

    PubMed Central

    Anderson, K.; El-Sheikh, A.; Newson, T.

    2004-01-01

    Structural engineering analysis tools have been used to improve the understanding of the biomechanical behaviour of the cornea. The research is a multi-disciplinary collaboration between structural engineers, mathematical and numerical analysts, ophthalmologists and clinicians. Mathematical shell analysis and nonlinear finite-element modelling have been used in conjunction with laboratory experiments to study the behaviour of the cornea under different loading states and to provide improved predictions of the mechanical response to disease and injury. The initial study involved laboratory tests and mathematical back analysis to determine the corneal material properties and topography. These data were then used to facilitate the construction of accurate finite-element models that are able to reliably trace the performance of cornea upon exposure to disease, injury or elevated intra-ocular pressure. The models are being adapted to study the response to keratoconus (a disease causing loss of corneal tissue) and to tonometry procedures, which are used to measure the intra-ocular pressure. This paper introduces these efforts as examples of the application of structural engineering analysis tools and shows their potential in the field of corneal biomechanics. PMID:16849148

  8. Thermo/opto/mechanical analysis of large apertures for exoplanet detection using Cielo

    NASA Astrophysics Data System (ADS)

    Jordan, Elizabeth O.; Chainyk, Mike; Habbal, Feras; Hoff, Claus; Levine, Marie; Moore, Greg

    2009-08-01

    The next generation of space telescopes will be designed to meet increasingly challenging science goals. The operating environment and required precision of these telescopes will make complete verification via ground tests impossible, and will place a greater reliance on numerical simulation. The current state of the art in thermal, mechanical and optical modeling involves three disparate computational models, several analysis codes and tools to transition results between these models. However, the active controls necessary to meet the next generation of requirements for space telescopes will require integrated thermal, structural, optical and controls analysis. To meet these challenges, JPL has developed Cielo, an in-house finite element tool capable of multi-physics simulations using a common finite element model, for thermal, structural and optical aberration analysis. In this paper, we will discuss the use of Cielo for analysis of a coronagraph and an occulter designed to observe Earth-like planets around nearby stars. We will compare thermal and structural results from Cielo with results from commercial off the shelf (COTS) tools to verify the new approach. We will perform variations of key parameters to demonstrate how margins and uncertainties can be quantified using the new approach.

  9. Analysis of the Mechanism of Gram Differentiation by Use of a Filter-Paper Chromatographic Technique

    PubMed Central

    Bartholomew, J. W.; Cromwell, Thomas; Gan, Richard

    1965-01-01

    Bartholomew, J. W. (University of Southern California, Los Angeles), Thomas Cromwell, and Richard Gan. Analysis of the mechanism of Gram differentiation by use of a filter-paper chromatographic technique. J. Bacteriol. 90:766–777. 1965.—Data are presented which demonstrate that the mechanism of gram-positivity could not be due solely to factors such as a single, specific gram-positive substrate, specific affinities of crystal violet for certain cellular components, a specific crystal violet-iodine-substrate complex, or to any specific characteristic of the dye, iodine, or solvent molecules. Ruptured cells of gram-positive organisms stain gram-negatively when subjected to a standard Gram-stain procedure. However, when stained fragments of broken cells were deposited in thick layers on the surface of filter-paper strips and exposed to decolorizers, the rate of dye release correlated with the Gram characteristic of the intact cell. Therefore, the intact cell in itself is not an absolute requirement for Gram differentiation. The data are interpreted as indicating that the mechanism of Gram differentiation primarily involves the rate of permeation of molecules (dye, iodine, solvent) through the interstitial spaces of cell-wall material. Images PMID:16562079

  10. Comparative sequence analysis suggests a conserved gating mechanism for TRP channels

    PubMed Central

    Palovcak, Eugene; Delemotte, Lucie; Klein, Michael L.

    2015-01-01

    The transient receptor potential (TRP) channel superfamily plays a central role in transducing diverse sensory stimuli in eukaryotes. Although dissimilar in sequence and domain organization, all known TRP channels act as polymodal cellular sensors and form tetrameric assemblies similar to those of their distant relatives, the voltage-gated potassium (Kv) channels. Here, we investigated the related questions of whether the allosteric mechanism underlying polymodal gating is common to all TRP channels, and how this mechanism differs from that underpinning Kv channel voltage sensitivity. To provide insight into these questions, we performed comparative sequence analysis on large, comprehensive ensembles of TRP and Kv channel sequences, contextualizing the patterns of conservation and correlation observed in the TRP channel sequences in light of the well-studied Kv channels. We report sequence features that are specific to TRP channels and, based on insight from recent TRPV1 structures, we suggest a model of TRP channel gating that differs substantially from the one mediating voltage sensitivity in Kv channels. The common mechanism underlying polymodal gating involves the displacement of a defect in the H-bond network of S6 that changes the orientation of the pore-lining residues at the hydrophobic gate. PMID:26078053

  11. Analysis of wear mechanism and influence factors of drum segment of hot rolling coiler

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Peng, Yan; Liu, Hongmin; Liu, Yunfei

    2013-03-01

    Because the work environment of segment is complex, and the wear failures usually happen, the wear mechanism corresponding to the load is a key factor for the solution of this problem. At present, many researchers have investigated the failure of segment, but have not taken into account the compositive influences of matching and coiling process. To investigate the wear failure of the drum segment of the hot rolling coiler, the MMU-5G abrasion tester is applied to simulate the wear behavior under different temperatures, different loads and different stages, and the friction coefficients and wear rates are acquired. Scanning electron microscopy(SEM) is used to observe the micro-morphology of worn surface, X-ray energy dispersive spectroscopy(EDS) is used to analyze the chemical composition of worn surface, finally the wear mechanism of segment in working process is judged and the influence regulars of the environmental factors on the material wear behaviors are found. The test and analysis results show that under certain load, the wear of the segment changes into oxidation wear from abrasive wear step by step with the temperature increases, and the wear degree reduces; under certain temperature, the main wear mechanism of segment changes into spalling wear from abrasive wear with the load increases, and the wear degree slightly increases. The proposed research provides a theoretical foundation and a practical reference for optimizing the wear behavior and extending the working life of segment.

  12. Organ-specific proteome analysis for identification of abiotic stress response mechanism in crop

    PubMed Central

    Komatsu, Setsuko; Hossain, Zahed

    2013-01-01

    Abiotic stresses, such as flooding, drought, salinity, and high/low temperatures, are the major constraints that global crop production faces at present. Plants respond to a stress by modulating abundance of candidate proteins, either by up-regulating expression or by the synthesizing novel proteins primarily associated with plant defense system. The cellular mechanisms of stress sensing and signal transduction into cellular organelles have been reported. Nevertheless, the responses of plant cells to abiotic stresses differ in each organ. As the correlation between the expression of mRNAs and the abundance of their corresponding proteins is difficult to assess in specific organs, proteomics techniques provide one of the best options for the functional analysis of translated regions of the genome. The present review summarizes the organ-specific proteome analyses for better understanding of the response mechanisms of crops to abiotic stresses, including flooding, drought, and salinity. The differential organ-specific responses against each of these stresses are discussed in detail to provide new insights into plant stress response mechanisms at protein level. PMID:23565117

  13. Thermal-Mechanical Analysis for in-Vessel Diagnostic Components in W7-X

    NASA Astrophysics Data System (ADS)

    Ye, M. Y.; Werner, A.; Hirsch, M.; Thomsen, H.; Weller, A.; König, R.

    2008-03-01

    For long pulse plasma operation of the W7-X stellarator, the most serious challenge for the design of in-vessel diagnostic systems is the thermo-mechanical problem. Thermal load from convective losses and from plasma radiation can be as high as 500 kW/m2 at some locations close to plasma. The typical thermal load from plasma radiation alone ranges from several 10 to 100 kW/m2 as derived from 3-D Monte-Carlo simulations. A finite element analysis (FEA-ANSYS) is conducted for a better understanding of thermo-mechanical effects on in-vessel diagnostic components and to guide the design of the diagnostic system for steady state operation. All in-vessel diagnostic components require active cooling. Besides for long-pulse plasma operation optical components must be optimized to minimize thermal deformations. In this paper, we present the thermo-mechanical analyses of the CO2-laser interferometer retro-reflectors, the diamagnetic loops and the soft X-ray multi camera tomography system (XMCTS).

  14. Failure analysis of radio frequency (rf) micro-electro-mechanical systems (MEMS)

    NASA Astrophysics Data System (ADS)

    Walraven, Jeremy A.; Cole, Edward I., Jr.; Sloan, Lynn R.; Hietala, Susan L.; Tigges, Chris P.; Dyck, Christopher W.

    2001-10-01

    MEMS are rapidly emerging as critical components in the telecommunications industry. This enabling technology is currently being implemented in a variety of product and engineering applications. MEMS are currently being used as optical switches to reroute light, tunable filters, and mechanical resonators. Radio frequency (RF) MEMS must be compatible with current Gallium Arsenide (GaAs) microwave integrated circuit (MMIC) processing technologies for maximum integration levels. The RF MEMS switch discussed in this paper was fabricated using various layers of polyimide, silicon oxynitride (SiON), gold, and aluminum monolithically fabricated on a GaAs substrate. Fig. 1 shows a metal contacting series switch. This switch consists of gold signal lines (transmission lines), and contact metallization. SiON was deposited to form the fixed-fixed beam, and aluminum was deposited to form the top actuation electrode. To ensure product performance and reliability, RF MEMS switches are tested at both the wafer and package levels. Various processing irregularities may pass the visual inspection but fail electrical testing. This paper will focus on the failure mechanisms found in the first generation of RF MEMS developed at Sandia National Laboratories. Various tools and techniques such as scanning electron microscopy (SEM), resistive contrast imaging (RCI), focused ion beam (FIB), and thermally-induced voltage alteration (TIVA) have been employed to diagnose the failure mechanisms. The analysis performed using these tools and techniques led to corrective actions implemented in the next generation of RF MEMS metal contacting series switches.

  15. Analysis of molecular structures and mechanisms for toxins derived from venomous animals.

    PubMed

    Rocha, L F O

    2016-04-01

    As predominant component in the venom of many dangerous animal species, toxins have been thoroughly investigated for drug design or as pharmacologic tools. The present study demonstrated the use of size and hydrophobicity of amino acid residues for the purposes of quantifying the valuable sequence-structure relationship and performing further analysis of interactional mechanisms in secondary structure elements (SSEs) for toxin native conformations. First, we showed that the presence of large and hydrophobic residues varying in availability in the primary sequences correspondingly affects the amount of these residues being used in the SSEs in accordance with linear behavioral patterns from empirical assessments of experimentally derived toxins and non-toxins. Subsequent derivation of prediction rules was established with the aim of analyzing molecular structures and mechanisms by means of 114 residue compositions for venom toxins. The obtained results concerning the linear behavioral patterns demonstrated the nature of the information transfer occurring from the primary to secondary structures. A dual action mechanism was established, taking into account steric and hydrophobic interactions. Finally, a new residue composition prediction method for SSEs of toxins was suggested. PMID:26707907

  16. Analysis of a school bus collision: mechanism of injury in the unrestrained child

    PubMed Central

    Lapner, Peter C.; Nguyen, Duong; Letts, Mervyn

    2003-01-01

    Introduction The most common type of school bus crash resulting in injury and death involves the “rollover” mechanism, which may be linked to bus design. To investigate this possibility, we carried out a detailed investigation of a severe school bus crash. Methods The crash involved 12 children, passengers in the school bus. Analysis included the determination of crash dynamics by examination of physical evidence at the crash site and deformation sustained by the structure of the bus and the other vehicle involved. The mechanism of injury was determined by comparing physical evidence collected inside the bus to injuries sustained by the children. Results Two children sustained severe injuries and 1 child was killed. The most common injuries involved the head, neck and shoulder as demonstrated by 3 illustrative reports. Specified changes to school bus design, based on mechanism of injury to the occupants include, in addition to the compartmentalization now in effect, more padding to the sides of the bus, over the window headers and on the panelling between the windows. Conclusions Injuries to the head, neck and spine are the most common types when children are involved in rollover school bus collisions. For additional safety, changes to the current bus design are needed. PMID:12930103

  17. Mechanical analysis of avian feet: multiarticular muscles in grasping and perching

    PubMed Central

    Backus, Spencer B.; Sustaita, Diego; Odhner, Lael U.; Dollar, Aaron M.

    2015-01-01

    The grasping capability of birds' feet is a hallmark of their evolution, but the mechanics of avian foot function are not well understood. Two evolutionary trends that contribute to the mechanical complexity of the avian foot are the variation in the relative lengths of the phalanges and the subdivision and variation of the digital flexor musculature observed among taxa. We modelled the grasping behaviour of a simplified bird foot in response to the downward and upward forces imparted by carrying and perching tasks, respectively. Specifically, we compared the performance of various foot geometries performing these tasks when actuated by distally inserted flexors only, versus by both distally inserted and proximally inserted flexors. Our analysis demonstrates that most species possess relative phalanx lengths that are conducive to grasps actuated only by a single distally inserted tendon per digit. Furthermore, proximally inserted flexors are often required during perching, but the distally inserted flexors are sufficient when grasping and carrying objects. These results are reflected in differences in the relative development of proximally and distally inserted digital flexor musculature among ‘perching’ and ‘grasping’ taxa. Thus, our results shed light on the relative roles of variation in phalanx length and digit flexor muscle distribution in an integrative, mechanical context. PMID:26064598

  18. Analysis of tonal noise generating mechanisms in low-speed axial-flow fans

    NASA Astrophysics Data System (ADS)

    Canepa, Edward; Cattanei, Andrea; Zecchin, Fabio Mazzocut

    2016-08-01

    The present paper reports a comparison of experimental SPL spectral data related to the tonal noise generated by axial-flow fans. A nine blade rotor has been operated at free discharge conditions and in four geometrical configurations in which different kinds of tonal noise generating mechanisms are present: large-scale inlet turbulent structures, tip-gap flow, turbulent wakes, and rotor-stator interaction. The measurements have been taken in a hemi-anechoic chamber at constant rotational speed and, in order to vary the acoustic source strength, during low angular acceleration, linear speed ramps. In order to avoid erroneous quantitative evaluations if the acoustic propagation effects are not considered, the acoustic response functions of the different test configurations have been computed by means of the spectral decomposition method. Then, the properties of the tonal noise generating mechanisms have been studied. To this aim, the constant-Strouhal number SPL, obtained by means of measurements taken during the speed ramps, have been compared with the propagation function. Finally, the analysis of the phase of the acoustic pressure has allowed to distinguish between random and deterministic tonal noise generating mechanisms and to collect information about the presence of important propagation effects.

  19. Parametric finite element analysis of physical stimuli resulting from mechanical stimulation of tissue engineered cartilage.

    PubMed

    Babalola, Omotunde M; Bonassar, Lawrence J

    2009-06-01

    While mechanical stimulation of cells seeded within scaffolds is widely thought to be beneficial, the amount of benefit observed is highly variable between experimental systems. Although studies have investigated specific experimental loading protocols thought to be advantageous for cartilage growth, less is known about the physical stimuli (e.g., pressures, velocities, and local strains) cells experience during these experiments. This study used results of a literature survey, which looked for patterns in the efficacy of mechanical stimulation of chondrocyte seeded scaffolds, to inform the modeling of spatial patterns of physical stimuli present in mechanically stimulated constructs. The literature survey revealed a large variation in conditions used in mechanical loading studies, with a peak to peak strain of 10% (i.e., the maximum amount of deformation experienced by the scaffold) at 1 Hz on agarose scaffolds being the most frequently studied parameters and scaffold. This loading frequency was then used as the basis for simulation in the finite element analyses. 2D axisymmetric finite element models of 2x4 mm2 scaffolds with 360 modulus/permeability combinations were constructed using COMSOL MULTIPHYSICS software. A time dependent coupled pore pressure/effective stress analysis was used to model fluid/solid interactions in the scaffolds upon loading. Loading was simulated using an impermeable frictionless loader on the top boundary with fluid and solid displacement confined to the radial axis. As expected, all scaffold materials exhibited classic poro-elastic behavior having pressurized cores with low fluid flow and edges with high radial fluid velocities. Under the simulation parameters of this study, PEG scaffolds had the highest pressure and radial fluid velocity but also the lowest shear stress and radial strain. Chitosan and KLD-12 simulated scaffold materials had the lowest radial strains and fluid velocities, with collagen scaffolds having the lowest

  20. Accuracy and reproducibility of bending stiffness measurements by mechanical response tissue analysis in artificial human ulnas.

    PubMed

    Arnold, Patricia A; Ellerbrock, Emily R; Bowman, Lyn; Loucks, Anne B

    2014-11-01

    Osteoporosis is characterized by reduced bone strength, but no FDA-approved medical device measures bone strength. Bone strength is strongly associated with bone stiffness, but no FDA-approved medical device measures bone stiffness either. Mechanical Response Tissue Analysis (MRTA) is a non-significant risk, non-invasive, radiation-free, vibration analysis technique for making immediate, direct functional measurements of the bending stiffness of long bones in humans in vivo. MRTA has been used for research purposes for more than 20 years, but little has been published about its accuracy. To begin to investigate its accuracy, we compared MRTA measurements of bending stiffness in 39 artificial human ulna bones to measurements made by Quasistatic Mechanical Testing (QMT). In the process, we also quantified the reproducibility (i.e., precision and repeatability) of both methods. MRTA precision (1.0±1.0%) and repeatability (3.1 ± 3.1%) were not as high as those of QMT (0.2 ± 0.2% and 1.3+1.7%, respectively; both p<10(-4)). The relationship between MRTA and QMT measurements of ulna bending stiffness was indistinguishable from the identity line (p=0.44) and paired measurements by the two methods agreed within a 95% confidence interval of ± 5%. If such accuracy can be achieved on real human ulnas in situ, and if the ulna is representative of the appendicular skeleton, MRTA may prove clinically useful. PMID:25261885

  1. Genomic and transcriptomic analysis of NDM-1 Klebsiella pneumoniae in spaceflight reveal mechanisms underlying environmental adaptability

    PubMed Central

    Li, Jia; Liu, Fei; Wang, Qi; Ge, Pupu; Woo, Patrick C. Y.; Yan, Jinghua; Zhao, Yanlin; Gao, George F.; Liu, Cui Hua; Liu, Changting

    2014-01-01

    The emergence and rapid spread of New Delhi Metallo-beta-lactamase-1 (NDM-1)-producing Klebsiella pneumoniae strains has caused a great concern worldwide. To better understand the mechanisms underlying environmental adaptation of those highly drug-resistant K. pneumoniae strains, we took advantage of the China's Shenzhou 10 spacecraft mission to conduct comparative genomic and transcriptomic analysis of a NDM-1 K. pneumoniae strain (ATCC BAA-2146) being cultivated under different conditions. The samples were recovered from semisolid medium placed on the ground (D strain), in simulated space condition (M strain), or in Shenzhou 10 spacecraft (T strain) for analysis. Our data revealed multiple variations underlying pathogen adaptation into different environments in terms of changes in morphology, H2O2 tolerance and biofilm formation ability, genomic stability and regulation of metabolic pathways. Additionally, we found a few non-coding RNAs to be differentially regulated. The results are helpful for better understanding the adaptive mechanisms of drug-resistant bacterial pathogens. PMID:25163721

  2. Dome design and coupled thermal-mechanical analysis of supersonic missile

    NASA Astrophysics Data System (ADS)

    Ai, Xing-qiao; Wei, Qun; Jia, Hong-guang

    2009-11-01

    A review of high-speed flow pressure and aerodynamic heating effect on Supersonic missile's dome is given. The dome should have excellent properties in optical, mechanical and chemical characteristics. A design of dome on supersonic mode is described according to tactical guide line of a missile. The dome made of quartz which is about 8mm thick and 141mm in window diameter. To check up the reliability of the dome, a reasonable finite element model (FEM) of dome is established, and a thermal-mechanical Analysis to the dome by finite element software NASTRAN has carried on, through these can obtained the distribution of temperature field and stress field when the speed is 2.3Ma. The results indicated that the stress was concentrated in the joint of the dome end and the Missile Section, and the maximum stress was 16.4Mpa. The stress of other nodes was smaller than the allowable stress of quartz glass. Reference to the results of the analysis, a lightweight revision to the dome structural dimension and a new method of dome fixing have put forward, which can reduce the stress concentration.

  3. Genomic and transcriptomic analysis of NDM-1 Klebsiella pneumoniae in spaceflight reveal mechanisms underlying environmental adaptability.

    PubMed

    Li, Jia; Liu, Fei; Wang, Qi; Ge, Pupu; Woo, Patrick C Y; Yan, Jinghua; Zhao, Yanlin; Gao, George F; Liu, Cui Hua; Liu, Changting

    2014-01-01

    The emergence and rapid spread of New Delhi Metallo-beta-lactamase-1 (NDM-1)-producing Klebsiella pneumoniae strains has caused a great concern worldwide. To better understand the mechanisms underlying environmental adaptation of those highly drug-resistant K. pneumoniae strains, we took advantage of the China's Shenzhou 10 spacecraft mission to conduct comparative genomic and transcriptomic analysis of a NDM-1 K. pneumoniae strain (ATCC BAA-2146) being cultivated under different conditions. The samples were recovered from semisolid medium placed on the ground (D strain), in simulated space condition (M strain), or in Shenzhou 10 spacecraft (T strain) for analysis. Our data revealed multiple variations underlying pathogen adaptation into different environments in terms of changes in morphology, H2O2 tolerance and biofilm formation ability, genomic stability and regulation of metabolic pathways. Additionally, we found a few non-coding RNAs to be differentially regulated. The results are helpful for better understanding the adaptive mechanisms of drug-resistant bacterial pathogens. PMID:25163721

  4. Statistical-Mechanical Analysis of Pre-training and Fine Tuning in Deep Learning

    NASA Astrophysics Data System (ADS)

    Ohzeki, Masayuki

    2015-03-01

    In this paper, we present a statistical-mechanical analysis of deep learning. We elucidate some of the essential components of deep learning — pre-training by unsupervised learning and fine tuning by supervised learning. We formulate the extraction of features from the training data as a margin criterion in a high-dimensional feature-vector space. The self-organized classifier is then supplied with small amounts of labelled data, as in deep learning. Although we employ a simple single-layer perceptron model, rather than directly analyzing a multi-layer neural network, we find a nontrivial phase transition that is dependent on the number of unlabelled data in the generalization error of the resultant classifier. In this sense, we evaluate the efficacy of the unsupervised learning component of deep learning. The analysis is performed by the replica method, which is a sophisticated tool in statistical mechanics. We validate our result in the manner of deep learning, using a simple iterative algorithm to learn the weight vector on the basis of belief propagation.

  5. Integrated analysis of genome-wide genetic and epigenetic association data for identification of disease mechanisms.

    PubMed

    Ke, Xiayi; Cortina-Borja, Mario; Silva, Bruno Cesar; Lowe, Robert; Rakyan, Vardhman; Balding, David

    2013-11-01

    Many human diseases are multifactorial, involving multiple genetic and environmental factors impacting on one or more biological pathways. Much of the environmental effect is believed to be mediated through epigenetic changes. Although many genome-wide genetic and epigenetic association studies have been conducted for different diseases and traits, it is still far from clear to what extent the genomic loci and biological pathways identified in the genetic and epigenetic studies are shared. There is also a lack of statistical tools to assess these important aspects of disease mechanisms. In the present study, we describe a protocol for the integrated analysis of genome-wide genetic and epigenetic data based on permutation of a sum statistic for the combined effects in a locus or pathway. The method was then applied to published type 1 diabetes (T1D) genome-wide- and epigenome-wide-association studies data to identify genomic loci and biological pathways that are associated with T1D genetically and epigenetically. Through combined analysis, novel loci and pathways were also identified, which could add to our understanding of disease mechanisms of T1D as well as complex diseases in general. PMID:24071862

  6. Analysis of the scattering mechanisms controlling electron mobility in β-Ga2O3 crystals

    NASA Astrophysics Data System (ADS)

    Parisini, Antonella; Fornari, Roberto

    2016-03-01

    Electron density and Hall mobility data were simultaneously analyzed in the frame of the relaxation time approximation in order to identify the main scattering mechanisms that limit the carrier mobility in β-Ga2O3 single crystals. The Hall factor correction was self-consistently included in the fitting procedure. The analysis indicates that low-energy optical phonons provide the main scattering mechanism, via lattice deformation. In this regard, a deformation potential of about 4 × 109 eV cm-1 was estimated. Furthermore, it is shown that the Hall coefficient and mobility can be measured by the usual experimental geometry, and the standard transport theory can be applied when off-diagonal elements of the resistivity tensor at zero magnetic field are negligible with respect to the diagonal ones. This directly follows from the analysis of the magneto-resistive tensor of a semiconductor with monoclinic structure. Such a requirement is satisfied under the hypothesis of nearly spherical energy surfaces, as has been reported to occur at the Γ minimum of the conduction band of β-Ga2O3.

  7. Genome-wide Comparative Analysis of Atopic Dermatitis and Psoriasis Gives Insight into Opposing Genetic Mechanisms

    PubMed Central

    Baurecht, Hansjörg; Hotze, Melanie; Brand, Stephan; Büning, Carsten; Cormican, Paul; Corvin, Aiden; Ellinghaus, David; Ellinghaus, Eva; Esparza-Gordillo, Jorge; Fölster-Holst, Regina; Franke, Andre; Gieger, Christian; Hubner, Norbert; Illig, Thomas; Irvine, Alan D.; Kabesch, Michael; Lee, Young A.E.; Lieb, Wolfgang; Marenholz, Ingo; McLean, W.H. Irwin; Morris, Derek W.; Mrowietz, Ulrich; Nair, Rajan; Nöthen, Markus M.; Novak, Natalija; O’Regan, Grainne M.; Schreiber, Stefan; Smith, Catherine; Strauch, Konstantin; Stuart, Philip E.; Trembath, Richard; Tsoi, Lam C.; Weichenthal, Michael; Barker, Jonathan; Elder, James T.; Weidinger, Stephan; Cordell, Heather J.; Brown, Sara J.

    2015-01-01

    Atopic dermatitis and psoriasis are the two most common immune-mediated inflammatory disorders affecting the skin. Genome-wide studies demonstrate a high degree of genetic overlap, but these diseases have mutually exclusive clinical phenotypes and opposing immune mechanisms. Despite their prevalence, atopic dermatitis and psoriasis very rarely co-occur within one individual. By utilizing genome-wide association study and ImmunoChip data from >19,000 individuals and methodologies developed from meta-analysis, we have identified opposing risk alleles at shared loci as well as independent disease-specific loci within the epidermal differentiation complex (chromosome 1q21.3), the Th2 locus control region (chromosome 5q31.1), and the major histocompatibility complex (chromosome 6p21–22). We further identified previously unreported pleiotropic alleles with opposing effects on atopic dermatitis and psoriasis risk in PRKRA and ANXA6/TNIP1. In contrast, there was no evidence for shared loci with effects operating in the same direction on both diseases. Our results show that atopic dermatitis and psoriasis have distinct genetic mechanisms with opposing effects in shared pathways influencing epidermal differentiation and immune response. The statistical analysis methods developed in the conduct of this study have produced additional insight from previously published data sets. The approach is likely to be applicable to the investigation of the genetic basis of other complex traits with overlapping and distinct clinical features. PMID:25574825

  8. Thermohydrodynamics analysis on the mechanism of bump formation in laser texturing

    NASA Astrophysics Data System (ADS)

    Ohmura, Etsuji; Murayama, Rina; Miyamoto, Isamu

    2000-11-01

    Laser texturing on a hard disk for a computer has been already used practically, but the mechanism of bump formation has not been elucidated yet. The purpose of this study is to elucidate the mechanism of bump formation in laser texturing by thermohydrodynamics analysis. Latent heat of evaporation, movement of gas and liquid interface, evaporation recoil pressure, Marangoni force that depends on temperature gradient and the surface tension are considered. The VOF (Volume of Fluid) method is used for the analysis of behavior of the free surface. Obtained results are as follows : (1) The downward flow is generated in the molten pool by the evaporation recoil pressure, and then it induces the outward flow in the radial direction. (2) After laser irradiation is stopped, the downward flow at the center of the molten pool and the outward flow in the radial direction are kept. Therefore, the center of the molten pool is lowered and the surface rises around the hole, that is, a bump is formed. (3) When the temperature coefficient of surface tension is negative, Marangoni force is most effective to the surface rise when the resolidification starts outside of the bump.

  9. Mechanical transmission in a Pacinian corpuscle. An analysis and a theory

    PubMed Central

    Loewenstein, W. R.; Skalak, R.

    1966-01-01

    1. An analysis is made of the transmission of mechanical forces through the Pacinian corpuscle. In particular, forces are analysed which produce pressure differences at the centre of the corpuscle and lead to excitation of the sensory nerve ending. 2. The main structural elements in force transmission through the corpuscle are the lamellae, their interconnexions, and the interlamellar fluid. The two former provide the elastic elements and constraint for the fluid; and the latter, the viscous elements. The mechanical equivalent incorporating these elements is a system of dashpots (the lamellar surfaces and the interlamellar fluid) and springs (the lamellae and their interconnexions); it is a mechanical filter which suppresses low frequencies. The dynamic and static patterns of lamella displacements in the equivalent are in close agreement with those observed in Pacinian corpuscles. 3. Steady-state and transient pressure fields were determined for the equivalent. Under static compression, only elastic forces exist in the corpuscle. Analysis shows that such forces are transmitted poorly from periphery to centre through the lamellated structure. The compliance of the lamellar interconnexions is so high in relation to that of the lamellae themselves, that most of the pressure load is carried by the outer lamellae. As a result, only a small fraction of the steady-state pressure at the outer surface reaches the centre of the corpuscle where the sensory ending is located. This is the mechanical basis of receptor adaptation. 4. Under dynamic compression, viscous forces develop in the corpuscle; and these account for most of the pressure at times too early for development of elastic deformations. Analysis shows that such forces are transmitted well. For example, if a typical corpuscle of 500μ diameter is compressed by 20μ linearly during 2 msec, the pressure differences near to the centre of the corpuscle are initially as high as at the periphery, and stay within the same

  10. Intraoral laser welding: ultrastructural and mechanical analysis to compare laboratory laser and dental laser.

    PubMed

    Fornaini, Carlo; Passaretti, Francesca; Villa, Elena; Rocca, Jean-Paul; Merigo, Elisabetta; Vescovi, Paolo; Meleti, Marco; Manfredi, Maddalena; Nammour, Samir

    2011-07-01

    The Nd:YAG laser has been used since 1970 in dental laboratories to weld metals on dental prostheses. Recently in several clinical cases, we have suggested that the Nd:YAG laser device commonly utilized in the dental office could be used to repair broken fixed, removable and orthodontic prostheses and to weld metals directly in the mouth. The aim of this work was to evaluate, using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and dynamic mechanical analysis (DMA), the quality of the weld and its mechanical strength, comparing a device normally used in dental laboratory and a device normally used in the dental office for oral surgery, the same as that described for intraoral welding. Metal plates of a Co-Cr-Mo dental alloy and steel orthodontic wires were subjected to four welding procedures: welding without filler metal using the laboratory laser, welding with filler metal using the laboratory laser, welding without filler metal using the office laser, and welding with filler metal using the office laser. The welded materials were then analysed by SEM, EDS and DMA. SEM analysis did not show significant differences between the samples although the plates welded using the office laser without filler metal showed a greater number of fissures than the other samples. EDS microanalysis of the welding zone showed a homogeneous composition of the metals. Mechanical tests showed similar elastic behaviours of the samples, with minimal differences between the samples welded with the two devices. No wire broke even under the maximum force applied by the analyser. This study seems to demonstrate that the welds produced using the office Nd:YAG laser device and the laboratory Nd:YAG laser device, as analysed by SEM, EDS and DMA, showed minimal and nonsignificant differences, although these findings need to be confirmed using a greater number of samples. PMID:20437262

  11. Quantitatively probing propensity for structural transitions in engineered virus nanoparticles by single-molecule mechanical analysis

    NASA Astrophysics Data System (ADS)

    Castellanos, Milagros; Carrillo, Pablo J. P.; Mateu, Mauricio G.

    2015-03-01

    Viruses are increasingly being studied from the perspective of fundamental physics at the nanoscale as biologically evolved nanodevices with many technological applications. In viral particles of the minute virus of mice (MVM), folded segments of the single-stranded DNA genome are bound to the capsid inner wall and act as molecular buttresses that increase locally the mechanical stiffness of the particle. We have explored whether a quantitative linkage exists in MVM particles between their DNA-mediated stiffening and impairment of a heat-induced, virus-inactivating structural change. A series of structurally modified virus particles with disrupted capsid-DNA interactions and/or distorted capsid cavities close to the DNA-binding sites were engineered and characterized, both in classic kinetics assays and by single-molecule mechanical analysis using atomic force microscopy. The rate constant of the virus inactivation reaction was found to decrease exponentially with the increase in elastic constant (stiffness) of the regions closer to DNA-binding sites. The application of transition state theory suggests that the height of the free energy barrier of the virus-inactivating structural transition increases linearly with local mechanical stiffness. From a virological perspective, the results indicate that infectious MVM particles may have acquired the biological advantage of increased survival under thermal stress by evolving architectural elements that rigidify the particle and impair non-productive structural changes. From a nanotechnological perspective, this study provides proof of principle that determination of mechanical stiffness and its manipulation by protein engineering may be applied for quantitatively probing and tuning the conformational dynamics of virus-based and other protein-based nanoassemblies.Viruses are increasingly being studied from the perspective of fundamental physics at the nanoscale as biologically evolved nanodevices with many technological

  12. Fermilab D-0 Experimental Facility: Energy conservation report and mechanical systems design optimization and cost analysis study

    SciTech Connect

    Krstulovich, S.F.

    1987-10-31

    This report is developed as part of the Fermilab D-0 Experimental Facility Project Title II Design Documentation Update. As such, it concentrates primarily on HVAC mechanical systems design optimization and cost analysis.

  13. A mechanical analysis of woodpecker drumming and its application to shock-absorbing systems.

    PubMed

    Yoon, Sang-Hee; Park, Sungmin

    2011-03-01

    A woodpecker is known to drum the hard woody surface of a tree at a rate of 18 to 22 times per second with a deceleration of 1200 g, yet with no sign of blackout or brain damage. As a model in nature, a woodpecker is studied to find clues to develop a shock-absorbing system for micromachined devices. Its advanced shock-absorbing mechanism, which cannot be explained merely by allometric scaling, is analyzed in terms of endoskeletal structures. In this analysis, the head structures (beak, hyoid, spongy bone, and skull bone with cerebrospinal fluid) of the golden-fronted woodpecker, Melanerpes aurifrons, are explored with x-ray computed tomography images, and their shock-absorbing mechanism is analyzed with a mechanical vibration model and an empirical method. Based on these analyses, a new shock-absorbing system is designed to protect commercial micromachined devices from unwanted high-g and high-frequency mechanical excitations. The new shock-absorbing system consists of close-packed microglasses within two metal enclosures and a viscoelastic layer fastened by steel bolts, which are biologically inspired from a spongy bone contained within a skull bone encompassed with the hyoid of a woodpecker. In the experimental characterizations using a 60 mm smoothbore air-gun, this bio-inspired shock-absorbing system shows a failure rate of 0.7% for the commercial micromachined devices at 60 000 g, whereas a conventional hard-resin method yields a failure rate of 26.4%, thus verifying remarkable improvement in the g-force tolerance of the commercial micromachined devices. PMID:21245520

  14. Flickering Analysis of Erythrocyte Mechanical Properties: Dependence on Oxygenation Level, Cell Shape, and Hydration Level

    PubMed Central

    Yoon, Young-Zoon; Hong, Ha; Brown, Aidan; Kim, Dong Chung; Kang, Dae Joon; Lew, Virgilio L.; Cicuta, Pietro

    2009-01-01

    Erythrocytes (red blood cells) play an essential role in the respiratory functions of vertebrates, carrying oxygen from lungs to tissues and CO2 from tissues to lungs. They are mechanically very soft, enabling circulation through small capillaries. The small thermally induced displacements of the membrane provide an important tool in the investigation of the mechanics of the cell membrane. However, despite numerous studies, uncertainties in the interpretation of the data, and in the values derived for the main parameters of cell mechanics, have rendered past conclusions from the fluctuation approach somewhat controversial. Here we revisit the experimental method and theoretical analysis of fluctuations, to adapt them to the case of cell contour fluctuations, which are readily observable experimentally. This enables direct measurements of membrane tension, of bending modulus, and of the viscosity of the cell cytoplasm. Of the various factors that influence the mechanical properties of the cell, we focus here on: 1), the level of oxygenation, as monitored by Raman spectrometry; 2), cell shape; and 3), the concentration of hemoglobin. The results show that, contrary to previous reports, there is no significant difference in cell tension and bending modulus between oxygenated and deoxygenated states, in line with the softness requirement for optimal circulatory flow in both states. On the other hand, tension and bending moduli of discocyte- and spherocyte-shaped cells differ markedly, in both the oxygenated and deoxygenated states. The tension in spherocytes is much higher, consistent with recent theoretical models that describe the transitions between red blood cell shapes as a function of membrane tension. Cell cytoplasmic viscosity is strongly influenced by the hydration state. The implications of these results to circulatory flow dynamics in physiological and pathological conditions are discussed. PMID:19751665

  15. A quantitative quantum-chemical analysis tool for the distribution of mechanical force in molecules

    SciTech Connect

    Stauch, Tim; Dreuw, Andreas

    2014-04-07

    The promising field of mechanochemistry suffers from a general lack of understanding of the distribution and propagation of force in a stretched molecule, which limits its applicability up to the present day. In this article, we introduce the JEDI (Judgement of Energy DIstribution) analysis, which is the first quantum chemical method that provides a quantitative understanding of the distribution of mechanical stress energy among all degrees of freedom in a molecule. The method is carried out on the basis of static or dynamic calculations under the influence of an external force and makes use of a Hessian matrix in redundant internal coordinates (bond lengths, bond angles, and dihedral angles), so that all relevant degrees of freedom of a molecule are included and mechanochemical processes can be interpreted in a chemically intuitive way. The JEDI method is characterized by its modest computational effort, with the calculation of the Hessian being the rate-determining step, and delivers, except for the harmonic approximation, exact ab initio results. We apply the JEDI analysis to several example molecules in both static quantum chemical calculations and Born-Oppenheimer Molecular Dynamics simulations in which molecules are subject to an external force, thus studying not only the distribution and the propagation of strain in mechanically deformed systems, but also gaining valuable insights into the mechanochemically induced isomerization of trans-3,4-dimethylcyclobutene to trans,trans-2,4-hexadiene. The JEDI analysis can potentially be used in the discussion of sonochemical reactions, molecular motors, mechanophores, and photoswitches as well as in the development of molecular force probes.

  16. Application of computational mechanics to the analysis of natural data: an example in geomagnetism.

    PubMed

    Clarke, Richard W; Freeman, Mervyn P; Watkins, Nicholas W

    2003-01-01

    We discuss how the ideal formalism of computational mechanics can be adapted to apply to a noninfinite series of corrupted and correlated data, that is typical of most observed natural time series. Specifically, a simple filter that removes the corruption that creates rare unphysical causal states is demonstrated, and the concept of effective soficity is introduced. We believe that computational mechanics cannot be applied to a noisy and finite data series without invoking an argument based upon effective soficity. A related distinction between noise and unresolved structure is also defined: Noise can only be eliminated by increasing the length of the time series, whereas the resolution of previously unresolved structure only requires the finite memory of the analysis to be increased. The benefits of these concepts are demonstrated in a simulated times series by (a) the effective elimination of white noise corruption from a periodic signal using the expletive filter and (b) the appearance of an effectively sofic region in the statistical complexity of a biased Poisson switch time series that is insensitive to changes in the word length (memory) used in the analysis. The new algorithm is then applied to an analysis of a real geomagnetic time series measured at Halley, Antarctica. Two principal components in the structure are detected that are interpreted as the diurnal variation due to the rotation of the Earth-based station under an electrical current pattern that is fixed with respect to the Sun-Earth axis and the random occurrence of a signature likely to be that of the magnetic substorm. In conclusion, some useful terminology for the discussion of model construction in general is introduced. PMID:12636581

  17. [Arc spectrum diagnostic and heat coupling mechanism analysis of double wire pulsed MIG welding].

    PubMed

    Liu, Yong-qiang; Li, Huan; Yang, Li-jun; Zheng, Kai; Gao, Ying

    2015-01-01

    A double wire pulsed MIG welding test system was built in the present paper, in order to analyze the heat-coupling mechanism of double wire pulsed MIG welding, and study are temperature field. Spectroscopic technique was used in diagnostic analysis of the are, plasma radiation was collected by using hollow probe method to obtain the arc plasma optical signal The electron temperature of double wire pulsed MIG welding arc plasma was calculated by using Boltzmann diagram method, the electron temperature distribution was obtained, a comprehensive analysis of the arc was conducted combined with the high speed camera technology and acquisition means of electricity signal. The innovation of this paper is the combination of high-speed camera image information of are and optical signal of arc plasma to analyze the coupling mechanism for dual arc, and a more intuitive analysis for are temperature field was conducted. The test results showed that a push-pull output was achieved and droplet transfer mode was a drop in a pulse in the welding process; Two arcs attracted each other under the action of a magnetic field, and shifted to the center of the arc in welding process, so a new heat center was formed at the geometric center of the double arc, and flowing up phenomenon occurred on the arc; Dual arc electronic temperature showed an inverted V-shaped distribution overall, and at the geometric center of the double arc, the arc electron temperature at 3 mm off the workpiece surface was the highest, which was 16,887.66 K, about 4,900 K higher than the lowest temperature 11,963.63 K. PMID:25993809

  18. Within-Breath Analysis of Respiratory Mechanics in Asthmatic Patients by Forced Oscillation

    PubMed Central

    Veiga, Juliana; Lopes, Agnaldo José; Jansen, José Manoel; de Melo, Pedro Lopes

    2009-01-01

    INTRODUCTION: The within-breath analysis of respiratory mechanics by the monofrequency Forced Oscillation Technique (mFOT) is of great interest in both physiopathology studies and the diagnosis of respiratory diseases. However, there are limited data on the use of this technique in the analysis of asthma. This study evaluates within-breath mechanics of asthmatic individuals and the contribution of the mFOT in the asthma diagnosis. METHODS: Twenty-two healthy and twenty-two asthmatic subjects, including patients with mild (n=8), moderate (n=8), and severe (n=6) obstruction, were studied. Forced Oscillation Technique data were interpreted using the mean respiratory impedance (Zt), the impedance during inspiration (Zi), expiration (Ze), at the beginning of inspiration (Zii), and at expiration (Zie). The peak-to-peak impedance (Zpp) was also calculated by the subtraction of Zii from Zie. Receiver operating characteristic curves were used to determine the sensitivity (Se) and specificity (Sp) of m Forced Oscillation Technique parameters in identifying asthma. RESULTS: Respiratory impedance values were significantly higher in asthmatics: Zt (p<0.001), Zi (p<0.001), Ze (p<0.001), Zii (p<0.001), Zie (p<0.001), and Zpp (p<0.003). The best parameters for detecting asthma were Zi, Zii, and Zie (Se=90.9%, Sp=90.9%), followed by Zt and Ze. These results are in close agreement with recently published theories and pathophysiological fundamentals. CONCLUSIONS: mFOT permits a non-invasive and detailed analysis in different phases of the respiratory cycle, providing parameters that are adequate for the diagnosis of asthma with high accuracy. These results confirm the high clinical and scientific potential of this methodology in the evaluation of asthmatic patients. PMID:19606241

  19. A quantitative quantum-chemical analysis tool for the distribution of mechanical force in molecules

    NASA Astrophysics Data System (ADS)

    Stauch, Tim; Dreuw, Andreas

    2014-04-01

    The promising field of mechanochemistry suffers from a general lack of understanding of the distribution and propagation of force in a stretched molecule, which limits its applicability up to the present day. In this article, we introduce the JEDI (Judgement of Energy DIstribution) analysis, which is the first quantum chemical method that provides a quantitative understanding of the distribution of mechanical stress energy among all degrees of freedom in a molecule. The method is carried out on the basis of static or dynamic calculations under the influence of an external force and makes use of a Hessian matrix in redundant internal coordinates (bond lengths, bond angles, and dihedral angles), so that all relevant degrees of freedom of a molecule are included and mechanochemical processes can be interpreted in a chemically intuitive way. The JEDI method is characterized by its modest computational effort, with the calculation of the Hessian being the rate-determining step, and delivers, except for the harmonic approximation, exact ab initio results. We apply the JEDI analysis to several example molecules in both static quantum chemical calculations and Born-Oppenheimer Molecular Dynamics simulations in which molecules are subject to an external force, thus studying not only the distribution and the propagation of strain in mechanically deformed systems, but also gaining valuable insights into the mechanochemically induced isomerization of trans-3,4-dimethylcyclobutene to trans,trans-2,4-hexadiene. The JEDI analysis can potentially be used in the discussion of sonochemical reactions, molecular motors, mechanophores, and photoswitches as well as in the development of molecular force probes.

  20. Fracture mechanics analysis of NGV fuel cylinders. Part 1: Steel cylinders

    NASA Astrophysics Data System (ADS)

    Connolly, M. P.; Hudak, S. J.; Roy, S.

    1993-02-01

    Compressed natural gas (CNG) cylinders for natural gas vehicles (NGVs) are subject to a combination of pressure cycles, associated with periodic refueling, and a potentially corrosive CNG environment. Under these conditions it has been shown that the life of the cylinder is governed by the corrosion-fatigue crack growth of internal flaws such as voids, pits or folds that may be present after manufacture. For NGV applications, these cylinders are required to operate for at least 15 years and the report, through a detailed fracture mechanics analysis, describes approaches to achieving the desired life. The analysis shows that a 15 year cylinder life can be obtained by using quality control to ensure that no initial defects greater than 0.045 in. X 0.090 in. exist after manufacture. Alternatively, gas drying can be used at the distribution stations to reduce the detrimental effects of the remaining CNG impurities, and thereby, produce long cylinder lives. The analysis also considers the role of in-service inspection/retest and shows that in-service NDE has little advantage, either technically or economically, for ensuring the fitness-for-service of steel NGV cylinders. The analysis also shows that hydrostatic testing of cylinders, either at manufacture or in service, is ineffective for detecting fatigue cracks and therefore should not be implemented as part of a fitness-for-service plan for NGV fuel cylinders. The issue of cylinder geometry was also considered and the analysis shows that improperly designed flat-bottomed CNG cylinders can result in premature fatigue failures originating at the inner wall in the transition region between the cylinder end and sidewall.

  1. Fabrication and Dynamic Mechanical Analysis of Hydroxyapatite Nanoparticle/Gelatin Porous Scaffolds

    NASA Astrophysics Data System (ADS)

    Ghossein, Hicham

    The application of engineered biomaterial scaffolds for hard tissue repair critically depends on the scaffold's internal architecture at various length scales. The pore size, shape, surface morphology, and pore connectivity are among the most important factors that affect the scaffold's mechanical properties and biointegration. Reported in this thesis are the results of the investigation of porous constructs fabricated by a freeze-drying process from synthetic nanosized hydroxyapatite / gelatin (nanoHA/Gel) dispersions with different nanoHA/Gel ratios (nanoHA loading was varied from 0 to 50 % by weight). The fabricated scaffolds had porosity up to 90% with pore size in the range of 100 - 500 im, and good distribution of HA nanoparticles within the gelatin matrix. Such porosity is considered to be close to optimal to promote a good cell adhesion in the potential applications of prepared constructs. The fabricated scaffolds have been investigated using X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and Dynamic Mechanical Analysis (DMA). Dynamic mechanical analysis of as-fabricated scaffolds revealed that the scaffolds achieved maximum bending and tensile moduli up to 1.28 GPa and 1.5 GPa, respectively, when nanoHA loading was around 30 % by weight. The bending modulus increases by a factor of 1.6, while the Tension modulus increased by a factor of 0.8 after the cross-linking of polymer. Higher nanoHA loading above 50 % by weight results in bending modulus of about 700 MPa and Tension modulus of about 200 MPa only. However, the cross-linking still enhanced the bending up to 1 GPa while it did not affect much the Tension modulus in 50% nanoHA/gelatin constructs. It has been shown that the cross-linking with glutaraldehyde solution improves the morphological structure of the scaffolds, while there was no apparent effect of the cross-linking on the chemical changes in both organic and inorganic content during the processing. The results of this

  2. Switching mechanism for TiO2 memristor and quantitative analysis of exponential model parameters

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Ping; Chen, Min; Shen, Yi

    2015-08-01

    The memristor, as the fourth basic circuit element, has drawn worldwide attention since its physical implementation was released by HP Labs in 2008. However, at the nano-scale, there are many difficulties for memristor physical realization. So a better understanding and analysis of a good model will help us to study the characteristics of a memristor. In this paper, we analyze a possible mechanism for the switching behavior of a memristor with a Pt/TiO2/Pt structure, and explain the changes of electronic barrier at the interface of Pt/TiO2. Then, a quantitative analysis about each parameter in the exponential model of memristor is conducted based on the calculation results. The analysis results are validated by simulation results. The efforts made in this paper will provide researchers with theoretical guidance on choosing appropriate values for (α, β, χ, γ) in this exponential model. Project supported by the National Natural Science Foundation of China (Grant Nos. 61374150 and 61374171), the State Key Program of the National Natural Science Foundation of China (Grant No. 61134012), the National Basic Research Program of China (Grant No. 2011CB710606), and the Fundamental Research Funds for the Central Universities, China (Grant No. 2013TS126).

  3. Metabolomic analysis reveals mechanism of antioxidant butylated hydroxyanisole on lipid accumulation in Crypthecodinium cohnii.

    PubMed

    Sui, Xiao; Niu, Xiangfeng; Shi, Mengliang; Pei, Guangsheng; Li, Jinghan; Chen, Lei; Wang, Jiangxin; Zhang, Weiwen

    2014-12-24

    The heterotrophic dinoflagellate alga Crypthecodinium cohnii is known to accumulate lipids with a high fraction of docosahexaenoic acid (DHA). In this study, we first evaluated two antioxidant compounds, butylated hydroxyanisole (BHA) and propyl gallate (PG), for their effects on lipid accumulation in C. cohnii. The results showed that antioxidant BHA could increase lipid accumulation in C. cohnii by 8.80% at a final concentration of 30 μM, while PG had no obvious effect on lipid accumulation at the tested concentrations. To decipher the molecular mechanism responsible for the increased lipid accumulation by BHA, we employed an integrated GC-MS and LC-MS metabolomic approach to determine the time-series metabolic profiles with or without BHA, and then subjected the metabolomic data to a principal component analysis (PCA) and a weighted gene coexpression network analysis (WGCNA) network analyses to identify the key metabolic modules and metabolites possibly relevant to the increased lipid accumulation. LC-MS analysis showed that several metabolites, including NADPH, could be important for the stimulation role of BHA on lipid accumulation. Meanwhile GC-MS and network analyses allowed identification of eight metabolic modules and nine hub metabolites possibly relevant to the stimulation role of BHA in C. cohnii. The study provided a metabolomics view of the BHA mode of action on lipid accumulation in C. cohnii, and the information could be valuable for a better understanding of antioxidant effects on lipid accumulation in other microalgae as well. PMID:25436856

  4. Damage-Resistant Composites Using Electrospun Nanofibers: A Multiscale Analysis of the Toughening Mechanisms.

    PubMed

    Daelemans, Lode; van der Heijden, Sam; De Baere, Ives; Rahier, Hubert; Van Paepegem, Wim; De Clerck, Karen

    2016-05-11

    nanofiber bridging mechanism expresses itself is different for each scale and dependent on parameters linked to a certain scale. The multiscale analysis of the toughening mechanisms reported in this paper is therefore crucial for understanding the behavior of nanofiber toughened composites, and as such allows for designing novel, damage-resistant, nanofiber-toughened materials. PMID:27088482

  5. Characterization of the mechanical properties of skin by inverse analysis combined with the indentation test.

    PubMed

    Delalleau, Alexandre; Josse, Gwendal; Lagarde, Jean-Michel; Zahouani, Hassan; Bergheau, Jean-Michel

    2006-01-01

    the Institution of Mechanical Engineers 208, 217-222] This analysis will be extended to more realistic models in further works. PMID:15990103

  6. Analysis of the mechanical characteristics of aluminum-lithium 2195 weldments

    NASA Astrophysics Data System (ADS)

    Deng, Xinhui

    Aluminum-lithium 2195 plate is a new generation of structural material used in space shuttle fuel tank. These aluminum-lithium plates are joined together by using Variable Polarity Plasma Arc (VPPA) welding process. Because of the low ductility of welds, the mechanical property of this structural material is limited, since the welding zone is the weakest area in the structure. The mechanical properties and microstructure of welds are influenced by many factors such as welding process parameters, filler material, welding geometry, and so on. By using experimental method this paper studied the deformation characteristics of the VPPA welds joined by 0.25 inch thick 2195 Al-Li alloy plates using 4043 Al-Si filler material. It describes the effect of weld defects such as porosity and micro-crack on the crack initiation and the fracture mode of the welds. It describes the flow strength and ductility of each zone in the weld. This study investigated the local strain distributions on the crown side and the root side of the welds. This study also investigated the effect of temperature, different solution treatment on the tensile properties of the welds. The aim of this study is also to better understand the effect of weld geometry on the failure mechanism of the welds and their mechanical properties. All examinations were performed on tensile specimens of the welds. The standard tensile tests were utilized to investigate the mechanical properties of the welds in different conditions. In order to investigate the mechanism of fracture and the effect of weld defects, some welds were tested after removal of fusion zone reinforcement. The fractographic examinations revealed that the fracture of aluminum-lithium alloy 2195 VPPA weld tensile specimen originates at the root corner then path to the crown corner in the same side of the fusion zone. However, the weld specimens without fusion zone reinforcement have crack initiation in the middle of the fusion zone. The failure is

  7. Experimental measurement and modeling analysis on mechanical properties of tensor tympani tendon.

    PubMed

    Cheng, Tao; Gan, Rong Z

    2008-04-01

    In this paper, we report mechanical properties of the tensor tympani tendon of human ear measured from uniaxial tensile, stress relaxation and failure tests. The hyperelastic Ogden model and digital image correlation method were employed to analyze experimental data. The constitutive equation of the tendon was derived through data iteration processes, and Young's modulus was presented as a function of stress. The viscoelastic property of the tendon was described by stress relaxation function and hysteresis. Furthermore, three-dimensional finite element analysis was carried out on five tendon models to investigate relationship between the structure and properties. The dimensions of the tendon were also measured by image processing techniques and presented with statistic significance. The structure and properties of the tensor tympani tendon reported in this study add new data into the study of ear tissue biomechanics. PMID:17553724

  8. Molecular Dynamics Simulation and Statistics Analysis Reveals the Defense Response Mechanism in Plants

    NASA Astrophysics Data System (ADS)

    Liu, Zhichao; Zhao, Yunjie; Zeng, Chen; Computational Biophysics Lab Team

    As the main protein of the bacterial flagella, flagellin plays an important role in perception and defense response. The newly discovered locus, FLS2, is ubiquitously expressed. FLS2 encodes a putative receptor kinase and shares many homologies with some plant resistance genes and even with some components of immune system of mammals and insects. In Arabidopsis, FLS2 perception is achieved by the recognition of epitope flg22, which induces FLS2 heteromerization with BAK1 and finally the plant immunity. Here we use both analytical methods such as Direct Coupling Analysis (DCA) and Molecular Dynamics (MD) Simulations to get a better understanding of the defense mechanism of FLS2. This may facilitate a redesign of flg22 or de-novo design for desired specificity and potency to extend the immune properties of FLS2 to other important crops and vegetables.

  9. Dynamic Analysis and Design of Separation Screen Mechanism in a Plant of Moisturized Wastes

    NASA Astrophysics Data System (ADS)

    Moon, Byung Young; Kim, Kwang Hoon; Kwak, Kwang Hoon; Kang, Gyung Ju; Hong, Chul Hyun

    In this study, theoretical super screen vibration analysis has been carried out to predict the dynamic characteristics of interactive waste particles. The vibrating screen is modeled of three assemblies such as screen, wastes guide, and supported screen. Then materials (or particles) of different size is to be separated by using the eccentric vibrator and classifying tilt plates. In processing separation mechanism, much lighter construction wastes (wood, Styrofoam, etc) and heavier materials are separated by staying time delay in a super screen. The design results, separation screen were able to know that small and larger particles are conspicuous difference each motion character according to trajectory particles, and small particles raise the probability in classifying tilt plates.

  10. Crater modification by gravity - A mechanical analysis of slumping. [on moon

    NASA Technical Reports Server (NTRS)

    Melosh, H. J.

    1977-01-01

    An analysis of the stability of a crater from a mechanical point of view indicates that the observed slumping of lunar craters requires a perfectly plastic constitutive relation for the lunar surface rock. The angle of internal friction of this material must be less than a few degrees. The evidence for a perfectly plastic constitutive relation is described, and a simplified model of a crater in a perfectly plastic medium is used to investigate the nature of its collapse. Crater stability is found to depend principally upon a dimensionless parameter equal to the product of the density, acceleration of gravity, and depth divided by the yield strength. Criteria for stability, 'slope failures', and 'floor failures' are reported.

  11. Heat transfer analysis of a programmable Josephson voltage standard chip operated with a mechanical cooler

    NASA Astrophysics Data System (ADS)

    Takahashi, Hikari; Maruyama, Michitaka; Amagai, Yasutaka; Yamamori, Hirotake; Kaneko, Nobu-hisa; Kiryu, Shogo

    2015-11-01

    We are developing a 10 V programmable Josephson voltage standard (PJVS) system using a 10 K mechanical cooler that enables liquid-helium-free operation. In our previous experiments, we identified a problem that the optimum bias operating points may be affected by the heating effect of the chip depending on the output voltage. In this study, we have observed cross-sectional and in-plane structures of the PJVS chip module in order to determine the cause of the heating effect. We perform a heat transfer analysis using the finite element method with several models based on the observation results. We confirm a temperature increase of approximately 100 mK at the chip surface, due mainly to unintended voids in the InSn solder.

  12. Analysis of suitable geometrical parameters for designing a tendon-driven under-actuated mechanical finger

    NASA Astrophysics Data System (ADS)

    Penta, Francesco; Rossi, Cesare; Savino, Sergio

    2016-06-01

    This study aims to optimize the geometrical parameters of an under-actuated mechanical finger by conducting a theoretical analysis of these parameters. The finger is actuated by a flexion tendon and an extension tendon. The considered parameters are the tendon guide positions with respect to the hinges. By applying such an optimization, the correct kinematical and dynamical behavior of the closing cycle of the finger can be obtained. The results of this study are useful for avoiding the snapthrough and the single joint hyperflexion, which are the two breakdowns most frequently observed during experimentation on prototypes. Diagrams are established to identify the optimum values for the tendon guides position of a finger with specified dimensions. The findings of this study can serve as guide for future finger design.

  13. Inner crack reconstruction and mechanical analysis for rock-specimen-based phase measuring profilometry

    NASA Astrophysics Data System (ADS)

    Cao, Yiping; He, Yuhang

    2009-12-01

    A higher precise inner crack three-dimenssional(3D) reconstructed method of rock specimens is presented. Two inner shapes of the crack are measured with Phase Measuring Profilometry (PMP), and their edges are drawn out by height information instead of the traditional method based on gray information. Subsequently contour matching and height matching are carried out with algorithms due to maximum correlativity. The inner width and volume of the crack are educed according to the fissure of a rock specimen's outer surface, and the 3D profile of the crack is reconstructed with a high repetitive precision superior to 20μm. The proposed method is effective for evaluating the crack's width of rock specimens in the exploitation of petroleum and natural gas with a mechanical analysis method. The experiment shows its feasibility and practicability.

  14. Inner crack reconstruction and mechanical analysis for rock-specimen-based phase measuring profilometry

    NASA Astrophysics Data System (ADS)

    Cao, Yiping; He, Yuhang

    2010-03-01

    A higher precise inner crack three-dimenssional(3D) reconstructed method of rock specimens is presented. Two inner shapes of the crack are measured with Phase Measuring Profilometry (PMP), and their edges are drawn out by height information instead of the traditional method based on gray information. Subsequently contour matching and height matching are carried out with algorithms due to maximum correlativity. The inner width and volume of the crack are educed according to the fissure of a rock specimen's outer surface, and the 3D profile of the crack is reconstructed with a high repetitive precision superior to 20μm. The proposed method is effective for evaluating the crack's width of rock specimens in the exploitation of petroleum and natural gas with a mechanical analysis method. The experiment shows its feasibility and practicability.

  15. A fracture mechanics analysis of impact damage in a thick composite laminate

    NASA Technical Reports Server (NTRS)

    Poe, C. C., Jr.

    1985-01-01

    Graphite/epoxy filament-wound cases (FWC) for the solid rocket motors of the space shuttle are being made by NASA. The FWC cases are wound with AS4W graphite fiber impregnated with an epoxy resin and are about 1.4 inches or more thick. Graphite-epoxy composite laminates, unlike metals, can be damaged easily by low velocity impacts of objects like dropped tools. The residual tension strength of the FWC laminate, after impact, is being studied at Langley Research Center. The conditions that give minimum visual evidence of damage are being emphasized. A fracture mechanics analysis was developed to predict the residual strength, after impact, using radiographs to measure the size of the damage and an equivalent surface crack to represent the damage.

  16. Limit Analysis for the Mechanical Structure of the ITER Neutron Shielding Block

    NASA Astrophysics Data System (ADS)

    Hao, Junchuan; Song, Yuntao; Du, Shuangsong; Wang, Zhongwei; Xu, Yang; Feng, Changle

    2013-04-01

    The ITER neutron shielding blocks are located between the inner shell and the outer shell of the vacuum vessel (VV) with the main function of providing neutron shielding. Considering the combined loads of the shielding blocks during the plasma operation of the ITER, limit analysis for one typical ferromagnetic (FM) shielding block has been performed and the structural design has been evaluated based on the American Society of Mechanical Engineers (ASME) criterion and European standards. Results show that the collapse load of this shielding block is three times the specified load, which is much higher than the design requirement of 1.25. The structure of this neutron shielding block has a sufficient safety margin.

  17. Global analysis of fungal morphology exposes mechanisms of host cell escape

    PubMed Central

    O’Meara, Teresa R.; Veri, Amanda O.; Ketela, Troy; Jiang, Bo; Roemer, Terry; Cowen, Leah E.

    2015-01-01

    Developmental transitions between single-cell yeast and multicellular filaments underpin virulence of diverse fungal pathogens. For the leading human fungal pathogen Candida albicans, filamentation is thought to be required for immune cell escape via induction of an inflammatory programmed cell death. Here we perform a genome-scale analysis of C. albicans morphogenesis and identify 102 negative morphogenetic regulators and 872 positive regulators, highlighting key roles for ergosterol biosynthesis and N-linked glycosylation. We demonstrate that C. albicans filamentation is not required for escape from host immune cells; instead, macrophage pyroptosis is driven by fungal cell-wall remodelling and exposure of glycosylated proteins in response to the macrophage phagosome. The capacity of killed, previously phagocytized cells to drive macrophage lysis is also observed with the distantly related fungal pathogen Cryptococcus neoformans. This study provides a global view of morphogenetic circuitry governing a key virulence trait, and illuminates a new mechanism by which fungi trigger host cell death. PMID:25824284

  18. Mechanical Model Analysis for Quantitative Evaluation of Liver Fibrosis Based on Ultrasound Tissue Elasticity Imaging

    NASA Astrophysics Data System (ADS)

    Shiina, Tsuyoshi; Maki, Tomonori; Yamakawa, Makoto; Mitake, Tsuyoshi; Kudo, Masatoshi; Fujimoto, Kenji

    2012-07-01

    Precise evaluation of the stage of chronic hepatitis C with respect to fibrosis has become an important issue to prevent the occurrence of cirrhosis and to initiate appropriate therapeutic intervention such as viral eradication using interferon. Ultrasound tissue elasticity imaging, i.e., elastography can visualize tissue hardness/softness, and its clinical usefulness has been studied to detect and evaluate tumors. We have recently reported that the texture of elasticity image changes as fibrosis progresses. To evaluate fibrosis progression quantitatively on the basis of ultrasound tissue elasticity imaging, we introduced a mechanical model of fibrosis progression and simulated the process by which hepatic fibrosis affects elasticity images and compared the results with those clinical data analysis. As a result, it was confirmed that even in diffuse diseases like chronic hepatitis, the patterns of elasticity images are related to fibrous structural changes caused by hepatic disease and can be used to derive features for quantitative evaluation of fibrosis stage.

  19. Parallel Performance Analysis between Free Response Environments and the Force Concept Inventory in Introductory Mechanics Courses

    NASA Astrophysics Data System (ADS)

    Bobbitt, Nicole; Wade, Aaron; Prayaga, Chandra

    2013-03-01

    This paper reports our attempts to: 1) create a problem solving situation that folds in both kinematics and force discussions 2) find a way to model and predict common thought processes that cause typical misconceptions identified by the Force Concept Inventory (FCI). Two pen and paper test questions were designed with these goals in mind, both broken into specific elements to arrive at a quantifiable fragmentation of the necessary thought processes required to solve the problem. These results were compared to pre- and post-FCI data to analyze the common misconceptions as defined by FCI. The data was analysed using factor analysis to group performance across the two environments. Two styles of grading were used to highlight the effectiveness of this method. Ultimately this, and any future questions, would become a tool in the classroom to pinpoint the critical ideas with which a typical student struggles during an introductory mechanics course.

  20. [Intermediate experiment and mechanism analysis of flue gas desulfurization technology by circulating fluidized bed].

    PubMed

    Zhao, Xudong; Wu, Shaohua; Ma, Chunyuan; Qin, Yukun

    2002-03-01

    A new Circulating Fluidized Bed was designed for intermediate experiment of flue gas desulphurization, in which the flue gas flow rate was 3500 m3/h. By using it, the basic experiments were carried out to study the influence of Ca/S and supersaturated temperature on desulphurization efficiency and the effect of the recycling solid particle in the sulfur removal column on desulphurization performance. The results showed when Ca/S = 1.2, the desulphurization efficiency was increased by 15% through the recycle of solid particle; the gas velocity inside the bed could be designed higher. The mechanism analysis were also studied and the method to increase effective resident time was introduced. PMID:12048805

  1. Application of bifurcation analysis for determining the mechanism of coding of nociceptive signals

    NASA Astrophysics Data System (ADS)

    Dik, O. E.; Shelykh, T. N.; Plakhova, V. B.; Nozdrachev, A. D.; Podzorova, S. A.; Krylov, B. V.

    2015-10-01

    The patch clamp method is used for studying the characteristics of slow sodium channels responsible for coding of nociceptive signals. Quantitative estimates of rate constants of transitions of "normal" and pharmacologically modified activation gating mechanisms of these channels are obtained. A mathematical model of the type of Hogdkin-Huxley nociceptive neuron membrane is constructed. Cometic acid, which is a drug substance of a new nonopioid analgesic, is used as a pharmacological agent. The application of bifurcation analysis makes it possible to outline the boundaries of the region in which a periodic impulse activity is generated. This boundary separates the set of values of the model parameter for which periodic pulsation is observed from the values for which such pulsations are absent or damped. The results show that the finest effect of modulation of physical characteristic of a part of a protein molecule and its effective charge suppresses the excitability of the nociceptive neuron membrane and, hence, leads to rapid reduction of pain.

  2. Stress accumulation process in and around the Atotsugawa fault, central Japan, estimated from focal mechanism analysis

    NASA Astrophysics Data System (ADS)

    Takada, Youichiro; Katsumata, Kei; Katao, Hiroshi; Kosuga, Masahiro; Iio, Yoshihisa; Sagiya, Takeshi

    2016-07-01

    We estimated 275 focal mechanisms from P-wave first-motion polarities of small earthquakes obtained in an extensive seismic survey during 2004-2008 in and around the Atotsugawa fault, central Japan, where ongoing dextral shear strain concentration has been observed. Along the fault trace, the azimuth direction of P-axes is oriented WNW-ESE, which agrees well with previous studies. The regional stress disturbance is detected by stress inversion analysis. The azimuth of the maximum principal stress axis systematically rotates counterclockwise as the distance from the fault trace decreases. The regional stress disturbance is explained by a cumulative slip deficit in the shallower portion of the Atotsugawa fault relative to the surrounding fault surface (i.e., the eastern, western, and deeper extensions of the fault plane).

  3. Thermal, Mechanical and Chemical Analysis for VELOX -Verification Experiments for Lunar Oxygen Production

    NASA Astrophysics Data System (ADS)

    Lange, Caroline; Ksenik, Eugen; Braukhane, Andy; Richter, Lutz

    One major aspect for the development of a long-term human presence on the moon will be sustainability and autonomy of any kind of a permanent base. Important resources, such as breathable air and water for the survival of the crew on the lunar surface will have to be extracted in-situ from the lunar regolith, the major resource on the Moon, which covers the first meter of the lunar surface and contains about 45 At the DLR Bremen we are interested in a compact and flexible lab experimenting facility, which shall demonstrate the feasibility of this process by extracting oxygen out of lunar Regolith, respectively soil simulants and certain minerals in the laboratory case. For this purpose, we have investigated important boundary conditions such as temperatures during the process, chemical reaction characteristics and material properties for the buildup of the facility and established basic requirements which shall be analyzed within this paper. These requirements have been used for the concept development and outline of the facility, which is currently under construction and will be subject to initial tests in the near future. This paper will focus mainly on the theoretical aspects of the facility development. Great effort has been put into the thermal and mechanical outline and pre-analysis of components and the system in a whole. Basic aspects that have been investigated are: 1. Selection of suitable materials for the furnace chamber configuration to provide a high-temperature capable operating mode. 2. Theoretical heat transfer analysis of the designed furnace chamber assembly with subsequent validation with the aid of measured values of the constructed demonstration plant. 3. Description of chemical conversion processes for Hydrogen reduction of Lunar Regolith with corresponding analysis of thermal and reaction times under different boundary conditions. 4. Investigation of the high-temperature mechanical behavior of the constructed furnace chamber with regard to

  4. Cluster analysis of spontaneous preterm birth phenotypes identifies potential associations among preterm birth mechanisms

    PubMed Central

    Esplin, M Sean; Manuck, Tracy A.; Varner, Michael W.; Christensen, Bryce; Biggio, Joseph; Bukowski, Radek; Parry, Samuel; Zhang, Heping; Huang, Hao; Andrews, William; Saade, George; Sadovsky, Yoel; Reddy, Uma M.; Ilekis, John

    2015-01-01

    Objective We sought to employ an innovative tool based on common biological pathways to identify specific phenotypes among women with spontaneous preterm birth (SPTB), in order to enhance investigators' ability to identify to highlight common mechanisms and underlying genetic factors responsible for SPTB. Study Design A secondary analysis of a prospective case-control multicenter study of SPTB. All cases delivered a preterm singleton at SPTB ≤34.0 weeks gestation. Each woman was assessed for the presence of underlying SPTB etiologies. A hierarchical cluster analysis was used to identify groups of women with homogeneous phenotypic profiles. One of the phenotypic clusters was selected for candidate gene association analysis using VEGAS software. Results 1028 women with SPTB were assigned phenotypes. Hierarchical clustering of the phenotypes revealed five major clusters. Cluster 1 (N=445) was characterized by maternal stress, cluster 2 (N=294) by premature membrane rupture, cluster 3 (N=120) by familial factors, and cluster 4 (N=63) by maternal comorbidities. Cluster 5 (N=106) was multifactorial, characterized by infection (INF), decidual hemorrhage (DH) and placental dysfunction (PD). These three phenotypes were highly correlated by Chi-square analysis [PD and DH (p<2.2e-6); PD and INF (p=6.2e-10); INF and DH (p=0.0036)]. Gene-based testing identified the INS (insulin) gene as significantly associated with cluster 3 of SPTB. Conclusion We identified 5 major clusters of SPTB based on a phenotype tool and hierarchal clustering. There was significant correlation between several of the phenotypes. The INS gene was associated with familial factors underlying SPTB. PMID:26070700

  5. Analysis of the Transcriptional Differences between Indigenous and Invasive Whiteflies Reveals Possible Mechanisms of Whitefly Invasion

    PubMed Central

    Wang, Yong-Liang; Wang, Yu-Jun; Luan, Jun-Bo; Yan, Gen-Hong; Liu, Shu-Sheng; Wang, Xiao-Wei

    2013-01-01

    Background The whitefly Bemisa tabaci is a species complex of more than 31 cryptic species which include some of the most destructive invasive pests of crops worldwide. Among them, Middle East-Asia Minor 1 (MEAM1) and Mediterranean have invaded many countries and displaced the native whitefly species. The successful invasion of the two species is largely due to their wide range of host plants, high resistance to insecticides and remarkable tolerance to environmental stresses. However, the molecular differences between invasive and indigenous whiteflies remain largely unknown. Methodology/Principal Findings Here the global transcriptional difference between the two invasive whitefly species (MEAM1, MED) and one indigenous whitefly species (Asia II 3) were analyzed using the Illumina sequencing. Our analysis indicated that 2,422 genes between MEAM1 and MED; 3,073 genes between MEAM1 and Asia II 3; and 3,644 genes between MED and Asia II 3 were differentially expressed. Gene Ontology enrichment analysis revealed that the differently expressed genes between the invasive and indigenous whiteflies were significantly enriched in the term of ‘oxidoreductase activity’. Pathway enrichment analysis showed that carbohydrate, amino acid and glycerolipid metabolisms were more active in MEAM1 and MED than in Asia II 3, which may contribute to their differences in biological characteristics. Our analysis also illustrated that the majority of genes involved in ‘drug metabolic pathway’ were expressed at a higher level in MEAM1 and MED than in Asia II 3. Taken together, these results revealed that the genes related to basic metabolism and detoxification were expressed at an elevated level in the invasive whiteflies, which might be responsible for their higher resistance to insecticides and environmental stresses. Conclusions/Significance The extensive comparison of MEAM1, MED and Asia II 3 gene expression may serve as an invaluable resource for revealing the molecular

  6. Mechanism of MicroRNA-Target Interaction: Molecular Dynamics Simulations and Thermodynamics Analysis

    PubMed Central

    Wang, Yonghua; Li, Yan; Ma, Zhi; Yang, Wei; Ai, Chunzhi

    2010-01-01

    MicroRNAs (miRNAs) are endogenously produced ∼21-nt riboregulators that associate with Argonaute (Ago) proteins to direct mRNA cleavage or repress the translation of complementary RNAs. Capturing the molecular mechanisms of miRNA interacting with its target will not only reinforce the understanding of underlying RNA interference but also fuel the design of more effective small-interfering RNA strands. To address this, in the present work the RNA-bound (Ago-miRNA, Ago-miRNA-target) and RNA-free Ago forms were analyzed by performing both molecular dynamics simulations and thermodynamic analysis. Based on the principal component analysis results of the simulation trajectories as well as the correlation analysis in fluctuations of residues, we discover that: 1) three important (PAZ, Mid and PIWI) domains exist in Argonaute which define the global dynamics of the protein; 2) the interdomain correlated movements are so crucial for the interaction of Ago-RNAs that they not only facilitate the relaxation of the interactions between residues surrounding the RNA binding channel but also induce certain conformational changes; and 3) it is just these conformational changes that expand the cavity of the active site and open putative pathways for both the substrate uptake and product release. In addition, by thermodynamic analysis we also discover that for both the guide RNA 5′-end recognition and the facilitated site-specific cleavage of the target, the presence of two metal ions (of Mg2+) plays a predominant role, and this conclusion is consistent with the observed enzyme catalytic cleavage activity in the ternary complex (Ago-miRNA-mRNA). Our results find that it is the set of arginine amino acids concentrated in the nucleotide-binding channel in Ago, instead of the conventionally-deemed seed base-paring, that makes greater contributions in stabilizing the binding of the nucleic acids to Ago. PMID:20686687

  7. Transcriptomic Analysis of the Host Response to Giardia duodenalis Infection Reveals Redundant Mechanisms for Parasite Control

    PubMed Central

    Tako, Ernest A.; Hassimi, Maryam F.; Li, Erqiu; Singer, Steven M.

    2013-01-01

    ABSTRACT The immune system has numerous mechanisms that it can use to combat pathogens and eliminate infections. Nevertheless, studies of immune responses often focus on single pathways required for protective responses. We applied microarray analysis of RNA in order to investigate the types of immune responses produced against infection with the intestinal pathogen Giardia duodenalis. Infection with G. duodenalis is one of the most common causes of diarrheal disease in the world. While several potential antiparasitic effector mechanisms, including complement lysis, nitric oxide (NO), and α-defensin peptides, have been shown to inhibit parasite growth or kill Giardia in vitro, studies in vivo have thus far shown clear roles only for antibody and mast cell responses in parasite control. A total of 96 transcripts were identified as being upregulated or repressed more than 2-fold in the small intestine 10 days following infection. Microarray data were validated using quantitative PCR. The most abundant category of transcripts was antibody genes, while the most highly induced transcripts were all mast cell proteases. Among the other induced transcripts was matrix metalloprotease 7 (Mmp7), the protease responsible for production of mature α-defensins in mice. While infections in Mmp7-deficient mice showed only a small increase in parasite numbers, combined genetic deletion of Mmp7 and inducible nitric oxide synthase (iNOS, Nos2) or pharmacological blockade of iNOS in Mmp7-deficient mice resulted in significant increases in parasite loads following infection. Thus, α-defensins and NO are redundant mechanisms for control of Giardia infections in vivo. PMID:24194537

  8. A state-space analysis of mechanical energy generation, absorption, and transfer during pedaling.

    PubMed

    Fregly, B J; Zajac, F E

    1996-01-01

    Seated ergometer pedaling is a motor task ideal for studying basic mechanisms of human bipedal coordination because, in contrast to standing and walking, fewer degrees of freedom are being controlled and upright balance is not a factor. As a step toward understanding how individual muscles coordinate pedaling, we investigated how individual net muscle joint torques and non-muscular (e.g. centripetal, coriolis, and gravity) forces of the lower limbs generate, absorb, and transfer mechanical energy in order to propel the crank and recover the limb. This was accomplished using a mechanical power analysis derived entirely from the closed-form state-space dynamical equations of a two-legged pedaling model that accounted for both the limb segmental and crank load dynamics. Based on a pedaling simulation that reproduced experimental kinematic and kinetic trajectories, we found that the net ankle and hip extensor joint torques function 'synergistically' to deliver energy to the crank during the downstroke. The net hip extensor joint torque generates energy to the limb, while the net ankle extensor joint torque transfers this energy from the limb to the crank. In contrast, net knee extensor and flexor joint torques function 'independently' by generating energy to the crank through the top and bottom of the stroke, respectively. The net ankle joint torque transfers and the net knee joint torque generates energy to the crank by contributing to the driving component of the pedal reaction force. During the upstroke, net ankle extensor joint torque transfers energy from the crank to the limb to restore the potential energy of the limb. In both halves of the crank cycle, gravity forces augment the crank-limb energy transfer performed by the net ankle extensor joint torque. PMID:8839020

  9. Dynamic analysis of propulsion mechanism directly driven by wave energy for marine mobile buoy

    NASA Astrophysics Data System (ADS)

    Yu, Zhenjiang; Zheng, Zhongqiang; Yang, Xiaoguang; Chang, Zongyu

    2016-05-01

    Marine mobile buoy(MMB) have many potential applications in the maritime industry and ocean science. Great progress has been made, however the technology in this area is far from maturity in theory and faced with many difficulties in application. A dynamic model of the propulsion mechanism is very necessary for optimizing the parameters of the MMB, especially with consideration of hydrodynamic force. The principle of wave-driven propulsion mechanism is briefly introduced. To set a theory foundation for study on the MMB, a dynamic model of the propulsion mechanism of the MMB is obtained. The responses of the motion of the platform and the hydrofoil are obtained by using a numerical integration method to solve the ordinary differential equations. A simplified form of the motion equations is reached by omitting terms with high order small values. The relationship among the heave motion of the buoy, stiffness of the elastic components, and the forward speed can be obtained by using these simplified equations. The dynamic analysis show the following: The angle of displacement of foil is fairly small with the biggest value around 0.3 rad; The speed of mobile buoy and the angle of hydrofoil increased gradually with the increase of heave motion of buoy; The relationship among heaven motion, stiffness and attack angle is that heave motion leads to the angle change of foil whereas the item of speed or push function is determined by vertical velocity and angle, therefore, the heave motion and stiffness can affect the motion of buoy significantly if the size of hydrofoil is kept constant. The proposed model is provided to optimize the parameters of the MMB and a foundation is laid for improving the performance of the MMB.

  10. Analysis of Focal Mechanism and Microseismicity around the Lusi Mud Eruption Site, East Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Karyono, Karyono; Obermann, Anne; Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Abdurrokhim, Abdurrokhim; Masturyono, Masturyono; Hadi, Soffian

    2016-04-01

    The 29th of May 2006 numerous eruption sites started in northeast Java, Indonesia following to a M6.3 earthquake striking the island.Within a few weeks an area or nearly 2 km2 was covered by boiling mud and rock fragments and a prominent central crater (named Lusi) has been erupting for the last 9.5 years. The M.6.3 seismic event also triggered the activation of the Watukosek strike slip fault system that originates from the Arjuno-Welirang volcanic complex and extends to the northeast of Java hosting Lusi and other mud volcanoes. Since 2006 this fault system has been reactivated in numerous instances mostly following to regional seismic and volcanic activity. However the mechanism controlling this activity have never been investigated and remain poorly understood. In order to investigate the relationship existing between seismicity, volcanism, faulting and Lusi activity, we have deployed a network of 31 seismometers in the framework of the ERC-Lusi Lab project. This network covers a large region that monitors the Lusi activity, the Watukosek fault system and the neighboring Arjuno-Welirang volcanic complex. In particular, to understand the consistent pattern of the source mechanism, relative to the general tectonic stress in the study area, a detailed analysis has been carried out by performing the moment tensor inversion for the near field data collected from the network stations. Furthermore these data have been combined with the near field data from the regional network of the Meteorological, Climatological and Geophysical Agency of Indonesia that covers the whole country on a broader scale. Keywords: Lusi, microseismic event, focal mechanism

  11. Exploratory factor analysis for differentiating sensory and mechanical variables related to muscle-tendon unit elongation

    PubMed Central

    Chagas, Mauro H.; Magalhães, Fabrício A.; Peixoto, Gustavo H. C.; Pereira, Beatriz M.; Andrade, André G. P.; Menzel, Hans-Joachim K.

    2016-01-01

    ABSTRACT Background Stretching exercises are able to promote adaptations in the muscle-tendon unit (MTU), which can be tested through physiological and biomechanical variables. Identifying the key variables in MTU adaptations is crucial to improvements in training. Objective To perform an exploratory factor analysis (EFA) involving the variables often used to evaluate the response of the MTU to stretching exercises. Method Maximum joint range of motion (ROMMAX), ROM at first sensation of stretching (FSTROM), peak torque (torqueMAX), passive stiffness, normalized stiffness, passive energy, and normalized energy were investigated in 36 participants during passive knee extension on an isokinetic dynamometer. Stiffness and energy values were normalized by the muscle cross-sectional area and their passive mode assured by monitoring the EMG activity. Results EFA revealed two major factors that explained 89.68% of the total variance: 53.13% was explained by the variables torqueMAX, passive stiffness, normalized stiffness, passive energy, and normalized energy, whereas the remaining 36.55% was explained by the variables ROMMAX and FSTROM. Conclusion This result supports the literature wherein two main hypotheses (mechanical and sensory theories) have been suggested to describe the adaptations of the MTU to stretching exercises. Contrary to some studies, in the present investigation torqueMAX was significantly correlated with the variables of the mechanical theory rather than those of the sensory theory. Therefore, a new approach was proposed to explain the behavior of the torqueMAX during stretching exercises. PMID:27437715

  12. Transcriptome analysis of genetic mechanism of growth curve inflection point using a pig model.

    PubMed

    Shen, Linyuan; Zhang, Shunhua; Zhu, Li

    2015-12-01

    Animal growth curves play an important role for animal breeders to optimize feeding and management strategies (De Lange et al., 2001 [1]; Brossard et al., 2009 [2]; Strathe et al., 2010 [3]). However, the genetic mechanism of the phenotypic difference between the inflection point and noninflection points of the growth curve remains unclear. Here, we report the differentially expressed gene pattern in pig longissimus dorsi among three typical time points of the growth curve, inflection point (IP), before inflection point (BIP) and after inflection point (AIP). The whole genome RNA-seq data was deposited at GenBank under the accession number PRJNA2284587. The RNA-seq libraries generated 117 million reads of 5.89 gigabases in length. Totals of 21,331, 20,996 and 20,139 expressed transcripts were identified in IP, UIP and AIP, respectively. Furthermore, we identified 757 differentially expressed genes (DEGs) between IP and UIP, and 271 DEGs between AIP and IP. Function enrichment analysis of DEGs found that the highly expressed genes in IP were mainly enriched in energy metabolism, global transcriptional activity and bone development intensity. This study contributes to reveal the genetic mechanism of growth curve inflection point. PMID:26697358

  13. Modelling and analysis of bacterial tracks suggest an active reorientation mechanism in Rhodobacter sphaeroides

    PubMed Central

    Rosser, Gabriel; Baker, Ruth E.; Armitage, Judith P.; Fletcher, Alexander G.

    2014-01-01

    Most free-swimming bacteria move in approximately straight lines, interspersed with random reorientation phases. A key open question concerns varying mechanisms by which reorientation occurs. We combine mathematical modelling with analysis of a large tracking dataset to study the poorly understood reorientation mechanism in the monoflagellate species Rhodobacter sphaeroides. The flagellum on this species rotates counterclockwise to propel the bacterium, periodically ceasing rotation to enable reorientation. When rotation restarts the cell body usually points in a new direction. It has been assumed that the new direction is simply the result of Brownian rotation. We consider three variants of a self-propelled particle model of bacterial motility. The first considers rotational diffusion only, corresponding to a non-chemotactic mutant strain. Two further models incorporate stochastic reorientations, describing ‘run-and-tumble’ motility. We derive expressions for key summary statistics and simulate each model using a stochastic computational algorithm. We also discuss the effect of cell geometry on rotational diffusion. Working with a previously published tracking dataset, we compare predictions of the models with data on individual stopping events in R. sphaeroides. This provides strong evidence that this species undergoes some form of active reorientation rather than simple reorientation by Brownian rotation. PMID:24872500

  14. Systematic Analysis of the Molecular Mechanism Underlying Decidualization Using a Text Mining Approach.

    PubMed

    Liu, Ji-Long; Wang, Tong-Song

    2015-01-01

    Decidualization is a crucial process for successful embryo implantation and pregnancy in humans. Defects in decidualization during early pregnancy are associated with several pregnancy complications, such as pre-eclampsia, intrauterine growth restriction and recurrent pregnancy loss. However, the mechanism underlying decidualization remains poorly understood. In the present study, we performed a systematic analysis of decidualization-related genes using text mining. We identified 286 genes for humans and 287 genes for mice respectively, with an overlap of 111 genes shared by both species. Through enrichment test, we demonstrated that although divergence was observed, the majority of enriched gene ontology terms and pathways were shared by both species, suggesting that functional categories were more conserved than individual genes. We further constructed a decidualization-related protein-protein interaction network consisted of 344 nodes connected via 1,541 edges. We prioritized genes in this network and identified 12 genes that may be key regulators of decidualization. These findings would provide some clues for further research on the mechanism underlying decidualization. PMID:26222155

  15. Systematic Analysis of the Molecular Mechanism Underlying Decidualization Using a Text Mining Approach

    PubMed Central

    Liu, Ji-Long; Wang, Tong-Song

    2015-01-01

    Decidualization is a crucial process for successful embryo implantation and pregnancy in humans. Defects in decidualization during early pregnancy are associated with several pregnancy complications, such as pre-eclampsia, intrauterine growth restriction and recurrent pregnancy loss. However, the mechanism underlying decidualization remains poorly understood. In the present study, we performed a systematic analysis of decidualization-related genes using text mining. We identified 286 genes for humans and 287 genes for mice respectively, with an overlap of 111 genes shared by both species. Through enrichment test, we demonstrated that although divergence was observed, the majority of enriched gene ontology terms and pathways were shared by both species, suggesting that functional categories were more conserved than individual genes. We further constructed a decidualization-related protein-protein interaction network consisted of 344 nodes connected via 1,541 edges. We prioritized genes in this network and identified 12 genes that may be key regulators of decidualization. These findings would provide some clues for further research on the mechanism underlying decidualization. PMID:26222155

  16. Characterization of three-dimensional anisotropic heart valve tissue mechanical properties using inverse finite element analysis.

    PubMed

    Abbasi, Mostafa; Barakat, Mohammed S; Vahidkhah, Koohyar; Azadani, Ali N

    2016-09-01

    Computational modeling has an important role in design and assessment of medical devices. In computational simulations, considering accurate constitutive models is of the utmost importance to capture mechanical response of soft tissue and biomedical materials under physiological loading conditions. Lack of comprehensive three-dimensional constitutive models for soft tissue limits the effectiveness of computational modeling in research and development of medical devices. The aim of this study was to use inverse finite element (FE) analysis to determine three-dimensional mechanical properties of bovine pericardial leaflets of a surgical bioprosthesis under dynamic loading condition. Using inverse parameter estimation, 3D anisotropic Fung model parameters were estimated for the leaflets. The FE simulations were validated using experimental in-vitro measurements, and the impact of different constitutive material models was investigated on leaflet stress distribution. The results of this study showed that the anisotropic Fung model accurately simulated the leaflet deformation and coaptation during valve opening and closing. During systole, the peak stress reached to 3.17MPa at the leaflet boundary while during diastole high stress regions were primarily observed in the commissures with the peak stress of 1.17MPa. In addition, the Rayleigh damping coefficient that was introduced to FE simulations to simulate viscous damping effects of surrounding fluid was determined. PMID:27173827

  17. Algebraic solution for the forward displacement analysis of the general 6-6 stewart mechanism

    NASA Astrophysics Data System (ADS)

    Wei, Feng; Wei, Shimin; Zhang, Ying; Liao, Qizheng

    2016-01-01

    The solution for the forward displacement analysis(FDA) of the general 6-6 Stewart mechanism(i.e., the connection points of the moving and fixed platforms are not restricted to lying in a plane) has been extensively studied, but the efficiency of the solution remains to be effectively addressed. To this end, an algebraic elimination method is proposed for the FDA of the general 6-6 Stewart mechanism. The kinematic constraint equations are built using conformal geometric algebra(CGA). The kinematic constraint equations are transformed by a substitution of variables into seven equations with seven unknown variables. According to the characteristic of anti-symmetric matrices, the aforementioned seven equations can be further transformed into seven equations with four unknown variables by a substitution of variables using the Gröbner basis. Its elimination weight is increased through changing the degree of one variable, and sixteen equations with four unknown variables can be obtained using the Gröbner basis. A 40th-degree univariate polynomial equation is derived by constructing a relatively small-sized 9´9 Sylvester resultant matrix. Finally, two numerical examples are employed to verify the proposed method. The results indicate that the proposed method can effectively improve the efficiency of solution and reduce the computational burden because of the small-sized resultant matrix.

  18. Mechanical properties and microstructure analysis of fly ash geopolymeric recycled concrete.

    PubMed

    Shi, X S; Collins, F G; Zhao, X L; Wang, Q Y

    2012-10-30

    Six mixtures with different recycled aggregate (RA) replacement ratios of 0%, 50% and 100% were designed to manufacture recycled aggregate concrete (RAC) and alkali-activated fly ash geopolymeric recycled concrete (GRC). The physical and mechanical properties were investigated indicating different performances from each other. Optical microscopy under transmitted light and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) were carried out in this study in order to identify the mechanism underlying the effects of the geopolymer and RA on concrete properties. The features of aggregates, paste and interfacial transition zone (ITZ) were compared and discussed. Experimental results indicate that using alkali-activated fly ash geopolymer as replacement of ordinary Portland cement (OPC) effectively improved the compressive strength. With increasing of RA contents in both RAC and GRC, the compressive strength decreased gradually. The microstructure analysis shows that, on one hand, the presence of RA weakens the strength of the aggregates and the structure of ITZs; on the other hand, due to the alkali-activated fly ash in geopolymer concrete, the contents of Portlandite (Ca(OH)(2)) and voids were reduced, as well as improved the matrix homogeneity. The microstructure of GRC was changed by different reaction products, such as aluminosilicate gel. PMID:22954605

  19. Security Enhancement Mechanism Based on Contextual Authentication and Role Analysis for 2G-RFID Systems

    PubMed Central

    Tang, Wan; Chen, Min; Ni, Jin; Yang, Ximin

    2011-01-01

    The traditional Radio Frequency Identification (RFID) system, in which the information maintained in tags is passive and static, has no intelligent decision-making ability to suit application and environment dynamics. The Second-Generation RFID (2G-RFID) system, referred as 2G-RFID-sys, is an evolution of the traditional RFID system to ensure better quality of service in future networks. Due to the openness of the active mobile codes in the 2G-RFID system, the realization of conveying intelligence brings a critical issue: how can we make sure the backend system will interpret and execute mobile codes in the right way without misuse so as to avoid malicious attacks? To address this issue, this paper expands the concept of Role-Based Access Control (RBAC) by introducing context-aware computing, and then designs a secure middleware for backend systems, named Two-Level Security Enhancement Mechanism or 2L-SEM, in order to ensure the usability and validity of the mobile code through contextual authentication and role analysis. According to the given contextual restrictions, 2L-SEM can filtrate the illegal and invalid mobile codes contained in tags. Finally, a reference architecture and its typical application are given to illustrate the implementation of 2L-SEM in a 2G-RFID system, along with the simulation results to evaluate how the proposed mechanism can guarantee secure execution of mobile codes for the system. PMID:22163983

  20. Integrated proteomics and metabolomics analysis of rat testis: Mechanism of arsenic-induced male reproductive toxicity

    PubMed Central

    Huang, Qingyu; Luo, Lianzhong; Alamdar, Ambreen; Zhang, Jie; Liu, Liangpo; Tian, Meiping; Eqani, Syed Ali Musstjab Akber Shah; Shen, Heqing

    2016-01-01

    Arsenic is a widespread metalloid in environment, whose exposure has been associated with a broad spectrum of toxic effects. However, a global view of arsenic-induced male reproductive toxicity is still lack, and the underlying mechanisms remain largely unclear. Our results revealed that arsenic exposure decreased testosterone level and reduced sperm quality in rats. By conducting an integrated proteomics and metabolomics analysis, the present study aims to investigate the global influence of arsenic exposure on the proteome and metabolome in rat testis. The abundance of 70 proteins (36 up-regulated and 34 down-regulated) and 13 metabolites (8 increased and 5 decreased) were found to be significantly altered by arsenic treatment. Among these, 19 proteins and 2 metabolites were specifically related to male reproductive system development and function, including spermatogenesis, sperm function and fertilization, fertility, internal genitalia development, and mating behavior. It is further proposed that arsenic mainly impaired spermatogenesis and fertilization via aberrant modulation of these male reproduction-related proteins and metabolites, which may be mediated by the ERK/AKT/NF-κB-dependent signaling pathway. Overall, these findings will aid our understanding of the mechanisms responsible for arsenic-induced male reproductive toxicity, and from such studies useful biomarkers indicative of arsenic exposure could be discovered. PMID:27585557

  1. Design and modal analysis of optical and mechanical structures of a space infrared camera

    NASA Astrophysics Data System (ADS)

    Zhang, Guangyu; Sun, Dewei; Long, Funian

    2008-10-01

    Space infrared cameras have been widely used for weather prediction, earth resource detection, military reconnaissance and astronomy observation. In order to design and produce an excellent space camera, the optical and mechanical structures of the camera are deeply investigated. Firstly, according to the technical targets and interface requirements for infrared sensor, optical modulation transfer function (MTF) must be up to 0.65 in the central field and more than 0.55 in the marginal field at the cut-off frequency of the optical system. Secondly, in accordance with the requirement of optical system, the structure of body tube is designed and a new type of material- graphite fiber reinforced aluminium matrix composite (Gr/Al composite) is used for the first time. The weight of Gr/Al composite body tube is 31.8% lighter than that of Titanium alloy. Thirdly, in terms of the theory of modal analysis, the resonance frequencies and modal sharps of body tube are acquired. The first order resonance frequency is 292Hz. Finally, the test of random vibration is conducted. Experimental results indicate that optical and mechanical systems do not change after vibration test. Namely, the research above suggests that space infrared camera has an important utility value in the space remote sensing field.

  2. [Anti-depressive mechanism of Fufang Chaigui prescription based on neuroendocrine hormone and metabolomic correlation analysis].

    PubMed

    Chen, Lei; Liu, Huan; Chen, Jian-li; Gao, Xiao-xia; Zhou, Yu-zhi; Tian, Jun-sheng; Qin, Xue-mei

    2015-10-01

    To elucidate the anti-depressive effect of Fufang Chaigui prescription and its mechanism and investigate its effect on neuroendocrine hormone, rats were included into a chronic unpredictable mild stress (CUMS) model for 28 d, and drugs were administered at the same time. During the period, rats' behaviors were observed and the blood was collected by using ELISA to determine representative hormone concentrations of HPAA, HPTA and HPGA. The changes in endogenous metabolites were analyzed by using H NMR metabolomics to seek the potential biomarkers. Results showed Fufang Chaigui prescription could improve the behaviors of CUMS rats obviously, increase contents of ACTH, CORT, T₃and decrease contents of TSH and TESTO and regulate the levels of lactate, α-glucose, choline, N-acetylglycoprotein, trimethylamine oxide and leucine to get closer to the contents of control group. The results of correlation analysis indicated that HPTA was associated with glycometabolism, amino acid metabolism and choline metabolism. And HPAA was related to glycometabolism and amino acid metabolism. However, HPGA was only correlated with glycometabolism. In conclusion, Fufang Chaigui prescription could show an obvious anti-depressive effect and its underlying mechanism might involve regulations of neuroendocrine function and pathways of glycometabolism, amino acid metabolism and choline metabolism. PMID:27062831

  3. Viscoelastic characterization of compacted pharmaceutical excipient materials by analysis of frequency-dependent mechanical relaxation processes.

    PubMed

    Welch, K; Mousavi, S; Lundberg, B; Strømme, M

    2005-09-01

    A newly developed method for determining the frequency-dependent complex Young's modulus was employed to analyze the mechanical response of compacted microcrystalline cellulose, sorbitol, ethyl cellulose and starch for frequencies up to 20 kHz. A Debye-like relaxation was observed in all the studied pharmaceutical excipient materials and a comparison with corresponding dielectric spectroscopy data was made. The location in frequency of the relaxation peak was shown to correlate to the measured tensile strength of the tablets, and the relaxation was interpreted as the vibrational response of the interparticle hydrogen and van der Waals bindings in the tablets. Further, the measured relaxation strength, holding information about the energy loss involved in the relaxation processes, showed that the weakest material in terms of tensile strength, starch, is the material among the four tested ones that is able to absorb the most energy within its structure when exposed to external perturbations inducing vibrations in the studied frequency range. The results indicate that mechanical relaxation analysis performed over relatively broad frequency ranges should be useful for predicting material properties of importance for the functionality of a material in applications such as, e.g., drug delivery, drug storage and handling, and also for clarifying the origin of hitherto unexplained molecular processes. PMID:16184321

  4. Analysis of tablet compaction. I. Characterization of mechanical behavior of powder and powder/tooling friction.

    PubMed

    Cunningham, J C; Sinka, I C; Zavaliangos, A

    2004-08-01

    In this first of two articles on the modeling of tablet compaction, the experimental inputs related to the constitutive model of the powder and the powder/tooling friction are determined. The continuum-based analysis of tableting makes use of an elasto-plastic model, which incorporates the elements of yield, plastic flow potential, and hardening, to describe the mechanical behavior of microcrystalline cellulose over the range of densities experienced during tableting. Specifically, a modified Drucker-Prager/cap plasticity model, which includes material parameters such as cohesion, internal friction, and hydrostatic yield pressure that evolve with the internal state variable relative density, was applied. Linear elasticity is assumed with the elastic parameters, Young's modulus, and Poisson's ratio dependent on the relative density. The calibration techniques were developed based on a series of simple mechanical tests including diametrical compression, simple compression, and die compaction using an instrumented die. The friction behavior is measured using an instrumented die and the experimental data are analyzed using the method of differential slices. The constitutive model and frictional properties are essential experimental inputs to the finite element-based model described in the companion article. PMID:15236452

  5. Viscoelastic characterization of compacted pharmaceutical excipient materials by analysis of frequency-dependent mechanical relaxation processes

    NASA Astrophysics Data System (ADS)

    Welch, K.; Mousavi, S.; Lundberg, B.; Strømme, M.

    2005-09-01

    A newly developed method for determining the frequency-dependent complex Young's modulus was employed to analyze the mechanical response of compacted microcrystalline cellulose, sorbitol, ethyl cellulose and starch for frequencies up to 20 kHz. A Debye-like relaxation was observed in all the studied pharmaceutical excipient materials and a comparison with corresponding dielectric spectroscopy data was made. The location in frequency of the relaxation peak was shown to correlate to the measured tensile strength of the tablets, and the relaxation was interpreted as the vibrational response of the interparticle hydrogen and van der Waals bindings in the tablets. Further, the measured relaxation strength, holding information about the energy loss involved in the relaxation processes, showed that the weakest material in terms of tensile strength, starch, is the material among the four tested ones that is able to absorb the most energy within its structure when exposed to external perturbations inducing vibrations in the studied frequency range. The results indicate that mechanical relaxation analysis performed over relatively broad frequency ranges should be useful for predicting material properties of importance for the functionality of a material in applications such as, e.g., drug delivery, drug storage and handling, and also for clarifying the origin of hitherto unexplained molecular processes.

  6. Dynamic mechanical analysis and esterase degradation of dentin adhesives containing a branched methacrylate

    PubMed Central

    Park, Jong-Gu; Ye, Qiang; Topp, Elizabeth M.; Lee, Chi H.; Kostoryz, Elisabet L.; Misra, Anil; Spencer, Paulette

    2010-01-01

    A study of the dynamic mechanical properties and the enzymatic degradation of new dentin adhesives containing a multifunctional methacrylate are described. Adhesives contained 2-hydroxyethyl methacrylate (HEMA), 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]-propane (BisGMA), and a new multifunctional methacrylate with a branched side chain-trimethylolpropane mono allyl ether dimethacrylate (TMPEDMA). Adhesives were photopolymerized in the presence of 0, 8 and 16 wt% water to simulate wet bonding conditions in the mouth and compared to control adhesives. The degree of conversion as a function of irradiation time was comparable for experimental and control adhesives. In dynamic mechanical analysis (DMA), broad tan δ peaks were obtained for all samples, indicating that the polymerized networks are heterogeneous; comparison of the full-width-at-half-maximum values obtained from the tan δ curves indicated increased heterogeneity for samples cured in the presence of water and/or containing TMPEDMA. The experimental adhesive showed higher Tg and higher rubbery modulus indicating increased crosslink density as compared to the control. The improvement in esterase resistance afforded by adhesives containing the TMPEDMA is greater when this material is photopolymerized in the presence of water, suggesting better performance in the moist environment of the mouth. The improved esterase resistance of the new adhesive could be explained in terms of the densely crosslinked network structure and/or the steric hindrance of branched alkyl side chains. PMID:19358261

  7. Mesoscale thermal-mechanical analysis of shocked induced granular explosives and polymer-bonded explosives

    NASA Astrophysics Data System (ADS)

    Wang, Xinjie; Wu, Yanqing; Huang, Fenglei

    2015-06-01

    The thermal-mechanical response of HMX-based granular explosives (GXs) and polymer-bonded explosives (PBXs) with variable number of crystals from 10 to 100 under impact loading is investigated with finite element software ABAQUS. A series of three dimensional mesoscale calculations are carried out with the crystal plasticity constitutive model for HMX crystals that accounts for nonlinear elasticity and crystalline plasticity and the viscoelastic model for the polymer binder. To make the analysis comparable, the morphology and the size of HMX crystals are kept the same for both GXs and PBXs. In order to quantify the effect of polymer binder under different strain rate, the calculation models are impacted with initial boundary velocities from 10 to 100 m/s. The results shows that the average pressure of PBXs is approximately 50% higher than GXs and that the localized stress and temperature is highly increased with the polymer binder, which indicates the crystal anisotropy as well as the polymer binder plays an important role in influencing the stress and thermal response of HMX crystals. The thermal-mechanical response analyzed here is essential to predict the formation of hot spot and the ignition of explosives.

  8. Integrated proteomics and metabolomics analysis of rat testis: Mechanism of arsenic-induced male reproductive toxicity.

    PubMed

    Huang, Qingyu; Luo, Lianzhong; Alamdar, Ambreen; Zhang, Jie; Liu, Liangpo; Tian, Meiping; Eqani, Syed Ali Musstjab Akber Shah; Shen, Heqing

    2016-01-01

    Arsenic is a widespread metalloid in environment, whose exposure has been associated with a broad spectrum of toxic effects. However, a global view of arsenic-induced male reproductive toxicity is still lack, and the underlying mechanisms remain largely unclear. Our results revealed that arsenic exposure decreased testosterone level and reduced sperm quality in rats. By conducting an integrated proteomics and metabolomics analysis, the present study aims to investigate the global influence of arsenic exposure on the proteome and metabolome in rat testis. The abundance of 70 proteins (36 up-regulated and 34 down-regulated) and 13 metabolites (8 increased and 5 decreased) were found to be significantly altered by arsenic treatment. Among these, 19 proteins and 2 metabolites were specifically related to male reproductive system development and function, including spermatogenesis, sperm function and fertilization, fertility, internal genitalia development, and mating behavior. It is further proposed that arsenic mainly impaired spermatogenesis and fertilization via aberrant modulation of these male reproduction-related proteins and metabolites, which may be mediated by the ERK/AKT/NF-κB-dependent signaling pathway. Overall, these findings will aid our understanding of the mechanisms responsible for arsenic-induced male reproductive toxicity, and from such studies useful biomarkers indicative of arsenic exposure could be discovered. PMID:27585557

  9. Detailed analysis of surface asperity deformation mechanism in diffusion bonding of steel hollow structural components

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Li, H.; Li, M. Q.

    2016-05-01

    This study focused on the detailed analysis of surface asperity deformation mechanism in similar diffusion bonding as well as on the fabrication of high quality martensitic stainless steel hollow structural components. A special surface with regular patterns was processed to be joined so as to observe the extent of surface asperity deformation under different bonding pressures. Results showed that an undamaged hollow structural component has been obtained with full interfacial contact and the same shear strength to that of base material. Fracture surface characteristic combined with surface roughness profiles distinctly revealed the enhanced surface asperity deformation as the applied pressure increases. The influence of surface asperity deformation mechanism on joint formation was analyzed: (a) surface asperity deformation not only directly expanded the interfacial contact areas, but also released deformation heat and caused defects, indirectly accelerating atomic diffusion, then benefits to void shrinkage; (b) surface asperity deformation readily introduced stored energy difference between two opposite sides of interface grain boundary, resulting in strain induced interface grain boundary migration. In addition, the influence of void on interface grain boundary migration was analyzed in detail.

  10. Image-based mechanical analysis of stent deformation: concept and exemplary implementation for aortic valve stents.

    PubMed

    Gessat, Michael; Hopf, Raoul; Pollok, Thomas; Russ, Christoph; Frauenfelder, Thomas; Sündermann, Simon Harald; Hirsch, Sven; Mazza, Edoardo; Székely, Gábor; Falk, Volkmar

    2014-01-01

    An approach for extracting the radial force load on an implanted stent from medical images is proposed. To exemplify the approach, a system is presented which computes a radial force estimation from computer tomography images acquired from patients who underwent transcatheter aortic valve implantation (TAVI). The deformed shape of the implanted valve prosthesis' Nitinol frame is extracted from the images. A set of displacement vectors is computed that parameterizes the observed deformation. An iterative relaxation algorithm is employed to adapt the information extracted from the images to a finite-element model of the stent, and the radial components of the interaction forces between the stent and the tissue are extracted. For the evaluation of the method, tests were run using the clinical data from 21 patients. Stent modeling and extraction of the radial forces were successful in 18 cases. Synthetic test cases were generated, in addition, for assessing the sensitivity to the measurement errors. In a sensitivity analysis, the geometric error of the stent reconstruction was below 0.3 mm, which is below the image resolution. The distribution of the radial forces was qualitatively and quantitatively reasonable. An uncertainty remains in the quantitative evaluation of the radial forces due to the uncertainty in defining a radial direction on the deformed stent. With our approach, the mechanical situation of TAVI stents after the implantation can be studied in vivo, which may help to understand the mechanisms that lead to the complications and improve stent design. PMID:24626769

  11. Crack healing in cross-ply composites observed by dynamic mechanical analysis

    NASA Astrophysics Data System (ADS)

    Nielsen, Christian; Nemat-Nasser, Sia

    2015-03-01

    Cross-ply composites with healable polymer matrices are characterized using dynamic mechanical analysis (DMA). The [90,0]s samples are prepared by embedding layers of unidirectional glass or carbon fibers in 2MEP4FS, a polymer with thermally reversible covalent cross-links, which has been shown to be capable of healing internal cracks and fully recovering fracture toughness when the crack surfaces are kept in contact. After fabrication, cracks in the composites' transverse plies are observed due to residual thermal stresses introduced during processing. Single cantilever bending DMA measurements show the samples exhibit periods of increasing storage moduli with increasing temperature. These results are accurately modeled as a one-dimensional composite, which captures the underlying physics of the phenomenon. The effect of cracks on the stiffness is accounted for by a shear-lag model. The predicted crack density of the glass fiber composite is shown to fall within a range observed from microscopy images. Crack healing occurs as a function of temperature, with chemistry and mechanics-based rationales given for the onset and conclusion of healing. The model captures the essential physics of the phenomenon and yields results in accord with experimental observations.

  12. Fatigue and life prediction for cobalt-chromium stents: A fracture mechanics analysis.

    PubMed

    Marrey, Ramesh V; Burgermeister, Robert; Grishaber, Randy B; Ritchie, R O

    2006-03-01

    To design against premature mechanical failure, most implant devices such as coronary and endovascular stents are assessed on the basis of survival, i.e., if a fatigue life of 10(8) cycles is required, testing is performed to ascertain whether the device will survive 10(8) cycles under accelerated in vitro loading conditions. This is a far from satisfactory approach as the safety factors, which essentially tell you how close you are to failure, remain unknown; rather, the probability of fatigue failure should instead be assessed on the basis of testing to failure. In this work, a new damage-tolerant analysis of a cardiovascular stent is presented, where the design life is conservatively evaluated using a fracture mechanics methodology. In addition to enabling estimates of safe in vivo lifetimes to be made, this approach serves to quantify the effect of flaws in terms of their potential effect on device failure, and as such provides a rational basis for quality control. PMID:16260033

  13. Aging of ErT2 thin films: ERD analysis of mechanical property changes

    SciTech Connect

    Knapp, James A; Bond, Gillian

    2010-01-01

    Rare earth tritide films evolve as tritium decays into 3He, which forms bubbles that influence long-term film stability in applications such as neutron generators. We followed the properties of model ErT2 films as they aged using ERD analysis to monitor T and 3He profiles, nanoindentation testing for mechanical properties and transmission electron microscopy to characterize bubble growth. The profiles of T and 3He are separately measured in ERD using a E - E detector, taking advantage of the differences in energy loss within the E detector. The composition measured by ERD followed the expected build-up of 3He up to near critical release, where 3He begins to escape from the film as bubbles overlap. These measurements complement observations of the changing mechanical properties of these films, where the observed behavior divided into two regimes: a substantial increase in layer hardness but elasticity little changed over 18 months, followed by a decrease in elastic stiffness and a modest decrease in hardness over the final 24 months. The evolution of properties has been explained by a combination of dislocation pinning by the bubbles, elastic softening as the bubbles occupy an increasing fraction of the material, and details of bubble growth modes. The ERD measurements confirm that the changes in properties are due to changes in bubble morphology and not to changes in 3He or T content.

  14. A New Approximate Fracture Mechanics Analysis Methodology for Composites with a Crack or Hole

    NASA Technical Reports Server (NTRS)

    Tsai, H. C.; Arocho, A.

    1990-01-01

    A new approximate theory which links the inherent flaw concept with the theory of crack tip stress singularities at a bi-material interface was developed. Three assumptions were made: (1) the existence of inherent flaw (i.e., damage zone) at the tip of the crack, (2) a fracture of the filamentary composites initiates at a crack lying in the matrix material at the interface of the matrix/filament, and (3) the laminate fails whenever the principal load-carrying laminae fails. This third assumption implies that for a laminate consisting of 0 degree plies, cracks into matrix perpendicular to the 0 degree filaments are the triggering mechanism for the final failure. Based on this theory, a parameter bar K sub Q which is similar to the stress intensity factor for isotropic materials but with a different dimension was defined. Utilizing existing test data, it was found that bar K sub Q can be treated as a material constant. Based on this finding a fracture mechanics analysis methodology was developed. The analytical results are correlated well with test results. This new approximate theory can apply to both brittle and metal matrix composite laminates with crack or hole.

  15. Network-Based Analysis of Nutraceuticals in Human Hepatocellular Carcinomas Reveals Mechanisms of Chemopreventive Action.

    PubMed

    Michailidou, M; Melas, I N; Messinis, D E; Klamt, S; Alexopoulos, L G; Kolisis, F N; Loutrari, H

    2015-06-01

    Chronic inflammation is associated with the development of human hepatocellular carcinoma (HCC), an essentially incurable cancer. Anti-inflammatory nutraceuticals have emerged as promising candidates against HCC, yet the mechanisms through which they influence the cell signaling machinery to impose phenotypic changes remain unresolved. Herein we implemented a systems biology approach in HCC cells, based on the integration of cytokine release and phospoproteomic data from high-throughput xMAP Luminex assays to elucidate the action mode of prominent nutraceuticals in terms of topology alterations of HCC-specific signaling networks. An optimization algorithm based on SigNetTrainer, an Integer Linear Programming formulation, was applied to construct networks linking signal transduction to cytokine secretion by combining prior knowledge of protein connectivity with proteomic data. Our analysis identified the most probable target phosphoproteins of interrogated compounds and predicted translational control as a new mechanism underlying their anticytokine action. Induced alterations corroborated with inhibition of HCC-driven angiogenesis and metastasis. PMID:26225263

  16. Security enhancement mechanism based on contextual authentication and role analysis for 2G-RFID systems.

    PubMed

    Tang, Wan; Chen, Min; Ni, Jin; Yang, Ximin

    2011-01-01

    The traditional Radio Frequency Identification (RFID) system, in which the information maintained in tags is passive and static, has no intelligent decision-making ability to suit application and environment dynamics. The Second-Generation RFID (2G-RFID) system, referred as 2G-RFID-sys, is an evolution of the traditional RFID system to ensure better quality of service in future networks. Due to the openness of the active mobile codes in the 2G-RFID system, the realization of conveying intelligence brings a critical issue: how can we make sure the backend system will interpret and execute mobile codes in the right way without misuse so as to avoid malicious attacks? To address this issue, this paper expands the concept of Role-Based Access Control (RBAC) by introducing context-aware computing, and then designs a secure middleware for backend systems, named Two-Level Security Enhancement Mechanism or 2L-SEM, in order to ensure the usability and validity of the mobile code through contextual authentication and role analysis. According to the given contextual restrictions, 2L-SEM can filtrate the illegal and invalid mobile codes contained in tags. Finally, a reference architecture and its typical application are given to illustrate the implementation of 2L-SEM in a 2G-RFID system, along with the simulation results to evaluate how the proposed mechanism can guarantee secure execution of mobile codes for the system. PMID:22163983

  17. Network-Based Analysis of Nutraceuticals in Human Hepatocellular Carcinomas Reveals Mechanisms of Chemopreventive Action

    PubMed Central

    Michailidou, M; Melas, IN; Messinis, DE; Klamt, S; Alexopoulos, LG; Kolisis, FN; Loutrari, H

    2015-01-01

    Chronic inflammation is associated with the development of human hepatocellular carcinoma (HCC), an essentially incurable cancer. Anti-inflammatory nutraceuticals have emerged as promising candidates against HCC, yet the mechanisms through which they influence the cell signaling machinery to impose phenotypic changes remain unresolved. Herein we implemented a systems biology approach in HCC cells, based on the integration of cytokine release and phospoproteomic data from high-throughput xMAP Luminex assays to elucidate the action mode of prominent nutraceuticals in terms of topology alterations of HCC-specific signaling networks. An optimization algorithm based on SigNetTrainer, an Integer Linear Programming formulation, was applied to construct networks linking signal transduction to cytokine secretion by combining prior knowledge of protein connectivity with proteomic data. Our analysis identified the most probable target phosphoproteins of interrogated compounds and predicted translational control as a new mechanism underlying their anticytokine action. Induced alterations corroborated with inhibition of HCC-driven angiogenesis and metastasis. PMID:26225263

  18. Molecular Mechanisms of Chronic Kidney Transplant Rejection via Large-Scale Proteogenomic Analysis of Tissue Biopsies

    PubMed Central

    Nakorchevsky, Aleksey; Hewel, Johannes A.; Kurian, Sunil M.; Mondala, Tony S.; Campbell, Daniel; Head, Steve R.; Marsh, Christopher L.; Yates, John R.

    2010-01-01

    The most common cause of kidney transplant failure is the poorly characterized histopathologic entity interstitial fibrosis and tubular atrophy (IFTA). There are no known unifying mechanisms, no effective therapy, and no proven preventive strategies. Possible mechanisms include chronic immune rejection, inflammation, drug toxicity, and chronic kidney injury from secondary factors. To gain further mechanistic insight, we conducted a large-scale proteogenomic study of kidney transplant biopsies with IFTA of varying severity. We acquired proteomic data using tandem mass spectrometry with subsequent quantification, analysis of differential protein expression, validation, and functional annotations to known molecular networks. We performed genome-wide expression profiling in parallel. More than 1400 proteins with unique expression profiles traced the progression from normal transplant biopsies to biopsies with mild to moderate and severe disease. Multiple sets of proteins were mapped to different functional pathways, many increasing with histologic severity, including immune responses, inflammatory cell activation, and apoptosis consistent with the chronic rejection hypothesis. Two examples include the extensive population of the alternative rather than the classical complement pathway, previously not appreciated for IFTA, and a comprehensive control network for the actin cytoskeleton and cell signaling of the acute-phase response. In summary, this proteomic effort using kidney tissue contributes mechanistic insight into several biologic processes associated with IFTA. PMID:20093355

  19. Groundwater source contamination mechanisms: Physicochemical profile clustering, risk factor analysis and multivariate modelling

    NASA Astrophysics Data System (ADS)

    Hynds, Paul; Misstear, Bruce D.; Gill, Laurence W.; Murphy, Heather M.

    2014-04-01

    An integrated domestic well sampling and "susceptibility assessment" programme was undertaken in the Republic of Ireland from April 2008 to November 2010. Overall, 211 domestic wells were sampled, assessed and collated with local climate data. Based upon groundwater physicochemical profile, three clusters have been identified and characterised by source type (borehole or hand-dug well) and local geological setting. Statistical analysis indicates that cluster membership is significantly associated with the prevalence of bacteria (p = 0.001), with mean Escherichia coli presence within clusters ranging from 15.4% (Cluster-1) to 47.6% (Cluster-3). Bivariate risk factor analysis shows that on-site septic tank presence was the only risk factor significantly associated (p < 0.05) with bacterial presence within all clusters. Point agriculture adjacency was significantly associated with both borehole-related clusters. Well design criteria were associated with hand-dug wells and boreholes in areas characterised by high permeability subsoils, while local geological setting was significant for hand-dug wells and boreholes in areas dominated by low/moderate permeability subsoils. Multivariate susceptibility models were developed for all clusters, with predictive accuracies of 84% (Cluster-1) to 91% (Cluster-2) achieved. Septic tank setback was a common variable within all multivariate models, while agricultural sources were also significant, albeit to a lesser degree. Furthermore, well liner clearance was a significant factor in all models, indicating that direct surface ingress is a significant well contamination mechanism. Identification and elucidation of cluster-specific contamination mechanisms may be used to develop improved overall risk management and wellhead protection strategies, while also informing future remediation and maintenance efforts.

  20. Analysis of Gpr126 function defines distinct mechanisms controlling the initiation and maturation of myelin

    PubMed Central

    Glenn, Thomas D.; Talbot, William S.

    2013-01-01

    In peripheral nerves, Schwann cells form the myelin sheath, which allows the efficient propagation of action potentials along axons. The transcription factor Krox20 regulates the initiation of myelination in Schwann cells and is also required to maintain mature myelin. The adhesion G protein-coupled receptor (GPCR) Gpr126 is essential for Schwann cells to initiate myelination, but previous studies have not addressed the role of Gpr126 signaling in myelin maturation and maintenance. Through analysis of Gpr126 in zebrafish, we define two distinct mechanisms controlling the initiation and maturation of myelin. We show that gpr126 mutant Schwann cells elaborate mature myelin sheaths and maintain krox20 expression for months, provided that the early signaling defect is bypassed by transient elevation of cAMP. At the onset of myelination, Gpr126 and protein kinase A (PKA) function as a switch that allows Schwann cells to initiate krox20 expression and myelination. After myelination is initiated, krox20 expression is maintained and myelin maturation proceeds independently of Gpr126 signaling. Transgenic analysis indicates that the Krox20 cis-regulatory myelinating Schwann cell element (MSE) becomes active at the onset of myelination and that this activity is dependent on Gpr126 signaling. Activity of the MSE declines after initiation, suggesting that other elements are responsible for maintaining krox20 expression in mature nerves. We also show that elevated cAMP does not initiate myelination in the absence of functional Neuregulin 1 (Nrg1) signaling. These results indicate that the mechanisms regulating the initiation of myelination are distinct from those mediating the maturation and maintenance of myelin. PMID:23804499

  1. Reproducibility analysis of measurements with a mechanical semiautomatic eye model for evaluation of intraocular lenses

    NASA Astrophysics Data System (ADS)

    Rank, Elisabet; Traxler, Lukas; Bayer, Natascha; Reutterer, Bernd; Lux, Kirsten; Drauschke, Andreas

    2014-03-01

    Mechanical eye models are used to validate ex vivo the optical quality of intraocular lenses (IOLs). The quality measurement and test instructions for IOLs are defined in the ISO 11979-2. However, it was mentioned in literature that these test instructions could lead to inaccurate measurements in case of some modern IOL designs. Reproducibility of alignment and measurement processes are presented, performed with a semiautomatic mechanical ex vivo eye model based on optical properties published by Liou and Brennan in the scale 1:1. The cornea, the iris aperture and the IOL itself are separately changeable within the eye model. The adjustment of the IOL can be manipulated by automatic decentration and tilt of the IOL in reference to the optical axis of the whole system, which is defined by the connection line of the central point of the artificial cornea and the iris aperture. With the presented measurement setup two quality criteria are measurable: the modulation transfer function (MTF) and the Strehl ratio. First the reproducibility of the alignment process for definition of initial conditions of the lateral position and tilt in reference to the optical axis of the system is investigated. Furthermore, different IOL holders are tested related to the stable holding of the IOL. The measurement is performed by a before-after comparison of the lens position using a typical decentration and tilt tolerance analysis path. Modulation transfer function MTF and Strehl ratio S before and after this tolerance analysis are compared and requirements for lens holder construction are deduced from the presented results.

  2. Groundwater source contamination mechanisms: physicochemical profile clustering, risk factor analysis and multivariate modelling.

    PubMed

    Hynds, Paul; Misstear, Bruce D; Gill, Laurence W; Murphy, Heather M

    2014-04-01

    An integrated domestic well sampling and "susceptibility assessment" programme was undertaken in the Republic of Ireland from April 2008 to November 2010. Overall, 211 domestic wells were sampled, assessed and collated with local climate data. Based upon groundwater physicochemical profile, three clusters have been identified and characterised by source type (borehole or hand-dug well) and local geological setting. Statistical analysis indicates that cluster membership is significantly associated with the prevalence of bacteria (p=0.001), with mean Escherichia coli presence within clusters ranging from 15.4% (Cluster-1) to 47.6% (Cluster-3). Bivariate risk factor analysis shows that on-site septic tank presence was the only risk factor significantly associated (p<0.05) with bacterial presence within all clusters. Point agriculture adjacency was significantly associated with both borehole-related clusters. Well design criteria were associated with hand-dug wells and boreholes in areas characterised by high permeability subsoils, while local geological setting was significant for hand-dug wells and boreholes in areas dominated by low/moderate permeability subsoils. Multivariate susceptibility models were developed for all clusters, with predictive accuracies of 84% (Cluster-1) to 91% (Cluster-2) achieved. Septic tank setback was a common variable within all multivariate models, while agricultural sources were also significant, albeit to a lesser degree. Furthermore, well liner clearance was a significant factor in all models, indicating that direct surface ingress is a significant well contamination mechanism. Identification and elucidation of cluster-specific contamination mechanisms may be used to develop improved overall risk management and wellhead protection strategies, while also informing future remediation and maintenance efforts. PMID:24583518

  3. Analysis of the Isolated SecA DEAD Motor Suggests a Mechanism for Chemical-Mechanical Coupling

    SciTech Connect

    Nithianantham, Stanley; Shilton, Brian H

    2011-09-28

    The preprotein cross-linking domain and C-terminal domains of Escherichia coli SecA were removed to create a minimal DEAD motor, SecA-DM. SecA-DM hydrolyzes ATP and has the same affinity for ADP as full-length SecA. The crystal structure of SecA-DM in complex with ADP was solved and shows the DEAD motor in a closed conformation. Comparison with the structure of the E. coli DEAD motor in an open conformation (Protein Data Bank ID 2FSI) indicates main-chain conformational changes in two critical sequences corresponding to Motif III and Motif V of the DEAD helicase family. The structures that the Motif III and Motif V sequences adopt in the DEAD motor open conformation are incompatible with the closed conformation. Therefore, when the DEAD motor makes the transition from open to closed, Motif III and Motif V are forced to change their conformations, which likely functions to regulate passage through the transition state for ATP hydrolysis. The transition state for ATP hydrolysis for the SecA DEAD motor was modeled based on the conformation of the Vasa helicase in complex with adenylyl imidodiphosphate and RNA (Protein Data Bank ID 2DB3). A mechanism for chemical-mechanical coupling emerges, where passage through the transition state for ATP hydrolysis is hindered by the conformational changes required in Motif III and Motif V, and may be promoted by binding interactions with the preprotein substrate and/or other translocase domains and subunits.

  4. Analysis of the Isolated SecA DEAD Motor Suggests a Mechanism for Chemical-Mechanical Coupling

    SciTech Connect

    Nithianantham, Stanley; Shilton, Brian H

    2010-09-20

    The preprotein cross-linking domain and C-terminal domains of Escherichia coli SecA were removed to create a minimal DEAD motor, SecA-DM. SecA-DM hydrolyzes ATP and has the same affinity for ADP as full-length SecA. The crystal structure of SecA-DM in complex with ADP was solved and shows the DEAD motor in a closed conformation. Comparison with the structure of the E. coli DEAD motor in an open conformation (Protein Data Bank ID 2FSI) indicates main-chain conformational changes in two critical sequences corresponding to Motif III and Motif V of the DEAD helicase family. The structures that the Motif III and Motif V sequences adopt in the DEAD motor open conformation are incompatible with the closed conformation. Therefore, when the DEAD motor makes the transition from open to closed, Motif III and Motif V are forced to change their conformations, which likely functions to regulate passage through the transition state for ATP hydrolysis. The transition state for ATP hydrolysis for the SecA DEAD motor was modeled based on the conformation of the Vasa helicase in complex with adenylyl imidodiphosphate and RNA (Protein Data Bank ID 2DB3). A mechanism for chemical-mechanical coupling emerges, where passage through the transition state for ATP hydrolysis is hindered by the conformational changes required in Motif III and Motif V, and may be promoted by binding interactions with the preprotein substrate and/or other translocase domains and subunits.

  5. Studies in photochemical smog chemistry. I. Atmospheric chemistry of toluene. II. Analysis of chemical reaction mechanisms for photochemical smog

    SciTech Connect

    Leone, J.A.

    1985-01-01

    This study focuses on two related topics in the gas phase organic chemistry of importance in urban air pollution. Part I describes an experimental and modeling effort aimed at developing a new explicit reaction mechanism for the atmospheric photooxidation of toluene. This mechanism is tested using experimental data from both indoor and outdoor smog chamber facilities. The predictions of the new reaction mechanism are found to be in good agreement with both sets of experimental data. Additional simulations performed with the new mechanism are used to investigate various mechanistic paths, and to gain insight into areas where the understanding is not complete. The outdoor experimental facility, which was built to provide the second set of experimental data, consists of a 65 cubic meter teflon smog chamber together with full instrumentation capable of measuring ozone, nitrogen dioxide, nitric oxide, peroxyacetyl nitrate (PAN), carbon monoxide, relative humidity, temperature, aerosol size distributions, and of course toluene and its photooxidation products. In Part II, a theoretical analysis of lumped chemical reaction mechanisms for photochemical smog is presented. Included is a description of a new counter species analysis technique which can be used to analyze any complex chemical reaction mechanism. Finally, a new lumped mechanism for photochemical smog is developed and tested against experimental data from two smog chamber facilities. Advantages of this mechanism relative to the existing lumped mechanisms are discussed.

  6. Mechanical analysis of wood-fiber cement sheets under constant and repeated loading

    NASA Astrophysics Data System (ADS)

    Teixeira, Divino Eterno

    Inorganic-bonded panels have been successfully utilized for many years around the world. Cellulose materials are extensively used for cement-bonded particleboard (CBP) and for fiber-reinforced cement (FRC) composites worldwide. Particularly in Europe, this family of composites is used, among other applications, for building construction. Use of wood-fiber cement (WFC) composites in North America has been steadily increasing over the last 10 years. Problems encountered with resin-bonded wood products used in exterior environments have resulted in litigation and search for viable products. WFC sheets are currently filling this need and gaining market share by virtue of their own superior properties. This study was designed to provide basic information currently lacking in literature and important to the wise application of WFC sheets. Experimental autoclaved WFC flat sheets made with kraft Douglas fir fiber and with recycled old corrugated containers (OCC) fiber were manufactured and the results compared with an available commercial product. This experimental program was subdivided into three manuscripts. The first manuscript evaluates whether the actual mechanical properties of WFC sheets can be predicted using nondestructive parameters of the material by applying stress wave time techniques. The second manuscript deals with characterization of the WFC sheets. Physical and mechanical properties were evaluated and results discussed with the use of a scanning electronic microscopic (SEM) analysis. Manuscript three examines the viscoelastic behavior of the material at constant and repeated loading conditions. The nondestructive evaluation (NDE) of the material showed good correlation between dynamic and static modulus of elasticity (MOE). A multivariate linear regression analysis provided the strongest correlation (R = 0.828) for static MOE as a function of wave speed, density, and dynamic MOE. Results from Manuscript 2 revealed that WFC sheets manufactured with

  7. Sensitivity and Uncertainty Analysis in Chemical Mechanisms for Air Quality Modeling

    NASA Astrophysics Data System (ADS)

    Gao, Dongfen

    1995-01-01

    Ambient ozone in urban and regional air pollution is a serious environmental problem. Air quality models can be used to predict ozone concentrations and explore control strategies. One important component of such air quality models is a chemical mechanism. Sensitivity and uncertainty analysis play an important role in the evaluation of the performance of air quality models. The uncertainties associated with the RADM2 chemical mechanism in predicted concentrations of O_3, HCHO, H _2rm O_2, PAN, and HNO _3 were estimated. Monte Carlo simulations with Latin Hypercube Sampling were used to estimate the overall uncertainties in concentrations of species of interest, due to uncertainties in chemical parameters. The parameters that were treated as random variables were identified through first-order sensitivity and uncertainty analyses. Recent estimates of uncertainties in rate parameters and product yields were used. The results showed the relative uncertainties in ozone predictions are +/-23-50% (1sigma relative to the mean) in urban cases, and less than +/-20% in rural cases. Uncertainties in HNO_3 concentrations are the smallest, followed by HCHO, O_3 and PAN. Predicted H_2rm O_2 concentrations have the highest uncertainties. Uncertainties in the differences of peak ozone concentrations between base and control cases were also studied. The results show that the uncertainties in the fractional reductions in ozone concentrations were 9-12% with NO_{rm x} control at an ROG/NO_{rm x} ratio of 24:1 and 11-33% with ROG control at an ROG/NO _{rm x} ratio of 6:1. Linear regression analysis of the Monte Carlo results showed that uncertainties in rate parameters for the formation of HNO_3, for the reaction of HCHO + hv to 2HO _2 + CO, for PAN chemistry and for the photolysis of NO_2 are most influential to ozone concentrations and differences of ozone. The parameters that are important to ozone concentrations also tend to be relatively influential to other key species

  8. Analysis of uncertainties in the regional acid deposition model, version 2 (RADM2), gas-phase chemical mechanism. Final report

    SciTech Connect

    Gao, D.; Milford, J.B.; Stockwell, W.R.

    1996-04-01

    This report describes the results of a detailed analysis of uncertainties in the RADM2 chemical mechanism, which was developed by Stockwell et al. (1990) for use in urban and regional scale models of the formation and transport of ozone and other photochemical air pollutants. The uncertainty analysis was conducted for box model simulations of chemical conditions representing summertime smog episodes in polluted rural and urban areas. Estimated uncertainties in the rate parameters and product yields of the mechanism were propagated through the simulations using Monte Carlo analysis with a Latin Hypercube Sampling scheme. Uncertainty estimates for the mechanism parameters were compiled from published reviews, supplemented as necessary by original estimates. Correlations between parameters were considered in the analysis as appropriate.

  9. Mechanical characterization and structural analysis of recycled fiber-reinforced-polymer resin-transfer-molded beams

    NASA Astrophysics Data System (ADS)

    Tan, Eugene Wie Loon

    1999-09-01

    The present investigation was focussed on the mechanical characterization and structural analysis of resin-transfer-molded beams containing recycled fiber-reinforced polymers. The beams were structurally reinforced with continuous unidirectional glass fibers. The reinforcing filler materials consisted entirely of recycled fiber-reinforced polymer wastes (trim and overspray). The principal resin was a 100-percent dicyclo-pentadiene unsaturated polyester specially formulated with very low viscosity for resin transfer molding. Variations of the resin transfer molding technique were employed to produce specimens for material characterization. The basic materials that constituted the structural beams, continuous-glass-fiber-reinforced, recycled-trim-filled and recycled-overspray-filled unsaturated polyesters, were fully characterized in axial and transverse compression and tension, and inplane and interlaminar shear, to ascertain their strengths, ultimate strains, elastic moduli and Poisson's ratios. Experimentally determined mechanical properties of the recycled-trim-filled and recycled-overspray-filled materials from the present investigation were superior to those of unsaturated polyester polymer concretes and Portland cement concretes. Mechanical testing and finite element analyses of flexure (1 x 1 x 20 in) and beam (2 x 4 x 40 in) specimens were conducted. These structurally-reinforced specimens were tested and analyzed in four-point, third-point flexure to determine their ultimate loads, maximum fiber stresses and mid-span deflections. The experimentally determined load capacities of these specimens were compared to those of equivalent steel-reinforced Portland cement concrete beams computed using reinforced concrete theory. Mechanics of materials beam theory was utilized to predict the ultimate loads and mid-span deflections of the flexure and beam specimens. However, these predictions proved to be severely inadequate. Finite element (fracture propagation

  10. Tensile behavior and dynamic mechanical analysis of novel poly(lactide/δ-valerolactone) statistical copolymers.

    PubMed

    Fernández, J; Larrañaga, A; Etxeberria, A; Sarasua, J R

    2014-07-01

    Lactide-co-δ-valerolactone copolymers (PLVL) have not attracted as much research interest as the more popular poly(lactide-co-ε-caprolactone) (PLCL) elastomeric materials. In this work the study of the mechanical performance is focused on the former with the aim of identifying the potential advantages of these thermoplastic elastomers for their application in the biomedical field. Mechanical testing (at 21°C and at 37°C) of at least 5 specimens and dynamic mechanical analysis (DMA) in duplicate were carried out on various PLVL, which include a moderately blocky l-lactide/δ-valerolactone copolymer (~70% of l-LA and R=0.68) and several that showed a random distribution of sequences (R~1): some terpolymers based on l-lactide, d-lactide and δ-valerolactone (with a lactone content of ~25 and ~14%) and a series of copolymers of l-LA and δ-VL having l-LA molar contents ranging from 69 to 74%. In view of the results, it can be concluded that noteworthy improvements in stiffness and strength were achieved by adding δ-VL to the reaction mix instead of ε-CL, although both monomers have analogous chemical properties. For example, a PLVL with a 75:25M composition of l-LA/δ-VL at 21°C presented a secant modulus of 213.7±36.5MPa and σu=14.7±1.4MPa whereas a previously studied PLCL of equal composition had a secant modulus and an ultimate stress value of 19.4±1.3MPa and 3.2±0.6MPa, respectively. At 37°C, the differences in the mechanical properties between the different PLVLs of this work were far less relevant, with most of them showing a fully elastomeric behavior. Referring to the DMA measurements, the reduction in the peak of tan δ (from ~2.5 to 0.5) through the glass transition was a clear indicator that crystalline domains formed during hydrolytic degradation in some of the polymers. However, the more amorphous PLVLs with short l-LA average sequence lengths (ll-LA<2.91) did not undergo changes in the storage modulus and tan δ curves after two weeks

  11. Mechanical Behavior Analysis of a Test Coil for MICE Coupling Solenoid during Quench

    SciTech Connect

    Pan, Heng; Wang, Li; Guo, Xinglong; Wu, Hong; Green, M.A.

    2009-10-28

    The coupling magnet for the Muon Ionization Cooling Experiment has a self-inductance of 592 H and the magnet stored energy of 13 MJ at a full current of 210 A for the worst operation case of the MICE channel. The high level of stored energy in the magnet can cause high peak temperature during a quench and induce considerable impact of stresses. One test coil was built in order to validate the design method and to practice the stress and strain situation to occur in the coupling coil. In this study, the analysis on stress redistribution during a quench with sub-divided winding was performed. The stress variation may bring about failure of impregnating material such as epoxy resin, which is the curse of a new normal zone arising. Spring models for impregnating epoxy and fiber-glass cloth in the coil were used to evaluate the mechanical disturbance by impregnated materials failure. This paper presents the detailed dynamic stress and stability analysis to assess the stress distribution during the quench process and to check whether the transient loads are acceptable for the magnet.

  12. Computational and numerical aspects of using the integral equation method for adhesive layer fracture mechanics analysis

    SciTech Connect

    Giurgiutiu, V.; Ionita, A.; Dillard, D.A.; Graffeo, J.K.

    1996-12-31

    Fracture mechanics analysis of adhesively bonded joints has attracted considerable attention in recent years. A possible approach to the analysis of adhesive layer cracks is to study a brittle adhesive between 2 elastic half-planes representing the substrates. A 2-material 3-region elasticity problem is set up and has to be solved. A modeling technique based on the work of Fleck, Hutchinson, and Suo is used. Two complex potential problems using Muskelishvili`s formulation are set up for the 3-region, 2-material model: (a) a distribution of edge dislocations is employed to simulate the crack and its near field; and (b) a crack-free problem is used to simulate the effect of the external loading applied in the far field. Superposition of the two problems is followed by matching tractions and displacements at the bimaterial boundaries. The Cauchy principal value integral is used to treat the singularities. Imposing the traction-free boundary conditions over the entire crack length yielded a linear system of two integral equations. The parameters of the problem are Dundurs` elastic mismatch coefficients, {alpha} and {beta}, and the ratio c/H representing the geometric position of the crack in the adhesive layer.

  13. Evaluation of hydrogen pressure vessels using slow strain rate testing and fracture mechanics analysis

    SciTech Connect

    Murray, S.H.; Desai, V.H.

    1998-12-31

    A total of 108 seamless, forged pressure vessels, fabricated from ASTM A372 type IV (UNS K14508) and type V low alloy steel, are currently in 4,200 psi (29 MPa) gaseous hydrogen (GH{sub 2}) service at the Kennedy Space Center`s (KSC) Space Shuttle Launch Complex 39 (LC-39). The vessels were originally used in 6,000 psi (41 MPa) GH{sub 2} service during the Apollo program. NASA recently received a letter of warning from the manufacturer of the vessels stating that the subject vessels should be now be removed from GH{sub 2} service due to the fact that the ultimate tensile strength (UTS) of many of the vessels exceeds the maximum limit of 126 ksi (869 MPa) now imposed on A372 steel intended for GH{sub 2} service, and therefore are susceptible to hydrogen environment embrittlement. Due to the expense associated with vessel replacement, it was decided to determine by testing and analysis whether or not the vessels needed to be removed from GH{sub 2} service. Slow strain rate testing was performed under hydrogen charging conditions to determine the value of the threshold fracture toughness for sustained loading crack growth in GH{sub 2}, (K{sub H}) for the vessel material, this value was then used in a fracture mechanics safe-life analysis (a 20-year service life was modeled) that indicated the vessels are safe for continued use.

  14. Vibrational analysis and formation mechanism of typical deep eutectic solvents: An experimental and theoretical study.

    PubMed

    Zhu, Siwen; Li, Hongping; Zhu, Wenshuai; Jiang, Wei; Wang, Chao; Wu, Peiwen; Zhang, Qi; Li, Huaming

    2016-07-01

    Deep eutectic solvents (DESs), as ionic liquid analogues for green solvents, have gained increasing attentions in chemistry. In this work, three typical kinds of DESs (ChCl/Gly, ChCl/AcOH and ChCl/Urea) were successfully synthesized and characterized by Fourier transform infrared spectroscopy (FTIR) and Raman. Then comprehensive and systematical analyses were performed by the methods of density functional theory (DFT). Two methods (B3LYP/6-311++G(2d,p) and dispersion-corrected B3LYP-D3/6-311++G(2d,p)) were employed to investigate the structures, vibrational frequencies and assign their ownership of vibrational modes for the DESs, respectively. Nearly all the experimental characteristic peaks of IR and Raman were identified according to the calculated results. By linear fitting of the combined calculated vs experimental vibration frequencies, it can be found that both of the two methods are excellent to reproduce the experimental results. Besides, hydrogen bonds were proved to exist in DESs by IR spectrum, structure analysis and RDG analysis. This work was aimed at predicting and understanding the vibrational spectra of the three typical DESs based on DFT methods. Moreover, by comparing experimental and theoretical results, it provides us a deep understanding of the formation mechanisms of DESs. PMID:27450770

  15. NASCRAC - A computer code for fracture mechanics analysis of crack growth

    NASA Technical Reports Server (NTRS)

    Harris, D. O.; Eason, E. D.; Thomas, J. M.; Bianca, C. J.; Salter, L. D.

    1987-01-01

    NASCRAC - a computer code for fracture mechanics analysis of crack growth - is described in this paper. The need for such a code is increasing as requirements grow for high reliability and low weight in aerospace components. The code is comprehensive and versatile, as well as user friendly. The major purpose of the code is calculation of fatigue, corrosion fatigue, or stress corrosion crack growth, and a variety of crack growth relations can be selected by the user. Additionally, crack retardation models are included. A very wide variety of stress intensity factor solutions are contained in the code, and extensive use is made of influence functions. This allows complex stress gradients in three-dimensional crack problems to be treated easily and economically. In cases where previous stress intensity factor solutions are not adequate, new influence functions can be calculated by the code. Additional features include incorporation of J-integral solutions from the literature and a capability for estimating elastic-plastic stress redistribution from the results of a corresponding elastic analysis. An example problem is presented which shows typical outputs from the code.

  16. The Mechanical Analysis of the Biofilm Streamer Nucleation and Geometry Characterization in Microfluidic Channels

    PubMed Central

    Wang, Xiaoling; Hao, Mudong; Du, Xin; Wang, Guoqing; Matsushita, Jun-ichi

    2016-01-01

    Bacteria can form biofilm streamers in microfluidic channels with various geometries. Experiments show that the streamer geometry, such as its shape or thickness, depends on the fluid velocity and the geometry and curvature of the microfluidic channel. In the paper, a mechanical analysis of the flow field is made in different channels, which shows that the secondary flow in the channel is the reason for streamer nucleation and that the shear stress distribution decides the streamer geometry including shape and thickness. Through a finite elements simulation, we obtain the secondary flow forming positions in both static and rotating channels: positions that are the location of nucleation of the streamer. Thick or wide biofilm streamers occur at the points of minimum shear stress in static channels. Furthermore, in rotating channels, spiral-like streamers form, due to the helical shape of the minimum shear stress distribution. The findings may allow the prevention of biofilm formation and also the removal of bacteria adhered onto certain surfaces in channels with small cross sections. The analysis also indicates how one can obtain desirable biofilm streamers by control of the channel geometry and the loading conditions. PMID:27313658

  17. Development of Probabilistic Fracture Mechanics Analysis Code for Pipes with Stress Corrosion Cracks

    NASA Astrophysics Data System (ADS)

    Machida, Hideo; Arakawa, Manabu; Yamashita, Norimichi; Yoshimura, Shinobu

    Risk-Informed integrity management methodologies have been developed for Japanese nuclear power plants. One of the issues of concern is the reliability assessment of piping with flaws due to stress corrosion cracking (SCC). Therefore, the probabilistic fracture mechanics analysis code has been developed, which can perform the reliability assessment for austenitic stainless steel piping with flaws due to SCC. This paper describes technical basis of this code. This method is based on Monte-Carlo technique considering many sample cases in a piping section, where the initiation and growth of cracks are calculated and piping failures, including leaks and rapture, are evaluated. A notable feature is that multiple cracks can be treated, consequently, assessment of coalescence of cracks and intricate break evaluation of piping section have been included. Moreover, the in-service inspection (ISI) and integrity evaluation by Fitness-for-Service (FFS) code are integrated into the analysis, and the contribution to failure probability decrease can be assessed. Key parameters are determined on a probability basis with the designated probability type throughout the procedure. Size, location and time of crack initiation, coefficients of crack growth due to SCC and factors for piping failure are included in those parameters. With this method the reliability level of the piping through the operation periods can be estimated and the contribution of various parameters including ISI can be quantitatively evaluated.

  18. Molecular mechanisms associated with breast cancer based on integrated gene expression profiling by bioinformatics analysis.

    PubMed

    Wu, Di; Han, Bing; Guo, Liang; Fan, Zhimin

    2016-07-01

    In this study, we aimed to gain more insights into the underlying molecular mechanisms responsible for breast cancer (BC) progression. Three gene expression profiles of human BC were integrated and used to screen the differentially expressed genes (DEGs) between healthy breast samples and BC samples. Protein-protein interaction (PPI) network of DEGs was constructed by mapping DEGs into the Search Tool for the Retrieval of Interacting Genes (STRING) database; then the subnetworks of PPI were constructed with plug-in, MCODE and DEGs in Subnetwork 1 were analysed based on Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway database ( http://www.genome.jp/kegg /). In addition, co-expression network of DEGs was established using the Cytoscape. Totalally 931 DEGs were selected, including 340 up-regulated genes and 591 down-regulated genes. KEGG pathway analysis for DEGs in Subnetwork 1 showed that the pathogenesis of BC was associated with cell cycle, oocyte meiosis, progesterone-mediated oocyte maturation and p53 signalling pathways. Meanwhile, the most significant-related DEGs were found by co-expression network analysis of DEGs. In conclusion, CCNG1 might be involved in the progression of BC via inhibiting cell proliferation, and ADAMTS1 might play a crucial role in BC development through the regulation of angiogenesis. PMID:26804550

  19. The application of computational mechanics to the analysis of natural data: An example in geomagnetism.

    NASA Astrophysics Data System (ADS)

    Watkins, Nicholas; Clarke, Richard; Freeman, Mervyn

    2002-11-01

    We discuss how the ideal formalism of Computational Mechanics can be adapted to apply to a non-infinite series of corrupted and correlated data, that is typical of most observed natural time series. Specifically, a simple filter that removes the corruption that creates rare unphysical causal states is demonstrated, and the new concept of effective soficity is introduced. The benefits of these new concepts are demonstrated on simulated time series by (a) the effective elimination of white noise corruption from a periodic signal using the expletive filter and (b) the appearance of an effectively sofic region in the statistical complexity of a biased Poisson switch time series that is insensitive to changes in the word length (memory) used in the analysis. The new algorithm is then applied to analysis of a real geomagnetic time series measured at Halley, Antarctica. Two principal components in the structure are detected that are interpreted as the diurnal variation due to the rotation of the earth-based station under an electrical current pattern that is fixed with respect to the sun-earth axis and the random occurrence of a signature likely to be that of the magnetic substorm. In conclusion, a hypothesis is advanced about model construction in general (see also Clarke et al; arXiv::cond-mat/0110228).

  20. Approach to Analysis of Mechanical Behavior of Textile Composites by Inclusion Element Method

    NASA Astrophysics Data System (ADS)

    Tsujikami, Tetsuya; Horikawa, Takeshi; Hirosawa, Satoru; Zako, Masaru

    The inclusion element method with a simple grid model has been proposed as one of the analytical techniques of the mechanical behavior of textile composites, and the effectiveness of this method has been verified. The inclusion element method is applicable to the analysis of all types of textile composites because the element stiffness obtained by the inclusion method through cooperation with a fabric structure simulator is used. From the result of the analysis by the inclusion element method, it has been confirmed that the peculiar crimp-interchange of woven composites occurs and high tensile stress arises at the elements with fiber bundles oriented in the load direction. A comparison between the analyses using a real model and the inclusion element model has shown relatively good agreement. Although the analytical result is greatly dependent on the grid pattern, the inclusion element method can provide a sufficient accuracy of results even when the number of elements in the model is lower than that in the real model.

  1. Analysis of mechanical strength to fixing the femoral neck fracture in synthetic bone type Asnis

    PubMed Central

    Freitas, Anderson; Lula, Welder Fernandes; de Oliveira, Jonathan Sampaio; Maciel, Rafael Almeida; Souto, Diogo Ranier de Macedo; Godinho, Patrick Fernandes

    2014-01-01

    OBJECTIVE: To analyze the results of biomechanical assays of fixation of Pauwels type III femoral neck fracture in synthetic bone, using 7.5mm cannulated screws in inverted triangle formation, in relation to the control group. METHODS: Ten synthetic bones were used, from a domestic brand, divided into two groups: test and control. In the test group, a 70° tilt osteotomy of the femoral neck was fixated using three cannulated screws in inverted triangle formation. The resistance of this fixation and its rotational deviation were analyzed at 5mm displacement (phase 1) and 10mm displacement (phase 2). The control group was tested in its integrity until the fracture of the femoral neck occurred. The Mann-Whitney test was used for group analysis and comparison. RESULTS: The values in the test group in phase 1, in samples 1-5, showed a mean of 579N and SD =77N. Rotational deviations showed a mean of 3.33°, SD = 2.63°. In phase 2, the mean was 696N and SD =106N. The values of the maximum load in the control group had a mean of 1329N and SD=177N. CONCLUSION: The analysis of mechanical strength between the groups determined a statistically significant lower value in the test group. Level of Evidence III, Control Case. PMID:25246851

  2. Tools for Accurate and Efficient Analysis of Complex Evolutionary Mechanisms in Microbial Genomes. Final Report

    SciTech Connect

    Nakhleh, Luay

    2014-03-12

    I proposed to develop computationally efficient tools for accurate detection and reconstruction of microbes' complex evolutionary mechanisms, thus enabling rapid and accurate annotation, analysis and understanding of their genomes. To achieve this goal, I proposed to address three aspects. (1) Mathematical modeling. A major challenge facing the accurate detection of HGT is that of distinguishing between these two events on the one hand and other events that have similar "effects." I proposed to develop a novel mathematical approach for distinguishing among these events. Further, I proposed to develop a set of novel optimization criteria for the evolutionary analysis of microbial genomes in the presence of these complex evolutionary events. (2) Algorithm design. In this aspect of the project, I proposed to develop an array of e cient and accurate algorithms for analyzing microbial genomes based on the formulated optimization criteria. Further, I proposed to test the viability of the criteria and the accuracy of the algorithms in an experimental setting using both synthetic as well as biological data. (3) Software development. I proposed the nal outcome to be a suite of software tools which implements the mathematical models as well as the algorithms developed.

  3. In-depth quantitative analysis of the microstructures produced by Surface Mechanical Attrition Treatment (SMAT)

    SciTech Connect

    Samih, Y.; Beausir, B.; Bolle, B.; Grosdidier, T.

    2013-09-15

    Electron BackScattered Diffraction (EBSD) maps are used to characterize quantitatively the graded microstructure formed by Surface Mechanical Attrition Treatment (SMAT) and applied here to the 316L stainless steel. In particular, the analysis of GNDs – coupled with relevant and reliable criteria – was used to depict the thickness of each zone identified in the SMAT-affected layers: (i) the “ultrafine grain” (UFG) zone present at the extreme top surface, (ii), the “transition zone” where grains were fragmented under the heavy plastic deformation and, finally, (iii) the “deformed zone” where initial grains are simply deformed. The interest of this procedure is illustrated through the comparative analysis of the effect of some SMAT processing parameters (amplitude of vibration and treatment duration). The UFG and transition zones are more significantly modified than the overall affected thickness under our tested conditions. - Highlights: • EBSD maps are used to characterize quantitatively the microstructure of SMAT treated samples. • Calculation of the GND density to quantify strain gradients • A new method to depict the different zone thicknesses in the SMAT affected layer • Effects of SMAT processing parameters on the surface microstructure evolution.

  4. An Analysis of Change Mechanisms in Government Budgets on Science and Technology

    NASA Astrophysics Data System (ADS)

    Jung, C.

    2012-12-01

    Recent studies on policy changes have shown that there are limitations of incrementalism and that there no longer exists a general theory that can explain policy change. A number of studies have been conducted to examine policy changes in terms of drastic changes in budgets or policy agenda. According to the Punctuated Equilibrium Theory (PET), policy change is punctuated by long periods of stability, and large, but rare, changes due to shifts in society or the government. Although the reasons for these drastic changes are interpreted mainly from external events, the exact mechanisms of these changes are still not known. In this study, we assume that the punctuated budget changes are a result of not only external events but also the bureaucratic power of government departments. We attempt to identify the regularity of budget change pattern due to these internal characteristics (bureaucratic power). In order to understand budget changes caused by external events, especially for science and technology, the ARIMA-Intervention analysis was implemented. The results showed that the ARIMA-Intervention analysis explained the abrupt change in budget well. This means that a change in budget cannot be explained as incrementalism. Also, we analyzed the budget change kurtosis of government department along with various policy and organization types. Normally, a high kurtosis means there is a high probability of a punctuated equilibrium. The results show that science and technology agency as well as productive, delivery, and transfer agencies have a relatively high kurtosis.;

  5. Effects of alpha-amylase reaction mechanisms on analysis of resistant-starch contents.

    PubMed

    Moore, Samuel A; Ai, Yongfeng; Chang, Fengdan; Jane, Jay-lin

    2015-01-22

    This study aimed to understand differences in the resistant starch (RS) contents of native and modified starches obtained using two standard methods of RS content analysis: AOAC Method 991.43 and 2002.02. The largest differences were observed in native potato starch, cross-linked wheat distarch phosphate, and high-amylose corn starch stearic-acid complex (RS5) between using AOAC Method 991.43 with Bacillus licheniformis α-amylase (BL) and AOAC Method 2002.02 with porcine pancreatic α-amylase (PPA). To determine possible reasons for these differences, we hydrolyzed raw-starch granules with BL and PPA with equal activity at pH 6.9 and 37°C for up to 84 h and observed the starch granules displayed distinct morphological differences after the hydrolysis. Starches hydrolyzed by BL showed erosion on the surface of the granules; those hydrolyzed by PPA showed pitting on granule surfaces. These results suggested that enzyme reaction mechanisms, including the sizes of the binding sites and the reaction patterns of the two enzymes, contributed to the differences in the RS contents obtained using different methods of RS analysis. PMID:25439920

  6. The Mechanical Analysis of the Biofilm Streamer Nucleation and Geometry Characterization in Microfluidic Channels.

    PubMed

    Wang, Xiaoling; Hao, Mudong; Du, Xin; Wang, Guoqing; Matsushita, Jun-Ichi

    2016-01-01

    Bacteria can form biofilm streamers in microfluidic channels with various geometries. Experiments show that the streamer geometry, such as its shape or thickness, depends on the fluid velocity and the geometry and curvature of the microfluidic channel. In the paper, a mechanical analysis of the flow field is made in different channels, which shows that the secondary flow in the channel is the reason for streamer nucleation and that the shear stress distribution decides the streamer geometry including shape and thickness. Through a finite elements simulation, we obtain the secondary flow forming positions in both static and rotating channels: positions that are the location of nucleation of the streamer. Thick or wide biofilm streamers occur at the points of minimum shear stress in static channels. Furthermore, in rotating channels, spiral-like streamers form, due to the helical shape of the minimum shear stress distribution. The findings may allow the prevention of biofilm formation and also the removal of bacteria adhered onto certain surfaces in channels with small cross sections. The analysis also indicates how one can obtain desirable biofilm streamers by control of the channel geometry and the loading conditions. PMID:27313658

  7. Global analysis of p53-regulated transcription identifies its direct targets and unexpected regulatory mechanisms

    PubMed Central

    Allen, Mary Ann; Andrysik, Zdenek; Dengler, Veronica L; Mellert, Hestia S; Guarnieri, Anna; Freeman, Justin A; Sullivan, Kelly D; Galbraith, Matthew D; Luo, Xin; Kraus, W Lee; Dowell, Robin D; Espinosa, Joaquin M

    2014-01-01

    The p53 transcription factor is a potent suppressor of tumor growth. We report here an analysis of its direct transcriptional program using Global Run-On sequencing (GRO-seq). Shortly after MDM2 inhibition by Nutlin-3, low levels of p53 rapidly activate ∼200 genes, most of them not previously established as direct targets. This immediate response involves all canonical p53 effector pathways, including apoptosis. Comparative global analysis of RNA synthesis vs steady state levels revealed that microarray profiling fails to identify low abundance transcripts directly activated by p53. Interestingly, p53 represses a subset of its activation targets before MDM2 inhibition. GRO-seq uncovered a plethora of gene-specific regulatory features affecting key survival and apoptotic genes within the p53 network. p53 regulates hundreds of enhancer-derived RNAs. Strikingly, direct p53 targets harbor pre-activated enhancers highly transcribed in p53 null cells. Altogether, these results enable the study of many uncharacterized p53 target genes and unexpected regulatory mechanisms. DOI: http://dx.doi.org/10.7554/eLife.02200.001 PMID:24867637

  8. Identification of B cells participated in the mechanism of postmenopausal women osteoporosis using microarray analysis

    PubMed Central

    Yan, Bing; Li, Jie; Zhang, Li

    2015-01-01

    To further understand the molecular mechanism of lymphocytes B cells in postmenopausal women osteoporosis. Microarray data (GSE7429) were downloaded from Gene Expression Omnibus, in which B cells were separated from the whole blood of postmenopausal women, including 10 with high bone mineral density (BMD) and 10 with low BMD. Differentially expressed genes (DEGs) between high and low BMD women were identified by Student’s t-test, and P < 0.01 was used as the significant criterion. Functional enrichment analysis was performed for up- and down-regulated DEGs using KEGG, REACTOME, and Gene Ontology (GO) databases. Protein-protein interaction network (PPI) of up- and down-regulated DEGs was respectively constructed by Cytoscape software using the STRING data. Total of 169 up-regulated and 69 down-regulated DEGs were identified. Functional enrichment analysis indicated that the genes (ITPA, ATIC, UMPS, HPRT1, COX10 and COX15) might participate in metabolic pathways, MAP3K10 and MAP3K9 might participate in the activation of JNKK activity, COX10 and COX15 might involve in mitochondrial electron transport, and ATIC, UMPS and HPRT1 might involve in transferase activity. MAPK3, ITPA, ATIC, UMPS and HPRT1 with a higher degree in PPI network were identified. MAPK3, MAP3K10, MAP3K9, COX10, COX15, ATIC, UMPS and HPRT1 might participate in the pathogenesis of osteoporosis. PMID:25785089

  9. Thigmomorphogenesis: anatomical, morphological and mechanical analysis of genetically different sibs of Pinus taeda in response to mechanical perturbation

    NASA Technical Reports Server (NTRS)

    Telewski, F. W.; Jaffe, M. J.

    1986-01-01

    Twenty-three open pollinated families (half-sibs) and four controlled pollinated families (full-sibs) of Pinus taeda L. (loblolly pine) were grown in a greenhouse and analyzed for changes induced by mechanical perturbation (MP). These changes included inhibition of stem and needle elongation, bracing of branch nodes, and increased radial growth in the direction of the MP. Inhibition of stem elongation was the least variable feature measured. Leaf extension and stem diameter were highly variable between half-sibs. MP induced increased drag in greenhouse grown P. taeda in wind-tunnel tests. In P. taeda, MP induced decreased flexibility and increased elasticity and plasticity of the stem. The increased radial growth of the stems overrode the increase in elasticity, resulting in an overall decrease in flexibility. MP trees had a higher rupture point than non-MP controls. Increased radial growth is a result of more rapid cell divisions of the vascular cambium, resulting in increased numbers of tracheids. The decreased leader growth is partly due to a decreased tracheid length in response to MP.

  10. Mechanical Analysis of Feeding Behavior in the Extinct “Terror Bird” Andalgalornis steulleti (Gruiformes: Phorusrhacidae)

    PubMed Central

    Degrange, Federico J.; Tambussi, Claudia P.; Moreno, Karen; Witmer, Lawrence M.; Wroe, Stephen

    2010-01-01

    The South American phorusrhacid bird radiation comprised at least 18 species of small to gigantic terrestrial predators for which there are no close modern analogs. Here we perform functional analyses of the skull of the medium-sized (∼40 kg) patagornithine phorusrhacid Andalgalornis steulleti (upper Miocene–lower Pliocene, Andalgalá Formation, Catamarca, Argentina) to assess its mechanical performance in a comparative context. Based on computed tomographic (CT) scanning and morphological analysis, the skull of Andalgalornis steulleti is interpreted as showing features reflecting loss of intracranial immobility. Discrete anatomical attributes permitting such cranial kinesis are widespread phorusrhacids outgroups, but this is the first clear evidence of loss of cranial kinesis in a gruiform bird and may be among the best documented cases among all birds. This apomorphic loss is interpreted as an adaptation for enhanced craniofacial rigidity, particularly with regard to sagittal loading. We apply a Finite Element approach to a three-dimensional (3D) model of the skull. Based on regression analysis we estimate the bite force of Andalgalornis at the bill tip to be 133 N. Relative to results obtained from Finite Element Analysis of one of its closest living relatives (seriema) and a large predatory bird (eagle), the phorusrhacid's skull shows relatively high stress under lateral loadings, but low stress where force is applied dorsoventrally (sagittally) and in “pullback” simulations. Given the relative weakness of the skull mediolaterally, it seems unlikely that Andalgalornis engaged in potentially risky behaviors that involved subduing large, struggling prey with its beak. We suggest that it either consumed smaller prey that could be killed and consumed more safely (e.g., swallowed whole) or that it used multiple well-targeted sagittal strikes with the beak in a repetitive attack-and-retreat strategy. PMID:20805872

  11. Combined probabilistic and principal component analysis approach for multivariate sensitivity evaluation and application to implanted patellofemoral mechanics.

    PubMed

    Fitzpatrick, Clare K; Baldwin, Mark A; Rullkoetter, Paul J; Laz, Peter J

    2011-01-01

    Many aspects of biomechanics are variable in nature, including patient geometry, joint mechanics, implant alignment and clinical outcomes. Probabilistic methods have been applied in computational models to predict distributions of performance given uncertain or variable parameters. Sensitivity analysis is commonly used in conjunction with probabilistic methods to identify the parameters that most significantly affect the performance outcome; however, it does not consider coupled relationships for multiple output measures. Principal component analysis (PCA) has been applied to characterize common modes of variation in shape and kinematics. In this study, a novel, combined probabilistic and PCA approach was developed to characterize relationships between multiple input parameters and output measures. To demonstrate the benefits of the approach, it was applied to implanted patellofemoral (PF) mechanics to characterize relationships between femoral and patellar component alignment and loading and the resulting joint mechanics. Prior studies assessing PF sensitivity have performed individual perturbation of alignment parameters. However, the probabilistic and PCA approach enabled a more holistic evaluation of sensitivity, including identification of combinations of alignment parameters that most significantly contributed to kinematic and contact mechanics outcomes throughout the flexion cycle, and the predictive capability to estimate joint mechanics based on alignment conditions without requiring additional analysis. The approach showed comparable results for Monte Carlo sampling with 500 trials and the more efficient Latin Hypercube sampling with 50 trials. The probabilistic and PCA approach has broad applicability to biomechanical analysis and can provide insight into the interdependencies between implant design, alignment and the resulting mechanics. PMID:20825941

  12. A novel classification of planar four-bar linkages and its application to the mechanical analysis of animal systems.

    PubMed

    Muller, M

    1996-05-29

    A novel classification of planar four-bar linkages is presented based on the systematical variation of one, two or three bar lengths and studying the transmission properties (input-output curves) of the linkages. This classification is better suited to the study of biological systems than the classical Grashof-classification used in engineering as it considers the change of structural elements, in evolution for example, instead of evaluating the possibilities for the rotation of a particular bar. The mechanical features of a wide range of planar linkages in vertebrates, described by various authors, have been included in this classification. Examples are: skull-levation and jaw-protrusion mechanisms in fishes, reptiles and birds, the coral crushing apparatus of parrotfishes, and catapult-mechanisms in feeding pipefishes. Four-bar replacement mechanisms, e.g., crank-slider mechanisms in feeding systems of fishes and cam-mechanisms in mammalian limb-joints, and more complex linkages than four-bar ones, e.g., six-bar linkages and interconnected four-bar linkages in fish feeding mechanisms are also discussed. In this way, an overview is obtained of the applicability of planar linkage theory in animal mechanics to mechanical functioning and the effect of possible variations of bar lengths and working ranges in evolution. Four-bar system analysis often provides a rigorous method of simplifying the study of complex biological mechanisms. The acceptable width-range of necessary and undesired hysteresis ('play') in biological linkages is also discussed. PMID:8927640

  13. Analysis of crustal deformation in Luzon, Philippines using geodetic observations and earthquake focal mechanisms

    NASA Astrophysics Data System (ADS)

    Galgana, Gerald; Hamburger, Michael; McCaffrey, Robert; Corpuz, Ernesto; Chen, Qizhi

    2007-03-01

    We utilize regional GPS velocities from Luzon, Philippines, with focal mechanism data from the Harvard Centroid Moment Tensor (CMT) Catalog, to constrain tectonic deformation in the complex plate boundary zone between the Philippine Sea Plate and Eurasia (the Sundaland block). Processed satellite imagery and digital elevation models are used with existing gravity anomaly, seismicity, and geologic maps to define a suite of six elastic blocks. Geodetic and focal mechanism data are inverted simultaneously to estimate plate rotations and fault-locking parameters for each of the tectonic blocks and faults comprising Luzon. Major tectonic structures that were found to absorb the plate convergence include the Manila Trench (20-100 mm yr - 1 ) and East Luzon Trough (˜ 9-15 mm yr - 1 )/Philippine Trench (˜ 29-34 mm yr - 1 ), which accommodate eastward and westward subduction beneath Luzon, respectively; the left-lateral strike-slip Philippine Fault (˜ 20-40 mm yr - 1 ), and its northward extensions, the Northern Cordillera Fault (˜ 17-37 mm yr - 1 transtension), and the Digdig Fault (˜ 17-27 mm yr - 1 transpression). The Macolod Corridor, a zone of active volcanism, crustal thinning, extension, and extensive normal and strike-slip faulting in southwestern Luzon, is associated with left-lateral, transtensional slip of ˜ 5-10 mm yr - 1 . The Marikina Fault, which separates the Central Luzon block from the Southwestern Luzon block, reveals ˜ 10-12 mm yr - 1 of left-lateral transpression. Our analysis suggests that much of the Philippine Fault and associated splays are locked to partly coupled, while the Manila and Philippine trenches appear to be poorly coupled. Luzon is best characterized as a tectonically active plate boundary zone, comprising six mobile elastic tectonic blocks between two active subduction zones. The Philippine Fault and associated intra-arc faults accommodate much of the trench-parallel component of relative plate motion.

  14. Integrative analysis of transgenic alfalfa (Medicago sativa L.) suggests new metabolic control mechanisms for monolignol biosynthesis.

    PubMed

    Lee, Yun; Chen, Fang; Gallego-Giraldo, Lina; Dixon, Richard A; Voit, Eberhard O

    2011-05-01

    The entanglement of lignin polymers with cellulose and hemicellulose in plant cell walls is a major biological barrier to the economically viable production of biofuels from woody biomass. Recent efforts of reducing this recalcitrance with transgenic techniques have been showing promise for ameliorating or even obviating the need for costly pretreatments that are otherwise required to remove lignin from cellulose and hemicelluloses. At the same time, genetic manipulations of lignin biosynthetic enzymes have sometimes yielded unforeseen consequences on lignin composition, thus raising the question of whether the current understanding of the pathway is indeed correct. To address this question systemically, we developed and applied a novel modeling approach that, instead of analyzing the pathway within a single target context, permits a comprehensive, simultaneous investigation of different datasets in wild type and transgenic plants. Specifically, the proposed approach combines static flux-based analysis with a Monte Carlo simulation in which very many randomly chosen sets of parameter values are evaluated against kinetic models of lignin biosynthesis in different stem internodes of wild type and lignin-modified alfalfa plants. In addition to four new postulates that address the reversibility of some key reactions, the modeling effort led to two novel postulates regarding the control of the lignin biosynthetic pathway. The first posits functionally independent pathways toward the synthesis of different lignin monomers, while the second postulate proposes a novel feedforward regulatory mechanism. Subsequent laboratory experiments have identified the signaling molecule salicylic acid as a potential mediator of the postulated control mechanism. Overall, the results demonstrate that mathematical modeling can be a valuable complement to conventional transgenic approaches and that it can provide biological insights that are otherwise difficult to obtain. PMID:21625579

  15. Intravascular laser speckle imaging for the mechanical analysis of coronary plaques (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hosoda, Masaki; Wang, Jing; Tsikudi, Diane; Nadkarni, Seemantini

    2016-02-01

    Acute myocardial infarction is frequently caused by the rupture of coronary plaques with severely compromised viscoelastic properties. We have developed a new optical technology termed intravascular laser speckle imaging (ILSI) that evaluates plaque viscoelastic properties, by measuring the time scale (time constant, τ) of temporally evolving laser speckle fluctuations. To enable coronary evaluation in vivo, an optical ILSI catheter has been developed that accomplishes omni-directional illumination and viewing of the entire coronary circumference without the need for mechanical rotation. Here, we describe the capability of ILSI for evaluating human coronary atherosclerosis in cadaveric hearts. ILSI was conducted in conjunction with optical coherence tomography (OCT) imaging in five human cadaveric hearts. The left coronary artery (LCA), left anterior descending (LAD), left circumflex artery (LCx), and right coronary artery (RCA) segments were resected and secured on custom-developed coronary holders to enable accurate co-registration between ILSI, OCT, and histopathology. Speckle time constants, τ, calculated from each ILSI section were compared with lipid and collagen content measured from quantitative Histopathological analysis of the corresponding Oil Red O and Picrosirius Red stained sections. Because the presence of low viscosity lipid elicits rapid speckle fluctuations, we observed an inverse correlation between τ measured by ILSI and lipid content (R= -0.64, p< 0.05). In contrast, the higher viscoelastic modulus of fibrous regions resulted in a positive correlation between τ and collagen content (R= 0.54, p< 0.05). These results demonstrate the feasibility of conducting ILSI evaluation of arterial mechanical properties using a miniaturized omni-directional catheter.

  16. Compound specific stable isotope analysis (CSIA) to characterize transformation mechanisms of α-hexachlorocyclohexane.

    PubMed

    Zhang, Ning; Bashir, Safdar; Qin, Jinyi; Schindelka, Janine; Fischer, Anko; Nijenhuis, Ivonne; Herrmann, Hartmut; Wick, Lukas Y; Richnow, Hans H

    2014-09-15

    A systematic investigation of environmentally relevant transformation processes of alpha-hexachlorocyclohexane (α-HCH) was performed in order to explore the potential of compound specific stable isotope analysis (CSIA) to characterize reaction mechanisms. The carbon isotope enrichment factors (ɛC) for the chemical transformations of α-HCH via direct photolysis, indirect photolysis (UV/H2O2), hydrolysis, electro-reduction or reduction by Fe(0) were quantified and compared to those previously published for biodegradation. Hydrogen abstraction by hydroxyl radicals generated by UV/H2O2 led to ɛC of -1.9 ± 0.2 ‰ with an apparent kinetic carbon isotope effect (AKIEC) of 1.012 ± 0.001. Dehydrochlorination by alkaline hydrolysis yielded ɛC of -7.6 ± 0.4 ‰ with AKIEC of 1.048 ± 0.003. Dechlorination either by homolytic bond cleavage in direct photolysis (ɛC=-2.8 ± 0.2 ‰) or single-electron transfer in electro-reduction (ɛC=-3.8 ± 0.4 ‰) corresponded to AKIEC of 1.017 ± 0.001 and 1.023 ± 0.003, respectively. Dichloroelimination catalyzed by Fe(0) via two-electron transfers resulted in ɛC of -4.9 ± 0.1 ‰. AKIEC values assuming either a concerted or a stepwise mechanism were 1.030 ± 0.0006 and 1.015 ± 0.0003, respectively. Contrary to biodegradation, no enantioselectivity of α-HCH was observed in chemical reactions, which might be used to discriminate chemical and biological in situ transformations. PMID:25238192

  17. Structural analysis of the catalytic mechanism and stereoselectivity in Streptomyces coelicolor alditol oxidase.

    PubMed

    Forneris, Federico; Heuts, Dominic P H M; Delvecchio, Manuela; Rovida, Stefano; Fraaije, Marco W; Mattevi, Andrea

    2008-01-22

    Alditol oxidase (AldO) from Streptomyces coelicolor A3(2) is a soluble monomeric flavin-dependent oxidase that performs selective oxidation of the terminal primary hydroxyl group of several alditols. Here, we report the crystal structure of the recombinant enzyme in its native state and in complex with both six-carbon (mannitol and sorbitol) and five-carbon substrates (xylitol). AldO shares the same folding topology of the members of the vanillyl-alcohol oxidase family of flavoenzymes and exhibits a covalently linked FAD which is located at the bottom of a funnel-shaped pocket that forms the active site. The high resolution of the three-dimensional structures highlights a well-defined hydrogen-bonding network that tightly constrains the substrate in the productive conformation for catalysis. Substrate binding occurs through a lock-and-key mechanism and does not induce conformational changes with respect to the ligand-free protein. A network of charged residues is proposed to favor catalysis through stabilization of the deprotonated form of the substrate. A His side chain acts as back door that "pushes" the substrate-reactive carbon atom toward the N5-C4a locus of the flavin. Analysis of the three-dimensional structure reveals possible pathways for diffusion of molecular oxygen and a small cavity on the re side of the flavin that may host oxygen during FAD reoxidation. These features combined with the tight shape of the catalytic site provide insights into the mechanism of AldO-mediated regioselective oxidation reactions and its substrate specificity. PMID:18154360

  18. Design and analysis of a novel mechanical loading machine for dynamic in vivo axial loading

    NASA Astrophysics Data System (ADS)

    Macione, James; Nesbitt, Sterling; Pandit, Vaibhav; Kotha, Shiva

    2012-02-01

    This paper describes the construction of a loading machine for performing in vivo, dynamic mechanical loading of the rodent forearm. The loading machine utilizes a unique type of electromagnetic actuator with no mechanically resistive components (servotube), allowing highly accurate loads to be created. A regression analysis of the force created by the actuator with respect to the input voltage demonstrates high linear correlation (R2 = 1). When the linear correlation is used to create dynamic loading waveforms in the frequency (0.5-10 Hz) and load (1-50 N) range used for in vivo loading, less than 1% normalized root mean square error (NRMSE) is computed. Larger NRMSE is found at increased frequencies, with 5%-8% occurring at 40 Hz, and reasons are discussed. Amplifiers (strain gauge, linear voltage displacement transducer (LVDT), and load cell) are constructed, calibrated, and integrated, to allow well-resolved dynamic measurements to be recorded at each program cycle. Each of the amplifiers uses an active filter with cutoff frequency at the maximum in vivo loading frequencies (50 Hz) so that electronic noise generated by the servo drive and actuator are reduced. The LVDT and load cell amplifiers allow evaluation of stress-strain relationships to determine if in vivo bone damage is occurring. The strain gauge amplifier allows dynamic force to strain calibrations to occur for animals of different sex, age, and strain. Unique features are integrated into the loading system, including a weightless mode, which allows the limbs of anesthetized animals to be quickly positioned and removed. Although the device is constructed for in vivo axial bone loading, it can be used within constraints, as a general measurement instrument in a laboratory setting.

  19. A multiscale analysis of drought and pluvial mechanisms for the Southeastern United States

    NASA Astrophysics Data System (ADS)

    Kam, Jonghun; Sheffield, Justin; Wood, Eric F.

    2014-06-01

    The Southeast (SE) U.S. has experienced several severe droughts over the past 30 years, with the most recent drought during 2006-2008 causing agricultural impacts of $1 billion. However, the mechanisms that lead to droughts over the region and their persistence have been poorly understood due to the region's humid coastal environment and its complex climate. In this study, we carry out a multiscale analysis of drought mechanisms for the SE U.S. over 1979-2008 using the North American Regional Reanalysis (NARR) to identify conditions associated with drought and contrast with those associated with pluvials. These conditions include land surface drought propagation, land-atmosphere feedbacks, regional moisture sources, persistent atmospheric patterns, and larger-scale oceanic conditions. Typical conditions for SE U.S. droughts (pluvials) are identified as follows: (1) weaker (stronger) southerly meridional fluxes and weaker (stronger) westerly zonal fluxes, (2) strong moisture flux divergence (convergence) by transient eddies, and (3) strong (weak) coupling between the land surface and atmosphere. The NARR demonstrates that historic SE droughts are mainly derived from a combination of a strong North Atlantic subtropical high (NASH) and Icelandic Low (IL) during summer and winter, respectively, which peak 1 month earlier than the onset of the drought. The land surface plays a moderate role in drought occurrence over the SE via recycling of precipitation, and the oceans show an asymmetric influence on droughts and pluvials depending on the season. This study suggests that the NASH and IL can be used as a predictor for SE droughts at 1 month lead despite the overall that it represents an atmospheric forcing.

  20. Modeling the hydrological and mechanical effect of roots in shallow landslide analysis

    NASA Astrophysics Data System (ADS)

    Arnone, Elisa; Caracciolo, Domenico; Noto, Leonardo V.; Preti, Federico; Bras, Rafael L.

    2015-04-01

    The additional cohesion exercised by vegetation roots (cr) provides an important contribution to the slope stability. This study proposes a methodology for estimating the cr term in a hillslope landslide analysis within a coupled ecohydrological-stability model. The coupled model simulates the spatial distribution and temporal dynamics of the Factor of Safety (FS) as a function of soil moisture dynamics, by taking into account the hydrological effects of vegetation through the root water uptaking. The additional mechanical root cohesion is estimated in a Fiber Bundle Model framework that allows for the evaluation of the root strength as a function of stress-strain relationships of populations of fibers. The use of such a model requires the knowledge of the root architecture to evaluate the additional reinforcement from each root diameter class. The root architecture is reproduced by fitting a probability density function to the distribution of the number of roots with depth, within a branching topology scheme based on the Leonardo's rule that gives an estimation of the root diameters. The methodology has been tested in a simple synthetic hillslope with different configurations of vegetation types, i.e. tree and shrubs, and soil types, i.e. clay and loam. Parameters of the topological model have been calibrated through observed depth profiles of root number, diameters and area of two species representative of the two considered vegetation types. Preliminary results demonstrated the high flexibility of the topological model here used, with consistent and promising outcoms in terms of root cohesion, significantly lower than values obtained with the more popular Wu/Waldron model. The simple case study highlighted the importance of both the root mechanical resistance and the root interactions with the main eco-hydrological processes. The hydrological effect of roots can be more significant than the mechanical one, especially for tree species on clayey soils. The root

  1. Thermo-Mechanical Analysis of Coated Particle Fuel Experiencing a Fast Control Rod Ejection Transient

    SciTech Connect

    Ortensi, J.; Brian Boer; Abderrafi M. Ougouag

    2010-10-01

    A rapid increase of the temperature and the mechanical stress is expected in TRISO coated particle fuel that experiences a fast Total Control Rod Ejection (CRE) transient event. During this event the reactor power in the pebble bed core increases significantly for a short time interval. The power is deposited instantly and locally in the fuel kernel. This could result in a rapid increase of the pressure in the buffer layer of the coated fuel particle and, consequently, in an increase of the coating stresses. These stresses determine the mechanical failure probability of the coatings, which serve as the containment of radioactive fission products in the Pebble Bed Reactor (PBR). A new calculation procedure has been implemented at the Idaho National Laboratory (INL), which analyzes the transient fuel performance behavior of TRISO fuel particles in PBRs. This early capability can easily be extended to prismatic designs, given the availability of neutronic and thermal-fluid solvers. The full-core coupled neutronic and thermal-fluid analysis has been modeled with CYNOD-THERMIX. The temperature fields for the fuel kernel and the particle coatings, as well as the gas pressures in the buffer layer, are calculated with the THETRIS module explicitly during the transient calculation. Results from this module are part of the feedback loop within the neutronic-thermal fluid iterations performed for each time step. The temperature and internal pressure values for each pebble type in each region of the core are then input to the PArticle STress Analysis (PASTA) code, which determines the particle coating stresses and the fraction of failed particles. This paper presents an investigation of a Total Control Rod Ejection (TCRE) incident in the 400 MWth Pebble Bed Modular reactor design using the above described calculation procedure. The transient corresponds to a reactivity insertion of $3 (~2000 pcm) reaching 35 times the nominal power in 0.5 seconds. For each position in the core

  2. Kinematic Accuracy Analysis of Lead Screw W Insertion Mechanism with Flexibility

    NASA Astrophysics Data System (ADS)

    He, Hu; Zhang, Lei; Kong, Jiayuan

    According to the actual requirements of w insertion, a set of variable lead screw w mechanism was designed, motion characteristics of the mechanism were analyzed and kinematics simulation was carried out with MATLAB. Mechanism precision was analyzed with the analytical method and the error coefficient curve of each component in the mechanism was obtained. Dynamics simulation for rigid mechanism and mechanism with flexibility in different speed was conducted with ADAMS, furthermore, real-time elastic deformation of the flexible Connecting rod was obtained. In consideration of the influences of the elastic connecting rod, the outputs motion error and elastic deformation of components were increased with the speed of the loom.

  3. Analysis of the development of wave mechanics: aspects from the history of physics and the philosophy of science

    SciTech Connect

    Kuhn, W.

    1988-03-01

    This review and analysis of wave mechanics and the role played by Erwin Schroedinger in its development begins with a biographical sketch of Schroedinger and his scientific and philosophical association with physicists contemporary to him and engaged also in wave and quantum studies. The paper then goes on to establish the philosophical and historical aspects behind Schroedinger's contribution to quantum mechanics and discusses his more personal dilemma over the changes in wave and particle physics in which he was instrumental.

  4. Analysis of In Situ Mechanical Properties of Phases in High-Alloyed White Iron Measured by Grid Nanoindentation

    NASA Astrophysics Data System (ADS)

    Chen, Ling; Ståhl, Jan Eric; Zhou, Jinming

    2015-10-01

    The paper presents an analysis of the in situ mechanical properties (e.g., hardness, elastic modulus, and volume fraction) of phases in high-alloy white iron measured by grid nanoindentation statistically, to reveal the contributions of individual phase properties to the global properties of the material. The in situ mechanical properties of phases measured by grid indentation were validated through targeted indentation. Gaussian and Weibull mixture models were used in analyzing the grid nanoindentation measurements to assess the goodness-of-fit of the indentation data. The nanohardness and indentation modulus measured by grid nanoindentation were directly correlated to the microstructural characteristics of the sample materials. The statistical analysis results were also compared with the mechanical properties and volume fractions obtained using targeted indentation and quantitative metallography based on microstructure analysis to validate the statistical results. The influences of heat treatment on the microstructure, hardness, and elastic modulus of individual phases in the material are also discussed.

  5. Proteomic Analysis of Tardigrades: Towards a Better Understanding of Molecular Mechanisms by Anhydrobiotic Organisms

    PubMed Central

    Schokraie, Elham; Hotz-Wagenblatt, Agnes; Warnken, Uwe; Mali, Brahim; Frohme, Marcus; Förster, Frank; Dandekar, Thomas; Hengherr, Steffen; Schill, Ralph O.; Schnölzer, Martina

    2010-01-01

    Background Tardigrades are small, multicellular invertebrates which are able to survive times of unfavourable environmental conditions using their well-known capability to undergo cryptobiosis at any stage of their life cycle. Milnesium tardigradum has become a powerful model system for the analysis of cryptobiosis. While some genetic information is already available for Milnesium tardigradum the proteome is still to be discovered. Principal Findings Here we present to the best of our knowledge the first comprehensive study of Milnesium tardigradum on the protein level. To establish a proteome reference map we developed optimized protocols for protein extraction from tardigrades in the active state and for separation of proteins by high resolution two-dimensional gel electrophoresis. Since only limited sequence information of M. tardigradum on the genome and gene expression level is available to date in public databases we initiated in parallel a tardigrade EST sequencing project to allow for protein identification by electrospray ionization tandem mass spectrometry. 271 out of 606 analyzed protein spots could be identified by searching against the publicly available NCBInr database as well as our newly established tardigrade protein database corresponding to 144 unique proteins. Another 150 spots could be identified in the tardigrade clustered EST database corresponding to 36 unique contigs and ESTs. Proteins with annotated function were further categorized in more detail by their molecular function, biological process and cellular component. For the proteins of unknown function more information could be obtained by performing a protein domain annotation analysis. Our results include proteins like protein member of different heat shock protein families and LEA group 3, which might play important roles in surviving extreme conditions. Conclusions The proteome reference map of Milnesium tardigradum provides the basis for further studies in order to identify and

  6. Systematic analysis of intracellular mechanisms of propanol production in the engineered Thermobifida fusca B6 strain.

    PubMed

    Deng, Yu; Fisher, Adam B; Fong, Stephen S

    2015-10-01

    Thermobifida fusca is a moderately thermophilic actinobacterium naturally capable of utilizing lignocellulosic biomass. The B6 strain of T. fusca was previously engineered to produce 1-propanol directly on lignocellulosic biomass by expressing a bifunctional butyraldehyde/alcohol dehydrogenase (adhE2). To characterize the intracellular mechanisms related to the accumulation of 1-propanol, the engineered B6 and wild-type (WT) strains were systematically compared by analysis of the transcriptome and intracellular metabolome during exponential growth on glucose, cellobiose, and Avicel. Of the 18 known cellulases in T. fusca, 10 cellulase genes were transcriptionally expressed on all three substrates along with three hemicellulases. Transcriptomic analysis of cellodextrin and cellulose transport revealed that Tfu_0936 (multiple sugar transport system permease) was the key enzyme regulating the uptake of sugars in T. fusca. For both WT and B6 strains, it was found that growth in oxygen-limited conditions resulted in a blocked tricarboxylic acid (TCA) cycle caused by repressed expression of Tfu_1925 (aconitate hydratase). Further, the transcriptome suggested a pathway for synthesizing succinyl-CoA: oxaloacetate to malate (by malate dehydrogenase), malate to fumarate (by fumarate hydratase), and fumarate to succinate (by succinate dehydrogenase/fumarate reductase) which was ultimately converted to succinyl-CoA by succinyl-CoA synthetase. Both the transcriptome and the intracellular metabolome confirmed that 1-propanol was produced through succinyl-CoA, L-methylmalonyl-CoA, D-methylmalonyl-CoA, and propionyl-CoA in the B6 strain. PMID:26227414

  7. [Analysis on Mechanism of Rainout Carried by Wet Stack of Thermal Power Plant].

    PubMed

    Ouyang, Li-hua; Zhuang, Ye; Liu, Ke-wei; Chen, Zhen-yu; Gu, Peng

    2015-06-01

    Rainout from wet-stack took placed in many thermal power plants with WFGD system. Research on causes of the rainout is important to solve the problem. The objective of this research is to analyze the mechanism of rainout. Field study was performed to collect experimental data in one thermal power plant, including the amount of desulfurization slurry carried by wet flue gas, liquor condensate from wet duct, and droplets from the wet stack. Source apportionment analysis was carried out based on physical and chemical data of liquid sample and solid sample. The result showed that mist eliminator operated well, which met the performance guarantee value. But the total amount of desulfurization slurry in flue gas and the sulfate concentration in liquid condensate discharge from the wet duct/stack increased. The liquid condensate accumulated in the wet duct/stack led to liquid re-entrainment. In conclusion, the rainout in this power plant was caused by the short of wet ductwork or liquid discharge system, the droplets caused by re-entrainment carried by the saturated gas released from the stack. The main undissolved components of the rainout were composite carbonate and aluminosilicate. Although ash concentration in this WFGD met the regulation criteria, source apportionment analysis showed that fly ash contributed to rainout was accounted for 60%. This percentage value was same as the data of solid particles in the condensate. It is important to optimize the wet ductwork, wet stack liner, liquid collectors and drainage. Avoiding the accumulation from saturated vapor thermal condensation is an effective way to solve the wet stack rainout. PMID:26387297

  8. Kinematic Analysis and Synthesis of a 3-URU Pure Rotational Parallel Mechanism with Respect to Singularity and Workspace

    NASA Astrophysics Data System (ADS)

    Huda, Syamsul; Takeda, Yukio

    This paper concerns kinematics and dimensional synthesis of a three universal-revolute-universal (3-URU) pure rotational parallel mechanism. The mechanism is composed of a base, a platform and three symmetric limbs consisting of U-R-U joints. This mechanism is a spatial non-overconstrained mechanism with three degrees of freedom. The joints in each limb are so arranged to perform pure rotational motion of the platform around a specific point. Equations for inverse displacement analysis and singularities were derived to investigate the relationship of the kinematic constants to the solution of the inverse kinematics and singularities. Based on the results, a dimensional synthesis procedure for the 3-URU parallel mechanism considering singularities and the workspace was proposed. A numerical example was also presented to illustrate the synthesis method.

  9. Numerical analysis of a smart composite material mechanical component using an embedded long period grating fiber sensor

    NASA Astrophysics Data System (ADS)

    Savastru, Dan; Miclos, Sorin; Savastru, Roxana; Lancranjan, Ion I.

    2015-05-01

    Results obtained by FEM analysis of a smart mechanical part manufactured of reinforced composite materials with embedded long period grating fiber sensors (LPGFS) used for operation monitoring are presented. Fiber smart reinforced composite materials because of their fundamental importance across a broad range of industrial applications, as aerospace industry. The main purpose of the performed numerical analysis consists in final improved design of composite mechanical components providing a feedback useful for further automation of the whole system. The performed numerical analysis is pointing to a correlation of composite material internal mechanical loads applied to LPGFS with the NIR absorption bands peak wavelength shifts. One main idea of the performed numerical analysis relies on the observed fact that a LPGFS embedded inside a composite material undergoes mechanical loads created by the micro scale roughness of the composite fiber network. The effect of this mechanical load consists in bending of the LPGFS. The shifting towards IR and broadening of absorption bands appeared in the LPGFS transmission spectra is modeled according to this observation using the coupled mode approach.

  10. Iron deficiency resistance mechanisms enlightened by gene expression analysis in Paenibacillus riograndensis SBR5.

    PubMed

    Sperb, Edilena Reis; Tadra-Sfeir, Michelle Zibetti; Sperotto, Raul Antônio; Fernandes, Gabriela de Carvalho; Pedrosa, Fábio de Oliveira; de Souza, Emanuel Maltempi; Passaglia, Luciane Maria Pereira

    2016-01-01

    Despite its importance in growth and cell division, iron metabolism is still poorly understood in microorganisms, especially in Gram-positive bacteria. In this work, we used RNA sequencing technology to elucidate global mechanisms involved in iron starvation resistance in Paenibacillus riograndensis SBR5, a potential plant growth-promoting bacterium. Iron deficiency caused several changes in gene expression, and 150 differentially expressed genes were found: 71 genes were overexpressed and 79 genes were underexpressed. Eight genes for which expression was at least twice as high or twice as low in iron-limited condition compared with iron-sufficient condition were chosen for RT-qPCR analysis to validate the RNA seq data. In general, most genes exhibited the same pattern of expression after 24 h of P. riograndensis growth under iron-limiting condition. Our results suggest that, during iron deficiency, bacteria express several genes related to nutrient uptake when they start to grow to obtain all of the molecules necessary for maintaining major cellular processes. However, once iron becomes highly limiting and is no longer able to sustain exponential growth, bacteria begin to express genes related to several processes, like sporulation and DNA protection, as a way of resisting this stress. PMID:27130283

  11. Analysis of intermediary scan-lens and tube-lens mechanisms for optical coherence tomography.

    PubMed

    Atry, Farid; Pashaie, Ramin

    2016-02-01

    Combining an optical coherence tomography (OCT) scanner with other techniques such as optogenetic neurostimulation or fluorescence imaging requires integrating auxiliary components into the optical path of the setup. Due to the short scanning distance of most OCT objectives, adding scan and tube lenses in the device is essential to open space between the back-focal-plane of the objective and center of mass of the mirrors in the galvanometer. The effect of the scan and tube lenses on the focal spot size of the scanner using off-the-shelf components are theoretically explored for three different designs in this paper. Two lens mechanisms were implemented and tested in a custom-built OCT scanner to experimentally measure point-spread functions. Based on our analysis, proper form of a four-element semi-Plössl lens provides a superior performance compared with an achromatic doublet when used as a scan/tube lens. The former lens design provides close to diffraction-limited resolution for scan angles up to 6.4°; however, due to aberrations in an achromatic doublet, the later design offers diffraction-limited resolution confined to 2° scan angles. PMID:26836064

  12. [Rapid inactivation mechanism of copper to Tubifex tubifex and its application analysis in water plant].

    PubMed

    Huang, Ting-lin; Nie, Xiao-bao; Zhang, Jin-song; Li, Wei; Li, Xiao-yu

    2010-02-01

    The fluctuation of *OH concentration in Tubifex tubifex exposed to copper was investigated by Fluorospectrophotometry using terephthalic acid (TA) as *OH trapping agent. Catalase (CAT) activity in T. tubifex was quantified after 30 minutes contact with copper. Inactivation effect and lipid peroxidation produce malondialderhyde (MDA) of T. tubifex were also studied. Results showed that copper had significant inactivation effect on T. tsubifex. 100% inactivation efficiency was obtained when copper levels was 1 mg x L(-1). One of the inactivation mechanisms is inducing *OH increase in T. tubifex, which results in oxidative stress and lipid peroxidation. The increment of *OH concentration was 69.2% when copper lever was 0.05 mg x L(-1). The significant decrease of CAT activity showed copper could inhibit CAT activity to increase its oxidative stress to T. tubifex. Between 0.05-0.25 mg x L(-1), copper induced significant MDA increase, which meant lipid peroxidation. The changes of inactivation efficiency, *OH, CAT and MDA showed that the inactivation effect of copper on T. tubifex did not result only from oxidative stress and lipid peroxidation induced by *OH itself. Feasibility analysis of using copper to inactivate T. tubifex for water plant showed when sand filter was immersed by 1 mg x L(-1) copper for 30 min and then began backwashing, residual copper concentration was only 4.3 microg x L(-1). PMID:20391698

  13. Analysis of the mechanism and regulation of lactose transport and metabolism in Clostridium acetobutylicum ATCC 824.

    PubMed

    Yu, Yang; Tangney, Martin; Aass, Hans C; Mitchell, Wilfrid J

    2007-03-01

    Although the acetone-butanol-ethanol fermentation of Clostridium acetobutylicum is currently uneconomic, the ability of the bacterium to metabolize a wide range of carbohydrates offers the potential for revival based on the use of cheap, low-grade substrates. We have investigated the uptake and metabolism of lactose, the major sugar in industrial whey waste, by C. acetobutylicum ATCC 824. Lactose is taken up via a phosphoenolpyruvate-dependent phosphotransferase system (PTS) comprising both soluble and membrane-associated components, and the resulting phosphorylated derivative is hydrolyzed by a phospho-beta-galactosidase. These activities are induced during growth on lactose but are absent in glucose-grown cells. Analysis of the C. acetobutylicum genome sequence identified a gene system, lacRFEG, encoding a transcriptional regulator of the DeoR family, IIA and IICB components of a lactose PTS, and phospho-beta-galactosidase. During growth in medium containing both glucose and lactose, C. acetobutylicum exhibited a classical diauxic growth, and the lac operon was not expressed until glucose was exhausted from the medium. The presence upstream of lacR of a potential catabolite responsive element (cre) encompassing the transcriptional start site is indicative of the mechanism of carbon catabolite repression characteristic of low-GC gram-positive bacteria. A pathway for the uptake and metabolism of lactose by this industrially important organism is proposed. PMID:17209069

  14. Development of Geohazard Estimation Program through the Analysis of Subsidence Mechanism

    NASA Astrophysics Data System (ADS)

    Choi, S. O.; Min, K.

    2006-12-01

    Surface subsidence which occurs with several reasons, such as collapse of gangway, discharge of groundwater, compaction of weak rock mass, and tunnel excavation in shallow depth, gives rise to a serious problem in national infra-structures. Especially the subsidence occurs in urban area can make a huge problem in residential buildings or ground structures, to threaten the personal right to live. However the several decades' research on subsidence in Korea has been performed in a passive manner. Subsidence occurrence could not be predicted precisely, therefore a severe geohazard problem has been produced occasionally. In this study, consequently, the mechanism of subsidence has been examined first to quantify the process of subsidence occurrence. Through the quantitative analysis on the major geotechnical parameters affecting on the subsidence process, the passive approach on subsidence can be overcome. With many kinds of numerical studies, the major geotechnical parameters have been selected and the weighted values have been defined for each parameter. Also the authors developed the numerical program which can estimate the possibility of subsidence occurrence, and proposed the decision method for objective and quantitative guideline. It is anticipated that this research will be helpful to establish the geohazard map on subsidence occurrence area.

  15. Analysis of EMSE and mechanical properties of sputter coated electrospun nanofibers

    NASA Astrophysics Data System (ADS)

    Erdem, Ramazan; İlhan, Mustafa; Sancak, Erhan

    2016-09-01

    PA6 nanofibers were electrospun successfully and sputter coated with gold and palladium to create functional nanofibrous membranes that possess electromagnetic shielding ability. Properties of the electrospinning solutions were analyzed in terms of viscosity, conductivity and pH values. Coating thicknesses of the nanofibrous membranes were determined as 50 nm and 100 nm. Morphology of the nanofibrous membranes were observed by SEM analysis. Elemental composition of the specimens was explored by using Energy Dispersive Spectroscopy. Results revealed that defect free and uniform nanofibers were obtained, and the diameters of the fibers were changed after coating. Tensile strength and elongation measurements confirmed that the mechanical characteristics of the nanofibrous membranes were merely altered after coating. Electromagnetic Shielding Effectiveness (EMSE) of the nanofibers was determined according to the ASTM D4935-10 protocol by using coaxial transmission line measurement technique in the frequency range of 15-3000 MHz. It was observed that 100 nm coated membrane performed better EMSE than uncoated and 50 nm coated nanofibrous membranes.

  16. STEAM: a software tool based on empirical analysis for micro electro mechanical systems

    NASA Astrophysics Data System (ADS)

    Devasia, Archana; Pasupuleti, Ajay; Sahin, Ferat

    2006-03-01

    In this research a generalized software framework that enables accurate computer aided design of MEMS devices is developed. The proposed simulation engine utilizes a novel material property estimation technique that generates effective material properties at the microscopic level. The material property models were developed based on empirical analysis and the behavior extraction of standard test structures. A literature review is provided on the physical phenomena that govern the mechanical behavior of thin films materials. This survey indicates that the present day models operate under a wide range of assumptions that may not be applicable to the micro-world. Thus, this methodology is foreseen to be an essential tool for MEMS designers as it would develop empirical models that relate the loading parameters, material properties, and the geometry of the microstructures with its performance characteristics. This process involves learning the relationship between the above parameters using non-parametric learning algorithms such as radial basis function networks and genetic algorithms. The proposed simulation engine has a graphical user interface (GUI) which is very adaptable, flexible, and transparent. The GUI is able to encompass all parameters associated with the determination of the desired material property so as to create models that provide an accurate estimation of the desired property. This technique was verified by fabricating and simulating bilayer cantilevers consisting of aluminum and glass (TEOS oxide) in our previous work. The results obtained were found to be very encouraging.

  17. Analysis of Curved Sandwich Panels Subjected to Combined Temperature Gradient and Mechanical Loads

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Starnes, James H., Jr.; Peters, Jeanne M.

    1998-01-01

    The results of a detailed study of the nonlinear response of curved sandwich panels with composite face sheets and subjected to a temperature gradient through-the-thickness combined with mechanical loadings are presented. The analysis is based on a first-order shear-deformation Sanders-Budiansky type theory with the effects of large displacements, moderate rotations, transverse shear deformation and laminated anisotropic material behavior included. A mixed formulation is used with the fundamental unknowns consisting of the generalized displacements and the stress resultants of the panel. The nonlinear displacements, strain energy, principal strains, transverse shear stresses, transverse shear strain energy density, and their hierarchical sensitivity coefficients are evaluated. The hierarchical sensitivity coefficients measure the sensitivity of the nonlinear response to variations in the panel parameters, the effective properties of the face sheet layers and the core, and the micromechanical parameters. Numerical results are presented for cylindrical panels subjected to combined pressure loading, edge shortening or extension, edge shear and a temperature gradient through the thickness. The results show the effects of variations in the loading and the panel aspect ratio, on the nonlinear response and its sensitivity to changes in the various panel, effective layer and micromechanical parameters.

  18. Mechanical and thermal analysis of beryllium windows for RF cavities in a muon cooling channel

    SciTech Connect

    Li, Derun; Ladran, A.; Lozano, D.; Rimmer, R.

    2002-05-30

    Thin beryllium windows (foils) may be utilized to increase shunt impedance of closed-cell RF cavities. These windows are subject to ohmic heating from RF currents. The resulting temperature gradients in the windows can produce out of plane displacements that detune the cavity frequency. The window displacement can be reduced or eliminated by pre-stressing the foils in tension. Because of possible variations during manufacture, it is important to quantify the actual prestress of a Be window before it is put into service. We present the thermal and mechanical analyses of such windows under typical operating conditions and describe a simple non-destructive means to quantify the pre-stress using the acoustic signature of a window. Using finite element analysis, thin plate theory and physical measurements of the vibration modes of a window we attempted to characterize the actual Be window pre-stress in a small number of commercially sourced windows (30% of yield strength is typical). This method can be used for any window material and size, but this study focused on 16 cm diameter Be Windows ranging in thickness from 125 microns to 508 microns and with varying pre-stresses. The method can be used to nondestructively test future Be windows for the desired prestress.

  19. Fiber-reinforced composite analysis using optical coherence tomography after mechanical and thermal cycling

    NASA Astrophysics Data System (ADS)

    Kyotoku, B. B. C.; Braz, A. K. S.; Braz, R.; Gomes, A. S. L.

    2007-02-01

    Fiber-reinforced composites are new materials which have been used for a variety of dental applications, including tooth splinting, replacement of missing teeth, treatment of dental emergencies, reinforcement of resin provisional fixed prosthodontic restorations, orthodontic retention, and other clinical applications. Different fiber types are available, but little clinical information has been disseminated. The traditional microscopy investigation, most commonly used to study this material, is a destructive technique, which requires specimen sectioning and are essentially surface measurements. On the basis of these considerations, the aim of this research is to analyze the interior of a dental sample reinforced with fiber after a mechanical and thermal cycling to emulate oral conditions using optical coherence tomography (OCT). The device we are using is a home built Fourier domain OCT working at 800 nm with 6 μm resolution. The results are compared with microscopy images to validate OCT as a working method. In long term, fractures allow bacterial invasion provoking plaque and calculus formation that can cause caries and periodontal disease. Therefore, non invasive imaging of the bridge fiber enables the possibility of periodic clinical evaluation to ensure the patient health. Furthermore, OCT images can provide a powerful method for quantitative analysis of crack propagation, and can potentially be used for in vivo assessment.

  20. Sensitivity analysis of a mixed-phase chemical mechanism using automatic differentiation

    SciTech Connect

    Zhang, Y.; Easter, R.C.

    1998-08-01

    A sensitivity analysis of a comprehensive mixed-phase chemical mechanism is conducted under a variety of atmospheric conditions. The local sensitivities of gas and aqueous phase species concentrations with respect to a variety of model parameters are calculated using the novel automatic differentiation ADIFOR tool. The main chemical reaction pathways in all phases, interfacial mass transfer processes, and ambient physical parameters that affect tropospheric O{sub 3} formation and O{sub 3}-precursor relations under all modeled conditions are identified and analyzed. The results show that the presence of clouds not only reduces many gas phase species concentrations and the total oxidizing capacity but alters O{sub 3}-precursor relations. Decreases in gas phase concentrations and photochemical formation rates of O{sub 3} can be up to 9{percent} and 100{percent}, respectively, depending on the preexisting atmospheric conditions. The decrease in O{sub 3} formation is primarily caused by the aqueous phase reactions of O{sub 2}{sup {minus}} with dissolved HO{sub 2} and O{sub 3} under most cloudy conditions. {copyright} 1998 American Geophysical Union

  1. Analysis of the main optical mechanisms responsible for fragmentation of gold nanoparticles by femtosecond laser radiation

    SciTech Connect

    Videla, F. A.; Schinca, D. C.; Scaffardi, L. B.; Torchia, G. A.; Moreno, P.; Roso, L.

    2010-06-15

    Studies of fragmentation process of gold nanoparticles (Nps) in deionized water after generation by femtosecond laser ablation were performed. To analyze the fragmentation process, direct IR ultrafast pulses or super-continuum (SC) radiation focused in the colloidal solution were used in separate steps. IR pulses and SC generated externally in a sapphire crystal or directly inside the water were applied under low fluence regime. In the latter cases, to evaluate the effect on fragmentation of the different spectral bands present in the SC, we have determined different efficiency regions characterized by means of the product between the spectral response and the optical extinction spectrum corresponding to the initial Nps solution. From the analysis of this product function, we can conclude that the main fragmentation mechanism is due to linear absorption in the visible region. Likewise, the SC generated in water resulted more efficient than the SC obtained externally by a sapphire crystal. This fact may be attributed to the blue broadening of the water SC spectrum (as compared with the sapphire SC) due to the large intensity used for its generation. Transmission electron microscopy and small angle x-ray scattering measurements support the results found from optical extinction spectroscopy.

  2. Closed-form analysis of fiber-matrix interface stresses under thermo-mechanical loadings

    NASA Technical Reports Server (NTRS)

    Naik, Rajiv A.; Crews, John H., Jr.

    1992-01-01

    Closed form techniques for calculating fiber matrix (FM) interface stresses, using repeating square and diamond regular arrays, were presented for a unidirectional composite under thermo-mechanical loadings. An Airy's stress function micromechanics approach from the literature, developed for calculating overall composite moduli, was extended in the present study to compute FM interface stresses for a unidirectional graphite/epoxy (AS4/3501-6) composite under thermal, longitudinal, transverse, transverse shear, and longitudinal shear loadings. Comparison with finite element results indicate excellent agreement of the FM interface stresses for the square array. Under thermal and longitudinal loading, the square array has the same FM peak stresses as the diamond array. The square array predicted higher stress concentrations under transverse normal and longitudinal shear loadings than the diamond array. Under transverse shear loading, the square array had a higher stress concentration while the diamond array had a higher radial stress concentration. Stress concentration factors under transverse shear and longitudinal shear loadings were very sensitive to fiber volume fraction. The present analysis provides a simple way to calculate accurate FM interface stresses for both the square and diamond array configurations.

  3. Hop (Humulus lupulus L.) response mechanisms in drought stress: Proteomic analysis with physiology.

    PubMed

    Kolenc, Zala; Vodnik, Dominik; Mandelc, Stanislav; Javornik, Branka; Kastelec, Damijana; Čerenak, Andreja

    2016-08-01

    Drought is one of the major environmental devastating stressors that impair the growth and productivity of crop plants. Despite the relevance of drought stress, changes in physiology and resistance mechanisms are not completely understood for certain crops, including hop (Humulus lupulus L.). In this research the drought response of hop was studied using a conventional physiological approach (gas exchange techniques, fluorescence, relative water content measurements) and proteomic analysis (2D-DIGE). Plants of two cultivars (Aurora and Savinjski golding) were exposed to progressive drought in a pot experiment and analysed at different stress stages (mild, moderate and severe). Measurements of relative water content revealed a hydrostable water balance of hop. Photosynthesis was decreased due to stomatal and non-stomatal limitation to the same extent in both cultivars. Of 28 identified differentially abundant proteins, the majority were down regulated and included in photosynthetic (41%) and sugar metabolism (33%). Fifteen % of identified proteins were classified into the nitrogen metabolism, 4% were related to a ROS related pathway and 7% to other functions. PMID:27085598

  4. Glass transitions in native silk fibres studied by dynamic mechanical thermal analysis.

    PubMed

    Guan, Juan; Wang, Yu; Mortimer, Beth; Holland, Chris; Shao, Zhengzhong; Porter, David; Vollrath, Fritz

    2016-07-01

    Silks are a family of semi-crystalline structural materials, spun naturally by insects, spiders and even crustaceans. Compared to the characteristic β-sheet crystalline structure in silks, the non-crystalline structure and its composition deserves more attention as it is equally critical to the filaments' high toughness and strength. Here we further unravel the structure-property relationship in silks using Dynamic Mechanical Thermal Analysis (DMTA). This technique allows us to examine the most important structural relaxation event of the disordered structure the disordered structure, the glass transition (GT), in native silk fibres of the lepidopteran Bombyx mori and Antheraea pernyi and the spider Nephila edulis. The measured glass transition temperature Tg, loss tangent tan δ and dynamic storage modulus are quantitatively modelled based on Group Interaction Modelling (GIM). The "variability" issue in native silks can be conveniently explained by the different degrees of structural disorder as revealed by DMTA. The new insights will facilitate a more comprehensive understanding of the structure-property relations for a wide range of biopolymers. PMID:27320178

  5. Behavior and mechanism of arsenate adsorption on activated natural siderite: evidences from FTIR and XANES analysis.

    PubMed

    Zhao, Kai; Guo, Huaming

    2014-02-01

    Activated natural siderite (ANS) was used to investigate its characteristics and mechanisms of As(V) adsorption from aqueous solution. Batch tests were carried out to determine effects of contact time, initial As(V) concentration, temperature, pH, background electrolyte, and coexisting anions on As(V) adsorption. Arsenic(V) adsorption on ANS well-fitted pseudo-second-order kinetics. ANS showed a high-adsorption capacity of 2.19 mg/g estimated from Langmuir isotherm at 25 °C. Thermodynamic studies indicated that As(V) adsorption on ANS was spontaneous, favorable, and endothermic. ANS adsorbed As(V) efficiently in a relatively wide pH range between 2.0 and 10.0, although the removal efficiency was slightly higher in acidic conditions than that in basic conditions. Effects of background electrolyte and coexisting anions were not significant within the concentration ranges observed in high As groundwater. Results of XRD and Fe K-edge XANES analysis suggested ANS acted as an Fe(II)/(III) hybrid system, which was quite effective in adsorbing As from aqueous solution. There was no As redox transformation during adsorption, although Fe(II) oxidation occurred in the system. Two infrared bands at 787 and 872 cm(-1) after As(V) adsorption suggested that As(V) should be predominantly adsorbed on ANS via inner-sphere bidendate binuclear surface complexes. PMID:24014199

  6. Nonlinear thermo-mechanical analysis of stiffened composite laminates by a new finite element

    NASA Astrophysics Data System (ADS)

    Barut, Atila

    A new stiffened shell element combining shallow beam and shallow shell elements is developed for geometrically nonlinear analysis of stiffened composite laminates under thermal and/or mechanical loading. The formulation of this element is based on the principal of virtual displacements in conjunction with the co-rotational form of the total Lagrangian description of motion. In the finite element formulation, both the shell and the beam (stiffener) elements account for transverse shear deformations and material anisotropy. The cross-section of the stiffener (beam) can be arbitrary in geometry and lamination. In order to combine the stiffener with the shell element, constraint conditions are applied to the displacement and rotation fields of the stiffener. These constraint conditions ensure that the cross-section of the stiffener remains co-planar with the shell section after deformation. The resulting expressions for the displacement and rotation fields of the stiffener involve only the nodal unknowns of the shell element, thus reducing the total number of degrees of freedom. Also, the discretization of the entire stiffened shell structure becomes more flexible.

  7. Analysis of Yttrium-Barium-Copper-Oxide by x ray diffraction and mechanical characterization

    NASA Technical Reports Server (NTRS)

    Arsenovic, Petar

    1992-01-01

    The efforts in developing high-temperature superconductor (HTSC) YBa2Cu3O7 electrical leads are to benefit future NASA missions that will carry payloads with sensitive instruments operating at cryogenic temperatures. Present-day leads made of copper or magnesium are responsible for as much as 50 percent of the parasitic heat load on cryogenic systems. A reduction of this load could be achieved by replacing the conventional materials with HTSC ceramic electrical leads. Superconductor quality has become a concern in the industry, as has the development of effective evaluation methods. The factors that need to be examined for these materials include material purity, mechanical properties, and superconducting ability below the critical temperature. We applied several methods to study these factors: thermogravimetric analysis, x-ray diffraction, tensile testing, and laser-generated ultrasound. Our objectives were to determine the average tensile strength and Young's modulus of the HTSC material and to compare them to those values for copper and manganin.

  8. Regulation and mechanism of potassium release from barley roots: an in planta 42K+ analysis.

    PubMed

    Coskun, Devrim; Britto, Dev T; Kronzucker, Herbert J

    2010-12-01

    Potassium (K(+) ) flux into plant cells is a well-characterized ion transport phenomenon. By contrast, little is known about the mechanisms and regulation of K(+) flux from the cell. Here, we present a radioisotopic analysis of K(+) fluxes from roots of intact barley (Hordeum vulgare), in the context of recent discoveries in the molecular biology and electrophysiology of this process. Plants were labelled with (42)K(+), and kinetics of its release from roots were monitored at low (0.1 mM) or high (1.0 mM) external K concentration, [K(+)](ext), and with the application of channel modulators and nutrient shifts. At 0.1 (but not 1.0) mM [K(+)], where K(+) efflux is thought to be mediated by K(+)-outward-rectifying channels, (42)K(+) efflux was inhibited by the channel blockers barium (Ba(2+)), caesium (Cs(+)), tetraethylammonium (TEA(+)), and lanthanum (La(3+)). Ammonium and nitrate (10 mM) stimulated and inhibited (42)K(+) efflux, respectively, while 10 mM [K(+)](ext) or [Rb(+) ](ext) decreased it. No evidence for the involvement of ATP-binding cassettes, nonselective cation channels, or active K(+)-efflux pumps was found. Our study provides new evidence for the thermodynamic transition between high- and low-affinity transport, from the efflux perspective, identifying the operation of channels at low [K(+)], and the cessation of transmembrane efflux at high [K(+)]. PMID:20731780

  9. Time-frequency analysis of transient pressure signals for a mechanical heart valve cavitation study.

    PubMed

    Yu, A A; White, J A; Hwang, N H

    1998-01-01

    A series of transient pressure signals (TPSs) can be measured using a miniature pressure transducer mounted near the tip of the inflow side of a mechanical heart valve (MHV) occluder during closure. A relationship appears to exist between the intensity and pattern of the TPS and the cavitation potential of a MHV. To study the relationship between MHV cavitation and the TPSs, we installed an MHV in a valve testing chamber of a digitally controlled burst test loop. A charge coupled device (CCD) camera and a personal computer based image grabbing program was used to visualize cavitation bubbles appearing on or near the occluder surface. One bileaflet MHV was used as the model for this study. Cavitation bubbles were observed within 300 microsec of the leaflet/housing impact. The valve was tested at various driving pressures between 100 and 1,300 mmHg. MHV cavitation bubble intensities were qualitatively classified into three categories: 1) strong, 2) weak, and 3) none. Digital images of the MHV occluder inflow surface were recorded simultaneously with the TPSs. TPSs were studied by the time-frequency analysis method (spectrogram) and correlated to MHV cavitation potential. The intensity of the cavitation bubbles was found to be associated with burst test loop driving pressures during leaflet closure. PMID:9804476

  10. Dynamic Analysis of Flexible Slider-Crank Mechanisms with Non-Linear Finite Element Method

    NASA Astrophysics Data System (ADS)

    CHEN, J.-S.; HUANG, C.-L.

    2001-09-01

    Previous research in finite element formulation of flexible mechanisms usually neglected high order terms in the strain-energy function. In particular, the quartic term of the displacement gradient is always neglected due to the common belief that it is not important in the dynamic analysis. In this paper, we show that this physical intuition is not always valid. By retaining all the high order terms in the strain-energy function the equations of motion naturally become non-linear, which can then be solved by the Newmark method. In the low-speed range it is found that the dynamic responses predicted by non-linear and linear approaches indeed make no significant difference. However, when the rotation speed increases up to about one-fifth of the fundamental bending natural frequency of the connecting rod, simplified approaches begin to incur noticeable error. Specifically, for a connecting rod with a slenderness ratio of 0·01 the conventional simplified approaches overestimate the vibration amplitude almost 10-fold when the rotation speed is comparable to the fundamental natural frequency of the connecting rod. Therefore, non-linear finite element formulation taking into account the complete non-linear strain is needed in analyzing high-speed flexible mechnisms with slender links.

  11. Viscoelastic properties of polymer surfaces investigated by nanoscale dynamic mechanical analysis

    NASA Astrophysics Data System (ADS)

    Chakravartula, A.; Komvopoulos, K.

    2006-03-01

    The viscoelastic properties of polymer surfaces were investigated by nanoscale dynamic mechanical analysis (nano-DMA) involving contact force modulation in the frequency range of 10-200Hz. Nano-DMA experiments were performed with a Berkovich diamond tip of nominal radius of curvature equal to ˜100nm under a mean contact force of 8-10μN and alternating force equal to 2% of the mean force. Variations in the loss tangent, storage modulus, and loss modulus of low- and high-density polyethylene and ultrahigh molecular weight polyethylene with the force frequency demonstrated significantly different viscoelastic behaviors for shallow depths (<40nm) than for relatively large depths (i.e., 75-100nm). The effects of alternating force frequency and indentation depth on the viscoelastic properties of the different polyethylene materials are interpreted in terms of the microstructure characteristics and the molecular chain mobility at the polymer surfaces. The results show that nano-DMA is an effective technique for nanoscale studies of the viscoelastic behavior of polymer surfaces.

  12. Mechanisms of anterior cruciate ligament injuries in elite women's netball: a systematic video analysis.

    PubMed

    Stuelcken, Max C; Mellifont, Daniel B; Gorman, Adam D; Sayers, Mark G L

    2016-08-01

    This study involved a systematic video analysis of 16 anterior cruciate ligament (ACL) injuries sustained by elite-level netball players during televised games in order to describe the game situation, the movement patterns involved, the player's behaviour, and a potential injury mechanism. Eight of the ACL injuries were classified as "indirect contact" and eight as "non-contact". Two common scenarios were identified. In Scenario A the player was jumping to receive or intercept a pass and whilst competing for the ball experienced a perturbation in the air. As a result the player's landing was unbalanced with loading occurring predominantly on the knee of the injured side. In Scenario B the player was generally in a good position at ground contact, but then noticeably altered the alignment of the trunk before the landing was completed. This involved rotating and laterally flexing the trunk without altering the alignment of the feet. Apparent knee valgus collapse on the knee of the injured side was observed in 3/6 Scenario A cases and 5/6 Scenario B cases. Players may benefit from landing training programmes that incorporate tasks that use a ball and include decision-making components or require players to learn to cope with being unbalanced. PMID:26644060

  13. Financial Analysis of Incentive Mechanisms to Promote Energy Efficiency: Case Study of a Prototypical Southwest Utility

    SciTech Connect

    Cappers, Peter; Goldman, Charles; Chait, Michele; Edgar, George; Schlegel, Jeff; Shirley, Wayne

    2009-03-04

    alternative incentive approaches on utility shareholders and customers if energy efficiency is implemented under various utility operating, cost, and supply conditions.We used and adapted a spreadsheet-based financial model (the Benefits Calculator) which was developed originally as a tool to support the National Action Plan for Energy Efficiency (NAPEE). The major steps in our analysis are displayed graphically in Figure ES- 1. Two main inputs are required: (1) characterization of the utility which includes its initial financial and physical market position, a forecast of the utility?s future sales, peak demand, and resource strategy to meet projected growth; and (2) characterization of the Demand-Side Resource (DSR) portfolio ? projected electricity and demand savings, costs and economic lifetime of a portfolio of energy efficiency (and/or demand response) programs that the utility is planning or considering implementing during the analysis period. The Benefits Calculator also estimates total resource costs and benefits of the DSR portfolio using a forecast of avoided capacity and energy costs. The Benefits Calculator then uses inputs provided in the Utility Characterization to produce a ?business-as usual? base case as well as alternative scenarios that include energy efficiency resources, including the corresponding utility financial budgets required in each case. If a decoupling and/or a shareholder incentive mechanism are instituted, the Benefits Calculator model readjusts the utility?s revenue requirement and retail rates accordingly. Finally, for each scenario, the Benefits Calculator produces several metrics that provides insights on how energy efficiency resources, decoupling and/or a shareholder incentive mechanism impacts utility shareholders (e.g. overall earnings, return on equity), ratepayers (e.g., average customer bills and rates) and society (e.g. net resource benefits).

  14. Temporal Correlations In Natural Time Analysis and Tsallis Non Extensive Statistical Mechanics

    NASA Astrophysics Data System (ADS)

    Sarlis, N. V.; Varotsos, P.; Skordas, E. S.

    2015-12-01

    Upon analyzing the seismic catalog in a new time domain termed natural time[1-3] and employing a sliding natural time window comprising a number of events that would occur in a few months, we find that the fluctuations β of the order parameter of seismicity[4] show a minimum βmin a few months before major earthquakes (EQs)[5,6]. Such a minimum appears simultaneously[7] with the initiation of Seismic Electric Signals activity[8] being the first time in which two geophysical observables of different nature exhibit simultaneous anomalous behavior before major EQs. In addition, we show[9] that each precursory βmin is preceded as well as followed by characteristic changes of temporal correlations between EQ magnitudes identified by the celebrated Detrended Fluctuation Analysis of magnitude time series. We indicate that Tsallis non extensive statistical mechanics[10], in the frame of which kappa distributions arise[11], can capture temporal correlations between EQ magnitudes if complemented with natural time analysis [12]. References P.A. Varotsos, N.V. Sarlis, and E.S. Skordas, Phys Rev E, 66 (2002) 011902. P.A. Varotsos et al., Phys Rev E 72 (2005) 041103. Varotsos P. A., Sarlis N. V. and Skordas E. S., Natural Time Analysis: The new view of time. (Springer-Verlag, Berlin Heidelberg) 2011. N. V. Sarlis, E. S. Skordas and P. A. Varotsos, EPL 91 (2010) 59001. N. V. Sarlis et al., Proc Natl Acad Sci USA 110 (2013) 13734. N. V. Sarlis et al., Proc Natl Acad Sci USA 112 (2015) 986. P. A. Varotsos et al., Tectonophysics, 589 (2013) 116. P. Varotsos and M. Lazaridou, Tectonophysics 188 (1991) 321. P. A. Varotsos, N. V. Sarlis, and E. S. Skordas, J Geophys Res Space Physics, 119 (2014), 9192, doi: 10.1002/2014JA0205800. C. Tsallis, J Stat Phys 52 (1988) 479. G. Livadiotis, and D. J. McComas, J Geophys Res 114 (2009) A11105, doi:10.1029/2009JA014352. N. V. Sarlis, E. S. Skordas and P. A. Varotsos, Phys Rev E 82 (2010) 021110.

  15. Elucidation of reaction mechanism involved in the formation of LaNiO3 from XRD and TG analysis

    NASA Astrophysics Data System (ADS)

    Dharmadhikari, Dipti V.; Athawale, Anjali A.

    2013-06-01

    The present work is focused on the synthesis and elucidation of reaction mechanism involved in the formation of LaNiO3 with the help of X-ray diffraction (XRD) and thermogravimetric (TG) analysis. LaNiO3 was synthesized by hydrothermal method by heating at 160°C under autogenous pressure for 6h. Pure phase product was obtained after calcining the hydrothermally activated product for 6h at 700°C. The various phases of the product obtained after hydrothermal treatment and calcination followed by the formation of pure phase nanocrystalline lanthanum nickel oxide could be determined from XRD analysis of the samples. The reaction mechanism and phase formation temperature has been interpreted by thermogravimetric analysis of the hydrothermally synthesized product and XRD analysis.

  16. Experimentation and analysis of mechanical behavior modification of titanium matrix composites through controlled fiber placement

    NASA Astrophysics Data System (ADS)

    Bowman, Cheryl Lynne

    Titanium composites reinforced with SiC fibers in a uniaxial direction are being considered for various high temperature applications which require high specific strength or stiffness in the primary loading direction. However the very low tensile and creep strength of these composites in the transverse direction (loading perpendicular to the fiber axis) limits their use in many practical applications. Recent advances in composite fabrication techniques have provided not only better control of fiber volume fraction and distribution, but also the ability to control the relative fiber placement. The goal of this research was produce continuously reinforced SiC/Ti composites with precise fiber arrangement in order to ascertain the significance of fiber arrangements on transverse mechanical properties. In this study, TIMETAL 21S and Ti-6-4 composites reinforced with SCS-6 SiC fibers were produced with six distinct fiber placement arrangements. The effect of fiber placement on uniaxial tensile and creep behaviors was assessed and the results compared to analytical predictions. Consistent with analytical predictions, the fiber arrangements used in this study did not significantly change the longitudinal tensile behavior, but differences were obtained in the transverse loading response. For example, a diamond (non-equilateral triangle) fiber packing was found to have a higher transverse ultimate tensile strength and better transverse creep resistance than a rectangular fiber packing arrangement for a given volume fraction and fiber spacing (within-ply vs. between-ply). Initially this result appeared to be in contrast to previous computational and analytical simulations which predicted more favorable mechanical behavior for rectangular-type arrangements. However, this experimental/predictive conflict was resolved, in part, by simply defining a fiber spacing ratio which could describe both rectangular type and diamond-type arrangements. The computationally efficient

  17. Analytical solution of the time-dependent Bloch NMR flow equations: a translational mechanical analysis

    NASA Astrophysics Data System (ADS)

    Awojoyogbe, O. B.

    2004-08-01

    Various biological and physiological properties of living tissue can be studied by means of nuclear magnetic resonance techniques. Unfortunately, the basic physics of extracting the relevant information from the solution of Bloch nuclear magnetic resource (NMR) equations to accurately monitor the clinical state of biological systems is still not yet fully understood. Presently, there are no simple closed solutions known to the Bloch equations for a general RF excitation. Therefore the translational mechanical analysis of the Bloch NMR equations presented in this study, which can be taken as definitions of new functions to be studied in detail may reveal very important information from which various NMR flow parameters can be derived. Fortunately, many of the most important but hidden applications of blood flow parameters can be revealed without too much difficulty if appropriate mathematical techniques are used to solve the equations. In this study we are concerned with a mathematical study of the laws of NMR physics from the point of view of translational mechanical theory. The important contribution of this study is that solutions to the Bloch NMR flow equations do always exist and can be found as accurately as desired. We shall restrict our attention to cases where the radio frequency field can be treated by simple analytical methods. First we shall derive a time dependant second-order non-homogeneous linear differential equation from the Bloch NMR equation in term of the equilibrium magnetization M0, RF B1( t) field, T1 and T2 relaxation times. Then, we would develop a general method of solving the differential equation for the cases when RF B1( t)=0, and when RF B1( t)≠0. This allows us to obtain the intrinsic or natural behavior of the NMR system as well as the response of the system under investigation to a specific influence of external force to the system. Specifically, we consider the case where the RF B1 varies harmonically with time. Here the complete

  18. Architectural Analysis of Human Abdominal Wall Muscles: Implications for Mechanical Function

    PubMed Central

    Brown, Stephen H. M.; Ward, Samuel R.; Cook, Mark S.; Lieber, Richard L.

    2010-01-01

    Study Design Cadaveric analysis of human abdominal muscle architecture. Objective To quantify the architectural properties of rectus abdominis (RA), external oblique (EO), internal oblique (IO) and transverse abdominis (TrA), and model mechanical function in light of these new data. Summary of Background Data Knowledge of muscle architecture provides the structural basis for predicting muscle function. Abdominal muscles greatly affect spine loading, stability, injury prevention and rehabilitation; however, their architectural properties are unknown. Methods Abdominal muscles from eleven elderly human cadavers were removed intact, separated into regions and micro-dissected for quantification of physiological cross-sectional area (PCSA), fascicle length and sarcomere length. From these data, sarcomere operating length ranges were calculated. Results IO had the largest PCSA and RA the smallest, and would thus generate the largest and smallest isometric forces, respectively. RA had the longest fascicle length, followed by EO, and would thus be capable of generating force over the widest range of lengths. Measured sarcomere lengths, in the post-mortem neutral spine posture, were significantly longer in RA and EO (3.29±0.07 and 3.18±0.11 μm) compared to IO and TrA (2.61±0.06 and 2.58±0.05 μm) (p < 0.0001). Biomechanical modeling predicted that RA, EO and TrA act at optimal force-generating length in the mid-range of lumbar spine flexion, where IO can generate approximately 90% of its maximum force. Conclusions These data provide clinically relevant insights into the ability of the abdominal wall muscles to generate force and change length throughout the lumbar spine range of motion. This will impact the understanding of potential postures in which the force-generating and spine stabilizing ability of these muscles become compromised, which can guide exercise/rehabilitation development and prescription. Future work should explore the mechanical interactions among

  19. Global Analysis of the Evolution and Mechanism of Echinocandin Resistance in Candida glabrata

    PubMed Central

    Singh-Babak, Sheena D.; Babak, Tomas; Diezmann, Stephanie; Hill, Jessica A.; Xie, Jinglin Lucy; Chen, Ying-Lien; Poutanen, Susan M.; Rennie, Robert P.; Heitman, Joseph; Cowen, Leah E.

    2012-01-01

    The evolution of drug resistance has a profound impact on human health. Candida glabrata is a leading human fungal pathogen that can rapidly evolve resistance to echinocandins, which target cell wall biosynthesis and are front-line therapeutics for Candida infections. Here, we provide the first global analysis of mutations accompanying the evolution of fungal drug resistance in a human host utilizing a series of C. glabrata isolates that evolved echinocandin resistance in a patient treated with the echinocandin caspofungin for recurring bloodstream candidemia. Whole genome sequencing identified a mutation in the drug target, FKS2, accompanying a major resistance increase, and 8 additional non-synonymous mutations. The FKS2-T1987C mutation was sufficient for echinocandin resistance, and associated with a fitness cost that was mitigated with further evolution, observed in vitro and in a murine model of systemic candidemia. A CDC6-A511G(K171E) mutation acquired before FKS2-T1987C(S663P), conferred a small resistance increase. Elevated dosage of CDC55, which acquired a C463T(P155S) mutation after FKS2-T1987C(S663P), ameliorated fitness. To discover strategies to abrogate echinocandin resistance, we focused on the molecular chaperone Hsp90 and downstream effector calcineurin. Genetic or pharmacological compromise of Hsp90 or calcineurin function reduced basal tolerance and resistance. Hsp90 and calcineurin were required for caspofungin-dependent FKS2 induction, providing a mechanism governing echinocandin resistance. A mitochondrial respiration-defective petite mutant in the series revealed that the petite phenotype does not confer echinocandin resistance, but renders strains refractory to synergy between echinocandins and Hsp90 or calcineurin inhibitors. The kidneys of mice infected with the petite mutant were sterile, while those infected with the HSP90-repressible strain had reduced fungal burden. We provide the first global view of mutations accompanying the

  20. Kinematics analysis and optimization of the fast shearing-extrusion joining mechanism for solid-state metal

    NASA Astrophysics Data System (ADS)

    Zhang, Shuangjie; Yao, Yunfeng; Li, Lingchong; Wang, Lijuan; Li, Junxia; Li, Qiang

    2015-11-01

    Dynamical Joining of the solid-state metal is the key technology to realize endless hot rolling. The heating and laser welding method both require long joining time. Based on super deformation method, a 7-bar and 2-slider mechanism was developed in Japan, and the joining time is less than 0.5 s, however the length of each bar are not reported and this mechanism is complex. A relatively simple 6-bar and 1-slider mechanism is put forward, which can realize the shearing and extrusion motion of the top and bottom blades with a speed approximately equal to the speed of the metal plates. In order to study the kinematics property of the double blades, based on complex vector method, the multi-rigid-body model is built, and the displacement and speed functions of the double blades, the joining time and joining thickness are deduced, the kinematics analysis shows that the initial parameters can't satisfy the joining process. Hence, optimization of this mechanism is employed using genetic algorithm(GA) and the optimization parameters of this mechanism are obtained, the kinematics analysis show that the joining time is less than 0.1 s, the joining thickness is more than 80% of the thickness of the solid-state metal, and the horizontal speeds of the blades are improved. A new mechanism is provided for the joining of the solid-state metal and a foundation is laid for the design of the device.

  1. Conformational analysis of methylphenidate: comparison of molecular orbital and molecular mechanics methods.

    PubMed

    Gilbert, Kathleen M; Skawinski, William J; Misra, Milind; Paris, Kristina A; Naik, Neelam H; Buono, Ronald A; Deutsch, Howard M; Venanzi, Carol A

    2004-11-01

    Methylphenidate (MP) binds to the cocaine binding site on the dopamine transporter and inhibits reuptake of dopamine, but does not appear to have the same abuse potential as cocaine. This study, part of a comprehensive effort to identify a drug treatment for cocaine abuse, investigates the effect of choice of calculation technique and of solvent model on the conformational potential energy surface (PES) of MP and a rigid methylphenidate (RMP) analogue which exhibits the same dopamine transporter binding affinity as MP. Conformational analysis was carried out by the AM1 and AM1/SM5.4 semiempirical molecular orbital methods, a molecular mechanics method (Tripos force field with the dielectric set equal to that of vacuum or water) and the HF/6-31G* molecular orbital method in vacuum phase. Although all three methods differ somewhat in the local details of the PES, the general trends are the same for neutral and protonated MP. In vacuum phase, protonation has a distinctive effect in decreasing the regions of space available to the local conformational minima. Solvent has little effect on the PES of the neutral molecule and tends to stabilize the protonated species. The random search (RS) conformational analysis technique using the Tripos force field was found to be capable of locating the minima found by the molecular orbital methods using systematic grid search. This suggests that the RS/Tripos force field/vacuum phase protocol is a reasonable choice for locating the local minima of MP. However, the Tripos force field gave significantly larger phenyl ring rotational barriers than the molecular orbital methods for MP and RMP. For both the neutral and protonated cases, all three methods found the phenyl ring rotational barriers for the RMP conformers/invertamers (denoted as cte, tte, and cta) to be: cte, tte > MP > cta. Solvation has negligible effect on the phenyl ring rotational barrier of RMP. The B3LYP/6-31G* density functional method was used to calculate the

  2. Jupiter System Data Analysis Program: Mechanisms, Manifestation, and Implications of Cryomagmatism on Europa

    NASA Technical Reports Server (NTRS)

    Fagents, Sarah A.

    2003-01-01

    The objectives of the work completed under NASA Grant NAG5-8898 were (i) to document and characterize the low-albedo diffuse surfaces associated with triple bands and lenticulae, (ii) to determine their mechanisms of formation, and (iii) to assess the implications of these features for the resurfacing (in space and time) of the Europa and the nature of the Europan interior. The approach involved a combination of processing and analysis of Solid State Imaging data returned by the Galileo spacecraft during the primary and extended mission phases, together with numerical modeling of the physical processes interpreted to the observed features. We have modeled the formation of Europan triple explosive venting of cryoclastic material from bands and lenticulae halos by two processes: (i) a liquid layer in the Europan interior, and (ii) lag deposit formation by the thermal influence of subsurface cryomagmatic intrusions. We favor the latter hypothesis for explaining these features, and further suggest that a liquid water or brine intrusion is required to provide sufficient lateral heating of surface ice to explain the 25 km size of the largest features. (Solid ice diapirs, even under the most favorable conditions, become thermally exhausted before they heat significant lateral distances). We argue that water circulating in open fractures, or repeated cryomagmatic 'diking' events would provide sufficient thermal input to produce the observed features. Thus our work argues for the existence of a liquid beneath Europa's surface. Our results might most easily be explained by the presence of a continuous liquid layer (the putative Europan ocean); this would concur with the findings of the Galileo magnetometer team. However, we cannot rule out the possibility that discrete liquid pockets provide injections of fluid closer to the surface.

  3. Kinetic analysis and molecular modeling of the inhibition mechanism of roneparstat (SST0001) on human heparanase

    PubMed Central

    Pala, Daniele; Rivara, Silvia; Mor, Marco; Milazzo, Ferdinando Maria; Roscilli, Giuseppe; Pavoni, Emiliano; Giannini, Giuseppe

    2016-01-01

    Heparanase is a β-d-glucuronidase which cleaves heparan sulfate chains in the extracellular matrix and on cellular membranes. A dysregulated heparanase activity is intimately associated with cell invasion, tumor metastasis and angiogenesis, making heparanase an attractive target for the development of anticancer therapies. SST0001 (roneparstat; Sigma-Tau Research Switzerland S.A.) is a non-anticoagulant 100% N-acetylated and glycol-split heparin acting as a potent heparanase inhibitor, currently in phase I in advanced multiple myeloma. Herein, the kinetics of heparanase inhibition by roneparstat is reported. The analysis of dose-inhibition curves confirmed the high potency of roneparstat (IC50 ≈ 3 nM) and showed, at higher concentrations, a Hill coefficient consistent with the engagement of two molecules of inhibitor. A homology model of human heparanase GS3 construct was built and used for docking experiments with inhibitor fragments. The model has high structural similarity with the recently reported crystal structure of human heparanase. Different interaction schemes are proposed, which support the hypothesis of a complex binding mechanism involving the recruitment of one or multiple roneparstat chains, depending on its concentration. In particular, docking solutions were obtained in which (i) a single roneparstat molecule interacts with both heparin-binding domains (HBDs) of heparanase or (ii) two fragments of roneparstat interact with either HBD-1 or HBD-2, consistent with the possibility of different inhibitor:enzyme binding stoichiometries. This study provides unique insights into the mode of action of roneparstat as well as clues of its interaction with heparanase at a molecular level, which could be exploited to design novel potential inhibitor molecules. PMID:26762172

  4. An examination of the regulatory mechanism of Pxdn mutation-induced eye disorders using microarray analysis

    PubMed Central

    YANG, YANG; XING, YIQIAO; LIANG, CHAOQUN; HU, LIYA; XU, FEI; MEI, QI

    2016-01-01

    The present study aimed to identify biomarkers for peroxidasin (Pxdn) mutation-induced eye disorders and study the underlying mechanisms involved in this process. The microarray dataset GSE49704 was used, which encompasses 4 mouse samples from embryos with Pxdn mutation and 4 samples from normal tissues. After data preprocessing, the differentially expressed genes (DEGs) between Pxdn mutation and normal tissues were identified using the t-test in the limma package, followed by functional enrichment analysis. The protein-protein interaction (PPI) network was constructed based on the STRING database, and the transcriptional regulatory (TR) network was established using the GeneCodis database. Subsequently, the overlapping DEGs with high degrees in two networks were identified, as well as the sub-network extracted from the TR network. In total, 121 (75 upregulated and 46 downregulated) DEGs were identified, and these DEGs play important roles in biological processes (BPs), including neuron development and differentiation. A PPI network containing 25 nodes such as actin, alpha 1, skeletal muscle (Acta1) and troponin C type 2 (fast) (Tnnc2), and a TR network including 120 nodes were built. By comparing the two networks, seven crucial genes which overlapped were identified, including cyclin-dependent kinase inhibitor 1B (Cdkn1b), Acta1 and troponin T type 3 (Tnnt3). In the sub-network, Cdkn1b was predicted as the target of miRNAs such as mmu-miR-24 and transcription factors (TFs) including forkhead box O4 (FOXO4) and activating enhancer binding protein 4 (AP4). Thus, we suggest that seven crucial genes, including Cdkn1b, Acta1 and Tnnt3, play important roles in the progression of eye disorders such as glaucoma. We suggest that Cdkn1b exert its effects via the inhibition of proliferation and is mediated by mmu-miR-24 and targeted by the TFs FOXO4 and AP4. PMID:27121343

  5. On rail vehicle vibrations induced by track unevenness: Analysis of the excitation mechanism

    NASA Astrophysics Data System (ADS)

    Cheli, F.; Corradi, R.

    2011-07-01

    This paper deals with the analysis of the vibrations induced on the carbody of a rail vehicle by track unevenness. Attention is focused on the excitation mechanism of the carbody vibration modes, which has a strong influence on the vehicle's comfort. At first the problem is investigated through a simple three-degree-of-freedom analytical model, and the phenomenon of the critical velocities is analysed, pointing out how both rigid and flexible carbody vibration modes can be excited to a different extent, depending on the vehicle speed, and how they combine to produce the final carbody accelerations. Then the dynamic response of a real vehicle running on irregular track is simulated through a more detailed multibody model, suitable for quantitatively reproducing its dynamic behaviour in the 0-25 Hz frequency range. The 68 degrees-of-freedom of this model correspond to 35 rigid vibration modes of the vehicle components (carbody, bogie frames and wheelsets), plus the 33 carbody flexible modes which fall into the frequency-range of interest. In the last part of the paper, the obtained numerical results are compared to the experimental data collected during on-line tests, showing how the adopted numerical model accurately simulates the dynamic behaviour of the real vehicle at the different velocities, with very good agreement. The results presented in the paper demonstrate that the excitation of the flexible modes may have a decisive effect on carbody accelerations and that introducing carbody flexibility in the vehicle model turns out to be unavoidable for properly predicting a rail vehicle comfort performance.

  6. Comparative Analysis of Latex Transcriptome Reveals Putative Molecular Mechanisms Underlying Super Productivity of Hevea brasiliensis

    PubMed Central

    Li, Heping; Fan, Yujie; Yang, Jianghua; Qi, Jiyan; Li, Huibo

    2013-01-01

    Increasing demand for natural rubber prompts studies into the mechanisms governing the productivity of rubber tree (Heveabrasiliensis). It is very interesting to notice that a rubber tree of clone PR107 in Yunnan, China is reported to yield more than 20 times higher than the average rubber tree. This super-high-yielding (SHY) rubber tree (designated as SY107), produced 4.12 kg of latex (cytoplasm of rubber producing laticifers, containing about 30% of rubber) per tapping, more than 7-fold higher than that of the control. This rubber tree is therefore a good material to study how the rubber production is regulated at a molecular aspect. A comprehensive cDNA-AFLP transcript profiling was performed on the latex of SY107 and its average counterparts by using the 384 selective primer pairs for two restriction enzyme combinations (ApoI/MseI and TaqI/MseI). A total of 746 differentially expressed (DE) transcript-derived fragments (TDFs) were identified, of which the expression patterns of 453 TDFs were further confirmed by RT-PCR. These RT-PCR confirmed TDFs represented 352 non-redundant genes, of which 215 had known or partially known functions and were grouped into 10 functional categories. The top three largest categories were transcription and protein synthesis (representing 24.7% of the total genes), defense and stress (15.3%), and primary and secondary metabolism (14.0%). Detailed analysis of the DE-genes suggests notable characteristics of SHY phenotype in improved sucrose loading capability, rubber biosynthesis-preferred sugar utilization, enhanced general metabolism and timely stress alleviation. However, the SHY phenotype has little correlation with rubber-biosynthesis pathway genes. PMID:24066172

  7. Design Analysis and Thermo-mechanical Fatigue of a Polyimide Composite for Combustion Chamber Support

    NASA Technical Reports Server (NTRS)

    Thesken, J. C.; Melis, M.; Shin, E.; Sutter, J.; Burke, Chris

    2004-01-01

    Polyimide composites are being evaluated for use in lightweight support structures designed to preserve the ideal flow geometry within thin shell combustion chambers of future space launch propulsion systems. Principles of lightweight design and innovative manufacturing techniques have yielded a sandwich structure with an outer face sheet of carbon fiber polyimide matrix composite. While the continuous carbon fiber enables laminated skin of high specific stiffness; the polyimide matrix materials ensure that the rigidity and durability is maintained at operation temperatures of 316 C. Significant weight savings over all metal support structures are expected. The protypical structure is the result of ongoing collaboration, between Boeing and NASA-GRC seeking to introduce polyimide composites to the harsh environmental and loads familiar to space launch propulsion systems. Design trade analyses were carried out using relevant closed form solutions, approximations for sandwich beams/panels and finite element analysis. Analyses confirm the significant thermal stresses exist when combining materials whose coefficients of thermal expansion (CTEs) differ by a factor of about 10 for materials such as a polymer composite and metallic structures. The ramifications on design and manufacturing alternatives are reviewed and discussed. Due to stringent durability and safety requirements, serious consideration is being given to the synergistic effects of temperature and mechanical loads. The candidate structure operates at 316 C, about 80% of the glass transition temperature T(sub g). Earlier thermomechanical fatigue (TMF) investigations of chopped fiber polyimide composites made this near to T(sub g), showed that cyclic temperature and stress promoted excessive creep damage and strain accumulation. Here it is important to verify that such response is limited in continuous fiber laminates.

  8. Formaldehyde exposure and leukemia: a new meta-analysis and potential mechanisms.

    PubMed

    Zhang, Luoping; Steinmaus, Craig; Eastmond, David A; Xin, Xianjun K; Smith, Martyn T

    2009-01-01

    Formaldehyde is an economically important chemical, to which more than 2 million U.S. workers are occupationally exposed. Substantially more people are exposed to formaldehyde environmentally, as it is generated by automobile engines, is a component of tobacco smoke and is released from household products, including furniture, particleboard, plywood, and carpeting. The International Agency for Research on Cancer (IARC) recently classified formaldehyde as a human carcinogen that causes nasopharyngeal cancer and also concluded that there is "strong but not sufficient evidence for a causal association between leukemia and occupational exposure to formaldehyde". Here, we review the epidemiological studies published to date on formaldehyde-exposed workers and professionals in relation to lymphohematopoietic malignances. In a new meta-analysis of these studies, focusing on occupations known to have high formaldehyde exposure, we show that summary relative risks (RRs) were elevated in 15 studies of leukemia (RR=1.54; confidence interval (CI), 1.18-2.00) with the highest relative risks seen in the six studies of myeloid leukemia (RR=1.90; 95% CI, 1.31-2.76). The biological plausibility of this observed association is discussed and potential mechanisms proposed. We hypothesize that formaldehyde may act on bone marrow directly or, alternatively, may cause leukemia by damaging the hematopoietic stem or early progenitor cells that are located in the circulating blood or nasal passages, which then travel to the bone marrow and become leukemic stem cells. To test these hypotheses, we recommend that future studies apply biomarkers validated for other chemical leukemogens to the study of formaldehyde. PMID:18674636

  9. The study of epigenetic mechanisms based on the analysis of histone modification patterns by flow cytometry.

    PubMed

    Watson, Maria; Chow, Sue; Barsyte, Dalia; Arrowsmith, Cheryl; Shankey, T Vincent; Minden, Mark; Hedley, David

    2014-01-01

    Epigenetic regulation of genes involved in cell growth, survival, or differentiation through histone modifications is an important determinant of cancer development and outcome. The basic science of epigenetics uses analytical tools that, although powerful, are not well suited to the analysis of heterogeneous cell populations found in human cancers, or for monitoring the effects of drugs designed to modulate epigenetic mechanisms in patients. To address this, we selected three clinically relevant histone marks (H3K27me3, H3K9ac, and H3K9me2), modulated their expression levels by in vitro treatments to generate high and low expressing control cells, and tested the relative sensitivity of candidate antibodies to detect the differences in expression levels by flow cytoametry using a range of sample preparation techniques. We identified monoclonal antibodies to all three histone marks that were suitable for flow cytoametry. Staining intensities were reduced with increasing formaldehyde concentration, and were not affected by ionic strength or by alcohol treatment. A protocol suitable for clinical samples was then developed, to allow combined labeling of histone marks and surface antigens while preserving light scatter signals. This was applied to normal donor blood, and to samples obtained from 25 patients with leukemia (predominantly acute myeloid leukemia). Significant cellular heterogeneity in H3K9ac and H3K27me3 staining was seen in normal peripheral blood, but the patterns were very similar between individual donors. In contrast, H3K27me3 in particular showed considerable inter-patient heterogeneity in the leukemia cell populations. Although further refinements are likely needed to fully optimize sample staining protocols, "flow epigenetics" appears to be technically feasible, and to have potential both in basic research, and in clinical application. PMID:24038859

  10. Analysis of regulatory mechanism after ErbB4 gene mutation based on local modeling methodology.

    PubMed

    Chen, C L; Zhao, J W

    2016-01-01

    ErbB4 is an oncogene belonging to the epidermal growth factor receptor family and contributes to the occurrence and development of multiple cancers, such as gastric, breast, and colorectal cancers. Therefore, studies of the regulation of ErbB4 in cancerigenic pathway will advance molecular targeted therapy. Advanced bioinformatic analysis softwares, such as ExPASy, Predictprotei, QUARK, and I-TASSER, were used to analyze the regulatory mechanism after ErbB4 gene mutation in terms of amino acid sequence, primary, secondary, and tertiary structure of the protein and upstream-downstream receptor/ligands. Mutation of the 19th and 113th amino acids at the carboxyl terminus of ErbB4 protein did not affect its biological nature, but its secondary structure changed and protein binding sites were near 2 mutational sites; moreover, after mutation introduction, additional binding sites were observed. Tertiary structure modeling indicated that local structure of ErbB4 was changed from an α helical conformation into a β chain folding structure; the α helical conformation is the functional site of protein, while active sites are typically near junctions between helical regions, thus the helical structures are easily destroyed and change into folding structures or other structures after stretching. Mutable sites of ErbB4 is exact binding sites where dimer formed with other epidermal growth factor family proteins; mutation enabled the ErbB4 receptor to bind to neuregulin 1 ligand without dimer formation, disrupting the signal transduction pathway and affecting ErbB4 function. PMID:27323039

  11. Kinetic analysis and molecular modeling of the inhibition mechanism of roneparstat (SST0001) on human heparanase.

    PubMed

    Pala, Daniele; Rivara, Silvia; Mor, Marco; Milazzo, Ferdinando Maria; Roscilli, Giuseppe; Pavoni, Emiliano; Giannini, Giuseppe

    2016-06-01

    Heparanase is a β-d-glucuronidase which cleaves heparan sulfate chains in the extracellular matrix and on cellular membranes. A dysregulated heparanase activity is intimately associated with cell invasion, tumor metastasis and angiogenesis, making heparanase an attractive target for the development of anticancer therapies. SST0001 (roneparstat; Sigma-Tau Research Switzerland S.A.) is a non-anticoagulant 100% N-acetylated and glycol-split heparin acting as a potent heparanase inhibitor, currently in phase I in advanced multiple myeloma. Herein, the kinetics of heparanase inhibition by roneparstat is reported. The analysis of dose-inhibition curves confirmed the high potency of roneparstat (IC50 ≈ 3 nM) and showed, at higher concentrations, a Hill coefficient consistent with the engagement of two molecules of inhibitor. A homology model of human heparanase GS3 construct was built and used for docking experiments with inhibitor fragments. The model has high structural similarity with the recently reported crystal structure of human heparanase. Different interaction schemes are proposed, which support the hypothesis of a complex binding mechanism involving the recruitment of one or multiple roneparstat chains, depending on its concentration. In particular, docking solutions were obtained in which (i) a single roneparstat molecule interacts with both heparin-binding domains (HBDs) of heparanase or (ii) two fragments of roneparstat interact with either HBD-1 or HBD-2, consistent with the possibility of different inhibitor:enzyme binding stoichiometries. This study provides unique insights into the mode of action of roneparstat as well as clues of its interaction with heparanase at a molecular level, which could be exploited to design novel potential inhibitor molecules. PMID:26762172

  12. Constraining AGN triggering mechanisms through the clustering analysis of active black holes

    NASA Astrophysics Data System (ADS)

    Gatti, M.; Shankar, F.; Bouillot, V.; Menci, N.; Lamastra, A.; Hirschmann, M.; Fiore, F.

    2016-02-01

    The triggering mechanisms for active galactic nuclei (AGN) are still debated. Some of the most popular ones include galaxy interactions (IT) and disc instabilities (DIs). Using an advanced semi-analytic model (SAM) of galaxy formation, coupled to accurate halo occupation distribution modelling, we investigate the imprint left by each separate triggering process on the clustering strength of AGN at small and large scales. Our main results are as follows: (i) DIs, irrespective of their exact implementation in the SAM, tend to fall short in triggering AGN activity in galaxies at the centre of haloes with Mh > 1013.5 h-1 M⊙. On the contrary, the IT scenario predicts abundance of active central galaxies that generally agrees well with observations at every halo mass. (ii) The relative number of satellite AGN in DIs at intermediate-to-low luminosities is always significantly higher than in IT models, especially in groups and clusters. The low AGN satellite fraction predicted for the IT scenario might suggest that different feeding modes could simultaneously contribute to the triggering of satellite AGN. (iii) Both scenarios are quite degenerate in matching large-scale clustering measurements, suggesting that the sole average bias might not be an effective observational constraint. (iv) Our analysis suggests the presence of both a mild luminosity and a more consistent redshift dependence in the AGN clustering, with AGN inhabiting progressively less massive dark matter haloes as the redshift increases. We also discuss the impact of different observational selection cuts in measuring AGN clustering, including possible discrepancies between optical and X-ray surveys.

  13. Comparison of mechanical stress and change in bone mineral density between two types of femoral implant using finite element analysis.

    PubMed

    Hirata, Yasuhide; Inaba, Yutaka; Kobayashi, Naomi; Ike, Hiroyuki; Fujimaki, Hiroshi; Saito, Tomoyuki

    2013-12-01

    Stress shielding after total hip arthroplasty (THA) remains an unsolved issue. Various patterns of mechanical stress appear according to the type of femoral stem used. To compare differences in mechanical stress conditions between Zweymuller type and fit-and-fill type stems, finite element analysis (FEA) was performed. Differences in bone mineral density (BMD) changes in the femur were also compared. Maximum stress was confirmed in Gruen zone 4, whereas zone 1 had the minimum amount of stress with both types of implant. The Zweymuller stem group had less mechanical stress and lower BMD in zone 7 than the fit-and-fill stem group. In conclusion, differences in mechanical stress may be related to changes in BMD after THA. PMID:23683518

  14. Modeling and analysis of deployment dynamics for a novel ring mechanism

    NASA Astrophysics Data System (ADS)

    Li, Bing; Qi, Xiaozhi; Huang, Hailin; Xu, Wenfu

    2016-03-01

    With the development of satellite-communication and earth-observation technologies, the demands for large and light space-deployable antennas have become more and more urgent. In this paper, a deployable ring mechanism capable of supporting a large flexible cable net antenna reflector is presented. The mechanism is driven by torsion springs and controlled by cables. It is composed of multiple deployable modules and has a high deploy/fold ratio, therefore, it has good application prospects. To improve the reliability of the mechanism, a dynamic simulation must be conducted at the design stage to investigate the mechanical characteristics. First, a full kinematic model is established and the position, velocity, and acceleration of the mechanism are analyzed. Next, taking into account the influence of the flexible cable net, frictional damping and the torsion springs, the deployment dynamics of the mechanism are modeled by using a Lagrange's method. Finally, forward dynamics and inverse dynamics simulations are conducted to investigate the rules the governing system-energy variation, and the influence of viscous damping on the motion of the mechanism. A modified deployment motion planning method based on force-control is proposed, and the relationships between control force and motion are ascertained and verified by a prototype of the ring mechanism.

  15. Finite element procedures for coupled linear analysis of heat transfer, fluid and solid mechanics

    NASA Technical Reports Server (NTRS)

    Sutjahjo, Edhi; Chamis, Christos C.

    1993-01-01

    Coupled finite element formulations for fluid mechanics, heat transfer, and solid mechanics are derived from the conservation laws for energy, mass, and momentum. To model the physics of interactions among the participating disciplines, the linearized equations are coupled by combining domain and boundary coupling procedures. Iterative numerical solution strategy is presented to solve the equations, with the partitioning of temporal discretization implemented.

  16. An Analysis of Agricultural Mechanics Safety Practices in Agricultural Science Laboratories.

    ERIC Educational Resources Information Center

    Swan, Michael K.

    North Dakota secondary agricultural mechanics instructors were surveyed regarding instructional methods and materials, safety practices, and equipment used in the agricultural mechanics laboratory. Usable responses were received from 69 of 89 instructors via self-administered mailed questionnaires. Findings were consistent with results of similar…

  17. An Analysis of Applied Mechanics Contest for Senior High School Students in Taiwan

    ERIC Educational Resources Information Center

    Chen, Nelson Cheng-Chih; Chen, Ching-Hao; Lin, Ming-chun

    2008-01-01

    The applied mechanics education contest hosted by STAM (Society of Theoretical Applied Mechanics) has been held in Taiwan for several years. The contest pattern has been changed from a simple written test to an experiment-oriented test after the NSTM (National Science and Technology Museum) proceeded to hold the competition in 2005. The major…

  18. Identification of Drought Tolerant Mechanisms in Maize Seedlings Based on Transcriptome Analysis of Recombination Inbred Lines.

    PubMed

    Min, Haowei; Chen, Chengxuan; Wei, Shaowei; Shang, Xiaoling; Sun, Meiyun; Xia, Ran; Liu, Xiangguo; Hao, Dongyun; Chen, Huabang; Xie, Qi

    2016-01-01

    Zea mays is an important crop that is sensitive to drought stress, but survival rates and growth status remain strong in some drought-tolerant lines under stress conditions. Under drought conditions, many biological processes, such as photosynthesis, carbohydrate metabolism and energy metabolism, are suppressed, while little is known about how the transcripts of genes respond to drought stress in the genome-wide rang in the seedling stage. In our study, the transcriptome profiles of two maize recombination inbred lines (drought-tolerant RIL70 and drought-sensitive RIL93) were analyzed at different drought stages to elucidate the dynamic mechanisms underlying drought tolerance in maize seedlings during drought conditions. Different numbers of differentially expressed genes presented in the different stages of drought stress in the two RILs, for the numbers of RIL93 vs. RIL70 were: 9 vs. 358, 477 vs. 103, and 5207 vs. 152 respectively in DT1, DT2, and DT5. Gene Ontology enrichment analysis revealed that in the initial drought-stressed stage, the primary differentially expressed genes involved in cell wall biosynthesis and transmembrane transport biological processes were overrepresented in RIL70 compared to RIL93. On the contrary, differentially expressed genes profiles presented at 2 and 5 day-treatments, the primary differentially expressed genes involved in response to stress, protein folding, oxidation-reduction, photosynthesis and carbohydrate metabolism, were overrepresented in RIL93 compared to RIL70. In addition, the transcription of genes encoding key members of the cell cycle and cell division processes were blocked, but ABA- and programmed cell death-related processes responded positively in RIL93. In contrast, the expression of cell cycle genes, ABA- and programmed cell death-related genes was relatively stable in RIL70. The results we obtained supported the working hypothesis that signaling events associated with turgor homeostasis, as established by

  19. An examination of the regulatory mechanism of Pxdn mutation-induced eye disorders using microarray analysis.

    PubMed

    Yang, Yang; Xing, Yiqiao; Liang, Chaoqun; Hu, Liya; Xu, Fei; Mei, Qi

    2016-06-01

    The present study aimed to identify biomarkers for peroxidasin (Pxdn) mutation-induced eye disorders and study the underlying mechanisms involved in this process. The microarray dataset GSE49704 was used, which encompasses 4 mouse samples from embryos with Pxdn mutation and 4 samples from normal tissues. After data preprocessing, the differentially expressed genes (DEGs) between Pxdn mutation and normal tissues were identified using the t-test in the limma package, followed by functional enrichment analysis. The protein-protein interaction (PPI) network was constructed based on the STRING database, and the transcriptional regulatory (TR) network was established using the GeneCodis database. Subsequently, the overlapping DEGs with high degrees in two networks were identified, as well as the sub-network extracted from the TR network. In total, 121 (75 upregulated and 46 downregulated) DEGs were identified, and these DEGs play important roles in biological processes (BPs), including neuron development and differentiation. A PPI network containing 25 nodes such as actin, alpha 1, skeletal muscle (Acta1) and troponin C type 2 (fast) (Tnnc2), and a TR network including 120 nodes were built. By comparing the two networks, seven crucial genes which overlapped were identified, including cyclin‑dependent kinase inhibitor 1B (Cdkn1b), Acta1 and troponin T type 3 (Tnnt3). In the sub-network, Cdkn1b was predicted as the target of miRNAs such as mmu-miR-24 and transcription factors (TFs) including forkhead box O4 (FOXO4) and activating enhancer binding protein 4 (AP4). Thus, we suggest that seven crucial genes, including Cdkn1b, Acta1 and Tnnt3, play important roles in the progression of eye disorders such as glaucoma. We suggest that Cdkn1b exert its effects via the inhibition of proliferation and is mediated by mmu-miR-24 and targeted by the TFs FOXO4 and AP4. PMID:27121343

  20. Application of slip-line analysis to the mechanical model of active accretionary wedge

    NASA Astrophysics Data System (ADS)

    Song, I.; Lee, H.; Kim, J.

    2012-04-01

    An active accretionary wedge is formed from sediments accreted continuously at a continental margin by a subducting plate and mechanically characterized by a plane-strain compressive frictional flow throughout its entire volume. Continuous deformation induced by incoming sediments raises the distortional stress eventually leading to an ultimate condition known as a critical state. According to the critical taper theory (Davis et al., JGR, 1983), the angle of wedge increases as the incoming materials are accreted into the wedge until it reaches a critical value where the shear force on the basal detachment is in equilibrium with the basal friction. Under this concept, we applied the plastic slip-line theory for the computation of stress and velocity fields throughout the continuously deforming area of the wedge. For the simplicity, we assumed that the tapered wedge overlying a basal décollement fault is described by a perfectly plastic rheology complying with the Coulomb failure criterion and the associated flow rule. A complete description of soil rheology at the critical state requires the determination of stress tensors and velocity vectors at given points within the deforming region. For the boundary condition of stress, the effective normal and shear tractions on the upper surface of wedge are equal to zero, and thus the maximum principal stress acts parallel to the surface. Considering the two-dimensional plane strain deformation, we numerically obtained the slip-line solution for the mean effective stress with respect to the orientation of the maximum principal stress at each intersection point of the potential (conjugate) slip lines given by the Coulomb criterion. Then the maximum shear stress was calculated using the failure criterion. After the stress solution was yielded, the velocity field was determined by the same procedure using the boundary condition of the velocity of incoming sediments obtained from the velocity of subducting plate. Our result