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Sample records for mechanical characterization method

  1. Novel method for mechanical characterization of polymeric nanofibers

    NASA Astrophysics Data System (ADS)

    Naraghi, Mohammad; Chasiotis, Ioannis; Kahn, Harold; Wen, Yongkui; Dzenis, Yuris

    2007-08-01

    A novel method to perform nanoscale mechanical characterization of highly deformable nanofibers has been developed. A microelectromechanical system (MEMS) test platform with an on-chip leaf-spring load cell that was tuned with the aid of a focused ion beam was built for fiber gripping and force measurement and it was actuated with an external piezoelectric transducer. Submicron scale tensile tests were performed in ambient conditions under an optical microscope. Engineering stresses and strains were obtained directly from images of the MEMS platform, by extracting the relative rigid body displacements of the device components by digital image correlation. The accuracy in determining displacements by this optical method was shown to be better than 50nm. In the application of this method, the mechanical behavior of electrospun polyacrylonitrite nanofibers with diameters ranging from 300to600nm was investigated. The stress-strain curves demonstrated an apparent elastic-perfectly plastic behavior with elastic modulus of 7.6±1.5GPa and large irreversible strains that exceeded 220%. The large fiber stretch ratios were the result of a cascade of periodic necks that formed during cold drawing of the nanofibers.

  2. Methods for characterization of mechanical and electrical prosthetic vacuum pumps.

    PubMed

    Komolafe, Oluseeni; Wood, Sean; Caldwell, Ryan; Hansen, Andrew; Fatone, Stefania

    2013-01-01

    Despite increasingly widespread adoption of vacuum-assisted suspension systems in prosthetic clinical practices, there remain gaps in the body of scientific knowledge guiding clinicians' choices of existing products. In this study, we identified important pump-performance metrics and developed techniques to objectively characterize the evacuation performance of prosthetic vacuum pumps. The sensitivity of the proposed techniques was assessed by characterizing the evacuation performance of two electrical (Harmony e-Pulse [Ottobock; Duderstadt, Germany] and LimbLogic VS [Ohio Willow Wood; Mt. Sterling, Ohio]) and three mechanical (Harmony P2, Harmony HD, and Harmony P3 [Ottobock]) prosthetic pumps in bench-top testing. Five fixed volume chambers ranging from 33 cm(3) (2 in.(3)) to 197 cm(3) (12 in.(3)) were used to represent different air volume spaces between a prosthetic socket and a liner-clad residual limb. All measurements were obtained at a vacuum gauge pressure of 57.6 kPa (17 inHg). The proposed techniques demonstrated sensitivity to the different electrical and mechanical pumps and, to a lesser degree, to the different setting adjustments of each pump. The sensitivity was less pronounced for the mechanical pumps, and future improvements for testing of mechanical vacuum pumps were proposed. Overall, this study successfully offers techniques feasible as standards for assessing the evacuation performance of prosthetic vacuum pump devices.

  3. Assessment of Proper Bonding Methods and Mechanical Characterization FPGA CQFPs

    NASA Technical Reports Server (NTRS)

    Davis, Milton C.

    2008-01-01

    This presentation discusses fractured leads on field-programmable gate array (FPGA) during flight vibration. Actions taken to determine root cause and resolution of the failure include finite element analysis (FEA) and vibration testing and scanning electron microscopy (with X-ray microanalysis) and energy dispersive spectrometry (SEM/EDS) failure assessment. Bonding methods for surface mount parts is assessed, including critical analysis and assessment of random fatigue damage. Regarding ceramic quad flat pack (CQFP) lead fracture, after disassembling the attitude control electronics (ACE) configuration, photographs showed six leads cracked on FPGA RTSX72SU-1 CQ208B package located on the RWIC card. An identical package (FPGA RTSX32SU-1 CQ208B) mounted on the RWIC did not results in cracked pins due to vibration. FPGA lead failure theories include workmanship issues in the lead-forming, material defect in the leads of the FPGA packages, and the insecure mounting of the board in the card guides, among other theories. Studies were conducted using simple calculations to determine the response and fatigue life of the package. Shorter packages exhibited more response when loaded by out-of-plane displacement of PCB while taller packages exhibit more response when loaded by in-plane acceleration of PCB. Additionally, under-fill did not contribute to reducing stress in leads due to out-of-plane PCB loading or from component twisting, as much as corner bonding. The combination of corner bond and under-fill is best to address mechanical and thermal S/C environment. Test results of bonded parts showed reduced (dampened) amplitude and slightly shifted peaks at the un-bonded natural frequency and an additional response at the bonded frequency. Stress due to PCBB out-of-plane loading was decreased on in the corners when only a corner bond was used. Future work may address CQFP fatigue assessment, including the investigation of discrepancy in predicted fatigue damage, as well as

  4. Nondestructive Methods to Characterize Rock Mechanical Properties at Low-Temperature: Applications for Asteroid Capture Technologies

    NASA Astrophysics Data System (ADS)

    Savage, Kara A.

    Recent government initiatives and commercial activities have targeted asteroids for in situ material characterization, manipulation, and possible resource extraction. Most of these activities and missions have proposed significant robotic components, given the risks and costs associated with manned missions. To successfully execute these robotic activities, detailed mechanical characteristics of the target space bodies must be known prior to contact, in order to appropriately plan and direct the autonomous robotic protocols. Unfortunately, current estimates of asteroid mechanical properties are based on limited direct information, and significant uncertainty remains specifically concerning internal structures, strengths, and elastic properties of asteroids. One proposed method to elucidate this information is through in situ, nondestructive testing of asteroid material immediately after contact, but prior to any manipulation or resource extraction activities. While numerous nondestructive rock characterization techniques have been widely deployed for terrestrial applications, these methods must be adapted to account for unique properties of asteroid material and environmental conditions of space. For example, asteroid surface temperatures may range from -100°C to 30°C due to diurnal cycling, and these low temperatures are especially noteworthy due to their deleterious influence on non-destructive testing. As a result, this thesis investigates the effect of low temperature on the mechanical characteristics and nondestructive technique responses of rock material. Initially, a novel method to produce low temperature rock samples was developed. Dry ice and methanol cooling baths of specific formulations were used to decrease rock to temperatures ranging from -60°C to 0°C. At these temperatures, shale, chalk, and limestone rock samples were exposed to several nondestructive and conventional mechanical tests, including Schmidt hammer, ultrasonic pulse velocity, point

  5. Characterization methods of bone-implant-interfaces of bioresorbable and titanium implants by fracture mechanical means.

    PubMed

    Tschegg, E K; Lindtner, R A; Doblhoff-Dier, V; Stanzl-Tschegg, S E; Holzlechner, G; Castellani, C; Imwinkelried, T; Weinberg, A

    2011-07-01

    Bioresorbable materials for implants have become increasingly researched over the last years. The bone-implant-interfaces of three different implant materials, namely a new bioresorbable magnesium alloy, a new self-reinforced polymer implant and a conventional titanium alloy, were tested using various methods: push-out tests, SEM and EDX analyses as well as surface analyses based on stereoscopic 3D pictures were conducted. The fracture energy is proposed as a very significant reference value for characterizing the mechanical performance of a bone-implant system. By using a video-extensometer system instead of, as is commonly done, tracking the movement of the crosshead in the push-out tests, the accuracy of measurement could be increased.

  6. Characterization methods

    SciTech Connect

    Glass, J.T.

    1993-01-01

    Methods discussed in this compilation of notes and diagrams are Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and other surface analysis techniques (auger electron spectroscopy, x-ray photoelectron spectroscopy, electron energy loss spectroscopy, and scanning tunnelling microscopy). A comparative evaluation of different techniques is performed. In-vacuo and in-situ analyses are described.

  7. Nano-mechanical characterization of disassembling amyloid fibrils using the Peak Force QNM method.

    PubMed

    Wang, Wenpin; Guo, Zongxia; Sun, Jing; Li, Zhibo

    2017-02-01

    The comprehensive understanding of disassembly mechanism of amyloid fibrils requires nano-scale characterization of the mechanical properties of amyloid fibrils during the disassembly process. In this work, gemini surfactant C12 C6 C12 Br2 micelles were used as a probe to disassemble Aβ(1-40) fibrils. The microstructure evolution and nano-mechanical properties of Aβ(1-40) fibrils during the disassembly process were systematically investigated by the Peak Force Quantitative Nano-mechanical (PF-QNM) technique. The results show an obvious decrease in Young's modulus of mature fibrils with high β-sheet contents (2.4 ± 1.0 GPa) in comparison to the resulting peptide/surfactant complexes (1.1 ± 0.8 GPa) with loose surface structures. Interestingly, the Young's modulus of spherical peptide/surfactant complexes on the core was more than 3 GPa. This strategy can be used as a standard protocol to investigate the interaction mechanism between amyloid fibrils and small molecules, which may open up new possibilities to explore the mechanism of relevant human diseases.

  8. "METHOD": A tool for mechanical, electrical, thermal, and optical characterization of single lens module design

    NASA Astrophysics Data System (ADS)

    Besson, Pierre; Dominguez, Cesar; Voarino, Philippe; Garcia-Linares, Pablo; Weick, Clement; Lemiti, Mustapha; Baudrit, Mathieu

    2015-09-01

    The optical characterization and electrical performance evaluation are essential in the design and optimization of a concentrator photovoltaic system. The geometry, materials, and size of concentrator optics are diverse and different environmental conditions impact their performance. CEA has developed a new concentrator photovoltaic system characterization bench, METHOD, which enables multi-physics optimization studies. The lens and cell temperatures are controlled independently with the METHOD to study their isolated effects on the electrical and optical performance of the system. These influences can be studied in terms of their effect on optical efficiency, focal distance, spectral sensitivity, electrical efficiency, or cell current matching. Furthermore, the irradiance map of a concentrator optic can be mapped to study its variations versus the focal length or the lens temperature. The present work shows this application to analyze the performance of a Fresnel lens linking temperature to optical and electrical performance.

  9. New Method for Characterizing the State of Optical and Opto-Mechanical Systems

    NASA Technical Reports Server (NTRS)

    Keski-Kuha, Ritva; Saif, Babak; Feinberg, Lee; Chaney, David; Bluth, Marcel; Greenfield, Perry; Hack, Warren; Smith, Scott; Sanders, James

    2014-01-01

    James Webb Space Telescope Optical Telescope Element (OTE) is a three mirror anastigmat consisting of a 6.5 m primary mirror (PM), secondary mirror (SM) and a tertiary mirror. The primary mirror is made out of 18 segments. The telescope and instruments will be assembled at Goddard Space Flight Center (GSFC) to make it the Optical Telescope Element-Integrated Science Instrument Module (OTIS). The OTIS will go through environmental testing at GSFC before being transported to Johnson Space Center for testing at cryogenic temperature. The objective of the primary mirror Center of Curvature test (CoC) is to characterize the PM before and after the environmental testing for workmanship. This paper discusses the CoC test including both a surface figure test and a new method for characterizing the state of the primary mirror using high speed dynamics interferometry.

  10. Mechanical properties of polycrystalline translucent cubic boron nitride as characterized by the Vickers indentation method

    SciTech Connect

    Taniguchi, Takashi; Akaishi, Minoru; Yamaoka, Shinobu

    1996-02-01

    Mechanical properties of polycrystalline translucent cubic boron nitride (cBN) were characterized by Vickers indentation measurement. The calculated hardness decreased from 54 to 49 GPa as the load increased to 39 N, and then remained constant for values above this load. According to the relationship between crack length and applied indentation load, the formation of the median/radial type of cracks seems to take place at an applied load above 29 N. Assuming that the ratio of hardness and Young`s modulus is constant in the polycrystalline cBN, the fracture toughness, K{sub IC}, of cBN was estimated to be 5.0 {+-} 0.5 MPa {center_dot} m{sup 1/2}.

  11. Nanomechanical Pyrolytic Carbon Resonators: Novel Fabrication Method and Characterization of Mechanical Properties

    PubMed Central

    Kurek, Maksymilian; Larsen, Frederik K.; Larsen, Peter E.; Schmid, Silvan; Boisen, Anja; Keller, Stephan S.

    2016-01-01

    Micro- and nanomechanical string resonators, which essentially are highly stressed bridges, are of particular interest for micro- and nanomechanical sensing because they exhibit resonant behavior with exceptionally high quality factors. Here, we fabricated and characterized nanomechanical pyrolytic carbon resonators (strings and cantilevers) obtained through pyrolysis of photoresist precursors. The developed fabrication process consists of only three processing steps: photolithography, dry etching and pyrolysis. Two different fabrication strategies with two different photoresists, namely SU-8 2005 (negative) and AZ 5214e (positive), were compared. The resonant behavior of the pyrolytic resonators was characterized at room temperature and in high vacuum using a laser Doppler vibrometer. The experimental data was used to estimate the Young’s modulus of pyrolytic carbon and the tensile stress in the string resonators. The Young’s moduli were calculated to be 74 ± 8 GPa with SU-8 and 115 ± 8 GPa with AZ 5214e as the precursor. The tensile stress in the string resonators was 33 ± 7 MPa with AZ 5214e as the precursor. The string resonators displayed maximal quality factor values of up to 3000 for 525-µm-long structures. PMID:27428980

  12. Characterization Methods of Encapsulates

    NASA Astrophysics Data System (ADS)

    Zhang, Zhibing; Law, Daniel; Lian, Guoping

    , reliable methods which can be used to characterize these properties of encapsulates are vital. In this chapter, the state-of-art of these methods, their principles and applications, and release mechanisms are described as follows.

  13. Methods of micro- and nanoindentation for characterization of local physical and mechanical properties of multiphase materials

    NASA Astrophysics Data System (ADS)

    Tyurin, Alexander I.; Victorov, Sergey D.; Kochanov, Alexey N.; Shuklinov, Alexey V.; Pirozhkova, Tatyana S.

    2016-11-01

    Processes of local deformation and fracture of the surface of a number of rocks (ferruginous quartzite, granite, marble, serpentine, anthracite, sandstone) are studied by means of micro- and nanoindentation under high local loadings. Numerical values of elastic, plastic and strength (hardness, Young's modulus, fracture toughness, etc.) properties of rock specimens are defined in a wide range of loads and indentation depth h (from 10 nm to 50 µm). The influence of size effects on hardness is studied, including in other physical and mechanical properties of individual phases and interphase boundaries of a wide range of rocks. Moreover, nonmonotonic dependences of hardness of certain mineral components of studied rock specimens are identified on the micro- and nanoscale. It is found that the hardness of individual mineral phases naturally increases with decreasing indentation depth up to 60-120 nm depending on the type of a rock specimen and the phase type, and then begins falling. Values of the coefficient of fracture toughness, separate mineral phases and interphase fusion boundaries of different types are identified. It is revealed that hematite in ferruginous quartzite has the greatest value of the fracture toughness factor while anthracite has the lowest one. The strongest ones are boundaries of fusion of mineral components of ferruginous quartzite and the lowest ones are boundaries of individual phase fusion in anthracite.

  14. A new mechanical characterization method for thin film microactuators and its application to NiTiCi shape memory alloy

    SciTech Connect

    Seward, Kirk P.

    1999-06-01

    In an effort to develop a more full characterization tool of shape memory alloys, a new technique is presented for the mechanical characterization of microactuators and applied to SMA thin films. A test instrument was designed to utilize a spring-loaded transducer in measuring displacements with resolution of 1.5 pm and forces with resolution of 0.2 mN. Employing an out-of-plane loading method for freestanding SMA thin films, strain resolution of 30με and stress resolution of 2.5 MPa were achieved. This new testing method is presented against previous SMA characterization methods for purposes of comparison. Four mm long, 2 μm thick NiTiCu ligaments suspended across open windows were bulk micromachined for use in the out-of-plane stress and strain measurements. The fabrication process used to micromachine the ligaments is presented step-by-step, alongside methods of fabrication that failed to produce testable ligaments. Static analysis showed that 63% of the applied strain was recovered while ligaments were subjected to tensile stresses of 870 MPa. In terms of recoverable stress and recoverable strain, the ligaments achieved maximum recovery of 700 MPa and 3.0% strain. No permanent deformations were seen in any ligament during deflection measurements. Maximum actuation forces and displacements produced by the 4 mm ligaments situated on 1 cm square test chips were 56 mN and 300 μm, respectively. Fatigue analysis of the ligaments showed degradation in recoverable strain from 0.33% to 0.24% with 200,000 cycles, corresponding to deflections of 90 μm and forces of 25 mN. Cycling also produced a wavering shape memory effect late in ligament life, leading to broad inconsistencies of as much as 35% deviation from average. Unexpected phenomena like stress-induced martensitic twinning that leads to less recoverable stress and the shape memory behavior of long life devices are addressed. Finally, a model for design of microactuators using shape memory alloys is presented

  15. Characterization of freshly retrieved preantral follicles using a low-invasive, mechanical isolation method extended to different ruminant species.

    PubMed

    Langbeen, A; Jorssen, E P A; Fransen, E; Rodriguez, A P A; García, M Chong; Leroy, J L M R; Bols, P E J

    2015-10-01

    Due to the increased interest in preantral follicular physiology, non-invasive retrieval and morphological classification are crucial. Therefore, this study aimed: (1) to standardize a minimally invasive isolation protocol, applicable to three ruminant species; (2) to morphologically classify preantral follicles upon retrieval; and (3) to describe morphological features of freshly retrieved follicles compared with follicle characteristics using invasive methods. Bovine, caprine and ovine ovarian cortex strips were retrieved from slaughterhouse ovaries and dispersed. This suspension was filtered, centrifuged, re-suspended and transferred to a Petri dish, to which 0.025 mg/ml neutral red (NR) was added to assess the viability of the isolated follicles. Between 59 and 191 follicles per follicle class and per species were collected and classified by light microscopy, based on follicular cell morphology. Subsequently, follicle diameters were measured. The proposed isolation protocol was applicable to all three species and showed a significant, expected increase in diameter with developmental stage. With an average diameter of 37 ± 5 μm for primordial follicles, 47 ± 6.3 μm for primary follicles and 67.1 ± 13.1 μm for secondary follicles, no significant difference in diameter among the three species was observed. Bovine, caprine and ovine follicles (63, 59 and 50% respectively) were graded as viable upon retrieval. Using the same morphological characteristics as determined by invasive techniques [e.g. haematoxylin-eosin (HE) sections], cumulus cell morphology and follicle diameter could be used routinely to classify freshly retrieved follicles. Finally, we applied a mechanical, minimally invasive, follicle isolation protocol and extended it to three ruminant species, yielding viable preantral follicles without compromising further in vitro processing and allowing routine follicle characterization upon retrieval.

  16. Waste Characterization Methods

    SciTech Connect

    Vigil-Holterman, Luciana R.; Naranjo, Felicia Danielle

    2016-02-02

    This report discusses ways to classify waste as outlined by LANL. Waste Generators must make a waste determination and characterize regulated waste by appropriate analytical testing or use of acceptable knowledge (AK). Use of AK for characterization requires several source documents. Waste characterization documentation must be accurate, sufficient, and current (i.e., updated); relevant and traceable to the waste stream’s generation, characterization, and management; and not merely a list of information sources.

  17. Inverse characterization method for mechanical properties of strain/strain-rate/temperature/temperature-history dependent steel sheets and its application for hot press forming

    NASA Astrophysics Data System (ADS)

    Kim, Hyunki; Kim, Dongun; Ahn, Kanghwan; Yoo, Donghoon; Son, Hyun-Sung; Kim, Gyo-Sung; Chung, Kwansoo

    2015-09-01

    In order to measure the flow curves of steel sheets at high temperatures, which are dependent on strain and strain rate as well as temperature and temperature history, a tensile test machine and specimens were newly developed in this work. Besides, an indirect method to characterize mechanical properties at high temperatures was developed by combining experiments and its numerical analysis, in which temperature history were also accounted for. Ultimately, a modified Johnson-Cook type hardening law, accounting for the dependence of hardening behavior with deterioration on strain rate as well as temperature, was successfully developed covering both pre- and post-ultimate tensile strength ranges for a hot press forming steel sheet. The calibrated hardening law obtained based on the inverse characterization method was then applied and validated for hot press forming of a 2-D mini-bumper as for distributions of temperature history, thickness and hardness considering the continuous cooling transformation diagram. The results showed reasonably good agreement with experiments

  18. Characterization and mechanical separation of metals from computer Printed Circuit Boards (PCBs) based on mineral processing methods.

    PubMed

    Sarvar, Mojtaba; Salarirad, Mohammad Mehdi; Shabani, Mohammad Amin

    2015-11-01

    In this paper, a novel mechanical process is proposed for enriching metal content of computer Printed Circuit Boards (PCBs). The PCBs are crushed and divided into three different size fractions namely: -0.59, +0.59 to 1.68 and +1.68 mm. Wet jigging and froth flotation methods are selected for metal enrichment. The coarse size fraction (+1.68 mm) is processed by jigging. The plastic free product is grinded and screened. The oversized product is separated as the first concentrate. It was rich of metal because the grinding process was selective. The undersized product is processed by froth flotation. Based on the obtained results, the middle size fraction (+0.59 to 1.68 mm) and the small size fraction (-0.59 mm) are processed by wet jigging and froth flotation respectively. The wet jigging process is optimized by investigating the effect of pulsation frequency and water flow rate. The results of examining the effect of particle size, solid to liquid ratio, conditioning time and using apolar collector showed that collectorless flotation is a promising method for separating nonmetals of PCBs. 95.6%, 97.5% and 85% of metal content of coarse size, middle size and small size fraction are recovered. The grades of obtained concentrates were 63.3%, 92.5% and 75% respectively. The total recovery is calculated as 95.64% and the grade of the final concentrate was 71.26%. Determining the grade of copper and gold in the final product reveals that 4.95% of copper and 24.46% of gold are lost during the concentration. The major part of the lost gold is accumulated in froth flotation tail.

  19. A novel inorganic precipitation-peptization method for VO2 sol and VO2 nanoparticles preparation: Synthesis, characterization and mechanism.

    PubMed

    Li, Yao; Jiang, Peng; Xiang, Wei; Ran, Fanyong; Cao, Wenbin

    2016-01-15

    In this paper, a simple, safe and cost-saving precipitation-peptization method was proposed to prepare VO2 sol by using inorganic VOSO4-NH3⋅H2O-H2O2 reactants system in air under room temperature. In this process, VOSO4 was firstly precipitated to form VO(OH)2, then monometallic species of VO(O2)(OH)(-) were formed through the coordination between VO(OH)2 and H2O2. The rearrangement of VO(O2)(OH)(-) in a nonplanar pattern and intermolecular condensation reactions result in multinuclear species. Finally, VO2 sol is prepared through the condensation reactions between the multinuclear species. After drying the obtained sol at 40°C, VO2 xerogel exhibiting monoclinic crystal structure with the space group of C2/m was prepared. The crystal structure of VO2 nanoparticles was transferred to monoclinic crystal structure with the space group of P21/c (VO2(M)) by annealing the xerogel at 550°C. Both XRD and TEM analysis indicated that the nanoparticles possess good crystallinity with crystallite size of 34.5nm as estimated by Scherrer's method. These results suggest that the VO2 sol has been prepared successfully through the proposed simple method.

  20. Advanced Fine Particulate Characterization Methods

    SciTech Connect

    Steven Benson; Lingbu Kong; Alexander Azenkeng; Jason Laumb; Robert Jensen; Edwin Olson; Jill MacKenzie; A.M. Rokanuzzaman

    2007-01-31

    The characterization and control of emissions from combustion sources are of significant importance in improving local and regional air quality. Such emissions include fine particulate matter, organic carbon compounds, and NO{sub x} and SO{sub 2} gases, along with mercury and other toxic metals. This project involved four activities including Further Development of Analytical Techniques for PM{sub 10} and PM{sub 2.5} Characterization and Source Apportionment and Management, Organic Carbonaceous Particulate and Metal Speciation for Source Apportionment Studies, Quantum Modeling, and High-Potassium Carbon Production with Biomass-Coal Blending. The key accomplishments included the development of improved automated methods to characterize the inorganic and organic components particulate matter. The methods involved the use of scanning electron microscopy and x-ray microanalysis for the inorganic fraction and a combination of extractive methods combined with near-edge x-ray absorption fine structure to characterize the organic fraction. These methods have direction application for source apportionment studies of PM because they provide detailed inorganic analysis along with total organic and elemental carbon (OC/EC) quantification. Quantum modeling using density functional theory (DFT) calculations was used to further elucidate a recently developed mechanistic model for mercury speciation in coal combustion systems and interactions on activated carbon. Reaction energies, enthalpies, free energies and binding energies of Hg species to the prototype molecules were derived from the data obtained in these calculations. Bimolecular rate constants for the various elementary steps in the mechanism have been estimated using the hard-sphere collision theory approximation, and the results seem to indicate that extremely fast kinetics could be involved in these surface reactions. Activated carbon was produced from a blend of lignite coal from the Center Mine in North Dakota and

  1. Mechanical Characterization of Mancos Shale

    NASA Astrophysics Data System (ADS)

    Broome, S.; Ingraham, M. D.; Dewers, T. A.

    2015-12-01

    A series of tests on Mancos shale have been undertaken to determine the failure surface and to characterize anisotropy. This work supports additional studies which are being performed on the same block of shale; fracture toughness, permeability, and chemical analysis. Mechanical tests are being conducted after specimens were conditioned for at least two weeks at 70% constant relative humidity conditions. Specimens are tested under drained conditions, with the constant relative humidity condition maintained on the downstream side of the specimen. The upstream is sealed. Anisotropy is determined through testing specimens that have been cored parallel and perpendicular to the bedding plane. Preliminary results show that when loaded parallel to bedding the shale is roughly 50% weaker. Test are run under constant mean stress conditions when possible (excepting indirect tension, unconfined compression, and hydrostatic). Tests are run in hydrostatic compaction to the desired mean stress, then differential stress is applied axially in displacement control to failure. The constant mean stress condition is maintained by decreasing the confining pressure by half of the increase in the axial stress. Results will be compared to typical failure criteria to investigate the effectiveness of capturing the behavior of the shale with traditional failure theory. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2015-6107 A.

  2. Comparison of two experimental methods for the mechanical characterization of thin or thick films from the study of micromachined circular diaphragms.

    PubMed

    Malhaire, C

    2012-05-01

    The purpose of this study was to compare two experimental methods and evaluate the effectiveness of a set of analytical models in order to measure the initial stress and the Young's modulus value of thin and thick film materials. Two types of experiments were performed on micromachined circular diaphragms: bulge testing and vibrometry. The range of validity and accuracy of the analytical models with respect to the vibration of the diaphragms was discussed from the finite element simulations. It was shown that the a/t ratio should be considered carefully to determine the value of the Young's modulus by vibrometry with an acceptable error. A relative error of approximately ±10% on E was obtained for a/t ≤ 750. For 750 ≤ a/t ≤ 1000, the value of the dimensionless parameter k must also be considered. It has been shown that the residual stress value can be obtained with an accuracy of 10% or less, given that k > 12. As an illustration, experimental methods and models were applied to the characterization of a thick electroplated gold film and a sputter-deposited Inconel thin film. Circular structures were defined by vertical sidewalls etched on the back of a Si wafer using the deep reactive ion etching technique. In addition to analytical models, parametric finite element simulations and a design optimization technique were used to determine the material's mechanical properties. The static deflections of the diaphragms were measured as a function of the applied pressure. The resonant frequencies and mode shapes of the vibrating structures were observed under vacuum by white-light interferometric microscopy. For gold, it was found that E = (53 ± 20) GPa and σ(0) = (180 ± 10) MPa. For Inconel, it was found that E = (157 ± 14) GPa and σ(0) = (172 ± 5) MPa.

  3. Comparison of two experimental methods for the mechanical characterization of thin or thick films from the study of micromachined circular diaphragms

    NASA Astrophysics Data System (ADS)

    Malhaire, C.

    2012-05-01

    The purpose of this study was to compare two experimental methods and evaluate the effectiveness of a set of analytical models in order to measure the initial stress and the Young's modulus value of thin and thick film materials. Two types of experiments were performed on micromachined circular diaphragms: bulge testing and vibrometry. The range of validity and accuracy of the analytical models with respect to the vibration of the diaphragms was discussed from the finite element simulations. It was shown that the a/t ratio should be considered carefully to determine the value of the Young's modulus by vibrometry with an acceptable error. A relative error of approximately ±10% on E was obtained for a/t ≤ 750. For 750 ≤ a/t ≤ 1000, the value of the dimensionless parameter k must also be considered. It has been shown that the residual stress value can be obtained with an accuracy of 10% or less, given that k > 12. As an illustration, experimental methods and models were applied to the characterization of a thick electroplated gold film and a sputter-deposited Inconel thin film. Circular structures were defined by vertical sidewalls etched on the back of a Si wafer using the deep reactive ion etching technique. In addition to analytical models, parametric finite element simulations and a design optimization technique were used to determine the material's mechanical properties. The static deflections of the diaphragms were measured as a function of the applied pressure. The resonant frequencies and mode shapes of the vibrating structures were observed under vacuum by white-light interferometric microscopy. For gold, it was found that E = (53 ± 20) GPa and σ0 = (180 ± 10) MPa. For Inconel, it was found that E = (157 ± 14) GPa and σ0 = (172 ± 5) MPa.

  4. Processing and Mechanical Characterization of Polyurea Aerogels

    DTIC Science & Technology

    2011-01-01

    PROCESSING AND MECHANICAL CHARACTERIZATION OF POLYUREA AEROGELS by JARED MICHAEL LOEBS A THESIS Presented to the Faculty of the Graduate School of...SUBTITLE Processing and Mechanical Characterization of Polyurea Aerogels 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6...distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT The use of aerogels historically has been limited to extreme cases largely in part to the nature

  5. Mechanical and Thermal Characterization of Silica Nanocomposites

    NASA Astrophysics Data System (ADS)

    Cunningham, Anthony Lamar

    Polymer nanocomposites are a class of materials containing nanoparticles with a large interfacial surface area. Only a small quantity of nanoparticles are needed to provide superior multifunctional properties; such as mechanical, thermal, electrical, and moisture absorption properties in polymers. Nanoparticles tend to agglomerate, so special techniques are required for homogeneous distribution. Nanosilica is now readily available as colloidal sols, for example; Nanopox RTM F400 (supplied by Evonik Nanoresins AG, Germany). The nanoparticles are first synthesized from aqueous sodium silicate solution, and then undergo a surface modification process with organosilane and matrix exchange. F400 contains 40%wt silica nanoparticles colloidally dispersed in a DGEBA epoxy resin. The mean particle diameter is about 20 nm with a narrow distribution range of about 5 to 35 nm. The objectives of this study are to develop a reproducible processing method for nanosilica enhanced resin systems used in the manufacturing of fiber reinforced composites that will be characterized for mechanical and thermal properties. Research has concluded that shows improvements in the properties of the matrix material when processed in loading variations of 0 to 25%wt silica nanoparticles. The loadings were also used to manufacture fiberglass reinforced nanocomposite laminates and also tested for mechanical and thermal properties.

  6. Comparison of the direct burst pressure and the ring tensile test methods for mechanical characterization of tissue-engineered vascular substitutes.

    PubMed

    Laterreur, Véronique; Ruel, Jean; Auger, François A; Vallières, Karine; Tremblay, Catherine; Lacroix, Dan; Tondreau, Maxime; Bourget, Jean-Michel; Germain, Lucie

    2014-06-01

    Tissue engineering provides a promising alternative for small diameter vascular grafts, especially with the self-assembly method. It is crucial that these grafts possess mechanical properties that allow them to withstand physiological flow and pressure without being damaged. Therefore, an accurate assessment of their mechanical properties, especially the burst pressure, is essential prior to clinical release. In this study, the burst pressure of self-assembled tissue-engineered vascular substitutes was first measured by the direct method, which consists in pressurizing the construct with fluid until tissue failure. It was then compared to the burst pressure estimated by Laplace׳s law using data from a ring tensile test. The major advantage of this last method is that it requires a significantly smaller tissue sample. However, it has been reported as overestimating the burst pressure compared to a direct measurement. In the present report, it was found that an accurate estimation of the burst pressure may be obtained from a ring tensile test when failure internal diameter is used as the diameter parameter in Laplace׳s law. Overestimation occurs with the method previously reported, i.e. when the unloaded internal diameter is used for calculations. The estimation of other mechanical properties was also investigated. It was demonstrated that data from a ring tensile test provide an accurate estimate of the failure strain and the stiffness of the constructs when compared to measurements with the direct method.

  7. Mechanical characterization of seismic base isolation elastomers

    SciTech Connect

    Kulak, R.F.; Hughes, T.H.

    1991-01-01

    From the various devices proposed for seismic isolators, the laminated elastomer bearing is emerging as the preferred device for large buildings/structures, such as nuclear reactor plants. The laminated bearing is constructed from alternating thin layers of elastomer and metallic plates (shims). The elastomer is usually a carbon filled natural rubber that exhibits damping when subjected to shear. Recently, some blends of natural and synthetic rubbers have appeared. Before candidate elastomers can be used in seismic isolation bearings, their response to design-basis loads and beyond- design-basis loads must be determined. This entails the development of constitutive models and and then the determination of associated material parameters through specimen testing. This paper describes the methods used to obtain data for characterizing the mechanical response of elastomers used for seismic isolation. The data provides a data base for use in determining material parameters associated with nonlinear constitutive models. In addition, the paper presents a definition for a damping ratio that does not exhibit the usual reduction at higher strain cycles. 2 refs., 6 figs., 1 tab.

  8. Finite element model of surface acoustic wave method for mechanical characterization of patterned thin films of the ultra-large scaled integrated interconnect.

    PubMed

    Xiao, Xia; Shan, Xingmeng; Tao, Ye; Sun, Yuan; Kikkawa, Takamaro

    2013-02-01

    Surface acoustic waves (SAWs) technique is a promising method to determine the mechanical properties of thin low dielectric constant (low-k) dielectrics by matching the experimental dispersion curve with the theoretical dispersion curves. However, it is difficult to calculate the dispersion curves when SAWs propagate along patterned structure. In this paper, finite element method (FEM) is applied to obtain the numerical dispersion results of SAWs propagating on patterned film. Periodic boundary condition and plane-strain model is used to improve the computation speed. Four structures of bulk silicon, single layered low-k film, two layered Cu and SiO2 film, and patterned film, are simulated in this paper. The dispersion curves of single low-k films derived from the FEM simulation agree very well with those calculated by traditional method, which verifies the correct employment of the FEM approach. Dispersion curves of two patterned film structure of Cu and SiO2 with difference metal wire width are obtained. Effective Young's moduli are achieved by fitting the FEM simulated results with those of traditional theoretical calculation through least square error method.

  9. Computational Methods in Continuum Mechanics

    DTIC Science & Technology

    1993-11-30

    ftruet11ft bwalch.Aq 0.4.oiqn 04ta tou.MtC’ gahimtc" n matod .nAfitang In@ data 01#04141. OAd co0noIDW~ng And tft@nq the ~OIWCI&Qn of 1,onjt~omt .nd~ml...AD-A27S 560 DTIC\\3\\Ul3 10 S ELECTE1 FEB 9 1994 I c I £ COMPUTATIONAL METHODS IN CONTINUUM MECHANICS By Bolindra N . Borah N.C. A&T State University...PAGE 0me No 0.704-0158 io (reorovtnq burden ’Of .t..i e’iortion of Information is estimted to ’Adoraw 1O4 .0 e~o- * n th.n I~c ot.. "o.vw.n. q

  10. Mechanical property characterization of intraply hybrid composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sinclair, J. H.

    1979-01-01

    An investigation was conducted to characterize the mechanical properties of intraply hybrids made from graphite fiber/epoxy matrix (primary composites) hybridized with varying amounts of secondary composites made from S-glass or Kevlar 49 fibers. The tests were conducted using thin laminates having the same thickness. The specimens for these tests were instrumented with strain gages to determine stress-strain behavior. Significant results are included.

  11. Zeolite membranes: microstructure characterization and permeation mechanisms.

    PubMed

    Yu, Miao; Noble, Richard D; Falconer, John L

    2011-11-15

    Since their first synthesis in the 1940s, zeolites have found wide applications in catalysis, ion-exchange, and adsorption. Although the uniform, molecular-size pores of zeolites and their excellent thermal and chemical stability suggest that zeolites could be an ideal membrane material, continuous polycrystalline zeolite layers for separations were first prepared in the 1990s. Initial attempts to grow continuous zeolite layers on porous supports by in situ hydrothermal synthesis have resulted in membranes with the potential to separate molecules based on differences in molecular size and adsorption strength. Since then, further synthesis efforts have led to the preparation of many types of zeolite membranes and better quality membranes. However, the microstructure features of these membranes, such as defect size, number, and distribution as well as structure flexibility were poorly understood, and the fundamental mechanisms of permeation (adsorption and diffusion), especially for mixtures, were not clear. These gaps in understanding have hindered the design and control of separation processes using zeolite membranes. In this Account, we describe our efforts to characterize microstructures of zeolite membranes and to understand the fundamental adsorption and diffusion behavior of permeating solutes. This Account will focus on the MFI membranes which have been the most widely used but will also present results on other types of zeolite membranes. Using permeation, x-ray diffraction, and optical measurements, we found that the zeolite membrane structures are flexible. The size of defects changed due to adsorption and with variations in temperature. These changes in defect sizes can significantly affect the permeation properties of the membranes. We designed methods to measure mixture adsorption in zeolite crystals from the liquid phase, pure component adsorption in zeolite membranes, and diffusion through zeolite membranes. We hope that better understanding can lead

  12. Mechanical Characterization of Rigid Polyurethane Foams

    SciTech Connect

    Lu, Wei-Yang

    2014-12-01

    Foam materials are used to protect sensitive components from impact loading. In order to predict and simulate the foam performance under various loading conditions, a validated foam model is needed and the mechanical properties of foams need to be characterized. Uniaxial compression and tension tests were conducted for different densities of foams under various temperatures and loading rates. Crush stress, tensile strength, and elastic modulus were obtained. A newly developed confined compression experiment provided data for investigating the foam flow direction. A biaxial tension experiment was also developed to explore the damage surface of a rigid polyurethane foam.

  13. Polylactides-Methods of synthesis and characterization.

    PubMed

    Pretula, Julia; Slomkowski, Stanislaw; Penczek, Stanislaw

    2016-12-15

    Polylactides with various molar masses, microstructures and crystallinities are used as degradable and biocompatible polymers suitable for preparation of drug carriers and temporary medical implants. This paper presents state of current knowledge on synthesis of lactic acids, high purity lactide monomers and their polymerization. Syntheses of high molar mass polylactides by polycondensation of lactic acid and by ring-opening polymerization of lactides are described and their advantages and disadvantages are discussed. Mechanisms of lactide polymerization initiated by metal alkoxides are described. There are presented also results of more recent studies of polymerization initiated with the so-called "no metal" organocatalysts; both anionic and cationic. Presented are advantages and limitations of synthesis of PLA by all the major polymerization processes until now. Some properties of PLA and most important methods used for PLA characterization are also described.

  14. Optical and Mechanical Characterization of Chemical Mechanical Planarization Pad Surfaces

    NASA Astrophysics Data System (ADS)

    Ting Sun,; Yun Zhuang,; Leonard Borucki,; Ara Philipossian,

    2010-04-01

    Both contact and non-contact methods are used to analyze surface properties of three types of chemical mechanical planarization (CMP) pads: plain, XY grooved, and concentrically grooved. Optical interferometry is used to probe the pad surface without contact and to produce a surface height probability density function (PDF). The right hand contacting tail of the PDF is often found to be exponential for CMP pads and a decay length (λ) as a measure of pad surface abruptness can be extracted. An incremental loading device is developed and used to measure the pad surface mechanical response. A pad-wafer contact model based on Greenwood and Williamson theory is used to interpret the nonlinear features of the pad surface compression data, which, furthermore, enables independent calculation of λ from mechanical data. Surface abruptness (λ) extracted from both methods (optical and mechanical) is found to be consistent for all three types of pads. No significant difference is observed in the pad surface abruptness among the three types of pads.

  15. Mechanical property characterization of intraply hybrid composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sinclair, J. H.

    1979-01-01

    An investigation of the mechanical properties of intraply hybrids made from graphite fiber/epoxy matrix hybridized with secondary S-glass or Kevlar 49 fiber composites is presented. The specimen stress-strain behavior was determined, showing that mechanical properties of intraply hybrid composites can be measured with available methods such as the ten-degree off-axis test for intralaminar shear, and conventional tests for tensile, flexure, and Izod impact properties. The results also showed that combinations of high modulus graphite/S-glass/epoxy matrix composites exist which yield intraply hybrid laminates with the best 'balanced' properties, and that the translation efficiency of mechanical properties from the constituent composites to intraply hybrids may be assessed with a simple equation.

  16. Battery Vent Mechanism And Method

    DOEpatents

    Ching, Larry K. W.

    2000-02-15

    Disclosed herein is a venting mechanism for a battery. The venting mechanism includes a battery vent structure which is located on the battery cover and may be integrally formed therewith. The venting mechanism includes an opening extending through the battery cover such that the opening communicates with a plurality of battery cells located within the battery case. The venting mechanism also includes a vent manifold which attaches to the battery vent structure. The vent manifold includes a first opening which communicates with the battery vent structure opening and second and third openings which allow the vent manifold to be connected to two separate conduits. In this manner, a plurality of batteries may be interconnected for venting purposes, thus eliminating the need to provide separate vent lines for each battery. The vent manifold may be attached to the battery vent structure by a spin-welding technique. To facilitate this technique, the vent manifold may be provided with a flange portion which fits into a corresponding groove portion on the battery vent structure. The vent manifold includes an internal chamber which is large enough to completely house a conventional battery flame arrester and overpressure safety valve. In this manner, the vent manifold, when installed, lessens the likelihood of tampering with the flame arrester and safety valve.

  17. Structural Embeddings: Mechanization with Method

    NASA Technical Reports Server (NTRS)

    Munoz, Cesar; Rushby, John

    1999-01-01

    The most powerful tools for analysis of formal specifications are general-purpose theorem provers and model checkers, but these tools provide scant methodological support. Conversely, those approaches that do provide a well-developed method generally have less powerful automation. It is natural, therefore, to try to combine the better-developed methods with the more powerful general-purpose tools. An obstacle is that the methods and the tools often employ very different logics. We argue that methods are separable from their logics and are largely concerned with the structure and organization of specifications. We, propose a technique called structural embedding that allows the structural elements of a method to be supported by a general-purpose tool, while substituting the logic of the tool for that of the method. We have found this technique quite effective and we provide some examples of its application. We also suggest how general-purpose systems could be restructured to support this activity better.

  18. Thermo-mechanical characterization of silicone foams

    SciTech Connect

    Rangaswamy, Partha; Smith, Nickolaus A.; Cady, Carl M.; Lewis, Matthew W.

    2015-10-01

    Cellular solids such as elastomeric foams are used in many structural applications to absorb and dissipate energy, due to their light weight (low density) and high energy absorption capability. In this paper we will discuss foams derived from S5370, a silicone foam formulation developed by Dow Corning. In the application presented, the foam is consolidated into a cushion component of constant thickness but variable density. A mechanical material model developed by Lewis (2013), predicts material response, in part, as a function of relative density. To determine the required parameters for this model we have obtained the mechanical response in compression for ambient, cold and hot temperatures. The variable density cushion provided samples sufficient samples so that the effect of sample initial density on the mechanical response could be studied. The mechanical response data showed extreme sensitivity to relative density. We also observed at strains corresponding to 1 MPa a linear relationship between strain and initial density for all temperatures. Samples taken from parts with a history of thermal cycling demonstrated a stiffening response that was a function of temperature, with the trend of more stiffness as temperature increased above ambient. This observation is in agreement with the entropic effects on the thermo-mechanical behavior of silicone polymers. In this study, we present the experimental methods necessary for the development of a material model, the testing protocol, analysis of test data, and a discussion of load (stress) and gap (strain) as a function of sample initial densities and temperatures

  19. Electro-mechanical characterization of structural supercapacitors

    NASA Astrophysics Data System (ADS)

    Gallagher, T.; LaMaster, D.; Ciocanel, C.; Browder, C.

    2012-04-01

    The paper presents electrical and mechanical properties of structural supercapacitors and discusses limitations associated with the approach taken for the electrical properties evaluation. The structural supercapacitors characterized in this work had the electrodes made of carbon fiber weave, separator made of several cellulose based products, and the solid electrolyte made as PEGDGE based polymer blend. The reported electrical properties include capacitance and leakage resistance; the former was measured using cyclic voltammetry. Mechanical properties have been evaluated thorough tensile and three point bending tests performed on structural supercapacitor coupons. The results indicate that the separator material plays an important role on the electrical as well as mechanical properties of the structural capacitor, and that Celgard 3501 used as separator leads to most benefits for both mechanical and electrical properties. Specific capacitance and leakage resistance as high as 1.4kF/m3 and 380kΩ, respectively, were achieved. Two types of solid polymer electrolytes were used in fabrication, with one leading to higher and more consistent leakage resistance values at the expense of a slight decrease in specific capacitance when compared to the other SPE formulation. The ultimate tensile strength and modulus of elasticity of the developed power storage composite were evaluated at 466MPa and 18.9MPa, respectively. These values are 58% and 69% of the tensile strength and modulus of elasticity values measured for a single layer composite material made with the same type of carbon fiber and with a West System 105 epoxy instead of solid polymer electrolyte.

  20. New method for the fabrication of highly osteoconductive β-1,3-glucan/HA scaffold for bone tissue engineering: Structural, mechanical, and biological characterization.

    PubMed

    Klimek, Katarzyna; Przekora, Agata; Pałka, Krzysztof; Ginalska, Grażyna

    2016-10-01

    Recent studies have shown that thermal method for β-1,3-glucan (curdlan) gelation performed at temperature above 80°C enables fabrication of biocompatible bone scaffolds. The aim of this study was to establish new method for fabrication of β-1,3-glucan/hydroxyapatite (glu/HA) scaffold using ion-exchanging dialysis for curdlan gelation that allows for the modifications of the glu/HA material with thermo-sensitive agents like growth factors or adhesive proteins. Obtained results reveal that fabricated scaffold appears to be highly osteoconductive as it is nontoxic, promotes osteoblast growth and proliferation as well as increases bone alkaline phosphatase level thereby enhancing cell differentiation. It was demonstrated that developed new method for the glu/HA scaffold fabrication allows to obtain material that not only can be modified with thermo-sensitive agents at the stage of production process but also is a promising candidate for bone tissue engineering applications to act as a framework for osteoblasts to spread and form new bone. It should be noted that dialysis method for curdlan gelation has never been used before to fabricate bone scaffold. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2528-2536, 2016.

  1. Evaluation of Electrochemical Methods for Electrolyte Characterization

    NASA Technical Reports Server (NTRS)

    Heidersbach, Robert H.

    2001-01-01

    This report documents summer research efforts in an attempt to develop an electrochemical method of characterizing electrolytes. The ultimate objective of the characterization would be to determine the composition and corrosivity of Martian soil. Results are presented using potentiodynamic scans, Tafel extrapolations, and resistivity tests in a variety of water-based electrolytes.

  2. Characterization, mechanical, and corrosion properties of chromium carbide films by using a 90° bend magnetic filtered cathodic vacuum arc (FCVA) method

    NASA Astrophysics Data System (ADS)

    Wang, Chih-Chiang; Lin, Chun-Chun; Chen, Ya-Chyi; Shieu, Fuh-Sheng; Shih, Han C.

    2016-09-01

    The 90° bend magnetic FCVA that equipped with the target of Cr (99.95%) and C2H2/Ar gas mixture deposited a high quality of chromium carbide films on the AISI D2 steel and Si wafer. The FCVA has been employed to eliminate the macroparticles during the film deposition. Various deposition temperatures of ambient temperature, 300, and 500° and negative substrate bias voltages ranging from -50 to -550V were applied. The microstructure of chromium carbide films was investigated by GIXRD and HRTEM. The atomic concentrations of C and Cr were measured by AES. The chemical bonding was elucidated by XPS, showing that the total C-Cr bond contents increased with increasing deposition temperature. As the substrate bias voltage increased from -50 to -550V, the phase transformed from amorphous to crystalline Cr3C2. The mechanical properties were evaluated by nanoindetation, nanoscratch, and scratch test. The surface roughness decreased from 2.05 to 0.34nm and the friction coefficient decreased from 0.28(amorphous) to 0.22(crystalline) as the substrate bias voltage increased from -50 to -550V. The corrosion resistance showed that the Cr3C2 coated steel had the noticeable increasing with the negative bias voltage up to -550V, and the pitting corrosion did not appear on the Cr3C2 coated steel.

  3. Application of geophysical methods for fracture characterization

    SciTech Connect

    Lee, K.H.; Majer, E.L.; McEvilly, T.V. |; Morrison, H.F. |

    1990-01-01

    One of the most crucial needs in the design and implementation of an underground waste isolation facility is a reliable method for the detection and characterization of fractures in zones away from boreholes or subsurface workings. Geophysical methods may represent a solution to this problem. If fractures represent anomalies in the elastic properties or conductive properties of the rocks, then the seismic and electrical techniques may be useful in detecting and characterizing fracture properties. 7 refs., 3 figs.

  4. Radical SAM, A Novel Protein Superfamily Linking Unresolved Steps in Familiar Biosynthetic Pathways with Radical Mechanisms: Functional Characterization Using New Analysis and Information Visualization Methods

    SciTech Connect

    Sofia, Heidi J.; Chen, Guang; Hetzler, Elizabeth G.; Reyes Spindola, Jorge F.; Miller, Nancy E.

    2001-03-01

    A large protein superfamily with over 500 members has been discovered and analyzed using powerful new bioinformatics and information visualization methods. Evidence exists that these proteins generate a 5?-deoxyadenosyl radical by reductive cleavage of S-adenosylmethionine (SAM) through an unusual Fe-S center. Radical SAM superfamily proteins function in DNA precursor, vitamin, cofactor, antibiotic, and herbicide biosynthesis in a collection of basic and familiar pathways. One of the members is interferon-inducible and is considered a candidate drug target for osteoporosis. The identification of this superfamily suggests that radical-based catalysis is important in a number of previously well-studied but unresolved biochemical pathways.

  5. Multigrid methods in structural mechanics

    NASA Technical Reports Server (NTRS)

    Raju, I. S.; Bigelow, C. A.; Taasan, S.; Hussaini, M. Y.

    1986-01-01

    Although the application of multigrid methods to the equations of elasticity has been suggested, few such applications have been reported in the literature. In the present work, multigrid techniques are applied to the finite element analysis of a simply supported Bernoulli-Euler beam, and various aspects of the multigrid algorithm are studied and explained in detail. In this study, six grid levels were used to model half the beam. With linear prolongation and sequential ordering, the multigrid algorithm yielded results which were of machine accuracy with work equivalent to 200 standard Gauss-Seidel iterations on the fine grid. Also with linear prolongation and sequential ordering, the V(1,n) cycle with n greater than 2 yielded better convergence rates than the V(n,1) cycle. The restriction and prolongation operators were derived based on energy principles. Conserving energy during the inter-grid transfers required that the prolongation operator be the transpose of the restriction operator, and led to improved convergence rates. With energy-conserving prolongation and sequential ordering, the multigrid algorithm yielded results of machine accuracy with a work equivalent to 45 Gauss-Seidel iterations on the fine grid. The red-black ordering of relaxations yielded solutions of machine accuracy in a single V(1,1) cycle, which required work equivalent to about 4 iterations on the finest grid level.

  6. Thermal-Mechanical Noise Based CMUT Characterization and Sensing

    PubMed Central

    Gurun, Gokce; Hochman, Michael; Hasler, Paul; Degertekin, F. Levent

    2012-01-01

    When capacitive micromachined ultrasonic transducers (CMUTs) are monolithically integrated with custom-designed low-noise electronics, the output noise of the system can be dominated by the CMUT thermal-mechanical noise both in air and in immersion even for devices with low capacitance. Since the thermal-mechanical noise can be related to the electrical admittance of the CMUTs, this provides an effective means of device characterization. This approach yields a novel method to test the functionality and uniformity of CMUT arrays and the integrated electronics where a direct connection to CMUT array element terminals is not available. These measurements can be performed in air at the wafer level, suitable for batch manufacturing and testing. We demonstrate this method on the elements of an 800-μm diameter CMUT-on-CMOS array designed for intravascular imaging in the 10-20 MHz range. Noise measurements in air show the expected resonance behavior and spring softening effects. Noise measurements in immersion for the same array provide useful information on both the acoustic cross talk and radiation properties of the CMUT array elements. The good agreement between a CMUT model based on finite difference and boundary element method and the noise measurements validates the model and indicates that the output noise is indeed dominated by thermal-mechanical noise. The measurement method can be exploited to implement CMUT based passive sensors to measure immersion medium properties, or other parameters affecting the electro-mechanics of the CMUT structure. PMID:22718877

  7. Overview of geotechnical methods to characterize rock masses

    SciTech Connect

    Heuze, F.E.

    1981-12-01

    The methods that are used to characterize discontinuous rock masses from a geotechnical point of view are summarized. Emphasis is put on providing key references on each subject. The topics of exploration, in-situ stresses, mechanical properties, thermal properties, and hydraulic properties are addressed.

  8. Mechanical characterization and reliability of films and coatings

    NASA Astrophysics Data System (ADS)

    Thurn, Jeremy Adam

    This work describes newly-developed and conventional mechanical characterization techniques for films and coatings and the use of such techniques in conjunction with fracture models to examine the reliability of brittle film and coating systems. A wide range of film and coating systems is examined, emphasizing the generality of both the characterization techniques and the analysis methods. Emphasis is placed on systems of technological importance including dielectric films (such as silicon dioxide, amorphous silicon, silicon nitride, silicon oxy-nitride, and low-dielectric constant silsesquioxane) on silicon substrates for the microelectronics and micro-electromechanical systems (MEMS) industries, and alumina films on alumina titanium-carbide substrates for the magnetic recording head industry. Characterization techniques include depth-sensing indentation at ultra-microscopic and macroscopic dimensions ("nanoindentation" and "macroindentation," respectively), conventional Vickers hardness testing in inert and reactive environments, and substrate curvature measurements for film stress determination at elevated temperatures. Analysis is carried out using newly-developed and conventional analytic constitutive models as well as numerical simulations using finite element methods. The first part of the thesis describes the experimental techniques and analysis methods to deduce the elastic, plastic, fracture, and adhesive properties of brittle films and coatings. The second part focuses on the thermomechanical and environmental reliability of dielectric films for microelectronic applications based on experimental results and numerical analysis.

  9. The Challenge of Characterizing Operations in the Mechanisms Underlying Behavior

    ERIC Educational Resources Information Center

    Bechtel, William

    2005-01-01

    Neuroscience and cognitive science seek to explain behavioral regularities in terms of underlying mechanisms. An important element of a mechanistic explanation is a characterization of the operations of the parts of the mechanism. The challenge in characterizing such operations is illustrated by an example from the history of physiological…

  10. Characterizing the mechanical behavior of the zebrafish germ layers

    NASA Astrophysics Data System (ADS)

    Kealhofer, David; Serwane, Friedhelm; Mongera, Alessandro; Rowghanian, Payam; Lucio, Adam; Campàs, Otger

    Organ morphogenesis and the development of the animal body plan involve complex spatial and temporal control of tissue- and cell-level mechanics. A prime example is the generation of stresses by individual cells to reorganize the tissue. These processes have remained poorly understood due to a lack of techniques to characterize the local constitutive law of the material, which relates local cellular forces to the resulting tissue flows. We have developed a method for quantitative, local in vivo study of material properties in living tissue using magnetic droplet probes. We use this technique to study the material properties of the different zebrafish germ layers using aggregates of zebrafish mesendodermal and ectodermal cells as a model system. These aggregates are ideal for controlled studies of the mechanics of individual germ layers because of the homogeneity of the cell type and the simple spherical geometry. Furthermore, the numerous molecular tools and transgenic lines already developed for this model organism can be applied to these aggregates, allowing us to characterize the contributions of cell cortex tension and cell adhesion to the mechanical properties of the zebrafish germ layers.

  11. Electrochemical capacitors: mechanism, materials, systems, characterization and applications.

    PubMed

    Wang, Yonggang; Song, Yanfang; Xia, Yongyao

    2016-10-24

    Electrochemical capacitors (i.e. supercapacitors) include electrochemical double-layer capacitors that depend on the charge storage of ion adsorption and pseudo-capacitors that are based on charge storage involving fast surface redox reactions. The energy storage capacities of supercapacitors are several orders of magnitude higher than those of conventional dielectric capacitors, but are much lower than those of secondary batteries. They typically have high power density, long cyclic stability and high safety, and thus can be considered as an alternative or complement to rechargeable batteries in applications that require high power delivery or fast energy harvesting. This article reviews the latest progress in supercapacitors in charge storage mechanisms, electrode materials, electrolyte materials, systems, characterization methods, and applications. In particular, the newly developed charge storage mechanism for intercalative pseudocapacitive behaviour, which bridges the gap between battery behaviour and conventional pseudocapacitive behaviour, is also clarified for comparison. Finally, the prospects and challenges associated with supercapacitors in practical applications are also discussed.

  12. Failure mechanism characterization of platinum alloy

    NASA Technical Reports Server (NTRS)

    Rosen, J. M.; Mcfarlen, W. T.

    1986-01-01

    This article describes procedures and results of testing performed on a platinum/10-percent rhodium, thin-wall tubular product. The purpose of the testing was to develop exemplar SEM fractographs to be used to characterize failures under various environmental conditions. Conditions evaluated for the platinum alloys included high temperature, hydrogen environment, braze metal contamination, and cyclic loading.

  13. Processing and mechanical characterization of alumina laminates

    NASA Astrophysics Data System (ADS)

    Montgomery, John K.

    2002-08-01

    Single-phase ceramics that combine property gradients or steps in monolithic bodies are sought as alternatives to ceramic composites made of dissimilar materials. This work describes novel processing methods to produce stepped-density (or laminated) alumina single-phase bodies that maintain their mechanical integrity. One arrangement consists of a stiff, dense bulk material with a thin, flaw tolerant, porous exterior layer. Another configuration consists of a lightweight, low-density bulk material with a thin, hard, wear resistant exterior layer. Alumina laminates with strong interfaces have been successfully produced in this work using two different direct-casting processes. Gelcasting is a useful near-net shape processing technique that has been combined with several techniques, such as reaction bonding of aluminum oxide and the use of starch as a fugative filler, to successfully produced stepped-density alumina laminates. The other direct casting process that has been developed in this work is thermoreversible gelcasting (TRG). This is a reversible gelation process that has been used to produce near-net shape dense ceramic bodies. Also, individual layers can be stacked together and heated to produce laminates. Bilayer laminate samples were produced with varied thickness of porous and dense layers. It was shown that due to the difference in modulus and hardness, transverse cracking is found upon Hertzian contact when the dense layer is on the exterior. In the opposite arrangement, compacted damage zones formed in the porous material and no damage occurred in the underlying dense layer. Flaw tolerant behavior of the porous exterior/dense underlayer was examined by measuring biaxial strength as a function of Vickers indentation load. It was found that the thinnest layer of porous material results in the greatest flaw tolerance. Also, higher strength was exhibited at large indentation loads when compared to dense monoliths. The calculated stresses on the surfaces

  14. Characterization of mechanical heterogeneity in amorphous solids

    NASA Astrophysics Data System (ADS)

    Peng, H. L.; Li, M. Z.; Sun, B. A.; Wang, W. H.

    2012-07-01

    The structural geometry and size distribution of the local atomic rearrangements induced by external stress in amorphous solids are investigated by molecular dynamics studies. We find that the size distribution exhibits a generic power-law behavior and their structural geometry shows fractal feature. This indicates that the local atomic rearrangements in amorphous solids are self-organized during deformation. A simple theoretical model based on the interaction of the heterogeneous elastic field sources is proposed which predicts the power-law scaling and characterizes the properties of the local atomic rearrangements in amorphous solids.

  15. Mechanical characterization of commercial biodegradable plastic films

    NASA Astrophysics Data System (ADS)

    Vanstrom, Joseph R.

    Polylactic acid (PLA) is a biodegradable plastic that is relatively new compared to other plastics in use throughout industry. The material is produced by the polymerization of lactic acid which is produced by the fermentation of starches derived from renewable feedstocks such as corn. Polylactic acid can be manufactured to fit a wide variety of applications. This study details the mechanical and morphological properties of selected commercially available PLA film products. Testing was conducted at Iowa State University and in conjunction with the United States Department of Agriculture (USDA) BioPreferred ProgramRTM. Results acquired by Iowa State were compared to a similar study performed by the Cortec Corporation in 2006. The PLA films tested at Iowa State were acquired in 2009 and 2010. In addition to these two studies at ISU, the films that were acquired in 2009 were aged for a year in a controlled environment and then re-tested to determine effects of time (ageing) on the mechanical properties. All films displayed anisotropic properties which were confirmed by inspection of the films with polarized light. The mechanical testing of the films followed American Society for Testing and Materials (ASTM) standards. Mechanical characteristics included: tensile strength (ASTM D882), elongation of material at failure (ASTM D882), impact resistance (ASTM D1922), and tear resistance (ASTM D4272). The observed values amongst all the films ranged as followed: tensile strength 33.65--8.54 MPa; elongation at failure 1,665.1%--47.2%; tear resistance 3.61--0.46 N; and puncture resistance 2.22--0.28 J. There were significant differences between the observed data for a number of films and the reported data published by the Cortec Corp. In addition, there were significant differences between the newly acquired material from 2009 and 2010, as well as the newly acquired materials in 2009 and the aged 2009 materials, suggesting that ageing and manufacturing date had an effect on

  16. Enhanced damage characterization using wavefield imaging methods

    NASA Astrophysics Data System (ADS)

    Blackshire, James L.

    2017-02-01

    Wavefield imaging methods are becoming a popular tool for characterizing and studying elastic field interactions in a wide variety of material systems. By using a scanning laser vibrometry detection system, the transient displacement fields generated by an ultrasonic source can be visualized and studied in detail. As a tool for quantitative nondestructive evaluation, the visualization of elastic waves provides a unique opportunity for understanding the scattering of elastic waves from insipient damage, where the detection and characterization of damage features using ultrasound can be enhanced in many instances. In the present effort, the detection and direct imaging of fatigue cracks in metals, and delaminations in composites, is described. An examination of the transient displacement fields near the scattering sites show additional details related to the local damage morphology, which can be difficult to account for using traditional far-field NDE sensing methods. A combination of forward models and experimental wavefield imaging methods were used to explore enhancement opportunities for the full 3-dimensional characterization of surface-breaking cracks and delaminations.

  17. Characterization methods for ultrasonic test systems

    SciTech Connect

    Busse, L.J.; Becker, F.L.; Bowey, R.E.; Doctor, S.R.; Gribble, R.P.; Posakony, G.J.

    1982-07-01

    Methods for the characterization of ultrasonic transducers (search units) and instruments are presented. The instrument system is considered as three separate components consisting of a transducer, a receiver-display, and a pulser. The operation of each component is assessed independently. The methods presented were chosen because they provide the greatest amount of information about component operation and were not chosen based upon such conditions as cost, ease of operation, field implementation, etc. The results of evaluating a number of commercially available ultrasonic test instruments are presented.

  18. Characterizing Cell Mechanics with AFM and Microfluidics

    NASA Astrophysics Data System (ADS)

    Walter, N.; Micoulet, A.; Suresh, S.; Spatz, J. P.

    2007-03-01

    Cell mechanical properties and functionality are mainly determined by the cytoskeleton, besides the cell membrane, the nucleus and the cytosol, and depend on various parameters e.g. surface chemistry and rigidity, surface area and time available for cell spreading, nutrients and drugs provided in the culture medium. Human epithelial pancreatic and mammary cancer cells and their keratin intermediate filaments are the main focus of our work. We use Atomic Force Microscopy (AFM) to study cells adhering to substrates and Microfluidic Channels to probe cells in suspension, respectively. Local and global properties are extracted by varying AFM probe tip size and the available adhesion area for cells. Depth-sensing, instrumented indentation tests with AFM show a clear difference in contact stiffness for cells that are spread of controlled substrates and those that are loosely attached. Microfluidic Channels are utilized in parallel to evaluate cell deformation and ``flow resistance'', which are dependent on channel cross section, flow rate, cell nucleus size and the mechanical properties of cytoskeleton and membrane. The results from the study are used to provide some broad and quantitative assessments of the connections between cellular/subcellular mechanics and biochemical origins of disease states.

  19. Computational Methods for Structural Mechanics and Dynamics

    NASA Technical Reports Server (NTRS)

    Stroud, W. Jefferson (Editor); Housner, Jerrold M. (Editor); Tanner, John A. (Editor); Hayduk, Robert J. (Editor)

    1989-01-01

    Topics addressed include: transient dynamics; transient finite element method; transient analysis in impact and crash dynamic studies; multibody computer codes; dynamic analysis of space structures; multibody mechanics and manipulators; spatial and coplanar linkage systems; flexible body simulation; multibody dynamics; dynamical systems; and nonlinear characteristics of joints.

  20. Characterizing Mechanisms of Resistance to Androgen Deprivation in Prostate Cancer

    DTIC Science & Technology

    2015-11-01

    AWARD NUMBER: W81XWH-13-1-0161 TITLE: Characterizing Mechanisms of Resistance to Androgen Deprivation in Prostate Cancer PRINCIPAL...INVESTIGATOR: Ginevra Botta CONTRACTING ORGANIZATION: DANA-FARBER CANCER INSTITUTE BOSTON MA 02215 REPORT DATE: November 2015 TYPE OF REPORT: Final...Characterizing mechanisms of Resistance to Androgen Deprivation in Prostate Cancer 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-13-1-0161 5c. PROGRAM

  1. Simple micromechanical model of protein crystals for their mechanical characterizations

    NASA Astrophysics Data System (ADS)

    Yoon, G.; Eom, K.; Na, S.

    2010-06-01

    Proteins have been known to perform the excellent mechanical functions and exhibit the remarkable mechanical properties such as high fracture toughness in spider silk protein [1]. This indicates that the mechanical characterization of protein molecules and/or crystals is very essential to understand such remarkable mechanical function of protein molecules. In this study, for gaining insight into mechanical behavior of protein crystals, we developed the micromechanical model by using the empirical potential field prescribed to alpha carbon atoms of a protein crystal in a unit cell. We consider the simple protein crystals for their mechanical behavior under tensile loading to be compared with full atomic models

  2. Mechanical diode: Comparing numerical and experimental characterizations

    SciTech Connect

    Sagartz, M.J.; Segalman, D.; Simmermacher, T.

    1998-02-01

    In this introductory work, joint compliance is studied in both a numerical and experimental setting. A simple bolted interface is used as the test article and compliance is measured for the joint in both compression and in tension. This simple interface is shown to exhibit a strong non-linearity near the transition from compression to tension (or vice-versa). Modeling issues pertaining to numerically solving for the compliance are addressed. It is shown that the model predictions, in spite of convergence being very sensitive to numerical artifacts of the interface model, are in good agreement with experimentally measured strains and joint compliances. The joint behavior is a mechanical analogy to a diode, i.e., in compression, the joint is very stiff, acting almost as a rigid link, while in tension the joint is relatively soft, acting as a spring.

  3. Boundary characterization of microstructures through thermo-mechanical testing

    NASA Astrophysics Data System (ADS)

    Rinaldi, G.; Packirisamy, M.; Stiharu, I.

    2006-03-01

    A variety of silicon foundry processes available for microsystem implementation are available at the present time. The manufacturing methods and the associated process tolerances employed at a particular foundry will determine the performance of the finished devices. Moreover, micro-electro-mechanical systems (MEMS) often require processes that are difficult to control. Device-to-device variations can occur even in batch microfabricated systems. One particular limitation of MEMS foundry processes, in general, is associated with non-classical boundary support conditions due to over/under etching of silicon. These non-classical support conditions will affect the static and dynamic performance of the microsystem. This condition has important implications in atomic force microscopy applications where the targeted natural frequencies are given a wide tolerance due in large part to microfabrication limitations. This paper presents the boundary characterization of single crystal silicon microcantilevers through thermo-mechanical testing. A non-contact optical sensing approach is used for the experimentation. The Rayleigh-Ritz energy method incorporating boundary characteristic orthogonal polynomials is used for the prediction analysis.

  4. Characterizing mechanical effects of aging damage

    SciTech Connect

    Sewell, T.D.; Chen, S.P.; Schoonover, J.R.; Trent, B.C.; Howe, P.M.; Hjelm, R.P.; Browning, R.V.

    1998-12-01

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal was to develop and apply several different experimental and theoretical/computational tools to better understand physical and chemical aging phenomena in plastic-bonded high explosives, and to develop a methodology for predicting the likely effects of aging on the mechanical properties of the composite based on input from these fundamental studies. Initial comparisons were done for spectra of fresh and aged Esane, as well as PBX-9501, and the authors found differences in the carbonyl region of the spectrum, which possibly reflect differences in hydrogen bonding due to aging phenomena. The micromechanical model of composites was extended to study various volume fractions of HMX with binders. The results showed that, as the binder fraction increases, there is a decrease in the maximum stress that can be supported but an increase in the percent strain at final fracture. A more realistic microstructural model was obtained through the use of a phase field model. Using this model, the authors have studied the microstructural evolution as a function of the grain boundary energy vs. misorientation relationship. The initial results indicate that there are some changes in the grain growth rate when the grain-boundary energy dependence on the angle is not constant. They also find that solute tends to segregate at the grain boundary and slows the grain growth kinetics.

  5. Characterizing Deletion Transformations across Dialects using a Sophisticated Tying Mechanism

    DTIC Science & Technology

    2011-03-30

    suggest nrle candidates for further linguistic studies. Potential appli- cations include forensic phonetics, accent training, and dialect recognition...03-2011 Technical Paper MAR 2011 - APR 2011 Characterizing Deletion Transformations across Dialects using a Sophisticated Tying Mechanism FA8720-05...modeling deletion transformations between dialects . We empirically show that the proposed tying mechanism reduces deletion errors by 33% when compared to a

  6. Method Of Characterizing An Electrode Binder

    DOEpatents

    Cocciantelli, Jean-Michel; Coco, Isabelle; Villenave, Jean-Jacques

    1999-05-11

    In a method of characterizing a polymer binder for cell electrodes in contact with an electrolyte and including a current collector and a paste containing an electrochemically active material and said binder, a spreading coefficient of the binder on the active material is calculated from the measured angle of contact between standard liquids and the active material and the binder, respectively. An interaction energy of the binder with the electrolyte is calculated from the measured angle of contact between the electrolyte and the binder. The binder is selected such that the spreading coefficient is less than zero and the interaction energy is at least 60 mJ/m.sup.2.

  7. Mechanical Characterization of Nodular Ductile Iron

    SciTech Connect

    Springer, H K

    2012-01-03

    The objective of this study is to characterize the strength and fracture response of nodular ductile iron (NDI) and its underlying ferritic matrix phase. Quasistatic and split Hopkinson pressure bar (SHPB) compression tests were performed on NDI and a model material for the NDI matrix phase (Fe-Si alloy). Smooth and notch round bar (NRB) samples were loaded in tension until fracture to determine strain-at-failure with varying stress triaxiality. Multiple tests were performed on each small and large smooth bar samples to obtain fracture statistics with sample size. Fracture statistics are important for initializing simulations of fragmentation events. Johnson-Cook strength models were developed for the NDI and the Fe-Si alloy. NDI strength model parameters are: A = 525 MPa, B = 650 MPa, n = 0.6, and C = 0.0205. The average SHPB experimental strain-rate of 2312/s was used for the reference strain-rate in this model. Fe-Si alloy strength model parameters are: A=560 MPa, B = 625 MPa, n = 0.5, and C = 0.02. The average SHPB experimental strain-rate of 2850/s was used for the reference strain-rate in this model. A Johnson-Cook failure model was developed for NDI with model parameters: D{sub 1} = 0.029, D{sub 2} = 0.44, D{sub 3} = -1.5, and D{sub 4} = D{sub 5} = 0. An exponential relationship was developed for the elongation-at-failure statistics as a function of length-scale with model parameters: S{sub f1} = 0.108, S{sub f2} = -0.00169, and L{sub m} = 32.4 {mu}m. NDI strength and failure models, including failure statistics, will be used in continuum-scale simulations of explosively-driven ring fragmentation. The Fe-Si alloy strength model will be used in mesoscale simulations of spall fracture in NDI, where the NDI matrix phase is captured explicitly.

  8. Physico-mechanical characterization of adobe bricks from Cyprus

    NASA Astrophysics Data System (ADS)

    Ioannou, I.; Illampas, R.; Charmpis, D. C.

    2012-04-01

    Adobe bricks have been used in the construction of buildings for thousands of years. In our days, adobe masonry is no longer a prevailing form of construction. However, a great number of earthen buildings still survives in most regions of the world and constitutes an essential part of the international architectural and cultural heritage. Furthermore, efforts are currently being made to reintroduce adobes as an environmentally-friendly building material to contemporary architecture within the context of sustainable development. Despite the long-term use of adobes and their importance for the society, our knowledge of many aspects of this material is still rather limited. As a result, there are many ongoing research initiatives worldwide aiming to investigate the physicochemical and mechanical properties of adobe bricks and related durability problems. In this paper, we present our work (which is funded by the Cyprus Research Promotion Foundation Project EΠIXEIPHΣEIΣ/ΠPOION/0609/41, the Republic of Cyprus and the European Regional Development Fund) on the physico-mechanical characterization of adobes from Cyprus. In the absence of standardized procedures for most of the tests carried out, testing methodologies that either refer to other types of masonry materials and/or are encountered in the literature are adopted. The results show that adobes are mostly composed of random quantities of silt and clay. Calcite is also predominant in the X-ray diffraction analyses patterns. The average capillary water absorption coefficient of the test specimens rarely exceeds 1 mm/min1/2 (when measured against a saturated sponge surface), while their thermal conductivity is around 0.55 W/mK. Extensive experimental data on the material's mechanical behaviour show that adobes' response to compression is characterized by intense deformability. The average value of compressive strength depends greatly on the form of specimen examined (cube, cylinder, prism) and the failure criterion

  9. Automated Weld Characterization Using the Thermoelectric Method

    NASA Technical Reports Server (NTRS)

    Fulton, J. P.; Wincheski, B.; Namkung, M.

    1992-01-01

    The effective assessment of the integrity of welds is a complicated NDE problem that continues to be a challenge. To be able to completely characterize a weld, detailed knowledge of its tensile strength, ductility, hardness, microstructure, macrostructure, and chemical composition is needed. NDE techniques which can provide information on any of these features are extremely important. In this paper, we examine a seldom used approach based on the thermoelectric (TE) effect for characterizing welds and their associated heat affected zone (HAZ). The thermoelectric method monitors the thermoelectric power which is sensitive to small changes in the kinetics of the conduction electrons near the Fermi surface that can be caused by changes in the local microstructure. The technique has been applied to metal sorting, quality testing, flaw detection, thickness gauging of layers, and microscopic structural analysis. To demonstrate the effectiveness of the technique for characterizing welds, a series of tungsten-inert-gas welded Inconel-718 samples were scanned with a computer controlled TE probe. The samples were then analyzed using a scanning electron microscope and Rockwell hardness tests to characterize the weld and the associated HAZ. We then correlated the results with the TE measurements to provide quantitative information on the size of the HAZ and the degree of hardness of the material in the weld region. This provides potentially valuable information on the strength and fatigue life of the weld. We begin the paper by providing a brief review of the TE technique and then highlight some of the factors that can effect the measurements. Next, we provide an overview of the experimental procedure and discuss the results. Finally, we summarize our findings and consider areas for future research.

  10. Mechanical Characterization of Molecular Assemblies at Oil/Water Interfaces

    NASA Astrophysics Data System (ADS)

    Yuan, Wa

    The self-assembly of charged molecules in liquid phases and their ability to form functional layers at immiscible interfaces are areas of great interest. However, the implementation of these assemblies is often limited by a lack of understanding of the detailed assembly mechanisms. In order to enhance the performance of interfacial assemblies it is essential to be able to characterize the physical and mechanical properties of assembled layers, as well as develop model systems that will allow us to examine the factors that govern their interaction with the surrounding environment. The key purpose of this thesis is to develop an understanding of some of the important factors influencing interfacial assemblies at immiscible liquid interfaces. The first portion of the work involves mechanical characterization of interfacial layers formed by large amphiphilic molecules. The study of block and gradient copolymers, reveals the effect of copolymer sequence distribution on the ability of these molecules to form interfacial assemblies. Specifically, the unique network structure formed by gradient copolymers at oil/water interfaces enables us to create a robust membrane at the interface by ionic crosslinking. The second part of this thesis explores smaller molecule assemblies at liquid interfaces, including commonly used commercial surfactant (span 80) and nano particles (graphene oxide). Both studies demonstrate an interesting correlation between molecular structure and overall properties of the assembled layers. Factors such as interfacial density, particle sizes and pH can greatly influence the structure of the assembled layers, resulting in interesting phenomena such as spontaneous emulsification, wrinkling and layer collapse. The bulk of the oil/water interface study was performed using axisymmetric drop shape analysis (DSA), which successfully quantifies the mechanical tension in the interfacial layer. This analysis was further extended by a development of a double

  11. New methods for quantum mechanical reaction dynamics

    SciTech Connect

    Thompson, Ward Hugh

    1996-12-01

    Quantum mechanical methods are developed to describe the dynamics of bimolecular chemical reactions. We focus on developing approaches for directly calculating the desired quantity of interest. Methods for the calculation of single matrix elements of the scattering matrix (S-matrix) and initial state-selected reaction probabilities are presented. This is accomplished by the use of absorbing boundary conditions (ABC) to obtain a localized (L2) representation of the outgoing wave scattering Green`s function. This approach enables the efficient calculation of only a single column of the S-matrix with a proportionate savings in effort over the calculation of the entire S-matrix. Applying this method to the calculation of the initial (or final) state-selected reaction probability, a more averaged quantity, requires even less effort than the state-to-state S-matrix elements. It is shown how the same representation of the Green`s function can be effectively applied to the calculation of negative ion photodetachment intensities. Photodetachment spectroscopy of the anion ABC- can be a very useful method for obtaining detailed information about the neutral ABC potential energy surface, particularly if the ABC- geometry is similar to the transition state of the neutral ABC. Total and arrangement-selected photodetachment spectra are calculated for the H3O- system, providing information about the potential energy surface for the OH + H2 reaction when compared with experimental results. Finally, we present methods for the direct calculation of the thermal rate constant from the flux-position and flux-flux correlation functions. The spirit of transition state theory is invoked by concentrating on the short time dynamics in the area around the transition state that determine reactivity. These methods are made efficient by evaluating the required quantum mechanical trace in the basis of eigenstates of the

  12. Smart Optical Material Characterization System and Method

    NASA Technical Reports Server (NTRS)

    Choi, Sang Hyouk (Inventor); Park, Yeonjoon (Inventor)

    2015-01-01

    Disclosed is a system and method for characterizing optical materials, using steps and equipment for generating a coherent laser light, filtering the light to remove high order spatial components, collecting the filtered light and forming a parallel light beam, splitting the parallel beam into a first direction and a second direction wherein the parallel beam travelling in the second direction travels toward the material sample so that the parallel beam passes through the sample, applying various physical quantities to the sample, reflecting the beam travelling in the first direction to produce a first reflected beam, reflecting the beam that passes through the sample to produce a second reflected beam that travels back through the sample, combining the second reflected beam after it travels back though the sample with the first reflected beam, sensing the light beam produced by combining the first and second reflected beams, and processing the sensed beam to determine sample characteristics and properties.

  13. HEFF---A user`s manual and guide for the HEFF code for thermal-mechanical analysis using the boundary-element method; Version 4.1: Yucca Mountain Site Characterization Project

    SciTech Connect

    St. John, C.M.; Sanjeevan, K.

    1991-12-01

    The HEFF Code combines a simple boundary-element method of stress analysis with the closed form solutions for constant or exponentially decaying heat sources in an infinite elastic body to obtain an approximate method for analysis of underground excavations in a rock mass with heat generation. This manual describes the theoretical basis for the code, the code structure, model preparation, and step taken to assure that the code correctly performs its intended functions. The material contained within the report addresses the Software Quality Assurance Requirements for the Yucca Mountain Site Characterization Project. 13 refs., 26 figs., 14 tabs.

  14. Integrating asthma hazard characterization methods for consumer products.

    PubMed

    Maier, A; Vincent, M J; Gadagbui, B; Patterson, J; Beckett, W; Dalton, P; Kimber, I; Selgrade, M J K

    2014-10-01

    Despite extensive study, definitive conclusions regarding the relationship between asthma and consumer products remain elusive. Uncertainties reflect the multi-faceted nature of asthma (i.e., contributions of immunologic and non-immunologic mechanisms). Many substances used in consumer products are associated with occupational asthma or asthma-like syndromes. However, risk assessment methods do not adequately predict the potential for consumer product exposures to trigger asthma and related syndromes under lower-level end-user conditions. A decision tree system is required to characterize asthma and respiratory-related hazards associated with consumer products. A system can be built to incorporate the best features of existing guidance, frameworks, and models using a weight-of-evidence (WoE) approach. With this goal in mind, we have evaluated chemical hazard characterization methods for asthma and asthma-like responses. Despite the wealth of information available, current hazard characterization methods do not definitively identify whether a particular ingredient will cause or exacerbate asthma, asthma-like responses, or sensitization of the respiratory tract at lower levels associated with consumer product use. Effective use of hierarchical lines of evidence relies on consideration of the relevance and potency of assays, organization of assays by mode of action, and better assay validation. It is anticipated that the analysis of existing methods will support the development of a refined WoE approach.

  15. Frequency-Domain Methods for Characterization of Pulsed Power Diagnostics

    SciTech Connect

    White, A D; Anderson, R A; Ferriera, T J; Goerz, D A

    2009-07-27

    This paper discusses methods of frequency-domain characterization of pulsed power sensors using vector network analyzer and spectrum analyzer techniques that offer significant simplification over time-domain methods, while mitigating or minimizing the effect of the difficulties present in time domain characterization. These methods are applicable to characterization of a wide variety of sensors.

  16. Marine electromagnetic methods for gas hydrate characterization

    NASA Astrophysics Data System (ADS)

    Weitemeyer, Karen Andrea

    Gas hydrate is a type of clathrate consisting of a gas molecule (usually methane) encased in a water lattice, and is found worldwide in marine and permafrost regions. Hydrate is important because it is a geo-hazard, has potential as an energy resource, and is a possible contributor to climate change. There are large uncertainties about the global amount of hydrate present, partly because the characterization of hydrate with seismic methods is unreliable. Marine electromagnetic (EM) methods can be used to image the bulk resistivity structure of the subsurface and are able to augment seismic data to provide valuable information about gas hydrate distribution in the marine environment. Marine controlled source electromagnetic (CSEM) sounding data from a pilot survey at Hydrate Ridge, located on the Cascadia subduction zone, show that regions with higher concentrations of hydrate are resistive. The apparent resistivities computed from the CSEM data are consistent for both apparent resistivity pseudosections and two-dimensional regularized inversion results. The 2D inversion results provide evidence of a strong resistor near the seismic bottom simulating reflector (BSR), and geologic structures are imaged to about a kilometer depth. Comparisons with electrical resistivity logging while drilling (LWD) data from Ocean Drilling Program Leg 204 show a general agreement except for one of three sites where the CSEM inversion shows a large resistor at depth as compared to the LWD. An overlay of the CSEM inversion with a collocated seismic line 230 from Trehu et al. (2001) exhibits remarkable similarities with the sedimentary layering, geologic structures, and the seismic BSR. Magnetotelluric (MT) sounding data collected simultaneously during the CSEM survey provide an electrical image of the oceanic crust and mantle (50 km depth) and the folding associated with the accretionary complex (top 2 km depth). In addition, the MT model provides a complementary low-resolution image of

  17. Herbicide resistance in weeds: Survey, characterization, and mechanisms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The goal of this paper is to present a systematic diagnostic approach towards the characterization of herbicide resistance in a given weed population with regards to profile (single, multiple, cross resistance), magnitude (fold level), mechanism, and related bio-physiological aspects. Diagnosing her...

  18. Mechanical Characterization and Corrosion Testing of X608 Al Alloy

    SciTech Connect

    Prabhakaran, Ramprashad; Choi, Jung-Pyung; Stephens, Elizabeth V.; Catalini, David; Lavender, Curt A.; Rohatgi, Aashish

    2016-02-07

    This paper describes the mechanical characterization and corrosion testing of X608 Al alloy that is being considered for A-pillar covers for heavy-duty truck applications. Recently, PNNL developed a thermo-mechanical process to stamp A-pillar covers at room temperature using this alloy, and the full-size prototype was successfully stamped by a tier-1 supplier. This study was conducted to obtain additional important information related to the newly developed forming process, and to further improve its mechanical properties. The solutionization temperature, pre-strain and paint-bake heat-treatment were found to influence the alloy’s fabricability and mechanical properties. Natural aging effect on the formability was investigated by limiting dome height (LDH) tests. Preliminary corrosion experiments showed that the employed thermo-mechanical treatments did not significantly affect the corrosion behavior of Al X608.

  19. A method for characterizing aerodynamic sound sources in turbomachines

    NASA Astrophysics Data System (ADS)

    Mongeau, L.; Thompson, D. E.; Mclaughlin, D. K.

    1995-03-01

    A method based on Weidemann's acoustic similarity laws [1] was used to investigate the aerodynamic sound generated by a partially ducted centrifugal pump rotor. The primary objective of the method was to determine the spectral characteristics of the sound source by isolating the effects of acoustic phenomena such as duct resonances or sound reflections. Pump-radiated sound pressure spectra were measured for different impeller rotational speeds, keeping the operating condition constant. The spectra, assumed to be expressed as the product of a source spectral distribution function and an acoustic frequency response function, were then decomposed into a product form following a computer-implemented algorithm. The method was successful in accurately determining the spectral distribution of the broadband aerodynamic noise generating mechanisms involved and that of the acoustic frequency response of the system. The absolute levels of the source function and the acoustic function were established by assuming that, over a limited low frequency range, the average gain of the frequency response function is unity so that comparisons between different pump operating conditions could be made. The source spectral distribution was found to be independent of the microphone location and the acoustic loading. When applicable, this method therefore allows the characterization of aerodynamic sound sources by measuring ordinary sound pressure spectra, at any one point around the source, without having to isolate the source from the system. The source characterization method was instrumental in the study of sound generation by rotating stall presented in a previous publication [2].

  20. Characterization and redox mechanism of asthma in the elderly

    PubMed Central

    Zuo, Li; Pannell, Benjamin K.; Liu, Zewen

    2016-01-01

    Asthma is a chronic disease characterized by reversible airflow limitation, coughing, bronchial constriction, and an inflammatory immune response. While asthma has frequently been categorized as emerging in childhood, evidence has begun to reveal that the elderly population is certainly susceptible to late-onset, or even long-standing asthma. Non-atopic asthma, most commonly found in elderly patients is associated with elevated levels of serum and sputum neutrophils and may be more detrimental than atopic asthma. The mortality of asthma is high in the elderly since these patients often possess more severe symptoms than younger populations. The redox mechanisms that mediate inflammatory reactions during asthma have not been thoroughly interpreted in the context of aging. Thus, we review the asthmatic symptoms related to reactive oxygen species (ROS) and reactive nitrogen species (RNS) in seniors. Moreover, immune status in the elderly is weakened in part by immunosenescence, which is broadly defined as the decline in functionality of the immune system that corresponds with increasing age. The effects of immunosenescence on the expression of biomarkers potentially utilized in the clinical diagnosis of asthma remain unclear. It has also been shown that existing asthma treatments are less effective in the elderly. Thus, it is necessary that clinicians approach the diagnosis and treatment of asthmatic senior patients using innovative methods. Asthma in the elderly demands more intentional diagnostic and therapeutic research since it is potentially one of the few causes of mortality and morbidity in the elderly that is largely reversible. PMID:26843624

  1. A Practical Quantum Mechanics Molecular Mechanics Method for the Dynamical Study of Reactions in Biomolecules.

    PubMed

    Mendieta-Moreno, Jesús I; Marcos-Alcalde, Iñigo; Trabada, Daniel G; Gómez-Puertas, Paulino; Ortega, José; Mendieta, Jesús

    2015-01-01

    Quantum mechanics/molecular mechanics (QM/MM) methods are excellent tools for the modeling of biomolecular reactions. Recently, we have implemented a new QM/MM method (Fireball/Amber), which combines an efficient density functional theory method (Fireball) and a well-recognized molecular dynamics package (Amber), offering an excellent balance between accuracy and sampling capabilities. Here, we present a detailed explanation of the Fireball method and Fireball/Amber implementation. We also discuss how this tool can be used to analyze reactions in biomolecules using steered molecular dynamics simulations. The potential of this approach is shown by the analysis of a reaction catalyzed by the enzyme triose-phosphate isomerase (TIM). The conformational space and energetic landscape for this reaction are analyzed without a priori assumptions about the protonation states of the different residues during the reaction. The results offer a detailed description of the reaction and reveal some new features of the catalytic mechanism. In particular, we find a new reaction mechanism that is characterized by the intramolecular proton transfer from O1 to O2 and the simultaneous proton transfer from Glu 165 to C2.

  2. Mechanical characterization of low dimensional nanomaterials and polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Gao, Hongsheng

    This research was aimed to characterize the mechanical properties of low dimensional nanomaterials and polymer nanocomposites, and to study the reinforcing mechanisms of nanoscale reinforcements. The nanomaterials studied were zero-dimensional nanomaterial--cuprous oxide (Cu2O) nanocubes, one-dimensional nanomaterials--silver nanowires and silicon oxide (SiO2) nanowires, and two-dimensional nanomaterial--nanometer-thick montmorillonite clay platelets. The hardness and elastic moduli of solid Cu 2O nanocubes and silver nanowires were measured by directly indenting individual cubes/wires using a nanoindenter. The elastic modulus of amorphous SiO2 nanowires was measured by performing three-point bending on suspended wires with an atomic force microscope (AFM) tip. The elastic modulus of the nanometer-thick clay platelets was assessed by the modulus mapping technique. An array of nanoscale indents was successfully made on a nanowire. The nanowires were cut to the length as needed. The nanoindentation approach permits the direct machining of individual nanowires without complications of conventional lithography. The nanomechanical properties of single-walled carbon nanotube (SWCNT)-reinforced epoxy composites with varying nanotube concentrations were measured by nanoindentation/nanoscratch techniques. Hardness and elastic modulus were measured using a nanoindenter. Viscoelastic properties of the nanocomposites were measured using nanoindentation dynamic mechanical analysis tests. The SWCNT reinforcing mechanisms were further studied by both Halpin-Tsai and Mori-Tanaka theories, which were found applicable to SWCNT-reinforced, amorphous-polymer composites. The possible reinforcing mechanisms that work in polymer-SWCNT composites and reasons responsible for SWCNTs' low mechanical reinforcement were analyzed. Nanoclay-reinforced agarose nanocomposites with varying clay concentrations were structurally and mechanically characterized. Structural characterization was carried

  3. Estimation of mechanical properties of nanomaterials using artificial intelligence methods

    NASA Astrophysics Data System (ADS)

    Vijayaraghavan, V.; Garg, A.; Wong, C. H.; Tai, K.

    2014-09-01

    Computational modeling tools such as molecular dynamics (MD), ab initio, finite element modeling or continuum mechanics models have been extensively applied to study the properties of carbon nanotubes (CNTs) based on given input variables such as temperature, geometry and defects. Artificial intelligence techniques can be used to further complement the application of numerical methods in characterizing the properties of CNTs. In this paper, we have introduced the application of multi-gene genetic programming (MGGP) and support vector regression to formulate the mathematical relationship between the compressive strength of CNTs and input variables such as temperature and diameter. The predictions of compressive strength of CNTs made by these models are compared to those generated using MD simulations. The results indicate that MGGP method can be deployed as a powerful method for predicting the compressive strength of the carbon nanotubes.

  4. Apparatus and method for generating mechanical waves

    DOEpatents

    Allensworth, D.L.; Chen, P.J.

    1982-10-25

    Mechanical waves are generated in a medium by subjecting an electromechanical element to an alternating electric field having a frequency which induces mechanical resonance therein and is below any electrical resonance frequency thereof.

  5. Apparatus and method for generating mechanical waves

    DOEpatents

    Allensworth, Dwight L.; Chen, Peter J.

    1985-01-01

    Mechanical waves are generated in a medium by subjecting an electromechanical element to an alternating electric field having a frequency which induces mechanical resonance therein and is below any electrical resonance frequency thereof.

  6. Entropic Lattice Boltzmann Methods for Fluid Mechanics

    NASA Astrophysics Data System (ADS)

    Chikatamarla, Shyam; Boesch, Fabian; Sichau, David; Karlin, Ilya

    2013-11-01

    With its roots in statistical mechanics and kinetic theory, the lattice Boltzmann method (LBM) is a paradigm-changing innovation, offering for the first time an intrinsically parallel CFD algorithm. Over the past two decades, LBM has achieved numerous results in the field of CFD and is now in a position to challenge state-of-the art CFD techniques. Our major restyling of LBM resulted in an unconditionally stable entropic LBM which restored Second Law (Boltzmann H theorem) in the LBM kinetics and thus enabled affordable direct simulations of fluid turbulence. We review here recent advances in ELBM as a practical, modeling-free tool for simulation of turbulent flows in complex geometries. We shall present recent simulations including turbulent channel flow, flow past a circular cylinder, knotted vortex tubes, and flow past a surface mounted cube. ELBM listed all admissible lattices supporting a discrete entropy function and has classified them in hierarchically increasing order of accuracy. Applications of these higher-order lattices to simulations of turbulence and thermal flows shall also be presented. This work was supported CSCS grant s437.

  7. Progress of Stirling cycle analysis and loss mechanism characterization

    SciTech Connect

    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. Requirements for improving modeling and design are discussed. 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. 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.

  9. Testing techniques for mechanical characterization of rapidly solidified materials

    NASA Technical Reports Server (NTRS)

    Koch, C. C.

    1986-01-01

    Mechanical property testing techniques are reviewed for rapidly solidified materials. Mechanical testing of rapidly solidified materials is complicated by the fact that in most cases at least one dimension of the material is very small (less than 100 microns). For some geometries, i.e., powder or thin surface layers, microhardness is the only feasible mechanical test. The ribbon geometry which is obtained by the melt-spinning method, however, has been used for a variety of mechanical property measurements including elastic properties, tensile properties, fracture toughness, creep, and fatigue. These techniques are described with emphasis placed on the precautions required by the restricted geometry of rapidly solidified specimens.

  10. Metallic syntactic foams synthesis, characterization and mechanical properties

    NASA Astrophysics Data System (ADS)

    Castro, Gerhard

    In this study, we report two procedures for producing lab-scale syntactic steel by melt infiltration of millimeter-sized alumina microspheres: mechanical pressure infiltration and gravity-fed infiltration. Both methods yield foam with uniform distributions of microspheres and negligible unintended porosity. The most critical parameters in the manufacture of the syntactic steel foams are the melt temperature and the preheat temperature of the microspheres prior to infiltration. The preheatment temperature of the microspheres must be close to the melting temperature of steel. Syntactic steel foams with relative density of about half of solid steel densities were produced using monosized microspheres randomly situated in a mold. Microspheres with a diameter of 1.27 mm were used for the mechanical pressure infiltration method and microspheres with a diameter of 4.45 mm for the gravity-fed infiltration method. Different steel chemical compositions were selected to produce steel foams of different inherent yield strength: including several ferritic-pearlitic steels and one TRIP steel (TRansformation-Induced Plasticity). The resultant foams were characterized by chemical and microstructural analysis. The microstructure of the samples consisted of blends of ferritic and pearlitic constituents in varying proportions for the ferritic-pearlitic steels, while the cast TRIP steel matrix presented an austenitic microstructure. The basic mechanical properties of the steel syntactic foams were studied under compression loading. The pearlitic syntactic foams have greater compression strength and energy absorption capacity than the ferritic syntactic foams, but the TRIP steel syntactic foam exhibited the highest compression strength and highest energy absorption capacity. The properties of the steel syntactic foams were compared to those of other steel foams, aluminum foams and other cellular structures reported in the literature. We present also the compression and impact behavior

  11. Packaging and characterization of micro-opto-electro-mechanical systems

    NASA Astrophysics Data System (ADS)

    Saupe, Ray; Otto, Thomas; Stock, Volker; Fritzsch, Uwe; Gessner, Thomas

    2004-04-01

    Modern optical analytics require more and more compact and cost-effective modules for analysis of surfaces, solids, thin films, powders, pastes, gels, liquids and alike. Thereby a fast and non-invasive measurement is often necessary. Microsystem technology, more precisely Micro-Opto-Electro-Mechanical System (MOEMS) technology is suitable for the realization of such modules. Different miniaturized optical analyzers employing MOEMS have been developed at the Fraunhofer Institute for Reliability and Microintegration (IZM) in collaboration with the Center for Microtechnologies (ZfM) and the company COLOUR CONTROL Farbmesstechnik GmbH. These devices are based on the principle of spectral sensing in the infrared range. Due to the requirement of compact dimensions and short optical paths a high packaging accuracy is necessary. In the development process different setups with a continuous packaging improvement have been realized. The first packaging principle was based on particularly assembled laser-cut stainless steel sheets and optical standard components. The design requires exact positioning of the functional elements to attain a sufficient optical resolution. The reduction of the active components by means of monolithic combinations was one improvement. Further progress could be achieved by a package made of aluminum cast, whose models were provided using modern methods of rapid prototyping. Consequently adjustment tolerances will be minimized and the vibration stability will be increased. During the development process, simulations and characterization of the system are essential to obtain necessary improvements. Thereby an evaluation of the packaging accuracy regarding its influence on the defocus was made. According to precision and reproducibility, the optical and electrical performance are being tested.

  12. Characterization of nano-wear mechanisms of hard disk coatings

    NASA Astrophysics Data System (ADS)

    Kim, Woo Seok; Kim, Jang-Kyo; Hwang, Pyung

    2001-05-01

    The wear mechanisms of carbon coated computer hard disks with laser-textured (LT) and mechanically-textured (MT) surfaces were characterized after contact start/stop (CSS) cyclic tests. Various analytical and mechanical testing techniques were employed to study the changes in topography, roughness, chemical elements, mechanical properties, and friction characteristics of the coating and lubricant. These techniques include: the atomic force microscopy (AFM), continuous nano-indentation test, nano-scratch test, time-of-flight secondary ion mass spectroscopy (TOF-SIMS), and Auger electron spectroscopy (AES). The CSS test at 15 k cycles resulted in tangible reductions of surface roughness of approximately 3.0 nm and 5.8 nm, respectively, for the LT bump and MT zone. The elastic modulus and hardness values increased after the CSS test, indicating strain hardening of the top coating layer. A critical load was identified for adhesion failure between the magnetic layer and the Ni-P layer. The TOF-SIMS analysis also revealed reductions in the intensities of all lubricant elements, indicating wear of the lubricant applied on the disk surface. All foregoing results confirm the usefulness of the characterization techniques employed to detect the subtle changes in disk surface characteristics.

  13. The Challenge of Characterizing Operations in the Mechanisms Underlying Behavior

    PubMed Central

    Bechtel, William

    2005-01-01

    Neuroscience and cognitive science seek to explain behavioral regularities in terms of underlying mechanisms. An important element of a mechanistic explanation is a characterization of the operations of the parts of the mechanism. The challenge in characterizing such operations is illustrated by an example from the history of physiological chemistry in which some investigators tried to characterize the internal operations in the same terms as the overall physiological system while others appealed to elemental chemistry. In order for biochemistry to become successful, researchers had to identify a new level of operations involving operations over molecular groups. Existing attempts at mechanistic explanation of behavior are in a situation comparable to earlier approaches to physiological chemistry, drawing their inspiration either from overall psychology activities or from low-level neural processes. Successful mechanistic explanations of behavior require the discovery of the appropriate component operations. Such discovery is a daunting challenge but one on which success will be beneficial to both behavioral scientists and cognitive and neuroscientists. PMID:16596967

  14. Characterization of Solder Joint Reliability Using Cyclic Mechanical Fatigue Testing

    NASA Astrophysics Data System (ADS)

    Kim, Choong-Un; Bang, Woong-Ho; Xu, Huili; Lee, Tae-Kyu

    2013-10-01

    This article summarizes the mechanics of two mechanical fatigue methods, cyclic bending fatigue and shear fatigue, in inducing failure in solder joints in package assemblies, and it presents the characteristics of fatigue failures resulting from these methods using example cases of Sn-Pb eutectic and Sn-rich Pb-free solder alloys. Numerical simulation suggests that both testing configurations induce fatigue failure by the crack-opening mode. In the case of bending fatigue, the strain induced by the bending displacement is found to be sensitive to chip geometry, and it induces fatigue cracks mainly at the solder matrix adjacent to the printed circuit board interface. In case of shear fatigue, the failure location is firmly fixed at the solder neck, created by solder mask, where an abrupt change in the solder geometry occurs. Both methods conclude that the Coffin-Manson model is the most appropriate model for the isothermal mechanical fatigue of solder alloys. An analysis of fatigue characteristics using the frame of the Coffin-Manson model produces several insightful results, such as the reason why Pb-free alloys show higher fatigue resistance than Sn-Pb alloys even if they are generally more brittle. Our analysis suggests that it is related to higher work hardening. All these results indicate that mechanical fatigue can be an extremely useful method for fast screening of defective package structures and also in gaining a better understanding of fatigue failure mechanism and prediction of reliability in solder joints.

  15. Towards the mechanical characterization of abdominal wall by inverse analysis.

    PubMed

    Simón-Allué, R; Calvo, B; Oberai, A A; Barbone, P E

    2017-02-01

    The aim of this study is to characterize the passive mechanical behaviour of abdominal wall in vivo in an animal model using only external cameras and numerical analysis. The main objective lies in defining a methodology that provides in vivo information of a specific patient without altering mechanical properties. It is demonstrated in the mechanical study of abdomen for hernia purposes. Mechanical tests consisted on pneumoperitoneum tests performed on New Zealand rabbits, where inner pressure was varied from 0mmHg to 12mmHg. Changes in the external abdominal surface were recorded and several points were tracked. Based on their coordinates we reconstructed a 3D finite element model of the abdominal wall, considering an incompressible hyperelastic material model defined by two parameters. The spatial distributions of these parameters (shear modulus and non linear parameter) were calculated by inverse analysis, using two different types of regularization: Total Variation Diminishing (TVD) and Tikhonov (H(1)). After solving the inverse problem, the distribution of the material parameters were obtained along the abdominal surface. Accuracy of the results was evaluated for the last level of pressure. Results revealed a higher value of the shear modulus in a wide stripe along the craneo-caudal direction, associated with the presence of linea alba in conjunction with fascias and rectus abdominis. Non linear parameter distribution was smoother and the location of higher values varied with the regularization type. Both regularizations proved to yield in an accurate predicted displacement field, but H(1) obtained a smoother material parameter distribution while TVD included some discontinuities. The methodology here presented was able to characterize in vivo the passive non linear mechanical response of the abdominal wall.

  16. Fabrication and Mechanical Characterization of Hydrogel Infused Network Silk Scaffolds

    PubMed Central

    Kundanati, Lakshminath; Singh, Saket K.; Mandal, Biman B.; Murthy, Tejas G.; Gundiah, Namrata; Pugno, Nicola M.

    2016-01-01

    Development and characterization of porous scaffolds for tissue engineering and regenerative medicine is of great importance. In recent times, silk scaffolds were developed and successfully tested in tissue engineering and drug release applications. We developed a novel composite scaffold by mechanical infusion of silk hydrogel matrix into a highly porous network silk scaffold. The mechanical behaviour of these scaffolds was thoroughly examined for their possible use in load bearing applications. Firstly, unconfined compression experiments show that the denser composite scaffolds displayed significant enhancement in the elastic modulus as compared to either of the components. This effect was examined and further explained with the help of foam mechanics principles. Secondly, results from confined compression experiments that resemble loading of cartilage in confinement, showed nonlinear material responses for all scaffolds. Finally, the confined creep experiments were performed to calculate the hydraulic permeability of the scaffolds using soil mechanics principles. Our results show that composite scaffolds with some modifications can be a potential candidate for use of cartilage like applications. We hope such approaches help in developing novel scaffolds for tissue engineering by providing an understanding of the mechanics and can further be used to develop graded scaffolds by targeted infusion in specific regions. PMID:27681725

  17. Optofluidic nanotweezer methods for characterizing nanoparticles and viruses (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Erickson, David

    2016-03-01

    Direct measurements of the strength of particle interactions are critical for characterizing the stability and behavior of colloidal and nanoparticle suspensions. Current techniques are limited in their ability to measure pico-newton scale interaction forces on sub-micrometer particles due to signal detection limits, thermal noise, and throughput. We have recently developed a technique for making direct mechanical measurements of the force and work associated with the steric and electrostatic effects that stabilize colloidal nanoparticles. "Nanophotonic Force Microscopy", as we call it, is unique in that it uses statistical methods to provide direct measurements of these forces at the individual particle scale, while still being sufficiently high-throughput to produce meaningful population level data. In this talk I will introduce the technology, it's advantages, and some of the major uses. Specific case studies will include label-free monitoring of binding of individual antibodies onto single viruses and the measurement of the strength of nanoparticle coatings used for steric stabilization.

  18. Microstructural and mechanical characterization of Al–Zn–Si nanocomposites

    SciTech Connect

    García-Villarreal, S.; Chávez-Valdez, A.; Moreno, K.J.; Leyva, C.; Aguilar-Martínez, J.A.; Hurtado, A.; Arizmendi-Morquecho, A.

    2013-09-15

    In this paper the addition of silicon nanoparticles into Al–Zn alloys to form metallic matrix nanocomposites by mechanical alloying process was investigated. The influence of various process parameters such as milling time and Si concentration in the Al–Zn matrix has an interesting effect on the microstructure and mechanical properties of the synthesized nanocomposites. The microstructural characterization of the nanocomposites was evaluated by transmission electron microscopy and energy dispersive X-ray spectroscopy (TEM–EDXS) and the mechanical properties were measured by nanoindentation and micro-hardness tests. The results showed that during mechanical milling Si is added to the Al–Zn matrix achieving a uniform and homogeneous dispersion. After solidification, it forms small particles of AlZnSi with blocky morphology in interdendritic regions. The nanoindentation profiles showed that the elastic modulus and hardness properties increase with increasing milling time. However, a high concentration of Si (> 1.2 wt.%) results in a saturation of Si in the Al–Zn matrix, which adversely affects the mechanical properties. Thus, it is important to tune the milling time and concentration of Si added to the Al–Zn alloys to control the growth of brittle phases that result in reduction of the mechanical properties of the material. - Highlights: • A novel technique for addition of Si nanocomposites into Al–Zn liquid alloy is reported. • Good dispersion and homogeneity of Si in the Al–Zn matrix are obtained. • Increasing Si content above 1.2 wt.% decreases the mechanical properties of Al–Zn alloy. • The saturation point of Si in 1.2 wt.% differs from Galvalume® composition. • The Al–Zn–1.5Si alloy with addition of nanocomposite shows 5.7 GPa of hardness.

  19. Mechanical property characterization of polymeric composites reinforced by continuous microfibers

    NASA Astrophysics Data System (ADS)

    Zubayar, Ali

    Innumerable experimental works have been conducted to study the effect of polymerization on the potential properties of the composites. Experimental techniques are employed to understand the effects of various fibers, their volume fractions and matrix properties in polymer composites. However, these experiments require fabrication of various composites which are time consuming and cost prohibitive. Advances in computational micromechanics allow us to study the various polymer based composites by using finite element simulations. The mechanical properties of continuous fiber composite strands are directional. In traditional continuous fiber laminated composites, all fibers lie in the same plane. This provides very desirable increases in the in-plane mechanical properties, but little in the transverse mechanical properties. The effect of different fiber/matrix combinations with various orientations is also available. Overall mechanical properties of different micro continuous fiber reinforced composites with orthogonal geometry are still unavailable in the contemporary research field. In this research, the mechanical properties of advanced polymeric composite reinforced by continuous micro fiber will be characterized based on analytical investigation and FE computational modeling. Initially, we have chosen IM7/PEEK, Carbon Fiber/Nylon 6, and Carbon Fiber/Epoxy as three different case study materials for analysis. To obtain the equivalent properties of the micro-hetero structures, a concept of micro-scale representative volume elements (RVEs) is introduced. Five types of micro scale RVEs (3 square and 2 hexagonal) containing a continuous micro fiber in the polymer matrix were designed. Uniaxial tensile, lateral expansion and transverse shear tests on each RVE were designed and conducted by the finite element computer modeling software ANSYS. The formulae based on elasticity theory were derived for extracting the equivalent mechanical properties (Young's moduli, shear

  20. In situ mechanical characterization of the cell nucleus by atomic force microscopy.

    PubMed

    Liu, Haijiao; Wen, Jun; Xiao, Yun; Liu, Jun; Hopyan, Sevan; Radisic, Milica; Simmons, Craig A; Sun, Yu

    2014-04-22

    The study of nuclear mechanical properties can provide insights into nuclear dynamics and its role in cellular mechanotransduction. While several methods have been developed to characterize nuclear mechanical properties, direct intracellular probing of the nucleus in situ is challenging. Here, a modified AFM (atomic force microscopy) needle penetration technique is demonstrated to mechanically characterize cell nuclei in situ. Cytoplasmic and nuclear stiffness were determined based on two different segments on the AFM indentation curves and were correlated with simultaneous confocal Z-stack microscopy reconstructions. On the basis of direct intracellular measurement, we show that the isolated nuclei from fibroblast-like cells exhibited significantly lower Young's moduli than intact nuclei in situ. We also show that there is in situ nucleus softening in the highly metastatic bladder cancer cell line T24 when compared to its less metastatic counterpart RT4. This technique has potential to become a reliable quantitative measurement tool for intracellular mechanics studies.

  1. Characterizing the Mechanical Properties of Running-Specific Prostheses

    PubMed Central

    Beck, Owen N.; Taboga, Paolo; Grabowski, Alena M.

    2016-01-01

    The mechanical stiffness of running-specific prostheses likely affects the functional abilities of athletes with leg amputations. However, each prosthetic manufacturer recommends prostheses based on subjective stiffness categories rather than performance based metrics. The actual mechanical stiffness values of running-specific prostheses (i.e. kN/m) are unknown. Consequently, we sought to characterize and disseminate the stiffness values of running-specific prostheses so that researchers, clinicians, and athletes can objectively evaluate prosthetic function. We characterized the stiffness values of 55 running-specific prostheses across various models, stiffness categories, and heights using forces and angles representative of those measured from athletes with transtibial amputations during running. Characterizing prosthetic force-displacement profiles with a 2nd degree polynomial explained 4.4% more of the variance than a linear function (p<0.001). The prosthetic stiffness values of manufacturer recommended stiffness categories varied between prosthetic models (p<0.001). Also, prosthetic stiffness was 10% to 39% less at angles typical of running 3 m/s and 6 m/s (10°-25°) compared to neutral (0°) (p<0.001). Furthermore, prosthetic stiffness was inversely related to height in J-shaped (p<0.001), but not C-shaped, prostheses. Running-specific prostheses should be tested under the demands of the respective activity in order to derive relevant characterizations of stiffness and function. In all, our results indicate that when athletes with leg amputations alter prosthetic model, height, and/or sagittal plane alignment, their prosthetic stiffness profiles also change; therefore variations in comfort, performance, etc. may be indirectly due to altered stiffness. PMID:27973573

  2. Characterization of shape memory alloys for safety mechanisms.

    SciTech Connect

    McLaughlin, Jarred T.; Buchheit, Thomas Edward; Massad, Jordan Elias

    2008-03-01

    Shape memory alloys (SMAs) are metals that exhibit large recoverable strains and exert large forces with tremendous energy densities. The behavior of SMAs is thermomechanically coupled. Their response to temperature is sensitive to their loading condition and their response to loading is sensitive to their thermal condition. This coupled behavior is not to be circumvented, but to be confronted and understood, since it is what manifests SMA's superior clamping performance. To reasonably characterize the coupled behavior of SMA clamping rings used in safety mechanisms, we conduct a series of experiments on SMA samples. The results of the tests will allow increased fidelity in modeling and failure analysis of parts.

  3. Novel analytical methods for the characterization of oral wafers.

    PubMed

    Garsuch, Verena; Breitkreutz, Jörg

    2009-09-01

    This study aims at compensating the lack of adequate methods for the characterization of the novel dosage forms buccal wafers by applying recent advanced analytical techniques. Fast-dissolving oral wafers need special methods for assessing their properties in drug development and quality control. For morphologic investigations, scanning electron microscopy (SEM) and near-infrared chemical imaging (NIR-CI) were used. Differences in the distribution of the active pharmaceutical ingredient within wafers can be depicted by NIR-CI. Film thickness was determined by micrometer screw and coating thickness gauge revealing no significant differences between the obtained values. To distinguish between the mechanical properties of different polymers, tensile test was performed. Suitable methods to predict disintegration behaviour are thermomechanical analysis and contact angle measurement. The determination of drug release was carried out by three different methods. Fibre-optic sensor systems allow an online measurement of the drug release profiles and the thorough analysis even within the first seconds of disintegration and drug dissolution.

  4. Mechanical characterization and modeling of brazed EUROFER-tungsten-joints

    NASA Astrophysics Data System (ADS)

    Chehtov, T.; Aktaa, J.; Kraft, O.

    2007-08-01

    Within the scope of the European fusion power plant study for development of a He-cooled divertor, a tungsten-steel joint has been considered. A preferable joining technique is high temperature brazing. Brazed joints of dissimilar materials suffer from a mismatch in coefficients of thermal expansion. The components of the joint are exposed to mechanical and cyclic thermal loads which give rise to development of high stresses and could lead to failure. Brazed joints of tungsten alloy and ferritic-martensitic steel using different brazing filler materials were studied both experimentally and theoretically. Finite element computations have been performed to calculate the stress distribution and to investigate their evolution within the course of the operational thermal load. Sample joint specimen have been brazed, investigated with respect to their microstructure, and mechanically characterized by performing bend and notched bar impact testing at different temperatures. Some plastic deformation and relatively low impact energies were measured.

  5. Characterization of Thermal and Mechanical Impact on Aluminum Honeycomb Structures

    NASA Technical Reports Server (NTRS)

    Robinson, Christen M.

    2013-01-01

    This study supports NASA Kennedy Space Center's research in the area of intelligent thermal management systems and multifunctional thermal systems. This project addresses the evaluation of the mechanical and thermal properties of metallic cellular solid (MCS) materials; those that are lightweight; high strength, tunable, multifunctional and affordable. A portion of the work includes understanding the mechanical properties of honeycomb structured cellular solids upon impact testing under ambient, water-immersed, liquid nitrogen-cooled, and liquid nitrogen-immersed conditions. Additionally, this study will address characterization techniques of the aluminum honeycomb's ability to resist multiple high-rate loadings or impacts in varying environmental conditions, using various techniques for the quantitative and qualitative determination for commercial applicability.

  6. General Characterization Methods for Photoelectrochemical Cells for Solar Water Splitting.

    PubMed

    Shi, Xinjian; Cai, Lili; Ma, Ming; Zheng, Xiaolin; Park, Jong Hyeok

    2015-10-12

    Photoelectrochemical (PEC) water splitting is a very promising technology that converts water into clean hydrogen fuel and oxygen by using solar light. However, the characterization methods for PEC cells are diverse and a systematic introduction to characterization methods for PEC cells has rarely been attempted. Unlike most other review articles that focus mainly on the material used for the working electrodes of PEC cells, this review introduces general characterization methods for PEC cells, including their basic configurations and methods for characterizing their performance under various conditions, regardless of the materials used. Detailed experimental operation procedures with theoretical information are provided for each characterization method. The PEC research area is rapidly expanding and more researchers are beginning to devote themselves to related work. Therefore, the content of this Minireview can provide entry-level knowledge to beginners in the area of PEC, which might accelerate progress in this area.

  7. Methods for Characterization of Alternative RNA Splicing.

    PubMed

    Harvey, Samuel E; Cheng, Chonghui

    2016-01-01

    Quantification of alternative splicing to detect the abundance of differentially spliced isoforms of a gene in total RNA can be accomplished via RT-PCR using both quantitative real-time and semi-quantitative PCR methods. These methods require careful PCR primer design to ensure specific detection of particular splice isoforms. We also describe analysis of alternative splicing using a splicing "minigene" in mammalian cell tissue culture to facilitate investigation of the regulation of alternative splicing of a particular exon of interest.

  8. Stirling engine control mechanism and method

    DOEpatents

    Dineen, John J.

    1983-01-01

    A reciprocating-to-rotating motion conversion and power control device for a Stirling engine includes a hub mounted on an offset portion of the output shaft for rotation relative to the shaft and for sliding motion therealong which causes the hub to tilt relative to the axis of rotation of the shaft. This changes the angle of inclination of the hub relative to the shaft axis and changes the axial stroke of a set of arms connected to the hub and nutating therewith. A hydraulic actuating mechanism is connected to the hub for moving its axial position along the shaft. A balancing wheel is linked to the hub and changes its angle of inclination as the angle of inclination of the hub changes to maintain the mechanism in perfect balance throughout its range of motion.

  9. Characterization of bulk superconductors through EBSD methods

    NASA Astrophysics Data System (ADS)

    Koblischka, M. R.; Koblischka-Veneva, A.

    2003-10-01

    The application of electron backscatter diffraction (EBSD) technique to bulk high- Tc superconductors is presented and reviewed. Due to the ceramic nature and the complex crystallographic unit cells of the perovskite-type high- Tc superconductors, the EBSD analysis is not yet as common as it deserves. We have successfully performed EBSD analysis on a variety of high- Tc compounds and samples including polycrystalline YBCO (pure and doped by alkali metals), melt-textured YBCO, thin and thick films of YBCO; the “green phase” Y 2BaCuO 5, thin film and melt-textured NdBa 2Cu 3O x and Bi-2212 single crystals and tapes. It is shown that the surface preparation of the samples is crucial due to the small information depth (up to 100 nm) of the EBSD technique. High quality Kikuchi patterns are the requirement in order to enable the automated EBSD mapping, which yields phase distributions, individual grain orientations and the misorientation angle distribution. The results can be presented in form of mappings, as charts, and as pole figures. These informations are required for a better understanding of the growth mechanism(s) of bulk high- Tc superconductors intended for applications.

  10. A thermoluminescent method for aerosol characterization

    NASA Technical Reports Server (NTRS)

    Long, E. R., Jr.; Rogowski, R. S.

    1976-01-01

    A thermoluminescent method has been used to study the interactions of aerosols with ozone. The preliminary results show that ozone reacts with many compounds found in aerosols, and that the thermoluminescence curves obtained from ozonated aerosols are characteristic of the aerosol. The results suggest several important applications of the thermoluminescent method: development of a detector for identification of effluent sources; a sensitive experimental tool for study of heterogeneous chemistry; evaluation of importance of aerosols in atmospheric chemistry; and study of formation of toxic, electronically excited species in airborne particles.

  11. Raman spectroscopic instrumentation and plasmonic methods for material characterization

    NASA Astrophysics Data System (ADS)

    Tanaka, Kazuki

    The advent of nanotechnology has led to incredible growth in how we consume, make and approach advanced materials. By exploiting nanoscale material properties, unique control of optical, thermal, mechanical, and electrical characteristics becomes possible. This thesis describes the development of a novel localized surface plasmon resonant (LSPR) color sensitive photosensor, based on functionalization of gold nanoparticles onto tianium dioxide nanowires and sensing by a metal-semiconducting nanowire-metal photodiode structure. This LSPR photosensor has been integrated into a system that incorporates Raman spectroscopy, microfluidics, optical trapping, and sorting flow cytometry into a unique material characterization system called the microfluidic optical fiber trapping Raman sorting flow cytometer (MOFTRSFC). Raman spectroscopy is utilized as a powerful molecular characterization technique used to analyze biological, mineralogical and nanomaterial samples. To combat the inherently weak Raman signal, plasmonic methods have been applied to exploit surface enhanced Raman scattering (SERS) and localized surface plasmon resonance (LSPR), increasing Raman intensity by up to 5 orders of magnitude. The resultant MOFTRSFC system is a prototype instrument that can effectively trap, analyze, and sort micron-sized dielectric particles and biological cells. Raman spectroscopy has been presented in several modalities, including the development of a portable near-infrared Raman spectrometer and other emerging technologies.

  12. Methods of characterization of synthetic opal films

    NASA Astrophysics Data System (ADS)

    Koryukin, A. V.; Akhmadeev, A. A.; Salakhov, M. Kh

    2013-12-01

    We developed methods for determination of thickness, number of layers and filling fraction of silica particles for synthetic opals. We show that the filling fraction is considerably less than for ideal close-packed structure, which is important for practical and theoretical applications.

  13. Nanomechanical characterization and molecular mechanism study of nanoparticle reinforced and cross-linked chitosan biopolymer.

    PubMed

    Rath, Amrita; Mathesan, Santhosh; Ghosh, Pijush

    2015-03-01

    Chitosan (CS) is a biomaterial that offers many sophisticated and innovative applications in the biomedical field owing to its excellent characteristics of biodegradability, biocompatibility and non-toxicity. However, very low mechanical properties of chitosan polymer impose restriction on its further development. Cross-linking and nanoparticle reinforcement are the two possible methods to improve the mechanical properties of chitosan films. In this research, these two methods are adopted individually by using tripolyphosphate as cross-linker and nano-hydroxyapatite as particle reinforcement. The nanomechanical characterizations under static loading conditions are performed on these modified chitosan films. It is observed that nanoparticle reinforcement provided necessary mechanical properties such as ductility and modulus. The mechanisms involved in improvement of mechanical properties due to particle reinforcement are studied by molecular dynamics (MD). Further, improvement in mechanical properties due to combination of particle reinforcement and cross-linking agent with chitosan is investigated. The stress relaxation behavior for all these types of films is characterized under dynamic loading conditions using dynamic mechanical analysis (nanoDMA) experiment. A viscoelastic solid like response is observed for all types of film with modulus relaxing by 3-6% of its initial value. A suitable generalized Maxwell model is fitted with the obtained viscoelastic response of these films. The response to nano-scratch behavior is also studied for particle reinforced composite films.

  14. Characterization of mechanical properties of materials using ultrasound broadband spectroscopy.

    PubMed

    Agrawal, Megha; Prasad, Abhinav; Bellare, Jayesh R; Seshia, Ashwin A

    2016-01-01

    This article explores the characterization of homogenous materials (metals, alloys, glass and polymers) by a simple broadband ultrasonic interrogation method. The novelty lies in the use of ultrasound in a continuous way with very low input power (0 dBm or less) and analysis of the transmitted acoustic wave spectrum for material property characterization like speed of sound, density and dimensions of a material. Measurements were conducted on various thicknesses of samples immersed in liquid where continuous-wave, frequency swept ultrasonic energy was incident normal to the sample surface. The electro-acoustic transmission response is analyzed in the frequency domain with respect to a specifically constructed multi-layered analytical model. From the acoustic signature of the sample materials, material properties such as speed of sound and acoustic impedance can be calculated with experimentally derived values found to be in general agreement with the literature and with pulse-echo technique establishing the basis for a non-contact and non-destructive technique for material characterization. Further, by looking at the frequency spacing of the peaks of water when the sample is immersed, the thickness of the sample can be calculated independently from the acoustic response. This technique can prove to be an effective non-contact, non-destructive and fast material characterization technique for a wide variety of materials.

  15. Method For Characterizing Residual Stress In Metals

    DOEpatents

    Jacobson, Loren A.; Michel, David J.; Wyatt, Jeffrey R.

    2002-12-03

    A method is provided for measuring the residual stress in metals. The method includes the steps of drilling one or more holes in a metal workpiece to a preselected depth and mounting one or more acoustic sensors on the metal workpiece and connecting the sensors to an electronic detecting and recording device. A liquid metal capable of penetrating into the metal workpiece placed at the bottom of the hole or holes. A recording is made over a period of time (typically within about two hours) of the magnitude and number of noise events which occur as the liquid metal penetrates into the metal workpiece. The magnitude and number of noise events are then correlated to the internal stress in the region of the workpiece at the bottom of the hole.

  16. a Novel Method for Gas Sensors Characterization

    NASA Astrophysics Data System (ADS)

    Mielle, P.; Marquis, F.; Trivier, V.

    2000-12-01

    For E-nose applications, sensors are never specified towards the aroma chemicals, because it is difficult to generate a known amount of chemical vapours from a condensed phase. A method was developed, that allows the specification of gas sensors towards food samples, using a GC/sensors coupling. We have found the ADL lower than the GC-FID detector, and an unexpected response for E.V. Olive Oil.

  17. Biochemical and mechanical characterization of Nereis worm jaws

    NASA Astrophysics Data System (ADS)

    Broomell, Christopher C.

    The ultimate goal of biomimetics is to elucidate the design principles governing performance in biological materials and apply them to engineering systems. Successful transfer of these principles will require a thorough understanding of the complex interplay between molecular composition, organization and mechanical properties of the material. This dissertation describes the mechanical and biochemical characterization of jaws from the marine polychaete Nereis virens. Nereid jaws possess remarkable mechanical properties considering their predominantly organic composition. Hardness and stiffness are comparable to human dentin. However, in stark contrast to dentin, in Nereis these properties are achieved without mineralization. The role of metal ions in jaw sclerotization is addressed. In the pristine state, Zn ions are concentrated at the tip and toothed-edge of the jaw and are critical for hardness and modulus; both properties are reduced by ˜70% following Zn removal by treatment with EDTA. Furthermore, metal content in the jaw can be manipulated by soaking Zn-depleted samples in metal solutions; the comparative effects of treatment with alternative transition metals under both dry and hydrated conditions are described. The molecular composition of the jaw is also addressed. Protein comprises ˜90% of the jaw mass; amino acid analysis indicates that histidine is increased in the hardened, Zn-rich tip. The major protein component in Nereid jaw extracts is purified and characterized by partial peptide mapping and isolation of a partial clone from a jaw pulp cDNA library. Nvjp-1 is a 38 kDa glycine- histidine-rich protein and is believed to be the principle structural protein in the hardened jaw tip. The effects of selected environmental factors on Nvjp-1 structure and assembly are described. Transition from low to high pH is accompanied by changes in secondary structure and a significant molecular elongation. Furthermore, exposure to transition metals, notably Zn and

  18. Versatile and inexpensive Hall-Effect force sensor for mechanical characterization of soft biological materials.

    PubMed

    Backman, Daniel E; LeSavage, Bauer L; Wong, Joyce Y

    2017-01-25

    Mismatch of hierarchical structure and mechanical properties between tissue-engineered implants and native tissue may result in signal cues that negatively impact repair and remodeling. With bottom-up tissue engineering approaches, designing tissue components with proper microscale mechanical properties is crucial to achieve necessary macroscale properties in the final implant. However, characterizing microscale mechanical properties is challenging, and current methods do not provide the versatility and sensitivity required to measure these fragile, soft biological materials. Here, we developed a novel, highly sensitive Hall-Effect based force sensor that is capable of measuring mechanical properties of biological materials over wide force ranges (μN to N), allowing its use at all steps in layer-by-layer fabrication of engineered tissues. The force sensor design can be easily customized to measure specific force ranges, while remaining easy to fabricate using inexpensive, commercial materials. Although we used the force sensor to characterize mechanics of single-layer cell sheets and silk fibers, the design can be easily adapted for different applications spanning larger force ranges (>N). This platform is thus a novel, versatile, and practical tool for mechanically characterizing biological and biomimetic materials.

  19. Characterizing Cardiac Molecular Mechanisms of Mammalian Hibernation via Quantitative Proteogenomics.

    PubMed

    Vermillion, Katie L; Jagtap, Pratik; Johnson, James E; Griffin, Timothy J; Andrews, Matthew T

    2015-11-06

    This study uses advanced proteogenomic approaches in a nonmodel organism to elucidate cardioprotective mechanisms used during mammalian hibernation. Mammalian hibernation is characterized by drastic reductions in body temperature, heart rate, metabolism, and oxygen consumption. These changes pose significant challenges to the physiology of hibernators, especially for the heart, which maintains function throughout the extreme conditions, resembling ischemia and reperfusion. To identify novel cardioadaptive strategies, we merged large-scale RNA-seq data with large-scale iTRAQ-based proteomic data in heart tissue from 13-lined ground squirrels (Ictidomys tridecemlineatus) throughout the circannual cycle. Protein identification and data analysis were run through Galaxy-P, a new multiomic data analysis platform enabling effective integration of RNA-seq and MS/MS proteomic data. Galaxy-P uses flexible, modular workflows that combine customized sequence database searching and iTRAQ quantification to identify novel ground squirrel-specific protein sequences and provide insight into molecular mechanisms of hibernation. This study allowed for the quantification of 2007 identified cardiac proteins, including over 350 peptide sequences derived from previously uncharacterized protein products. Identification of these peptides allows for improved genomic annotation of this nonmodel organism, as well as identification of potential splice variants, mutations, and genome reorganizations that provides insights into novel cardioprotective mechanisms used during hibernation.

  20. Clinical characterization and molecular mechanisms of statin myopathy.

    PubMed

    Toth, Peter P; Harper, Charles R; Jacobson, Terry A

    2008-08-01

    Myopathy has been reported in a small percentage of statin-treated patients for the past 30 years, but the etiologic mechanisms for inducing muscle injury have not yet been fully characterized. Statin-induced myopathy is now understood to be a heterogeneous condition that may be due to: mechanisms of the drug itself; interactions with other drugs; or genetic, metabolic and immunological vulnerabilities in individual patients. In some cases, statins may unmask latent conditions (e.g., asymptomatic baseline myopathy) that predispose patients to muscle toxicity. The definitions, epidemiology, clinical features, risk factors and proposed mechanisms of statin-induced myopathy are reviewed. Muscle metabolism can be adversely impacted by statin therapy, including changes in fatty acid oxidation, possibly reduced coenzyme Q(10) biosynthesis, and increased myocyte protein degradation via the activity of atrogin-1 and the ubiquitin-proteasome pathway. Statin therapy may also activate a variety of autoimmune phenomena that potentiate myocellular injury. Improving our understanding of statin-induced myopathy is a high clinical priority given the large number of patients eligible for statin therapy and the fact that the development of myalgia and myopathy are leading reasons cited by patients for statin discontinuation.

  1. Phenomenological and mechanics aspects of nondestructive evaluation and characterization by sound and ultrasound of material and fracture properties

    NASA Technical Reports Server (NTRS)

    Fu, L. S. W.

    1982-01-01

    Developments in fracture mechanics and elastic wave theory enhance the understanding of many physical phenomena in a mathematical context. Available literature in the material, and fracture characterization by NDT, and the related mathematical methods in mechanics that provide fundamental underlying principles for its interpretation and evaluation are reviewed. Information on the energy release mechanism of defects and the interaction of microstructures within the material is basic in the formulation of the mechanics problems that supply guidance for nondestructive evaluation (NDE).

  2. Synthesis and characterization of the mechanical behavior of mechanically strong porous nanostructured materials

    NASA Astrophysics Data System (ADS)

    Churu, Habel Gitogo

    Aerogels are three-dimensional assemblies of nano-particles that are typically synthesized through the sol-gel process and then dried by replacing the pore filling solvent with air. This work presents a robust method to manufacture both organic and inorganic aerogel so that mass production can be done more easily and at a substantially low cost of production. The inherent problems associated with typical aerogel materials such as fragility, hydrophilicity as well as requirement to use supercritical drier are addressed by nano-casting a conformal polymer layer on inorganic templated aerogels, while the microstructure of organic aerogels are refined so that they can be dried in ambient condition. Thus large pieces of aerogels have been synthesized and characterized to ascertain the mechanical properties so that design of components and structures can be done with ease. The first part of this work deals with inorganic templated silica aerogels whose morphology has been optimized to overcome fragility and allow for large samples to be produced. As such a microstructure akin to the naturally occurring honeycomb structure is produced resulting in a material, whose energy absorption is about 187 j/g, indicating that they are far stronger than most manmade materials in production. The second part of this work present a careful synthesis of organic polyurea aerogels whole morphology is varied from nano fibrous at the low density end to nano particulate at the high density end. By so doing we synthesized a nanostructured material which can be dried in ambient conditions at a much lower bulk density (0.2 g/ cm3) that earlier reported. In addition the materials have very high dimensional stability such that they retain their shape and size from the mold even after ambient drying. With that, this work seeks to resolve the inherent problems of aerogel materials, both organic and inorganic that makes them hard to economically mass produce.

  3. Standard method for characterizing SERS substrates

    NASA Astrophysics Data System (ADS)

    Guicheteau, Jason A.; Hankus, Mikella E.; Christesen, Steven D.; Fountain, Augustus W., III; Pellegrino, Paul M.; Emmons, Erik D.; Tripathi, Ashish; Wilcox, Phillip; Emge, Darren

    2012-06-01

    We present the methodology and results of a standard assessment protocol to evaluate disparate SERS substrates that were developed for the Defense Advanced Research Programs Agency (DARPA) SERS Science and Technology Fundamentals Program. The results presented are a snapshot of a collaborative effort between the US Army Edgewood Chemical Biological Center, and the US Army Research Laboratory-Aldelphi Laboratory Center to develop a quantitative analytical method with spectroscopic figures of merit to unambiguously compare the sensitivity and reproducibility of various SERS substrates submitted by the program participants. We present the design of a common assessment protocol and the definition of a SERS enhancement value (SEV) in order to effectively compare SERS active surfaces.

  4. Applying analytical and experimental methods to characterize engineered components

    NASA Astrophysics Data System (ADS)

    Munn, Brian S.

    A variety of analytical and experimental methods were employed to characterize two very different types of engineered components. The engineered components of interest were monolithic silicon carbide tiles and M12 x 1.75 Class 9.8 steel fasteners. A new application applying the hole drilling technique was developed on monolithic silicon-carbide tiles of varying thicknesses. This work was driven by a need to first develop a reliable method to measure residual stresses and, then, to validate the methodology through characterizing residual stresses on the tiles of interest. The residual stresses measured in all tiles were tensile in nature. The highest residual stresses were measured at the surface, and decreased exponentially. There was also a trend for the residual tensile stresses to decrease with increasing specimen thickness. Thermal-mechanical interactions were successfully analyzed via a one-way, coupled FEA modeled approach. The key input for a successful FEA analysis was an appropriate heat transfer rate. By varying the heat transfer rate in the FEA model and, then, comparing stress output to experimental residual stress values, provided a favorable numerical solution in determining a heat transfer rate. Fatigue behavior of a M12 x 1.75 Class 9.8 steel test fastener was extensively studied through the use of a variety of experimental and analytical techniques. Of particular interest, was the underlying interaction between notch plasticity and overall fatigue behavior. A very large data set of fastener fatigue behavior was generated with respect to mean stress. A series of endurance limit curves were established for different mean stress values ranging from minimal to the yield strength of the steel fastener (0 ≤ sigmam ≤ sigmay). This wide range in mean stress values created a change in notch tip plasticity which caused a local diminishing of the mean stress increasing expected fatigue life. The change in notch plasticity was identified by residual stress

  5. Mechanical biocompatibility of prosthetic meshes: a comprehensive protocol for mechanical characterization.

    PubMed

    Maurer, M M; Röhrnbauer, B; Feola, A; Deprest, J; Mazza, E

    2014-12-01

    This study is aimed at a comprehensive and extensive characterization of the mechanical biocompatibility of mesh prostheses. A robust and simple experimental protocol and a set of parameters is proposed, addressing stiffness under uniaxial and biaxial loading conditions, anisotropy, influence of prior deformation history, local mismatch of deformation mechanisms, and changes in mechanical properties when embedded in a homogeneous matrix. These parameters can form the basis for comparison of different mesh types and for evaluation of their mechanical biocompatibility. Measurements were performed on nine mesh types used for hernia and/or pelvic repair, including heavier as well as lighter implants and covering a wide range of mechanical responses. A total of 93 experiments were performed and all parameters are represented for each mesh in a single diagram to facilitate the quantitative assessment of implant characteristics and their comparison. The mechanics of implants is a critical factor determining clinical performance which should be accounted for in mesh selection and for development of future implants.

  6. Novel method to characterize superhydrophobic coatings.

    PubMed

    Samaha, Mohamed A; Vahedi Tafreshi, Hooman; Gad-el-Hak, Mohamed

    2013-04-01

    Superhydrophobic coatings possess a strong water-repellent characteristic, which, among several other potential applications, enhances the mobility of water droplets over the surface. The coating traps air within its micropores, such that a submerged moving body experiences shear-free and no-slip regions over, respectively, the air pockets and the solid surface. This, in turn, may lead to significant skin-friction reduction. The coating maintains its superhydrophobicity as long as the air remains entrapped. It is therefore of great interest to precisely measure the amount of trapped air, which is particularly difficult to estimate for coatings with disordered microstructures. A novel method to measure the effective thickness and gas volume fraction of superhydrophobic coatings with either ordered or random microroughness is advanced. The technique is applied to both aerogel and electrospun fibrous coatings. The experiments utilize a sensitive weighing scale (down to 10(-4) gm) and height gauge (down to 10 μm) to determine the buoyancy force on an immersed, coated glass-slide substrate. The measured force is used to calculate the volume fraction of entrapped air. The coating's effective thickness also follows from the same calculations. The sensitivity of our particular scale enables the measuring of thicknesses down to 3 μm, which is not readily possible with conventional thickness gauges. Smaller thicknesses could be measured using more sensitive scales.

  7. Characterization of Release Mechanism in Polymeric Drug Delivery Systems

    NASA Astrophysics Data System (ADS)

    Laplante, Arthur James; Plachy, Robin Marie; Aou, Kaoru; Ferguson, Jake; Hsu, Shaw Ling

    2006-03-01

    Our polymeric drug delivery system is based on our understanding of phase behavior of polymers [e.g poly(lactic acid)], low molecular drugs and various solvents used in processing. Clearly the different morphologies achieved, based on different phase separation kinetics, can affect drug release rates. Release of drugs, in most cases, involves the exchange between the extraction media and drug. We have characterized the transport behavior using a number of unique techniques. Reflectance infrared spectroscopy has given us a detailed description of the release rate of drugs into the extraction media. Surface plasmon resonance has shown the overall mass loss. UV-visible spectroscopy has yielded the concentration of drug in the solution. These measurements are compared to the release mechanism based on Fickian diffusion. The two step release rates observed can only be explained by taking into account differences in the morphological features of the phase separated films.

  8. Material, Mechanical, and Tribological Characterization of Laser-Treated Surfaces

    NASA Astrophysics Data System (ADS)

    Yilbas, Bekir Sami; Kumar, Aditya; Bhushan, Bharat; Aleem, B. J. Abdul

    2014-10-01

    Laser treatment under nitrogen assisting gas environment of cobalt-nickel-chromium-tungsten-based superalloy and high-velocity oxygen-fuel thermal spray coating of nickel-chromium-based superalloy on carbon steel was carried out to improve mechanical and tribological properties. Superalloy surface was preprepared to include B4C particles at the surface prior to the laser treatment process. Material and morphological changes in the laser-treated samples were examined using scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction (XRD) analysis. Residual stresses present at the surface region of the laser-treated layer were determined from the XRD data. The microhardness of the laser-treated surface was measured by indentation tests. Fracture toughness of the coating surfaces before and after laser treatment were also measured using overload indentation tests. Macrowear and macrofriction characterization were carried out using pin-on-disk tests.

  9. Metrology and characterization of application specific chemical mechanical polishing pads

    NASA Astrophysics Data System (ADS)

    Zantye, Parshuram B.; Mudhivarthi, S.; Kumar, Ashok; Obeng, Yaw

    2005-09-01

    There is a need for metrology, characterization, and optimization of chemical mechanical polishing (CMP) pad architecture before being put into service. A polishing pad which is made up of polyolefin material instead of conventional polyurethane has been developed. The surface of the pad has been modified to match the hardness of the surface of the material that is being polished. In this research, we coated the pad with tetraethylorthosilicate using plasma enhanced chemical vapor deposition for varying durations of time for optimum pad output. The pad was then extensively characterized using the several standard metrology techniques such as scanning electron microscopy, x-ray photoelectron spectroscopy, nanoindentation, etc. The CMP performance evaluation of all the candidate pads along with in situ measurement of dynamic coefficients of friction, material removal rate, and acoustic emission was done using CETR CP-4™ bench top CMP tester. There was a correlation and interdependence of the pad coating time and surface chemical, micromechanical, and tribological properties. However, their impact on the pad CMP performance was found to be indirect. Based upon these findings, suggestions were given for final pad architecture for commercialization. The demonstrated methodology can also be implemented for parametric optimization of novel polishing pads in the future.

  10. Optical and mechanical characterization and analysis of nanoscale systems

    NASA Astrophysics Data System (ADS)

    Lamont, Daniel N.

    This thesis discusses research focused on the analysis and characterization of nanoscale systems. These studies are organized into three sections based on the research topic and methodology: Part I describes research using scanning probe microscopy, Part II describes research using photonic crystals and Part III describes research using spectroscopy. A brief description of the studies contained in each part follows. Part I discusses our work using scanning probe microscopy. In Chapter 3, we present our work using apertureless scanning near-field optical microscopy to study the optical properties of an isolated subwavelength slit in a gold film, while in chapter 4 atomic force microscopy and a three point bending model are used to explore the mechanical properties of individual multiwall boron nitride nanotubes. Part II includes our studies of photonic crystals. In Chapter 6 we discuss the fabrication and characterization of a photonic crystal material that utilizes electrostatic colloidal crystal array self assembly to form a highly ordered, non closed packed template; and in Chapter 7 we discuss the fabrication and characterization of a novel, simple and efficient approach to rapidly fabricate large-area 2D particle arrays on water surfaces. Finally, in Part III we present our spectroscopic studies. In Chapter 9 we use fluorescence quenching and fluorescence lifetime measurements to study electron transfer in aggregates of cadmium selenide and cadmium telluride nanoparticles assemblies. Chapter 10 features our work using the electronic structure of zinc sulfide semiconductor nanoparticles to sensitize the luminescence of Tb3+ and Eu 3+ lanthanide cations, and Chapter 11 presents our recent work studying photo-induced electron transfer between donor and acceptor moieties attached to a cleft-forming bridge. v.

  11. ASTM test methods for composite characterization and evaluation

    NASA Technical Reports Server (NTRS)

    Masters, John E.

    1994-01-01

    A discussion of the American Society for Testing and Materials is given. Under the topic of composite materials characterization and evaluation, general industry practice and test methods for textile composites are presented.

  12. Optical characterization of high speed microscanners based on static slit profiling method

    NASA Astrophysics Data System (ADS)

    Alaa Elhady, A.; Sabry, Yasser M.; Khalil, Diaa

    2017-01-01

    Optical characterization of high-speed microscanners is a challenging task that usually requires special high speed, extremely expensive camera systems. This paper presents a novel simple method to characterize the scanned beam spot profile and size in high-speed optical scanners under operation. It allows measuring the beam profile and the spot sizes at different scanning angles. The method is analyzed theoretically and applied experimentally on the characterization of a Micro Electro Mechanical MEMS scanner operating at 2.6 kHz. The variation of the spot size versus the scanning angle, up to ±15°, is extracted and the dynamic bending curvature effect of the micromirror is predicted.

  13. In Situ Mechanical Testing Techniques for Real-Time Materials Deformation Characterization

    NASA Astrophysics Data System (ADS)

    Rudolf, Chris; Boesl, Benjamin; Agarwal, Arvind

    2016-01-01

    In situ mechanical property testing has the ability to enhance quantitative characterization of materials by revealing the occurring deformation behavior in real time. This article will summarize select recent testing performed inside a scanning electron microscope on various materials including metals, ceramics, composites, coatings, and 3-Dimensional graphene foam. Tensile and indentation testing methods are outlined with case studies and preliminary data. The benefits of performing a novel double-torsion testing technique in situ are also proposed.

  14. Exactly Embedded Wavefunction Methods for Characterizing Nitrogen Reduction Catalysis

    DTIC Science & Technology

    2015-01-15

    AFRL-OSR-VA-TR-2015-0038 Exactly Embedded Wavefunction Methods for Characterizing Nitrogen THOMAS MILLER CALIFORNIA INSTITUTE OF TECHNOLOGY Final...SUBTITLE Exactly Embedded Wavefunction Methods for Characterizing Nitrogen Reduction Catalysis 5a. CONTRACT NUMBER N/A 5b. GRANT NUMBER FA9550...catalysis, such as hydrogen and nitrogen reduction. In a significant methodological advance from the past year, we developed an accurate and

  15. Fracture mechanics life analytical methods verification testing

    NASA Technical Reports Server (NTRS)

    Favenesi, J. A.; Clemmons, T. G.; Lambert, T. J.

    1994-01-01

    Verification and validation of the basic information capabilities in NASCRAC has been completed. The basic information includes computation of K versus a, J versus a, and crack opening area versus a. These quantities represent building blocks which NASCRAC uses in its other computations such as fatigue crack life and tearing instability. Several methods were used to verify and validate the basic information capabilities. The simple configurations such as the compact tension specimen and a crack in a finite plate were verified and validated versus handbook solutions for simple loads. For general loads using weight functions, offline integration using standard FORTRAN routines was performed. For more complicated configurations such as corner cracks and semielliptical cracks, NASCRAC solutions were verified and validated versus published results and finite element analyses. A few minor problems were identified in the basic information capabilities of the simple configurations. In the more complicated configurations, significant differences between NASCRAC and reference solutions were observed because NASCRAC calculates its solutions as averaged values across the entire crack front whereas the reference solutions were computed for a single point.

  16. Fracture mechanics life analytical methods verification testing

    NASA Technical Reports Server (NTRS)

    Favenesi, J. A.; Clemons, T. G.; Riddell, W. T.; Ingraffea, A. R.; Wawrzynek, P. A.

    1994-01-01

    The objective was to evaluate NASCRAC (trademark) version 2.0, a second generation fracture analysis code, for verification and validity. NASCRAC was evaluated using a combination of comparisons to the literature, closed-form solutions, numerical analyses, and tests. Several limitations and minor errors were detected. Additionally, a number of major flaws were discovered. These major flaws were generally due to application of a specific method or theory, not due to programming logic. Results are presented for the following program capabilities: K versus a, J versus a, crack opening area, life calculation due to fatigue crack growth, tolerable crack size, proof test logic, tearing instability, creep crack growth, crack transitioning, crack retardation due to overloads, and elastic-plastic stress redistribution. It is concluded that the code is an acceptable fracture tool for K solutions of simplified geometries, for a limited number of J and crack opening area solutions, and for fatigue crack propagation with the Paris equation and constant amplitude loads when the Paris equation is applicable.

  17. Polydimethylsiloxane thin film characterization using all-optical photoacoustic mechanism.

    PubMed

    Zou, Xiaotian; Wu, Nan; Tian, Ye; Zhang, Yang; Wang, Xingwei

    2013-09-01

    This paper presents a nondestructive ultrasound testing method for characterization of the resonant frequencies of polydimethylsiloxane (PDMS) thin film by using a miniature fiber optic photoacoustic (PA) probe. The PA probe was fabricated with an optical fiber and a synthesized gold nanocomposite. During the experiment, a cured PDMS thin film with a thickness of 220 μm was immersed into a water medium using a custom-designed holder to clamp the film. An acoustic pulse was generated by the PA probe and propagated through the water media to excite the fixed film. A fiber optic pressure sensor based on the Fabry-Perot principle was used to collect the excited acoustic signals on the other side of the film. The acquired response of the acoustic pulse was used to compute the resonant frequencies of the PDMS thin film based on a deconvolution method.

  18. Design and characterization of an Antenna Pointing Mechanism for on-orbit servicing missions

    NASA Astrophysics Data System (ADS)

    Purschke, R.; Hoehn, A.

    The goal of this work was to (1) define parameters to characterize a pointing mechanism, (2) design a setup to test these parameters and, (3) verify the test methods by comparing the results to the theoretically calculated or independently verified numbers. The verification of the test results was conducted with an in-house built Antenna Pointing Mechanism for on-orbit servicing applications. The test setup was developed to find a method to measure the behavior of a pointing mechanism. This was realized by mounting a Laser pointer on the antenna interface of the mechanism and pointing it towards a two-dimensional Position Sensitive Detector, providing means to resolve small motions, and to derive velocity and acceleration of the mechanism. The results show good correlation for characteristic parameters such as pointing velocity and acceleration, repeatability, resolution and pointing accuracy of the mechanism. In future work this test method will be qualified for and used to compare the performance of the mechanism at different environmental conditions such as vacuum, temperature and microgravity.

  19. Characterization of reward and effort mechanisms in apathy.

    PubMed

    Bonnelle, Valerie; Veromann, Kai-Riin; Burnett Heyes, Stephanie; Lo Sterzo, Elena; Manohar, Sanjay; Husain, Masud

    2015-01-01

    Apathy is a common but poorly understood condition with a wide societal impact observed in several brain disorders as well as, to some extent, in the normal population. Hence the need for better characterization of the underlying mechanisms. The processes by which individuals decide to attribute physical effort to obtain rewards might be particularly relevant to relate to apathy traits. Here, we designed two paradigms to assess individual differences in physical effort production and effort-based decision-making and their relation to apathy in healthy people. Apathy scores were measured using a modified version of the Lille Apathy Rating Scale, suitable for use in a non-clinical population. In the first study, apathy scores were correlated with the degree to which stake (reward on offer) and difficulty level impacts on physical effort production. Individuals with relatively high apathy traits showed an increased modulation of effort while more motivated individuals generally exerted greater force across different levels of stake. To clarify the underlying mechanisms for this behavior, we designed a second task that allows independent titration of stake and effort levels for which subjects are willing to engage in an effortful response to obtain a reward. Our results suggest that apathy traits in the normal population are related to the way reward subjectively affects the estimation of effort costs, and more particularly manifest as decreased willingness to exert effort when rewards are small, or below threshold. The tasks we introduce here may provide useful tools to further investigate apathy in clinical populations.

  20. Method for material characterization in a non-anechoic environment

    NASA Astrophysics Data System (ADS)

    Pometcu, L.; Sharaiha, A.; Benzerga, R.; Tamas, R. D.; Pouliguen, P.

    2016-04-01

    This paper presents a characterization method for extracting the reflection coefficient of materials and the real part of their permittivity. The characterization is performed in a real environment, as opposed to the classical measurement methods that require an anechoic chamber. In order to reduce the effects of the multipath propagation, a free space bistatic measurement was performed at different distances material-antennas in far field. By using a Teflon sample and a commercial absorbing material sample, measurements have been performed in order to validate the characterization technique.

  1. Synthesis, characterization and interaction mechanism of new oxadiazolo-phthalimides as peripheral analgesics. IV

    NASA Astrophysics Data System (ADS)

    Antunes, Roberto; Batista, Hildson; Srivastava, Rajendra M.; Thomas, George; Araújo, Clidenor C.; Longo, Ricardo L.; Magalhães, Hélio; Leão, Marcelo B. C.; Pavão, Antônio C.

    2003-11-01

    The synthesis, characterization and spectroscopic studies of compounds 6a- g with analgesic activity is described. A new model of interaction between the drug and the enzyme is suggested. Application of the Resonance Valence Bond theory led us to propose, for the first time, an entirely new mechanism involving an electron transfer from the amino acid residue of the enzyme to the drug. Theoretical studies of various transition states involved in the interaction mechanism employing the semi-empirical molecular orbital calculations (AM1 method) have been carried out. This article also deals with an extensive study of the structure-activity relationships of seven oxadiazolo-phthalimides 6a- g.

  2. Solution-adaptive finite element method in computational fracture mechanics

    NASA Technical Reports Server (NTRS)

    Min, J. B.; Bass, J. M.; Spradley, L. W.

    1993-01-01

    Some recent results obtained using solution-adaptive finite element method in linear elastic two-dimensional fracture mechanics problems are presented. The focus is on the basic issue of adaptive finite element method for validating the applications of new methodology to fracture mechanics problems by computing demonstration problems and comparing the stress intensity factors to analytical results.

  3. Mechanical characterization of TiO{sub 2} nanofibers produced by different electrospinning techniques

    SciTech Connect

    Vahtrus, Mikk; Šutka, Andris; Vlassov, Sergei; Šutka, Anna; Polyakov, Boris; Saar, Rando; Dorogin, Leonid; Lõhmus, Rünno

    2015-02-15

    In this work TiO{sub 2} nanofibers produced by needle and needleless electrospinning processes from the same precursor were characterized and compared using Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and in situ SEM nanomechanical testing. Phase composition, morphology, Young's modulus and bending strength values were found. Weibull statistics was used to evaluate and compare uniformity of mechanical properties of nanofibers produced by two different methods. It is shown that both methods yield nanofibers with very similar properties. - Graphical abstract: Display Omitted - Highlights: • TiO{sub 2} nanofibers were produced by needle and needleless electrospinning processes. • Structure was studied by Raman spectroscopy and electron microscopy methods. • Mechanical properties were measured using advanced in situ SEM cantilevered beam bending technique. • Both methods yield nanofibers with very similar properties.

  4. A new method for anisotropic materials characterization based on phased-array ultrasonic transducers technology

    SciTech Connect

    Frenet, D.; Calmon, P.; Paradis, L.

    1999-12-02

    A method for materials characterization based on the utilization of a ultrasonic array transducer of conical shape has been developed at the CEA. The specific design of this transducer allows the generation and the detection of leaky surface acoustic waves (LSAW) in an efficient way. Additionally, anisotropic materials can be investigated in several azimuthal directions without any mechanical movement. The characterization process relies on the velocity measurement of the LSAW. Experimental results on both isotropic an anisotropic material are reported.

  5. The characterization of kerogen-analytical limitations and method design

    SciTech Connect

    Larter, S.R.

    1987-04-01

    Methods suitable for high resolution total molecular characterization of kerogens and other polymeric SOM are necessary for a quantitative understanding of hydrocarbon maturation and migration phenomena in addition to being a requirement for a systematic understanding of kerogen based fuel utilization. Gas chromatographic methods, in conjunction with analytical pyrolysis methods, have proven successful in the rapid superficial characterization of kerogen pyrolysates. Most applications involve qualitative or semi-quantitative assessment of the relative concentration of aliphatic, aromatic, or oxygen-containing species in a kerogen pyrolysate. More recently, the use of alkylated polystyrene internal standards has allowed the direct determination of parameters related to the abundance of, for example, normal alkyl groups or single ring aromatic species in kerogens. The future of methods of this type for improved kerogen typing is critically discussed. The conceptual design and feasibility of methods suitable for the more complete characterization of complex geopolymers on the molecular level is discussed with practical examples.

  6. Transuranic waste characterization sampling and analysis methods manual. Revision 1

    SciTech Connect

    Suermann, J.F.

    1996-04-01

    This Methods Manual provides a unified source of information on the sampling and analytical techniques that enable Department of Energy (DOE) facilities to comply with the requirements established in the current revision of the Transuranic Waste Characterization Quality Assurance Program Plan (QAPP) for the Waste Isolation Pilot Plant (WIPP) Transuranic (TRU) Waste Characterization Program (the Program) and the WIPP Waste Analysis Plan. This Methods Manual includes all of the testing, sampling, and analytical methodologies accepted by DOE for use in implementing the Program requirements specified in the QAPP and the WIPP Waste Analysis Plan. The procedures in this Methods Manual are comprehensive and detailed and are designed to provide the necessary guidance for the preparation of site-specific procedures. With some analytical methods, such as Gas Chromatography/Mass Spectrometry, the Methods Manual procedures may be used directly. With other methods, such as nondestructive characterization, the Methods Manual provides guidance rather than a step-by-step procedure. Sites must meet all of the specified quality control requirements of the applicable procedure. Each DOE site must document the details of the procedures it will use and demonstrate the efficacy of such procedures to the Manager, National TRU Program Waste Characterization, during Waste Characterization and Certification audits.

  7. Mechanical and structural characterizations of gamma- and alpha-alumina nanofibers

    SciTech Connect

    Vahtrus, Mikk; Umalas, Madis; Polyakov, Boris; Dorogin, Leonid; Saar, Rando; Tamme, Maret; Saal, Kristjan; Lõhmus, Rünno; Vlassov, Sergei

    2015-09-15

    We investigate the applicability of alumina nanofibers as a potential reinforcement material in ceramic matrix compounds by comparing the mechanical properties of individual nanofibers before and after annealing at 1400 °C. Mechanical testing is performed inside a scanning electron microscope (SEM), which enables observation in real time of the deformation and fracture of the fibers under loading, thereby providing a close-up inspection of the freshly fractured area in vacuum. Improvement of both the Young's modulus and the breaking strength for annealed nanofibers is demonstrated. Mechanical testing is supplemented with the structural characterization of the fibers before and after annealing using SEM, transmission electron microscopy and X-ray diffraction methods. - Highlights: • Mechanical properties of individual alumina nanofibers were measured using in situ SEM cantilevered beam bending technique. • Improvement of mechanical properties of the alumina fibers after annealing at 1400 °C is demonstrated. • Formation of branched structures is demonstrated and their mechanical properties are studied. • XRD and electron microscopy were used for structural characterization of untreated and annealed nanofibers.

  8. Characterization of a possible uptake mechanism of selective antibacterial peptides.

    PubMed

    Polanco, Carlos; Samaniego, José Lino; Castañón-González, Jorge Alberto; Buhse, Thomas; Sordo, Marili Leopold

    2013-01-01

    Selective antibacterial peptides containing less than 30 amino acid residues, cationic, with amphipathic properties, have been the subject of several studies due to their active participation and beneficial effects in strengthening the immune system of all living organisms. This manuscript reports the results of a comparison between the group of selective antibacterial peptides and another group called "cell penetrating peptides". An important number of the selective antibacterial peptides are cell penetrating peptides, suggesting that their toxicity is related to their uptake mechanism. The verification of this observation also includes the adaptation of a method previously published, called Polarity index, which reproduces and confirms the action of this new set of peptides. The efficiency of this method was verified based on four different databases, yielding a high score. The verification was based exclusively on the peptides already reported in the databases which have been experimentally verified.

  9. Simulated scaling method for localized enhanced sampling and simultaneous "alchemical" free energy simulations: a general method for molecular mechanical, quantum mechanical, and quantum mechanical/molecular mechanical simulations.

    PubMed

    Li, Hongzhi; Fajer, Mikolai; Yang, Wei

    2007-01-14

    A potential scaling version of simulated tempering is presented to efficiently sample configuration space in a localized region. The present "simulated scaling" method is developed with a Wang-Landau type of updating scheme in order to quickly flatten the distributions in the scaling parameter lambdam space. This proposal is meaningful for a broad range of biophysical problems, in which localized sampling is required. Besides its superior capability and robustness in localized conformational sampling, this simulated scaling method can also naturally lead to efficient "alchemical" free energy predictions when dual-topology alchemical hybrid potential is applied; thereby simultaneously, both of the chemically and conformationally distinct portions of two end point chemical states can be efficiently sampled. As demonstrated in this work, the present method is also feasible for the quantum mechanical and quantum mechanical/molecular mechanical simulations.

  10. Generating and characterizing the mechanical properties of cell-derived matrices using atomic force microscopy.

    PubMed

    Tello, Marta; Spenlé, Caroline; Hemmerlé, Joseph; Mercier, Luc; Fabre, Roxane; Allio, Guillaume; Simon-Assmann, Patricia; Goetz, Jacky G

    2016-02-01

    Mechanical interaction between cells and their surrounding extracellular matrix (ECM) controls key processes such as proliferation, differentiation and motility. For many years, two-dimensional (2D) models were used to better understand the interactions between cells and their surrounding ECM. More recently, variation of the mechanical properties of tissues has been reported to play a major role in physiological and pathological scenarios such as cancer progression. The 3D architecture of the ECM finely tunes cellular behavior to perform physiologically relevant tasks. Technical limitations prevented scientists from obtaining accurate assessment of the mechanical properties of physiologically realistic matrices. There is therefore a need for combining the production of high-quality cell-derived 3D matrices (CDMs) and the characterization of their topographical and mechanical properties. Here, we describe methods that allow to accurately measure the young modulus of matrices produced by various cellular types. In the first part, we will describe and review several protocols for generating CDMs matrices from endothelial, epithelial, fibroblastic, muscle and mesenchymal stem cells. We will discuss tools allowing the characterization of the topographical details as well as of the protein content of such CDMs. In a second part, we will report the methodologies that can be used, based on atomic force microscopy, to accurately evaluate the stiffness properties of the CDMs through the quantification of their young modulus. Altogether, such methodologies allow characterizing the stiffness and topography of matrices deposited by the cells, which is key for the understanding of cellular behavior in physiological conditions.

  11. Shear wave elastography plaque characterization with mechanical testing validation: a phantom study

    NASA Astrophysics Data System (ADS)

    Widman, E.; Maksuti, E.; Larsson, D.; Urban, M. W.; Bjällmark, A.; Larsson, M.

    2015-04-01

    Determining plaque vulnerability is critical when selecting the most suitable treatment for patients with atherosclerotic plaque. Currently, clinical non-invasive ultrasound-based methods for plaque characterization are limited to visual assessment of plaque morphology and new quantitative methods are needed. In this study, shear wave elastography (SWE) was used to characterize hard and soft plaque mimicking inclusions in six common carotid artery phantoms by using phase velocity analysis in static and dynamic environments. The results were validated with mechanical tensile testing. In the static environment, SWE measured a mean shear modulus of 5.8  ±  0.3 kPa and 106.2  ±  17.2 kPa versus 3.3  ±  0.5 kPa and 98.3  ±  3.4 kPa measured by mechanical testing in the soft and hard plaques respectively. Furthermore, it was possible to measure the plaques’ shear moduli throughout a simulated cardiac cycle. The results show good agreement between SWE and mechanical testing and indicate the possibility for in vivo arterial plaque characterization using SWE.

  12. Mechanical force characterization in manipulating live cells with optical tweezers.

    PubMed

    Wu, Yanhua; Sun, Dong; Huang, Wenhao

    2011-02-24

    Laser trapping with optical tweezers is a noninvasive manipulation technique and has received increasing attentions in biological applications. Understanding forces exerted on live cells is essential to cell biomechanical characterizations. Traditional numerical or experimental force measurement assumes live cells as ideal objects, ignoring their complicated inner structures and rough membranes. In this paper, we propose a new experimental method to calibrate the trapping and drag forces acted on live cells. Binding a micro polystyrene sphere to a live cell and moving the mixture with optical tweezers, we can obtain the drag force on the cell by subtracting the drag force on the sphere from the total drag force on the mixture, under the condition of extremely low Reynolds number. The trapping force on the cell is then obtained from the drag force when the cell is in force equilibrium state. Experiments on numerous live cells demonstrate the effectiveness of the proposed force calibration approach.

  13. Mechanical characterization of stomach tissue under uniaxial tensile action.

    PubMed

    Jia, Z G; Li, W; Zhou, Z R

    2015-02-26

    In this article, the tensile properties of gastric wall were investigated by using biomechanical test and theoretical analysis. The samples of porcine stomach strips from smaller and greater curvature of the stomach were cut in longitudinal and circumferential direction, respectively. The loading-unloading, stress relaxation, strain creep, tensile fracture tests were performed at mucosa-submucosa, serosa-muscle and intact layer, respectively. Results showed that the biomechanical properties of the porcine stomach depended on the layers, orientations and locations of the gastric wall and presented typical viscoelastic, nonlinear and anisotropic mechanical properties. During loading-unloading test, the stress of serosa-muscle layer in the longitudinal direction was 15-20% more than that in the circumferential direction at 12% stretch ratio, while it could reach about 40% for the intact layer and 50% for the mucosa-submucosa layer. The results of stress relaxation and strain creep showed that the variation degree was obviously faster in the circumferential direction than that in the longitudinal direction, and the ultimate residual values were also different for the different layers, orientations and locations. In the process of fracture test, the serosa-muscle layer fractured firstly followed by the mucosa-submucosa layer when the intact layer was tested, the longitudinal strips firstly began to fracture and the required stress value was about twice as much as that in the circumferential strips. The anisotropy and heterogeneity of mechanical characterization of the porcine stomach were related to its complicated geometry, structure and functions. The results would help us to understand the biomechanics of soft organ tissue.

  14. New Laboratory Methods for Characterizing the Immersion Factors for Irradiance

    NASA Technical Reports Server (NTRS)

    Hooker, Stanford B. (Editor); Firestone, Elaine R. (Editor); Zibordi, Giuseppe; DAlimonte, Davide; vaderLinde, Dirk; Brown, James W.

    2003-01-01

    The experimental determination of the immersion factor, I(sub f)(lambda), of irradiance collectors is a requirement of any in-water radiometer. The eighth SeaWiFS Intercalibration Round-Robin Experiment (SIRREX-8) showed different implementations, at different laboratories, of the same I(sub f)(lambda) measurement protocol. The different implementations make use of different setups, volumes, and water types. Consequently, they exhibit different accuracies and require different execution times for characterizing an irradiance sensor. In view of standardizing the characterization of I(sub f)(lambda) values for in-water radiometers, together with an increase in the accuracy of methods and a decrease in the execution time, alternative methods are presented, and assessed versus the traditional method. The proposed new laboratory methods include: a) the continuous method, in which optical measurements taken with discrete water depths are substituted by continuous profiles created by removing the water from the water vessel at a constant flow rate (which significantly reduces the time required for the characterization of a single radiometer); and b) the Compact Portable Advanced Characterization Tank (ComPACT) method, in which the commonly used large tanks are replaced by a small water vessel, thereby allowing the determination of I(sub f)(lambda) values with a small water volume, and more importantly, permitting I(sub f)(lambda) characterizations with pure water. Intercomparisons between the continuous and the traditional method showed results within the variance of I(sub f) (lambda) determinations. The use of the continuous method, however, showed a much shorter realization time. Intercomparisons between the ComPACT and the traditional method showed generally higher I(sub f)(lambda) values for the former. This is in agreement with the generalized expectations of a reduction in scattering effects, because of the use of pure water with the ComPACT method versus the use of

  15. Methods for Characterization of Batteries Using Acoustic Interrogation

    NASA Astrophysics Data System (ADS)

    Bhadra, Shoham

    Batteries are a ubiquitous form of electrochemical energy storage, but thus far the methods for measuring the mechanical properties of batteries and their component materials in operando have lagged far behind the methods for measuring the corresponding electrical properties. In this thesis, I demonstrate methods for determining the changes in materials properties of an electrochemical energy storage cell both ex situ and in operando.. I begin by establishing the impact of micro-scale morphology changes on the macro-scale dynamic mechanical response in commercial alkaline AA cells. Using a bounce test, the coefficient of restitution (COR) of the cell is shown to increase non-linearly as a function of state of charge (SOC). I show that the reason for the increase in the COR stems from the spatially-dependent oxidation of the Zn anode, with an initial increase corresponding to the formation of a percolation pathway of ZnO-clad Zn particles spanning the radius of the anode. The subsequent saturation of the COR is shown to result from the ultimate solidification and desiccation of the Zn anode. Building from this, I present a generalized in operando solution for materials characterization in batteries using ultrasonic interrogation. The materials properties of battery components change during charge and discharge, resulting in a change in the sound speed of the materials. By attaching transducers to a battery during cycling and sending ultrasonic pulses through each cell I observe the changes in the time of flight (ToF) of the pulses, both in reflection and transmission. I show that the changes in ToF correspond to both SOC and state of health (SOH) in a variety of battery chemistries and geometries, and detail a corresponding acoustic conservation law model framework. Finally, I perform these electrochemical acoustic time of flight (EAToF) experiments on commercial alkaline AA cells. By correlating the results with energy dispersive x-ray diffraction (EDXRD) data and

  16. Mechanical characterization and comparison of energy storage and return prostheses.

    PubMed

    Rigney, Stacey M; Simmons, Anne; Kark, Lauren

    2017-03-01

    The suitability of finite element analysis (FEA) for standardizing the mechanical characterization of energy storage and return (ESAR) prostheses was investigated. A methodology consisting of both experimental and numerical analysis was proposed and trialed for the Vari-flex(®) Modular(TM), Flex-foot Cheetah and Cheetah Xtreme by Össur(®) and a 1E90 Sprinter by Ottobock(®). Gait analysis was conducted to determine suitable orientation angles for non-destructive testing (NDT) of the ESAR prostheses followed by a quasi-static inverse FEA procedure within COMSOL Multiphysics(®), where the NDT conditions were replicated to determine the homogenized material properties of the prostheses. The prostheses' loading response under bodyweight for an 80kg person was then simulated, using both Eigenfrequency and time-dependent analysis. The apparent stiffness under bodyweight was determined to be 94.7, 48.6, 57.4 and 65.0Nmm(-1) for the Vari-flex(®) Modular(TM), Flex-foot Cheetah, Cheetah Xtreme and 1E90 Sprinter, respectively. Both the energy stored and returned by the prostheses varied negatively with stiffness, yet the overall efficiency of the prostheses were similar, at 52.7, 52.0, 51.7 and 52.4% for the abovementioned prostheses. The proposed methodology allows the standardized assessment and comparison of ESAR prostheses without the confounding influences of subject-specific gait characteristics.

  17. Methodology Using Inverse Methods for Pit Characterization in Multilayer Structures

    NASA Astrophysics Data System (ADS)

    Aldrin, John C.; Sabbagh, Harold A.; Sabbagh, Elias H.; Murphy, R. Kim; Concordia, Michael; Judd, David R.; Lindgren, Eric; Knopp, Jeremy

    2006-03-01

    This paper presents a methodology incorporating ultrasonic and eddy current data and NDE models to characterize pits in first and second layers. Approaches such as equivalent pit dimensions, approximate probe models, and iterative inversion schemes were designed to improve the reliability and speed of inverse methods for second layer pit characterization. A novel clutter removal algorithm was developed to compensate for coherent background noise. Validation was achieved using artificial and real pitting corrosion samples.

  18. Methods of Isolation and Characterization of Oligogalacturonide Elicitors.

    PubMed

    Benedetti, Manuel; Mattei, Benedetta; Pontiggia, Daniela; Salvi, Gianni; Savatin, Daniel Valentin; Ferrari, Simone

    2017-01-01

    Oligogalacturonides (OGs) are pectic fragments derived from the partial degradation of homogalacturonan in the plant cell wall and able to elicit plant defence responses. Recent methodological advances in the isolation of OGs from plant tissues and their characterization have confirmed their role as bona fide plant Damage-Associated Molecular Patterns. Here, we describe the methods for the isolation of OGs from Arabidopsis leaf tissues and for the characterization of OG structure and biological activity.

  19. High Temperature Mechanical Characterization of Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, John Z.

    1998-01-01

    A high temperature mechanical characterization laboratory has been assembled at NASA Lewis Research Center. One contribution of this work is to test ceramic matrix composite specimens in tension in environmental extremes. Two high temperature tensile testing systems were assembled. The systems were assembled based on the performance and experience of other laboratories and meeting projected service conditions for the materials in question. The systems use frames with an electric actuator and a center screw. A PC based data acquisition and analysis system is used to collect and analyze the data. Mechanical extensometers are used to measure specimen strain. Thermocouples, placed near the specimen, are used to measure the specimen gage section temperature. The system for testing in air has a resistance element furnace with molybdenum disilicide elements and pneumatic grips with water cooling attached to hydraulic alignment devices. The system for testing in an inert gas has a graphite resistance element furnace in a chamber with rigidly mounted, water cooled, hydraulically actuated grips. Unidirectional SiC fiber reinforced reaction bonded Si3N4 and triaxially woven, two dimensional, SiC fiber reinforced enhanced SiC composites were tested in unidirectional tension. Theories for predicting the Young's modulus, modulus near the ultimate strength, first matrix cracking stress, and ultimate strength were applied and evaluated for suitability in predicting the mechanical behavior of SiC/RBSN and enhanced SiC/SiC composites. The SiC/RBSN composite exhibited pseudo tough behavior (increased area under the stress/strain curve) from 22 C to 1500 C. The rule of mixtures provides a good estimate of the Young's modulus of the SiC/RBSN composite using the constituent properties from room temperature to 1440 C for short term static tensile tests in air or nitrogen. The rule of mixtures significantly overestimates the secondary modulus near the ultimate strength. The ACK theory

  20. Mechanical characterization of coir/palmyra waste fiber hybrid composites

    NASA Astrophysics Data System (ADS)

    Arumugaprabu, V.; Uthayakumar, M.; Cardona, F.; Sultan, M. T. H.

    2016-10-01

    In the present days, the utilization of palmyra fiber in automotive and aerospace applications has increased drastically due to its high strength and low weight. This research focuses on the development of composite materials using palmyra waste and coir fiber with polyester as a matrix. The mechanical properties such as tensile, flexural and impact strength of composites were investigated. Palmyra waste fiber and coir fiber with relative varying weight percentage in the ratio of 50:50, 40:60, 30:70 and 20:80 had been considered for the study. The composites were prepared by the compression moulding method. In addition, the prepared composites were subjected to moisture studies for 24 hours, 48 hours and 72 hours to know the composite resistance to water absorption. The results showed an increase in all the mechanical properties from the addition of palmyra waste. After analysing the results obtained from the study, a suitable application in the automobile and aerospace industries is suggested for the new developed composite.

  1. Molecular Mechanics: The Method and Its Underlying Philosophy.

    ERIC Educational Resources Information Center

    Boyd, Donald B.; Lipkowitz, Kenny B.

    1982-01-01

    Molecular mechanics is a nonquantum mechanical method for solving problems concerning molecular geometries and energy. Methodology based on: the principle of combining potential energy functions of all structural features of a particular molecule into a total force field; derivation of basic equations; and use of available computer programs is…

  2. Atomistic insight into the catalytic mechanism of glycosyltransferases by combined quantum mechanics/molecular mechanics (QM/MM) methods.

    PubMed

    Tvaroška, Igor

    2015-02-11

    Glycosyltransferases catalyze the formation of glycosidic bonds by assisting the transfer of a sugar residue from donors to specific acceptor molecules. Although structural and kinetic data have provided insight into mechanistic strategies employed by these enzymes, molecular modeling studies are essential for the understanding of glycosyltransferase catalyzed reactions at the atomistic level. For such modeling, combined quantum mechanics/molecular mechanics (QM/MM) methods have emerged as crucial. These methods allow the modeling of enzymatic reactions by using quantum mechanical methods for the calculation of the electronic structure of the active site models and treating the remaining enzyme environment by faster molecular mechanics methods. Herein, the application of QM/MM methods to glycosyltransferase catalyzed reactions is reviewed, and the insight from modeling of glycosyl transfer into the mechanisms and transition states structures of both inverting and retaining glycosyltransferases are discussed.

  3. Electrical and Mechanical Characterizations of Nanocomposite Insulation for HTS Systems

    SciTech Connect

    Walsh, J K; Fabian, Paul E; Hooker, M W; Lizotte, M J; Tuncer, Enis; Sauers, Isidor

    2011-01-01

    As HTS wire technology continues to advance, a critical need has emerged for dielectric materials that can be used in superconducting components such as terminations, fault current limiters, transformers, and motors. To address this need, CTD is developing nanocomposite insulations based on epoxy and benzoxazine chemistries. Depending on part geometry, some processing methods are more efficient than others. For this reason, CTD is investigating both fiber-reinforced and filled resin systems for use in these applications. A thorough set of electrical testing including AC breakdown, breakdown as a function of thickness, and flashover shows promising performance characteristics. In addition, mechanical testing (short beam shear and compression) indicate that these new materials to have as good or better performance than G10.

  4. Characterization of Heat Waves in the Sahel and associated mechanisms

    NASA Astrophysics Data System (ADS)

    Oueslati, Boutheina; Pohl, Benjamin; Moron, Vincent; Rome, Sandra

    2016-04-01

    Large efforts are made to investigate the heat waves (HW) in developed countries because of their devastating impacts on society, economy and environment. This interest increased after the intense event over Europe during summer 2003. However, HWs are still understudied over developing countries. This is particularly true in West Africa, and especially in the Sahel, where temperatures recurrently reach critical values, such as during the 2010 HW event. Understanding the Sahelian HWs and associated health risks constitute the main objective of ACASIS, a 4-year project funded by the French Agence Nationale de la Recherche. Our work contributes to this project and aims at characterizing the Sahelian HWs and understanding the mechanisms associated with such extreme events. There is no universal definition of a HW event, since it is highly dependent on the sector (human health, agriculture, transport...) and region of interest. In our case, a HW is defined when the heat index of the day and of the night exceeds the 90th percentile for at least 3 consecutive days (Rome et al. 2016, in preparation). This index combines temperature and relative humidity in order to determine the human-perceived equivalent temperature (definition adapted from Steadman, 1979). Intrinsic properties of Sahelian HW are analyzed from the Global Summary of the Day (GSOD) synoptic observations and ERA-interim reanalyses over 1979-2014 during boreal spring seasons (April-May-June), the warmest period of the year in the Central Sahel. ERA-interim captures well the observed interannual variability and seasonal cycle at the regional scale, as well as the 1979-2014 increasing linear trend of springtime HW occurrences in the Sahel. Reanalyses, however, overestimate the duration, spatial extent of HW, and underestimate their intensity. For both GSOD and ERA-interim, we show that, over the last three decades, Sahelian HWs tend to become more frequent, last longer, cover larger areas and reach higher

  5. Combined quantum mechanics/molecular mechanics (QM/MM) methods in computational enzymology.

    PubMed

    van der Kamp, Marc W; Mulholland, Adrian J

    2013-04-23

    Computational enzymology is a rapidly maturing field that is increasingly integral to understanding mechanisms of enzyme-catalyzed reactions and their practical applications. Combined quantum mechanics/molecular mechanics (QM/MM) methods are important in this field. By treating the reacting species with a quantum mechanical method (i.e., a method that calculates the electronic structure of the active site) and including the enzyme environment with simpler molecular mechanical methods, enzyme reactions can be modeled. Here, we review QM/MM methods and their application to enzyme-catalyzed reactions to investigate fundamental and practical problems in enzymology. A range of QM/MM methods is available, from cheaper and more approximate methods, which can be used for molecular dynamics simulations, to highly accurate electronic structure methods. We discuss how modeling of reactions using such methods can provide detailed insight into enzyme mechanisms and illustrate this by reviewing some recent applications. We outline some practical considerations for such simulations. Further, we highlight applications that show how QM/MM methods can contribute to the practical development and application of enzymology, e.g., in the interpretation and prediction of the effects of mutagenesis and in drug and catalyst design.

  6. Mechanical modeling of battery separator based on microstructure image analysis and stochastic characterization

    NASA Astrophysics Data System (ADS)

    Xu, Hongyi; Zhu, Min; Marcicki, James; Yang, Xiao Guang

    2017-03-01

    A microstructure-based modeling method is developed to predict the mechanical behaviors of lithium-ion battery separators. Existing battery separator modeling methods cannot capture the structural features on the microscale. To overcome this issue, we propose an image-based microstructure Representative Volume Element (RVE) modeling method, which facilitates the understanding of the separators' complex macro mechanical behaviors from the perspective of microstructural features. A generic image processing workflow is developed to identify different phases in the microscopic image. The processed RVE image supplies microstructural information to the Finite Element Analysis (FEA). Both mechanical behavior and microstructure evolution are obtained from the simulation. The evolution of microstructure features is quantified using the stochastic microstructure characterization methods. The proposed method successfully captures the anisotropic behavior of the separator under tensile test, and provides insights into the microstructure deformation, such as the growth of voids. We apply the proposed method to a commercially available separator as the demonstration. The analysis results are validated using experimental testing results that are reported in literature.

  7. Mechanical characterization of dental ceramics by hertzian contacts.

    PubMed

    Peterson, I M; Pajares, A; Lawn, B R; Thompson, V P; Rekow, E D

    1998-04-01

    Hertzian indentation testing is proposed as a protocol for evaluating the role of microstructure in the mechanical response of dental ceramics. A major advantage of Hertzian indentation over more traditional fracture-testing methodologies is that it emulates the loading conditions experienced by dental restorations: Clinical variables (masticatory force and cuspal curvature) identify closely with Hertzian variables (contact load and sphere radius). In this paper, Hertzian responses on four generic dental ceramics systems-micaceous glass-ceramics, glass-infiltrated alumina, feldspathic porcelain, and transformable zirconiaare presented as case studies. Ceramographic sectioning by means of a "bonded-interface" technique provides new information on the contact damage modes. Two distinct modes are observed: "brittle" mode, classic macroscopic fracture outside the contact (ring, or cone cracks), driven by tensile stresses; and "quasi-plastic" mode, a relatively new kind of deformation below the contact (diffuse microdamage), driven by shear stresses. A progressive transition from the first to the second mode with increasing microstructural heterogeneity is observed. The degree of quasi-plasticity is readily apparent as deviations from ideal linear elastic responses on indentation stress-strain curves. Plots of threshold loads for the initiation of both fracture and deformation modes as a function of indenter radius constitute "damage maps" for the evaluation of prospective restoration damage under typical masticatory conditions. The degree of damage in both modes evolves progressively with load above the thresholds. Strength tests on indented specimens quantify sustainable stress levels on restoration materials after damage. The most brittle responses are observed in the fine glass-ceramics and porcelain; conversely, the most quasi-plastic responses are observed in the coarse glass-ceramics and zirconia; the medium glass-ceramics and alumina exhibit intermediate

  8. Micro-mechanical properties of fiber composites characterized by X-ray refraction (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Trappe, Volker; Hentschel, Manfred; Ivers, Heinz

    2005-05-01

    Fiber Reinforced Plastics (FRP) are increasingly applied in transportation systems (aircraft, railway, automotive) and infrastructure industries due to the good specific properties of high strength at low weight. Advanced FRP structures have to endure high mechanical and environmental loading. Therefore the durability and reliability depends much more on the micro mechanical properties as on the global strength. X-ray refraction topography is a powerful tool for the characterization of inner surfaces in materials. Applied to fiber composites the presented investigations give information about the mean diameter of the fibers, orientation and the quality of impregnation. Strong correlations were found between fiber matrix debonding and micro cracking and the stress state due to mechanical loading. Additionally a new method for a quantitative determination of transverse and shear strength in a complex laminate is presented. Therefore the X-Ray refraction technique is applied on-line during tensile load of specimens.

  9. Soil characterization methods for unsaturated low-level waste sites

    SciTech Connect

    Wierenga, P.J.; Young, M.H. . Dept. of Soil and Water Science); Gee, G.W.; Kincaid, C.T. ); Hills, R.G. . Dept. of Mechanical Engineering); Nicholson, T.J.; Cady, R.E. )

    1993-01-01

    To support a license application for the disposal of low-level radioactive waste (LLW), applicants must characterize the unsaturated zone and demonstrate that waste will not migrate from the facility boundary. This document provides a strategy for developing this characterization plan. It describes principles of contaminant flow and transport, site characterization and monitoring strategies, and data management. It also discusses methods and practices that are currently used to monitor properties and conditions in the soil profile, how these properties influence water and waste migration, and why they are important to the license application. The methods part of the document is divided into sections on laboratory and field-based properties, then further subdivided into the description of methods for determining 18 physical, flow, and transport properties. Because of the availability of detailed procedures in many texts and journal articles, the reader is often directed for details to the available literature. References are made to experiments performed at the Las Cruces Trench site, New Mexico, that support LLW site characterization activities. A major contribution from the Las Cruces study is the experience gained in handling data sets for site characterization and the subsequent use of these data sets in modeling studies.

  10. Computational structural mechanics methods research using an evolving framework

    NASA Technical Reports Server (NTRS)

    Knight, N. F., Jr.; Lotts, C. G.; Gillian, R. E.

    1990-01-01

    Advanced structural analysis and computational methods that exploit high-performance computers are being developed in a computational structural mechanics research activity sponsored by the NASA Langley Research Center. These new methods are developed in an evolving framework and applied to representative complex structural analysis problems from the aerospace industry. An overview of the methods development environment is presented, and methods research areas are described. Selected application studies are also summarized.

  11. Bayesian methods for characterizing unknown parameters of material models

    DOE PAGES

    Emery, J. M.; Grigoriu, M. D.; Field Jr., R. V.

    2016-02-04

    A Bayesian framework is developed for characterizing the unknown parameters of probabilistic models for material properties. In this framework, the unknown parameters are viewed as random and described by their posterior distributions obtained from prior information and measurements of quantities of interest that are observable and depend on the unknown parameters. The proposed Bayesian method is applied to characterize an unknown spatial correlation of the conductivity field in the definition of a stochastic transport equation and to solve this equation by Monte Carlo simulation and stochastic reduced order models (SROMs). As a result, the Bayesian method is also employed tomore » characterize unknown parameters of material properties for laser welds from measurements of peak forces sustained by these welds.« less

  12. Bayesian methods for characterizing unknown parameters of material models

    SciTech Connect

    Emery, J. M.; Grigoriu, M. D.; Field Jr., R. V.

    2016-02-04

    A Bayesian framework is developed for characterizing the unknown parameters of probabilistic models for material properties. In this framework, the unknown parameters are viewed as random and described by their posterior distributions obtained from prior information and measurements of quantities of interest that are observable and depend on the unknown parameters. The proposed Bayesian method is applied to characterize an unknown spatial correlation of the conductivity field in the definition of a stochastic transport equation and to solve this equation by Monte Carlo simulation and stochastic reduced order models (SROMs). As a result, the Bayesian method is also employed to characterize unknown parameters of material properties for laser welds from measurements of peak forces sustained by these welds.

  13. Method for hygromechanical characterization of graphite/epoxy composite

    NASA Technical Reports Server (NTRS)

    Yaniv, Gershon; Peimanidis, Gus; Daniel, Isaac M.

    1987-01-01

    An experimental method is described for measuring hygroscopic swelling strains and mechanical strains of moisture-conditioned composite specimens. The method consists of embedding encapsulated strain gages in the midplane of the composite laminate; thus it does not interfere with normal moisture diffusion. It is particularly suited for measuring moisture swelling coefficients and for mechanical testing of moisture-conditioned specimens at high strain rates. Results obtained by the embedded gage method were shown to be more reliable and reproducible than those obtained by surface gages, dial gages, or extensometers.

  14. Polarity functions' characterization and the mechanism of starch modification by DC glow discharge plasma.

    PubMed

    Khorram, S; Zakerhamidi, M S; Karimzadeh, Z

    2015-01-01

    The wheat starch was investigated, before and after exposure to the argon and oxygen glow discharge plasma, without any added chemical reagents, using a novel media polarity functions method. The mechanisms of modification of starch in plasma discharge irradiation were explained using some methods such as; NMR, IR spectroscopy, Kamlet-Abboud-Taft polarity functions (specific and nonspecific interaction) of modified starch. The starch modification, by plasma treatment, shows valuable changes with plasma gas and relative ionized or active species. Characterizations indicate that argon glow discharge plasma increases crosslink in C-2 site of starch. Also, oxygen plasma discharge irradiation tends to oxidize the OH group in C-6 site of carbonyl group. Furthermore, the reported mechanisms show the highest efficiency, because of the stereo-chemical orientation of active sites of starch and plasma potential of wall in plasma media.

  15. A Method for Characterizing the Surface Cleanliness During Adhesion Testing

    DTIC Science & Technology

    1969-03-01

    It has been shown that the degree of adhesion of metals depends upon the surface cleanliness . This paper presents a method that was used to...characterize the surface cleanliness of nickel during an adhesion experiment. The change in the work function of the surface as the metal was cleaned was used

  16. Methods And Devices For Characterizing Duplex Nucleic Acid Molecules

    DOEpatents

    Akeson, Mark; Vercoutere, Wenonah; Haussler, David; Winters-Hilt, Stephen

    2005-08-30

    Methods and devices are provided for characterizing a duplex nucleic acid, e.g., a duplex DNA molecule. In the subject methods, a fluid conducting medium that includes a duplex nucleic acid molecule is contacted with a nanopore under the influence of an applied electric field and the resulting changes in current through the nanopore caused by the duplex nucleic acid molecule are monitored. The observed changes in current through the nanopore are then employed as a set of data values to characterize the duplex nucleic acid, where the set of data values may be employed in raw form or manipulated, e.g., into a current blockade profile. Also provided are nanopore devices for practicing the subject methods, where the subject nanopore devices are characterized by the presence of an algorithm which directs a processing means to employ monitored changes in current through a nanopore to characterize a duplex nucleic acid molecule responsible for the current changes. The subject methods and devices find use in a variety of applications, including, among other applications, the identification of an analyte duplex DNA molecule in a sample, the specific base sequence at a single nulceotide polymorphism (SNP), and the sequencing of duplex DNA molecules.

  17. Surface nanocrystallization of Ti-6Al-4V alloy: microstructural and mechanical characterization.

    PubMed

    Pi, Y; Agoda-Tandjawa, G; Potiron, S; Demangel, C; Retraint, D; Benhayoune, H

    2012-06-01

    In this study, microstructural and mechanical properties of Ti-6Al-4V alloy, before and after the SMA treatment (SMAT) as well as the duplex SMAT/Nitriding process at different treatment conditions, were investigated in order to deepen the knowledge of these properties for biomedical devices. For that purpose, tribological (wear resistance, coefficient of friction) and mechanical (Vickers microhardness) tests were performed. To carry out the microstructural and surface topographical characterization of the samples, the scanning electron microscopy (SEM) and the 3D-SEM reconstruction from stereoscopic images have been used. By means of profiles deduced from the 3D images, the surface roughness has been calculated. The obtained results allowed to find an interesting SMAT condition which, followed by nitriding at low temperature, can greatly improve tribological and mechanical properties of Ti-6Al-4V alloy. It was also shown from SEM characterization and the original method of 3D-SEM reconstruction, that SMAT can reduce the machined grooves and consequently the roughness of the samples decreases. Moreover, we demonstrated, for the first time, that instead of usual etching method, the ionic polishing allowed to reveal the grains, the grain boundaries and the twins as well as the surface nanocrystalline layer generated by SMAT. Thus, the thickness of the SMATed layer decreases with the nitriding temperature, whereas the surface grain size increases.

  18. Fast on-wafer electrical, mechanical, and electromechanical characterization of piezoresistive cantilever force sensors.

    PubMed

    Tosolini, G; Villanueva, L G; Perez-Murano, F; Bausells, J

    2012-01-01

    Validation of a technological process requires an intensive characterization of the performance of the resulting devices, circuits, or systems. The technology for the fabrication of micro and nanoelectromechanical systems (MEMS and NEMS) is evolving rapidly, with new kind of device concepts for applications like sensing or harvesting are being proposed and demonstrated. However, the characterization tools and methods for these new devices are still not fully developed. Here, we present an on-wafer, highly precise, and rapid characterization method to measure the mechanical, electrical, and electromechanical properties of piezoresistive cantilevers. The setup is based on a combination of probe-card and atomic force microscopy technology, it allows accessing many devices across a wafer and it can be applied to a broad range of MEMS and NEMS. Using this setup we have characterized the performance of multiple submicron thick piezoresistive cantilever force sensors. For the best design we have obtained a force sensitivity Re(F) = 158μV/nN, a noise of 5.8 μV (1 Hz-1 kHz) and a minimum detectable force of 37 pN with a relative standard deviation of σ(r) ≈ 8%. This small value of σ(r), together with a high fabrication yield >95%, validates our fabrication technology. These devices are intended to be used as bio-molecular detectors for the measurement of intermolecular forces between ligand and receptor molecule pairs.

  19. Method of predicting mechanical properties of decayed wood

    DOEpatents

    Kelley, Stephen S.

    2003-07-15

    A method for determining the mechanical properties of decayed wood that has been exposed to wood decay microorganisms, comprising: a) illuminating a surface of decayed wood that has been exposed to wood decay microorganisms with wavelengths from visible and near infrared (VIS-NIR) spectra; b) analyzing the surface of the decayed wood using a spectrometric method, the method generating a first spectral data of wavelengths in VIS-NIR spectra region; and c) using a multivariate analysis to predict mechanical properties of decayed wood by comparing the first spectral data with a calibration model, the calibration model comprising a second spectrometric method of spectral data of wavelengths in VIS-NIR spectra obtained from a reference decay wood, the second spectral data being correlated with a known mechanical property analytical result obtained from the reference decayed wood.

  20. Electrochemical characterization of anode passivation mechanisms in copper electrorefining

    NASA Astrophysics Data System (ADS)

    Moats, Michael Scott

    Anode passivation can decrease productivity and quality while increasing costs in modern copper electrorefineries. This investigation utilized electrochemical techniques to characterize the passivation behavior of anode samples from ten different operating companies. It is believed that this collection of anodes is the most diverse set ever to be assembled to study the effect of anode composition on passivation. Chronopotentiometry was the main electrochemical technique, employing a current density of 3820 A m-2. From statistical analysis of the passivation characteristics, increasing selenium, tellurium, silver, lead and nickel were shown to accelerate passivation. Arsenic was the only anode impurity that inhibited passivation. Oxygen was shown to accelerate passivation when increased from 500 to 1500 ppm, but further increases did not adversely affect passivation. Nine electrolyte variables were also examined. Increasing the copper, sulfuric acid or sulfate concentration of the electrolyte accelerated passivation. Arsenic in the electrolyte had no effect on passivation. Chloride and optimal concentrations of thiourea and glue delayed passivation. Linear sweep voltammetry, cyclic voltammetry, and impedance spectroscopy provided complementary information. Analysis of the electrochemical results led to the development of a unified passivation mechanism. Anode passivation results from the formation of inhibiting films. Careful examination of the potential details, especially those found in the oscillations just prior to passivation, demonstrated the importance of slimes, copper sulfate and copper oxide. Slimes confine dissolution to their pores and inhibit diffusion. This can lead to copper sulfate precipitation, which blocks more of the surface area. Copper oxide forms because of the resulting increase in potential at the interface between the copper sulfate and anode. Ultimate passivation occurs when the anode potential is high enough to stabilize the oxide film in

  1. Characterizing thermal sweeping: a rapid disc dispersal mechanism

    NASA Astrophysics Data System (ADS)

    Owen, James E.; Hudoba de Badyn, Mathias; Clarke, Cathie J.; Robins, Luke

    2013-12-01

    We consider the properties of protoplanetary discs that are undergoing inside-out clearing by photoevaporation. In particular, we aim to characterize the conditions under which a protoplanetary disc may undergo `thermal sweeping', a rapid (≲104 years) disc destruction mechanism proposed to occur when a clearing disc reaches sufficiently low surface density at its inner edge and where the disc is unstable to runaway penetration by the X-rays. We use a large suite of 1D radiation-hydrodynamic simulations to probe the observable parameter space, which is unfeasible in higher dimensions. These models allow us to determine the surface density at which thermal sweeping will take over the disc's evolution and to evaluate this critical surface density as a function of X-ray luminosity, stellar mass and inner hole radius. We find that this critical surface density scales linearly with X-ray luminosity, increases with inner hole radius and decreases with stellar mass, and we develop an analytic model that reproduces these results. This surface density criterion is then used to determine the evolutionary state of protoplanetary discs at the point that they become unstable to destruction by thermal sweeping. We find that transition discs created by photoevaporation will undergo thermal sweeping when their inner holes reach 20-40 au, implying that transition discs with large holes and no accretion (which were previously a predicted outcome of the later stages of all flavours of the photoevaporation model) will not form. Thermal sweeping thus avoids the production of large numbers of large, non-accreting holes (which are not observed) and implies that the majority of holes created by photoevaporation should still be accreting. We emphasize that the surface density criteria that we have developed apply to all situations where the disc develops an inner hole that is optically thin to X-rays. It thus applies not only to the case of holes originally created by photoevaporation but

  2. 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

  3. Suction based mechanical characterization of superficial facial soft tissues.

    PubMed

    Weickenmeier, J; Jabareen, M; Mazza, E

    2015-12-16

    The present study is aimed at a combined experimental and numerical investigation of the mechanical response of superficial facial tissues. Suction based experiments provide the location, time, and history dependent behavior of skin and SMAS (superficial musculoaponeurotic system) by means of Cutometer and Aspiration measurements. The suction method is particularly suitable for in vivo, multi-axial testing of soft biological tissue including a high repeatability in subsequent tests. The campaign comprises three measurement sites in the face, i.e. jaw, parotid, and forehead, using two different loading profiles (instantaneous loading and a linearly increasing and decreasing loading curve), multiple loading magnitudes, and cyclic loading cases to quantify history dependent behavior. In an inverse finite element analysis based on anatomically detailed models an optimized set of material parameters for the implementation of an elastic-viscoplastic material model was determined, yielding an initial shear modulus of 2.32kPa for skin and 0.05kPa for SMAS, respectively. Apex displacements at maximum instantaneous and linear loading showed significant location specificity with variations of up to 18% with respect to the facial average response while observing variations in repeated measurements in the same location of less than 12%. In summary, the proposed parameter sets for skin and SMAS are shown to provide remarkable agreement between the experimentally observed and numerically predicted tissue response under all loading conditions considered in the present study, including cyclic tests.

  4. A new method for colors characterization of colored stainless steel using CIE and Munsell color systems

    NASA Astrophysics Data System (ADS)

    Ji, Keming; Xue, Yongqiang; Cui, Zixiang

    2015-09-01

    It is important to establish an accurate and comprehensive method of characterizing colors of colored stainless steel and understand the changing mechanism and the regularity of colors for the research, production and application of colored stainless steel. In this work, the method which combines reflectance-wavelength with both CIE and Munsell color systems is studied, the changing regularity of hue, brightness and saturation with increasing coloring potential differences is investigated, and the mechanism of color changing is discussed. The results show that by using this method the colors of colored stainless steel can be accurately and comprehensively characterized; with coloring potential differences and colored film thickness increasing, the peaks and troughs of the reflectance curves in visible region move toward long wave, causing the cyclically changing of hue and brightness; the amplitude of reflectance curves increases, resulting in growing of the saturation; the CIE 1931 coordinate curve of colors counterclockwise and cyclically changes around the equal energy light spot.

  5. DNAPL characterization using the Ribbon NAPL sampler: Methods and results

    SciTech Connect

    Riha, B.D.

    2000-04-25

    The Ribbon NAPL Sampler (RNS) is a direct sampling device that provides detailed depth discrete mapping of Non Aqueous Phase Liquids (NAPLs) in a borehole. This characterization method provides a yes or no answer to the presence of NAPLs and is used to complement and enhance other characterization techniques. Several cone penetrometer deployment methods are in use and methods for other drilling techniques are under development. The RNS has been deployed in the vadose and saturated zones at four different sites. Three of the sites contain DNAPLs from cleaning and degreasing operations and the fourth site contains creosote from a wood preserving plant. A brief description of the process history and geology is provided for each site. Where available, lithology and contaminant concentration information is provided and discussed in context with the RNS results.

  6. Ultrasonic Method for Deployment Mechanism Bolt Element Preload Verification

    NASA Technical Reports Server (NTRS)

    Johnson, Eric C.; Kim, Yong M.; Morris, Fred A.; Mitchell, Joel; Pan, Robert B.

    2014-01-01

    Deployment mechanisms play a pivotal role in mission success. These mechanisms often incorporate bolt elements for which a preload within a specified range is essential for proper operation. A common practice is to torque these bolt elements to a specified value during installation. The resulting preload, however, can vary significantly with applied torque for a number of reasons. The goal of this effort was to investigate ultrasonic methods as an alternative for bolt preload verification in such deployment mechanisms. A family of non-explosive release mechanisms widely used by satellite manufacturers was chosen for the work. A willing contractor permitted measurements on a sampling of bolt elements for these release mechanisms that were installed by a technician following a standard practice. A variation of approximately 50% (+/- 25%) in the resultant preloads was observed. An alternative ultrasonic method to set the preloads was then developed and calibration data was accumulated. The method was demonstrated on bolt elements installed in a fixture instrumented with a calibrated load cell and designed to mimic production practice. The ultrasonic method yielded results within +/- 3% of the load cell reading. The contractor has since adopted the alternative method for its future production. Introduction

  7. Mechanical characterization and structural assessment of biocomposites for construction

    NASA Astrophysics Data System (ADS)

    Christian, Sarah Jane

    The objective of this dissertation is to assess whether or not two particular biocomposite materials, made from hemp fabric and cellulose acetate or polyhydroxybutyrate matrices, are capable of being used for structural and/or construction purposes within in the construction and building industry. The objective of this dissertation was addressed by conducting research to meet the following three goals: (1) to measure the basic mechanical properties of hemp/cellulose acetate and hemp/PHB biocomposites and evaluate if they suitable for use in construction applications, (2) to determine how quickly moisture diffuses into the biocomposite materials and how the moisture affects the mechanical behavior, and (3) to determine how well simple models can predict behavior of structural scale laminates in tension and flexure using biocomposite ply behavior. Compression molding was used to manufacturing the biocomposites from hemp fabric and the themoplastic matrices: cellulose acetate and polyhydroxybutyrate. Four methods for determining the fiber volume fraction were evaluated, and the dissolution method, using different solvents for each matrix type, was used to determine the fiber volume fraction for each composite plate manufactured. Both types of biocomposite were tested in tension, compression, shear, and flexure and the measured properties were compared to wood and engineered wood products to assess whether the biocomposite properties are suitable for use in the construction industry. The biocomposites were conditioned in a humid environment to determine the rate of moisture diffusion into the materials. Then saturated specimens and specimens that were saturated and then dried were tested in tension to evaluate how moisture absorption affects the mechanical behavior of the biocomposites. Finally, simple models of laminate behavior based on laminate plate theory were evaluated to determine if ply level behavior could be used to predict structural scale laminate behavior

  8. Methods to characterize non-Gaussian noise in TAMA

    NASA Astrophysics Data System (ADS)

    Ando, Masaki; Arai, K.; Takahashi, R.; Tatsumi, D.; Beyersdorf, P.; Kawamura, S.; Miyoki, S.; Mio, N.; Moriwaki, S.; Numata, K.; Kanda, N.; Aso, Y.; Fujimoto, M.-K.; Tsubono, K.; Kuroda, K.; TAMA Collaboration

    2003-09-01

    We present a data characterization method for the main output signal of the interferometric gravitational-wave detector, in particular targetting at effective detection of burst gravitational waves from stellar core collapse. The time scale of non-Gaussian events is evaluated in this method, and events with longer time scale than real signals are rejected as non-Gaussian noises. As a result of data analysis using 1000 h of real data with the interferometric gravitational-wave detector TAMA300, the false-alarm rate was improved 103 times with this non-Gaussian noise evaluation and rejection method.

  9. The numerical mirage method for photothermal characterization of materials.

    PubMed

    Demko, Michael T; Hostler, Stephen R; Abramson, Alexis R

    2008-04-01

    Noncontact thermal measurement techniques offer rapid thermal characterization without modification or destruction of the sample being studied. A simple and versatile method has been developed, termed the "numerical mirage method," that utilizes the transient photothermal deflection of a laser beam traversing a modulated temperature gradient. This method expands the range and simplifies the experimental procedure of traditional mirage methods. A numerical solver is used to create accurate deflection profile models and a linear curve fitting routine is developed, from which the thermal diffusivity of a material may be determined. This method allows for rapid modification of sample and heating configurations. Verification of the method is performed on bismuth and fused quartz reference samples, and good agreement with literature is obtained.

  10. Material mechanical characterization method for multiple strains and strain rates

    SciTech Connect

    Erdmand, III, Donald L.; Kunc, Vlastimil; Simunovic, Srdjan; Wang, Yanli

    2016-01-19

    A specimen for measuring a material under multiple strains and strain rates. The specimen including a body having first and second ends and a gage region disposed between the first and second ends, wherein the body has a central, longitudinal axis passing through the first and second ends. The gage region includes a first gage section and a second gage section, wherein the first gage section defines a first cross-sectional area that is defined by a first plane that extends through the first gage section and is perpendicular to the central, longitudinal axis. The second gage section defines a second cross-sectional area that is defined by a second plane that extends through the second gage section and is perpendicular to the central, longitudinal axis and wherein the first cross-sectional area is different in size than the second cross-sectional area.

  11. Integral structural-functional method for characterizing microbial populations

    NASA Astrophysics Data System (ADS)

    Yakushev, A. V.

    2015-04-01

    An original integral structural-functional method has been proposed for characterizing microbial communities. The novelty of the approach is the in situ study of microorganisms based on the growth kinetics of microbial associations in liquid nutrient broth media under selective conditions rather than on the level of taxa or large functional groups. The method involves the analysis of the integral growth model of a periodic culture. The kinetic parameters of such associations reflect their capacity of growing on different media, i.e., their physiological diversity, and the metabolic capacity of the microorganisms for growth on a nutrient medium. Therefore, the obtained parameters are determined by the features of the microbial ecological strategies. The inoculation of a dense medium from the original inoculate allows characterizing the taxonomic composition of the dominants in the soil community. The inoculation from the associations developed on selective media characterizes the composition of syntrophic groups, which fulfill a specific function in nature. This method is of greater information value than the classical methods of inoculation on selective media.

  12. Damage mechanics characterization on fatigue behavior of a solder joint material

    SciTech Connect

    Chow, C.L.; Yang, F.; Fang, H.E.

    1998-08-01

    This paper presents the first part of a comprehensive mechanics approach capable of predicting the integrity and reliability of solder joint material under fatigue loading without viscoplastic damage considerations. A separate report will be made to present a comprehensive damage model describing life prediction of the solder material under thermomechanical fatigue loading. The method is based on a theory of damage mechanics which makes possible a macroscopic description of the successive material deterioration caused by the presence of microcracks/voids in engineering materials. A damage mechanics model based on the thermodynamic theory of irreversible processes with internal state variables is proposed and used to provide a unified approach in characterizing the cyclic behavior of a typical solder material. With the introduction of a damage effect tensor, the constitutive equations are derived to enable the formulation of a fatigue damage dissipative potential function and a fatigue damage criterion. The fatigue evolution is subsequently developed based on the hypothesis that the overall damage is induced by the accumulation of fatigue and plastic damage. This damage mechanics approach offers a systematic and versatile means that is effective in modeling the entire process of material failure ranging from damage initiation and propagation leading eventually to macro-crack initiation and growth. As the model takes into account the load history effect and the interaction between plasticity damage and fatigue damage, with the aid of a modified general purpose finite element program, the method can readily be applied to estimate the fatigue life of solder joints under different loading conditions.

  13. Tracer Methods for Characterizing Fracture Creation in Engineered Geothermal Systems

    SciTech Connect

    Rose, Peter; Harris, Joel

    2014-05-08

    The aim of this proposal is to develop, through novel high-temperature-tracing approaches, three technologies for characterizing fracture creation within Engineered Geothermal Systems (EGS). The objective of a first task is to identify, develop and demonstrate adsorbing tracers for characterizing interwell reservoir-rock surface areas and fracture spacing. The objective of a second task is to develop and demonstrate a methodology for measuring fracture surface areas adjacent to single wells. The objective of a third task is to design, fabricate and test an instrument that makes use of tracers for measuring fluid flow between newly created fractures and wellbores. In one method of deployment, it will be used to identify qualitatively which fractures were activated during a hydraulic stimulation experiment. In a second method of deployment, it will serve to measure quantitatively the rate of fluid flowing from one or more activated fracture during a production test following a hydraulic stimulation.

  14. Histotripsy Methods in Mechanical Disintegration of Tissue: Toward Clinical Applications

    PubMed Central

    Khokhlova, VA; Fowlkes, JB; Roberts, WW; Schade, GR; Xu, Z; Khokhlova, TD; Hall, TL; Maxwell, AD; Wang, YN; Cain, CA

    2015-01-01

    Purpose In high intensity focused ultrasound (HIFU) therapy, an ultrasound beam is focused within the body to locally affect the targeted site without damaging intervening tissues. The most common HIFU regime is thermal ablation. Recently, there has been increasing interest in generating purely mechanical lesions in tissue (histotripsy). This paper provides an overview of several studies on the development of histotripsy methods toward clinical applications. Material and Methods Two histotripsy approaches and examples of their applications are presented. In one approach, sequences of high-amplitude, short (microsecond-long), focused ultrasound pulses periodically produce dense, energetic bubble clouds that mechanically disintegrate tissue. In an alternative approach, longer (millisecond-long) pulses with shock fronts generate boiling bubbles and the interaction of shock fronts with the resulting vapor cavity causes tissue disintegration. Results Recent pre-clinical studies on histotripsy are reviewed for treating benign prostatic hyperplasia (BPH), liver and kidney tumors, kidney stone fragmentation, enhancing antitumor immune response, and tissue decellularization for regenerative medicine applications. Potential clinical advantages of the histotripsy methods are discussed. Conclusions Histotripsy methods can be used to mechanically ablate a wide variety of tissues, whilst selectivity sparing structures such as large vessels. Both ultrasound and MR imaging can be used for targeting and monitoring the treatment in real time. Although the two approaches utilize different mechanisms for tissue disintegration, both have many of the same advantages and offer a promising alternative method of noninvasive surgery. PMID:25707817

  15. Monitoring Healing Progression and Characterizing the Mechanical Environment in Preclinical Models for Bone Tissue Engineering.

    PubMed

    Fountain, Stephanie; Windolf, Markus; Henkel, Jan; Tavakoli, Aramesh; Schuetz, Michael A; Hutmacher, Dietmar W; Epari, Devakara R

    2015-12-15

    The treatment of large segmental bone defects remains a significant clinical challenge. Due to limitations surrounding the use of bone grafts, tissue-engineered constructs for the repair of large bone defects could offer an alternative. Before translation of any newly developed tissue engineering (TE) approach to the clinic, efficacy of the treatment must be shown in a validated preclinical large animal model. Currently, biomechanical testing, histology, and microcomputed tomography are performed to assess the quality and quantity of the regenerated bone. However, in vivo monitoring of the progression of healing is seldom performed, which could reveal important information regarding time to restoration of mechanical function and acceleration of regeneration. Furthermore, since the mechanical environment is known to influence bone regeneration, and limb loading of the animals can poorly be controlled, characterizing activity and load history could provide the ability to explain variability in the acquired data sets and potentially outliers based on abnormal loading. Many approaches have been devised to monitor the progression of healing and characterize the mechanical environment in fracture healing studies. In this article, we review previous methods and share results of recent work of our group toward developing and implementing a comprehensive biomechanical monitoring system to study bone regeneration in preclinical TE studies.

  16. Characterization of wafer charging mechanisms and oxide survival prediction methodology

    SciTech Connect

    Lukaszek, W.; Dixon, W.; Vella, M.; Messick, C.; Reno, S.; Shideler, J.

    1994-04-01

    Unipolar, EEPROM-based peak potential sensors and current sensors have been used to characterize the I-V relationship of charging transients which devices normally experience during the course of ion implantation. The results indicate that the charging sources may appear to behave like current-sources or voltage-sources, depending on the impedance of the load. This behavior may be understood in terms of plasma concepts. The ability to empirically characterize the I-V characteristics of charging sources using the CHARM-2 monitor wafers opens the way for prediction of failure rates of oxides subjected to specific processes, if the oxide Q{sub bd} distributions are known.

  17. Analytical Methods for Biomass Characterization during Pretreatment and Bioconversion

    SciTech Connect

    Pu, Yunqiao; Meng, Xianzhi; Yoo, Chang Geun; Li, Mi; Ragauskas, Arthur J

    2016-01-01

    Lignocellulosic biomass has been introduced as a promising resource for alternative fuels and chemicals because of its abundance and complement for petroleum resources. Biomass is a complex biopolymer and its compositional and structural characteristics largely vary depending on its species as well as growth environments. Because of complexity and variety of biomass, understanding its physicochemical characteristics is a key for effective biomass utilization. Characterization of biomass does not only provide critical information of biomass during pretreatment and bioconversion, but also give valuable insights on how to utilize the biomass. For better understanding biomass characteristics, good grasp and proper selection of analytical methods are necessary. This chapter introduces existing analytical approaches that are widely employed for biomass characterization during biomass pretreatment and conversion process. Diverse analytical methods using Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) spectroscopy for biomass characterization are reviewed. In addition, biomass accessibility methods by analyzing surface properties of biomass are also summarized in this chapter.

  18. 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.

  19. Peripapillary and posterior scleral mechanics--part II: experimental and inverse finite element characterization.

    PubMed

    Girard, Michaël J A; Downs, J Crawford; Bottlang, Michael; Burgoyne, Claude F; Suh, J-K Francis

    2009-05-01

    The posterior sclera likely plays an important role in the development of glaucoma, and accurate characterization of its mechanical properties is needed to understand its impact on the more delicate optic nerve head--the primary site of damage in the disease. The posterior scleral shells from both eyes of one rhesus monkey were individually mounted on a custom-built pressurization apparatus. Intraocular pressure was incrementally increased from 5 mm Hg to 45 mm Hg, and the 3D displacements were measured using electronic speckle pattern interferometry. Finite element meshes of each posterior scleral shell were reconstructed from data generated by a 3D digitizer arm (shape) and a 20 MHz ultrasound transducer (thickness). An anisotropic hyperelastic constitutive model described in a companion paper (Girard, Downs, Burgoyne, and Suh, 2009, "Peripapillary and Posterior Scleral Mechanics--Part I: Development of an Anisotropic Hyperelastic Constitutive Model," ASME J. Biomech. Eng., 131, p. 051011), which includes stretch-induced stiffening and multidirectional alignment of the collagen fibers, was applied to each reconstructed mesh. Surface node displacements of each model were fitted to the experimental displacements using an inverse finite element method, which estimated a unique set of 13 model parameters. The predictions of the proposed constitutive model matched the 3D experimental displacements well. In both eyes, the tangent modulus increased dramatically with IOP, which indicates that the sclera is mechanically nonlinear. The sclera adjacent to the optic nerve head, known as the peripapillary sclera, was thickest and exhibited the lowest tangent modulus, which might have contributed to the uniform distribution of the structural stiffness for each entire scleral shell. Posterior scleral deformation following acute IOP elevations appears to be nonlinear and governed by the underlying scleral collagen microstructure as predicted by finite element modeling. The

  20. Characterization of Tensile Mechanical Behavior of MSCs/PLCL Hybrid Layered Sheet

    PubMed Central

    Pangesty, Azizah Intan; Arahira, Takaaki; Todo, Mitsugu

    2016-01-01

    A layered construct was developed by combining a porous polymer sheet and a cell sheet as a tissue engineered vascular patch. The primary objective of this study is to investigate the influence of mesenchymal stem cells (MSCs) sheet on the tensile mechanical properties of porous poly-(l-lactide-co-ε-caprolactone) (PLCL) sheet. The porous PLCL sheet was fabricated by the solid-liquid phase separation method and the following freeze-drying method. The MSCs sheet, prepared by the temperature-responsive dish, was then layered on the top of the PLCL sheet and cultured for 2 weeks. During the in vitro study, cellular properties such as cell infiltration, spreading and proliferation were evaluated. Tensile test of the layered construct was performed periodically to characterize the tensile mechanical behavior. The tensile properties were then correlated with the cellular properties to understand the effect of MSCs sheet on the variation of the mechanical behavior during the in vitro study. It was found that MSCs from the cell sheet were able to migrate into the PLCL sheet and actively proliferated into the porous structure then formed a new layer of MSCs on the opposite surface of the PLCL sheet. Mechanical evaluation revealed that the PLCL sheet with MSCs showed enhancement of tensile strength and strain energy density at the first week of culture which is characterized as the effect of MSCs proliferation and its infiltration into the porous structure of the PLCL sheet. New technique was presented to develop tissue engineered patch by combining MSCs sheet and porous PLCL sheet, and it is expected that the layered patch may prolong biomechanical stability when implanted in vivo. PMID:27271675

  1. Characterization of Tensile Mechanical Behavior of MSCs/PLCL Hybrid Layered Sheet.

    PubMed

    Pangesty, Azizah Intan; Arahira, Takaaki; Todo, Mitsugu

    2016-06-03

    A layered construct was developed by combining a porous polymer sheet and a cell sheet as a tissue engineered vascular patch. The primary objective of this study is to investigate the influence of mesenchymal stem cells (MSCs) sheet on the tensile mechanical properties of porous poly-(l-lactide-co-ε-caprolactone) (PLCL) sheet. The porous PLCL sheet was fabricated by the solid-liquid phase separation method and the following freeze-drying method. The MSCs sheet, prepared by the temperature-responsive dish, was then layered on the top of the PLCL sheet and cultured for 2 weeks. During the in vitro study, cellular properties such as cell infiltration, spreading and proliferation were evaluated. Tensile test of the layered construct was performed periodically to characterize the tensile mechanical behavior. The tensile properties were then correlated with the cellular properties to understand the effect of MSCs sheet on the variation of the mechanical behavior during the in vitro study. It was found that MSCs from the cell sheet were able to migrate into the PLCL sheet and actively proliferated into the porous structure then formed a new layer of MSCs on the opposite surface of the PLCL sheet. Mechanical evaluation revealed that the PLCL sheet with MSCs showed enhancement of tensile strength and strain energy density at the first week of culture which is characterized as the effect of MSCs proliferation and its infiltration into the porous structure of the PLCL sheet. New technique was presented to develop tissue engineered patch by combining MSCs sheet and porous PLCL sheet, and it is expected that the layered patch may prolong biomechanical stability when implanted in vivo.

  2. A review of dynamic mechanical characterization of high temperature PMR polyimides and composites

    NASA Technical Reports Server (NTRS)

    Pater, Ruth H.

    1988-01-01

    This paper reviews the applications of dynamic mechanical characterization for high-temperature PMR polyimides and their graphite-fiber-reinforced composites. This characterization technique provides insights into the processability, performance, and structure property relationships of the polyimides and composites. The dynamic mechanical properties of various molding powders, commercially obtained prepregs, neat resins, and as-fabricated as well as aged composites are presented. Some applied aspects of the dynamic mechanical data are discussed.

  3. Formation and Failure of Elastomer Networks via Thermal, Mechanical and Surface Characterization

    DTIC Science & Technology

    1979-12-01

    Cootinue on reverse side If O.cesearyn7md Identity by block number) .4Fracture mechanism IGA TMA SBR Degradation ZnO particles ESCA Oxidative embrittlement Z...TARADC6M and EARCH TECHNICAL REPORT : NO. 12498 FORMATION AND FAILURE OF -ELASTOMER NETWORKS VIA " THERMAL, MECHANICAL AND SURFACE CHARACTERIZATION...PERIOD COVERED Foratonand Failure of Elastomer Networks via Final ½,chnical Rtepo¶t * hermal, Mechanical and Surface Characterization@ Aug. e4

  4. The contour method: a new approach in experimental mechanics

    SciTech Connect

    Prime, Michael B

    2009-01-01

    The recently developed contour method can measure complex residual-stress maps in situations where other measurement methods cannot. This talk first describes the principle of the contour method. A part is cut in two using a precise and low-stress cutting technique such as electric discharge machining. The contour of the resulting new surface, which will not be flat if residual stresses are relaxed by the cutting, is then measured. Finally, a conceptually simple finite element analysis determines the original residual stresses from the measured contour. Next, this talk gives several examples of applications. The method is validated by comparing with neutron diffraction measurements in an indented steel disk and in a friction stir weld between dissimilar aluminum alloys. Several applications are shown that demonstrate the power of the contour method: large aluminum forgings, railroad rails, and welds. Finally, this talk discusses why the contour method is significant departure from conventional experimental mechanics. Other relaxation method, for example hole-drilling, can only measure a 1-D profile of residual stresses, and yet they require a complicated inverse calculation to determine the stresses from the strain data. The contour method gives a 2-D stress map over a full cross-section, yet a direct calculation is all that is needed to reduce the data. The reason for these advantages lies in a subtle but fundamental departure from conventional experimental mechanics. Applying new technology to old methods like will not give similar advances, but the new approach also introduces new errors.

  5. Mechanical Characterization of Mesoscale Interfaces Using Indentation Techniques

    NASA Astrophysics Data System (ADS)

    Kalidindi, Surya R.; Mohan, Soumya; Rossi, Alicia

    2017-01-01

    Mesoscale interfaces and interphases play a central role in controlling the many macroscale mechanical properties and performance characteristics of structural materials. Modern instrumented indenters present an unprecedented opportunity to measure, reliably and consistently, the local mechanical responses at a multitude of length scales ranging from tens of nanometers to hundreds of microns. When these high-fidelity measurements are combined with rigorous data analyses protocols, it is possible to systematically study the mechanical role of individual mesoscale interfaces and quantify their contributions to the overall mechanical response of the material system . The advantages of these new measurement and analyses protocols as well as the potential for development and implementation of novel high-throughput assays is discussed.

  6. Design and Characterization of a Novel Knee Articulation Mechanism

    NASA Astrophysics Data System (ADS)

    Olinski, M.; Gronowicz, A.; Handke, A.; Ceccarelli, M.

    2016-08-01

    The paper is focused on designing a novel controllable and adjustable mechanism for reproducing human knee joint's complex motion by taking into account the flexion/extension movement in the sagittal plane, in combination with roll and slide. Main requirements for a knee rehabilitation supporting device are specified by researching the knee's anatomy and already existing mechanisms. A three degree of freedom (3 DOF) system (four-bar like linkage with controlled variable lengths of rockers) is synthesised to perform the reference path of instantaneous centre of rotation (ICR). Finally, a preliminary design of the adaptive mechanism is elaborated and a numerical model is built in Adams. Numerical results are derived from simulations that are presented to evaluate the accuracy of the reproduced movement and the mechanism's capabilities.

  7. Feed mechanism and method for feeding minute items

    DOEpatents

    Stringer, Timothy Kent; Yerganian, Simon Scott

    2009-10-20

    A feeding mechanism and method for feeding minute items, such as capacitors, resistors, or solder preforms. The mechanism is adapted to receive a plurality of the randomly-positioned and randomly-oriented extremely small or minute items, and to isolate, orient, and position one or more of the items in a specific repeatable pickup location wherefrom they may be removed for use by, for example, a computer-controlled automated assembly machine. The mechanism comprises a sliding shelf adapted to receive and support the items; a wiper arm adapted to achieve a single even layer of the items; and a pushing arm adapted to push the items into the pickup location. The mechanism can be adapted for providing the items with a more exact orientation, and can also be adapted for use in a liquid environment.

  8. Feed mechanism and method for feeding minute items

    DOEpatents

    Stringer, Timothy Kent; Yerganian, Simon Scott

    2012-11-06

    A feeding mechanism and method for feeding minute items, such as capacitors, resistors, or solder preforms. The mechanism is adapted to receive a plurality of the randomly-positioned and randomly-oriented extremely small or minute items, and to isolate, orient, and position the items in a specific repeatable pickup location wherefrom they may be removed for use by, for example, a computer-controlled automated assembly machine. The mechanism comprises a sliding shelf adapted to receive and support the items; a wiper arm adapted to achieve a single even layer of the items; and a pushing arm adapted to push the items into the pickup location. The mechanism can be adapted for providing the items with a more exact orientation, and can also be adapted for use in a liquid environment.

  9. Human skeletal muscle behavior in vivo: Finite element implementation, experiment, and passive mechanical characterization.

    PubMed

    Clemen, Christof B; Benderoth, Günther E K; Schmidt, Andreas; Hübner, Frank; Vogl, Thomas J; Silber, Gerhard

    2017-01-01

    In this study, useful methods for active human skeletal muscle material parameter determination are provided. First, a straightforward approach to the implementation of a transversely isotropic hyperelastic continuum mechanical material model in an invariant formulation is presented. This procedure is found to be feasible even if the strain energy is formulated in terms of invariants other than those predetermined by the software's requirements. Next, an appropriate experimental setup for the observation of activation-dependent material behavior, corresponding data acquisition, and evaluation is given. Geometry reconstruction based on magnetic resonance imaging of different deformation states is used to generate realistic, subject-specific finite element models of the upper arm. Using the deterministic SIMPLEX optimization strategy, a convenient quasi-static passive-elastic material characterization is pursued; the results of this approach used to characterize the behavior of human biceps in vivo indicate the feasibility of the illustrated methods to identify active material parameters comprising multiple loading modes. A comparison of a contact simulation incorporating the optimized parameters to a reconstructed deformed geometry of an indented upper arm shows the validity of the obtained results regarding deformation scenarios perpendicular to the effective direction of the nonactivated biceps. However, for a valid, activatable, general-purpose material characterization, the material model needs some modifications as well as a multicriteria optimization of the force-displacement data for different loading modes.

  10. Characterization and development mechanism of Apios americana tuber starch

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Apios americana is a wild legume-bearing plant with edible tubers. Domestication of Apios is in progress because of the superior nutritional value and health benefits of the tuber. Objectives of this study were to: 1) characterize physicochemical properties of Apios-tuber starch; and 2) understand d...

  11. Method for loading shape memory polymer gripper mechanisms

    DOEpatents

    Lee, Abraham P.; Benett, William J.; Schumann, Daniel L.; Krulevitch, Peter A.; Fitch, Joseph P.

    2002-01-01

    A method and apparatus for loading deposit material, such as an embolic coil, into a shape memory polymer (SMP) gripping/release mechanism. The apparatus enables the application of uniform pressure to secure a grip by the SMP mechanism on the deposit material via differential pressure between, for example, vacuum within the SMP mechanism and hydrostatic water pressure on the exterior of the SMP mechanism. The SMP tubing material of the mechanism is heated to above the glass transformation temperature (Tg) while reshaping, and subsequently cooled to below Tg to freeze the shape. The heating and/or cooling may, for example, be provided by the same water applied for pressurization or the heating can be applied by optical fibers packaged to the SMP mechanism for directing a laser beam, for example, thereunto. At a point of use, the deposit material is released from the SMP mechanism by reheating the SMP material to above the temperature Tg whereby it returns to its initial shape. The reheating of the SMP material may be carried out by injecting heated fluid (water) through an associated catheter or by optical fibers and an associated beam of laser light, for example.

  12. Viscoelastic characterization of elliptical mechanical heterogeneities using a semi-analytical shear-wave scattering model for elastometry measures.

    PubMed

    Montagnon, Emmanuel; Hadj-Henni, Anis; Schmitt, Cédric; Cloutier, Guy

    2013-04-07

    This paper presents a semi-analytical model of shear wave scattering by a viscoelastic elliptical structure embedded in a viscoelastic medium, and its application in the context of dynamic elastography imaging. The commonly used assumption of mechanical homogeneity in the inversion process is removed introducing a priori geometrical information to model physical interactions of plane shear waves with the confined mechanical heterogeneity. Theoretical results are first validated using the finite element method for various mechanical configurations and incidence angles. Secondly, an inverse problem is formulated to assess viscoelastic parameters of both the elliptic inclusion and its surrounding medium, and applied in vitro to characterize mechanical properties of agar-gelatin phantoms. The robustness of the proposed inversion method is then assessed under various noise conditions, biased geometrical parameters and compared to direct inversion, phase gradient and time-of-flight methods. The proposed elastometry method appears reliable in the context of estimating confined lesion viscoelastic parameters.

  13. A multiscale quantum mechanics/electromagnetics method for device simulations.

    PubMed

    Yam, ChiYung; Meng, Lingyi; Zhang, Yu; Chen, GuanHua

    2015-04-07

    Multiscale modeling has become a popular tool for research applying to different areas including materials science, microelectronics, biology, chemistry, etc. In this tutorial review, we describe a newly developed multiscale computational method, incorporating quantum mechanics into electronic device modeling with the electromagnetic environment included through classical electrodynamics. In the quantum mechanics/electromagnetics (QM/EM) method, the regions of the system where active electron scattering processes take place are treated quantum mechanically, while the surroundings are described by Maxwell's equations and a semiclassical drift-diffusion model. The QM model and the EM model are solved, respectively, in different regions of the system in a self-consistent manner. Potential distributions and current densities at the interface between QM and EM regions are employed as the boundary conditions for the quantum mechanical and electromagnetic simulations, respectively. The method is illustrated in the simulation of several realistic systems. In the case of junctionless field-effect transistors, transfer characteristics are obtained and a good agreement between experiments and simulations is achieved. Optical properties of a tandem photovoltaic cell are studied and the simulations demonstrate that multiple QM regions are coupled through the classical EM model. Finally, the study of a carbon nanotube-based molecular device shows the accuracy and efficiency of the QM/EM method.

  14. Histotripsy methods in mechanical disintegration of tissue: towards clinical applications.

    PubMed

    Khokhlova, Vera A; Fowlkes, J Brian; Roberts, William W; Schade, George R; Xu, Zhen; Khokhlova, Tatiana D; Hall, Timothy L; Maxwell, Adam D; Wang, Yak-Nam; Cain, Charles A

    2015-03-01

    In high intensity focused ultrasound (HIFU) therapy, an ultrasound beam is focused within the body to locally affect the targeted site without damaging intervening tissues. The most common HIFU regime is thermal ablation. Recently there has been increasing interest in generating purely mechanical lesions in tissue (histotripsy). This paper provides an overview of several studies on the development of histotripsy methods toward clinical applications. Two histotripsy approaches and examples of their applications are presented. In one approach, sequences of high-amplitude, short (microsecond-long), focused ultrasound pulses periodically produce dense, energetic bubble clouds that mechanically disintegrate tissue. In an alternative approach, longer (millisecond-long) pulses with shock fronts generate boiling bubbles and the interaction of shock fronts with the resulting vapour cavity causes tissue disintegration. Recent preclinical studies on histotripsy are reviewed for treating benign prostatic hyperplasia (BPH), liver and kidney tumours, kidney stone fragmentation, enhancing anti-tumour immune response, and tissue decellularisation for regenerative medicine applications. Potential clinical advantages of the histotripsy methods are discussed. Histotripsy methods can be used to mechanically ablate a wide variety of tissues, whilst selectivity sparing structures such as large vessels. Both ultrasound and MR imaging can be used for targeting and monitoring the treatment in real time. Although the two approaches utilise different mechanisms for tissue disintegration, both have many of the same advantages and offer a promising alternative method of non-invasive surgery.

  15. Environmentally-controlled Microtensile Testing of Mechanically-adaptive Polymer Nanocomposites for ex vivo Characterization

    PubMed Central

    Hess, Allison E.; Potter, Kelsey A.; Tyler, Dustin J.; Zorman, Christian A.; Capadona, Jeffrey R.

    2013-01-01

    Implantable microdevices are gaining significant attention for several biomedical applications1-4. Such devices have been made from a range of materials, each offering its own advantages and shortcomings5,6. Most prominently, due to the microscale device dimensions, a high modulus is required to facilitate implantation into living tissue. Conversely, the stiffness of the device should match the surrounding tissue to minimize induced local strain7-9. Therefore, we recently developed a new class of bio-inspired materials to meet these requirements by responding to environmental stimuli with a change in mechanical properties10-14. Specifically, our poly(vinyl acetate)-based nanocomposite (PVAc-NC) displays a reduction in stiffness when exposed to water and elevated temperatures (e.g. body temperature). Unfortunately, few methods exist to quantify the stiffness of materials in vivo15, and mechanical testing outside of the physiological environment often requires large samples inappropriate for implantation. Further, stimuli-responsive materials may quickly recover their initial stiffness after explantation. Therefore, we have developed a method by which the mechanical properties of implanted microsamples can be measured ex vivo, with simulated physiological conditions maintained using moisture and temperature control13,16,17. To this end, a custom microtensile tester was designed to accommodate microscale samples13,17 with widely-varying Young's moduli (range of 10 MPa to 5 GPa). As our interests are in the application of PVAc-NC as a biologically-adaptable neural probe substrate, a tool capable of mechanical characterization of samples at the microscale was necessary. This tool was adapted to provide humidity and temperature control, which minimized sample drying and cooling17. As a result, the mechanical characteristics of the explanted sample closely reflect those of the sample just prior to explantation. The overall goal of this method is to quantitatively assess

  16. Perspective: Quantum mechanical methods in biochemistry and biophysics

    PubMed Central

    Cui, Qiang

    2016-01-01

    In this perspective article, I discuss several research topics relevant to quantum mechanical (QM) methods in biophysical and biochemical applications. Due to the immense complexity of biological problems, the key is to develop methods that are able to strike the proper balance of computational efficiency and accuracy for the problem of interest. Therefore, in addition to the development of novel ab initio and density functional theory based QM methods for the study of reactive events that involve complex motifs such as transition metal clusters in metalloenzymes, it is equally important to develop inexpensive QM methods and advanced classical or quantal force fields to describe different physicochemical properties of biomolecules and their behaviors in complex environments. Maintaining a solid connection of these more approximate methods with rigorous QM methods is essential to their transferability and robustness. Comparison to diverse experimental observables helps validate computational models and mechanistic hypotheses as well as driving further development of computational methodologies. PMID:27782516

  17. Perspective: Quantum mechanical methods in biochemistry and biophysics.

    PubMed

    Cui, Qiang

    2016-10-14

    In this perspective article, I discuss several research topics relevant to quantum mechanical (QM) methods in biophysical and biochemical applications. Due to the immense complexity of biological problems, the key is to develop methods that are able to strike the proper balance of computational efficiency and accuracy for the problem of interest. Therefore, in addition to the development of novel ab initio and density functional theory based QM methods for the study of reactive events that involve complex motifs such as transition metal clusters in metalloenzymes, it is equally important to develop inexpensive QM methods and advanced classical or quantal force fields to describe different physicochemical properties of biomolecules and their behaviors in complex environments. Maintaining a solid connection of these more approximate methods with rigorous QM methods is essential to their transferability and robustness. Comparison to diverse experimental observables helps validate computational models and mechanistic hypotheses as well as driving further development of computational methodologies.

  18. Perspective: Quantum mechanical methods in biochemistry and biophysics

    NASA Astrophysics Data System (ADS)

    Cui, Qiang

    2016-10-01

    In this perspective article, I discuss several research topics relevant to quantum mechanical (QM) methods in biophysical and biochemical applications. Due to the immense complexity of biological problems, the key is to develop methods that are able to strike the proper balance of computational efficiency and accuracy for the problem of interest. Therefore, in addition to the development of novel ab initio and density functional theory based QM methods for the study of reactive events that involve complex motifs such as transition metal clusters in metalloenzymes, it is equally important to develop inexpensive QM methods and advanced classical or quantal force fields to describe different physicochemical properties of biomolecules and their behaviors in complex environments. Maintaining a solid connection of these more approximate methods with rigorous QM methods is essential to their transferability and robustness. Comparison to diverse experimental observables helps validate computational models and mechanistic hypotheses as well as driving further development of computational methodologies.

  19. Characterization of High Temperature Mechanical Properties Using Laser Ultrasound

    SciTech Connect

    David Hurley; Stephen Reese; Farhad Farzbod; Rory Kennedy

    2012-05-01

    Mechanical properties are controlled to a large degree by defect structures such as dislocations and grain boundaries. These microstructural features involve a perturbation of the perfect crystal lattice (i.e. strain fields). Viewed in this context, high frequency strain waves (i.e. ultrasound) provide a natural choice to study microstructure mediated mechanical properties. In this presentation we use laser ultrasound to probe mechanical properties of materials. This approach utilizes lasers to excite and detect ultrasonic waves, and as a consequence has unique advantages over other methods—it is noncontacting, requires no couplant or invasive sample preparation (other than that used in metallurgical analysis), and has the demonstrated capability to probe microstructure on a micron scale. Laser techniques are highly reproducible enabling sophisticated, microstructurally informed data analysis. Since light is being used for generation and detection of the ultrasonic wave, the specimen being examined is not mechanically coupled to the transducer. As a result, laser ultrasound can be carried out remotely, an especially attractive characteristic for in situ measurements in severe environments. Several examples involving laser ultrasound to measure mechanical properties in high temperature environments will be presented. Emphasis will be place on understanding the role of grain microstructure.

  20. Control of chaos: methods and applications in mechanics.

    PubMed

    Fradkov, Alexander L; Evans, Robin J; Andrievsky, Boris R

    2006-09-15

    A survey of the field related to control of chaotic systems is presented. Several major branches of research that are discussed are feed-forward ('non-feedback') control (based on periodic excitation of the system), the 'Ott-Grebogi-Yorke method' (based on the linearization of the Poincaré map), the 'Pyragas method' (based on a time-delayed feedback), traditional for control-engineering methods including linear, nonlinear and adaptive control. Other areas of research such as control of distributed (spatio-temporal and delayed) systems, chaotic mixing are outlined. Applications to control of chaotic mechanical systems are discussed.

  1. The method of lines in three dimensional fracture mechanics

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, J.; Berke, L.

    1980-01-01

    A review of recent developments in the calculation of design parameters for fracture mechanics by the method of lines (MOL) is presented. Three dimensional elastic and elasto-plastic formulations are examined and results from previous and current research activities are reported. The application of MOL to the appropriate partial differential equations of equilibrium leads to coupled sets of simultaneous ordinary differential equations. Solutions of these equations are obtained by the Peano-Baker and by the recurrance relations methods. The advantages and limitations of both solution methods from the computational standpoint are summarized.

  2. Nanoscale structural and mechanical characterization of natural nanocomposites: Seashells

    NASA Astrophysics Data System (ADS)

    Li, Xiaodong

    2007-03-01

    Seashells are natural nanocomposites with superior mechanical strength and toughness. What is the secret recipe that Mother Nature uses to fabricate seashells? What roles do the nanoscale structures play in the inelasticity and toughening of seashells? Can we learn from this to produce seashell-like nanocomposites? The focus of this article is nacre (mother-of-pearl). The recent discovery of nanoparticles in nacre is summarized, and the role these nanoparticles play in nacre’s toughness is elucidated. It was found that rotation and deformation of aragonite nanoparticles are the two prominent mechanisms contributing to energy dissipation in nacre. The biopolymer spacing between nanoparticles facilitates the particle rotation process. This article also presents future challenges in the study of nacre’s nanoscale structure and mechanical properties.

  3. Characterizing lentic freshwater fish assemblages using multiple sampling methods

    USGS Publications Warehouse

    Fischer, Jesse R.; Quist, Michael

    2014-01-01

    Characterizing fish assemblages in lentic ecosystems is difficult, and multiple sampling methods are almost always necessary to gain reliable estimates of indices such as species richness. However, most research focused on lentic fish sampling methodology has targeted recreationally important species, and little to no information is available regarding the influence of multiple methods and timing (i.e., temporal variation) on characterizing entire fish assemblages. Therefore, six lakes and impoundments (48–1,557 ha surface area) were sampled seasonally with seven gear types to evaluate the combined influence of sampling methods and timing on the number of species and individuals sampled. Probabilities of detection for species indicated strong selectivities and seasonal trends that provide guidance on optimal seasons to use gears when targeting multiple species. The evaluation of species richness and number of individuals sampled using multiple gear combinations demonstrated that appreciable benefits over relatively few gears (e.g., to four) used in optimal seasons were not present. Specifically, over 90 % of the species encountered with all gear types and season combinations (N = 19) from six lakes and reservoirs were sampled with nighttime boat electrofishing in the fall and benthic trawling, modified-fyke, and mini-fyke netting during the summer. Our results indicated that the characterization of lentic fish assemblages was highly influenced by the selection of sampling gears and seasons, but did not appear to be influenced by waterbody type (i.e., natural lake, impoundment). The standardization of data collected with multiple methods and seasons to account for bias is imperative to monitoring of lentic ecosystems and will provide researchers with increased reliability in their interpretations and decisions made using information on lentic fish assemblages.

  4. A Novel Method for Characterizing Spacesuit Mobility Through Metabolic Cost

    NASA Technical Reports Server (NTRS)

    McFarland, Shane M.; Norcross, Jason R.

    2014-01-01

    Historically, spacesuit mobility has been characterized by directly measuring both range of motion and joint torque of individual anatomic joints. The work detailed herein aims to improve on this method, which is often prone to uncertainly, lack of repeatability, and a general lack of applicability to real-world functional tasks. Specifically, the goal of this work is to characterize suited mobility performance by directly measuring the metabolic performance of the occupant. Pilot testing was conducted in 2013, employing three subjects performing a range of functional tasks in two different suits prototypes, the Mark III and Z-1. Cursory analysis of the results shows the approach has merit, with consistent performance trends toward one suit over the other. Forward work includes the need to look at more subjects, a refined task set, and another suit in a different mass/mobility regime to validate the approach.

  5. Characterization of Engineered L1 Retrotransposition Events: The Recovery Method.

    PubMed

    Cano, David; Morell, Santiago; Pulgarin, Andres J; Amador, Suyapa; Garcia-Pérez, Jose L

    2016-01-01

    Long Interspersed Element class 1 retrotransposons (LINE-1 or L1) are abundant Transposable Elements in mammalian genomes and their mobility continues to impact the human genome. The development of engineered retrotransposition assays has been instrumental to understand how these elements are regulated and to identify domains involved in the process of retrotransposition. Additionally, the modification of a retrotransposition indicator cassette has allowed developing straightforward approaches to characterize the site of new L1 insertions in cultured cells. In this chapter, we describe a method termed "L1-recovery" that has been used to characterize the site of insertion on engineered L1 retrotransposition events in cultured mammalian cells. Notably, the recovery assay is based on a genetic strategy and avoids the use of PCR and thus reduces to a minimum the appearance of false positives/artifacts.

  6. Tip Characterization Method using Multi-feature Characterizer for CD-AFM

    PubMed Central

    Orji, Ndubuisi G.; Itoh, Hiroshi; Wang, Chumei; Dixson, Ronald G.; Walecki, Peter S.; Schmidt, Sebastian W.; Irmer, Bernd

    2016-01-01

    In atomic force microscopy (AFM) metrology, the tip is a key source of uncertainty. Images taken with an AFM show a change in feature width and shape that depends on tip geometry. This geometric dilation is more pronounced when measuring features with high aspect ratios, and makes it difficult to obtain absolute dimensions. In order to accurately measure nanoscale features using an AFM, the tip dimensions should be known with a high degree of precision. We evaluate a new AFM tip characterizer, and apply it to critical dimension AFM (CD-AFM) tips used for high aspect ratio features. The characterizer is made up of comb-shaped lines and spaces, and includes a series of gratings that could be used as an integrated nanoscale length reference. We also demonstrate a simulation method that could be used to specify what range of tip sizes and shapes the characterizer can measure. Our experiments show that for non re-entrant features, the results obtained with this characterizer are consistent to 1 nm with the results obtained by using widely accepted but slower methods that are common practice in CD-AFM metrology. A validation of the integrated length standard using displacement interferometry indicates a uniformity of better than 0.75%, suggesting that the sample could be used as highly accurate and SI traceable lateral scale for the whole evaluation process. PMID:26720439

  7. Magnetic microposts for mechanical stimulation of biological cells: Fabrication, characterization, and analysis

    NASA Astrophysics Data System (ADS)

    Sniadecki, Nathan J.; Lamb, Corinne M.; Liu, Yaohua; Chen, Christopher S.; Reich, Daniel H.

    2008-04-01

    Cells use force as a mechanical signal to sense and respond to their microenvironment. Understanding how mechanical forces affect living cells requires the development of tool sets that can apply nanoscale forces and also measure cellular traction forces. However, there has been a lack of techniques that integrate actuation and sensing components to study force as a mechanical signal. Here, we describe a system that uses an array of elastomeric microposts to apply external forces to cells through cobalt nanowires embedded inside the microposts. We first biochemically treat the posts' surfaces to restrict cell adhesion to the posts' tips. Then by applying a uniform magnetic field (B<0.3T), we induce magnetic torque on the nanowires that is transmitted to a cell's adhesion site as an external force. We have achieved external forces of up to 45nN, which is in the upper range of current nanoscale force-probing techniques. Nonmagnetic microposts, similarly prepared but without nanowires, surround the magnetic microposts and are used to measure the traction forces and changes in cell mechanics. We record the magnitude and direction of the external force and the traction forces by optically measuring the deflection of the microposts, which linearly deflect as cantilever springs. With this approach, we can measure traction forces before and after force stimulation in order to monitor cellular response to forces. We present the fabrication methods, magnetic force characterization, and image analysis techniques used to achieve the measurements.

  8. Preparation, characterization, and enhanced thermal and mechanical properties of epoxy-titania composites.

    PubMed

    Rubab, Zakya; Afzal, Adeel; Siddiqi, Humaira M; Saeed, Shaukat

    2014-01-01

    This paper presents the synthesis and thermal and mechanical properties of epoxy-titania composites. First, submicron titania particles are prepared via surfactant-free sol-gel method using TiCl₄ as precursor. These particles are subsequently used as inorganic fillers (or reinforcement) for thermally cured epoxy polymers. Epoxy-titania composites are prepared via mechanical mixing of titania particles with liquid epoxy resin and subsequently curing the mixture with an aliphatic diamine. The amount of titania particles integrated into epoxy matrix is varied between 2.5 and 10.0 wt.% to investigate the effect of sub-micron titania particles on thermal and mechanical properties of epoxy-titania composites. These composites are characterized by X-ray photoelectron (XPS) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric (TG), and mechanical analyses. It is found that sub-micron titania particles significantly enhance the glass transition temperature (>6.7%), thermal oxidative stability (>12.0%), tensile strength (>21.8%), and Young's modulus (>16.8%) of epoxy polymers. Epoxy-titania composites with 5.0 wt.% sub-micron titania particles perform best at elevated temperatures as well as under high stress.

  9. Characterization of nutraceuticals and functional foods by innovative HPLC methods.

    PubMed

    Corradini, Claudio; Galanti, Roberta; Nicoletti, Isabella

    2002-04-01

    In recent years there is a growing interest in food and food ingredient which may provide health benefits. Food as well as food ingredients containing health-preserving components, are not considered conventional food, but can be defined as functional food. To characterise such foods, as well as nutraceuticals specific, high sensitive and reproducible analytical methodologies are needed. In light of this importance we set out to develop innovative HPLC methods employing reversed phase narrow bore column and high-performance anion-exchange chromatographic methods coupled with pulsed amperometric detection (HPAEC-PAD), which are specific for carbohydrate analysis. The developed methods were applied for the separation and quantification of citrus flavonoids and to characterize fructooligosaccharide (FOS) and fructans added to functional foods and nutraceuticals.

  10. Total Gamma Count Rate Analysis Method for Nondestructive Assay Characterization

    SciTech Connect

    Cecilia R. Hoffman; Yale D. Harker

    2006-03-01

    A new approach to nondestructively characterize waste for disposal, based on total gamma response, has been developed at the Idaho Cleanup Project by CH2M-WG Idaho, LLC and Idaho State University, and is called the total gamma count rate analysis method. The total gamma count rate analysis method measures gamma interactions that produce energetic electrons or positrons in a detector. Based on previous experience with waste assays, the radionuclide content of the waste container is then determined. This approach potentially can yield minimum detection limits of less than 10 nCi/g. The importance of this method is twofold. First, determination of transuranic activity can be made for waste containers that are below the traditional minimum detection limits. Second, waste above 10 nCi/g and below 100 nCi/g can be identified, and a potential path for disposal resolved.

  11. Molecular Diagnostic Methods for Detection and Characterization of Human Noroviruses

    PubMed Central

    Chen, Haifeng; Hu, Yuan

    2016-01-01

    Human noroviruses are a group of viral agents that afflict people of all age groups. The viruses are now recognized as the most common causative agent of nonbacterial acute gastroenteritis and foodborne viral illness worldwide. However, they have been considered to play insignificant roles in the disease burden of acute gastroenteritis for the past decades until the recent advent of new and more sensitive molecular diagnostic methods. The availability and application of the molecular diagnostic methods have led to enhanced detection of noroviruses in clinical, food and environmental samples, significantly increasing the recognition of noroviruses as an etiologic agent of epidemic and sporadic acute gastroenteritis. This article aims to summarize recent efforts made for the development of molecular methods for the detection and characterization of human noroviruses. PMID:27335620

  12. Mechanical characterization of hydroxyapatite, thermoelectric materials and doped ceria

    NASA Astrophysics Data System (ADS)

    Fan, Xiaofeng

    For a variety of applications of brittle ceramic materials, porosity plays a critical role structurally and/or functionally, such as in engineered bone scaffolds, thermoelectric materials and in solid oxide fuel cells. The presence of porosity will affect the mechanical properties, which are essential to the design and application of porous brittle materials. In this study, the mechanical property versus microstructure relations for bioceramics, thermoelectric (TE) materials and solid oxide fuel cells were investigated. For the bioceramic material hydroxyapatite (HA), the Young's modulus was measured using resonant ultrasound spectroscopy (RUS) as a function of (i) porosity and (ii) microcracking damage state. The fracture strength was measured as a function of porosity using biaxial flexure testing, and the distribution of the fracture strength was studied by Weibull analysis. For the natural mineral tetrahedrite based solid solution thermoelectric material (Cu10Zn2As4S13 - Cu 12Sb4S13), the elastic moduli, hardness and fracture toughness were studied as a function of (i) composition and (ii) ball milling time. For ZiNiSn, a thermoelectric half-Heusler compound, the elastic modulus---porosity and hardness---porosity relations were examined. For the solid oxide fuel cell material, gadolina doped ceria (GDC), the elastic moduli including Young's modulus, shear modulus, bulk modulus and Poisson's ratio were measured by RUS as a function of porosity. The hardness was evaluated by Vickers indentation technique as a function of porosity. The results of the mechanical property versus microstructure relations obtained in this study are of great importance for the design and fabrication of reliable components with service life and a safety factor. The Weibull modulus, which is a measure of the scatter in fracture strength, is the gauge of the mechanical reliability. The elastic moduli and Poisson's ratio are needed in analytical or numerical models of the thermal and

  13. Characterization of fatigue mechanisms in nickel-based superalloys

    NASA Astrophysics Data System (ADS)

    Yablinsky, Clarissa A.

    Ni-based superalloys are important for turbine engine airfoil applications. Historically, creep has been the main failure mode and thus creep mechanisms have been the subject of numerous studies. However, modern airfoil designs maintain cooler temperatures, and consequently creep is no longer the primary failure mode. Rather, in the cooled components, experience and experimental studies have shown that fatigue is the life-limiting factor. The changing cause of failure highlighted the need for a comprehensive study of fatigue deformation mechanisms. Information about crack propagation and the associated deformation mechanisms has allowed appropriate design changes based on fatigue as a life-limiting factor. The focus of the study will be on a monocrystalline Ni-based superalloy, Rene N5, which is currently used for airfoils. Compact tension specimens were tested under cyclic loading conditions to determine the influence of microstructure and material properties on crack propagation and fatigue failure. The crack growth rate as a function of temperature, environment, frequency, and crystallographic orientation was determined. High resolution scanning electron microscopy was used to examine the fracture surface on length scales from nano to macro. Deformation mechanisms in the plastic zone ahead of the crack tip and within the plastic wake of the crack were studied using TEM and FIB techniques. Environment and frequency seem to have a larger effect on fatigue crack growth rates and threshold stress intensity factor ranges, while temperature and orientation effects are present, but not as dramatic. In the normal blade orientation, (001)[100], mode I crack propagation was prevalent, with mode II crack propagation found at higher DeltaK values. Interdendritic particles appear to be slowing crack growth rates in the threshold region of specimens tested in air. Microstructural analysis showed no change in gamma' precipitate size or morphology with temperature or stress

  14. Characterization of Some Methods of Preparation for Bioactive Glass Coating on Implants

    NASA Astrophysics Data System (ADS)

    Ma, Jie; Chen, Chuanzhong; Yao, Liang; Bao, Quanhe

    Since the discovery of Bioglass® by Hench, bioactive glasses have been used in many medical applications, such as drug delivery systems, nonload-bearing implants, and bone cements because of their excellent bioactivity and biocompatibility. However, due to their poor mechanical properties, these glasses cannot be used in load-bearing applications, where the metallic alloys are still main materials. One useful approach to solving the mechanical limitations of bioactive glasses is to apply the glasses as the coating on mechanically tough substrates; it was also recognized early that bioactive glasses could be used as coatings for prosthetic metallic implants. In this paper, the mechanism, characterization, and current status of some methods of preparation for bioactive glass coating on implants are introduced. In the end, to get the homogeneous and compact coating with perfect bonding strength, some ideas of improving the performance of coatings are also presented.

  15. A novel method for material characterization of reusable products.

    PubMed

    Fortuna, Lorena M; Diyamandoglu, Vasil

    2016-06-01

    Product reuse contributes favorably to waste management and resource recovery by diverting products from terminal disposal to second-hand urban markets. Many organizations with social mission incorporate in their activities the process of reuse, thus making valuable products available to second-hand customers through their thrift stores. Data management and product classification are an important aspect of quantitative analysis of second-hand products circulating through reuse organizations. The New York City Center for Materials Reuse has, for the last 10years, organized the reuse activities of most not for profit organizations, and collected valuable information on the strengths and weaknesses of their operations. One such finding is the casual, and inconsistent approach used by these organizations to keep a record of the level and value of the reuse efforts they undertake. This paper describes a novel methodology developed to standardize record keeping and characterize commonly reused post-consumer products by assessing the outgoing product flow from reuse organizations. The approach groups material composition of individual products into main product categories, creating a simplified method to characterize products. Furthermore, by linking product categories and material composition, the method creates a matrix to help identify the material composition of products handled by reuse organizations. As part of the methodology, whenever adequate data are not available about certain types of products, a process identified as "field characterization study" is proposed and incorporated in the implementation to develop meaningful and useful data on the weight and material composition. Finally, the method incorporates the estimation of the environmental impact of reuse using standard models available through the U.S. Environmental Protection Agency and other worldwide entities. The diversified weight and size of products poses a challenge to the statistical significance

  16. Non-contact method for characterization of a rotational table

    NASA Astrophysics Data System (ADS)

    La Moure Shattuck, Judson, III; Parisi, Vincent M.; Smerdon, Arryn J.

    2007-04-01

    The United States Air Force (USAF) uses and evaluates a variety of helmet-mounted trackers for incorporation into their high performance aircraft. The primary head tracker technologies commercially available are magnetic trackers, inertial trackers, and optical trackers. Each head tracker has a unique method of determining the pilot's head position within the cockpit of the aircraft. Magnetic trackers generally have a small head mounted size and minimal head weight. Because they sense a generated magnetic field, their accuracy can be affected by other magnetic fields or ferrous components within the cockpit. Inertial trackers cover the entire head motion box but require constant motion in order to accommodate drifting of the inertial sensors or a secondary system that updates the inertial system, often referred to as a hybrid system. Although optical head trackers (OHT) are immune to magnetic fields some of their limitations may be daylight/night vision goggle (NVG) compatibility issues and, depending on system configuration, may require numerous emitters and/or receivers to cover a large head motion box and provide a wide field of regard. The Dynamic Tracker Test Fixture (DTTF) was designed by the Helmet Mounted Sensory Technology (HMST) laboratory to accurately measure azimuth rotation in both static and dynamic conditions for the purpose of determining the accuracy of a variety of head trackers. Before the DTTF could be used as an evaluation tool, it required characterization to determine the amount and location of any induced elevation or roll as the table rotated in azimuth. Optimally, the characterization method would not affect the DTTF's movement so a non-contact method was devised. This paper describes the characterization process and its results.

  17. Mechanical and Microstructural Characterization of an Aluminum Bearing Trip Steel

    NASA Astrophysics Data System (ADS)

    Monsalve, Alberto; Guzmán, Alexis; De Barbieri, Flavio; Artigas, Alfredo; Carvajal, Linton; Bustos, Oscar; Garza-Montes-de Oca, Nelson F.; Colás, Rafael

    2016-06-01

    The mechanical properties and microstructural characteristics of a steel able to sustain the TRIP-effect were studied. The material was prepared by taking in mind the partial substitution of silicon by aluminum following a processing route that included hot forging, hot and cold rolling, intercritical annealing, and a final bainitic isothermal treatment. The mechanical properties that were obtained resulted to be above those of commercial a 780 TRIP steel. The TRIP phenomenon was confirmed by the change in retained austenite before and after deforming the steel; X-ray diffraction was used to evaluate the volume content of retained austenite. Formability of the steel under study can be rationalized in terms of the texture developed in the material.

  18. Characterization of mechanical and biochemical properties of developing embryonic tendon

    PubMed Central

    Marturano, Joseph E.; Arena, Jeffrey D.; Schiller, Zachary A.; Georgakoudi, Irene; Kuo, Catherine K.

    2013-01-01

    Tendons have uniquely high tensile strength, critical to their function to transfer force from muscle to bone. When injured, their innate healing response results in aberrant matrix organization and functional properties. Efforts to regenerate tendon are challenged by limited understanding of its normal development. Consequently, there are few known markers to assess tendon formation and parameters to design tissue engineering scaffolds. We profiled mechanical and biological properties of embryonic tendon and demonstrated functional properties of developing tendon are not wholly reflected by protein expression and tissue morphology. Using force volume-atomic force microscopy, we found that nano- and microscale tendon elastic moduli increase nonlinearly and become increasingly spatially heterogeneous during embryonic development. When we analyzed potential biochemical contributors to modulus, we found statistically significant but weak correlation between elastic modulus and collagen content, and no correlation with DNA or glycosaminoglycan content, indicating there are additional contributors to mechanical properties. To investigate collagen cross-linking as a potential contributor, we inhibited lysyl oxidase-mediated collagen cross-linking, which significantly reduced tendon elastic modulus without affecting collagen morphology or DNA, glycosaminoglycan, and collagen content. This suggests that lysyl oxidase-mediated cross-linking plays a significant role in the development of embryonic tendon functional properties and demonstrates that changes in cross-links alter mechanical properties without affecting matrix content and organization. Taken together, these data demonstrate the importance of functional markers to assess tendon development and provide a profile of tenogenic mechanical properties that may be implemented in tissue engineering scaffold design to mechanoregulate new tendon regeneration. PMID:23576745

  19. Mechanics of F-actin characterized with microfabricated cantilevers.

    PubMed Central

    Liu, Xiumei; Pollack, Gerald H

    2002-01-01

    In this report we characterized the longitudinal elasticity of single actin filaments manipulated by novel silicon-nitride microfabricated levers. Single actin filaments were stretched from zero tension to maximal physiological tension, P(0). The obtained length-tension relation was nonlinear in the low-tension range (0-50 pN) with a resultant strain of approximately 0.4-0.6% and then became linear at moderate to high tensions (approximately 50-230 pN). In this region, the stretching stiffness of a single rhodamine-phalloidin-labeled, 1-microm-long F-actin is 34.5 +/- 3.5 pN/nm. Such a length-tension relation could be characterized by an entropic-enthalpic worm-like chain model, which ascribes most of the energy consumed in the nonlinear portion to overcoming thermal undulations arising from the filament's interaction with surrounding solution and the linear portion to the intrinsic stretching elasticity. By fitting the experimental data with such a worm-like chain model, an estimation of persistence length of approximately 8.75 microm was derived. These results suggest that F-actin is more compliant than previously thought and that thin filament compliance may account for a substantial fraction of the sarcomere's elasticity. PMID:12414703

  20. Apparatus and method for characterizing conductivity of materials

    DOEpatents

    Doss, J.D.

    1988-04-13

    Apparatus and method for noncontact, radio-frequency shielding current characterization of materials. Self- or mutual inductance changes in one or more inductive elements, respectively, occur when materials capable of supporting shielding currents are placed in proximity thereto, or undergo change in resistivity while in place. Such changes can be observed by incorporating the inductor(s) in a resonant circuit and determining the frequency of oscillation or by measuring the voltage induced on a coupled inductive element. The present invention is useful for determining the critical temperature and superconducting transition width for superconducting samples. 8 figs.

  1. Method and apparatus for characterizing reflected ultrasonic pulses

    NASA Technical Reports Server (NTRS)

    Yost, William T. (Inventor); Cantrell, John H., Jr. (Inventor)

    1991-01-01

    The invention is a method of and apparatus for characterizing the amplitudes of a sequence of reflected pulses R1, R2, and R3 by converting them into corresponding electric signals E1, E2, and E3 to substantially the same value during each sequence thereby restoring the reflected pulses R1, R2, and R3 to their initial reflection values by timing means, an exponential generator, and a time gain compensator. Envelope and baseline reject circuits permit the display and accurate location of the time spaced sequence of electric signals having substantially the same amplitude on a measurement scale on a suitable video display or oscilloscope.

  2. Tensor analysis methods for activity characterization in spatiotemporal data

    SciTech Connect

    Haass, Michael Joseph; Van Benthem, Mark Hilary; Ochoa, Edward M.

    2014-03-01

    Tensor (multiway array) factorization and decomposition offers unique advantages for activity characterization in spatio-temporal datasets because these methods are compatible with sparse matrices and maintain multiway structure that is otherwise lost in collapsing for regular matrix factorization. This report describes our research as part of the PANTHER LDRD Grand Challenge to develop a foundational basis of mathematical techniques and visualizations that enable unsophisticated users (e.g. users who are not steeped in the mathematical details of matrix algebra and mulitway computations) to discover hidden patterns in large spatiotemporal data sets.

  3. Mechanical characterization of commercially made carbon-fiber-reinforced polymethylmethacrylate.

    PubMed

    Saha, S; Pal, S

    1986-01-01

    Acrylic bone cement is significantly weaker and of lower modulus of elasticity than compact bone. It is also weaker in tension than in compression. This limits its use in orthopedics to areas where tensile stresses were minimum. Many authors have shown that addition of small percentages of fiber reinforcement by hand mixing improved the mechanical properties significantly but with variable results. In this investigation we have examined the mechanical properties of machine-mixed, commercially available carbon-fiber-reinforced bone cement. Appropriate samples of normal low-viscosity cement and carbon-fiber-reinforced cement were prepared and tested mechanically. Carbon fiber increased the tensile strength and modulus by 30% and 35.8% respectively. The compression strength and modulus, however, increased by only 10.7%. Similarly, bending and shear strengths improved by 29.5% and 18.5%, respectively. Diametral compression strength, which is an indirect measure of tensile strength, however, showed only 6.2% improvement. The maximum temperature rise during polymerization was also reduced significantly by the fiber reinforcement.

  4. Systematic characterization of porosity and mass transport and mechanical properties of porous polyurethane scaffolds.

    PubMed

    Wang, Yu-Fu; Barrera, Carlos M; Dauer, Edward A; Gu, Weiyong; Andreopoulos, Fotios; Huang, C-Y Charles

    2017-01-01

    One of the key challenges in porous scaffold design is to create a porous structure with desired mechanical function and mass transport properties which support delivery of biofactors and development of function tissue substitute. In recent years, polyurethane (PU) has become one of the most popular biomaterials in various tissue engineering fields. However, there are no studies fully investigating the relations between porosity and both mass transport and mechanical properties of PU porous scaffolds. In this paper, we fabricated PU scaffolds by combining phase inversion and salt (sodium chloride) leaching methods. The tensile and compressive moduli were examined on PU scaffolds fabricated with different PU concentrations (25%, 20% and 15% w/v) and salt/PU weight ratios (9/1, 6/1, 3/1 and 0/1). The mass transport properties of PU scaffolds including hydraulic permeability and glucose diffusivity were also measured. Furthermore, the relationships between the porosity and mass transport and mechanical properties of porous PU scaffold were systemically investigated. The results demonstrated that porosity is a key parameter which governs both mass transport and mechanical properties of porous PU scaffolds. With similar pore sizes, the mass transport and mechanical properties of porous PU scaffold can be described as single functions of porosity regardless of initial PU concentration. The relationships between scaffold porosity and properties can be utilized to facilitate porous PU scaffold fabrication with specific mass transport and mechanical properties. The systematic approach established in this study can be applied to characterization of other biomaterials for scaffold design and fabrication.

  5. Mechanical spectrum study of glass transition by a composite method

    NASA Astrophysics Data System (ADS)

    Yuan, Y. H.; Zhang, L.; Wang, X. L.; Ying, X. N.; Yan, F.; Huang, Y. N.; Zhu, J. S.; Wang, Y. N.

    2009-11-01

    Normalized mechanical spectra of glycerol, 1,2-propanediol carbonate and poly(vinyl chloride)/di(2-ethyl-hexyl) phthalate (PVC/DOP) blends were studied in the temperature range from 100 to 300 K by a composite method. The dynamic glass transition was observed, which exhibits a peak of temperature-dependent loss modulus. The peak moves toward higher temperature with higher measuring frequency, which accords with the relaxation feature of the dynamic glass transition. Another characteristic temperature can be marked in the mechanical spectrum by the onset of storage modulus change, which is labeled as T gm. T gm is found to be nearly equal to the calorimetric glass transition temperature in glycerol, 1,2-propanediol carbonate and di(2-ethyl-hexyl) phthalate. As we expected, this onset temperature in the mechanical spectrum has an intimate relation with the calorimetric glass transition of materials, and it can be regarded as a representative when the calorimetric glass transition temperature is not available. Finally, normalized mechanical spectra of PVC/DOP blends with different PVC content were obtained and mechanical glass transition temperatures T gm were determined.

  6. Impetus of composite mechanics on test methods for fiber composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1978-01-01

    The impetus of composite mechanics on composite test methods and/or on interpreting test results is described by using examples from composite micromechanics, composite macromechanics and laminate theory. The specific examples included contributions such as criteria for selecting resin matrices for improved composite strength, the 10 deg off-axis tensile test, criteria for configuring hybrids and superhybrids for improved impact resistance and the reduced bending rigidities concept for buckling and vibration analyses.

  7. Computational alanine scanning with linear scaling semiempirical quantum mechanical methods.

    PubMed

    Diller, David J; Humblet, Christine; Zhang, Xiaohua; Westerhoff, Lance M

    2010-08-01

    Alanine scanning is a powerful experimental tool for understanding the key interactions in protein-protein interfaces. Linear scaling semiempirical quantum mechanical calculations are now sufficiently fast and robust to allow meaningful calculations on large systems such as proteins, RNA and DNA. In particular, they have proven useful in understanding protein-ligand interactions. Here we ask the question: can these linear scaling quantum mechanical methods developed for protein-ligand scoring be useful for computational alanine scanning? To answer this question, we assembled 15 protein-protein complexes with available crystal structures and sufficient alanine scanning data. In all, the data set contains Delta Delta Gs for 400 single point alanine mutations of these 15 complexes. We show that with only one adjusted parameter the quantum mechanics-based methods outperform both buried accessible surface area and a potential of mean force and compare favorably to a variety of published empirical methods. Finally, we closely examined the outliers in the data set and discuss some of the challenges that arise from this examination.

  8. First Resistance Mechanisms Characterization in Glyphosate-Resistant Leptochloa virgata

    PubMed Central

    Alcántara-de la Cruz, Ricardo; Rojano-Delgado, Antonia M.; Giménez, María J.; Cruz-Hipolito, Hugo E.; Domínguez-Valenzuela, José A.; Barro, Francisco; De Prado, Rafael

    2016-01-01

    Leptochloa virgata (L.) P. Beauv. is an annual weed common in citrus groves in the states of Puebla and Veracruz, Mexico limiting their production. Since 2010, several L. virgata populations were identified as being resistant to glyphosate, but studies of their resistance mechanisms developed by this species have been conducted. In this work, three glyphosate-resistant populations (R8, R14, and R15) collected in citrus orchards from Mexico, were used to study their resistance mechanisms comparing them to one susceptible population (S). Dose-response and shikimic acid accumulation assays confirmed the glyphosate resistance of the three resistant populations. Higher doses of up to 720 g ae ha-1 (field dose) were needed to control by 50% plants of resistant populations. The S population absorbed between 7 and 13% more 14C-glyphosate than resistant ones, and translocated up to 32.2% of 14C-glyphosate to the roots at 96 h after treatment (HAT). The R8, R14, and R15 populations translocated only 24.5, 26.5, and 21.9%, respectively. The enzyme activity of 5-enolpyruvyl shikimate-3-phosphate synthase (EPSPS) was not different in the S, R8 and R14 populations. The R15 Population exhibited 165.9 times greater EPSPS activity. Additionally, this population showed a higher EPSPS basal activity and a substitution in the codon 106 from Proline to Serine in the EPSPS protein sequence. EPSPS gene expression in the R15 population was similar to that of S population. In conclusion, the three resistant L. virgata populations show reduced absorption and translocation of 14C-glyphosate. Moreover, a mutation and an enhanced EPSPS basal activity at target-site level confers higher resistance to glyphosate. These results describe for the first time the glyphosate resistance mechanisms developed by resistant L. virgata populations of citrus orchards from Mexico. PMID:27917189

  9. A mechanical diode: Comparing numerical and experimental characterizations

    SciTech Connect

    Simmermacher, T.; Segalman, D.; Sagartz, M.

    1997-12-01

    The predictive modeling of vibration of many structural systems is crippled by an inability to predictively model the mechanics of joints. The lack of understanding of joint dynamics is evidenced by the substantial uncertainty of joint compliances in the numerical models and by the complete inability to predict joint damping. The lore is that at low amplitudes, joint mechanics are associated with Coulomb friction and stick-slip phenomena and that at high amplitudes, impact processes result in dissipation as well as shift of energy to other frequencies. Inadequate understanding of the physics precludes reliable predictions. In this introductory work, joint compliance is studied in both a numerical and experimental setting. A simple bolted interface is used as the test article and compliance is measured for the joint in both compression and in tension. This simple interface is shown to exhibit a strong non-linearity near the transition from compression to tension (or vice-versa). Modeling issues pertaining to numerically solving for the compliance are addressed. It is shown that the model predicts the experimental strains and compliance fairly well. It will be seen that the joint behavior is a mechanical analogy to a diode. In compression, the joint is very stiff, acting almost as a rigid link, while in tension the joint is soft, acting as a soft spring. Although there have been many other studies performed on bolted joints, the variety of joint geometries has demonstrated large variations in behavior. This study is an attempt to quantify the behavior of typical joints found in today`s weapon systems.

  10. Dynamic Mechanical Characterization of Thin Film Polymer Nanocomposites

    NASA Technical Reports Server (NTRS)

    Herring, Helen M.; Gates, Thomas S. (Technical Monitor)

    2003-01-01

    Many new materials are being produced for aerospace applications with the objective of maximizing certain ideal properties without sacrificing others. Polymer composites in various forms and configurations are being developed in an effort to provide lighter weight construction and better thermal and electrical properties and still maintain adequate strength and stability. To this end, thin film polymer nanocomposites, synthesized for the purpose of influencing electrical conductivity using metal oxide particles as filler without incurring losses in mechanical properties, were examined to determine elastic modulus and degree of dispersion of particles. The effects of various metal oxides on these properties will be discussed.

  11. Apparatus and method for characterizing ultrafast polarization varying optical pulses

    DOEpatents

    Smirl, Arthur; Trebino, Rick P.

    1999-08-10

    Practical techniques are described for characterizing ultrafast potentially ultraweak, ultrashort optical pulses. The techniques are particularly suited to the measurement of signals from nonlinear optical materials characterization experiments, whose signals are generally too weak for full characterization using conventional techniques.

  12. Statistical Methods for Characterizing Variability in Stellar Spectra

    NASA Astrophysics Data System (ADS)

    Cisewski, Jessi; Yale Astrostatistics

    2017-01-01

    Recent years have seen a proliferation in the number of exoplanets discovered. One technique for uncovering exoplanets relies on the detection of subtle shifts in the stellar spectra due to the Doppler effect caused by an orbiting object. However, stellar activity can cause distortions in the spectra that mimic the imprint of an orbiting exoplanet. The collection of stellar spectra potentially contains more information than is traditionally used for estimating its radial velocity curve. I will discuss some statistical methods that can be used for characterizing the sources of variability in the spectra. Statistical assessment of stellar spectra is a focus of the Statistical and Applied Mathematical Sciences Institute (SAMSI)'s yearlong program on Statistical, Mathematical and Computational Methods for Astronomy's Working Group IV (Astrophysical Populations).

  13. Nondestructive characterization methods for monolithic solid oxide fuel cells

    SciTech Connect

    Ellingson, W.A.

    1993-01-01

    Monolithic solid oxide fuel cells (MSOFCS) represent a potential breakthrough in fuel cell technology, provided that reliable fabrication methods can be developed. Fabrication difficulties arise in several steps of the processing: First is the fabrication of uniform thin (305 {mu}m) single-layer and trilayer green tapes (the trilayer tapes of anode/electrolyte/cathode and anode/interconnect/cathode must have similar coefficients of thermal expansion to sinter uniformly and to have the necessary electrochemical properties); Second is the development of fuel and oxidant channels in which residual stresses are likely to develop in the tapes; Third is the fabrication of a ``complete`` cell for which the bond quality between layers and the quality of the trilayers must be established; and Last, attachment of fuel and oxidant manifolds and verification of seal integrity. Purpose of this report is to assess nondestructive characterization methods that could be developed for application to laboratory, prototype, and full-scale MSOFCs.

  14. Characterization of peak flow events with local singularity method

    NASA Astrophysics Data System (ADS)

    Cheng, Q.; Li, L.; Wang, L.

    2009-07-01

    Three methods, return period, power-law frequency plot (concentration-area) and local singularity index, are introduced in the paper for characterizing peak flow events from river flow data for the past 100 years from 1900 to 2000 recorded at 25 selected gauging stations on rivers in the Oak Ridges Moraine (ORM) area, Canada. First a traditional method, return period, was applied to the maximum annual river flow data. Whereas the Pearson III distribution generally fits the values, a power-law frequency plot (C-A) on the basis of self-similarity principle provides an effective mean for distinguishing "extremely" large flow events from the regular flow events. While the latter show a power-law distribution, about 10 large flow events manifest departure from the power-law distribution and these flow events can be classified into a separate group most of which are related to flood events. It is shown that the relation between the average water releases over a time period after flow peak and the time duration may follow a power-law distribution. The exponent of the power-law or singularity index estimated from this power-law relation may be used to characterize non-linearity of peak flow recessions. Viewing large peak flow events or floods as singular processes can anticipate the application of power-law models not only for characterizing the frequency distribution of peak flow events, for example, power-law relation between the number and size of floods, but also for describing local singularity of processes such as power-law relation between the amount of water released versus releasing time. With the introduction and validation of singularity of peak flow events, alternative power-law models can be used to depict the recession property as well as other types of non-linear properties.

  15. Physical and chemical methods for the characterization of hazardous wastes

    NASA Astrophysics Data System (ADS)

    Francis, C. W.; Maskarinec, M. P.; Lee, D. W.

    Numerous test methods have been proposed and developed to evaluate the hazards associated with handling and disposal of wastes in landfills. The major concern is the leaching of toxic constituents from the wastes. The fate of hazardous constituents in landfilled wastes is highly dependent on the physical and chemical characteristics of the waste. Thus, the primary objective in the selection of waste characterization procedures should be focused on those methods that gauge the fate of the waste's hazardous constituents in a specific landfill environment. Waste characterization in the United States has centered around the characteristics of ignitability, corrosivity, reactivity, and toxicity. The strategy employed in the development of most regulatory waste characterization procedures has been a pass or fail approach, usually tied to some form of a mismanagement scenario for that waste. For example, USEPA has chosen the disposal of a waste in a municipal waste landfill as a mismanagement scenario for the development of the waste leaching tests to determine the toxicity characteristic. Many wastes, such as large-volume utility wastes or mining wastes, are not disposed of in municipal waste landfills. As a consequence, more effort is needed in the development of waste leaching tests that determine the long-term leaching characteristics of that waste in the landfill environment in which the waste is to be disposed. Waste leaching models also need to be developed and tested as to their ability to simulate actual disposal environments. These models need to be compared with laboratory leaching tests, and, if practical, coupled with groundwater transport models.

  16. Characterizing Awake and Anesthetized States Using a Dimensionality Reduction Method.

    PubMed

    Mirsadeghi, M; Behnam, H; Shalbaf, R; Jelveh Moghadam, H

    2016-01-01

    Distinguishing between awake and anesthetized states is one of the important problems in surgery. Vital signals contain valuable information that can be used in prediction of different levels of anesthesia. Some monitors based on electroencephalogram (EEG) such as the Bispectral (BIS) index have been proposed in recent years. This study proposes a new method for characterizing between awake and anesthetized states. We validated our method by obtaining data from 25 patients during the cardiac surgery that requires cardiopulmonary bypass. At first, some linear and non-linear features are extracted from EEG signals. Then a method called "LLE"(Locally Linear Embedding) is used to map high-dimensional features in a three-dimensional output space. Finally, low dimensional data are used as an input to a quadratic discriminant analyzer (QDA). The experimental results indicate that an overall accuracy of 88.4 % can be obtained using this method for classifying the EEG signal into conscious and unconscious states for all patients. Considering the reliability of this method, we can develop a new EEG monitoring system that could assist the anesthesiologists to estimate the depth of anesthesia accurately.

  17. Synthesis and characterization of iron orthophosphate by solution combustion method

    SciTech Connect

    Baykan, Demet; Oztas, Nursen Altuntas

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► Solution combustion synthesis was firstly employed to prepare FePO{sub 4}. ► Pure, well-crystallized and porous FePO{sub 4} was obtained and characterized. ► The results proved SCS a time saving and practically applicable method. -- Abstract: The present work applies solution combustion synthesis (SCS) by employing glycine as organic fuel to stimulate the synthesis of pure iron orthophosphate with well-defined reaction parameters. The structural and morphological properties of the products were characterized and confirmed by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and surface analyzer, respectively. Thermal behaviors were also investigated by TG/DT analyses. The optimal condition was set at 500 °C in a few minutes, giving pure iron orthophosphate with a good level of crystallinity and 11,769 m{sup 2}/g surface area. The results proved SCS a time saving and practically applicable method.

  18. Hydrogeological-Geophysical Methods for Subsurface Site Characterization - Final Report

    SciTech Connect

    Rubin, Yoram

    2001-01-01

    The goal of this research project is to increase water savings and show better ecological control of natural vegetation by developing hydrogeological-geophysical methods for characterizing the permeability and content of water in soil. The ground penetrating radar (GPR) tool was developed and used as the surface geophysical method for monitoring water content. Initial results using the tool suggest that surface GPR is a viable technique for obtaining precision volumetric water content profile estimates, and that laboratory-derived petrophysical relationships could be applied to field-scale GPR data. A field-scale bacterial transport study was conducted within an uncontaminated sandy Pleistocene aquifer to evaluate the importance of heterogeneity in controlling the transport of bacteria. Geochemical, hydrological, geological, and geophysical data were collected to characterize the site prior to and after chemical and bacterial injection experiments. Study results shows that, even within the fairly uniform shallow marine deposits of the narrow channel focus area, heterogeneity existed that influenced the chemical tracer transport over lateral distances of a few meters and vertical distances of less than a half meter. The interpretation of data suggest that the incorporation of geophysical data with limited hydrological data may provide valuable information about the stratigraphy, log conductivity values, and the spatial correlation structure of log conductivity, which have traditionally been obtainable only by performing extensive and intrusive hydrological sampling.

  19. Method to characterize dielectric properties of powdery substances

    NASA Astrophysics Data System (ADS)

    Tuhkala, M.; Juuti, J.; Jantunen, H.

    2013-07-01

    An open ended coaxial cavity method for dielectric characterization of powdery substance operating at 4.5 GHz in TEM mode is presented. Classical mixing rules and electromagnetic modeling were utilized with measured effective permittivities and Q factors to determine the relative permittivity and dielectric loss tangent of different powders with ɛr up to 30. The modeling enabled determination of the correction factor for the simplified equation for the relative permittivity of an open ended coaxial resonator and mixing rules having the best correlation with experiments. SiO2, Al2O3, LTCC CT 2000, ZrO2, and La2O3 powders were used in the experiments. Based on the measured properties and Bruggeman symmetric and Looyenga mixing rules, the determined dielectric characteristics of the powders exhibited good correlation with values in the literature. The presented characterization method enabled the determination of dielectric properties of powdery substances within the presented range, and therefore could be applied to various research fields and applications where dielectric properties of powders need to be known and controlled.

  20. Mechanical Characterization of Composites and Foams for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Veazie, D. R.; Glinsey, C.; Webb, M. M.; Norman, M.; Meador, Michael A. (Technical Monitor)

    2000-01-01

    Experimental studies to investigate the mechanical properties of ultra-lightweight polyimide foams for space applications, compression after impact (CAI) properties for low velocity impact of sandwich composites, and aspen fiber/polypropylene composites containing an interface adhesive additive, Maleic Anhydride Grafted Polypropylene (MAPP), were performed at Clark Atlanta University. Tensile, compression, flexural, and shear modulus tests were performed on TEEK foams categorized by their densities and relative cost according to ASTM specifications. Results showed that the mechanical properties of the foams increased as a function of higher price and increasing density. The CAI properties of Nomex/phenolic honeycomb core, fiberglass/epoxy facesheet sandwich composites for two damage arrangements were compared using different levels of impact energy ranging from 0 - 452 Joules. Impact on the thin side showed slightly more retention of CAI strength at low impact levels, whereas higher residual compressive strength was observed from impact on the thick side at higher impact levels. The aspen fiber/polypropylene composites studied are composed of various percentages (by weight) of aspen fiber and polypropylene ranging from 30%-60% and 40%-100%, respectively. Results showed that the MAPP increases tensile and flexural strength, while having no significant influence on tensile and flexural modulus.

  1. Knowledge Discovery Process for Characterization of Materials Failure Mechanism

    NASA Technical Reports Server (NTRS)

    Cios, Krzysztof J.

    1999-01-01

    It is the intent of this project to provide a platform to visualize the various data collected from stress-strain testing of composite ceramic matrix materials. The data collected from the stress-strain tests are acoustic emissions (AE). As a material is subjected to a stress-strain test, various failure mechanisms occur in the material. The recorded sounds emitted during the test may correspond to various failure mechanisms. This project, thus, will give a possible way to visualize the data and data derived from the recorded AE. The stress-strain testing was performed on several composite matrix material combinations. Each of these tests produced anywhere from 1000 to 10,000+ AE events. For each AE event recorded, several characteristics in both the time and frequency domains are created. This project has two goals. First, this project will provide a summation page for a selected waveform. This page will include all of the characteristics determined from the AE event waveform along with graphs of the AE event waveform and its corresponding Power Spectrum. The other function of this project is to retrieve and display selected AE event waveforms for comparison.

  2. Characterization of mechanical properties of leather with airborne ultrasonics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A nondestructive method to accurately evaluate the quality of hides and leather is urgently needed by leather and hide industries. We previously reported the research results for airborne ultrasonic (AU) testing using non-contact transducers to evaluate the quality of hides and leather. The abilit...

  3. Microstructural Characterization and Mechanical Properties of PA11 Nanocomposite Fibers

    NASA Astrophysics Data System (ADS)

    Latko, Paulina; Kolbuk, Dorota; Kozera, Rafal; Boczkowska, Anna

    2016-01-01

    Polyamide 11/multi-walled carbon nanotubes nanocomposite fibers with weight fraction 2, 4, and 6 wt.% and diameter 80 μm were prepared with a twin screw mini-extruder. The morphology and degree of dispersion of the multi-walled carbon nanotubes in the fibers was investigated by using scanning and transmission electron microscopy. In turn, the molecular structure was indicated by using wide-angle x-ray scattering and correlated with thermal analysis. It was found that carbon nanotubes lead to the formation of α phase in the fibers and they show medial level of alignment within the length of the fiber. Mechanical analysis of the fibers shows that apart from the crystallinity content, the tensile strength is strongly dependent on the macroscopic defects of the surface of the fibers. Nanocomposite fibers based on polyamide 11 with carbon nanotubes can be used as a precursor for non-woven or woven fabrics manufacturing process.

  4. Mechanical and swelling behaviour of well characterized polybutadiene networks

    NASA Technical Reports Server (NTRS)

    Mckenna, Gregory B.; Hinkley, Jeffrey A.

    1986-01-01

    Endlinking of hydroxyl-terminated polybutadiene with the appropriate isocyanate has been used to prepare well characterized networks. Two networks have been studied with molecular weights of the prepolymers being 6100 and 2400 g/mole by g.p.c. Cylindrical specimens were prepared and the derivatives of the stored energy function with respect to the stretch invariants were determined by torque and normal force measurements in torsion. From these data the Valanis-Landel (1967) stored energy function derivatives w-prime(lambda) were determined for both networks. The stored energy function for the junction constraint model of Flory (1953, 1977, 1979, 1985) which is a special form of the Valanis-Landel function, has been fitted to that determined from the experiments. The contributions to the stored energy function from the phantom network and from the junction constraints respectively do not agree with predictions from the topologies of the networks. In spite of this, the form of w-prime(lambda) for the junction constraint model gives an excellent 'curve fit' to the data. Comparison is also made with equilibrium swelling.

  5. Characterization of copper-cementite nanocomposite produced by mechanical alloying

    SciTech Connect

    Carvalho, P.A. . E-mail: pac@ist.utl.pt; Fonseca, I.; Marques, M.T.; Correia, J.B.; Almeida, A.; Vilar, R.

    2005-02-01

    A copper-iron carbide nanocomposite has been synthesized by high-energy milling of elemental powders (Cu{sub 69}-Fe{sub 23}-C{sub 8}), followed by annealing at 873 K. Phase identification and microstructure characterization have been carried out by transmission electron microscopy and energy dispersive spectroscopy. The carbide phase found in the as-milled material has been identified as Fe{sub 3}C and/or Fe{sub 7}C{sub 3}, but clearly only Fe{sub 3}C was present after annealing. Overall, grain sizes ranged from 10 to 50 nm in the as-milled condition and from 30 to 160 nm after annealing, with the carbide phase presenting a higher growth rate than copper. Stacking faults and a dispersion of Cu nanoparticles (5-10 nm) have been detected in annealed cementite while copper grains exhibited twins on (1 1 1) planes. Cementite growth could be evaluated in terms of precipitate growth theory. The remarkable thermal stability of the copper matrix is proposed to be related to solute drag effects.

  6. A high throughput array microscope for the mechanical characterization of biomaterials

    NASA Astrophysics Data System (ADS)

    Cribb, Jeremy; Osborne, Lukas D.; Hsiao, Joe Ping-Lin; Vicci, Leandra; Meshram, Alok; O'Brien, E. Tim; Spero, Richard Chasen; Taylor, Russell; Superfine, Richard

    2015-02-01

    In the last decade, the emergence of high throughput screening has enabled the development of novel drug therapies and elucidated many complex cellular processes. Concurrently, the mechanobiology community has developed tools and methods to show that the dysregulation of biophysical properties and the biochemical mechanisms controlling those properties contribute significantly to many human diseases. Despite these advances, a complete understanding of the connection between biomechanics and disease will require advances in instrumentation that enable parallelized, high throughput assays capable of probing complex signaling pathways, studying biology in physiologically relevant conditions, and capturing specimen and mechanical heterogeneity. Traditional biophysical instruments are unable to meet this need. To address the challenge of large-scale, parallelized biophysical measurements, we have developed an automated array high-throughput microscope system that utilizes passive microbead diffusion to characterize mechanical properties of biomaterials. The instrument is capable of acquiring data on twelve-channels simultaneously, where each channel in the system can independently drive two-channel fluorescence imaging at up to 50 frames per second. We employ this system to measure the concentration-dependent apparent viscosity of hyaluronan, an essential polymer found in connective tissue and whose expression has been implicated in cancer progression.

  7. A high throughput array microscope for the mechanical characterization of biomaterials

    PubMed Central

    Cribb, Jeremy; Osborne, Lukas D.; Hsiao, Joe Ping-Lin; Vicci, Leandra; Meshram, Alok; O’Brien, E. Tim; Spero, Richard Chasen; Taylor, Russell; Superfine, Richard

    2015-01-01

    In the last decade, the emergence of high throughput screening has enabled the development of novel drug therapies and elucidated many complex cellular processes. Concurrently, the mechanobiology community has developed tools and methods to show that the dysregulation of biophysical properties and the biochemical mechanisms controlling those properties contribute significantly to many human diseases. Despite these advances, a complete understanding of the connection between biomechanics and disease will require advances in instrumentation that enable parallelized, high throughput assays capable of probing complex signaling pathways, studying biology in physiologically relevant conditions, and capturing specimen and mechanical heterogeneity. Traditional biophysical instruments are unable to meet this need. To address the challenge of large-scale, parallelized biophysical measurements, we have developed an automated array high-throughput microscope system that utilizes passive microbead diffusion to characterize mechanical properties of biomaterials. The instrument is capable of acquiring data on twelve-channels simultaneously, where each channel in the system can independently drive two-channel fluorescence imaging at up to 50 frames per second. We employ this system to measure the concentration-dependent apparent viscosity of hyaluronan, an essential polymer found in connective tissue and whose expression has been implicated in cancer progression. PMID:25725856

  8. Steered Molecular Dynamics Methods Applied to Enzyme Mechanism and Energetics.

    PubMed

    Ramírez, C L; Martí, M A; Roitberg, A E

    2016-01-01

    One of the main goals of chemistry is to understand the underlying principles of chemical reactions, in terms of both its reaction mechanism and the thermodynamics that govern it. Using hybrid quantum mechanics/molecular mechanics (QM/MM)-based methods in combination with a biased sampling scheme, it is possible to simulate chemical reactions occurring inside complex environments such as an enzyme, or aqueous solution, and determining the corresponding free energy profile, which provides direct comparison with experimental determined kinetic and equilibrium parameters. Among the most promising biasing schemes is the multiple steered molecular dynamics method, which in combination with Jarzynski's Relationship (JR) allows obtaining the equilibrium free energy profile, from a finite set of nonequilibrium reactive trajectories by exponentially averaging the individual work profiles. However, obtaining statistically converged and accurate profiles is far from easy and may result in increased computational cost if the selected steering speed and number of trajectories are inappropriately chosen. In this small review, using the extensively studied chorismate to prephenate conversion reaction, we first present a systematic study of how key parameters such as pulling speed, number of trajectories, and reaction progress are related to the resulting work distributions and in turn the accuracy of the free energy obtained with JR. Second, and in the context of QM/MM strategies, we introduce the Hybrid Differential Relaxation Algorithm, and show how it allows obtaining more accurate free energy profiles using faster pulling speeds and smaller number of trajectories and thus smaller computational cost.

  9. Characterization of Al–Al{sub 4}C{sub 3} nanocomposites produced by mechanical milling

    SciTech Connect

    Santos-Beltrán, A.; Morales-Rodriguez, H.; Gallegos-Orozco, V.; Baldenebro-Lopez, F.

    2015-08-15

    In this work, a mixture of Al–C–Al{sub 4}C{sub 3} nanopowder previously synthesized by mechanical milling and subsequent thermal treatment was used to reinforce the Al matrix. The nanocomposites were fabricated via high-energy ball milling and subsequent sintering process for different periods of time at 550 °C. Hardness and compression tests were performed to evaluate the mechanical properties of the nanocomposites in the as-milled and sintered conditions. According to the results the reinforcement located in the grain boundaries is responsible for the brittle behavior observed in the nanocomposites during the compression test. The combined effect of sintering and precipitation mechanisms produced an evident increase of the strength of the Al matrix at a relatively short sintering time. By using the Rietveld method the crystallite size and microstrain measurements were determined and correlated with the microhardness values. For the proper characterization of the nanoparticles present in the Al matrix, atomic force microscopy and high resolution electron microscopy were used. - Highlights: • Nanostructured Al{sub 4}C{sub 3} reinforcement was fabricated via mechanical milling and heat treatment. • We found a significant increase of the mechanical properties at short sintering times. • The formation of Al{sub 4}C{sub 3} with during sintering time restricted the excessive growth of the crystallite. • Al{sub 4}C{sub 3} located in the grain boundaries causes brittle fracture observed in compression tests. • There is a correlation between, crystallite size and microstrain values with microhardness.

  10. Amyloid oligomer structure characterization from simulations: A general method

    SciTech Connect

    Nguyen, Phuong H.; Li, Mai Suan

    2014-03-07

    Amyloid oligomers and plaques are composed of multiple chemically identical proteins. Therefore, one of the first fundamental problems in the characterization of structures from simulations is the treatment of the degeneracy, i.e., the permutation of the molecules. Second, the intramolecular and intermolecular degrees of freedom of the various molecules must be taken into account. Currently, the well-known dihedral principal component analysis method only considers the intramolecular degrees of freedom, and other methods employing collective variables can only describe intermolecular degrees of freedom at the global level. With this in mind, we propose a general method that identifies all the structures accurately. The basis idea is that the intramolecular and intermolecular states are described in terms of combinations of single-molecule and double-molecule states, respectively, and the overall structures of oligomers are the product basis of the intramolecular and intermolecular states. This way, the degeneracy is automatically avoided. The method is illustrated on the conformational ensemble of the tetramer of the Alzheimer's peptide Aβ{sub 9−40}, resulting from two atomistic molecular dynamics simulations in explicit solvent, each of 200 ns, starting from two distinct structures.

  11. Amyloid oligomer structure characterization from simulations: A general method

    NASA Astrophysics Data System (ADS)

    Nguyen, Phuong H.; Li, Mai Suan; Derreumaux, Philippe

    2014-03-01

    Amyloid oligomers and plaques are composed of multiple chemically identical proteins. Therefore, one of the first fundamental problems in the characterization of structures from simulations is the treatment of the degeneracy, i.e., the permutation of the molecules. Second, the intramolecular and intermolecular degrees of freedom of the various molecules must be taken into account. Currently, the well-known dihedral principal component analysis method only considers the intramolecular degrees of freedom, and other methods employing collective variables can only describe intermolecular degrees of freedom at the global level. With this in mind, we propose a general method that identifies all the structures accurately. The basis idea is that the intramolecular and intermolecular states are described in terms of combinations of single-molecule and double-molecule states, respectively, and the overall structures of oligomers are the product basis of the intramolecular and intermolecular states. This way, the degeneracy is automatically avoided. The method is illustrated on the conformational ensemble of the tetramer of the Alzheimer's peptide Aβ9-40, resulting from two atomistic molecular dynamics simulations in explicit solvent, each of 200 ns, starting from two distinct structures.

  12. Amyloid oligomer structure characterization from simulations: a general method.

    PubMed

    Nguyen, Phuong H; Li, Mai Suan; Derreumaux, Philippe

    2014-03-07

    Amyloid oligomers and plaques are composed of multiple chemically identical proteins. Therefore, one of the first fundamental problems in the characterization of structures from simulations is the treatment of the degeneracy, i.e., the permutation of the molecules. Second, the intramolecular and intermolecular degrees of freedom of the various molecules must be taken into account. Currently, the well-known dihedral principal component analysis method only considers the intramolecular degrees of freedom, and other methods employing collective variables can only describe intermolecular degrees of freedom at the global level. With this in mind, we propose a general method that identifies all the structures accurately. The basis idea is that the intramolecular and intermolecular states are described in terms of combinations of single-molecule and double-molecule states, respectively, and the overall structures of oligomers are the product basis of the intramolecular and intermolecular states. This way, the degeneracy is automatically avoided. The method is illustrated on the conformational ensemble of the tetramer of the Alzheimer's peptide Aβ9-40, resulting from two atomistic molecular dynamics simulations in explicit solvent, each of 200 ns, starting from two distinct structures.

  13. [A method of desulfurization with calcium sulfite and it's mechanism].

    PubMed

    Tong, Z; Chen, Z; Peng, Z

    2001-09-01

    Directing to the scaling problem lying in wet desulfurization with lime slurry, a method of desulfurization with calcium sulfite was proposed. Reaction mechanism and the effects of different conditions on desulfurization efficiency were studied. The optimum conditions were obtained, i.e. air velocity of 2.75 m/s in empty tower, L/G = 3.0 L/m3, solid content 6.7%, air temperature 31 degrees C, concentration inlet of SO2 1500 x 10(-6) and inlet suspension pH of 8.0. Under the conditions, the desulfurization efficiency was about 87%. The presented method theoretically and practically solved the scaling problems, which is a novel indirect lime-method with Ca-contained material as desulfurization agent.

  14. Development of a synchrotron biaxial tensile device for in situ characterization of thin films mechanical response

    SciTech Connect

    Geandier, G.; Thiaudiere, D.; Bouaffad, A.; Randriamazaoro, R. N.; Chiron, R.; Castelnau, O.; Faurie, D.; Djaziri, S.; Lamongie, B.; Diot, Y.; Le Bourhis, E.; Renault, P. O.; Goudeau, P.; Hild, F.

    2010-10-15

    We have developed on the DIFFABS-SOLEIL beamline a biaxial tensile machine working in the synchrotron environment for in situ diffraction characterization of thin polycrystalline films mechanical response. The machine has been designed to test compliant substrates coated by the studied films under controlled, applied strain field. Technological challenges comprise the sample design including fixation of the substrate ends, the related generation of a uniform strain field in the studied (central) volume, and the operations from the beamline pilot. Preliminary tests on 150 nm thick W films deposited onto polyimide cruciform substrates are presented. The obtained results for applied strains using x-ray diffraction and digital image correlation methods clearly show the full potentialities of this new setup.

  15. Impulse response method for characterization of echogenic liposomesa)

    PubMed Central

    Raymond, Jason L.; Luan, Ying; van Rooij, Tom; Kooiman, Klazina; Huang, Shao-Ling; McPherson, David D.; Versluis, Michel; de Jong, Nico; Holland, Christy K.

    2015-01-01

    An optical characterization method is presented based on the use of the impulse response to characterize the damping imparted by the shell of an air-filled ultrasound contrast agent (UCA). The interfacial shell viscosity was estimated based on the unforced decaying response of individual echogenic liposomes (ELIP) exposed to a broadband acoustic impulse excitation. Radius versus time response was measured optically based on recordings acquired using an ultra-high-speed camera. The method provided an efficient approach that enabled statistical measurements on 106 individual ELIP. A decrease in shell viscosity, from 2.1 × 10−8 to 2.5 × 10−9 kg/s, was observed with increasing dilatation rate, from 0.5 × 106 to 1 × 107 s−1. This nonlinear behavior has been reported in other studies of lipid-shelled UCAs and is consistent with rheological shear-thinning. The measured shell viscosity for the ELIP formulation used in this study [κs = (2.1 ± 1.0) × 10−8 kg/s] was in quantitative agreement with previously reported values on a population of ELIP and is consistent with other lipid-shelled UCAs. The acoustic response of ELIP therefore is similar to other lipid-shelled UCAs despite loading with air instead of perfluorocarbon gas. The methods described here can provide an accurate estimate of the shell viscosity and damping for individual UCA microbubbles. PMID:25920822

  16. Mechanical Characterization of Nanoporous Thin Films by Nanoindentation and Laser-induced Surface Acoustic Waves

    NASA Astrophysics Data System (ADS)

    Chow, Gabriel

    wavelengths are micrometers in scale whereas indentation depths are usually confined to the nanometer scale. This dissertation demonstrates the effectiveness of LiSAW on both thin porous layers and rough surfaces and shows the challenges faced by nanoindentation on the same films. Zeolite thin films are studied extensively in this work as a model system because of their porous crystalline framework and enormous economic market. Many types of zeolite exist and their widely varying structures and levels of porosity present a unique opportunity for mechanical characterization. For a fully dense ZSM-5 type zeolite with wear and corrosion resistance properties, nanoindentation was used to compare its mechanical properties to industrial chromium and cadmium films. Through tribological and indentation tests, it was shown that the zeolite film possesses exceptional resilience and hardness therefore demonstrating superior wear resistance to chromium and cadmium. This also highlighted the quality of nanoindentation measurements on thick dense layers where traditional nanoindentation excels. Nanoindentation was then performed on porous and non-porous MFI zeolite films with low-k (low dielectric constant) properties. These films were softer and much thinner than the ZSM-5 coatings resulting in significant substrate effects, evidenced by inflation of the measurements from the hard silicon substrate, during indentation. Such effects were avoided with the LiSAW technique on the same films where properties were readily extracted without complications. An alternative indentation analysis method was demonstrated to produce accurate mechanical measurements in line with the LiSAW results, but the non-traditional technique requires substantial computational intensity. Thus LiSAW was proven to be an accurate and efficient means of mechanical characterization for thin porous layers. The case for LiSAW was further supported by utilizing the technique on a porous nanostructured V2O5 electrode film

  17. Electrical, Mechanical, and Morphological Characterization of Carbon Nanotube filled Polymeric Nanofibers

    NASA Astrophysics Data System (ADS)

    Gorga, Russell; Clarke, Laura; McCullen, Seth; Ojha, Satyajeet; Roberts, Wesley

    2006-03-01

    This work focuses on the inclusion of conductive nanotubes into polymeric matrices with the end goal of creating conductive nanocomposites. This investigation has been carried out by uniform dispersion of multi-walled carbon nanotubes in aqueous solutions of polyvinyl alcohol (PVA) and polyethylene oxide (PEO), which are inherently nonconductive polymers. To fabricate these structures we are using the electrospinning process encompassing an array of collection methods including parallel bars and a static plate. Carbon nanotubes are known to have excellent electrical conductivity and mechanical properties. This investigation shows that the inclusion of carbon nanotubes increases the electronic conduction in these polymers and enhances the mechanical properties of the composites. Dispersion of these nanotubes is the key factor in this process; gum Arabic and surfactants have been utilized for the dispersion of these nanotubes. Conductivity measurements have been carried out by two point probe method and by performing sensitive current and conductance measurements with a femtoammeter. Further morphological characterization has been performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).^1 Department of Textile Engineering, Chemistry, and Science ^2 Department of Physics

  18. Characterization of Novel Molecular Mechanisms Favoring Rac1 Membrane Translocation.

    PubMed

    Castro-Castro, Antonio; Muriel, Olivia; Del Pozo, Miguel A; Bustelo, Xosé R

    2016-01-01

    The Rac1 GTPase plays key roles in cytoskeletal organization, cell motility and a variety of physiological and disease-linked responses. Wild type Rac1 signaling entails dissociation of the GTPase from cytosolic Rac1-Rho GDP dissociation inhibitor (GDI) complexes, translocation to membranes, activation by exchange factors, effector binding, and activation of downstream signaling cascades. Out of those steps, membrane translocation is the less understood. Using transfections of a expression cDNA library in cells expressing a Rac1 bioreporter, we previously identified a cytoskeletal feedback loop nucleated by the F-actin binding protein coronin 1A (Coro1A) that promotes Rac1 translocation to the plasma membrane by facilitating the Pak-dependent dissociation of Rac1-Rho GDI complexes. This screening identified other potential regulators of this process, including WDR26, basigin, and TMEM8A. Here, we show that WDR26 promotes Rac1 translocation following a Coro1A-like and Coro1A-dependent mechanism. By contrast, basigin and TMEM8A stabilize Rac1 at the plasma membrane by inhibiting the internalization of caveolin-rich membrane subdomains. This latter pathway is F-actin-dependent but Coro1A-, Pak- and Rho GDI-independent.

  19. Microstructural and mechanical characterization of laser deposited advanced materials

    NASA Astrophysics Data System (ADS)

    Sistla, Harihar Rakshit

    Additive manufacturing in the form of laser deposition is a unique way to manufacture near net shape metallic components from advanced materials. Rapid solidification facilitates the extension of solid solubility, compositional flexibility and decrease in micro-segregation in the melt among other advantages. The current work investigates the employment of laser deposition to fabricate the following: 1. Functionally gradient materials: This allows grading dissimilar materials compositionally to tailor specific properties of both these materials into a single component. Specific compositions of the candidate materials (SS 316, Inconel 625 and Ti64) were blended and deposited to study the brittle intermetallics reported in these systems. 2. High entropy alloys: These are multi- component alloys with equiatomic compositions of 5 or more elements. The ratio of Al to Ni was decreased to observe the transition of solid solution from a BCC to an FCC crystal structure in the AlFeCoCrNi system. 3. Structurally amorphous alloys: Zr-based metallic glasses have been reported to have high glass forming ability. These alloys have been laser deposited so as to rapidly cool them from the melt into an amorphous state. Microstructural analysis and X-ray diffraction were used to study the phase formation, and hardness was measured to estimate the mechanical properties.

  20. Mechanical characterization of artificial muscles with computer vision

    NASA Astrophysics Data System (ADS)

    Verdu, R.; Morales-Sanchez, Juan; Fernandez-Romero, Antonio J.; Cortes, M. T.; Otero, Toribio F.; Weruaga-Prieto, Luis

    2002-07-01

    Conducting polymers are new materials that were developed in the late 1970s as intrinsically electronic conductors at the molecular level. The presence of polymer, solvent, and ionic components reminds one of the composition of the materials chosen by nature to produce muscles, neurons, and skin in living creatures. The ability to transform electrical energy into mechanical energy through an electrochemical reaction, promoting film swelling and shrinking during oxidation or reduction, respectively, produces a macroscopic change in its volume. On specially designed bi-layer polymeric stripes this conformational change gives rise to stripe curl and bending, where the position or angle of the free end of the polymeric stripe is directly related to the degree of oxidation, or charged consumed. Study of these curvature variations has been currently performed only in a manual basis. In this paper we propose a preliminary study of the polymeric muscle electromechanical properties by using a computer vision system. The vision system required is simple: it is composed of cameras for tracking the muscle from different angles and special algorithms, based on active contours, to analyse the deformable motion. Graphical results support the validity of this approach, which opens the way for performing automatic testing on artificial muscles with commercial purposes.

  1. Characterization of Novel Molecular Mechanisms Favoring Rac1 Membrane Translocation

    PubMed Central

    Castro-Castro, Antonio; Muriel, Olivia; del Pozo, Miguel A.

    2016-01-01

    The Rac1 GTPase plays key roles in cytoskeletal organization, cell motility and a variety of physiological and disease-linked responses. Wild type Rac1 signaling entails dissociation of the GTPase from cytosolic Rac1-Rho GDP dissociation inhibitor (GDI) complexes, translocation to membranes, activation by exchange factors, effector binding, and activation of downstream signaling cascades. Out of those steps, membrane translocation is the less understood. Using transfections of a expression cDNA library in cells expressing a Rac1 bioreporter, we previously identified a cytoskeletal feedback loop nucleated by the F-actin binding protein coronin 1A (Coro1A) that promotes Rac1 translocation to the plasma membrane by facilitating the Pak-dependent dissociation of Rac1-Rho GDI complexes. This screening identified other potential regulators of this process, including WDR26, basigin, and TMEM8A. Here, we show that WDR26 promotes Rac1 translocation following a Coro1A-like and Coro1A-dependent mechanism. By contrast, basigin and TMEM8A stabilize Rac1 at the plasma membrane by inhibiting the internalization of caveolin-rich membrane subdomains. This latter pathway is F-actin-dependent but Coro1A-, Pak- and Rho GDI-independent. PMID:27835684

  2. Structural and Mechanical Characterization of Thermally Treated Conch Shells

    NASA Astrophysics Data System (ADS)

    Li, Haoze; Jin, Dalai; Li, Rui; Li, Xiaodong

    2015-04-01

    Seashells are natural nanocomposite armors with an exceptional combination of strength and toughness. Conch shells have a crossed-lamellar structure constructed with aragonite and biopolymer. Thermal treatment uncovered a nanoscale hierarchical structure in shell's third-order lamellae. Individual third-order lamellae were found to consist of aragonite nanoparticles cemented with biopolymer. The biopolymer renders conch shells joint increase in strength, ductility and fracture energy, and especially the fracture energy increase is more remarkable. The shell's aragonite transformed to calcite at 407°C and lime at 607°C. The shell's biopolymer was burned out in the thermal treatment at 310°C, leading to 1.7% mass loss. The crossed-lamellar structure remained in the 500°C thermally treated shell. The 900°C heat treatment destroyed the crossed-lamellar architecture completely. Thermal treatment resulted in reduction in mechanical properties due to the joint effects—burning out of biopolymer, phase transformation, and destruction of structural integrity. The findings advance our understanding of conch shell's architecture and provide new guidelines for the design and manufacturing of bio-inspired materials.

  3. MECHANICAL PROPERTY CHARACTERIZATIONS AND PERFORMANCE MODELING OF SOFC SEALS

    SciTech Connect

    Koeppel, Brian J.; Vetrano, John S.; Nguyen, Ba Nghiep; Sun, Xin; Khaleel, Mohammad A.

    2008-03-26

    This study provides modeling tools for the design of reliable seals for SOFC stacks. The work consists of 1) experimental testing to determine fundamental properties of SOFC sealing materials, and 2) numerical modeling of stacks and sealing systems. The material tests capture relevant temperature-dependent physical and mechanical data needed by the analytical models such as thermal expansion, strength, fracture toughness, and relaxation behavior for glass-ceramic seals and other materials. Testing has been performed on both homogenous specimens and multiple material assemblies to investigate the effect of interfacial reactions. A viscoelastic continuum damage model for a glass-ceramic seal was developed to capture the nonlinear behavior of this material at high temperatures. This model was implemented in the MSC MARC finite element code and was used for a detailed analysis of a planar SOFC stack under thermal cycling conditions. Realistic thermal loads for the stack were obtained using PNNL’s in-house multiphysics solver. The accumulated seal damage and component stresses were evaluated for multiple thermal loading cycles, and regions of high seal damage susceptible to cracking were identified. Selected test results, numerical model development, and analysis results will be presented.

  4. Spectroscopic Methods of Remote Sensing for Vegetation Characterization

    NASA Astrophysics Data System (ADS)

    Kokaly, R. F.

    2013-12-01

    Imaging spectroscopy (IS), often referred to as hyperspectral remote sensing, is one of the latest innovations in a very long history of spectroscopy. Spectroscopic methods have been used for understanding the composition of the world around us, as well as, the solar system and distant parts of the universe. Continuous sampling of the electromagnetic spectrum in narrow bands is what separates IS from previous forms of remote sensing. Terrestrial imaging spectrometers often have hundreds of channels that cover the wavelength range of reflected solar radiation, including the visible, near-infrared (NIR), and shortwave infrared (SWIR) regions. In part due to the large number of channels, a wide variety of methods have been applied to extract information from IS data sets. These can be grouped into several broad classes, including: multi-channel indices, statistical procedures, full spectrum mixing models, and spectroscopic methods. Spectroscopic methods carry on the more than 150 year history of laboratory-based spectroscopy applied to material identification and characterization. Spectroscopic methods of IS relate the positions and shapes of spectral features resolved by airborne and spaceborne sensors to the biochemical and physical composition of vegetation in a pixel. The chlorophyll 680nm, water 980nm, water 1200nm, SWIR 1700nm, SWIR 2100nm, and SWIR 2300nm features have been the subject of study. Spectral feature analysis (SFA) involves isolating such an absorption feature using continuum removal (CR) and calculating descriptors of the feature, such as center position, depth, width, area, and asymmetry. SFA has been applied to quantify pigment and non-pigment biochemical concentrations in leaves, plants, and canopies. Spectral feature comparison (SFC) utilizes CR of features in each pixel's spectrum and linear regression with continuum-removed features in reference spectra in a library of known vegetation types to map vegetation species and communities. SFC has

  5. Engineering Change Management Method Framework in Mechanical Engineering

    NASA Astrophysics Data System (ADS)

    Stekolschik, Alexander

    2016-11-01

    Engineering changes make an impact on different process chains in and outside the company, and lead to most error costs and time shifts. In fact, 30 to 50 per cent of development costs result from technical changes. Controlling engineering change processes can help us to avoid errors and risks, and contribute to cost optimization and a shorter time to market. This paper presents a method framework for controlling engineering changes at mechanical engineering companies. The developed classification of engineering changes and accordingly process requirements build the basis for the method framework. The developed method framework comprises two main areas: special data objects managed in different engineering IT tools and process framework. Objects from both areas are building blocks that can be selected to the overall business process based on the engineering process type and change classification. The process framework contains steps for the creation of change objects (both for overall change and for parts), change implementation, and release. Companies can select singleprocess building blocks from the framework, depending on the product development process and change impact. The developed change framework has been implemented at a division (10,000 employees) of a big German mechanical engineering company.

  6. Mechanical characterization of composite repairs for fiberglass wind turbine blades

    NASA Astrophysics Data System (ADS)

    Chawla, Tanveer Singh

    While in service, wind turbine blades experience various modes of loading. An example is impact loading in the form of hail or bird strikes, which might lead to localized damage or formation of cracks a few plies deep on the blade surface. One of the methods to conduct repairs on wind turbine blades that are damaged while in service is hand lay-up of the repair part after grinding out the damaged portion and some of its surrounding area. The resin used for such repairs usually differs from the parent plate resin in composition and properties such as gel time, viscosity, etc. As a result the properties of the repaired parts are not the same as that of the undamaged blades. Subsequent repetitive loading can be detrimental to weak repairs to such an extent so as to cause delamination at the parent-repair bondline causing the repairs to eventually fall off the blade. Thus the strength and toughness of the repair are of critical importance. Initial part of this work consists of an effort to increase repair strength by identifying an optimum hand layup repair resin for fiberglass wind turbine blades currently being manufactured by a global company. As delamination of the repair from the parent blade is a major concern and unidirectional glass fibers along with a polymer resin are used to manufacture blades under consideration, testing method detailed in ASTM D 5528 (Test Method for Mode I Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites) was followed to determine propagation fracture toughness values of the prospective vinyl ester repair resin candidates. These values were compared to those for a base polyester repair resin used by the company. Experimental procedure and results obtained from the above mentioned testing using double cantilever beam (DCB) specimens are detailed. Three new repair resins were shortlisted through mode I testing. It was also found that variation in the depth of the ground top ply of the parent part

  7. Methods to Characterize the Oligonucleotide Functionalization of Quantum Dots.

    PubMed

    Weichelt, Richard; Leubner, Susanne; Henning-Knechtel, Anja; Mertig, Michael; Gaponik, Nikolai; Schmidt, Thorsten-Lars; Eychmüller, Alexander

    2016-09-01

    Currently, DNA nanotechnology offers the most programmable, scalable, and accurate route for the self-assembly of matter with nanometer precision into 1, 2, or 3D structures. One example is DNA origami that is well suited to serve as a molecularly defined "breadboard", and thus, to organize various nanomaterials such as nanoparticles into hybrid systems. Since the controlled assembly of quantum dots (QDs) is of high interest in the field of photonics and other optoelectronic applications, a more detailed view on the functionalization of QDs with oligonucleotides shall be achieved. In this work, four different methods are presented to characterize the functionalization of thiol-capped cadmium telluride QDs with oligonucleotides and for the precise quantification of the number of oligonucleotides bound to the QD surface. This study enables applications requiring the self-assembly of semiconductor-oligonucleotide hybrid materials and proves the conjugation success in a simple and straightforward manner.

  8. Application of high level wavefunction methods in quantum mechanics/molecular mechanics hybrid schemes.

    PubMed

    Mata, Ricardo A

    2010-05-21

    In this Perspective, several developments in the field of quantum mechanics/molecular mechanics (QM/MM) approaches are reviewed. Emphasis is placed on the use of correlated wavefunction theory and new state of the art methods for the treatment of large quantum systems. Until recently, computational chemistry approaches to large/complex chemical problems have seldom been considered as tools for quantitative predictions. However, due to the tremendous development of computational resources and new quantum chemical methods, it is nowadays possible to describe the electronic structure of biomolecules at levels of theory which a decade ago were only possible for system sizes of up to 20 atoms. These advances are here outlined in the context of QM/MM. The article concludes with a short outlook on upcoming developments and possible bottlenecks for future applications.

  9. Efficient hybrid-symbolic methods for quantum mechanical calculations

    NASA Astrophysics Data System (ADS)

    Scott, T. C.; Zhang, Wenxing

    2015-06-01

    We present hybrid symbolic-numerical tools to generate optimized numerical code for rapid prototyping and fast numerical computation starting from a computer algebra system (CAS) and tailored to any given quantum mechanical problem. Although a major focus concerns the quantum chemistry methods of H. Nakatsuji which has yielded successful and very accurate eigensolutions for small atoms and molecules, the tools are general and may be applied to any basis set calculation with a variational principle applied to its linear and non-linear parameters.

  10. On the Use of Accelerated Test Methods for Characterization of Advanced Composite Materials

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.

    2003-01-01

    A rational approach to the problem of accelerated testing for material characterization of advanced polymer matrix composites is discussed. The experimental and analytical methods provided should be viewed as a set of tools useful in the screening of material systems for long-term engineering properties in aerospace applications. Consideration is given to long-term exposure in extreme environments that include elevated temperature, reduced temperature, moisture, oxygen, and mechanical load. Analytical formulations useful for predictive models that are based on the principles of time-based superposition are presented. The need for reproducible mechanisms, indicator properties, and real-time data are outlined as well as the methodologies for determining specific aging mechanisms.

  11. Mechanical characterization of densely welded Apache Leap tuff

    SciTech Connect

    Fuenkajorn, K.; Daemen, J.J.K.

    1991-06-01

    An empirical criterion is formulated to describe the compressive strength of the densely welded Apache Leap tuff. The criterion incorporates the effects of size, L/D ratio, loading rate and density variations. The criterion improves the correlation between the test results and the failure envelope. Uniaxial and triaxial compressive strengths, Brazilian tensile strength and elastic properties of the densely welded brown unit of the Apache Leap tuff have been determined using the ASTM standard test methods. All tuff samples are tested dry at room temperature (22 {plus_minus} 2{degrees}C), and have the core axis normal to the flow layers. The uniaxial compressive strength is 73.2 {plus_minus} 16.5 MPa. The Brazilian tensile strength is 5.12 {plus_minus} 1.2 MPa. The Young`s modulus and Poisson`s ratio are 22.6 {plus_minus} 5.7 GPa and 0.20 {plus_minus} 0.03. Smoothness and perpendicularity do not fully meet the ASTM requirements for all samples, due to the presence of voids and inclusions on the sample surfaces and the sample preparation methods. The investigations of loading rate, L/D radio and cyclic loading effects on the compressive strength and of the size effect on the tensile strength are not conclusive. The Coulomb strength criterion adequately represents the failure envelope of the tuff under confining pressures from 0 to 62 MPa. Cohesion and internal friction angle are 16 MPa and 43 degrees. The brown unit of the Apache Leap tuff is highly heterogeneous as suggested by large variations of the test results. The high intrinsic variability of the tuff is probably caused by the presence of flow layers and by nonuniform distributions of inclusions, voids and degree of welding. Similar variability of the properties has been found in publications on the Topopah Spring tuff at Yucca Mountain. 57 refs., 32 figs., 29 tabs.

  12. An electromagnetic induction method for underground target detection and characterization

    SciTech Connect

    Bartel, L.C.; Cress, D.H.

    1997-01-01

    An improved capability for subsurface structure detection is needed to support military and nonproliferation requirements for inspection and for surveillance of activities of threatening nations. As part of the DOE/NN-20 program to apply geophysical methods to detect and characterize underground facilities, Sandia National Laboratories (SNL) initiated an electromagnetic induction (EMI) project to evaluate low frequency electromagnetic (EM) techniques for subsurface structure detection. Low frequency, in this case, extended from kilohertz to hundreds of kilohertz. An EMI survey procedure had already been developed for borehole imaging of coal seams and had successfully been applied in a surface mode to detect a drug smuggling tunnel. The SNL project has focused on building upon the success of that procedure and applying it to surface and low altitude airborne platforms. Part of SNL`s work has focused on improving that technology through improved hardware and data processing. The improved hardware development has been performed utilizing Laboratory Directed Research and Development (LDRD) funding. In addition, SNL`s effort focused on: (1) improvements in modeling of the basic geophysics of the illuminating electromagnetic field and its coupling to the underground target (partially funded using LDRD funds) and (2) development of techniques for phase-based and multi-frequency processing and spatial processing to support subsurface target detection and characterization. The products of this project are: (1) an evaluation of an improved EM gradiometer, (2) an improved gradiometer concept for possible future development, (3) an improved modeling capability, (4) demonstration of an EM wave migration method for target recognition, and a demonstration that the technology is capable of detecting targets to depths exceeding 25 meters.

  13. Dynamic characterization of satellite components through non-invasive methods

    SciTech Connect

    Mullens, Joshua G; Wiest, Heather K; Mascarenas, David D; Park, Gyuhae

    2011-01-24

    The rapid deployment of satellites is hindered by the need to flight-qualify their components and the resulting mechanical assembly. Conventional methods for qualification testing of satellite components are costly and time consuming. Furthermore, full-scale vehicles must be subjected to launch loads during testing. The harsh testing environment increases the risk of component damage during qualification. The focus of this research effort was to assess the performance of Structural Health Monitoring (SHM) techniques as replacement for traditional vibration testing. SHM techniques were applied on a small-scale structure representative of a responsive satellite. The test structure consisted of an extruded aluminum space-frame covered with aluminum shear plates, which was assembled using bolted joints. Multiple piezoelectric patches were bonded to the test structure and acted as combined actuators and sensors. Various methods of SHM were explored including impedance-based health monitoring, wave propagation, and conventional frequency response functions. Using these methods in conjunction with finite element modeling, the dynamic properties of the test structure were established and areas of potential damage were identified and localized. The adequacy of the results from each SHM method was validated by comparison to results from conventional vibration testing.

  14. Dynamic characterization of satellite components through non-invasive methods

    SciTech Connect

    Mullins, Joshua G; Wiest, Heather K; Mascarenas, David D. L.; Macknelly, David

    2010-10-21

    The rapid deployment of satellites is hindered by the need to flight-qualify their components and the resulting mechanical assembly. Conventional methods for qualification testing of satellite components are costly and time consuming. Furthermore, full-scale vehicles must be subjected to launch loads during testing. This harsh testing environment increases the risk of component damage during qualification. The focus of this research effort was to assess the performance of Structural Health Monitoring (SHM) techniques as a replacement for traditional vibration testing. SHM techniques were applied on a small-scale structure representative of a responsive satellite. The test structure consisted of an extruded aluminum space-frame covered with aluminum shear plates, which was assembled using bolted joints. Multiple piezoelectric patches were bonded to the test structure and acted as combined actuators and sensors. Various methods of SHM were explored including impedance-based health monitoring, wave propagation, and conventional frequency response functions. Using these methods in conjunction with finite element modelling, the dynamic properties of the test structure were established and areas of potential damage were identified and localized. The adequacy of the results from each SHM method was validated by comparison to results from conventional vibration testing.

  15. The instanton method and its numerical implementation in fluid mechanics

    NASA Astrophysics Data System (ADS)

    Grafke, Tobias; Grauer, Rainer; Schäfer, Tobias

    2015-08-01

    A precise characterization of structures occurring in turbulent fluid flows at high Reynolds numbers is one of the last open problems of classical physics. In this review we discuss recent developments related to the application of instanton methods to turbulence. Instantons are saddle point configurations of the underlying path integrals. They are equivalent to minimizers of the related Freidlin-Wentzell action and known to be able to characterize rare events in such systems. While there is an impressive body of work concerning their analytical description, this review focuses on the question on how to compute these minimizers numerically. In a short introduction we present the relevant mathematical and physical background before we discuss the stochastic Burgers equation in detail. We present algorithms to compute instantons numerically by an efficient solution of the corresponding Euler-Lagrange equations. A second focus is the discussion of a recently developed numerical filtering technique that allows to extract instantons from direct numerical simulations. In the following we present modifications of the algorithms to make them efficient when applied to two- or three-dimensional (2D or 3D) fluid dynamical problems. We illustrate these ideas using the 2D Burgers equation and the 3D Navier-Stokes equations.

  16. Insights into Protein–Ligand Interactions: Mechanisms, Models, and Methods

    PubMed Central

    Du, Xing; Li, Yi; Xia, Yuan-Ling; Ai, Shi-Meng; Liang, Jing; Sang, Peng; Ji, Xing-Lai; Liu, Shu-Qun

    2016-01-01

    Molecular recognition, which is the process of biological macromolecules interacting with each other or various small molecules with a high specificity and affinity to form a specific complex, constitutes the basis of all processes in living organisms. Proteins, an important class of biological macromolecules, realize their functions through binding to themselves or other molecules. A detailed understanding of the protein–ligand interactions is therefore central to understanding biology at the molecular level. Moreover, knowledge of the mechanisms responsible for the protein-ligand recognition and binding will also facilitate the discovery, design, and development of drugs. In the present review, first, the physicochemical mechanisms underlying protein–ligand binding, including the binding kinetics, thermodynamic concepts and relationships, and binding driving forces, are introduced and rationalized. Next, three currently existing protein-ligand binding models—the “lock-and-key”, “induced fit”, and “conformational selection”—are described and their underlying thermodynamic mechanisms are discussed. Finally, the methods available for investigating protein–ligand binding affinity, including experimental and theoretical/computational approaches, are introduced, and their advantages, disadvantages, and challenges are discussed. PMID:26821017

  17. Studies on sulfate attack: Mechanisms, test methods, and modeling

    NASA Astrophysics Data System (ADS)

    Santhanam, Manu

    The objective of this research study was to investigate various issues pertaining to the mechanism, testing methods, and modeling of sulfate attack in concrete. The study was divided into the following segments: (1) effect of gypsum formation on the expansion of mortars, (2) attack by the magnesium ion, (3) sulfate attack in the presence of chloride ions---differentiating seawater and groundwater attack, (4) use of admixtures to mitigate sulfate attack---entrained air, sodium citrate, silica fume, and metakaolin, (5) effects of temperature and concentration of the attack solution, (6) development of new test methods using concrete specimens, and (7) modeling of the sulfate attack phenomenon. Mortar specimens using portland cement (PC) and tricalcium silicate (C 3S), with or without mineral admixtures, were prepared and immersed in different sulfate solutions. In addition to this, portland cement concrete specimens were also prepared and subjected to complete and partial immersion in sulfate solutions. Physical measurements, chemical analyses and microstructural studies were performed periodically on the specimens. Gypsum formation was seen to cause expansion of the C3S mortar specimens. Statistical analyses of the data also indicated that the quantity of gypsum was the most significant factor controlling the expansion of mortar bars. The attack by magnesium ion was found to drive the reaction towards the formation of brucite. Decalcification of the C-S-H and its subsequent conversion to the non-cementitious M-S-H was identified as the mechanism of destruction in magnesium sulfate attack. Mineral admixtures were beneficial in combating sodium sulfate attack, while reducing the resistance to magnesium sulfate attack. Air entrainment did not change the measured physical properties, but reduced the visible distress of the mortars. Sodium citrate caused a substantial reduction in the rate of damage of the mortars due to its retarding effect. Temperature and

  18. Design of a mechanical test to characterize sheet metals - Optimization using B-splines or cubic splines

    NASA Astrophysics Data System (ADS)

    Souto, Nelson; Thuillier, Sandrine; Andrade-Campos, A.

    2016-10-01

    Nowadays, full-field measurement methods are largely used to acquire the strain field developed by heterogeneous mechanical tests. Recent material parameters identification strategies based on a single heterogeneous test have been proposed considering that an inhomogeneous strain field can lead to a more complete mechanical characterization of the sheet metals. The purpose of this work is the design of a heterogeneous test promoting an enhanced mechanical behavior characterization of thin metallic sheets, under several strain paths and strain amplitudes. To achieve this goal, a design optimization strategy finding the appropriate specimen shape of the heterogeneous test by using either B-Splines or cubic splines was developed. The influence of using approximation or interpolation curves, respectively, was investigated in order to determine the most effective approach for achieving a better shape design. The optimization process is guided by an indicator criterion which evaluates, quantitatively, the strain field information provided by the mechanical test. Moreover, the design of the heterogeneous test is based on the resemblance with the experimental reality, since a rigid tool leading to uniaxial loading path is used for applying the displacement in a similar way as universal standard testing machines. The results obtained reveal that the optimization strategy using B-Splines curve approximation led to a heterogeneous test providing larger strain field information for characterizing the mechanical behavior of sheet metals.

  19. A method of damage mechanics analysis for solder material

    SciTech Connect

    Fang, H.E.; Chow, C.L.; Yang, Fan

    1997-06-01

    This paper presents as a method of damage mechanics analysis for solder joint material stressed to extensive plastic deformation. The material chosen for the current work is the 60Sn-40Pb eutectic alloy due to its wide use. The analysis is based on the thermodynamic theory of irreversible processes. With the introduction of a set of internal state variables, known as damage variables, and a damage effect tensor, a damage dissipative potential function is proposed to enable the formulation of the constitutive equations of elasticity and plasticity coupled with damage. The equations of damage evolution are also derived to monitor damage initiation and growth. Before a damage analysis can be performed with a finite element analysis, the mechanical properties of the chosen solder joint material and its damage variables must first be determined. A method of experimental analysis was developed and used to successfully measure the highly strain sensitive 60Sn-40Pb solder material. The measured properties are presented and various characteristics of the solder material are examined and discussed. 7 refs., 8 figs.

  20. A remotely operated FIMEC apparatus for the mechanical characterization of neutron irradiated materials

    NASA Astrophysics Data System (ADS)

    Donato, A.; Gondi, P.; Montanari, R.; Moreschi, L.; Sili, A.; Storai, S.

    1998-10-01

    From Flat-top Cylinder Indenter for Mechanical Characterization (FIMEC) test yield stress and tensile strength can be obtained. Results regarding different materials, most of them of fusion interest, show the general validity of the method. Moreover, indication on the ductile to brittle transition temperature (DBTT) of martensitic steels has been drawn by performing tests at different temperatures. FIMEC offers the possibility to perform several tests on a small volume of material, e.g. it has been estimated that 18 indentations can be made on a single disk ( Φ=25 mm, h=5 mm). For this reason, its application is of interest to characterize materials irradiated in the future IFMIF or in other sources with a limited irradiation volume. A remotely operated apparatus has been designed and costructed to work in hot cell on irradiated samples. It employs a WC punch ( Φ=1 mm) and can operate at temperatures in the range between -180°C and +200°C. Details of the apparatus are presented.

  1. Synthesis, structural characterization and formation mechanism of ferroelectric bismuth vanadate nanotubes.

    PubMed

    Singh, Satyendra; Kumari, Neelam; Varma, K B R; Krupanidhi, S B

    2009-11-01

    We report the synthesis and structural characterization of ferroelectric bismuth vanadate (Bi2VO5.5) (BVO) nanotubes within the nanoporous anodic aluminum oxide (AAO) templates via sol-gel method. The as-prepared BVO nanotubes were characterized by X-ray powder diffraction (XRD), Scanning Electron Microscope (SEM), High-Resolution Transmission Electron Microscope (HRTEM) and the stoichiometry of the nanotubes was established by energy-dispersive X-ray spectroscopy (EDX). Postannealed (675 degrees C for 1 h), BVO nanotubes were a polycrystalline and the XRD studies confirmed the crystal structure to be orthorhombic. The uniformity in diameter and length of the nanotubes as reveled by the TEM and SEM suggested that these were influenced to a guest extent by the thickness and pore diameter of the nanoporous AAO template. EDX analysis demonstrated the formation of stoichiometric Bi2VO5.5 phase. HRTEM confirmed that the obtained BVO nanotubes were made up of nanoparticles of 5-9 nm range. The possible formation mechanism of nanotubes was elucidated.

  2. An efficient method for the calculation of quantum mechanics/molecular mechanics free energies

    NASA Astrophysics Data System (ADS)

    Woods, Christopher J.; Manby, Frederick R.; Mulholland, Adrian J.

    2008-01-01

    The combination of quantum mechanics (QM) with molecular mechanics (MM) offers a route to improved accuracy in the study of biological systems, and there is now significant research effort being spent to develop QM/MM methods that can be applied to the calculation of relative free energies. Currently, the computational expense of the QM part of the calculation means that there is no single method that achieves both efficiency and rigor; either the QM/MM free energy method is rigorous and computationally expensive, or the method introduces efficiency-led assumptions that can lead to errors in the result, or a lack of generality of application. In this paper we demonstrate a combined approach to form a single, efficient, and, in principle, exact QM/MM free energy method. We demonstrate the application of this method by using it to explore the difference in hydration of water and methane. We demonstrate that it is possible to calculate highly converged QM/MM relative free energies at the MP2/aug-cc-pVDZ/OPLS level within just two days of computation, using commodity processors, and show how the method allows consistent, high-quality sampling of complex solvent configurational change, both when perturbing hydrophilic water into hydrophobic methane, and also when moving from a MM Hamiltonian to a QM/MM Hamiltonian. The results demonstrate the validity and power of this methodology, and raise important questions regarding the compatibility of MM and QM/MM forcefields, and offer a potential route to improved compatibility.

  3. Integrated Force Method Solution to Indeterminate Structural Mechanics Problems

    NASA Technical Reports Server (NTRS)

    Patnaik, Surya N.; Hopkins, Dale A.; Halford, Gary R.

    2004-01-01

    Strength of materials problems have been classified into determinate and indeterminate problems. Determinate analysis primarily based on the equilibrium concept is well understood. Solutions of indeterminate problems required additional compatibility conditions, and its comprehension was not exclusive. A solution to indeterminate problem is generated by manipulating the equilibrium concept, either by rewriting in the displacement variables or through the cutting and closing gap technique of the redundant force method. Compatibility improvisation has made analysis cumbersome. The authors have researched and understood the compatibility theory. Solutions can be generated with equal emphasis on the equilibrium and compatibility concepts. This technique is called the Integrated Force Method (IFM). Forces are the primary unknowns of IFM. Displacements are back-calculated from forces. IFM equations are manipulated to obtain the Dual Integrated Force Method (IFMD). Displacement is the primary variable of IFMD and force is back-calculated. The subject is introduced through response variables: force, deformation, displacement; and underlying concepts: equilibrium equation, force deformation relation, deformation displacement relation, and compatibility condition. Mechanical load, temperature variation, and support settling are equally emphasized. The basic theory is discussed. A set of examples illustrate the new concepts. IFM and IFMD based finite element methods are introduced for simple problems.

  4. Frequency-domain multiscale quantum mechanics/electromagnetics simulation method

    SciTech Connect

    Meng, Lingyi; Yin, Zhenyu; Yam, ChiYung E-mail: ghc@everest.hku.hk; Koo, SiuKong; Chen, GuanHua E-mail: ghc@everest.hku.hk; Chen, Quan; Wong, Ngai

    2013-12-28

    A frequency-domain quantum mechanics and electromagnetics (QM/EM) method is developed. Compared with the time-domain QM/EM method [Meng et al., J. Chem. Theory Comput. 8, 1190–1199 (2012)], the newly developed frequency-domain QM/EM method could effectively capture the dynamic properties of electronic devices over a broader range of operating frequencies. The system is divided into QM and EM regions and solved in a self-consistent manner via updating the boundary conditions at the QM and EM interface. The calculated potential distributions and current densities at the interface are taken as the boundary conditions for the QM and EM calculations, respectively, which facilitate the information exchange between the QM and EM calculations and ensure that the potential, charge, and current distributions are continuous across the QM/EM interface. Via Fourier transformation, the dynamic admittance calculated from the time-domain and frequency-domain QM/EM methods is compared for a carbon nanotube based molecular device.

  5. Application of the perturbation method in mechanics of deformable solids

    NASA Astrophysics Data System (ADS)

    Minaeva, N. V.

    2008-02-01

    Although the solutions of the classical problems of continuum mechanics have been studied sufficiently well, the smallest deviations, for example, of the body boundary or of the material characteristics from the traditional values prevent one from obtaining exact solutions of these problems. In this case, one has to use approximate methods, the most common of which is the perturbation method. The problems studied in [1-6] belong to classical problems in which the perturbation method is used to study the behavior of deformable bodies. A wide survey of studies analyzing the perturbations of the body boundary shape caused by variations in its stress-strain state is given in [5, 6]. In numerous studies, it was noted that the problem on the convergence of approximate solutions and hence the studies of the continuous dependence of the solution of the original problem on the characteristics of perturbations ("imperfections") play an important role. In the present paper, we analyze the forms of mathematical models of deformable bodies by studying whether the solution of the original problem continuously depends on the characteristics of the perturbed shape of the body boundary on which the boundary conditions are posed in terms of stresses and on the characteristics of the material properties. We use the results of this analysis to conclude that, when using the perturbation method, one should state the boundary conditions in terms of stresses on the boundary of the real body in stressed state.

  6. Apparatus and method for characterizing ultrafast polarization varying optical pulses

    DOEpatents

    Smirl, A.; Trebino, R.P.

    1999-08-10

    Practical techniques are described for characterizing ultrafast potentially ultraweak, ultrashort optical pulses. The techniques are particularly suited to the measurement of signals from nonlinear optical materials characterization experiments, whose signals are generally too weak for full characterization using conventional techniques. 2 figs.

  7. A spatiotemporal characterization method for the dynamic cytoskeleton

    PubMed Central

    Alhussein, Ghada; Shanti, Aya; Farhat, Ilyas A. H.; Timraz, Sara B. H.; Alwahab, Noaf S. A.; Pearson, Yanthe E.; Martin, Matthew N.; Christoforou, Nicolas

    2016-01-01

    The significant gap between quantitative and qualitative understanding of cytoskeletal function is a pressing problem; microscopy and labeling techniques have improved qualitative investigations of localized cytoskeleton behavior, whereas quantitative analyses of whole cell cytoskeleton networks remain challenging. Here we present a method that accurately quantifies cytoskeleton dynamics. Our approach digitally subdivides cytoskeleton images using interrogation windows, within which box‐counting is used to infer a fractal dimension (D f) to characterize spatial arrangement, and gray value intensity (GVI) to determine actin density. A partitioning algorithm further obtains cytoskeleton characteristics from the perinuclear, cytosolic, and periphery cellular regions. We validated our measurement approach on Cytochalasin‐treated cells using transgenically modified dermal fibroblast cells expressing fluorescent actin cytoskeletons. This method differentiates between normal and chemically disrupted actin networks, and quantifies rates of cytoskeletal degradation. Furthermore, GVI distributions were found to be inversely proportional to D f, having several biophysical implications for cytoskeleton formation/degradation. We additionally demonstrated detection sensitivity of differences in D f and GVI for cells seeded on substrates with varying degrees of stiffness, and coated with different attachment proteins. This general approach can be further implemented to gain insights on dynamic growth, disruption, and structure of the cytoskeleton (and other complex biological morphology) due to biological, chemical, or physical stimuli. © 2016 The Authors. Cytoskeleton Published by Wiley Periodicals, Inc. PMID:27015595

  8. Recombination in viruses: mechanisms, methods of study, and evolutionary consequences.

    PubMed

    Pérez-Losada, Marcos; Arenas, Miguel; Galán, Juan Carlos; Palero, Ferran; González-Candelas, Fernando

    2015-03-01

    Recombination is a pervasive process generating diversity in most viruses. It joins variants that arise independently within the same molecule, creating new opportunities for viruses to overcome selective pressures and to adapt to new environments and hosts. Consequently, the analysis of viral recombination attracts the interest of clinicians, epidemiologists, molecular biologists and evolutionary biologists. In this review we present an overview of three major areas related to viral recombination: (i) the molecular mechanisms that underlie recombination in model viruses, including DNA-viruses (Herpesvirus) and RNA-viruses (Human Influenza Virus and Human Immunodeficiency Virus), (ii) the analytical procedures to detect recombination in viral sequences and to determine the recombination breakpoints, along with the conceptual and methodological tools currently used and a brief overview of the impact of new sequencing technologies on the detection of recombination, and (iii) the major areas in the evolutionary analysis of viral populations on which recombination has an impact. These include the evaluation of selective pressures acting on viral populations, the application of evolutionary reconstructions in the characterization of centralized genes for vaccine design, and the evaluation of linkage disequilibrium and population structure.

  9. A rotating disk electrokinetic method for characterizing polyelectrolyte pharmaceutical gels.

    PubMed

    Qu, Beibei; Lee, Ping I

    2012-05-01

    Charge groups in polyelectrolyte gels can affect the entrapment and release of ionic drugs as well as influencing the stability of colloidal and nanoparticulate drug delivery systems. An accurate knowledge of gel charge properties is therefore important to the understanding and design of such drug delivery systems. Existing rotating disk method for quantifying the surface potential of flat surfaces is based on the classical electrokinetic model that neglects the effect of surface conductivity and is therefore only applicable to ion-impenetrable hard surfaces. This classical electrokinetic model would be inaccurate for polyelectrolyte gel systems involving ion-penetrable charged layers or "soft" surfaces. In this study, we developed a new rotating disk model for characterizing charge properties of ion penetrable soft surfaces and tested it on polyvinyl alcohol (PVA)/polyacrylic acid (PAA), gelatin, and gelatin/PAA polyelectrolyte gels. In addition to classical electrokinetic parameters, the contribution of surface conductivity known to be very significant for soft and ion-penetrable gel surfaces has been taken into account in this new rotating disk model. Based on this new approach, two rotating gel disks of different radius but with identical gel composition and preparation procedures were employed for determining the gel surface potential and density of fixed charge groups. A comparison of the resulting data with that obtained from existing rotating disk model ignoring the surface conductivity reveals a significant underestimation of the gel surface potential and the density of fixed charge groups by the ion-impenetrable hard surface approach. Our results thus confirm that the contribution of surface conductivity is significant in the electrokinetic characterization of polyelectrolyte gels that can be evaluated with our new rotating disk model.

  10. Quantum mechanical approaches to in silico enzyme characterization and drug design

    SciTech Connect

    Nilmeier, J P; Fattebert, J L; Jacobson, M P; Kalyanaraman, C

    2012-01-17

    The astonishing, exponentially increasing rates of genome sequencing has led to one of the most significant challenges for the biological and computational sciences in the 21st century: assigning the likely functions of the encoded proteins. Enzymes represent a particular challenge, and a critical one, because the universe of enzymes is likely to contain many novel functions that may be useful for synthetic biology, or as drug targets. Current approaches to protein annotation are largely based on bioinformatics. At the simplest level, this annotation involves transferring the annotations of characterized enzymes to related sequences. In practice, however, there is no simple, sequence based criterion for transferring annotations, and bioinformatics alone cannot propose new enzymatic functions. Structure-based computational methods have the potential to address these limitations, by identifying potential substrates of enzymes, as we and others have shown. One successful approach has used in silico 'docking' methods, more commonly applied in structure-based drug design, to identify possible metabolite substrates. A major limitation of this approach is that it only considers substrate binding, and does not directly assess the potential of the enzyme to catalyze a particular reaction using a particular substrate. That is, substrate binding affinity is necessary but not sufficient to assign function. A reaction profile is ultimately what is needed for a more complete quantitative description of function. To address this rather fundamental limitation, they propose to use quantum mechanical methods to explicitly compute transition state barriers that govern the rates of catalysis. Although quantum mechanical, and mixed quantum/classical (QM/MM), methods have been used extensively to investigate enzymatic reactions, the focus has been primarily on elucidating complex reaction mechanisms. Here, the key catalytic steps are known, and they use these methods quantify substrate

  11. Insights into the Thiamine Diphosphate Enzyme Activation Mechanism: Computational Model for Transketolase Using a Quantum Mechanical/Molecular Mechanical Method.

    PubMed

    Nauton, Lionel; Hélaine, Virgil; Théry, Vincent; Hecquet, Laurence

    2016-04-12

    We propose the first computational model for transketolase (TK), a thiamine diphosphate (ThDP)-dependent enzyme, using a quantum mechanical/molecular mechanical method on the basis of crystallographic TK structures from yeast and Escherichia coli, together with experimental kinetic data reported in the literature with wild-type and mutant TK. This model allowed us to define a new route for ThDP activation in the enzyme environment. We evidenced a strong interaction between ThDP and Glu418B of the TK active site, itself stabilized by Glu162A. The crucial point highlighted here is that deprotonation of ThDP C2 is not performed by ThDP N4' as reported in the literature, but by His481B, involving a HOH688A molecule bridge. Thus, ThDP N4' is converted from an amino form to an iminium form, ensuring the stabilization of the C2 carbanion or carbene. Finally, ThDP activation proceeds via an intermolecular process and not by an intramolecular one as reported in the literature. More generally, this proposed ThDP activation mechanism can be applied to some other ThDP-dependent enzymes and used to define the entire TK mechanism with donor and acceptor substrates more accurately.

  12. A Novel Method for Characterizing Spacesuit Mobility through Metabolic Cost

    NASA Technical Reports Server (NTRS)

    McFarland, Shane; Norcross, Jason

    2014-01-01

    Spacesuit mobility has historically been defined and characterized by a combination of range of motion and joint torque of the individual anatomical joints when performing isolated motions meant to drive that joint only in a given orthogonal plane. While this has been the standard approach for several decades, there are numerous shortcomings that suit designers and engineers would like to see rectified. First, the lack of a standardized method for collecting both range of motion and joint torque translates to many different test setups, procedures and methods of data analysis. Second, all of these previously used methods for data collection lack some degree of repeatability, even within the same test setup and the same conductor; in addition, attempts at higher fidelity data collection techniques require high overhead and cost with minimal improvement. Lastly, isolated motions in standard anatomical planes are not representative of real-world tasks that a crewmember would be performing during an EVA, be it microgravity or surface exploration based. To address these shortcomings, options are being explored within the Space Suit and Crew Survival Systems Branch to ascertain the feasibility of an alternative approach to defining mobility - one that is more repeatable, lower overhead, and more tied to functional EVA tasks. This paper serves to document the first attempt at such an alternative option - one that looks at the metabolic energy-cost of a spacesuit. In other words, can we objectively compare the mobility of a spacesuit by evaluating the metabolic cost of that suit to the wearer while performing a battery of functional EVA tasks?

  13. Site characterization for calibration of radiometric sensors using vicarious method

    NASA Astrophysics Data System (ADS)

    Parihar, Shailesh; Rathore, L. S.; Mohapatra, M.; Sharma, A. K.; Mitra, A. K.; Bhatla, R.; Singh, R. S.; Desai, Yogdeep; Srivastava, Shailendra S.

    2016-05-01

    Radiometric performances of earth observation satellite/sensors vary from ground pre-launch calibration campaign to post launch period extended to lifetime of the satellite due to launching vibrations. Therefore calibration is carried out worldwide through various methods throughout satellite lifetime. In India Indian Space Research Organization (ISRO) calibrates the sensor of Resourcesat-2 satellite by vicarious method. One of these vicarious calibration methods is the reflectance-based approach that is applied in this study for radiometric calibration of sensors on-board Resouresat-2 satellite. The results of ground-based measurement of atmospheric conditions and surface reflectance are made at Bap, Rajasthan Calibration/Validation (Cal/Val) site. Cal/Val observations at site were carried out with hyper-spectral Spectroradiometer covering spectral range of 350nm- 2500nm for radiometric characterization of the site. The Sunphotometer/Ozonometer for measuring the atmospheric parameters has also been used. The calibrated radiance is converted to absolute at-sensor spectral reflectance and Top-Of-Atmosphere (TOA) radiance. TOA radiance was computed using radiative transfer model `Second simulation of the satellite signal in the solar spectrum' (6S), which can accurately simulate the problems introduced by the presence of the atmosphere along the path from Sun to target (surface) to Sensor. The methodology for band averaged reflectance retrieval and spectral reflectance fitting process are described. Then the spectral reflectance and atmospheric parameters are put into 6S code to predict TOA radiance which compare with Resourcesat-2 radiance. Spectral signature and its reflectance ratio indicate the uniformity of the site. Thus the study proves that the selected site is suitable for vicarious calibration of sensor of Resourcesat-2. Further the study demonstrates the procedure for similar exercise for site selection for Cal/Val analysis of other satellite over India

  14. Characterizing depth-dependent refractive index of articular cartilage subjected to mechanical wear or enzymic degeneration

    NASA Astrophysics Data System (ADS)

    Wang, Kuyu; Wu, Jianping; Day, Robert; Kirk, Thomas Brett; Hu, Xiaozhi

    2016-09-01

    Utilizing a laser scanning confocal microscope system, the refractive indices of articular cartilage (AC) with mechanical or biochemical degenerations were characterized to investigate whether potential correlations exist between refractive index (RI) and cartilage degeneration. The cartilage samples collected from the medial femoral condyles of kangaroo knees were mechanically degenerated under different loading patterns or digested in trypsin solution with different concentrations. The sequences of RI were then measured from cartilage surface to deep region and the fluctuations of RI were quantified considering combined effects of fluctuating frequency and amplitude. The compositional and microstructural alterations of cartilage samples were assessed with histological methods. Along with the loss of proteoglycans, the average RI of cartilage increased and the local fluctuation of RI became stronger. Short-term high-speed test induced little influence to both the depth fluctuation and overall level of RI. Long-term low-speed test increased the fluctuation of RI but the average RI was barely changed. The results substantially demonstrate that RI of AC varies with both compositional and structural alterations and is potentially an indicator for the degeneration of AC.

  15. Mechanical and tribological characterization of TiB2 thin films.

    PubMed

    Silva, F J G; Casais, R C B; Martinho, R P; Baptista, A P M

    2012-12-01

    Titanium Diboride (TiB2) presents high mechanical and physical properties. Some wear studies were also carried out in order to evaluate its tribological properties. One of the most popular wear tests for thin films is the ball-cratering configuration. This work was focused on the study of the tribological properties of TiB2 thin films using micro-abrasion tests and following the BS EN 1071-6: 2007 standard. Due to high hardness usually patented by these films, diamond was selected as abrasive on micro-abrasion tests. Micro-abrasion wear tests were performed under five different durations, using the same normal load, speed rotation and ball. Films were deposited by unbalanced magnetron sputtering Physical Vapour Deposition (PVD) technique using TiB2 targets. TiB2 films were characterized using different methods as Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Electron Probe Micro-Analyser (EPMA), Ultra Micro Hardness and Scratch-test Analysis, allowing to confirm that TiB2 presents adequate mechanical and physical properties. Ratio between hardness (coating and abrasive particles), wear resistance and wear coefficient were studied, showing that TiB2 films shows excellent properties for tribological applications.

  16. Fabrication and mechanical characterization of long and different penetrating length neural microelectrode arrays

    NASA Astrophysics Data System (ADS)

    Goncalves, S. B.; Peixoto, A. C.; Silva, A. F.; Correia, J. H.

    2015-05-01

    This paper presents a detailed description of the design, fabrication and mechanical characterization of 3D microelectrode arrays (MEA) that comprise high aspect-ratio shafts and different penetrating lengths of electrodes (from 3 mm to 4 mm). The array’s design relies only on a bulk silicon substrate dicing saw technology. The encapsulation process is accomplished by a medical epoxy resin and platinum is used as the transduction layer between the probe and neural tissue. The probe’s mechanical behaviour can significantly affect the neural tissue during implantation time. Thus, we measured the MEA maximum insertion force in an agar gel phantom and a porcine cadaver brain. Successful 3D MEA were produced with shafts of 3 mm, 3.5 mm and 4 mm in length. At a speed of 180 mm min-1, the MEA show maximum penetrating forces per electrode of 2.65 mN and 12.5 mN for agar and brain tissue, respectively. A simple and reproducible fabrication method was demonstrated, capable of producing longer penetrating shafts than previously reported arrays using the same fabrication technology. Furthermore, shafts with sharp tips were achieved in the fabrication process simply by using a V-shaped blade.

  17. Fabrication and mechanical characterization of a polyvinyl alcohol sponge for tissue engineering applications.

    PubMed

    Karimi, A; Navidbakhsh, M; Faghihi, S

    2014-05-01

    Polyvinyl alcohol (PVA) sponges are widely used for clinical applications, including ophthalmic surgical treatments, wound healing and tissue engineering. There is, however, a lack of sufficient data on the mechanical properties of PVA sponges. In this study, a biomechanical method is used to characterize the elastic modulus, maximum stress and strain as well as the swelling ratio of a fabricated PVA sponge (P-sponge) and it is compared with two commercially available PVA sponges (CENEFOM and EYETEC). The results indicate that the elastic modulus of the P-sponge is 5.32% and 13.45% lower than that of the CENEFOM and EYETEC sponges, while it bears 4.11% more and 10.37% less stress compared to the CENEFOM and EYETEC sponges, respectively. The P-sponge shows a maximum strain of 32% more than the EYETEC sponge as well as a 26.78% higher swelling ratio, which is a significantly higher absorbency compared to the CENEFOM. It is believed that the results of this study would help for a better understanding of the extension, rupture and swelling mechanism of PVA sponges, which could lead to crucial improvement in the design and application of PVA-based materials in ophthalmic and plastic surgeries as well as wound healing and tissue engineering.

  18. Structure and Mechanical Characterization of DNA i-Motif Nanowires by Molecular Dynamics Simulation

    PubMed Central

    Singh, Raghvendra Pratap; Blossey, Ralf; Cleri, Fabrizio

    2013-01-01

    We studied the structure and mechanical properties of DNA i-motif nanowires by means of molecular dynamics computer simulations. We built up to 230 nm-long nanowires, based on a repeated TC5 sequence from crystallographic data, fully relaxed and equilibrated in water. The unusual C⋅C+ stacked structure, formed by four ssDNA strands arranged in an intercalated tetramer, is here fully characterized both statically and dynamically. By applying stretching, compression, and bending deformations with the steered molecular dynamics and umbrella sampling methods, we extract the apparent Young’s and bending moduli of the nanowire, as well as estimates for the tensile strength and persistence length. According to our results, the i-motif nanowire shares similarities with structural proteins, as far as its tensile stiffness, but is closer to nucleic acids and flexible proteins, as far as its bending rigidity is concerned. Furthermore, thanks to its very thin cross section, the apparent tensile toughness is close to that of a metal. Besides their yet to be clarified biological significance, i-motif nanowires may qualify as interesting candidates for nanotechnology templates, due to such outstanding mechanical properties. PMID:24359754

  19. Detailed characterization of lithium diffusion mechanisms in crystalline silicon using the kinetic Activation-Relaxation Technique

    NASA Astrophysics Data System (ADS)

    Trochet, Mickaël; Restrepo Gutierrez, Oscar Antonio; Mousseau, Normand

    Silicon displays a potential for high-capacity anode material for lithium-ion batteries as it can absorb large quantities of this metal. Yet, very little is understood about the evolution of diffusion mechanisms and migration barriers as the concentration of lithium increases. Until now, for example, simulations studies were limited by the time scale over which diffusion takes place. Here, we use the kinetic activation relaxation technique (kART), an unbiased off-lattice Monte Carlo method with on-the fly catalog building, coupled with the ReaxFF forcefield to follow diffusion of Li in c - Si over timescale of seconds and more at room temperature, obtaining detailed information about the whole set of possible diffusion mechanisms as the local environment evolves. We first present a detailed characterization of Li diffusion in the presence of 1 to 3 impurities and then show the evolution of systems with a higher concentration of solute as Li aggregate. These results provide a first detailed picture of the onset of Li aggregating into this high-capacity material, as it modifies the structure through local rearrangements and long-range elastic deformations, crucial information for the development of the next generation of high-capacity anode. ∖pard ∖pard.

  20. Nonlinear viscoelastic characterization of polymer materials using a dynamic-mechanical methodology

    NASA Technical Reports Server (NTRS)

    Strganac, Thomas W.; Payne, Debbie Flowers; Biskup, Bruce A.; Letton, Alan

    1995-01-01

    Polymer materials retrieved from LDEF exhibit nonlinear constitutive behavior; thus the authors present a method to characterize nonlinear viscoelastic behavior using measurements from dynamic (oscillatory) mechanical tests. Frequency-derived measurements are transformed into time-domain properties providing the capability to predict long term material performance without a lengthy experimentation program. Results are presented for thin-film high-performance polymer materials used in the fabrication of high-altitude scientific balloons. Predictions based upon a linear test and analysis approach are shown to deteriorate for moderate to high stress levels expected for extended applications. Tests verify that nonlinear viscoelastic response is induced by large stresses. Hence, an approach is developed in which the stress-dependent behavior is examined in a manner analogous to modeling temperature-dependent behavior with time-temperature correspondence and superposition principles. The development leads to time-stress correspondence and superposition of measurements obtained through dynamic mechanical tests. Predictions of material behavior using measurements based upon linear and nonlinear approaches are compared with experimental results obtained from traditional creep tests. Excellent agreement is shown for the nonlinear model.

  1. Mechanical properties of CFF/MC/SF composite prepared using vacuum infusion impregnation method

    NASA Astrophysics Data System (ADS)

    Xu, Lixin; Jiang, Aixiong; Yang, Zhiwei; Guan, Houbing; Jia, Hong; Min, Mengyu

    Carbon fiber felt (CFF)/microfine cement (MC)/silica fume (SF) composite was fabricated by using vacuum infusion impregnation method to infiltrate mechanically stirred mixing slurry of MC, SF, and water into CFF. MC, SF, and water were mixed, with a water-cement ratio of 0.5, SF was used to in place of MC in percentages of 0%, 5%, 10%, 15%, 20%, 25%, 30% and 35%. Drainage method was used to determine the density of CFF/MC/SF composite. The bending strength and compressive strength of CFF/MC/SF composite were characterized by universal testing machine. The microstructure of the fracture surface of CFF/MC/SF composite was studied by scanning electron microscopy. Toughening mechanism of CFF/MC/SF composite was also analyzed. The results show that the density and mechanical strength of CFF/MC/SF composites first increases and then decreases as SF content increases. Crack propagation process includes several toughening and reinforcing mechanisms, such as, fiber/matrix debonding, fiber bridging, fiber friction, crack deflection, and fiber pull-out. At 20% SF content, the compactness and mechanical strength of the CFF/MC/SF composite are optimum, with density, flexural strength, and compressive strength at 1.53 g/cm3, 51.08 MPa, and 53.56 MPa, respectively.

  2. A short course on quantum mechanics and methods of quantization

    NASA Astrophysics Data System (ADS)

    Ercolessi, Elisa

    2015-07-01

    These notes collect the lectures given by the author to the "XXIII International Workshop on Geometry and Physics" held in Granada (Spain) in September 2014. The first part of this paper aims at introducing a mathematical oriented reader to the realm of Quantum Mechanics (QM) and then to present the geometric structures that underline the mathematical formalism of QM which, contrary to what is usually done in Classical Mechanics (CM), are usually not taught in introductory courses. The mathematics related to Hilbert spaces and Differential Geometry are assumed to be known by the reader. In the second part, we concentrate on some quantization procedures, that are founded on the geometric structures of QM — as we have described them in the first part — and represent the ones that are more operatively used in modern theoretical physics. We will discuss first the so-called Coherent State Approach which, mainly complemented by "Feynman Path Integral Technique", is the method which is most widely used in quantum field theory. Finally, we will describe the "Weyl Quantization Approach" which is at the origin of modern tomographic techniques, originally used in optics and now in quantum information theory.

  3. Finite element methods of studying mechanical factors in blood flow.

    PubMed

    Davids, N

    1981-01-01

    This paper reviews some biomechanical analyses of blood flow in large arteries based on a general computer modeling using the finite element method. We study the following question: What is the role played by the interrelated factors of mechanical stress, flow irregularities, and diffusion through the endothelium on the etiology of atherosclerosis or the aggravation of vascular injury. It presents the computational features of the method and stresses the physiological significance of the results, such as the effect of geometric complexities, material nonlinearities, and non-Newtonian rheology of the blood. The specific mechanical and fluid dynamic factors analyzed are wall shear stress, flow profiles, and pressure variations. After simulating tubes of circular cross section, we apply the analysis to a number of physiological situations of significance, including blood flow in the entrance region, at bifurcations, in the annular region between an inserted catheter of varying diameter and the vessel. A model study of pulsatile flow in a 60 degree bifurcated channel of velocity profiles provided corroborative measurements of these processes with special emphasis on reversed or distributed flow conditions. The corresponding analysis was extended to the situation in which flow separates and reverses in the neighborhood of stagnation points. This required developing the nonlinear expression for the convective velocity change in the medium. A computer algorithm was developed to handle simultaneous effects of pressure and viscous forces on velocity change across the element and applied to the canine prebranch arterial segment. For mean physiological flow conditions, low shear stresses (0-10 dynes/cm2) are predicted near the wall in the diverging plane, higher values (50 dynes/cm2) along the converging sides of the wall. Backflow is predicted along the outer wall, pressure recovery prior to and into the branches, and a peak shear at the divider lip.

  4. Characterization of edible film fabricated with channel catfish (Ictalurus punctatus) gelatin extract using selected pretreatment methods.

    PubMed

    Zhang, S; Wang, Y; Herring, J L; Oh, J-H

    2007-11-01

    Farm-raised catfish are important to the economy of the southeastern states in the United States, and catfish processing produces about 55% of by-products for inexpensive sale. Therefore, the utilization of catfish by-products is of great interest to the catfish industry. The objectives of this research were to determine the optimum pretreatment method to extract catfish gelatin for edible film application, and to characterize physical, mechanical, and barrier properties of edible films fabricated with catfish skin gelatin. Catfish skins obtained from a local plant were treated with 6 selected pretreatment methods. The main extraction was performed with deionized water at 50 degrees C after pretreatment. The gelatin yield was calculated and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was performed to characterize molecular weight (MW) profile. Color, tensile strength (TS), elongation, and water barrier property were determined to characterize the fabricated catfish gelatin films. From the results of gelatin yield, color, SDS-PAGE, as well as mechanical and barrier properties of the film, the pretreatment method with 0.25 M NaOH and 0.09 M acetic acid, followed by extraction at 50 degrees C for 3 h, was determined as the optimum extraction method. The catfish gelatin exhibited higher MW fractions than commercial mammalian gelatin. The catfish gelatin extracts possessed film-forming properties determined by TS, elongation, and water vapor permeability (WVP) comparable to those of commercial mammalian gelatin. The selected formula for catfish gelatin film was determined as 1% gelatin and 20% glycerol, resulting in greatest TS and lowest WVP.

  5. Common Practice Lightning Strike Protection Characterization Technique to Quantify Damage Mechanisms on Composite Substrates

    NASA Technical Reports Server (NTRS)

    Szatkowski, George N.; Dudley, Kenneth L.; Koppen, Sandra V.; Ely, Jay J.; Nguyen, Truong X.; Ticatch, Larry A.; Mielnik, John J.; Mcneill, Patrick A.

    2013-01-01

    heating parameters which occur during lightning attachment. Following guidance defined in the universal common practice LSP test documents, protected and unprotected CFRP panels were evaluated at 20, 40 and 100KAmps. This report presents analyzed data demonstrating the scientific usefulness of the common practice approach. Descriptions of the common practice CFRP test articles, LSP test bed fixture, and monitoring techniques to capture the electrical, mechanical and thermal parameters during lightning attachment are presented here. Two methods of measuring the electrical currents were evaluated, inductive current probes and a newly developed fiberoptic sensor. Two mechanical displacement methods were also examined, optical laser measurement sensors and a digital imaging correlation camera system. Recommendations are provided to help users implement the common practice test approach and obtain LSP test characterizations comparable across data sets.

  6. Molecular methods for identification and characterization of novel papillomaviruses.

    PubMed

    Kocjan, B J; Bzhalava, D; Forslund, O; Dillner, J; Poljak, M

    2015-09-01

    Papillomaviruses (PV) are a remarkably heterogeneous family of small DNA viruses that infect a wide variety of vertebrate species and are aetiologically linked with the development of various neoplastic changes of the skin and mucosal epithelia. Based on nucleotide similarity, PVs are hierarchically classified into genera, species and types. Novel human PV (HPV) types are given a unique number only after the whole genome has been cloned and deposited with the International HPV Reference Center. As of 9 March 2015, 200 different HPV types, belonging to 49 species, had been recognized by the International HPV Reference Center. In addition, 131 animal PV types identified from 66 different animal species exist. Recent advances in molecular techniques have resulted in an explosive increase in the identification of novel HPV types and novel subgenomic HPV sequences in the last few years. Among PV genera, the γ-PV genus has been growing most rapidly in recent years with 80 completely sequenced HPV types, followed by α-PV and β-PV genera that have 65 and 51 recognized HPV types, respectively. We reviewed in detail the contemporary molecular methods most often used for identification and characterization of novel PV types, including PCR, rolling circle amplification and next-generation sequencing. Furthermore, we present a short overview of 12 and 10 novel HPV types recently identified in Sweden and Slovenia, respectively. Finally, an update on the International Human Papillomavirus Reference Center is provided.

  7. Characterization of nuclear graphite elastic properties using laser ultrasonic methods

    NASA Astrophysics Data System (ADS)

    Zeng, Fan W.; Han, Karen; Olasov, Lauren R.; Gallego, Nidia C.; Contescu, Cristian I.; Spicer, James B.

    2015-05-01

    Laser ultrasonic methods have been used to characterize the elastic behaviors of commercially-available and legacy nuclear graphites. Since ultrasonic techniques are sensitive to various aspects of graphite microstructure including preferred grain orientation, microcrack orientation and porosity, laser ultrasonics is a candidate technique for monitoring graphite degradation and structural integrity in environments expected in high-temperature, gas-cooled nuclear reactors. Aspects of materials texture can be assessed by studying ultrasonic wavespeeds as a function of propagation direction and polarization. Shear wave birefringence measurements, in particular, can be used to evaluate elastic anisotropy. In this work, laser ultrasonic measurements of graphite moduli have been made to provide insight into the relationship between the microstructures and the macroscopic stiffnesses of these materials. In particular, laser ultrasonic measurements have been made using laser line sources to produce shear waves with specific polarizations. By varying the line orientation relative to the sample, shear wave birefringence measurements have been recorded. Results from shear wave birefringence measurements show that an isostatically molded graphite, such as PCIB, behaves isotropically, while an extruded graphite, such as H-451, displays significant ultrasonic texture. Graphites have complicated microstructures that depend on the manufacturing processes used, and ultrasonic texture in these materials could originate from grain orientation and preferred microcrack alignment. Effects on material isotropy due to service related microstructural changes are possible and the ultimate aim of this work is to determine the degree to which these changes can be assessed nondestructively using laser ultrasonics measurements.

  8. Characterization of nuclear graphite elastic properties using laser ultrasonic methods

    SciTech Connect

    Zeng, Fan W; Han, Karen; Olasov, Lauren R; Gallego, Nidia C; Contescu, Cristian I; Spicer, James B

    2015-01-01

    Laser ultrasonic methods have been used to characterize the elastic behaviors of commercially-available and legacy nuclear graphites. Since ultrasonic techniques are sensitive to various aspects of graphite microstructure including preferred grain orientation, microcrack orientation and porosity, laser ultrasonics is a candidate technique for monitoring graphite degradation and structural integrity in environments expected in high-temperature, gas-cooled nuclear reactors. Aspects of materials texture can be assessed by studying ultrasonic wavespeeds as a function of propagation direction and polarization. Shear wave birefringence measurements, in particular, can be used to evaluate elastic anisotropy. In this work, laser ultrasonic measurements of graphite moduli have been made to provide insight into the relationship between the microstructures and the macroscopic stiffnesses of these materials. In particular, laser ultrasonic measurements have been made using laser line sources to produce shear waves with specific polarizations. By varying the line orientation relative to the sample, shear wave birefringence measurements have been recorded. Results from shear wave birefringence measurements show that an isostatically molded graphite, such as PCIB, behaves isotropically, while an extruded graphite, such as H-451, displays significant ultrasonic texture. Graphites have complicated microstructures that depend on the manufacturing processes used, and ultrasonic texture in these materials could originate from grain orientation and preferred microcrack alignment. Effects on material isotropy due to service related microstructural changes are possible and the ultimate aim of this work is to determine the degree to which these changes can be assessed nondestructively using laser ultrasonics measurements

  9. Mechanical and interfacial characterization of laser welded Co-Cr alloy with different joint configurations

    PubMed Central

    Kokolis, John; Chakmakchi, Makdad; Theocharopoulos, Antonios; Prombonas, Anthony

    2015-01-01

    PURPOSE The mechanical and interfacial characterization of laser welded Co-Cr alloy with two different joint designs. MATERIALS AND METHODS Dumbbell cast specimens (n=30) were divided into 3 groups (R, I, K, n=10). Group R consisted of intact specimens, group I of specimens sectioned with a straight cut, and group K of specimens with a 45° bevel made at the one welding edge. The microstructure and the elemental distributions of alloy and welding regions were examined by an SEM/EDX analysis and then specimens were loaded in tension up to fracture. The tensile strength (TS) and elongation (ε) were determined and statistically compared among groups employing 1-way ANOVA, SNK multiple comparison test (α=.05) and Weibull analysis where Weibull modulus m and characteristic strength σο were identified. Fractured surfaces were imaged by a SEM. RESULTS SEM/EDX analysis showed that cast alloy consists of two phases with differences in mean atomic number contrast, while no mean atomic number was identified for welded regions. EDX analysis revealed an increased Cr and Mo content at the alloy-joint interface. All mechanical properties of group I (TS, ε, m and σο) were found inferior to R while group K showed intermediated values without significant differences to R and I, apart from elongation with group R. The fractured surfaces of all groups showed extensive dendritic pattern although with a finer structure in the case of welded groups. CONCLUSION The K shape joint configuration should be preferred over the I, as it demonstrates improved mechanical strength and survival probability. PMID:25722836

  10. Multi-scale mechanical characterization of scaffolds for heart valve tissue engineering.

    PubMed

    Argento, G; Simonet, M; Oomens, C W J; Baaijens, F P T

    2012-11-15

    Electrospinning is a promising technology to produce scaffolds for cardiovascular tissue engineering. Each electrospun scaffold is characterized by a complex micro-scale structure that is responsible for its macroscopic mechanical behavior. In this study, we focus on the development and the validation of a computational micro-scale model that takes into account the structural features of the electrospun material, and is suitable for studying the multi-scale scaffold mechanics. We show that the computational tool developed is able to describe and predict the mechanical behavior of electrospun scaffolds characterized by different microstructures. Moreover, we explore the global mechanical properties of valve-shaped scaffolds with different microstructural features, and compare the deformation of these scaffolds when submitted to diastolic pressures with a tissue engineered and a native valve. It is shown that a pronounced degree of anisotropy is necessary to reproduce the deformation patterns observed in the native heart valve.

  11. Characterizing motion contour detection mechanisms and equivalent mechanisms in the luminance domain.

    PubMed

    Durant, Szonya; Zanker, Johannes M

    2009-01-23

    Motion-defined contours are ecologically important cues to object boundaries in complex fields of optic flow. We designed a novel stimulus in which the velocities of randomly positioned dots are defined by a 2D Gabor function, resulting in a motion-defined pattern with a clear orientation. We found that the number of correct responses in a vertical/horizontal orientation discrimination task increases and saturates with size of the Gabor envelope at around 4-5 degrees full width at half height. The number of correct responses decreases with higher spatial frequency of the Gabor patterns. The best performance occurs at 0.1 cycles/degree, when only a single contour is visible. Using elliptical Gabor stimuli, we found that accuracy is higher if the patch is elongated along the contours (rather than orthogonal to them), confirming the existence of an elongated detector mechanism for a single contour. We compared tuning properties for motion-defined Gabor patterns with sparsely defined luminance Gabor patterns and found similar results, but only at low sampling densities. The nature of the information and the strength of the signal influence the properties of luminance contour detection mechanisms, whereas motion contour detection may be limited by the sparse visual representation of the motion field.

  12. A simple calibration method for mechanically braked cycle ergometers.

    PubMed

    Van Praagh, E; Bedu, M; Roddier, P; Coudert, J

    1992-01-01

    The calibration of cycle ergometers should be checked regularly. Some studies have shown calibration errors of more than 40%. A simple, inexpensive calibrating method for mechanically braked cycle ergometers was developed and tried out on a new type of ergocycle. The cycle ergometer was elevated and the crank replaced by a pulley fitted to the shaft. The crank speed (rpm) increased linearly as a function of time when different masses were applied on the pulley. For a given braking force on the cycle ergometer, different accelerations corresponding to the increased pulley forces could be measured. When extrapolating for zero acceleration, it was possible to determine a "limit-force" which allowed the system to be in equilibrium. Additional force creates motion. The same experiments were repeated with increasing braking forces. Using the differently sized gear sprockets of the transmission system, it was possible to calculate the actual force, including all the resistances. The actual force found by the calibrating method was then compared with the indicated force proposed by the manufacturer. With increasing forces, the relative errors decreased from 9.6 to 2.9%. The cycle ergometer calibrated by this technique meets the standards recommended in exercise physiology.

  13. Preparation and mechanical characterization of polycaprolactone/graphene oxide biocomposite nanofibers

    NASA Astrophysics Data System (ADS)

    Lopresti, Francesco; Maio, Andrea; Botta, Luigi; Scaffaro, Roberto

    2016-05-01

    Biocomposite nanofiber scaffolds of polycaprolactone (PCL) filled with graphene oxide (GO) were prepared using electrospinning technology. Morphological and mechanical properties of the scaffolds were characterized in dry and wet environment. The results showed that the successful incorporation of GO nanosheets into PCL polymer nanofibers improved their mechanical properties. Furthermore it was demonstrated the higher performance achieved when GO is filled at low concentration in the nanofibers.

  14. Optical method for determining the mechanical properties of a material

    DOEpatents

    Maris, H.J.; Stoner, R.J.

    1998-12-01

    Disclosed is a method for characterizing a sample, comprising the steps of: (a) acquiring data from the sample using at least one probe beam wavelength to measure, for times less than a few nanoseconds, a change in the reflectivity of the sample induced by a pump beam; (b) analyzing the data to determine at least one material property by comparing a background signal component of the data with data obtained for a similar delay time range from one or more samples prepared under conditions known to give rise to certain physical and chemical material properties; and (c) analyzing a component of the measured time dependent reflectivity caused by ultrasonic waves generated by the pump beam using the at least one determined material property. The first step of analyzing may include a step of interpolating between reference samples to obtain an intermediate set of material properties. The material properties may include sound velocity, density, and optical constants. In one embodiment, only a correlation is made with the background signal, and at least one of the structural phase, grain orientation, and stoichiometry is determined. 14 figs.

  15. Optical method for determining the mechanical properties of a material

    DOEpatents

    Maris, Humphrey J.; Stoner, Robert J.

    1998-01-01

    Disclosed is a method for characterizing a sample, comprising the steps of: (a) acquiring data from the sample using at least one probe beam wavelength to measure, for times less than a few nanoseconds, a change in the reflectivity of the sample induced by a pump beam; (b) analyzing the data to determine at least one material property by comparing a background signal component of the data with data obtained for a similar delay time range from one or more samples prepared under conditions known to give rise to certain physical and chemical material properties; and (c) analyzing a component of the measured time dependent reflectivity caused by ultrasonic waves generated by the pump beam using the at least one determined material property. The first step of analyzing may include a step of interpolating between reference samples to obtain an intermediate set of material properties. The material properties may include sound velocity, density, and optical constants. In one embodiment, only a correlation is made with the background signal, and at least one of the structural phase, grain orientation, and stoichiometry is determined.

  16. Phototoxicity: Its Mechanism and Animal Alternative Test Methods

    PubMed Central

    Park, Hyeonji; Lim, Kyung-Min

    2015-01-01

    The skin exposure to solar irradiation and photoreactive xenobiotics may produce abnormal skin reaction, phototoxicity. Phototoxicity is an acute light-induced response, which occurs when photoreacive chemicals are activated by solar lights and transformed into products cytotoxic against the skin cells. Multifarious symptoms of phototoxicity are identified, skin irritation, erythema, pruritis, and edema that are similar to those of the exaggerated sunburn. Diverse organic chemicals, especially drugs, are known to induce phototoxicity, which is probably from the common possession of UV-absorbing benzene or heterocyclic rings in their molecular structures. Both UVB (290~320 nm) and UVA (320~400 nm) are responsible for the manifestation of phototoxicity. Absorption of photons and absorbed energy (hv) by photoactive chemicals results in molecular changes or generates reactive oxygen species and depending on the way how endogenous molecules are affected by phototoxicants, mechanisms of phototoxcity is categorized into two modes of action: Direct when unstable species from excited state directly react with the endogenous molecules, and indirect when endogeneous molecules react with secondary photoproducts. In order to identify phototoxic potential of a chemical, various test methods have been introduced. Focus is given to animal alternative test methods, i.e., in vitro, and in chemico assays as well as in vivo. 3T3 neutral red uptake assay, erythrocyte photohemolysis test, and phototoxicity test using human 3-dimensional (3D) epidermis model are examples of in vitro assays. In chemico methods evaluate the generation of reactive oxygen species or DNA strand break activity employing plasmid for chemicals, or drugs with phototoxic potential. PMID:26191378

  17. Biophysical response of living cells to boron nitride nanoparticles: uptake mechanism and bio-mechanical characterization

    NASA Astrophysics Data System (ADS)

    Rasel, Md. Alim Iftekhar; Li, Tong; Nguyen, Trung Dung; Singh, Sanjleena; Zhou, Yinghong; Xiao, Yin; Gu, YuanTong

    2015-11-01

    Boron nitride nanomaterials have attracted significant interest due to their superior chemical and physical properties. Despite these novel properties, investigation on the interaction between boron nitride nanoparticle (BN NP) and living systems has been limited. In this study, BN NP (100-250 nm) is assessed as a promising biomaterial for medical applications. The toxicity of BN NP is evaluated by assessing the cells behaviours both biologically (MTT assay, ROS detection etc.) and physically (atomic force microscopy). The uptake mechanism of BN NP is studied by analysing the alternations in cellular morphology based on cell imaging techniques. The results demonstrate in vitro cytocompatibility of BN NP with immense potential for use as an effective nanoparticle for various bio-medical applications.

  18. Conical intersections in solution: formulation, algorithm, and implementation with combined quantum mechanics/molecular mechanics method.

    PubMed

    Cui, Ganglong; Yang, Weitao

    2011-05-28

    The significance of conical intersections in photophysics, photochemistry, and photodissociation of polyatomic molecules in gas phase has been demonstrated by numerous experimental and theoretical studies. Optimization of conical intersections of small- and medium-size molecules in gas phase has currently become a routine optimization process, as it has been implemented in many electronic structure packages. However, optimization of conical intersections of small- and medium-size molecules in solution or macromolecules remains inefficient, even poorly defined, due to large number of degrees of freedom and costly evaluations of gradient difference and nonadiabatic coupling vectors. In this work, based on the sequential quantum mechanics and molecular mechanics (QM/MM) and QM/MM-minimum free energy path methods, we have designed two conical intersection optimization methods for small- and medium-size molecules in solution or macromolecules. The first one is sequential QM conical intersection optimization and MM minimization for potential energy surfaces; the second one is sequential QM conical intersection optimization and MM sampling for potential of mean force surfaces, i.e., free energy surfaces. In such methods, the region where electronic structures change remarkably is placed into the QM subsystem, while the rest of the system is placed into the MM subsystem; thus, dimensionalities of gradient difference and nonadiabatic coupling vectors are decreased due to the relatively small QM subsystem. Furthermore, in comparison with the concurrent optimization scheme, sequential QM conical intersection optimization and MM minimization or sampling reduce the number of evaluations of gradient difference and nonadiabatic coupling vectors because these vectors need to be calculated only when the QM subsystem moves, independent of the MM minimization or sampling. Taken together, costly evaluations of gradient difference and nonadiabatic coupling vectors in solution or

  19. Method for microbubble characterization using primary radiation force.

    PubMed

    Vos, Hendrik J; Guidi, Francesco; Boni, Enrico; Tortoli, Piero

    2007-07-01

    Medical ultrasound contrast agents (UCAs) have evolved from straight image enhancers to pathophysiological markers and drug delivery vehicles. However, the exact dynamic behavior of the encapsulated bubbles composing UCAs is still not entirely known. In this article, we propose to characterize full populations of UCAs, by looking at the translational effects of ultrasound radiation force on each bubble in a diluted population. The setup involves a sensitive, fully programmable transmitter/receiver and two unconventional, real-time display modes. Such display modes are used to measure the displacements produced by irradiation at frequencies in the range 2-8 MHz and pressures between 150 kPa and 1.5 MPa. The behavior of individual bubbles freely moving in a water tank is clearly observed, and it is shown that it depends on the bubble physical dimensions as well as on the viscoelastic properties of the encapsulation. A new method also is distilled that estimates the viscoelastic properties of bubble encapsulation by fitting the experimental bubble velocities to values simulated by a numerical model based on the modified Herring equation and the Bjerknes force. The fit results are a shear modulus of 18 MPa and a viscosity of 0.23 Pas for a thermoplastic PVC-AN shell. Phospholipid shell elasticity and friction parameter of the experimental contrast agent are estimated as 0.8 N/m and 1 10(-7) kg/s, respectively (shear modulus of 32 MPa and viscosity of 0.19 Pas, assuming 4-nm shell thickness).

  20. Mechanical Properties of Sisal/Coir Fiber Reinforced Hybrid Composites Fabricated by Cold Pressing Method

    NASA Astrophysics Data System (ADS)

    Akash; Sreenivasa Rao, K. V.; Venkatesha Gupta, N. S.; kumar, D. S. Arun

    2016-09-01

    Bio-composites have less density and are environmental friendly materials that require less energy during production and subsequent machining. This paper reports the mechanical and water absorption properties of sodium hydroxide (NaOH) treated sisal and coir fiber reinforced epoxy resin thermo set hybrid composites. The hybrid composites were prepared by traditional cold pressing method at room temperature with applied pressure of 410.4 kg/cm2 for 3 hours pressurization time. The mechanical properties were characterized according to ASTM standards. Hybrid composites with 40wt% of sisal and coir fiber were found to possess higher tensile strength of 48.2MPa and flexural strength of 76.68 MPa among the fabricated hybrid composite specimens. Absorption of water increases with increasing fiber volume. The experimental result also show that the sisal and coir fibers are promising reinforcement for use in low cost bio-composites which have high strength to weight ratio.

  1. A new two-alternative forced choice method for the unbiased characterization of perceptual bias and discriminability.

    PubMed

    Jogan, Matjaž; Stocker, Alan A

    2014-03-13

    Perception is often biased by secondary stimulus attributes (e.g., stimulus noise, attention, or spatial context). A correct quantitative characterization of perceptual bias is essential for testing hypotheses about the underlying perceptual mechanisms and computations. We demonstrate that the standard two-alternative forced choice (2AFC) method can lead to incorrect estimates of perceptual bias. We present a new 2AFC method that solves this problem by asking subjects to judge the relative perceptual distances between the test and each of two reference stimuli. Naïve subjects can easily perform this task. We successfully validated the new method with a visual motion-discrimination experiment. We demonstrate that the method permits an efficient and accurate characterization of perceptual bias and simultaneously provides measures of discriminability for both the reference and test stimulus, all from a single stimulus condition. This makes it an attractive choice for the characterization of perceptual bias and discriminability in a wide variety of psychophysical experiments.

  2. Assessing the reliability of nondestructive evaluation methods for damage characterization

    NASA Astrophysics Data System (ADS)

    Aldrin, John C.; Annis, Charles; Sabbagh, Harold A.; Knopp, Jeremy S.; Lindgren, Eric A.

    2014-02-01

    A comprehensive approach to NDE characterization error evaluation is presented that follows the framework of the `ahat-versus-a' model evaluation process for probability of detection (POD) assessment. Before characterization error model building is performed, an intermediate step must evaluate the presence and frequency of several possible classes of poor characterization results. A case study is introduced based on the estimation the length, depth and width of surface breaking cracks using bolt hole eddy current (BHEC) NDE. This study highlights the importance of engineering and statistical expertise in the model-building process to ensure all key effects and possible interactions are addressed.

  3. Microstructural and Mechanical Behavior Characterization of Ultrasonically Consolidated Titanium-Aluminum Laminates

    DTIC Science & Technology

    2009-02-01

    provide high hardness and stiffness, the consolidated laminates were heat-treated in a variety of conditions to form intermetallic titanium aluminide ...the consolidated laminates were heat-treated in a variety of conditions to form intermetallic titanium aluminide (TiAl3) layers. The resulting CP...Microstructural and Mechanical Behavior Characterization of Ultrasonically Consolidated Titanium - Aluminum Laminates by Tomoko Sano, James

  4. Quantitative shear wave imaging optical coherence tomography for noncontact mechanical characterization of myocardium

    NASA Astrophysics Data System (ADS)

    Wang, Shang; Lopez, Andrew L.; Morikawa, Yuka; Tao, Ge; Li, Jiasong; Larina, Irina V.; Martin, James F.; Larin, Kirill V.

    2015-03-01

    Optical coherence elastography (OCE) is an emerging low-coherence imaging technique that provides noninvasive assessment of tissue biomechanics with high spatial resolution. Among various OCE methods, the capability of quantitative measurement of tissue elasticity is of great importance for tissue characterization and pathology detection across different samples. Here we report a quantitative OCE technique, termed quantitative shear wave imaging optical coherence tomography (Q-SWI-OCT), which enables noncontact measurement of tissue Young's modulus based on the ultra-fast imaging of the shear wave propagation inside the sample. A focused air-puff device is used to interrogate the tissue with a low-pressure short-duration air stream that stimulates a localized displacement with the scale at micron level. The propagation of this tissue deformation in the form of shear wave is captured by a phase-sensitive OCT system running with the scan of the M-mode imaging over the path of the wave propagation. The temporal characteristics of the shear wave is quantified based on the cross-correlation of the tissue deformation profiles at all the measurement locations, and linear regression is utilized to fit the data plotted in the domain of time delay versus wave propagation distance. The wave group velocity is thus calculated, which results in the quantitative measurement of the Young's modulus. As the feasibility demonstration, experiments are performed on tissuemimicking phantoms with different agar concentrations and the quantified elasticity values with Q-SWI-OCT agree well with the uniaxial compression tests. For functional characterization of myocardium with this OCE technique, we perform our pilot experiments on ex vivo mouse cardiac muscle tissues with two studies, including 1) elasticity difference of cardiac muscle under relaxation and contract conditions and 2) mechanical heterogeneity of the heart introduced by the muscle fiber orientation. Our results suggest the

  5. Nondestructive Method for Bulk Chemical Characterization of Barred Olivine Chondrules

    NASA Astrophysics Data System (ADS)

    Montoya-Perez, M. A.; Cervantes-de la Cruz, K. E.; Ruvalcaba-Sil, J. L.

    2017-02-01

    This work develops a bulk chemical characterization of barred olivine chondrules based on the XRF analysis using a portable equipment at the National Research and Conservation Science Laboratory of Cultural Heritage (LANCIC-IF) in Mexico City.

  6. Application of an ESI-QTOF method for the detailed characterization of GSK-3β inhibitors.

    PubMed

    De Simone, Angela; Fiori, Jessica; Naldi, Marina; D'Urzo, Annalisa; Tumiatti, Vincenzo; Milelli, Andrea; Andrisano, Vincenza

    2017-02-27

    The crucial role of Glycogen Synthase Kinase 3 (GSK-3β) as a pivotal player in Alzheimer's Disease (AD) has recently inspired significant attempts to design and synthesize potent kinase inhibitors. In fact GSK-3β is considered the main kinase which catalyzes the microtubule-associated protein tau hyper-phosphorylation and the neurofibrillary tangles (NFT) in vitro and in vivo, The first classes of GSK-3β inhibitors were classified as ATP-competitive and, therefore, they lack of an efficient degree of selectivity over other kinases. In light of this consideration, many efforts are devoted to characterize new non ATP-competitive GSK-3β inhibitors, endowed with high selectivity. In parallel, there is an urgent need to develop new analytical methodologies for the hit selection (highthroughput screening) and ligand binding characterization in terms of potency, affinity and mechanism of action. The new methodology for GSK-3β enzymatic activity determination can be adopted as a realistic alternative to the currently used radioactive, luminescence and fluorescence detection methods, each showing limitations in terms of safety and interferences. Herein, we propose an alternative and selective electrospray ionization quadrupole time-of-flight (ESI-QTOF) method, based on the direct quantification of phosphorylated substrate muscle glycogen synthase GSM, a peptide resembling the high affinity sequence of natural substrate muscle glycogen synthase 1, for the detailed characterization of GSK-3β inhibitors. The method was validated in terms of accuracy and reproducibility of GSM signal intensity with a relative standard deviation RSD% value of 3.55%; Limit of Detection (LOD): 0.006μM; Lower Limit of Quantification (LLOQ): 0.02μM; linearity r(2) 0.9951. The kinetic constants (KM and vmax) of the GSK-3β catalyzed kinase reaction and the inhibitory potency of known ligands (IC50), were determined. All the obtained results were in agreement with those reported in literature

  7. Investigation of the surface generation mechanism of mechanical polishing engineering ceramics using discrete element method

    NASA Astrophysics Data System (ADS)

    Han, Xuesong

    2014-09-01

    Machining technology about ceramics has been developed very fast over recent years due to the growing industrial demand of higher machining accuracy and better surface quality of ceramic elements, while the nature of hard and brittle ceramics makes it difficult to acquire damage-free and ultra-smooth surface. Ceramic bulk can be treated as an assemblage of discrete particles bonded together randomly as the micro-structure of ceramics consists of crystal particles and pores, and the inter-granular fracture of the ceramics can be naturally represented by the separation of particles due to breakage of bonds. Discrete element method (DEM) provides a promising approach for constructing an effective model to describe the tool-workpiece interaction and can serve as a predicting simulation tool in analyzing the complicated surface generation mechanism and is employed in this research to simulate the mechanical polishing process of ceramics and surface integrity. In this work, a densely packed particle assembly system of the polycrystalline Si3N4 has been generated using bonded-particle model to represent the ceramic workpiece numerically. The simulation results justify that the common critical depth of cut cannot be used as the effective parameters for evaluating brittle to ductile transformation in ceramic polishing process. Therefore, a generalized criterion of defining the range of ductile regime machining has been developed based on the numerical results. Furthermore, different distribution of pressure chain is observed with different depth of cut which ought to have intense relationship with special structure of ceramics. This study also justified the advantage of DEM model in its capability of revealing the mechanical behaviors of ceramics at micro-scale.

  8. Mechanical modulation method for ultrasensitive phase measurements in photonics biosensing.

    PubMed

    Patskovsky, S; Maisonneuve, M; Meunier, M; Kabashin, A V

    2008-12-22

    A novel polarimetry methodology for phase-sensitive measurements in single reflection geometry is proposed for applications in optical transduction-based biological sensing. The methodology uses altering step-like chopper-based mechanical phase modulation for orthogonal s- and p- polarizations of light reflected from the sensing interface and the extraction of phase information at different harmonics of the modulation. We show that even under a relatively simple experimental arrangement, the methodology provides the resolution of phase measurements as low as 0.007 deg. We also examine the proposed approach using Total Internal Reflection (TIR) and Surface Plasmon Resonance (SPR) geometries. For TIR geometry, the response appears to be strongly dependent on the prism material with the best values for high refractive index Si. The detection limit for Si-based TIR is estimated as 10(-5) in terms Refractive Index Units (RIU) change. SPR geometry offers much stronger phase response due to a much sharper phase characteristics. With the detection limit of 3.2*10(-7) RIU, the proposed methodology provides one of best sensitivities for phase-sensitive SPR devices. Advantages of the proposed method include high sensitivity, simplicity of experimental setup and noise immunity as a result of a high stability modulation.

  9. [Endocrine xenoestrogenics disrupters: molecular mechanisms and detection methods].

    PubMed

    Mnif, Wissem; Pillon, Arnaud; Balaguer, Patrick; Bartegi, Aghleb

    2007-01-01

    The attention paid to endocriniens modulators for purpose micropolluants (endocrine disrupters) has been increasingly studied these last years particularly on animals. The results of this study raised big concerns from Doctors and Biologists on the eventual risks human health can face. Indeed, endocrine systems of the body play an essential and pervasive role in both the short- and long-term regulation of metabolic processes. Nutritional, behavioural, and reproductive processes are intricately regulated by endocrine systems, as are growth (including bone growth/remodelling), gut, cardiovascular, and kidney function and responses to all forms of stress. Disorders of any of the endocrine system, involving both over- and under-active hormone secretion, result inevitably in disease, the effects of which may extend to many different organs and functions and are often debilitating or life-threatening. Viewed from this general perspective, the threat posed from environmental chemicals with endocrine activity (either agonist or antagonistic) is potentially serious. However, the fact that humans and wildlife are exposed to such chemicals does not necessarily mean that clinically manifest disturbance of the relevant endocrine system will result, because much depends on the level and duration of exposure and on the timing of exposure. Indeed, a large numbers of environmental estrogens are suspected of altering human health as well as the marine ecosystem balance. The objective of this review is to study the different molecular mechanisms of these xenoestrogenes micropolluants, in order to emphasize their potential risk and to present some of the different experimental methods for their detection.

  10. Recent advancements in mechanical reduction methods: particulate systems.

    PubMed

    Leleux, Jardin; Williams, Robert O

    2014-03-01

    The screening of new active pharmaceutical ingredients (APIs) has become more streamlined and as a result the number of new drugs in the pipeline is steadily increasing. However, a major limiting factor of new API approval and market introduction is the low solubility associated with a large percentage of these new drugs. While many modification strategies have been studied to improve solubility such as salt formation and addition of cosolvents, most provide only marginal success and have severe disadvantages. One of the most successful methods to date is the mechanical reduction of drug particle size, inherently increasing the surface area of the particles and, as described by the Noyes-Whitney equation, the dissolution rate. Drug micronization has been the gold standard to achieve these improvements; however, the extremely low solubility of some new chemical entities is not significantly affected by size reduction in this range. A reduction in size to the nanometric scale is necessary. Bottom-up and top-down techniques are utilized to produce drug crystals in this size range; however, as discussed in this review, top-down approaches have provided greater enhancements in drug usability on the industrial scale. The six FDA approved products that all exploit top-down approaches confirm this. In this review, the advantages and disadvantages of both approaches will be discussed in addition to specific top-down techniques and the improvements they contribute to the pharmaceutical field.

  11. Integrated Surface and Mechanical Characterization of Freestanding Biological and Other Nano-Structures Using Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Xin

    film promises a broad range of potential applications in electronic devices due to unique electrical and mechanical properties. SWCNT thin film is transferred onto micro-patterned SU-8 strips using wet contact print method, forming a freestanding nano-structure. AFM with tipless cantilever is used to deform the suspended thin film under mixed bending and stretching for mechanical and electromechanical characterization. The experiment helps to construct the base for next generation flexible electronic devices with fundamental understanding in morphology-property relation.

  12. Biosorption of Cu(II) from aqueous solution by Fucus serratus: surface characterization and sorption mechanisms.

    PubMed

    Ahmady-Asbchin, Salman; Andrès, Yves; Gérente, Claire; Cloirec, Pierre Le

    2008-09-01

    In this work, the brown alga Fucus serratus (FS) used as a low cost sorbent has been studied for the biosorption of copper(II) ions in batch reactors. Firstly, the characterization of the surface functional groups was performed with two methods: a qualitatively analysis with the study of FT-IR spectrum and a quantitatively determination with potentiometric titrations. From this latter, a total proton exchange capacity of 3.15 mmolg(-1) was extrapolated from the FS previously protonated. This value was similar to the total acidity of 3.56 mmolg(-1) deduced from the Gran method. Using the single extrapolation method, three kinds of acidic functional groups with three intrinsic pK(a) were determined at 3.5, 8.2 and 9.6. The point of zero net proton charge (PZNPC) was found close to pH 6.3. Secondly, the biosorption of copper ions was studied. The equilibrium time was about 350 min and the adsorption equilibrium data were well described by the Langmuir's equation. The maximum adsorption capacity has been extrapolated to 1.60 mmolg(-1). The release of calcium and magnesium ions was also measured in relation to the copper biosorption. Finally, the efficiency of this biosorbent in natural tap water for the removal of copper was also investigated. All these observations indicate that the copper biosorption on FS is mainly based on ion exchange mechanism and this biomass could be then a suitable sorbent for the removal of heavy metals from wastewaters.

  13. Characterization of Solid Polymers, Ceramic Gap Filler, and Closed-Cell Polymer Foam Using Low-Load Test Methods

    NASA Technical Reports Server (NTRS)

    Herring, Helen M.

    2008-01-01

    Various solid polymers, polymer-based composites, and closed-cell polymer foam are being characterized to determine their mechanical properties, using low-load test methods. The residual mechanical properties of these materials after environmental exposure or extreme usage conditions determines their value in aerospace structural applications. In this experimental study, four separate polymers were evaluated to measure their individual mechanical responses after thermal aging and moisture exposure by dynamic mechanical analysis. A ceramic gap filler, used in the gaps between the tiles on the Space Shuttle, was also tested, using dynamic mechanical analysis to determine material property limits during flight. Closed-cell polymer foam, used for the Space Shuttle External Tank insulation, was tested under low load levels to evaluate how the foam's mechanical properties are affected by various loading and unloading scenarios.

  14. Investigation of methods for fabricating, characterizing, and transporting cryogenic inertial-confinement-fusion tartets

    SciTech Connect

    Fanning, J.J.; Kim, K.

    1981-01-01

    The objective of this work is to investigate methods for fabricating, characterizing and transporting cryogenic inertial confinement fusion targets on a continuous basis. A microprocessor-based data acquisition system has been built that converts a complete target image to digital data, which are then analyzed by automated software procedures. The low temperatures required to freeze the hydrogen isotopes contained in a target is provided by a cryogenic cold chamber capable of attaining 15 K. A new method for target manipulation and positioning is studied that employs molecular gas beams to levitate a target and an electrostatic quadrupole structure to provide for its lateral containment. Since the electrostatic target-positioning scheme requires that the targets be charged, preliminary investigation has been carried out for a target-charging mechanism based on ion-bombardment.

  15. NMR and computational methods in the structural and dynamic characterization of ligand-receptor interactions.

    PubMed

    Ghitti, Michela; Musco, Giovanna; Spitaleri, Andrea

    2014-01-01

    The recurrent failures in drug discovery campaigns, the asymmetry between the enormous financial investments and the relatively scarce results have fostered the development of strategies based on complementary methods. In this context in recent years the rigid lock-and-key binding concept had to be revisited in favour of a dynamic model of molecular recognition accounting for conformational changes of both the ligand and the receptor. The high level of complexity required by a dynamic description of the processes underlying molecular recognition requires a multidisciplinary investigation approach. In this perspective, the combination of nuclear magnetic resonance spectroscopy with molecular docking, conformational searches along with molecular dynamics simulations has given new insights into the dynamic mechanisms governing ligand receptor interactions, thus giving an enormous contribution to the identification and design of new and effective drugs. Herein a succinct overview on the applications of both NMR and computational methods to the structural and dynamic characterization of ligand-receptor interactions will be presented.

  16. Characterization and diagnostic methods for geomagnetic auroral infrasound waves

    NASA Astrophysics Data System (ADS)

    Oldham, Justin J.

    Infrasonic perturbations resulting from auroral activity have been observed since the 1950's. In the last decade advances in infrasonic microphone sensitivity, high latitude sensor coverage, time series analysis methods and computational efficiency have elucidated new types of auroral infrasound. Persistent periods of infrasonic activity associated with geomagnetic sub-storms have been termed geomagnetic auroral infrasound waves [GAIW]. We consider 63 GAIW events recorded by the Fairbanks, AK infrasonic array I53US ranging from 2003 to 2014 and encompassing a complete solar cycle. We make observations of the acoustic features of these events alongside magnetometer, riometer, and all-sky camera data in an effort to quantify the ionospheric conditions suitable for infrasound generation. We find that, on average, the generation mechanism for GAIW is confined to a region centered about ~60 0 longitude east of the anti-Sun-Earth line and at ~770 North latitude. We note furthermore that in all cases considered wherein imaging riometer data are available, that dynamic regions of heightened ionospheric conductivity periodically cross the overhead zenith. Consistent features in concurrent magnetometer conditions are also noted, with irregular oscillations in the horizontal component of the field ubiquitous in all cases. In an effort to produce ionosphere based infrasound free from the clutter and unknowns typical of geophysical observations, an experiment was undertaken at the High Frequency Active Auroral Research Program [HAARP] facility in 2012. Infrasonic signals appearing to originate from a source region overhead were observed briefly on 9 August 2012. The signals were observed during a period when an electrojet current was presumed to have passed overhead and while the facilities radio transmitter was periodically heating the lower ionosphere. Our results suggest dynamic auroral electrojet currents as primary sources of much of the observed infrasound, with

  17. Characterizing the mechanism of thiazolidinedione-induced hepatotoxicity: An in vitro model in mitochondria

    SciTech Connect

    Hu, Dan; Wu, Chun-qi; Li, Ze-jun; Liu, Yue; Fan, Xing; Wang, Quan-jun; Ding, Ri-gao

    2015-04-15

    Objective: To characterize the mechanism of action of thiazolidinedione (TZD)-induced liver mitochondrial toxicity caused by troglitazone, rosiglitazone, and pioglitazone in HepaRG cells. Methods: Human hepatoma cells (HepaRG) were treated with troglitazone, rosiglitazone, or pioglitazone (12.5, 25, and 50 μM) for 48 h. The Seahorse Biosciences XF24 Flux Analyzer was used to measure mitochondrial oxygen consumption. The effect of TZDs on reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were detected by flow cytometry. The mitochondrial ultrastructure of HepaRG cells was observed under a transmission electrical microscope (TEM). mtDNA content was evaluated by real-time PCR, and ATP content and mitochondrial respiratory chain (MRC) complex I, II, III, IV activity were measured via chemiluminescence. Results were considered statistically significant at p < 0.05. Results: Among the three drugs, troglitazone exhibited the highest potency, followed by rosiglitazone, and then pioglitazone. The TZDs caused varying degrees of mitochondrial respiratory function disorders including decreases in oxygen consumption, MRC activity, and ATP level, and an elevation in ROS level. TZD treatment resulted in mtDNA content decline, reduction in MMP, and alterations of mitochondrial structure. Conclusion: All investigated TZDs show a certain degree of mitochondrial toxicity, with troglitazone exhibiting the highest potency. The underlying mechanism of TZD-induced hepatotoxicity may be associated with alterations in mitochondrial respiratory function disorders, oxidative stress, and changes in membrane permeability. These parameters may be used early in drug development to further optimize risk:benefit profiles. - Highlights: • We compared three TZD mitochondrial toxicity characteristics in HepaRG cells. • TZD induced respiratory disorders and mitochondrial structural damage. • Mitochondrial toxicity evaluation presents guidance value for hepatotoxicity.

  18. Excitation of Rat Cerebellar Golgi Cells by Ethanol: Further Characterization of the Mechanism

    PubMed Central

    Botta, Paolo; de Souza, Fabio M. Simões; Sangrey, Thomas; De Schutter, Erik; Valenzuela, C. Fernando

    2012-01-01

    Background Studies with rodents suggest that acute ethanol exposure impairs information flow through the cerebellar cortex, in part, by increasing GABAergic input to granule cells. Experiments suggest that an increase in the excitability of specialized GABAergic interneurons that regulate granule cell activity (i.e. Golgi cells, GoCs) contributes to this effect. In GoCs, ethanol increases spontaneous action potential firing frequency, decreased the afterhyperpolarization amplitude, and depolarized the membrane potential. Studies suggest that these effects could be mediated by inhibition of the Na+/K+ ATPase. The purpose of this study was to characterize the potential role of other GoC conductances in the mechanism of action of ethanol. Methods Computer modeling techniques and patch-clamp electrophysiological recordings with acute slices from rat cerebella were used for these studies. Results Computer modeling suggested that modulation of subthreshold Na+ channels, hyperpolarization activated currents and several K+ conductances could explain some but not all actions of ethanol on GoCs. Electrophysiological studies did not find evidence consistent with a contribution of these conductances. Quinidine, a non-selective blocker of several types of channels (including several K+ channels) that also antagonizes the Na+/K+ ATPase, reduced the effect of ethanol on GoC firing. Conclusions These findings lend further support to the conclusion that ethanol increases GoC excitability via modulation of the Na+/K+ ATPase, and suggest that a quinidine-sensitive K+ channel may also play a role in the mechanism of action of ethanol. PMID:22004123

  19. Electron beam crosslinked gels—Preparation, characterization and their effect on the mechanical, dynamic mechanical and rheological properties of rubbers

    NASA Astrophysics Data System (ADS)

    Mitra, Suman; Chattopadhyay, Santanu; Sabharwal, Sunil; Bhowmick, Anil K.

    2010-03-01

    Electron beam (EB) crosslinked natural rubber (NR) gels were prepared by curing NR latex with EB irradiation over a range of doses from 2.5 to 20 kGy using butyl acrylate as sensitizer. The NR gels were systematically characterized by solvent swelling, dynamic light scattering, mechanical and dynamic mechanical properties. These gels were introduced in virgin NR and styrene butadiene rubber (SBR) matrices at 2, 4, 8 and 16 phr concentration. Addition of the gels improved the mechanical and dynamic mechanical properties of NR and SBR considerably. For example, 16 phr of 20 kGy EB-irradiated gel-filled NR showed a tensile strength of 3.53 MPa compared to 1.85 MPa of virgin NR. Introduction of gels in NR shifted the glass transition temperature to a higher temperature. A similar effect was observed in the case of NR gel-filled SBR systems. Morphology of the gel-filled systems was studied with atomic force microscopy. The NR gels also improved the processability of the virgin rubbers greatly. Both the shear viscosity and the die swell values of EB-irradiated gel-filled NR and SBR were lower than their virgin counterparts as investigated by capillary rheometer.

  20. Mechanical and optical characterization of bio-nanocomposite from pineapple leaf fiber material for food packaging

    NASA Astrophysics Data System (ADS)

    Nikmatin, Siti; Rudwiyanti, Jerry R.; Prasetyo, Kurnia W.; Yedi, Dwi A.

    2015-01-01

    The utilization of Bio-nanocomposite material that was derived from pineapple leaf fiber as filler and tapioca starch with plasticizer glycerol as a matrix for food packaging can reduce the use of plastic that usually was made from petroleum materials. It is important to develop and producethis environmental friendly plastic because of limited availability of petroleum nowadays. The process of synthesize and characterization tapioca starch with the plasticizer glycerol bionanocomposites using print method had been conducted. There were 3 samples with different filler concentration variation; 3%, 4% and 5%.The results of mechanical test from each sample showed that bio-nanocomposite with 5% filler concentration was the optimum sample with 4.6320 MPa for tensile strength test and 24.87% for the elongation test. Based on the result of optical test for each sample was gained that along with the increasing of concentration filler would make the absorbance value of the sample became decreased, bio-nanocomposite with 5% filler concentration had several peaks with low absorbance values. The first peak was in 253 nm of wavelength regionwith absorbance of 0.131%, and the second peak was in 343 nmwavelength region and absorbance was 0.087%.

  1. Structural characterization of mechanically milled ZnO: influence of zirconia milling media

    NASA Astrophysics Data System (ADS)

    Vojisavljević, K.; Šćepanović, M.; Srećković, T.; Grujić-Brojčin, M.; Branković, Z.; Branković, G.

    2008-11-01

    Zinc oxide nanoparticles were obtained by milling in a planetary ball mill with a zirconia milling assembly for up to 5 h in air. The samples were characterized by scanning electron microscopy, x-ray diffraction (XRD) and Raman spectroscopy methods. The deviation of the lattice parameters from single crystal values was related to defect creation and increase of strain inside the hexagonal lattice of milled ZnO nanoparticles. The observed redshift and peak broadening of the major first-order Raman modes were ascribed to the formation of intrinsic defects by mechanical milling combined with the effects of phonon confinement in nanosized powders. To investigate the type of intrinsic defects and impurities introduced during milling, it was necessary to analyze both milled and thermally treated ZnO. After thermal treatment, the intensity of the Raman spectra increased and the peak positions reverted to values similar to those in unmilled ZnO powder, pointing to defect annihilation. XRD patterns of sintered samples confirmed the existence of zirconia impurities and the Rietveld analysis revealed a small amount of zirconium introduced in the ZnO crystal lattice on the Zn sites or interstitial sites. The large influence of those impurities on the micro-Raman spectra of thermally treated samples was observed in this study.

  2. Electrical Impedance Spectroscopy for Electro-Mechanical Characterization of Conductive Fabrics

    PubMed Central

    Bera, Tushar Kanti; Mohamadou, Youssoufa; Lee, Kyounghun; Wi, Hun; Oh, Tong In; Woo, Eung Je; Soleimani, Manuchehr; Seo, Jin Keun

    2014-01-01

    When we use a conductive fabric as a pressure sensor, it is necessary to quantitatively understand its electromechanical property related with the applied pressure. We investigated electromechanical properties of three different conductive fabrics using the electrical impedance spectroscopy (EIS). We found that their electrical impedance spectra depend not only on the electrical properties of the conductive yarns, but also on their weaving structures. When we apply a mechanical tension or compression, there occur structural deformations in the conductive fabrics altering their apparent electrical impedance spectra. For a stretchable conductive fabric, the impedance magnitude increased or decreased under tension or compression, respectively. For an almost non-stretchable conductive fabric, both tension and compression resulted in decreased impedance values since the applied tension failed to elongate the fabric. To measure both tension and compression separately, it is desirable to use a stretchable conductive fabric. For any conductive fabric chosen as a pressure-sensing material, its resistivity under no loading conditions must be carefully chosen since it determines a measurable range of the impedance values subject to different amounts of loadings. We suggest the EIS method to characterize the electromechanical property of a conductive fabric in designing a thin and flexible fabric pressure sensor. PMID:24892493

  3. TiO2 nanocomposites: Preparation, characterization, mechanical and biological properties

    NASA Astrophysics Data System (ADS)

    Koşarsoy, Gözde; Şen, Elif Hilal; Aksöz, Nilüfer; İde, Semra; Aksoy, Hüsnü

    2014-11-01

    Some novel nanocomposites, which contain different concentrations of TiO2 nanopowders, were firstly prepared by using marble dust with convenient chemical components. Their nano structures characterized and distributions of the nano-aggregations related with internal structural content of the samples have been determined by X-ray Scattering Methods (SAXS and WAXS) and mechanical properties were determined by using strain-stress measurements to increase their potential usage possibility as building materials in health and research centers. In the last and important part of the study, Candida albicans and Aspergillus niger which are a significant risk to medical patients were used to investigate originally prepared nanostructured samples' photocatalyst effect. During the last part of the study, effect of UV and visible light on photocatalyst nanocomposites were also researched. Heterogeneous photocatalysts can carry out advanced oxidation processes used for an antimicrobial effect on microorganisms. TiO2 nanoparticles as one of heterogeneous photocatalysts have been shown to exhibit strong cytotoxicity when exposed to UV and visible light.

  4. Nanomechanical and Electro-mechanical Characterization of Materials for Flexible Electrodes Applications

    NASA Astrophysics Data System (ADS)

    Peng, Cheng

    Flexible electronics attract research and commercial interests in last 2 decades for its flexibility, low cost, light weight and etc. To develop and improve the electro-mechanical properties of flexible electrodes is the most critical and important step. In this work, we have performed nanomechanical and electromechanical characterization of materials for flexible electrode applications, including metallic nanowires (NWs), indium tin oxide (ITO)-based and carbon nanotube (CNT)-based electrodes. First, we designed and developed four different testing platforms for nanomechanical and electro-mechanical characterization purpose. For the nano/sub-micro size samples, the micro mechanical devices can be used for uniaxial and bi-axial loading tests. For the macro size samples, the micro tester will be used for in situ monotonic tensile test, while the fatigue tester can be used for in situ cyclic tensile or bending testing purpose. Secondly, we have investigated mechanical behaviors of single crystalline Ni nanowires and single crystalline Cu nanowires under uni-axial tensile loading inside a scanning electron microscope (SEM) chamber. We demonstrated both size and strain-rate dependence on yield stress of single-crystalline Ni NWs with varying diameters (from 100 nm to 300 nm), and the molecular dynamics (MD) simulation helped to confirm and understand the experimental phenomena. Also, two different fracture modes, namely ductile and brittle-like fractures, were found in the same batch of Cu nanowire samples. Finally, we studied the electro-mechanical behaviors of flexible electrodes in macro scale. We reported a coherent study integrating in situ electro-mechanical experiments and mechanics modeling to decipher the failure mechanics of ITO-based and CNTbased electrodes under tension. It is believed that our combined experimental and simulation results provide some further insights into the important yet complicated deformation mechanisms for nanoscale metals and

  5. Characterization of cationic starch flocculants synthesized by dry process with ball milling activating method.

    PubMed

    Su, Yuting; Du, Hongying; Huo, Yinqiang; Xu, Yongliang; Wang, Jie; Wang, Liying; Zhao, Siming; Xiong, Shanbai

    2016-06-01

    The cationic starch flocculants were synthesized by the reaction of maize starch which was activated by a ball-milling treatment with 2,3-epoxypropyl trimethyl ammonium chlorides (ETMAC) using the dry method. The cationic starches were characterized by several approaches including scanning electron microscope (SEM), degree of substitution (DS), infrared spectrum (IR), X-ray diffraction (XRD), flocculating activity, electron spin resonance (ESR), and solid-state nuclear magnetic resonance (NMR). The effect of mechanical activation on starch etherifying modification was investigated. The mechanical activation cracked starch granules and destructed their crystal structures. This resulted in enhancements to the reaction activity and reaction efficiency, which was approved by ESR and solid state NMR. The starch flocculants, synthesized by the reaction of mechanically activated starches at 90°C for 2.5h with ETMAC at molar ratio of 0.40:1.00, showed good flocculation activity. The substitution degree (0.300) and reaction efficiency (75.06%) of starch flocculants synthesized with mechanically activated starches were significantly greater than those of starch flocculants with native starches (P<0.05).

  6. Study of borehole probing methods to improve the ground characterization

    NASA Astrophysics Data System (ADS)

    Naeimipour, Ali

    Collecting geological information allows for optimizing ground control measures in underground structures. This includes understanding of the joints and discontinuities and rock strength to develop rock mass classifications. An ideal approach to collect such information is through correlating the drilling data from the roofbolters to assess rock strength and void location and properties. The current instrumented roofbolters are capable of providing some information on these properties but not fully developed for accurate ground characterization. To enhance existing systems additional instrumentation and testing was conducted in laboratory and field conditions. However, to define the geology along the boreholes, the use of probing was deemed to be most efficient approach for locating joints and structures in the ground and evaluation of rock strength. Therefore, this research focuses on selection and evaluation of proper borehole probes that can offer a reliable assessment of rock mass structure and rock strength. In particular, attention was paid to borehole televiewer to characterize rock mass structures and joints and development of mechanical rock scratcher for determination of rock strength. Rock bolt boreholes are commonly drilled in the ribs and the roof of underground environments. They are often small (about 1.5 inches) and short (mostly 2-3 meter). Most of them are oriented upward and thus, mostly dry or perhaps wet but not filled with water. No suitable system is available for probing in such conditions to identify the voids/joints and specifically to measure rock strength for evaluation of rock mass and related optimization of ground support design. A preliminary scan of available borehole probes proved that the best options for evaluation of rock structure is through analysis of borehole images, captured by optical televiewers. Laboratory and field trials with showed that these systems can be used to facilitate measurement of the location, frequency and

  7. Apparatus and method for sensing motion in a microelectro-mechanical system

    DOEpatents

    Dickey, Fred M.; Holswade, Scott C.

    1999-01-01

    An apparatus and method are disclosed for optically sensing motion in a microelectromechanical system (also termed a MEMS device) formed by surface micromachining or LIGA. The apparatus operates by reflecting or scattering a light beam off a corrugated surface (e.g. gear teeth or a reference feature) of a moveable member (e.g. a gear, rack or linkage) within the MEMS device and detecting the reflected or scattered light. The apparatus can be used to characterize a MEMS device, measuring one or more performance characteristic such as spring and damping coefficients, torque and friction, or uniformity of motion of the moveable member. The apparatus can also be used to determine the direction and extent of motion of the moveable member; or to determine a particular mechanical state that a MEMS device is in. Finally, the apparatus and method can be used for providing feedback to the MEMS device to improve performance and reliability.

  8. Characterization of mechanical properties of lamellar structure of the aortic wall: Effect of aging.

    PubMed

    Taghizadeh, Hadi; Tafazzoli-Shadpour, Mohammad

    2017-01-01

    Arterial wall tissues are sensitive to their mechanical surroundings and remodel their structure and mechanical properties when subjected to mechanical stimuli such as increased arterial pressure. Such remodeling is evident in hypertension and aging. Aging is characterized by stiffening of the artery wall which is assigned to disturbed elastin function and increased collagen content. To better understand and provide new insight on microstructural changes induced by aging, the lamellar model of the aortic media was utilized to characterize and compare wall structure and mechanical behavior of the young and old human thoracic aortic samples. Such model regards arterial media as two sets of alternating concentric layers, namely sheets of elastin and interlamellar layers. Histological and biaxial tests were performed and microstructural features and stress-strain curves of media were evaluated in young and old age groups. Then using optimization algorithms and hyperelastic constitutive equations the stress-strain curves of layers were evaluated for both age groups. Results indicated slight elevation in the volume fraction of interlamellar layer among old subjects most probably due to age related collagen deposition. Aging indicated substantial stiffening of interlamellar layers accompanied by noticeable softening of elastic lamellae. The general significant stiffening of old samples were attributed to both increase of volume fraction of interlamellar layers and earlier recruitment of collagen fibers during load bearing due to functional loss of elastin within wall lamellae. Mechanical characterization of lamellar structure of wall media is beneficial in study of arterial remodeling in response to alternated mechanical environment in aging and clinical conditions through coupling of wall microstructure and mechanical behavior.

  9. Method of long-term corrosion-mechanical tests of metal of gas industry pipes

    SciTech Connect

    Gutman, E.M.; Zainullin, R.S.

    1987-10-01

    The resistance of the metal of gas industry pipes to hydrogen-sulfide (sulfide) cracking is usually evaluated on the basis of the results of long-term corrosion-mechanical tests on cylindrical specimens (diameter 6 mm) in the conditions of uniaxial tensile loading generated by the force constant with time. Because of the comparatively large dimensions of devices for producing the stress state in these specimens, it is difficult to carry out large-scale corrosion-mechanical tests. The authors assume that it is more advantageous to evaluate the hydrogen-sulfide cracking resistance of gas industry pipes on the basis of the results of corrosion-mechanical tests on semicircular specimens compressed or tensile-loaded at the ends. The method proposed was used in long-term corrosion-mechanical tests on the metal of seamless pipes made of low-alloy (08G2SFT) and low-carbon (St20) steels. The steel with the lower ratio of the yield stress to ultimate strength k/sub TB/ is characterized by a higher limit of the long-term corrosion strength expressed in the fractions of the yield stress of the metal. This indicates that it is useful to take into account the k/sub TB/ ratio in determining the safety factor of the strength of the gas industry pipes.

  10. Synthesis and characterization of mesoporous MgO by template-free hydrothermal method

    SciTech Connect

    Cui, Hongmei; Wu, Xiaofeng; Chen, Yunfa; Boughton, R.I.

    2014-02-01

    Highlights: • A simple synthesis of porous MgO with diameter size from 3 to 10 μm without any templates. • Effect of temperature and time were investigated. • Systematic characterization by TG/DTA, XRD, SEM, TEM, and nitrogen adsorption–desorption isotherm of MgO. • A possible formation and crystal growth mechanism of mesopores MgO is proposed. - Abstract: Mesoporous MgO particles have been synthesized through a novel template-free hydrothermal co-precipitation method using a Mg(NO{sub 3}){sub 2} solution as the magnesium source and NaCO{sub 3} as precipitant. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N{sub 2} adsorption–desorption analysis. The results indicate that the MgO samples have a disordered mesoporous structure, a large BET surface area, and a large pore volume. The effect of reaction temperature on the MgO product BET surface area was studied. A possible formation and crystal growth mechanism for mesoporous MgO is proposed.

  11. Method for Characterizing and Identifying Task Evoked Pupillary Responses During Varying Workload Levels

    DTIC Science & Technology

    2011-09-01

    Method for Characterizing and Identifying Task Evoked Pupillary Responses During Varying Workload Levels Allan Fong1, Ciara Sibley2, Joseph...have been shown to correlate with increases in mental workload. This paper proposes an automated method for characterizing and identifying task evoked...pupillary responses (TEPR) during various workload levels. This method captures findings and observations from previous TEPR studies in an automated

  12. Methods to identify and characterize developmental neurotoxicity for human health risk assessment. I: behavioral effects.

    PubMed Central

    Cory-Slechta, D A; Crofton, K M; Foran, J A; Ross, J F; Sheets, L P; Weiss, B; Mileson, B

    2001-01-01

    Alterations in nervous system function after exposure to a developmental neurotoxicant may be identified and characterized using neurobehavioral methods. A number of methods can evaluate alterations in sensory, motor, and cognitive functions in laboratory animals exposed to toxicants during nervous system development. Fundamental issues underlying proper use and interpretation of these methods include a) consideration of the scientific goal in experimental design, b) selection of an appropriate animal model, c) expertise of the investigator, d) adequate statistical analysis, and e) proper data interpretation. Strengths and weaknesses of the assessment methods include sensitivity, selectivity, practicality, and variability. Research could improve current behavioral methods by providing a better understanding of the relationship between alterations in motor function and changes in the underlying structure of these systems. Research is also needed to develop simple and sensitive assays for use in screening assessments of sensory and cognitive function. Assessment methods are being developed to examine other nervous system functions, including social behavior, autonomic processes, and biologic rhythms. Social behaviors are modified by many classes of developmental neurotoxicants and hormonally active compounds that may act either through neuroendocrine mechanisms or by directly influencing brain morphology or neurochemistry. Autonomic and thermoregulatory functions have been the province of physiologists and neurobiologists rather than toxicologists, but this may change as developmental neurotoxicology progresses and toxicologists apply techniques developed by other disciplines to examine changes in function after toxicant exposure. PMID:11250808

  13. Review of Collagen I Hydrogels for Bioengineered Tissue Microenvironments: Characterization of Mechanics, Structure, and Transport

    PubMed Central

    Vlachos, Pavlos P.; Rylander, Marissa Nichole

    2014-01-01

    Type I collagen hydrogels have been used successfully as three-dimensional substrates for cell culture and have shown promise as scaffolds for engineered tissues and tumors. A critical step in the development of collagen hydrogels as viable tissue mimics is quantitative characterization of hydrogel properties and their correlation with fabrication parameters, which enables hydrogels to be tuned to match specific tissues or fulfill engineering requirements. A significant body of work has been devoted to characterization of collagen I hydrogels; however, due to the breadth of materials and techniques used for characterization, published data are often disjoint and hence their utility to the community is reduced. This review aims to determine the parameter space covered by existing data and identify key gaps in the literature so that future characterization and use of collagen I hydrogels for research can be most efficiently conducted. This review is divided into three sections: (1) relevant fabrication parameters are introduced and several of the most popular methods of controlling and regulating them are described, (2) hydrogel properties most relevant for tissue engineering are presented and discussed along with their characterization techniques, (3) the state of collagen I hydrogel characterization is recapitulated and future directions are proposed. Ultimately, this review can serve as a resource for selection of fabrication parameters and material characterization methodologies in order to increase the usefulness of future collagen-hydrogel-based characterization studies and tissue engineering experiments. PMID:24923709

  14. Crystallographic, Microstructural, and Mechanical Characterization of Dynamically Processed EP741NP Superalloy

    NASA Astrophysics Data System (ADS)

    Sharma, A. D.; Sharma, A. K.; Thakur, N.

    2016-08-01

    Considerable progress has been made for the solidification of metal powders with improved properties by using varieties of metallurgical methods. However, solidification of superalloy powders offers many difficulties under traditional processes. This article outlines an extensive program being undertaken to produce monoliths of superalloys with enhanced microstructural and mechanical properties. EP741NP superalloy has been subjected to explosive shock wave loading to obtain uniform and crack-free monoliths. An axisymmetric cylindrical configuration with a plastic explosive of high-detonation velocity has been used to consolidate the superalloy powder nearer to its theoretical density (~98 pct). By careful design of experiments, detonation velocity has been measured vis-à-vis compaction of metal powders in a single-shot experiment by employing instrumented detonics. The shock-processed specimens characterized for phase, lattice parameter, and structural variation by X-ray diffraction technique show intact crystalline structure. Results obtained from Williamson-Hall method indicate small micro-strain (2.8 × 10-3) and decreased crystallite size. Energy-dispersive spectroscopy suggests no segregation within the specimens. Scanning electron microscopy shows fracture-less and micro-cracks/void-free compacts of superalloy indicating satisfactory sub-structural strength. Indentation experiments with variable loads (1.96 N and 2.94 N) performed on the shock-processed specimen cut along transverse section show high order of Vicker's micro-hardness value up to 486 H v. The tensile and compressive strengths of the superalloy monoliths cut along the consolidation axes have been found to be 824 and 834 MPa, respectively.

  15. Site characterization in densely fractured dolomite: Comparison of methods

    USGS Publications Warehouse

    Muldoon, M.; Bradbury, K.R.

    2005-01-01

    One of the challenges in characterizing fractured-rock aquifers is determining whether the equivalent porous medium approximation is valid at the problem scale. Detailed hydrogeologic characterization completed at a small study site in a densely fractured dolomite has yielded an extensive data set that was used to evaluate the utility of the continuum and discrete-fracture approaches to aquifer characterization. There are two near-vertical sets of fractures at the site; near-horizontal bedding-plane partings constitute a third fracture set. Eighteen boreholes, including five coreholes, were drilled to a depth of ???10.6 m. Borehole geophysical logs revealed several laterally extensive horizontal fractures and dissolution zones. Flowmeter and short-interval packer testing identified which of these features were hydraulically important. A monitoring system, consisting of short-interval piezometers and multilevel samplers, was designed to monitor four horizontal fractures and two dissolution zones. The resulting network consisted of >70 sampling points and allowed detailed monitoring of head distributions in three dimensions. Comparison of distributions of hydraulic head - and hydraulic conductivity determined by these two approaches suggests that even in a densely fractured-carbonate aquifer, a characterization approach using traditional long-interval monitoring wells is inadequate to characterize ground water movement for the purposes of regulatory monitoring or site remediation. In addition, traditional multiwell pumping tests yield an average or bulk hydraulic conductivity that is not adequate for predicting rapid ground water travel times through the fracture network, and the pumping test response does not appear to be an adequate tool for assessing whether the porous medium approximation is valid. Copyright ?? 2005 National Ground Water Association.

  16. Site characterization in densely fractured dolomite: comparison of methods.

    PubMed

    Muldoon, Maureen; Bradbury, Ken R

    2005-01-01

    One of the challenges in characterizing fractured-rock aquifers is determining whether the equivalent porous medium approximation is valid at the problem scale. Detailed hydrogeologic characterization completed at a small study site in a densely fractured dolomite has yielded an extensive data set that was used to evaluate the utility of the continuum and discrete-fracture approaches to aquifer characterization. There are two near-vertical sets of fractures at the site; near-horizontal bedding-plane partings constitute a third fracture set. Eighteen boreholes, including five coreholes, were drilled to a depth of approximately 10.6 m. Borehole geophysical logs revealed several laterally extensive horizontal fractures and dissolution zones. Flowmeter and short-interval packer testing identified which of these features were hydraulically important. A monitoring system, consisting of short-interval piezometers and multilevel samplers, was designed to monitor four horizontal fractures and two dissolution zones. The resulting network consisted of >70 sampling points and allowed detailed monitoring of head distributions in three dimensions. Comparison of distributions of hydraulic head and hydraulic conductivity determined by these two approaches suggests that even in a densely fractured-carbonate aquifer, a characterization approach using traditional long-interval monitoring wells is inadequate to characterize ground water movement for the purposes of regulatory monitoring or site remediation. In addition, traditional multiwell pumping tests yield an average or bulk hydraulic conductivity that is not adequate for predicting rapid ground water travel times through the fracture network, and the pumping test response does not appear to be an adequate tool for assessing whether the porous medium approximation is valid.

  17. Molecular mechanics methods for individual carbon nanotubes and nanotube assemblies

    NASA Astrophysics Data System (ADS)

    Eberhardt, Oliver; Wallmersperger, Thomas

    2015-04-01

    Since many years, carbon nanotubes (CNTs) have been considered for a wide range of applications due to their outstanding mechanical properties. CNTs are tubular structures, showing a graphene like hexagonal lattice. Our interest in the calculation of the mechanical properties is motivated by several applications which demand the knowledge of the material behavior. One application in which the knowledge of the material behavior is vital is the CNT based fiber. Due to the excellent stiffness and strength of the individual CNTs, these fibers are expected to be a promising successor for state of the art carbon fibers. However, the mechanical properties of the fibers fall back behind the properties of individual CNTs. It is assumed that this gap in the properties is a result of the van-der-Waals interactions of the individual CNTs within the fiber. In order to understand the mechanical behavior of the fibers we apply a molecular mechanics approach. The mechanical properties of the individual CNTs are investigated by using a modified structural molecular mechanics approach. This is done by calculating the properties of a truss-beam element framework representing the CNT with the help of a chemical force field. Furthermore, we also investigate the interactions of CNTs arranged in basic CNT assemblies, mimicking the ones in a simple CNT fiber. We consider the van-der-Waals interactions in the structure and calculate the potential surface of the CNT assemblies.

  18. Mechanical properties of plastics predetermined by empirical method

    NASA Technical Reports Server (NTRS)

    Lohr, J. J.; Parker, J. A.

    1964-01-01

    To predetermine the mechanical properties of rigid plastics as a function of plasticizer content and composition, a set of equations has been empirically derived. These relate strain rate, yield stress, temperature, and weight fraction of the plasticizer.

  19. Vibrating-traction method for mechanical joint distraction.

    PubMed

    Minagi, S; Sakiya, M; Sato, T; Matsunaga, T; Natsuaki, N

    2000-08-01

    Mechanical static traction has been adopted as one of the treatment procedures for joint diseases and fractures. The effect of mechanical vibration on the mechanical traction of the temporomandibular joint was studied in six human subjects. A mechanical traction force of 2000 gf was applied as a dynamic traction force with mechanical vibration or as a static traction force. The dynamic traction force with vibration was applied for 5 min to the right temporomandibular joint using a vibrating-traction apparatus which generated mechanical vibrations of 1000, 3000 or 4000 Hz. Application of a static traction force for 5 min was used as a control condition. Vertical condylar displacement was mathematically evaluated from the deviation of the mandible using Eddy current displacement sensors which were attached to the maxillary dental arch. Among the three vibration frequencies, 3000 Hz resulted in the maximum vertical condylar displacement for all six subjects, showing the mean condylar displacement of 668+/-242 microm. In contrast, vibrations of 1000 and 4000 Hz showed a smaller traction effect. Application of the static traction force for 5 min resulted in a mean vertical condylar displacement of 5.7+/-4.9 microm, showing almost no traction effect to the joint. From the results of this study, it was revealed that vibrating traction could distract a joint more effectively than could static traction and that the traction force necessary for effective vibrating traction was less than that for static traction.

  20. Methods of failure and reliability assessment for mechanical heart pumps.

    PubMed

    Patel, Sonna M; Allaire, Paul E; Wood, Houston G; Throckmorton, Amy L; Tribble, Curt G; Olsen, Don B

    2005-01-01

    Medical Instrumentation (AAMI), and the Bethesda Conference. It further discusses studies that evaluate the failure, reliability, and safety of artificial blood pumps including in vitro and in vivo testing. A descriptive summary of mechanical and human error studies and methods of artificial blood pumps is detailed.

  1. Development of nanoindentation techniques for characterizing local mechanical properties of soft materials

    NASA Astrophysics Data System (ADS)

    Wood, Charles David

    Indentation has become a popular mechanical characterization technique due to the promise of high-resolution maps of material stiffness. Due to the far-reaching nature of the testing framework, indentation tests can occur on nearly any material type and on any length scale. In this dissertation, we will look at three different materials systems and demonstrate new and unique uses for the indentation framework. These results will provide information not available by other methodologies, thereby proving its universal value. Two different indentation schemes are employed, either probing the top surface of cross-section samples or by probing into the thickness of a thin film. The differences between each of the studies highlight the importance of sample geometry/orientation, contact conditions, material response, etc. First, we will use indentation to probe local regions near carbon nanotube/glass fiber hybrid composites in an epoxy matrix. Indentations were performed to determine the radial gradient of modulus enhancements from the glass fiber surface. The results from indentation demonstrated that spatial reinforcement due to the presence of nanotubes was tied to fiber morphology and not the local morphology of carbon nanotubes. Secondly, we look at rubber and filler interaction on two different levels; macroscale and nanoscale. On the nanoscale, we show that interactions at the filler/polymer interface create regions of altered polymer mobility. These regions are influenced by geometric and chemical confinement, which increase the stiffness of these small regions (< 200nm). We employ two different indentation methods to highlight how contact orientation determines the nature of our results. Ultra-soft materials, such as hydrogels and tissues, pose rather unique challenges when they are tested mechanically. However, with tissues and gels, the sensitivity of the machines is challenged and therefore protocols must be developed to produce accurate results. We validate

  2. Mechanical Characterization of Photo-crosslinked, Thermoresponsive Hydrogel Thin Films via AFM Nanoindentation

    NASA Astrophysics Data System (ADS)

    Le, Thao; Aidala, Katherine; Hayward, Ryan

    2014-03-01

    Thin hydrogel films with patterned swelling are known to buckle into programmed three-dimensional shapes, offering approaches to fabricate reversibly self-folding micro-devices for actuators and drug delivery devices. To precisely control the shapes adopted, it is important to quantitatively understand the relationship between swelling and mechanical properties. Furthermore, to understand the buckling pathways and the mechanical responses of the swelled materials, it is also important to identify how the gels undergo stress relaxation. However, the low moduli, high water contents, and micrometer-scale thicknesses of these materials have so far made mechanical characterization difficult. In this study, we use an AFM nanoindentation technique to characterize the mechanical properties of photo-crosslinked, thermoresponsive poly(N-isopropylacrylamide) hydrogel thin films. Simultaneously, we conduct stress relaxation experiments at microscopic indentation lengths to differentiate between the effects of viscoelastic and poroelastic response mechanisms. This research was funded by the Army Research Office through W911NF-11-1-0080 and the NSF Materials Research Science and Engineering Center at the University of Massachusetts through DMR-0820506.

  3. Tunable mechanical monolithic sensors for large band low frequency monitoring and characterization of sites and structures

    NASA Astrophysics Data System (ADS)

    Barone, F.; Giordano, G.; Acernese, F.; Romano, R.

    2016-10-01

    Among the different mechanical architectures present in literature, the Watts linkage is one of the most promising ones for the implementation of a new class of mechanical accelerometers (horizontal, vertical and angular). In this paper, we present monolithic implementations of uniaxial and triaxial mechanical seismometers and accelerometers based on the UNISA Folded Pendulum mechanical configuration, optimized for low frequency characterization of sites (including underground sites) and structures as inertial sensor (seismometer). This mechanical architecture allows the design and implementation of very large band monolithic sensors (10-7Hz 102 Hz), whose sensitivities for the most common applications are defined by the noise introduced by their readouts (e.g. ¡ 10-12 m/sqrt(Hz) with classical LVDT readouts). These unique features, coupled other relevant properties like scalability, compactness, lightness, high directivity, frequency tunability (typical resonance frequencies in the band 10-1 Hz 102 Hz), very high immunity to environmental noises and low cost make this class of sensors very effective for the implementation of uniaxial (horizontal and/or vertical) and triaxial seismometers and accelerometers for ground, space and underwater applications, including UHV and cryogenics ones. Typical applications of this class of monolithic sensors are in the field of earthquake engineering, seismology, geophysics, civil engineering, characterization of sites (including underground sites), structures (e.g. buildings, bridges, historical monuments), and, in general, in all applications requiring large band-low frequency performances coupled with high sensitivities and compactness.

  4. Nondestructive testing and characterization of residual stress field using an ultrasonic method

    NASA Astrophysics Data System (ADS)

    Song, Wentao; Xu, Chunguang; Pan, Qinxue; Song, Jianfeng

    2016-03-01

    To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient field by ultrasonic method is proposed based on acoustoelasticity theory. By carrying out theoretical analysis, the sensitivity coefficients of different types of ultrasonic are obtained by taking the low carbon steel(12%C) as a research object. By fixing the interval distance between sending and receiving transducers, the mathematical expressions of the change of stress and the variation of time are established. To design one sending-one receiving and oblique incidence ultrasonic detection probes, according to Snell law, the critically refracted longitudinal wave (LCR wave) is excited at a certain depth of the fixed distance of the tested components. Then, the relationship between the depth of LCR wave detection and the center frequency of the probe in Q235 steel is obtained through experimental study. To detect the stress gradient in the depth direction, a stress gradient LCR wave detection model is established, through which the stress gradient formula is derived by the relationship between center frequency and detecting depth. A C-shaped stress specimen of Q235 steel is designed to conduct stress loading tests, and the stress is measured with the five group probes at different center frequencies. The accuracy of ultrasonic testing is verified by X-ray stress analyzer. The stress value of each specific depth is calculated using the stress gradient formula. Accordingly, the ultrasonic characterization of residual stress field is realized. Characterization results show that the stress gradient distribution is consistent with the simulation in ANSYS. The new technology can be widely applied in the detection of the residual stress gradient field caused by mechanical processing, such as welding and shot peening.

  5. On the characterization of the heterogeneous mechanical response of human brain tissue.

    PubMed

    Forte, Antonio E; Gentleman, Stephen M; Dini, Daniele

    2016-12-08

    The mechanical characterization of brain tissue is a complex task that scientists have tried to accomplish for over 50 years. The results in the literature often differ by orders of magnitude because of the lack of a standard testing protocol. Different testing conditions (including humidity, temperature, strain rate), the methodology adopted, and the variety of the species analysed are all potential sources of discrepancies in the measurements. In this work, we present a rigorous experimental investigation on the mechanical properties of human brain, covering both grey and white matter. The influence of testing conditions is also shown and thoroughly discussed. The material characterization performed is finally adopted to provide inputs to a mathematical formulation suitable for numerical simulations of brain deformation during surgical procedures.

  6. Design and Characterization of Mechanism-Based Inhibitors for the Tyrosine Aminomutase SgTAM

    SciTech Connect

    Montavon,T.; Christianson, C.; Festin, G.; Shen, B.; Bruner, S.

    2008-01-01

    The synthesis and evaluation of two classes of inhibitors for SgTAM, a 4-methylideneimidazole-5-one (MIO) containing tyrosine aminomutase, are described. A mechanism-based strategy was used to design analogs that mimic the substrate or product of the reaction and form covalent interactions with the enzyme through the MIO prosthetic group. The analogs were characterized by measuring inhibition constants and X-ray crystallographic structural analysis of the co-complexes bound to the aminomutase, SgTAM.

  7. Mining Host-Pathogen Protein Interactions to Characterize Burkholderia mallei Infectivity Mechanisms

    DTIC Science & Technology

    2015-03-04

    RESEARCH ARTICLE Mining Host-Pathogen Protein Interactions to Characterize Burkholderia mallei Infectivity Mechanisms Vesna Memišević1, Nela...were shown to attenuate disease progression in an aerosol infection animal model using the virulent Burkholderia mallei ATCC 23344 strain. Here, we...host-cell environment for the successful establishment of host infections and intracellular spread. PLOS Computational Biology | DOI:10.1371

  8. The adapted augmented Lagrangian method: a new method for the resolution of the mechanical frictional contact problem

    NASA Astrophysics Data System (ADS)

    Bussetta, Philippe; Marceau, Daniel; Ponthot, Jean-Philippe

    2012-02-01

    The aim of this work is to propose a new numerical method for solving the mechanical frictional contact problem in the general case of multi-bodies in a three dimensional space. This method is called adapted augmented Lagrangian method (AALM) and can be used in a multi-physical context (like thermo-electro-mechanical fields problems). This paper presents this new method and its advantages over other classical methods such as penalty method (PM), adapted penalty method (APM) and, augmented Lagrangian method (ALM). In addition, the efficiency and the reliability of the AALM are proved with some academic problems and an industrial thermo-electromechanical problem.

  9. Mechanism for and method of biasing magnetic sensor

    DOEpatents

    Kautz, David R.

    2007-12-04

    A magnetic sensor package having a biasing mechanism involving a coil-generated, resistor-controlled magnetic field for providing a desired biasing effect. In a preferred illustrated embodiment, the package broadly comprises a substrate; a magnetic sensor element; a biasing mechanism, including a coil and a first resistance element; an amplification mechanism; a filter capacitor element; and an encapsulant. The sensor is positioned within the coil. A current applied to the coil produces a biasing magnetic field. The biasing magnetic field is controlled by selecting a resistance value for the first resistance element which achieves the desired biasing effect. The first resistance element preferably includes a plurality of selectable resistors, the selection of one or more of which sets the resistance value.

  10. Method for characterization of the redox condition of cementitious materials

    SciTech Connect

    Almond, Philip M.; Langton, Christine A.; Stefanko, David B.

    2015-12-22

    Disclosed are methods for determining the redox condition of cementitious materials. The methods are leaching methods that utilize an in situ redox indicator that is present in the cementitious materials as formed. The in situ redox indicator leaches from cementitious material and, when the leaching process is carried out under anaerobic conditions can be utilized to determine the redox condition of the material. The in situ redox indicator can exhibit distinct characteristics in the leachate depending upon the redox condition of the indicator.

  11. Methods for characterizing, classifying, and identifying unknowns in samples

    DOEpatents

    Grate, Jay W [West Richland, WA; Wise, Barry M [Manson, WA

    2002-01-01

    Disclosed is a method for taking the data generated from an array of responses from a multichannel instrument, and determining the characteristics of a chemical in the sample without the necessity of calibrating or training the instrument with known samples containing the same chemical. The characteristics determined by the method are then used to classify and identify the chemical in the sample. The method can also be used to quantify the concentration of the chemical in the sample.

  12. Methods for characterizing, classifying, and identifying unknowns in samples

    DOEpatents

    Grate, Jay W.; Wise, Barry M.

    2003-08-12

    Disclosed is a method for taking the data generated from an array of responses from a multichannel instrument, and determining the characteristics of a chemical in the sample without the necessity of calibrating or training the instrument with known samples containing the same chemical. The characteristics determined by the method are then used to classify and identify the chemical in the sample. The method can also be used to quantify the concentration of the chemical in the sample.

  13. Gelation Mechanisms and Characterization of Electrochemically Generated Protein Films at Metal Interfaces

    NASA Astrophysics Data System (ADS)

    Martin, Elizabeth J.

    Although the electrochemical behavior of metals used in orthopedic implants has been studied extensively, the material interactions with proteins during corrosion processes remains poorly understood. Some studies suggest that metal-protein interactions accelerate corrosion, while others suggest that proteins protect the material from degradation. Corrosion of implant materials is a major concern due to the metal ion release that can sometimes cause adverse local tissue reactions and ultimately, failure of the implant. The initial purpose of this research was therefore to study the corrosion behavior of CoCrMo, an alloy commonly used in hip replacements, with a quartz crystal microbalance (QCM) in physiologically relevant media. The QCM enables in situ characterization of surface changes accompanying corrosion and is sensitive to viscoelastic effects at its surface. Results of QCM studies in proteinaceous media showed film deposition on the alloy surface under electrochemical conditions that otherwise produced mass loss if proteins were not present in the electrolyte. Additional studies on pure Co, Cr, and Mo demonstrated that the protein films also form on Mo surfaces after a release of molybdate ions, suggesting that these ions are essential for film formation. The electrochemically generated protein films are reminiscent of carbonaceous films that form on implant surfaces in vivo, therefore a second goal of the research was to delineate mechanisms that cause the films to form. In the second stage of this research, electrochemical QCM tests were conducted on models of the CoCrMo system consisting of Cr electrodes in proteinaceous or polymeric media containing dissolved molybdate ions. Studies indicated that films can be generated through electrochemical processes so long as both amine functional groups and molybdate ions are present in the electrolyte solution. These results suggest that the films form due to an ionic cross-linking reaction between the positively

  14. Gradient plasticity crack tip characterization by means of the extended finite element method

    NASA Astrophysics Data System (ADS)

    Martínez-Pañeda, E.; Natarajan, S.; Bordas, S.

    2017-01-01

    Strain gradient plasticity theories are being widely used for fracture assessment, as they provide a richer description of crack tip fields by incorporating the influence of geometrically necessary dislocations. Characterizing the behavior at the small scales involved in crack tip deformation requires, however, the use of a very refined mesh within microns to the crack. In this work a novel and efficient gradient-enhanced numerical framework is developed by means of the extended finite element method (X-FEM). A mechanism-based gradient plasticity model is employed and the approximation of the displacement field is enriched with the stress singularity of the gradient-dominated solution. Results reveal that the proposed numerical methodology largely outperforms the standard finite element approach. The present work could have important implications on the use of microstructurally-motivated models in large scale applications. The non-linear X-FEM code developed in MATLAB can be downloaded from http://www.empaneda.com/codes.

  15. Review of geophysical characterization methods used at the Hanford Site

    SciTech Connect

    GV Last; DG Horton

    2000-03-23

    This paper presents a review of geophysical methods used at Hanford in two parts: (1) shallow surface-based geophysical methods and (2) borehole geophysical methods. This review was not intended to be ``all encompassing'' but should represent the vast majority (>90% complete) of geophysical work conducted onsite and aimed at hazardous waste investigations in the vadose zone and/or uppermost groundwater aquifers. This review did not cover geophysical methods aimed at large-scale geologic structures or seismicity and, in particular, did not include those efforts conducted in support of the Basalt Waste Isolation Program. This review focused primarily on the more recent efforts.

  16. Biophysics of cancer progression and high-throughput mechanical characterization of biomaterials

    NASA Astrophysics Data System (ADS)

    Osborne, Lukas Dylan

    Cancer metastasis involves a series of events known as the metastatic cascade. In this complex progression, cancer cells detach from the primary tumor, invade the surrounding stromal space, transmigrate the vascular system, and establish secondary tumors at distal sites. Specific mechanical phenotypes are likely adopted to enable cells to successfully navigate the mechanical environments encountered during metastasis. To examine the role of cell mechanics in cancer progression, I employed force-consistent biophysical and biochemical assays to characterize the mechanistic links between stiffness, stiffness response and cell invasion during the epithelial to mesenchymal transition (EMT). EMT is an essential physiological process, whose abnormal reactivation has been implicated in the detachment of cancer cells from epithelial tissue and their subsequent invasion into stromal tissue. I demonstrate that epithelial-state cells respond to force by evoking a stiffening response, and that after EMT, mesenchymal-state cells have reduced stiffness but also lose the ability to increase their stiffness in response to force. Using loss and gain of function studies, two proteins are established as functional connections between attenuated stiffness and stiffness response and the increased invasion capacity acquired after EMT. To enable larger scale assays to more fully explore the connection between biomechanics and cancer, I discuss the development of an automated array high throughput (AHT) microscope. The AHT system is shown to implement passive microbead rheology to accurately characterize the mechanical properties of biomaterials. Compared to manually performed mechanical characterizations, the AHT system executes experiments in two orders of magnitude less time. Finally, I use the AHT microscope to study the effect of gain of function oncogenic molecules on cell stiffness. I find evidence that our assay can identify alterations in cell stiffness due to constitutive

  17. Apparatus and method for the characterization of respirable aerosols

    DOEpatents

    Clark, Douglas K.; Hodges, Bradley W.; Bush, Jesse D.; Mishima, Jofu

    2016-05-31

    An apparatus for the characterization of respirable aerosols, including: a burn chamber configured to selectively contain a sample that is selectively heated to generate an aerosol; a heating assembly disposed within the burn chamber adjacent to the sample; and a sampling segment coupled to the burn chamber and configured to collect the aerosol such that it may be analyzed. The apparatus also includes an optional sight window disposed in a wall of the burn chamber such that the sample may be viewed during heating. Optionally, the sample includes one of a Lanthanide, an Actinide, and a Transition metal.

  18. Computational Methods for Structural Mechanics and Dynamics, part 1

    NASA Technical Reports Server (NTRS)

    Stroud, W. Jefferson (Editor); Housner, Jerrold M. (Editor); Tanner, John A. (Editor); Hayduk, Robert J. (Editor)

    1989-01-01

    The structural analysis methods research has several goals. One goal is to develop analysis methods that are general. This goal of generality leads naturally to finite-element methods, but the research will also include other structural analysis methods. Another goal is that the methods be amenable to error analysis; that is, given a physical problem and a mathematical model of that problem, an analyst would like to know the probable error in predicting a given response quantity. The ultimate objective is to specify the error tolerances and to use automated logic to adjust the mathematical model or solution strategy to obtain that accuracy. A third goal is to develop structural analysis methods that can exploit parallel processing computers. The structural analysis methods research will focus initially on three types of problems: local/global nonlinear stress analysis, nonlinear transient dynamics, and tire modeling.

  19. Hidden algebra method (quasi-exact-solvability in quantum mechanics)

    SciTech Connect

    Turbiner, Alexander

    1996-02-20

    A general introduction to quasi-exactly-solvable problems of quantum mechanics is presented. Main attention is given to multidimensional quasi-exactly-solvable and exactly-solvable Schroedinger operators. Exact-solvability of the Calogero and Sutherland N-body problems ass ociated with an existence of the hidden algebra slN is discussed extensively.

  20. Spectroscopic characterization of the binding mechanism of fluorescein and carboxyfluorescein in human serum albumin

    NASA Astrophysics Data System (ADS)

    Sulaiman, Saba A. J.; Kulathunga, H. Udani; Abou-Zied, Osama K.

    2015-03-01

    Fluorescein (FL) and some of its precursors have proven to be effective fluorescent tracers in pharmaceutical and medical applications owing to their high quantum yield of fluorescence in physiological conditions and their high membrane permeability. In order to protect FL from metabolic effects during the process of its delivery, human serum albumin (HSA) has been used as a carrier because of its compatibility with the human body. In the present work, we used spectroscopic methods to characterize the binding mechanisms of FL and one of its derivatives, 5(6)- carboxyfluorescein (CFL), in the HSA protein. The absorbance change of the two ligands (FL and CFL) was quantified as a function of the HSA concentration and the results indicate a moderate binding strength for the two ligands inside HSA (1.00 +/- 0.12 x 104 M-1). The quenching effect of FL(CFL) on the fluorescence intensity of W214 (the sole tryptophan in HSA) indicates that FL and CFL occupy Site I in the protein which is known to bind several hydrophobic drugs. By performing site-competitive experiments, the location of the ligands is determined to be similar to that of the anticoagulant drug warfarin. At higher ratios of [ligand]/[HSA], we observed an upward curvature in the Stern-Volmer plots which indicates that the ligands occupy more pockets in Site I, close to W214. Our results indicate that both ligands bind in HSA with a moderate strength that should not affect their release when used as fluorescent reporters. The chemical and physical identities of the two ligands are also preserved inside the HSA binding sites.

  1. Characterization of Mechanical Properties of Nuclear Graphite Using Subsize Specimens and Reusing Tested Specimens

    SciTech Connect

    Ji Hyun, Yoon; Byun, Thak Sang; Strizak, Joe P; Snead, Lance Lewis

    2011-01-01

    The mechanical properties of NBG-18 nuclear grade graphite have been characterized using small specimen test techniques and statistical treatment on the test results. New fracture strength and toughness test techniques were developed to use subsize cylindrical specimens with glued heads and to reuse their broken halves. Three sets of subsize cylindrical specimens with the different diameters of 4 mm, 8 mm, and 12 mm were tested to obtain tensile fracture strength. The longer piece of the broken halves was cracked from side surfaces and tested under three-point bend loading to obtain fracture toughness. Both the strength and fracture toughness data were analyzed using Weibull distribution models focusing on size effect. The mean fracture strength decreased from 22.9 MPa to 21.5 MPa as the diameter increased from 4 mm to 12 mm, and the mean strength of 15.9 mm diameter standard specimen, 20.9 MPa, was on the extended trend line. These fracture strength data indicate that in the given diameter range the size effect is not significant and much smaller than that predicted by the Weibull statistics-based model. Further, no noticeable size effect existed in the fracture toughness data, whose mean values were in a narrow range of 1.21 1.26 MPa. The Weibull moduli measured for fracture strength and fracture toughness datasets were around 10. It is therefore believed that the small or negligible size effect enables to use the subsize specimens and that the new fracture toughness test method to reuse the broken specimens to help minimize irradiation space and radioactive waste.

  2. Ghrelin prevents tumour- and cisplatin-induced muscle wasting: characterization of multiple mechanisms involved

    PubMed Central

    Chen, Ji-an; Splenser, Andres; Guillory, Bobby; Luo, Jiaohua; Mendiratta, Meenal; Belinova, Blaga; Halder, Tripti; Zhang, Guohua; Li, Yi-Ping; Garcia, Jose M

    2015-01-01

    Background Cachexia and muscle atrophy are common consequences of cancer and chemotherapy administration. The novel hormone ghrelin has been proposed as a treatment for this condition. Increases in food intake and direct effects on muscle proteolysis and protein synthesis are likely to mediate these effects, but the pathways leading to these events are not well understood. Methods We characterized molecular pathways involved in muscle atrophy induced by Lewis lung carcinoma (LLC) tumour implantation in c57/bl6 adult male mice and by administration of the chemotherapeutic agent cisplatin in mice and in C2C12 myotubes. The effects of exogenous ghrelin administration and its mechanisms of action were examined in these settings. Results Tumour implantation and cisplatin induced muscle atrophy by activating pro-inflammatory cytokines, p38-C/EBP-β, and myostatin, and by down-regulating Akt, myoD, and myogenin, leading to activation of ubiquitin-proteasome-mediated proteolysis and muscle weakness. Tumour implantation also increased mortality. In vitro, cisplatin up-regulated myostatin and atrogin-1 by activating C/EBP-β and FoxO1/3. Ghrelin prevented these changes in vivo and in vitro, significantly increasing muscle mass (P < 0.05 for LLC and P < 0.01 for cisplatin models) and grip strength (P = 0.038 for LLC and P = 0.001 for cisplatin models) and improving survival (P = 0.021 for LLC model). Conclusion Ghrelin prevents muscle atrophy by down-regulating inflammation, p38/C/EBP-β/myostatin, and activating Akt, myogenin, and myoD. These changes appear, at least in part, to target muscle cells directly. Ghrelin administration in this setting is associated with improved muscle strength and survival. PMID:26136189

  3. Characterization of the dominant structural vibration of hearing aid receivers: Towards the moderation of mechanical feedback in hearing aids

    NASA Astrophysics Data System (ADS)

    Varanda, Brenno R.

    Presented are the results from the experimental, analytical, and computational analyses accomplished to characterize the mechanical vibration of hearing aid receivers, a key electro-acoustic component of hearing aids. The function of a receiver in a hearing aid is to provide an amplified sound signal into the ear canal. Unfortunately, as the receiver produces sound, it also undergoes vibration which can be transmitted through the hearing aid package to the microphones, resulting in undesirable feedback oscillations. To gain more knowledge and control on the source of these feedback oscillations, a dynamic rigid body model of the receiver is proposed. The rigid body model captures the essential dynamic features of the receiver. The model is represented by two hinged rigid bodies, under an equal and opposite dynamic moment load, and connected to each other by a torsional spring and damper. The mechanical coupling ratio between the two rigid bodies is proved to be acoustically independent. A method is introduced to estimate the parameters for the proposed model using experimental data. An equivalent finite element analysis model is established and tested against a known and characterized mechanical attachment. The simulated model successfully predicts the structural dynamic response showing excellent agreement between the finite element analysis and measured results.

  4. Ultrasound Imaging Techniques for Spatiotemporal Characterization of Composition, Microstructure, and Mechanical Properties in Tissue Engineering.

    PubMed

    Deng, Cheri X; Hong, Xiaowei; Stegemann, Jan P

    2016-08-01

    Ultrasound techniques are increasingly being used to quantitatively characterize both native and engineered tissues. This review provides an overview and selected examples of the main techniques used in these applications. Grayscale imaging has been used to characterize extracellular matrix deposition, and quantitative ultrasound imaging based on the integrated backscatter coefficient has been applied to estimating cell concentrations and matrix morphology in tissue engineering. Spectral analysis has been employed to characterize the concentration and spatial distribution of mineral particles in a construct, as well as to monitor mineral deposition by cells over time. Ultrasound techniques have also been used to measure the mechanical properties of native and engineered tissues. Conventional ultrasound elasticity imaging and acoustic radiation force imaging have been applied to detect regions of altered stiffness within tissues. Sonorheometry and monitoring of steady-state excitation and recovery have been used to characterize viscoelastic properties of tissue using a single transducer to both deform and image the sample. Dual-mode ultrasound elastography uses separate ultrasound transducers to produce a more potent deformation force to microscale characterization of viscoelasticity of hydrogel constructs. These ultrasound-based techniques have high potential to impact the field of tissue engineering as they are further developed and their range of applications expands.

  5. Computational Biology Methods for Characterization of Pluripotent Cells.

    PubMed

    Araúzo-Bravo, Marcos J

    2016-01-01

    Pluripotent cells are a powerful tool for regenerative medicine and drug discovery. Several techniques have been developed to induce pluripotency, or to extract pluripotent cells from different tissues and biological fluids. However, the characterization of pluripotency requires tedious, expensive, time-consuming, and not always reliable wet-lab experiments; thus, an easy, standard quality-control protocol of pluripotency assessment remains to be established. Here to help comes the use of high-throughput techniques, and in particular, the employment of gene expression microarrays, which has become a complementary technique for cellular characterization. Research has shown that the transcriptomics comparison with an Embryonic Stem Cell (ESC) of reference is a good approach to assess the pluripotency. Under the premise that the best protocol is a computer software source code, here I propose and explain line by line a software protocol coded in R-Bioconductor for pluripotency assessment based on the comparison of transcriptomics data of pluripotent cells with an ESC of reference. I provide advice for experimental design, warning about possible pitfalls, and guides for results interpretation.

  6. Characterization of activated sludge exocellular polymers using several cation-associated extraction methods.

    PubMed

    Park, Chul; Novak, John T

    2007-04-01

    Evaluation of prior research and preliminary investigations in our laboratory led to the development of an extraction strategy that can be used to target different cations in activated sludge floc and extract their associated extracellular polymeric substances (EPS). The methods we used were the cation exchange resin (CER) procedure, base extraction, and sulfide addition to extract EPS linked with divalent cations, Al, and Fe, respectively. A comparison of sludge cations before and after CER extraction revealed that most of Ca(2+) and Mg(2+) were removed while Fe and Al remained intact, suggesting that this method is highly selective for Ca(2+) and Mg(2+)-bound EPS. The correlation between sludge Fe and sulfide-extracted EPS was indicative of selectivity of this method for Fe-bound EPS. The base extraction was less specific than the other methods but it was the method releasing the largest amount of Al into the extract, indicating that the method extracted Al-bound EPS. Concomitantly, the composition of extracted EPS and the amino acid composition differed for the three methods, indicating that EPS associated with different metals were not the same. The change in EPS following anaerobic and aerobic digestion was also characterized by the three extraction methods. CER-extracted EPS were reduced after aerobic digestion while they changed little by anaerobic digestion. On the other hand, anaerobic digestion was associated with the decrease in sulfide-extracted EPS. These results suggest that different types of cation-EPS binding mechanisms exist in activated sludge and that each cation-associated EPS fraction imparts unique digestion characteristics to activated sludge.

  7. Material Characterization methods in InAs/InAsSb Type-II superlattices

    SciTech Connect

    Kadlec, Emil Andrew

    2016-12-01

    This document presents a thesis proposal with three topics. It describes an in-depth comparison of lifetime measurement methods for material characterization of InAs/InAsSb type-II superlattices; develops a characterization method based on the 2nd harmonic of a modulated carrier density; and relates lifetime measurements to device performance.

  8. Mechanical and optical characterization of tungsten oxynitride (W-O-N) nano-coatings

    NASA Astrophysics Data System (ADS)

    Nunez, Oscar Roberto

    Aation and cation doping of transition metal oxides has recently gained attention as a viable option to design materials for application in solar energy conversion, photo-catalysis, transparent electrodes, photo-electrochemical cells, electrochromics and flat panel displays in optoelectronics. Specifically, nitrogen doped tungsten oxide (WO3) has gained much attention for its ability to facilitate optical property tuning while also demonstrating enhanced photo-catalytic and photochemical properties. The effect of nitrogen chemistry and mechanics on the optical and mechanical properties of tungsten oxynitride (W-O-N) nano-coatings is studied in detail in this work. The W-O-N coatings were deposited by direct current (DC) sputtering to a thickness of ˜100 nm and the structural, compositional, optical and mechanical properties were characterized in order to gain a deeper understanding of the effects of nitrogen incorporation and chemical composition. All the W-O-N coatings fabricated under variable nitrogen gas flow rate were amorphous. X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS) measurements revealed that nitrogen incorporation is effective only for a nitrogen gas flow rates ?9 sccm. Optical characterization using ultraviolet-visible-near infrared (UV-VIS-NIR) spectroscopy and spectroscopic ellipsometry (SE) indicate that the nitrogen incorporation induced effects on the optical parameters is significant. The band gap (Eg) values decreased from ˜2.99 eV to ˜1.89 eV indicating a transition from insulating WO3 to metallic-like W-N phase. Nano-mechanical characterization using indentation revealed a corresponding change in mechanical properties; maximum values of 4.46 GPa and 98.5 GPa were noted for hardness and Young?s modulus, respectively. The results demonstrate a clear relationship between the mechanical, physical and optical properties of amorphous W-O-N nano-coatings. The correlation presented in this thesis could

  9. Irritable bowel syndrome: methods, mechanisms, and pathophysiology. Methods to assess visceral hypersensitivity in irritable bowel syndrome.

    PubMed

    Keszthelyi, D; Troost, F J; Masclee, A A

    2012-07-15

    Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder, characterized by recurrent abdominal pain or discomfort in combination with disturbed bowel habits in the absence of identifiable organic cause. Visceral hypersensitivity has emerged as a key hypothesis in explaining the painful symptoms in IBS and has been proposed as a "biological hallmark" for the condition. Current techniques of assessing visceral perception include the computerized barostat using rectal distensions, registering responses induced by sensory stimuli including the flexor reflex and cerebral evoked potentials, as well as brain imaging modalities such as functional magnetic resonance imaging and positron emission tomography. These methods have provided further insight into alterations in pain processing in IBS, although the most optimal method and condition remain to be established. In an attempt to give an overview of these methods, a literature search in the electronic databases PubMed and MEDLINE was executed using the search terms "assessment of visceral pain/visceral nociception/visceral hypersensitivity" and "irritable bowel syndrome." Both original articles and review articles were considered for data extraction. This review aims to discuss currently used modalities in assessing visceral perception, along with advantages and limitations, and aims also to define future directions for methodological aspects in visceral pain research. Although novel paradigms such as brain imaging and neurophysiological recordings have been introduced in the study of visceral pain, confirmative studies are warranted to establish their robustness and clinical relevance. Therefore, subjective verbal reporting following rectal distension currently remains the best-validated technique in assessing visceral perception in IBS.

  10. Development of characterization tools for reliability testing of micro-electro-mechanical system actuators

    NASA Astrophysics Data System (ADS)

    Smith, Norman F.; Eaton, William P.; Tanner, Danelle M.; Allen, James J.

    1999-08-01

    Characterization tools have been developed to study the performance characteristics and reliability of surface micromachined actuators. These tools include: (1) the ability to electrically stimulate or stress the actuator, (2) the capability to visually inspect the devices in operation, (3) a method for capturing operational information, and (4) a method to extract performance characteristics from the operational information. Additionally, a novel test structure has been developed to measure electrostatic forces developed by a comb drive actuator.

  11. Characterization of resistance mechanisms to powdery mildew (Erysiphe betae) in beet (Beta vulgaris).

    PubMed

    Fernández-Aparicio, Mónica; Prats, Elena; Emeran, Amero A; Rubiales, Diego

    2009-04-01

    Beet powdery mildew incited by Erysiphe betae is a serious foliar fungal disease of worldwide distribution causing losses of up to 30%. In the present work, we searched for resistance in a germplasm collection of 184 genotypes of Beta vulgaris including fodder (51 genotypes), garden (60 genotypes), leaf (51 genotypes), and sugar (22 genotypes) beet types. Resistant genotypes were identified in the four beet types under study. In addition, mechanisms underlying resistance were dissected through histological studies. These revealed different resistance mechanisms acting at different fungal developmental stages, i.e., penetration resistance, early and late cell death, or posthaustorial resistance. Most genotypes were able to hamper fungal development at several stages. The later are interesting for breeding aiming to resistance durability. Furthermore, characterization of defense mechanisms will be useful for further cellular and molecular studies to unravel the bases of resistance in this species.

  12. Characterization of mechanical behavior of an epithelial monolayer in response to epidermal growth factor stimulation

    SciTech Connect

    Yang, Ruiguo; Chen, Jennifer Y.; Xi, Ning; Lai, King Wai Chiu; Qu, Chengeng; Fung, Carmen Kar Man; Penn, Lynn S.; Xi, Jun

    2012-03-10

    Cell signaling often causes changes in cellular mechanical properties. Knowledge of such changes can ultimately lead to insight into the complex network of cell signaling. In the current study, we employed a combination of atomic force microscopy (AFM) and quartz crystal microbalance with dissipation monitoring (QCM-D) to characterize the mechanical behavior of A431 cells in response to epidermal growth factor receptor (EGFR) signaling. From AFM, which probes the upper portion of an individual cell in a monolayer of cells, we observed increases in energy dissipation, Young's modulus, and hysteresivity. Increases in hysteresivity imply a shift toward a more fluid-like mechanical ordering state in the bodies of the cells. From QCM-D, which probes the basal area of the monolayer of cells collectively, we observed decreases in energy dissipation factor. This result suggests a shift toward a more solid-like state in the basal areas of the cells. The comparative analysis of these results indicates a regionally specific mechanical behavior of the cell in response to EGFR signaling and suggests a correlation between the time-dependent mechanical responses and the dynamic process of EGFR signaling. This study also demonstrates that a combination of AFM and QCM-D is able to provide a more complete and refined mechanical profile of the cells during cell signaling. -- Highlights: Black-Right-Pointing-Pointer The EGF-induced cellular mechanical response is regionally specific. Black-Right-Pointing-Pointer The EGF-induced cellular mechanical response is time and dose dependent. Black-Right-Pointing-Pointer A combination of AFM and QCM-D provides a more complete mechanical profile of cells.

  13. Orientation effects in Cl + H2 inelastic collisions: characterization of the mechanisms.

    PubMed

    Aldegunde, J; Aoiz, F J; González-Sánchez, L; Jambrina, P G; de Miranda, M P; Sáez-Rábanos, V

    2012-02-28

    Based on quantum mechanical scattering (QM) calculations, we have analyzed the polarization of the product hydrogen molecule in Cl + H(2) (v = 0, j = 0) inelastic collisions. The spatial arrangements adopted by the rotational angular momentum and internuclear axis of the departing molecule have been characterized and used to prove that two distinct mechanisms, corresponding to different dynamical regimes, are responsible for the inelastic collisions. Such mechanisms, named as low-b and high-b, correlate with well defined ranges of impact parameter values, add in an essentially incoherent way, and can be clearly differentiated through the quantum mechanical polarization moment that measures the orientation of the products rotational angular momentum with respect to the scattering plane. Other directional effects turn out to fail when it comes to distinguishing the mechanisms. Quasiclassical trajectories (QCT) calculations have been used as a supplement to the purely quantum mechanical analysis. By combining QM and QCT results, which are in very good agreement, we have succeeded in obtaining a clear and meaningful picture of how the two types of collisions take place.

  14. A Fast Method of Fully Characterizing Sputtering Angular Dependence (Preprint)

    DTIC Science & Technology

    2008-06-17

    A new method has been demonstrated in which a single experiment is used to fully define the sputtering angular dependence of a given material. The...profilometry; the full sputtering angular dependence curve is then extracted using a numerical approach.

  15. Non-Intrusive Optical Diagnostic Methods for Flowfield Characterization

    NASA Technical Reports Server (NTRS)

    Tabibi, Bagher M.; Terrell, Charles A.; Spraggins, Darrell; Lee, Ja. H.; Weinstein, Leonard M.

    1997-01-01

    Non-intrusive optical diagnostic techniques such as Electron Beam Fluorescence (EBF), Laser-Induced Fluorescence (LIF), and Focusing Schlieren (FS) have been setup for high-speed flow characterization and large flowfield visualization, respectively. Fluorescence emission from the First Negative band of N2(+) with the (0,0) vibration transition (at lambda =391.44 nm) was obtained using the EBF technique and a quenching rate of N2(+)* molecules by argon gas was reported. A very high sensitivity FS system was built and applied in the High-Speed Flow Generator (HFG) at NASA LaRC. A LIF system is available at the Advanced Propulsion Laboratory (APL) on campus and a plume exhaust velocity measurement, measuring the Doppler shift from lambda = 728.7 nm of argon gas, is under way.

  16. Development of Methods of Characterizing Coal in Its Plastic State

    NASA Technical Reports Server (NTRS)

    Lloyd, W. G.

    1978-01-01

    Coal in its plastic state (typically 400-460 C) was examined by the isothermal Gieseler plastometry of seven selected coals of widely varying plastic properties. Kinetic models were proposed for the isothermal plastometric curves. Plastic behavior was compared with a variety of laboratory analyses and characterizations of these coals, including classical coal analysis; mineral analysis; microstructural analysis (extractable fractions, surface area measurement, and petrographic analysis); and thermal analysis (thermogravimetric analysis, thermomechanical analysis, and differential scanning calorimetry). The phenomenon of a sharp, large, poorly reproducible exotherm in the differential scanning calorimetric analysis of coking coals was examined. Several coal extrudates show mineral distribution, organic maceral composition and overall calorific value to be little affected by 800 F extrusion. Volatile matter and plastic properties are moderately reduced, and the network structure (as gauged by extractables) appears to be slightly degraded in the extrusion process.

  17. Mechanic-electrical transformations in the Kelvin method

    NASA Astrophysics Data System (ADS)

    Zharkikh, Yu. S.; Lysochenko, S. V.

    2017-04-01

    To explain the initiation mechanism of alternating current in an electric circuit containing the dynamic capacitor a model of mechanic- electrical transformation is suggested to use. In such a model, electric charges disposed between the capacitor plates serve as a cause of measured signal in contrast to the contact potential difference, which is considered as the main base in the Kelvin's model. If one of the plates moves periodically, then the conditions of the charges screening are changed and thereby the capacitor recharging current is arise. The measuring is based on compensation of the recharging current by current, which generated by a source of electromotive force (EMF). The compensation voltage depends on both the distribution of ions or dipoles over the studied surface and the charges creating the surface potential barrier. This voltage is independent on the bulk electro-physical characteristics of a solid.

  18. A Physical Molecular Mechanics Method for Damped Dispersion.

    PubMed

    Verma, Pragya; Wang, Bo; Fernandez, Laura E; Truhlar, Donald G

    2017-03-22

    Damped dispersion can be a significant component of the interaction energy in many physical and chemical processes, for example, physisorption and noncovalent complexation. For physically interpreting and modeling such processes, it is convenient to have an analytic method to calculate damped dispersion that is readily applicable across the entire periodic table. Of the available methods to calculate damped dispersion energy for interacting systems with overlapping charge distributions, we select symmetry-adapted perturbation theory (SAPT) as providing a reasonable definition, and of the possible analytic forms, we choose the D3(BJ) method. However, the available parameterizations of D3(BJ) include not only damped dispersion energy but also corrections for errors in specific exchange-correlation functionals. Here we present a parameterization that provides a physical measure of damped dispersion without such density functional corrections. The method generalizes an earlier method of Pernal and coworkers to all elements from hydrogen to plutonium.

  19. Nucleosome positioning in yeasts: methods, maps, and mechanisms.

    PubMed

    Lieleg, Corinna; Krietenstein, Nils; Walker, Maria; Korber, Philipp

    2015-06-01

    Eukaryotic nuclear DNA is packaged into nucleosomes. During the past decade, genome-wide nucleosome mapping across species revealed the high degree of order in nucleosome positioning. There is a conserved stereotypical nucleosome organization around transcription start sites (TSSs) with a nucleosome-depleted region (NDR) upstream of the TSS and a TSS-aligned regular array of evenly spaced nucleosomes downstream over the gene body. As nucleosomes largely impede access to DNA and thereby provide an important level of genome regulation, it is of general interest to understand the mechanisms generating nucleosome positioning and especially the stereotypical NDR-array pattern. We focus here on the most advanced models, unicellular yeasts, and review the progress in mapping nucleosomes and which nucleosome positioning mechanisms are discussed. There are four mechanistic aspects: How are NDRs generated? How are individual nucleosomes positioned, especially those flanking the NDRs? How are nucleosomes evenly spaced leading to regular arrays? How are regular arrays aligned at TSSs? The main candidates for nucleosome positioning determinants are intrinsic DNA binding preferences of the histone octamer, specific DNA binding factors, nucleosome remodeling enzymes, transcription, and statistical positioning. We summarize the state of the art in an integrative model where nucleosomes are positioned by a combination of all these candidate determinants. We highlight the predominance of active mechanisms involving nucleosome remodeling enzymes which may be recruited by DNA binding factors and the transcription machinery. While this mechanistic framework emerged clearly during recent years, the involved factors and their mechanisms are still poorly understood and require future efforts combining in vivo and in vitro approaches.

  20. Competing indentation deformation mechanisms in glass using different strengthening methods

    NASA Astrophysics Data System (ADS)

    Luo, Jian; Lezzi, Peter; Vargheese, K. Deenamma; Tandia, Adama; Harris, Jason; Mauro, John

    2016-11-01

    Chemical strengthening via ion exchange, thermal tempering, and lamination are proven techniques for strengthening of oxide glasses. For each of these techniques, the strengthening mechanism is conventionally ascribed to the linear superposition of the compressive stress profile on the glass surface. However, in this work we use molecular dynamics simulations to reveal the underlying indentation deformation mechanism beyond the simple linear superposition of compressive and indentation stresses. In particular, the plastic zone can be dramatically different from the commonly assumed hemispherical shape, which leads to a completely different stress field and resulting crack system. We show that the indentation-induced fracture is controlled by two competing mechanisms: the compressive stress itself and a potential reduction in free volume that can increase the driving force for crack formation. Chemical strengthening via ion exchange tends to escalate the competition between these two effects, while thermal tempering tends to reduce it. Lamination of glasses with differential thermal expansion falls in between. The crack system also depends on the indenter geometry and the loading stage, i.e., loading vs. after unloading. It is observed that combining thermal tempering or high free volume content with ion exchange or lamination can impart a relatively high compressive stress and reduce the driving force for crack formation. Therefore, such a combined approach might offer the best overall crack resistance for oxide glasses.

  1. Thermal-Conductivity Characterization of Gas Diffusion Layer in Proton Exchange Membrane Fuel Cells and Electrolyzers Under Mechanical Loading

    NASA Astrophysics Data System (ADS)

    Hamour, M.; Garnier, J. P.; Grandidier, J. C.; Ouibrahim, A.; Martemianov, S.

    2011-05-01

    Accurate information on the temperature field and associated heat transfer rates is particularly important for proton exchange membrane fuel cells (PEMFC) and PEM electrolyzers. An important parameter in fuel cell and electrolyzer performance analysis is the effective thermal conductivity of the gas diffusion layer (GDL) which is a solid porous medium. Usually, this parameter is introduced in modeling and performance analysis without taking into account the dependence of the GDL thermal conductivity λ (in W · m-1 · K-1) on mechanical compression. Nevertheless, mechanical stresses arising in an operating system can change significantly the thermal conductivity and heat exchange. Metrology allowing the characterization of the GDL thermal conductivity as a function of the applied mechanical compression has been developed in this study using the transient hot-wire technique (THW). This method is the best for obtaining standard reference data in fluids, but it is rarely used for thermal-conductivity measurements in solids. The experiments provided with Quintech carbon cloth indicate a strong dependence (up to 300%) of the thermal conductivity λ on the applied mechanical load. The experiments have been provided in the pressure range 0 < p < 8 MPa which corresponds to stresses arising in fuel cells. All obtained experimental results have been fitted by the equation λ = 0.9log(12 p + 17)(1 - 0.4e-50 p ) with 9% uncertainty. The obtained experimental dependence can be used for correct modeling of coupled thermo/electro-mechanical phenomena in fuel cells and electrolyzers. Special attention has been devoted to justification of the main hypotheses of the THW method and for estimation of the possible influence of the contact resistances. For this purpose, measurements with a different number of carbon cloth layers have been provided. The conducted experiments indicate the independence of the measured thermal conductivity on the number of GDL layers and, thus, justify the

  2. Reflexion measurements for inverse characterization of steel diffusion bond mechanical properties

    NASA Astrophysics Data System (ADS)

    Le Bourdais, Florian; Cachon, Lionel; Rigal, Emmanuel

    2017-02-01

    The present work describes a non-destructive testing method aimed at securing high manufacturing quality of the innovative compact heat exchanger developed under the framework of the CEA R&D program dedicated to the Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID). The heat exchanger assembly procedure currently proposed involves high temperature and high pressure diffusion welding of stainless steel plates. The aim of the non-destructive method presented herein is to characterize the quality of the welds obtained through this assembly process. Based on a low-frequency model developed by Baik and Thompson [1], pulse-echo normal incidence measurements are calibrated according to a specific procedure and allow the determination of the welding interface stiffness using a nonlinear fitting procedure in the frequency domain. Performing the characterization of plates after diffusion welding using this method allows a useful assessment of the material state as a function of the diffusion bonding process.

  3. Stability Characterization of Quinazoline Derivative BG1188 by Optical Methods

    NASA Astrophysics Data System (ADS)

    Militaru, Andra; Smarandache, Adriana; Mahamoud, Abdallah; Damian, Victor; Ganea, Paul; Alibert, Sandrine; Pagès, Jean-Marie; Pascu, Mihail-Lucian

    2011-08-01

    3-[2-(dimethylamino)ethyl]-6-nitroquinazolin-4(3H)-one, labeled BG1188, is a new synthesized compound, out of a series of quinazoline derivatives developed to fight the multidrug resistance of antibiotics acquired by bacteria. A characterization of the BG1188 powder was made using FTIR spectra in order to evidence the functional groups in the medicine's molecule. The ultraviolet-visible (UV-Vis) absorption spectra were used to study the stability of the BG1188 solutions in two solvents and at different temperatures. BG1188 concentration in ultrapure water was varied between 2×10-3 M (stock solution) and 10-6 M. The concentration recommended by higher activity on bacteria was 10-3 M. For the same reason, this was the utilized concentration of BG1188 in dimethyl sulfoxide (DMSO). Time stability was characterized by comparing the time evolution of the UV-Vis absorption spectra of the BG1188 solutions in ultrapure de-ionized water or in DMSO. The spectra were recorded daily for about 4 months after the preparation for the BG1188 solutions in ultrapure water. Generally, samples are stable within the experimental errors at concentrations higher than 10-5 M, but the stability time interval may vary from 119 days at 10-4 M to 34 days at 10-5 M. Time evolution of the absorption spectra at 10-3 M in ultrapure water shows reproducibility within the measuring errors (±1.045%) for time intervals up to 1032 hours (more than 40 days) after preparation. On the other hand, BG1188 solutions in DMSO may be considered unstable because the absorption spectra modify in terms of peak shapes and intensities, indicating that the samples exhibit modifications immediately after preparation. Regardless the solvent used, some aggregation phenomena took place and wire-like aggregates were observed in all the solutions with the naked eye. These aggregates were analyzed, tentatively, using optical microscopy and FTIR.

  4. Characterization of microcapsules: recommended methods based on round-robin testing.

    PubMed

    Rosiński, S; Grigorescu, G; Lewińska, D; Ritzén, L G; Viernstein, H; Teunou, E; Poncelet, D; Zhang, Z; Fan, X; Serp, D; Marison, I; Hunkeler, D

    2002-01-01

    Alginate beads, as well as microcapsules based on alginate, cellulose sulphate and polymethylene-co-guanidine, were produced at diameters of 0.4, 1.0 and 1.5 mm. These standard materials were tested, by independent laboratories, in regards to water activity, bead or capsule size, mechanical resistance and transport behaviour. The water activity and mechanical resistance were observed to increase with bead and capsule size. Transport properties (ingress) were assessed using a variety of low molar mass and macromolecular probes. It was observed that the penetration of Vitamin B12 increased with bead diameter, as did dextran penetration. However, for the membrane-containing microcapsules, larger membrane thickness, observed for the larger capsules, retarded ingress. The authors, who are part of a European working group, recommend that permeability be assessed either using a large range of probes or a broad molar mass standard, with measurements at one or two molar masses insufficient to simulate the behaviour in application. Mechanical compression is seen as a good means to estimate elasticity and rupture of beads and capsules, with the sensitivity of the force transducer, which can vary from microN to tens of N, required to be tuned to the anticipated bead or capsule strength. Overall, with the exception of the mechanical properties, the precision in the inter-laboratory testing was good. Furthermore, the various methods of assessing transport properties agreed, in ranking, for the beads and capsules characterized, with gels having smaller radii being less permeable. For microcapsules, the permeation across the membrane dominates the ingress, and thicker membranes have lower permeability.

  5. A novel image-based quantitative method for the characterization of NETosis

    PubMed Central

    Zhao, Wenpu; Fogg, Darin K.; Kaplan, Mariana J.

    2015-01-01

    NETosis is a newly recognized mechanism of programmed neutrophil death. It is characterized by a stepwise progression of chromatin decondensation, membrane rupture, and release of bactericidal DNA-based structures called neutrophil extracellular traps (NETs). Conventional ‘suicidal’ NETosis has been described in pathogenic models of systemic autoimmune disorders. Recent in vivo studies suggest that a process of ‘vital’ NETosis also exists, in which chromatin is condensed and membrane integrity is preserved. Techniques to assess ‘suicidal’ or ‘vital’ NET formation in a specific, quantitative, rapid and semiautomated way have been lacking, hindering the characterization of this process. Here we have developed a new method to simultaneously assess both ‘suicidal’ and ‘vital’ NETosis, using high-speed multi-spectral imaging coupled to morphometric image analysis, to quantify spontaneous NET formation observed ex-vivo or stimulus-induced NET formation triggered in vitro. Use of imaging flow cytometry allows automated, quantitative and rapid analysis of subcellular morphology and texture, and introduces the potential for further investigation using NETosis as a biomarker in pre-clinical and clinical studies. PMID:26003624

  6. Reverse micelle mediated synthesis, processing, mechanical and biological characterization of hydroxyapatite nanopowders for bone graft application

    NASA Astrophysics Data System (ADS)

    Banerjee, Ashis

    Hydroxyapatite (HA) is the most widely used bioceramic material in bone graft applications because of its compositional similarity with natural bone. However, synthetic HA does not show similar mechanical and biological properties to the inorganic component of bone. Properties of ceramic material depend on starting materials, processing techniques, densification and microstructure of the final product. The objective of this research was to process HA whisker reinforced HA composite using HA nanopowders and whiskers. HA nanopowders with different length scale and morphology were synthesized by reverse micelle system using NP5 and NP12 as surfactants and cyclohexane as organic solvent. The lowest average aspect ratio was 1.357+/-0.39 with average particle size of 66 nm and the highest average aspect ratio was 7.277+/-3.227 with average length of 150 nm and width of 20 nm, were synthesized. Micron sized HA whiskers with aspect ratio between 20 and 50, average particle length of 15 mum and width of 400 nm was synthesized using urea as a precipitating agent. Desired microstructure was obtained after sintering with spherical HA nanopowder and whiskers along with dopants. Addition of whiskers decreased density of the sintered compacts. However, at 10 wt% whisker content sample showed microhardness and fracture toughness of 3.6 GPa and 1.5 MPa.m1/2, respectively, and a compressive strength of 80 MPa was obtained. Mineralization study in simulated body fluid (SBF) showed formation of apatite layer on the dense HA compacts indicating a good tendency of bond formation with natural bone. Cytotoxicity results showed excellent cell attachment on the HA surface. In the Appendices, 3 journal articles have been attached which describe synthesis, processing and characterization of undoped and doped PZT nanopowders. Free standing and agglomerated PZT nanopowders were synthesized by the sucrose templated method and the citrate nitrate autocombustion method. Particle size in the range

  7. The Use of Seismic Coda to Characterize the Source Mechanisms of Induced Earthquakes

    NASA Astrophysics Data System (ADS)

    Reiter, D. T.; Leidig, M.; Yoo, S.; Mayeda, K. M.

    2012-12-01

    In recent years the injection of wastewater from petroleum production activities into disposal wells has been implicated in some unusual local seismicity. The potential seismic hazard associated with waste fluid disposal wells is so far poorly understood. Improving our understanding of the mechanics and physics of induced earthquakes is an important goal that will help mitigate seismic risk before disposal operations begin. To address this issue we adapted a set of data analysis techniques from seismic nuclear test-ban monitoring to the local scale (i.e., on the order of several spatial kilometers). In this paper we summarize the results of applying some of the methods to data from a temporary deployment of broadband stations surrounding a saltwater disposal well (SWD) near the Dallas-Fort Worth (DFW) airport. The sequence of small events (less than M 3.3) starting in late October 2008 provides a good test bed for the application of in-depth analysis to data recorded on a very sparse seismic network. In particular, we studied the amplitude behavior of the DFW data using the scattered seismic wave field, or so-called "coda", which has unique properties that makes its use ideal for sparse station monitoring at local distances. Because local scattered waves sample the subsurface via multiple reflections and 3-D scattering, amplitude measurements made from coda envelopes reach a steady decay that is purely a function of the average medium properties that encompass the volume surrounding the source and seismic station, irrespective of source size. As such, the scattered waves behave very predictably within a region and can be used for estimates of magnitude and other source-related characteristics (e.g., earthquake stress drop, radiated seismic energy, seismic moment) that are significantly more stable than traditional approaches that utilize the direct waves such as P and S. Because the coda averages over the 3-D crustal heterogeneity as well as the source radiation

  8. Quantitative, Qualitative and Geospatial Methods to Characterize HIV Risk Environments

    PubMed Central

    Conners, Erin E.; West, Brooke S.; Roth, Alexis M.; Meckel-Parker, Kristen G.; Kwan, Mei-Po; Magis-Rodriguez, Carlos; Staines-Orozco, Hugo; Clapp, John D.; Brouwer, Kimberly C.

    2016-01-01

    Increasingly, ‘place’, including physical and geographical characteristics as well as social meanings, is recognized as an important factor driving individual and community health risks. This is especially true among marginalized populations in low and middle income countries (LMIC), whose environments may also be more difficult to study using traditional methods. In the NIH-funded longitudinal study Mapa de Salud, we employed a novel approach to exploring the risk environment of female sex workers (FSWs) in two Mexico/U.S. border cities, Tijuana and Ciudad Juárez. In this paper we describe the development, implementation, and feasibility of a mix of quantitative and qualitative tools used to capture the HIV risk environments of FSWs in an LMIC setting. The methods were: 1) Participatory mapping; 2) Quantitative interviews; 3) Sex work venue field observation; 4) Time-location-activity diaries; 5) In-depth interviews about daily activity spaces. We found that the mixed-methodology outlined was both feasible to implement and acceptable to participants. These methods can generate geospatial data to assess the role of the environment on drug and sexual risk behaviors among high risk populations. Additionally, the adaptation of existing methods for marginalized populations in resource constrained contexts provides new opportunities for informing public health interventions. PMID:27191846

  9. Quantitative, Qualitative and Geospatial Methods to Characterize HIV Risk Environments.

    PubMed

    Conners, Erin E; West, Brooke S; Roth, Alexis M; Meckel-Parker, Kristen G; Kwan, Mei-Po; Magis-Rodriguez, Carlos; Staines-Orozco, Hugo; Clapp, John D; Brouwer, Kimberly C

    2016-01-01

    Increasingly, 'place', including physical and geographical characteristics as well as social meanings, is recognized as an important factor driving individual and community health risks. This is especially true among marginalized populations in low and middle income countries (LMIC), whose environments may also be more difficult to study using traditional methods. In the NIH-funded longitudinal study Mapa de Salud, we employed a novel approach to exploring the risk environment of female sex workers (FSWs) in two Mexico/U.S. border cities, Tijuana and Ciudad Juárez. In this paper we describe the development, implementation, and feasibility of a mix of quantitative and qualitative tools used to capture the HIV risk environments of FSWs in an LMIC setting. The methods were: 1) Participatory mapping; 2) Quantitative interviews; 3) Sex work venue field observation; 4) Time-location-activity diaries; 5) In-depth interviews about daily activity spaces. We found that the mixed-methodology outlined was both feasible to implement and acceptable to participants. These methods can generate geospatial data to assess the role of the environment on drug and sexual risk behaviors among high risk populations. Additionally, the adaptation of existing methods for marginalized populations in resource constrained contexts provides new opportunities for informing public health interventions.

  10. Microbiological characterization of vermicomposts by the method of multisubstrate testing

    NASA Astrophysics Data System (ADS)

    Yakushev, A. V.; Byzov, B. A.

    2008-11-01

    A new modification of the method of multisubstrate testing (MST, BIOLOG) is suggested. It is based on the kinetic description of bacterial growth on nutrient media during 50 h. The results of the MST represent a set of three parameters (the initial optical density, the maximum specific growth rate, and the maximum optical density) of an equation describing the growth of microbial communities on individual substrates. Methods of multivariate statistics (cluster and discriminant analyses) have been used to compare these parameters for 24 organic substrates. It is supposed that a more detailed description of the growth of microorganisms should improve the information capacity of the MST method. The effect of earthworms on vermicomposting has been studied experimentally with the MST method. An empirical rule allowing one to distinguish between vermicomposts and ordinary composts using the results of MST is suggested. Manure, earthy matter from the intestinal tracts of earthworms ( Eisenia andrei), and their coprolites have been subjected to MST. A functional similarity between manure and fresh coprolites has been found. Also, three different lots of industrial vermicomposts have been compared. The cluster analysis has demonstrated a significant difference between them. The clusters depend on the nature of the initial substrates used for preparing these vermicomposts. Thus, unification of the initial substrates used for composting is necessary to obtain standardized vermicomposts.

  11. Quantitative methods to characterize morphological properties of cell lines.

    PubMed

    Mancia, Annalaura; Elliott, John T; Halter, Michael; Bhadriraju, Kiran; Tona, Alessandro; Spurlin, Tighe A; Middlebrooks, Bobby L; Baatz, John E; Warr, Gregory W; Plant, Anne L

    2012-07-01

    Descriptive terms are often used to characterize cells in culture, but the use of nonquantitative and poorly defined terms can lead to ambiguities when comparing data from different laboratories. Although recently there has been a good deal of interest in unambiguous identification of cell lines via their genetic markers, it is also critical to have definitive, quantitative metrics to describe cell phenotypic characteristics. Quantitative metrics of cell phenotype will aid the comparison of data from experiments performed at different times and in different laboratories where influences such as the age of the population and differences in culture conditions or protocols can potentially affect cellular metabolic state and gene expression in the absence of changes in the genetic profile. Here, we present examples of robust methodologies for quantitatively assessing characteristics of cell morphology and cell-cell interactions, and of growth rates of cells within the population. We performed these analyses with endothelial cell lines derived from dolphin, bovine and human, and with a mouse fibroblast cell line. These metrics quantify some characteristics of these cells lines that clearly distinguish them from one another, and provide quantitative information on phenotypic changes in one of the cell lines over large number of passages.

  12. Membrane Characterization by Microscopic and Scattering Methods: Multiscale Structure

    PubMed Central

    Tamime, Rahma; Wyart, Yvan; Siozade, Laure; Baudin, Isabelle; Deumie, Carole; Glucina, Karl; Moulin, Philippe

    2011-01-01

    Several microscopic and scattering techniques at different observation scales (from atomic to macroscopic) were used to characterize both surface and bulk properties of four new flat-sheet polyethersulfone (PES) membranes (10, 30, 100 and 300 kDa) and new 100 kDa hollow fibers (PVDF). Scanning Electron Microscopy (SEM) with “in lens” detection was used to obtain information on the pore sizes of the skin layers at the atomic scale. White Light Interferometry (WLI) and Atomic Force Microscopy (AFM) using different scales (for WLI: windows: 900 × 900 μm2 and 360 × 360 μm2; number of points: 1024; for AFM: windows: 50 × 50 μm2 and 5 × 5 μm2; number of points: 512) showed that the membrane roughness increases markedly with the observation scale and that there is a continuity between the different scan sizes for the determination of the RMS roughness. High angular resolution ellipsometric measurements were used to obtain the signature of each cut-off and the origin of the scattering was identified as coming from the membrane bulk. PMID:24957612

  13. Membrane characterization by microscopic and scattering methods: multiscale structure.

    PubMed

    Tamime, Rahma; Wyart, Yvan; Siozade, Laure; Baudin, Isabelle; Deumie, Carole; Glucina, Karl; Moulin, Philippe

    2011-04-13

    Several microscopic and scattering techniques at different observation scales (from atomic to macroscopic) were used to characterize both surface and bulk properties of four new flat-sheet polyethersulfone (PES) membranes (10, 30, 100 and 300 kDa) and new 100 kDa hollow fibers (PVDF). Scanning Electron Microscopy (SEM) with "in lens" detection was used to obtain information on the pore sizes of the skin layers at the atomic scale. White Light Interferometry (WLI) and Atomic Force Microscopy (AFM) using different scales (for WLI: windows: 900 × 900 µm2 and 360 × 360 µm2; number of points: 1024; for AFM: windows: 50 × 50 µm2 and 5 × 5 µm2; number of points: 512) showed that the membrane roughness increases markedly with the observation scale and that there is a continuity between the different scan sizes for the determination of the RMS roughness. High angular resolution ellipsometric measurements were used to obtain the signature of each cut-off and the origin of the scattering was identified as coming from the membrane bulk.

  14. [Characterization of flowability of pharmaceutical powders based on multivariate analysis method].

    PubMed

    Du, Yan; Zhao, Li-Jie; Xiong, Yao-Kun; Li, Xiao-Hai; Wang, Song-Tao; Feng, Yi; Xu, De-Sheng

    2012-09-01

    The main methods of characterizing the flowability of pharmaceutical powders include repose angle method, HR method, Carr's index method, Jenike flow function method, fractal dimension method, and mass flow rate method, etc. Regarding powders with different flowabilities as the research subject, comprehensive features of pharmaceutical materials were investigated and characterized. The multivariate analysis method was employed to evaluate and analyze flowability values of the tested pharmaceutical materials. Comparing with the method of the mass flow rate, it was feasible to use multivariate analysis method to evaluate the flowability of powders. Simultaneously, the flowability of pharmaceutical materials could be ranked and definitely quantified, and critical values be determined according to the actual production, which has promoted the previous methods dependent only on the single parameter, i.e. repose angle and compression degree methods. A relatively objective standard method of evaluating flowability of powders is formed.

  15. A thermodynamic theory for characterizing thermo-mechanical response of polymers during crystallization

    SciTech Connect

    Negahban, M.

    1995-12-31

    A thermodynamic theory will be presented to capture the thermo-mechanical characteristics associated with crystallization of polymers. The basic characteristics associated with crystallization consists of (a) crystallization in polymers is considered a gradual transition from an amorphous polymer to a semi-crystalline polymer, (b) there is a volume reduction associated with crystallization as the material moves to the denser morphology of the crystal structure, (c) there is a substantial stiffening of the polymer, (d) there is stress relaxation associated with crystallization for polymers under a constant stretch, (e) there is creep associated with crystallization in polymers under a fixed load. These and other characteristics are modeled in a multi-dimensional thermodynamic theory. As a first example, the simplest possible constitutive assumptions are studied in relation to characterizing the behavior of natural rubber. Natural rubber is selected due to the abundance of information on its thermo-mechanical behavior. This work is an extension to non-isothermal thermodynamic processes of previous work on characterizing the mechanical effects of polymer crystallization under isothermal conditions.

  16. Three-dimensional EBSD characterization of thermo-mechanical fatigue crack morphology in compacted graphite iron

    SciTech Connect

    Pirgazi, Hadi; Ghodrat, Sepideh; Kestens, Leo A.I.

    2014-04-01

    In cylinder heads made of compacted graphitic iron (CGI), heating and cooling cycles can lead to localized cracking due to thermo-mechanical fatigue (TMF). To meticulously characterize the complex crack path morphology of CGI under TMF condition, in relation to microstructural features and to find out how and by which mechanisms the cracks predominantly develop, three-dimensional electron back scattering diffraction (EBSD) was employed. Based on the precise quantitative microstructural analysis, it is found that graphite particles not only play a crucial role in the crack initiation, but also are of primary significance for crack propagation, i.e. crack growth is enhanced by the presence of graphite particles. Furthermore, the density of graphite particles on the fracture plane is more than double as high as in any other arbitrary plane of the structure. The obtained results did not indicate a particular crystallographic preference of fracture plane, i.e. the crystal plane parallel to the fracture plane was nearly of random orientation. - Highlights: • Crystallographic features of a thermo-mechanical fatigue (TMF) crack were studied. • Wide-field 3D EBSD is used to characterize the TMF crack morphology. • Data processing was applied on a large length scale of the order of millimeters. • Graphite density in the fracture plane is much higher than any other random plane. • It is revealed that crack growth is enhanced by the presence of graphite particles.

  17. An efficient quantum mechanical method for radical pair recombination reactions

    NASA Astrophysics Data System (ADS)

    Lewis, Alan M.; Fay, Thomas P.; Manolopoulos, David E.

    2016-12-01

    The standard quantum mechanical expressions for the singlet and triplet survival probabilities and product yields of a radical pair recombination reaction involve a trace over the states in a combined electronic and nuclear spin Hilbert space. If this trace is evaluated deterministically, by performing a separate time-dependent wavepacket calculation for each initial state in the Hilbert space, the computational effort scales as O (Z2log ⁡Z ) , where Z is the total number of nuclear spin states. Here we show that the trace can also be evaluated stochastically, by exploiting the properties of spin coherent states. This results in a computational effort of O (M Z log ⁡Z ) , where M is the number of Monte Carlo samples needed for convergence. Example calculations on a strongly coupled radical pair with Z >106 show that the singlet yield can be converged to graphical accuracy using just M =200 samples, resulting in a speed up by a factor of >5000 over a standard deterministic calculation. We expect that this factor will greatly facilitate future quantum mechanical simulations of a wide variety of radical pairs of interest in chemistry and biology.

  18. Transplantation models to characterize the mechanisms of stem cell-induced islet regeneration.

    PubMed

    Bell, Gillian I; Seneviratne, Ayesh K; Nasri, Grace N; Hess, David A

    2013-09-20

    This unit describes our current knowledge regarding the isolation human bone marrow-derived progenitor cells for the paracrine stimulation of islet regeneration after transplantation into immunodeficient mouse models of diabetes. By using high aldehyde dehydrogenase (ALDH(hi) ) activity, a conserved function in multiple stem cell lineages, a mixed population of hematopoietic, endothelial, and mesenchymal progenitor cells can be efficiently purified using flow cytometry. We describe in vitro approaches to characterize and expand these distinct cell types. Importantly, these cell types can be transplanted into immunodeficient mice rendered beta-cell deficient by streptozotocin (STZ) treatment, in order monitor functional recovery from hyperglycemia and to characterize endogenous islet regeneration via paracrine mechanisms. Herein, we provide detailed protocols for: (1) isolation and characterization of ALDH(hi) cells for the establishment of hematopoietic and multipotent-stromal progenitor lineages; (2) intravenous and intrapancreatic transplantation of human stem cell subtypes for the quantification of glycemic recovery in STZ-treated immunodeficient mice; and (3) immunohistochemical characterization of islet recovery via the stimulation of islet neogenic, beta-cell proliferative, and islet revascularization programs. Collectively, these systems can be used to support the pre-clinical development of human progenitor cell-based therapies to treat diabetes via islet regeneration.

  19. Rapid characterization of titanium microstructural features for specific modelling of mechanical properties

    NASA Astrophysics Data System (ADS)

    Searles, T.; Tiley, J.; Tanner, A.; Williams, R.; Rollins, B.; Lee, E.; Kar, S.; Banerjee, R.; Fraser, H. L.

    2005-01-01

    Mechanical properties of α/β Ti alloys are closely related to their microstructure. The complexity of the microstructural features involved makes it rather difficult to develop models for predicting properties of these alloys. Advances in stereology and microscopy permit rapid characterization of various features in Ti alloys including Widmanstätten α-laths, grain sizes, grain shapes, colony structures and volume fractions of different phases. This research documents the stereology procedures for characterizing microstructural features in Ti alloys, including the use of three-dimensional serial sectioning and reconstruction procedures for developing through material measurements. The resulting data indicate the powerful characterization processes now available, and the ability to rapidly assess microstructural features in Ti alloys. The processes were tested using Ti-62222 by serial sectioning the sample and conducting automated stereology protocols to determine features. In addition, three-dimensional reconstruction was completed on a Ti-6242 sample to evaluate lath interactions within the alloy. Results indicate the tremendous potential for characterizing microstructures using advanced techniques.

  20. Robust diffraction correction method for high-frequency ultrasonic tissue characterization

    NASA Astrophysics Data System (ADS)

    Raju, Balasundar

    2001-05-01

    The computation of quantitative ultrasonic parameters such as the attenuation or backscatter coefficient requires compensation for diffraction effects. In this work a simple and accurate diffraction correction method for skin characterization requiring only a single focal zone is developed. The advantage of this method is that the transducer need not be mechanically repositioned to collect data from several focal zones, thereby reducing the time of imaging and preventing motion artifacts. Data were first collected under controlled conditions from skin of volunteers using a high-frequency system (center frequency=33 MHz, BW=28 MHz) at 19 focal zones through axial translation. Using these data, mean backscatter power spectra were computed as a function of the distance between the transducer and the tissue, which then served as empirical diffraction correction curves for subsequent data. The method was demonstrated on patients patch-tested for contact dermatitis. The computed attenuation coefficient slope was significantly (p<0.05) lower at the affected site (0.13+/-0.02 dB/mm/MHz) compared to nearby normal skin (0.2+/-0.05 dB/mm/MHz). The mean backscatter level was also significantly lower at the affected site (6.7+/-2.1 in arbitrary units) compared to normal skin (11.3+/-3.2). These results show diffraction corrected ultrasonic parameters can differentiate normal from affected skin tissues.

  1. Interferometer and analysis methods for the in vitro characterization of dynamic fluid layers on contact lenses

    NASA Astrophysics Data System (ADS)

    Primeau, Brian C.; Greivenkamp, John E.

    2012-06-01

    The anterior refracting surface of the eye when wearing a contact lens is the thin fluid layer that forms on the surface of the contact lens. Under normal conditions, this fluid layer is less than 10 μm thick. The fluid layer thickness and topography change over time and are affected by the material properties of the contact lens and may affect vision quality and comfort. An in vitro method of characterizing dynamic fluid layers applied to contact lenses mounted on mechanical substrates has been developed by use of a phase-shifting Twyman-Green interferometer. This interferometer continuously measures light reflected from the surface of the fluid layer, allowing precision analysis of the dynamic fluid layer. Movies showing this fluid layer behavior can be generated. Quantitative analysis beyond typical contact angle or visual inspection methods is provided. Different fluid and contact lens material combinations have been evaluated, and variations in fluid layer properties have been observed. This paper discusses the interferometer design and analysis methods used. Example measurement results of different contact lens are presented.

  2. Characterization of gold kiwifruit pectin from fruit of different maturities and extraction methods.

    PubMed

    Yuliarti, Oni; Matia-Merino, Lara; Goh, Kelvin K T; Mawson, John; Williams, Martin A K; Brennan, Charles

    2015-01-01

    Studies on gold kiwifruit pectins are limited. In this work, the characterization of pectin isolated from two different stages of maturity of gold kiwifruit, namely early harvested fruit (EHF) and main harvested fruit (MHF) isolated by three methods (acid, water, enzymatic) was carried out. Pectins isolated from MHF were higher in galacturonic acid content (52-59% w/w) and weight-average molecular weights (Mw, 1.7-3.8 × 10(6)g/mol) compared with EHF pectins (29-49% w/w and 0.2-1.7 × 10(6)g/mol respectively). Enzymatic treatment gave the highest yield but lowest in Mw, viscosity and mechanical spectra for both maturities. The pectin of both maturities was classified as high-methoxyl pectin with the degree of esterification ranged from 82% to 90%. Water-extracted MHF pectin molecules had the highest RMS radius (182.7 nm) and Mw (3.75 × 10(6)g/mol). The water extraction method appeared to retain the native state of pectin molecules compared with acid and enzymatic extraction methods based on the Mw and viscosity data.

  3. Characterization of Olive Oil by Ultrasonic and Physico-chemical Methods

    NASA Astrophysics Data System (ADS)

    Alouache, B.; Khechena, F. K.; Lecheb, F.; Boutkedjirt, T.

    Olive oil excels by its nutritional and medicinal benefits. It can be consumed without any treatment. However, its quality can be altered by inadequate storage conditions or if it is mixed with other kinds of oils. The objective of this work is to demonstrate the ability of ultrasonic methods to characterize and control olive oil quality. By using of a transducer of 2.25 MHz nominal frequency, in pulse echo mode, ultrasonic parameters, such as propagation velocity and attenuation,have been measured for pure olive oil and for its mixtures with sunflower oil at different proportions. Mechanical properties, such as density and viscosity, have also been determined. The results of ultrasonic measurements are consistent with those obtained by physico-chemical methods, such as rancidity degree, acid index, UV specific extinction coefficient and viscosity. They show that the ultrasonic method allows to distinguish between mixtures at different proportions. The study allows concluding that ultrasound techniques can be considered as a useful complement to existing physico-chemical analysis techniques.

  4. Robust diffraction correction method for high-frequency ultrasonic tissue characterization

    NASA Astrophysics Data System (ADS)

    Raju, Balasundar

    2004-05-01

    The computation of quantitative ultrasonic parameters such as the attenuation or backscatter coefficient requires compensation for diffraction effects. In this work a simple and accurate diffraction correction method for skin characterization requiring only a single focal zone is developed. The advantage of this method is that the transducer need not be mechanically repositioned to collect data from several focal zones, thereby reducing the time of imaging and preventing motion artifacts. Data were first collected under controlled conditions from skin of volunteers using a high-frequency system (center frequency=33 MHz, BW=28 MHz) at 19 focal zones through axial translation. Using these data, mean backscatter power spectra were computed as a function of the distance between the transducer and the tissue, which then served as empirical diffraction correction curves for subsequent data. The method was demonstrated on patients patch-tested for contact dermatitis. The computed attenuation coefficient slope was significantly (p<0.05) lower at the affected site (0.13+/-0.02 dB/mm/MHz) compared to nearby normal skin (0.2+/-0.05 dB/mm/MHz). The mean backscatter level was also significantly lower at the affected site (6.7+/-2.1 in arbitrary units) compared to normal skin (11.3+/-3.2). These results show diffraction corrected ultrasonic parameters can differentiate normal from affected skin tissues.

  5. Application of Patterson-function direct methods to materials characterization.

    PubMed

    Rius, Jordi

    2014-09-01

    The aim of this article is a general description of the so-called Patterson-function direct methods (PFDM), from their origin to their present state. It covers a 20-year period of methodological contributions to crystal structure solution, most of them published in Acta Crystallographica Section A. The common feature of these variants of direct methods is the introduction of the experimental intensities in the form of the Fourier coefficients of origin-free Patterson-type functions, which allows the active use of both strong and weak reflections. The different optimization algorithms are discussed and their performances compared. This review focuses not only on those PFDM applications related to powder diffraction data but also on some recent results obtained with electron diffraction tomography data.

  6. Characterization of Meta-Materials Using Computational Electromagnetic Methods

    NASA Technical Reports Server (NTRS)

    Deshpande, Manohar; Shin, Joon

    2005-01-01

    An efficient and powerful computational method is presented to synthesize a meta-material to specified electromagnetic properties. Using the periodicity of meta-materials, the Finite Element Methodology (FEM) is developed to estimate the reflection and transmission through the meta-material structure for a normal plane wave incidence. For efficient computations of the reflection and transmission over a wide band frequency range through a meta-material a Finite Difference Time Domain (FDTD) approach is also developed. Using the Nicholson-Ross method and the Genetic Algorithms, a robust procedure to extract electromagnetic properties of meta-material from the knowledge of its reflection and transmission coefficients is described. Few numerical examples are also presented to validate the present approach.

  7. Application of Patterson-function direct methods to materials characterization

    PubMed Central

    Rius, Jordi

    2014-01-01

    The aim of this article is a general description of the so-called Patterson-function direct methods (PFDM), from their origin to their present state. It covers a 20-year period of methodological contributions to crystal structure solution, most of them published in Acta Crystallographica Section A. The common feature of these variants of direct methods is the introduction of the experimental intensities in the form of the Fourier coefficients of origin-free Patterson-type functions, which allows the active use of both strong and weak reflections. The different optimization algorithms are discussed and their performances compared. This review focuses not only on those PFDM applications related to powder diffraction data but also on some recent results obtained with electron diffraction tomography data. PMID:25295171

  8. Review of Physical and Chemical Methods for Characterization of Fuels

    DTIC Science & Technology

    1981-12-01

    Chromatography-New Evaluation Methods of Mathematical Dead Time," Instituto de Quimica Fisica "Rocasolano", Madrid, Spain, Journal of Chromatographic Science...34Separation and Iden- tification of Aldehydes and Ketones From an Irati Oil Shale Bitumen. Use of the Solid Phase Extractor Technique," Instituto de Quimica ...discrepancies possibly caused bydifferences in 2 dynamometer type and ambient conditions. 41. Author Unknown, U.S. Army Test and Evaluation Test Operations

  9. Mechanical Behavior of Al-SiC Nanolaminate Composites Using Micro-Scale Testing Methods

    NASA Astrophysics Data System (ADS)

    Mayer, Carl Randolph

    Nanolaminate composite materials consist of alternating layers of materials at the nanoscale (≤100 nm). Due to the nanometer scale thickness of their layers, these materials display unique and tailorable properties. This enables us to alter both mechanical attributes such as strength and wear properties, as well as functional characteristics such as biocompatibility, optical, and electronic properties. This dissertation focuses on understanding the mechanical behavior of the Al-SiC system. From a practical perspective, these materials exhibit a combination of high toughness and strength which is attractive for many applications. Scientifically, these materials are interesting due to the large elastic modulus mismatch between the layers. This, paired with the small layer thickness, allows a unique opportunity for scientists to study the plastic deformation of metals under extreme amounts of constraint. Previous studies are limited in scope and a more diverse range of mechanical characterization is required to understand both the advantages and limitations of these materials. One of the major challenges with testing these materials is that they are only able to be made in thicknesses on the order of micrometers so the testing methods are limited to small volume techniques. This work makes use of both microscale testing techniques from the literature as well as novel methodologies. Using these techniques we are able to gain insight into aspects of the material's mechanical behavior such as the effects of layer orientation, flaw dependent fracture, tension-compression asymmetry, fracture toughness as a function of layer thickness, and shear behavior as a function of layer thickness.

  10. Characterization method of hydrophobic anti-icing coatings

    NASA Astrophysics Data System (ADS)

    Morita, Katsuaki; Sakaue, Hirotaka

    2015-11-01

    For anti-icing, supercooled water should be removed before frozen onto the contact surface. We use a hydrophobic coating for anti-icing and introduce the static- and dynamic-evaluation methods. The methods describe the contact surface between the hydrophobic surface and a supercooled-water droplet. The former is based on the contact angle, and the latter is based on the sliding angle. The temperature factor is included in these models to evaluate the hydrophobic coating under the supercooled conditions. Four hydrophobic coatings are experimentally evaluated based on the static- and dynamic evaluation methods: C1-C3 (commercial fluorocarbon coatings), and Jaxa coating (original fluorocarbon coating). These are evaluated under the supercooled conditions of -10 to 0 °C. The static-evaluation shows variations in the temperature. However, change in the contact angle by the temperature is relatively small compared to that of the sliding angle for the dynamic evaluation. Only C3 and Jaxa coatings are tolerant to the sliding angle under the supercooled conditions tested. The dynamic evaluation shows that even if the coating is hydrophobic, the dynamic evaluation should be included to understand the characteristic of removal for a supercooled-water droplet.

  11. Characterization method of hydrophobic anti-icing coatings.

    PubMed

    Morita, Katsuaki; Sakaue, Hirotaka

    2015-11-01

    For anti-icing, supercooled water should be removed before frozen onto the contact surface. We use a hydrophobic coating for anti-icing and introduce the static- and dynamic-evaluation methods. The methods describe the contact surface between the hydrophobic surface and a supercooled-water droplet. The former is based on the contact angle, and the latter is based on the sliding angle. The temperature factor is included in these models to evaluate the hydrophobic coating under the supercooled conditions. Four hydrophobic coatings are experimentally evaluated based on the static- and dynamic evaluation methods: C1-C3 (commercial fluorocarbon coatings), and Jaxa coating (original fluorocarbon coating). These are evaluated under the supercooled conditions of -10 to 0 °C. The static-evaluation shows variations in the temperature. However, change in the contact angle by the temperature is relatively small compared to that of the sliding angle for the dynamic evaluation. Only C3 and Jaxa coatings are tolerant to the sliding angle under the supercooled conditions tested. The dynamic evaluation shows that even if the coating is hydrophobic, the dynamic evaluation should be included to understand the characteristic of removal for a supercooled-water droplet.

  12. Webcam autofocus mechanism used as a delay line for the characterization of femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Castro-Marín, Pablo; Kapellmann-Zafra, Gabriel; Garduño-Mejía, Jesús; Rosete-Aguilar, Martha; Román-Moreno, Carlos J.

    2015-08-01

    In this work, we present an electromagnetic focusing mechanism (EFM), from a commercial webcam, implemented as a delay line of a femtosecond laser pulse characterization system. The characterization system consists on a second order autocorrelator based on a two-photon-absorption detection. The results presented here were performed for two different home-made femtosecond oscillators: Ti:sapph @ 820 nm and highly chirped pulses generated with an Erbium Doped Fiber @ 1550 nm. The EFM applied as a delay line represents an excellent alternative due its performance in terms of stability, resolution, and long scan range up to 3 ps. Due its low power consumption, the device can be connected through the Universal Serial Bus (USB) port. Details of components, schematics of electronic controls, and detection systems are presented.

  13. Nondestructive techniques for characterizing mechanical properties of structural materials - An overview

    NASA Technical Reports Server (NTRS)

    Vary, A.; Klima, S. J.

    1986-01-01

    An overview of nondestructive evaluation (NDE) is presented to indicate the availability and application potentials of techniques for quantitative characterization of the mechanical properties of structural materials. The purpose is to review NDE techniques that go beyond the usual emphasis on flow detection and characterization. Discussed are current and emerging NDE techniques that can verify and monitor entrinsic properties (e.g., tensile, shear, and yield strengths; fracture toughness, hardness, ductility; elastic moduli) and underlying microstructural and morphological factors. Most of the techniques described are, at present, neither widely applied nor widely accepted in commerce and industry because they are still emerging from the laboratory. The limitations of the techniques may be overcome by advances in applications research and instrumentation technology and perhaps by accommodations for their use in the design of structural parts.

  14. Webcam autofocus mechanism used as a delay line for the characterization of femtosecond pulses

    SciTech Connect

    Castro-Marín, Pablo; Kapellmann-Zafra, Gabriel; Garduño-Mejía, Jesús Rosete-Aguilar, Martha; Román-Moreno, Carlos J.

    2015-08-15

    In this work, we present an electromagnetic focusing mechanism (EFM), from a commercial webcam, implemented as a delay line of a femtosecond laser pulse characterization system. The characterization system consists on a second order autocorrelator based on a two-photon-absorption detection. The results presented here were performed for two different home-made femtosecond oscillators: Ti:sapph @ 820 nm and highly chirped pulses generated with an Erbium Doped Fiber @ 1550 nm. The EFM applied as a delay line represents an excellent alternative due its performance in terms of stability, resolution, and long scan range up to 3 ps. Due its low power consumption, the device can be connected through the Universal Serial Bus (USB) port. Details of components, schematics of electronic controls, and detection systems are presented.

  15. Characterization of HTPB-based solid fuel formulations: Performance, mechanical properties, and pollution

    NASA Astrophysics Data System (ADS)

    DeLuca, L. T.; Galfetti, L.; Maggi, F.; Colombo, G.; Merotto, L.; Boiocchi, M.; Paravan, C.; Reina, A.; Tadini, P.; Fanton, L.

    2013-12-01

    Features such as safety, low-cost, and throttleability make hybrid rocket engines an attractive option for suborbital flights and space exploration missions in general. While the domain of possible liquid oxidizers is well characterized, the choice of a suitable solid fuel is still a matter of investigation. Space Propulsion Laboratory (SPLab) at Politecnico di Milano has developed a series of proprietary techniques to evaluate, on a relative grading, the quality of innovative solid fuels while visualizing at the same time their flame structure. But a serious alert was recently notified that soot emission from hydrocarbon fuels has the potential to contribute to global climate change. In this paper, HTPB polymer has been taken as baseline and characterized at laboratory level in terms of ballistic properties, mechanical testing, and thermochemical calculations.

  16. Nondestructive techniques for characterizing mechanical properties of structural materials: An overview

    NASA Technical Reports Server (NTRS)

    Vary, A.; Klima, S. J.

    1985-01-01

    An overview of nondestructive evaluation (NDE) is presented to indicate the availability and application potentials of techniques for quantitative characterization of the mechanical properties of structural materials. The purpose is to review NDE techniques that go beyond the usual emphasis on flaw detection and characterization. Discussed are current and emerging NDE techniques that can verify and monitor entrinsic properties (e.g., tensile, shear, and yield strengths; fracture toughness, hardness, ductility; elastic moduli) and underlying microstructural and morphological factors. Most of the techniques described are, at present, neither widely applied nor widely accepted in commerce and industry because they are still emerging from the laboratory. The limitations of the techniques may be overcome by advances in applications research and instrumentation technology and perhaps by accommodations for their use in the design of structural parts.

  17. Characterization of Cracking Mechanisms of Carbon Anodes Used in Aluminum Industry by Optical Microscopy and Tomography

    NASA Astrophysics Data System (ADS)

    Amrani, Salah; Kocaefe, Duygu; Kocaefe, Yasar; Bhattacharyay, Dipankar; Bouazara, Mohamed; Morais, Brigitte

    2016-10-01

    The objective of this work is to understand the different mechanisms of crack formation in dense anodes used in the aluminum industry. The first approach used is based on the qualitative characterization of the surface cracks and the depth of these cracks. The second approach, which constitutes a quantitative characterization, is carried out by determining the distribution of the crack width along its length as well as the percentage of the surface containing cracks. A qualitative analysis of crack formation was also carried out using 3D tomography. It was observed that mixing and forming conditions have a significant effect on crack formation in green anodes. The devolatilization of pitch during baking causes the formation and propagation of cracks in baked anodes in which large particles control the direction of crack propagation.

  18. Application the particle method in problems of mechanics deformable media

    NASA Astrophysics Data System (ADS)

    Berezhnoi, D. V.; Gabsalikova, N. F.; Miheev, V. V.

    2016-11-01

    The work implemented method of deformation of ground-based particle method, which is a collection of mineral grains, which are linked to some system of forces on the contact areas between the mineral particles. Two-parameter potential Lennard-Jones and it is modified version were selected for describing the behavior of ground. Some model problems of straining layer of ground in the gravity field was decided. The calculations were performed on a heterogeneous computing cluster, on each of the seven components that were installed on three GPU AMD Radeon HD 7970.

  19. An alternative method to characterize the surface urban heat island.

    PubMed

    Martin, Philippe; Baudouin, Yves; Gachon, Philippe

    2015-07-01

    An urban heat island (UHI) is a relative measure defined as a metropolitan area that is warmer than the surrounding suburban or rural areas. The UHI nomenclature includes a surface urban heat island (SUHI) definition that describes the land surface temperature (LST) differences between urban and suburban areas. The complexity involved in selecting an urban core and external thermal reference for estimating the magnitude of a UHI led us to develop a new definition of SUHIs that excludes any rural comparison. The thermal reference of these newly defined surface intra-urban heat islands (SIUHIs) is based on various temperature thresholds above the spatial average of LSTs within the city's administrative limits. A time series of images from Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) from 1984 to 2011 was used to estimate the LST over the warm season in Montreal, Québec, Canada. Different SIUHI categories were analyzed in consideration of the global solar radiation (GSR) conditions that prevailed before each acquisition date of the Landsat images. The results show that the cumulative GSR observed 24 to 48 h prior to the satellite overpass is significantly linked with the occurrence of the highest SIUHI categories (thresholds of +3 to +7 °C above the mean spatial LST within Montreal city). The highest correlation (≈0.8) is obtained between a pixel-based temperature that is 6 °C hotter than the city's mean LST (SIUHI + 6) after only 24 h of cumulative GSR. SIUHI + 6 can then be used as a thermal threshold that characterizes hotspots within the city. This identification approach can be viewed as a useful criterion or as an initial step toward the development of heat health watch and warning system (HHWWS), especially during the occurrence of severe heat spells across urban areas.

  20. An alternative method to characterize the surface urban heat island

    NASA Astrophysics Data System (ADS)

    Martin, Philippe; Baudouin, Yves; Gachon, Philippe

    2015-07-01

    An urban heat island (UHI) is a relative measure defined as a metropolitan area that is warmer than the surrounding suburban or rural areas. The UHI nomenclature includes a surface urban heat island (SUHI) definition that describes the land surface temperature (LST) differences between urban and suburban areas. The complexity involved in selecting an urban core and external thermal reference for estimating the magnitude of a UHI led us to develop a new definition of SUHIs that excludes any rural comparison. The thermal reference of these newly defined surface intra-urban heat islands (SIUHIs) is based on various temperature thresholds above the spatial average of LSTs within the city's administrative limits. A time series of images from Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) from 1984 to 2011 was used to estimate the LST over the warm season in Montreal, Québec, Canada. Different SIUHI categories were analyzed in consideration of the global solar radiation (GSR) conditions that prevailed before each acquisition date of the Landsat images. The results show that the cumulative GSR observed 24 to 48 h prior to the satellite overpass is significantly linked with the occurrence of the highest SIUHI categories (thresholds of +3 to +7 °C above the mean spatial LST within Montreal city). The highest correlation (≈0.8) is obtained between a pixel-based temperature that is 6 °C hotter than the city's mean LST (SIUHI + 6) after only 24 h of cumulative GSR. SIUHI + 6 can then be used as a thermal threshold that characterizes hotspots within the city. This identification approach can be viewed as a useful criterion or as an initial step toward the development of heat health watch and warning system (HHWWS), especially during the occurrence of severe heat spells across urban areas.

  1. Field methods for rapidly characterizing paint waste during bridge rehabilitation.

    PubMed

    Shu, Zhan; Axe, Lisa; Jahan, Kauser; Ramanujachary, Kandalam V

    2015-09-01

    For Department of Transportation (DOT) agencies, bridge rehabilitation involving paint removal results in waste that is often managed as hazardous. Hence, an approach that provides field characterization of the waste classification would be beneficial. In this study, an analysis of variables critical to the leaching process was conducted to develop a predictive tool for waste classification. This approach first involved identifying mechanistic processes that control leaching. Because steel grit is used to remove paint, elevated iron concentrations remain in the paint waste. As such, iron oxide coatings provide an important surface for metal adsorption. The diffuse layer model was invoked (logKMe=4.65 for Pb and logKMe=2.11 for Cr), where 90% of the data were captured within the 95% confidence level. Based on an understanding of mechanistic processes along with principal component analysis (PCA) of data obtained from field-portable X-ray fluorescence (FP-XRF), statistically-based models for leaching from paint waste were developed. Modeling resulted in 96% of the data falling within the 95% confidence level for Pb (R(2) 0.6-0.9, p ⩽ 0.04), Ba (R(2) 0.5-0.7, p ⩽ 0.1), and Zn (R(2) 0.6-0.7, p ⩽ 0.08). However, the regression model obtained for Cr leaching was not significant (R(2) 0.3-0.5, p ⩽ 0.75). The results of this work may assist DOT agencies with applying a predictive tool in the field that addresses the mobility of trace metals as well as disposal and management of paint waste during bridge rehabilitation.

  2. Risk-Informed Safety Margin Characterization Methods Development Work

    SciTech Connect

    Smith, Curtis L; Ma, Zhegang; Riley, Tom; Mandelli, Diego; Nielsen, Joseph W; Alfonsi, Andrea; Rabiti, Cristian

    2014-09-01

    This report summarizes the research activity developed during the Fiscal year 2014 within the Risk Informed Safety Margin and Characterization (RISMC) pathway within the Light Water Reactor Sustainability (LWRS) campaign. This research activity is complementary to the one presented in the INL/EXT-??? report which shows advances Probabilistic Risk Assessment Analysis using RAVEN and RELAP-7 in conjunction to novel flooding simulation tools. Here we present several analyses that prove the values of the RISMC approach in order to assess risk associated to nuclear power plants (NPPs). We focus on simulation based PRA which, in contrast to classical PRA, heavily employs system simulator codes. Firstly we compare, these two types of analyses, classical and RISMC, for a Boiling water reactor (BWR) station black out (SBO) initiating event. Secondly we present an extended BWR SBO analysis using RAVEN and RELAP-5 which address the comments and suggestions received about he original analysis presented in INL/EXT-???. This time we focus more on the stochastic analysis such probability of core damage and on the determination of the most risk-relevant factors. We also show some preliminary results regarding the comparison between RELAP5-3D and the new code RELAP-7 for a simplified Pressurized Water Reactors system. Lastly we present some conceptual ideas regarding the possibility to extended the RISMC capabilities from an off-line tool (i.e., as PRA analysis tool) to an online-tool. In this new configuration, RISMC capabilities can be used to assist and inform reactor operator during real accident scenarios.

  3. Functional methods underlying classical mechanics, relativity and quantum theory

    NASA Astrophysics Data System (ADS)

    Kryukov, A.

    2013-04-01

    The paper investigates the physical content of a recently proposed mathematical framework that unifies the standard formalisms of classical mechanics, relativity and quantum theory. In the framework states of a classical particle are identified with Dirac delta functions. The classical space is "made" of these functions and becomes a submanifold in a Hilbert space of states of the particle. The resulting embedding of the classical space into the space of states is highly non-trivial and accounts for numerous deep relations between classical and quantum physics and relativity. One of the most striking results is the proof that the normal probability distribution of position of a macroscopic particle (equivalently, position of the corresponding delta state within the classical space submanifold) yields the Born rule for transitions between arbitrary quantum states.

  4. Apparatus and method for high-speed characterization of surfaces

    NASA Technical Reports Server (NTRS)

    Hooker, Jeffery A. (Inventor); Simmons, Stephen M. (Inventor)

    1997-01-01

    This invention permits rapid determination of a three-dimensional contour of an object. The apparatus directs a laser beam onto a point on an object, and the scattered light is received by a position sensitive detector (PSD). The location at which scattered light is received can be related to the displacement of the point on the object, using basic trigonometry. The laser beam is deflected non-mechanically, by passing it through a crystal whose index of refraction is varied in a controlled manner. By proper control of the index of refraction, one can scan the beam across a desired area of the object, without using any moving parts, and can therefore obtain complete information about the contour of the object. The device operates without making any conventional images, and is therefore much faster than comparable devices of the prior art. Also, the laser and beam deflector can be housed in a small optical head which enables the device to reach normally inaccessible areas. The device can compare the test object with a reference object, or it can compare two objects for differences.

  5. Characterization of the Space Shuttle Ascent Debris using CFD Methods

    NASA Technical Reports Server (NTRS)

    Murman, Scott M.; Aftosmis, Michael J.; Rogers, Stuart E.

    2005-01-01

    After video analysis of space shuttle flight STS-107's ascent showed that an object shed from the bipod-ramp region impacted the left wing, a transport analysis was initiated to determine a credible flight path and impact velocity for the piece of debris. This debris transport analysis was performed both during orbit, and after the subsequent re-entry accident. The analysis provided an accurate prediction of the velocity a large piece of foam bipod ramp would have as it impacted the wing leading edge. This prediction was corroborated by video analysis and fully-coupled CFD/six degree of freedom (DOF) simulations. While the prediction of impact velocity was accurate enough to predict critical damage in this case, one of the recommendations of the Columbia Accident Investigation Board (CAIB) for return-to-flight (RTF) was to analyze the complete debris environment experienced by the shuttle stack on ascent. This includes categorizing all possible debris sources, their probable geometric and aerodynamic characteristics, and their potential for damage. This paper is chiefly concerned with predicting the aerodynamic characteristics of a variety of potential debris sources (insulating foam and cork, nose-cone ablator, ice, ...) for the shuttle ascent configuration using CFD methods. These aerodynamic characteristics are used in the debris transport analysis to predict flight path, impact velocity and angle, and provide statistical variation to perform risk analyses where appropriate. The debris aerodynamic characteristics are difficult to determine using traditional methods, such as static or dynamic test data, due to the scaling requirements of simulating a typical debris event. The use of CFD methods has been a critical element for building confidence in the accuracy of the debris transport code by bridging the gap between existing aerodynamic data and the dynamics of full-scale, in-flight events.

  6. Pendant bubble method for an accurate characterization of superhydrophobic surfaces.

    PubMed

    Ling, William Yeong Liang; Ng, Tuck Wah; Neild, Adrian

    2011-12-06

    The commonly used sessile drop method for measuring contact angles and surface tension suffers from errors on superhydrophobic surfaces. This occurs from unavoidable experimental error in determining the vertical location of the liquid-solid-vapor interface due to a camera's finite pixel resolution, thereby necessitating the development and application of subpixel algorithms. We demonstrate here the advantage of a pendant bubble in decreasing the resulting error prior to the application of additional algorithms. For sessile drops to attain an equivalent accuracy, the pixel count would have to be increased by 2 orders of magnitude.

  7. Mechanical and thermal properties of nanomaterials at sub-50nm dimensions characterized using coherent EUV beams

    NASA Astrophysics Data System (ADS)

    Hoogeboom-Pot, Kathleen; Hernandez-Charpak, Jorge; Frazer, Travis; Gu, Xiaokun; Turgut, Emrah; Anderson, Erik; Chao, Weilun; Shaw, Justin; Yang, Ronggui; Murnane, Margaret; Kapteyn, Henry; Nardi, Damiano

    2015-03-01

    Coherent extreme ultraviolet beams from tabletop high harmonic generation offer several revolutionary capabilities for observing nanoscale systems on their intrinsic length and time scales. By launching and monitoring hypersonic acoustic waves in such systems, we characterize the mechanical properties of sub-10nm layers and find that the material densities remain close to their bulk values while their elastic properties are significantly modified. Moreover, within the same measurement, by following the heat dissipation dynamics from 30-750nm-wide nanowires, we uncover a new thermal transport regime in which closely-spaced nanoscale heat sources can surprisingly cool more efficiently than widelyspaced heat sources of the same size.

  8. Characterization of Diversity in Toxicity Mechanism Using In Vitro Cytotoxicity Assays in Quantitative High Throughput Screening

    PubMed Central

    Huang, Ruili; Southall, Noel; Cho, Ming-Hsuang; Xia, Menghang; Inglese, James; Austin, Christopher P.

    2009-01-01

    Assessing the potential health risks of environmental chemical compounds is an expensive undertaking which has motivated the development of new alternatives to traditional in vivo toxicological testing. One approach is to stage the evaluation, beginning with less expensive and higher throughput in vitro testing before progressing to more definitive trials. In vitro testing can be used to generate a hypothesis about a compound's mechanism of action, which can then be used to design an appropriate in vivo experiment. Here we begin to address the question of how to design such a battery of in vitro cell-based assays by combining data from two different types of assays, cell viability and caspase activation, with the aim of elucidating mechanism of action. Because caspase activation is a transient event during apoptosis, it is not possible to design a single end-point assay protocol that would identify all instances of compound-induced caspase activation. Nevertheless, useful information about compound mechanism of action can be obtained from these assays in combination with cell viability data. Unsupervised clustering in combination with Dunn's cluster validity index is a robust method for identifying mechanisms of action without requiring any a priori knowledge about mechanisms of toxicity. The performance of this clustering method is evaluated by comparing the clustering results against literature annotations of compound mechanisms. PMID:18281954

  9. Biogeographical characterization of Saccharomyces cerevisiae wine yeast by molecular methods

    PubMed Central

    Tofalo, Rosanna; Perpetuini, Giorgia; Schirone, Maria; Fasoli, Giuseppe; Aguzzi, Irene; Corsetti, Aldo; Suzzi, Giovanna

    2013-01-01

    Biogeography is the descriptive and explanatory study of spatial patterns and processes involved in the distribution of biodiversity. Without biogeography, it would be difficult to study the diversity of microorganisms because there would be no way to visualize patterns in variation. Saccharomyces cerevisiae, “the wine yeast,” is the most important species involved in alcoholic fermentation, and in vineyard ecosystems, it follows the principle of “everything is everywhere.” Agricultural practices such as farming (organic versus conventional) and floor management systems have selected different populations within this species that are phylogenetically distinct. In fact, recent ecological and geographic studies highlighted that unique strains are associated with particular grape varieties in specific geographical locations. These studies also highlighted that significant diversity and regional character, or ‘terroir,’ have been introduced into the winemaking process via this association. This diversity of wild strains preserves typicity, the high quality, and the unique flavor of wines. Recently, different molecular methods were developed to study population dynamics of S. cerevisiae strains in both vineyards and wineries. In this review, we will provide an update on the current molecular methods used to reveal the geographical distribution of S. cerevisiae wine yeast. PMID:23805132

  10. Characterization of a simplified method of cryopreserving human parathyroid tissue.

    PubMed

    Saxe, A W; Gibson, G W; Kay, S

    1990-12-01

    Cryopreservation of human parathyroid tissue plays an important role in managing difficult parathyroid disease. It also can permit investigators to conduct experiments without dependence on the operating room schedule. Availability of cryopreservation has been limited by the perceived need for expensive, complex equipment. We adapted a simple method of freezing cell suspensions to freezing human parathyroid tissue. Vials containing human parathyroid in culture media, dimethylsulfoxide, and patient serum were placed in a plastic rack in a metal pan containing prechilled (4 degrees C) ethanol and placed in a -70 degrees C freezer. We compared viability (trypan blue dye exclusion by collagenase dispersed cells) of tissue frozen in this manner to that of tissue frozen in a programmable liquid nitrogen freezer at 1 degrees C per minute, a cooling rate recommended for human parathyroid tissue. The viability of 30 patients' samples cooled in liquid nitrogen (average length of storage 5 months) was 74% +/- 15% and that of 64 patients' samples cooled in ethanol (average length of storage 26 months) was 71% +/- 15%. Viability of 19 samples of fresh tissue was 79% +/- 10%. Neither method had a statistically significant correlation between length of storage and viability. Successful cryopreservation with simplified technology may expand the availability of parathyroid tissue to meet both clinical and investigative requirements.

  11. An Extensive Unified Thermo-Electric Module Characterization Method

    PubMed Central

    Attivissimo, Filippo; Guarnieri Calò Carducci, Carlo; Lanzolla, Anna Maria Lucia; Spadavecchia, Maurizio

    2016-01-01

    Thermo-Electric Modules (TEMs) are being increasingly used in power generation as a valid alternative to batteries, providing autonomy to sensor nodes or entire Wireless Sensor Networks, especially for energy harvesting applications. Often, manufacturers provide some essential parameters under determined conditions, like for example, maximum temperature difference between the surfaces of the TEM or for maximum heat absorption, but in many cases, a TEM-based system is operated under the best conditions only for a fraction of the time, thus, when dynamic working conditions occur, the performance estimation of TEMs is crucial to determine their actual efficiency. The focus of this work is on using a novel procedure to estimate the parameters of both the electrical and thermal equivalent model and investigate their relationship with the operating temperature and the temperature gradient. The novelty of the method consists in the use of a simple test configuration to stimulate the modules and simultaneously acquire electrical and thermal data to obtain all parameters in a single test. Two different current profiles are proposed as possible stimuli, which use depends on the available test instrumentation, and relative performance are compared both quantitatively and qualitatively, in terms of standard deviation and estimation uncertainty. Obtained results, besides agreeing with both technical literature and a further estimation method based on module specifications, also provides the designer a detailed description of the module behavior, useful to simulate its performance in different scenarios. PMID:27983575

  12. An Automated Method for Characterizing the Relaxedness of Galaxy Clusters

    SciTech Connect

    George, Matt; /Harvard Coll. Observ. /SLAC

    2005-12-15

    Relaxed galaxy clusters are useful tools for probing cosmological parameters like the gas mass fraction of the universe. Selecting relaxed clusters for this purpose can be a time-consuming and subjective task, so we present methods to automate parts of the process. We fit elliptical isophotes to a diverse sample of Chandra cluster data and summarize other methods for quantifying relaxedness which will be included in future work. Analysis of the results of tests from isophote fitting, combined with numerical simulations of cluster structures and comparison to previous classifications will allow us to formulate criteria for selection of relaxed clusters. We find that they tend to have core radii less than approximately 60 kpc from King model fits, shifts in isophote centroids of less than 25 kpc over a range in semi-major axes of several hundred kpc, and significantly greater surface brightness profile gradients within 30 kpc of their cores than unrelaxed clusters. These criteria will help with future cosmological work as larger amounts of cluster data are taken and need objective classification.

  13. Purification and Characterization of Bovine Serum Albumin Using Chromatographic Method

    PubMed Central

    Balkani, Sanaz; Shamekhi, Sara; Raoufinia, Ramin; Parvan, Reza; Abdolalizadeh, Jalal

    2016-01-01

    Purpose: Albumin is an abundant protein of blood and has many biopharmaceutical applications. The aim of this study was to purify bovine serum albumin (BSA) using produced rabbit anti-BSA antibody. Methods: The polyclonal antibody was produced against the BSA in rabbits. Then, the pure BSA was injected to three white New Zealand rabbits. ELISA test was done to evaluate antibody production. After antibody purification,the purified antibody was attached to CNBr-activated sepharose and finally it was used for purification of albumin from bovine serum. Western blotting analysis was used for functional assessment of immunoaffinity purified BSA. Results: The titer of anti-bovine albumin determined by ELISA was obtained 1: 256000. The SDS-PAGE showed up to 98% purity of isolated BSA and western blotting confirmed the BSA functionality. Purified bovine serum albumin by affinity chromatography showed a single band with molecular weight of 66 KDa. Conclusion: Affinity chromatography using produced rabbit anti-BSA antibody would be an economical and safe method for purification of BSA. PMID:28101473

  14. A General Quantum Mechanical Method to Predict Positron Spectroscopy

    DTIC Science & Technology

    2007-06-01

    70 6.2.3 Positronic Systems for Modeling and Experiment 71 Appendix A. Electron-Positron Annihilation Observables from NEO-HF and NEO-MP2...spectroscopy (PAS) experiments are widely used to study materials defects, including point defects in semiconductors and voids in composite materials...addition to traditional PAS techniques, experiments involving VFRs are also discussed. In Section 2.2, methods for modeling positron interaction with

  15. Innovating Method of Existing Mechanical Product Based on TRIZ Theory

    NASA Astrophysics Data System (ADS)

    Zhao, Cunyou; Shi, Dongyan; Wu, Han

    Main way of product development is adaptive design and variant design based on existing product. In this paper, conceptual design frame and its flow model of innovating products is put forward through combining the methods of conceptual design and TRIZ theory. Process system model of innovating design that includes requirement analysis, total function analysis and decomposing, engineering problem analysis, finding solution of engineering problem and primarily design is constructed and this establishes the base for innovating design of existing product.

  16. Method of Testing and Predicting Failures of Electronic Mechanical Systems

    NASA Technical Reports Server (NTRS)

    Iverson, David L.; Patterson-Hine, Frances A.

    1996-01-01

    A method employing a knowledge base of human expertise comprising a reliability model analysis implemented for diagnostic routines is disclosed. The reliability analysis comprises digraph models that determine target events created by hardware failures human actions, and other factors affecting the system operation. The reliability analysis contains a wealth of human expertise information that is used to build automatic diagnostic routines and which provides a knowledge base that can be used to solve other artificial intelligence problems.

  17. Nanomechanical characterization and mechanical integrity of unaged and aged Li-ion battery cathodes

    NASA Astrophysics Data System (ADS)

    Ramdon, Sanjay; Bhushan, Bharat

    2014-01-01

    Lithium-ion (Li-ion) batteries have been implemented for numerous applications, one of which is in plug-in hybrid electric vehicles (PHEV) and pure electric vehicles (EV). In an effort to prolong battery life it is important to understand the mechanisms that cause reduced battery capacity with aging. In this work, nanomechanical characterization and mechanical integrity studies were carried out on unaged and aged LiFePO4 battery cathodes using atomic force microscopy (AFM) and nanoindentation. Changes in hardness, elastic modulus, creep, nanowear, nanoscratch and nanofriction properties were measured. Measured changes are believed to occur as a result of coarsening and agglomeration of LiFePO4 nanoparticles.

  18. Characterization of the mechanical properties of HL-1 cardiomyocytes with high throughput magnetic tweezers

    SciTech Connect

    Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-08-03

    We characterized the mechanical properties of cardiomyocyte-like HL-1 cells using our recently developed multi-pole magnetic tweezers. With the optimized design, both high force and high throughput are achieved at the same time. Force up to 100 pN can be applied on a 1 μm diameter superparamagnetic bead in a workspace with 60 μm radius, which is encircled symmetrically by 3 sharp magnetic tips. By adjusting the coil currents, both the strength and direction of force can be controlled. The result shows that both viscosity and shear elastic modulus of HL-1 cells exhibit an approximately log-normal distribution. The cells became stiffer as they matured, consistent with a transition from proliferating cells to contractile muscle tissue. Moreover, the mechanical properties of HL-1 cells show high heterogeneity, which agrees well with their physiological structure.

  19. A probabilistic approach to rock mechanical property characterization for nuclear waste repository design

    SciTech Connect

    Kim, Kunsoo; Gao, Hang

    1996-04-01

    A probabilistic approach is proposed for the characterization of host rock mechanical properties at the Yucca Mountain site. This approach helps define the probability distribution of rock properties by utilizing extreme value statistics and Monte Carlo simulation. We analyze mechanical property data of tuff obtained by the NNWSI Project to assess the utility of the methodology. The analysis indicates that laboratory measured strength and deformation data of Calico Hills and Bullfrog tuffs follow an extremal. probability distribution (the third type asymptotic distribution of the smallest values). Monte Carlo simulation is carried out to estimate rock mass deformation moduli using a one-dimensional tuff model proposed by Zimmermann and Finley. We suggest that the results of these analyses be incorporated into the repository design.

  20. Mechanical and microstructural characterization of Al7075/SiC nanocomposites fabricated by dynamic compaction

    NASA Astrophysics Data System (ADS)

    Atrian, A.; Majzoobi, G. H.; Enayati, M. H.; Bakhtiari, H.

    2014-03-01

    This paper describes the synthesis of Al7075 metal matrix composites reinforced with SiC, and the characterization of their microstructure and mechanical behavior. The mechanically milled Al7075 micron-sized powder and SiC nanoparticles are dynamically compacted using a drop hammer device. This compaction is performed at different temperatures and for various volume fractions of SiC nanoparticles. The relative density is directly related to the compaction temperature rise and indirectly related to the content of SiC nanoparticle reinforcement, respectively. Furthermore, increasing the amount of SiC nanoparticles improves the strength, stiffness, and hardness of the compacted specimens. The increase in hardness and strength may be attributed to the inherent hardness of the nanoparticles, and other phenomena such as thermal mismatch and crack shielding. Nevertheless, clustering of the nanoparticles at aluminum particle boundaries make these regions become a source of concentrated stress, which reduces the load carrying capacity of the compacted nanocomposite.

  1. Applications of Principled Search Methods in Climate Influences and Mechanisms

    NASA Technical Reports Server (NTRS)

    Glymour, Clark

    2005-01-01

    Forest and grass fires cause economic losses in the billions of dollars in the U.S. alone. In addition, boreal forests constitute a large carbon store; it has been estimated that, were no burning to occur, an additional 7 gigatons of carbon would be sequestered in boreal soils each century. Effective wildfire suppression requires anticipation of locales and times for which wildfire is most probable, preferably with a two to four week forecast, so that limited resources can be efficiently deployed. The United States Forest Service (USFS), and other experts and agencies have developed several measures of fire risk combining physical principles and expert judgment, and have used them in automated procedures for forecasting fire risk. Forecasting accuracies for some fire risk indices in combination with climate and other variables have been estimated for specific locations, with the value of fire risk index variables assessed by their statistical significance in regressions. In other cases, the MAPSS forecasts [23, 241 for example, forecasting accuracy has been estimated only by simulated data. We describe alternative forecasting methods that predict fire probability by locale and time using statistical or machine learning procedures trained on historical data, and we give comparative assessments of their forecasting accuracy for one fire season year, April- October, 2003, for all U.S. Forest Service lands. Aside from providing an accuracy baseline for other forecasting methods, the results illustrate the interdependence between the statistical significance of prediction variables and the forecasting method used.

  2. Characterization of mechanical damage mechanisms in ceramic composite materials. Technical report, 23 May 1987-24 May 1988

    SciTech Connect

    Lankford, J.

    1988-09-01

    High-strain-rate compressive failure mechanisms in fiber-reinforced ceramic-matrix composite materials were characterized. These are contrasted with composite damage development at low-strain rates, and with the dynamic failure of monolithic ceramics. It is shown that it is possible to derive major strain-rate strengthening benefits if a major fraction of the fiber reinforcement is aligned with the load axis. This effect considerably exceeds the inertial microfracture strengthening observed in monolithic ceramics, and non-aligned composites. Its basis is shown to be the trans-specimen propagation time period for heterogeneously-nucleated, high-strain kink bands. A brief study on zirconia focused on the remarkable inverse strength-strain rate result previously observed for both fully and partially-stabilized zirconia single crystals, whereby the strength decreased with increasing strain rate. Based on the hypothesis that the suppression of microplastic flow, hence, local stress relaxation, might be responsible for this behavior, fully stabilized (i.e., non-transformable) specimens were strain-gaged and subjected to compressive microstrain. The rather stunning observation was that the crystals are highly microplastic, exhibiting plastic yield on loading and anelasticity and reverse plasticity upon unloading. These results clearly support the hypothesis that with increasing strain rate, microcracking is favored at the expense of microplasticity.

  3. Characterizing the Mechanical Properties of Actual SAC105, SAC305, and SAC405 Solder Joints by Digital Image Correlation

    NASA Astrophysics Data System (ADS)

    Nguyen, T. T.; Yu, D.; Park, S. B.

    2011-06-01

    This paper presents the characterization of the mechanical properties of three lead-free solder alloys 95.5Sn-4.0Ag-0.5Cu (SAC405), 96.5Sn-3.0Ag-0.5Cu (SAC305), and 98.5Sn-1.0Ag-0.5Cu (SAC105) at the solder joint scale. Several actual ChipArray ® ball grid array (CABGA) packages were cross-sectioned, polished, and used as test vehicles. Compressive tests were performed using a nanocharacterization system over the temperature range of 25°C to 105°C. Images of the cross-sectioned solder joints were recorded by microscope during the tests. The recorded images were then processed by using a digital image correlation (DIC) program to calculate the displacement and strain fields on the solder joints. Finite-element method (FEM) modeling was used to extract the Poisson's ratio, Young's modulus, and coefficient of thermal expansion (CTE) of the solder alloys over the temperature range. The methodology developed in this paper enables characterization of the mechanical properties of the actual solder joints at low strain range with high accuracy.

  4. Mechanical characterization of thin TiO2 films by means of microelectromechanical systems-based cantilevers.

    PubMed

    Adami, A; Decarli, M; Bartali, R; Micheli, V; Laidani, N; Lorenzelli, L

    2010-01-01

    The measurement of mechanical parameters by means of microcantilever structures offers a reliable and accurate alternative to traditional methods, especially when dealing with thin films, which are extensively used in microfabrication technology and nanotechnology. In this work, microelectromechanical systems (MEMS)-based piezoresistive cantilevers were realized and used for the determination of Young's modulus and residual stress of thin titanium dioxide (TiO(2)) deposited by sputtering from a TiO(2) target using a rf plasma discharge. Films were deposited at different thicknesses, ranging from a few to a hundred nanometers. Dedicated silicon microcantilevers were designed through an optimization of geometrical parameters with the development of analytical as well as numerical models. Young's modulus and residual stress of sputtered TiO(2) films were assessed by using both mechanical characterization based on scanning profilometers and piezoresistive sensing elements integrated in the silicon cantilevers. Results of MEMS-based characterization were combined with the tribological and morphological properties measured by microscratch test and x-ray diffraction analysis.

  5. Precipitation method and characterization of cobalt oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Prabaharan, D. Durai Manoharadoss; Sadaiyandi, K.; Mahendran, M.; Sagadevan, Suresh

    2017-04-01

    Cobalt oxide (Co3O4) nanoparticles were synthesized using precipitation method. The X-ray diffraction (XRD) pattern was used to determine the structure of Co3O4 nanoparticles. The presence of Co3O4 nanoparticles was confirmed by the FTIR spectrum. The fact about the surface morphology of Co3O4 nanoparticles was revealed by scanning electron microscopic analysis. Transmission electron microscopy was used to measure the particle size of the Co3O4 nanoparticles. The absorption spectrum made it possible to analyze the optical properties of Co3O4 nanoparticles. This work contributes to the study of dielectric properties such as the dielectric loss and the dielectric constant of Co3O4 nanoparticles, at varied frequencies and temperatures. The magnetic properties of the Co3O4 nanoparticles were also investigated.

  6. Characterization of Space Shuttle Ascent Debris Aerodynamics Using CFD Methods

    NASA Technical Reports Server (NTRS)

    Murman, Scott M.; Aftosmis, Michael J.; Rogers, Stuart E.

    2005-01-01

    An automated Computational Fluid Dynamics process for determining the aerodynamic Characteristics of debris shedding from the Space Shuttle Launch Vehicle during ascent is presented. This process uses Cartesian fully-coupled, six-degree-of-freedom simulations of isolated debris pieces in a Monte Carlo fashion to produce models for the drag and crossrange behavior over a range of debris shapes and shedding scenarios. A validation of the Cartesian methods against ballistic range data for insulating foam debris shapes at flight conditions, as well as validation of the resulting models, are both contained. These models are integrated with the existing shuttle debris transport analysis software to provide an accurate and efficient engineering tool for analyzing debris sources and their potential for damage.

  7. New methodology for mechanical characterization of human superficial facial tissue anisotropic behaviour in vivo.

    PubMed

    Then, C; Stassen, B; Depta, K; Silber, G

    2017-02-21

    Mechanical characterization of human superficial facial tissue has important applications in biomedical science, computer assisted forensics, graphics, and consumer goods development. Specifically, the latter may include facial hair removal devices. Predictive accuracy of numerical models and their ability to elucidate biomechanically relevant questions depends on the acquisition of experimental data and mechanical tissue behavior representation. Anisotropic viscoelastic behavioral characterization of human facial tissue, deformed in vivo with finite strain, however, is sparse. Employing an experimental-numerical approach, a procedure is presented to evaluate multidirectional tensile properties of superficial tissue layers of the face in vivo. Specifically, in addition to stress relaxation, displacement-controlled multi-step ramp-and-hold protocols were performed to separate elastic from inelastic properties. For numerical representation, an anisotropic hyperelastic material model in conjunction with a time domain linear viscoelasticity formulation with Prony series was employed. Model parameters were inversely derived, employing finite element models, using multi-criteria optimization. The methodology provides insight into mechanical superficial facial tissue properties. Experimental data shows pronounced anisotropy, especially with large strain. The stress relaxation rate does not depend on the loading direction, but is strain-dependent. Preconditioning eliminates equilibrium hysteresis effects and leads to stress-strain repeatability. In the preconditioned state tissue stiffness and hysteresis insensitivity to strain rate in the applied range is evident. The employed material model fits the nonlinear anisotropic elastic results and the viscoelasticity model reasonably reproduces time-dependent results. Inversely deduced maximum anisotropic long-term shear modulus of linear elasticity is G∞,max(aniso)=2.43kPa and instantaneous initial shear modulus at an

  8. PSF and MTF Measurement Methods for Thick CCD Sensor Characterization

    SciTech Connect

    Takacs, P.Z.; Kotov, I.; Frank, J.; O'Connor, P.; Radeka, V.; Lawrence, D.M.

    2010-06-30

    Knowledge of the point spread function (PSF) of the sensors to be used in the Large Synoptic Survey Telescope (LSST) camera is essential for optimal extraction of subtle galaxy shape distortions caused by gravitational weak lensing. We have developed a number of techniques for measuring the PSF of candidate CCD sensors to be used in the LSST camera, each with its own strengths and weaknesses. The two main optical PSF measurement techniques that we use are the direct Virtual Knife Edge (VKE) scan as developed by Karcher, et al. and the indirect interference fringe method after Andersen and Sorensen that measures the modulation transfer function (MTF) directly. The PSF is derived from the MTF by Fourier transform. Other non-optical PSF measurement techniques that we employ include {sup 55}Fe x-ray cluster image size measurements and statistical distribution analysis, and cosmic ray muon track size measurements, but are not addressed here. The VKE technique utilizes a diffraction-limited spot produced by a Point-Projection Microscope (PPM) that is scanned across the sensor with sub-pixel resolution. This technique closely simulates the actual operating condition of the sensor in the telescope with the source spot size having an f/number close to the actual telescope design value. The interference fringe method uses a simple equal-optical-path Michelson-type interferometer with a single-mode fiber source that produces interference fringes with 100% contrast over a wide spatial frequency range sufficient to measure the MTF of the sensor directly. The merits of each measurement technique and results from the various measurement techniques on prototype LSST sensors are presented and compared.

  9. Mechanical and Biomechanical Characterization of a Polyurethane Nucleus Replacement Device Injected and Cured In Situ Within a Balloon

    PubMed Central

    Ordway, Nathaniel R.; Myint, Khin; Martz, Erik; Yuan, Hansen A.

    2008-01-01

    Background The DASCOR device has recently been introduced as an innovative nucleus replacement alternative for the treatment of low-back pain caused by degenerative intervertebral disc disease. The purpose of this study was to characterize, through a series of preclinical mechanical bench and biomechanical tests, the effectiveness of this device. Methods A number of samples were created using similar preparation methods in order to characterize the nucleus replacement device in multiple mechanical bench tests, using ASTM-guided protocols, where appropriate. Mechanical bench testing included static testing to characterize the device's compressive, shear properties, and fatigue testing to determine the device's compressive fatigue strength, wear, and durability. Biomechanical testing, using human cadaveric lumbar spines, was also conducted to determine the ability of the device to restore multidirectional segmental flexibility and to determine its resulting endplate contact stress. Results The static compressive and shear moduli of the nucleus replacement device were determined to be between 4.2–5.6 MPa and 1.4–1.9 MPa, respectively. Similarly, the ultimate compressive and shear strength were 12,400 N and 6,993 N, respectively. The maximum axial compressive fatigue strength of the tested device that was able to withstand a runout without failure was determined to be approximately 3 MPa. The wear assessment determined that the device is durable and yielded minimal wear rates of 0.29mg/Mc. Finally, the biomechanical testing demonstrated that the device can restore the multidirectional segmental flexibility to a level seen in the intact condition while concurrently producing a uniform endplate contact stress. Conclusions The results of the present study provided a mechanical justification supporting the clinical use of the nucleus replacement device and also help explain and support the positive clinical results obtained from two European studies and one US pilot

  10. Mixed ab initio quantum mechanics/molecular mechanics methods using frozen orbitals with applications to peptides and proteins

    NASA Astrophysics Data System (ADS)

    Philipp, Dean Michael

    Methodology is discussed for mixed ab initio quantum mechanics/molecular mechanics modeling of systems where the quantum mechanics (QM) and molecular mechanics (MM) regions are within the same molecule. The ab initio QM calculations are at the restricted Hartree-Fock level using the pseudospectral method of the Jaguar program while the MM part is treated with the OPLS force fields implemented in the IMPACT program. The interface between the QM and MM regions, in particular, is elaborated upon, as it is dealt with by ``breaking'' bonds at the boundaries and using Boys-localized orbitals found from model molecules in place of the bonds. These orbitals are kept frozen during QM calculations. The mixed modeling presented here can be used for single point energy calculations and geometry optimizations. Results from tests of the method to find relative conformational energies and geometries of alanine tetrapeptides are presented along with comparisons to pure QM and pure MM calculations.

  11. Nano-mechanical characterization of tension-sensitive helix bundles in talin rod.

    PubMed

    Maki, Koichiro; Nakao, Nobuhiko; Adachi, Taiji

    2017-03-04

    Tension-induced exposure of a cryptic signaling binding site is one of the most fundamental mechanisms in molecular mechanotransduction. Helix bundles in rod domains of talin, a tension-sensing protein at focal adhesions, unfurl under tension to expose cryptic vinculin binding sites. Although the difference in their mechanical stabilities would determine which helix bundle is tension-sensitive, their respective mechanical behaviors under tension have not been characterized. In this study, we evaluated the mechanical behaviors of residues 486-654 and 754-889 of talin, which form helix bundles with low and high tension-sensitivity, by employing AFM nano-tensile testing. As a result, residues 754-889 exhibited lower unfolding energy for complete unfolding than residues 486-654. In addition, we found that residues 754-889 transition into intermediate conformations under lower tension than residues 486-654. Furthermore, residues 754-889 showed shorter persistence length in the intermediate conformation than residues 486-654, suggesting that residues 754-889 under tension exhibit separated α-helices, while residues 486-654 assume a compact conformation with inter-helix interactions. Therefore, we suggest that residues 754-889 of talin work as a tension-sensitive domain to recruit vinculin at the early stage of focal adhesion development, while residues 486-654 contribute to rather robust tension-sensitivity by recruiting vinculin under high tension.

  12. Characterization of biaxial mechanical behavior of porcine aorta under gradual elastin degradation.

    PubMed

    Zeinali-Davarani, Shahrokh; Chow, Ming-Jay; Turcotte, Raphaël; Zhang, Yanhang

    2013-07-01

    Arteries are composed of multiple constituents that endow the wall with proper structure and function. Many vascular diseases are associated with prominent mechanical and biological alterations in the wall constituents. In this study, planar biaxial tensile test data of elastase-treated porcine aortic tissue (Chow et al. in Biomech Model Mechanobiol 2013) is re-examined to characterize the altered mechanical behavior at multiple stages of digestion through constitutive modeling. Exponential-based as well as recruitment-based strain energy functions are employed and the associated constitutive parameters for individual digestion stages are identified using nonlinear parameter estimation. It is shown that when the major portion of elastin is degraded from a cut-open artery in the load-free state, the embedded collagen fibers are recruited at lower stretch levels under biaxial loads, leading to a rapid stiffening behavior of the tissue. Multiphoton microscopy illustrates that the collagen waviness decreases significantly with the degradation time, resulting in a rapid recruitment when the tissue is loaded. It is concluded that even when residual stresses are released, there exists an intrinsic mechanical interaction between arterial elastin and collagen that determines the mechanics of arteries and carries important implications to vascular mechanobiology.

  13. Mechanical characterization of bucky gel morphing nanocomposite for actuating/sensing applications

    NASA Astrophysics Data System (ADS)

    Kadhoda Ghamsari, Ali; Jin, Yoonyoung; Woldesenbet, Eyassu

    2012-04-01

    Since the demonstration of the bucky gel actuator (BGA) in 2005, a great deal of effort has been exerted to develop novel applications for this electro-active morphing nanocomposite. This three-layered bimorph nanocomposite can be easily fabricated, operated in air and driven with a few volts. The BGA with improved mechanical strength is an excellent candidate for application in macro- to micro-scale smart structures with actuating and sensing capabilities. However, developing new applications requires identifying and understanding the effective design parameters and mechanical properties, respectively. There has been limited published studies on the mechanical properties of BGA. In this study, the effect of three parameters—layer thickness, carbon nanotube type and weight fraction of components—on the mechanical properties was investigated. Samples were characterized via nano-indentation and DMA. The BGA composed of 22 wt% single-walled carbon nanotubes and 45 wt% ionic liquid exhibited the highest hardness, adhesion, viscosity, and elastic and storage moduli. This study revealed the important role of the carbon nanotube type on BGA adhesion. Samples made with multi-walled carbon nanotubes had the lowest adhesion, which is a required factor in applications such as microfluidics.

  14. Compilation of methods in orbital mechanics and solar geometry

    NASA Technical Reports Server (NTRS)

    Buglia, James J.

    1988-01-01

    This paper contains a collection of computational algorithms for determining geocentric ephemerides of Earth satellites, useful for both mission planning and data reduction applications. Special emphasis is placed on the computation of sidereal time, and on the determination of the geocentric coordinate of the center of the Sun, all to the accuracy found in the Astronomical Almanac. The report is completely self-contained in that no requirement is placed on any external source of information, and hence, these methods are ideal for computer application.

  15. Formulations and computational methods for contact problems in solid mechanics

    NASA Astrophysics Data System (ADS)

    Mirar, Anand Ramchandra

    2000-11-01

    A study of existing formulations and computational methods for contact problems is conducted. The purpose is to gain insights into the solution procedures and pinpoint their limitations so that alternate procedures can be developed. Three such procedures based on the augmented Lagrangian method (ALM) are proposed. Small-scale benchmark problems are solved analytically as well as numerically to study the existing and proposed methods. The variational inequality formulation for frictionless contact is studied using the two bar truss-wall problem in a closed form. Sub-differential formulation is investigated using the spring-wall contact and the truss-wall friction problems. A two-phase analytical procedure is developed for solving the truss-wall frictional contact benchmark problem. The variational equality formulation for contact problems is studied using the penalty method along with the Newton-Raphson procedure. Limitations of such procedures, mainly due to their dependence on the user defined parameters (i.e., the penalty values and the number of time steps), are identified. Based on the study it is concluded that alternate formulations need to be developed. Frictionless contact formulation is developed using the basic concepts of ALM from optimization theory. A new frictional contact formulation (ALM1) is then developed employing ALM. Automatic penalty update procedure is used to eliminate dependence of the solution on the penalty values. Dependence of the solution on the number of time steps in the existing as well as ALM1 formulations is attributed to a flaw in the return mapping procedure for friction. Another new frictional contact formulation (ALM2) is developed to eliminate the dependence of solution on the number of time steps along with the penalty values. Effectiveness of ALM2 is demonstrated by solving the two bar and five bar truss-wall problems. The solutions are compared with the analytical and existing formulations. Design sensitivity analysis of

  16. Improvement of mechanical properties of polymeric composites: Experimental methods and new systems

    NASA Astrophysics Data System (ADS)

    Nguyen, Felix Nhanchau

    Filler- (e.g., particulate or fiber) reinforced structural polymers or polymeric composites have changed the way things are made. Today, they are found, for example, in air/ground transportation vehicles, sporting goods, ballistic barrier applications and weapons, electronic packaging, musical instruments, fashion items, and more. As the demand increases, so does the desire to have not only well balanced mechanical properties, but also light weight and low cost. This leads to a constant search for novel constituents and additives, new fabrication methods and analytical techniques. To achieve new or improved composite materials requires more than the identification of the right reinforcements to be used with the right polymer matrix at the right loading. Also, an optimized adhesion between the two phases and a toughened matrix system are needed. This calls for new methods to predict, modify and assess the level of adhesion, and new developments in matrix tougheners to minimize compromises in other mechanical/thermal properties. Furthermore, structural optimization, associated with fabrication (e.g., avoidance of fiber-fiber touching or particle aggregation), and sometimes special properties, such as electrical conductivity or magnetic susceptibility are necessary. Finally, the composite system's durability, often under hostile conditions, is generally mandatory. The present study researches new predictive and experimental methods for optimizing and characterizing filler-matrix adhesion and develops a new type of epoxy tougheners. Specifically, (1) a simple thermodynamic parameter evaluated by UNIFAC is applied successfully to screen out candidate adhesion promoters, which is necessary for optimization of the physio-chemical interactions between the two phases; (2) an optical-acoustical mechanical test assisted with an acoustic emission technique is developed to de-convolute filler debonding/delamination among many other micro failure events, and (3) novel core

  17. Reconstruction of dynamical perturbations in optical systems by opto-mechanical simulation methods

    NASA Astrophysics Data System (ADS)

    Gilbergs, H.; Wengert, N.; Frenner, K.; Eberhard, P.; Osten, W.

    2012-03-01

    High-performance objectives pose very strict limitations on errors present in the system. External mechanical influences can induce structural vibrations in such a system, leading to small deviations of the position and tilt of the optical components inside the objective from the undisturbed system. This can have an impact on the imaging performance, causing blurred images or broadened structures in lithography processes. A concept to detect the motion of the components of an optical system is presented and demonstrated on a simulated system. The method is based on a combination of optical simulation together with mechanical simulation and inverse problem theory. On the optical side raytracing is used for the generation of wavefront data of the system in its current state. A Shack-Hartmann sensor is implemented as a model to gather this data. The sensor can capture wavefront data with high repetition rates to resolve the periodic motion of the vibrating parts. The mechanical side of the system is simulated using multibody dynamics. The system is modeled as a set of rigid bodies (lenses, mounts, barrel), represented by rigid masses connected by springs that represent the coupling between the individual parts. External excitations cause the objective to vibrate. The vibration can be characterized by the eigenmodes and eigenfrequencies of the system. Every state of the movement during the vibration can be expressed as a linear combination of the eigenmodes. The reconstruction of the system geometry from the wavefront data is an inverse problem. Therefore, Tikhonov regularization is used in the process in order to achieve more accurate reconstruction results. This method relies on a certain amount of a-priori information on the system. The mechanical properties of the system are a great source of such information. It is taken into account by performing the calculation in the coordinate system spanned by the eigenmodes of the objective and using information on the

  18. Advanced methods for preparation and characterization of infrared detector materials

    NASA Technical Reports Server (NTRS)

    Broerman, J. G.; Morris, B. J.; Meschter, P. J.

    1983-01-01

    Crystals were prepared by the Bridgman-Stockbarger method with a wide range of crystal growth rates and temperature gradients adequate to prevent constitutional supercooling under diffusion-limited, steady-state, growth conditions. The longitudinal compositional gradients for different growth conditions and alloy compositions were calculated and compared with experimental data to develop a quantitative model of solute redistribution during the crystal growth of the alloys. Measurements were performed to ascertain the effect of growth conditions on radial compositional gradients. The pseudobinary HgTe-CdTe constitutional phase diagram was determined by precision differential-thermal-analysis measurements and used to calculate the segregation coefficient of Cd as a function of x and interface temperature. Experiments were conducted to determine the ternary phase equilibria in selected regions of the Hg-Cd-Te constitutional phase diagram. Electron and hole mobilities as functions of temperature were analyzed to establish charge-carrier scattering probabilities. Computer algorithms specific to Hg(1-x)CdxTe were developed for calculations of the charge-carrier concentration, charge-carrier mobilities, Hall coefficient, and Dermi Fermi energy as functions of x, temperature, ionized donor and acceptor concentrations, and neutral defect concentrations.

  19. Study Methods to Characterize and Implement Thermography Nondestructive Evaluation (NDE)

    NASA Technical Reports Server (NTRS)

    Walker, James L.

    1998-01-01

    The limits and conditions under which an infrared thermographic nondestructive evaluation can be utilized to assess the quality of aerospace hardware is demonstrated in this research effort. The primary focus of this work is on applying thermography to the inspection of advanced composite structures such as would be found in the International Space Station Instrumentation Racks, Space Shuttle Cargo Bay Doors, Bantam RP-1 tank or RSRM Nose Cone. Here, the detection of delamination, disbond, inclusion and porosity type defects are of primary interest. In addition to composites, an extensive research effort has been initiated to determine how well a thermographic evaluation can detect leaks and disbonds in pressurized metallic systems "i.e. the Space Shuttle Main Engine Nozzles". In either case, research into developing practical inspection procedures was conducted and thermographic inspections were performed on a myriad of test samples, subscale demonstration articles and "simulated" flight hardware. All test samples were fabricated as close to their respective structural counterparts as possible except with intentional defects for NDE qualification. As an added benefit of this effort to create simulated defects, methods were devised for defect fabrication that may be useful in future NDE qualification ventures.

  20. Application of thermal methods for characterization of steel welded joints

    NASA Astrophysics Data System (ADS)

    Galietti, U.; Palumbo, D.

    2010-06-01

    Despite the large number of proposals in the field of fatigue prediction of welded joints, a globally accepted and unified theory, which applies easily to any load condition, does not exist. Real life components, indeed, differ in geometry and/or type of load from the structural design for which they are regarded by Standards, so that a lot of precautionary safety factors are used that lead to an underestimation of the actual fatigue life of joints. Infrared thermography has a great potential in this field, both from structural and thermomechanical points of view. It enables a full field stress analysis with a sufficient spatial resolution so that the complexity of the stress state at the weld toe and its time evolution are taken into account, emphasizing anomalies that may predict structural failure. A new methods for evaluation fatigue limit damage is presented in this paper and in particular interesting results derived from analysis of the evolution of thermoelastic signal phase. Variations in the value of signal phase indicate a not elastic behaviour and plastic dissipation in the material.