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Sample records for autogenous shrinkage cracking

  1. Temperature dependence of autogenous shrinkage of silica fume cement pastes with a very low water–binder ratio

    SciTech Connect

    Maruyama, I.; Teramoto, A.

    2013-08-15

    Ultra-high-strength concrete with a large unit cement content undergoes considerable temperature increase inside members due to hydration heat, leading to a higher risk of internal cracking. Hence, the temperature dependence of autogenous shrinkage of cement pastes made with silica fume premixed cement with a water–binder ratio of 0.15 was studied extensively. Development of autogenous shrinkage showed different behaviors before and after the inflection point, and dependence on the temperature after mixing and subsequent temperature histories. The difference in autogenous shrinkage behavior poses problems for winter construction because autogenous shrinkage may increase with decrease in temperature after mixing before the inflection point and with increase in temperature inside concrete members with large cross sections.

  2. Study on effects of solar radiation and rain on shrinkage, shrinkage cracking and creep of concrete

    SciTech Connect

    Asamoto, Shingo; Ohtsuka, Ayumu; Kuwahara, Yuta; Miura, Chikako

    2011-06-15

    In this paper, the effects of actual environmental actions on shrinkage, creep and shrinkage cracking of concrete are studied comprehensively. Prismatic specimens of plain concrete were exposed to three sets of artificial outdoor conditions with or without solar radiation and rain to examine the shrinkage. For the purpose of studying shrinkage cracking behavior, prismatic concrete specimens with reinforcing steel were also subjected to the above conditions at the same time. The shrinkage behavior is described focusing on the effects of solar radiation and rain based on the moisture loss. The significant environment actions to induce shrinkage cracks are investigated from viewpoints of the amount of the shrinkage and the tensile strength. Finally, specific compressive creep behavior according to solar radiation and rainfall is discussed. It is found that rain can greatly inhibit the progresses of concrete shrinkage and creep while solar radiation is likely to promote shrinkage cracking and creep.

  3. Self-healing of drying shrinkage cracks in cement-based materials incorporating reactive MgO

    NASA Astrophysics Data System (ADS)

    Qureshi, T. S.; Al-Tabbaa, A.

    2016-08-01

    Excessive drying shrinkage is one of the major issues of concern for longevity and reduced strength performance of concrete structures. It can cause the formation of cracks in the concrete. This research aims to improve the autogenous self-healing capacity of traditional Portland cement (PC) systems, adding expansive minerals such as reactive magnesium oxide (MgO) in terms of drying shrinkage crack healing. Two different reactive grades (high ‘N50’and moderately high ‘92-200’) of MgO were added with PC. Cracks were induced in the samples with restraining end prisms through natural drying shrinkage over 28 days after casting. Samples were then cured under water for 28 and 56 days, and self-healing capacity was investigated in terms of mechanical strength recovery, crack sealing efficiency and improvement in durability. Finally, microstructures of the healing materials were investigated using FT-IR, XRD, and SEM-EDX. Overall N50 mixes show higher expansion and drying shrinkage compared to 92-200 mixes. Autogenous self-healing performance of the MgO containing samples were much higher compared to control (only PC) mixes. Cracks up to 500 μm were sealed in most MgO containing samples after 28 days. In the microstructural investigations, highly expansive Mg-rich hydro-carbonate bridges were found along with traditional calcium-based, self-healing compounds (calcite, portlandite, calcium silicate hydrates and ettringite).

  4. Evaluation of shrinkage and cracking in concrete of ring test by acoustic emission method

    NASA Astrophysics Data System (ADS)

    Watanabe, Takeshi; Hashimoto, Chikanori

    2015-03-01

    Drying shrinkage of concrete is one of the typical problems related to reduce durability and defilation of concrete structures. Lime stone, expansive additive and low-heat Portland cement are used to reduce drying shrinkage in Japan. Drying shrinkage is commonly evaluated by methods of measurement for length change of mortar and concrete. In these methods, there is detected strain due to drying shrinkage of free body, although visible cracking does not occur. In this study, the ring test was employed to detect strain and age cracking of concrete. The acoustic emission (AE) method was adopted to detect micro cracking due to shrinkage. It was recognized that in concrete using lime stone, expansive additive and low-heat Portland cement are effective to decrease drying shrinkage and visible cracking. Micro cracking due to shrinkage of this concrete was detected and evaluated by the AE method.

  5. Evaluation and Observation of Autogenous Healing Ability of Bond Cracks along Rebar.

    PubMed

    Kang, Choonghyun; Kunieda, Minoru

    2014-04-17

    Micro cracks occurring in concrete around tensile rebar is well known latent damage phenomenon. These micro cracks develop, and can be detected after reaching the surface of the concrete. Detection of these cracks before they are fully formed is preferable, but observing the whole crack structure is difficult. Another problem is repairing micro cracks under the concrete surface. The autogenous ability of bond cracks along rebar was evaluated using the air permeability test. Air permeability coefficients were measured before and after tensile loading, and experimental air permeability coefficients became larger near cracks along rebar as a result of tensile loading. Recuring for 28 days after tensile loading made the air permeability coefficients smaller, but this restriction only occurred during water recuring. Observation of crack patterns helped the understanding of change in the air permeability coefficients. Several small cracks along rebar were observed after tensile loading, and most cracks along rebar were not found after water recuring. On the other hand, the crack pattern did not change after air recuring. These results indicate that bond cracks along rebar can be closed by autogenous healing, and cause the air permeability coefficients.

  6. Development of high shrinkage polyethylene terephthalate (PET) shape memory polymer tendons for concrete crack closure

    NASA Astrophysics Data System (ADS)

    Teall, Oliver; Pilegis, Martins; Sweeney, John; Gough, Tim; Thompson, Glen; Jefferson, Anthony; Lark, Robert; Gardner, Diane

    2017-04-01

    The shrinkage force exerted by restrained shape memory polymers (SMPs) can potentially be used to close cracks in structural concrete. This paper describes the physical processing and experimental work undertaken to develop high shrinkage die-drawn polyethylene terephthalate (PET) SMP tendons for use within a crack closure system. The extrusion and die-drawing procedure used to manufacture a series of PET tendon samples is described. The results from a set of restrained shrinkage tests, undertaken at differing activation temperatures, are also presented along with the mechanical properties of the most promising samples. The stress developed within the tendons is found to be related to the activation temperature, the cross-sectional area and to the draw rate used during manufacture. Comparisons with commercially-available PET strip samples used in previous research are made, demonstrating an increase in restrained shrinkage stress by a factor of two for manufactured PET filament samples.

  7. Measurement of shrinkage and cracking in lyophilized amorphous cakes. Part IV: Effects of freezing protocol.

    PubMed

    Ullrich, Sabine; Seyferth, Stefan; Lee, Geoffrey

    2015-11-10

    The shrinkage and cracking of pure trehalose cakes during lyophilization has been determined quantitatively using different protocols for the freezing step. The influences of shelf cooling rate and of a two-step freezing protocol with holding and annealing phases were investigated. A small change in the shelf cooling rate from 0.4°C to 0.2°C per minute produced surprisingly large increases in shrinkage and reductions in cracking over all trehalose concentrations up to 30% w/v. The two-step freezing protocol also increased shrinkage and reduced cracking in the final-product cakes, especially at trehalose concentrations ≥ 15% and with large vial fill height. A combination of two-step freezing with use of TopLyo vials produced less than 1.5% cracking even at high trehalose concentrations and large fill height. The results give further confirmation of the causal linkage of shrinkage and cracking during lyophilization, and also illustrate how cracking can be greatly reduced by manipulating the freezing protocol. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Effectiveness of Fiber Reinforcement on the Mechanical Properties and Shrinkage Cracking of Recycled Fine Aggregate Concrete

    PubMed Central

    Nam, Jeongsoo; Kim, Gyuyong; Yoo, Jaechul; Choe, Gyeongcheol; Kim, Hongseop; Choi, Hyeonggil; Kim, Youngduck

    2016-01-01

    This paper presents an experimental study conducted to investigate the effect of fiber reinforcement on the mechanical properties and shrinkage cracking of recycled fine aggregate concrete (RFAC) with two types of fiber—polyvinyl alcohol (PVA) and nylon. A small fiber volume fraction, such as 0.05% or 0.1%, in RFAC with polyvinyl alcohol or nylon fibers was used for optimum efficiency in minimum quantity. Additionally, to make a comparative evaluation of the mechanical properties and shrinkage cracking, we examined natural fine aggregate concrete as well. The test results revealed that the addition of fibers and fine aggregates plays an important role in improving the mechanical performance of the investigated concrete specimens as well as controlling their cracking behavior. The mechanical properties such as compressive strength, splitting tensile strength, and flexural strength of fiber-reinforced RFAC were slightly better than those of non-fiber-reinforced RFAC. The shrinkage cracking behavior was examined using plat-ring-type and slab-type tests. The fiber-reinforced RFAC showed a greater reduction in the surface cracks than non-fiber-reinforced concrete. The addition of fibers at a small volume fraction in RFAC is more effective for drying shrinkage cracks than for improving mechanical performance. PMID:28773256

  9. Effectiveness of Fiber Reinforcement on the Mechanical Properties and Shrinkage Cracking of Recycled Fine Aggregate Concrete.

    PubMed

    Nam, Jeongsoo; Kim, Gyuyong; Yoo, Jaechul; Choe, Gyeongcheol; Kim, Hongseop; Choi, Hyeonggil; Kim, Youngduck

    2016-02-26

    This paper presents an experimental study conducted to investigate the effect of fiber reinforcement on the mechanical properties and shrinkage cracking of recycled fine aggregate concrete (RFAC) with two types of fiber-polyvinyl alcohol (PVA) and nylon. A small fiber volume fraction, such as 0.05% or 0.1%, in RFAC with polyvinyl alcohol or nylon fibers was used for optimum efficiency in minimum quantity. Additionally, to make a comparative evaluation of the mechanical properties and shrinkage cracking, we examined natural fine aggregate concrete as well. The test results revealed that the addition of fibers and fine aggregates plays an important role in improving the mechanical performance of the investigated concrete specimens as well as controlling their cracking behavior. The mechanical properties such as compressive strength, splitting tensile strength, and flexural strength of fiber-reinforced RFAC were slightly better than those of non-fiber-reinforced RFAC. The shrinkage cracking behavior was examined using plat-ring-type and slab-type tests. The fiber-reinforced RFAC showed a greater reduction in the surface cracks than non-fiber-reinforced concrete. The addition of fibers at a small volume fraction in RFAC is more effective for drying shrinkage cracks than for improving mechanical performance.

  10. Assessment and prediction of drying shrinkage cracking in bonded mortar overlays

    SciTech Connect

    Beushausen, Hans Chilwesa, Masuzyo

    2013-11-15

    Restrained drying shrinkage cracking was investigated on composite beams consisting of substrate concrete and bonded mortar overlays, and compared to the performance of the same mortars when subjected to the ring test. Stress development and cracking in the composite specimens were analytically modeled and predicted based on the measurement of relevant time-dependent material properties such as drying shrinkage, elastic modulus, tensile relaxation and tensile strength. Overlay cracking in the composite beams could be very well predicted with the analytical model. The ring test provided a useful qualitative comparison of the cracking performance of the mortars. The duration of curing was found to only have a minor influence on crack development. This was ascribed to the fact that prolonged curing has a beneficial effect on tensile strength at the onset of stress development, but is in the same time not beneficial to the values of tensile relaxation and elastic modulus. -- Highlights: •Parameter study on material characteristics influencing overlay cracking. •Analytical model gives good quantitative indication of overlay cracking. •Ring test presents good qualitative indication of overlay cracking. •Curing duration has little effect on overlay cracking.

  11. Restrained shrinkage cracking in fiber reinforced concrete: A novel test technique

    SciTech Connect

    Banthia, N.; Yan, C.; Mindess, S.

    1996-01-01

    A novel experimental technique was developed to assess the cracking potential of cement-based materials when used as a bonded overlay. Specimens were cast directly on to a substrate and the assembly was subjected to a drying environment to induce cracking. Lengths and widths of the resulting cracks in the overlay were monitored as a function of time. The use of fibers was found to be very effective not only in reducing the widths of the shrinkage cracks but also in allowing multiple cracking to occur. Interestingly, these two phenomena occurred only up to a fiber volume fraction of 0.5%; at 1% by volume of fibers, only minimal cracking was seen to occur even under a particularly severe environment.

  12. Effect of multivalent ions on the swelling and mechanical behavior of superabsorbent polymers (SAPs) for mitigation of mortar autogenous shrinkage

    NASA Astrophysics Data System (ADS)

    Zhu, Qian

    The chemical and physical structure-property relationships of model superabsorbent polymer (SAP) hydrogels were characterized with respect to swelling behavior and mechanical properties in different ionic solutions (Na+, Ca2+, and Al3+). The model hydrogels were composed of poly(sodium acrylate-acrylamide) (PANa-PAM) copolymer with varying concentrations of PANa (0, 17, 33, 67, and 83 wt.%) and covalent crosslinking densities of 1, 1.5, and 2 wt.%. By synthesizing the hydrogels in-house, systems with independently tunable amounts of covalent crosslinking and anionic functional groups were created, allowing for the relative effects of covalent and ionic crosslinking on the properties of the hydrogels to be directly quantified. It was found that the presence of Ca2+ and Al3+ in the absorbed fluid significantly decreased the swelling capacity and altered the swelling kinetics of the PANa-PAM hydrogels. The presence of Al 3+ in solution resulted in the unexpected formation of a mechanically stiff barrier layer at the hydrogel's surface, which hindered the release of fluid and caused the overall elastic modulus of the hydrogel to increase from O(10 kPa) for hydrogels immersed in Ca2+ solutions to O(100 kPa) for hydrogels immersed in Al3+ solutions. Tensile tests performed on isolated specimens of the stiff barrier layer yielded elastic moduli in the O(50-100 MPa) range. Further experiments proved that PANa-PAM hydrogels are effective to keep mortar internal relative humidity at high value (~98%) during setting and also PANa-PAM decreased the autogenous shrinkage of mortar to less than 50 microstrain while plain mortar showed 350 microstrain.

  13. Polymerization stresses in low-shrinkage dental resin composites measured by crack analysis.

    PubMed

    Yamamoto, Takatsugu; Kubota, Yu; Momoi, Yasuko; Ferracane, Jack L

    2012-09-01

    The objective of this study was to compare several dental restoratives currently advertised as low-shrinkage composites (Clearfil Majesty Posterior, Kalore, Reflexions XLS Dentin and Venus Diamond) with a microfill composite (Heliomolar) in terms of polymerization stress, polymerization shrinkage and elastic modulus. Cracks were made at several distances from the edge of a precision cavity in a soda-lime glass disk. The composites were placed into the cavity and lengths of the cracks were measured before and after light curing. Polymerization stresses generated in the glass at 2 and 10 min after the irradiation were calculated from the crack lengths and K(c) of the glass. Polymerization shrinkage and elastic modulus of the composites also were measured at 2 and 10 min after irradiation using a video-imaging device and a nanoindenter, respectively. The data were statistically analyzed by ANOVAs and Tukey's test (p<0.05). The stress was significantly affected by composite brand, distance and time. The stress was directly proportional to time and inversely proportional to distance from the edge of the cavity. Clearfil Majesty Posterior demonstrated the highest stress and it resulted in the fracture of the glass at 2 min. Venus Diamond and Heliomolar exhibited the greatest shrinkage at both times. The elastic moduli of Clearfil Majesty Posterior and Reflexions XLS Dentin were greatest at 2 and 10 min, respectively. Among the four low-shrinkage composites, two demonstrated significantly reduced polymerization stress compared to Heliomolar, which has previously been shown in in vitro tests to generate low curing stress. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  14. Investigation of Hot Cracking Behavior in Transverse Mechanically Arc Oscillated Autogenous AA2014 T6 TIG Welds

    NASA Astrophysics Data System (ADS)

    Biradar, N. S.; Raman, R.

    2012-09-01

    Hot cracking studies on autogenous AA2014 T6 TIG welds were carried out. Significant cracking was observed during linear and circular welding test (CWT) on 4-mm-thick plates. Weld metal grain structure and amount of liquid distribution during the terminal stages of solidification were the key cause for hot cracking in aluminum welds. Square-wave AC TIG welding with transverse mechanical arc oscillation (TMAO) was employed to study the cracking behavior during linear and CWT. TMAO welds with amplitude = 0.9 mm and frequency = 0.5 Hz showed significant reduction in cracking tendency. The increase in cracking resistance in the arc-oscillated weld was attributed to grain refinement and improved weld bead morphology, which improved the weld metal ductility and uniformity, respectively, of residual tensile stresses that developed during welding. The obtained results were comparable to those of reported favorable results of electromagnetic arc oscillation.

  15. Development and construction of low-cracking high-performance concrete (LC-HPC) bridge decks: Free shrinkage tests, restrained ring tests, construction experience, and crack survey results

    NASA Astrophysics Data System (ADS)

    Yuan, Jiqiu

    2011-12-01

    The development, construction, and evaluation of low-cracking high-performance concrete (LC-HPC) bridge decks are described based on laboratory test results and experiences gained during the construction of 13 LC-HPC bridge decks in Kansas, along with another deck bid under the LC-HPC specifications but for which the owner did not enforce the specification. This study is divided into four parts covering (1) an evaluation of the free shrinkage properties of LC-HPC candidate mixtures, (2) an investigation of the relationship between the evaporable water content in the cement paste and the free shrinkage of concrete, (3) a study of the restrained shrinkage performance of concrete using restrained ring tests, and (4) a description of the construction and preliminary evaluation of LC-HPC and control bridge decks constructed in Kansas. The first portion of the study involves evaluating the effects of the duration of curing, fly ash, and a shrinkage reducing admixture (SRA) on the free-shrinkage characteristics of concrete mixtures. The results indicate that an increase of curing period reduces free shrinkage. With 7 days of curing, concretes containing fly ash as a partial replacement for cement exhibit higher free shrinkage than concretes with 100% portland cement. When the curing period is increased to 14, 28, and 56 days, the adverse effect of adding fly ash on free shrinkage is minimized and finally reversed. The addition of an SRA significantly reduces free shrinkage for both the 100% portland cement mixture and the mixture containing fly ash. The second portion of the study investigates the relationship between the evaporable water content in the cement paste and the free shrinkage of concrete. A linear relationship between free shrinkage and evaporable water content in the cement paste is observed. For a given mixture, specimens cured for a longer period contain less evaporable water and exhibit lower free shrinkage and less weight loss in the free shrinkage

  16. Measurement of shrinkage and cracking in lyophilized amorphous cakes, part 3: hydrophobic vials and the question of adhesion.

    PubMed

    Ullrich, Sabine; Seyferth, Stefan; Lee, Geoffrey

    2015-06-01

    The importance of cake adhesion to the inside vial wall during lyophilization of amorphous trehalose cakes was determined by using hydrophobized vials. The degrees of cake shrinkage and cracking were determined independently by photographic imaging of the cake top surface in a dark cell. Additionally, measurements with microcomputed tomography were performed. Adhesion is found to be a determining factor in both cake shrinkage and cracking. The correlation between cake detachment from the vial inner wall and trehalose concentration indicates that adhesion of the frozen solute phase is a determining factor in shrinkage. The hydrophobized vials give reduced cracking at trehalose concentrations of up to 15%. The reduced wetting of the hydrophobized inside vial wall gives a planar cake topography with a uniform distribution of cracks within the cake.

  17. Shrinkage Cracking: A mechanism for self-sustaining carbon mineralization reactions in olivine rocks

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xing, T.; Xiao, X.; De Andrade, V. J. D.; Karato, S. I.

    2015-12-01

    The hydration and carbonation of olivine results in an up to ~44% increase in solid molar volume, which may choke off of fluid supply and passivate reactive surfaces, thus preventing further carbonation reactions. The carbonation of olivine has ben studied extensively in the laboratory. To date, observations from these experimental studies indicate that carbonation reaction rates generally decrease with time and the extent of carbonation is limited in olivine rocks. Field studies, however, show that 100% hydration and carbonation occur naturally in ultramafic rocks. The disagreement between the laboratory results under controlled conditions and the field observations underlines the lack of understanding of the mechanisms responsible for the self-sustaining carbonation interaction in nature. We developed a state-of-the-art pressurized hydrothermal cell that is transparent to X-rays to characterize the real-time evolution of pore geometry during fluid-rock interaction using in-situ synchrotron-based X-ray microtomography. Through a time series of high-resolution 3-dimensional images, we document the microstructural evolution of a porous olivine aggregate reacting with a sodium bicarbonate solution at elevated pressure and temperature conditions. We observed porosity increases, near constant rate of crystal growth, and pervasive reaction-induced fractures. Based on the nanometer scale tomography data, we propose that shrinkage cracking is the mechanism responsible for producing new reactive surface and keep the carbonation reaction self-sustaining in our experiment. Shrinkage cracks are commonly observed in drying mud ponds, cooling lava flows and ice wedge fields. Stretching of a contracting surface bonded to a substrate of nearly constant dimensions leads to a stress buildup in the surface layer. When the stress exceeds the tensile strength, polygonal cracks develop in the surface layer. In our experiments, the stretching mismatch between the surface and interior of

  18. Field Method for Measuring the Shrinkage/Swelling Dynamics of Cracks Using a Low-Cost ``Crack-o-meter''

    NASA Astrophysics Data System (ADS)

    Stewart, R. D.; Abou Najm, M. R.; Rupp, D. E.; Selker, J. S.

    2010-12-01

    Shrinking/swelling soils are characterized by transient crack networks which function as dominant controls on the partitioning of surface and subsurface flow, the rate and depth of percolation, and evaporation rates. For such soils, understanding the dynamics of cracks is critical to accurately quantify their influence on groundwater recharge, stream-flow generation, and solute transport, among other component of a site’s hydrology. We propose a low-cost method for measuring transient crack-volume using a sealed plastic bag connected by a hose to a PVC standpipe. The empty bag is placed into the crack, and then water is added via the standpipe, until the bag has expanded to the boundaries of the crack and some water remains in the standpipe. As the crack shrinks or swells, its volume changes, causing water displacement within the bag, which is measured as a corresponding change in water level in the standpipe. An automated level logger within the standpipe is used to record changes in water level, which are converted to volumetric changes from the known internal cross-sectional area of the standpipe. The volume of water filling the bag is accurately measured at the start and completion of the experiment (to check for leakage). Adding the startup volume to the cumulative temporal volumetric change in the standpipe provides a simple and accurate method for monitoring transient crack volume. Currently, the design is undergoing preliminary testing in a field site in Ninhue, Chile, and field and laboratory testing in Corvallis, Oregon. Initial results from the Chilean field site suggest that the crack-o-meters are responding to the closing of cracks, but further effort is needed to calibrate and validate the results. We hope that these low-cost “crack-o-meters” will become useful and simple tools for researchers to quantify temporal changes in crack volume with the objective of incorporating these results into hydrological modeling efforts.

  19. Crack Mitigation in Concrete: Superabsorbent Polymers as Key to Success?

    PubMed Central

    Mignon, Arn; Snoeck, Didier; Dubruel, Peter; Van Vlierberghe, Sandra; De Belie, Nele

    2017-01-01

    Cracking is a major concern in building applications. Cracks may arise from shrinkage, freeze/thawing and/or structural stresses, amongst others. Several solutions can be found but superabsorbent polymers (SAPs) seem to be interesting to counteract these problems. At an early age, the absorbed water by the SAPs may be used to mitigate autogenous and plastic shrinkage. The formed macro pores may increase the freeze/thaw resistance. The swelling upon water ingress may seal a crack from intruding fluids and may regain the overall water-tightness. The latter water may promote autogenous healing. The use of superabsorbent polymers is thus very interesting. This review paper summarizes the current research and gives a critical note towards the use of superabsorbent polymers in cementitious materials. PMID:28772599

  20. Crack Mitigation in Concrete: Superabsorbent Polymers as Key to Success?

    PubMed

    Mignon, Arn; Snoeck, Didier; Dubruel, Peter; Van Vlierberghe, Sandra; De Belie, Nele

    2017-02-28

    Cracking is a major concern in building applications. Cracks may arise from shrinkage, freeze/thawing and/or structural stresses, amongst others. Several solutions can be found but superabsorbent polymers (SAPs) seem to be interesting to counteract these problems. At an early age, the absorbed water by the SAPs may be used to mitigate autogenous and plastic shrinkage. The formed macro pores may increase the freeze/thaw resistance. The swelling upon water ingress may seal a crack from intruding fluids and may regain the overall water-tightness. The latter water may promote autogenous healing. The use of superabsorbent polymers is thus very interesting. This review paper summarizes the current research and gives a critical note towards the use of superabsorbent polymers in cementitious materials.

  1. Coupling Soil Water Movement and Discrete Element Method for Evaluating the Effects of Shrinkage Cracking on Soil Hydraulic Properties

    NASA Astrophysics Data System (ADS)

    Jabakhanji, R.

    2010-12-01

    Due to the heterogeneous nature of the soil medium and the dynamic relationship between structure, function, and water movement, soil-water movement phenomena are complex systems with emergent behavior that varies across spatiotemporal scales of observation. Understanding how information is transferred from one scale to another is essential to produce accurate hydrologic and transport models and for proper scaling and integration of processes, constitutive models, and parameters from various measurement scales. We propose a modeling approach that couple soil water movement with the mechanical deformations it induces. The aim is to capture the formation of shrinkage and/or swelling cracks, and track them, in order to evaluate their effect on the hydraulic properties of the soil observed at the field scale compared to the properties determined at the laboratory scale. This approach is based on the Pedostructure soil-water model proposed by Braudeau et al., and a discrete representation of the soil medium. The latter will be shared by a discrete element method (DEM) mechanical model and a water movement model represented as a network of reservoirs and connecting pipes. Moisture will flow from one reservoir to another depending on the potential difference between the reservoirs and the conductivity of the connecting pipe. Consequently, water potentials and conductivities, as well as the volume of each reservoir, will be updated according to the Pedostructure model. The volumetric strains induced by this water movement will feed into the mechanical DEM model, and the forces between the reservoirs will be calculated. If a contact force reaches failure, it will be severed and moisture exchange will stop through this pipe, in turn altering the path of the subsequent mechanical steps. We will present some preliminary results showing promising agreement between the discrete water movement model and existing experimental data in determining soil moisture profile evolution.

  2. Autogenic training.

    PubMed

    Benor, R

    1996-10-01

    Westernized medicine has conditioned us to rely on the outer physician; Autogenic Training (AT) enables us to find and develop an intimate relationship with our own inner physician and healer. This article outlines the historical and theoretical background to AT. The training process is described and reference is made to research literature which illustrates those individuals, illnesses, and conditions which respond favourably to AT. Drawing on the current mind-body science of Psychoneuroimmunology (PNI), AT is seen as a significant member of the growing body of PNI techniques, research, and complementary therapies in the UK.

  3. A new system for crack closure of cementitious materials using shrinkable polymers

    SciTech Connect

    Jefferson, Anthony; Joseph, Christopher; Lark, Robert; Isaacs, Ben; Dunn, Simon; Weager, Brendon

    2010-05-15

    This paper presents details of an original crack-closure system for cementitious materials using shrinkable polymer tendons. The system involves the incorporation of unbonded pre-oriented polymer tendons in cementitious beams. Crack closure is achieved by thermally activating the shrinkage mechanism of the restrained polymer tendons after the cement-based material has undergone initial curing. The feasibility of the system is demonstrated in a series of small scale experiments on pre-cracked prismatic mortar specimens. The results from these tests show that, upon activation, the polymer tendon completely closes the preformed macro-cracks and imparts a significant stress across the crack faces. The potential of the system to enhance the natural autogenous crack healing process and generally improve the durability of concrete structures is addressed.

  4. Analysis, prediction, and case studies of early-age cracking in bridge decks

    NASA Astrophysics Data System (ADS)

    ElSafty, Adel; Graeff, Matthew K.; El-Gharib, Georges; Abdel-Mohti, Ahmed; Mike Jackson, N.

    2016-06-01

    Early-age cracking can adversely affect strength, serviceability, and durability of concrete bridge decks. Early age is defined as the period after final setting, during which concrete properties change rapidly. Many factors can cause early-age bridge deck cracking including temperature change, hydration, plastic shrinkage, autogenous shrinkage, and drying shrinkage. The cracking may also increase the effect of freeze and thaw cycles and may lead to corrosion of reinforcement. This research paper presents an analysis of causes and factors affecting early-age cracking. It also provides a tool developed to predict the likelihood and initiation of early-age cracking of concrete bridge decks. Understanding the concrete properties is essential so that the developed tool can accurately model the mechanisms contributing to the cracking of concrete bridge decks. The user interface of the implemented computer Excel program enables the user to input the properties of the concrete being monitored. The research study and the developed spreadsheet were used to comprehensively investigate the issue of concrete deck cracking. The spreadsheet is designed to be a user-friendly calculation tool for concrete mixture proportioning, temperature prediction, thermal analysis, and tensile cracking prediction. The study also provides review and makes recommendations on the deck cracking based mainly on the Florida Department of Transportation specifications and Structures Design Guidelines, and Bridge Design Manuals of other states. The results were also compared with that of other commercially available software programs that predict early-age cracking in concrete slabs, concrete pavement, and reinforced concrete bridge decks. The outcome of this study can identify a set of recommendations to limit the deck cracking problem and maintain a longer service life of bridges.

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    MedlinePlus

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    MedlinePlus

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  7. PLASTIC SHRINKAGE CONTROLLING EFFECT BY POLYPROPYLENE SHORT FIBER WITH HYDROPHILY

    NASA Astrophysics Data System (ADS)

    Hosoda, Akira; Sadatsuki, Yoshitomo; Oshima, Akihiro; Ishii, Akina; Tsubaki, Tatsuya

    The aim of this research is to clarify the mechanism of controlling plastic shrinkage crack by adding small amout of synthetic short fiber, and to propose optimum polypropylene short fiber to control plastic shrinkage crack. In this research, the effect of the hydrophily of polypropylene fiber was investigated in the amount of plastic shrinkage of mortar, total area of plastic shrinkage crack, and bond properties between fiber and mortar. The plastic shrinkage test of morar was conducted under high temperature, low relative humidity, and constant wind velocity. When polypropylene fiber had hydrophily, the amount of plastic shrinkage of mortar was restrained, which was because cement paste in morar was captured by hydrophilic fiber and then bleeding of mortar was restrained. With hydrophily, plastic shrinkage of mortar was restrained and bridging effect was improved due to better bond, which led to remarkable reduction of plastic shrinkage crack. Based on experimental results, the way of developing optimum polypropylene short fiber for actual construction was proposed. The fiber should have large hydrophily and small diameter, and should be used in as small amount as possible in order not to disturb workability of concrete.

  8. Veterinary autogenous vaccines.

    PubMed

    Hera, A; Bures, J

    2004-01-01

    Autogenous vaccines remain a regulatory issue. They are demanded by practising veterinarians and by animal owners and they are quite widely used, mainly in Central European Countries, the Czech Republic, Hungary and Slovak Republic having probably the longest tradition with these products in Central Europe. The scope given in Article 3, Para. 2 (and/or Article 4 for some countries) of Directive 2001/82/EC applies to these products in the Acceding Countries. As these products are exempt from the harmonised regulation at the EU level, they are regulated by individual countries, the regulation varying from practically no regulatory measures in certain countries to a quite complex and demanding regulation in the other countries. Both risks and benefits are related to these products and they shall be taken into account when regulatory measures are considered. The major risks related to veterinary autogenous vaccines relate to possibility of transmission of TSE agents or other viral, bacterial and/or fungal contaminants. As appropriate and well balanced regulation of these products is deemed necessary, considering the risks related to these products, and based on the fact that national regulatory measures could be considered as a trade barrier under certain circumstances, harmonisation of the key issues or legal admission of the nationally based regulatory measures, including movement of these products from the other Member States, shall be laid down in the EU legislation. The veterinary autogenous vaccines complying with basic quality and safety requirements are thus a very useful tool in the animal health and welfare management but their use should be restricted to situations where there is no authorised veterinary medicinal product available and veterinary autogenous vaccines must not be allowed to replace good farming or veterinary practices.

  9. Autogen Version 2.0

    NASA Technical Reports Server (NTRS)

    Gladden, Roy

    2007-01-01

    Version 2.0 of the autogen software has been released. "Autogen" (automated sequence generation) signifies both a process and software used to implement the process of automated generation of sequences of commands in a standard format for uplink to spacecraft. Autogen requires fewer workers than are needed for older manual sequence-generation processes and reduces sequence-generation times from weeks to minutes.

  10. New methods to quantify the cracking performance of cementitious systems made with internal curing

    NASA Astrophysics Data System (ADS)

    Schlitter, John L.

    which is located outside of the sample to provide restraint against expansion. Second, the standard ring test is a passive test that only relies on the autogenous and drying shrinkage of the mixture to induce cracking. The dual ring test can be an active test because it has the ability to vary the temperature of the specimen in order to induce thermal stress and produce cracking. This ability enables the study of the restrained cracking capacity as the mixture ages in order to quantify crack sensitive periods of time. Measurements made with the dual ring quantify the benefits from using larger amounts of internal curing. Mixtures that resupplied internal curing water to match that of chemical shrinkage could sustain three times the magnitude of thermal change before cracking. The second device discussed in this thesis is a large scale slab testing device. This device tests the cracking potential of 15' long by 4" thick by 24" wide slab specimens in an environmentally controlled chamber. The current standard testing devices can be considered small scale and encounter problems when linking their results to the field due to size effects. Therefore, the large scale slab testing device was developed in order to calibrate the results of smaller scale tests to real world field conditions such as a pavement or bridge deck. Measurements made with the large scale testing device showed that the cracking propensity of the internally cured mixtures was reduced and that a significant benefit could be realized.

  11. Comparison of shrinkage related properties of various patch repair materials

    NASA Astrophysics Data System (ADS)

    Kristiawan, S. A.; Fitrianto, R. S.

    2017-02-01

    A patch repair material has been developed in the form of unsaturated polyester resin (UPR)-mortar. The performance and durability of this material are governed by its compatibility with the concrete being repaired. One of the compatibility issue that should be tackled is the dimensional compatibility as a result of differential shrinkage between the repair material and the concrete substrate. This research aims to evaluate such shrinkage related properties of UPR-mortar and to compare with those of other patch repair materials. The investigation includes the following aspects: free shrinkage, resistance to delamination and cracking. The results indicate that UPR-mortar poses a lower free shrinkage, lower risk of both delamination and cracking tendency in comparison to other repair materials.

  12. Autogenic training and dream recall.

    PubMed

    Schredl, M; Doll, E

    1997-06-01

    The present study has investigated the relationship between Autogenic Training and dream recall for 112 participants in 16 beginning courses of 10 wk. Analyses confirmed the hypothesis that learning and practicing this relaxation technique enhanced dream recall.

  13. Kinetics of corneal thermal shrinkage

    NASA Astrophysics Data System (ADS)

    Borja, David; Manns, Fabrice; Lee, William E.; Parel, Jean-Marie

    2004-07-01

    Purpose: The purpose of this study was to determine the effects of temperature and heating duration on the kinetics of thermal shrinkage in corneal strips using a custom-made shrinkage device. Methods: Thermal shrinkage was induced and measured in corneal strips under a constant load placed while bathed in 25% Dextran irrigation solution. A study was performed on 57 Florida Lions Eye Bank donated human cadaver eyes to determine the effect of temperature on the amount and rate of thermal shrinkage. Further experiments were performed on 20 human cadaver eyes to determine the effects of heating duration on permanent shrinkage. Data analysis was performed to determine the effects of temperature, heating duration, and age on the amount and kinetics of shrinkage. Results: Shrinkage consisted of two phases: a shrinkage phase during heating and a regression phase after heating. Permanent shrinkage increased with temperature and duration. The shrinkage and regression time constants followed Arrhenius type temperature dependence. The shrinkage time constants where calculated to be 67, 84, 121, 560 and 1112 (s) at 80, 75, 70, 65, and 60°C respectively. At 65°C the permanent shrinkage time constant was calculated to be 945s. Conclusion: These results show that shrinkage treatments need to raise the temperature of the tissue above 75°C for several seconds in order to prevent regression of the shrinkage effect immediately after treatment and to induce the maximum amount of permanent irreversible shrinkage.

  14. 9 CFR 113.113 - Autogenous biologics.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Inactivated Bacterial Products § 113.113 Autogenous biologics. Autogenous biologics shall be prepared from... which are not adjacent to the herd of origin, but which he or she considers to be at risk of infection... or subserial of autogenous bacterial product other than the first serial or subserial produced from...

  15. Comment on autogenic training and hypertension.

    PubMed

    Sakai, M; Sato, T; Takeichi, M; Fakunishi, I

    1997-06-01

    We comment on a report by Watanabe, et al. regarding the effects of autogenic training on hypertension. Using previous reports in the United States, we mention methodological problems on how to evaluate the effects of autogenic training and express our hope that they would provide further research to clarify the effects of autogenic training on hypertension.

  16. Roof System EPDM Shrinkage.

    ERIC Educational Resources Information Center

    Betker, Edward

    1998-01-01

    Looks at Ethylene Propylene Diene Terpolymer rubber roof membranes and the potential problems associated with this material's shrinkage. Discusses how long such a roof should perform and issues affecting repair or replacement. Recommends that a building's function be considered in any roofing decision. (RJM)

  17. Roof System EPDM Shrinkage.

    ERIC Educational Resources Information Center

    Betker, Edward

    1998-01-01

    Looks at Ethylene Propylene Diene Terpolymer rubber roof membranes and the potential problems associated with this material's shrinkage. Discusses how long such a roof should perform and issues affecting repair or replacement. Recommends that a building's function be considered in any roofing decision. (RJM)

  18. Development of spraying agent for reducing drying shrinkage of mortar

    NASA Astrophysics Data System (ADS)

    Fujiwara, Hiromi; Maruoka, Masanori; Liu, Lingling

    2017-02-01

    Mortar used to repair is sometimes exposed to drying state in early ages after construction and a few days later water is sprayed frequently on the surface of the mortar in order to prevent cracks. This research studied on shrinkage characteristic of mortar subjected to drying conditions like this. The result showed that the water spraying on the mortar after initial drying did not have any effect to prevent shrinkage, but increased. And it also showed when various chemical agents are mixed and used in watersprayingit had the prevention effect on shrinkage. This report was to understand this kind of phenomenon and clarify the mechanism. In addition, based on the results, the new spraying agent was developed to reduce drying shrinkage.

  19. Cure shrinkage in casting resins

    SciTech Connect

    Spencer, J. Brock

    2015-02-01

    A method is described whereby the shrinkage of a casting resin can be determined. Values for the shrinkage of several resin systems in frequent use by Sandia have been measured. A discussion of possible methods for determining the stresses generated by cure shrinkage and thermal contraction is also included.

  20. Plastic shrinkage of mortars with shrinkage reducing admixture and lightweight aggregates studied by neutron tomography

    SciTech Connect

    Wyrzykowski, Mateusz; Trtik, Pavel; Münch, Beat; Weiss, Jason; Vontobel, Peter; Lura, Pietro

    2015-07-15

    Water transport in fresh, highly permeable concrete and rapid water evaporation from the concrete surface during the first few hours after placement are the key parameters influencing plastic shrinkage cracking. In this work, neutron tomography was used to determine both the water loss from the concrete surface due to evaporation and the redistribution of fluid that occurs in fresh mortars exposed to external drying. In addition to the reference mortar with a water to cement ratio (w/c) of 0.30, a mortar with the addition of pre-wetted lightweight aggregates (LWA) and a mortar with a shrinkage reducing admixture (SRA) were tested. The addition of SRA reduced the evaporation rate from the mortar at the initial stages of drying and reduced the total water loss. The pre-wetted LWA released a large part of the absorbed water as a consequence of capillary pressure developing in the fresh mortar due to evaporation.

  1. Effects of powder characteristics on injection molding and burnout cracking

    SciTech Connect

    Bandyopadhyay, G.; French, K.W. )

    1994-03-01

    Silicon nitride particle size and size distributions were varied widely to determine their effects on burnout cracking of injection-molded test parts containing thick and thin sections. Elimination of internal cracking required significant burnout shrinkage, which did not occur by changes of particle size and size distribution. However, isopressing of test parts after burnout provided the dimensional shrinkage necessary for producing crack-free components.

  2. AutoGen Version 5.0

    NASA Technical Reports Server (NTRS)

    Gladden, Roy E.; Khanampornpan, Teerapat; Fisher, Forest W.

    2010-01-01

    Version 5.0 of the AutoGen software has been released. Previous versions, variously denoted Autogen and autogen, were reported in two articles: Automated Sequence Generation Process and Software (NPO-30746), Software Tech Briefs (Special Supplement to NASA Tech Briefs), September 2007, page 30, and Autogen Version 2.0 (NPO- 41501), NASA Tech Briefs, Vol. 31, No. 10 (October 2007), page 58. To recapitulate: AutoGen (now signifying automatic sequence generation ) automates the generation of sequences of commands in a standard format for uplink to spacecraft. AutoGen requires fewer workers than are needed for older manual sequence-generation processes, and greatly reduces sequence-generation times. The sequences are embodied in spacecraft activity sequence files (SASFs). AutoGen automates generation of SASFs by use of another previously reported program called APGEN. AutoGen encodes knowledge of different mission phases and of how the resultant commands must differ among the phases. AutoGen also provides means for customizing sequences through use of configuration files. The approach followed in developing AutoGen has involved encoding the behaviors of a system into a model and encoding algorithms for context-sensitive customizations of the modeled behaviors. This version of AutoGen addressed the MRO (Mars Reconnaissance Orbiter) primary science phase (PSP) mission phase. On previous Mars missions this phase has more commonly been referred to as mapping phase. This version addressed the unique aspects of sequencing orbital operations and specifically the mission specific adaptation of orbital operations for MRO. This version also includes capabilities for MRO s role in Mars relay support for UHF relay communications with the MER rovers and the Phoenix lander.

  3. Store Security: Internal Shrinkage Control.

    ERIC Educational Resources Information Center

    Everhardt, Richard M.

    The document presents a 10-week training program designed to provide helpful and proven methods for controlling internal shrinkage in retail stores. Shrinkage includes the three problems of shoplifting, employee theft, and errors, each of which is addressed by the course. Ohio's laws are also discussed. The format for the course content section is…

  4. Early age stresses and creep-shrinkage interaction of restrained concrete

    NASA Astrophysics Data System (ADS)

    Altoubat, Salah Ahmed

    2000-10-01

    Experimental and numerical analyses were performed to characterize the early age tensile creep and shrinkage behavior of concrete. A uniaxial restrained shrinkage test was developed. The experiment tested two identical specimens: restrained and unrestrained. The test was controlled by computer, and the shrinkage deformation was checked continuously and compared to a threshold value of 5 mum, which when exceeded, triggered an increase in tensile load to recover the shrinkage strain in the restrained specimen. Thus, a restrained condition is achieved and the stress generated by shrinkage mechanisms was measurable. The experiment revealed how shrinkage stresses developed and how creep mechanisms reduced shrinkage strain. The tests revealed that shrinkage stresses in the first days after casting are significant and caused fracture of the concrete. The rate of stress evolution influenced the time and stress of first cracking. The tensile creep of concrete formed a substantial part of the time dependent deformation and reduced the shrinkage stresses by 50%. A method separating drying creep mechanisms of concrete into stress-induced shrinkage and microcracking was developed. The method required measurement of creep and shrinkage of concrete under drying, sealed, and moist curing conditions. The moist-curing test produce the basic creep; the sealed test provided data on basic creep and stress-induced shrinkage, and the drying test provided data on basic creep, stress-induced shrinkage and microcracking. The basic creep results of young concrete indicated a high creep rate in the initial 10--20 hours after loading. Then, the rate decreased and the creep function approached a stable value. The initial rate of creep was sensitive to age at loading in the first two days, and became age-independent after a few days. The analysis revealed stress-induced shrinkage as a major mechanism of drying creep for plain and fiber reinforced concrete (FRC). Microcracking forms a significant

  5. Documenting AUTOGEN and APGEN Model Files

    NASA Technical Reports Server (NTRS)

    Gladden, Roy E.; Khanampompan, Teerapat; Fisher, Forest W.; DelGuericio, Chris c.

    2008-01-01

    A computer program called "autogen hypertext map generator" satisfies a need for documenting and assisting in visualization of, and navigation through, model files used in the AUTOGEN and APGEN software mentioned in the two immediately preceding articles. This program parses autogen script files, autogen model files, PERL scripts, and apgen activity-definition files and produces a hypertext map of the files to aid in the navigation of the model. This program also provides a facility for adding notes and descriptions, beyond what is in the source model represented by the hypertext map. Further, this program provides access to a summary of the model through variable, function, sub routine, activity and resource declarations as well as providing full access to the source model and source code. The use of the tool enables easy access to the declarations and the ability to traverse routines and calls while analyzing the model.

  6. 9 CFR 113.113 - Autogenous biologics.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... biologic shall not exceed 18 months from the date of harvest. (c) Testing requirements for autogenous... described in the filed outline of production or shall at least be standardized to contain an antigenic mass...

  7. A novel two-dimensional method to measure surface shrinkage in cementitious materials

    SciTech Connect

    Chen, T.C.; Ferraro, C.C.; Yin, W.Q.; Ishee, C.A.; Ifju, P.G.

    2010-05-15

    A novel experimental technique, Cure Reference Method (CRM), was developed for the measurement of surface shrinkage in cementitious materials. The technique combines the replication of diffraction grating on a specimen during the curing process and the use of high-sensitivity moire interferometry. Once demolded, the specimen was stored in an environmental chamber in order to establish specific curing conditions. Measurements were conducted on a daily basis for the duration of 7 days by recording a set of the consecutive phase shifted fringe patterns using the Portable Engineering Moire interferometer II (PEMI II). An automated fringe analysis system was developed and used to obtain displacement and strain information in two dimenzsions. Surface shrinkage behavior in both cement paste and mortar specimens was investigated by the use of the technique under controlled temperature and humidity conditions. Furthermore, an experimental control was developed in an effort to remove the effects of drying shrinkage on cementitious specimens at early ages. This was done in an effort to explore the relative contribution of autogenous shrinkage to the overall shrinkage in cementitious materials.

  8. Evaluation of autogenous grafts used in vestibuloplasty.

    PubMed

    Metin, M; Dolanmaz, D; Alkan, A

    2003-01-01

    Vestibuloplasty is indicated when prosthesis stability is poor due to mandibular or maxillary atrophy. The use of autogenous grafts to provide sufficient vestibular depth is widely accepted. In this retrospective study, the outcomes of vestibuloplasty performed on 41 patients using various types of autogenous grafts (full-thickness skin, dermal, reversed dermal, meshed skin and palatal mucosal) are presented. The best results were obtained with palatal mucosal grafts, but graft size is limited. Meshed skin grafts were shown to be the best alternative.

  9. Crack opening: from colloidal systems to paintings.

    PubMed

    Léang, Marguerite; Giorgiutti-Dauphiné, Frédérique; Lee, Lay-Theng; Pauchard, Ludovic

    2017-08-30

    Shrinkage cracks are observed in many materials, particularly in paintings where great interest lies in deducing quantitative information on the material with the aim of proposing authentication methods. We present experimental measurements on the crack opening induced by the drying of colloidal layers and compare these results to the case of a pictorial layer. We propose a simple model to predict the crack width as a function of the thickness of the drying layer, based on the balance between the drying stress buildup and the shear frictional stress with the substrate. Key parameters of the model include the mechanical properties that are measured experimentally using micro-indentation testing. A good agreement between theory and experimental data for both colloidal layers and the real painting is found. These results, by comparing the shrinkage cracks in model layers and in pictorial layers, validate the method based on the use of colloidal systems to simulate and to reproduce drying cracks in paintings.

  10. The origin of early age expansions induced in cementitious materials containing shrinkage reducing admixtures

    SciTech Connect

    Sant, Gaurav; Lothenbach, Barbara; Juilland, Patrick; Le Saout, Gwenn; Weiss, Jason; Scrivener, Karen

    2011-03-15

    Studies on the early-age shrinkage behavior of cement pastes, mortars, and concretes containing shrinkage reducing admixtures (SRAs) have indicated these mixtures frequently exhibit an expansion shortly after setting. While the magnitude of the expansion has been noted to be a function of the chemistry of the cement and the admixture dosage; the cause of the expansion is not clearly understood. This investigation uses measurements of autogenous deformation, X-ray diffraction, pore solution analysis, thermogravimetry, and scanning electron microscopy to study the early-age properties and describe the mechanism of the expansion in OPC pastes made with and without SRA. The composition of the pore solution indicates that the presence of the SRA increases the portlandite oversaturation level in solution which can result in higher crystallization stresses which could lead to an expansion. This observation is supported by deformation calculations for the systems examined.

  11. Modeling of NTD resist shrinkage

    NASA Astrophysics Data System (ADS)

    Mülders, Thomas; Stock, Hans-Jürgen; Küchler, Bernd; Klostermann, Ulrich; Gao, Weimin; Demmerle, Wolfgang

    2017-03-01

    Recent chemically amplified resists used for Negative Tone Development (NTD) processes exhibit a significant amount of resist shrinkage during post-exposure-bake (PEB). Some NTD resists show up to 25% thickness loss during PEB in the exposed regions. A detailed analysis of this and other experimental observations is published elsewhere.1 In particular, it has also been demonstrated that the shrinkage during PEB can have a strong impact on both, the CDs and the resist profile shapes which are formed after Negative Tone Development. We therefore highlight the necessity to augment physical modeling of the PEB process step for these NTD photoresists. To account for the shrinkage process during PEB in lithography simulations we start with the following modeling assumptions: The tendency for shrinkage is due to the collapse of the void space (free volume) which is formed after evaporation of the volatile byproduct of the de-protection reaction. However, this will not only induce a (vertical) resist height loss but causes also lateral displacements inside the resist. This yields distorted concentration profiles of all the species that are typically tracked during PEB simulations. In particular, a distorted degree of protection after PEB will result in resist profiles with tilted sidewall angles and changed CDs. As will be shown these effects are strongly pitch-dependent and must be accounted for in a physical simulation approach as well as in OPC modeling. In this work, we discuss our simulation approach to account for mechanical deformations. Using exemplary simulations, we determine the impact of the main effects which are captured by the model. In order to validate the simulation model, the simulated effect of shrinkage-induced mechanical deformations during PEB on CDs and on resist profiles is compared with experimental data.

  12. Development of early age shrinkage stresses in reinforced concrete bridge decks

    NASA Astrophysics Data System (ADS)

    William, Gergis W.; Shoukry, Samir N.; Riad, Mourad Y.

    2008-12-01

    This paper describes the instrumentation and data analysis of a reinforced concrete bridge deck constructed on 3-span continuous steel girders in Evansville, West Virginia. An instrumentation system consisting of 232 sensors is developed and implemented specifically to measure strains and temperature in concrete deck, strains in longitudinal and transverse rebars, the overall contraction and expansion of concrete deck, and crack openings. Data from all sensors are automatically collected every 30 minutes starting at the time of placing the concrete deck. Measured strain and temperature time-histories were used to calculate the stresses, which were processed to attenuate the thermal effects due to daily temperature changes and isolate the drying shrinkage component. The results indicated that most of concrete shrinkage occurs during the first three days. Under the constraining effects from stay-in-place forms and reinforcement, early age shrinkage leads to elevated longitudinal stress, which is the main factor responsible for crack initiation.

  13. 30 CFR 35.20 - Autogenous-ignition temperature test.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Autogenous-ignition temperature test. 35.20... Autogenous-ignition temperature test. (a) Purpose. The purpose of this test, referred to hereinafter as the ignition-temperature test, is to determine the lowest autogenous-ignition temperature of a hydraulic fluid...

  14. 30 CFR 35.20 - Autogenous-ignition temperature test.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Autogenous-ignition temperature test. 35.20... Autogenous-ignition temperature test. (a) Purpose. The purpose of this test, referred to hereinafter as the ignition-temperature test, is to determine the lowest autogenous-ignition temperature of a hydraulic fluid...

  15. 30 CFR 35.20 - Autogenous-ignition temperature test.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Autogenous-ignition temperature test. 35.20... Autogenous-ignition temperature test. (a) Purpose. The purpose of this test, referred to hereinafter as the ignition-temperature test, is to determine the lowest autogenous-ignition temperature of a hydraulic fluid...

  16. 30 CFR 35.20 - Autogenous-ignition temperature test.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Autogenous-ignition temperature test. 35.20... Autogenous-ignition temperature test. (a) Purpose. The purpose of this test, referred to hereinafter as the ignition-temperature test, is to determine the lowest autogenous-ignition temperature of a hydraulic fluid...

  17. Effect of the key mixture parameters on shrinkage of reactive powder concrete.

    PubMed

    Ahmad, Shamsad; Zubair, Ahmed; Maslehuddin, Mohammed

    2014-01-01

    Reactive powder concrete (RPC) mixtures are reported to have excellent mechanical and durability characteristics. However, such concrete mixtures having high amount of cementitious materials may have high early shrinkage causing cracking of concrete. In the present work, an attempt has been made to study the simultaneous effects of three key mixture parameters on shrinkage of the RPC mixtures. Considering three different levels of the three key mixture factors, a total of 27 mixtures of RPC were prepared according to 3(3) factorial experiment design. The specimens belonging to all 27 mixtures were monitored for shrinkage at different ages over a total period of 90 days. The test results were plotted to observe the variation of shrinkage with time and to see the effects of the key mixture factors. The experimental data pertaining to 90-day shrinkage were used to conduct analysis of variance to identify significance of each factor and to obtain an empirical equation correlating the shrinkage of RPC with the three key mixture factors. The rate of development of shrinkage at early ages was higher. The water to binder ratio was found to be the most prominent factor followed by cement content with the least effect of silica fume content.

  18. Effect of the Key Mixture Parameters on Shrinkage of Reactive Powder Concrete

    PubMed Central

    Zubair, Ahmed

    2014-01-01

    Reactive powder concrete (RPC) mixtures are reported to have excellent mechanical and durability characteristics. However, such concrete mixtures having high amount of cementitious materials may have high early shrinkage causing cracking of concrete. In the present work, an attempt has been made to study the simultaneous effects of three key mixture parameters on shrinkage of the RPC mixtures. Considering three different levels of the three key mixture factors, a total of 27 mixtures of RPC were prepared according to 33 factorial experiment design. The specimens belonging to all 27 mixtures were monitored for shrinkage at different ages over a total period of 90 days. The test results were plotted to observe the variation of shrinkage with time and to see the effects of the key mixture factors. The experimental data pertaining to 90-day shrinkage were used to conduct analysis of variance to identify significance of each factor and to obtain an empirical equation correlating the shrinkage of RPC with the three key mixture factors. The rate of development of shrinkage at early ages was higher. The water to binder ratio was found to be the most prominent factor followed by cement content with the least effect of silica fume content. PMID:25050395

  19. Management of pain through autogenic training.

    PubMed

    Kanji, N

    2000-08-01

    Physical and emotional pain are an inevitable part of human existence and are without natural antidotes. In view of this, and in the light of increasing professional reluctance to depend on analgesics, this paper proposes the widespread application of autogenic training, a relaxation technique which has been seen to confront pain very effectively, and also to reduce substantially drugs dependency. It analyses autogenic training in respect of some of the more common pain-allied disorders such as childbirth, headaches and migraines, back pain, cancer and palliative care, and cardiology.

  20. Cure shrinkage of thermoset composites

    SciTech Connect

    Russell, J.D. )

    1993-01-01

    The shrinkage of thermoset composites during cure was studied using a volumetric dilatometer. The material systems studied were AS4 carbon fiber/Hercules' 3501-6 epoxy, IM7 carbon fiber/Hercules 8551-7A toughened epoxy and IM7 carbon fiber/BASF's 5250-4 bismaleimide. Shrinkage of the samples due to both polymerization and thermal expansion effects was seen. The volume changes of the materials during cure were then compared to results from dynamic mechanical analysis (DMA) and dielectric cure monitoring. Maximums in volume corresponded to minimums in storage and loss modulus from DMA and maximums in the dielectric loss factor. Resin shrinkage during the 177 deg C (350 F) hold corresponded to the onset of polymerization seen by the rapid increase in the storage modulus and the decrease in the dielectric loss factor response due to reduced ion mobility. These results show that volumetric dilatometry can be an effective tool in the development of materials processing strategies and can be useful in studying residual stresses in composites. 9 refs.

  1. Towards a better understanding of the cracking behavior in soils

    USDA-ARS?s Scientific Manuscript database

    Understanding and modeling shrinkage-induced cracks helps bridge the gap between flow problem in the laboratory and at the field. Modeling flow at the field scale with Darcian fluxes developed at the laboratory scales is challenged with preferential flows attributed to the cracking behavior of soils...

  2. 9 CFR 113.113 - Autogenous biologics.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...) Identification. All microorganisms used for the production of autogenous biologics shall be identified as follows: Bacteria, fungi, and mycoplasma shall be identified at least to genus and species. Viruses shall be... of origin. (iv) Identification of microorganism(s), at least to genus. (v) Diagnosis or...

  3. Autogenic dynamics of debris-flow fans

    NASA Astrophysics Data System (ADS)

    van den Berg, Wilco; de Haas, Tjalling; Braat, Lisanne; Kleinhans, Maarten

    2015-04-01

    Alluvial fans develop their semi-conical shape by cyclic avulsion of their geomorphologically active sector from a fixed fan apex. These cyclic avulsions have been attributed to both allogenic and autogenic forcings and processes. Autogenic dynamics have been extensively studied on fluvial fans through physical scale experiments, and are governed by cyclic alternations of aggradation by unconfined sheet flow, fanhead incision leading to channelized flow, channel backfilling and avulsion. On debris-flow fans, however, autogenic dynamics have not yet been directly observed. We experimentally created debris-flow fans under constant extrinsic forcings, and show that autogenic dynamics are a fundamental intrinsic process on debris-flow fans. We found that autogenic cycles on debris-flow fans are driven by sequences of backfilling, avulsion and channelization, similar to the cycles on fluvial fans. However, the processes that govern these sequences are unique for debris-flow fans, and differ fundamentally from the processes that govern autogenic dynamics on fluvial fans. We experimentally observed that backfilling commenced after the debris flows reached their maximum possible extent. The next debris flows then progressively became shorter, driven by feedbacks on fan morphology and flow-dynamics. The progressively decreasing debris-flow length caused in-channel sedimentation, which led to increasing channel overflow and wider debris flows. This reduced the impulse of the liquefied flow body to the flow front, which then further reduced flow velocity and runout length, and induced further in-channel sedimentation. This commenced a positive feedback wherein debris flows became increasingly short and wide, until the channel was completely filled and the apex cross-profile was plano-convex. At this point, there was no preferential transport direction by channelization, and the debris flows progressively avulsed towards the steepest, preferential, flow path. Simultaneously

  4. Corrosion cracking

    SciTech Connect

    Goel, V.S.

    1985-01-01

    This book presents the papers given at a conference on alloy corrosion cracking. Topics considered at the conference included the effect of niobium addition on intergranular stress corrosion cracking, corrosion-fatigue cracking in fossil-fueled-boilers, fracture toughness, fracture modes, hydrogen-induced thresholds, electrochemical and hydrogen permeation studies, the effect of seawater on fatigue crack propagation of wells for offshore structures, the corrosion fatigue of carbon steels in seawater, and stress corrosion cracking and the mechanical strength of alloy 600.

  5. Shrinkage modeling of concrete reinforced by palm fibres in hot dry environments

    NASA Astrophysics Data System (ADS)

    Akchiche, Hamida; Kriker, Abdelouahed

    2017-02-01

    The cement materials, such as concrete and conventional mortar present very little resistance to traction and cracking, these hydraulic materials which induces large withdrawals on materials and cracks in structures. The hot dry environments such as: the Saharan regions of Algeria, Indeed, concrete structures in these regions are very fragile, and present high shrinkage. Strengthening of these materials by fibers can provide technical solutions for improving the mechanical performance. The aim of this study is firstly, to reduce the shrinkage of conventional concrete with its reinforcement with date palm fibers. In fact, Algeria has an extraordinary resources in natural fibers (from Palm, Abaca, Hemp) but without valorization in practical areas, especially in building materials. Secondly, to model the shrinkage behavior of concrete was reinforced by date palm fibers. In the literature, several models for still fiber concrete were founded but few are offers for natural fiber concretes. To do so, a still fiber concretes model of YOUNG - CHERN was used. According to the results, a reduction of shrinkage with reinforcement by date palm fibers was showed. A good ability of molding of shrinkage of date palm reinforced concrete with YOUNG - CHERN Modified model was obtained. In fact, a good correlation between experimental data and the model data was recorded.

  6. Cracking of high-solids epoxy coatings on steel structures in The Netherlands

    SciTech Connect

    Bijen, J. ); Montfort, J. van

    1999-05-01

    High-solids epoxy coatings on steel flood barriers in The Netherlands showed cracking shortly after application. An investigation revealed the cause of cracking. It appeared that shrinkage-induced stresses caused the coatings to fail. Two cracking phenomena are described and simulated by an accelerated test and computer modeling.

  7. Shrinkage approach for EEG covariance matrix estimation.

    PubMed

    Beltrachini, Leandro; von Ellenrieder, Nicolas; Muravchik, Carlos H

    2010-01-01

    We present a shrinkage estimator for the EEG spatial covariance matrix of the background activity. We show that such an estimator has some advantages over the maximum likelihood and sample covariance estimators when the number of available data to carry out the estimation is low. We find sufficient conditions for the consistency of the shrinkage estimators and results concerning their numerical stability. We compare several shrinkage schemes and show how to improve the estimator by incorporating known structure of the covariance matrix.

  8. Devitrification and shrinkage behavior of silica fibers

    NASA Technical Reports Server (NTRS)

    Zaplatynsky, I.

    1972-01-01

    Devitrification and shrinkage of three batches of silica fibers were investigated in the temperature range of 1200 to 1350 C. Fibers with high water and impurity content devitrified rapidly to cristobalite and quartz and exhibited rapid, but the least amount of, shrinkage. A batch with low water and impurity content devitrified more slowly to cristobalite only and underwent severe shrinkage by the mechanism of viscous flow. A third batch of intermediate purity level and low water content devitrified at a moderate rate mainly to cristobalite but shrunk very rapidly. Completely devitrified silica fibers did not exhibit any further shrinkage.

  9. Autogenic drainage: efficacy of a simplified method.

    PubMed

    Lindemann, H; Boldt, A; Kieselmann, R

    1990-01-01

    A simplified and modified technique of the original autogenic drainage (AD) is described which is supplemented by breathing against an external flow resistance. The new method allows a better teaching and learning. It's efficacy is proven by means of a comparative trial of AD and PEP physiotherapy (i.e. expiration against a defined stenosis). The autogenic drainage (AD) was introduced by a Belgian working group (2). The basic idea was to support the elimination of mucus by deep breathing and by repressing the cough as long as possible. However, a rather sophisticated method impeded teaching and learning of AD (1). Thus, till now, there are only preliminary results which suggest the efficacy of AD (e.g. 3). Therefore, a simplified technique was developed and examined with regard to its sputum eliminating effect.

  10. Autogenic Drainage in Children With Cystic Fibrosis.

    PubMed

    Corten, Lieselotte; Morrow, Brenda M

    2017-04-01

    Airway clearance is an essential part of the management of cystic fibrosis (CF) as it facilitates clearance of viscous pulmonary secretions. This review aimed to determine the effect of autogenic drainage (AD) and assisted autogenic drainage (AAD) compared with no, sham, or other types of airway clearance in children with CF. Two pediatric randomized cross-over trials were identified on the use of AD in children with CF; no studies were available on the use of AAD. In one study AD had a positive influence on the Huang score, and is preferred over postural drainage in this population. We could not determine the efficacy of AD and AAD in children with CF. We recommend the implementation of pediatric-specific randomized controlled trials with adequate sample sizes, appropriate clinical outcome measures, and analysis of adverse effects.

  11. VOLUMETRIC POLYMERIZATION SHRINKAGE OF CONTEMPORARY COMPOSITE RESINS

    PubMed Central

    Nagem, Halim; Nagem, Haline Drumond; Francisconi, Paulo Afonso Silveira; Franco, Eduardo Batista; Mondelli, Rafael Francisco Lia; Coutinho, Kennedy Queiroz

    2007-01-01

    The polymerization shrinkage of composite resins may affect negatively the clinical outcome of the restoration. Extensive research has been carried out to develop new formulations of composite resins in order to provide good handling characteristics and some dimensional stability during polymerization. The purpose of this study was to analyze, in vitro, the magnitude of the volumetric polymerization shrinkage of 7 contemporary composite resins (Definite, Suprafill, SureFil, Filtek Z250, Fill Magic, Alert, and Solitaire) to determine whether there are differences among these materials. The tests were conducted with precision of 0.1 mg. The volumetric shrinkage was measured by hydrostatic weighing before and after polymerization and calculated by known mathematical equations. One-way ANOVA (á=0.05) was used to determine statistically significant differences in volumetric shrinkage among the tested composite resins. Suprafill (1.87±0.01) and Definite (1.89±0.01) shrank significantly less than the other composite resins. SureFil (2.01±0.06), Filtek Z250 (1.99±0.03), and Fill Magic (2.02±0.02) presented intermediate levels of polymerization shrinkage. Alert and Solitaire presented the highest degree of polymerization shrinkage. Knowing the polymerization shrinkage rates of the commercially available composite resins, the dentist would be able to choose between using composite resins with lower polymerization shrinkage rates or adopting technical or operational procedures to minimize the adverse effects deriving from resin contraction during light-activation. PMID:19089177

  12. A cure shrinkage model for analyzing the stresses and strains in encapsulated assemblies

    SciTech Connect

    Chambers, R.S.; Lagasse, R.R.; Guess, T.R.; Plazek, D.J.; Bero, C.

    1992-12-31

    Electrical component assemblies are encapsulated to provide delicate parts with voltage isolation and protection against damage caused by shock, vibration, and harsh atmospheric environments. During cure, thermosetting resins shrink and harden simultaneously. If the natural deformation of the resin is constrained by adhesion to the mold or to relatively stiff embedded components, cure shrinkage stresses are generated in the encapsulant. Subsequent cooling or thermal cycling produces additional stresses that are caused by the mismatches in thermal strains among the materials in the encapsulated assembly. Although cure shrinkage stresses frequently are neglected because they are considerably smaller than thermal stresses, cure shrinkage stresses can cause delamination or fractures in the encapsulant, since the partially cured resin is not as tough as the fully cured material. Cracks generated during cure can compromise performance (e. g., permit dielectric breakdown), degrade a component`s protection, and grow under subsequent thermal cycling producing residual stresses that differ from those found in uncracked assemblies. 3 refs., 11 figs.

  13. A cure shrinkage model for analyzing the stresses and strains in encapsulated assemblies

    NASA Astrophysics Data System (ADS)

    Chambers, R. S.; Lagasse, R. R.; Guess, T. R.; Plazek, D. J.; Bero, C.

    Electrical component assemblies are encapsulated to provide delicate parts with voltage isolation and protection against damage caused by shock, vibration, and harsh atmospheric environments. During cure, thermosetting resins shrink and harden simultaneously. If the natural deformation of the resin is constrained by adhesion to the mold or to relatively stiff embedded components, cure shrinkage stresses are generated in the encapsulant. Subsequent cooling or thermal cycling produces additional stresses that are caused by the mismatches in thermal strains among the materials in the encapsulated assembly. Although cure shrinkage stresses frequently are neglected because they are considerably smaller than thermal stresses, cure shrinkage stresses can cause delamination or fractures in the encapsulant, since the partially cured resin is not as tough as the fully cured material. Cracks generated during cure can compromise performance (e.g., permit dielectric breakdown), degrade a component's protection, and grow under subsequent thermal cycling producing residual stresses that differ from those found in uncracked assemblies.

  14. A cure shrinkage model for analyzing the stresses and strains in encapsulated assemblies

    SciTech Connect

    Chambers, R.S.; Lagasse, R.R.; Guess, T.R. ); Plazek, D.J.; Bero, C. . Dept. of Materials Science and Engineering)

    1992-01-01

    Electrical component assemblies are encapsulated to provide delicate parts with voltage isolation and protection against damage caused by shock, vibration, and harsh atmospheric environments. During cure, thermosetting resins shrink and harden simultaneously. If the natural deformation of the resin is constrained by adhesion to the mold or to relatively stiff embedded components, cure shrinkage stresses are generated in the encapsulant. Subsequent cooling or thermal cycling produces additional stresses that are caused by the mismatches in thermal strains among the materials in the encapsulated assembly. Although cure shrinkage stresses frequently are neglected because they are considerably smaller than thermal stresses, cure shrinkage stresses can cause delamination or fractures in the encapsulant, since the partially cured resin is not as tough as the fully cured material. Cracks generated during cure can compromise performance (e. g., permit dielectric breakdown), degrade a component's protection, and grow under subsequent thermal cycling producing residual stresses that differ from those found in uncracked assemblies. 3 refs., 11 figs.

  15. Compressed sensing recovery via nonconvex shrinkage penalties

    NASA Astrophysics Data System (ADS)

    Woodworth, Joseph; Chartrand, Rick

    2016-07-01

    The {{\\ell }}0 minimization of compressed sensing is often relaxed to {{\\ell }}1, which yields easy computation using the shrinkage mapping known as soft thresholding, and can be shown to recover the original solution under certain hypotheses. Recent work has derived a general class of shrinkages and associated nonconvex penalties that better approximate the original {{\\ell }}0 penalty and empirically can recover the original solution from fewer measurements. We specifically examine p-shrinkage and firm thresholding. In this work, we prove that given data and a measurement matrix from a broad class of matrices, one can choose parameters for these classes of shrinkages to guarantee exact recovery of the sparsest solution. We further prove convergence of the algorithm iterative p-shrinkage (IPS) for solving one such relaxed problem.

  16. Accounting for PDMS shrinkage when replicating structures

    NASA Astrophysics Data System (ADS)

    Hannibal Madsen, Morten; Feidenhans'l, Nikolaj A.; Hansen, Poul-Erik; Garnæs, Jørgen; Dirscherl, Kai

    2014-12-01

    Polydimethylsiloxane (PDMS) is a widely used material for fabrication of microfluidic devices and for replication of micro- and nanotextured surfaces. Shrinkage of PDMS in the fabrication process can lead to leaking devices and poor alignment of layers. However, corrections to the mold master are seldom applied to counteract the shrinkage of PDMS. Also, to perform metrological measurements using replica techniques one has to take the shrinkage into account. Thus we report a study of the shrinkage of PDMS with several different mixing ratios and curing temperatures. The shrinkage factor, with its associated uncertainty, for PDMS in the range 40 to 120 °C is provided. By applying this correction factor, it is possible to replicate structures with a standard uncertainty of less than 0.2% in lateral dimensions using typical curing temperatures and PDMS mixing ratios in the range 1:6 to 1:20 (agent:base).

  17. [Sinus lift with autogenous bone graft: surgical technique].

    PubMed

    Thiéry, G; Coulet, O; Adam, S; Lari, N

    2008-12-01

    Insufficient maxillar bone crest does not allow dental implant placement. The sinus lift technique with an autogenous bone graft compensates this deficiency. This technique is performed in two steps: iliac autogenous bone harvesting and sinus graft. After describing the possible complications, the various approaches of this technique are presented. This pre-implant surgery must be performed by experienced surgeons.

  18. The versatile autogenous rib graft in septorhinoplasty.

    PubMed

    Sherris, D A; Kern, E B

    1998-01-01

    In the graft depleted revision rhinoplasty patient and the patient with major tissue needs, alternatives to septal and conchal cartilage grafts are needed. The costal cartilage graft and rib bone/costal cartilage combination graft are excellent alternatives. In this study 14 patients received 40 grafts from 20 autogenous ribs harvested during septorhinoplasty. Materials were harvested for use as septal replacement grafts, cantilevered grafts, dorsal onlay grafts, columellar struts, and tip grafts. Patient followup was 6 to 31 months, and no evidence of graft resorption or warpage was evident during that period. Complications of harvest were minimal, and harvest techniques are detailed.

  19. Shrinkage assessment of low shrinkage composites using micro-computed tomography.

    PubMed

    Hirata, Ronaldo; Clozza, Emanuele; Giannini, Marcelo; Farrokhmanesh, Ehsan; Janal, Malvin; Tovar, Nick; Bonfante, Estevam A; Coelho, Paulo G

    2015-05-01

    The aim of this study was to quantify the polymerization volumetric shrinkage of one regular and two low shrinkage bulk fill composites in class I cavities with or without an adhesive layer, using three-dimensional (3D) micro-computed tomography (μCT). Class I cavity preparations (2.5 mm depth × 4 mm length × 4 mm wide) were standardized in 36 extracted human third molars, which were randomly divided in six groups (n = 6 each) as follows: Group VIT (regular composite without bonding agent); Group SDR (low shrinkage flowable composite without bonding agent); Group TET (low shrinkage composite without bonding agent); Group VIT/P (regular composite with bonding agent); Group SDR/X (low shrinkage flowable composite with bonding agent); TET/T (low shrinkage composite with bonding agent). Each tooth was scanned via µCT at cavity preparation, immediately after cavity filling, and after light-curing. Acquired μCT data were imported into Amira software for analysis and volume values evaluated between steps from cavity preparation until light-curing. Both low shrinkage composites showed a significantly less volumetric shrinkage than VIT. The use of dental adhesive significantly decreased the average volumetric contraction similarly for the three composites, by about 20%. Both low shrinkage composites showed less volumetric polymerization contraction than the regular composite. The use of dental adhesive decreased the total volumetric shrinkage for all evaluated composites. © 2014 Wiley Periodicals, Inc.

  20. Autogenous augmentation mammaplasty with microsurgical tissue transfer.

    PubMed

    Allen, Robert J; Heitland, Andreas S

    2003-07-01

    Many patients dream of reducing their abdominal or gluteal fat tissue and, in the same procedure, enlarging their breasts without the need for implants and their related problems. Following this demand, a new "natural" alternative to breast augmentation with autogenous tissue is presented. Since 1993, 16 patients have undergone either unilateral or bilateral breast augmentation with free fat transfer. These 20 augmentation mammaplasties consisted of nine deep inferior epigastric perforator flaps, eight superior gluteal artery perforator flaps, and three superficial inferior epigastric artery flaps. The postoperative results were judged aesthetically by independent examiners and by the patients according to Netscher's score. The additional operations for final shaping of the breasts and the postoperative complications at the donor and recipient sites are reported. The augmented breasts improved the aesthetic proportions more than 100 percent. All flaps survived, and except for minor postoperative complications such as small areas of wound dehiscence, the breasts could be shaped aesthetically in a second-stage procedure several weeks later. Breast augmentation with autogenous tissue offers a natural alternative to alloplastic augmentation mammaplasty.

  1. Development of novel low shrinkage dental nanocomposite

    NASA Astrophysics Data System (ADS)

    Sun, Yi; Wu, Xiaorong; Liu, Yanju; Xie, Weili; Sun, Shouhua

    2009-07-01

    It has been the focus to develop low shrinkage dental composite resins in recent ten years. A major difficulty in developing low shrinkage dental materials is their deficiency in mechanical properties to clinical use. This paper reviews the present investigations of low shrinkage dental composite resins and attempts to develop a novel system with multifunctional POSS incorporated. In this paper, it is especially interesting to evaluate the influences of shrinkage with different weight percentage of POSS (0~15wt%) incorporated in dental composite resins. Their double bond conversions are evaluated and their microstructures are characterized with Fourier-transform infra-red spectroscopy and X-ray diffraction. Their mechanical properties are also presented in this paper. The results show that the shrinkage of nanocomposites with POSS can be reduced effectively from 3.53% to 2.18%. The mechanical properties of this novel system, such as strength, hardness and toughness, are also enhanced greatly. Especially with 2wt%POSS incorporated, the best integrative improved effects are revealed. The mechanism of shrinkage is discussed.

  2. Estimating crack growth in temperature damaged concrete

    NASA Astrophysics Data System (ADS)

    Recalde, Juan Jose

    2009-12-01

    Evaluation of the structural condition of deteriorated concrete infrastructure and evaluation of new sustainable cementitious materials require an understanding of how the material will respond to applied loads and environmental exposures. A fundamental understanding of how microstructural changes in these materials relate to changes in mechanical properties and changes in fluid penetrability is needed. The ability to provide rapid, inexpensive assessment of material characteristics and relevant engineering properties is valuable for decision making and asset management purposes. In this investigation, the effects of changes in dynamic elastic properties with water content and fluid penetrability properties before and after a 300°C exposure were investigated based on estimates of the crack density parameter from dry and saturated cracked media. The experimental and analytical techniques described in this dissertation allow calculation of a value for the crack density parameter using nondestructive determination of wet and dry dynamic shear modulus of relatively thin disks. The techniques were used to compare a conventional concrete mixture to several mixtures with enhanced sustainability characteristics. The three enhanced sustainable materials investigated were a very high fly ash mixture, a magnesium phosphate cement based mortar, and a magnesium phosphate cement based concrete, and were compared to a conventional concrete mixture. The analysis provided both quantitative assessment of changes with high temperature damage and autogenous healing, and estimates of changes in mean crack trace lengths. The results showed that water interaction, deterioration due to damage, and autogenous healing recovery were different for the magnesium phosphate cement based mixtures than the portland cement based concrete mixtures. A strong correlation was found between log-transformed Air Permeability Index, dynamic shear modulus, and crack density parameter. The findings imply

  3. Autogenous Bone Reconstruction of Large Secondary Skull Defects.

    PubMed

    Fearon, Jeffrey A; Griner, Devan; Ditthakasem, Kanlaya; Herbert, Morley

    2017-02-01

    The authors sought to ascertain the upper limits of secondary skull defect size amenable to autogenous reconstructions and to examine outcomes of a surgical series. Published data for autogenous and alloplastic skull reconstructions were also examined to explore associations that might guide treatment. A retrospective review of autogenously reconstructed secondary skull defects was undertaken. A structured literature review was also performed to assess potential differences in reported outcomes between autogenous bone and synthetic alloplastic skull reconstructions. Weighted risks were calculated for statistical testing. Ninety-six patients underwent autogenous skull reconstruction for an average defect size of 93 cm (range, 4 to 506 cm) at a mean age of 12.9 years. The mean operative time was 3.4 hours, 2 percent required allogeneic blood transfusions, and the average length of stay was less than 3 days. The mean length of follow-up was 28 months. There were no postoperative infections requiring surgery, but one patient underwent secondary grafting for partial bone resorption. An analysis of 34 studies revealed that complications, infections, and reoperations were more commonly reported with alloplastic than with autogenous reconstructions (relative risk, 1.57, 4.8, and 1.48, respectively). Autogenous reconstructions are feasible, with minimal associated morbidity, for patients with skull defect sizes as large as 500 cm. A structured literature review suggests that autogenous bone reconstructions are associated with lower reported infection, complication, and reoperation rates compared with synthetic alloplasts. Based on these findings, surgeons might consider using autogenous reconstructions even for larger skull defects. Therapeutic, IV.

  4. [Autogenic training in psychophysiological preparation for parachute jumps].

    PubMed

    Reshetnikov, M M

    1978-01-01

    The efficiency of specific psychophysiological preparation--autogenic training--to parachute jumps was measured in two groups of cadets (test subjects and controls). Hetero- and autogenic training was carried out according to a scheme specially developed for this type of activity. The study of questionnaires and physiological data demonstrated that the specific psychophysiological preparation by means of autogenic training for a certain type of activity helped to develop active self-control over one's own state and emotions, alleviated tension, arrested adverse neurotic manifestations (sleep disturbances, depression, anxiety), contributed to the feeling of confidence in the successful completion of the jump and promoted positive tuning towards subsequent jumps.

  5. Autogenous Transplantation for Replacing a Hopeless Tooth

    PubMed Central

    Zakershahrak, Mehrsa; Moshari, Amirabbas; Vatanpour, Mehdi; Khalilak, Zohreh; Jalali Ara, Afsoon

    2017-01-01

    Autogenous tooth transplantation (ATT) is a simple and reasonable choice for replacing the missing teeth when a proper donor tooth is available. This report presents a case of successful ATT of a maxillary right third molar for replacement of mandibular right second molar with a concomitant endodontic-periodontal disease. The mandibular second molar was believed to be hopeless due to a severe damage to coronal tooth structure, inappropriate root canal treatment and apical radiolucency. After extraction of mandibular second molar and maxillary third molar (the donor), the tooth was re-implanted into the extracted socket of second molar site. Root canal therapy was then performed. After 3 years, clinical and radiographic examinations revealed satisfying results, with no signs and symptoms. The patient is asymptomatic and the transplanted tooth is still functional with no signs of marginal periodontal pathosis. Radiographies showed bone regeneration in the site of previous extensive periapical lesion, normal periodontal ligament with no signs of root resorption. PMID:28179939

  6. Heat shrinkage of electron beam modified EVA

    NASA Astrophysics Data System (ADS)

    Datta, Sujit K.; Chaki, T. K.; Tikku, V. K.; Pradhan, N. K.; Bhowmick, A. K.

    1997-10-01

    Heat shrinkage of electron beam modified ethylene vinyl acetate copolymer (EVA) has been investigated over a range of times, temperatures, stretching, irradiation doses and trimethylolpropane trimethacrylate (TMPTMA) levels. The irradiated (radiation dose 50 kGy and TMPTMA level 1%) and stretched (100% elongation) sample shrinks to a maximum level when kept at 453K temperature for 60 s. The heat shrinkage of samples irradiated with radiation doses of 20, 50, 100 and 150 kGy increases sharply with increasing stretching in the initial stage. Amnesia rating decreases with increasing radiation dose and TMPTMA level as well as gel content. The high radiation dose and TMPTMA level lower the heat shrinkage due to the chain scission. The effect of temperature at which extension is carried out on heat shrinkage is marginal. The irradiated (radiation dose 50 kGy and TMPTMA level 1%) EVA tubes of different dimensions expanded in a laboratory grade tube expander show similar behaviour at 453K and 60 s. The X-ray and DSC studies reveal that the crystallinity increases on stretching due to orientation of chains and it decreases to a considerable extent on heat shrinking. The theoretical and experimental values of heat shrinkage for tubes and rectangular strips are in good accord, when the radiation dose is 50 kGy and TMPTMA level 1%.

  7. Airway physiology, autogenic drainage, and active cycle of breathing.

    PubMed

    Lapin, Craig D

    2002-07-01

    Airway clearance techniques are used to aid in mucus clearance in a variety of disease states. Autogenic drainage and active-cycle-of-breathing technique are 2 such modalities that rely heavily on basic airway physiology to enhance clearance. In this review I discuss the equal pressure point, huffing, and asynchronous and collateral ventilation, and review the literature and theory regarding autogenic drainage and active cycle of breathing. Selection of airway clearance techniques is discussed in the light of evidence-based medicine.

  8. Technique to eliminate helium induced weld cracking in stainless steels

    SciTech Connect

    Chin-An Wang; Chin, B.A.; Grossbeck, M.L.

    1992-12-31

    Experiments have shown that Type 316 stainless steel is susceptible to heat-affected-zone (HAZ) cracking upon cooling when welded using the gas tungsten arc (GTA) process under lateral constraint. The cracking has been hypothesized to be caused by stress-assisted helium bubble growth and rupture at grain boundaries. This study utilized an experimental welding setup which enabled different compressive stresses to be applied to the plates during welding. Autogenous GTA welds were produced in Type 316 stainless steel doped with 256 appm helium. The application of a compressive stress, 55 Mpa, during welding suppressed the previously observed catastrophic cracking. Detailed examinations conducted after welding showed a dramatic change in helium bubble morphology. Grain boundary bubble growth along directions parallel to the weld was suppressed. Results suggest that stress-modified welding techniques may be used to suppress or eliminate helium-induced cracking during joining of irradiated materials.

  9. STRESS CORROSION CRACKING IN TEAR DROP SPECIMENS

    SciTech Connect

    Lam, P; Philip Zapp, P; Jonathan Duffey, J; Kerry Dunn, K

    2009-05-01

    Laboratory tests were conducted to investigate the stress corrosion cracking (SCC) of 304L stainless steel used to construct the containment vessels for the storage of plutonium-bearing materials. The tear drop corrosion specimens each with an autogenous weld in the center were placed in contact with moist plutonium oxide and chloride salt mixtures. Cracking was found in two of the specimens in the heat affected zone (HAZ) at the apex area. Finite element analysis was performed to simulate the specimen fabrication for determining the internal stress which caused SCC to occur. It was found that the tensile stress at the crack initiation site was about 30% lower than the highest stress which had been shifted to the shoulders of the specimen due to the specimen fabrication process. This finding appears to indicate that the SCC initiation took place in favor of the possibly weaker weld/base metal interface at a sufficiently high level of background stress. The base material, even subject to a higher tensile stress, was not cracked. The relieving of tensile stress due to SCC initiation and growth in the HAZ and the weld might have foreclosed the potential for cracking at the specimen shoulders where higher stress was found.

  10. Correction of EB-induced shrinkage in contour measurements

    NASA Astrophysics Data System (ADS)

    Ohashi, Takeyoshi; Hotta, Shoji; Yamaguchi, Atsuko; Tanaka, Junichi; Kawada, Hiroki

    2014-04-01

    We have proposed a new method for correcting electron beam (EB)-induced photoresist shrinkage in two-dimensional pattern contours extracted from a scanning electron microscope image. This method restores the original shrinkage-free contour from the experimentally determined "shrunk contour", based on a shrinkage model which takes into account of the elastic nature of the shrinkage phenomena caused by the photoresist-volume reduction. Verification of this shrinkage model was demonstrated by using ArF resist patterns as follows. First, the model was calibrated with the shrinkage data of several line patters with different linewidth prior to the contour correction. Next, the amount of shrinkage of elbow patterns was measured by comparing its contours obtained with small and sufficiently large EB dosages. It was found that the shrinkage of the inner edge of the elbow corner was smaller than that of the outer edge, which can be interpreted as a result of the elastic deformation. Finally, validity of shrinkage correction was examined. The model calculation correctly reproduced the observed shrinkage including its dependence on the location in the pattern. The restored contour showed a good consistency with the experimental results and the total root-mean-square error of the shrinkage correction was 0.5 nm. This result confirmed that our shrinkage model adequately describes the shrinkage of two dimensional patterns. Consequently, proposed shrinkage correction method is expected to improve the accuracy of contour measurements by a critical dimension-scanning electron microscope.

  11. Remodeling of Autogenous Bone Grafts after Osteotome Sinus Floor Elevation Assessed by Limited Cone Beam Computed Tomography

    PubMed Central

    Nishida, Tetsuya; Takenouchi, Yuka; Mori, Kyoko; Ariji, Miyuki; Nishida, Kaori; Ito, Koichi

    2013-01-01

    This study assessed the radiographic appearance of bone graft domes longitudinally after osteotome sinus floor elevation using cone beam computed tomography (CBCT). This study presents the radiological findings of a 6-month follow-up CBCT study in maxillary osteotome sinus floor elevation. We examined 52 patients with a crestal bone height of less than 8 mm in the posterior maxilla who required sinus augmentation. Implants (n = 91) were subsequently placed in regenerated bone following osteotome sinus floor elevation; autogenous bone was used as the augmentation material. In all cases, the grafted augmentation material tended to be absorbed, but at least 1 mm of grafted augmentation material was recognized around the implant fixtures on CBCT at the second implant operation. The border between the grafted augmentation material and the existing bone was indistinct. The grafted area apical to the implants undergoes shrinkage and remodeling. It was suggested that sufficient grafted autogenous bone changes into bone to support an implant. PMID:23956747

  12. Cracking catalyst

    SciTech Connect

    Otterstedt, J. E. A.; Jaras, S. G.; Pudas, R.; Upson, L. L.

    1985-05-07

    A cracking catalyst having good resistance to metal poisoning has at least two particle fractions of different particle sizes, the cracking catalyzing zeolite material being concentrated to the coarser particle size fractions, and the finer particle size fractions being formed from material having relatively lower or no or insignificant cracking catalyzing activity. The particles of the finer particle size fractions have a matrix of kaolin and amorphous alumina--silica and may contain for example, an SO /SUB x/ eliminating additive such as Al/sub 2/O/sub 3/, CaO and/or MgO. The coarser particle size fractions having cracking catalyzing effect have a mean particle size of from 80 to 125 ..mu..m and the finer particle size fractions a mean particle size of from 30 to 75 ..mu..m. The coarser particle size fractions have a zeolite content of at least 20 weight % and may have a zeolite content of up to 100 weight %, the remainder consisting essentially of material which has relatively lower or no or insignificant cracking-catalyzing activity and which consists of kaolin and amorphous alumina-silica. The catalyst mass as a whole may have a zeolite content of up to 50 weight %.

  13. Creep and shrinkage effects on integral abutment bridges

    NASA Astrophysics Data System (ADS)

    Munuswamy, Sivakumar

    Integral abutment bridges provide bridge engineers an economical design alternative to traditional bridges with expansion joints owing to the benefits, arising from elimination of expensive joints installation and reduced maintenance cost. The superstructure for integral abutment bridges is cast integrally with abutments. Time-dependent effects of creep, shrinkage of concrete, relaxation of prestressing steel, temperature gradient, restraints provided by abutment foundation and backfill and statical indeterminacy of the structure introduce time-dependent variations in the redundant forces. An analytical model and numerical procedure to predict instantaneous linear behavior and non-linear time dependent long-term behavior of continuous composite superstructure are developed in which the redundant forces in the integral abutment bridges are derived considering the time-dependent effects. The redistributions of moments due to time-dependent effects have been considered in the analysis. The analysis includes nonlinearity due to cracking of the concrete, as well as the time-dependent deformations. American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO) models for creep and shrinkage are considered in modeling the time dependent material behavior. The variations in the material property of the cross-section corresponding to the constituent materials are incorporated and age-adjusted effective modulus method with relaxation procedure is followed to include the creep behavior of concrete. The partial restraint provided by the abutment-pile-soil system is modeled using discrete spring stiffness as translational and rotational degrees of freedom. Numerical simulation of the behavior is carried out on continuous composite integral abutment bridges and the deformations and stresses due to time-dependent effects due to typical sustained loads are computed. The results from the analytical model are compared with the

  14. Compensating for Shrinkage in Machined Ceramics

    NASA Technical Reports Server (NTRS)

    Aguilar, L.; Fitchett, B. T.

    1986-01-01

    Technique insures machined ceramics shrink to correct dimensions after baked in kiln. New method automatically compensates during machining for shrinkage later, when part baked. Applicable to numerically controlled machines that include provision to adjust for variations in cuttingtool size, but do not provide for automatic verification of dimensions of machined parts.

  15. A Bayesian Shrinkage Approach for AMMI Models.

    PubMed

    da Silva, Carlos Pereira; de Oliveira, Luciano Antonio; Nuvunga, Joel Jorge; Pamplona, Andrezza Kéllen Alves; Balestre, Marcio

    2015-01-01

    Linear-bilinear models, especially the additive main effects and multiplicative interaction (AMMI) model, are widely applicable to genotype-by-environment interaction (GEI) studies in plant breeding programs. These models allow a parsimonious modeling of GE interactions, retaining a small number of principal components in the analysis. However, one aspect of the AMMI model that is still debated is the selection criteria for determining the number of multiplicative terms required to describe the GE interaction pattern. Shrinkage estimators have been proposed as selection criteria for the GE interaction components. In this study, a Bayesian approach was combined with the AMMI model with shrinkage estimators for the principal components. A total of 55 maize genotypes were evaluated in nine different environments using a complete blocks design with three replicates. The results show that the traditional Bayesian AMMI model produces low shrinkage of singular values but avoids the usual pitfalls in determining the credible intervals in the biplot. On the other hand, Bayesian shrinkage AMMI models have difficulty with the credible interval for model parameters, but produce stronger shrinkage of the principal components, converging to GE matrices that have more shrinkage than those obtained using mixed models. This characteristic allowed more parsimonious models to be chosen, and resulted in models being selected that were similar to those obtained by the Cornelius F-test (α = 0.05) in traditional AMMI models and cross validation based on leave-one-out. This characteristic allowed more parsimonious models to be chosen and more GEI pattern retained on the first two components. The resulting model chosen by posterior distribution of singular value was also similar to those produced by the cross-validation approach in traditional AMMI models. Our method enables the estimation of credible interval for AMMI biplot plus the choice of AMMI model based on direct posterior

  16. A Bayesian Shrinkage Approach for AMMI Models

    PubMed Central

    de Oliveira, Luciano Antonio; Nuvunga, Joel Jorge; Pamplona, Andrezza Kéllen Alves

    2015-01-01

    Linear-bilinear models, especially the additive main effects and multiplicative interaction (AMMI) model, are widely applicable to genotype-by-environment interaction (GEI) studies in plant breeding programs. These models allow a parsimonious modeling of GE interactions, retaining a small number of principal components in the analysis. However, one aspect of the AMMI model that is still debated is the selection criteria for determining the number of multiplicative terms required to describe the GE interaction pattern. Shrinkage estimators have been proposed as selection criteria for the GE interaction components. In this study, a Bayesian approach was combined with the AMMI model with shrinkage estimators for the principal components. A total of 55 maize genotypes were evaluated in nine different environments using a complete blocks design with three replicates. The results show that the traditional Bayesian AMMI model produces low shrinkage of singular values but avoids the usual pitfalls in determining the credible intervals in the biplot. On the other hand, Bayesian shrinkage AMMI models have difficulty with the credible interval for model parameters, but produce stronger shrinkage of the principal components, converging to GE matrices that have more shrinkage than those obtained using mixed models. This characteristic allowed more parsimonious models to be chosen, and resulted in models being selected that were similar to those obtained by the Cornelius F-test (α = 0.05) in traditional AMMI models and cross validation based on leave-one-out. This characteristic allowed more parsimonious models to be chosen and more GEI pattern retained on the first two components. The resulting model chosen by posterior distribution of singular value was also similar to those produced by the cross-validation approach in traditional AMMI models. Our method enables the estimation of credible interval for AMMI biplot plus the choice of AMMI model based on direct posterior

  17. Matrix cracking in brittle-matrix composites with tailored interfaces

    SciTech Connect

    Danchaivijit, S.; Chao, L.Y.; Shetty, D.K.

    1995-10-01

    Matrix cracking from controlled through cracks with bridging filaments was studied in a model unidirectional composite of SiC filaments in an epoxy-bonded alumina matrix. An unbonded, frictional interface was produced by moderating the curing shrinkage of the epoxy with the alumina filler and coating the filaments with a releasing agent. Uniaxial tension test specimens (2.5 x 25 x 125 mm) with filament-bridged through cracks were fabricated by a novel two-step casting technique involving casting, precracking and joining of cracked and uncracked sections. Distinct matrix-cracking stresses, corresponding to the extension of the filament-bridged cracks, were measured in uniaxial tension tests using a high-sensitivity extensometer. The crack-length dependence of the matrix-cracking stress was found to be in good agreement with the prediction of a fracture-mechanics analysis that employed a new crack-closure force-crack-opening displacement relation in the calculation of the stress intensity for fiber-bridged cracks. The prediction was based on independent experimental measurements of the matrix fracture toughness (K{sub cm}), the interfacial sliding friction stress ({tau}) and the residual stress in the matrix ({sigma}{sub m}{sup I}). The matrix-cracking stress for crack lengths (2a) greater than 3 mm was independent of the crack length and agreed with the prediction of the steady-state theory of Budiansky, Hutchinson and Evans. Tests on specimens without the deliberately introduced cracks indicated a matrix-cracking stress significantly higher than the steady-state stress.

  18. Alveolar bone changes in autogenous tooth transplantation.

    PubMed

    Waikakul, Aurasa; Punwutikorn, Jirapun; Kasetsuwan, Julalux; Korsuwannawong, Suwanna

    2011-03-01

    To assess the alveolar bone formation after autogenous tooth transplantation by conventional radiographic method and digital subtraction radiography. This retrospective study was done in 54 of 136 patients who received the third molar tooth transplantation and attended the first week, as well as the 1-, 3-, 6-, 9-, and 12-month follow-up. Postoperative periapical radiographs were subsequently evaluated by direct visual interpretation and digital subtraction radiography. The data were analyzed by using McNemar test and 1-way repeated-measure analysis of variance as well as Bonferroni multiple comparison. Fifty-four cases of transplantation were studied. Most of them had normal wound healing. The direct radiographic interpretation and digital subtraction radiography found significant alveolar bone formation in the first-and the third-month follow-ups (P < .05). Lamina dura appeared in the third month and kept increasing until the sixth month. Postoperative radiographs revealed the distinctive bone formation up to the third month. The clinical and radiographic assessment found that the third molar transplants could bear a normal chewing load within 3 months. Copyright © 2011 Mosby, Inc. All rights reserved.

  19. Effect of expansive admixtures on the shrinkage and mechanical properties of high-performance fiber-reinforced cement composites.

    PubMed

    Choi, Won-Chang; Yun, Hyun-Do

    2013-01-01

    High-performance fiber-reinforced cement composites (HPFRCCs) are characterized by strain-hardening and multiple cracking during the inelastic deformation process, but they also develop high shrinkage strain. This study investigates the effects of replacing Portland cement with calcium sulfoaluminate-based expansive admixtures (CSA EXAs) to compensate for the shrinkage and associated mechanical behavior of HPFRCCs. Two types of CSA EXA (CSA-K and CSA-J), each with a different chemical composition, are used in this study. Various replacement ratios (0%, 8%, 10%, 12%, and 14% by weight of cement) of CSA EXA are considered for the design of HPFRCC mixtures reinforced with 1.5% polyethylene (PE) fibers by volume. Mechanical properties, such as shrinkage compensation, compressive strength, flexural strength, and direct tensile strength, of the HPFRCC mixtures are examined. Also, crack width and development are investigated to determine the effects of the EXAs on the performance of the HPFRCC mixtures, and a performance index is used to quantify the performance of mixture. The results indicate that replacements of 10% CSA-K (Type 1) and 8% CSA-J (Type 2) considerably enhance the mechanical properties and reduce shrinkage of HPFRCCs.

  20. Effect of Expansive Admixtures on the Shrinkage and Mechanical Properties of High-Performance Fiber-Reinforced Cement Composites

    PubMed Central

    Choi, Won-Chang; Yun, Hyun-Do

    2013-01-01

    High-performance fiber-reinforced cement composites (HPFRCCs) are characterized by strain-hardening and multiple cracking during the inelastic deformation process, but they also develop high shrinkage strain. This study investigates the effects of replacing Portland cement with calcium sulfoaluminate-based expansive admixtures (CSA EXAs) to compensate for the shrinkage and associated mechanical behavior of HPFRCCs. Two types of CSA EXA (CSA-K and CSA-J), each with a different chemical composition, are used in this study. Various replacement ratios (0%, 8%, 10%, 12%, and 14% by weight of cement) of CSA EXA are considered for the design of HPFRCC mixtures reinforced with 1.5% polyethylene (PE) fibers by volume. Mechanical properties, such as shrinkage compensation, compressive strength, flexural strength, and direct tensile strength, of the HPFRCC mixtures are examined. Also, crack width and development are investigated to determine the effects of the EXAs on the performance of the HPFRCC mixtures, and a performance index is used to quantify the performance of mixture. The results indicate that replacements of 10% CSA-K (Type 1) and 8% CSA-J (Type 2) considerably enhance the mechanical properties and reduce shrinkage of HPFRCCs. PMID:24376382

  1. Shrinkage of Dental Composite in Simulated Cavity Measured with Digital Image Correlation

    PubMed Central

    Li, Jianying; Thakur, Preetanjali; Fok, Alex S. L.

    2014-01-01

    Polymerization shrinkage of dental resin composites can lead to restoration debonding or cracked tooth tissues in composite-restored teeth. In order to understand where and how shrinkage strain and stress develop in such restored teeth, Digital Image Correlation (DIC) was used to provide a comprehensive view of the displacement and strain distributions within model restorations that had undergone polymerization shrinkage. Specimens with model cavities were made of cylindrical glass rods with both diameter and length being 10 mm. The dimensions of the mesial-occlusal-distal (MOD) cavity prepared in each specimen measured 3 mm and 2 mm in width and depth, respectively. After filling the cavity with resin composite, the surface under observation was sprayed with first a thin layer of white paint and then fine black charcoal powder to create high-contrast speckles. Pictures of that surface were then taken before curing and 5 min after. Finally, the two pictures were correlated using DIC software to calculate the displacement and strain distributions. The resin composite shrunk vertically towards the bottom of the cavity, with the top center portion of the restoration having the largest downward displacement. At the same time, it shrunk horizontally towards its vertical midline. Shrinkage of the composite stretched the material in the vicinity of the “tooth-restoration” interface, resulting in cuspal deflections and high tensile strains around the restoration. Material close to the cavity walls or floor had direct strains mostly in the directions perpendicular to the interfaces. Summation of the two direct strain components showed a relatively uniform distribution around the restoration and its magnitude equaled approximately to the volumetric shrinkage strain of the material. PMID:25079865

  2. Desiccation cracks in siliciclastic deposits: Microbial mat-related compared to abiotic sedimentary origin

    NASA Astrophysics Data System (ADS)

    Kovalchuk, Olga; Owttrim, George W.; Konhauser, Kurt O.; Gingras, Murray K.

    2017-01-01

    Siliciclastic sediment colonized by microbial mats yield a set of distinct sedimentary fabrics that are collectively called "mat-related structures (MRS)". In the rock record, versatile cracks are observed in biostabilized strata, but the mechanisms responsible for their formation remain debated. Microbially stabilized sediments produce desiccation cracks that serve as modern analogs for fossil microbial cracks. However, since both microbial mat shrinkage and clay shrinkage may contribute to the formation of these desiccation cracks, it is difficult to isolate the influence of the microbial mat on the resulting crack formation, distribution and morphology. To address this issue, we conducted a series of desiccation experiments that determine differences between microbially influenced desiccation cracks (i.e. biotic) and those formed in identical, but sterilized (i.e. abiotic) siliciclastic sediment. Three sediment mixtures were used: (1) very fine-sized sand, (2) mixed (ungraded) silt/clay, and (3) normally graded silt/clay. In all of the experiments, the water-rich microbial mat contracted substantially while drying, producing isolated pockets of shallow, but wide cracks, the distribution of which was controlled by heterogeneities in the mat structure and thickness variations of the mat. In the clay-poor substratum, the microbial mat was the only crack-forming mechanism, while in the clay-rich substrata (experiments 2 and 3) desiccation cracks were more strongly influenced by clay shrinkage. The abiotic clay-rich sediment produced a polygonal network of deep cracks intersecting at 90-120o junctions. In the biotic clay-rich experiments, the microbial mat modified these desiccation features by withstanding crack propagation or by producing curled-up crack polygon margins. Even though a microbial mat shrinks substantially with desiccation, its cohesive nature and heterogeneous distribution prevents the formation of a regular crack network, but its shallow penetration

  3. Phobic postural vertigo treated with autogenic training: a case report

    PubMed Central

    Goto, Fumiyuki; Nakai, Kimiko; Kunihiro, Takanobu; Ogawa, Kaoru

    2008-01-01

    Background Patients suffering from dizziness due to vertigo are commonly encountered in the department of otolaryngology. If various clinical examinations do not reveal any objective findings, then the patients are referred to the department of internal medicine or psychiatry. In many cases, the diagnosis is psychological dizziness. Phobic postural vertigo, which was first reported by Brandt T et al in 1994, is supposed to be a type of psychological dizziness. The diagnosis is based on 6 characteristics proposed by Brandt et al. Patients are usually treated with conventional medical therapy, but some cases may be refractory to such a therapy. Psychotherapy is recommended in some cases; however, psychotherapy including autogenic training, which can be used for general relaxation, is not widely accepted. This paper describes the successful administration of autogenic training in a patient suffering from phobic postural vertigo. Case presentation We present a case of a patient who suffered from phobic postural vertigo. A 37-year-old female complained of dizziness. She had started experiencing dizziness almost 3 years She was intractable to many sort of conventional therapy. In the end, her symptom disappeared after introduction of autogenic training. Conclusion Autogenic training can be a viable and acceptable treatment option for phobic postural vertigo patients who fail to respond to other therapies. This case emphasizes the importance of autogenic training as a method to control symptom of phobic postural vertigo. PMID:18826607

  4. Effect of disorder on shrinkage-induced fragmentation of a thin brittle layer

    NASA Astrophysics Data System (ADS)

    Halász, Zoltán; Nakahara, Akio; Kitsunezaki, So; Kun, Ferenc

    2017-09-01

    We investigate the effect of the amount of disorder on the shrinkage-induced cracking of a thin brittle layer attached to a substrate. Based on a discrete element model we study how the dynamics of cracking and the size of fragments evolve when the amount of disorder is varied. In the model a thin layer is discretized on a random lattice of Voronoi polygons attached to a substrate. Two sources of disorder are considered: structural disorder captured by the local variation of the stiffness and strength disorder represented by the random strength of cohesive elements between polygons. Increasing the amount of strength disorder, our calculations reveal a transition from a cellular crack pattern, generated by the sequential branching and merging of cracks, to a disordered ensemble of cracks where the merging of randomly nucleated microcracks dominate. In the limit of low disorder, the statistics of fragment size is described by a log-normal distribution; however, in the limit of high disorder, a power-law distribution is obtained.

  5. [Effects of autogenic training in elderly patients].

    PubMed

    Kircher, T; Teutsch, E; Wormstall, H; Buchkremer, G; Thimm, E

    2002-04-01

    Autogenic training (AT) is a widely available relaxation method with beneficial outcome on physiological and psychological functioning. In our study, we wanted to test the effects of an AT course in cognitively impaired, frail elderly. After a 3 month waiting period (control), AT courses (intervention) of 3 months duration were offered in 2 nursing homes. Thirty-two frail elderly took part in the study, 24 of them had a psychiatric diagnosis (mean age 82.1 +/- 7.2 years, CAMCOG 75.5 +/- 15.7, MMSE 23.3 +/- 4.3, HAMD 10.0 +/- 3.6, NOSGER 57.2 +/- 18.4, AT-SYM 32.9 +/- 17.6 points). Eight participants dropped out during the waiting period, 8 during the course. From the 16 participants, 15 (94%) were able to learn the AT according to subjective, 9 (54%) according to objective criteria. The ability to practice the AT successfully correlated with the CAMCOG (p = 0.001) and the NOSGER (p = 0.01) score. Participants with a dementia syndrome had major difficulties, whereas age, depressiveness, and number of complaints (AT-SYM) had no influence on the ability to learn the AT. There was no intervention effect, measured with the HAMD, NOSGER, AT-SYM and MMSE. In the pre-post comparison of training sessions, a significant improvement in general well being was found (p < 0.001). Mentally impaired, frail elderly participants are able to learn the AT. Cognitive impairment is disadvantageous for a successful participation.

  6. Salivation quantum--stomatopyrosis--autogenic training.

    PubMed

    Pokupec, Josipa-Sanja Gruden; Gruden, Vladimir; Biocina-Lukenda, Dolores

    2009-09-01

    Stomatopyrosis of 'burning mouth' syndrome, in a narrower sense of definition, is a condition characterized by sensation of burning and heating in mouth, despite its normal mucosa. This research has been directed towards treatment of stomatopyrosis, putting emphasis on the implementation of psychopharmacotherapy and psychotherapy. The research was conducted on altogether 120 respondents suffering from stomatopyrosis. The respondents were divided into two equal groups: each one comprising 60 members. All the respondents were treated by means of a standard topical therapy. All the patients were assessed clinically and by means of psychological tests measuring depression and anxiety four times: once before the treatment, after one month, after two months and after four months since the beginning of the treatment. The acquired data were afterwards statistically processed. When grading the symptoms on VAS, i.e. visual analogous scale, the subjective assessment of symptoms was marked as 7-8 cm, which shows a high degree of burning sensation. According to our study, the quantity of saliva, which was at the beginning of the research slightly decreased, normalized after the treatment. Apart from the clinical investigation of stomatopyrosis, we applied Depression and Anxiety questionnaires. On the basis of our research, we have concluded the following: the comorbidity of stomatopyrosis with the phenomena of anxiety and depression proves that, among other factors, there is a psychogenic aetiology of this disease. Autogenic training, which is a psychotherapeutic anxiolytic technique, is a therapy of choice for stomatopyrosis, which contributes not only to the elimination of oral complaints, but to the emotional rehabilitation of the patients as well, and to the reduction of dryness in the mouth.

  7. Creeping attachment: autogenous graft vs dermal matrix allograft.

    PubMed

    Haeri, A; Parsell, D

    2000-09-01

    For many years, free autogenous grafts have been used as a method of gaining keratinized tissue around teeth with mucogingival problems. Creeping attachment using autogenous graft material has been actively studied. In addition, biocompatible, acellular connective-tissue material has recently been used as an alternative to free gingival grafts to increase the zone of keratinization. This report presents a patient with bilateral mucogingival defects in the canine and premolar areas. The patient received an autogenous graft on one side and a dermal matrix allograft on the contralateral side. Creeping attachments were measured and compared at 3 months and 12 months after surgery. After 12 months of healing, an average of 1.23 mm of creeping attachment was measured on the free gingival graft side and 0.96 mm of creeping attachment was measured with the dermal matrix allograft.

  8. Recanalization of failed autogenous conduit utilizing laser revascularization.

    PubMed

    Chander, Rajiv K; Oza, Parind; Patel, Mayank; Balar, Nilesh

    2011-10-01

    The traditional approach for the treatment of restenosis of autogenous vein bypass has been revision of bypass with vein patch angioplasty, interposition jump graft, or thrombectomy procedures for those patients with extensive occlusive disease and limb-threatening ischemia. Endovascular intervention traditionally involves angioplasty of the graft; however, vessels with diffuse disease or extensive longitudinal lesions are generally difficult to revascularize utilizing this technique. Surgical revision of a threatened autogenous vein graft may carry a morbidity rate as high as 13.6%. We present a series of cases in which excimer laser atherectomy (LA) was used to recanalize an occluded autogenous saphenous vein bypass. Of the occluded vein bypasses failed angioplasty and were successfully atherectomized with LA measuring lengths of 35 and 30 cm, respectively. The infrainguinal has a 6-month follow-up, while the infragencular has a follow-up of 1 year, with resolution of presenting symptoms.

  9. Osseointegrated alloplastic versus autogenous ear reconstruction: criteria for treatment selection.

    PubMed

    Wilkes, G H; Wolfaardt, J F

    1994-04-01

    Fifty-five patients with major ear deformities were reconstructed during the period 1982-1993 with autogenous tissue. Fourteen patients were reconstructed with osseointegrated auricular prostheses during the period 1989-1993. Both procedures were done at the same institution by the same surgeon. The advantages and disadvantages of each approach were considered, and our criteria for treatment selection were developed. Our main indications for autogenous reconstruction include classical microtia, relatively normal lower one-third of the ear, patient preference, and less compliant patients. The main indications for osseointegrated alloplastic reconstruction include following major cancer extirpation, poor local tissue, absence of the lower half of the ear, salvage following unsuccessful autogenous reconstruction, and poor operative risks. Because of their success, osseointegrated auricular reconstructions should be added to the armamentarium of the reconstructive surgeon.

  10. Discrete multiscale wavelet shrinkage and integrodifferential equations

    NASA Astrophysics Data System (ADS)

    Didas, S.; Steidl, G.; Weickert, J.

    2008-04-01

    We investigate the relation between discrete wavelet shrinkage and integrodifferential equations in the context of simplification and denoising of one-dimensional signals. In the continuous setting, strong connections between these two approaches were discovered in 6 (see references). The key observation is that the wavelet transform can be understood as derivative operator after the convolution with a smoothing kernel. In this paper, we extend these ideas to the practically relevant discrete setting with both orthogonal and biorthogonal wavelets. In the discrete case, the behaviour of the smoothing kernels for different scales requires additional investigation. The results of discrete multiscale wavelet shrinkage and related discrete versions of integrodifferential equations are compared with respect to their denoising quality by numerical experiments.

  11. Cartilage repair with autogenic perichondrium cell and polylactic acid grafts.

    PubMed

    Dounchis, J S; Bae, W C; Chen, A C; Sah, R L; Coutts, R D; Amiel, D

    2000-08-01

    The repair of articular cartilage injuries remains a challenge, with many of the current therapeutic strategies based on the grafting or recruitment of chondrogenic tissues or cells. This 1-year study compared the repair of a 3.7-mm diameter by 3-mm deep osteochondral defect in the medial femoral condyle of 24 New Zealand White rabbits; the defect was obtained using an autogenic perichondrium cell polylactic acid composite graft with a contralateral control in which the osteochondral defect remained empty. To elucidate the effect of host immune responses on the repair process after perichondrium cell transplantation, the results of the autogenic perichondrium cell polylactic acid graft group were compared with those obtained in the authors' previous 1-year study of allogenic perichondrium cell polylactic acid composite grafts implanted in a similar model. One year after surgery, the repair site underwent gross inspection and histologic, histomorphometric, biochemical, and biomechanical analyses. The autogenic perichondrium cell polylactic acid graft group (92%) and the control group in which the osteochondral defect remained empty (88%) resulted in a high percentage of grossly acceptable repairs. The autogenic grafts appeared to augment the intrinsic healing capacity of the animals (as compared with the animals in the No Implant Group). The autogenic perichondrium cell polylactic and grafts improved the histologic appearance and percentage of Type II collagen of the cartilaginous repair tissue. Compared with allogenic grafts, the autogenic grafts had better reconstitution of the subchondral bone. However, the results of this experimental model suggest a suboptimal concentration of glycosaminoglycans in the neocartilage matrix, a depressed surface of the repair tissue, a histologic appearance that was not equivalent to that of normal articular cartilage, and reduced biomechanical properties for the repair tissue. The future application of growth factors to this

  12. Self-repair of cracks in brittle material systems

    NASA Astrophysics Data System (ADS)

    Dry, Carolyn M.

    2016-04-01

    One of the most effective uses for self repair is in material systems that crack because the cracks can allow the repair chemical to flow into the crack damage sites in all three dimensions. In order for the repair chemical to stay in the damage site and flow along to all the crack and repair there must be enough chemical to fill the entire crack. The repair chemical must be designed appropriately for the particular crack size and total volume of cracks. In each of the three examples of self repair in crackable brittle systems, the viscosity and chemical makeup and volume of the repair chemicals used is different for each system. Further the chemical delivery system has to be designed for each application also. Test results from self repair of three brittle systems are discussed. In "Self Repair of Concrete Bridges and Infrastructure" two chemicals were used due to different placements in bridges to repair different types of cracks- surface shrinkage and shear cracks, In "Airplane Wings and Fuselage, in Graphite" the composite has very different properties than the concrete bridges. In the graphite for airplane components the chemical also had to survive the high processing temperatures. In this composite the cracks were so definite and deep and thin that the repair chemical could flow easily and repair in all layers of the composite. In "Ceramic/Composite Demonstrating Self Repair" the self repair system not only repaired the broken ceramic but also rebounded the composite to the ceramic layer

  13. Shrinkage measurement for holographic recording materials

    NASA Astrophysics Data System (ADS)

    Fernández, R.; Gallego, S.; Márquez, A.; Francés, J.; Navarro Fuster, V.; Neipp, C.; Ortuño, M.; Beléndez, A.; Pascual, I.

    2017-05-01

    There is an increasing demand for new holographic recording materials. One of them are photopolymers, which are becoming a classic media in this field. Their versatility is well known and new possibilities are being created by including new components, such as nanoparticles or dispersed liquid crystal molecules in classical formulations, making them interesting for additional applications in which the thin film preparation and the structural modification have a fundamental importance. Prior to obtaining a wide commercialization of displays based on photopolymers, one of the key aspects is to achieve a complete characterization of them. In this sense, one of the main parameters to estimate and control is the shrinkage of these materials. The volume variations change the angular response of the hologram in two aspects, the angular selectivity and the maximum diffraction efficiency. One criteria for the recording material to be used in a holographic data storage application is the shrinkage, maximum of 0.5%. Along this work, we compare two different methods to measure the holographic recording material shrinkage. The first one is measuring the angle of propagation for both diffracted orders +/-1 when slanted gratings are recorded, so that an accurate value of the grating vector can be calculated. The second one is based on interference measurements at zero spatial frequency limit. We calculate the shrinkage for three different photopolymers: a polyvinyl alcohol acrylamide (PVA/AA) based photopolymer, one of the greenest photopolymers whose patent belongs to the Alicante University called Biophotopol and on the last place a holographic-dispersed liquid crystal photopolymer (H-PDLC).

  14. Compensating For Shrinkage In A Cryogenic Seal

    NASA Technical Reports Server (NTRS)

    Hill, Arnold E.

    1993-01-01

    Proposed design for seals in liquid-hydrogen plumbing eliminates leaks caused by contraction of seals at low operating temperature. Each seal consists of rubber, polytetrafluorethylene, or lead O-ring including hollow core filled with water. At temperature of liquid hydrogen, anomalous expansion of water keeps seal gland filled and leaktight despite shrinkage of surrounding O-ring material. Design also used in systems using cryogenic fluids other than liquid hydrogen.

  15. Nearest shrunken centroids via alternative genewise shrinkages

    PubMed Central

    Choi, Byeong Yeob; Bair, Eric; Lee, Jae Won

    2017-01-01

    Nearest shrunken centroids (NSC) is a popular classification method for microarray data. NSC calculates centroids for each class and “shrinks” the centroids toward 0 using soft thresholding. Future observations are then assigned to the class with the minimum distance between the observation and the (shrunken) centroid. Under certain conditions the soft shrinkage used by NSC is equivalent to a LASSO penalty. However, this penalty can produce biased estimates when the true coefficients are large. In addition, NSC ignores the fact that multiple measures of the same gene are likely to be related to one another. We consider several alternative genewise shrinkage methods to address the aforementioned shortcomings of NSC. Three alternative penalties were considered: the smoothly clipped absolute deviation (SCAD), the adaptive LASSO (ADA), and the minimax concave penalty (MCP). We also showed that NSC can be performed in a genewise manner. Classification methods were derived for each alternative shrinkage method or alternative genewise penalty, and the performance of each new classification method was compared with that of conventional NSC on several simulated and real microarray data sets. Moreover, we applied the geometric mean approach for the alternative penalty functions. In general the alternative (genewise) penalties required fewer genes than NSC. The geometric mean of the class-specific prediction accuracies was improved, as well as the overall predictive accuracy in some cases. These results indicate that these alternative penalties should be considered when using NSC. PMID:28199352

  16. Shrinkage deformation of cement foam concrete

    NASA Astrophysics Data System (ADS)

    Kudyakov, A. I.; Steshenko, A. B.

    2015-01-01

    The article presents the results of research of dispersion-reinforced cement foam concrete with chrysotile asbestos fibers. The goal was to study the patterns of influence of chrysotile asbestos fibers on drying shrinkage deformation of cement foam concrete of natural hardening. The chrysotile asbestos fiber contains cylindrical fiber shaped particles with a diameter of 0.55 micron to 8 microns, which are composed of nanostructures of the same form with diameters up to 55 nm and length up to 22 microns. Taking into account the wall thickness, effective reinforcement can be achieved only by microtube foam materials, the so- called carbon nanotubes, the dimensions of which are of power less that the wall pore diameter. The presence of not reinforced foam concrete pores with perforated walls causes a decrease in its strength, decreases the mechanical properties of the investigated material and increases its shrinkage. The microstructure investigation results have shown that introduction of chrysotile asbestos fibers in an amount of 2 % by weight of cement provides the finely porous foam concrete structure with more uniform size closed pores, which are uniformly distributed over the volume. This reduces the shrinkage deformation of foam concrete by 50%.

  17. Bi-autogenous ovarian cycles in Egyptian Aedes caspius Pallas (Diptera:Culicidae).

    PubMed

    Farid, H A; Gad, A M; Hassan, M M

    1989-01-01

    Autogenous Aedes (Ochlerotatus) caspius Pallas from Aswan deposits 1 to 2 egg batches without a blood meal. Repeated ovarian developmental cycles were responsible for the bi-ovipositional pattern as indicated by the presence of 2 dilatations in the ovariolar pedicel of bi-autogenous females and by the early stages of development of the ovaries (II and II B) observed 1-3 days following initial oviposition, later stages of maturation occurred progressively. Three levels of autogeny were distinguished within the population: mono-autogenous females that deposited 1 egg batch and were unable to initiate further oogenesis (54.4%), mono-autogenous females in which various degrees of vitellogenesis developed posterior to initial sole oviposition (40%) and bi-autogenous females (5.6%) that deposited 2 autogenous egg batches but were unable to develop any further oogenesis. The fecundity of mono-autogenous females (about 56 eggs) whether they could develop a 2nd autogenous cycle or not, was comparable to that of bi-autogenous mosquitoes in their initial egg batch (53 eggs), suggesting that ability to develop a subsequent autogenous follicular cycle is determined by factors independent of nutrient reserves accumulated during the larval stage. The 2nd egg batch of bi-autogenous females was smaller (21 eggs) than the initial batch. The total reproductive effort of bi-autogenous individuals (about 74 eggs) was superior to that of mono-autogenous females. However, bi-autogenous females laid the totality of their eggs within about 16 days, whereas the average initial gonotrophic cycle of mono-autogenous females was 6 days. It is concluded that bi-autogeny in Ae. caspius would be of little value in the population increase although it may contribute maintaining the species when the host is not available.

  18. Comparative Study of Shrinkage and Non-Shrinkage Model of Food Drying

    NASA Astrophysics Data System (ADS)

    Shahari, N.; Jamil, N.; Rasmani, KA.

    2016-08-01

    A single phase heat and mass model has always been used to represent the moisture and temperature distribution during the drying of food. Several effects of the drying process, such as physical and structural changes, have been considered in order to increase understanding of the movement of water and temperature. However, the comparison between the heat and mass equation with and without structural change (in terms of shrinkage), which can affect the accuracy of the prediction model, has been little investigated. In this paper, two mathematical models to describe the heat and mass transfer in food, with and without the assumption of structural change, were analysed. The equations were solved using the finite difference method. The converted coordinate system was introduced within the numerical computations for the shrinkage model. The result shows that the temperature with shrinkage predicts a higher temperature at a specific time compared to that of the non-shrinkage model. Furthermore, the predicted moisture content decreased faster at a specific time when the shrinkage effect was included in the model.

  19. Polymerization shrinkage assessment of dental resin composites: a literature review.

    PubMed

    Kaisarly, Dalia; Gezawi, Moataz El

    2016-09-01

    Composite restorations are widely used worldwide, but the polymerization shrinkage is their main disadvantage that may lead to clinical failures and adverse consequences. This review reports, currently available in vitro techniques and methods used for assessing the polymerization shrinkage. The focus lies on recent methods employing three-dimensional micro-CT data for the evaluation of polymerization shrinkage: volumetric measurement and the shrinkage vector evaluation through tracing particles before and after polymerization. Original research articles reporting in vitro shrinkage measurements and shrinkage stresses were included in electronic and hand-search. Earlier methods are easier, faster and less expensive. The procedures of scanning the samples in the micro-CT and performing the shrinkage vector evaluation are time consuming and complicated. Moreover, the respective software is not commercially available and the various methods for shrinkage vector evaluation are based on different mathematical principles. Nevertheless, these methods provide clinically relevant information and give insight into the internal shrinkage behavior of composite applied in cavities and how boundary conditions affect the shrinkage vectors. The traditional methods give comparative information on polymerization shrinkage of resin composites, whereas using three-dimensional micro-CT data for volumetric shrinkage measurement and the shrinkage vector evaluation is a highly accurate method. The methods employing micro-CT data give the researchers knowledge related to the application method and the boundary conditions of restorations for visualizing the shrinkage effects that could not be seen otherwise. Consequently, this knowledge can be transferred to the clinical situation to optimize the material manipulation and application techniques for improved outcomes.

  20. Autogenous Metallic Pipe Leak Repair in Potable Water Systems.

    PubMed

    Tang, Min; Triantafyllidou, Simoni; Edwards, Marc A

    2015-07-21

    Copper and iron pipes have a remarkable capability for autogenous repair (self-repair) of leaks in potable water systems. Field studies revealed exemplars that metallic pipe leaks caused by nails, rocks, and erosion corrosion autogenously repaired, as confirmed in the laboratory experiments. This work demonstrated that 100% (N = 26) of 150 μm leaks contacting representative bulk potable water in copper pipes sealed autogenously via formation of corrosion precipitates at 20-40 psi, pH 3.0-11.0, and with upward and downward leak orientations. Similar leaks in carbon steel pipes at 20 psi self-repaired at pH 5.5 and 8.5, but two leaks did not self-repair permanently at pH 11.0 suggesting that water chemistry may control the durability of materials that seal the leaks and therefore the permanence of repair. Larger 400 μm holes in copper pipes had much lower (0-33%) success of self-repair at pH 3.0-11.0, whereas all 400 μm holes in carbon steel pipes at 20 psi self-repaired at pH 4.0-11.0. Pressure tests indicated that some of the repairs created at 20-40 psi ambient pressure could withstand more than 100 psi without failure. Autogenous repair has implications for understanding patterns of pipe failures, extending the lifetime of decaying infrastructure, and developing new plumbing materials.

  1. Treatment of Childhood Migraine Using Autogenic Feedback Training.

    ERIC Educational Resources Information Center

    Labbe, Elise L.

    1984-01-01

    Compared autogenic feedback training with a waiting-list control group as a treatment for children (N=28) with migraine headaches. Children in the treatment condition were significantly improved at the end of treatment and at one-month and six-month follow-up. No improvement was found for the children in the control condition. (BH)

  2. Mandibular Tori: A source of autogenous bone graft

    PubMed Central

    Santhanakrishnan, Muthukumar; Rangarao, Suresh

    2014-01-01

    Restoration of lost alveolar bone support remains as one of the main objectives of periodontal surgery. Amongst the various types of bone grafts available for grafting procedures, autogenous bone grafts are considered to be the gold standard in alveolar defect reconstruction. Although there are various sources for autogenous grafts including the mandibular symphysis and ramus, they are almost invariably not contiguous with the area to be augmented. An alternative mandibular donor site that is continuous with the recipient area and would eliminate the need for an extra surgical site is the tori/exostoses. Bone grafting was planned for this patient as there were angular bone loss present between 35-36 and 36-37. As the volume of bone required was less and bilateral tori were present on the lingual side above the mylohyoid line, the tori was removed and used as a source of autogenous bone graft, which were unnecessary bony extensions present on the mandible and continuous with the recipient area. Post-operative radiographs taken at 6 and 12 month intervals showed good bone fill and also areas of previous pockets, which did not probe after treatment indicates the success of the treatment. The use of mandibular tori as a source of autogenous bone graft should be considered whenever a patient requires bone grafting procedure to be done and presents with a tori. PMID:25624635

  3. Treatment of Childhood Migraine Using Autogenic Feedback Training.

    ERIC Educational Resources Information Center

    Labbe, Elise L.

    1984-01-01

    Compared autogenic feedback training with a waiting-list control group as a treatment for children (N=28) with migraine headaches. Children in the treatment condition were significantly improved at the end of treatment and at one-month and six-month follow-up. No improvement was found for the children in the control condition. (BH)

  4. Autogenic training: a narrative and quantitative review of clinical outcome.

    PubMed

    Linden, W

    1994-09-01

    This review of controlled outcome research on Autogenic Training complements the literature by pooling narrative and quantitative approaches, by including only studies with experimental controls, by integrating the English and German literature, and by adding research findings published since the last review. Whereas previous reviews have already reported positive effects of Autogenic Training for migraine, insomnia, and test anxiety, additional supportive findings for angina pectoris, asthma, childbirth, eczema, hypertension, infertility, Raynaud's disease, and recovery from myocardial infarction are discussed here. The impact of protocol variations on outcome is described, and the specificity of Autogenic Training relative to other stress management techniques is highlighted. Quantitative findings suggested that Autogenic Training was associated with medium-sized pre- to posttreatment effects ranging from d = .43 for biological indices of change to d = .58 for psychological and behavioral indices thus matching effect sizes for other biobehavioral treatment techniques like biofeedback and muscular relaxation. Length of treatment did not affect clinical outcome. The discussion emphasizes how narrative and quantitative strategies complement one another.

  5. 30 CFR 35.20 - Autogenous-ignition temperature test.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Autogenous-ignition temperature test. 35.20 Section 35.20 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR TESTING... commercial 200 ml. borosilicate glass Erlenmeyer flask. (2) Thermocouples. Calibrated thermocouples—iron...

  6. Do low-shrink composites reduce polymerization shrinkage effects?

    PubMed

    Tantbirojn, D; Pfeifer, C S; Braga, R R; Versluis, A

    2011-05-01

    Progress in polymer science has led to continuous reduction of polymerization shrinkage, exemplified by a new generation of "low-shrink composites". The common inference that shrinkage stress effects will be reduced in teeth restored with such restoratives with lower shrinkage was tested in extracted human premolars. Mesio-occluso-distal slot-shaped cavities were cut and restored with a conventional (SupremePlus) or low-shrink (RefleXions, Premise, Kalore, and LS) composite (N = 5). We digitized the coronal surfaces before and 10 min after restoration to determine cuspal deflection from the buccal and lingual volume change/area. We also determined the main properties involved (total shrinkage, post-gel shrinkage, degree of conversion, and elastic modulus), as well as microleakage, to verify adequate bonding. It was shown that, due to shrinkage stresses, buccal and lingual surfaces pulled inward after restoration (9-14 microns). Only Kalore and LS resulted in significantly lower tooth deformation (ANOVA/Student-Newman-Keuls post hoc, p = 0.05). The other two low-shrink composites, despite having the lowest and highest total shrinkage values, did not cause significant differences in cuspal deflection. Deflection seemed most related to the combination of post-gel shrinkage and elastic modulus. Therefore, even for significantly lower total shrinkage values, shrinkage stress is not necessarily reduced.

  7. Assessment of the autogenous bone graft for sinus elevation

    PubMed Central

    Peng, Wang; Cho, Hyun-Young; Pae, Sang-Pill; Jung, Bum-Sang; Cho, Hyun-Woo; Seo, Ji-Hoon

    2013-01-01

    Objectives The posterior maxillary region often provides a limited bone volume for dental implants. Maxillary sinus elevation via inserting a bone graft through a window opened in the lateral sinus wall has become the most common surgical procedure for increasing the alveolar bone height in place of dental implants in the posterior maxillary region. The purpose of this article is to assess the change of bone volume and the clinical effects of dental implant placement in sites with maxillary sinus floor elevation and autogenous bone graft through the lateral window approach. Materials and Methods In this article, the analysis data were collected from 64 dental implants that were placed in 24 patients with 29 lacks of the bone volume posterior maxillary region from June 2004 to April 2011, at the Department of Oral and Maxillofacial Surgery, Inha University Hospital. Panoramic views were taken before the surgery, after the surgery, 6 months after the surgery, and at the time of the final follow-up. The influence of the factors on the grafted bone material resorption rate was evaluated according to the patient characteristics (age and gender), graft material, implant installation stage, implant size, implant placement region, local infection, surgical complication, and residual alveolar bone height. Results The bone graft resorption rate of male patients at the final follow-up was significantly higher than the rate of female patients. The single autogenous bone-grafted site was significantly more resorbed than the autogenous bone combined with the Bio-Oss grafted site. The implant installation stage and residual alveolar height showed a significant correlation with the resorption rate of maxillary sinus bone graft material. The success rate and survival rate of the implant were 92.2% and 100%, respectively. Conclusion Maxillary sinus elevation procedure with autogenous bone graft or autogenous bone in combination with Bio-Oss is a predictable treatment method for

  8. Entropic shrinkage of an oxide glass

    NASA Astrophysics Data System (ADS)

    Inaba, Seiji; Hosono, Hideo; Ito, Setsuro

    2015-03-01

    Entropic elasticity, a property typical of rubbers and well known in organic polymers with appropriate network structures, is not known to occur in oxide glasses. Here, we report the occurrence of entropic elasticity in phosphate-glass fibres with highly anisotropic structures, drawn by mechanical elongation from supercooled liquids. We observed a large lengthwise shrinkage of ~35% for phosphate glasses with an enhanced one-dimensional structure, as well as a distinct endotherm on reheating them up to temperatures between that of the glass transition temperature and the softening temperature. Our results strongly suggest the possibility of designing oxide glasses with a rubbery nature at high temperatures.

  9. Entropic shrinkage of an oxide glass.

    PubMed

    Inaba, Seiji; Hosono, Hideo; Ito, Setsuro

    2015-03-01

    Entropic elasticity, a property typical of rubbers and well known in organic polymers with appropriate network structures, is not known to occur in oxide glasses. Here, we report the occurrence of entropic elasticity in phosphate-glass fibres with highly anisotropic structures, drawn by mechanical elongation from supercooled liquids. We observed a large lengthwise shrinkage of ~35% for phosphate glasses with an enhanced one-dimensional structure, as well as a distinct endotherm on reheating them up to temperatures between that of the glass transition temperature and the softening temperature. Our results strongly suggest the possibility of designing oxide glasses with a rubbery nature at high temperatures.

  10. Autogenous bone graft: basic science and clinical implications.

    PubMed

    Rogers, Gary F; Greene, Arin K

    2012-01-01

    No single biomaterial is optimum for every craniomaxillofacial application. Instead, surgeons should consider the advantages and disadvantages of each alternative in a given clinical situation, and select the material with lowest overall cost and morbidity, and the highest likelihood of success. Autogenous bone is still considered the gold standard for most applications; it becomes vascularized and osseointegrates with surrounding bone, thus minimizing the risk of infection, dislodgement, or break-down. Limitations include added operative time for graft harvest, donor site morbidity, graft resorption, molding challenges, and limited availability, especially in the pediatric population. Numerous alternatives to bone graft have become available to address these limitations; unfortunately, most of these products are expensive, do not osseointegrate, and have unpredictable biologic activity. Understanding the physiologic behavior of autogenous bone graft can help clarify the indications for its use and provide a conceptual framework for achieving the best possible outcome when this alternative is chosen.

  11. Autogenic training alters cerebral activation patterns in fMRI.

    PubMed

    Schlamann, Marc; Naglatzki, Ryan; de Greiff, Armin; Forsting, Michael; Gizewski, Elke R

    2010-10-01

    Cerebral activation patterns during the first three auto-suggestive phases of autogenic training (AT) were investigated in relation to perceived experiences. Nineteen volunteers trained in AT and 19 controls were studied with fMRI during the first steps of autogenic training. FMRI revealed activation of the left postcentral areas during AT in those with experience in AT, which also correlated with the level of AT experience. Activation of prefrontal and insular cortex was significantly higher in the group with experience in AT while insular activation was correlated with number years of simple relaxation exercises. Specific activation in subjects experienced in AT may represent a training effect. Furthermore, the correlation of insular activation suggests that these subjects are different from untrained subjects in emotional processing or self-awareness.

  12. [Development of Autogenic Training Clinical Effectiveness Scale (ATCES)].

    PubMed

    Ikezuki, Makoto; Miyauchi, Yuko; Yamaguchi, Hajime; Koshikawa, Fusako

    2002-02-01

    The purpose of the present study was to develop a scale measuring clinical effectiveness of autogenic training. In Study 1, 167 undergraduates completed a survey of items concerning physical and mental states, which were thought to vary in the course of autogenic training. With item and factor analyses, 20 items were selected, and the resulting scale (ATCES) had high discrimination and clear factor structure. In Study 2, reliability and concurrent and clinical validity of the scale were examined with three groups of respondents: 85 mentally healthy, 31 control, 13 clinical persons. The scale showed a high test-retest correlation (r = .83) and alpha coefficient (alpha = .86). ATCES had a Pearson correlation coefficient of r = .56 with General Health Questionnaire (GHQ-12), and r = .73 with trait anxiety (STAI-T). And ATCES successfully discriminated the mentally healthy and clinical groups in terms of clinical effectiveness. These results demonstrated high reliability and sufficient concurrent and clinical validity of the new scale.

  13. Crack, crack house sex, and HIV risk.

    PubMed

    Inciardi, J A

    1995-06-01

    Limited attention has been focused on HIV risk behaviors of crack smokers and their sex partners, yet there is evidence that the crack house and the crack-using life-style may be playing significant roles in the transmission of HIV and other sexually transmitted diseases. The purposes of this research were to study the attributes and patterns of "sex for crack" exchanges, particularly those that occurred in crack houses, and to assess their potential impact on the spread of HIV. Structured interviews were conducted with 17 men and 35 women in Miami, Florida, who were regular users of crack and who had exchanged sex for crack (or for money to buy crack) during the past 30 days. In addition, participant observation was conducted in 8 Miami crack houses. Interview and observational data suggest that individuals who exchange sex for crack do so with considerable frequency, and through a variety of sexual activities. Systematic data indicated that almost a third of the men and 89% of the women had had 100 or more sex partners during the 30-day period prior to study recruitment. Not only were sexual activities anonymous, extremely frequent, varied, uninhibited (often undertaken in public areas of crack houses), and with multiple partners but, in addition, condoms were not used during the majority of contacts. Of the 37 subjects who were tested for HIV and received their test results 31% of the men and 21% of the women were HIV seropositive.

  14. The Effect of Cementation and Autogenous Bone Grafting on Allograft Union and Incorporation

    DTIC Science & Technology

    1994-02-09

    Cameron Station Alexandria, VA 22304-6145 RE: Grant no. N00014-93-1-0745; The effect of cementation and autogenous bone grafting on allograft union...of Wisconsin System Title of Project: The Effect of Cementation and Autogenous Bone Grafting on Allograft Union and Incorporation Grant Number...cantilever bending, and torsion tests. 94-05018 94 2 1 5 004 IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII The Effect of Cementation and Autogenous Bone Grafting

  15. Factors affecting the shrinkage of fly ash geopolymers

    NASA Astrophysics Data System (ADS)

    Ridtirud, Charoenchai; Chindaprasirt, Prinya; Pimraksa, Kedsarin

    2011-02-01

    The shrinkage of fly ash geopolymers was studied in the present study. Fly ash was used as the source material for making the geopolymers. The effects of the concentration of NaOH, sodium silicate-to-NaOH ratio, liquid-to-ash ratio, curing temperature, and curing time on shrinkage were investigated. The geopolymers were cured at 25, 40, and 60°C, respectively. The results indicate that the shrinkage of geopolymers is strongly dependent on curing temperature and liquid-to-ash ratio. The increase in shrinkage is associated with the low strength development of geopolymers. It is also found that NaOH concentration and sodium silicate-to-NaOH ratio also affect the shrinkage of geopolymers but to a lesser extent.

  16. The treatment of recalcitrant post-traumatic nightmares with autogenic training and autogenic abreaction: a case study.

    PubMed

    Sadigh, M R

    1999-09-01

    Recurrent and frightening dreams are commonly experienced by patients who suffer from post-traumatic stress disorder after a motor vehicle accident. Such nocturnal episodes, if left untreated, can result in the experience of severe distress with physical, emotional, and psychophysiological concomitant. The present single-case study investigated the effects of the standard autogenic exercises and autogenic abreaction in reducing the frequency and severity of post-traumatic nightmares in a survivor of a car crash. The patient was also instructed in two additional organ-specific formulas in order to improve her sleep. The results of the study showed that the interventions were successful in effectively treating the patient's distressing nightmares. Follow-up data suggested that the treatment effects persisted after the termination of therapy. Suggestions for future investigations are discussed.

  17. Autogenic limits on allogenic controls of submarine landform evolution

    NASA Astrophysics Data System (ADS)

    Dorrell, R. M.; McCaffrey, W. D.; Burns, A. D.

    2014-12-01

    Seafloor channel avulsion events recorded in the stratigraphic architecture of submarine fans are often identified as signals of boundary change of the associated sediment supply system. However, interpretation of such signals that are persevered in the rock record is complicated by the interplay between internal (autogenic) forcing and external (allogenic) forcing on the system which may have caused the avulsion of the channel. To investigate the importance of autogenic forcing on seafloor channel evolution, novel models have been constructed which calculate the width-averaged growth of a channel levee system with progressive deposition. These models demonstrate that seafloor channel-levee systems are inherently unstable and will avulse purely subject to autogenic forcing. It is demonstrated that this instability arises as a function of geometric constraints on the cross-sectional shape of the evolving channel and its bounding levees under aggradational flow conditions. Analytical solutions to these simplified models demonstrate that change in the area of the channel is given by the comparative rate at which the bounding outer levee and channel are built up. Whilst the outer levee is built up faster than the channel, there is a relative increase in channel size - increasing the degree by which a flow is confined and thus the decreasing the likelihood of an avulsion. However, if the channel is built up faster than the outer levee the degree by which the flow is confined by the channel will decrease, and thus the likelihood of avulsion will increase. It is seen that as bounding levees become large, and thus cannot be built up as fast as the channel, the evolution of the channel is inherently limited. However, autogenic channel-levee instability likely arises over very long time periods, with the half-life of channel decay proportional to the channel-levee system size. Thus, it is expected that additional external (allogenic) forcing, such as boundary condition

  18. Effective Expansion: Balance between Shrinkage and Hygroscopic Expansion.

    PubMed

    Suiter, E A; Watson, L E; Tantbirojn, D; Lou, J S B; Versluis, A

    2016-05-01

    The purpose of this study was to investigate the relationship between hygroscopic expansion and polymerization shrinkage for compensation of polymerization shrinkage stresses in a restored tooth. One resin-modified glass-ionomer (RMGI) (Ketac Nano, 3M ESPE), 2 compomers (Dyract, Dentsply; Compoglass, Ivoclar), and a universal resin-based composite (Esthet•X HD, Dentsply) were tested. Volumetric change after polymerization ("total shrinkage") and during 4 wk of water storage at 37°C was measured using an optical method (n= 10). Post-gel shrinkage was measured during polymerization using a strain gauge method (n= 10). Extracted human molars with large mesio-occluso-distal slot preparations were restored with the tested restorative materials. Tooth surfaces at baseline (preparation), after restoration, and during 4 wk of 37°C water storage were scanned with an optical scanner to determine cuspal flexure (n= 8). Occlusal interface integrity was measured using dye penetration. Data were analyzed using analysis of variance and post hoc tests (significance level 0.05). All tested materials shrunk after polymerization. RMGI had the highest total shrinkage (4.65%) but lowest post-gel shrinkage (0.35%). Shrinkage values dropped significantly during storage in water but had not completely compensated polymerization shrinkage after 4 wk. All restored teeth initially exhibited inward (negative) cuspal flexure due to polymerization shrinkage. Cuspal flexure with the RMGI restoration was significantly less (-6.4 µm) than with the other materials (-12.1 to -14.1 µm). After 1 d, cuspal flexure reversed to +5.0 µm cuspal expansion with the RMGI and increased to +9.3 µm at 4 wk. After 4 wk, hygroscopic expansion compensated cuspal flexure in a compomer (Compoglass) and reduced flexure with Dyract and resin-based composite. Marginal integrity (93.7% intact restoration wall) was best for the Compoglass restorations and lowest (73.1%) for the RMGI restorations. Hygroscopic

  19. Polymerization shrinkage, modulus, and shrinkage stress related to tooth-restoration interfacial debonding in bulk-fill composites.

    PubMed

    Kim, Ryan Jin-Young; Kim, Yu-Jin; Choi, Nak-Sam; Lee, In-Bog

    2015-04-01

    The aim of the present study was to measure the polymerization shrinkage, modulus, and shrinkage stress of bulk-fill and conventional composites during polymerization and to investigate the relationship between tooth-composite interfacial debonding and shrinkage stress of the composites. Polymerization shrinkage, dynamic modulus, and shrinkage stress of two high-viscosity bulk-fill (SonicFill (SF)/Tetric N-Ceram Bulk-Fill (TNB)) and two low-viscosity bulk-fill composites (Filtek Bulk-Fill (FB)/SureFil SDR Flow (SDR)) as well as one high-viscosity conventional (Filtek Z250 (Z250)) and one low-viscosity conventional composite (Filtek Z350 XT Flowable (Z350F)) were measured using custom-made instruments. Acoustic emission (AE) analysis was performed to evaluate the tooth-composite interfacial debonding during polymerization of the composites in Class 1 cavities on extracted third molars. The low-viscosity composites exhibited higher shrinkage and lower modulus than the high-viscosity composites. Polymerization shrinkage at 10 min ranged between 2.05% (SF) and 3.53% (Z350F). Polymerization shrinkage stress values at 10 min ranged between 1.68MPa (SDR) and 3.51MPa (Z350F). The number of AE events was highest in Z350F and lowest in SDR. Composites that exhibited greater polymerization shrinkage stress generated more tooth-composite interfacial debonding. In contrast to similar outcomes among the high-viscosity composites (conventional: Z250, bulk-fill: TNB and SF), the low-viscosity bulk-fill composites (FB and SDR) demonstrated better results in terms of polymerization shrinkage stress and tooth-composite interfacial debonding than did the low-viscosity conventional composite (Z350F). Despite the better performance by some of the bulk-fill composites, clinicians should be aware that the bulk-fill composites are not perfect substitutes for conventional composites. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Gear Crack Propagation Investigation

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Reduced weight is a major design goal in aircraft power transmissions. Some gear designs incorporate thin rims to help meet this goal. Thin rims, however, may lead to bending fatigue cracks. These cracks may propagate through a gear tooth or into the gear rim. A crack that propagates through a tooth would probably not be catastrophic, and ample warning of a failure could be possible. On the other hand, a crack that propagates through the rim would be catastrophic. Such cracks could lead to disengagement of a rotor or propeller from an engine, loss of an aircraft, and fatalities. To help create and validate tools for the gear designer, the NASA Lewis Research Center performed in-house analytical and experimental studies to investigate the effect of rim thickness on gear-tooth crack propagation. Our goal was to determine whether cracks grew through gear teeth (benign failure mode) or through gear rims (catastrophic failure mode) for various rim thicknesses. In addition, we investigated the effect of rim thickness on crack propagation life. A finite-element-based computer program simulated gear-tooth crack propagation. The analysis used principles of linear elastic fracture mechanics, and quarter-point, triangular elements were used at the crack tip to represent the stress singularity. The program had an automated crack propagation option in which cracks were grown numerically via an automated remeshing scheme. Crack-tip stress-intensity factors were estimated to determine crack-propagation direction. Also, various fatigue crack growth models were used to estimate crack-propagation life. Experiments were performed in Lewis' Spur Gear Fatigue Rig to validate predicted crack propagation results. Gears with various backup ratios were tested to validate crack-path predictions. Also, test gears were installed with special crack-propagation gages in the tooth fillet region to measure bending-fatigue crack growth. From both predictions and tests, gears with backup ratios

  1. Anisotropic shrinkage characteristics of tape cast alumina

    NASA Astrophysics Data System (ADS)

    Patwardhan, Jaideep Suresh

    Dimensional control during sintering is a major issue in ceramics processing to avoid high post-sintering costs associated with machining of the fired ceramic part to desired tolerances and dimensions. Ceramic forming processes such as tape casting, injection molding, and extrusion involve shear of anisotropic particles resulting in preferential alignment of the particles in the green body. This preferential alignment causes directionality in mechanical, electrical, optical, and magnetic properties and most importantly warpage or distortion during sintering. A large effort has been devoted to synthesizing ceramic green bodies with minimal density gradients and uniform packing and modeling the sintering behavior evolution but little effort has been devoted to characterizing orientation of particles and the effect of preferential alignment on sintering shrinkage anisotropy. A systematic study was initiated to study the effect of processing variables such as shear rate, solids loading, temperature, and binder content on aqueous tape cast alumina. Three different alumina systems: A16-SG, Baikowski RC-UFX DBM and RC-LS DBM were investigated. Aqueous tapes of high solids loading alumina (56 vol. %) were tape cast at various speeds and thicknesses and assuming plane Couette flow a shear rate regime of 21--270 s-1 was investigated. Higher shear rates and high solids loading resulted in higher in-plane anisotropy whereas the anisotropy in the thickness direction was higher for low solids loading systems. The anisotropy was found to be fairly constant above a certain critical shear rate (˜100 s-1) irrespective of the temperature and the solids loading and this correlated with the viscosity-shear rate relationship of the cast slips. The higher shrinkage anisotropy in the thickness direction for the low solids loading systems (35 and 45 vol. %) was attributed to the higher amount of organics in the slip required to sustain the suitable viscosity for tape casting and

  2. Alternative methods for determining shrinkage in restorative resin composites.

    PubMed

    de Melo Monteiro, Gabriela Queiroz; Montes, Marcos Antonio Japiassú Resende; Rolim, Tiago Vieira; de Oliveira Mota, Cláudia Cristina Brainer; de Barros Correia Kyotoku, Bernardo; Gomes, Anderson Stevens Leônidas; de Freitas, Anderson Zanardi

    2011-08-01

    The purpose of this study was to evaluate polymerization shrinkage of resin composites using a coordinate measuring machine, optical coherence tomography and a more widely known method, such as Archimedes Principle. Two null hypothesis were tested: (1) there are no differences between the materials tested; (2) there are no differences between the methods used for polymerization shrinkage measurements. Polymerization shrinkage of seven resin-based dental composites (Filtek Z250™, Filtek Z350™, Filtek P90™/3M ESPE, Esthet-X™, TPH Spectrum™/Dentsply 4 Seasons™, Tetric Ceram™/Ivoclar-Vivadent) was measured. For coordinate measuring machine measurements, composites were applied to a cylindrical Teflon mold (7 mm × 2 mm), polymerized and removed from the mold. The difference between the volume of the mold and the volume of the specimen was calculated as a percentage. Optical coherence tomography was also used for linear shrinkage evaluations. The thickness of the specimens was measured before and after photoactivation. Polymerization shrinkage was also measured using Archimedes Principle of buoyancy (n=5). Statistical analysis of the data was performed with ANOVA and the Games-Howell test. The results show that polymerization shrinkage values vary with the method used. Despite numerical differences the ranking of the resins was very similar with Filtek P90 presenting the lowest shrinkage values. Because of the variations in the results, reported values could only be used to compare materials within the same method. However, it is possible rank composites for polymerization shrinkage and to relate these data from different test methods. Independently of the method used, reduced polymerization shrinkage was found for silorane resin-based composite. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  3. Crack spectra analysis

    SciTech Connect

    Tiernan, M.

    1980-09-01

    Crack spectra derived from velocity data have been shown to exhibit systematics which reflect microstructural and textural differences between samples (Warren and Tiernan, 1980). Further research into both properties and information content of crack spectra have yielded the following: Spectral features are reproducible even at low pressures; certain observed spectral features may correspond to non-in-situ crack populations created during sample retrieval; the functional form of a crack spectra may be diagnostic of the sample's grain texture; hysteresis is observed in crack spectra between up and down pressure runs - it may be due to friction between the faces of closed crack populations.

  4. CELL SHRINKAGE AND MONOVALENT CATION FLUXES

    PubMed Central

    Bortner, Carl D.; Cidlowski, John A.

    2007-01-01

    The loss of cell volume or cell shrinkage has been a morphological hallmark of the programmed cell death process known as apoptosis. This isotonic loss of cell volume has recently been term apoptotic volume decrease or AVD to distinguish it from inherent volume regulatory responses that occurs in cells under anisotonic conditions. Recent studies examining the intracellular signaling pathways that result in this unique cellular characteristic have determined that a fundamental movement of ions, particularly monovalent ions, underlie the AVD process and plays an important role on controlling the cell death process. An efflux of intracellular potassium was shown to be a critical aspect of the AVD process, as preventing this ion loss could protect cells from apoptosis. However, potassium plays a complex role as a loss of intracellular potassium has also been shown to be beneficial to the health of the cell. Additionally, the mechanisms that a cell employs to achieve this loss of intracellular potassium vary depending on the cell type and stimulus used to induce apoptosis, suggesting multiple ways exist to accomplish the same goal of AVD. Additionally, sodium and chloride have been shown to play a vital role during cell death in both the signaling and control of AVD in various apoptotic model systems. This review examines the relationship between this morphological change and intracellular monovalent ions during apoptosis. PMID:17321483

  5. Model Shrinkage for Discriminative Language Models

    NASA Astrophysics Data System (ADS)

    Oba, Takanobu; Hori, Takaaki; Nakamura, Atsushi; Ito, Akinori

    This paper describes a technique for overcoming the model shrinkage problem in automatic speech recognition (ASR), which allows application developers and users to control the model size with less degradation of accuracy. Recently, models for ASR systems tend to be large and this can constitute a bottleneck for developers and users without special knowledge of ASR with respect to introducing the ASR function. Specifically, discriminative language models (DLMs) are usually designed in a high-dimensional parameter space, although DLMs have gained increasing attention as an approach for improving recognition accuracy. Our proposed method can be applied to linear models including DLMs, in which the score of an input sample is given by the inner product of its features and the model parameters, but our proposed method can shrink models in an easy computation by obtaining simple statistics, which are square sums of feature values appearing in a data set. Our experimental results show that our proposed method can shrink a DLM with little degradation in accuracy and perform properly whether or not the data for obtaining the statistics are the same as the data for training the model.

  6. Shrinkage covariance matrix approach for microarray data

    NASA Astrophysics Data System (ADS)

    Karjanto, Suryaefiza; Aripin, Rasimah

    2013-04-01

    Microarray technology was developed for the purpose of monitoring the expression levels of thousands of genes. A microarray data set typically consists of tens of thousands of genes (variables) from just dozens of samples due to various constraints including the high cost of producing microarray chips. As a result, the widely used standard covariance estimator is not appropriate for this purpose. One such technique is the Hotelling's T2 statistic which is a multivariate test statistic for comparing means between two groups. It requires that the number of observations (n) exceeds the number of genes (p) in the set but in microarray studies it is common that n < p. This leads to a biased estimate of the covariance matrix. In this study, the Hotelling's T2 statistic with the shrinkage approach is proposed to estimate the covariance matrix for testing differential gene expression. The performance of this approach is then compared with other commonly used multivariate tests using a widely analysed diabetes data set as illustrations. The results across the methods are consistent, implying that this approach provides an alternative to existing techniques.

  7. Comparison of Polymerization Shrinkage, Physical Properties, and Marginal Adaptation of Flowable and Restorative Bulk Fill Resin-Based Composites.

    PubMed

    Jung, J H; Park, S H

    The purpose of this study was to compare the marginal adaptation of two flowable bulk fill resin-based composites (FB-RBCs), two restorative bulk fill resin-based composites (RB-RBCs), and one regular incremental-fill RBC in MOD cavities in vitro. Additionally, the influence of linear polymerization shrinkage, shrinkage force, flexural modulus, and bottom/top surface hardness ratio on the marginal adaptation was evaluated. A Class II MOD cavity was prepared in 40 extracted sound lower molars. In group 1 (control group), the preparation was filled with Filtek Z350 (Z3, 3M ESPE, St Paul, MN, USA) using the incremental filling technique. The FB-RBCs, SDR (SD, group 2) (Dentsply Caulk, Milford, DE, USA) and Venus Bulk Fill (VB, group 3) (Heraeus Kulzer, Dormagen, Germany), were placed in the core portion of the cavity first, and Z350 was filled in the remaining cavity. The RB-RBCs, Tetric N-Ceram Bulkfill (TB, group 4) (Ivoclar Vivadent, Schaan, Liechtenstein) and SonicFill (SF, Group 5) (Kerr, West Collins, Orange, CA, USA), were bulk filled into the preparation. Images of the magnified marginal area were captured under 100× magnification before and after thermomechanical loading, and the percentage ratio of the imperfect margin (%IMwhole) was calculated. Gaps, cracks in the enamel layer, and chipping of composite, enamel, or dentin were all considered to be imperfect margins. Linear polymerization shrinkage, polymerization shrinkage force, flexural strength, flexural modulus, and bottom/top surface hardness ratio of were measured. Eight specimens were allocated for each material for each test. One-way analysis of variance with the Scheffé test was used to compare the groups at a 95% confidence level. Before thermomechanical loading, %IMwhole was in the order of group 3 ≤ groups 2 and 5 ≤ groups 1 and 4 (p=0.011), whereas after loading, it was in the order of group 4 ≤ group 5 ≤ group 1 ≤ groups 2 and 3 (p<0.001). The order of materials were Z3 < TB and SF

  8. A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems.

    PubMed

    Luković, Mladena; Šavija, Branko; Schlangen, Erik; Ye, Guang; van Breugel, Klaas

    2016-07-14

    Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical simulations combined with experimental observations can be of great use when determining the influence of these parameters on the performance of repair systems. In this work, a lattice type model was used to simulate first the moisture transport inside a repair system and then the resulting damage as a function of time. 3D simulations were performed, and damage patterns were qualitatively verified with experimental results and cracking tendencies in different brittle and ductile materials. The influence of substrate surface preparation, bond strength between the two materials, and thickness of the repair material were investigated. Benefits of using a specially tailored fibre reinforced material, namely strain hardening cementitious composite (SHCC), for controlling the damage development due to drying shrinkage in concrete repairs was also examined.

  9. A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems

    PubMed Central

    Luković, Mladena; Šavija, Branko; Schlangen, Erik; Ye, Guang; van Breugel, Klaas

    2016-01-01

    Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical simulations combined with experimental observations can be of great use when determining the influence of these parameters on the performance of repair systems. In this work, a lattice type model was used to simulate first the moisture transport inside a repair system and then the resulting damage as a function of time. 3D simulations were performed, and damage patterns were qualitatively verified with experimental results and cracking tendencies in different brittle and ductile materials. The influence of substrate surface preparation, bond strength between the two materials, and thickness of the repair material were investigated. Benefits of using a specially tailored fibre reinforced material, namely strain hardening cementitious composite (SHCC), for controlling the damage development due to drying shrinkage in concrete repairs was also examined. PMID:28773696

  10. Gear crack propagation investigations

    NASA Technical Reports Server (NTRS)

    Lewicki, David G.; Ballarini, Roberto

    1996-01-01

    Analytical and experimental studies were performed to investigate the effect of gear rim thickness on crack propagation life. The FRANC (FRacture ANalysis Code) computer program was used to simulate crack propagation. The FRANC program used principles of linear elastic fracture mechanics, finite element modeling, and a unique re-meshing scheme to determine crack tip stress distributions, estimate stress intensity factors, and model crack propagation. Various fatigue crack growth models were used to estimate crack propagation life based on the calculated stress intensity factors. Experimental tests were performed in a gear fatigue rig to validate predicted crack propagation results. Test gears were installed with special crack propagation gages in the tooth fillet region to measure bending fatigue crack growth. Good correlation between predicted and measured crack growth was achieved when the fatigue crack closure concept was introduced into the analysis. As the gear rim thickness decreased, the compressive cyclic stress in the gear tooth fillet region increased. This retarded crack growth and increased the number of crack propagation cycles to failure.

  11. Autogenous Regulation of Splicing of the Transcript of a Yeast Ribosomal Protein Gene

    NASA Astrophysics Data System (ADS)

    Dabeva, Mariana D.; Post-Beittenmiller, Martha A.; Warner, Jonathan R.

    1986-08-01

    The gene for a yeast ribosomal protein, RPL32, contains a single intron. The product of this gene appears to participate in feedback control of the splicing of the intron from the transcript. This autogenous regulation of splicing provides a striking analogy to the autogenous regulation of translation of ribosomal proteins in Escherichia coli.

  12. The Influence of Biofeedback and Autogenic Training on Motion Sickness Tolerance

    DTIC Science & Technology

    1994-11-01

    The Influence of Biofeedback and Autogenic Training on Motion Sickness Tolerance 4. DESCRIP’TIVE NOTES (the category of the document, e.g., technical...second Coriolis sessions, subjects in the experimental groups received five episodes of autogenic feedback (biofeedback) training with either true

  13. The Application of Autogenic Feedback Training in a Smoking Termination Program.

    ERIC Educational Resources Information Center

    Boullion, Jean K.; Chen, W. William

    1980-01-01

    Autogenic feedback training was an effective adjunct to a smoking termination program. An 81 percent reduction in smoking activity was found for the subjects who received the training. Achieving relaxation and reducing anxiety through autogenic feedback training helped subjects restore their self-confidence and deal with stress. (Author)

  14. [Efficiency of autogenous training in medical rehabilitation of patients with irritable colon syndrome with constipation dominance].

    PubMed

    Pakhomova, I V; Aĭvazian, T A; Zaĭtsev, V P; Gusakova, E V; Molina, L P

    2008-01-01

    It was established that use of autogenous training makes possible to increase efficiency of the therapy, leading to considerable more evident improvement of somatic and psychotic state, decrease of pain syndrome. Predictors of efficiency of autogenous training were marked out. Indications for use the method in medical rehabilitation of patients with irritable colon syndrome with constipation dominance were elaborated.

  15. Permeability Enhancement in Fine-Grained Sediments by Chemically Induced Clay Fabric Shrinkage

    SciTech Connect

    Wijesinghe, A M; Kansa, E J; Viani, B E; Blake, R G; Roberts, J J; Huber, R D

    2004-02-26

    The National Research Council [1] identified the entrapment of contaminants in fine-grained clay-bearing soils as a major impediment to the timely and cost-effective remediation of groundwater to regulatory standards. Contaminants trapped in low-permeability, low-diffusivity, high-sorptivity clays are not accessible to advective flushing by treatment fluids from permeable zones, and slowly diffuse out to recontaminate previously cleaned permeable strata. We propose to overcome this barrier to effective remediation by exploiting the ability of certain nontoxic EPA-approved chemicals (e.g., ethanol) to shrink and alter the fabric of clays, and thereby create macro-porosity and crack networks in fine-grained sediments. This would significantly reduce the distance and time scales of diffusive mass transport to advectively flushed boundaries, to yield orders of magnitude reduction in the time required to complete remediation. Given that effective solutions to this central problem of subsurface remediation do not yet exist, the cost and time benefits of successful deployment of this novel concept, both as a stand-alone technology and as an enabling pre-treatment for other remedial technologies that rely on advective delivery, is likely to be very large. This project, funded as a 1-year feasibility study by LLNL's LDRD Program, is a multi-directorate, multi-disciplinary effort that leverages expertise from the Energy & Environment Directorate, the Environmental Restoration Division, and the Manufacturing & Materials Evaluation Division of Mechanical Engineering. In this feasibility study, a ''proof-of-principle'' experiment was performed to answer the central question: ''Can clay shrinkage induced by ethanol in clay-bearing sediments overcome realistic confining stresses, crack clay, and increase its effective permeability by orders of magnitude within a time that is much smaller than the time required for diffusive mass transport of ethanol in the unaltered sediment

  16. Location, location &size: defects close to surfaces dominate fatigue crack initiation.

    PubMed

    Serrano-Munoz, Itziar; Buffiere, Jean-Yves; Mokso, Rajmund; Verdu, Catherine; Nadot, Yves

    2017-03-27

    Metallic cast components inevitably contain defects such as shrinkage cavities which are inherent to the solidification process. Those defects are known to significantly alter the fatigue life of components. Yet very little is known, quantitatively, on the dangerosity of internal casting defects compared to surface ones. In this study, fatigue specimens containing controlled internal defects (shrinkage pores) are used to foster internal cracking. In situ fatigue tests monitored by X ray synchrotron tomography revealed that the internal nucleation and propagation of cracks was systematically overran by surface cracking initiated at castings defects up to ten times smaller than the internal ones. These findings indicate that the presence of internal defects in cast components can be tolerated to a larger extent than is allowed by nowadays standards.

  17. Location, location & size: defects close to surfaces dominate fatigue crack initiation

    PubMed Central

    Serrano-Munoz, Itziar; Buffiere, Jean-Yves; Mokso, Rajmund; Verdu, Catherine; Nadot, Yves

    2017-01-01

    Metallic cast components inevitably contain defects such as shrinkage cavities which are inherent to the solidification process. Those defects are known to significantly alter the fatigue life of components. Yet very little is known, quantitatively, on the dangerosity of internal casting defects compared to surface ones. In this study, fatigue specimens containing controlled internal defects (shrinkage pores) are used to foster internal cracking. In situ fatigue tests monitored by X ray synchrotron tomography revealed that the internal nucleation and propagation of cracks was systematically overran by surface cracking initiated at castings defects up to ten times smaller than the internal ones. These findings indicate that the presence of internal defects in cast components can be tolerated to a larger extent than is allowed by nowadays standards PMID:28345599

  18. Cocaine (Coke, Crack) Facts

    MedlinePlus

    ... That People Abuse » Cocaine (Coke, Crack) Facts Cocaine (Coke, Crack) Facts Listen Cocaine is a white ... Version Download "My life was built around getting cocaine and getting high." ©istock.com/ Marjot Stacey is ...

  19. Autogenic-feedback training: A countermeasure for orthostatic intolerance

    NASA Technical Reports Server (NTRS)

    Cowings, Patricia S.; Toscano, William B.; Kamiya, Joe; Miller, Neal E.; Pickering, Thomas G.

    1991-01-01

    NASA has identified cardiovascular deconditioning as a serious biomedical problem associated with long-duration exposure to microgravity in space. High priority has been given to the development of countermeasures for this disorder and the resulting orthostatic intolerance experienced by crewmembers upon their return to the 1g norm of Earth. The present study was designed to examine the feasibility of training human subjects to control their own cardiovascular responses to gravitational stimulation (i.e., a tilt table). Using an operant conditioning procedure, Autogenic-Feedback Training (AFT), we would determine if subjects could learn to increase their own blood pressure voluntarily.

  20. Autogenous electrolyte, non-pyrolytically produced solid capacitor structure

    DOEpatents

    Sharp, D.J.; Armstrong, P.S.; Panitz, J.K.G.

    1998-03-17

    A solid electrolytic capacitor is described having a solid electrolyte comprising manganese dioxide dispersed in an aromatic polyamide capable of further cure to form polyimide linkages, the solid electrolyte being disposed between a first electrode made of valve metal covered by an anodic oxide film and a second electrode opposite the first electrode. The electrolyte autogenously produces water, oxygen, and hydroxyl groups which act as healing substances and is not itself produced pyrolytically. Reduction of the manganese dioxide and the water molecules released by formation of imide linkages result in substantially improved self-healing of anodic dielectric layer defects. 2 figs.

  1. Autogenous electrolyte, non-pyrolytically produced solid capacitor structure

    DOEpatents

    Sharp, Donald J.; Armstrong, Pamela S.; Panitz, Janda Kirk G.

    1998-01-01

    A solid electrolytic capacitor having a solid electrolyte comprising manganese dioxide dispersed in an aromatic polyamide capable of further cure to form polyimide linkages, the solid electrolyte being disposed between a first electrode made of valve metal covered by an anodic oxide film and a second electrode opposite the first electrode. The electrolyte autogenously produces water, oxygen, and hydroxyl groups which act as healing substances and is not itself produced pyrolytically. Reduction of the manganese dioxide and the water molecules released by formation of imide linkages result in substantially improved self-healing of anodic dielectric layer defects.

  2. Gorham's disease in humerus treated with autogenous vascularized fibular graft

    PubMed Central

    Kim, Jeung Woo; Kang, Hong Je; Kim, Dong Chul; Shin, Chang Hyun

    2017-01-01

    Gorham's disease is a rare disorder of the bone characterized by progressive massive osteolysis. The pathophysiology is unknown, and diagnosis is often difficult. Most cases are often recognized retrospectively. There is no standardized treatment and management for Gorham's disease. We report a case of an 18-year-old male presenting with a pathologic fracture in the humerus shaft diagnosed with Gorham's disease. Patient was treated with autogenous vascularized fibular graft with wide excision and a 10 years followup after first surgery. PMID:28400670

  3. Autogenous electrolyte, non-pyrolytically produced solid capacitor structure

    SciTech Connect

    Sharp, D.J.; Armstrong, P.S.; Paintz, J.K.G.

    1998-04-01

    This report discusses the design of a solid electrolytic capacitor having a solid electrolyte comprised of manganese dioxide dispersed in an aromatic polyamide capable of to forming polyimide linkages. This solid electrolyte being disposed between a first electrode made of valve metal covered by an anodic oxide film and a second electrode opposite the first electrode. The electrolyte autogenously produces water, oxygen, and hydroxyl groups which act as healing substances and is not itself produced pyrolytically. Reduction of the manganese dioxide and the water molecules released by formation of imide linkages result in substantially improved self-healing of anodic dielectric layer defects.

  4. Total autogenous mandibular reconstruction using virtual surgical planning.

    PubMed

    Winters, Ryan; Saad, Adam; Beahm, Donald David; Wise, Matthew Whitten; St Hilaire, Hugo

    2012-09-01

    Free fibula transfer has become the workhorse in mandibular reconstruction. Total mandibular reconstruction is an uncommon procedure with added complexity. Numerous techniques have been described for such reconstruction, many requiring a temporomandibular joint prosthesis. We present a novel method where simultaneous bilateral free fibula transfer utilizing preoperative virtual surgical planning was used to produce a total autogenous reconstruction. The virtual surgical planning allows to effectively quantify the bone stock required preoperatively and facilitates intraoperative modeling of the fibula. Therefore, a more anatomically correct reconstruction is obtained resulting in improved functional and aesthetic outcomes.

  5. A Study of the Thermal Profiles During Autogenous Arc Welding

    DTIC Science & Technology

    1989-03-01

    NAVAL POSTGRADUATE SCHOOL Monterey, California STA DTIC RAD ELECTE JUN 2 9 1989 • D THESIS A STUDY OF THE THERMAL PROFILES DURING AUTOGENOUS ARC...WELDING by Robert L. Ue March 1989 Thesis Advisor Yogendra Joshi Approved for public release; distribution is unlimited. j 7 .. 43 Unclassified security...L. LIe 13a T)pe of Report 13b Time Covered 14 Date of Report (year. month, day) 15 Page Count Master’s Thesis From To March 1989 163 16 Supplementary

  6. [A case of fibromyalgia treated with medical and autogenic training].

    PubMed

    Goto, Fumiyuki; Asama, Youji; Nakai, Kimiko

    2005-12-01

    Fibromyalgia, which is relatively rare, may include symptoms of dizziness, vertigo and tinnitus. Subject was 38 years old woman reporting vertigo and whole body pain. Cochleovestibular function was normal. Pain was gradually intensified during her outpatient clinic and she was admitted. Treatments including intramusclular injection of botulinus toxin and intravenous injection of steroid were applied. Psychological counseling and autogenic training were effective in relieving her pain and vertigo. During her admission, several spells of vertigo occurred but no nystagmus was found. The abnormality in proprioception and neural disintegration may be related to vertigo. Treatment should start as early as possible together with psychological therapy.

  7. Cryogenic Autogenous Pressurization Testing for Robotic Refueling Mission 3

    NASA Technical Reports Server (NTRS)

    Boyle, R.; DiPirro, M.; Tuttle, J.; Francis, J.; Mustafi, S.; Li, X.; Barfknecht, P.; DeLee, C. H.; McGuire, J.

    2015-01-01

    A wick-heater system has been selected for use to pressurize the Source Dewar of the Robotic Refueling Mission Phase 3 on-orbit cryogen transfer experiment payload for the International Space Station. Experimental results of autogenous pressurization of liquid argon and liquid nitrogen using a prototype wick-heater system are presented. The wick-heater generates gas to increase the pressure in the tank while maintaining a low bulk fluid temperature. Pressurization experiments were performed in 2013 to characterize the performance of the wick heater. This paper describes the experimental setup, pressurization results, and analytical model correlations.

  8. Influence of gelatinous fibers on the shrinkage of silver maple

    Treesearch

    Donals G. Arganbright; Dwight W. Bensend; Floyd G. Manwiller

    1970-01-01

    The degree of lean was found to have a significant influence on the logitudinal and transverse shrinkage of three soft maple trees. This may be accounted for by differences in the cell wall layer thickness and fibril angle.

  9. Color Image Denoising via Discriminatively Learned Iterative Shrinkage.

    PubMed

    Sun, Jian; Sun, Jian; Xu, Zingben

    2015-11-01

    In this paper, we propose a novel model, a discriminatively learned iterative shrinkage (DLIS) model, for color image denoising. The DLIS is a generalization of wavelet shrinkage by iteratively performing shrinkage over patch groups and whole image aggregation. We discriminatively learn the shrinkage functions and basis from the training pairs of noisy/noise-free images, which can adaptively handle different noise characteristics in luminance/chrominance channels, and the unknown structured noise in real-captured color images. Furthermore, to remove the splotchy real color noises, we design a Laplacian pyramid-based denoising framework to progressively recover the clean image from the coarsest scale to the finest scale by the DLIS model learned from the real color noises. Experiments show that our proposed approach can achieve the state-of-the-art denoising results on both synthetic denoising benchmark and real-captured color images.

  10. Tubing weld cracking test

    SciTech Connect

    Lundin, C.D.; Qiao, C.Y.P.

    1995-12-31

    A tubing weld cracking (TWC) test was developed for applications involving advanced austenitic alloys (such as modified 800H and 310HCbN). Compared to the Finger hot cracking test, the TWC test shows an enhanced ability to evaluate the crack sensitivity of tubing materials. The TWC test can evaluate the cracking tendency of base as well as filter materials. Thus, it is a useful tool for tubing suppliers, filler metal producers and fabricators.

  11. Method to determine factors contributing to thermoplastic sheet shrinkage

    NASA Astrophysics Data System (ADS)

    Rensch, Greg J.; Frye, Brad A.

    A test method is presented for the determination of shrinkage behavior in vacuum-formed thermoplastic resin sheeting, as presently simulated for various resin lots, sheet-gage thicknesses, sheet orientations, and mold profiles. The thermoforming machine and vacuum-forming mold characteristics are discussed. It is established that the four variable factors exert statistically significant effects on the shrinkage response of three Declar resin lots, but that these are of no real practical significance for either engineering or manufacturing operations.

  12. Nuclear shrinkage in live mouse hippocampal slices.

    PubMed

    Kasischke, K; Büchner, M; Ludolph, A C; Riepe, M W

    2001-05-01

    Brain slices are used extensively for biochemical, electrophysiological and molecular investigations. However, only the time frame for electrophysiological and biochemical investigations has as yet been defined. The goal of the present study was to investigate the time course of nuclear structure in live brain slices. Hippocampal slices (300 microm) were prepared from male CD1 mice (25-30 g), stained with Hoechst 33342 (10 microM), calcein-AM (2 microM) and ethidium homodimer (4 microM), and imaged with single- and dual-photon microscopy. The volume of CA1 pyramidal cell nuclei decreased from 759+/-229 microm3 in 40-50 microm depth 25 min after preparation to 453+/-169 microm3 (P<0.001) after 60 min, 315+/-112 microm3 (P<0.001) after 120 min and 128+/-71 microm3 (P<0.001) after 8 h. Similar results were obtained on a prolonged time scale in 70-80 microm depth and with an accelerated time scale in 20-30 microm depth. Live-dead staining showed that cell damage is progressing from the surface to deeper layers of the slices in a time-dependent fashion. We conclude that nuclei of CA1 hippocampal pyramidal cells show a time- and depth-dependent shrinkage converging 8 h after slice preparation to a volume of 90-130 microm; in any depth between 20 and 80 microm. The nucleus in the superficial 80 microm of each side appears dysfunctional even at times suitable for electrophysiological and biochemical experimentation in hippocampal slices. Molecular analysis of cell regulation in brain slices may, therefore, be time-dependently distorted by progressing cell death in at least half of the tissue under investigation.

  13. Variation of Shrinkage Strain within the Depth of Concrete Beams

    PubMed Central

    Jeong, Jong-Hyun; Park, Yeong-Seong; Lee, Yong-Hak

    2015-01-01

    The variation of shrinkage strain within beam depth was examined through four series of time-dependent laboratory experiments on unreinforced concrete beam specimens. Two types of beam specimens, horizontally cast and vertically cast, were tested; shrinkage variation was observed in the horizontally cast specimens. This indicated that the shrinkage variation within the beam depth was due to water bleeding and tamping during the placement of the fresh concrete. Shrinkage strains were measured within the beam depth by two types of strain gages, surface-attached and embedded. The shrinkage strain distribution within the beam depth showed a consistent tendency for the two types of gages. The test beams were cut into four sections after completion of the test, and the cutting planes were divided into four equal sub-areas to measure the aggregate concentration for each sub-area of the cutting plane. The aggregate concentration increased towards the bottom of the beam. The shrinkage strain distribution was estimated by Hobbs’ equation, which accounts for the change of aggregate volume concentration. PMID:28793677

  14. The measurement of polymerization shrinkage of composite resins with ESPI

    NASA Astrophysics Data System (ADS)

    Zhang, Zhang; Yang, Guo Biao

    2008-09-01

    In the current study, we used the method of electronic speckle pattern interferometry (ESPI) to measure polymerization shrinkage of composite resins. Standardized cavities were prepared and placed into the ESPI apparatus before the cavities were filled with composites (n=2) .The ESPI apparatus was constructed to measure the out-of-plane displacement of the resins surface during the polymerization. Experiments demonstrated that the ESPI technique was a viable method to measure the deformation of composite resins. It was responsive and sensitive to dimensional changes. We found that cavity shape, size and C- factor influenced the date of resins shrinkage. And the tooth deformation in response to polymerization of resins was measured by the ESPI too. We concluded that ESPI was a feasible method for assessing resins deformation induced by its polymerization shrinkage when it was bonded in tooth cavities. And the results were greatly influenced by the dimensions of cavities , or interface adhesive and so on. It could also measure the tooth deformation induced by shrinkage of bonded composite resins. We found that resins polymerization shrinkage date may overestimate shrinkage-induced tooth deformation.

  15. Crack initiation processes in acrylic bone cement.

    PubMed

    Sinnett-Jones, P E; Browne, M; Moffat, A J; Jeffers, J R T; Saffari, N; Buffière, J-Y; Sinclair, I

    2009-06-15

    A major constraint in improving the understanding of the micromechanics of the fatigue failure process and, hence, in optimizing bone cement performance is found in the uncertainties associated with monitoring the evolution of the internal defects that are believed to dominate in vivo failure. The present study aimed to synthesize high resolution imaging with complementary damage monitoring/detection techniques. As a result, evidence of the chronology of failure has been obtained. The earliest stages of crack initiation have been captured and it is proposed that, in the presence of a pore, crack initiation may occur away from the pore due to the combined influence of pore morphology and the presence of defects within regions of stress concentration. Furthermore, experimental evidence shows that large agglomerations of BaSO(4) are subject to microcracking during fatigue, although in the majority of cases, these are not the primary cause of failure. It is proposed that cracks may then remain contained within the agglomerations because of the clamping effect of the matrix during volumetric shrinkage upon curing.

  16. Autogenic-Feedback Training Exercise (AFTE) Method and System

    NASA Technical Reports Server (NTRS)

    Cowings, Patricia S. (Inventor)

    1997-01-01

    The Autogenic-Feedback Training Exercise (AFTE) method of the present invention is a combined application of physiologic and perceptual training techniques. such as autogenic therapy and biofeedback. This combined therapy approach produces a methodology that is appreciably more effective than either of the individual techniques used separately. The AFTE method enables sufficient magnitude of control necessary to significantly reduce the behavioral and physiologic reactions to severe environmental stressors. It produces learned effects that are persistent over time and are resistant to extinction and it can be administered in a short period of time. The AFTE method may be used efficiently in several applications, among which are the following: to improve pilot and crew performance during emergency flying conditions; to train people to prevent the occurrence of nausea and vomiting associated with motion and sea sickness, or morning sickness in early pregnancy; as a training method for preventing or counteracting air-sickness symptoms in high-performance military aircraft; for use as a method for cardiovascular training, as well as for multiple other autonomic responses, which may contribute to the alleviation of Space Motion Sickness (SMS) in astronauts and cosmonauts; training people suffering from migraine or tension headaches to control peripheral blood flow and reduce forehead and/or trapezius muscle tension; training elderly people suffering from fecal incontinence to control their sphincter muscles; training cancer patients to reduce the nauseagenic effects of chemotherapy; and training patients with Chronic Intestinal Pseudo-obstruction (CIP).

  17. Forced expiratory technique, directed cough, and autogenic drainage.

    PubMed

    Fink, James B

    2007-09-01

    In health, secretions produced in the respiratory tract are cleared by mucociliary transport, cephalad airflow bias, and cough. In disease, increased secretion viscosity and volume, dyskinesia of the cilia, and ineffective cough combine to reduce secretion clearance, leading to increased risk of infection. In obstructive lung disease these conditions are further complicated by early collapse of airways, due to airway compression, which traps both gas and secretions. Techniques have been developed to optimize expiratory flow and promote airway clearance. Directed cough, forced expiratory technique, active cycle of breathing, and autogenic drainage are all more effective than placebo and comparable in therapeutic effects to postural drainage; they require no special equipment or care-provider assistance for routine use. Researchers have suggested that standard chest physical therapy with active cycle of breathing and forced expiratory technique is more effective than chest physical therapy alone. Evidence-based reviews have suggested that, though successful adoption of techniques such as autogenic drainage may require greater control and training, patients with long-term secretion management problems should be taught as many of these techniques as they can master for adoption in their therapeutic routines.

  18. Autogenic heterotopic vascularized proximal interphalangeal joint transplantation in children.

    PubMed

    Chiu, David T W; Lee, Jonathan

    2011-03-01

    The proximal interphalangeal joint (PIP) joint is the most crucial joint for the functionality of a finger. For a child with complex injury of the hand every effort should be exercised to maximize function restoration. If the PIP joint is irreparably damaged, its reconstruction is indicated. The technique of autogenic heterotopic vascularized toe joint transplantation provides unique advantage of a composite transfer of skin, tendons, bone and joint alone with growth plate and its efficacy has been affirmed in children. It has been suggested that such transfers require intact flexor tendon to achieve satisfactory results, our experience however indicates quite the contrary. As evidenced by this report of a 7-year-old boy with abrasion and avulsion injury to his dominant right hand resulting in a complex defect with skin lose, extensor, flexor avulsion along with cominution of the PIP joint of his long finger. A surgical formulation of staged reconstruction scheme including an autogenic heterotopic vascularized toe joint transplantation led to complete functional restoration to his right hand.

  19. TESTING AND ANALYSIS OF CAP CONCRETE STRESS AND STRAIN DUE TO SHRINKAGE, CREEP, AND EXPANSION FINAL REPORT

    SciTech Connect

    Guerrero, H.; Restivo, M.

    2011-08-01

    In-situ decommissioning of Reactors P- and R- at the Savannah River Site will require filling the reactor vessels with a special concrete based on materials such as magnesium phosphate, calcium aluminate or silica fume. Then the reactor vessels will be overlain with an 8 ft. thick layer of Ordinary Portland Cement (OPC) steel reinforced concrete, called the 'Cap Concrete'. The integrity of this protective layer must be assured to last for a sufficiently long period of time to avoid ingress of water into the reactor vessel and possible movement of radioactive contamination into the environment. During drying of this Cap Concrete however, shrinkage strains are set up in the concrete as a result of diffusion and evaporation of water from the top surface. This shrinkage varies with depth in the poured slab due to a non-uniform moisture distribution. This differential shrinkage results in restraint of the upper layers with larger shrinkage by lower layers with lesser displacements. Tensile stresses can develop at the surface from the strain gradients in the bulk slab, which can lead to surface cracking. Further, a mechanism called creep occurs during the curing period or early age produces strains under the action of restraining forces. To investigate the potential for surface cracking, an experimental and analytical program was started under TTQAP SRNL-RP-2009-01184. Slab sections made of Cap Concrete mixture were instrumented with embedded strain gages and relative humidity sensors and tested under controlled environmental conditions of 23 C and relative humidities (RH) of 40% and 80% over a period of 50 days. Calculation methods were also developed for predictions of stress development in the full-scale concrete placement over the reactor vessels. These methods were evaluated by simulating conditions for the test specimens and the calculation results compared to the experimental data. A closely similar test with strain gages was performed by Kim and Lee for a

  20. Hot-cracking mechanism in CO/sub 2/ laser beam welds of dissimilar metals involving PH martensitic stainless steels

    SciTech Connect

    Cieslak, M.J.

    1987-02-01

    Autogenous CO/sub 2/ laser beam welds were made between Alloy HP 9-4-20 and both 15-5 PH and PH 13-8 Mo stainless steel. Small scale circular-patch test specimens revealed that the combination involving the Nb-bearing alloy, 15-5 PH, was far more crack susceptible than the combination involving the Nb-free alloy, PH 13-8 Mo. Analytical electron microscopy was used to identify an NbC/austenite eutectic-like constituent as being responsible for the cracking phenomenon.

  1. Hospital Universiti Sains Malaysia experience in orbital floor reconstruction: autogenous graft versus Medpor.

    PubMed

    Wajih, Wahid Abdullah Salem; Shaharuddin, Bakiah; Razak, Noor Hayati Abdul

    2011-06-01

    A normally restored orbital structure after reconstructive surgery would accelerate the return of orbital function. The aim of the present study was to compare the outcomes of 2 orbital implants: autogenous grafts and porous polyethylene (Medpor). A longitudinal study was conducted of all patients who had undergone orbital floor reconstruction using an autogenous graft or Medpor. The study participants were divided into 2 groups, and the postoperative outcomes were assessed clinically. Of the 26 patients, 14 (53.0%) had undergone surgery with an autogenous graft and 12 (46.2%) with Medpor. Postoperatively, no diplopia in the primary gaze was noted in any patient. However, down gaze and peripheral diplopia was found in 11.5% and 26.9% in the autogenous group and in 3.8% and 26.9% in the Medpor group, respectively (P = 1.24). Enophthalmos was present in 11.4% of the autogenous graft group and 15.3% of the Medpor group (P = .465). The Hess chart findings were abnormal in 11.4% of both groups (P = .062). Restriction of movement was observed in 1 patient (3.8%) from the autogenous group and 7.7% of the Medpor group (P = .574). Orbital floor reconstruction using an autogenous graft or Medpor showed comparable results. Copyright © 2011 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

  2. Clinical Analysis of Hemodialysis Vascular Access: Comparision of Autogenous Arterioveonus Fistula & Arteriovenous Prosthetic Graft

    PubMed Central

    Kim, Duk-Sil; Kim, Jun-Chul; Cho, Ji-Hyung; Kong, Joon-Hyuk; Park, Chang-Ryul

    2011-01-01

    Background Mature autogenous arteriovenous fistulas have better long term patency and require fewer secondary interventions compared to arteriovenous prosthetic graft. Our Study evaluated vascular patency rates and incidence of interventions in autogenous arteriovenous fistulas and grafts. Material and Methods A total of 166 vascular access operations were performed in 153 patients between December 2002 and November 2009. Thirty seven caeses were excluded due to primary access failure and loss of follow-up. One group of 92 autogenous arterioveous fistulas and the other group of 37 arteriovenous prosthetic grafts were evaluated retrospectively. Primary and secondary patency rates were estimated using the Kaplan-Meier method. Results The primary patency rate (84%, 67%, 51% vs. 51%, 22%, 9% at 1, 3, 5 year; p=0.0000) and secondary patency rate (96%, 88%, 68% vs. 88%, 65%, 16% at 1. 3, 5 year; p=0.0009) were better in autogenous fistula group than prosthetic graft group. Interventions to maintain secondary patency were required in 23% of the autogenous fistula group (average 0.06 procedures/patient/year) and 65% of prosthetic graft group (average 0.21 procedures/patient/year). So the autogenous fistula group had fewer intervention rate than prosthetic graft group (p=0.01) The risk factor of primary patency was diabetus combined with ischemic heart disease and the secondary patency's risk factor was age. Conclusion Autogenous arteriovenous fistulas showed better performance compared to prosthetic grafts in terms of primary & secondary patency and incidence of interventions. PMID:22263120

  3. Crack mitigation in concrete bridge decks through experimental analysis and computer modeling

    NASA Astrophysics Data System (ADS)

    Richardson, Douglas M.

    Bridge deck cracking can cause deterioration of bridge decks, leading to a shorter life span and poor performance. Throughout the US, cracking has been identified as a problem, with transverse cracking along the deck at regular spacings being the most prominent type. This problem is usually caused by drying shrinkage within the concrete. The material properties, restraint, and distances without expansion joints all affect the crack pattern within the deck. This study will delve into the reasons that bridge decks crack, the strains that are associated with drying shrinkage, and possible methods for abating its effects. The research is divided into two parts, the first being laboratory experimentation, which was conducted through the use of two 7 ft. x 10 ft. experimental concrete bridge bays. Each bay was instrumented with strain and temperature gages throughout the deck and girders, which collected data for six months. The first deck was poured with a control concrete mix used currently in Illinois. The second deck was poured with a type K expansive concrete, which could battle the effects of shrinkage. For both decks, the results suggest a compressive strain throughout the rebar and along the top surface of the concrete, except for the locations where cracks are found (at these locations the strain slopes upward into tension). The strain in the type K deck, though, was notably less than that in the control deck and the onset of cracking was delayed by three weeks, giving the indication of an improvement over the current mix design. The second portion of the research was focused on using a finite element model to replicate the bridge bay and study the results. Equivalent temperature loading was used to apply the shrinkage loads recorded during the experimental portion of the research. The model was then expanded to encompass a full-scale bridge and in order to provide some insight into shrinkage strain in the real world. The end goal is to help alleviate cracking

  4. Mediated patterning of sol-gel thin layers: Shrinkage, decohesion, and lift-off

    NASA Astrophysics Data System (ADS)

    Mikalsen, Erik Arthur

    This thesis explores the unique de-cohesion and lift-off processes that occur during mediated patterning of integrated sol-gel thin films of functional materials. Mediated deposition, an additive patterning approach, was introduced by Jeon et al. (J. Mater. Res., 10[12]: 2996--9 (1995)), where microcontact printing (mu-CP) facilitated the selective transfer of a molecular 'ink' (e.g., octadecyltrichlorosilane, ODTS) to the substrate, and de-cohesion of sol-gel films occurred exclusively above the printed ink regions after heat treatment (<150°C). Patterned sol-gel films of uniform thickness were revealed after facile lift-off of cracked fragments, without the use of etchants. In this thesis, the origin and mechanics of de-cohesion and lift-off were determined through direct observations and measurements. The disparate mechanical behaviors of sol-gel films on functionalized and unmodified surfaces were determined, with emphasis on interfacial strength, in-plane biaxial stress, thin film mechanics, and crack propagation for sol-gel layers on silicon, glass and fused silica substrates. In addition, direct patterning of sol-gel layers was demonstrated for the first time on curved glassy surfaces using mu-CP and mediated patterning methods. The shrinkage and densification of sol-gel layers were determined by in-situ and ex-situ measurements, where a ˜30% decrease in thickness (t) was typical during drying of sol-gel layers (T < 300°C). Constrained shrinkage, resulting from adhesion to the supporting silicon substrate, led to a coherent (crack-free) film with biaxial stresses of ˜200 MPa (t ˜ 50 nm). For ODTS-mediated sol-gel films, however, precise in-situ wafer curvature measurements determined that film stresses never exceeded 75 MPa. Additionally, interfacial adhesive strength between the substrate and the sol-gel film were evaluated for the first time using a unique pulsed-laser stress-wave technique. An adhesive strength threshold of 15 MPa was determined for

  5. Investigation of Helicopter Longeron Cracks

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Baughman, James; Wallace, Terryl A.

    2009-01-01

    Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurgical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces.

  6. Geosynthetic clay liners shrinkage under simulated daily thermal cycles.

    PubMed

    Sarabadani, Hamid; Rayhani, Mohammad T

    2014-06-01

    Geosynthetic clay liners are used as part of composite liner systems in municipal solid waste landfills and other applications to restrict the escape of contaminants into the surrounding environment. This is attainable provided that the geosynthetic clay liner panels continuously cover the subsoil. Previous case histories, however, have shown that some geosynthetic clay liner panels are prone to significant shrinkage and separation when an overlying geomembrane is exposed to solar radiation. Experimental models were initiated to evaluate the potential shrinkage of different geosynthetic clay liner products placed over sand and clay subsoils, subjected to simulated daily thermal cycles (60°C for 8 hours and 22°C for 16 hours) modelling field conditions in which the liner is exposed to solar radiation. The variation of geosynthetic clay liner shrinkage was evaluated at specified times by a photogrammetry technique. The manufacturing techniques, the initial moisture content, and the aspect ratio (ratio of length to width) of the geosynthetic clay liner were found to considerably affect the shrinkage of geosynthetic clay liners. The particle size distribution of the subsoil and the associated suction at the geosynthetic clay liner-subsoil interface was also found to have significant effects on the shrinkage of the geosynthetic clay liner.

  7. Nonlinear Crack Growth Monitoring

    SciTech Connect

    Welch, DE

    2001-03-27

    Oak Ridge National Laboratory has developed a new technique to monitor the growth of cracks in structural members, and to predict when failure due to this damage is imminent. This technique requires the measurement of global loadings and local deflections/strains at critical locations to indicate the increasing growth of hidden cracks with sufficient warning time prior to failure to take preventative action to correct the problem or retire the structure before failure. The techniques, as described in the referenced report have been proven on a laboratory scale to successfully detect the onset of failure due to fatigue cracking (including cracking of corroded samples), stress corrosion cracking, and low temperature creep crack growth, with a reasonable degree of warning before failure.

  8. Catalytic cracking of hydrocarbons

    SciTech Connect

    Absil, R.P.L.; Bowes, E.; Green, G.J.; Marler, D.O.; Shihabi, D.S.; Socha, R.F.

    1992-02-04

    This patent describes an improvement in a catalytic cracking process in which a hydrocarbon feed is cracked in a cracking zone in the absence of added hydrogen and in the presence of a circulating inventory of solid acidic cracking a catalyst which acquires a deposit of coke that contains chemically bound nitrogen while the cracking catalyst is in the cracking zone, the coke catalyst being circulated to t regeneration zone to convert the coke catalyst to a regenerated catalyst with the formation of a flue gas comprising nitrogen oxides: the improvement comprises incorporating into the circulating catalyst inventory an amount of additive particles comprising a synthetic porous crystalline material containing copper metal or cations, to reduce the content of nitrogen oxides in the flue gas.

  9. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Kim, K. S.; Vanstone, R. H.

    1992-01-01

    The purpose of this program was to extend the work performed in the base program (CR 182247) into the regime of time-dependent crack growth under isothermal and thermal mechanical fatigue (TMF) loading, where creep deformation also influences the crack growth behavior. The investigation was performed in a two-year, six-task, combined experimental and analytical program. The path-independent integrals for application to time-dependent crack growth were critically reviewed. The crack growth was simulated using a finite element method. The path-independent integrals were computed from the results of finite-element analyses. The ability of these integrals to correlate experimental crack growth data were evaluated under various loading and temperature conditions. The results indicate that some of these integrals are viable parameters for crack growth prediction at elevated temperatures.

  10. Autogenic reaction synthesis of photocatalysts for solar fuel generation

    SciTech Connect

    Ingram, Brian J.; Pol, Vilas G.; Cronauer, Donald C.; Ramanathan, Muruganathan

    2016-04-19

    In one preferred embodiment, a photocatalyst for conversion of carbon dioxide and water to a hydrocarbon and oxygen comprises at least one nanoparticulate metal or metal oxide material that is substantially free of a carbon coating, prepared by heating a metal-containing precursor compound in a sealed reactor under a pressure autogenically generated by dissociation of the precursor material in the sealed reactor at a temperature of at least about 600.degree. C. to form a nanoparticulate carbon-coated metal or metal oxide material, and subsequently substantially removing the carbon coating. The precursor material comprises a solid, solvent-free salt comprising a metal ion and at least one thermally decomposable carbon- and oxygen-containing counter-ion, and the metal of the salt is selected from the group consisting of Mn, Ti, Sn, V, Fe, Zn, Zr, Mo, Nb, W, Eu, La, Ce, In, and Si.

  11. Autogenic Feedback Training Applications for Man in Space

    NASA Technical Reports Server (NTRS)

    Cowings, Patricia S.; Wade, Charles E. (Technical Monitor)

    1994-01-01

    Finding an effective treatment for the motion sickness-like symptoms that occur in space has become a high priority for NASA. This paper reviews the back-round research and procedures of an experiment designed to prevent space motion sickness in shuttle crewmembers. The preventive method used, Autogenic - Feedback Training (AFT) involves training subjects to control voluntarily several of their own physiological responses to environmental stressors. AFT has been used reliably to increase tolerance to motion sickness during around based tests in over 300 men and women under a variety of conditions that induce motion sickness, and preliminary evidence from space suggests that AFT may be an effective treatment for space motion sickness as well. Other applications of AFT described include; (1) a potential treatment for post flight orthostatic intolerance, a serious biomedical problem resulting from long duration exposure to micro-g and (2) improving pilot performance during emergency flying conditions.

  12. Postoperative irradiation of fresh autogenic cancellous bone grafts

    SciTech Connect

    Schwartz, H.C.; Leake, D.L.; Kagan, A.R.; Snow, H.; Pizzoferrato, A.

    1986-01-01

    Discontinuity defects were created in the mandibles of dogs and then reconstructed immediately with fresh autogenic cancellous bone grafts and Dacron-urethane prostheses. The grafts were irradiated to a total dose of 5000 rads after waiting intervals of between 3 and 12 weeks. Nonirradiated grafts served as controls. The grafts were evaluated clinically, radiographically, and histologically. There was complete incorporation of all grafts, regardless of the interval between surgery and radiotherapy. There were no soft-tissue complications. The controls were distinguishable from the irradiated grafts only by the presence of hematopoietic bone marrow. Fibrofatty marrow was observed in the irradiated grafts. Theoretical support for this technique is found in the biology of cancellous bone grafting and the pathology of radiation injury. In view of the difficulties associated with mandibular bone grafting in preoperatively irradiated patients, a new method of reconstructing selected cancer patients who require both mandibular resection and radiotherapy is suggested.

  13. CRACK MODELLING FOR RADIOGRAPHY

    SciTech Connect

    Chady, T.; Napierala, L.

    2010-02-22

    In this paper, possibility of creation of three-dimensional crack models, both random type and based on real-life radiographic images is discussed. Method for storing cracks in a number of two-dimensional matrices, as well algorithm for their reconstruction into three-dimensional objects is presented. Also the possibility of using iterative algorithm for matching simulated images of cracks to real-life radiographic images is discussed.

  14. The cracked tooth.

    PubMed

    Zuckerman, G R

    1998-01-01

    Fractured molars and premolars are very common. Fractures usually result from cracks that develop and slowly extend until the tooth separates into buccal and lingual fragments. Sometimes, as these cracks expand, the patient exhibits symptoms of what is commonly referred to as "cracked tooth syndrome" (CTS). When CTS occurs, an opportunity exists to diagnose and treat these patients, to relieve their discomfort and prevent sequelae that would require more extensive treatment.

  15. Shrinkage Stresses Generated during Resin-Composite Applications: A Review

    PubMed Central

    Schneider, Luis Felipe J.; Cavalcante, Larissa Maria; Silikas, Nick

    2010-01-01

    Many developments have been made in the field of resin composites for dental applications. However, the manifestation of shrinkage due to the polymerization process continues to be a major problem. The material's shrinkage, associated with dynamic development of elastic modulus, creates stresses within the material and its interface with the tooth structure. As a consequence, marginal failure and subsequent secondary caries, marginal staining, restoration displacement, tooth fracture, and/or post-operative sensitivity are clinical drawbacks of resin-composite applications. The aim of the current paper is to present an overview about the shrinkage stresses created during resin-composite applications, consequences, and advances. The paper is based on results of many researches that are available in the literature. PMID:20948573

  16. Improving the Incoherence of a Learned Dictionary via Rank Shrinkage.

    PubMed

    Ubaru, Shashanka; Seghouane, Abd-Krim; Saad, Yousef

    2017-01-01

    This letter considers the problem of dictionary learning for sparse signal representation whose atoms have low mutual coherence. To learn such dictionaries, at each step, we first update the dictionary using the method of optimal directions (MOD) and then apply a dictionary rank shrinkage step to decrease its mutual coherence. In the rank shrinkage step, we first compute a rank 1 decomposition of the column-normalized least squares estimate of the dictionary obtained from the MOD step. We then shrink the rank of this learned dictionary by transforming the problem of reducing the rank to a nonnegative garrotte estimation problem and solving it using a path-wise coordinate descent approach. We establish theoretical results that show that the rank shrinkage step included will reduce the coherence of the dictionary, which is further validated by experimental results. Numerical experiments illustrating the performance of the proposed algorithm in comparison to various other well-known dictionary learning algorithms are also presented.

  17. Prediction of ALLOY SHRINKAGE FACTORS FOR THE INVESTMENT CASTING PROCESS

    SciTech Connect

    Sabau, Adrian S

    2006-01-01

    This study deals with the experimental measurements and numerical predictions of alloy shrinkage factors (SFs) related to the investment casting process. The dimensions of the A356 aluminum alloy casting were determined from the numerical simulation results of solidification, heat transfer, fluid dynamics, and deformation phenomena. The investment casting process was carried out using wax patterns of unfilled wax and shell molds that were made of fused silica with a zircon prime coat. The dimensions of the die tooling, wax pattern, and casting were measured, in order to determine the actual tooling allowances. Several numerical simulations were carried out, to assess the level of accuracy for the casting shrinkage. The solid fraction threshold, at which the transition from the fluid dynamics to the solid dynamics occurs, was found to be important in predicting shrinkage factors (SFs). It was found that accurate predictions were obtained for all measued dimensions when the shell mold was considered a deformable material.

  18. Compressive dynamic range imaging via Bayesian shrinkage dictionary learning

    NASA Astrophysics Data System (ADS)

    Yuan, Xin

    2016-12-01

    We apply the Bayesian shrinkage dictionary learning into compressive dynamic-range imaging. By attenuating the luminous intensity impinging upon the detector at the pixel level, we demonstrate a conceptual design of an 8-bit camera to sample high-dynamic-range scenes with a single snapshot. Coding strategies for both monochrome and color cameras are proposed. A Bayesian reconstruction algorithm is developed to learn a dictionary in situ on the sampled image, for joint reconstruction and demosaicking. We use global-local shrinkage priors to learn the dictionary and dictionary coefficients representing the data. Simulation results demonstrate the feasibility of the proposed camera and the superior performance of the Bayesian shrinkage dictionary learning algorithm.

  19. Brain shrinkage and subdural effusion associated with ACTH administration.

    PubMed

    Satoh, J; Takeshige, H; Hara, H; Fukuyama, Y

    1982-01-01

    Sequential computed tomographic (CT) studies of 11 patients (aged five months to seven years) with intractable epilepsy treated with synthetic ACTH-Z showed brain shrinkage in all cases. Brain shrinkage started to appear on daily ACTH injections for seven days, reached the maximum within four weeks of administration (14 injections every day and then 7 injections every other day), and almost returned to the original status in seven out of nine cases which were followed up for one to three months after the therapy. The subjects aged less than two years showed more remarkable brain shrinkage than did those aged more than five years. Furthermore, two other cases were complicated by subdural effusion after ACTH therapy. It is the authors' assumption that both of these phenomena are caused by the high concentration of corticosteroid through a change of the water and electrolyte contents in the brain.

  20. Bayesian Nonparametric Shrinkage Applied to Cepheid Star Oscillations.

    PubMed

    Berger, James; Jefferys, William; Müller, Peter

    2012-01-01

    Bayesian nonparametric regression with dependent wavelets has dual shrinkage properties: there is shrinkage through a dependent prior put on functional differences, and shrinkage through the setting of most of the wavelet coefficients to zero through Bayesian variable selection methods. The methodology can deal with unequally spaced data and is efficient because of the existence of fast moves in model space for the MCMC computation. The methodology is illustrated on the problem of modeling the oscillations of Cepheid variable stars; these are a class of pulsating variable stars with the useful property that their periods of variability are strongly correlated with their absolute luminosity. Once this relationship has been calibrated, knowledge of the period gives knowledge of the luminosity. This makes these stars useful as "standard candles" for estimating distances in the universe.

  1. Quenched catalytic cracking process

    SciTech Connect

    Krambeck, F.J.; Penick, J.E.; Schipper, P.H.

    1990-12-18

    This paper describes improvement in a fluidized catalytic cracking process wherein a fluidizable catalyst cracking catalyst and a hydrocarbon feed are charged to a reactor riser at catalytic riser cracking conditions to form catalytically cracked vapor product and spent catalyst which are discharged into a reactor vessel having a volume via a riser reactor outlet equipped with a separation means to produce a catalyst lean phase. It comprises: a majority of the cracked product, and a catalyst rich phase comprising a majority of the spend catalyst. The the catalyst rich phase is discharged into a dense bed of catalyst maintained below the riser outlet and the catalyst lean phase is discharged into the vessel for a time, and at a temperature, which cause unselective thermal cracking of the cracked product in the reactor volume before product is withdrawn from the vessel via a vessel outlet. The improvement comprises: addition, after riser cracking is completed, and after separation of cracked products from catalyst, of a quenching stream into the vessel above the dense bed of catalyst, via a quench stream addition point which allows the quench stream to contact at least a majority of the volume of the vessel above the dense bed.

  2. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Kim, K. S.; Vanstone, R. H.

    1989-01-01

    Alloy 718 crack growth experiments were conducted to assess the ability of the selected path-independent (P-I) integrals to describe the elevated temperature crack growth behavior. These tests were performed on single edge notch (SEN) specimens under displacement control with multiple extensometers to monitor the specimen and crack mouth opening displacement (CMOD). The displacements in these tests were sufficiently high to induce bulk cyclic inelastic deformation of the specimen. Under these conditions, the linear elastic fracture mechanics (LEFM) parameter K does not correlate the crack growth data. The experimentally measured displacement gradients at the end of specimen gage length were used as the boundary conditions in elastic-plastic finite element method (FEM) analyses. These analyses were performed with a node release approach using CYANIDE, a GEAE FEM code, which included a gap element which is capable of efficiently simulating crack closure. Excellent correlation was obtained between the experimentally measured and predicted variation of stress and CMOD with crack length and the stress-CMOD loops for Alloy 718 tests conducted at 538 C. This confirmed the accuracy of the FEM crack growth simulation approach. The experimentally measured crack growth rate data correlated well the selected P-I integrals. These investigations have produced significant progress in developing P-I integrals as non-linear fracture mechanics parameters. The results suggest that this methodology has the potential of accurately describing elevated temperature crack growth behavior under the combined influence of thermal cycling and bulk elastic-inelastic deformation states.

  3. Model-based adhesive shrinkage compensation for increased bonding repeatability

    NASA Astrophysics Data System (ADS)

    Müller, Tobias; Schlette, Christian; Lakshmanan, Shunmuganathan; Haag, Sebastian; Zontar, Daniel; Sauer, Sebastian; Wenzel, Christian; Brecher, Christian; Roβmann, Jürgen

    2016-03-01

    The assembly process of optical components consists of two phases - the alignment and the bonding phase. Precision - or better process repeatability - is limited by the latter one. The limitation of the alignment precision is given by the measurement equipment and the manipulation technology applied. Today's micromanipulators in combination with beam imaging setups allow for an alignment in the range of far below 100nm. However, once precisely aligned optics need to be fixed in their position. State o f the art in optics bonding for laser systems is adhesive bonding with UV-curing adhesives. Adhesive bonding is a multi-factorial process and thus subject to statistical process deviations. As a matter of fact, UV-curing adhesives inherit shrinkage effects during their curing process, making offsets for shrinkage compensation mandatory. Enhancing the process control of the adhesive bonding process is the major goal of the activities described in this paper. To improve the precision of shrinkage compensation a dynamic shrinkage prediction is envisioned by Fraunhofer IPT. Intense research activities are being practiced to gather a deeper understanding of the parameters influencing adhesive shrinkage behavior. These effects are of different nature - obviously being the raw adhesive material itself as well as its condition, the bonding geometry, environmental parameters like surrounding temperature and of course process parameters such as curing properties. Understanding the major parameters and linking them in a model-based shrinkage-prediction environment is the basis for improved process control. Results are being deployed by Fraunhofer in prototyping, as well as volume production solutions for laser systems.

  4. Shrinkage Prediction for the Investment Casting of Stainless Steels

    SciTech Connect

    Sabau, Adrian S

    2007-01-01

    In this study, the alloy shrinkage factors were obtained for the investment casting of 17-4PH stainless steel parts. For the investment casting process, unfilled wax and fused silica with a zircon prime coat were used for patterns and shell molds, respectively. Dimensions of the die tooling, wax pattern, and casting were measured using a Coordinate Measurement Machine in order to obtain the actual tooling allowances. The alloy dimensions were obtained from numerical simulation results of solidification, heat transfer, and deformation phenomena. The numerical simulation results for the shrinkage factors were compared with experimental results.

  5. Minimum risk wavelet shrinkage operator for Poisson image denoising.

    PubMed

    Cheng, Wu; Hirakawa, Keigo

    2015-05-01

    The pixel values of images taken by an image sensor are said to be corrupted by Poisson noise. To date, multiscale Poisson image denoising techniques have processed Haar frame and wavelet coefficients--the modeling of coefficients is enabled by the Skellam distribution analysis. We extend these results by solving for shrinkage operators for Skellam that minimizes the risk functional in the multiscale Poisson image denoising setting. The minimum risk shrinkage operator of this kind effectively produces denoised wavelet coefficients with minimum attainable L2 error.

  6. Silver-Coated Nylon Dressing Plus Active DC Microcurrent for Healing of Autogenous Skin Donor Sites

    DTIC Science & Technology

    2013-08-01

    Silver-Coated Nylon Dressing Plus Active DC Microcurrent for Healing of Autogenous Skin Donor Sites Edward W. Malin, MD, Chaya M. Galin, BSN, RN... microcurrent in comparison to silver-coated dressing with sham microcurrent on wound-closure time for autogenous skin donor sites. Methods: Four...hundred five patients were screened for treatment of their donor sites using a silver-coated nylon dressing with either sham or active microcurrent

  7. Measuring polymerization shrinkage of photo-activated restorative materials by a water-filled dilatometer.

    PubMed

    Lai, J H; Johnson, A E

    1993-03-01

    A water-filled dilatometer specifically designed for determining the polymerization shrinkage of photo-activated composite restorative materials was used to measure the polymerization shrinkage of three visible light-activated composites. Polymerization shrinkage values ranged from 1.82% for P-50 to 2.15% and 2.19% for Herculite XRV and Prisma APH, respectively. Shrinkage data obtained in this investigation were compared with the published data, and the factors which affect shrinkage measurements were reviewed. It was concluded that maintaining a constant temperature environment (+ or - 0.02 degrees C) for the dilatometer during the shrinkage test was the most critical factor for successful application of the dilatometer.

  8. Synthesis, characterization, shrinkage and curing kinetics of a new low-shrinkage urethane dimethacrylate monomer for dental applications.

    PubMed

    Atai, Mohammad; Ahmadi, Mehdi; Babanzadeh, Samal; Watts, David C

    2007-08-01

    The aim of the study was to synthesize and characterize an isophorone-based urethane dimethacrylate (IP-UDMA) resin-monomer and to investigate its shrinkage and curing kinetics. The IP-UDMA monomer was synthesized through the reaction of polyethylene glycol 400 and isophorone diisocyanate followed by reacting with HEMA to terminate it with methacrylate end groups. The reaction was followed using a standard back titration method and FTIR spectroscopy. The final product was purified and characterized using FTIR, (1)H NMR, elemental analysis and refractive index measurement. The shrinkage-strain of the specimens photopolymerized at circa 700mW/cm(2) was measured using the bonded-disk technique at 23, 35, and 45 degrees C. Initial shrinkage-strain-rates were obtained by numerical differentiation of shrinkage-strain data with respect to time. Degree-of-conversion of the specimens was measured using FTIR spectroscopy. The thermal curing kinetics of the monomer were also studied by differential scanning calorimetry (DSC). The characterization methods confirmed the suggested reaction route and the synthesized monomer. A low shrinkage-strain of about 4% was obtained for the new monomer. The results showed that the shrinkage-strain-rate of the monomer followed the autocatalytic model of Kamal and Sourour [Kamal MR, Sourour S. Kinetic and thermal characterization of thermoset cure. Polym Eng Sci 1973;13(1):59-64], which is used to describe the reaction kinetics of thermoset resins. The model parameters were calculated by linearization of the equation. The model prediction was in a good agreement with the experimental data. The properties of the new monomer compare favorably with properties of the commercially available resins.

  9. Pyrolytic carbon indentation crack morphology.

    PubMed

    Ely, J L; Stupka, J; Haubold, A D

    1996-06-01

    In studying fatigue and fracture behavior of brittle materials, Vickers diamond indentation cracks are often used. Many of the studies of indentation cracks use crack system models such as the radial-median crack or Palmqvist crack. These systems are also used to study small crack growth in brittle materials, and have been studied for pyrolytic carbon. However, the true morphology of these cracks in pyrolytic carbon coatings on graphite substrates have not been described. This study examined Vickers diamond and spherical ball indentation cracks in pyrolytic carbon coatings using several techniques, including serial metallographic cross sections, indentation fracture in bending, acoustic emission, and residual surface indentation scanning. The crack systems developed using these techniques were not typical of either radial median or Palmqvist systems. The morphology is unique to this material, possibly because of the coating thickness limitations. Given the difference in crack system, the application of standard indentation crack equations in studying fracture mechanics, especially for small cracks, must be questioned.

  10. Crack layer theory

    NASA Technical Reports Server (NTRS)

    Chudnovsky, A.

    1984-01-01

    A damage parameter is introduced in addition to conventional parameters of continuum mechanics and consider a crack surrounded by an array of microdefects within the continuum mechanics framework. A system consisting of the main crack and surrounding damage is called crack layer (CL). Crack layer propagation is an irreversible process. The general framework of the thermodynamics of irreversible processes are employed to identify the driving forces (causes) and to derive the constitutive equation of CL propagation, that is, the relationship between the rates of the crack growth and damage dissemination from one side and the conjugated thermodynamic forces from another. The proposed law of CL propagation is in good agreement with the experimental data on fatigue CL propagation in various materials. The theory also elaborates material toughness characterization.

  11. Stiffness and shrinkage of green and dry joists

    Treesearch

    Lyman W. Wood; Lawrence A. Soltis

    1964-01-01

    This report gives information on the edgewise modulus of elasticity, stiffness, and shrinkage of 360 joists in three species, three grades, and two sizes, each species obtained from two sources. Each joist was evaluated nondestructively at four moisture content values ranging from the green condition to about 11 percent. Information is also given on specific gravity,...

  12. Flowable composite resins: do they decrease microleakage and shrinkage stress?

    PubMed

    Conte, Nicholas R; Goodchild, Jason H

    2013-06-01

    All flowable composites shrink and undergo polymerization stress; however, new technologic developments have sought to minimize this, while streamlining dental techniques and producing better results. The new category of bulk-fill flowable composites promotes the effective use of 4-mm increments while decreasing shrinkage stresses generated during polymerization.

  13. Fast generation of computer-generated holograms using wavelet shrinkage.

    PubMed

    Shimobaba, Tomoyoshi; Ito, Tomoyoshi

    2017-01-09

    Computer-generated holograms (CGHs) are generated by superimposing complex amplitudes emitted from a number of object points. However, this superposition process remains very time-consuming even when using the latest computers. We propose a fast calculation algorithm for CGHs that uses a wavelet shrinkage method, eliminating small wavelet coefficient values to express approximated complex amplitudes using only a few representative wavelet coefficients.

  14. Small-crack test methods

    NASA Astrophysics Data System (ADS)

    Larsen, James M.; Allison, John E.

    This book contains chapters on fracture mechanics parameters for small fatigue cracks, monitoring small-crack growth by the replication method, measurement of small cracks by photomicroscopy (experiments and analysis), and experimental mechanics of microcracks. Other topics discussed are the real-time measurement of small-crack-opening behavior using an interferometric strain/displacement gage; direct current electrical potential measurement of the growth of small cracks; an ultrasonic method for the measurement of the size and opening behavior of small fatigue cracks; and the simulation of short crack and other low closure loading conditions, utilizing constant K(max) Delta-K-decreasing fatigue crack growth procedures.

  15. Polymerization shrinkage kinetics of dimethacrylate resin-cements.

    PubMed

    Spinell, Thomas; Schedle, Andreas; Watts, David C

    2009-08-01

    To determine polymerization shrinkage-strain (S(Y)) and shrinkage-stress (S(Z)) of six resin-cements and to compare their performance with the aid of degree of conversion (DC) data. Variolink 2 (VL2), Multilink Automix (MA), Multilink Sprint (MS, all Ivoclar-Vivadent), Nexus 2 (NX2), Maxcem (MX, both Kerr) and RelyX Unicem (RX, 3M-Espe) were investigated. MS, MX and RX were self-adhesive; others require a bonding-agent. All measurements were conducted at 23 degrees C for 60min (n=5), except 80min for RX, with materials self-cured only (sc) and dual-cured (dc); NX2 and VL2 were additionally light-cured only (lc). S(Y) was measured by the bonded-disk method [Watts DC, Cash AJ. Determination of polymerization shrinkage kinetics in visible-light-cured materials: methods development. Dent Mater 1991;7(4):281-7; Watts DC, Marouf AS. Optimal specimen geometry in bonded-disk shrinkage-strain measurements on light-cured biomaterials. Dent Mater 2000;16(6):447-51]; S(Z) by the Bioman instrument [Watts DC, Satterthwaite JD. Axial shrinkage-stress depends upon both C-factor and composite mass. Dent Mater 2008;24(1):1-8 [Epub October 24, 2007]; Watts DC, Marouf AS, Al-Hindi AM. Photo-polymerization shrinkage-stress kinetics in resin-composites: methods development. Dent Mater 2003;19(1):1-11]. Light-cure was achieved by QTH at 500mW/cm(2). The respective DCs were measured under the same conditions by FTIR-ATR spectroscopy. Data were analyzed by One-Way ANOVA plus Bonferroni test, and by t-test, at p<0.05. DC by self-curing was less than the DC by dual-curing, for all cements. Shrinkage-strain ranged from 1.77 to 5.29% and shrinkage-stress from 3.36 to 10.37MPa. NX2 and VL2 were not significantly different, when light-cured only. Except for RX, sc and dc shrinkage-strain varied maximally by 0.4%. MX showed the highest S(Y), RX the lowest. When sc, RX initially expanded by <0.5% (t approximately 5min). For most materials, S(Y) correlated with their filler loading. The highest

  16. Calcium channel blockers enhance sac shrinkage after endovascular aneurysm repair.

    PubMed

    Bailey, Marc A; Sohrabi, Soroush; Flood, Karen; Griffin, Kathryn J; Rashid, S Tawqeer; Johnson, Anne B; Baxter, Paul D; Patel, Jai V; Scott, D Julian A

    2012-06-01

    Sac shrinkage is a surrogate marker of success after endovascular aneurysm repair (EVAR). We set out to determine if any common cardioprotective medications had a beneficial effect on sac shrinkage. This retrospective observational study took place at Leeds Vascular Institute, a tertiary vascular unit in the Northern United Kingdom. The cohort comprised 149 patients undergoing EVAR between January 1, 2005, and December 31, 2008. Medication use was recorded at intervention (verified at study completion in 33 patients), and patients were monitored for 2 years. The main outcome measures were the effect of medication on sac shrinkage as determined by percentage change in maximal idealized cross-sectional area of the aneurysm at 1 month, 6 months, 1 year, and 2 years by linear regression model, in addition to 2-year endoleak and death rates determined by a binary logistic regression model. After exclusions, 112 patients, who were a median age of 78 years (interquartile range, 78-83 years), remained for analysis. The median Glasgow Aneurysm Score was 85 (interquartile range, 79-92). At 2 years, mortality was 13.4%, endoleak developed in 37.5%, and significant endoleak developed in 14.3%. Patients taking a calcium channel blocker had enhanced sac shrinkage, compared with those not taking a calcium channel blocker, by 6.6% at 6 months (-3.0% to 16.3%, P = .09), 12.3% at 1 year (2.9% to 21.7%, P = .008), and 13.1% at 2 years (0.005% to 26.2%, P = .007) independent of other medication use, graft type, endoleak development, or death. Enhanced sac shrinkage occurred after EVAR in patients taking calcium channel blockers. This warrants further study in other centers and at the molecular level. Copyright © 2012 Society for Vascular Surgery. Published by Mosby, Inc. All rights reserved.

  17. Using hyperbranched oligomer functionalized glass fillers to reduce shrinkage stress

    PubMed Central

    Ye, Sheng; Azarnoush, Setareh; Smith, Ian R.; Cramer, Neil B.; Stansbury, Jeffrey W.; Bowman, Christopher N

    2012-01-01

    Objective Fillers are widely utilized to enhance the mechanical properties of polymer resins. However, polymerization stress has the potential to increase due to the higher elastic modulus achieved upon filler addition. Here, we demonstrate a hyperbranched oligomer functionalized glass filler UV curable resin composite which is able to reduce the shrinkage stress without sacrificing mechanical properties. Methods A 16-functional alkene-terminated hyperbranched oligomer is synthesized by thiol-acrylate and thiol-yne reactions and the product structure is analyzed by 1H-NMR, mass spectroscopy, and gel permeation chromatography. Surface functionalization of the glass filler is measured by thermogravimetric analysis. Reaction kinetics, mechanical properties and shrinkage stress are studied via Fourier transform infrared spectroscopy, dynamic mechanical analysis and a tensometer, respectively. Results Silica nanoparticles are functionalized with a flexible 16-functional alkene-terminated hyperbranched oligomer which is synthesized by multistage thiol-ene/yne reactions. 93% of the particle surface was covered by this oligomer and an interfacial layer ranging from 0.7 – 4.5 nm thickness is generated. A composite system with these functionalized silica nanoparticles incorporated into the thiol-yne-methacrylate resin demonstrates 30% reduction of shrinkage stress (from 0.9 MPa to 0.6 MPa) without sacrificing the modulus (3100 ± 300 MPa) or glass transition temperature (62 ± 3 °C). Moreover, the shrinkage stress of the composite system builds up at much later stages of the polymerization as compared to the control system. Significance Due to the capability of reducing shrinkage stress without sacrificing mechanical properties, this composite system will be a great candidate for dental composite applications. PMID:22717296

  18. Cure shrinkage effects in epoxy and polycyanate matrix composites

    SciTech Connect

    Spellman, G.P.

    1995-12-22

    A relatively new advanced composite matrix, polycyanate ester, was evaluated for cure shrinkage. The chemical cure shrinkage of composites is difficult to model but a number of clever experimental techniques are available to the investigator. In this work the method of curing a prepreg layup on top of a previously cured laminate of identical ply composition is utilized. The polymeric matrices used in advanced composites have been primarily epoxies and therefore a common system of this type, Fiberite 3501-6, was used as a base case material. Three polycyanate matrix systems were selected for the study. These are: Fiberite 954-2A, YLA RS-3, and Bryte Technology BTCy-1. The first three of these systems were unidirectional prepreg with carbon fiber reinforcement. The Bryte Technology material was reinforced with E-glass fabric. The technique used to evaluate cure shrinkage results in distortion of the flatness of an otherwise symmetric laminate. The first laminate is cured in a conventional fashion. An identical layup is cured on this first laminate. During the second cure all constituents are exposed to the same thermal cycles. However, only the new portion of the laminate will experience volumetric changes associate with matrix cure. The additional strain of cure shrinkage results in an unsymmetric distribution of residual stresses and an associated warpage of the laminate. The baseline material, Fiberite 3501-6, exhibited cure shrinkage that was in accordance with expectations. Cure strains were {minus}4.5E-04. The YLA RS-3 material had cure strains somewhat lower at {minus}3.2E-04. The Fiberite 954-2A cure strain was {minus}1.5E-04 that is 70% lower than the baseline material. The glass fabric material with the Bryte BTCy-1 matrix did not result in meaningful results because the processing methods were not fully compatible with the material.

  19. Quantification of water penetration into concrete through cracks by neutron radiography

    NASA Astrophysics Data System (ADS)

    Kanematsu, M.; Maruyama, I.; Noguchi, T.; Iikura, H.; Tsuchiya, N.

    2009-06-01

    Improving the durability of concrete structures is one of the ways to contribute to the sustainable development of society, and it has also become a crucial issue from an environmental viewpoint. It is well known that moisture behavior in reinforced concrete is linked to phenomena such as cement hydration, volume change and cracking caused by drying shrinkage, rebar corrosion and water leakage that affect the durability of concrete. In this research, neutron radiography was applied for visualization and quantification of water penetration into concrete through cracks. It is clearly confirmed that TNR can make visible the water behavior in/near horizontal/vertical cracks and can quantify the rate of diffusion and concentration distribution of moisture with high spatial and time resolution. On detailed analysis, it is observed that water penetrates through the crack immediately after pouring and its migration speed and distribution depend on the moisture condition in the concrete.

  20. Untangling climatic and autogenic signals in peat records

    NASA Astrophysics Data System (ADS)

    Morris, Paul J.; Baird, Andrew J.; Young, Dylan M.; Swindles, Graeme T.

    2016-04-01

    Raised bogs contain potentially valuable information about Holocene climate change. However, autogenic processes may disconnect peatland hydrological behaviour from climate, and overwrite and degrade climatic signals in peat records. How can genuine climate signals be separated from autogenic changes? What level of detail of climatic information should we expect to be able to recover from peat-based reconstructions? We used an updated version of the DigiBog model to simulate peatland development and response to reconstructed Holocene rainfall and temperature reconstructions. The model represents key processes that are influential in peatland development and climate signal preservation, and includes a network of feedbacks between peat accumulation, decomposition, hydraulic structure and hydrological processes. It also incorporates the effects of temperature upon evapotranspiration, plant (litter) productivity and peat decomposition. Negative feedbacks in the model cause simulated water-table depths and peat humification records to exhibit homeostatic recovery from prescribed changes in rainfall, chiefly through changes in drainage. However, the simulated bogs show less resilience to changes in temperature, which cause lasting alterations to peatland structure and function and may therefore be more readily detectable in peat records. The network of feedbacks represented in DigiBog also provide both high- and low-pass filters for climatic information, meaning that the fidelity with which climate signals are preserved in simulated peatlands is determined by both the magnitude and the rate of climate change. Large-magnitude climatic events of an intermediate frequency (i.e., multi-decadal to centennial) are best preserved in the simulated bogs. We found that simulated humification records are further degraded by a phenomenon known as secondary decomposition. Decomposition signals are consistently offset from the climatic events that generate them, and decomposition

  1. Chronobiometric assessment of autogenic training effects upon blood pressure and heart rate.

    PubMed

    Watanabe, Y; Halberg, F; Cornélissen, G; Saito, Y; Fukuda, K; Otsuka, K; Kikuchi, T

    1996-12-01

    Autogenic training, a method of self-hypnosis, lowers the extent of within-day variation of systolic blood pressure assessed by the circadian double amplitude. The blood pressure and heart rate of ten patients, conventionally diagnosed as having hypertension or white-coat hypertension, were automatically monitored at 30-min intervals for 7 days before autogenic training and again for 7 days, at 1 or 2 months after the start of autogenic training (practiced three times daily). The circadian double amplitude of systolic blood pressure of the patients investigated was 3 to 17 mm Hg lower on autogenic training. In 5 patients, reductions by 7 to 17 mm Hg were statistically significant. These results are regarded as provisional statistics, the utility of which depends on replication. By contrast, the over-all group reduction of the circadian double amplitude of systolic blood pressure by 8 mm Hg on the average can be taken at face value. Autogenic training also lowered the circadian double amplitude of diastolic blood pressure, but the effect was small as was the effect of autogenic training upon the MESOR (a rhythm adjusted mean) and acrophase (a measure of the timing of over-all high values recurring each day). The effect of autogenic training upon the circadian double amplitude of systolic blood pressure suggests its trial as first-line treatment of patients with an excessive circadian blood pressure amplitude, a condition which, even in the absence of an elevated 24-hr, average of blood pressure, is associated with a large increase in the risk of developing ischemic stroke or nephropathy.

  2. A comparison of autogenous bone graft combined with deproteinized bovine bone and autogenous bone graft alone for treatment of alveolar cleft.

    PubMed

    Thuaksuban, N; Nuntanaranont, T; Pripatnanont, P

    2010-12-01

    This study assessed the use of composite autogenous bone and deproteinized bovine bone (DBB) for repairing alveolar cleft compared with autogenous bone alone in terms of clinical outcomes and patient morbidity. 30 patients with a mean age of 10.2±1.7 years were randomly divided into two groups. Group I used autogenous cancellous bone graft harvested from the anterior iliac crests by the conventional trapdoor approach. Group II used a composite of DBB and autogenous cancellous bone harvested by a trephine bone collector; the proportion of 1:1 by volume was used. The bone graft quantities of both groups decreased with time. Their average changes were not statistically different over 24 months after grafting. The canines of both groups could spontaneously or orthodontically erupt through the grafting areas. Patients in group II recovered from uncomfortable walking significantly faster than those in group I (p<0.05) and their duration of hospital stay was significantly shorter than those in group I (p<0.05). The average operation time, intra-operative blood loss and postoperative pain were less in group II than in group I (p>0.05). Copyright © 2010 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

  3. Shrinkage and footage loss from drying 4/4-inch hard maple lumber.

    Treesearch

    Daniel E. Dunmire

    1968-01-01

    Equations are presented for estimating shrinkage and resulting footage losses due to drying hard maple lumber. The equations, based on board shrinkage data taken from a representative lumber sample, are chiefly intended for use with lots of hard maple lumber, such as carloads, truckloads, or kiln loads, but also can be used for estimating the average shrinkage of...

  4. [Comparative study of polymerization shrinkage and related properties of flowable composites and an unfilled resin].

    PubMed

    Bukovinszky, Katalin; Molnár, Lilla; Bakó, József; Szalóki, Melinda; Hegedus, Csaba

    2014-03-01

    The polymerization shrinkage and shrinkage stress of dental composites are in the center of the interest of researchers and manufacturers. It is a great challenge to minimize this important property as low as possible. Many factors are related and are in complicated correlation with each other affecting the polymerization shrinkage. Polymerization shrinkage stress degree of conversion and elasticity has high importance from this aspect. Our aim was to study the polymerization shrinkage and related properties (modulus of elasticity, degree of conversion, shrinkage stress) of three flowable composite (Charisma Opal Flow, SDR, Filtek Ultimate) and an unfilled composite resin. Modulus of elasticity was measured using three point flexure tests on universal testing machine. The polymerization shrinkage stress was determined using bonded-disc technique. The degree of conversion measurements were performed by FT-IR spectroscopy. And the volumetric shrinkage was investigated using Archimedes principle and was measured on analytical balance with special additional equipment. The unfilled resin generally showed higher shrinkage (8,26%), shrinkage stress (0,8 MPa) and degree of conversion (38%), and presented the lowest modulus of elasticity (3047,02MPa). Highest values of unfilled resin correspond to the literature. The lack of fillers enlarges the shrinkage, and the shrinkage stress, but gives the higher flexibility and higher degree of conversion. Further investigations needs to be done to understand and reveal the differences between the composites.

  5. Dynamic correlations between heart and brain rhythm during Autogenic meditation.

    PubMed

    Kim, Dae-Keun; Lee, Kyung-Mi; Kim, Jongwha; Whang, Min-Cheol; Kang, Seung Wan

    2013-01-01

    This study is aimed to determine significant physiological parameters of brain and heart under meditative state, both in each activities and their dynamic correlations. Electrophysiological changes in response to meditation were explored in 12 healthy volunteers who completed 8 weeks of a basic training course in autogenic meditation. Heart coherence, representing the degree of ordering in oscillation of heart rhythm intervals, increased significantly during meditation. Relative EEG alpha power and alpha lagged coherence also increased. A significant slowing of parietal peak alpha frequency was observed. Parietal peak alpha power increased with increasing heart coherence during meditation, but no such relationship was observed during baseline. Average alpha lagged coherence also increased with increasing heart coherence during meditation, but weak opposite relationship was observed at baseline. Relative alpha power increased with increasing heart coherence during both meditation and baseline periods. Heart coherence can be a cardiac marker for the meditative state and also may be a general marker for the meditative state since heart coherence is strongly correlated with EEG alpha activities. It is expected that increasing heart coherence and the accompanying EEG alpha activations, heart brain synchronicity, would help recover physiological synchrony following a period of homeostatic depletion.

  6. Reorganization of the brain and heart rhythm during autogenic meditation.

    PubMed

    Kim, Dae-Keun; Rhee, Jyoo-Hi; Kang, Seung Wan

    2014-01-13

    The underlying changes in heart coherence that are associated with reported EEG changes in response to meditation have been explored. We measured EEG and heart rate variability (HRV) before and during autogenic meditation. Fourteen subjects participated in the study. Heart coherence scores were significantly increased during meditation compared to the baseline. We found near significant decrease in high beta absolute power, increase in alpha relative power and significant increases in lower (alpha) and higher (above beta) band coherence during 3~min epochs of heart coherent meditation compared to 3~min epochs of heart non-coherence at baseline. The coherence and relative power increase in alpha band and absolute power decrease in high beta band could reflect relaxation state during the heart coherent meditation. The coherence increase in the higher (above beta) band could reflect cortico-cortical local integration and thereby affect cognitive reorganization, simultaneously with relaxation. Further research is still needed for a confirmation of heart coherence as a simple window for the meditative state.

  7. Autogenic training: a meta-analysis of clinical outcome studies.

    PubMed

    Stetter, Friedhelm; Kupper, Sirko

    2002-03-01

    Autogenic training (AT) is a self-relaxation procedure by which a psychophysiological determined relaxation response is elicited. A meta-analysis was performed to evaluate the clinical effectiveness of AT. Seventy-three controlled outcome studies were found (published 1952-99). Sixty studies (35 randomized controlled trials [RCT]) qualified for inclusion in the meta-analysis. Medium-to-large effect sizes (ES) occurred for pre-post comparisons of disease-specific AT-effects, with the RCTs showing larger ES. When AT was compared to real control conditions, medium ES were found. Comparisons of AT versus other psychological treatment mostly resulted in no effects or small negative ES. This pattern of results was stable at follow-up. Unspecific AT-effects (i.e., effects on mood, cognitive performance, quality of life, and physiological variables) tended to be even larger than main effects. Separate meta-analyses for different disorders revealed a significant reduction of the heterogeneity of ES. Positive effects (medium range) of AT and of AT versus control in the meta-analysis of at least 3 studies were found for tension headache/migraine, mild-to-moderate essential hypertension, coronary heart disease, asthma bronchiale, somatoform pain disorder (unspecified type), Raynaud's disease, anxiety disorders, mild-to-moderate depression/dysthymia, and functional sleep disorders.

  8. Dynamic correlations between heart and brain rhythm during Autogenic meditation

    PubMed Central

    Kim, Dae-Keun; Lee, Kyung-Mi; Kim, Jongwha; Whang, Min-Cheol; Kang, Seung Wan

    2013-01-01

    This study is aimed to determine significant physiological parameters of brain and heart under meditative state, both in each activities and their dynamic correlations. Electrophysiological changes in response to meditation were explored in 12 healthy volunteers who completed 8 weeks of a basic training course in autogenic meditation. Heart coherence, representing the degree of ordering in oscillation of heart rhythm intervals, increased significantly during meditation. Relative EEG alpha power and alpha lagged coherence also increased. A significant slowing of parietal peak alpha frequency was observed. Parietal peak alpha power increased with increasing heart coherence during meditation, but no such relationship was observed during baseline. Average alpha lagged coherence also increased with increasing heart coherence during meditation, but weak opposite relationship was observed at baseline. Relative alpha power increased with increasing heart coherence during both meditation and baseline periods. Heart coherence can be a cardiac marker for the meditative state and also may be a general marker for the meditative state since heart coherence is strongly correlated with EEG alpha activities. It is expected that increasing heart coherence and the accompanying EEG alpha activations, heart brain synchronicity, would help recover physiological synchrony following a period of homeostatic depletion. PMID:23914165

  9. Sinusfloor elevation and grafting with autogenous iliac crest bone.

    PubMed

    van den Bergh, J P; ten Bruggenkate, C M; Krekeler, G; Tuinzing, D B

    1998-12-01

    Insufficient bone height in the posterior area of the maxilla, due to expansion of the maxillary sinus and atrophic reduction of the alveolar process of the maxilla, represents a contra-indication for insertion of dental implants. This anatomic problem can, in many cases, be solved by augmentation of the floor of the maxillary sinus. This surgical technique was introduced by Tatum. The so-called top hinge door method creates a new floor of the maxillary sinus at a more cranial level. Underneath this new floor the existing space is filled with a bone graft. Implantation in the alveolar process with increased bone height allows insertion of dental implants. This sinus grafting technique was used in the present study. In total, 62 sinusfloor elevations were performed with cancellous iliac bone grafts in 42 patients. In those 62 augmented sinuses, 161 ITI screw type implants were inserted. The follow-up was 1-6 years after implantation. In 2 cases infections occurred. One implant needed an extended integration time. No implants were lost. The ITI solid screw implant appears to be a suitable implant following sinusfloor elevation operations, due to its rough surface, its shape and the size of the thread. The sinusfloor elevation procedure with autogenous cancellous bone graft appears to be a valuable and reliable pre-implantological procedure, provided a proper pre-operative investigation and careful surgery are performed. This procedure allows dental implant placement with a high success rate.

  10. Quantity effect of radial cracks on the cracking propagation behavior and the crack morphology.

    PubMed

    Chen, Jingjing; Xu, Jun; Liu, Bohan; Yao, Xuefeng; Li, Yibing

    2014-01-01

    In this letter, the quantity effect of radial cracks on the cracking propagation behavior as well as the circular crack generation on the impacted glass plate within the sandwiched glass sheets are experimentally investigated via high-speed photography system. Results show that the radial crack velocity on the backing glass layer decreases with the crack number under the same impact conditions during large quantities of repeated experiments. Thus, the "energy conversion factor" is suggested to elucidate the physical relation between the cracking number and the crack propagation speed. Besides, the number of radial crack also takes the determinative effect in the crack morphology of the impacted glass plate. This study may shed lights on understanding the cracking and propagation mechanism in laminated glass structures and provide useful tool to explore the impact information on the cracking debris.

  11. Quantity Effect of Radial Cracks on the Cracking Propagation Behavior and the Crack Morphology

    PubMed Central

    Chen, Jingjing; Xu, Jun; Liu, Bohan; Yao, Xuefeng; Li, Yibing

    2014-01-01

    In this letter, the quantity effect of radial cracks on the cracking propagation behavior as well as the circular crack generation on the impacted glass plate within the sandwiched glass sheets are experimentally investigated via high-speed photography system. Results show that the radial crack velocity on the backing glass layer decreases with the crack number under the same impact conditions during large quantities of repeated experiments. Thus, the “energy conversion factor” is suggested to elucidate the physical relation between the cracking number and the crack propagation speed. Besides, the number of radial crack also takes the determinative effect in the crack morphology of the impacted glass plate. This study may shed lights on understanding the cracking and propagation mechanism in laminated glass structures and provide useful tool to explore the impact information on the cracking debris. PMID:25048684

  12. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Kim, K. S.; Vanstone, R. H.; Malik, S. N.; Laflen, J. H.

    1988-01-01

    A study was performed to examine the applicability of path-independent (P-I) integrals to crack growth problems in hot section components of gas turbine aircraft engines. Alloy 718 was used and the experimental parameters included combined temperature and strain cycling, thermal gradients, elastic-plastic strain levels, and mean strains. A literature review was conducted of proposed P-I integrals, and those capable of analyzing hot section component problems were selected and programmed into the postprocessor of a finite element code. Detailed elastic-plastic finite element analyses were conducted to simulate crack growth and crack closure of the test specimen, and to evaluate the P-I integrals. It was shown that the selected P-I integrals are very effective for predicting crack growth for isothermal conditions.

  13. Elevated temperature crack propagation

    NASA Astrophysics Data System (ADS)

    Orange, Thomas W.

    1994-02-01

    This paper is a summary of two NASA contracts on high temperature fatigue crack propagation in metals. The first evaluated the ability of fairly simple nonlinear fracture parameters to correlate crack propagation. Hastelloy-X specimens were tested under isothermal and thermomechanical cycling at temperatures up to 980 degrees C (1800 degrees F). The most successful correlating parameter was the crack tip opening displacement derived from the J-integral. The second evaluated the ability of several path-independent integrals to correlate crack propagation behavior. Inconel 718 specimens were tested under isothermal, thermomechanical, temperature gradient, and creep conditions at temperatures up to 650 degrees C (1200 degrees F). The integrals formulated by Blackburn and by Kishimoto correlated the data reasonably well under all test conditions.

  14. Elevated temperature crack propagation

    SciTech Connect

    Orange, T.W.

    1994-02-01

    This paper is a summary of two NASA contracts on high temperature fatigue crack propagation in metals. The first evaluated the ability of fairly simple nonlinear fracture parameters to correlate crack propagation. Hastelloy-X specimens were tested under isothermal and thermomechanical cycling at temperatures up to 980 degrees C (1800 degrees F). The most successful correlating parameter was the crack tip opening displacement derived from the J-integral. The second evaluated the ability of several path-independent integrals to correlate crack propagation behavior. Inconel 718 specimens were tested under isothermal, thermomechanical, temperature gradient, and creep conditions at temperatures up to 650 degrees C (1200 degrees F). The integrals formulated by Blackburn and by Kishimoto correlated the data reasonably well under all test conditions.

  15. Ethylene by Naphta Cracking

    ERIC Educational Resources Information Center

    Wiseman, Peter

    1977-01-01

    Presents a discussion of the manufacture of ethylene by thermal cracking of hydrocarbon feedstocks that is useful for introducing the subject of industrial chemistry into a chemistry curriculum. (MLH)

  16. Elevated Temperature Crack Propagation

    NASA Technical Reports Server (NTRS)

    Orange, Thomas W.

    1994-01-01

    This paper is a summary of two NASA contracts on high temperature fatigue crack propagation in metals. The first evaluated the ability of fairly simple nonlinear fracture parameters to correlate crack propagation. Hastelloy-X specimens were tested under isothermal and thermomechanical cycling at temperatures up to 980 degrees C (1800 degrees F). The most successful correlating parameter was the crack tip opening displacement derived from the J-integral. The second evaluated the ability of several path-independent integrals to correlate crack propagation behavior. Inconel 718 specimens were tested under isothermal, thermomechanical, temperature gradient, and creep conditions at temperatures up to 650 degrees C (1200 degrees F). The integrals formulated by Blackburn and by Kishimoto correlated the data reasonably well under all test conditions.

  17. Ethylene by Naphta Cracking

    ERIC Educational Resources Information Center

    Wiseman, Peter

    1977-01-01

    Presents a discussion of the manufacture of ethylene by thermal cracking of hydrocarbon feedstocks that is useful for introducing the subject of industrial chemistry into a chemistry curriculum. (MLH)

  18. Inspecting cracks in foam insulation

    NASA Technical Reports Server (NTRS)

    Cambell, L. W.; Jung, G. K.

    1979-01-01

    Dye solution indicates extent of cracking by penetrating crack and showing original crack depth clearly. Solution comprised of methylene blue in denatured ethyl alcohol penetrates cracks completely and evaporates quickly and is suitable technique for usage in environmental or structural tests.

  19. Inspecting cracks in foam insulation

    NASA Technical Reports Server (NTRS)

    Cambell, L. W.; Jung, G. K.

    1979-01-01

    Dye solution indicates extent of cracking by penetrating crack and showing original crack depth clearly. Solution comprised of methylene blue in denatured ethyl alcohol penetrates cracks completely and evaporates quickly and is suitable technique for usage in environmental or structural tests.

  20. Mechanics of Interface Cracks

    DTIC Science & Technology

    1990-09-27

    tip fields along with a correspondence of these fields to the well characterized small strain (HRR) fields in homogeneous media . In particular, it...crack dimension. Our results showed that for cases involving two elastic-plastic media that the fields, in both materials, are parts of a single...of an geneous media (e.g., Hutchinson, 1983). In one sense the work infinite crack embedded in an infinite bimaterial body (see Fig. complimented

  1. Cracked Plain, Buried Craters

    NASA Technical Reports Server (NTRS)

    2004-01-01

    4 September 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a cracked plain in western Utopia Planitia. The three circular crack patterns indicate the location of three buried meteor impact craters. These landforms are located near 41.9oN, 275.9oW. The image covers an area approximately 3 km (1.9 mi) across. Sunlight illuminates this scene from the lower left.

  2. Three-dimensional numerical simulation of weld solidification cracking

    NASA Astrophysics Data System (ADS)

    Wei, Y. H.; Dong, Z. B.; Liu, R. P.; Dong, Z. J.

    2005-04-01

    It is difficult to measure mechanical strain in the vicinity of a moving weld pool owing to the complex solidification process. Computational modelling of the welding process provides an effective method to study the stress/strain distributions of the weldment. In this paper, the driving force to weld solidification cracking, i.e. mechanical strain versus temperature at the trail of a weld molten pool, was modelled with the three-dimensional finite element analysis procedure. The dynamic stress/strain evolutions that contribute to the formation of solidification cracking have been calculated in the cracking susceptible temperature range. In the mechanical model, solidification effects, namely deformation in the weld pool, change of initial temperature for thermal stress/strain calculation, were treated by means of a dynamic element rebirth scheme. Solidification shrinkage was also taken into consideration in simulation. The results of comparison between the calculated driving force and the experimental measurements of the material resistance predict the susceptibility of solidification cracking.

  3. Numerical model predictions of autogenic fluvial terraces and comparison to climate change expectations

    NASA Astrophysics Data System (ADS)

    Limaye, Ajay B. S.; Lamb, Michael P.

    2016-03-01

    Terraces eroded into sediment (alluvial) and bedrock (strath) preserve an important history of river activity. River terraces are thought to form when a river switches from a period of slow vertical incision and valley widening to fast vertical incision and terrace abandonment. Consequently, terraces are often interpreted to reflect changing external drivers including tectonics, sea level, and climate. In contrast, the intrinsic unsteadiness of lateral migration in rivers may generate terraces even under constant rates of vertical incision without external forcing. To explore this mechanism, we simulate landscape evolution by a vertically incising, meandering river and isolate the age and geometry of autogenic river terraces. Modeled autogenic terraces form for a wide range of lateral and vertical incision rates and are often paired and longitudinally extensive for intermediate ratios of vertical-to-lateral erosion rate. Autogenic terraces have a characteristic reoccurrence time that scales with the time for relief generation. There is a preservation bias against older terraces due to reworking of previously visited parts of the valley. Evolving, spatial differences in bank strength between bedrock and sediment reduce terrace formation frequency and length, favor pairing, and can explain sublinear terrace margins at valley boundaries. Age differences and geometries for modeled autogenic terraces are consistent, in cases, with natural terraces and overlap with metrics commonly attributed to terrace formation due to climate change. We suggest a new phase space of terrace properties that may allow differentiation of autogenic terraces from terraces formed by external drivers.

  4. Pebble treatment and use at Cleveland-Cliffs` autogenous milling operations

    SciTech Connect

    Greenwood, B.R.; McIvor, R.E.

    1996-12-31

    Subsidiaries of Cleveland-Cliffs Inc. operate seven iron mining operations worldwide. Of these seven operations, four North American facilities employ autogenous milling. Two of these autogenous milling circuits are in northern Michigan, the Tilden and Empire Mines, one is in northern Minnesota, Hibbing Taconite, and the fourth is the Wabush Mine in Labrador. The original autogenous milling circuit developed by Cleveland-Cliffs was at the Empire Mine. Extensive laboratory, pilot plant and full-scale testing was conducted prior to commissioning this first iron ore autogenous circuit in 1963. Since the original circuits were installed at the four mines, modifications have been made based on pilot plant and full-scale plant tests that have resulted in significant improvements in primary mill throughputs. The following is a discussion of the autogenous milling circuits at Empire, Tilden and Hibtac and the changes to the circuits related to pebble treatment and use that have been and are scheduled to be made to increase feed rates and/or improve efficiency.

  5. Application of autogenic training for anxiety disorders: a clinical study in a psychiatric setting.

    PubMed

    Sakai, M

    1997-03-01

    The effects of autogenic training for anxiety disorders were investigated in a psychiatric setting of a medical school hospital and the predictors of this treatment outcome were identified. Fifty-five patients who meet the DSM-III-R criteria for anxiety disorders were treated individually with autogenic training by the author from October 1981 to October 1995. The medical records of the patients were investigated retrospectively. The results showed that the autogenic training was successful. Twenty-eight patients (51%) were cured, fourteen (25%) much improved, eight (15%) improved and five (9%) unchanged at the end of the treatment. Forty-two patients (76%) were assessed as having had successful treatment. Pretreatment variables, such as patient's clinical characteristics, did not provide a useful guide to the outcome. Four treatment variables did have a bearing on outcome. First, practicing the second standard autogenic training exercise was a satisfactory predictor of a better outcome. Second, practicing generalization training also was a useful predictor. Third, the application of other behavioral treatment techniques was found to be positively associated with outcome. Fourth, longer treatment periods were associated with a better outcome. These findings suggested that autogenic training could be of significant benefit for the treatment of anxiety disorders.

  6. A clinical study of autogenic training-based behavioral treatment for panic disorder.

    PubMed

    Sakai, M

    1996-03-01

    The present study investigated the effect of autogenic training-based behavioral treatment for panic disorder and identified the predictors of treatment outcome. Thirty-four patients meeting DSM-III-R criteria for panic disorder received autogenic training-based behavioral treatment from October 1981 to December 1994. They were treated individually by the author. The medical records of the patients were investigated for the purpose of this study. The results showed that this autogenic training-based behavioral treatment had successful results. Fifteen patients were cured, nine much improved, five improved, and five unchanged at the end of the treatment. Improvement trends were found as for the severity of panic attack and the severity of agoraphobic avoidance. No consistent findings about predictors emerged when such pretreatment variables as demographics and severity of symptoms were used to predict the outcome. Also, three treatment variables showed useful predictive power. First, practicing the second standard autogenic training exercise satisfactorily predicted better outcomes. Second, application of in vivo exposure was found to be positively associated with the treatment outcome in patients with agoraphobic avoidance. Third, longer treatment periods were associated with better outcomes. These findings suggested that the autogenic training-based behavioral treatment could provide relief to the majority of panic disorder patients.

  7. Modelling of elastoplastic damage in concrete due to desiccation shrinkage

    NASA Astrophysics Data System (ADS)

    Bourgeois, F.; Burlion, N.; Shao, J. F.

    2002-07-01

    We present a numerical modelling of elastoplastic damage due to drying shrinkage of concrete in the framework of mechanics of partially saturated porous media. An elastoplastic model coupled with isotropic damage is first formulated. Two plastic flow mechanisms are involved, controlled by applied stress and suction, respectively. A general concept of net effective stress is used in take into account effects of capillary pressure and material damage on stress-controlled plastic deformation. Damage evolution depends both on elastic and plastic strains. The model's parameters are determined or chosen from relevant experimental data. Comparisons between numerical simulations and experimental data are presented to show the capacity of model to reproduce mains features of concrete behaviour under mechanical loading and during drying shrinkage of concrete. An example of application concerning drying of a concrete wall is finally presented. The results obtained allow to show potential capacity of proposed model for numerical modelling of complex coupling processes in concrete structures.

  8. Glacier shrinkage driving global changes in downstream systems.

    PubMed

    Milner, Alexander M; Khamis, Kieran; Battin, Tom J; Brittain, John E; Barrand, Nicholas E; Füreder, Leopold; Cauvy-Fraunié, Sophie; Gíslason, Gísli Már; Jacobsen, Dean; Hannah, David M; Hodson, Andrew J; Hood, Eran; Lencioni, Valeria; Ólafsson, Jón S; Robinson, Christopher T; Tranter, Martyn; Brown, Lee E

    2017-09-12

    Glaciers cover ∼10% of the Earth's land surface, but they are shrinking rapidly across most parts of the world, leading to cascading impacts on downstream systems. Glaciers impart unique footprints on river flow at times when other water sources are low. Changes in river hydrology and morphology caused by climate-induced glacier loss are projected to be the greatest of any hydrological system, with major implications for riverine and near-shore marine environments. Here, we synthesize current evidence of how glacier shrinkage will alter hydrological regimes, sediment transport, and biogeochemical and contaminant fluxes from rivers to oceans. This will profoundly influence the natural environment, including many facets of biodiversity, and the ecosystem services that glacier-fed rivers provide to humans, particularly provision of water for agriculture, hydropower, and consumption. We conclude that human society must plan adaptation and mitigation measures for the full breadth of impacts in all affected regions caused by glacier shrinkage.

  9. New System of Shrinkage Measurement through Cement Mortars Drying

    PubMed Central

    Morón, Carlos; Saiz, Pablo; Ferrández, Daniel; García-Fuentevilla, Luisa

    2017-01-01

    Cement mortar is used as a conglomerate in the majority of construction work. There are multiple variants of cement according to the type of aggregate used in its fabrication. One of the major problems that occurs while working with this type of material is the excessive loss of moisture during cement hydration (setting and hardening), known as shrinkage, which provokes a great number of construction pathologies that are difficult to repair. In this way, the design of a new sensor able to measure the moisture loss of mortars at different age levels is useful to establish long-term predictions concerning mortar mass volume loss. The purpose of this research is the design and fabrication of a new capacitive sensor able to measure the moisture of mortars and to relate it with the shrinkage. PMID:28272297

  10. Reversible cerebral shrinkage in kwashiorkor: an MRI study.

    PubMed

    Gunston, G D; Burkimsher, D; Malan, H; Sive, A A

    1992-08-01

    Protein energy malnutrition is associated with cerebral atrophy which may be detrimental to intellectual development. The aim of this study was to document the anatomical abnormalities which lead to the appearance of cerebral atrophy using magnetic resonance imaging (MRI) in the acute stage of kwashiorkor and to monitor changes during nutritional rehabilitation. Twelve children aged 6 to 37 months requiring admission to hospital for the treatment of kwashiorkor were studied. The children were evaluated clinically, biochemically, and by MRI of their brains on admission and 30 and 90 days later. Brain shrinkage was present in every child on admission. White and grey matter appeared equally affected and the myelination was normal for age. At 90 days, the cerebral changes had resolved in nine and improved substantially in the remainder, by which time serum proteins and weight for age were within the normal range. The findings of this study suggest that brain shrinkage associated with kwashiorkor reverses rapidly with nutritional rehabilitation.

  11. Sealing of cracks in cement using microencapsulated sodium silicate

    NASA Astrophysics Data System (ADS)

    Giannaros, P.; Kanellopoulos, A.; Al-Tabbaa, A.

    2016-08-01

    Cement-based materials possess an inherent autogenous self-healing capability allowing them to seal, and potentially heal, microcracks. This can be improved through the addition of microencapsulated healing agents for autonomic self-healing. The fundamental principle of this self-healing mechanism is that when cracks propagate in the cementitious matrix, they rupture the dispersed capsules and their content (cargo material) is released into the crack volume. Various healing agents have been explored in the literature for their efficacy to recover mechanical and durability properties in cementitious materials. In these materials, the healing agents are most commonly encapsulated in macrocontainers (e.g. glass tubes or capsules) and placed into the material. In this work, microencapsulated sodium silicate in both liquid and solid form was added to cement specimens. Sodium silicate reacts with the calcium hydroxide in hydrated cement paste to form calcium-silicate-hydrate gel that fills cracks. The effect of microcapsule addition on rheological and mechanical properties of cement is reported. It is observed that the microcapsule addition inhibits compressive strength development in cement and this is observed through a plateau in strength between 28 and 56 days. The improvement in crack-sealing for microcapsule-containing specimens is quantified through sorptivity measurements over a 28 day healing period. After just seven days, the addition of 4% microcapsules resulted in a reduction in sorptivity of up to 45% when compared to specimens without any microcapsule addition. A qualitative description of the reaction between the cargo material and the cementitious matrix is also provided using x-ray diffraction analysis.

  12. Health, Height, Height Shrinkage, and SES at Older Ages: Evidence from China†

    PubMed Central

    Huang, Wei; Lei, Xiaoyan; Ridder, Geert; Strauss, John

    2015-01-01

    In this paper, we build on the literature that examines associations between height and health outcomes of the elderly. We investigate the associations of height shrinkage at older ages with socioeconomic status, finding that height shrinkage for both men and women is negatively associated with better schooling, current urban residence, and household per capita expenditures. We then investigate the relationships between pre-shrinkage height, height shrinkage, and a rich set of health outcomes of older respondents, finding that height shrinkage is positively associated with poor health outcomes across a variety of outcomes, being especially strong for cognition outcomes. PMID:26594311

  13. Visualization study on distortion of a metal frame by polymerization shrinkage and thermal contraction of resin.

    PubMed

    Kakino, Ken; Endo, Kazuhiko; Hashimoto, Masanori; Furuta, Kunihiko; Ohno, Hiroki

    2014-01-01

    Three types of metal specimens (ring-shaped, plate-shaped, and a simulated anterior arch) for distortion observations were made from Au-Ag-Pd-Cu alloy. Distortion due to polymerization shrinkage and thermal contraction of a heat-curing acrylic resin containing 4-META (4-methacryloyloxyethyl trimellitate anhydride, 4-META resin) could be visualized for the ring-shaped specimen, which showed increasing distortion of the metal frame upon adhesion of the resin to the outer metal surface. Distortion of the plateshaped specimen adhering to 4-META resin decreased with increasing thickness of the cured resin. The distortion of the metal frame simulating an anterior arch of a six-unit bridge with a facing composite resin showed that the curvature of the metal frame was larger after curing of the facing composite resin. However, it recovered most of its original curvature with an associated increase in the number of cracks between the crowns after trimming the resin to a tooth profile.

  14. COMPARATIVE ANALYSIS OF THE SHRINKAGE STRESS OF COMPOSITE RESINS

    PubMed Central

    Pereira, Rosana Aparecida; de Araujo, Paulo Amarante; Castañeda-Espinosa, Juan Carlos; Mondelli, Rafael Francisco Lia

    2008-01-01

    The aim of this study was to compare the shrinkage stress of composite resins by three methods. In the first method, composites were inserted between two stainless steel plates. One of the plates was connected to a 20 kgf load cell of a universal testing machine (EMIC-DL-500). In the second method, disk-shaped cavities were prepared in 2-mm-thick Teflon molds and filled with the different composites. Gaps between the composites and molds formed after polymerization were evaluated microscopically. In the third method, the wall-to-wall shrinkage stress of the resins that were placed in bovine dentin cavities was evaluated. The gaps were measured microscopically. Data were analyzed by one-way ANOVA and Tukey's test (α=0.05). The obtained contraction forces were: Grandio = 12.18 ± 0.428N; Filtek Z 250 = 11.80 ± 0.760N; Filtek Supreme = 11.80 ± 0.707 N; and Admira = 11.89 ± 0.647 N. The gaps obtained between composites and Teflon molds were: Filtek Z 250 = 0.51 ± 0.0357%; Filtek Supreme = 0.36 ± 0.0438%; Admira = 0.25 ± 0.0346% and Grandio = 0.16 ± 0.008%. The gaps obtained in wall-to-wall contraction were: Filtek Z 250 = 11.33 ± 2.160 μm; Filtek Supreme = 10.66 ± 1.211μm; Admira = 11.16 ± 2.041 μm and Grandio = 10.50 ± 1.224 μm. There were no significant differences among the composite resins obtained with the first (shrinkage stress generated during polymerization) and third method (wall-to-wall shrinkage). The composite resins obtained with the second method (Teflon method) differed significantly regarding gap formation. PMID:19089286

  15. The role of mutational dynamics in genome shrinkage.

    PubMed

    van Hoek, Milan J A; Hogeweg, Paulien

    2007-11-01

    Genome shrinkage occurs after whole genome duplications (WGDs) and in the evolution of parasitic or symbiotic species. The dynamics of this process, whether it occurs by single gene deletions or also by larger deletions are however unknown. In yeast, genome shrinkage has occurred after a WGD. Using a computational model of genome evolution, we show that in a random genome single gene deletions cannot explain the observed pattern of gene loss in yeast. The distribution of genes deleted per event can be very well described by a geometric distribution, with a mean of 1.1 genes per event. In terms of deletions of a stretch of base pairs, we find that a geometric distribution with an average of 500-600 base pairs per event describes the data very well. Moreover, in the model, as in the data, gene pairs that have a small intergenic distance are more likely to be both deleted. This proves that simultaneous deletion of multiple genes causes the observed pattern of gene deletions, rather than deletion of functionally clustered genes by selection. Furthermore, we found that in the bacterium Buchnera aphidicola larger deletions than in yeast are necessary to explain the clustering of deleted genes. We show that the excess clustering of deleted genes in B. aphidicola can be explained by the clustering of genes in operons. Therefore, we show that selection has little effect on the clustering of deleted genes after the WGD in yeast, while it has during genome shrinkage in B. aphidicola.

  16. Controlled Shrinkage of Expanded Glass Particles in Metal Syntactic Foams

    PubMed Central

    Al-Sahlani, Kadhim; Taherishargh, Mehdi; Kisi, Erich

    2017-01-01

    Metal matrix syntactic foams have been fabricated via counter-gravity infiltration of a packed bed of recycled expanded glass particles (EG) with A356 aluminum alloy. Particle shrinkage was studied and has been utilized to increase the particles’ strength and tailor the mechanical properties of the expanded glass/metal syntactic foam (EG-MSF). The crushing strength of particles could be doubled by shrinking them for 20 min at 700 °C. Owing to the low density of EG (0.20–0.26 g/cm3), the resulting foam exhibits a low density (1.03–1.19 g/cm3) that increases slightly due to particle shrinkage. Chemical and physical analyses of EG particles and the resulting foams were conducted. Furthermore, metal syntactic foam samples were tested in uni-axial compression tests. The stress-strain curves obtained exhibit three distinct regions: elastic deformation followed by a stress plateau and densification commencing at 70–80% macroscopic strain. Particle shrinkage increased the mechanical strength of the foam samples and their average plateau stress increased from 15.5 MPa to 26.7 MPa. PMID:28902158

  17. Controlled Shrinkage of Expanded Glass Particles in Metal Syntactic Foams.

    PubMed

    Al-Sahlani, Kadhim; Taherishargh, Mehdi; Kisi, Erich; Fiedler, Thomas

    2017-09-13

    Metal matrix syntactic foams have been fabricated via counter-gravity infiltration of a packed bed of recycled expanded glass particles (EG) with A356 aluminum alloy. Particle shrinkage was studied and has been utilized to increase the particles' strength and tailor the mechanical properties of the expanded glass/metal syntactic foam (EG-MSF). The crushing strength of particles could be doubled by shrinking them for 20 min at 700 °C. Owing to the low density of EG (0.20-0.26 g/cm³), the resulting foam exhibits a low density (1.03-1.19 g/cm³) that increases slightly due to particle shrinkage. Chemical and physical analyses of EG particles and the resulting foams were conducted. Furthermore, metal syntactic foam samples were tested in uni-axial compression tests. The stress-strain curves obtained exhibit three distinct regions: elastic deformation followed by a stress plateau and densification commencing at 70-80% macroscopic strain. Particle shrinkage increased the mechanical strength of the foam samples and their average plateau stress increased from 15.5 MPa to 26.7 MPa.

  18. Evaluation of the effect of crack closure on fatigue crack growth of simulated short cracks

    NASA Technical Reports Server (NTRS)

    Telesman, J.; Fisher, D. M.

    1984-01-01

    A test program was performed to determine the influence of crack closure on fatigue crack growth (FCG) rates of short cracks. By use of the standard compact tension specimen, test procedures were devised to evaluate closure loads in the wake of the crack behind its tip. The first procedure determined the magnitude of crack closure as a function of the fatigued crack wave by incrementally removing the contacting wake surfaces and measuring closure load at each increment. The second procedure used a low-high loading sequence to simulate short crack behavior. Based on the results, it was concluded that crack closure is not the major reason for the more rapid growth of short cracks as compared to long crack growth.

  19. Evaluation of Aquacel Ag for Autogenous Skin Donor Sites.

    PubMed

    Haith, Linwood R; Stair-Buchmann, Megan E; Ackerman, Bruce H; Herder, Diane; Reigart, Cynthia L; Stoering, Marla; Guilday, Robert E; Patton, Mary Lou; Ross, Kerry M

    2015-01-01

    An ongoing objective of burn research is to evaluate wound dressings and develop new treatments to expedite wound healing. This was a single-center, prospective, randomized, controlled study to evaluate the effectiveness of Aquacel Ag as a dressing for autogenous skin donor sites compared with Xeroform. We hypothesized that donor sites treated with Aquacel Ag would heal faster. Patients were considered for enrollment if they required skin grafting with two donor sites >100 cm at least 2 inches apart. Dressings were observed daily starting on post-op day #2 until discharge and then weekly in the outpatient burn clinic. Assessments evaluated pain, infection, and reapplication. Photographs were taken on post-op day #2, upon "90% re-epithelialization," and at post-op day #30-45. Scar assessments and blinded photographic reviews were completed to assess cosmetic healing. Twenty-nine patients completed the study. Re-epithelialization occurred faster with Xeroform (15.2 days vs. 17.6 days). Daily pain scores were higher with Xeroform (6.72 vs. 5.68) and Aquacel Ag needed to be replaced more often (1.72 times vs. 0.10 times). Three patients developed donor site infections with Aquacel Ag. Scar scores between the donor sites were not statistically significant. The blinded photo review concluded that Xeroform had a better cosmetic outcome (24 vs. 10%). Although patients complained of more pain with Xeroform, it demonstrated shorter healing times and better cosmetic outcomes. Aquacel Ag needed to be replaced more often and represented the only three donor site infections.

  20. Autogenous Regulation of Escherichia coli Polynucleotide Phosphorylase Expression Revisited▿ †

    PubMed Central

    Carzaniga, Thomas; Briani, Federica; Zangrossi, Sandro; Merlino, Giuseppe; Marchi, Paolo; Dehò, Gianni

    2009-01-01

    The Escherichia coli polynucleotide phosphorylase (PNPase; encoded by pnp), a phosphorolytic exoribonuclease, posttranscriptionally regulates its own expression at the level of mRNA stability and translation. Its primary transcript is very efficiently processed by RNase III, an endonuclease that makes a staggered double-strand cleavage about in the middle of a long stem-loop in the 5′-untranslated region. The processed pnp mRNA is then rapidly degraded in a PNPase-dependent manner. Two non-mutually exclusive models have been proposed to explain PNPase autogenous regulation. The earlier one suggested that PNPase impedes translation of the RNase III-processed pnp mRNA, thus exposing the transcript to degradative pathways. More recently, this has been replaced by the current model, which maintains that PNPase would simply degrade the promoter proximal small RNA generated by the RNase III endonucleolytic cleavage, thus destroying the double-stranded structure at the 5′ end that otherwise stabilizes the pnp mRNA. In our opinion, however, the first model was not completely ruled out. Moreover, the RNA decay pathway acting upon the pnp mRNA after disruption of the 5′ double-stranded structure remained to be determined. Here we provide additional support to the current model and show that the RNase III-processed pnp mRNA devoid of the double-stranded structure at its 5′ end is not translatable and is degraded by RNase E in a PNPase-independent manner. Thus, the role of PNPase in autoregulation is simply to remove, in concert with RNase III, the 5′ fragment of the cleaved structure that both allows translation and prevents the RNase E-mediated PNPase-independent degradation of the pnp transcript. PMID:19136586

  1. Autogenous regulation of Escherichia coli polynucleotide phosphorylase expression revisited.

    PubMed

    Carzaniga, Thomas; Briani, Federica; Zangrossi, Sandro; Merlino, Giuseppe; Marchi, Paolo; Dehò, Gianni

    2009-03-01

    The Escherichia coli polynucleotide phosphorylase (PNPase; encoded by pnp), a phosphorolytic exoribonuclease, posttranscriptionally regulates its own expression at the level of mRNA stability and translation. Its primary transcript is very efficiently processed by RNase III, an endonuclease that makes a staggered double-strand cleavage about in the middle of a long stem-loop in the 5'-untranslated region. The processed pnp mRNA is then rapidly degraded in a PNPase-dependent manner. Two non-mutually exclusive models have been proposed to explain PNPase autogenous regulation. The earlier one suggested that PNPase impedes translation of the RNase III-processed pnp mRNA, thus exposing the transcript to degradative pathways. More recently, this has been replaced by the current model, which maintains that PNPase would simply degrade the promoter proximal small RNA generated by the RNase III endonucleolytic cleavage, thus destroying the double-stranded structure at the 5' end that otherwise stabilizes the pnp mRNA. In our opinion, however, the first model was not completely ruled out. Moreover, the RNA decay pathway acting upon the pnp mRNA after disruption of the 5' double-stranded structure remained to be determined. Here we provide additional support to the current model and show that the RNase III-processed pnp mRNA devoid of the double-stranded structure at its 5' end is not translatable and is degraded by RNase E in a PNPase-independent manner. Thus, the role of PNPase in autoregulation is simply to remove, in concert with RNase III, the 5' fragment of the cleaved structure that both allows translation and prevents the RNase E-mediated PNPase-independent degradation of the pnp transcript.

  2. The fate of preserved homograft pericardium and autogenous pericardium within the heart

    PubMed Central

    Clarke, C. P.; Barratt-Boyes, B. G.; Sims, F. H.

    1968-01-01

    Animal experiments were performed to assess the usefulness of preserved homograft pericardium for intracardiac surgery, with particular reference to the problem of homograft mitral valve papillary muscle fixation. The fate of fresh autogenous pericardium was also studied. Both homograft and autogenous pericardium were destroyed and replaced by fibrous tissue. This reaction was faster when the pericardium was in direct contact with the blood stream and slower when it was buried within the myocardium. As homograft pericardium provided a more intense fibrous reaction than autogenous pericardium, it was considered to be very suitable for papillary muscle fixation and less suitable for other intracardiac procedures. The technique used for attaching the papillary muscle of a homograft mitral valve is briefly described. Images PMID:5654067

  3. Cloning and expression of autogenes encoding RNA polymerases of T7-like bacteriophages

    DOEpatents

    Studier, F.W.; Dubendorff, J.W.

    1998-11-03

    This invention relates to the cloning and expression of autogenes encoding RNA polymerases of T7 and T7-like bacteriophages, in which the RNA polymerase gene is transcribed from a promoter which is recognized by the encoded RNA polymerase. Cloning of T7 autogenes was achieved by reducing the activity of the RNA polymerase sufficiently to permit host cell growth. T7 RNA polymerase activity was controlled by combining two independent methods: lac-repression of the recombinant lac operator-T7 promoter in the autogene and inhibition of the polymerase by T7 lysozyme. Expression systems for producing the RNA polymerases of T7 and other T7-like bacteriophages, and expression systems for producing selected gene products are described, as well as other related materials and methods. 12 figs.

  4. Cloning and expression of autogenes encoding RNA polymerases of T7-like bacteriophages

    DOEpatents

    Studier, F.W.; Dubendorff, J.W.

    1998-10-20

    This invention relates to the cloning and expression of autogenes encoding RNA polymerases of T7 and T7-like bacteriophages, in which the RNA polymerase gene is transcribed from a promoter which is recognized by the encoded RNA polymerase. Cloning of T7 autogenes was achieved by reducing the activity of the RNA polymerase sufficiently to permit host cell growth. T7 RNA polymerase activity was controlled by combining two independent methods: lac-repression of the recombinant lac operator-T7 promoter in the autogene and inhibition of the polymerase by T7 lysozyme. Expression systems for producing the RNA polymerases of T7 and other T7-like bacteriophages, and expression systems for producing selected gene products are described, as well as other related materials and methods. 12 figs.

  5. Cloning and expression of autogenes encoding RNA polymerases of T7-like bacteriophages

    DOEpatents

    Studier, F. William; Dubendorff, John W.

    1998-01-01

    This invention relates to the cloning and expression of autogenes encoding RNA polymerases of T7 and T7-like bacteriophages, in which the RNA polymerase gene is transcribed from a promoter which is recognized by the encoded RNA polymerase. Cloning of T7 autogenes was achieved by reducing the activity of the RNA polymerase sufficiently to permit host cell growth. T7 RNA polymerase activity was controlled by combining two independent methods: lac-repression of the recombinant lac operator-T7 promoter in the autogene and inhibition of the polymerase by T7 lysozyme. Expression systems for producing the RNA polymerases of T7 and other T7-like bacteriophages, and expression systems for producing selected gene products are described, as well as other related materials and methods.

  6. Cloning and expression of autogenes encoding RNA poly,erases of T7-like bacteriophages

    DOEpatents

    Studier, F. William; Dubendorff, John W.

    1998-01-01

    This invention relates to the cloning and expression of autogenes encoding RNA polymerases of T7 and T7-like bacteriophages, in which the RNA polymerase gene is transcribed from a promoter which is recognized by the encoded RNA polymerase. Cloning of T7 autogenes was achieved by reducing the activity of the RNA polymerase sufficiently to permit host cell growth. T7 RNA polymerase activity was controlled by combining two independent methods: lac-repression of the recombinant lac operator-T7 promoter in the autogene and inhibition of the polymerase by T7 lysozyme. Expression systems for producing the RNA polymerases of T7 and other T7-like bacteriophages, and expression systems for producing selected gene products are described, as well as other related materials and methods.

  7. Untangling climate signals from autogenic changes in long-term peatland development

    NASA Astrophysics Data System (ADS)

    Morris, Paul J.; Baird, Andy J.; Young, Dylan M.; Swindles, Graeme T.

    2015-12-01

    Peatlands represent important archives of Holocene paleoclimatic information. However, autogenic processes may disconnect peatland hydrological behavior from climate and overwrite climatic signals in peat records. We use a simulation model of peatland development driven by a range of Holocene climate reconstructions to investigate climate signal preservation in peat records. Simulated water-table depths and peat decomposition profiles exhibit homeostatic recovery from prescribed changes in rainfall, whereas changes in temperature cause lasting alterations to peatland structure and function. Autogenic ecohydrological feedbacks provide both high- and low-pass filters for climatic information, particularly rainfall. Large-magnitude climatic changes of an intermediate temporal scale (i.e., multidecadal to centennial) are most readily preserved in our simulated peat records. Simulated decomposition signals are offset from the climatic changes that generate them due to a phenomenon known as secondary decomposition. Our study provides the mechanistic foundations for a framework to separate climatic and autogenic signals in peat records.

  8. Shrinkage processes in standard-size Norway spruce wood specimens with different vulnerability to cavitation

    PubMed Central

    ROSNER, SABINE; KARLSSON, BO; KONNERTH, JOHANNES; HANSMANN, CHRISTIAN

    2011-01-01

    Summary The aim of this study was to observe the radial shrinkage of Norway spruce [Picea abies (L. Karst.)] trunkwood specimens with different hydraulic vulnerability to cavitation from the fully saturated state until the overall shrinkage reaches a stable value, and to relate wood shrinkage and recovery from shrinkage to cavitations of the water column inside the tracheids. Radial shrinkage processes in standard-size sapwood specimens (6 mm × 6 mm × 100 mm; radial, tangential and longitudinal) obtained at different positions within the trunk, representing different ages of the cambium, were compared. Cavitation events were assessed by acoustic emission (AE) testing, hydraulic vulnerability by the AE feature analysis and shrinkage was calculated from the changes in contact pressure between the 150 kHz AE transducer and the wood specimen. Two shrinkage processes were observed in both juvenile (annual rings 1 and 2) and mature wood (annual rings 17–19), the first one termed tension shrinkage and the second one cell wall shrinkage process, which started when most of the tracheids reached relative water contents below fiber saturation. Maximum tension shrinkage coincided with high-energy AEs, and the periods of shrinkage recovery could be traced to tension release due to cavitation. Juvenile wood, which was less sensitive to cavitation, had lower earlywood tracheid diameters and was less prone to deformation due to tensile strain than mature wood, showed a lower cell wall shrinkage, and thus total shrinkage. Earlywood lumen diameters and maximum tension shrinkage were strongly positively related to each other, meaning that bigger tracheids are more prone to deformation at the same water tension than the smaller tracheids. PMID:19797244

  9. Autogenic synthesis of SnO{sub 2} materials and their structural, electrochemical, and optical properties

    SciTech Connect

    Pol, V.G.; Calderon-Moreno, J.M.; Thackeray, M.M.

    2012-12-15

    During autogenic reactions, organometallic precursors are decomposed above their critical temperature within an enclosed chamber at high temperatures and pressures. It has recently been established that such reactions can be used to synthesize carbon-coated metal oxide and metal phosphate nanoparticles. These materials are of interest as electrodes for lithium-ion batteries. In this paper, we report the autogenic fabrication of a carbon-coated SnO{sub 2} product and a carbon-free SnO{sub 2} product after removal of the carbon coating by combustion. The major objectives of the study were to monitor any beneficial effects that carbon-coated electrodes containing a lithium alloying element such as Sn might have in improving the electrical connectivity between electrode particles, which expand and contract significantly on lithiation and delithiation, and their utility in lithium cells. Specifically, we report the compositional, structural and morphological properties, and electrochemical behavior of carbon-coated SnO{sub 2} electrodes. Given the importance of the optical properties of SnO{sub 2}, we also describe the effects of the carbon coating on the optical absorbance and photoluminescence of autogenically-prepared SnO{sub 2} materials. - Graphical abstract: One-step, solvent-free autogenic reactions yield nanosized SnO{sub 2} nanoparticles, uniformly coated and interconnected by 2-4 nm carbon layers, with improved electrochemical performance. Highlights: Black-Right-Pointing-Pointer Distinctive autogenic process synthesized SnO{sub 2} nanoparticles coated with 2-4 nm carbon layers. Black-Right-Pointing-Pointer Carbon coating improved capacity retention and cycling stability of SnO{sub 2} nanoparticles. Black-Right-Pointing-Pointer Carbon coating quenched photoluminescence of SnO{sub 2} component in SnO{sub 2}-C composite. Black-Right-Pointing-Pointer Autogenic approach is extremely versatile, holds promise for designing new nanoarchitectures.

  10. Crack Driving Forces in a Multilayered Coating System for Ceramic Matrix Composite Substrates

    NASA Technical Reports Server (NTRS)

    Ghosn, Louis J.; Zhu, Dongming; Miller, Robert A.

    2005-01-01

    The effects of the top coating thickness, modulus and shrinkage strains on the crack driving forces for a baseline multilayer Yttria-Stabilized-Zirconia/Mullite/Si thermal and environment barrier coating (TEBC) system for SiC/SiC ceramic matrix composite substrates are determined for gas turbine applications. The crack driving forces increase with increasing modulus, and a low modulus thermal barrier coating material (below 10 GPa) will have no cracking issues under the thermal gradient condition analyzed. Since top coating sintering increases the crack driving forces with time, highly sintering resistant coatings are desirable to maintain a low tensile modulus and maintain a low crack driving force with time. Finite element results demonstrated that an advanced TEBC system, such as ZrO2/HfO2, which possesses improved sintering resistance and high temperature stability, exhibited excellent durability. A multi-vertical cracked structure with fine columnar spacing is an ideal strain tolerant coating capable of reducing the crack driving forces to an acceptable level even with a high modulus of 50 GPa.

  11. Autogenous bone graft harvest using reamer irrigator aspirator (RIA) technique for tibiotalocalcaneal arthrodesis.

    PubMed

    Cuttica, Daniel J; DeVries, J George; Hyer, Christopher F

    2010-01-01

    Tibiotalocalcaneal arthrodesis is a technically demanding procedure that can be associated with a high number of complications, including nonunion. Bone grafting is commonly used in arthrodesis procedures to decrease the risk of nonunion. In this article, we describe a technique that uses a reamer-irrigator-aspirator (RIA) method for procurement of autogenous bone graft for use in tibiotalocalcaneal arthrodesis fixated with a retrograde intramedullary nail. Using the RIA technique, autogenous bone graft can be readily obtained without the need for additional incisions and dissection, thereby minimizing the need for additional sources of bone graft.

  12. Autogenous vein graft thrombosis following exposure to calcium-free solutions (calcium paradox).

    PubMed

    Nozick, J H; Farnsworth, P; Montefusco, C M; Parsonnet, V; Ruigrok, T J; Zimmerman, A N

    1981-01-01

    The morphological and functional effects of calcium-free and calcium-containing solutions on canine jugular vein intima were examined under conditions which closely resemble those techniques currently employed in peripheral vascular and aortocoronary bypass surgery. Veins that had been exposed only to calcium-containing solutions remained patent for the duration of the experimental period. Vein perfusion with a calcium-free solution, however, resulted in disruption of the jugular vein intima once calcium ions were reintroduced. Autogenous as a femoral arterial graft became thrombosed within 60 minutes. It is therefore suggested that vein grafts of autogenous origin be irrigated with calcium-containing solutions to prevent intimal damage and thrombosis.

  13. [Predictors of efficiency of autogenous melodeclamation training in patients with chronic somatic pathology].

    PubMed

    Trdatian, N A

    2009-01-01

    This controlled study involving 99 patients with chronic somatic diseases (CSD) had the objective to identify psychological predictors of the efficiency of a new method of psychotherapy, namely autogenous melodeclamation training (AMDT). Dynamics of the psychological status of the patients in the course of therapy was assessed using SMOL test, Spilberger STAI test, overall health-physical activity-mood test, and Beck depression inventory. It was shown that moderately compromised psychological adaptation and minor depressive disorders were the most reliable predictors of marked improvement of the patients' psychological status under effect of autogenous melodeclamation training included in the combined rehabilitative therapy of chronic somatic diseases.

  14. Autogenic-feedback training - A treatment for motion and space sickness

    NASA Technical Reports Server (NTRS)

    Cowings, Patricia S.

    1990-01-01

    A training method for preventing the occurrence of motion sickness in humans, called autogenic-feedback training (AFT), is described. AFT is based on a combination of biofeedback and autogenic therapy which involves training physiological self-regulation as an alternative to pharmacological management. AFT was used to reliably increase tolerance to motion-sickness-inducing tests in both men and women ranging in age from 18 to 54 years. The effectiveness of AFT is found to be significantly higher than that of protective adaptation training. Data obtained show that there is no apparent effect from AFT on measures of vestibular perception and no side effects.

  15. Intermittent crack growth in fatigue

    NASA Astrophysics Data System (ADS)

    Kokkoniemi, R.; Miksic, A.; Ovaska, M.; Laurson, L.; Alava, M. J.

    2017-07-01

    Fatigue occurs under cyclic loading at stresses below a material’s static strength limit. We consider fatigue crack growth as a stochastic process and perform crack growth experiments in a metal (copper). We follow optically cracks propagating from initial edge notches. The main interest is in the dynamics of the crack growth—the Paris’ law and the initiation phase prior to that—and especially the intermittency this is discovered to display. How the sampling of the crack advancement, performed at regular intervals, influences such measurement results is analysed by the analogy of planar crack dynamics in slow, driven growth.

  16. Crack propagation in Hastelloy X

    SciTech Connect

    Weerasooriya, T.; Strizak, J.P.

    1980-05-01

    The fatigue and creep crack growth rates of Hastelloy X were examined both in air and impure helium. Creep crack growth rate is higher in air and impure helium at 650/sup 0/C. Initial creep crack growth from the original sharp fatigue crack is by an intergranular mode of fracture. As the cracking accelerates at higher stress intensities, growth is by a mixed mode of both intergranular and transgranular fracture. Fatigue crack growth rate increases with increasing temperature and decreasing frequency for the range of stress intensities reported in the literature and is lower in impure helium than in air.

  17. A Model for Prediction of Shrinkage Defects in Long and Short Freezing Range Materials

    SciTech Connect

    Reis, A.; Duarte, J. F.; Santos, A. D.; Magalhaes, A. B.; Houbaert, Y.

    2007-05-17

    The aim of the model presented in this paper is to capture the difference in solidification behaviour of long and short freezing materials. The shrinkage defects in short freezing materials tends to be internal, as porosity, while in long freezing materials these defects tend to be external in the form of surface depressions. To achieve this, a pressure drop based 3-D feeding flow model has been developed to evaluate shrinkage defects for casting alloys. A continuum formulation is used to describe the transport of mass, energy and momentum. It is assumed that during solidification the driving force for flow is shrinkage. A Darcy type source term has been included in the momentum equation to account for flow resistance in the mushy zone. A VOF free surface model has been used to describe shrinkage defects, i.e., external surface depressions and internal shrinkage porosities, while ensuring mass conservation. The model is used to calculate the shrinkage in a simple casting. The results shows internal and outside shrinkage defects depending on the freezing range of the metal. Short freezing range results mainly in internal shrinkage whereas the long freezing range results in external shrinkage. The expected shrinkage features are well described by the present model.

  18. A Model for Prediction of Shrinkage Defects in Long and Short Freezing Range Materials

    NASA Astrophysics Data System (ADS)

    Reis, A.; Xu, Zhi an; Duarte, J. F.; Santos, A. D.; Houbaert, Y.; Magalhães, A. B.

    2007-05-01

    The aim of the model presented in this paper is to capture the difference in solidification behaviour of long and short freezing materials. The shrinkage defects in short freezing materials tends to be internal, as porosity, while in long freezing materials these defects tend to be external in the form of surface depressions. To achieve this, a pressure drop based 3-D feeding flow model has been developed to evaluate shrinkage defects for casting alloys. A continuum formulation is used to describe the transport of mass, energy and momentum. It is assumed that during solidification the driving force for flow is shrinkage. A Darcy type source term has been included in the momentum equation to account for flow resistance in the mushy zone. A VOF free surface model has been used to describe shrinkage defects, i.e., external surface depressions and internal shrinkage porosities, while ensuring mass conservation. The model is used to calculate the shrinkage in a simple casting. The results shows internal and outside shrinkage defects depending on the freezing range of the metal. Short freezing range results mainly in internal shrinkage whereas the long freezing range results in external shrinkage. The expected shrinkage features are well described by the present model.

  19. Effect of modulated photo-activation on polymerization shrinkage behavior of dental restorative resin composites.

    PubMed

    Tauböck, Tobias T; Feilzer, Albert J; Buchalla, Wolfgang; Kleverlaan, Cornelis J; Krejci, Ivo; Attin, Thomas

    2014-08-01

    This study investigated the influence of modulated photo-activation on axial polymerization shrinkage, shrinkage force, and hardening of light- and dual-curing resin-based composites. Three light-curing resin composites (SDR bulk-fill, Esthet X flow, and Esthet X HD) and one dual-curing material (Rebilda DC) were subjected to different irradiation protocols with identical energy density (27 J cm(-2) ): high-intensity continuous light (HIC), low-intensity continuous light (LIC), soft-start (SS), and pulse-delay curing (PD). Axial shrinkage and shrinkage force of 1.5-mm-thick specimens were recorded in real time for 15 min using custom-made devices. Knoop hardness was determined at the end of the observation period. Statistical analysis revealed no significant differences among the curing protocols for both Knoop hardness and axial shrinkage, irrespective of the composite material. Pulse-delay curing generated the significantly lowest shrinkage forces within the three light-curing materials SDR bulk-fill, Esthet X flow, and Esthet X HD. High-intensity continuous light created the significantly highest shrinkage forces within Esthet X HD and Rebilda DC, and caused significantly higher forces than LIC within Esthet X flow. In conclusion, both the composite material and the applied curing protocol control shrinkage force formation. Pulse-delay curing decreases shrinkage forces compared with high-intensity continuous irradiation without affecting hardening and axial polymerization shrinkage. © 2014 Eur J Oral Sci.

  20. Catalytic cracking process

    SciTech Connect

    Aufdembrink, B.A.; Degnan, T.F.; Kresge, C.T.

    1990-01-23

    This patent describes a process for catalytically cracking a petroleum fraction to lighter hydrocarbons. The process comprises providing a feedstock containing a petroleum fraction and then contacting the feedstock with a catalyst under catalytic cracking conditions. The catalyst composition includes a titanometallate layered metal oxide material comprising a layered metal oxide material comprising a layered metal oxide and pillars of a chalcogenide of at least one element selected from Groups IB, IIB, IIIA, IIIB, IVB, VA, VB, VIA, VIIA and VIIIA of the Periodic Table of Elements separating the layers of the metal oxides.

  1. Method for Assessment of Changes in the Width of Cracks in Cement Composites with Use of Computer Image Processing and Analysis

    NASA Astrophysics Data System (ADS)

    Tomczak, Kamil; Jakubowski, Jacek; Fiołek, Przemysław

    2017-06-01

    Crack width measurement is an important element of research on the progress of self-healing cement composites. Due to the nature of this research, the method of measuring the width of cracks and their changes over time must meet specific requirements. The article presents a novel method of measuring crack width based on images from a scanner with an optical resolution of 6400 dpi, subject to initial image processing in the ImageJ development environment and further processing and analysis of results. After registering a series of images of the cracks at different times using SIFT conversion (Scale-Invariant Feature Transform), a dense network of line segments is created in all images, intersecting the cracks perpendicular to the local axes. Along these line segments, brightness profiles are extracted, which are the basis for determination of crack width. The distribution and rotation of the line of intersection in a regular layout, automation of transformations, management of images and profiles of brightness, and data analysis to determine the width of cracks and their changes over time are made automatically by own code in the ImageJ and VBA environment. The article describes the method, tests on its properties, sources of measurement uncertainty. It also presents an example of application of the method in research on autogenous self-healing of concrete, specifically the ability to reduce a sample crack width and its full closure within 28 days of the self-healing process.

  2. Exploiting tumor shrinkage through temporal optimization of radiotherapy

    NASA Astrophysics Data System (ADS)

    Unkelbach, Jan; Craft, David; Hong, Theodore; Papp, Dávid; Ramakrishnan, Jagdish; Salari, Ehsan; Wolfgang, John; Bortfeld, Thomas

    2014-06-01

    In multi-stage radiotherapy, a patient is treated in several stages separated by weeks or months. This regimen has been motivated mostly by radiobiological considerations, but also provides an approach to reduce normal tissue dose by exploiting tumor shrinkage. The paper considers the optimal design of multi-stage treatments, motivated by the clinical management of large liver tumors for which normal liver dose constraints prohibit the administration of an ablative radiation dose in a single treatment. We introduce a dynamic tumor model that incorporates three factors: radiation induced cell kill, tumor shrinkage, and tumor cell repopulation. The design of multi-stage radiotherapy is formulated as a mathematical optimization problem in which the total dose to the normal tissue is minimized, subject to delivering the prescribed dose to the tumor. Based on the model, we gain insight into the optimal administration of radiation over time, i.e. the optimal treatment gaps and dose levels. We analyze treatments consisting of two stages in detail. The analysis confirms the intuition that the second stage should be delivered just before the tumor size reaches a minimum and repopulation overcompensates shrinking. Furthermore, it was found that, for a large range of model parameters, approximately one-third of the dose should be delivered in the first stage. The projected benefit of multi-stage treatments in terms of normal tissue sparing depends on model assumptions. However, the model predicts large dose reductions by more than a factor of 2 for plausible model parameters. The analysis of the tumor model suggests that substantial reduction in normal tissue dose can be achieved by exploiting tumor shrinkage via an optimal design of multi-stage treatments. This suggests taking a fresh look at multi-stage radiotherapy for selected disease sites where substantial tumor regression translates into reduced target volumes.

  3. Effect of a weightlifting belt on spinal shrinkage.

    PubMed Central

    Bourne, N D; Reilly, T

    1991-01-01

    Spinal loading during weightlifting results in a loss of stature which has been attributed to a decrease in height of the intervertebral discs--so-called 'spinal shrinkage'. Belts are often used during the lifting of heavy weights, purportedly to support, stabilize and thereby attenuate the load on the spine. The purpose of this study was to examine the effects of a standard weightlifting belt in attenuating spinal shrinkage. Eight male subjects with a mean age of 24.8 years performed two sequences of circuit weight-training, one without a belt and on a separate occasion with a belt. The circuit training regimen consisted of six common weight-training exercises. These were performed in three sets of ten with a change of exercise after each set of ten repetitions. A stadiometer sensitive to within 0.01 mm was used to record alterations in stature. Measurements of stature were taken before and after completion of the circuit. The absolute visual analogue scale (AVAS) was used to measure the discomfort and pain intensity resulting from each of the two conditions. The circuit weight-training caused stature losses of 3.59mm without the belt and 2.87 mm with the belt (P greater than 0.05). The subjects complained of significantly less discomfort when the belt was worn (P less than 0.05). The degree of shrinkage was significantly correlated (r = 0.752, P less than 0.05) with perceived discomfort but only when the belt was not worn. These results suggest the potential benefits of wearing a weightlifting belt and support the hypothesis that the belt can help in stabilizing the trunk. Images Figure 1 PMID:1810615

  4. Polymerization shrinkage of flowable resin-based restorative materials.

    PubMed

    Stavridakis, Minos M; Dietschi, Didier; Krejci, Ivo

    2005-01-01

    This study measured the linear polymerization displacement and polymerization forces induced by polymerization shrinkage of a series of flowable resin-based restorative materials. The materials tested were 22 flowable resin-based restorative materials (Admira Flow, Aelite Flow, Aeliteflow LV, Aria, Crystal Essence, Definite Flow, Dyract Flow, Filtek Flow, FloRestore, Flow-it, Flow-Line, Freedom, Glacier, OmegaFlo, PermaFlo, Photo SC, Revolution 2, Star Flow, Synergy Flow, Tetric Flow, Ultraseal XT and Wave). Measurements for linear polymerization displacement and polymerization forces were performed using custom made measuring devices. Polymerization of the test materials was carried out for 60 seconds by means of a light curing unit, and each property was measured for 180 seconds from the start of curing in eight specimens for each material. Statistical evaluation of the data was performed with one-way analysis of variance (ANOVA), Tukey's Studentized Range (HSD) test (p=0.05) and simple linear regression. A wide range of values was recorded for linear polymerization displacement (26.61 to 80.74 microns) and polymerization forces (3.23 to 7.48 kilograms). Statistically significant differences among materials were found for both properties studied. Very few materials (Freedom, Glacier, and Photo SC) presented low values of linear polymerization displacement and polymerization forces (similar to hybrid resin composites), while the majority of materials presented very high values in both properties studied. Study of the shrinkage kinetics revealed the exponential growth process of both properties. The polymerization forces development exhibited a few seconds delay over linear polymerization displacement. Simple linear regression showed that the two polymerization shrinkage properties that were studied were not highly correlated (r2=0.59).

  5. Laser guide star spot shrinkage for affordable wavefront sensors

    NASA Astrophysics Data System (ADS)

    Jahn, Wilfried; Hugot, Emmanuel; Fusco, Thierry; Neichel, Benoit; Ferrari, Marc; Correia, Carlos; Pueyo, Laurent; Dohlen, Kjetil; Pascal, Sandrine; Vola, Pascal; Sauvage, Jean-François; El Hadi, Kacem; Gach, Jean Luc

    2016-07-01

    Innovative optical designs allow tackling the spot elongation issues in Shack-Hartman based laser guide star wavefront sensors. We propose two solutions using either a combination of two arrays of freeform microlenses, or a combination of freeform optics, to perform a shrinkage of the laser spots as well as a magnification of the SH focal plane. These approaches will drastically reduce the number of needed pixels, thus making possible the use of existing detectors. We present the recent advances on this activity as well as the estimation of performance, linearity and sensitivity of the compressed system in presence of aberrations.

  6. Sonar target enhancement by shrinkage of incoherent wavelet coefficients.

    PubMed

    Hunter, Alan J; van Vossen, Robbert

    2014-01-01

    Background reverberation can obscure useful features of the target echo response in broadband low-frequency sonar images, adversely affecting detection and classification performance. This paper describes a resolution and phase-preserving means of separating the target response from the background reverberation noise using a coherence-based wavelet shrinkage method proposed recently for de-noising magnetic resonance images. The algorithm weights the image wavelet coefficients in proportion to their coherence between different looks under the assumption that the target response is more coherent than the background. The algorithm is demonstrated successfully on experimental synthetic aperture sonar data from a broadband low-frequency sonar developed for buried object detection.

  7. Crack-free conditions in welding of glass by ultrashort laser pulse.

    PubMed

    Miyamoto, Isamu; Cvecek, Kristian; Schmidt, Michael

    2013-06-17

    The spatial distribution of the laser energy absorbed by nonlinear absorption process in bulk glass w(z) is determined and thermal cycles due to the successive ultrashort laser pulse (USLP) is simulated using w(z) based on the transient thermal conduction model. The thermal stress produced in internal melting of bulk glass by USLP is qualitatively analyzed based on a simple thermal stress model, and crack-free conditions are studied in glass having large coefficient of thermal expansion. In heating process, cracks are prevented when the laser pulse impinges into glass with temperatures higher than the softening temperature of glass. In cooling process, shrinkage stress is suppressed to prevent cracks, because the embedded molten pool produced by nonlinear absorption process behaves like an elastic body under the compressive stress field unlike the case of CW-laser welding where the molten pool having a free surface produced by linear absorption process is plastically deformed under the compressive stress field.

  8. Collar crack of birch

    Treesearch

    Alex L. Shigo

    1964-01-01

    The name "Collar crack" is suggested for a condition of birches observed in the past 4 years during field studies of forest disease problems in the White Mountains of New Hampshire. The first close observations of this condition were made during the summer of 1963. This is a report on those observations and an explanation of the possible cause.

  9. Cracking the Credit Hour

    ERIC Educational Resources Information Center

    Laitinen, Amy

    2012-01-01

    The basic currency of higher education--the credit hour--represents the root of many problems plaguing America's higher education system: the practice of measuring time rather than learning. "Cracking the Credit Hour" traces the history of this time-based unit, from the days of Andrew Carnegie to recent federal efforts to define a credit…

  10. Autogenic Training and Hand Temperature Biofeedback in the Treatment of Migraine: A Preliminary Analysis.

    ERIC Educational Resources Information Center

    Jessup, B.; And Others

    The possibility of alleviating migraine headaches by autogenic relaxation training, with or without hand temperature biofeedback, was assessed. The study examined five independent groups in a bi-directional control group design. Volunteer migraine sufferers served as subjects, each participating for 12 weeks. The first four weeks of the study were…

  11. The use of hydroxyapatite and autogenous cancellous bone grafts to repair bone defects in rats.

    PubMed

    Silva, R V; Camilli, J A; Bertran, C A; Moreira, N H

    2005-03-01

    Bone grafts are frequently used in the treatment of bone defects. Bone harvesting can cause postoperative complications and sometimes does not provide a sufficient quantity of bone. Therefore, synthetic biomaterials have been investigated as an alternative to autogenous bone grafts. The objective of this study was to evaluate the repair of bone defects by autogenous cancellous bone grafts or porous bioceramic discs of hydroxyapatite/phosphate cement mixture. Two 5-mm diameter defects were made in the skulls of rats and filled with the bioceramic material or cancellous bone. The rats were sacrificed 2, 4, 8 and 24 weeks after surgery and tissue samples were analyzed by radiography and histology. By the 24th week, the defects filled with autogenous cancellous bone grafts or bioceramic material showed similar volumes of bone tissue within the defect. However, defects treated with bioceramic material were almost completely closed as a result of the joining of ceramic fragments and the neoformed bone tissue, while those filled with autogenous grafts showed several areas filled with connective tissue. These results indicated that the osteointegration of bioceramic fragments allowed the reconstruction of parietal bone defects without the need for a bone graft.

  12. Clinical evaluation of ridge augmentation using autogenous tooth bone graft material: case series study.

    PubMed

    Lee, Ji-Young; Kim, Young-Kyun; Yi, Yang-Jin; Choi, Joon-Ho

    2013-08-01

    Interest in bone graft material has increased with regard to restoration in cases of bone defect around the implant. Autogenous tooth bone graft material was developed and commercialized in 2008. In this study, we evaluated the results of vertical and horizontal ridge augmentation with autogenous tooth bone graft material. This study targeted patients who had vertical or horizontal ridge augmentation using AutoBT from March 2009 to April 2010. We evaluated the age and gender of the subject patients, implant stability, adjunctive surgery, additional bone graft material and barrier membrane, post-operative complication, implant survival rate, and crestal bone loss. We performed vertical and horizontal ridge augmentation using powder- or block-type autogenous tooth bone graft material, and implant placement was performed on nine patients (male: 7, female: 2). The average age of patients was 49.88±12.98 years, and the post-operative follow-up period was 35±5.31 months. Post-operative complications included wound dehiscence (one case), hematoma (one case), and implant osseointegration failure (one case; survival rate: 96%); however, there were no complications related to bone graft material, such as infection. Average marginal bone loss after one-year loading was 0.12±0.19 mm. Therefore, excellent clinical results can be said to have been obtained. Excellent clinical results can be said to have been obtained with vertical and horizontal ridge augmentation using autogenous tooth bone graft material.

  13. Distinguishing allogenic from autogenic causes of bed elevation change in late Quaternary alluvial stratigraphic records

    NASA Astrophysics Data System (ADS)

    Daniels, J. Michael

    2008-10-01

    Allogenic and autogenic mechanisms both cause changes in the bed elevation of rivers and thereby influence the characteristics of alluvial stratigraphic records (ASRs). Allogenic forcing mechanisms can be grouped into five categories whose relative influence varies with timescale: climate, tectonism, base level, land use/land cover and direct human modification of channels. Late Quaternary ASRs are influenced by the greatest range of allogenic forcing variables with climate among the most important. Autogenic mechanisms of bed elevation change are ubiquitous throughout fluvial systems and are always time-transgressive. Autogenic bed elevation change propagates through drainage networks at predictable rates and results in a time-space envelope within which its effects are capable of operating. ASRs that can be correlated over geographical areas large enough and time intervals small enough to exist outside this envelope most likely result from allogenic forcing. This formulation represents a quantitative and geographic set of threshold criteria for distinguishing between autogenic and allogenic mechanisms. Over late Quaternary timescales (10 2 to 10 5 years) in tectonically stable regions climate change is the dominant allogenic mechanism and, therefore, the first-order control on the morphology, sedimentology, pedologic characteristics and chronology of alluvial stratigraphic records that meet or exceed the threshold criteria for demonstrating allogenic causality.

  14. Trait- and density-mediated indirect interactions initiated by an exotic invasive plant autogenic ecosystem engineer.

    PubMed

    Pearson, Dean E

    2010-10-01

    Indirect interactions are important for structuring ecological systems. However, research on indirect effects has been heavily biased toward top-down trophic interactions, and less is known about other indirect-interaction pathways. As autogenic ecosystem engineers, plants can serve as initiators of nontrophic indirect interactions that, like top-down pathways, can involve both trait-mediated indirect interactions (TMIIs) and density-mediated indirect interactions (DMIIs). Using microcosms, I examined a plant --> predator --> consumer interaction pathway involving the exotic autogenic ecosystem engineer Centaurea maculosa; native Dictyna spiders (which exhibit density and trait [web-building] responses to C. maculosa); Dictyna's insect prey, Urophora affinis; and Urophora's host plant (a secondary receiver species) to quantify DMIIs and TMIIs in an autogenic engineered pathway. Both DMIIs and TMIIs were strong enough to reduce Urophora populations, but only DMIIs, which were 4.3 times stronger than TMIIs, were strong enough to also reduce Urophora's fecundity and increase the fecundity of its host plant. Prior field studies support these results, suggesting that the differences between DMIIs and TMIIs are even stronger in nature. This study illustrates that autogenic ecosystem engineers can initiate powerful indirect interactions that generally parallel predator-initiated interactions but also differ in important functional ways.

  15. Autogenic Feedback Training (Body Fortran) with Biofeedback and the Computer for Self-Improvement and Change.

    ERIC Educational Resources Information Center

    Cassel, Russell N.; Sumintardja, Elmira Nasrudin

    1983-01-01

    Describes autogenic feedback training, which provides the basis whereby an individual is able to improve on well being through use of a technique described as "body fortran," implying that you program self as one programs a computer. Necessary requisites are described including relaxation training and the management of stress. (JAC)

  16. Autogenic Feedback Training (Body FORTRAN) for Musically Gifted Students at Bonita Vista High School.

    ERIC Educational Resources Information Center

    Lane, John M.

    1982-01-01

    The Gifted Self-Understanding Assessment Battery (GSAB) was given to 34 (27 females, 7 males) music students (aged 15-17) at Bonita Vista High School in Chula Vista (California). Biofeedback training and assessment were followed by individual counseling for Autogenic Feedback Training (AFT) to achieve improvement of the individual's own well…

  17. Osteogenesis and ototoxicity of a novel preparation of autogenous bone cement: implications for mastoid obliteration.

    PubMed

    Zou, Wenting; Chen, Xihui

    2014-12-01

    To study the osteogenesis and ototoxicity of autogenous bone cement. A randomized, prospective, controlled animal study. University laboratory. We created a critical defect on the bulla wall of guinea pigs. Fifty-three guinea pigs were divided into 3 groups. The defects were filled with autogenous bone cement (ABC) or autogenous bone dust (ABD) on the left side while the contralateral sides were kept intact as the blank control (BC) group or a defect was induced without obliteration as the operation control (OC) group (groups 1 and 2, n = 25 each). The animals were sacrificed at 2, 4, 8, and 12 weeks postoperatively. Group 3 (n = 3) was the ototoxicity positive control (OPC) group. The critical defects were evaluated for bone repair by histologic observation and computed tomography (CT), and the ototoxicity of the material was assessed by measuring shifts in the hearing threshold and changes in cochlear morphology. Antibiotic susceptibility testing of the material was also performed. Histologic observation and CT scans revealed complete bone repair in the ABC group at 12 weeks postoperatively, but progress was slower in the ABD group. The hearing threshold and cochlear morphology did not differ significantly between the preoperative and 12-week postoperative measurement. Autogenous bone dust inhibited some of the bacterial species commonly associated with chronic suppurative otitis media. Animals treated with ABC exhibited osteogenesis, with no ototoxicity and bacteriostasis compared with the use of ABD. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2014.

  18. Long-term follow-up of autogenous tooth bone graft blocks with dental implants.

    PubMed

    Kim, Young-Kyun; Pang, Kang-Mi; Yun, Pil-Young; Leem, Dae-Ho; Um, In-Woong

    2017-02-01

    Demineralized dentin matrix block (ABTB: Autogenous Tooth Bone Graft Block) is 3-D scaffold with same components and geometry with alveolar bone. ABTB is well incorporated and remodelled into cortico-cancellous bone with dental implant. The shape and volume were maintained with little marginal bone loss after average 44 months of follow-up.

  19. Autogenic Feedback Training (Body Fortran) with Biofeedback and the Computer for Self-Improvement and Change.

    ERIC Educational Resources Information Center

    Cassel, Russell N.; Sumintardja, Elmira Nasrudin

    1983-01-01

    Describes autogenic feedback training, which provides the basis whereby an individual is able to improve on well being through use of a technique described as "body fortran," implying that you program self as one programs a computer. Necessary requisites are described including relaxation training and the management of stress. (JAC)

  20. Irreversible optical clearing of rabbit dermis for autogenic corneal stroma transplantation.

    PubMed

    Tanaka, Yuji; Shi, Dong; Kubota, Akira; Takano, Yoshimasa; Fuse, Nobuo; Yamato, Masayuki; Okano, Teruo; Nishida, Kohji

    2011-10-01

    Tissue engineering and transplantation of autogenic grafts have been widely investigated for solving problems on current allograft treatments (i.g., donor shortage and rejection). However, it is difficult to obtain an autogenic corneal stromal replacement that is composed of transparent, tough, and thick collagen constructs by current cell culture-based tissue engineering. Aim of this study is to develop transparent dermis for an autogenic corneal stroma transplantation. This study examined dehydration at 4-8°C and carbodiimide cross-linking on cloudy rabbit dermis (approx. 1.8%-3.8% light transmittance at 550 nm) for dermis optical clearing. Transparency of dehydrated rabbit dermis was founded to be approx. 37.9%-41.4% at 550 nm. Additional cross-linking treatment on dehydrated dermis prevented from swelling and clouding in saline, and improved its transparency to be 56.9% at 550 nm. Rabbit corneal epithelium was found to regenerate on optically cleared dermis in vitro. Furthermore, no abnormal biological response (i.e., inflammation, vascularization, and the barrier defect of epithelia) or no optical functional change on optically cleared dermis was observed during its 4-week autogenic transplantation into rabbit corneal stromal pocket.

  1. Reduction of titanium dioxide to metallic titanium conducted under the autogenic pressure of the reactants.

    PubMed

    Eshed, Michal; Irzh, Alexander; Gedanken, Aharon

    2009-08-03

    We report on a reaction to convert titanium dioxide to titanium. The reduction reaction was done under the autogenic pressure of the reactants at 750 degrees C for 5 h. The MgO, a by-product, was removed by acids to obtain pure metallic titanium.

  2. Self-reinnervated muscles lose autogenic length feedback, but intermuscular feedback can recover functional connectivity.

    PubMed

    Lyle, Mark A; Prilutsky, Boris I; Gregor, Robert J; Abelew, Thomas A; Nichols, T Richard

    2016-09-01

    In this study, we sought to identify sensory circuitry responsible for motor deficits or compensatory adaptations after peripheral nerve cut and repair. Self-reinnervation of the ankle extensor muscles abolishes the stretch reflex and increases ankle yielding during downslope walking, but it remains unknown whether this finding generalizes to other muscle groups and whether muscles become completely deafferented. In decerebrate cats at least 19 wk after nerve cut and repair, we examined the influence of quadriceps (Q) muscles' self-reinnervation on autogenic length feedback, as well as intermuscular length and force feedback, among the primary extensor muscles in the cat hindlimb. Effects of gastrocnemius and soleus self-reinnervation on intermuscular circuitry were also evaluated. We found that autogenic length feedback was lost after Q self-reinnervation, indicating that loss of the stretch reflex appears to be a generalizable consequence of muscle self-reinnervation. However, intermuscular force and length feedback, evoked from self-reinnervated muscles, was preserved in most of the interactions evaluated with similar relative inhibitory or excitatory magnitudes. These data indicate that intermuscular spinal reflex circuitry has the ability to regain functional connectivity, but the restoration is not absolute. Explanations for the recovery of intermuscular feedback are discussed, based on identified mechanisms responsible for lost autogenic length feedback. Functional implications, due to permanent loss of autogenic length feedback and potential for compensatory adaptations from preserved intermuscular feedback, are discussed.

  3. Differentiation of human embryonic stem cells into clinically amenable keratinocytes in an autogenic environment.

    PubMed

    Kidwai, Fahad K; Liu, Hua; Toh, Wei Seong; Fu, Xin; Jokhun, Doorgesh S; Movahednia, Mohammad M; Li, Mingming; Zou, Yu; Squier, Christopher A; Phan, Toan T; Cao, Tong

    2013-03-01

    Human embryonic stem cells (hESCs)-derived keratinocytes hold great clinical and research potential. However, the current techniques are hampered by the use of xenogenic components that limits their clinical application. Here we demonstrated an efficient differentiation of H9 hESCs (H9-hESCs) into keratinocytes (H9-Kert) with the minimum use of animal-derived materials. For differentiation, we established two microenvironment systems originated from H9-hESCs (autogenic microenvironment). These autogenic microenvironment systems consist of an autogenic coculture system (ACC) and an autogenic feeder-free system (AFF). In addition, we showed a stage-specific effect of Activin in promoting keratinocyte differentiation from H9-hESCs while repressing the expression of early neural markers in the ACC system. Furthermore, we also explained the effect of Activin in construction of the AFF system made up of extracellular matrix similar to basement membrane extracted from H9-hESC-derived fibroblasts. H9-Kert differentiated in both systems expressed keratinocyte markers at mRNA and protein levels. H9-Kert were also able to undergo terminal differentiation in high Ca(2+) medium. These findings support the transition toward the establishment of an animal-free microenvironment for successful differentiation of hESCs into keratinocytes for potential clinical application.

  4. Autogenic Feedback Training (Body FORTRAN) for Musically Gifted Students at Bonita Vista High School.

    ERIC Educational Resources Information Center

    Lane, John M.

    1982-01-01

    The Gifted Self-Understanding Assessment Battery (GSAB) was given to 34 (27 females, 7 males) music students (aged 15-17) at Bonita Vista High School in Chula Vista (California). Biofeedback training and assessment were followed by individual counseling for Autogenic Feedback Training (AFT) to achieve improvement of the individual's own well…

  5. Apparatus for feeding fluidized bed incinerator, and method of autogenic operation of same

    SciTech Connect

    Nelson, J.F.

    1981-09-29

    This invention relates to an improved method and apparatus for continuous autogenic incineration of high-moisture easily friable combustible agglomerates in a fluidized-bed. The improvement comprises introducing the waste materials into the bed in a tube of air provided by supplemental air means which surrounds the in-bed feed means.

  6. Trait- and density-mediated indirect interactions initiated by an exotic invasive plant autogenic ecosystem engineer

    Treesearch

    Dean E. Pearson

    2010-01-01

    Indirect interactions are important for structuring ecological systems. However, research on indirect effects has been heavily biased toward top-down trophic interactions, and less is known about other indirect-interaction pathways. As autogenic ecosystem engineers, plants can serve as initiators of nontrophic indirect interactions that, like top-down pathways, can...

  7. Secondary skull reconstruction with autogenous split calvarial bone grafts versus nonautogenous materials.

    PubMed

    Lee, Hee Jong; Choi, Jong Woo; Chung, In Wook

    2014-07-01

    Skull reconstructions, which can be required for various reasons, including decompressive craniectomy, trauma, and tumors, are challenging issues in plastic surgery. Moreover, obtaining a low complication ratio in secondary skull reconstructions is more difficult than in primary skull reconstructions. Because standardized protocols have not been established, we here compare cranioplasty performance using fresh autogenous split calvarial bone grafts and allogenic or alloplastic materials in secondary revisional cases. Surgical correction of skull defects was performed in 25 patients in our center between 2005 and 2012. Only secondary cranioplasty cases were reviewed retrospectively. There were 17 men and 8 women, with ages ranging from 8 to 62 years at the time of surgery. The mean follow-up was 55.6 months. The surgical procedure in each case was a routine cranioplasty. In most of the cases, a 1-piece split calvarial bone graft was used while minimizing the separation of the bone flap into multiple pieces. In comparison with the skull reconstructional approach using nonautogenous materials, the functional and esthetic results of skull reconstruction using autogenous calvarial bone grafts were better and more consistent in secondary revisional cases. The group that received autogenous calvarial bone grafts showed a reconstruction success rate of 80% without esthetic and functional complications. In contrast, the group that received nonautogenous materials had a 30% success rate. Secondary cranial defect reconstructions with autogenous calvarial bone grafts showed better functional and esthetic results than skull reconstructions with nonautogenous materials.

  8. Autogenic Training and Hand Temperature Biofeedback in the Treatment of Migraine: A Preliminary Analysis.

    ERIC Educational Resources Information Center

    Jessup, B.; And Others

    The possibility of alleviating migraine headaches by autogenic relaxation training, with or without hand temperature biofeedback, was assessed. The study examined five independent groups in a bi-directional control group design. Volunteer migraine sufferers served as subjects, each participating for 12 weeks. The first four weeks of the study were…

  9. Long-term results with autogenous tissue repair of traumatic extremity vascular injuries.

    PubMed Central

    McCready, R A; Logan, N M; Daugherty, M E; Mattingly, S S; Crocker, C; Hyde, G L

    1987-01-01

    With extensive vascular injuries in which a vascular conduit is required, there is controversy as to whether an autogenous or prosthetic graft is preferable. The authors reviewed their experience with 91 extremity arterial injuries in which autogenous tissue was used to repair vascular injuries of the extremities. Twenty-two patients also had concomitant repair of associated venous injuries with autogenous vein grafts. Ten patients required amputations, despite patent grafts in five patients, because of severe muscle necrosis. Two patients had thrombosis of their vein grafts develop in the early postoperative period but did not require amputation. The authors identified only one late vein graft failure in a patient in whom an infected pseudoaneurysm developed. Three patients with extensive soft tissue injuries had infection develop in vein grafts, with subsequent massive bleeding that ultimately required arterial ligation. Among the 22 patients with repair of their venous injuries, occlusion of popliteal vein repairs was documented in two patients and suspected in three others. The remainder of patients had satisfactory results. The excellent results obtained in the vast majority of the authors' patients with extremity vascular injuries reinforces their preference for using autogenous tissue whenever a vascular conduit is required. Exceptions include patients with extensive soft tissue loss precluding adequate graft coverage, the repair of large vessels, and life-threatening emergencies when there is insufficient time to harvest and prepare a vein. PMID:3689017

  10. Brachial-brachial autogenous arteriovenous fistula in a dialysis patient with Staphylococcus aureus bacteremia.

    PubMed

    Sato, Yuichi; Miyamoto, Masahito; Yazawa, Masahiko; Nakazawa, Ryuto; Sasaki, Hideo; Miyano, Satetsu; Tsutsumi, Hisashi; Kimura, Kenjiro; Chikaraishi, Tatsuya

    2010-04-01

    As the number of patients on hemodialysis increases, there will also be an increase in the number of patients with inadequate superficial veins for the creation of an autogenous arteriovenous fistula (AVF). In those patients, medical devices such as vascular prostheses or tunneled-cuffed catheters are necessary to maintain dialysis access. However, these devices are frequently associated with bacterial infection. We recently encountered a dialysis patient who underwent tunneled-cuffed catheter insertion because of the lack of usable superficial veins for autogenous access, and this patient subsequently developed catheter-related Staphylococcus aureus bacteremia with multiple metastatic infections. Despite immediate removal of the catheter, the infection persisted over an extended period, which was a condition precluding the further use of catheters or other prosthetic materials. To handle this situation, we utilized the deep brachial vein to construct an autogenous AVF. After ligating numerous branches, the vein was anastomosed to the brachial artery and then transposed to the subcutaneous space. The newly constructed autogenous AVF, which successfully kept the patient free from foreign materials, greatly contributed to the relief of persistent infection. Although the brachial vein is rarely used for AVF creation, we suggest that it can serve as an option to create an alternative AVF in a patient with inadequate superficial veins.

  11. A fast-firing shrinkage rate controlled dilatometer using an infrared image furnace

    NASA Astrophysics Data System (ADS)

    Hackenberger, W. S.; Speyer, R. F.

    1994-03-01

    A novel dilatometer design is described for performing rate controlled sintering experiments on powder compacts. Previous rate controlled sintering systems, which control the shrinkage of a sintering compact, possessed only limited shrinkage rate control and shrinkage profile complexity due to the high thermal mass of conventional furnaces and dilatometers. The instrument described in this work features an infrared imaging furnace and a low thermal mass dilatometer assembly which together provide a very rapid temperature response. The system is capable of heating and cooling ceramic samples at up to 500 °C/min. Shrinkage control is accomplished using a modified, computer interfaced proportional-integral-derivative algorithm, and tests on glass-alumina composite samples demonstrated excellent shrinkage control with differences routinely less than 0.2% between the set point and actual shrinkage.

  12. Thermal cracking of retort oil

    SciTech Connect

    Dearth, J.D.; Smith, R.H.

    1980-10-14

    The thermal cracking of retort oil vapors in an elongated reactor is improved by passing the effluent oil vapors and gases from a retort to a thermal cracking unit before the temperature of the retort effluent falls below 680* F. This encourages the more desirable cracking reactions, increases the thermal efficiency of the process, and avoids preheater coking.

  13. A new method to measure the polymerization shrinkage kinetics of light cured composites.

    PubMed

    Lee, I B; Cho, B H; Son, H H; Um, C M

    2005-04-01

    This study was undertaken to develop a new measurement method to determine the initial dynamic volumetric shrinkage of composite resins during polymerization, and to investigate the effect of curing light intensity on the polymerization shrinkage kinetics. The instrument was basically an electromagnetic balance that was constructed with a force transducer using a position sensitive photo detector (PSPD) and a negative feedback servo amplifier. The volumetric change of composites during polymerization was detected continuously as a buoyancy change in distilled water by means of the Archimedes' principle. Using this new instrument, the dynamic patterns of the polymerization shrinkage of seven commercial composite resins were measured. The polymerization shrinkage of the composites was 1.92 approximately 4.05 volume %. The shrinkage of a packable composite was the lowest, and that of a flowable composite was the highest. The maximum rate of polymerization shrinkage increased with increasing light intensity but the peak shrinkage rate time decreased with increasing light intensity. A strong positive relationship was observed between the square root of the light intensity and the maximum shrinkage rate. The shrinkage rate per unit time, dVol%/dt, showed that the instrument can be a valuable research method for investigating the polymerization reaction kinetics. This new shrinkage-measuring instrument has some advantages that it was insensitive to temperature changes and could measure the dynamic volumetric shrinkage in real time without complicated processes. Therefore, it can be used to characterize the shrinkage kinetics in a wide range of commercial and experimental visible-light-cure materials in relation to their composition and chemistry.

  14. Response Predicting LTCC Firing Shrinkage: A Response Surface Analysis Study

    SciTech Connect

    Girardi, Michael; Barner, Gregg; Lopez, Cristie; Duncan, Brent; Zawicki, Larry

    2009-02-25

    The Low Temperature Cofired Ceramic (LTCC) technology is used in a variety of applications including military/space electronics, wireless communication, MEMS, medical and automotive electronics. The use of LTCC is growing due to the low cost of investment, short development time, good electrical and mechanical properties, high reliability, and flexibility in design integration (3 dimensional (3D) microstructures with cavities are possible)). The dimensional accuracy of the resulting x/y shrinkage of LTCC substrates is responsible for component assembly problems with the tolerance effect that increases in relation to the substrate size. Response Surface Analysis was used to predict product shrinkage based on specific process inputs (metal loading, layer count, lamination pressure, and tape thickness) with the ultimate goal to optimize manufacturing outputs (NC files, stencils, and screens) in achieving the final product design the first time. Three (3) regression models were developed for the DuPont 951 tape system with DuPont 5734 gold metallization based on green tape thickness.

  15. The Sparse Laplacian Shrinkage Estimator for High-Dimensional Regression

    PubMed Central

    Huang, Jian; Ma, Shuangge; Li, Hongzhe; Zhang, Cun-Hui

    2011-01-01

    We propose a new penalized method for variable selection and estimation that explicitly incorporates the correlation patterns among predictors. This method is based on a combination of the minimax concave penalty and Laplacian quadratic associated with a graph as the penalty function. We call it the sparse Laplacian shrinkage (SLS) method. The SLS uses the minimax concave penalty for encouraging sparsity and Laplacian quadratic penalty for promoting smoothness among coefficients associated with the correlated predictors. The SLS has a generalized grouping property with respect to the graph represented by the Laplacian quadratic. We show that the SLS possesses an oracle property in the sense that it is selection consistent and equal to the oracle Laplacian shrinkage estimator with high probability. This result holds in sparse, high-dimensional settings with p ≫ n under reasonable conditions. We derive a coordinate descent algorithm for computing the SLS estimates. Simulation studies are conducted to evaluate the performance of the SLS method and a real data example is used to illustrate its application. PMID:22102764

  16. Impaired decision-making and brain shrinkage in alcoholism.

    PubMed

    Le Berre, A-P; Rauchs, G; La Joie, R; Mézenge, F; Boudehent, C; Vabret, F; Segobin, S; Viader, F; Allain, P; Eustache, F; Pitel, A-L; Beaunieux, H

    2014-03-01

    Alcohol-dependent individuals usually favor instant gratification of alcohol use and ignore its long-term negative consequences, reflecting impaired decision-making. According to the somatic marker hypothesis, decision-making abilities are subtended by an extended brain network. As chronic alcohol consumption is known to be associated with brain shrinkage in this network, the present study investigated relationships between brain shrinkage and decision-making impairments in alcohol-dependent individuals early in abstinence using voxel-based morphometry. Thirty patients performed the Iowa Gambling Task and underwent a magnetic resonance imaging investigation (1.5T). Decision-making performances and brain data were compared with those of age-matched healthy controls. In the alcoholic group, a multiple regression analysis was conducted with two predictors (gray matter [GM] volume and decision-making measure) and two covariates (number of withdrawals and duration of alcoholism). Compared with controls, alcoholics had impaired decision-making and widespread reduced gray matter volume, especially in regions involved in decision-making. The regression analysis revealed links between high GM volume in the ventromedial prefrontal cortex, dorsal anterior cingulate cortex and right hippocampal formation, and high decision-making scores (P<0.001, uncorrected). Decision-making deficits in alcoholism may result from impairment of both emotional and cognitive networks. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  17. Application of autogenic training in patients with Ménière disease.

    PubMed

    Goto, Fumiyuki; Nakai, Kimiko; Ogawa, Kaoru

    2011-10-01

    Data are limited on the role of psychotherapy in the treatment of Ménière disease. We sought to document the effect of a psychotherapeutic technique known as autogenic training on clinical outcome in Ménière disease. Six patients with Ménière disease were studied. Retrospective chart review was conducted. All patients were refractory to conventional therapy and completed a course of autogenic training, which was offered as a complementary treatment. Autogenic training with initial psychological counseling was conducted by a clinical psychologist during 45-min sessions. Outcome measures assessed were the frequency of vertigo and functional levels 2 years after initiation of autogenic training. Functional levels were evaluated according to the 1995 guidelines of the American Academy of Otolaryngology-Head Neck Surgery (AAO-HNS). As a personality measure, we used the Maudsley Personality Inventory (MPI), devised by Eysenck, which measures neuroticism (N), extraversion (E), and propensity to lie (L). Five of six patients showed improved functional level after three to eight sessions of psychotherapy; hearing level did not change. The score of the N scale of the MPI was closely related to the number of psychotherapy sessions. Prognosis was evaluated based on the AAO-HNS reporting guidelines, as follows: A = 3, B = 1, C = 1, F = 1. The value of N in MPI was closely related to the number of psychological counseling sessions (R = 0.97, P < 0.05). In conclusion, autogenic training may enhance the mental well-being of patients with Ménière disease and improve clinical outcome.

  18. A Look at Type K Shrinkage-Compensating Cement Production and Specifications.

    DTIC Science & Technology

    1978-04-01

    minutes after demolding. All aggregate larger than 3/4—in. (19.0—mm) was wet screened from the mixture prior to casting the bars. rn. Drying Shrinkage ... aggregate , had 10 of the 19 cements exhibit more shrinkage than expansion. Although not measured , the shrinkage trends indicated that by 120 days age, 16...A0 A053 997 ARMY ENGINEER WATERWAYS EXPERIpq~~~ STATION VICKS5(~~ MISS F/s 11/2A LOOK AT TYPE K SHRINKAG ~_COMPCNSATING CEMENT PRODUCTION AND S

  19. A physical resist shrinkage model for full-chip lithography simulations

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Zheng, Leiwu; Ma, Maggie; Zhao, Qian; Fan, Yongfa; Zhang, Qiang; Feng, Mu; Guo, Xin; Wallow, Tom; Gronlund, Keith; Goossens, Ronald; Zhang, Gary; Lu, Yenwen

    2016-03-01

    Strong resist shrinkage effects have been widely observed in resist profiles after negative tone development (NTD) and therefore must be taken into account in computational lithography applications. However, existing lithography simulation tools, especially those designed for full-chip applications, lack resist shrinkage modeling capabilities because they are not needed until only recently when NTD processes begin to replace the conventional positive tone development (PTD) processes where resist shrinkage effects are negligible. In this work we describe the development of a physical resist shrinkage (PRS) model for full-chip lithography simulations and present its accuracy evaluation against experimental data.

  20. The leaf-area shrinkage effect can bias paleoclimate and ecology research.

    PubMed

    Blonder, Benjamin; Buzzard, Vanessa; Simova, Irena; Sloat, Lindsey; Boyle, Brad; Lipson, Rebecca; Aguilar-Beaucage, Brianna; Andrade, Angelina; Barber, Benjamin; Barnes, Chris; Bushey, Dharma; Cartagena, Paulina; Chaney, Max; Contreras, Karina; Cox, Mandarava; Cueto, Maya; Curtis, Cannon; Fisher, Mariah; Furst, Lindsey; Gallegos, Jessica; Hall, Ruby; Hauschild, Amelia; Jerez, Alex; Jones, Nadja; Klucas, Aaron; Kono, Anita; Lamb, Mary; Matthai, Jacob David Ruiz; McIntyre, Colten; McKenna, Joshua; Mosier, Nicholas; Navabi, Maya; Ochoa, Alex; Pace, Liam; Plassmann, Ryland; Richter, Rachel; Russakoff, Ben; Aubyn, Holden St; Stagg, Ryan; Sterner, Marley; Stewart, Emily; Thompson, Ting Ting; Thornton, Jake; Trujillo, Parker J; Volpe, Trevor J; Enquist, Brian J

    2012-11-01

    Leaf area is a key trait that links plant form, function, and environment. Measures of leaf area can be biased because leaf area is often estimated from dried or fossilized specimens that have shrunk by an unknown amount. We tested the common assumption that this shrinkage is negligible. We measured shrinkage by comparing dry and fresh leaf area in 3401 leaves of 380 temperate and tropical species and used phylogenetic and trait-based approaches to determine predictors of this shrinkage. We also tested the effects of rehydration and simulated fossilization on shrinkage in four species. We found that dried leaves shrink in area by an average of 22% and a maximum of 82%. Shrinkage in dried leaves can be predicted by multiple morphological traits with a standard deviation of 7.8%. We also found that mud burial, a proxy for compression fossilization, caused negligible shrinkage, and that rehydration, a potential treatment of dried herbarium specimens, eliminated shrinkage. Our findings indicate that the amount of shrinkage is driven by variation in leaf area, leaf thickness, evergreenness, and woodiness and can be reversed by rehydration. The amount of shrinkage may also be a useful trait related to ecologically and physiological differences in drought tolerance and plant life history.

  1. The effect of fiber orientation on the polymerization shrinkage strain of fiber-reinforced composites.

    PubMed

    Tezvergil, A; Lassila, L V J; Vallittu, P K

    2006-07-01

    The aim of this study was to characterize the linear polymerization shrinkage strain of glass fiber-reinforced composite (FRC) according to the fiber orientation. Test specimens (n=5) (10.0 x 10.0 x 1.5mm) were prepared from different brands of photopolymerizable resin-preimpregnated FRC; unidirectional continuous FRC, experimental random-oriented FRC, and bidirectional continuous FRC. As control materials, particulate filler composite resin and unfilled dimethacrylate monomer resin were used. Two uniaxial strain gages (gage length 2mm) were used to measure shrinkage strains in two directions: longitudinally and transversally to the fiber direction. The uncured composite or resin was placed on top of the strain gages, covered with a separating sheet and a glass plate, and irradiated for 40s with a light-curing unit. The shrinkage strain was monitored for 300 s. ANOVA and Tukey's posthoc test were used at a significance level of 0.05. ANOVA revealed that orientation of fiber and brand of material had a significant effect (P<0.05) on shrinkage strain. The unidirectional FRC revealed no shrinkage longitudinally to the fiber direction, whereas the shrinkage occurred transversally to the fiber direction. Particulate filler composite resin and unfilled resin revealed equal shrinkage strain in both of the measured directions. Anisotropic nature of FRC exists with regard to polymerization shrinkage strain. The variation of polymerization shrinkage strains of FRC compared to those of particulate filler composites and unfilled resin might be important for future clinical applications.

  2. A Review of Crack Closure

    DTIC Science & Technology

    1984-04-01

    OVERLOAD EFFECTS [27,32,36,55,65,80-94] 104 4.3 SHORT CRACK BEHAVIOUR 113 4.4 SURFACE CRACK BEHAVIOUR 116 4.5 EFFECT OF RESIDUAL STRESS 117 4.6...Compressive Stresses Developed 16 on a Growing Fatigue Crack During a Constant Amplitude Cyclic Load Control Test. 4 Plastic Zone and Residual Compressive... Stresses Developed 18 on a Saw Cut Sharp Crack During a Constant Amplitude Cyclic Load Control Test. Residual Stresses Developed in the Plane of Crack

  3. Sudden bending of cracked laminates

    NASA Technical Reports Server (NTRS)

    Sih, G. C.; Chen, E. P.

    1980-01-01

    A dynamic approximate laminated plate theory is developed with emphasis placed on obtaining effective solution for the crack configuration where the 1/square root of r stress singularity and the condition of plane strain are preserved. The radial distance r is measured from the crack edge. The results obtained show that the crack moment intensity tends to decrease as the crack length to laminate plate thickness is increased. Hence, a laminated plate has the desirable feature of stabilizing a through crack as it increases its length at constant load. Also, the level of the average load intensity transmitted to a through crack can be reduced by making the inner layers to be stiffer than the outer layers. The present theory, although approximate, is useful for analyzing laminate failure to crack propagation under dynamic load conditions.

  4. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Malik, S. N.; Vanstone, R. H.; Kim, K. S.; Laflen, J. H.

    1985-01-01

    The purpose is to determine the ability of currently available P-I integrals to correlate fatigue crack propagation under conditions that simulate the turbojet engine combustor liner environment. The utility of advanced fracture mechanics measurements will also be evaluated during the course of the program. To date, an appropriate specimen design, a crack displacement measurement method, and boundary condition simulation in the computational model of the specimen were achieved. Alloy 718 was selected as an analog material based on its ability to simulate high temperature behavior at lower temperatures. Tensile and cyclic tests were run at several strain rates so that an appropriate constitutive model could be developed. Suitable P-I integrals were programmed into a finite element post-processor for eventual comparison with experimental data.

  5. Cracked and Pitted Plain

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-536, 6 November 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a typical view--at 1.5 meters (5 feet) per pixel--of surfaces in far western Utopia Planitia. In this region, the plains have developed cracks and pit chains arranged in a polygonal pattern. The pits form by collapse along the trend of a previously-formed crack. This picture is located near 45.0oN, 275.4oW. This April 2003 image covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the lower left.

  6. Elevated temperature crack growth

    NASA Technical Reports Server (NTRS)

    Yau, J. F.; Malik, S. N.; Kim, K. S.; Vanstone, R. H.; Laflen, J. H.

    1985-01-01

    The objective of the Elevated Temperature Crack Growth Project is to evaluate proposed nonlinear fracture mechanics methods for application to combustor liners of aircraft gas turbine engines. During the first year of this program, proposed path-independent (P-I) integrals were reviewed for such applications. Several P-I integrals were implemented into a finite-element postprocessor which was developed and verified as part of the work. Alloy 718 was selected as the analog material for use in the forthcoming experimental work. A buttonhead, single-edge notch specimen was designed and verified for use in elevated-temperature strain control testing with significant inelastic strains. A crack mouth opening displacement measurement device was developed for further use.

  7. Statistical crack mechanics

    SciTech Connect

    Dienes, J.K.

    1983-01-01

    An alternative to the use of plasticity theory to characterize the inelastic behavior of solids is to represent the flaws by statistical methods. We have taken such an approach to study fragmentation because it offers a number of advantages. Foremost among these is that, by considering the effects of flaws, it becomes possible to address the underlying physics directly. For example, we have been able to explain why rocks exhibit large strain-rate effects (a consequence of the finite growth rate of cracks), why a spherical explosive imbedded in oil shale produces a cavity with a nearly square section (opening of bedding cracks) and why propellants may detonate following low-speed impact (a consequence of frictional hot spots).

  8. Subcritical crack growth in marble

    NASA Astrophysics Data System (ADS)

    Nara, Yoshitaka; Nishida, Yuki; Toshinori, Ii; Harui, Tomoki; Tanaka, Mayu; Kashiwaya, Koki

    2016-04-01

    It is essential to study time-dependent deformation and fracturing in various rock materials to prevent natural hazards related to the failure of a rock mass. In addition, information of time-dependent fracturing is essential to ensure the long-term stability of a rock mass surrounding various structures. Subcritical crack growth is one of the main causes of time-dependent fracturing in rock. It is known that subcritical crack growth is influenced by not only stress but also surrounding environment. Studies of subcritical crack growth have been widely conducted for silicate rocks such as igneous rocks and sandstones. By contrast, information of subcritical crack growth in carbonate rocks is not enough. Specifically, influence of surrounding environment on subcritical crack growth in carbonate rock should be clarified to ensure the long-term stability of a rock mass. In this study, subcritical crack growth in marble was investigated. Especially, the influence of the temperature, relative humidity and water on subcritical crack growth in marble is investigated. As rock samples, marbles obtained in Skopje-City in Macedonia and Carrara-City in Italy were used. To measure subcritical crack growth, we used the load relaxation method of the double-torsion (DT) test. All measurements by DT test were conducted under controlled temperature and relative humidity. For both marbles, it was shown that the crack velocity in marble in air increased with increasing relative humidity at a constant temperature. Additionally, the crack velocity in water was much higher than that in air. It was also found that the crack velocity increased with increasing temperature. It is considered that temperature and water have significant influences on subcritical crack growth in marble. For Carrara marble in air, it was recognized that the value of subcritical crack growth index became low when the crack velocity was higher than 10-4 m/s. This is similar to Region II of subcritical crack growth

  9. Internal curing with lightweight aggregate produced from biomass-derived waste

    SciTech Connect

    Lura, Pietro; Wyrzykowski, Mateusz; Tang, Clarence; Lehmann, Eberhard

    2014-05-01

    Shrinkage of concrete may lead to cracking and ultimately to a reduction of the service life of concrete structures. Among known methods for shrinkage mitigation, internal curing with porous aggregates was successfully utilized in the last couple of decades for decreasing autogenous and drying shrinkage. In this paper, the internal curing performance of pre-saturated lightweight aggregates produced from biomass-derived waste (bio-LWA) was studied. In the first part of this paper, the microstructure of the bio-LWA is investigated, with special focus on their pore structure and on their water absorption and desorption behavior. The bio-LWA has large porosity and coarse pore structure, which allows them to release the entrained water at early age and counteract self-desiccation and autogenous shrinkage. In the second part, the efficiency of internal curing in mortars incorporating the bio-LWA is examined by neutron tomography, internal relative humidity and autogenous deformation measurements.

  10. Early-age volume changes of extrudable reactive powder concrete

    NASA Astrophysics Data System (ADS)

    Cherkaoui, K.; Courtial, M.; Dunstetter, F.; Khelidj, A.; Mounanga, P.; de Noirfontaine, M. N.

    2010-06-01

    This article presents a study on the early-age autogenous deformations of Extrudable Reactive Powder Concretes (ERPCs), especially designed for the making of concrete pipes by extrusion. Different ERPC mixtures, with variable amounts of polycarboxylate superplasticizer (SP), have been investigated. Results on 28-day mechanical properties, early-age hydration rate, autogenous shrinkage and premature cracking risk are analyzed and discussed in relation with the ERPC mix parameters.

  11. Utopia Cracks and Polygons

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-339, 23 April 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a pattern of polygonal cracks and aligned, elliptical pits in western Utopia Planitia. The picture covers an area about 3 km (about 1.9 mi) wide near 44.9oN, 274.7oW. Sunlight illuminates the scene from the left.

  12. Catalytic cracking process

    SciTech Connect

    Chiang, R.L.; Perigard, R.G.; Rabo, J.A.

    1989-08-08

    This patent describes a process for catalytic cracking of hydrocarbon feedstocks. It comprises contacting the hydrocarbon feedstock under conditions effective to crack the feedstock with a catalyst. The catalyst is prepared by a process comprising the following step: contacting a fluid mixture of a large pore zeolite having a SiO/sub 2/Al/sub 2/O/sub 3/ ratio of about 3.5 to less than about 20 and an inorganic oxide matrix, with a fluoro salt of the formula A/sub (n-m)/(MF/sub n/)/sub z/. Wherein A is an organic or inorganic ionic moiety; (MF/sub n/)/sub z/ is a fluoroanion moiety comprising the element M; M is an element selected from the group of elements for Groups VB, VIB, VII, IIIA, IVA and VA of the Periodic Table of Elements; n is the coordination number of M; m is the valence of M and z is the valence or charge associated with A, at an effective pH value greater than about 3, at effective conditions of temperature and time to produce a catalyst product, whereby the cracking activity of the zeolite is enhanced.

  13. Elasto-plastic fracture mechanics of crack growth in soil

    NASA Astrophysics Data System (ADS)

    Hallett, P. D.; Newson, T. A.

    2003-04-01

    A predominant variable in soil structure formation and degradation is crack propagation. Empirical models exist to predict fracture but these do not describe the underlying physical processes. Theoretical fracture mechanics models have been applied to soil, but most are not applicable when soil is in a wet, plastic state. Since the onset of crack formation in soil tends to occur in this condition, physically sound elasto-plastic fracture mechanics approaches are long overdue. We address this weakness by applying a new elasto-plastic fracture mechanics approach to describe crack formation in plastic soil. Samples are fractured using a deep-notch (modified 4-point) bend test, with data on load transmission, sample bending, crack growth, and crack mouth opening collected to assess the crack opening angle (COA), the crack tip opening angle (CTOA) and the plastic energy dissipation rate (Dpl). These are all material properties that can be used directly to predict and describe crack propagation. CTOA will be used to discuss the results here, although a full description of the other parameters will be provided in the conference presentation. It provides a powerful parameter for describing soil cracking since CTOA is induced by soil shrinkage (an easily measured parameter) and can be used to describe elasto-plastic fracture in finite element modelling packages. The test variables we have studied to date are clay platelet orientation, soil texture, clay mineralogy, and pore water salinity. All samples were formed by consolidating a soil slurry with a 120 kPa vertical stress. Tests on pure kaolinite showed that platelet orientation did not affect CTOA which was 0.23 ± 0.02 for both conditions. Soil texture did have a marked influence, however, with silica sand:kaolinite mixes of 20:80 and 40:60 reducing CTOA to 0.14 ± 0.02 and 0.12 ± 0.01 respectively. These lower values of CTOA indicate that less strain is required to induce fracture when the amount of clay is lowered

  14. Investigation of Cracks Found in Helicopter Longerons

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Baughman, James M.; Wallace, Terryl A.

    2009-01-01

    Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurigical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces.

  15. Crosslink-induced shrinkage of grafted Gaussian chains

    NASA Astrophysics Data System (ADS)

    Benetatos, Panayotis

    2014-04-01

    The statistical mechanics of polymers grafted on surfaces has been the subject of intense research activity because of many potential applications. In this paper, we analytically investigate the conformational changes caused by a single crosslink on two ideal (Gaussian) chains grafted onto a rigid planar surface. Both the crosslink and the surface reduce the number of allowed configurations. In the absence of the hard substrate, the sole effect of the crosslink is a reduction in the effective Kuhn length of a tethered chain. The crosslink-induced shrinkage (collapse) of the grafted chains (mushrooms) turns out to be a reduction in the variance of the distribution of the height of the chain rather than a reduction of the height itself.

  16. Analysis of gene set using shrinkage covariance matrix approach

    NASA Astrophysics Data System (ADS)

    Karjanto, Suryaefiza; Aripin, Rasimah

    2013-09-01

    Microarray methodology has been exploited for different applications such as gene discovery and disease diagnosis. This technology is also used for quantitative and highly parallel measurements of gene expression. Recently, microarrays have been one of main interests of statisticians because they provide a perfect example of the paradigms of modern statistics. In this study, the alternative approach to estimate the covariance matrix has been proposed to solve the high dimensionality problem in microarrays. The extension of traditional Hotelling's T2 statistic is constructed for determining the significant gene sets across experimental conditions using shrinkage approach. Real data sets were used as illustrations to compare the performance of the proposed methods with other methods. The results across the methods are consistent, implying that this approach provides an alternative to existing techniques.

  17. Layer model for long-term deflection analysis of cracked reinforced concrete bending members

    NASA Astrophysics Data System (ADS)

    Bacinskas, Darius; Kaklauskas, Gintaris; Gribniak, Viktor; Sung, Wen-Pei; Shih, Ming-Hsiang

    2012-05-01

    A numerical technique has been proposed for the long-term deformation analysis of reinforced concrete members subjected to a bending moment. The technique based on the layer approach in a simple and rational way deals with such complex issues as concrete cracking and tension-stiffening as well as creep and shrinkage. The approach uses the material stress-strain relationships for compressive concrete, cracked tensile concrete and steel. Such effects as linear and nonlinear creep, cracking, tension-stiffening as well as the reduction in concrete tension strength due to sustained loading have been taken into account. The shrinkage effect has been modeled by means of adequate actions of axial force and bending moment. A statistical deflection calculation analysis has been carried out for 322 experimental reinforced concrete beams reported in the literature. The comparative analysis of the experimental and the modeling results has shown that the proposed technique has well captured the time-deflection behavior of reinforced concrete flexural members. The results of the predictions by ACI 318 and Eurocode 2 design codes have been also discussed.

  18. Mechanical properties, shrinkage stress, cuspal strain and fracture resistance of molars restored with bulk-fill composites and incremental filling technique.

    PubMed

    Rosatto, C M P; Bicalho, A A; Veríssimo, C; Bragança, G F; Rodrigues, M P; Tantbirojn, D; Versluis, A; Soares, C J

    2015-12-01

    To compare bulk-fill with incremental filling techniques for restoring large mesio-occlusal-distal (MOD) restorations. Seventy-five molars with MOD preparations were divided into five groups: Z350XT, incrementally filled with Filtek Z350XT and four bulk-fills-FBF/Z350XT, Filtek Bulk Fill/Filtek Z350XT; VBF/CHA, Venus Bulk Fill/Charisma Diamond; SDR/EST-X, SDR/Esthet-X HD; TEC, TetricEvoCeram Bulk Fill. Cuspal strains were measured using strain-gauges (n=10): CSt-Re, during restorative procedure; CSt-100N, during 100N occlusal loading; CSt-Fr, at fracture load. Before fracture load, teeth were load-cycled. Fracture resistance, fracture mode, and enamel cracks were recorded. The other five teeth were used for Elastic modulus (E) and Vickers hardness (VH). Post-gel shrinkage (Shr), diametral tensile strength (DTS) and compressive strength (CS) were determined (n=10). Shrinkage stresses were analyzed using finite element analysis. SDR had similar CS values as TEC, lower than all other composites. CHA had similar DTS values as Z350XT, higher than all other composites. Z350XT had the highest mean Shr and SDR the lowest Shr. New enamel cracks and propagation was observed after the restoration, regardless of filling technique. Z350XT had lower fracture resistance than bulk-fill composite techniques. No significant differences in failure modes were found. E and VH were constant through the depth for all techniques. Bulk-filling techniques had lower stresses compared to Z350XT. Flowable bulk-fill composites had lower mechanical properties than paste bulk-fill and conventional composites. All bulk-fill composites had lower post-gel shrinkage than conventional composite. Bulk-fill filling techniques resulted in lower cusp strain, shrinkage stress and higher fracture resistance. Using bulk-fill composites cause lower CSt wich indicates lower stress in restored tooth. Furthermore, bulk-fill composites have a higher fracture resistance. Therefore, clinicians may choose the bulk

  19. Prediction of Shrinkage Pore Volume Fraction Using a Dimensionless Niyama Criterion

    NASA Astrophysics Data System (ADS)

    Carlson, Kent D.; Beckermann, Christoph

    2009-01-01

    A method is presented to use a dimensionless form of the well-known Niyama criterion to directly predict the amount of shrinkage porosity that forms during solidification of metal alloy castings. The main advancement offered by this method is that it avoids the need to know the threshold Niyama value below which shrinkage porosity forms; such threshold values are generally unknown and alloy dependent. The dimensionless criterion accounts for both the local thermal conditions (as in the original Niyama criterion) and the properties and solidification characteristics of the alloy. Once a dimensionless Niyama criterion value is obtained from casting simulation results, the corresponding shrinkage pore volume fraction can be determined knowing only the solid fraction-temperature curve and the total solidification shrinkage of the alloy. Curves providing the shrinkage pore volume percentage as a function of the dimensionless Niyama criterion are given for WCB steel, aluminum alloy A356, and magnesium alloy AZ91D. The present method is used in a general-purpose casting simulation software package to predict shrinkage porosity in three-dimensional (3-D) castings. Comparisons between simulated and experimental shrinkage porosity results for a WCB steel plate casting demonstrate that this method can reasonably predict shrinkage. Additional simulations for magnesium alloy AZ91D illustrate that this method is applicable to a wide variety of alloys and casting conditions.

  20. Microstructurally based mechanisms for modeling shrinkage of cement paste at multiple levels

    SciTech Connect

    Jennings, H.M.; Xi, Yunping

    1993-07-15

    Shrinkage of cement paste is controlled by a number of mechanisms that operate in various parts of the microstructure and at various length scales. A model for creep and shrinkage can be developed by combining several models that describe phenomena at each of several length scales, ranging from the nanometer to the meter. This model is described and preliminary results are discussed.

  1. Post-resection mucosal margin shrinkage in oral cancer: quantification and significance.

    PubMed

    Mistry, Rajesh C; Qureshi, Sajid S; Kumaran, C

    2005-08-01

    The importance of tumor free margins in outcome of cancer surgery is well known. Often the pathological margins are reported to be significantly smaller than the in situ margins. This discrepancy is due to margin shrinkage the quantum of which has not been studied in patients with oral cancers. To quantify the shrinkage of mucosal margin following excision for carcinoma of the oral tongue and buccal mucosa. Mucosal margins were measured prior to resection and half an hour after excision in 27 patients with carcinoma of the tongue and buccal mucosa. The mean margin shrinkage was assessed and the variables affecting the quantum of shrinkage analyzed. The mean shrinkage from the in situ to the post resection margin status was 22.7% (P < 0.0001). The mean shrinkage of the tongue margins was 23.5%, compared to 21.2% for buccal mucosa margins. The mean shrinkage in T1/T2 tumors (25.6%) was significantly more than in T3/T4 (9.2%, P < 0.011). There is significant shrinkage of mucosal margins after surgery. Hence this should be considered and appropriate margins should be taken at initial resection to prevent the agony of post-operative positive surgical margins. Copyright 2005 Wiley-Liss, Inc.

  2. Modeling dental composite shrinkage by digital image correlation and finite element methods

    NASA Astrophysics Data System (ADS)

    Chen, Terry Yuan-Fang; Huang, Pin-Sheng; Chuang, Shu-Fen

    2014-10-01

    Dental composites are light-curable resin-based materials with an inherent defect of polymerization shrinkage which may cause tooth deflection and debonding of restorations. This study aimed to combine digital image correlation (DIC) and finite element analysis (FEA) to model the shrinkage behaviors under different light curing regimens. Extracted human molars were prepared with proximal cavities for composite restorations, and then divided into three groups to receive different light curing protocols: regular intensity, low intensity, and step-curing consisting of low and high intensities. For each tooth, the composite fillings were consecutively placed under both unbonded and bonded conditions. At first, the shrinkage of the unbonded restorations was analyzed by DIC and adopted as the setting of FEA. The simulated shrinkage behaviors obtained from FEA were further validated by the measurements in the bonded cases. The results showed that different light curing regimens affected the shrinkage in unbonded restorations, with regular intensity showing the greatest shrinkage strain on the top surface. The shrinkage centers in the bonded cases were located closer to the cavity floor than those in the unbonded cases, and were less affected by curing regimens. The FEA results showed that the stress was modulated by the accumulated light energy density, while step-curing may alleviate the tensile stress along the cavity walls. In this study, DIC provides a complete description of the polymerization shrinkage behaviors of dental composites, which may facilitate the stress analysis in the numerical investigation.

  3. Hardness, density, and shrinkage characteristics of silk-oak from Hawaii

    Treesearch

    R. L. Youngs

    1964-01-01

    Shrinkage, specific gravity, and hardness of two shipments of silk-oak (Grevillea robusta) from Hawaii were evaluated to provide basic information pertinent to the use of the wood for cabinet and furniture purposes. The wood resembles Hawaii-grown shamel ash (Fraxinus uhdei ) in the properties evaluated. Shrinkage compares well with that of black cherry, silver maple,...

  4. Interpretation of Coal-Seam Sequestration Data Using a New Swelling and Shrinkage Model

    SciTech Connect

    Siriwardane, H.J.; Smith, D.H.

    2006-10-01

    This paper deals with the influence of swelling and shrinkage of coal on the production of methane from, and sequestration of carbon dioxide in, a coalbed reservoir. A three-dimensional swelling and shrinkage model was developed. It is based on constitutive equations that account for coupled fluid pressure-deformation behavior of a porous medium that undergoes swelling and shrinkage. The swelling and shrinkage strains are computed on the basis of the amounts of different gases (e.g., CO2, CH4) sorbed or desorbed. The amounts of sorption and desorption are computed from measured isotherms with the aid of the Ideal Adsorbed Solution model for mixed gases. The permeability of the reservoir is modified according to the swelling-shrinkage model. The paper presents numerical results for the influence of swelling and shrinkage on reservoir performance during injection of carbon dioxide. The paper includes results from a number of examples, and analysis of a field injection into a coal seam at a site in the San Juan basin. Results show that with the incorporation of swelling and shrinkage into the analysis, it is possible to get a better history-match of production data. Results also show that coal swelling can reduce the injection volumes of carbon dioxide significantly. The interpretation of field data with the new swelling-shrinkage model shows that the coal swelling during carbon dioxide sequestration in coal-seams is an important factor that can influence field performance.

  5. Hyperosmotic and isosmotic shrinkage differentially affect protein phosphorylation and ion transport.

    PubMed

    Koltsova, Svetlana V; Akimova, Olga A; Kotelevtsev, Sergei V; Grygorczyk, Ryszard; Orlov, Sergei N

    2012-02-01

    In the present work, we compared the outcome of hyperosmotic and isosmotic shrinkage on ion transport and protein phosphorylation in C11-MDCK cells resembling intercalated cells from collecting ducts and in vascular smooth muscle cells (VSMC) from the rat aorta. Hyperosmotic shrinkage was triggered by cell exposure to hypertonic medium, whereas isosmotic shrinkage was evoked by cell transfer from an hypoosmotic to an isosmotic environment. Despite a similar cell volume decrease of 40%-50%, the consequences of hyperosmotic and isosmotic shrinkage on cellular functions were sharply different. In C11-MDCK and VSMC, hyperosmotic shrinkage completely inhibited Na(+),K(+)-ATPase and Na(+),P(i) cotransport. In contrast, in both types of cells isosmotic shrinkage slightly increased rather than suppressed Na(+),K(+)-ATPase and did not change Na(+),P(i) cotransport. In C11-MDCK cells, phosphorylation of JNK1/2 and Erk1/2 mitogen-activated protein kinases was augmented in hyperosmotically shrunken cells by ∼7- and 2-fold, respectively, but was not affected in cells subjected to isosmotic shrinkage. These results demonstrate that the data obtained in cells subjected to hyperosmotic shrinkage cannot be considered as sufficient proof implicating cell volume perturbations in the regulation of cellular functions under isosmotic conditions.

  6. Combination of thermal cracking with vacuum distillation of cracked tar

    SciTech Connect

    Telyashev, G.G.; Gimaev, R.N.; Makhov, A.F.; Usmanov, R.M.; Baimbetov, A.M.; Vafin, I.A.

    1987-11-01

    A method of obtaining greater amounts of distillate feedstocks from the heavy gasoil recovered by vacuum distillation of the products of thermal cracking of petroleum resids was examined. At the Novo-Ufa Petroleum Refinery, a two-furnace thermal cracking unit was reconstructed, adding a vacuum section for distillation of the cracked tar. A simplified flow plan of this unit is shown. Vacuum resid from atmospheric-vacuum tubestill units is heated in double-pipe heat exchangers, using heat from the gasoil and cracked tar. The new method makes it possible to curtail production of boiler fuel, expand the resources of feed, and improve the quality of petroleum coke.

  7. On the Crack Bifurcation and Fanning of Crack Growth Data

    NASA Technical Reports Server (NTRS)

    Forman, Royce G.; Zanganeh, Mohammad

    2015-01-01

    Crack growth data obtained from ASTM load shedding method for different R values show some fanning especially for aluminum alloys. It is believed by the authors and it has been shown before that the observed fanning is due to the crack bifurcation occurs in the near threshold region which is a function of intrinsic properties of the alloy. Therefore, validity of the ASTM load shedding test procedure and results is confirmed. However, this position has been argued by some experimentalists who believe the fanning is an artifact of the test procedure and thus the obtained results are invalid. It has been shown that using a special test procedure such as using compressively pre-cracked specimens will eliminate the fanning effect. Since not using the fanned data fit can result in a significantly lower calculated cyclic life, design of a component, particularly for rotorcraft and propeller systems will considerably be impacted and therefore this study is of paramount importance. In this effort both test procedures i.e. ASTM load shedding and the proposed compressive pre-cracking have been used to study the fatigue crack growth behavior of compact tension specimens made of aluminum alloy 2524-T3. Fatigue crack growth paths have been closely observed using SEM machines to investigate the effects of compression pre-cracking on the crack bifurcation behavior. The results of this study will shed a light on resolving the existing argument by better understanding of near threshold fatigue crack growth behavior.

  8. Monitoring of collagen shrinkage by use of second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Lin, Sung-Jan; Chen, Jau-Shiuh; Lo, Wen; Sun, Yen; Chen, Wei-Liang; Chan, Jung-Yi; Tan, Hsin-Yuan; Lin, Wei-Chou; Hsu, Chih-Jung; Young, Tai-Horng; Jee, Shiou-Hwa; Dong, Chen-Yuan

    2006-02-01

    Thermal treatment induced collagen shrinkage has a great number of applications in medical practice. Clinically, the there is lack of reliable non-invasive methods to quantify the shrinkage. Overt treatment by heat application can lead to devastating results. We investigate the serial changes of collagen shrinkage by thermal treatment of rat tail tendons. The change in length is correlated with the finding in second harmonic generation microscopy and histology. Rat tail tendon shortens progressively during initial thermal treatment. After a certain point in time, the length then remains almost constant despite further thermal treatment. The intensity of second harmonic generation signals also progressively decreases initially and then remains merely detectable upon further thermal treatment. It prompts us to develop a mathematic model to quantify the dependence of collagen shrinkage on changes of SHG intensity. Our results show that SHG intensity can be used to predict the degree of collagen shrinkage during thermal treatment for biomedical applications.

  9. Thermoelectrically controlled device for studies of temperature-induced corneal shrinkage

    NASA Astrophysics Data System (ADS)

    Borja, David; Manns, Fabrice; Fernandez, Viviana; Lamar, Peggy; Soederberg, Per G.; Parel, Jean-Marie A.

    2002-06-01

    The purpose of this study was to design and calibrate a device to measure the dynamics of thermal shrinkage in corneal and scleral strips. The apparatus consists of a thermoelectric cell controlled by a temperature controller designed to generate temperatures up to 90 degree(s)C in rectangular corneal strips; a copper cuvette filled with Dextran solution that holds the corneal strip and a displacement sensor that measures the change in length of the tissue during heat-induced shrinkage. The device was tested on corneal tissue from Florida Eye-Bank eyes that were cut into 2x4mm rectangular strips. Preliminary results indicate that our system can reproducibly create and accurately measure thermally induced corneal shrinkage. Shrinkage experiments will be used to optimize laser parameters for corneal shrinkage during laser thermokeratoplasty and laser scleral buckling.

  10. Preventing Cracking of Anodized Coatings

    NASA Technical Reports Server (NTRS)

    He, Charles C.; Heslin, Thomas M.

    1995-01-01

    Anodized coatings have been used as optical and thermal surfaces in spacecraft. Particulate contamination from cracked coatings is a concern for many applications. The major cause for the cracking is the difference in the coefficient of thermal expansion between the oxide coatings and the aluminum substrate. The loss of water when the coating is exposed to a vacuum also could induce cracking of the coating. Hot-water sealing was identified as the major cause for the cracking of the coatings because of the large temperature change when the parts were immersed in boiling water and the water was absorbed in the coating. when the hot-water sealing process was eliminated, the cracking resistance of the anodized coatings was greatly improved. Also, it was found that dyed black coatings were more susceptible than clear coatings to cracking during thermo-vacuum cyclings.

  11. Aerosol particle shrinkage event phenomenology in a South European suburban area during 2009-2015

    NASA Astrophysics Data System (ADS)

    Alonso-Blanco, E.; Gómez-Moreno, F. J.; Núñez, L.; Pujadas, M.; Cusack, M.; Artíñano, B.

    2017-07-01

    A high number of aerosol particle shrinkage cases (70) have been identified and analyzed from an extensive and representative database of aerosol size distributions obtained between 2009 and 2015 at an urban background site in Madrid (Spain). A descriptive classification based on the process from which the shrinkage began is proposed according which shrinkage events were divided into three groups: (1) NPF + shrinkage (NPF + S) events, (2) aerosol particle growth process + shrinkage (G + S) events, and (3) pure shrinkage (S) events. The largest number of shrinkages corresponded to the S-type followed by NPF + S, while the G + S events were the least frequent group recorded. Duration of shrinkages varied widely from 0.75 to 8.5 h and SR from -1.0 to -11.1 nm h-1. These processes typically occurred in the afternoon, around 18:00 UTC, caused by two situations: i) a wind speed increase usually associated with a change in the wind direction (over 60% of the observations) and ii) the reduction of photochemical activity at the end of the day. All shrinkages were detected during the warm period, mainly between May and August, when local meteorological conditions (high solar irradiance and temperature and low relative humidity), atmospheric processes (high photochemical activity) and availability of aerosol-forming precursors were favorable for their development. As a consequence of these processes, the particles concentration corresponding to the Aitken mode decreased into the nucleation mode. The accumulation mode did not undergo significant changes during these processes. In some cases, a dilution of the particulate content in the ambient air was observed. This work, goes further than others works dealing with aerosol particles shrinkages, as it incorporates as a main novelty a classification methodology for studying these processes. Moreover, compared to other studies, it is supported by a high and representative number of observations. Thus, this study contributes to

  12. Monitoring of pre-release cracks in prestressed concrete using fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Abdel-Jaber, Hiba; Glisic, Branko

    2015-04-01

    Prestressed concrete experiences low to no tensile stresses, which results in limiting the occurrence of cracks in prestressed concrete structures. However, the nature of construction of these structures requires the concrete not to be subjected to the compressive force from the prestressing tendons until after it has gained sufficient compressive strength. Although the structure is not subjected to any dead or live load during this period, it is influenced by shrinkage and thermal variations. Thus, the concrete can experience tensile stresses before the required compressive strength has been attained, which can result in the occurrence of "pre-release" cracks. Such cracks are visually closed after the transfer of the prestressing force. However, structural capacity and behavior can be impacted if cracks are not sufficiently closed. This paper researches a method for the verification of the status of pre-release cracks after transfer of the prestressing force, and it is oriented towards achievement of Level IV Structural Health Monitoring (SHM). The method relies on measurements from parallel long-gauge fiber optic sensors embedded in the concrete prior to pouring. The same sensor network is used for the detection and characterization of cracks, as well as the monitoring of the prestressing force transfer and the determination of the extent of closure of pre-release cracks. This paper outlines the researched method and presents its application to a real-life structure, the southeast leg of Streicker Bridge on the Princeton University campus. The application structure is a curved continuous girder that was constructed in 2009. Its deck experienced four pre-release cracks that were closed beyond the critical limits based on the results of this study.

  13. Effect of temperature and humidity on post-gel shrinkage, cusp deformation, bond strength and shrinkage stress - Construction of a chamber to simulate the oral environment.

    PubMed

    Bicalho, Aline Aredes; de Souza, Silas Júnior Boaventura; de Rosatto, Camila Maria Peres; Tantbirojn, Daranee; Versluis, Antheunis; Soares, Carlos José

    2015-12-01

    Evaluate the effect of environment on post-gel shrinkage (Shr), cuspal strains (CS), microtensile bond strength (μTBS), elastic modulus (E) and shrinkage stress in molars with large class II restorations. Sixty human molars received standardized Class II mesio-oclusal-distal cavity preparations. Restorations were made with two composites (CHA, Charisma Diamond, Heraus Kulzer and IPS Empress Direct, Ivoclar-Vivadent) using three environment conditions (22°C/50% humidity, 37°C/50% humidity and 37°C/90% humidity) simulated in custom developed chamber. Shr was measured using the strain gauge technique (n=10). CS was measured using strain gauges. Half of the teeth (n=5) were used to assess the elastic modulus (E) and Knoop hardness (KHN) at different depths using microhardness indentation. The other half (n=5) was used to measure the μTBS. The composites and environment conditions were simulated in a two-dimensional finite element analysis of a tooth restoration. Polymerization shrinkage was modeled using Shr data. The Shr, CS, μTBS, KHN and E data were statistically analyzed using two-way ANOVA and Tukey test (significance level: 0.05). Both composites had similar Shr, CS, μTBS and shrinkage stress. CHA had higher elastic modulus than IPS. Increasing temperature and humidity significantly increased Shr, CS and shrinkage stress. μTBS were similar for groups with lower humidity, irrespective of temperature, and higher with higher humidity. E and KHN were constant through the depth for CHA. E and KHN values were affected by environment only for IPS, mainly deeper in the cavity. Shrinkage stress at dentin/composite interface had high inverse correlation with μTBS. Shrinkage stress in enamel had high correlation with CS. Increasing temperature and humidity caused higher post-gel shrinkage and cusp deformation with higher shrinkage stresses in the tooth structure and tooth/restoration interface for both composites tested. The chamber developed for simulating the

  14. Augmentation of arthrodesis in dogs using a free autogenous omental graft

    PubMed Central

    Ree, Jennifer J.; Baltzer, Wendy I.; Townsend, Katy L.

    2016-01-01

    A technique for using free autogenous omental grafting with arthrodesis in dogs is described and radiographic osseous union and complications after surgery are evaluated. This retrospective study matched body weight and procedure type for 8 cases of pancarpal arthrodesis, 4 cases of pantarsal arthrodesis, and 2 cases of partial tarsal arthrodesis in dogs with omental and cancellous bone autograft (OBG group) and with cancellous bone autograft alone (BG group). Radiographs were reviewed 9 to 12 weeks after surgery to compare scores of radiographic osseous union and it was found that the OBG group had higher scores than the BG group. The BG group had significantly more major complications that required re-operation for implant removal or treatment of a deep infection compared to the OBG group. Overall, free autogenous omental grafts may be used to augment arthrodesis in dogs without significant morbidity and further investigation of its use to reduce major complications and speed bone healing are warranted. PMID:27493282

  15. Combined use of autogenic therapy and biofeedback in training effective control of heart rate by humans

    NASA Technical Reports Server (NTRS)

    Cowings, P. S.

    1977-01-01

    Experiments were performed on 24 men and women (aged 20-27 yr) in three equal groups who were taught to control their own heart rates by autogenic training and biofeedback under dark and sound-isolated conditions. Group I was parasympathetic dominant, group II was sympathetic dominant, and group III consisted of parasympathetic-dominant subjects and controls who received only biofeedback of their own heart rates. The results corroborate three hypotheses: (1) subjects with para-sympathetic-dominant autonomic profiles perform in a way that is both qualitatively and quantitatively different from subjects with sympathetic-dominant autonomic profiles; (2) tests of interindividual variability yield data relevant to individual performance in visceral learning tasks; and (3) the combined use of autogenic training, biofeedback, and verbal feedback is suitable for conditioning large stable autonomic responses in humans.

  16. Histologic study of the fate of autogenous auricular cartilage grafts in the human temporomandibular joint.

    PubMed

    Yih, W Y; Zysset, M; Merrill, R G

    1992-09-01

    Biopsies of 30 autogenous auricular cartilage grafts previously placed in 21 patients with ankylosis and arthropathy of the temporomandibular joint were studied. These joints were reoperated because of persistent pain and limitation of motion. Histologically, all grafts showed viability of the cartilage. Eighteen cartilage grafts placed after Proplast (Vitek, Inc, Houston, TX) or Silastic (Dow Corning, Midland, MI) implants had been removed, all showed foreign-body granuloma with coexistent intact cartilage grafts. This indicated that the autogenous auricular cartilage was resistant to the foreign-body reaction. All cartilage grafts were encased by fibrous tissue. This overgrowth of fibrous tissue may be responsible for the ankylosis. Seven grafts showed cartilaginous proliferation grossly and all showed proliferation histologically. The cartilage proliferation also may contribute to the persistent symptoms and recurrent limitation of joint motion.

  17. Combined use of autogenic therapy and biofeedback in training effective control of heart rate by humans

    NASA Technical Reports Server (NTRS)

    Cowings, P. S.

    1977-01-01

    Experiments were performed on 24 men and women (aged 20-27 yr) in three equal groups who were taught to control their own heart rates by autogenic training and biofeedback under dark and sound-isolated conditions. Group I was parasympathetic dominant, group II was sympathetic dominant, and group III consisted of parasympathetic-dominant subjects and controls who received only biofeedback of their own heart rates. The results corroborate three hypotheses: (1) subjects with para-sympathetic-dominant autonomic profiles perform in a way that is both qualitatively and quantitatively different from subjects with sympathetic-dominant autonomic profiles; (2) tests of interindividual variability yield data relevant to individual performance in visceral learning tasks; and (3) the combined use of autogenic training, biofeedback, and verbal feedback is suitable for conditioning large stable autonomic responses in humans.

  18. Success rates and immunologic responses of autogenic, allogenic, and xenogenic treatments to repair articular cartilage defects.

    PubMed

    Revell, Christopher M; Athanasiou, Kyriacos A

    2009-03-01

    This review examines current approaches available for articular cartilage repair, not only in terms of their regeneration potential, but also as a function of immunologic response. Autogenic repair techniques, including osteochondral plug transplantation, chondrocyte implantation, and microfracture, are the most widely accepted clinical treatment options due to the lack of immunogenic reactions, but only moderate graft success rates have been reported. Although suspended allogenic chondrocytes are shown to evoke an immune response upon implantation, allogenic osteochondral plugs and tissue-engineered grafts using allogenic chondrocytes exhibit a tolerable immunogenic response. Additionally, these repair techniques produce neotissue with success rates approaching those of currently available autogenic repair techniques, while simultaneously obviating their major hindrance of donor tissue scarcity. To date, limited research has been performed with xenogenic tissue, although several studies demonstrate the potential for its long-term success. This article focuses on the various treatment options for cartilage repair and their associated success rates and immunologic responses.

  19. Success Rates and Immunologic Responses of Autogenic, Allogenic, and Xenogenic Treatments to Repair Articular Cartilage Defects

    PubMed Central

    Revell, Christopher M.

    2009-01-01

    This review examines current approaches available for articular cartilage repair, not only in terms of their regeneration potential, but also as a function of immunologic response. Autogenic repair techniques, including osteochondral plug transplantation, chondrocyte implantation, and microfracture, are the most widely accepted clinical treatment options due to the lack of immunogenic reactions, but only moderate graft success rates have been reported. Although suspended allogenic chondrocytes are shown to evoke an immune response upon implantation, allogenic osteochondral plugs and tissue-engineered grafts using allogenic chondrocytes exhibit a tolerable immunogenic response. Additionally, these repair techniques produce neotissue with success rates approaching those of currently available autogenic repair techniques, while simultaneously obviating their major hindrance of donor tissue scarcity. To date, limited research has been performed with xenogenic tissue, although several studies demonstrate the potential for its long-term success. This article focuses on the various treatment options for cartilage repair and their associated success rates and immunologic responses. PMID:19063664

  20. Cracking in charged anisotropic cylinder

    NASA Astrophysics Data System (ADS)

    Sharif, M.; Sadiq, Sobia

    2017-06-01

    In this paper, we study the stability of static charged anisotropic cylindrically symmetric compact object through cracking. The Einstein-Maxwell field equations and conservation equation are formulated. We then apply local density perturbation and study the behavior of force distribution function. Finally, the cracking is explored for two models satisfying specific form of Chaplygin equation of state. It is found that these models exhibit cracking and the instability increases as the value of charge parameter is increased.

  1. Shuttle Fuel Feedliner Cracking Investigation

    NASA Technical Reports Server (NTRS)

    Nesman, Tomas E.; Turner, Jim (Technical Monitor)

    2002-01-01

    This presentation provides an overview of material covered during 'Space Shuttle Fuel Feedliner Cracking Investigation MSFC Fluids Workshop' held November 19-21, 2002. Topics covered include: cracks on fuel feed lines of Orbiter space shuttles, fluid driven cracking analysis, liner structural modes, structural motion in a fluid, fluid borne drivers, three dimensional computational fluid dynamics models, fluid borne drivers from pumps, amplification mechanisms, flow parameter mapping, and flight engine flow map.

  2. Three-Dimensional Gear Crack Propagation Studies

    NASA Technical Reports Server (NTRS)

    Lewicki, David G.; Sane, Ashok D.; Drago, Raymond J.; Wawrzynek, Paul A.

    1998-01-01

    Three-dimensional crack growth simulation was performed on a split-tooth gear design using boundary element modeling and linear elastic fracture mechanics. Initial cracks in the fillet of the teeth produced stress intensity factors of greater magnitude (and thus, greater crack growth rates) than those in the root or groove areas of the teeth. Crack growth simulation was performed on a case study to evaluate crack propagation paths. Tooth fracture was predicted from the crack growth simulation for an initial crack in the tooth fillet region. Tooth loads on the uncracked mesh of the split-tooth design were up to five times greater than those on the cracked mesh if equal deflections of the cracked and uncracked teeth were considered. Predicted crack shapes as well as crack propagation life are presented based on calculated stress intensity factors, mixed-mode crack propagation trajectory theories, and fatigue crack growth theories.

  3. Retrofitting olefin cracking plants

    SciTech Connect

    Sumner, C.; Fernandez-Baujin, J.M.

    1983-12-01

    This article discusses the retrofitting of liquid crackers which produce olefins so that gaseous feedstocks can be used. Naphtha and gas oil are the predominant design feedstocks for producing olefins. The price of gaseous feedstocks such as ethane, propane and butane have become economically more attractive than liquid feedstocks. Existing liquid crackers will be able to produce ethylene at 85% or higher capacity when cracking propane and butane feedstock with only minor changes. Topics considered include revamping for vacuum gas oil (VGO) feedstocks and revamping for liquefied petroleum gas (LPG) feedstocks.

  4. Mode II fatigue crack propagation.

    NASA Technical Reports Server (NTRS)

    Roberts, R.; Kibler, J. J.

    1971-01-01

    Fatigue crack propagation rates were obtained for 2024-T3 bare aluminum plates subjected to in-plane, mode I, extensional loads and transverse, mode II, bending loads. These results were compared to the results of Iida and Kobayashi for in-plane mode I-mode II extensional loads. The engineering significance of mode I-mode II fatigue crack growth is considered in view of the present results. A fatigue crack growth equation for handling mode I-mode II fatigue crack growth rates from existing mode I data is also discussed.

  5. Operational Applications of Autogenic Feedback Training Exercise as a Treatment for Airsickness in the Military

    NASA Technical Reports Server (NTRS)

    Gebreyesus, Fiyore; Cowings, Patricia S.; Toscano, William B.

    2012-01-01

    Airsickness is experienced by about 50% of military aviators some time in their career. Aviators who suffer from recurrent episodes of airsickness are typically referred to the Naval Aerospace Medical Institute (NAMI) at Pensacola where they undergo extensive evaluation and 8 weeks of training in the Self-Paced Airsickness Desensitization (SPAD) program. Researchers at NASA Ames have developed an alternative mitigation training program, Autogenic Feedback Training Exercise (AFTE) that has demonstrated an 80% success rate for improving motion sickness tolerance.

  6. Histologic assessment of a contiguous autogenous transplant in a human intrabony defect. A case report.

    PubMed

    Zubery, Y; Kozlovsky, A; Tal, H

    1993-01-01

    Increased blood supply, vital bone marrow cells, and minimal mobility may play a significant role in the success of osseous grafts, and are characteristics of the bone swaging grafting technique. As in all autogenous grafts, the risk of disease transmission is minimal. Previous reports of clinical success raise questions as to the type of tissue response to this procedure. This case report examines 8 months radiographic and histologic results of a clinically successful bone swaging graft.

  7. Sustainable exploitation and management of autogenic ecosystem engineers: application to oysters in Chesapeake Bay.

    PubMed

    Wilberg, Michael J; Wiedenmann, John R; Robinson, Jason M

    2013-06-01

    Autogenic ecosystem engineers are critically important parts of many marine and estuarine systems because of their substantial effect on ecosystem services. Oysters are of particular importance because of their capacity to modify coastal and estuarine habitats and the highly degraded status of their habitats worldwide. However, models to predict dynamics of ecosystem engineers have not previously included the effects of exploitation. We developed a linked population and habitat model for autogenic ecosystem engineers undergoing exploitation. We parameterized the model to represent eastern oyster (Crassostrea virginica) in upper Chesapeake Bay by selecting sets of parameter values that matched observed rates of change in abundance and habitat. We used the model to evaluate the effects of a range of management and restoration options including sustainability of historical fishing pressure, effectiveness of a newly enacted sanctuary program, and relative performance of two restoration approaches. In general, autogenic ecosystem engineers are expected to be substantially less resilient to fishing than an equivalent species that does not rely on itself for habitat. Historical fishing mortality rates in upper Chesapeake Bay for oysters were above the levels that would lead to extirpation. Reductions in fishing or closure of the fishery were projected to lead to long-term increases in abundance and habitat. For fisheries to become sustainable outside of sanctuaries, a substantial larval subsidy would be required from oysters within sanctuaries. Restoration efforts using high-relief reefs were predicted to allow recovery within a shorter period of time than low-relief reefs. Models such as ours, that allow for feedbacks between population and habitat dynamics, can be effective tools for guiding management and restoration of autogenic ecosystem engineers.

  8. [1st report on the use of an autogenous tissue adhesive in otorhinolaryngology].

    PubMed

    Wolf, G; Stammberger, H

    1985-04-01

    An autogenous tissue glue has been developed at the ENT Department of the University Clinic Graz. It is prepared from the patient's own plasma, and has the following advantages: There is no danger of transmitting infectious diseases, there are no problems with storage, temperature and expiration date. The glue is produced at room temperature and is cheap. The production and application of this autologous tissue glue are described and a first report is given on initial experiences.

  9. Use of autogenous saphenous vein as a conduit for mesenterico-left portal vein bypass.

    PubMed

    Query, Julie A; Sandler, Anthony D; Sharp, William J

    2007-06-01

    The authors describe a case of extrahepatic portal vein (EHPV) thrombosis and portal hypertension treated with a variant of mesenterico-left portal vein bypass (MLPVB) or Rex shunt. In this case, a segment of autogenous greater saphenous vein was used to bridge the distance between the left gastric vein inflow and the left portal vein. Use of such nontraditional conduit in similar circumstances may expand the application of portal revascularization/decompression procedures in treating these patients.

  10. Shear fatigue crack growth - A literature survey

    NASA Technical Reports Server (NTRS)

    Liu, H. W.

    1985-01-01

    Recent studies of shear crack growth are reviewed, emphasizing test methods and data analyses. The combined mode I and mode II elastic crack tip stress fields are considered. The development and design of the compact shear specimen are described, and the results of fatigue crack growth tests using compact shear specimens are reviewed. The fatigue crack growth tests are discussed and the results of inclined cracks in tensile panels, center cracks in plates under biaxial loading, cracked beam specimens with combined bending and shear loading, center-cracked panels and double edge-cracked plates under cyclic shear loading are examined and analyzed in detail.

  11. Analysis of the status of pre-release cracks in prestressed concrete structures using long-gauge sensors

    NASA Astrophysics Data System (ADS)

    Abdel-Jaber, H.; Glisic, B.

    2015-02-01

    Prestressed structures experience limited tensile stresses in concrete, which limits or completely eliminates the occurrence of cracks. However, in some cases, large tensile stresses can develop during the early age of the concrete due to thermal gradients and shrinkage effects. Such stresses can cause early-age cracks, termed ‘pre-release cracks’, which occur prior to the transfer of the prestressing force. When the prestressing force is applied to the cross-section, it is assumed that partial or full closure of the cracks occurs by virtue of the force transfer through the cracked cross-section. Verification of the closure of the cracks after the application of the prestressing force is important as it can either confirm continued structural integrity or indicate and approximate reduced structural capacity. Structural health monitoring (SHM) can be used for this purpose. This paper researches an SHM method that can be applied to prestressed beam structures to assess the condition of pre-release cracks. The sensor network used in this method consists of parallel long-gauge fiber optic strain sensors embedded in the concrete cross-sections at various locations. The same network is used for damage detection, i.e. detection and characterization of the pre-release cracks, and for monitoring the prestress force transfer. The method is validated on a real structure, a curved continuous girder. Results from the analysis confirm the safety and integrity of the structure. The method and its application are presented in this paper.

  12. Current understanding of stress-corrosion cracking

    SciTech Connect

    Parkins, R.N. )

    1992-12-01

    The mechanisms that cause stress corrosion cracking and the conditions in which they apply are reviewed. Attention is given to hydrogen-assisted cracking, film-induced cleavage, dissolution mechanisms, surface-mobility mechanism, cracking environments, deformation and cracking, and stochastic aspects of cracking. 70 refs.

  13. Phylogenetic Analysis of L4-Mediated Autogenous Control of the S10 Ribosomal Protein Operon

    PubMed Central

    Allen, Todd; Shen, Ping; Samsel, Leigh; Liu, Raymond; Lindahl, Lasse; Zengel, Janice M.

    1999-01-01

    We investigated the regulation of the S10 ribosomal protein (r-protein) operon among members of the gamma subdivision of the proteobacteria, which includes Escherichia coli. In E. coli, this 11-gene operon is autogenously controlled by r-protein L4. This regulation requires specific determinants within the untranslated leader of the mRNA. Secondary structure analysis of the S10 leaders of five enterobacteria (Salmonella typhimurium, Citrobacter freundii, Yersinia enterocolitica, Serratia marcescens, and Morganella morganii) and two nonenteric members of the gamma subdivision (Haemophilus influenzae and Vibrio cholerae) shows that these foreign leaders share significant structural homology with the E. coli leader, particularly in the region which is critical for L4-mediated autogenous control in E. coli. Moreover, these heterologous leaders produce a regulatory response to L4 oversynthesis in E. coli. Our results suggest that an E. coli-like L4-mediated regulatory mechanism may operate in all of these species. However, the mechanism is not universally conserved among the gamma subdivision members, since at least one, Pseudomonas aeruginosa, does not contain the required S10 leader features, and its leader cannot provide the signals for regulation by L4 in E. coli. We speculate that L4-mediated autogenous control developed during the evolution of the gamma branch of proteobacteria. PMID:10498727

  14. Phylogenetic analysis of L4-mediated autogenous control of the S10 ribosomal protein operon.

    PubMed

    Allen, T; Shen, P; Samsel, L; Liu, R; Lindahl, L; Zengel, J M

    1999-10-01

    We investigated the regulation of the S10 ribosomal protein (r-protein) operon among members of the gamma subdivision of the proteobacteria, which includes Escherichia coli. In E. coli, this 11-gene operon is autogenously controlled by r-protein L4. This regulation requires specific determinants within the untranslated leader of the mRNA. Secondary structure analysis of the S10 leaders of five enterobacteria (Salmonella typhimurium, Citrobacter freundii, Yersinia enterocolitica, Serratia marcescens, and Morganella morganii) and two nonenteric members of the gamma subdivision (Haemophilus influenzae and Vibrio cholerae) shows that these foreign leaders share significant structural homology with the E. coli leader, particularly in the region which is critical for L4-mediated autogenous control in E. coli. Moreover, these heterologous leaders produce a regulatory response to L4 oversynthesis in E. coli. Our results suggest that an E. coli-like L4-mediated regulatory mechanism may operate in all of these species. However, the mechanism is not universally conserved among the gamma subdivision members, since at least one, Pseudomonas aeruginosa, does not contain the required S10 leader features, and its leader cannot provide the signals for regulation by L4 in E. coli. We speculate that L4-mediated autogenous control developed during the evolution of the gamma branch of proteobacteria.

  15. Autogenous bone harvesting and grafting in advanced jaw resorption: morbidity, resorption and implant survival.

    PubMed

    Nkenke, Emeka; Neukam, Friedrich W

    2014-01-01

    To analyse the morbidity arising from autogenous bone graft harvesting, graft resorption and implant survival in grafted sites. Only comparative clinical trials on the harvest of autogenous bone grafts were selected. Studies were excluded if they compared autogenous bone grafts to bone substitutes or vascularised free bone grafts. A total of 24 studies were included in the review. Six intraoral or distant donor sites were identified. The highest level of evidence was reached by a randomised controlled trial. The mandibular ramus was the source of bone that was preferred by the patients. From this intraoral donor site bone was harvested under local anaesthesia on an outpatient basis. Patients' acceptance of chin bone harvesting was low. It led to a considerable morbidity that included pain, superficial skin sensitivity disorders and wound healing problems at the donor site. Patients even preferred iliac crest bone harvesting over bone harvesting from the chin, although this distant donor site required general anaesthesia and a hospital stay. The harvest of posterior iliac crest block led to less morbidity than the harvest of anterior iliac crest block grafts. When only cancellous bone was needed, percutaneous bone harvesting from the iliac crest led to less morbidity than an open approach to the iliac crest. Dependent on the required graft structure and amount of bone needed, ramus grafts, block bone grafts from the posterior iliac crest and cancellous bone grafts harvested with a trephine from the anterior iliac crest should be chosen.

  16. Bone regeneration in surgically created defects filled with autogenous bone: an epifluorescence microscopy analysis in rats

    PubMed Central

    GUSKUMA, Marcos Heidy; HOCHULI-VIEIRA, Eduardo; PEREIRA, Flávia Priscila; RANGEL-GARCIA JUNIOR, Idelmo; OKAMOTO, Roberta; OKAMOTO, Tetuo; MAGRO FILHO, Osvaldo

    2010-01-01

    Although the search for the ideal bone substitute has been the focus of a large number of studies, autogenous bone is still the gold standard for the filling of defects caused by pathologies and traumas, and mainly, for alveolar ridge reconstruction, allowing the titanium implants installation. Objectives The aim of this study was to evaluate the dynamics of autogenous bone graft incorporation process to surgically created defects in rat calvaria, using epifluorescence microscopy. Material and methods Five adult male rats weighing 200-300 g were used. The animals received two 5-mm-diameter bone defects bilaterally in each parietal bone with a trephine bur under general anesthesia. Two groups of defects were formed: a control group (n=5), in which the defects were filled with blood clot, and a graft group (n=5), in which the defects were filled with autogenous bone block, removed from the contralateral defect. The fluorochromes calcein and alizarin were applied at the 7th and 30th postoperative days, respectively. The animals were killed at 35 days. Results The mineralization process was more intense in the graft group (32.09%) and occurred mainly between 7 and 30 days, the period labeled by calcein (24.66%). Conclusions The fluorochromes showed to be appropriate to label mineralization areas. The interfacial areas between fluorochrome labels are important sources of information about the bone regeneration dynamics. PMID:20835568

  17. Technical innovations in ear reconstruction using a skin expander with autogenous cartilage grafts.

    PubMed

    Dashan, Yu; Haiyue, Jiang; Qinghua, Yang; Bo, Pan; Lin, Lin; Tailing, Wang; Yanmei, Wang; Xiao, Qin; Hongxing, Zhuang

    2008-01-01

    Pioneers such as Tanzer and Brent have established the foundations of microtia reconstruction using an autogenous costal cartilage framework. The framework and its skin coverage are the two limiting factors in ear reconstruction. At the present time autogenous rib cartilage and mastoid skin are still first choice materials for most surgeons. They have the combined advantages of well-matched texture and colour. To reconstruct a symmetrical, accurate, prominent auricle and minimise as much as possible the chest wall deformity caused by rib cartilage harvesting, we set out to improve our techniques for cartilaginous framework definition and to use the remnant ear to enhance the projection of the reconstructed ear. Since 2000, 342 cases (366 ears) were treated using our current techniques. Data pertaining to complications were recorded. Final results were assessed a minimum of 1 year postoperatively. The follow-up period ranged from 1 to 6 years. Most of the patients with microtia were satisfied with the results of their ear reconstruction. In conclusion, our techniques help to reduce the quantity of rib cartilage needed to fabricate ear framework and minimise chest wall deformity. The frameworks are accurate, prominent and stable. Reconstructed ears are similar in colour and appearance to the normal side. Our innovations are practical and reliable for microtia reconstruction using skin expanders in combination with a sculpted autogenous rib cartilage framework.

  18. Bone Formation in Maxillary Sinus Lift Using Autogenous Bone Graft at 2 and 6 Months

    PubMed Central

    Netto, Henrique Duque; Miranda Chaves, Maria das Graças Alfonso; Aatrstrup, Beatriz; Guerra, Renata; Olate, Sergio

    2016-01-01

    SUMMARY The aim of this study is to compare the bone formation in maxillary sinus lift with an autogenous bone graft in histological evaluation at 2 or 6 months. A comparative study was designed where 10 patients with missing teeth bilaterally in the posterior zone of the maxilla were selected. Patients received a particulate autogenous bone graft under the same surgical conditions, selecting a site to collect a biopsy and histological study at two months and another at six months postoperatively. Histomorphometry was performed and were used Kolmogorov-Smirnov test, student’s t-test and Spearman’s correlation coefficient, considering a value of p<0.05. Differences were observed in inflammatory infiltrate and vascularization characteristics; however, the group analyzed at two months presented 38.12% ± 6.64 % of mineralized tissue, whereas the group studied at 6 months presented an average of 38.45 ± 9.27 %. There were no statistical differences between the groups. It is concluded that the bone formation may be similar in intrasinus particulate autogenous bone grafts in evaluations at two or six months; under these conditions, early installation of implants is viable. PMID:27867255

  19. Clinical, haematological and radiological evaluation of fragmented autogenous cortical bone grafting of radius in dogs.

    PubMed

    Grover, R K; Sobti, V K

    1998-07-01

    In eight clinically healthy dogs, a midshaft diaphyseal defect of 2 cm was created in the right radius ulna. This gap was maintained by fixing a four hole sherman bone plate on the radius. In four dogs, the gap was filled with autogenous cancellous bone grafts (2-5 mm in diameter) harvested from the proximal end of the tibia (group 1). In the remaining 4 dogs, the fracture gap was filled with autogenous cortical bone fragments (ACBF) of 2-5 mm diameter made from the same 2 cm piece of bone removed from the radius. While comparing various clinical observations, it appeared that healing of the wounds and bearing of the weight on the grafted limb in dogs subjected to ACBF graft were similar to those given autogenous cancellous bone graft. In radiographs, taken on the 30th day in group 1, a fairly good amount of callus was found emerging from fracture ends but the whole of the bone graft area was not covered by bony density even on the 60th day. In group 2 (ACBF), 45th day radiograph revealed that the callus from the fracture end was mixing up with the cortical bone fragments, and at the 60th day, the callus was clearly found invading the cortical bone fragments grafted in the fracture gap.

  20. Differences in latent inhibition as a function of the autogenous-reactive OCD subtype.

    PubMed

    Lee, Han-Joo; Telch, Michael J

    2010-07-01

    We examined differences in a visual search-based latent inhibition (LI) task in 48 non-treatment seeking individuals diagnosed with obsessive-compulsive disorder (OCD) and 26 non-OCD controls, using a visual search-based LI task as a function of participants' primary obsessional presentation based on the autogenous-reactive subtype model of obsessions (Lee & Kwon, 2003; Lee & Telch, 2007). We hypothesized that LI would be significantly attenuated among OCD participants whose primary obsessions were characterized by aversive impulses, images, or thoughts with sexual, aggressive, blasphemous, and repulsive themes (autogenous obsessions) due to their weakened attentional inhibitory mechanisms and elevated schizotypal personality features, as compared with those whose primary obsessions were characterized by somewhat realistic aversive mental intrusions about contamination, mistakes, accidents, or disarray (reactive obsession) and non-OCD controls. Results showed that those primarily displaying autogenous obsessions failed to display LI, whereas those primarily displaying reactive obsessions and non-OCD controls displayed significant LI effects. Our data suggest that the magnitude of LI varies as a function of primary obsessional presentations among individuals with OCD.

  1. Eyelid-associated complications after autogenous fat injection for cosmetic forehead augmentation

    PubMed Central

    2013-01-01

    Background We report two cases of unilateral upper eyelid swelling with multiple small lumps as an unusual complication of autogenous fat injection for cosmetic forehead augmentation. Case presentation Two female patients were referred to our clinic for unusual unilateral eyelid swelling, with multiple small lumps. The duration of symptoms differed in each case, but both patients had a history of autogenous fat injection for cosmetic forehead augmentation at a local plastic surgery clinic. The lumps were small (diameter 5 mm~10 mm), palpable, hard, and nonmobile, and were evaluated by magnetic resonance imaging (MRI). Lumps from the eyelids of two patients were excised under general anesthesia. All of the masses were located deeply and found near the superior orbital rim or lateral orbital rim. The lumps exhibited chronic inflammation with fibrosis. Some of the lumps showed foamy histiocytic aggregation and foreign body lipogranuloma, resulting from iatrogenic fat injection. After excision, all masses and swelling disappeared, and moderate ptotic eyelid or lagophthalmos of affected eyes also improved. Conclusions To our knowledge, eyelid swelling with multiple lumps in the eyelid is a very rare complication of autogenous fat injection for cosmetic forehead augmentation. This report should be helpful for ophthalmic clinicians who encounter these unusual symptoms. PMID:23841959

  2. Histomorphometric Analysis of Contaminated Autogenous Tooth Graft Materials After Various Sterilization.

    PubMed

    Jin, Soo-Young; Kim, Su-Gwan; Oh, Ji-Su; You, Jae-Seek; Lim, Sung-Chul; Jeong, Mi-Ae; Kim, Jin-Son

    2016-02-01

    The purpose of this study was to evaluate histomorphometrically contaminated autogenous tooth graft materials, which were resterilized. The intentional defects (diameter: 8 mm, depth: 4 mm) were formed around implant fixture on the iliac crest of 6 mongrel dogs. Autogenous tooth graft materials were made by extracted premolars. After the contamination of the tooth materials, graft procedure was performed; no contaminated group (control group), contaminated groups (nonsterilization group [group 1], ethylene oxide [EO] gas group [group 2], and autoclave group [group 3]). The bone-to-implant contact (BIC) and the new bone formation rate (NBFR) were evaluated after sacrifice. The BIC and NBFR of groups 1 and 3 were significantly lower than the control group after 4 weeks. The BIC and NBRF of group 3 were significantly lower than the control group after 8 weeks. However, the BIC and NBRF of group 2 was not significantly different comparing with the control group after 4 and 8 weeks. Sterilization using EO gas may be more favorable than high-pressure sterilization in cases the reuse of contaminated autogenous tooth graft materials.

  3. Bone Formation in Maxillary Sinus Lift Using Autogenous Bone Graft at 2 and 6 Months.

    PubMed

    Netto, Henrique Duque; Miranda Chaves, Maria das Graças Alfonso; Aatrstrup, Beatriz; Guerra, Renata; Olate, Sergio

    2016-09-01

    The aim of this study is to compare the bone formation in maxillary sinus lift with an autogenous bone graft in histological evaluation at 2 or 6 months. A comparative study was designed where 10 patients with missing teeth bilaterally in the posterior zone of the maxilla were selected. Patients received a particulate autogenous bone graft under the same surgical conditions, selecting a site to collect a biopsy and histological study at two months and another at six months postoperatively. Histomorphometry was performed and were used Kolmogorov-Smirnov test, student's t-test and Spearman's correlation coefficient, considering a value of p<0.05. Differences were observed in inflammatory infiltrate and vascularization characteristics; however, the group analyzed at two months presented 38.12% ± 6.64 % of mineralized tissue, whereas the group studied at 6 months presented an average of 38.45 ± 9.27 %. There were no statistical differences between the groups. It is concluded that the bone formation may be similar in intrasinus particulate autogenous bone grafts in evaluations at two or six months; under these conditions, early installation of implants is viable.

  4. Alternative method to treat oroantral communication and fistula with autogenous bone graft and platelet rich firbin

    PubMed Central

    Niedzielska, Iwona; Borgiel-Marek, Halina; Różanowski, Bartosz

    2016-01-01

    Background Removing a tooth from the jaw results in the occurrence of oroantral communication in beneficial anatomic conditions or in the case of a iatrogenic effect. Popularized treatments of the oroantral communication have numerous faults. Large bone defect eliminates the chance to introduce an implant. Purpose of this work was assessment of the usefulness of autogenous bone graft and PRF in normal bone regeneration in the site of oroantral communication. Material and Methods Bone regeneration in the site of oroantral communication was assessed in 20 patients. Bone defects were supplemented autogenous bone graft from mental protuberance in 14 cases and from oblique line in 6 cases. The graft was covered with a PRF membrane. Results In the study group in all cases closure of the oroantral communication was observed. The average width of the alveolar was 13 mm and the average height was 12.5 mm. In 3 patients an average increase of alveolar height of 1.5 mm was observed. Conclusions This method may be the best option to prepare alveolar for new implant and prosthetic solutions. Key words:Oroantral communication, oroantral fistula, autogenous bone graft, bone regeneration, platelet rich fibrin. PMID:27475687

  5. Effect of Crack Opening on Penetrant Crack Detectability

    NASA Technical Reports Server (NTRS)

    Weaver, Devin

    2009-01-01

    Results: From the testing we were able to determine all the cracks within the test range were detectable or better with developer. Many of the indications after development lost their linearity and gave circular indications. Our tests were performed in a laboratory and our procedure would be difficult in an industrial setting. Conclusions: The "V" did not significantly affect our ability to detect the POD cracks with fluorescent penetrant. Conduct same experiment with more cracks. The 0.025 and 0.050 POD specimens are clean and documented with the SEM. Conduct water-wash fluorescent penetrant test at EAFB. The poppet cracks are tighter than the POD specimen cracks. Flight FCV poppets: 0.01 mils (0.3 microns) Langley fatigue cracked poppets: 0.02 mils (0.5 microns) POD specimen (post 5 mils): 0.05 mils (1.4 microns) We could not detect cracks in Langley fatigue-cracked poppets with fluorescent penetrant. Investigate inability of penetrant to wet the poppet surface.

  6. Thermo-mechanical simulations of early-age concrete cracking with durability predictions

    NASA Astrophysics Data System (ADS)

    Havlásek, Petr; Šmilauer, Vít; Hájková, Karolina; Baquerizo, Luis

    2017-09-01

    Concrete performance is strongly affected by mix design, thermal boundary conditions, its evolving mechanical properties, and internal/external restraints with consequences to possible cracking with impaired durability. Thermo-mechanical simulations are able to capture those relevant phenomena and boundary conditions for predicting temperature, strains, stresses or cracking in reinforced concrete structures. In this paper, we propose a weakly coupled thermo-mechanical model for early age concrete with an affinity-based hydration model for thermal part, taking into account concrete mix design, cement type and thermal boundary conditions. The mechanical part uses B3/B4 model for concrete creep and shrinkage with isotropic damage model for cracking, able to predict a crack width. All models have been implemented in an open-source OOFEM software package. Validations of thermo-mechanical simulations will be presented on several massive concrete structures, showing excellent temperature predictions. Likewise, strain validation demonstrates good predictions on a restrained reinforced concrete wall and concrete beam. Durability predictions stem from induction time of reinforcement corrosion, caused by carbonation and/or chloride ingress influenced by crack width. Reinforcement corrosion in concrete struts of a bridge will serve for validation.

  7. Importance of shrinkage in empirical bayes estimates for diagnostics: problems and solutions.

    PubMed

    Savic, Radojka M; Karlsson, Mats O

    2009-09-01

    Empirical Bayes ("post hoc") estimates (EBEs) of etas provide modelers with diagnostics: the EBEs themselves, individual prediction (IPRED), and residual errors (individual weighted residual (IWRES)). When data are uninformative at the individual level, the EBE distribution will shrink towards zero (eta-shrinkage, quantified as 1-SD(eta (EBE))/omega), IPREDs towards the corresponding observations, and IWRES towards zero (epsilon-shrinkage, quantified as 1-SD(IWRES)). These diagnostics are widely used in pharmacokinetic (PK) pharmacodynamic (PD) modeling; we investigate here their usefulness in the presence of shrinkage. Datasets were simulated from a range of PK PD models, EBEs estimated in non-linear mixed effects modeling based on the true or a misspecified model, and desired diagnostics evaluated both qualitatively and quantitatively. Identified consequences of eta-shrinkage on EBE-based model diagnostics include non-normal and/or asymmetric distribution of EBEs with their mean values ("ETABAR") significantly different from zero, even for a correctly specified model; EBE-EBE correlations and covariate relationships may be masked, falsely induced, or the shape of the true relationship distorted. Consequences of epsilon-shrinkage included low power of IPRED and IWRES to diagnose structural and residual error model misspecification, respectively. EBE-based diagnostics should be interpreted with caution whenever substantial eta- or epsilon-shrinkage exists (usually greater than 20% to 30%). Reporting the magnitude of eta- and epsilon-shrinkage will facilitate the informed use and interpretation of EBE-based diagnostics.

  8. Effect of plasma arc curing on polymerization shrinkage of orthodontic adhesive resins.

    PubMed

    Bang, H-C; Lim, B-S; Yoon, T-H; Lee, Y-K; Kim, C-W

    2004-08-01

    The purpose of this study was to evaluate the polymerization shrinkage of three orthodontic adhesive resins when polymerized with a high-energy plasma arc light (1340 mW cm(-2)) and a conventional halogen light (500 mW cm(-2)), and to correlate the polymerization shrinkage with the degree of conversion. To equalize the total light energy delivered to the adhesive resin, irradiation time was varied between 3 or 6 s for a plasma arc-curing unit, and 8 or 16 s for a halogen light-curing unit. The polymerization shrinkage of adhesive resins during the light-curing process was measured using a computer-controlled mercury dilatometer and the degree of conversion was measured using Fourier transform infrared spectroscopy. A plasma arccuring unit produced significantly lower polymerization shrinkage than a halogen light-curing unit when the equivalent total light energy was irradiated to the orthodontic adhesive resins (P < 0.05). The magnitude of polymerization shrinkage was significantly different depending on the kind of adhesive resins (P < 0.05), but there was no significant correlation between the filler fraction and the polymerization shrinkage (r2 = 0.039). There was strong correlation (r2 = 0.787) between the polymerization shrinkage and the degree of conversion with a halogen light-curing unit, but poor correlation (r2 = 0.377) was observed with a plasma arc-curing unit.

  9. Study of shrinkage-strain and contraction rates of commercial and experimental compomers.

    PubMed

    Latorre-García, Mariana; Alvarez-Gayosso, Carlos; Barceló-Santana, Federico; Vera-Graziano, Ricardo

    2006-11-01

    To asses the contraction rate and shrinkage-strain of a new experimental compomer in comparison with four commercial compomers and a flowable composite resin. Shrinkage-strain and contraction rate were calculated by measuring the deflection of a disc in a developed instrument using "bonded disk" method. Both shrinkage-strain and contraction rate are reported. Total shrinkage-strain for compomer systems varies from 2.59 to 3.34%, whereas the flowable composite resin showed a value of 3.50%. The contraction rate for compomers varies from 81.60 to 109.80 microm/min, whereas the flowable composite resin obtained 141.6 microm/min. Commercial compomers show a lower contraction rate than the control group, whereas the experimental group only shows statistical differences with a commercial compomer (Dyract AP). The shrinkage-strain and contraction rate results for the experimental compomer are as good as those obtained for a commercial flowable compomer and a flowable composite resin. The contraction rates of all compomers could be directly related to polymerization rates. The method used to measure shrinkage-strain and contraction rate is adequate because it simulates conditions in situ. It can be inferred that the contraction rate is directly related to shrinkage-strain.

  10. Experimental and theoretical modeling of shrinkage damage formation in fiber composites

    NASA Astrophysics Data System (ADS)

    Korotkov, V. N.; Rozenberg, B. A.

    1998-03-01

    The cure of a thermoset matrix in the formation of composites is always accompanied by chemical shrinkage that generates internal stresses. In composites with high fiber content, the matrix is cured under three-dimensionally constrained conditions. The results of the previous experimental and theoretical modeling of formation of shrinkage damage under these conditions in epoxy-amine systems are briefly discussed. The effect of the model geometry (tube and plate models), scale factor, cure schedule, and chemical structure of composites is analyzed. A theoretical model for predicting the possibility of formation of shrinkage damage in fiber composites is proposed. A regular square structure was considered. Analysis showed that the maximum level of shrinkage stress in the matrix at the ultimate fiber fraction ϕ+ was close to the stress level σ+ in an experimental long tube model, where the formation of shrinkage damage took place. The experimental results for the short tube model showed that the shrinkage damage in epoxy-amine systems occurred up to approximately σ+/3. The damage development took place within the whole range of fiber content from ϕ+ to ϕ* (where the shrinkage stress level was about σ+/3). In the long tube model, cohesive defects always nucleated inside the matrix. The damage grew, reached the inner surface of the tube, and then extended as adhesive debondings. A similar situation is expected in composites with a high fiber content. The damage considered is local, and the total monolithic character of a composite product is conserved.

  11. Repair of long bone defects with demineralized bone matrix and autogenous bone composite

    PubMed Central

    Ozdemir, Mehmet T; Kir, Mustafa Ç

    2011-01-01

    Background: Repair of diaphyseal bone defects is a challenging problem for orthopedic surgeons. In large bone defects the quantity of harvested autogenous bone may not be sufficient to fill the gap and then the use of synthetic or allogenic grafts along with autogenous bone becomes mandatory to achieve compact filling. Finding the optimal graft mixture for treatment of large diaphyseal defects is an important goal in contemporary orthopedics and this was the main focus of this study. The aim of this study is to investigate the efficacy of demineralized bone matrix (DBM) and autogenous cancellous bone (ACB) graft composite in a rabbit bilateral ulna segmental defect model. Materials and Methods: Twenty-seven adult female rabbits were divided into five groups. A two-centimeter piece of long bone on the midshaft of the ulna was osteotomized and removed from the rabbits’ forearms. In group 1 (n=7) the defects were treated with ACB, in group 2 (n=7) with DBM, and in group 3 (n=7) with ACB and DBM in the ratio of 1:1. Groups 4 and 5, with three rabbits in each group, were the negative and positive controls, respectively. Twelve weeks after implantation the rabbits were sacrificed and union was evaluated with radiograph (Faxitron), dual-energy x-ray absorptiometry (DEXA), and histological methods (decalcified sectioning). Results: Union rates and the volume of new bone in the different groups were as follows: group 1 - 92.8% union and 78.6% new bone; group 2 - 72.2% union and 63.6% new bone; and group 3 - 100% union and 100% new bone. DEXA results (bone mineral density [BMD]) were as follows: group 1 - 0.164 g/cm2, group 2 - 0.138 g/cm2, and group 3 - 0.194 g/cm2. Conclusions: DBM serves as a graft extender or enhancer for autogenous graft and decreases the need of autogenous bone graft in the treatment of bone defects. In this study, the DBM and ACB composite facilitated the healing process. The union rate was better with the combination than with the use of any one of

  12. Sinus floor augmentation with autogenous bone vs. a bovine-derived xenograft - a 5-year retrospective study.

    PubMed

    Lutz, Rainer; Berger-Fink, Susanne; Stockmann, Philipp; Neukam, Friedrich Wilhelm; Schlegel, Karl Andreas

    2015-06-01

    The long-term outcome after sinus augmentation with autogenous bone or a bovine xenograft (Bio-Oss(®)) was assessed in 47 patients. Inclusion criterion was a vertical dimension of the maxilla of <4 mm. After a functional loading period of 60 months, implant survival and reduction in the augmentation height were compared between the two groups evaluated. Sinus augmentation was performed using mandibular bone grafts or Bio-Oss(®). In the autogenous bone group, 70 implants were placed in 23 patients, while in the Bio-Oss(®) group, 24 patients received 98 implants. Fisher's exact test and equivalence testing were used to compare implant survival rates. The overall survival rate of the implants was 95.8% 5 years after implant insertion. In the autogenous bone group, the implants had a survival rate of 97.1%, while in the Bio-Oss(®) group, 94.9% of the implants survived. The difference was not statistically significant (P > 0.05); both treatments are equivalent (confidence interval 90%) for the equivalence interval [-0.1; 0.1]. 43.5% of the cases showed no reduction in the augmentation height 5 years after implant insertion, when augmentation was performed with autogenous bone, while in the Bio-Oss(®) group, no resorption was found in 50% of the augmented areas. Up to 25% reduction in augmentation height was found in 47.8% in the autogenous and in 45.8% in the Bio-Oss(®) group. In 8.7% of all cases in the autogenous bone group and in 4.2 % in the Bio-Oss(®) group, up to 50% of the augmented height was resorbed. After a 5 years evaluation period, Bio-Oss(®) as material for the indication maxillary sinus augmentation shows to be equivalent to autogenous bone grafting. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Effect of resin-composite filler particle size and shape on shrinkage-stress.

    PubMed

    Satterthwaite, Julian D; Maisuria, Amit; Vogel, Karin; Watts, David C

    2012-06-01

    The aim of this study was to investigate the effect of variations in filler particle size and shape on the polymerization shrinkage-stress kinetics of resin-composites. A model series of 12 VLC resin-composites were studied. The particulate dispersed phase volume fraction was 56.7%: these filler particles were systematically graded in size, and further were either spherical or irregular. A Bioman instrument (cantilever beam method) was employed to determine the shrinkage-stress kinetics following 40s irradiation (600 mW/cm(2)) at 23°C (n=3). All data were captured for 60 min and the final shrinkage-stress calculated. Shrinkage-stress varied between 3.86 MPa (SD 0.14) for S3 (spherical filler particles of 500 nm) and 8.44 MPa (SD 0.41) for I1 (irregular filler particles of 450 nm). The shrinkage-stress values were generally lower for those composites with spherical filler particles than those with irregular filler particles. The differences in shrinkage-stress with filler particle size and shape were statistically significant (p<0.001). Composites with spherical filler particles exhibit lower shrinkage-stress values compared to those with irregular filler particles. Shrinkage-stress and shrinkage-stress rate vary in a complex manner with variations in the size of the dispersed phase particles: a hypothesized explanation for the effect of filler particle size and shape is presented. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  14. Replica-Based Crack Inspection

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Willard, Scott A.; Smith, Stephen W.; Piascik, Robert S.

    2008-01-01

    Surface replication has been proposed as a method for crack detection in space shuttle main engine flowliner slots. The results of a feasibility study show that examination of surface replicas with a scanning electron microscope can result in the detection of cracks as small as 0.005 inch, and surface flaws as small as 0.001 inch, for the flowliner material.

  15. Experiences on IGSCC crack manufacturing

    SciTech Connect

    Veron, P.

    1997-02-01

    The author presents his experience in manufacturing IGSCC realistic defects, mainly in INCONEL 600 MA Steam Generator Tubes. From that experience he extracts some knowledge about this cracking (influence of chemistry in the environment, stress state, crack growth rate, and occurrence in laboratory condition of break before leak).

  16. Strain-induced band gap shrinkage in Ge grown on Si substrate

    NASA Astrophysics Data System (ADS)

    Ishikawa, Yasuhiko; Wada, Kazumi; Cannon, Douglas D.; Liu, Jifeng; Luan, Hsin-Chiao; Kimerling, Lionel C.

    2003-03-01

    Band gap shrinkage induced by tensile strain is shown for Ge directly grown on Si substrate. In Ge-on-Si pin diodes, photons having energy lower than the direct band gap of bulk Ge were efficiently detected. According to photoreflectance measurement, this property is due to band gap shrinkage. The origin of the shrinkage is not the Franz-Keldysh effect but rather tensile strain. It is discussed that the generation of such a tensile strain can be ascribed to the difference of thermal expansion between Ge and Si. Advantages of this tensile Ge for application to photodiode are also discussed.

  17. Method to measure the polymerization shrinkage of light-cured composites.

    PubMed

    Puckett, A D; Smith, R

    1992-07-01

    The polymerization shrinkage of light-cured dental composite resins has been reported to cause a marginal gap between the cavity wall and the restoration, leading to the premature and/or tensile stress failure of the composite restoration. This study measured the volumetric shrinkage of six light-cured posterior composites by measuring specific gravity differences between uncured and cured composite test specimens, using a modified version of ASTM method D792 "Specific Gravity and Density of Plastics by Displacement." The measured volumetric shrinkage ranged from 1.35% to 3.22%.

  18. Effects of drying conditions, admixtures and specimen size on shrinkage strains

    SciTech Connect

    Al-Saleh, Saleh A. . E-mail: alsaleh@dr.com; Al-Zaid, Rajeh Z.

    2006-10-15

    The paper presents the results of an experimental investigation on the effects of drying conditions, specimen size and presence of plasticizing admixture on the development of shrinkage strains. The measurements are taken in a harsh (50 deg. C and 5% R.H.) and a moderate environment (28 deg. C and 50% R.H.). The results include strain development at various levels of cross sections of concrete prisms. The drying conditions are found to be the dominant parameter affecting the shrinkage strain development particularly in specimens of smaller sizes. The effect of plasticizing admixture on shrinkage strains is negligible.

  19. Hydrocarbon cracking and reforming process

    SciTech Connect

    Le, Q.N.; Schipper, P.H.; Owen, H.

    1992-03-31

    This patent describes a process for upgrading paraffinic naphtha to high octane fuel. It comprises: contacting a fresh naphtha feedstock stream containing a major amount of C{sub 7+} alkanes and naphthenes with medium pore acid cracking catalyst under low pressure selective cracking conditions effective to produce 4-C5 isoalkene and C4-C5 isoalkane, the cracking catalyst being substantially free of hydrogenation-dehydrogenation metal components and having an acid cracking activity less than 15; separating cracking effluent to obtain an olefinic fraction rich in C4-C5 isoalkene and a C6+ fraction; etherifying the C4-C5 isoalkene fraction by catalytic reaction with lower alkanol to produce tertiary-alkyl ether product; and reforming the C6+ fraction to provide high octane gasoline components.

  20. Cracking in Drying Colloidal Films

    NASA Astrophysics Data System (ADS)

    Singh, Karnail B.; Tirumkudulu, Mahesh S.

    2007-05-01

    It has long been known that thick films of colloidal dispersions such as wet clays, paints, and coatings crack under drying. Although capillary stresses generated during drying have been recently identified as the cause for cracking, the existence of a maximum crack-free film thickness that depends on particle size, rigidity, and packing has not been understood. Here, we identify two distinct regimes for crack-free films based on the magnitude of compressive strain at the maximum attainable capillary pressure and show remarkable agreement of measurements with our theory. We anticipate our results to not only form the basis for design of coating formulations for the paints, coatings, and ceramics industry but also assist in the production of crack-free photonic band gap crystals.

  1. Laser-induced scleral shrinkage for refractive surgery

    NASA Astrophysics Data System (ADS)

    Ren, Qiushi; Simon, Gabriel; Parel, Jean-Marie A.; Shen, Jin-Hui

    1994-06-01

    We investigate the laser refractive scleroplasty (LRS) as a potential minimal-invasive method for correcting post-operative astigmatism. The scleral shrinkage near limbus was induced on 6 cadaver eyes using a 200 micrometers fiber optic probe coupled to a pulsed Ho:YAG laser. The diameter of the treatment spot was 0.8 mm. The output energy measured at tip was 60.2+/- 0.6 mJ. The treatments consisted of multiple sector patterns placed along the major axis of astigmatism parallel to the limbus, and round patterns placed along the limbus. Three treatment spots were applied on each side of the sector. The separation among sectors and limbus is 1 mm. Keratometry and topography of the cornea were measured after each sector or round pattern treatment. Effect of 5 and 10 pulses at each treatment spot were compared. Histology was performed to evaluate laser tissue damage. The major axis of astigmatism was shifted 90 degrees after the sector pattern treatment and amount of dioptric change increased when adding a new treatment or using more treatment pulses. However, the spherical equivalent of the eyes was essentially unchanged. The keratometry of the corneas remained the same after the round pattern treatment. Laser refractive scleroplasty may be applied for the correction of post-operative astigmatism.

  2. Gene Network Reconstruction using Global-Local Shrinkage Priors*

    PubMed Central

    Leday, Gwenaël G.R.; de Gunst, Mathisca C.M.; Kpogbezan, Gino B.; van der Vaart, Aad W.; van Wieringen, Wessel N.; van de Wiel, Mark A.

    2016-01-01

    Reconstructing a gene network from high-throughput molecular data is an important but challenging task, as the number of parameters to estimate easily is much larger than the sample size. A conventional remedy is to regularize or penalize the model likelihood. In network models, this is often done locally in the neighbourhood of each node or gene. However, estimation of the many regularization parameters is often difficult and can result in large statistical uncertainties. In this paper we propose to combine local regularization with global shrinkage of the regularization parameters to borrow strength between genes and improve inference. We employ a simple Bayesian model with non-sparse, conjugate priors to facilitate the use of fast variational approximations to posteriors. We discuss empirical Bayes estimation of hyper-parameters of the priors, and propose a novel approach to rank-based posterior thresholding. Using extensive model- and data-based simulations, we demonstrate that the proposed inference strategy outperforms popular (sparse) methods, yields more stable edges, and is more reproducible. The proposed method, termed ShrinkNet, is then applied to Glioblastoma to investigate the interactions between genes associated with patient survival. PMID:28408966

  3. Super-resolution optical telescopes with local light diffraction shrinkage.

    PubMed

    Wang, Changtao; Tang, Dongliang; Wang, Yanqin; Zhao, Zeyu; Wang, Jiong; Pu, Mingbo; Zhang, Yudong; Yan, Wei; Gao, Ping; Luo, Xiangang

    2015-12-18

    Suffering from giant size of objective lenses and infeasible manipulations of distant targets, telescopes could not seek helps from present super-resolution imaging, such as scanning near-field optical microscopy, perfect lens and stimulated emission depletion microscopy. In this paper, local light diffraction shrinkage associated with optical super-oscillatory phenomenon is proposed for real-time and optically restoring super-resolution imaging information in a telescope system. It is found that fine target features concealed in diffraction-limited optical images of a telescope could be observed in a small local field of view, benefiting from a relayed metasurface-based super-oscillatory imaging optics in which some local Fourier components beyond the cut-off frequency of telescope could be restored. As experimental examples, a minimal resolution to 0.55 of Rayleigh criterion is obtained, and imaging complex targets and large targets by superimposing multiple local fields of views are demonstrated as well. This investigation provides an access for real-time, incoherent and super-resolution telescopes without the manipulation of distant targets. More importantly, it gives counterintuitive evidence to the common knowledge that relayed optics could not deliver more imaging details than objective systems.

  4. Super-resolution optical telescopes with local light diffraction shrinkage

    NASA Astrophysics Data System (ADS)

    Wang, Changtao; Tang, Dongliang; Wang, Yanqin; Zhao, Zeyu; Wang, Jiong; Pu, Mingbo; Zhang, Yudong; Yan, Wei; Gao, Ping; Luo, Xiangang

    2015-12-01

    Suffering from giant size of objective lenses and infeasible manipulations of distant targets, telescopes could not seek helps from present super-resolution imaging, such as scanning near-field optical microscopy, perfect lens and stimulated emission depletion microscopy. In this paper, local light diffraction shrinkage associated with optical super-oscillatory phenomenon is proposed for real-time and optically restoring super-resolution imaging information in a telescope system. It is found that fine target features concealed in diffraction-limited optical images of a telescope could be observed in a small local field of view, benefiting from a relayed metasurface-based super-oscillatory imaging optics in which some local Fourier components beyond the cut-off frequency of telescope could be restored. As experimental examples, a minimal resolution to 0.55 of Rayleigh criterion is obtained, and imaging complex targets and large targets by superimposing multiple local fields of views are demonstrated as well. This investigation provides an access for real-time, incoherent and super-resolution telescopes without the manipulation of distant targets. More importantly, it gives counterintuitive evidence to the common knowledge that relayed optics could not deliver more imaging details than objective systems.

  5. Super-resolution optical telescopes with local light diffraction shrinkage

    PubMed Central

    Wang, Changtao; Tang, Dongliang; Wang, Yanqin; Zhao, Zeyu; Wang, Jiong; Pu, Mingbo; Zhang, Yudong; Yan, Wei; Gao, Ping; Luo, Xiangang

    2015-01-01

    Suffering from giant size of objective lenses and infeasible manipulations of distant targets, telescopes could not seek helps from present super-resolution imaging, such as scanning near-field optical microscopy, perfect lens and stimulated emission depletion microscopy. In this paper, local light diffraction shrinkage associated with optical super-oscillatory phenomenon is proposed for real-time and optically restoring super-resolution imaging information in a telescope system. It is found that fine target features concealed in diffraction-limited optical images of a telescope could be observed in a small local field of view, benefiting from a relayed metasurface-based super-oscillatory imaging optics in which some local Fourier components beyond the cut-off frequency of telescope could be restored. As experimental examples, a minimal resolution to 0.55 of Rayleigh criterion is obtained, and imaging complex targets and large targets by superimposing multiple local fields of views are demonstrated as well. This investigation provides an access for real-time, incoherent and super-resolution telescopes without the manipulation of distant targets. More importantly, it gives counterintuitive evidence to the common knowledge that relayed optics could not deliver more imaging details than objective systems. PMID:26677820

  6. INTER-GROUP IMAGE REGISTRATION BY HIERARCHICAL GRAPH SHRINKAGE.

    PubMed

    Ying, Shihui; Wu, Guorong; Liao, Shu; Shen, Dinggang

    2013-12-31

    In this paper, we propose a novel inter-group image registration method to register different groups of images (e.g., young and elderly brains) simultaneously. Specifically, we use a hierarchical two-level graph to model the distribution of entire images on the manifold, with intra-graph representing the image distribution in each group and the inter-graph describing the relationship between two groups. Then the procedure of inter-group registration is formulated as a dynamic evolution of graph shrinkage. The advantage of our method is that the topology of entire image distribution is explored to guide the image registration. In this way, each image coordinates with its neighboring images on the manifold to deform towards the population center, by following the deformation pathway simultaneously optimized within the graph. Our proposed method has been also compared with other state-of-the-art inter-group registration methods, where our method achieves better registration results in terms of registration accuracy and robustness.

  7. High speed thin plate fatigue crack monitor

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz A. (Inventor); Heyman, Joseph S. (Inventor); Namkung, Min (Inventor); Fulton, James P. (Inventor)

    1996-01-01

    A device and method are provided which non-destructively detect crack length and crack geometry in thin metallic plates. A non-contacting vibration apparatus produces resonant vibrations without introducing extraneous noise. Resulting resonant vibration shifts in cracked plates are correlated to known crack length in plates with similar resonant vibration shifts. In addition, acoustic emissions of cracks at resonance frequencies are correlated to acoustic emissions from known crack geometries.

  8. Three-dimensional crack closure behavior

    NASA Technical Reports Server (NTRS)

    Dawicke, D. S.; Grandt, A. F., Jr.; Newman, J. C., Jr.

    1990-01-01

    A crack closure measurement technique involving fatigue striations was used to produce a three-dimensional crack opening load profile for 2024-T351 aluminum alloy. The crack opening load profile, determined through the specimen thickness, was compared with crack opening load measurements made with strain gages and displacement gages. The results of this study indicate that a significant three-dimensional variation in crack closure behavior occurs in the alloy examined. An understanding of this phehomenon is important in understanding crack growth behavior, predicting crack shape changes, and interpreting 'standard' crack closure measurement techniques.

  9. Volumetric changes of the graft after maxillary sinus floor augmentation with Bio-Oss and autogenous bone in different ratios: a radiographic study in minipigs.

    PubMed

    Jensen, Thomas; Schou, Søren; Svendsen, Patricia A; Forman, Julie Lyng; Gundersen, Hans Jørgen G; Terheyden, Hendrik; Holmstrup, Palle

    2012-08-01

    The objective of the present study was to learn about the volumetric changes of the graft after maxillary sinus floor augmentation with Bio-Oss and autogenous bone from the iliac crest or the mandible in different ratios in minipigs. Bilateral maxillary sinus floor augmentation was performed in 40 minipigs with: (A) 100% autogenous bone, (B) 75% autogenous bone and 25% Bio-Oss, (C) 50% autogenous bone and 50% Bio-Oss, (D) 25% autogenous bone and 75% Bio-Oss, and (E) 100% Bio-Oss. The autogenous bone graft was harvested from the iliac crest or the mandible and the graft composition was selected at random and placed concomitant with implant placement. Computed tomographies of the maxillary sinuses were obtained preoperatively, immediately postoperatively, and at euthanasia after 12 weeks. The volumetric changes of the graft were estimated using the Cavalieri principle and expressed as mean percentage with a 95% confidence interval (CI). The mean volume of the graft was reduced by (A) 65% (95% CI: 60-70%), (B) 38% (95% CI: 35-41%), (C) 23% (95% CI: 21-25%), (D) 16% (95% CI: 12-21%), and (E) 6% (95% CI: 4-8%). The volumetric reduction was significantly influenced by the ratio of Bio-Oss and autogenous bone (P<0.001), but not by the origin of the autogenous bone graft (P=0.2). The volume of autogenous bone grafts from the iliac crest and the mandible is reduced significantly after maxillary sinus floor augmentation in minipigs. The graft volume is better preserved after the addition of Bio-Oss and the volumetric reduction is significantly influenced by the ratio of Bio-Oss and autogenous bone. However, further studies are needed addressing the amount of new bone formation and bone-to-implant contact before the final conclusion can be made about the optimal ratio of Bio-Oss and autogenous bone. © 2011 John Wiley & Sons A/S.

  10. Prediction of fatigue crack-growth patterns and lives in three-dimensional cracked bodies

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.; Raju, I. S.

    1986-01-01

    Fatigue crack growth patterns and lives for surface cracks, surface cracks at holes, and corner cracks at holes in three dimensional bodies were predicted using linear-elastic fracture mechanics concepts that were modified to account for crack-closure behavior. The predictions were made by using stress intensity factor equations for these crack configurations and the fatigue crack-growth (delta K against rate) relationship for the material of interest. The crack configurations were subjected to constant-amplitude fatigue loading under either remote tension or bending loads. The predicted crack growth patterns and crack growth lives for aluminum alloys agreed well with test data from the literature.

  11. Prediction of fatigue crack-growth patterns and lives in three-dimensional cracked bodies

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.; Raju, I. S.

    1984-01-01

    Fatigue crack growth patterns and lives for surface cracks, surface cracks at holes, and corner cracks at holes in three dimensional bodies were predicted using linear-elastic fracture mechanics concepts that were modified to account for crack-closure behavior. The predictions were made by using stress intensity factor equations for these crack configurations and the fatigue crack-growth (delta K against rate) relationship for the material of interest. The crack configurations were subjected to constant-amplitude fatigue loading under either remote tension or bending loads. The predicted crack growth patterns and crack growth lives for aluminum alloys agreed well with test data from the literature.

  12. Impact of hydraulic suction history on crack growth mechanics in soil

    NASA Astrophysics Data System (ADS)

    Yoshida, S.; Hallett, P. D.

    2008-05-01

    The mechanics of crack formation and the influence of soil stress history were described using the crack tip opening angle (CTOA) measured with fractography. Two soils were studied: a model soil consisting of 40% Ca-bentonite and 60% fine silica sand and a remolded paddy soil with similar clay content and mineralogy. Fracture testing used deep-notch bend specimens formed by molding soils at the liquid limit into rectangular bars, equilibrating to soil water suction ranging from 5 kPa to 50 kPa (with some 50 kPa specimens wetted to 5 kPa), and inserting a crack 0.4× specimen thickness. Bend tests at a constant displacement rate of 1 mm min-1 provided data on applied force and load point displacement. The growth and geometry of the cracks were quantified from a series of images to determine the CTOA. Modulus of rupture, evaluated from the peak force, increased as water suction increased. However, rewetting did not alter the peak stress from the 50 kPa value, indicating that shrinkage-induced consolidation was more important than the soil water suction at the onset of testing. CTOA measured during stable crack growth decreased with drying. CTOA decreased even further when specimens equilibrated initially to 50 kPa were rewetted to 5 kPa. These results suggested that CTOA was primarily governed by the stiffness, although rewetting probably altered the capillary stresses in advance of the crack tip. Our future work will combine CTOA with a model that couples hydrological and mechanical processes to take into account the dependency of CTOA on the soil water regime so that crack propagation in soil can be predicted.

  13. Interdendritic Strain and Macrosegregation-Coupled Phenomena for Interdendritic Crack Formation in Direct-Chill Cast Sheet Ingots

    NASA Astrophysics Data System (ADS)

    EL-Bealy, Mostafa Omar

    2012-06-01

    In a study of the early stages of dendritic solidification in the direct-chill cast sheet ingots, the coupled effect of interdendritic strain and macrosegregation on the interdendritic cracks formation in dendritic equiaxed structure has been investigated by the metallographic study of ingot samples and by performing a set of mathematical analyses for AA-6061 and AA-1050 aluminum alloys. The metallographic investigation contains microstructure examinations and macrosegregation measurements of collected samples from plant trials. The mathematical analysis consists of a two-dimensional (2-D) fluid flow, heat flow, interdendritic strain, and macrosegregation-coupled model. Also, a simple approach to measure interdendritic crack has been developed based on the accumulative interdendritic strain criterion, local dendritic phases, and the crystal distortion correlation factor resulting from steep positive local segregation. The model predications have clarified the effect of high positive macrosegregation on the surface and subsurface interdendritic crack formation. It has been revealed that interdendritic strain starts to generate just below the liquidus temperature, resulting from shrinkage of liquid→solid phase transformation and contraction of dendritic solid in the incoherent mushy region. In this region, the coupled effect of the shrinkage/contraction mechanism increases the interdendritic distances between equiaxed crystals and the interdendritic crack begins to nucleate. Subsequently, in the coherent mushy region, the different interdendritic strain sources start to affect significantly the distances between equiaxed crystals in a diverse way, and therefore, the final morphology of interdendritic crack begins to form. The mechanism of interdendritic crack formation during dendritic equiaxed structure solidification and the possible solutions to this problem are discussed.

  14. Use of autogenous bone and beta-tricalcium phosphate in maxillary sinus lifting: a prospective, randomized, volumetric computed tomography study.

    PubMed

    Gorla, L F de O; Spin-Neto, R; Boos, F B D J; Pereira, R dos S; Garcia-Junior, I R; Hochuli-Vieira, E

    2015-12-01

    The correction of bone defects can be performed using autogenous or alloplastic materials, such as beta-tricalcium phosphate (β-TCP). This study compared the changes in bone volume (CBV) after maxillary sinus lifting using autogenous bone (n = 12), autogenous bone associated with β-TCP 1:1 (ChronOS; DePuy Synthes, Paoli, CA, USA) (n = 9), and β-TCP alone (n = 11) as grafting material, by means of cone beam computed tomography (CBCT). CBV was evaluated by comparing CBCT scans obtained in the immediate postoperative period (5-7 days) and at 6 months postoperative in each group using OsiriX software (OsiriX Foundation, Geneva, Switzerland). The results showed an average resorption of 45.7 ± 18.6% for the autogenous bone group, 43.8 ± 18.4% for the autogenous bone+β-TCP group, and 38.3 ± 16.6% for the β-TCP group. All bone substitute materials tested in this study presented satisfactory results for maxillary sinus lifting procedures regarding the maintenance of graft volume during the healing phase before the insertion of implants, as assessed by means of CBCT. Copyright © 2015 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

  15. [Effect of hypnosis and autogenic training on acral circulation and coping with the illness in patients with progressive scleroderma].

    PubMed

    Seikowski, K; Weber, B; Haustein, U F

    1995-02-01

    In 12 patients with systemic sclerosis the influence of hypnosis and autogenic training on the acral blood circulation and the coping with the disease was investigated in a pilot study. In the first step significant increases in the skin temperature of the finger (mean +/- SD: 3.9 +/- 1.2 degrees C) could be found after relaxation hypnosis. In the second step six patients (study group) gained experience with autogenic training. The other six patients served as control group. In the study group, the skin temperature of the fingers (short-term effect) was significantly higher than in the control group (1.9 +/- 1.0 degrees C). Long-term effects of the autogenic training (mean acral rewarning time, duration and course of the Raynaud attacks, acral lesions of the hands, psychosomatic status of complaints, type of relation to the disease as precondition for coping with the disease) were not found within the relatively short follow-up period of 4 months. Two patients, however, reported that they could shorten the duration of Raynaud attacks by autogenic training. In our patients heterogenicity and an increased score of multiple psychosomatic complaints were registered at the outset. As far as the type of relation to the disease is concerned, the patients could be assessed as almost adapted. Hypnosis and autogenic training can be recommended as complementary therapy in systemic sclerosis.

  16. Autogenous bone graft combined with polylactic polyglycolic acid polymer for treatment of dehiscence around immediate dental implants.

    PubMed

    Hassan, Khalid S

    2009-11-01

    The use of composite bone grafts in dehiscence defects around immediate dental implants are aimed at improving the outcome of the regenerative process. The present study was designed to evaluate the efficacy of combinations of autogenous bone graft with a synthetic copolymer polylactic and polyglycolic acid (Fisiograft) on bone healing of buccal dehiscence defects around immediate dental implants. Sixteen adult male patients who each received an immediate implant for a single tooth replacement at a maxillary anterior or premolar site were included in this study. Patients were divided into 2 groups. One group received immediate dental implants augmented with autogenous bone graft combined with Fisiograft. The other group received immediate dental implants augmented with autogenous bone graft alone. The results revealed that both treatment modalities led to significant improvements for the primary outcome regarding bone fill as well as a significant reduction of probing pocket depth and gain of attachment level. Moreover, there were slightly statistically significant differences between the groups. In conclusion, the combination of autogenous bone graft and Fisiograft showed a slight superiority to autogenous bone graft alone, suggesting that it could be an optimum bone substitute for treatment of dehiscence around immediate dental implant.

  17. Characteristics of low polymerization shrinkage flowable resin composites in newly-developed cavity base materials for bulk filling technique.

    PubMed

    Nitta, Keiko; Nomoto, Rie; Tsubota, Yuji; Tsuchikawa, Masuji; Hayakawa, Tohru

    2017-06-23

    The purpose of this study was to evaluate polymerization shrinkage and other physical properties of newly-developed cavity base materials for bulk filling technique, with the brand name BULK BASE (BBS). Polymerization shrinkage was measured according to ISO/FDIS 17304. BBS showed the significantly lowest polymerization shrinkage and significantly higher depth of cure than conventional flowable resin composites (p<0.05). The Knoop hardness, flexural strength and elastic modulus of that were significantly lower than conventional flowable resin composites (p<0.05). BBS had the significantly greatest filler content (p<0.05). SEM images of the surface showed failure of fillers. The lowest polymerization shrinkage was due to the incorporation of a new type of low shrinkage monomer, which has urethane moieties. There were no clear correlations between inorganic filler contents and polymerization shrinkage, flexural strength and elastic modulus. In conclusion, the low polymerization shrinkage of BBS will be useful for cavity treatment in dental clinics.

  18. Numerical simulation on open wellbore shrinkage and casing equivalent stress in bedded salt rock stratum.

    PubMed

    Liu, Jianjun; Zhang, Linzhi; Zhao, Jinzhou

    2013-01-01

    Most salt rock has interbed of mudstone in China. Owing to the enormous difference of mechanical properties between the mudstone interbed and salt rock, the stress-strain and creep behaviors of salt rock are significantly influenced by neighboring mudstone interbed. In order to identify the rules of wellbore shrinkage and casings equivalent stress in bedded salt rock stratum, three-dimensional finite difference models were established. The effects of thickness and elasticity modulus of mudstone interbed on the open wellbore shrinkage and equivalent stress of casing after cementing operation were studied, respectively. The results indicate that the shrinkage of open wellbore and equivalent stress of casings decreases with the increase of mudstone interbed thickness. The increasing of elasticity modulus will reduce the shrinkage of open wellbore and casing equivalent stress. Research results can provide the scientific basis for the design of mud density and casing strength.

  19. Measurement of composite shrinkage using a fibre optic Bragg grating sensor.

    PubMed

    Milczewski, M S; Silva, J C C; Paterno, A S; Kuller, F; Kalinowski, H J

    2007-01-01

    Fibre Bragg grating is used to determine resin-based composite shrinkage. Two composite resins (Freedom from SDI and Z100 from 3M) were tested to determine the polymerization contraction behaviour. Each sample of resin was prepared with an embedded fibre Bragg grating. A LED activation unit with wavelength from 430 nm to 470 nm (Dabi Atlante) was used for resin polymerization. The wavelength position of the peak in the optical reflection spectra of the sensor was measured. The wavelength shift was related to the shrinkage deformation of the samples. Temperature and strain evolution during the curing phase of the material was monitored. The shrinkage in the longitudinal direction was 0.15 +/- 0.02% for resin Z100 (3M) and 0.06+/-0.01% for Freedom (SDI); two-thirds of shrinkage occurred after the first 50 s of illumination.

  20. Numerical Simulation on Open Wellbore Shrinkage and Casing Equivalent Stress in Bedded Salt Rock Stratum

    PubMed Central

    Liu, Jianjun

    2013-01-01

    Most salt rock has interbed of mudstone in China. Owing to the enormous difference of mechanical properties between the mudstone interbed and salt rock, the stress-strain and creep behaviors of salt rock are significantly influenced by neighboring mudstone interbed. In order to identify the rules of wellbore shrinkage and casings equivalent stress in bedded salt rock stratum, three-dimensional finite difference models were established. The effects of thickness and elasticity modulus of mudstone interbed on the open wellbore shrinkage and equivalent stress of casing after cementing operation were studied, respectively. The results indicate that the shrinkage of open wellbore and equivalent stress of casings decreases with the increase of mudstone interbed thickness. The increasing of elasticity modulus will reduce the shrinkage of open wellbore and casing equivalent stress. Research results can provide the scientific basis for the design of mud density and casing strength. PMID:24198726

  1. Mechanical properties, volumetric shrinkage and depth of cure of short fiber-reinforced resin composite.

    PubMed

    Tsujimoto, Akimasa; Barkmeier, Wayne W; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

    2016-01-01

    The mechanical properties, volumetric shrinkage and depth of cure of a short fiber-reinforced resin composite (SFRC) were investigated in this study and compared to both a bulk fill resin composite (BFRC) and conventional glass/ceramic-filled resin composite (CGRC). Fracture toughness, flexural properties, volumetric shrinkage and depth of cure of the SFRC, BFRC and CGRC were measured. SFRC had significantly higher fracture toughness than BFRCs and CGRCs. The flexural properties of SFRC were comparable with BFRCs and CGRCs. SFRC showed significantly lower volumetric shrinkage than the other tested resin composites. The depth of cure of the SFRC was similar to BFRCs and higher than CGRCs. The data from this laboratory investigation suggests that SFRC exhibits improvements in fracture toughness, volumetric shrinkage and depth of cure when compared with CGRC, but depth of cure of SFRC was similar to BFRC.

  2. Formation of a chronic pain syndrome due to mesh shrinkage after laparoscopic intraperitoneal onlay mesh (IPOM).

    PubMed

    Klein, Fritz; Ospina, Carlos; Rudolph, Birgit; Wüstefeld, Joost; Denecke, Timm; Neuhaus, Peter; Schmidt, Sven-Christian

    2012-10-01

    The case of a 58-year-old male patient who developed a chronic pain syndrome after laparoscopic intraperitoneal onlay mesh for treatment of a large symptomatic umbilical hernia combined with rectus diastasis is reported. Twelve months after an uncomplicated initial surgery, the patient presented with progressive signs of a foreign body sensation and pain in the anterior abdominal wall. Computed tomography examination revealed no pathologic findings but a marked shrinkage of the mesh implant. Because of further progressive symptoms, explorative laparotomy was performed. Mesh shrinkage and adhesions with a surrounding chronic tissue reaction were found as the cause of the pain syndrome. This case demonstrates a case of a chronic pain syndrome due to mesh shrinkage 12 months after initial ventral hernia repair. Mesh shrinkage should therefore be taken into consideration in patients with progressive pain chronic syndromes after laparoscopic ventral hernia repair.

  3. The effects of epoxy shrinkage on the Advanced X-ray Astrophysics Facility Technology Mirror Assembly

    NASA Technical Reports Server (NTRS)

    Cohen, L. M.

    1984-01-01

    A method is shown analytically which reduces the effects of epoxy shrinkage for an ultra-high precision X-ray telescope to within the system error budget. The three-dimensional shrinkage effects are discussed with reference to this telescope. The results of the analysis point to the use of an interrupted rather than continuous bond line as the best solution. Discussion of the finite element modelling techniques is included.

  4. Effect of Shrinkage on Primary Dendrite Arm Spacing during Binary Al-Si Alloy Solidification

    NASA Astrophysics Data System (ADS)

    Wang, Hongda; Hamed, Mohamed S.; Shankar, Sumanth

    2011-08-01

    Upward and downward directional solidification of hypoeutectic Al-Si alloys were numerically simulated inside a cylindrical container. Undercooling of the liquidus temperature prior to the solidification event was introduced in the numerical model. The finite-volume method was used to solve the energy, concentration, momentum, and continuity equations. Temperature and liquid concentrations inside the mushy zone were coupled with local equilibrium assumptions. An energy equation was applied to determine the liquid fraction inside the mushy zone while considering the temperature undercooling at the solidifying dendrite/liquid interface. Momentum and continuity equations were coupled by the SIMPLE algorithm. Flow velocity distribution at various times, G, R, λ 1, and solidification time at mushy zone/liquid interface during solidification were predicted. The effect of shrinkage during solidification on these solidification parameters was quantified. Transient temperature distribution, solidification time for the mushy zone/liquid interface, and λ 1 were validated by laboratory experiments. It was found that better agreement could be achieved when the fluid flow due to solidification shrinkage was considered. Considering shrinkage in upward solidification was found to only have a marginal effect on solidification parameters, such as G, R, and λ 1; whereas, in the downward solidification, fluid flow due to shrinkage had a significant effect on these solidification parameters. Considering shrinkage during downward solidification resulted in a smaller R, stronger fluid flow, and increased solidification time at the mushy zone/liquid interface. Further, the flow pattern was significantly altered when solidification shrinkage was considered in the simulation. The effect of shrinkage on G and λ 1 strongly depended on the instantaneous location of the mushy zone/liquid interface in the computational domain. The numerical results could be validated by experimental data

  5. Spacing of crack patterns driven by steady-state cooling or drying and influenced by a solidification boundary

    NASA Astrophysics Data System (ADS)

    Hofmann, Martin; Bahr, Hans-Achim; Weiss, Hans-Jürgen; Bahr, Ute; Balke, Herbert

    2011-03-01

    Regular columnar joints that originate from networklike crack patterns can be observed in basalt and, on a much smaller scale, in dried starch slurry. Here, the basalt columns are idealized by a periodic array of parallel cracks driven by steady-state cooling. By means of a bifurcation analysis, the minimal possible crack spacing for sustained propagation of the crack array is calculated. It can be shown qualitatively that the minimal possible crack spacing for sustained propagation increases with decreasing velocity. This is confirmed by numerical calculations. The latent heat released at the solidification front is taken into account in the thermomechanical linear-elastic model of propagating shrinkage. Our calculations show that the solidification front is positioned not far ahead of the crack tips, which influences the result considerably. The results agree reasonably well with new measured data of basalt columns. By use of the analogy between contraction due to cooling and that due to drying the model is applied for columns in dried cornstarch, too, showing good agreement with recent experimental data.

  6. Analysis of Crack Arrest Toughness.

    DTIC Science & Technology

    1988-01-15

    vload(m) vp tn(m) Vertical Source Load (kN) on wedge HY80 Finite Element 0.0122 0.0099 3.81x10 -4 144 Steel Calculations Experiment 0.0122 --- 3.74x10-4...curve, are bona fide measures of the fracture arrest capability of tough ductile steels . The second is that the J-values represent the crack driving...fibrous mode of crack extension. (b) A new test method for studying fast fracture and arrest in tough steels . (c) Measurements of fast fracture and crack

  7. Stress intensity and crack displacement for small edge cracks

    NASA Technical Reports Server (NTRS)

    Orange, Thomas W.

    1988-01-01

    The weight function method was used to derive stress intensity factors and crack mouth displacement coefficients for small edge cracks (less than 20 percent of the specimen width) in common fracture specimen configurations. Contact stresses due to point application of loads were found to be small but significant for three-point bending and insignificant for four-point bending. The results are compared with available equations and numerical solutions from the literature and with unpublished boundary collocation results.

  8. A computational algorithm for crack determination: The multiple crack case

    NASA Technical Reports Server (NTRS)

    Bryan, Kurt; Vogelius, Michael

    1992-01-01

    An algorithm for recovering a collection of linear cracks in a homogeneous electrical conductor from boundary measurements of voltages induced by specified current fluxes is developed. The technique is a variation of Newton's method and is based on taking weighted averages of the boundary data. The method also adaptively changes the applied current flux at each iteration to maintain maximum sensitivity to the estimated locations of the cracks.

  9. The effect of mucosal cuff shrinkage around dental implants during healing abutment replacement.

    PubMed

    Nissan, J; Zenziper, E; Rosner, O; Kolerman, R; Chaushu, L; Chaushu, G

    2015-10-01

    Soft tissue shrinkage during the course of restoring dental implants may result in biological and prosthodontic difficulties. This study was conducted to measure the continuous shrinkage of the mucosal cuff around dental implants following the removal of the healing abutment up to 60 s. Individuals treated with implant-supported fixed partial dentures were included. Implant data--location, type, length, diameter and healing abutments' dimensions--were recorded. Mucosal cuff shrinkage, following removal of the healing abutments, was measured in bucco-lingual direction at four time points--immediately after 20, 40 and 60 s. anova was used to for statistical analysis. Eighty-seven patients (49 women and 38 men) with a total of 311 implants were evaluated (120 maxilla; 191 mandible; 291 posterior segments; 20 anterior segments). Two-hundred and five (66%) implants displayed thick and 106 (34%) thin gingival biotype. Time was the sole statistically significant parameter affecting mucosal cuff shrinkage around dental implants (P < 0.001). From time 0 to 20, 40 and 60 s, the mean diameter changed from 4.1 to 4.07, 3.4 and 2.81 mm, respectively. The shrinkage was 1%, 17% and 31%, respectively. The gingival biotype had no statistically significant influence on mucosal cuff shrinkage (P = 0.672). Time required replacing a healing abutment with a prosthetic element should be minimised (up to 20/40 s), to avoid pain, discomfort and misfit. © 2015 John Wiley & Sons Ltd.

  10. Drying shrinkage of fibre-reinforced lightweight aggregate concrete containing fly ash

    SciTech Connect

    Kayali, O.; Haque, M.N.; Zhu, B.

    1999-11-01

    Lightweight aggregate concretes containing fly ash with a compressive strength between 61 to 67 NPa were produced. The lightweight aggregate used was sintered fly ash. The concretes were reinforced with either polypropylene or steel fibres. The fibres did not affect the compressive strength, but did increase the tensile strength of these concretes. The modulus of elasticity of all the lightweight concretes tested was about 21 GPa, compared to 35 GPa for the normal-weight concrete. Fibre reinforcement did not affect the value of the elastic modulus. This type of lightweight concrete, containing fly ash as 23% of the total cementitious content, resulted in long-term shrinkage that is nearly twice as large as normal-weight concrete of somewhat similar strength. Polypropylene fibre reinforcement did not reduce drying shrinkage, while steel fibres did. Early shrinkage behavior of this type of lightweight concrete was similar to normal-weight concrete. However, the rate of shrinkage of the lightweight concrete remained constant until nearly 100 days of drying. This is different from normal-weight concrete that showed appreciably after 56 days. Shrinkage of normal-weight concrete stabilized after 400 days, which shrinkage of lightweight concrete did not appear to stabilize after a similar period of continuous drying.

  11. Exploration of statistical shrinkage parameters of disproportionality methods in spontaneous reporting system of China.

    PubMed

    Wang, Jing; Ye, Xiao-Fei; Guo, Xiao-Jing; Zhu, Tian-Tian; Qi, Na; Hou, Yong-Fang; Zhang, Tian-Yi; Shi, Wen-Tao; Wei, Xin; Liu, Yu-Zhou; Wu, Gui-Zhi; He, Jia

    2015-09-01

    Statistical shrinkage is a potential statistical method to improve the accuracy of signal detection results and avoid spurious associations detected by disproportionality analyses. In this study, we introduced statistical shrinkage influence on disproportionality methods in spontaneous reporting system in China. We added the shrinkage parameters in the numerator and denominator, denoted as in the formula of disproportionality analysis. The shrinkage parameters were subjectively set to between 0 and 5, with an interval of 0.1. Adverse drug reaction product label database was deemed as a proxy of golden standard to evaluate the effect of statistical shrinkage. Reports in the years of 2010-2011 were extracted from the national spontaneous reporting system database as the data source for analysis in this study. When α was around 0.5, the Youden index reached the maximum for each disproportionality methods in this study. The value of 0.6 was suggested as the most appropriate statistical shrinkage parameter for reporting odds ratio and proportional reporting ratio and 0.2 for information component based on the spontaneous reporting system of China. Copyright © 2015 John Wiley & Sons, Ltd.

  12. Conversion-dependent shrinkage stress and strain in dental resins and composites.

    PubMed

    Stansbury, Jeffrey W; Trujillo-Lemon, Marianela; Lu, Hui; Ding, Xingzhe; Lin, Yan; Ge, Junhao

    2005-01-01

    The placement of dental composites is complicated by the contraction that accompanies polymerization of these materials. The resulting shrinkage stress that develops during cure of a bonded restoration can induce defects within the composite, the tooth or at the interface resulting in compromised clinical performance and/or esthetics. In light of the substantial efforts devoted to understanding and attempting to control shrinkage stress and strain in dental composite restoratives, this paper offers a perspective on the conversion dependent development of shrinkage and stress. The relationships between polymer property development and the physical evolution of the network structures associated with dental polymers as well as the interrelated kinetics of the photopolymerization reaction process are examined here. Some of the methods used to assess conversion in dental resins and composites are considered. In particular, newly introduced techniques that allow real time analysis of conversion by near-infrared spectroscopy to be coupled directly to simultaneous dynamic measurements of either shrinkage stress or strain are described. The results are compared with reports from the dental materials literature as well as complementary studies in other related fields of polymer science. The complex, nonlinear correlation between conversion, shrinkage and stress are highlighted. A brief review of some of the materials-based approaches designed to minimize polymerization shrinkage and stress is also provided.

  13. Microcomputed Tomography Evaluation of Polymerization Shrinkage of Class I Flowable Resin Composite Restorations.

    PubMed

    Sampaio, C S; Chiu, K-J; Farrokhmanesh, E; Janal, M; Puppin-Rontani, R M; Giannini, M; Bonfante, E A; Coelho, P G; Hirata, R

    The present study aimed to characterize the pattern and volume of polymerization shrinkage of flowable resin composites, including one conventional, two bulk fill, and one self-adhesive. Standardized class I preparations (2.5 mm depth × 4 mm length × 4 mm wide) were performed in 24 caries-free human third molars that were randomly divided in four groups, according to the resin composite and adhesive system used: group 1 = Permaflo + Peak Universal Bond (PP); group 2 = Filtek Bulk Fill + Scotchbond Universal (FS); group 3 = Surefil SDR + XP Bond (SX); and group 4 = Vertise flow self-adhering (VE) (n=6). Each tooth was scanned three times using a microcomputed tomography (μCT) apparatus. The first scan was done after the cavity preparation, the second after cavity filling with the flowable resin composite before curing, and the third after it was cured. The μCT images were imported into three-dimensional rendering software, and volumetric polymerization shrinkage percentage was calculated for each sample. Data were submitted to one-way analysis of variance and post hoc comparisons. No significant difference was observed among PP, FS, and VE. SX bulk fill resin composite presented the lowest values of volumetric shrinkage. Shrinkage was mostly observed along the occlusal surface and part of the pulpal floor. In conclusion, polymerization shrinkage outcomes in a 2.5-mm deep class I cavity were material dependent, although most materials did not differ. The location of shrinkage was mainly at the occlusal surface.

  14. Transient brain shrinkage in infantile spasms after ACTH treatment. Report of two cases.

    PubMed

    Maekawa, K; Ohta, H; Tamai, I

    1980-02-01

    This is the report of two cases of infantile spasms, manifesting transient brain shrinkage in computerized tomography (CT) after ACTH treatment. ACTH was given for 8 weeks to a 8-months-old Japanese girl with infantile spasms. First CT performed at 2 weeks after the final ACTH injection, displayed moderate brain shrinkage. Second CT at 4 months showed marked diminution of the shrinkage. ACTH was also given for 8 weeks to a 14 months old Japanese boy with infantile spasms. First CT, just before ACTH treatment, showed mild cortical atrophy, the second at 7 days after the final ACTH injection revealed marked brain shrinkage and moderate ventricular dilatation, and the third at 2 months, disclosed mild improvement of the shrinkage. ACTH or corticoateroid has widespread effects on the developing nervous system. In animal experiments, ACTH or steroids interfere with brain growth of young rats. CT findings of transient brain shrinkage in a child with infantile spasms might suggest that intensive treatment with ACTH or steroids in infancy interferes with brain growth as seen in the results of animal experiments.

  15. Effect of autogenic relaxation on depression among menopausal women in rural areas of Thiruvallur District (Tamil Nadu).

    PubMed

    Sujithra, S

    2014-01-01

    An experimental study was conducted among 60 menopausal women, 30 each in experimental and control group who met inclusion criteria. The menopausal women were identified in both the groups and level of depression was assessed using Cornell Dysthmia rating scale. Simple random sampling technique by lottery method was used for selecting the sample. Autogenic relaxation was practiced by the menopausal women for four weeks. The findings revealed that in experimental group, after intervention of autogenic relaxation on depression among menopausal women, 23 (76.7%) had mild depression. There was a statistically significant effectiveness in experimental group at the level of p < 0.05. There was a statistically significant association between the effectiveness of autogenic relaxation on depression among menopausal women in the post-experimental group with the type of family at the level of p < 0.05.

  16. A theory for the origin of a self-replicating chemical system. II - Computer simulation of the autogen

    NASA Technical Reports Server (NTRS)

    White, D. H.; Raab, M. S.

    1982-01-01

    In order to better understand the feasibility and limitations of the autogen (White 1980), a computer simulation based on the fluctuating clay environment was used to test whether autocatalytic growth would occur under various conditions. The results suggest that overall accuracies of replication and translation in the range of 90% and 10%, and protoenzyme turnover numbers of 10-120 monomers/protoenzyme/day are adequate for exponential growth. Nucleation of the components of the autogen from random background oligomers would be extremely rapid if oligomers lengths 2-6 were adequately functional, whereas oligomer lengths much greater than 10 are prohibited. The autogen would most likely nucleate and grow to dominance either rapidly (10-100 cycles of roughly 1 day each) or not at all.

  17. Augmentation of the rat jaw with autogeneic cortico-cancellous bone grafts and guided tissue regeneration.

    PubMed

    Donos, Nikolaos; Kostopoulos, Lambros; Karring, Thorkild

    2002-04-01

    The aim of the present study was to evaluate the effect of augmenting the maxillary alveolar ridge and the lateral aspect of the mandible with onlay autogeneic cortico-cancellous bone grafts that were covered with e-PTFE membranes. The experiment was carried out in 51 rats. In 15 rats, the edentulous maxillary jaw between the incisor and the first molar was augmented by means of an autogeneic ischiac bone graft that was fixed with a gold-coated microimplant. In one side, the graft was covered with an e-PTFE membrane, while the other side, which served as control, was treated without a membrane. In the other 36 rats, the lateral aspect of the mandible was augmented in both sides by means of an autogeneic ischiac bone graft that was fixed with a gold-coated or a titanium microimplant. In one side, the augmented area was covered with an e-PTFE membrane, while the contralateral side was treated without a membrane. Histological analysis at 60, 120 and 180 days after augmentation of the maxilla showed that, in the case of the test sites (where most of the membranes were either exposed or lost), the bone grafts presented extensive resorption and there was a lack of bone continuity between the graft and the recipient site. Similar findings were made at the non-membrane-treated control sides. In the case of augmentation of the mandible with membranes, the bone grafts were not resorbed, but were integrated into newly formed bone at the recipient site. In the control sides, the grafts presented varying degrees of resorption and integration into the recipient bone. It is concluded that, in comparison to bone grafting alone, onlay ischiac bone grafting combined with guided tissue regeneration eliminates the risk of bone graft resorption and ensures integration of the graft into newly formed bone at the recipient site, provided that closure of the operated area can be maintained during healing.

  18. Evaluation of ABM/P-15 versus autogenous bone in an ovine lumbar interbody fusion model

    PubMed Central

    Sherman, Blake P.; Lindley, Emily M.; Turner, A. Simon; Seim III, Howard B.; Benedict, James; Burger, Evalina L.

    2010-01-01

    A prospective, randomized study was performed in an ovine model to compare the efficacy of an anorganic bovine-derived hydroxyapatite matrix combined with a synthetic 15 amino acid residue (ABM/P-15) in facilitating lumbar interbody fusion when compared with autogenous bone harvested from the iliac crest. P-15 is a biomimetic to the cell-binding site of Type-I collagen for bone-forming cells. When combined with ABM, it creates the necessary scaffold to initiate cell invasion, binding, and subsequent osteogenesis. In this study, six adult ewes underwent anterior-lateral interbody fusion at L3/L4 and L4/L5 using PEEK interbody rings filled with autogenous bone at one level and ABM/P-15 at the other level and no additional instrumentation. Clinical CT scans were obtained at 3 and 6 months; micro-CT scans and histomorphometry analyses were performed after euthanization at 6 months. Clinical CT scan analysis showed that all autograft and ABM/P-15 treated levels had radiographically fused outside of the rings at the 3-month study time point. Although the clinical CT scans of the autograft treatment group showed significantly better fusion within the PEEK rings than ABM/P-15 at 3 months, micro-CT scans, clinical CT scans, and histomorphometric analyses showed there were no statistical differences between the two treatment groups at 6 months. Thus, ABM/P-15 was as successful as autogenous bone graft in producing lumbar spinal fusion in an ovine model, and it should be further evaluated in clinical studies. PMID:20694847

  19. Evaluation of ABM/P-15 versus autogenous bone in an ovine lumbar interbody fusion model.

    PubMed

    Sherman, Blake P; Lindley, Emily M; Turner, A Simon; Seim, Howard B; Benedict, James; Burger, Evalina L; Patel, Vikas V

    2010-12-01

    A prospective, randomized study was performed in an ovine model to compare the efficacy of an anorganic bovine-derived hydroxyapatite matrix combined with a synthetic 15 amino acid residue (ABM/P-15) in facilitating lumbar interbody fusion when compared with autogenous bone harvested from the iliac crest. P-15 is a biomimetic to the cell-binding site of Type-I collagen for bone-forming cells. When combined with ABM, it creates the necessary scaffold to initiate cell invasion, binding, and subsequent osteogenesis. In this study, six adult ewes underwent anterior-lateral interbody fusion at L3/L4 and L4/L5 using PEEK interbody rings filled with autogenous bone at one level and ABM/P-15 at the other level and no additional instrumentation. Clinical CT scans were obtained at 3 and 6 months; micro-CT scans and histomorphometry analyses were performed after euthanization at 6 months. Clinical CT scan analysis showed that all autograft and ABM/P-15 treated levels had radiographically fused outside of the rings at the 3-month study time point. Although the clinical CT scans of the autograft treatment group showed significantly better fusion within the PEEK rings than ABM/P-15 at 3 months, micro-CT scans, clinical CT scans, and histomorphometric analyses showed there were no statistical differences between the two treatment groups at 6 months. Thus, ABM/P-15 was as successful as autogenous bone graft in producing lumbar spinal fusion in an ovine model, and it should be further evaluated in clinical studies.

  20. Extensor-tendons reconstruction using autogenous palmaris longus tendon grafting for rheumatoid arthritis patients

    PubMed Central

    Chu, Po-Jung; Lee, Hung-Maan; Hou, Yao-Tung; Hung, Sheng-Tsai; Chen, Jung-Kuei; Shih, Jui-Tien

    2008-01-01

    Background The purpose of the study is to retrospectively review the clinical outcome of our study population of middle-aged RA patients who had suffered extensor-tendon rupture. We reported the outcome of autogenous palmaris tendon grafting of multiple extensor tendons at wrist level in 14 middle-aged rheumatoid patients. Methods Between Feb. 2000 to Feb. 2004, thirty-six ruptured wrist level extensor tendons were reconstructed in fourteen rheumatoid patients (11 women and three men) using autogenous palmaris longus tendon as a free interposition graft. In each case, the evaluation was based on both subjective and objective criteria, including the range of MCP joint flexion after surgery, the extension lag at the metacarpophalangeal joint before and after surgery, and the ability of the patient to work. Results and Discussion The average of follow-up was 54.1 months (range, 40 to 72 months). The average range of MCP joint flexion after reconstruction was 66°. The extension lag at the metacarpophalangeal joint significantly improved from a preoperative mean of 38° (range, 25°–60°) to a postoperative mean of 16° (range, 0°–30°). Subjectively all patients were satisfied with the clinical results, and achieved a return to their level of ability before tendon rupture. We found good functional results in our series of interposition grafting using palmaris longus to reconstruct extensor tendon defects in the rheumatoid patients. Conclusion Reconstruction for multiple tendon ruptures is a salvage procedure that is often associated with extensor lag and impairment of overall function. Early aggressive treatment of extensor tendon reconstruction using autogenous palmaris longus tendon as a free interposition graft in the rheumatoid wrist is another viable option to achieve good clinical functional result. PMID:18435845

  1. A comparison of autogenous theories for the origin of eukaryotic cells.

    PubMed

    Baum, David A

    2015-12-01

    Eukaryotic cells have many unique features that all evolved on the stem lineage of living eukaryotes, making it difficult to reconstruct the order in which they accumulated. Nuclear endosymbiotic theories hold that three prokaryotes (nucleus, cytoplasm, and mitochondrion) came together to form a eukaryotic cell, whereas autogenous models hold that the nucleus and cytoplasm formed through evolutionary changes in a single prokaryotic lineage. Given several problems with nuclear endosymbiotic theories, this review focuses on autogenous models. Until recently all autogenous models assumed an outside-in (OI) topology, proposing that the nuclear envelope was formed from membrane-bound vesicles within the original cell body. Buzz Baum and I recently proposed an inside-out (IO) alternative, suggesting that the nucleus corresponds to the original cell body, with the cytoplasmic compartment deriving from extracellular protrusions. In this review, I show that OI and IO models are compatible with both mitochondria early (ME) or mitochondria late (ML) formulations. Whereas ME models allow that the relationship between mitochondria and host was mutualistic from the outset, ML models imply that the association began with predation or parasitism, becoming mutualistic later. In either case, the mutualistic interaction that eventually formed was probably syntrophic. Diverse features of eukaryotic cell biology align well with the IOME model, but it would be premature to rule out the OIME model. ML models require that phagocytosis, a complex and energy expensive process, evolved before mitochondria, which seems unlikely. Nonetheless, further research is needed, especially resolution of the phylogenetic affinities of mitochondria. © 2015 Botanical Society of America.

  2. Autogenous bone block in the treatment of teeth with hopeless prognosis

    PubMed Central

    Pandit, Nymphea; Pandit, I. K.; Malik, Rajvir; Bali, Deepika; Jindal, Shaifi

    2012-01-01

    Background: Autogenous bone graft, although considered as a gold standard, has been relegated to background because of limited quantity and donor site morbidity. Revival of interest in its use has been reflected by its tremendous capacity for regeneration in less than ideal situation. Bone blocks have been used for implant site augmentation, with varied success. Aim: Aim of the study was to evaluate the efficacy of autogenous bone block in the regeneration of bone, for saving teeth with a hopeless prognosis. Settings and Design: A total of six patients and 12 sites with grade II and III mobile teeth were treated with autogenous bone blocks and fiber splinting. Subjects and Methods: Attachment loss, probing depths, and radiographic bone loss were recorded at baseline and at 12 months interval. Statistical Analysis Used: The Student paired t test was used for evaluation of the changes from baseline to 12 months. Results: At 12 months post-operatively, there was a highly significant amount of bone gain as compared to the baseline. The mean amount of bone loss reduced from 9.41 ± 1.16 to 5.41 ± 1.01. The clinical attachment loss reduced from 7.37 ± 1.24 mm to 3.79 ± 0.89 mm and probing depth reduced from 7 ± 1.67 mm to 5.5 ± 0.63 mm. The grafted bone was observed to have been incorporated with the host bone in most of the sites as evidenced by radiographs. Conclusions: For teeth with hopeless prognosis, this method can be considered to be a very viable alternative to extraction and replacement by costly implants. PMID:23633805

  3. Numerical Model Predictions for Autogenic Fluvial Terrace Formation and Comparison to Natural River Valleys

    NASA Astrophysics Data System (ADS)

    Limaye, A. B. S.; Lamb, M. P.

    2015-12-01

    Terraces cut into bedrock (strath) and sediment (fill-cut) offer key constraints on river evolution over millennial timescales, and are often interpreted to form during phases of increased river vertical incision driven by changes in climate or tectonics. Yet all actively meandering channels evolve their shapes through spatial and temporal changes in lateral erosion rates. Therefore, the sparsest requirement for a meandering river to generate terraces is that the intrinsically unsteady lateral erosion rate be coupled with relief generation by vertical incision, which need not be unsteady. In principle, this basic mechanism for terrace formation by meandering rivers should be possible in all fluvial environments, including for valleys with strath or fill-cut terraces, and may overprint signals from external drivers. We have used a numerical model of a vertically incising, meandering river to identify the age and geometric properties of autogenic terraces. Simulations indicate that autogenic terraces form with a recurrence timescale, set by the rate of relief generation, which may overlap with timescales for climate change. The autogenic terraces also have predictable geometries that can include slope proportional to the ratio of vertical incision rate to lateral erosion rate, pairing, and continuous along-valley extent. We compare these simulation results to data for terrace age and geometry from several well studied natural river valleys that span a wide range in terrace sizes and geometries, rock types, tectonic settings, incision rates, and hypothesized formation mechanisms. In cases, terrace age and geometric properties are consistent with formation by meandering with constant vertical incision rates. These similarities suggest that efforts to distinguish terraces that record signals from climatic and tectonic drivers are best focused on environments where terrace ages and geometries are far different than would be predicted by a constant vertical incision model.

  4. Autogenous temporalis fascia patch graft for porous polyethylene (Medpor) sphere orbital implant exposure

    PubMed Central

    Sagoo, M S; Olver, J M

    2004-01-01

    Background: Temporalis fascia has been recommended for hydroxyapatite sphere exposure. The aim of this study was to identify potential risk factors for exposure of porous polyethylene (Medpor) sphere implants and evaluate the use of autogenous temporalis fascia as a patch graft for exposure. Methods: A retrospective review of consecutive cases of porous polyethylene sphere orbital implant exposure. Results: Five cases presented between May 2000 and October 2001 (three males, two females; mean age 44.5 years). Three had enucleation (two with primary implants) and two had evisceration (one with primary implant). Exposure occurred in one primary, two secondary, and two replacement implants. Orbital implant diameter was 20 mm in four cases and 16 mm in one case (contracted socket). The mean time from implantation to exposure was 23 months (range 0.7–42.6). Three patients had secondary motility peg placement before exposure. The average time from last procedure (sphere implant or peg insertion) to exposure was 3 months (range 0.7–12.6). Four patients required surgical intervention, of which three needed more than one procedure. Autogenous temporalis fascia grafting successfully closed the defect without re-exposure in three of these four patients. The grafts were left bare in three patients, with a mean time to conjunctivalise of 2.4 months (range 1.6–3.2). Conclusions: Exposed porous polyethylene sphere implants were treated successfully with autogenous temporalis fascia graft in three of four patients. This technique is useful, the graft easy to harvest, and did not lead to prolonged socket inflammation, infection, or extrusion. PMID:15205243

  5. Autogenous temporalis fascia patch graft for porous polyethylene (Medpor) sphere orbital implant exposure.

    PubMed

    Sagoo, M S; Olver, J M

    2004-07-01

    Temporalis fascia has been recommended for hydroxyapatite sphere exposure. The aim of this study was to identify potential risk factors for exposure of porous polyethylene (Medpor) sphere implants and evaluate the use of autogenous temporalis fascia as a patch graft for exposure. A retrospective review of consecutive cases of porous polyethylene sphere orbital implant exposure. Five cases presented between May 2000 and October 2001 (three males, two females; mean age 44.5 years). Three had enucleation (two with primary implants) and two had evisceration (one with primary implant). Exposure occurred in one primary, two secondary, and two replacement implants. Orbital implant diameter was 20 mm in four cases and 16 mm in one case (contracted socket). The mean time from implantation to exposure was 23 months (range 0.7-42.6). Three patients had secondary motility peg placement before exposure. The average time from last procedure (sphere implant or peg insertion) to exposure was 3 months (range 0.7-12.6). Four patients required surgical intervention, of which three needed more than one procedure. Autogenous temporalis fascia grafting successfully closed the defect without re-exposure in three of these four patients. The grafts were left bare in three patients, with a mean time to conjunctivalise of 2.4 months (range 1.6-3.2). Exposed porous polyethylene sphere implants were treated successfully with autogenous temporalis fascia graft in three of four patients. This technique is useful, the graft easy to harvest, and did not lead to prolonged socket inflammation, infection, or extrusion.

  6. Cognitive therapy for autogenous and reactive obsessions: clinical and cognitive outcomes at post-treatment and 1-year follow-up.

    PubMed

    Belloch, Amparo; Cabedo, Elena; Carrió, Carmen; Larsson, Christina

    2010-08-01

    This study provides data about the differential effectiveness of cognitive therapy (CT) for obsessive-compulsive disorder (OCD) symptom presentation. Two OCD manifestations, autogenous and reactive, are considered. Seventy OCD patients started CT; 81.40% completed it and 72.85% were available 1 year later. Fifteen of the 57 treatment completers had autogenous obsessions, whereas 33 had reactive obsessions. Nine patients had both obsession modalities. Reactive patients were more severe, as they scored higher on thought suppression and on the dysfunctional beliefs of intolerance to uncertainty and perfectionism. Autogenous patients scored higher on the over-importance of thoughts beliefs. Although CT was effective in reducing OCD severity and the ascription to dysfunctional beliefs and neutralizing strategies in both the autogenous and the reactive patients, a significantly better outcome was observed for the autogenous patients, both at post-treatment (with 73.33% recovering versus 33.33% for reactives) and 1 year later.

  7. [Heterotopic osteogenesis of autogenous marrow stromal cells on ceramic bovine bone/ hydrogel scaffold].

    PubMed

    He, Dawei; Jin, Yan; Luo, Kai; Li, Shibao

    2006-02-01

    To observe the heterotopic osteogenesis of the autogenous marrow stromal cells (MSCs) on the ceramic bovine bone (CBB)/hydrogel scaffold (HG) and the effects of the recombinant human bone morphogenetic protein-2 (rhBMP-2) and the transforming growth factor beta (TGF-beta) on osteogenesis. The autogenous marrow stromal cells were cultured by the mineralized condition medium (10% FBS, dexamethasone 10 nmol, L-vitamin C 50 mg/L, beta-sodium glycerophosphate DMEM culture medium 10 mmol). At 5 days, the MSCs differentiation was observed by Type I collagen, the Mend calcium-cobalt staining, and the Von-Kossa staining. The cell suspension of 5 x 10(6)/ml was obtained. There were three groups: Group A: added in rhBMP-2 (10 microg)-TGF-beta (0.05 microg); Group B: added in TGF-beta (0.05 microg); and Group C (the control group): without the growth factor. Then, the MSCs loading on CBB/HG were embedded in the autogenous subcutaneous area at 4 and 8 weeks, and the osteogenesis was observed by the HE staining and the modified Mallory's trichrome staining, with an image analysis. Type I collagen and the bone morphogenetic synthesis were examined by the immunohistochemistry stains. Most MSCs induced by the mineralized condition medium at 5 days became smaller and polygon-shaped, and the cytodendrite became shorter. The MSCs were observed by the Mend calcium-cobalt staining. Some brown and black grains were found in the cytochylema. The MSCs were positive for the Type I collagen immunohistochemistry stains. At 20 days, the mineralized nubs were found by the Von Kossas stains. At 4 weeks, some strips of the new bone were observed by the HE staining and the modified Mallory's trichrome staining in all the groups. The bone matrix area was significantly larger in Group A than in Group B(P < 0.01). The average gray degrees of Type I collagen were lower in Groups A and B than in Group C. However, there was no significant difference in the bone morphogenesis among the three groups. At 8

  8. Autogenous bone grafts in the esthetic zone: optimizing the procedure using piezosurgery.

    PubMed

    Majewski, Piotr

    2012-12-01

    Soft and hard tissue defects pose a therapeutic challenge in modern implant dentistry. There are a multitude of surgical techniques available, and it is necessary to match the problem with the solution. This report describes the reconstruction of the alveolar ridge in the esthetic zone with the help of autogenous bone blocks harvested from the chin that were shaped to fit and stabilized at the recipient site. The procedures were performed using Piezosurgery, which made it possible to introduce surgical modifications and had a significant impact on the accuracy of the procedure. An observation period of 2 to 7 years showed positive stable results for treatment in terms of function and esthetics.

  9. Two cases of panic disorder treated with autogenic training and in vivo exposure without medication.

    PubMed

    Sakai, M; Takeichi, M

    1996-12-01

    The aim of this study was to use autogenic training in combination with in vivo exposure in the behavioral treatment of panic disorder without medication. Two cases of panic disorder with agoraphobic avoidance were presented. Case 1 was a 33 year old married female who exhibited mild panic symptoms, and case 2 was a 23 year old single male who had severe panic symptoms. Both subjects were successfully treated with the combination of these two techniques. Treatment effects were maintained for 9 years as a follow up in case 1, and for 4 years in case 2.

  10. [Essential hypertension and stress. When do yoga, psychotherapy and autogenic training help?].

    PubMed

    Herrmann, J M

    2002-05-09

    Psychosocial factors play an important role in the development and course of essential hypertension, although "stress" can account for only 10% of blood pressure variance. A variety of psychotherapeutic interventions, such as relaxation techniques (autogenic training or progressive muscular relaxation), behavioral therapy or biofeedback techniques, can lower elevated blood pressure by an average of 10 mmHg (systolic) and 5 mmHg (diastolic). As a "secondary effect", such measures may also prompt the hypertensive to adopt a more health-conscious lifestyle.

  11. Effect of Oxygen Concentration on Autogenous Ignition Temperature and Pneumatic Impact Ignitability of Nonmetallic Materials

    NASA Technical Reports Server (NTRS)

    Smith, Sarah

    2009-01-01

    Extensive test data exist on the ignitability of nonmetallic materials in pure oxygen, but these characteristics are not as well understood for lesser oxygen concentrations. In this study, autogenous ignition temperature testing and pneumatic impact testing were used to better understand the effects of oxygen concentration on ignition of nonmetallic materials. Tests were performed using oxygen concentrations of 21, 34, 45, and 100 %. The following materials were tested: PTFE Teflon(Registered Trademark), Buna-N, Silicone, Zytel(Registered Trademark) 42, Viton(registered Trademark) A, and Vespel(Registered Trademark) SP-21.

  12. Identifying autogenic sedimentation in fluvial-deltaic stratigraphy: Evaluating the effect of outcrop-quality data on the compensation statistic

    NASA Astrophysics Data System (ADS)

    Trampush, S. M.; Hajek, E. A.; Straub, K. M.; Chamberlin, E. P.

    2017-01-01

    Stratigraphy preserves an extensive record of Earth-surface dynamics acting over a range of scales in a variety of environments. To take advantage of this record, we first must distinguish depositional patterns that arise due to intrinsic (i.e., autogenic) landscape dynamics from sedimentation that results from changes in climate, tectonic, or eustatic boundary conditions. The compensation statistic is a quantitative tool that has been used to estimate scales and patterns of autogenic sedimentation in experimental deposits; it has been applied to a few outcrop studies, but its sensitivity to data limitations common in natural deposits remains unconstrained. To explore how the compensation statistic may be applied to outcrop data, we evaluate the sensitivity of the tool to stratigraphic data sets limited in extent and resolution by subsampling an autogenic experimental deposit to create pseudo-outcrop-scale data sets. Results show that for data sets more than 3 times thicker than a characteristic depositional element (e.g., channel or lobe), the compensation statistics that can be used reliably constrain the maximum scale of autogenic sedimentation even for low-resolution data sets. Additionally, we show that autogenic sedimentation patterns may be characterized as persistent, random, or compensational using the compensation statistic when data sets are high resolution. We demonstrate how these measurements can be applied to natural data sets with comparative case studies of two fluvial and two deltaic outcrops. These case studies show how the compensation statistic can provide insight into what controls the maximum scale of autogenic sedimentation in different systems and how landscape dynamics can produce organized sedimentation patterns over long time scales.

  13. Ten-year comparative analysis of bovine pericardium and autogenous vein for patch angioplasty in patients undergoing carotid endarterectomy.

    PubMed

    Kim, Ji-Hoon; Cho, Yong-Pil; Kwon, Tae-Won; Kim, Hyangkyoung; Kim, Geun-Eun

    2012-04-01

    To evaluate early and late clinical outcomes of carotid endarterectomy (CEA) with bovine pericardium patch in comparison with autogenous vein. During a 10-year period, 456 CEAs were performed using patch closure of the arteriotomy with bovine pericardium (252 cases) and autogenous vein (204 cases). Retrospectively, surgical outcomes were evaluated and compared regarding CEA-related parameters, early and late mortality and morbidity rates, and the incidence of restenosis and aneurysmal dilatation between patients with bovine pericardium patch closure and those with autogenous vein closure. The two groups were comparable regarding basic demographics, clinical data, and anatomic data, except the incidence of coronary or peripheral arterial diseases. In patients with bovine pericardium patch closure, the total operating time and carotid clamping duration were statistically significantly shorter than in those with autogenous vein closure (P < 0.01). During the early postoperative period, 10 major (stroke and death) complications (2.2%) occurred without statistically significant difference between the two groups. The incidence of early minor postoperative complications was less with bovine pericardium patch closure (5.6% vs. 10.8%; P < 0.05). With a mean follow-up of 62 months for bovine pericardium patch closure and 67 months for autogenous vein closure, the incidence of restenosis was similar, but aneurysmal dilatation was higher in patients with autogenous vein closure with a statistically significant difference (0% vs. 2.0%; P < 0.05). CEA with bovine pericardium patch angioplasty showed excellent early and late clinical outcomes. Our results demonstrated bovine pericardium to be a suitable patch material for routine use in CEA. Copyright © 2012 Annals of Vascular Surgery Inc. Published by Elsevier Inc. All rights reserved.

  14. Bone healing around nanocrystalline hydroxyapatite, deproteinized bovine bone mineral, biphasic calcium phosphate, and autogenous bone in mandibular bone defects.

    PubMed

    Broggini, Nina; Bosshardt, Dieter D; Jensen, Simon S; Bornstein, Michael M; Wang, Chun-Cheng; Buser, Daniel

    2015-10-01

    The individual healing profile of a given bone substitute with respect to osteogenic potential and substitution rate must be considered when selecting adjunctive grafting materials for bone regeneration procedures. In this study, standardized mandibular defects in minipigs were filled with nanocrystalline hydroxyapatite (HA-SiO), deproteinized bovine bone mineral (DBBM), biphasic calcium phosphate (BCP) with a 60/40% HA/β-TCP (BCP 60/40) ratio, or particulate autogenous bone (A) for histological and histomorphometric analysis. At 2 weeks, percent filler amongst the test groups (DBBM (35.65%), HA-SiO (34.47%), followed by BCP 60/40 (23.64%)) was significantly higher than the more rapidly substituted autogenous bone (17.1%). Autogenous bone yielded significantly more new bone (21.81%) over all test groups (4.91%-7.74%) and significantly more osteoid (5.53%) than BCP 60/40 (3%) and DBBM (2.25%). At 8 weeks, percent filler amongst the test groups (DBBM (31.6%), HA-SiO (31.23%), followed by BCP 60/40 (23.65%)) demonstrated a similar pattern and was again significantly higher as compared to autogenous bone (9.29%). Autogenous bone again exhibited statistically significantly greater new bone (55.13%) over HA-SiO (40.62%), BCP 60/40 (40.21%), and DBBM (36.35%). These results suggest that the osteogenic potential of HA-SiO and BCP is inferior when compared to autogenous bone. However, in instances where a low substitution rate is desired to maintain the volume stability of augmented sites, particularly in the esthetic zone, HA-SiO and DBBM may be favored.

  15. It Shrinks! It Cracks!

    NASA Image and Video Library

    2017-04-20

    Given enough time, impact craters on Mars tend to fill up with different materials. For instance, some craters on Mars had lakes inside them in the past. When these lakes dried out, they left behind traces of their past existence, such as sedimentary deposits (materials that were carried along with the running water into the lake inside the crater and then settled down). Some craters, especially in high latitudes, contain ice deposits that filled the crater when an earlier ice age allowed ice to extend into the crater's latitude. Here, NASA's Mars Reconnaissance Orbiter spies a crater that lies close to Elysium, a major volcanic system on Mars. The whole region surrounding the crater was at some point covered by lava from the volcano creating vast lava plains, and in the process, flooding impact craters in their way. When the lava eventually cooled down, it solidified and began to shrink in size. This shrinking led to formation of cracks on the surface of the lava that grew in a circular pattern matching the shape of the crater it was filling. Scientists can study these fractures and estimate how much it shrank in volume to better understand the properties of the lava (such as its temperature) during the time it filled the crater. https://photojournal.jpl.nasa.gov/catalog/PIA21596

  16. Peridynamic model for fatigue cracking.

    SciTech Connect

    Silling, Stewart Andrew; Abe Askari

    2014-10-01

    The peridynamic theory is an extension of traditional solid mechanics in which the field equations can be applied on discontinuities, such as growing cracks. This paper proposes a bond damage model within peridynamics to treat the nucleation and growth of cracks due to cyclic loading. Bond damage occurs according to the evolution of a variable called the "remaining life" of each bond that changes over time according to the cyclic strain in the bond. It is shown that the model reproduces the main features of S-N data for typical materials and also reproduces the Paris law for fatigue crack growth. Extensions of the model account for the effects of loading spectrum, fatigue limit, and variable load ratio. A three-dimensional example illustrates the nucleation and growth of a helical fatigue crack in the torsion of an aluminum alloy rod.

  17. Vibrations Caused By Cracked Turbopump Bearing Race

    NASA Technical Reports Server (NTRS)

    Goggin, David G.; Dweck, Robert A.

    1990-01-01

    Expansion gives rise to eccentricity. Report presents analysis of dynamic effects caused by cracking of inner race of ball bearing in turbopump. Crack manifested itself via increase in vibrations synchronous with rotation and smaller increase at twice frequency of rotation. Analysis conducted to verify these increases were caused solely by crack and to understand implications for future such cracks.

  18. Shaft vibrations in turbomachinery excited by cracks

    NASA Technical Reports Server (NTRS)

    Grabowski, B.

    1982-01-01

    During the past years the dynamic behavior of rotors with cracks has been investigated mainly theoretically. This paper deals with the comparison of analytical and experimental results of the dynamics of a rotor with an artificial crack. The experimental results verify the crack model used in the analysis. They show the general possibility to determine a crack by extended vibration control.

  19. Cocaine/Crack: The Big Lie.

    ERIC Educational Resources Information Center

    National Inst. on Drug Abuse (DHHS/PHS), Rockville, MD.

    This pamphlet focuses on cocaine and crack use and the addictive nature of cocaine/crack. It contains a set of 21 questions about crack and cocaine, each accompanied by a clear and complete response. Interspersed throughout the booklet are photographs and quotes from former cocaine or crack users/addicts. Questions and answers focus on what…

  20. 46 CFR 59.10-5 - Cracks.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... APPURTENANCES Welding Repairs to Boilers and Pressure Vessels in -Service § 59.10-5 Cracks. (a) Cracks extending... corrugated furnaces may be repaired by welding provided any one crack does not exceed 20 inches in length. (e... any direction, nor more than a total of four cracks in a drum, and further provided the welding...

  1. 46 CFR 59.10-5 - Cracks.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Cracks. 59.10-5 Section 59.10-5 Shipping COAST GUARD... APPURTENANCES Welding Repairs to Boilers and Pressure Vessels in -Service § 59.10-5 Cracks. (a) Cracks extending... cracks are veed out so that complete penetration of the weld metal is secured. (b) Circumferential...

  2. 21 CFR 137.190 - Cracked wheat.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 2 2011-04-01 2011-04-01 false Cracked wheat. 137.190 Section 137.190 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting...

  3. 21 CFR 137.190 - Cracked wheat.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Cracked wheat. 137.190 Section 137.190 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting...

  4. 21 CFR 137.190 - Cracked wheat.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 2 2012-04-01 2012-04-01 false Cracked wheat. 137.190 Section 137.190 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting...

  5. 21 CFR 137.190 - Cracked wheat.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 2 2013-04-01 2013-04-01 false Cracked wheat. 137.190 Section 137.190 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting...

  6. Initiation and propagation of small corner cracks

    NASA Technical Reports Server (NTRS)

    Ellyin, Ferdnand; Kujawski, Daniel; Craig, David F.

    1994-01-01

    The behaviour of small corner cracks, inclined or perpendicular to loading direction, is presented. There are two aspects to this investigation: initiation of small cracks and monitoring their subsequent growth. An initial pre-cracking procedure under cyclic compression is adopted to minimize the residual damage at the tip of the growing and self-arresting crack under cyclic compression. A final fatigue specimen, cut from the larger pre-cracked specimen, has two corner flaws. The opening load of corner flaw is monitored using a novel strain gauge approach. The behaviour of small corner cracks is described in terms of growth rate relative to the size of the crack and its shape.

  7. Microscopic origins of stochastic crack growth

    NASA Astrophysics Data System (ADS)

    Pardee, W. J.; Morris, W. L.; Cox, B. N.

    Physical arguments are made to obtain a mathematical model of the stochastic growth of surface fatigue cracks in a ductile metal alloy. The model is a set of coupled partial differential equations for the expected statistical density of cracks per unit area. The differential equations describe the smooth, deterministic local evolution of crack states, with the stochastic effects of abrupt local changes of material in the crack path appearing as transitions between distinct subspaces of single crack state space. Results are related to observables such as statistical distributions of crack growth rate and of time for at least one crack to reach macroscopic length.

  8. Short-Term Effect of Autogenic Drainage on Ventilation Inhomogeneity in Adult Subjects With Stable Non-Cystic Fibrosis Bronchiectasis.

    PubMed

    Poncin, William; Reychler, Grégory; Leeuwerck, Noémie; Bauwens, Nathalie; Aubriot, Anne-Sophie; Nader, Candice; Liistro, Giuseppe; Gohy, Sophie

    2017-05-01

    Lung clearance index (LCI), a measure of ventilation inhomogeneity derived from a multiple-breath washout test, is a promising tool for assessing airway function in patients with non-cystic fibrosis bronchiectasis. However, it is unknown whether ventilation inhomogeneity could improve after successful elimination of excessive secretions within bronchiectasis. The objective of this work was to assess the short-term effects of lung secretion clearance using the autogenic drainage technique on standard lung function tests and LCI in subjects with non-cystic fibrosis bronchiectasis. Nitrogen-based multiple-breath washout, spirometry, and body plethysmography tests were performed 30 min before autogenic drainage in adults with stable non-cystic fibrosis bronchiectasis. The autogenic drainage session was followed by a 5-min break, after which the tests were repeated in the same order. Sputum expectorated during autogenic drainage was quantified as dry weight and correlated with change between post- and pre-measurements (Δ). Paired t test or Wilcoxon signed-rank tests were used to compare pre- and post-autogenic drainage measurement outcomes. A P value of ≤.05 was considered as statistically significant. Twenty-four subjects were studied (18 females, median age [range]: 65 [21-81] y). Mean ± SD LCI significantly improved after autogenic drainage (10.88 ± 2.62 vs 10.53 ± 2.35, P = .042). However, only 20% of subjects with mucus hyperproduction during autogenic drainage had a ΔLCI that exceeded measurement variability. The percent of predicted slow vital capacity (SVC%) also slightly improved (88.7 ± 19.3% vs 90 ± 19.1%, P = .02). ΔLCI was inversely related to dry sputum weight (r = -.48, P = .02) and ΔSVC% (r = -.64, P = .001). ΔSVC% also correlated with dry sputum weight (r = 0.46, P = .02). In adults with non-cystic fibrosis bronchiectasis and mucus hypersecretion, autogenic drainage improved ventilation inhomogeneity. LCI change may be the result of the

  9. Mitigation of Crack Damage in Metallic Materials

    NASA Technical Reports Server (NTRS)

    Leser, Patrick E.; Newman, John A.; Smith, Stephen W.; Leser, William P.; Wincheski, Russell A.; Wallace, Terryl A.; Glaessgen, Edward H.; Piascik, Robert S.

    2014-01-01

    A system designed to mitigate or heal crack damage in metallic materials has been developed where the protected material or component is coated with a low-melting temperature film. After a crack is formed, the material is heated, melting the film which then infiltrates the crack opening through capillary action. Upon solidification, the healing material inhibits further crack damage in two ways. While the crack healing material is intact, it acts like an adhesive that bonds or bridges the crack faces together. After fatigue loading damages, the healing material in the crack mouth inhibits further crack growth by creating artificially-high crack closure levels. Mechanical test data show that this method sucessfully arrests or retards crack growth in laboratory specimens.

  10. Cracks in a Crater Ice

    NASA Image and Video Library

    2016-12-07

    Many impact craters on Mars were filled with ice in past climates. Sometimes this ice flows or slumps down the crater walls into the center and acquires concentric wrinkles as a result. This image shows an example of this. There are other ways that scientists know the material in the crater is icy. Surface cracks that form polygonal shapes cover the material in the crater. They are easy to see in this spring-time image because seasonal frost hides inside the cracks, outlining them in bright white. These cracks form because ice within the ground expands and contracts a lot as it warms and cools. Scientists can see similar cracks in icy areas of the Earth and other icy locations on Mars. If you look closely, you'll see small polygons inside larger ones. The small polygons are younger and the cracks shallower while the large ones are outlined with cracks that penetrate more deeply. http://photojournal.jpl.nasa.gov/catalog/PIA21215

  11. The kinetics of hydrocarbon cracking

    SciTech Connect

    Groten, W.A.; Wojciechowski, B.W. )

    1993-03-01

    A general kinetic model which describes the catalytic cracking of pure hydrocarbons is presented. The model includes a monomolecular cracking path based on the Langmuir adsorption isotherm as well as a bimolecular path, following Rideal kinetics, which accounts for the possibility of a chain cracking mechanism being involved. Catalyst decay is accounted for using the time-on-stream-decay function. Fitting of experimental data from n-nonane cracking on USHY at 673 K, combined with Monte Carlo simulations indicates that, in that case, the total catalytic activity could include between 0 and 90% of activity due to chain processes. This large margin of error stems from the combined effects of a large decay rate, forcing the experimenter to use average conversion data, and of experimental error. Fitting of the model to previously published cracking data for 2-methylpentane on USHY showed that the model lacks a suitable parameter to account for thermal reactions which were not accounted for in the original data set. This observation supports the impression that the model is sensitive to departures from the postulated mechanism. The above kinetic model has also been fitted to the results of n-nonane cracking at three temperatures as well as to previously published data for various other linear paraffins. 32 refs., 17 figs., 6 tabs.

  12. Ductility dip cracking susceptibility of Inconel Filler Metal 52 and Inconel Alloy 690

    SciTech Connect

    Kikel, J.M.; Parker, D.M.

    1998-06-01

    Alloy 690 and Filler Metal 52 have become the materials of choice for commercial nuclear steam generator applications in recent years. Filler Metal 52 exhibits improved resistance to weld solidification and weld-metal liquation cracking as compared to other nickel-based filler metals. However, recently published work indicates that Filler Metal 52 is susceptible to ductility dip cracking (DDC) in highly restrained applications. Susceptibility to fusion zone DDC was evaluated using the transverse varestraint test method, while heat affected zone (HAZ) DDC susceptibility was evaluated using a newly developed spot-on-spot varestraint test method. Alloy 690 and Filler Metal 52 cracking susceptibility was compared to the DDC susceptibility of Alloy 600, Filler Metal 52, and Filler Metal 625. In addition, the effect of grain size and orientation on cracking susceptibility was also included in this study. Alloy 690, Filler Metal 82, Filler Metal 52, and Filler Metal 625 were found more susceptible to fusion zone DDC than Alloy 600. Filler Metal 52 and Alloy 690 were found more susceptible to HAZ DDC when compared to wrought Alloy 600, Filler Metal 82 and Filler Metal 625. Filler Metal 52 exhibited the greatest susceptibility to HAZ DDC of all the weld metals evaluated. The base materials were found much more resistant to HAZ DDC in the wrought condition than when autogenously welded. A smaller grain size was found to offer greater resistance to DDC. For weld metal where grain size is difficult to control, a change in grain orientation was found to improve resistance to DDC.

  13. Fatigue Growth and Closure of Short Cracks

    DTIC Science & Technology

    1989-06-03

    TESTS 87 4.5 SHORT CRACK FATIGUE TESTS IN NOTCHED SPECIMENS 101 5. DISCUSSION 5.1 DURABILITY ANALYSIS - EQUIVALENT INITIAL FLAW SIZE 232 5.2 SHORT... equivalent initial flaw size approach, (2) effects of plasticity, (3) crack closure response of long cracks and (4) crack closure response of short...cracks. 5.1 EQUIVALENT INITIAL FLAW SIZE - DURABILITY ANALYSIS Aerospace structures were Initially designed on a safe-life approach. The underlying

  14. Cracks in Utopia

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Many of the craters found on the northern plains of Mars have been partly filled or buried by some material (possibly sediment). The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image presented here (MOC2-136b, above left) shows a high-resolution view of a tiny portion of the floor of one of these northern plains craters. The crater, located in Utopia Planitia at 44oN, 258oW, is shown on the right (MOC2-136a)with a small white box to indicate the location of the MOC image. The MOC image reveals that the material covering the floor of this crater is cracked and pitted. The origin and source of material that has been deposited in this crater is unknown.

    The MOC image was acquired in June 1999 and covers an area only 1.1 kilometers (0.7 miles) wide at a resolution of 1.8 meters (6 feet) per pixel. The context picture is a mosaic of Viking 2 orbiter images 010B53 and 010B55, taken in 1976. Both images are illuminated from the left. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  15. Leaf shrinkage with dehydration: coordination with hydraulic vulnerability and drought tolerance.

    PubMed

    Scoffoni, Christine; Vuong, Christine; Diep, Steven; Cochard, Hervé; Sack, Lawren

    2014-04-01

    Leaf shrinkage with dehydration has attracted attention for over 100 years, especially as it becomes visibly extreme during drought. However, little has been known of its correlation with physiology. Computer simulations of the leaf hydraulic system showed that a reduction of hydraulic conductance of the mesophyll pathways outside the xylem would cause a strong decline of leaf hydraulic conductance (K(leaf)). For 14 diverse species, we tested the hypothesis that shrinkage during dehydration (i.e. in whole leaf, cell and airspace thickness, and leaf area) is associated with reduction in K(leaf) at declining leaf water potential (Ψ(leaf)). We tested hypotheses for the linkage of leaf shrinkage with structural and physiological water relations parameters, including modulus of elasticity, osmotic pressure at full turgor, turgor loss point (TLP), and cuticular conductance. Species originating from moist habitats showed substantial shrinkage during dehydration before reaching TLP, in contrast with species originating from dry habitats. Across species, the decline of K(leaf) with mild dehydration (i.e. the initial slope of the K(leaf) versus Ψ(leaf) curve) correlated with the decline of leaf thickness (the slope of the leaf thickness versus Ψ(leaf) curve), as expected based on predictions from computer simulations. Leaf thickness shrinkage before TLP correlated across species with lower modulus of elasticity and with less negative osmotic pressure at full turgor, as did leaf area shrinkage between full turgor and oven desiccation. These findings point to a role for leaf shrinkage in hydraulic decline during mild dehydration, with potential impacts on drought adaptation for cells and leaves, influencing plant ecological distributions.

  16. Leaf Shrinkage with Dehydration: Coordination with Hydraulic Vulnerability and Drought Tolerance1[C][W][OPEN

    PubMed Central

    Scoffoni, Christine; Vuong, Christine; Diep, Steven; Cochard, Hervé; Sack, Lawren

    2014-01-01

    Leaf shrinkage with dehydration has attracted attention for over 100 years, especially as it becomes visibly extreme during drought. However, little has been known of its correlation with physiology. Computer simulations of the leaf hydraulic system showed that a reduction of hydraulic conductance of the mesophyll pathways outside the xylem would cause a strong decline of leaf hydraulic conductance (Kleaf). For 14 diverse species, we tested the hypothesis that shrinkage during dehydration (i.e. in whole leaf, cell and airspace thickness, and leaf area) is associated with reduction in Kleaf at declining leaf water potential (Ψleaf). We tested hypotheses for the linkage of leaf shrinkage with structural and physiological water relations parameters, including modulus of elasticity, osmotic pressure at full turgor, turgor loss point (TLP), and cuticular conductance. Species originating from moist habitats showed substantial shrinkage during dehydration before reaching TLP, in contrast with species originating from dry habitats. Across species, the decline of Kleaf with mild dehydration (i.e. the initial slope of the Kleaf versus Ψleaf curve) correlated with the decline of leaf thickness (the slope of the leaf thickness versus Ψleaf curve), as expected based on predictions from computer simulations. Leaf thickness shrinkage before TLP correlated across species with lower modulus of elasticity and with less negative osmotic pressure at full turgor, as did leaf area shrinkage between full turgor and oven desiccation. These findings point to a role for leaf shrinkage in hydraulic decline during mild dehydration, with potential impacts on drought adaptation for cells and leaves, influencing plant ecological distributions. PMID:24306532

  17. Improving Reliability of Subject-Level Resting-State fMRI Parcellation with Shrinkage Estimators

    PubMed Central

    Mejia, Amanda F.; Nebel, Mary Beth; Shou, Haochang; Crainiceanu, Ciprian M.; Pekar, James J.; Mostofsky, Stewart; Caffo, Brian; Lindquist, Martin A.

    2015-01-01

    A recent interest in resting state functional magnetic resonance imaging (rsfMRI) lies in subdividing the human brain into anatomically and functionally distinct regions of interest. For example, brain parcellation is often a necessary step for defining the network nodes used in connectivity studies. While inference has traditionally been performed on group-level data, there is a growing interest in parcellating single subject data. However, this is difficult due to the inherent low signal-to-noise ratio of rsfMRI data, combined with typically short scan lengths. A large number of brain parcellation approaches employ clustering, which begins with a measure of similarity or distance between voxels. The goal of this work is to improve the reproducibility of single-subject parcellation using shrinkage-based estimators of such measures, allowing the noisy subject-specific estimator to “borrow strength” in a principled manner from a larger population of subjects. We present several empirical Bayes shrinkage estimators and outline methods for shrinkage when multiple scans are not available for each subject. We perform shrinkage on raw inter-voxel correlation estimates and use both raw and shrinkage estimates to produce parcellations by performing clustering on the voxels. While we employ a standard spectral clustering approach, our proposed method is agnostic to the choice of clustering method and can be used as a pre-processing step for any clustering algorithm. Using two datasets – a simulated dataset where the true parcellation is known and is subject-specific and a test-retest dataset consisting of two 7-minute resting-state fMRI scans from 20 subjects – we show that parcellations produced from shrinkage correlation estimates have higher reliability and validity than those produced from raw correlation estimates. Application to test-retest data shows that using shrinkage estimators increases the reproducibility of subject-specific parcellations of the motor

  18. Time dependence of composite shrinkage using halogen and LED light curing.

    PubMed

    Uhl, Alexander; Mills, Robin W; Rzanny, Angelika E; Jandt, Klaus D

    2005-03-01

    The polymerization shrinkage of light cured dental composites presents the major drawback for these aesthetically adaptable restorative materials. LED based light curing technology has recently become commercially available. Therefore, the aim of the present study was to investigate if there was a statistically significant difference in linear and volumetric composite shrinkage strain if a LED LCU is used for the light curing process rather than a conventional halogen LCU. The volumetric shrinkage strain was determined using the Archimedes buoyancy principle after 5, 10, 20, 40 s of light curing and after 120 s following the 40 s light curing time period. The linear shrinkage strain was determined with a dynamic mechanical analyzer for the composites Z100, Spectrum, Solitaire2 and Definite polymerized with the LCUs Trilight (halogen), Freelight I (LED) and LED63 (LED LCU prototype). The changes in irradiance and spectra of the LCUs were measured after 0, 312 and 360 min of duty time. In general there was no considerable difference in shrinkage of the composites Z100, Spectrum or Solitaire2 when the LED63 was used instead of the Trilight. There was, however, a statistically significant difference in shrinkage strain when the composite Definite was polymerized with the LED63 instead of the Trilight. The spectrum of the Trilight changed during the experiment considerably whereas the LED63 showed an almost constant light output. The Freelight I dropped considerably in irradiance and had to be withdrawn from the study because of technical problems. The composites containing only the photoinitiator camphorquinone showed similar shrinkage strain behaviour when a LED or halogen LCU is used for the polymerization. The irradiance of some LED LCUs can also decrease over time and should therefore be checked on a regular basis.

  19. Temperature-dependent biphasic shrinkage of lipid-coated bubbles in ultrasound.

    PubMed

    Cox, Debra J; Thomas, James L

    2013-04-09

    Lipid-coated microbubbles and emulsions are of interest as possible ultrasound-mediated drug delivery vehicles and for their interesting behaviors and fundamental properties. We and others have noted that bubbles coated with the long chain saturated phospholipid distearoylphosphatidylcholine (DSPC) rapidly shrink to a quasistable size when repeatedly insonated with short ultrasound pulses; such stability may adversely affect the bubble's subsequent ability to deliver its pharmacological cargo. Bubbles coated with the unsaturated lipid dioleoylphosphatidylcholine (DOPC) did not show stability but did undergo an abrupt change from rapid initial shrinkage to a slow persistent shrinkage, leading ultimately to dissolution or dispersion. As DOPC and DSPC differ not only in chain saturation but also phase behavior, we performed additional studies using dimyristoyl PC (DMPC) as a coat lipid and controlled the solution temperature to study bubble behavior on exposure to repeated ultrasound pulses for the same coat, in both fluid and gel phases. We find, first, that essentially all bubbles show an initially rapid shrinkage, in which gas loss exceeds the limit imposed by gas diffusion into the surrounding medium; this rapid shrinkage may be evidence of nanoscopic bubble fragmentation. Second, upon reaching a fraction of their initial size, bubbles begin a slower shrinkage with a shrinkage rate that depends on the resting phase state of the coat lipid: fluid DMPC monolayers give a more rapid shrinkage than gel phase. DOPC-coated bubbles showed no temperature-dependent responses in the same temperature range. The results are especially interesting in that bubble compression during the pulse is likely to adiabatically heat the bubble and fluidize the coat, regardless of its initial phase state; thus, some structural feature of the resting coat, such as defect lines in the gel phase, may be important in the subsequent response to the ~3 μs ultrasound pulse.

  20. Formation of shrinkage porosity during solidification of steel: Numerical simulation and experimental validation

    NASA Astrophysics Data System (ADS)

    Riedler, M.; Michelic, S.; Bernhard, C.

    2016-07-01

    The phase transformations in solidification of steel are accompanied by shrinkage and sudden changes in the solubility of alloying elements, resulting in negative side effects as micro- and macrosegregation and the formation of gas and shrinkage porosities. This paper deals with the numerical and experimental simulation of the formation of shrinkage porosity during the solidification of steel. First the physical basics for the mechanism of shrinkage pore formation will be discussed. The main reason for this type of porosity is the restraint of fluid flow in the mushy zone which leads to a pressure drop. The pressure decreases from the dendrite tip to the root. When the pressure falls below a critical value, a pore can form. The second part of the paper deals with different approaches for the prediction of the formation of shrinkage porosity. The most common one according to these models is the usage of a simple criterion function, like the Niyama criterion. For the computation of the porosity criterion the thermal gradient, cooling rate and solidification rate must be known, easily to determine from numerical simulation. More complex simulation tools like ProCAST include higher sophisticated models, which allow further calculations of the shrinkage cavity. Finally, the different approaches will be applied to a benchmark laboratory experiment. The presented results deal with an ingot casting experiment under variation of taper. The dominant influence of mould taper on the formation of shrinkage porosities can both be demonstrated by the lab experiment as well as numerical simulations. These results serve for the optimization of all ingot layouts for lab castings at the Chair of Ferrous Metallurgy.

  1. Formation and interpretation of dilatant echelon cracks.

    USGS Publications Warehouse

    Pollard, D.D.; Segall, P.; Delaney, P.T.

    1982-01-01

    The relative displacements of the walls of many veins, joints, and dikes demonstrate that these structures are dilatant cracks. We infer that dilatant cracks propagate in a principal stress plane, normal to the maximum tensile or least compressive stress. Arrays of echelon crack segments appear to emerge from the peripheries of some dilatant cracks. Breakdown of a parent crack into an echelon array may be initiated by a spatial or temporal rotation of the remote principal stresses about an axis parallel to the crack propagation direction. Near the parent-crack tip, a rotation of the local principal stresses is induced in the same sense, but not necessarily through the same angle. Incipient echelon cracks form at the parent-crack tip normal to the local maximum tensile stress. Further longitudinal growth along surfaces that twist about axes parallel to the propagation direction realigns each echelon crack into a remote principal stress plane. The walls of these twisted cracks may be idealized as helicoidal surfaces. An array of helicoidal cracks sweeps out less surface area than one parent crack twisting through the same angle. Thus, many echelon cracks grow from a single parent because the work done in creating the array, as measured by its surface area decreases as the number of cracks increases. -from Authors

  2. Observation of Intralaminar Cracking in the Edge Crack Torsion Specimen

    NASA Technical Reports Server (NTRS)

    Czabaj, Michael W.; Ratcliffe, James G.; Davidson, Barry D.

    2013-01-01

    The edge crack torsion (ECT) test is evaluated to determine its suitability for measuring fracture toughness associated with mode III delamination growth onset. A series of ECT specimens with preimplanted inserts with different lengths is tested and examined using nondestructive and destructive techniques. Ultrasonic inspection of all tested specimens reveals that delamination growth occurs at one interface ply beneath the intended midplane interface. Sectioning and optical microscopy suggest that the observed delamination growth results from coalescence of angled intralaminar matrix cracks that form and extend across the midplane plies. The relative orientation of these cracks is approximately 45 deg with respect to the midplane, suggesting their formation is caused by resolved principal tensile stresses arising due to the global mode-III shear loading. Examination of ECT specimens tested to loads below the level corresponding to delamination growth onset reveals that initiation of intralaminar cracking approximately coincides with the onset of nonlinearity in the specimen's force-displacement response. The existence of intralaminar cracking prior to delamination growth onset and the resulting delamination extension at an unintended interface render the ECT test, in its current form, unsuitable for characterization of mode III delamination growth onset. The broader implications of the mechanisms observed in this study are also discussed with respect to the current understanding of shear-driven delamination in tape-laminate composites.

  3. The Volume Behavior of Autogenous Iliac Bone Grafts After Sinus Floor Elevation: A Clinical Pilot Study.

    PubMed

    Gerressen, Marcus; Riediger, Dieter; Hilgers, Ralf-Dieter; Hölzle, Frank; Noroozi, Nelson; Ghassemi, Alireza

    2015-06-01

    Iliac crest is still regarded as one of the most viable source of autogenous graft materials for extensive sinus floor elevation. Three-dimensional resorption behavior has to be taken into account in anticipation of the subsequent insertion of dental implants. We performed 3-dimensional volume measurements of the inserted bone transplants in 11 patients (6 women and 5 men; mean age = 2.3 years) who underwent bilateral sinus floor elevation with autogenous iliac crest grafts. In order to determine the respective bone graft volumes, cone-beam computerized tomography studies of the maxillary sinuses were carried out directly after the operation (T0), as well as 3 months (T1) and 6 months (T2) postoperatively. The acquired DICOM (Digital Imaging and Communications in Medicine) data sets were evaluated using suitable analysis software. We evaluated statistical significance of graft volumes changes using a linear mixed model with the grouping factors for time, age, side, and sex with a significance level of P = .05. 38.9% of the initial bone graft volume, which amounted to 4.2 cm(3), was resorbed until T1. At T2, the average volume again decreased significantly by 18.9 % to finally reach 1.8 cm(3). The results show neither age nor side dependency and apply equally to both sexes. Without functional load, iliac bone grafts feature low-volume stability in sinus-augmentation surgery. Further clinical and animal studies should be done to detect the optimal timing for implant placement.

  4. Biofeedback, autogenic training, and progressive relaxation in the treatment of Raynaud's disease: a comparative study.

    PubMed

    Keefe, F J; Surwit, R S; Pilon, R N

    1980-01-01

    Twenty-one female patients suffering from diagnosed idiopathic Raynaud's Disease were trained to raise digital skin temperature using either autogenic training, progressive muscle relaxation, or a combination of autogenic training and skin temperature feedback. Patients were instructed in the treatment procedures in three one-hour group sessions spaced one week apart. All patients were instructed to practice what they had learned twice a day at home. Patients kept records of the frequency of vasospastic attacks occurring over a four-week baseline period, and during the first four weeks and the ninth week of training. In addition, patients underwent four laboratory cold stress tests during which they were instructed to maintain digital temperature as the ambient temperature was slowly dropped from 26 degrees to 17 degrees C. Cold stress tests were given during week 1 of baseline and during weeks 1, 3, and 5 of training. No significant differences between the three behavioral treatment procedures were obtained. In addition, the ability of patients to maintain digital temperature during the cold stress challenge showed significant improvement from the first to the last tests. Symptomatic improvement was maintained by all patients nine weeks after the start of training. The implications of these findings for the behavioral treatment of Raynaud's Disease are discussed.

  5. Autogenic succession and deterministic recovery following disturbance in soil bacterial communities

    PubMed Central

    Jurburg, Stephanie D.; Nunes, Inês; Stegen, James C.; Le Roux, Xavier; Priemé, Anders; Sørensen, Søren J.; Salles, Joana Falcão

    2017-01-01

    The response of bacterial communities to environmental change may affect local to global nutrient cycles. However the dynamics of these communities following disturbance are poorly understood, given that they are often evaluated over macro-ecological time scales and end-point measurements. In order to understand the successional trajectory of soil bacterial communities following disturbances and the mechanisms controlling these dynamics at a scale relevant for these organisms, we subjected soil microcosms to a heat disturbance and followed the community composition of active bacteria over 50 days. The disturbance imposed a strong selective pressure that persisted for up to 10 days, after which the importance of stochastic processes increased. Three successional stages were detected: a primary response in which surviving taxa increased in abundance; a secondary response phase during which community dynamics slowed down, and a stability phase (after 29 days), during which the community tended towards its original composition. Phylogenetic turnover patterns indicated that the community experienced stronger deterministic selection during recovery. Thus, soil bacterial communities, despite their extreme diversity and functional redundancy, respond to disturbances like many macro-ecological systems and exhibit path-dependent, autogenic dynamics during secondary succession. These results highlight the role of autogenic factors and successional dynamics in microbial recovery. PMID:28383027

  6. Comparative study of two autogenous graft techniques using piezosurgery for sinus lifting.

    PubMed

    Camargo Filho, Geraldo Prestes de; Corrêa, Luciana; Costa, Claudio; Pannuti, Claudio Mendes; Schmelzeisen, Rainer; Luz, João Gualberto de Cerqueira

    2010-12-01

    Maxillary sinus lifting is a technique, in which, a possible complication is sinus membrane perforation. The aim of this study was to compare two techniques using ultrasound surgery to perform autogenous graft for maxillary sinus lifting. Ten rabbits were used in the study, one of them did not undergo surgery. The other nine rabbits had their maxillary sinuses filled with autogenous bone grafts collected from the external skull diploe in particulate form on the right side, and shaved on the left side, both with ultrasonic device. Data on bone density in left and right maxillary sinus, obtained by computed tomography in transverse and longitudinal sections, recorded 90 days after the grafts, were statistically compared. There were no statistically significant differences between the two techniques that used shaved and particulate bone collected by means of ultrasonic device from rabbit skulls. Assessment of operative procedures led to the conclusion that piezoelectric ultrasound was shown to be a safe tool in the surgical approach to the maxillary sinus of rabbits, allowing sinus membrane integrity to be maintained during surgical procedures.

  7. Simultaneous maxillary sinus lifting and implant placement with autogenous parietal bone graft: outcome of 17 cases.

    PubMed

    Sakka, Salah; Krenkel, Christian

    2011-04-01

    The aim of this study was to retrospectively evaluate the surgical technique of sinus floor elevation with autogenous parietal bone grafting in conjunction with immediate dental implants for the reconstruction of the maxilla in deficient maxillary alveolar ridges. Seventeen patients who underwent sinus floor elevation with bone graft from the parietal bone between 2005 and 2007 were included in the study. Cases of extremely deficient bone level in the alveolar ridge<4mm were included in the study. Seventy-seven implants (49 Staumann®, 24 Replace® and 4 Ankylos®) with different length and diameter were placed immediately after the graft was placed. Strict oral hygiene was required for the patients. Presurgical and postsurgical panoramic radiographs were taken. A high-quality reconstruction with an increase in lifted sinus bone height was achieved with parietal bone particulates. Seventy-three implants were clinically osseointegrated and four implants were lost giving a success rate 94.8%. No correlation was found between failure and the surgery. The encouraging results of this study suggest that the technique of reconstruction of the sinus floor and the resorbed alveolar ridge using an autogenous parietal bone graft is reliable, giving the surgeon the opportunity to successfully perform immediate implant placement in more difficult and deficient maxillary alveolar bone height. Copyright © 2010. Published by Elsevier Ltd.

  8. Comparison of the effect of three autogenous bone harvesting methods on cell viability in rabbits

    PubMed Central

    Moradi Haghgoo, Janet; Arabi, Seyed Reza; Hosseinipanah, Seyyed Mohammad; Solgi, Ghasem; Rastegarfard, Neda; Farhadian, Maryam

    2017-01-01

    Background. This study was designed to compare the viability of autogenous bone grafts, harvested using different methods, in order to determine the best harvesting technique with respect to more viable cells. Methods. In this animal experimental study, three harvesting methods, including manual instrument (chisel), rotary device and piezosurgery, were used for harvesting bone grafts from the lateral body of the mandible on the left and right sides of 10 rabbits. In each group, 20 bone samples were collected and their viability was assessed using MTS kit. Statistical analyses, including ANOVA and post hoc Tukey tests, were used for evaluating significant differences between the groups. Results. One-way ANOVA showed significant differences between all the groups (P=0.000). Data analysis using post hoc Tukey tests indicated that manual instrument and piezosurgery had no significant differences with regard to cell viability (P=0.749) and the cell viability in both groups was higher than that with the use of a rotary instrument (P=0.000). Conclusion. Autogenous bone grafts harvested with a manual instrument and piezosurgery had more viable cells in comparison to the bone chips harvested with a rotary device. PMID:28748046

  9. Alternative surgical treatment of paralytic lagophthalmos using autogenic cartilage grafts and canthopexy.

    PubMed

    Friedhofer, Henri; Coltro, Pedro Soler; Vassiliadis, Aneta Hionia; Nigro, Marcelus Vinícius; Saito, Fábio Lopes; Moura, Tatiana; Faria, José Carlos; Ferreira, Marcus Castro

    2013-08-01

    This study aims to analyze the use of autogenic auricular cartilage grafts as weight for the upper eyelid in conjunction with lateral canthopexy for patients with mild paralytic lagophthalmos. This procedure was also accompanied by elevation of the lower eyelid using the cartilage graft for moderate cases. We conducted a retrospective study including case series of 30 patients with paralytic lagophthalmos from 1997 to 2010. For mild cases, cartilage from the auricular scapha was placed in pretarsal space of the upper eyelid and cartilage from the concha was inserted in preaponeurotic space and then sutured to the levator aponeurosis in conjunction with lateral canthopexy. For moderate cases, lower eyelid was also elevated by suturing cartilage graft to tarsum and resting it by the inferior orbital rim. All patients had some degree of keratopathy before the intervention. After treatment, they presented with evident clinical improvement, reduction of eye symptoms, and resolution of keratopathy. During the mean postoperative follow-up of 37.3 months, none of the patients presented with cartilage graft exposition, reabsorption, visibility, infection, or warping. Complete eye closure was achieved in 24 (80%) patients, whereas the remaining 6 (20%) patients had residual asymptomatic lagophthalmos. The intervention using autogenic auricular cartilage grafts explained in this study was only effective for the treatment of mild and moderate cases of paralytic lagophthalmos. This outpatient surgery is associated with low morbidity and achievement of functional and aesthetic improvement.

  10. Full-thickness tissue engineered skin constructed with autogenic bone marrow mesenchymal stem cells.

    PubMed

    He, LiJuan; Nan, Xue; Wang, YunFang; Guan, LiDong; Bai, CiXian; Shi, ShuangShuang; Yuan, HongFeng; Chen, Lin; Liu, Daqing; Pei, Xuetao

    2007-08-01

    To explore the feasibility of repairing clinical cutaneous deficiency, autogenic bone marrow mesenchymal stem cells (BMSCs) were isolated and differentiated into epidermal cells and fibroblasts in vitro supplemented with different inducing factors and biomaterials to construct functional tissueengineered skin. The results showed that after 72 h induction, BMSCs displayed morphologic changes such as typical epidermal cell arrangement, from spindle shape to round or oval; tonofibrils, melanosomes and keratohyaline granules were observed under a transmission electronic microscope. The differentiated cells expressed epidermal stem cell surface marker CK19 (59.66% +/- 4.2%) and epidermal cells differentiation marker CK10. In addition, the induced epidermal cells acquired the anti-radiation capacity featured by lowered apoptosis following exposure to UVB. On the other hand, the collagen microfibrils deposition was noticed under a transmission electronic microscope after differentiating into dermis fibroblasts; RT-PCR identified collagen type I mRNA expression in differentiated cells; radioimmunoassay detected the secretion of interleukin-6 (IL-6) and interleukin-8 (IL-8) (up to 115.06 pg/mL and 0.84 ng/mL, respectively). Further in vivo implanting BMSCs with scaffold material shortened skin wound repair significantly. In one word, autogenic BMSCs have the potential to differentiate into epidermal cells and fibroblasts in vitro, and show clinical feasibility acting as epidermis-like and dermis-like seed cells in skin engineering.

  11. [Use of supportive autogenic training in multiple morbidity in geriatric psychiatry patients].

    PubMed

    Kircher, T; Stetter, F; Wormstall, H

    1997-01-01

    23 multimorbid, geronto-psychiatric patients, aged 60 years or older, participated in a "supportive" course of autogenic training according to Schultz. Participating in the course an average of 7 +/- 3 weeks, 17 (76%) of the subjects were able to learn the training. In general, subjects reported a better general condition after the training sessions, measured with visual analogue scales (p < 0.001). The psychopathological status improved significantly during the time of the course (BPRS: p < 0.001; GDS: p < 0.001). No significant change was found in the cognitive state (MMSE) and the statements on the "list of complaints" ("Beschwerdenliste"). The global training success was better in the psychopathological less affected than in the more severely ill (BPRS prior r = 0.64, p = 0.001, GDS prior r = 0.46, p < 0.05). No correlation was found between training success and age, number of somatic diseases, number of medication, MMSE and the "Beschwerdenliste". Autogenic training is a useful component in psychotherapeutic and psychiatric therapy for elderly multimorbid in- and outpatients. A half-open group, two therapy sessions per week, reciting the training formulae aloud, a structured, simple setting and co-therapists proved to be worthwhile.

  12. Autogenic succession and deterministic recovery following disturbance in soil bacterial communities.

    PubMed

    Jurburg, Stephanie D; Nunes, Inês; Stegen, James C; Le Roux, Xavier; Priemé, Anders; Sørensen, Søren J; Salles, Joana Falcão

    2017-04-06

    The response of bacterial communities to environmental change may affect local to global nutrient cycles. However the dynamics of these communities following disturbance are poorly understood, given that they are often evaluated over macro-ecological time scales and end-point measurements. In order to understand the successional trajectory of soil bacterial communities following disturbances and the mechanisms controlling these dynamics at a scale relevant for these organisms, we subjected soil microcosms to a heat disturbance and followed the community composition of active bacteria over 50 days. The disturbance imposed a strong selective pressure that persisted for up to 10 days, after which the importance of stochastic processes increased. Three successional stages were detected: a primary response in which surviving taxa increased in abundance; a secondary response phase during which community dynamics slowed down, and a stability phase (after 29 days), during which the community tended towards its original composition. Phylogenetic turnover patterns indicated that the community experienced stronger deterministic selection during recovery. Thus, soil bacterial communities, despite their extreme diversity and functional redundancy, respond to disturbances like many macro-ecological systems and exhibit path-dependent, autogenic dynamics during secondary succession. These results highlight the role of autogenic factors and successional dynamics in microbial recovery.

  13. Autogenous cultured growth plate chondrocyte transplantation in the treatment of physeal injury in rabbits

    PubMed Central

    Tomaszewski, R.; Bohosiewicz, J.; Gap, A.; Bursig, H.; Wysocka, A.

    2014-01-01

    Objectives The aim of this experimental study on New Zealand’s white rabbits was to investigate the transplantation of autogenous growth plate cells in order to treat the injured growth plate. They were assessed in terms of measurements of radiological tibial varus and histological characteristics. Methods An experimental model of plate growth medial partial resection of the tibia in 14 New Zealand white rabbits was created. During this surgical procedure the plate growth cells were collected and cultured. While the second surgery was being performed, the autologous cultured growth plate cells were grafted at the right tibia, whereas the left tibia was used as a control group. Results Histological examinations showed that the grafted right tibia presented the regular shape of the plate growth with hypertrophic maturation, chondrocyte columniation and endochondral calcification. Radiological study shows that the mean tibial deformity at the left angle was 20.29° (6.25 to 33) and 7.21° (5 to 10) in the right angle. Conclusion This study has demonstrated that grafting of autogenous cultured growth plate cells into a defect of the medial aspect of the proximal tibial physis can prevent bone bridge formation, growth arrest and the development of varus deformity. Cite this article: Bone Joint Res 2014;3:310–16 PMID:25376625

  14. Crack healing in alumina bioceramics.

    PubMed

    Fischer, H; Weiss, R; Telle, R

    2008-03-01

    Microscopic cracks can occur at the surface of oxide ceramic restorations as a result of the manufacturing process and mainly due to the final mechanical preparation in the dental laboratory. A method is presented to heal up such microscopic cracks by a glass infiltration process. Bar specimens made of high purity bio-alumina were manufactured. On two batches of specimens microscopic cracks were induced using the Vickers indentation technique. The small microscopic cracks at the tip of the resulting half-penny-shape cracks were extended by the bridge loading method. The indentation pattern of the specimens of one batch was subsequently glass-infiltrated. The surface layers of the specimens with the Vickers indentation were removed by grinding as far as only the extended microscopic cracks (with and without glass) remained at the surface. The strengths of untreated, micro-damaged, and micro-damaged and glass-infiltrated specimens were determined. The microstructure of the fracture surfaces was analyzed using SEM. The characteristic strength of the specimens decreased from sigma(0)=378 to 196 MPa and the Weibull modulus from m=13.7 to 2.3 due to the micro-damaging. The strength and the scatter-in-strength were significantly improved by the glass infiltration process. The strength of the "healed" specimens (sigma(0)=434 MPa, m=17.3) was even better than that of the untreated samples. Microscopic cracks that can occur at the surface of dental restorations made of alumina like abutments or cores of crowns and bridges during the manufacturing and preparation process could reliably be healed by a glass infiltration process.

  15. Non-Ionotropic NMDA Receptor Signaling Drives Activity-Induced Dendritic Spine Shrinkage.

    PubMed

    Stein, Ivar S; Gray, John A; Zito, Karen

    2015-09-02

    The elimination of dendritic spine synapses is a critical step in the refinement of neuronal circuits during development of the cerebral cortex. Several studies have shown that activity-induced shrinkage and retraction of dendritic spines depend on activation of the NMDA-type glutamate receptor (NMDAR), which leads to influx of extracellular calcium ions and activation of calcium-dependent phosphatases that modify regulators of the spine cytoskeleton, suggesting that influx of extracellular calcium ions drives spine shrinkage. Intriguingly, a recent report revealed a novel non-ionotropic function of the NMDAR in the regulation of synaptic strength, which relies on glutamate binding but is independent of ion flux through the receptor (Nabavi et al., 2013). Here, we tested whether non-ionotropic NMDAR signaling could also play a role in driving structural plasticity of dendritic spines. Using two-photon glutamate uncaging and time-lapse imaging of rat hippocampal CA1 neurons, we show that low-frequency glutamatergic stimulation results in shrinkage of dendritic spines even in the presence of the NMDAR d-serine/glycine binding site antagonist 7-chlorokynurenic acid (7CK), which fully blocks NMDAR-mediated currents and Ca(2+) transients. Notably, application of 7CK or MK-801 also converts spine enlargement resulting from a high-frequency uncaging stimulus into spine shrinkage, demonstrating that strong Ca(2+) influx through the NMDAR normally overcomes a non-ionotropic shrinkage signal to drive spine growth. Our results support a model in which NMDAR signaling, independent of ion flux, drives structural shrinkage at spiny synapses. Dendritic spine elimination is vital for the refinement of neural circuits during development and has been linked to improvements in behavioral performance in the adult. Spine shrinkage and elimination have been widely accepted to depend on Ca(2+) influx through NMDA-type glutamate receptors (NMDARs) in conjunction with long-term depression

  16. Effect of mixing technique on shrinkage rate of one polyether and two polyvinyl siloxane impression materials.

    PubMed

    Lampé, István; Marton, Sándor; Hegedüs, Csaba

    2004-01-01

    Different mixing techniques may affect the quality of set impression materials. Therefore, dimensional accuracy is the most important factor when constructing a passive and accurate prosthesis. In this study, observation of the shrinkage rate of one polyether and two polyvinyl siloxane impression materials, which are both commercially available for cartridge- and hand-mix techniques, was used for comparative analysis. The hypothesis was that the cartridgemix technique would produce a more precise impression. The authors also sought to confirm the hypothesis that the studied materials would remain stable after setting. The low-viscosity polyether material was Permadyne Garant 2:1, type 3 (ESPE). The polyvinyl siloxane materials were: (1) medium-viscosity Provil Novo Medium, cartridge- and hand-mix type 2 (Heraeus Kulzer); and (2) low-viscosity President, hand- and cartridge-mix type 3 (Coltène). Measurements were made according to American Dental Association specification No. 19. Ten specimens were made of each impression material; the same examiner measured each specimen 10 times. Shrinkage rates of the same materials mixed using different techniques were compared 30 minutes, 24 hours, and 72 hours after mixing. Dimensional changes at the different measuring times were also compared. The results were statistically analyzed and compared with the SPSS for Windows program package, version 11.0 (SPSS); a two-sample t test was applied to compare the mixing techniques at every measuring time; and a Friedman test was used to analyze the changes in shrinkage rate during the evaluation period (P > .05). Figure 1 shows the shrinkage rate data for all materials. Statistical analysis showed no significant difference at any measuring point when the mixing techniques of the polyvinyl siloxane materials were compared. However, analysis showed significant differences for both hand- and cartridge-mixed materials when measurements at 30 minutes, 24 hours, and 72 hours were compared

  17. Modified creep and shrinkage prediction model B3 for serviceability limit state analysis of composite slabs

    NASA Astrophysics Data System (ADS)

    Gholamhoseini, Alireza

    2016-03-01

    Relatively little research has been reported on the time-dependent in-service behavior of composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. This paper presents the results of long-term laboratory tests on composite slabs subjected to both drying shrinkage and sustained loads. Based on laboratory measurements, a design model for the shrinkage strain profile through the thickness of a slab is proposed. The design model is based on some modifications to an existing creep and shrinkage prediction model B3. In addition, an analytical model is developed to calculate the time-dependent deflection of composite slabs taking into account the time-dependent effects of creep and shrinkage. The calculated deflections are shown to be in good agreement with the experimental measurements.

  18. Control of polymerization shrinkage and stress in nanogel-modified monomer and composite materials

    PubMed Central

    Moraes, Rafael R.; Garcia, Jeffrey W.; Barros, Matthew D.; Lewis, Steven H.; Pfeifer, Carmem S.; Liu, JianCheng; Stansbury, Jeffrey W.

    2011-01-01

    Objectives This study demonstrates the effects of nano-scale prepolymer particles as additives to model dental monomer and composite formulations. Methods Discrete nanogel particles were prepared by solution photopolymerization of isobornyl methacrylate and urethane dimethacrylate in the presence of a chain transfer agent, which also provided a means to attach reactive groups to the prepolymer. Nanogel was added to triethylene glycol dimethacrylate (TEGDMA) in increments between 5 and 40 wt% with resin viscosity, reaction kinetics, shrinkage, mechanical properties, stress and optical properties evaluated. Maximum loading of barium glass filler was determined as a function of nanogel content and composites with varied nanogel content but uniform filler loading were compared in terms of consistency, conversion, shrinkage and mechanical properties. Results High conversion, high molecular weight internally crosslinked and cyclized nanogel prepolymer was efficiently prepared and redispersed into TEGDMA with an exponential rise in viscosity accompanying nanogel content. Nanogel addition at any level produced no deleterious effects on reaction kinetics, conversion or mechanical properties, as long as reactive nanogels were used. A reduction in polymerization shrinkage and stress was achieved in proportion to nanogel content. Even at high nanogel concentrations, the maximum loading of glass filler was only marginally reduced relative to the control and high strength composite materials with low shrinkage were obtained. Significance The use of reactive nanogels offers a versatile platform from which resin and composite handling properties can be adjusted while the polymerization shrinkage and stress development that challenge the adhesive bonding of dental restoratives are controllably reduced. PMID:21388669

  19. A Pore-Centric Model for Combined Shrinkage and Gas Porosity in Alloy Solidification

    NASA Astrophysics Data System (ADS)

    Khalajzadeh, Vahid; Carlson, Kent D.; Backman, Daniel G.; Beckermann, Christoph

    2017-04-01

    A unified model has been developed for combined gas- and shrinkage-induced pore formation during solidification of metal alloys. The model is based on a pore-centric approach, in which the temporal evolution of the pore radius is calculated as a function of cooling rate, thermal gradient, gas diffusion, and shrinkage. It accounts for the effect of porosity formation on the liquid velocity within the mushy zone. Simulations for an aluminum alloy show that the porosity transitions smoothly from shrinkage-induced to gas-induced as the Niyama value is increased. A Blake (cavitation) instability is observed to occur when the porosity is both gas- and shrinkage-driven. A revised dimensionless Niyama curve for pure shrinkage is presented. The experimentally observed gas porosity trend that the pore volume decreases with increasing cooling rate is well predicted. The pore-centric formulation allows the present model to be solved locally, at any point in a casting, during a regular casting simulation.

  20. Perceptual shrinkage of a one-way motion path with high-speed motion

    PubMed Central

    Nakajima, Yutaka; Sakaguchi, Yutaka

    2016-01-01

    Back-and-forth motion induces perceptual shrinkage of the motion path, but such shrinkage is hardly perceived for one-way motion. If the shrinkage is caused by temporal averaging of stimulus position around the endpoints, it should also be induced for one-way motion at higher motion speeds. In psychophysical experiments with a high-speed projector, we tested this conjecture for a one-way motion stimulus at various speeds (4–100 deg/s) along a straight path. Results showed that perceptual shrinkage of the motion path was robustly observed in higher-speed motion (faster than 66.7 deg/s). In addition, the amount of the forwards shift at the onset position was larger than that of the backwards shift at the offset position. These results demonstrate that high-speed motion can induce shrinkage, even for a one-way motion path. This can be explained by the view that perceptual position is represented by the integration of the temporal average of instantaneous position and the motion representation. PMID:27464844