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Sample records for alloy shrinkage factors

  1. 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.

  2. Alloy Shrinkage factors for the investment casting of 17-4PH stainless steel parts

    SciTech Connect

    Sabau, Adrian S; Porter, Wallace D

    2008-01-01

    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. For all the properties, the experimental data available in the literature did not cover the entire temperature range necessary for process simulation. A comparison between the predicted material property data measured property data is made. It was found that most material properties were accurately predicted over the most of the temperature range of the process. Several assumptions were made in order to obtain a complete set of mechanical property data at high temperatures. Thermal expansion measurements for the 17-4PH alloy were conducted at heating and cooling. As a function of temperature, the thermal expansion for both the alloy and shell mold materials showed different evolution at heating and cooling. Thus, one generic simulation were performed with thermal expansion obtained at heating and another one with thermal expansion obtained at cooling. The alloy dimensions were obtained from numerical simulation results of solidification, heat transfer, and deformation phenomena. As compared with experimental results, the numerical simulation results for the shrinkage factors were slightly over-predicted.

  3. 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.

  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. Influencing Factors for Abdominal Aortic Aneurysm Sac Shrinkage and Enlargement after EVAR: Clinical Reviews before Introduction of Preoperative Coil Embolization

    PubMed Central

    Hiraoka, Arudo; Totsugawa, Toshinori; Tamura, Kentaro; Ishida, Atsuhisa; Sakaguchi, Taichi; Yoshitaka, Hidenori

    2014-01-01

    Background: We previously reported effectiveness of coil embolization (CE) to aortic branched vessels before endovascular aortic repair (EVAR) for abdominal aortic aneurysm (AAA) because of significant shrinkage of aneurysmal sac. In this study, we investigated EVAR cases to clarify influential factors of aneurysmal shrinkage and enlargement. Methods: 148 consecutive cases before the introduction of CE were retrospectively reviewed based on the presence of PT2EL (persistent type 2 endoleak) and change in sac diameter after EVAR by multivariate analysis. Results: (A) PT2EL risk factors were patent inferior mesenteric artery (IMA) and thinner mural thrombus inside aneurysmal sac. (B) Sac enlargement risk factors were antiplatelet intake, PT2EL, and female gender. (C) Sac shrinkage predictive factors were the absences of thoracic aortic aneurysm, antiplatelet intake, PT2EL, and coronary artery disease. Conclusion: CE to IMA was considered to be effective because patent IMA and antiplatelet intake were significant risk factors for sac enlargement. So, more meticulous therapeutic strategy, including treatment priority (AAA first or CAD first) and choice of treatment (EVAR vs. AAA) based on anatomical features of AAA was required to improve late outcomes. PMID:25298830

  6. Low shrinkage composite resins: influence on sealing ability in unfavorable C-factor cavities.

    PubMed

    Klautau, Eliza Burlamaqui; Carneiro, Karina Kato; Lobato, Marcelo Figueiredo; Machado, Sissy Maria Mendes; Silva e Souza, Mário Honorato

    2011-01-01

    The present investigation observed the sealing ability of low shrinkage composite resins in large and deep cavities, placed and photocured in one increment. Large, deep cavities (5.0 mm diameter and 2.5 mm deep) surrounded by enamel were prepared in bovine teeth, which were then divided into five groups. Groups 1, 2, 3 and 4: acid conditioning + Adper Single Bond (3M/ESPE, St Paul, MN, USA) and restoration with Aelite LS Posterior (BISCO Inc. Schaumburg, IL, USA) (G1); Filtek Z-350 (3M/ESPE,St Paul, MN, USA) (G2); Filtek Z-350 Flow (3M/ESPE, St Paul, MN, USA) (G3); Premisa (KERR Corporation, Orange, CA, USA) (G4). Group 5: Silorane Adhesive system (3M/ESPE, St Paul, MN, USA) + restoration with Filtek Low Shrinkage Posterior P90 (3M/ESPE, St Paul, MN, USA). After polymerization, the teeth were immersed in 0.5% basic fuchsine solution and immediately washed. Using the Imagetool Software, the extent of dye along the margins was calculated as a percentage of total perimeter. The restorations were then transversally sectioned and the depth of dye penetration was calculated in mm, using the same software. Kruskal-Wallis analysis for all groups showed no statistical differences for extent (p = 0.54) or depth (p = 0.8364) of dye penetration. According to this methodology, the so-called low shrinkage composite resins had the same sealing ability compared to regular and flowable nanocomposite materials. PMID:21359445

  7. Many-Body Effects on Bandgap Shrinkage, Effective Masses, and Alpha Factor

    NASA Technical Reports Server (NTRS)

    Li, Jian-Zhong; Ning, C. Z.; Woo, Alex C. (Technical Monitor)

    2000-01-01

    Many-body Coulomb effects influence the operation of quantum-well (QW) laser diode (LD) strongly. In the present work, we study a two-band electron-hole plasma (EHP) within the Hatree-Fock approximation and the single plasmon pole approximation for static screening. Full inclusion of momentum dependence in the many-body effects is considered. An empirical expression for carrier density dependence of the bandgap renormalization (BGR) in an 8 nm GaAs/Al(0.3)G(4.7)As single QW will be given, which demonstrates a non-universal scaling behavior for quasi-two-dimension structures, due to size-dependent efficiency of screening. In addition, effective mass renormalization (EMR) due to momentum-dependent self-energy many-body correction, for both electrons and holes is studied and serves as another manifestation of the many-body effects. Finally, the effects on carrier density dependence of the alpha factor is evaluated to assess the sensitivity of the full inclusion of momentum dependence.

  8. State-dependent diffusion of actin-depolymerizing factor/cofilin underlies the enlargement and shrinkage of dendritic spines

    PubMed Central

    Noguchi, Jun; Hayama, Tatsuya; Watanabe, Satoshi; Ucar, Hasan; Yagishita, Sho; Takahashi, Noriko; Kasai, Haruo

    2016-01-01

    Dendritic spines are the postsynaptic sites of most excitatory synapses in the brain, and spine enlargement and shrinkage give rise to long-term potentiation and depression of synapses, respectively. Because spine structural plasticity is accompanied by remodeling of actin scaffolds, we hypothesized that the filamentous actin regulatory protein cofilin plays a crucial role in this process. Here we investigated the diffusional properties of cofilin, the actin-severing and depolymerizing actions of which are activated by dephosphorylation. Cofilin diffusion was measured using fluorescently labeled cofilin fusion proteins and two-photon imaging. We show that cofilins are highly diffusible along dendrites in the resting state. However, during spine enlargement, wild-type cofilin and a phosphomimetic cofilin mutant remain confined to the stimulated spine, whereas a nonphosphorylatable mutant does not. Moreover, inhibition of cofilin phosphorylation with a competitive peptide disables spine enlargement, suggesting that phosphorylated-cofilin accumulation is a key regulator of enlargement, which is localized to individual spines. Conversely, spine shrinkage spreads to neighboring spines, even though triggered by weaker stimuli than enlargement. Diffusion of exogenous cofilin injected into a pyramidal neuron soma causes spine shrinkage and reduced PSD95 in spines, suggesting that diffusion of dephosphorylated endogenous cofilin underlies the spreading of spine shrinkage and long-term depression. PMID:27595610

  9. State-dependent diffusion of actin-depolymerizing factor/cofilin underlies the enlargement and shrinkage of dendritic spines.

    PubMed

    Noguchi, Jun; Hayama, Tatsuya; Watanabe, Satoshi; Ucar, Hasan; Yagishita, Sho; Takahashi, Noriko; Kasai, Haruo

    2016-01-01

    Dendritic spines are the postsynaptic sites of most excitatory synapses in the brain, and spine enlargement and shrinkage give rise to long-term potentiation and depression of synapses, respectively. Because spine structural plasticity is accompanied by remodeling of actin scaffolds, we hypothesized that the filamentous actin regulatory protein cofilin plays a crucial role in this process. Here we investigated the diffusional properties of cofilin, the actin-severing and depolymerizing actions of which are activated by dephosphorylation. Cofilin diffusion was measured using fluorescently labeled cofilin fusion proteins and two-photon imaging. We show that cofilins are highly diffusible along dendrites in the resting state. However, during spine enlargement, wild-type cofilin and a phosphomimetic cofilin mutant remain confined to the stimulated spine, whereas a nonphosphorylatable mutant does not. Moreover, inhibition of cofilin phosphorylation with a competitive peptide disables spine enlargement, suggesting that phosphorylated-cofilin accumulation is a key regulator of enlargement, which is localized to individual spines. Conversely, spine shrinkage spreads to neighboring spines, even though triggered by weaker stimuli than enlargement. Diffusion of exogenous cofilin injected into a pyramidal neuron soma causes spine shrinkage and reduced PSD95 in spines, suggesting that diffusion of dephosphorylated endogenous cofilin underlies the spreading of spine shrinkage and long-term depression. PMID:27595610

  10. Shrinkage Behavior of Polystyrene-based Foam Molded Parts Depending on Volatile Matter Content and Other Factors

    NASA Astrophysics Data System (ADS)

    Ghafafian, Carineh

    Polymer foam materials play a large role in the modern world. Expanded polystyrene (EPS) bead foam is a lightweight, low density, and good thermal and acoustic insulating material whose properties make it attractive for a number of applications, especially as building insulation. However, EPS also experiences post-molding shrinkage; it shrinks dimensionally from its molded size after processing. This means parts must be stored in warehouses until they are considered stable by the industry standard, DIN EN 1603. This often takes 11--18 weeks and is thus very timely and expensive. This study aims to decrease the post-molding shrinkage time of EPS foam by understanding the mechanisms of shrinkage behavior. Samples were split into two groups based on their amount of initial volatile matter content and storage conditions, then compared to a control group. Based on thermogravimetric analysis and gas chromatography with mass spectrometry, the volatile matter content and composition was found to not be the sole contributor to EPS foam dimensional stability. Residual stress testing was done with the hole drilling method and Raman spectroscopy. As this type of testing has not been done with polymer foams before, the aim was to see if either method could reliably produce residual stress values. Both methods measured residual stress values with unknown accuracy. All samples stored at a higher temperature (60°C) reached dimensional stability by the end of this study. Thus, air diffusion into EPS foam, encouraged by the high temperature storage, was found to play a significant role in post-molding shrinkage.

  11. 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.

  12. Spontaneous shrinkage of vestibular schwannoma

    PubMed Central

    Romani, Rossana; Pollock, Jonathan

    2016-01-01

    Background: “Watch, wait, and rescan” (WWR) has an established place as a successful management option for a significant proportion of vestibular schwannomas (VS) as an alternative to microsurgical removal or stereotactic radiotherapy. VS may grow slowly and continuously, followed by stagnation or even shrinkage. We present two case reports of spontaneous shrinkage of VS along with a review of the literature. Case Description: A 29-year-old female presented with a progressive history of visual blurring and intermittent diplopia over 2 months. A 29 mm of maximum intracranial diameter (ICD) VS with secondary obstructive hydrocephalus was diagnosed. The patient underwent a ventriculo-peritoneal shunt with resolution of her symptoms and opted for initial WWR management. Interval scanning between 2007 and 2014 showed progressive reduction in the maximum ICD together with reduction in the degree of central tumor enhancement. Maximum ICD at most recent follow up was 22 mm. A 28-year-old female was referred with right sensorineural deafness. A right VS of maximum ICD of 27 mm was diagnosed. Initial WWR management was planned after discussion. Serial imaging showed an initial increase in the size of the tumor followed by progressive reduction in size. The most recent follow up showed a maximum ICD of 20 mm. Conclusion: Early WWR management can be associated with spontaneous shrinkage of VS over time. Prospective clinical study of larger numbers of such cases using the UK VS database may help to identify predictive factors for the spontaneous regression of VS. PMID:27280055

  13. 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)

  14. 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…

  15. Regional brain shrinkage and change in cognitive performance over two years: The bidirectional influences of the brain and cognitive reserve factors.

    PubMed

    Persson, Ninni; Ghisletta, Paolo; Dahle, Cheryl L; Bender, Andrew R; Yang, Yiqin; Yuan, Peng; Daugherty, Ana M; Raz, Naftali

    2016-02-01

    We examined relationships between regional brain shrinkage and changes in cognitive performance, while taking into account the influence of chronological age, vascular risk, Apolipoprotein E variant and socioeconomic status. Regional brain volumes and cognitive performance were assessed in 167 healthy adults (age 19-79 at baseline), 90 of whom returned for the follow-up after two years. Brain volumes were measured in six regions of interest (ROIs): lateral prefrontal cortex (LPFC), prefrontal white matter (PFw), hippocampus (Hc), parahippocampal gyrus (PhG), cerebellar hemispheres (CbH), and primary visual cortex (VC), and cognitive performance was evaluated in three domains: episodic memory (EM), fluid intelligence (Gf), and vocabulary (V). Average volume loss was observed in Hc, PhG and CbH, but reliable individual differences were noted in all examined ROIs. Average positive change was observed in EM and V performance but not in Gf scores, yet only the last evidenced individual differences in change. We observed reciprocal influences among neuroanatomical and cognitive variables. Larger brain volumes at baseline predicted greater individual gains in Gf, but differences in LPFC volume change were in part explained by baseline level of cognitive performance. In one region (PFw), individual change in volume was coupled with change in Gf. Larger initial brain volumes did not predict slower shrinkage. The results underscore the complex role of brain maintenance and cognitive reserve in adult development. PMID:26584866

  16. 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.

  17. Shrinkage during holographic recording in photopolymer films determined by holographic interferometry.

    PubMed

    Moothanchery, Mohesh; Bavigadda, Viswanath; Toal, Vincent; Naydenova, Izabela

    2013-12-10

    Shrinkage of photopolymer materials is an important factor for their use in holographic data storage and for fabrication of holographic optical elements. Dimensional change in the holographic element leads to a requirement for compensation in the reading angle and/or wavelength. Normally, shrinkage is studied at the end of the polymerization process and no information about the dynamics is obtained. The aim of this study was to use holographic interferometry to measure the shrinkage that occurs during holographic recording of transmission diffraction gratings in acrylamide photopolymer layers. Shrinkage in photopolymer layers can be measured over the whole recorded area by real-time capture of holographic interferograms at regular intervals during holographic recording using a complimentary metal-oxide-semiconductor camera. The optical path length change, and hence the shrinkage, are determined from the captured fringe patterns. Through analysis of the real-time shrinkage curves, it is possible to distinguish two processes that determine the value of shrinkage in the photopolymer layer. These processes are ascribed to monomer polymerization and crosslinking of polymer chains. The dependence of shrinkage of the layers on the conditions of recording such as recording intensity, single or double beam exposure, and the physical properties of the layers, such as thickness, were studied. Higher shrinkage was observed with recordings at lower intensities and in thinner layers. Increased shrinkage was also observed in the case of single beam polymerization in comparison to the case of double beam holographic exposure. PMID:24513896

  18. Factors affecting chromium carbide precipitate dissolution during alloy oxidation

    SciTech Connect

    Durham, R.N.; Gleeson, B.; Young, D.J.

    1998-08-01

    Ferrous alloys containing significant volume fractions of chromium carbides were formulated so as to contain an overall chromium level of 15% (by weight) but a nominal metal matrix chromium concentration of only 11%. Their oxidation at 850 C in pure oxygen led to either protective Cr{sub 2}O{sub 3} scale formation accompanied by subsurface carbide dissolution or rapid growth of iron-rich oxide scales associated with rapid alloy surface recession, which engulfed the carbides before they could dissolve. Carbide size was important in austenitic alloys: an as-cast Fe-15Cr-0.5C alloy contained relatively coarse carbides and failed to form a Cr{sub 2}O{sub 3} scale, whereas the same alloy when hot-forged to produce very fine carbides oxidized protectively. In ferritic alloys, however, even coarse carbides dissolved sufficiently rapidly to provide the chromium flux necessary to form and maintain the growth of a Cr{sub 2}O{sub 3} scale, a result attributed to the high diffusivity of the ferrite phase. Small additions of silicon to the as-cast Fe-15Cr-0.5C alloy rendered it ferritic and led to protective cr{sub 2}O{sub 3} growth. However, when the silicon-containing alloy was made austenitic (by the addition of nickel), it still formed a protective Cr{sub 2}O{sub 3} scale, showing that the principal function of silicon was in modifying the scale-alloy interface.

  19. Scale Shrinkage in Vertical Equating.

    ERIC Educational Resources Information Center

    Camilli, Gregory; And Others

    1993-01-01

    Three potential causes of scale shrinkage (measurement error, restriction of range, and multidimensionality) in item response theory vertical equating are discussed, and a more comprehensive model-based approach to establishing vertical scales is described. Test data from the National Assessment of Educational Progress are used to illustrate the…

  20. Shrinkage estimators for covariance matrices.

    PubMed

    Daniels, M J; Kass, R E

    2001-12-01

    Estimation of covariance matrices in small samples has been studied by many authors. Standard estimators, like the unstructured maximum likelihood estimator (ML) or restricted maximum likelihood (REML) estimator, can be very unstable with the smallest estimated eigenvalues being too small and the largest too big. A standard approach to more stably estimating the matrix in small samples is to compute the ML or REML estimator under some simple structure that involves estimation of fewer parameters, such as compound symmetry or independence. However, these estimators will not be consistent unless the hypothesized structure is correct. If interest focuses on estimation of regression coefficients with correlated (or longitudinal) data, a sandwich estimator of the covariance matrix may be used to provide standard errors for the estimated coefficients that are robust in the sense that they remain consistent under misspecification of the covariance structure. With large matrices, however, the inefficiency of the sandwich estimator becomes worrisome. We consider here two general shrinkage approaches to estimating the covariance matrix and regression coefficients. The first involves shrinking the eigenvalues of the unstructured ML or REML estimator. The second involves shrinking an unstructured estimator toward a structured estimator. For both cases, the data determine the amount of shrinkage. These estimators are consistent and give consistent and asymptotically efficient estimates for regression coefficients. Simulations show the improved operating characteristics of the shrinkage estimators of the covariance matrix and the regression coefficients in finite samples. The final estimator chosen includes a combination of both shrinkage approaches, i.e., shrinking the eigenvalues and then shrinking toward structure. We illustrate our approach on a sleep EEG study that requires estimation of a 24 x 24 covariance matrix and for which inferences on mean parameters critically

  1. 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.

  2. Polymerization shrinkage stress of composites photoactivated by different light sources.

    PubMed

    Pires-de-Souza, Fernanda de Carvalho Panzeri; Drubi Filho, Brahim; Casemiro, Luciana Assirati; Garcia, Lucas da Fonseca Roberti; Consani, Simonides

    2009-01-01

    The purpose of this study was to compare the polymerization shrinkage stress of composite resins (microfilled, microhybrid and hybrid) photoactivated by quartz-tungsten halogen light (QTH) and light-emitting diode (LED). Glass rods (5.0 mm x 5.0 cm) were fabricated and had one of the surfaces air-abraded with aluminum oxide and coated with a layer of an adhesive system, which was photoactivated with the QTH unit. The glass rods were vertically assembled, in pairs, to a universal testing machine and the composites were applied to the lower rod. The upper rod was placed closer, at 2 mm, and an extensometer was attached to the rods. The 20 composites were polymerized by either QTH (n=10) or LED (n=10) curing units. Polymerization was carried out using 2 devices positioned in opposite sides, which were simultaneously activated for 40 s. Shrinkage stress was analyzed twice: shortly after polymerization (t40s) and 10 min later (t10min). Data were analyzed statistically by 2-way ANOVA and Tukey's test (alpha=5%). The shrinkage stress for all composites was higher at t10min than at t40s, regardless of the activation source. Microfilled composite resins showed lower shrinkage stress values compared to the other composite resins. For the hybrid and microhybrid composite resins, the light source had no influence on the shrinkage stress, except for microfilled composite at t10min. It may be concluded that the composition of composite resins is the factor with the strongest influence on shrinkage stress. PMID:20069256

  3. 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

  4. 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. PMID:25050395

  5. 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.

  6. Factors affecting the optical properties of Pd-free Au-Pt-based dental alloys.

    PubMed

    Shiraishi, Takanobu; Takuma, Yasuko; Miura, Eri; Tanaka, Yasuhiro; Hisatsune, Kunihiro

    2003-12-01

    The optical properties of experimental Au-Pt-based alloys containing a small amount of In, Sn, and Zn were investigated by spectrophotometric colorimetry to extract factors affecting color of Au-Pt-based high-karat dental alloys. It was found that the optical properties of Au-Pt-based alloys are strongly affected by the number of valence electrons per atom in an alloy, namely, the electron:atom ratio, e/a. That is, by increasing the e/a-value, activities of reflection in the long-wavelength range and absorption in the short-wavelength range in the visible spectrum apparently increased. As a result, the maximum slope of the spectral reflectance curve at the absorption edge, which is located near 515 nm (approximately 2.4 eV), apparently increased with e/a-value. Due to this effect, the b*-coordinate (yellow-blue) in the CIELAB color space considerably increased and the a*-coordinate (red-green) slightly increased with e/a-value. The addition of a third element with a higher number of valence electrons to the binary Au-Pt alloy is, therefore, effective in giving a gold tinge to the parent Au-Pt alloy. This information may be useful in controlling the color of Au-Pt-based dental alloys. PMID:15348493

  7. An important factor powerfully influencing the Al Ni-based alloys' glass-forming ability

    NASA Astrophysics Data System (ADS)

    Bo, Zhang; Xiufang, Bian; Chunxia, Fu; Na, Han; Jiankun, Zhou; Weimin, Wang

    2005-12-01

    In order to get better glass-forming abilities (GFAs), Ni atoms are partially replaced by Cu and Co atoms in Al84Ni12Zr4 alloys. Thermal analysis shows that the reduced crystallization temperature Trx has no direct correlation with the GFA of the alloys. However, it is notable that prepeaks have been found in the total structure factors of the amorphous Al84Ni(12-x)Zr4Cux and Al84Ni(12-x)Zr4Cox alloys. In addition, the results prove that the intensity of the prepeaks influences the GFA powerfully. The amorphous alloys with larger intensity of the prepeak show better GFA. The influence of prepeaks on the GFA can be explained by the atomic configuration difference among the liquid, crystal and glass states.

  8. 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.

  9. Factors Affecting the Hydrogen Environment Assisted Cracking Resistance of an AL-Zn-Mg-(Cu) Alloy

    SciTech Connect

    Young, G A; Scully, J R

    2002-04-09

    Precipitation hardenable Al-Zn-Mg alloys are susceptible to hydrogen environment assisted cracking (HEAC) when exposed to aqueous environments. In Al-Zn-Mg-Cu alloys, overaged tempers are used to increase HEAC resistance at the expense of strength but overaging has little benefit in low copper alloys. However, the mechanism or mechanisms by which overaging imparts HEAC resistance is poorly understood. The present research investigated hydrogen uptake, diffusion, and crack growth rate in 90% relative humidity (RH) air for both a commercial copper bearing Al-Zn-Mg-Cu alloy (AA 7050) and a low copper variant of this alloy in order to better understand the factors which affect HEAC resistance. Experimental methods used to evaluate hydrogen concentrations local to a surface and near a crack tip include nuclear reaction analysis (NRA), focused ion beam, secondary ion mass spectroscopy (FIB/SIMS) and thermal desorption spectroscopy (TDS). Results show that overaging the copper bearing alloys both inhibits hydrogen ingress from oxide covered surfaces and decreases the apparent hydrogen diffusion rates in the metal.

  10. 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.

  11. Factors Affecting the Hydrogen Environment Assisted Cracking Resistance of an Al-Zn-Mg-(Cu) Alloy

    SciTech Connect

    G.A. Young; J.R. Scully

    2001-09-12

    It is well established that Al-Zn-Mg-(Cu) aluminum alloys are susceptible to hydrogen environment assisted cracking (HEAC) when exposed to aqueous environments. In Al-Zn-Mg-Cu alloys, overaged tempers are commonly used to increase HEAC resistance at the expense of strength. Overaging has little benefit in low copper alloys. However, the mechanism or mechanisms by which overaging imparts HEAC resistance is poorly understood. The present research investigated hydrogen uptake, diffusion, and crack growth rate in 90% relative humidity (RH) air for both a commercial copper bearing Al-Zn-Mg-Cu alloy (AA 7050) and a low copper variant of this alloy in order to better understand the factors which affect HEAC resistance. Experimental methods used to evaluate hydrogen concentrations local to a surface and near a crack tip include nuclear reaction analysis (NRA), focused ion beam, secondary ion mass spectroscopy (FIB/SIMS) and thermal desorption spectroscopy (TDS). When freshly bared coupons of AA 7050 are exposed to 90 C, 90% RH air, hydrogen ingress follows inverse-logarithmic-type kinetics and is equivalent for underaged (HEAC susceptible) and overaged (HEAC resistant) tempers. However, when the native oxide is allowed to form (24 hrs in 25 C, 40% RH lab air) prior to exposure to 90 C, 90% RH air, underaged alloy shows significantly greater hydrogen ingress than the overaged alloy. Humid air is a very aggressive environment producing local ({approx}1{micro}m) hydrogen concentrations in excess of 10,000 wt. ppm at 90 C. In the copper bearing alloy, overaging also effects the apparent diffusivity of hydrogen. As AA 7050 is aged from underaged {yields} peak aged {yields} overaged, the activation energy for hydrogen diffusion increases and the apparent diffusivity for hydrogen decreases, In the low copper alloy, overaging has little effect on hydrogen diffusion. Comparison of the apparent activation energies for hydrogen diffusion and for K independent (stage II) crack growth

  12. On the Approximations of the Factors of Surface Segregation in Binary Alloys

    NASA Astrophysics Data System (ADS)

    Mezey, L. Z.; Giber, J.

    1983-07-01

    A new "Complex Calculation of Surface Segregation" (CCSS) method (presented elsewhere in greater detail) is first outlined and the factors of surface segregation are identified. The approximate description of these by subsequent structure model refinements is then discussed. It is shown by some considerations and by numerical results on the AgPd alloy as well, that such refinements lead to consequent diminutions of the surface free enthalpy. On this basis optimal values of calculational parameters, characteristic of surface conditions, may be calculated.

  13. 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%.

  14. 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.

  15. Factors affecting the strength of multipass low-alloy steel weld metal

    NASA Technical Reports Server (NTRS)

    Krantz, B. M.

    1972-01-01

    The mechanical properties of multipass high-strength steel weld metals depend upon several factors, among the most important being: (1) The interaction between the alloy composition and weld metal cooling rate which determines the as-deposited microstructure; and (2) the thermal effects of subsequent passes on each underlying pass which alter the original microstructure. The bulk properties of a multipass weld are therefore governed by both the initial microstructure of each weld pass and its subsequent thermal history. Data obtained for a high strength low alloy steel weld metal confirmed that a simple correlation exists between mechanical properties and welding conditions if the latter are in turn correlated as weld cooling rate.

  16. Influence of archaeological environment factors in alteration processes of copper alloy artifacts.

    PubMed

    Sandu, Ioan Gabriel; Mircea, Otilia; Vasilache, Viorica; Sandu, Ion

    2012-12-01

    The article presents the experimental results obtained by combining noninvasive techniques (OM, SEM/EDX, XRF) to analyze three artifacts made of copper alloys discovered in a inhumation tomb (2) and in the soil profile (1) in archaeological sites from Neamt County Romania. To uncover the mechanism of alteration thereof during their longtime underground stay in specific chemical conditions and under the influence of other pedological factors, the corrosion products must be identified. The excess of the chloride ion, from burial site, disturbs the Liesegang effect, transforming the bulk in a stratified sponge structure with chlorapatite and hydroxyapatite. Some of the compounds from primary and secondary patina can be found on the surface of the bulk, as color stains. The presence of alloy components (Cu, Sn, Pb, Zn, Fe, etc.) and of the underground contamination components, allowed us to establish the origin of the ore, the manufacture technology and we identified other materials which affected the artifacts after abandonment. PMID:22865394

  17. Early sac shrinkage predicts a low risk of late complications after endovascular aortic aneurysm repair

    PubMed Central

    Bastos Gonçalves, F; Baderkhan, H; Verhagen, H J M; Wanhainen, A; Björck, M; Stolker, R J; Hoeks, S E; Mani, K

    2014-01-01

    Background Aneurysm shrinkage has been proposed as a marker of successful endovascular aneurysm repair (EVAR). Patients with early postoperative shrinkage may experience fewer subsequent complications, and consequently require less intensive surveillance. Methods Patients undergoing EVAR from 2000 to 2011 at three vascular centres (in 2 countries), who had two imaging examinations (postoperative and after 6–18 months), were included. Maximum diameter, complications and secondary interventions during follow-up were registered. Patients were categorized according to early sac dynamics. The primary endpoint was freedom from late complications. Secondary endpoints were freedom from secondary intervention, postimplant rupture and direct (type I/III) endoleaks. Results Some 597 EVARs (71·1 per cent of all EVARs) were included. No shrinkage was observed in 284 patients (47·6 per cent), moderate shrinkage (5–9 mm) in 142 (23·8 per cent) and major shrinkage (at least 10 mm) in 171 patients (28·6 per cent). Four years after the index imaging, the rate of freedom from complications was 84·3 (95 per cent confidence interval 78·7 to 89·8), 88·1 (80·6 to 95·5) and 94·4 (90·1 to 98·7) per cent respectively. No shrinkage was an independent risk factor for late complications compared with major shrinkage (hazard ratio (HR) 3·11; P < 0·001). Moderate compared with major shrinkage (HR 2·10; P = 0·022), early postoperative complications (HR 3·34; P < 0·001) and increasing abdominal aortic aneurysm baseline diameter (HR 1·02; P = 0·001) were also risk factors for late complications. Freedom from secondary interventions and direct endoleaks was greater for patients with major sac shrinkage. Conclusion Early change in aneurysm sac diameter is a strong predictor of late complications after EVAR. Patients with major sac shrinkage have a very low risk of complications for up to 5 years. This parameter may be used to tailor postoperative surveillance. PMID:24752772

  18. 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.

  19. Cross-Validation, Shrinkage, and Multiple Regression.

    ERIC Educational Resources Information Center

    Hynes, Kevin

    One aspect of multiple regression--the shrinkage of the multiple correlation coefficient on cross-validation is reviewed. The paper consists of four sections. In section one, the distinction between a fixed and a random multiple regression model is made explicit. In section two, the cross-validation paradigm and an explanation for the occurrence…

  20. 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

  1. 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

  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. Polymerization shrinkage, flexural and compression properties of low-shrinkage dental resin composites.

    PubMed

    Park, Jeong-Kil; Lee, Geun-Ho; Kim, Jong-Hwa; Park, Mi-Gyoung; Ko, Ching-Chang; Kim, Hyung-Il; Kwon, Yong Hoon

    2014-01-01

    This study evaluated the polymerization shrinkage, flexural and compressive properties of low-shrinkage resin composites. For the study, four methacrylate-based and one silorane-based resin composites were light cured using three different light-curing units (LCUs) and their polymerization shrinkage, flexural (strength (FS) and modulus (FM)) and compressive (strength (CS) and modulus (CM)) properties were evaluated. Data were statistically analyzed using ANOVA and a post-hoc Tukey test. The polymerization shrinkage ranged approximately 7.6-14.2 μm for 2-mm thick specimens depending on the resin product and LCU. Filtek LS showed the least shrinkage while the rest shrank approximately 13.2-14.2 μm. However, Filtek LS showed the greatest shrinkage difference for the used LCUs. FS and CS of the tested specimens ranged 96.2-152.1 MPa and 239.2-288.4 MPa, respectively, depending on the resin product and LCU. The highest and lowest FS and FM were recorded for the methacrylate-based resin composites. Among the specimens, Filtek LS showed the lowest CS and CM. PMID:24492120

  4. TUNGSTEN BASE ALLOYS

    DOEpatents

    Schell, D.H.; Sheinberg, H.

    1959-12-15

    A high-density quaternary tungsten-base alloy having high mechanical strength and good machinability composed of about 2 wt.% Ni, 3 wt.% Cu, 5 wt.% Pb, and 90wt.% W is described. This alloy can be formed by the powder metallurgy technique of hot pressing in a graphite die without causing a reaction between charge and the die and without formation of a carbide case on the final compact, thereby enabling re-use of the graphite die. The alloy is formable at hot- pressing temperatures of from about 1200 to about 1350 deg C. In addition, there is little component shrinkage, thereby eliminating the necessity of subsequent extensive surface machining.

  5. Tool-to-tool matching issues due to photoresist shrinkage effects

    NASA Astrophysics Data System (ADS)

    Bunday, Benjamin; Cordes, Aaron; Hartig, Carsten; Allgair, John; Vaid, Alok; Solecky, Eric; Rana, Narender

    2011-03-01

    Photoresist shrinkage is an important systematic uncertainty source in critical dimension-scanning electron microscope (CD-SEM) metrology of lithographic features. In terms of metrology gauge metrics, it influences both the precision and the accuracy of CD-SEM measurements, while locally damaging the sample. Minimization or elimination of shrinkage is desirable, yet elusive. Because this error source will furthermore be a factor in CD-SEM metrology on polymer materials, learning to work around this issue is necessary. Tool-to-tool matching is another important component of measurement uncertainty that metrologists must control in high volume manufacturing, and photoresist samples are a most difficult case due to shrinkage effects, as tool-to-tool biases can vary based on the sample or other parameters. In this work, we explore different shrinkage effects and their influence on matching. This will include an investigation of how the photoresist shrinkage rate varies with time from the chemical development of the photoresists, which necessitates that measurements on different tools within a group be performed in rapid succession to avoid additional error. The differences in shrinkage rates between static and dynamic load/unload cases will also be addressed, as these effects also influence matching. The results of these dynamic effect experiments will be shown to have far-reaching implications for the shrinkage phenomenon in general. Finally, various sampling schemes for matching will be explored, through both simulation and experiment, for use with shrinking materials. Included is a method whereby various fleet tools measure different locations, once per tool, within a uniform line/space grating. Finally, we will assess how well matching can be achieved using these techniques.

  6. Distinct spontaneous shrinkage of a sporadic vestibular schwannoma.

    PubMed

    Huang, Xiaowen; Caye-Thomasen, Per; Stangerup, Sven-Eric

    2013-04-01

    We present a case with outspoken spontaneous vestibular schwannoma shrinkage and review the related literature. The patient was initially diagnosed with a left-sided, intrameatal vestibular schwannoma, which subsequently grew into the cerebello-pontine angle (CPA), followed by total shrinkage of the CPA component without any intervention over a 12-year observation period. The literature on spontaneous tumor shrinkage was retrieved by searching the subject terms "vestibular schwannoma, conservative management" in PubMed/MEDLINE database, without a time limit. Of the published data, the articles on "shrinkage" or "negative growth" or "regression" or "involution" of the tumor were selected, and the contents on the rate, extent and mechanism of spontaneous tumor shrinkage were extracted and reviewed. The reported rate of spontaneous shrinkage of vestibular schwannoma is 5-10% of patients managed conservatively. Extreme shrinkage of the tumor may occur spontaneously. PMID:22858145

  7. Shrinkage and growth compensation in common sunflowers: refining estimates of damage

    USGS Publications Warehouse

    Sedgwick, James A.; Oldemeye, John L.; Swenson, Elizabeth L.

    1986-01-01

    Shrinkage and growth compensation of artificially damaged common sunflowers (Helianthus annuus) were studied in central North Dakota during 1981-1982 in an effort to increase accuracy of estimates of blackbird damage to sunflowers. In both years, as plants matured damaged areas on seedheads shrank at a greater rate than the sunflower heads themselves. This differential shrinkage resulted in an underestimation of the area damaged. Sunflower head and damaged-area shrinkage varied widely by time and degree of damage and by size of the seedhead damaged. Because variation in shrinkage by time of damage was so large, predicting when blackbird damage occurs may be the most important factor in estimating seed loss. Yield'occupied seed area was greater (P < 0.05) for damaged than undamaged heads and tended to increase as degree of damage inflicted increased, indicating growth compensation was occurring in response to lost seeds. Yields of undamaged seeds in seedheads damaged during early seed development were higher than those of heads damaged later. This suggested that there was a period of maximal response to damage when plants were best able to redirect growth to seeds remaining in the head. Sunflowers appear to be able to compensate for damage of ≤ 15% of the total hear area. Estimates of damage can be improved by applying empirical results of differential shrinkage and growth compensations.

  8. 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%.

  9. Silorane- and high filled-based "low-shrinkage" resin composites: shrinkage, flexural strength and modulus.

    PubMed

    Arrais, Cesar Augusto Galvão; Oliveira, Marcelo Tavares de; Mettenburg, Donald; Rueggeberg, Frederick Allen; Giannini, Marcelo

    2013-01-01

    This study compared the volumetric shrinkage (VS), flexural strength (FS) and flexural modulus (FM) properties of the low-shrinkage resin composite Aelite LS (Bisco) to those of Filtek LS (3M ESPE) and two regular dimethacrylate-based resin composites, the microfilled Heliomolar (Ivoclar Vivadent) and the microhybrid Aelite Universal (Bisco). The composites (n = 5) were placed on the Teflon pedestal of a video-imaging device, and VS was recorded every minute for 5 min after 40 s of light exposure. For the FS and FM tests, resin discs (0.6 mm in thickness and 6.0 mm in diameter) were obtained (n = 12) and submitted to a piston-ring biaxial test in a universal testing machine. VS, FS, and FM data were submitted to two-way repeated measures and one-way ANOVA, respectively, followed by Tukey's post-hoc test (a = 5%). Filtek LS showed lower VS than did Aelite LS, which in turn showed lower shrinkage than did the other composites. Aelite Universal and Filtek LS exhibited higher FS than did Heliomolar and Aelite LS, both of which exhibited the highest FM. No significant difference in FM was noted between Filtek LS and Aelite Universal, while Heliomolar exhibited the lowest values. Aelite LS was not as effective as Filtek LS regarding shrinkage, although both low-shrinkage composites showed lower VS than did the other composites. Only Filtek LS exhibited FS and FM comparable to those of the regular microhybrid dimethacrylate-based resin composite. PMID:23459774

  10. 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. PMID:21282725

  11. Properties of high-performance concrete containing shrinkage-reducing admixture

    SciTech Connect

    Folliard, K.J.; Berke, N.S.

    1997-09-01

    The effects of a recently developed shrinkage-reducing admixture on high-performance concrete properties are described. High-performance concrete mixtures containing silica fume were cast with and without shrinkage-reducing admixture. The mechanical properties, drying shrinkage, and resistance to restrained shrinkage cracking were investigated. The results show that the shrinkage-reducing admixture effectively reduced the shrinkage of high-performance concrete, and resulted in a significant decrease in restrained shrinkage cracking.

  12. Analysis of Factors Influencing Measurement Accuracy of Al Alloy Tensile Test Results

    NASA Astrophysics Data System (ADS)

    Podgornik, Bojan; Žužek, Borut; Sedlaček, Marko; Kevorkijan, Varužan; Hostej, Boris

    2016-02-01

    In order to properly use materials in design, a complete understanding of and information on their mechanical properties, such as yield and ultimate tensile strength must be obtained. Furthermore, as the design of automotive parts is constantly pushed toward higher limits, excessive measuring uncertainty can lead to unexpected premature failure of the component, thus requiring reliable determination of material properties with low uncertainty. The aim of the present work was to evaluate the effect of different metrology factors, including the number of tested samples, specimens machining and surface quality, specimens input diameter, type of testing and human error on the tensile test results and measurement uncertainty when performed on 2xxx series Al alloy. Results show that the most significant contribution to measurement uncertainty comes from the number of samples tested, which can even exceed 1 %. Furthermore, moving from experimental laboratory conditions to very intense industrial environment further amplifies measurement uncertainty, where even if using automated systems human error cannot be neglected.

  13. Factors Affecting Stable Planar Growth During the Directional Solidification of Hypermonotectic Aluminum-indium Alloys. Ph.D. Thesis

    SciTech Connect

    Dwyer, Z.B.

    1994-01-01

    Immiscible (monotectic) alloy systems have become materials of interest due to their unique potential applications, which include bearing materials, catalysts, permanent magnets, and fine particle superconductors. For some of these applications, a microstructure containing continuous aligned fibers is desired. In-situ fibrous growth has been observed in directionally solidified alloys of monotectic composition. However, for the proposed applications, a greater volume fraction of the fibrous phase is needed than is available in alloys of monotectic composition. In order to obtain this greater volume fraction of the fibrous phase, alloys of hypermonotectic composition are necessary. However, when alloys of hypermonotectic composition are directionally solidified, there are two factors which can disrupt in-situ fibrous growth. These factors are buoyancy-driven convection and constitutional supercooling. A theoretical model containing the effects of both convection and constitutional supercooling has been developed and applied to the immiscible aluminum-indium system. The resulting stability limit diagram predicts the theoretical composition limits for stable growth as a function of solidification front velocity. This research has concentrated on experimentally verifying the theoretical limits of stable growth. By directionally solidifying samples over a range of compositions and growth rates, the region of stable growth was determined by examining both the microstructure and the composition profile developed in the samples. The results indicate that the theoretical limits of stable growth predicted by the stability limit diagram are a conservative estimate of the region of stable growth.

  14. Nanozeolites doped photopolymer layers with reduced shrinkage.

    PubMed

    Moothanchery, Mohesh; Naydenova, Izabela; Mintova, Svetlana; Toal, Vincent

    2011-12-01

    An acrylamide based photopolymer doped with pure silica MFI-type zeolite (silicalite-1) nanoparticles has been characterized for holographic recording purposes. The concentrations of the silicalite-1 nanoparticles in the photopolymer layers were 1, 2.5, 5 and 7.5 wt. %. The inclusion of silicalite-1 nanoparticle in the photopolymer has resulted in an increase of the diffraction efficiency by up to 40%, and decrease of the shrinkage from 1.32% to 0.57%. The best results were obtained in layers doped with 5 wt. % silicalite-1 nanoparticles. PMID:22273971

  15. Shrinkage, stress, and modulus of dimethacrylate, ormocer, and silorane composites

    PubMed Central

    Bacchi, Atais; Feitosa, Victor Pinheiro; da Silva Fonseca, Andrea Soares Quirino; Cavalcante, Larissa Maria Assad; Silikas, Nikolaos; Schneider, Luis Felipe Jochins

    2015-01-01

    Purpose: to evaluate the shrinkage, polymerization stress, elastic and bulk modulus resulting from composites formulated by siloranes, 2nd generation ormocers, and dimethacrylates. Materials and Methods: The bonded disc method was used to evaluate volumetric shrinkage. The polymerization stress was evaluated by mean of the Bioman. Cylindrical specimens (5 mm thickness and 6 mm diameter) were submitted to gradual loading. Young's and bulk modulus were obtained from the slope of the stress/strain curve. Data were analyzed using one-way analysis of variance and Tukey's test (5%). Results: Grandio and ormocer showed significant higher elastic and bulk modulus. Silorane presented significant lowest bulk modulus and maximum shrinkage. Ormocer and silorane presented lower values for the maximum rate of shrinkage. Extra-low shrinkage (ELS) composite presented the greatest maximum shrinkage. The higher maximum rate of shrinkage was attained by Grandio and ELS, statistically similar from each other. The silorane showed lower values of maximum stress and maximum rate of stress. The higher values of maximum stress were presented by ELS and Grandio, statistical similar between them. Grandio showed the significantly greatest maximum rate of stress. Conclusion: Silorane showed to promote lower shrinkage/stress among the composites, with the lowest elastic modulus. Ormocer showed lower shrinkage/stress than methacrylates despite of its high modulus. PMID:26430302

  16. The influence of polymerization shrinkage of resin cements on bonding to metal.

    PubMed

    Verzijden, C W; Feilzer, A J; Creugers, N H; Davidson, C L

    1992-02-01

    During the setting of a resin composite cement (RCC) used as an adhesive between a resin-bonded bridge and tooth structure, the adhesion may be disrupted by the development of shrinkage stress. The aim of this study was to investigate the influence of the shrinkage stress of three different RCCs on their adhesive and cohesive qualities when bonded to metal surfaces in a rigid set-up. Two opposing parallel NiCr discs (Wiron 77) were mounted in a tensilometer at a mutual distance of 200 microns and cemented with Panavia Ex, Clearfil F2, or Microfill Pontic C. The alloy surfaces were treated by either electrolytic etching, sand-blasting, silane-coating, or tin-plating. During setting, the discs were kept at their original mutual distance to simulate the extreme clinical situation of "complete" rigidity, where the casting and the tooth cannot move toward each other. The developing shrinkage stress was recorded continuously. During setting, the adhesive strength of the RCCs to silane-coated surfaces was always higher than their early cohesive strength. Electrolytically-etched surfaces as well as sand-blasted surfaces showed, in almost all cases, adhesive failure. The tin-plated samples showed mainly adhesive failure at the metal/resin interface. The highest bond strength values were found for silane-coated surfaces in combination with Clearfil F2. PMID:1556300

  17. Experimental validation of 2D profile photoresist shrinkage model

    NASA Astrophysics Data System (ADS)

    Bunday, Benjamin; Cordes, Aaron; Self, Andy; Ferry, Lorena; Danilevsky, Alex

    2011-03-01

    For many years, lithographic resolution has been the main obstacle in allowing the pace of transistor densification to meet Moore's Law. For the 32 nm node and beyond, new lithography techniques will be used, including immersion ArF (iArF) lithography and extreme ultraviolet lithography (EUVL). As in the past, these techniques will use new types of photoresists with the capability to print smaller feature widths and pitches. These smaller feature sizes will also require the use of thinner layers of photoresists, such as under 100 nm. In previous papers, we focused on ArF and iArF photoresist shrinkage. We evaluated the magnitude of shrinkage for both R&D and mature resists as a function of chemical formulation, lithographic sensitivity, scanning electron microscope (SEM) beam condition, and feature size. Shrinkage results were determined by the well accepted methodology described in SEMATECH's CD-SEM Unified Specification. In other associated works, we first developed a 1-D model for resist shrinkage for the bottom linewidth and then a 2-D profile model that accounted for shrinkage of all aspects of a trapezoidal profile along a given linescan. A fundamental understanding of the phenomenology of the shrinkage trends was achieved, including how the shrinkage behaves differently for different sized and shaped features. In the 1-D case, calibration of the parameters to describe the photoresist material and the electron beam was all that was required to fit the models to real shrinkage data, as long as the photoresist was thick enough that the beam could not penetrate the entire layer of resist. The later 2-D model included improvements for solving the CD shrinkage in thin photoresists, which is now of great interest for upcoming realistic lithographic processing to explore the change in resist profile with electron dose and to predict the influence of initial resist profile on shrinkage characteristics. The 2-D model also included shrinkage due to both the primary

  18. Influence of germanium nano-inclusions on the thermoelectric power factor of bulk bismuth telluride alloy

    SciTech Connect

    Satyala, Nikhil; Zamanipour, Zahra; Norouzzadeh, Payam; Krasinski, Jerzy S.; Vashaee, Daryoosh; Tahmasbi Rad, Armin; Tayebi, Lobat

    2014-05-28

    Nanocomposite thermoelectric compound of bismuth telluride (Bi{sub 2}Te{sub 3}) with 5 at. % germanium nano-inclusions was prepared via mechanically alloying and sintering techniques. The influence of Ge nano-inclusions and long duration annealing on the thermoelectric properties of nanostructured Bi{sub 2}Te{sub 3} were investigated. It was found that annealing has significant effect on the carrier concentration, Seebeck coefficient, and the power factor of the thermoelectric compound. The systematic heat treatment also reduced the density of donor type defects thereby decreasing the electron concentration. While the as-pressed nanocomposite materials showed n-type properties, it was observed that with the increase of annealing time, the nanocomposite gradually transformed to an abundantly hole-dominated (p-type) sample. The long duration annealing (∼500 h) resulted in a significantly enhanced electrical conductivity pertaining to the augmentation in the density and the structural properties of the sample. Therefore, a simultaneous enhancement in both electrical and Seebeck coefficient characteristics resulted in a remarkable increase in the thermoelectric power factor.

  19. Porcine intestinal mast cells. Evaluation of different fixatives for histochemical staining techniques considering tissue shrinkage.

    PubMed

    Rieger, J; Twardziok, S; Huenigen, H; Hirschberg, R M; Plendl, J

    2013-01-01

    Staining of mast cells (MCs), including porcine ones, is critically dependent upon the fixation and staining technique. In the pig, mucosal and submucosal MCs do not stain or stain only faintly after formalin fixation. Some fixation methods are particularly recommended for MC staining, for example the fixation with Carnoy or lead salts. Zinc salt fixation (ZSF) has been reported to work excellently for the preservation of fixation-sensitive antigens. The aim of this study was to establish a reliable histological method for counting of MCs in the porcine intestinum. For this purpose, different tissue fixation and staining methods that also allow potential subsequent immunohistochemical investigations were evaluated in the porcine mucosa, as well as submucosa of small and large intestine. Tissues were fixed in Carnoy, lead acetate, lead nitrate, Zamboni and ZSF and stained subsequently with either polychromatic methylene blue, alcian blue or toluidine blue. For the first time our study reveals that ZSF, a heavy metal fixative, preserves metachromatic staining of porcine MCs. Zamboni fixation was not suitable for histochemical visualization of MCs in the pig intestine. All other tested fixatives were suitable. Alcian blue and toluidine blue co-stained intestinal goblet cells which made a prima facie identification of MCs difficult. The polychromatic methylene blue proved to be the optimal staining. In order to compare MC counting results of the different fixation methods, tissue shrinkage was taken into account. As even the same fixation caused shrinkage-differences between tissue from small and large intestine, different factors for each single fixation and intestinal localization had to be calculated. Tissue shrinkage varied between 19% and 57%, the highest tissue shrinkage was found after fixation with ZSF in the large intestine, the lowest one in the small intestine after lead acetate fixation. Our study emphasizes that MC counting results from data using

  20. Dynamics of tissue shrinkage during ablative temperature exposures

    PubMed Central

    Rossmann, Christian; Garrett-Mayer, Elizabeth; Rattay, Frank; Haemmerich, Dieter

    2014-01-01

    There is a lack of studies that examine dynamics of heat-induced shrinkage of organ tissues. Clinical procedures such as radiofrequency ablation, microwave ablation or high-intensity focused ultrasound, use heat to treat diseases such as cancer and cardiac arrhythmia. When heat is applied to tissues, shrinkage occurs due to protein denaturation, dehydration, and contraction of collagen at temperatures greater 50ºC. This is particularly relevant for image-guided procedures such as tumor ablation, where pre- and post-treatment images are compared and any changes in dimensions must be considered to avoid misinterpretations of the treatment outcome. We present data from ex vivo, isothermal shrinkage tests in porcine liver tissue, where axial changes in tissue length were recorded during 15 minutes of heating to temperatures between 60 and 95ºC. A mathematical model was developed to accurately describe the time and temperature-dependent shrinkage behavior. Shrinkage dynamics had same characteristics independent of temperature; the estimated relative shrinkage, adjusted for time since death, after 15 min heating to temperatures of 60, 65, 75, 85 and 95ºC, was 12.3, 13.8, 16.6, 19.2, and 21.7%, respectively. Our results demonstrate shrinkage dynamics of organ tissues, and suggest the importance of considering tissue shrinkage for thermal ablative treatments. PMID:24345880

  1. COMBINED BLEACHING, SHRINKAGE PREVENTION, AND BIOPOLISHING OF WOOL FABRICS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We had established that alkaline hydrogen peroxide systems that included dicyandiamide, gluconic acid, and Triton X surfactant, used alone or followed by enzyme treatments, controlled shrinkage in wool fabrics to 2.95% and 1.16%, respectively. We have perfected this system for complete shrinkage co...

  2. 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.

  3. 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.

  4. Mechanisms for shrinkage fracturing at Meridiani Planum

    NASA Astrophysics Data System (ADS)

    Watters, W. A.; Squyres, S. W.

    2009-12-01

    We investigate the role of water in fracturing at Meridiani Planum with the aim of shedding light on the history of densely-fractured outcroppings of light-toned rocks at low-latitudes on Mars. The fractures that occur throughout the inter-crater plains at Meridiani exhibit many characteristics of shrinkage cracks: they have significant width (i.e., not hairline), commonly connect in 90-degree and 120-degree junctions, and exhibit a "hierarchical" organization: i.e., the longest fractures are widest, and narrower fractures terminate against wider fractures at 90-degree junctions (T-shaped). Using the Pancam and Navcam stereo-pair images acquired by the Opportunity rover, we have measured the geometric scaling of fracture networks at Meridiani (e.g., fracture width vs. fracture separation) as well as the total volume change. We have also characterized the diversity of patterns in detail, as well as the modification of fractures and polygonal "tiles" by wind-blown sand abrasion. Identical observations were carried-out for an analogue site where similar fractures are ubiquitous in the playas of Death Valley, California, and where modification processes are also comparable. By also estimating the expected volume change and results from numerical models of shrinkage fracturing, we evaluate the likelihood of three candidate contraction mechanisms: loss of water bound in hydrated minerals (dehydration), loss of water from pore spaces (desiccation), and contraction from cooling (thermal fracturing). The evidence to date favors the second of these (desiccation); this result would have significant implications for the history of Meridiani since the time when sulfate-rich sediments were deposited.

  5. 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

  6. Nano-sized precipitate stability and its controlling factors in a NiAl-strengthened ferritic alloy

    DOE PAGESBeta

    Sun, Zhiqian; Song, Gian; Ilavsky, Jan; Ghosh, Gautam; Liaw, Peter K.

    2015-11-05

    Coherent B2-ordered NiAl-type precipitates have been used to reinforce solid-solution bodycentered- cubic iron for high-temperature application in fossil-energy power plants. In this study, the stability of nano-sized precipitates in a NiAl-strengthened ferritic alloy was investigated at 700 - 950°C using ultra-small angle X-ray scattering and electron microscopies. Here we show that the coarsening kinetics of NiAl-type precipitates is in excellent agreement with the ripening model in multicomponent alloys. We further demonstrate that the interfacial energy between the matrix and NiAl-type precipitates is strongly dependent to differences in the matrix/precipitate compositions. The results profile the ripening process in multicomponent alloys bymore » illustrating controlling factors (i.e., interfacial energy, diffusivities, and element partitioning). As a result, the study provides guidelines to design and develop high-temperature alloys with stable microstructures for long-term service.« less

  7. Nano-sized precipitate stability and its controlling factors in a NiAl-strengthened ferritic alloy

    PubMed Central

    Sun, Zhiqian; Song, Gian; Ilavsky, Jan; Ghosh, Gautam; Liaw, Peter K.

    2015-01-01

    Coherent B2-ordered NiAl-type precipitates have been used to reinforce solid-solution body-centered-cubic iron for high-temperature application in fossil-energy power plants. In this study, we investigate the stability of nano-sized precipitates in a NiAl-strengthened ferritic alloy at 700–950 °C using ultra-small angle X-ray scattering and electron microscopies. Here we show that the coarsening kinetics of NiAl-type precipitates is in excellent agreement with the ripening model in multicomponent alloys. We further demonstrate that the interfacial energy between the matrix and NiAl-type precipitates is strongly dependent on differences in the matrix/precipitate compositions. Our results profile the ripening process in multicomponent alloys by illustrating controlling factors of interfacial energy, diffusivities, and element partitioning. The study provides guidelines to design and develop high-temperature alloys with stable microstructures for long-term service. PMID:26537060

  8. Nano-sized precipitate stability and its controlling factors in a NiAl-strengthened ferritic alloy

    SciTech Connect

    Sun, Zhiqian; Song, Gian; Ilavsky, Jan; Ghosh, Gautam; Liaw, Peter K.

    2015-11-05

    Coherent B2-ordered NiAl-type precipitates have been used to reinforce solid-solution bodycentered- cubic iron for high-temperature application in fossil-energy power plants. In this study, the stability of nano-sized precipitates in a NiAl-strengthened ferritic alloy was investigated at 700 - 950°C using ultra-small angle X-ray scattering and electron microscopies. Here we show that the coarsening kinetics of NiAl-type precipitates is in excellent agreement with the ripening model in multicomponent alloys. We further demonstrate that the interfacial energy between the matrix and NiAl-type precipitates is strongly dependent to differences in the matrix/precipitate compositions. The results profile the ripening process in multicomponent alloys by illustrating controlling factors (i.e., interfacial energy, diffusivities, and element partitioning). As a result, the study provides guidelines to design and develop high-temperature alloys with stable microstructures for long-term service.

  9. Cure shrinkage in epoxy grouts for grouted repairs

    NASA Astrophysics Data System (ADS)

    Shamsuddoha, Md.; Islam, Md. Mainul; Aravinthan, Thiru; Manalo, Allan; Lau, Kin-tak

    2013-08-01

    Structures can go through harsh environmental adversity and can experience material loss and cracks during their service lives. Infill material is used to ensure a supporting bed for a grouted repair. Epoxy grouts are used for repairing and rehabilitating structures, such as foundations, bridges, piers, transportation pipelines, etc., because they are resistant to typical chemicals and possess superior mechanical properties than other grouts. The resin based infill used inside the void or cracked space of the repair is vulnerable to shrinkage. When these filled grouts have high resin content, cracks can develop from residual stresses, which can affect the load transfer performance. It follows that interlayer separation and cracking of infill layer can occur in a grouted repair. In this study, volumetric shrinkage of two epoxy grouts was measured over 28 days using a Pycnometer. The highest volumetric shrinkage measured after 7 days was found to be 2.72%. The results suggest that the volumetric shrinkage can be reduced to 1.1% after 7 days, through the introduction of a coarse aggregate filler; a 2.5 times reduction in shrinkage. About 98% and 92% of the total shrinkage over the 28 day period, of the unfilled and filled grouts respectively, was found to occur within 7 days of mixing. The gel-time shrinkages were also calculated, to determine the "postgel" part of the curing contraction which subsequently produces residual stresses in the hardened grout systems.

  10. 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

  11. Interrelation of material microstructure, ultrasonic factors, and fracture toughness of two phase titanium alloy

    NASA Technical Reports Server (NTRS)

    Vary, A.; Hull, D. R.

    1982-01-01

    The pivotal role of an alpha-beta phase microstructure in governing fracture toughness in a titanium alloy, Ti-662, is demonstrated. The interrelation of microstructure and fracture toughness is demonstrated using ultrasonic measurement techniques originally developed for nondestructive evaluation and material property characterization. It is shown that the findings determined from ultrasonic measurements agree with conclusions based on metallurgical, metallographic, and fractographic observations concerning the importance of alpha-beta morphology in controlling fracture toughness in two phase titanium alloys.

  12. Phenomenology of electron-beam-induced photoresist shrinkage trends

    NASA Astrophysics Data System (ADS)

    Bunday, Benjamin; Cordes, Aaron; Allgair, John; Tileli, Vasiliki; Avitan, Yohanan; Peltinov, Ram; Bar-zvi, Maayan; Adan, Ofer; Cottrell, Eric; Hand, Sean

    2009-03-01

    For many years, lithographic resolution has been the main obstacle in keeping the pace of transistor densification to meet Moore's Law. For the 45 nm node and beyond, new lithography techniques are being considered, including immersion ArF (iArF) lithography and extreme ultraviolet lithography (EUVL). As in the past, these techniques will use new types of photoresists with the capability to print 45 nm node (and beyond) feature widths and pitches. In a previous paper [1], we focused on ArF and iArF photoresist shrinkage. We evaluated the magnitude of shrinkage for both R&D and mature resists as a function of chemical formulation, lithographic sensitivity, scanning electron microscope (SEM) beam condition, and feature size. Shrinkage results were determined by the well accepted methodology described in ISMI's CD-SEM Unified Specification [2]. A model for resist shrinkage, while derived elsewhere [3], was presented, that can be used to curve-fit to the shrinkage data resulting from multiple repeated measurements of resist features. Parameters in the curve-fit allow for metrics quantifying total shrinkage, shrinkage rate, and initial critical dimension (CD) from before e-beam exposure. The ability to know this original CD is the most desirable result; in this work, the ability to use extrapolation to solve for a given original CD value was also experimentally validated by CD-atomic force microscope (AFM) reference metrology. Historically, many different conflicting shrinkage results have been obtained among the many works generated through the litho-metrology community. This work, backed up by an exhaustive dataset, will present an explanation that makes sense of these apparent discrepancies. Past models for resist shrinkage inherently assumed that the photoresist line is wider than the region of the photoresist to be shrunk [3], or, in other words, the e-beam never penetrates enough to reach all material in the interior of a feature; consequently, not all photoresist

  13. Probing the origins and control of shrinkage stress in dental resin-composites: I. Shrinkage stress characterization technique.

    PubMed

    Lu, H; Stansbury, J W; Dickens, S H; Eichmiller, F C; Bowman, C N

    2004-10-01

    The accurate and reliable characterization of the polymerization shrinkage stress is becoming increasingly important, as the shrinkage stress still is a major drawback of current dimethacrylate-based dental materials and restricts its range of applications. The purpose of this research is to develop a novel shrinkage stress measurement device to elucidate the shrinkage stress evolution of dental restorative composites while allowing for controlled sample deformation during the polymerization. Furthermore, the device is designed to mimic the clinically relevant cusp-to-cusp displacement by systematically adjusting the instrument compliance, the bonded surface area/unbonded area by sample geometry, and the total bonded area by sample diameter. The stress measurement device based on the cantilever beam deflection theory has been successfully developed and characterized using a commercial dental composite. It was shown that this device is a highly effective, practical and reliable shrinkage stress measurement tool, which enables its facile applications to the investigation of shrinkage stress kinetics of both commercial and experimental composites, as well as for probing various aspects that dictate shrinkage stress development. PMID:15516870

  14. Straining graphene using thin film shrinkage methods.

    PubMed

    Shioya, Hiroki; Craciun, Monica F; Russo, Saverio; Yamamoto, Michihisa; Tarucha, Seigo

    2014-03-12

    Theoretical works suggest the possibility and usefulness of strain engineering of graphene by predicting remarkable properties, such as Dirac cone merging, bandgap opening and pseudo magnetic field generation. However, most of these predictions have not yet been confirmed because it is experimentally difficult to control the magnitude and type (e.g., uniaxial, biaxial, and so forth) of strain in graphene devices. Here we report two novel methods to apply strain without bending the substrate. We employ thin films of evaporated metal and organic insulator deposited on graphene, which shrink after electron beam irradiation or heat application. These methods make it possible to apply both biaxial strain and in-plane isotropic compressive strain in a well-controlled manner. Raman spectroscopy measurements show a clear splitting of the degenerate states of the G-band in the case of biaxial strain, and G-band blue shift without splitting in the case of in-plane isotropic compressive strain. In the case of biaxial strain application, we find out the ratio of the strain component perpendicular to the stretching direction is at least three times larger than what was previously observed, indicating that shrinkage of the metal or organic insulator deposited on graphene induces both tensile and compressive strain in this atomically thin material. Our studies present for the first time a viable way to apply strain to graphene without the need to bend the substrate. PMID:24490629

  15. Straining Graphene Using Thin Film Shrinkage Methods

    PubMed Central

    2014-01-01

    Theoretical works suggest the possibility and usefulness of strain engineering of graphene by predicting remarkable properties, such as Dirac cone merging, bandgap opening and pseudo magnetic field generation. However, most of these predictions have not yet been confirmed because it is experimentally difficult to control the magnitude and type (e.g., uniaxial, biaxial, and so forth) of strain in graphene devices. Here we report two novel methods to apply strain without bending the substrate. We employ thin films of evaporated metal and organic insulator deposited on graphene, which shrink after electron beam irradiation or heat application. These methods make it possible to apply both biaxial strain and in-plane isotropic compressive strain in a well-controlled manner. Raman spectroscopy measurements show a clear splitting of the degenerate states of the G-band in the case of biaxial strain, and G-band blue shift without splitting in the case of in-plane isotropic compressive strain. In the case of biaxial strain application, we find out the ratio of the strain component perpendicular to the stretching direction is at least three times larger than what was previously observed, indicating that shrinkage of the metal or organic insulator deposited on graphene induces both tensile and compressive strain in this atomically thin material. Our studies present for the first time a viable way to apply strain to graphene without the need to bend the substrate. PMID:24490629

  16. 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.

  17. Influence of Kinetic and Thermodynamic Factors on the Glass-Forming Ability of Zirconium-Based Bulk Amorphous Alloys

    SciTech Connect

    Mukherjee, S.; Johnson, W.L.; Rhim, W.-K.; Schroers, J.

    2005-06-24

    The time-temperature-transformation curves for three zirconium-based bulk amorphous alloys are measured to identify the primary factors influencing their glass-forming ability. The melt viscosity is found to have the most pronounced influence on the glass-forming ability compared to other thermodynamic factors. Surprisingly, it is found that the better glass former has a lower crystal-melt interfacial tension. This contradictory finding is explained by the icosahedral short-range order of the undercooled liquid, which on one hand reduces the interfacial tension, while on the other hand increases its viscosity.

  18. Applying strain into graphene by SU-8 resist shrinkage

    NASA Astrophysics Data System (ADS)

    Takamura, Makoto; Hibino, Hiroki; Yamamoto, Hideki

    2016-07-01

    We investigated the use of the shrinkage of SU-8 resist caused by thermal annealing to apply strain into graphene grown by the chemical-vapor-deposition (CVD) method. We demonstrate that the shrinkage of resist deposited on top of graphene on a substrate induces a local tensile strain within a distance of 1–2 μm from the edge of the resist. The thermal shrinkage of SU-8 will allow us to design the local strain in graphene on substrates. We also show that the shrinkage induces a large tensile strain in graphene suspended between two bars of SU-8. We expect that a much larger strain can be induced by suppressing defects in CVD-grown graphene.

  19. NSCLC tumor shrinkage prediction using quantitative image features.

    PubMed

    Hunter, Luke A; Chen, Yi Pei; Zhang, Lifei; Matney, Jason E; Choi, Haesun; Kry, Stephen F; Martel, Mary K; Stingo, Francesco; Liao, Zhongxing; Gomez, Daniel; Yang, Jinzhong; Court, Laurence E

    2016-04-01

    The objective of this study was to develop a quantitative image feature model to predict non-small cell lung cancer (NSCLC) volume shrinkage from pre-treatment CT images. 64 stage II-IIIB NSCLC patients with similar treatments were all imaged using the same CT scanner and protocol. For each patient, the planning gross tumor volume (GTV) was deformed onto the week 6 treatment image, and tumor shrinkage was quantified as the deformed GTV volume divided by the planning GTV volume. Geometric, intensity histogram, absolute gradient image, co-occurrence matrix, and run-length matrix image features were extracted from each planning GTV. Prediction models were generated using principal component regression with simulated annealing subset selection. Performance was quantified using the mean squared error (MSE) between the predicted and observed tumor shrinkages. Permutation tests were used to validate the results. The optimal prediction model gave a strong correlation between the observed and predicted tumor shrinkages with r=0.81 and MSE=8.60×10(-3). Compared to predictions based on the mean population shrinkage this resulted in a 2.92 fold reduction in MSE. In conclusion, this study indicated that quantitative image features extracted from existing pre-treatment CT images can successfully predict tumor shrinkage and provide additional information for clinical decisions regarding patient risk stratification, treatment, and prognosis. PMID:26878137

  20. Porcine Intestinal Mast Cells. Evaluation of Different Fixatives for Histochemical Staining Techniques Considering Tissue Shrinkage

    PubMed Central

    Rieger, J.; Twardziok, S.; Huenigen, H.; Hirschberg, R.M.; Plendl, J.

    2013-01-01

    Staining of mast cells (MCs), including porcine ones, is critically dependent upon the fixation and staining technique. In the pig, mucosal and submucosal MCs do not stain or stain only faintly after formalin fixation. Some fixation methods are particularly recommended for MC staining, for example the fixation with Carnoy or lead salts. Zinc salt fixation (ZSF) has been reported to work excellently for the preservation of fixation-sensitive antigens. The aim of this study was to establish a reliable histological method for counting of MCs in the porcine intestinum. For this purpose, different tissue fixation and staining methods that also allow potential subsequent immunohistochemical investigations were evaluated in the porcine mucosa, as well as submucosa of small and large intestine. Tissues were fixed in Carnoy, lead acetate, lead nitrate, Zamboni and ZSF and stained subsequently with either polychromatic methylene blue, alcian blue or toluidine blue. For the first time our study reveals that ZSF, a heavy metal fixative, preserves metachromatic staining of porcine MCs. Zamboni fixation was not suitable for histochemical visualization of MCs in the pig intestine. All other tested fixatives were suitable. Alcian blue and toluidine blue co-stained intestinal goblet cells which made a prima facie identification of MCs difficult. The polychromatic methylene blue proved to be the optimal staining. In order to compare MC counting results of the different fixation methods, tissue shrinkage was taken into account. As even the same fixation caused shrinkagedifferences between tissue from small and large intestine, different factors for each single fixation and intestinal localization had to be calculated. Tissue shrinkage varied between 19% and 57%, the highest tissue shrinkage was found after fixation with ZSF in the large intestine, the lowest one in the small intestine after lead acetate fixation. Our study emphasizes that MC counting results from data using different

  1. VERIFICATION OF 3-PHASES COMPOSITE MODEL FOR DRYING SHRINKAGE OF CONCRETE WITH DEFFERENT AGGREGATE PROPERTIES

    NASA Astrophysics Data System (ADS)

    Tanaka, Kie; Shima, Hiroshi

    Properties of aggregate are not taken into account in current codes for drying shrinkage of concrete although the drying shrinkage is affected by the properties of aggregate. Aggregate restrains cement paste from shrinkage so that the drying shrinkage of concrete is controlled by drying shrinkage and Young's modulus of aggregate itself. The effect of the aggregate properties on drying shrinkage of concrete can be calculated by composite model in which concrete consists of cement paste and aggregate. Several different kind of coarse aggregate were used in order to verify a 3-phases composite model for drying shrinkage. Drying shrinkage and Young's modulus of cement paste, aggregate and concrete were measured. It was verified that drying shrinkage of concrete can be estimated accurately by the composite model associating with both drying shrinkage and Young's modulus of aggregate.

  2. Monte Carlo Simulation Using Johnson Potential on Gd-Mg Alloy for Debye-Waller Factor and Debye Temperature

    NASA Astrophysics Data System (ADS)

    Chitra, S.; Ramachandran, K.

    Monte Carlo simulation (MCS) on the thermal properties in Gd-Mg alloy becomes essential as there are only limited experiments available. A realistic Johnson potential is used to workout the specific heats for various temperatures and hence the Debye temperature. The results from the present simulation technique are very well compared with our shell model calculation. The need of better X-ray measurements for Debye-Waller factor and Debye temperature other than the measurements of Subadhra and Sirdeshmukh, is discussed in detail.

  3. Influence of light-curing protocols on polymerization shrinkage and shrinkage force of a dual-cured core build-up resin composite.

    PubMed

    Tauböck, Tobias T; Bortolotto, Tissiana; Buchalla, Wolfgang; Attin, Thomas; Krejci, Ivo

    2010-08-01

    This study investigated the influence of time delay and duration of photo-activation on linear polymerization shrinkage, shrinkage force, and hardening of a dual-cured core build-up resin composite. The test material (Rebilda DC) was light-cured for 20 or 60 s either early (2 min) or late (7 min) after the start of mixing. Non-irradiated self-cured specimens served as controls. Linear shrinkage and shrinkage force were measured for 60 min using custom-made devices. Knoop hardness was determined at the end of the observation period. Self-cured controls, showing a linear shrinkage similar to that of specimens early light-cured for 20 s generated the lowest shrinkage force and hardness. A shorter light exposure time (20 s vs. 60 s) reduced linear shrinkage, shrinkage force, and hardness when early light-curing was performed, but did not affect the three properties in specimens light-cured late after the start of mixing. Late photo-activation increased linear shrinkage, irrespective of irradiation time, and resulted in a higher shrinkage force and hardness for short light exposure time. A moderate correlation was found between the two shrinkage properties studied (r(2) = 0.65). In conclusion, improvements in shrinkage behavior of the tested core build-up material were associated with inferior hardening, making it important to adapt curing protocols to the clinical situation. PMID:20662918

  4. Precise control of critical dimension shrinkage and enlargement by in-situ polysilicon etch

    NASA Astrophysics Data System (ADS)

    Linliu, Kung; Kuo, Mai-Rue

    2000-07-01

    The control of critical dimension shrinkage and enlargement of polysilicon line or space obtained precisely using in- situ process with different ratio of gas combination is investigate din this paper. A polysilicon line could be etched down to 0.054 micrometers from 0.22 micrometers of the original critical dimension (CD). The CD shrinking rate of polysilicon line is 2.48 nm per second per side. On the other hand, the space can also be trimmed down to 0.03 micrometers from the original CD of 0.3 micrometers . The CD enlarging rate of polysilicon rate is 0.421 nm per second per side using the present polymer deposition method. The factors that cause shrinkage and enlargement of CD are the etching of photoresist and the deposition of polymer on the surface of photoresist, respectively. The oxygen-rich gas is used for the shrinkage of CD and the fluorocarbon-rich gas is used for the enlargement of CD. Therefore, a critical dimension could not afforded by the present existed optical photolithography tool or method might probably be solved by alternative innovation such as the plasma dry etching technology.

  5. Identification of signalling cascades involved in red blood cell shrinkage and vesiculation

    PubMed Central

    Kostova, Elena B.; Beuger, Boukje M.; Klei, Thomas R.L.; Halonen, Pasi; Lieftink, Cor; Beijersbergen, Roderick; van den Berg, Timo K.; van Bruggen, Robin

    2015-01-01

    Even though red blood cell (RBC) vesiculation is a well-documented phenomenon, notably in the context of RBC aging and blood transfusion, the exact signalling pathways and kinases involved in this process remain largely unknown. We have established a screening method for RBC vesicle shedding using the Ca2+ ionophore ionomycin which is a rapid and efficient method to promote vesiculation. In order to identify novel pathways stimulating vesiculation in RBC, we screened two libraries: the Library of Pharmacologically Active Compounds (LOPAC) and the Selleckchem Kinase Inhibitor Library for their effects on RBC from healthy donors. We investigated compounds triggering vesiculation and compounds inhibiting vesiculation induced by ionomycin. We identified 12 LOPAC compounds, nine kinase inhibitors and one kinase activator which induced RBC shrinkage and vesiculation. Thus, we discovered several novel pathways involved in vesiculation including G protein-coupled receptor (GPCR) signalling, the phosphoinositide 3-kinase (PI3K)–Akt (protein kinase B) pathway, the Jak–STAT (Janus kinase–signal transducer and activator of transcription) pathway and the Raf–MEK (mitogen-activated protein kinase kinase)–ERK (extracellular signal-regulated kinase) pathway. Moreover, we demonstrated a link between casein kinase 2 (CK2) and RBC shrinkage via regulation of the Gardos channel activity. In addition, our data showed that inhibition of several kinases with unknown functions in mature RBC, including Alk (anaplastic lymphoma kinase) kinase and vascular endothelial growth factor receptor 2 (VEGFR-2), induced RBC shrinkage and vesiculation. PMID:25757360

  6. The shrinkage behavior and surface topographical investigation for micro metal injection molding

    NASA Astrophysics Data System (ADS)

    Islam, A.; Giannekas, N.; Marhöfer, D. M.; Tosello, G.; Hansen, H. N.

    2015-05-01

    Metal injection molding (MIM) is a near net shape manufacturing technology that can produce highly complex and dimensionally stable parts for high end engineering applications. Despite the recent growth and industrial interest, micro metal molding is yet to be the field of extensive research especially when it is compared with micro molding of thermoplastics. The current paper presents a thorough investigation on the process of metal injection molding where it systematically characterizes the effects of important process conditions on the shrinkage and surface quality of molded parts with micro features. Effects of geometrical factors like feature dimensions and distance from the gate on the replication quality are studied. The influence of process conditions on the achievable roughness for the final metal parts is discussed based on the experimental findings. The test geometry is characterized by 2½D surface structures containing thin ribs of different aspect ratios and thicknesses in the sub-mm dimensional range. The test parts were molded from Catamold 316L with a conventional injection molding machine. Afterwards, the parts were de-binded and sintered to produce the final test samples. Among the different process parameters studied, the melt temperature was the most influential parameters for better replication and dimensional stability of the final part. The results presented in the paper clearly show that the shrinkage in metal part is not uniform in the micro scale. It depends on the feature dimensions and also on the process conditions. A thin section of the part exhibits higher relative shrinkage compared with a thicker section. Based on these findings, it can be concluded that a micro part molded by MIM process will have higher relative shrinkage compared to a macro part made with the same process.

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

    PubMed

    Sarabadani, Hamid; Rayhani, Mohammad T

    2014-04-01

    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. PMID:24718363

  8. Comparative analysis of polymerization shrinkage of different resin composites.

    PubMed

    Barretto, Iana Coutinho; Pontes, Luana Farias; Carneiro, Karina Kato; Araujo, Jesuina Lamartine Nogueira; Ballester, Rafael Yague; Silva, Cecy Martins

    2015-01-01

    This study sought to compare the shrinkage of 3 resin composites after polymerization, using different curing modes and 2 methods of analysis, with 45 samples in each group. To evaluate free linear shrinkage, specimens were prepared in Teflon molds (8 mm diameter x 2 mm thick) with 1 of 2 methacrylate-based resins or a silorane-based resin. To evaluate wall-to-wall shrinkage, cavities (1.5 mm thick x 3 mm diameter) were prepared in 45 healthy bovine incisors and then restored. In both tests, the same curing lights were used: conventional quartz-tungsten-halogen, a conventional light-emitting diode (LED), and an exponential LED. Gaps were measured microscopically, and the gap percentage was calculated. The results were analyzed by 2-way ANOVA and Tukey's test (α = 0.05). Curing modes differed significantly in the free linear shrinkage test group, while resin composites did not. In the wall-to-wall shrinkage group, there were significant differences between the resin composites. PMID:25734285

  9. Factors which control the swelling of FeCrNi ternary austenitic alloys

    NASA Astrophysics Data System (ADS)

    Garner, F. A.; Black, C. A.; Edwards, D. J.

    1997-06-01

    In agreement with limited earlier studies, a comprehensive irradiation experiment conducted in both EBR-II and FFTF demonstrates that while cold-working usually decreases void swelling of ternary FeCrNi alloys at relatively low irradiation temperatures, it in general increases swelling at higher irradiation temperatures. Aging of cold-worked specimens to produce cellular dislocation networks tends to further increase swelling, especially at higher nickel levels. The swelling of ternary alloy at lower nickel levels also appears to be sensitive to details of the preirradiation annealing treatment. The differences in the details of reactor operating conditions also exert an influence on void nucleation and thereby on the duration of the transient regime of swelling. In the current irradiation series this leads to the swelling developed in EBR-II at ˜ 30 dpa being consistently larger than that in FFTF. All of these results confirm an earlier conclusion that the primary variability of void swelling of FeCrNi alloys lies in the incubation and transient regimes, rather than in the steady-state swelling rate regime. Under certain conditions, the transient regime can be made to approach 0 dpa.

  10. STUDY ON THE EVALUATION FOR DRYING SHRINKAGE PROPERTIES OF COARSE AGGREGATE

    NASA Astrophysics Data System (ADS)

    Yamada, Hiroshi; Katahira, Hiroshi; Watanabe, Hiroshi

    Drying shrinkage of coarse aggregate is one of principal indexes to evaluate drying shrinkage of concrete. However, testing of drying shrinkage of a coarse aggregate particle has not been commonly conducted. We carried out measurement of drying shrinkage of a coarse aggregate particle using wire strain gauges and discussed the variation in the measurement. We found that variation among particles in drying shrinkage strain of coarse aggregate is intrinsic and much bigger than test result due to the simplified unidirectional strain measurement under the assumption of ignoring multi-axial strain field. Strong relationship between the mean value of drying shrinkage strain of coarse aggregate and drying shrinkage strain of concrete prism specimens was observed, which indicates that measured drying shrinkage strain of aggregate particles intrinsically contains large variation, however the mean value is an effective index to estimate drying shrinkage of concrete.

  11. Impact of Reaction Shrinkage on Stress in Semiconductor Packages

    NASA Astrophysics Data System (ADS)

    Mengel, Manfred; Mahler, Joachim

    2009-11-01

    The reliability of a semiconductor package is strongly influenced by the adhesion and temperature behavior of the package encapsulant. This study considers the effect of mold shrinkage during the encapsulation molding process. Four commercially available molds were investigated using warpage and thermomechanical analysis. It could be demonstrated that, for all four types, when molded on a silicon substrate, the temperature at which no stress occurred was in a range of 28-60°C above the molding temperature. This is caused by the shrinkage due to a crosslinking reaction of the mold polymer during the molding process. For a more precise understanding and simulation of the stress behavior inside a molded package, the effect of reaction shrinkage has to be considered.

  12. 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

  13. 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. PMID:24368873

  14. A shrinkage probability hypothesis density filter for multitarget tracking

    NASA Astrophysics Data System (ADS)

    Tong, Huisi; Zhang, Hao; Meng, Huadong; Wang, Xiqin

    2011-12-01

    In radar systems, tracking targets in low signal-to-noise ratio (SNR) environments is a very important task. There are some algorithms designed for multitarget tracking. Their performances, however, are not satisfactory in low SNR environments. Track-before-detect (TBD) algorithms have been developed as a class of improved methods for tracking in low SNR environments. However, multitarget TBD is still an open issue. In this article, multitarget TBD measurements are modeled, and a highly efficient filter in the framework of finite set statistics (FISST) is designed. Then, the probability hypothesis density (PHD) filter is applied to multitarget TBD. Indeed, to solve the problem of the target and noise not being separated correctly when the SNR is low, a shrinkage-PHD filter is derived, and the optimal parameter for shrinkage operation is obtained by certain optimization procedures. Through simulation results, it is shown that our method can track targets with high accuracy by taking advantage of shrinkage operations.

  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

    specimens than those cured for a shorter period. The third portion of the study evaluates the cracking tendency of concrete mixtures using the restrained ring tests. Different concrete ring thicknesses and drying conditions have been tested. The results indicate that specimens with thinner concrete rings crack earlier than those with thicker concrete rings. Exposing specimens to severe drying conditions results in the earlier formation of cracks, although it does not result in increased crack width. Mixtures with a lower water-cement (w/c) ratio crack earlier than mixtures with a higher w/c ratio. Concretes with a higher paste content crack earlier than concretes with a lower paste content. The final portion of the study details the development, construction, and preliminary performance (with most bridges at three years of age) of LC-HPC and control bridge decks in Kansas. The results indicate that the techniques embodied in the LC-HPC bridge deck specifications are easy to learn. Contractor personnel can be trained in a relatively short time. The techniques used for LC-HPC bridge decks are effective in reducing bridge deck cracking. The crack surveys indicate that LC-HPC bridge decks are performing much better than the control decks, with average crack densities reduced by about seventy five percent at three years of age. The factors that may affect bridge deck cracking are analyzed. The analyses indicate that an increase in paste content, slump, compressive strength, maximum daily air temperature, and daily air temperature range causes increased crack densities. Contractor techniques influence cracking. Keywords: bridge construction, bridge deck, contractor, concrete mix design, compressive strength, cracking, curing, evaporable water, fly ash, free shrinkage, high-performance concrete, non-evaporable water, paste content, restrained shrinkage, restrained ring tests, shrinkage reducing admixture, slump

  16. Shrinkage stress development in dental composites—An analytical treatment

    PubMed Central

    Fok, Alex S.L.

    2013-01-01

    Objectives The aim of this paper is to develop a comprehensive mathematical model for shrinkage stress development in dental composites that can account for the combined effect of material properties, specimen geometry and external constraints. Methods A viscoelastic model that includes the composite’s elastic, creep and shrinkage strains, and their interaction with the sample’s dimensions and the external constraint is developed. The model contains two dimensionless parameters. The first one represents the compliance of the external constraint relative to that of the composite sample, and the second controls the rate of shrinkage stress decay through creep. The resulting differential equation is solved for two special cases: zero compliance and zero creep. Predictions for shrinkage stress measurements are then made using the analytical solutions for instruments with different compliances, samples with different thicknesses and composites with different filler fractions. Results The model correctly predicts how shrinkage stress increases with time, its dependence on the interaction between the entire system’s compliance and the material properties, and the effect of the filler fraction on its maximum value. Comparisons with reported shrinkage stress measurements have provided very good agreement between theory and experiments. Significance The results provided by the model can help to resolve most, if not all, of the seemingly conflicting experimental observations reported in the literature. They can also provide some useful guidelines for optimizing the mechanical performance of dental composite restorations. The compliance ratio, a new parameter derived from the model, represents a fuller description of the constraints of the system. PMID:24029101

  17. 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.

  18. ACCELERATED MRI USING ITERATIVE NON-LOCAL SHRINKAGE

    PubMed Central

    Mohsin, Yasir Q.; Ongie, Gregory; Jacob, Mathews

    2015-01-01

    We introduce a fast iterative non-local shrinkage algorithm to recover MRI data from undersampled Fourier measurements. This approach is enabled by the reformulation of current non-local schemes as an alternating algorithm to minimize a global criterion. The proposed algorithm alternates between a non-local shrinkage step and a quadratic subproblem. The resulting algorithm is observed to be considerably faster than current alternating non-local algorithms. We use efficient continuation strategies to minimize local minima issues. The comparisons of the proposed scheme with state-of-the-art regularization schemes show a considerable reduction in alias artifacts and preservation of edges. PMID:25570265

  19. Water transfer properties and shrinkage in lime-based rendering mortars

    NASA Astrophysics Data System (ADS)

    Arizzi, A.; Cultrone, G.

    2012-04-01

    aspect to be considered in the evaluation of the decay caused by water is the high shrinkage suffered by renders when they are applied on an extended surface (i.e. a wall), especially when they are aerial lime-based mortars. The shrinkage causes the formation of fissures that become an easy way for water to entry and diffuse through the mortar pore system. This factor is rarely taken into consideration during the hydric assays performed in the laboratory, since mortar samples of 4x4x16 or 4x4x4 cm in size do not undergo to such degree of shrinkage. For this reason, we have also studied the shrinkage of these mortars and considered it in the final assessment of mortars hydric properties. The shrinkage was evaluated according to a non-standardized method, by means of a shrinkage-measuring device that measures the mortar dimensional variations over time. This measurement has shown that the highest the lime content the biggest the mortar shrinkage and, consequently, the strongest the decay due to water.

  20. Effect of power density on shrinkage of dental resin materials.

    PubMed

    Oberholzer, Theunis G; Pameijer, Cornelis H; Grobler, Sias R; Rossouw, Roelof J

    2003-01-01

    This study compares volumetric changes and rates of shrinkage during different stages of polymerization of dental resin composites and compomers exposed to the same total energy by using two different combinations of power density and exposure duration. A hybrid composite and its equivalent flowable and a compomer and its equivalent flowable were exposed using a halogen curing unit set at 400 mW/cm2 for 40 seconds and 800 mW/cm2 for 20 seconds: delivering 16 J/cm2 in both cases. Volumetric changes were recorded every 0.5 seconds using a mercury dilatometer. Ten replications per test condition were performed and the data were subjected to ANOVA. Statistically significant differences in shrinkage values and rates among different power densities were determined by means of paired t-tests at a 95% confidence level. Significantly more shrinkage (p<0.05) was found for the higher filled materials, Z250 and Dyract AP, when higher power density was used. However, no significant differences were found between their flowable counterparts when exposed to various power densities. Of the four materials, only Dyract AP exhibited no significant difference in shrinkage rate when various power densities were used. All the other materials exhibited significantly higher rates (p<0.05) at the higher power density. PMID:14531610

  1. Validity Shrinkage in Ridge Regression: A Simulation Study.

    ERIC Educational Resources Information Center

    Faden, Vivian; Bobko, Philip

    1982-01-01

    Ridge regression offers advantages over ordinary least squares estimation when a validity shrinkage criterion is considered. Comparisons of cross-validated multiple correlations indicate that ridge estimation is superior when the predictors are multicollinear, the number of predictors is large relative to sample size, and the population multiple…

  2. Scale Shrinkage and the Estimation of Latent Distribution Parameters.

    ERIC Educational Resources Information Center

    Camilli, Gregory

    1988-01-01

    The phenomenon of scale shrinkage is examined. Focus is on the pattern of decreasing variances in item response theory scale scores from fall to spring within a grade. It is demonstrated that questions concerning population distributions of true ability can be addressed with empirical Bayes techniques. (TJH)

  3. Shrinkage Estimation of Linear Combinations of True Scores.

    ERIC Educational Resources Information Center

    Longford, Nicholas T.

    1997-01-01

    It is demonstrated that, in the presence of population information, a linear combination of true scores can be estimated more efficiently than by the same linear combination of the observed scores. Three criteria for optimality are discussed, but they yield the same solution, described as a multivariate shrinkage estimator. (Author/SLD)

  4. Bayesian Shrinkage Analysis of Quantitative Trait Loci for Dynamic Traits

    PubMed Central

    Yang, Runqing; Xu, Shizhong

    2007-01-01

    Many quantitative traits are measured repeatedly during the life of an organism. Such traits are called dynamic traits. The pattern of the changes of a dynamic trait is called the growth trajectory. Studying the growth trajectory may enhance our understanding of the genetic architecture of the growth trajectory. Recently, we developed an interval-mapping procedure to map QTL for dynamic traits under the maximum-likelihood framework. We fit the growth trajectory by Legendre polynomials. The method intended to map one QTL at a time and the entire QTL analysis involved scanning the entire genome by fitting multiple single-QTL models. In this study, we propose a Bayesian shrinkage analysis for estimating and mapping multiple QTL in a single model. The method is a combination between the shrinkage mapping for individual quantitative traits and the Legendre polynomial analysis for dynamic traits. The multiple-QTL model is implemented in two ways: (1) a fixed-interval approach where a QTL is placed in each marker interval and (2) a moving-interval approach where the position of a QTL can be searched in a range that covers many marker intervals. Simulation study shows that the Bayesian shrinkage method generates much better signals for QTL than the interval-mapping approach. We propose several alternative methods to present the results of the Bayesian shrinkage analysis. In particular, we found that the Wald test-statistic profile can serve as a mechanism to test the significance of a putative QTL. PMID:17435239

  5. Are trees able to grow in periods of stem shrinkage?

    PubMed

    Zweifel, Roman; Haeni, Matthias; Buchmann, Nina; Eugster, Werner

    2016-08-01

    Separating continuously measured stem radius (SR) fluctuations into growth-induced irreversible stem expansion (GRO) and tree water deficit-induced reversible stem shrinkage (TWD) requires a conceptualization of potential growth processes that may occur during periods of shrinking and expanding SR below a precedent maximum. Here, we investigated two physiological concepts: the linear growth (LG) concept, assuming linear growth, versus the zero growth (ZG) concept, assuming no growth during periods of stem shrinkage. We evaluated the physiological mechanisms underlying these two concepts and assessed their respective plausibilities using SR data obtained from 15 deciduous and evergreen trees. The application of the LG concept produced steady growth rates, whereas growth rates varied strongly under the ZG concept, more in accordance with mechanistic expectations. Further, growth increased for a maximum of 120 min after periods of stem shrinkage, indicating limited growth activity during those periods. However, this extra growth was found to be a small fraction of total growth only. Furthermore, TWD under the ZG concept was better explained by a hydraulic plant model than TWD under the LG concept. We conclude that periods of stem shrinkage allow for very little growth in the four tree species investigated. However, further studies should focus on obtaining independent growth data to ultimately validate these findings. PMID:27189708

  6. In vitro and in vivo degradation and mechanical properties of ZEK100 magnesium alloy coated with alginate, chitosan and mechano-growth factor.

    PubMed

    Gao, Hong; Zhang, Meng; Zhao, Jin; Gao, Lilan; Li, Mingshuo

    2016-06-01

    The biocompatibility, ultimate loading capacity and biodegradability of magnesium alloy make it an ideal candidate in biomedical fields. Fabrications of multilayered coatings carrying sodium alginate (ALG), chitosan (CHI) and mechano-growth factor (MGF) on fluoride-pretreated ZEK100 magnesium alloy have been obtained via layer by layer (LBL) to reduce the degradation rate of magnesium alloy in this study. The modified surfaces of ZEK100 substrates were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) and CARE EUT-1020 tester. Results reveal that multilayer-coated magnesium alloy can be successfully obtained with smooth surface morphology, and the mechanical properties of coated samples are almost the same as those of uncoated samples. However, the fatigue life of coated ZEK100 is slightly larger than that of uncoated samples after 1 day of immersion. By comparing the degradation of uncoated and multilayer-coated ZEK100 samples in vitro and in vivo, respectively, it is found that the degradation rate of ZEK100 samples can be inhibited by LBL modification on the surface of the sample; and the corrosion rate in vivo is lower than that in vitro, which help solve the rapid degradation problem of magnesium alloy. In terms of the visible symptom of tissues in the left femur medullary cavity and material responses on the surface, multilayer-coated ZEK100 magnesium alloy has a good biocompatibility. These results indicate that multilayer-coated ZEK100 may be a promising material for bone tissue repair. PMID:27040239

  7. Measurement Error, Multidimensionality, and Scale Shrinkage: A Reply to Yen and Burket.

    ERIC Educational Resources Information Center

    Camilli, Gregory

    1999-01-01

    Yen and Burket suggested that shrinkage in vertical equating cannot be understood apart from multidimensionality. Reviews research on reliability, multidimensionality, and scale shrinkage, and explores issues of practical importance to educators. (SLD)

  8. 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.

  9. Correction factors for on-line microprobe analysis of multielement alloy systems

    NASA Technical Reports Server (NTRS)

    Unnam, J.; Tenney, D. R.; Brewer, W. D.

    1977-01-01

    An on-line correction technique was developed for the conversion of electron probe X-ray intensities into concentrations of emitting elements. This technique consisted of off-line calculation and representation of binary interaction data which were read into an on-line minicomputer to calculate variable correction coefficients. These coefficients were used to correct the X-ray data without significantly increasing computer core requirements. The binary interaction data were obtained by running Colby's MAGIC 4 program in the reverse mode. The data for each binary interaction were represented by polynomial coefficients obtained by least-squares fitting a third-order polynomial. Polynomial coefficients were generated for most of the common binary interactions at different accelerating potentials and are included. Results are presented for the analyses of several alloy standards to demonstrate the applicability of this correction procedure.

  10. DETERMINATION OF IN-VITRO LUNG SOLUBILITY AND INTAKE-TO-DOSE CONVERSION FACTOR FOR TRITIATED LANTHANUM NICKEL ALUMINUM ALLOY

    SciTech Connect

    Farfan, E.; Labone, T.; Staack, G.; Cheng, Y.; Zhou, Y.; Varallo, T.

    2011-11-11

    A sample of tritiated lanthanum nickel aluminum alloy (LaNi4.25Al0.75 or LANA.75) similar to that used at the Savannah River Site Tritium Facilities was analyzed to estimate the particle size distribution of this metal tritide powder and the rate, at which this material dissolves in the human respiratory tract after it is inhaled. This information is used to calculate the committed effective dose received by a worker after inhaling the material. These doses, which were calculated using the same methodology given in the DOE Tritium Handbook, are presented as inhalation intake-to-dose conversion factors (DCF). The DCF for this metal tritide is less than the DCF for tritiated water and radiation worker bioassay programs designed for tritiated water are adequate to monitor for intakes of this material.

  11. TH-E-BRF-01: Exploiting Tumor Shrinkage in Split-Course Radiotherapy

    SciTech Connect

    Unkelbach, J; Craft, D; Hong, T; Papp, D; Wolfgang, J; Bortfeld, T; Ramakrishnan, J; Salari, E

    2014-06-15

    Purpose: In split-course radiotherapy, a patient is treated in several stages separated by weeks or months. This regimen has been motivated by radiobiological considerations. However, using modern image-guidance, it also provides an approach to reduce normal tissue dose by exploiting tumor shrinkage. In this work, we consider the optimal design of split-course 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. Methods: We introduce a dynamic tumor model that incorporates three factors: radiation induced cell kill, tumor shrinkage, and tumor cell repopulation. The design of splitcourse radiotherapy is formulated as a mathematical optimization problem in which the total dose to the liver 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. Results: 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 split-course treatments in terms of liver sparing depends on model assumptions. However, the model predicts large liver dose reductions by more than a factor of two for plausible model parameters. Conclusion: 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 split-course radiotherapy for selected disease sites where substantial tumor regression translates into reduced

  12. A Monte Carlo Evaluation of Estimated Parameters of Five Shrinkage Estimate Formuli.

    ERIC Educational Resources Information Center

    Newman, Isadore; And Others

    A Monte Carlo study was conducted to estimate the efficiency of and the relationship between five equations and the use of cross validation as methods for estimating shrinkage in multiple correlations. Two of the methods were intended to estimate shrinkage to population values and the other methods were intended to estimate shrinkage from sample…

  13. A Monte Carlo Evaluation of Estimated Parameters of Five Shrinkage Estimate Formuli.

    ERIC Educational Resources Information Center

    Newman, Isadore; And Others

    1979-01-01

    A Monte Carlo simulation was employed to determine the accuracy with which the shrinkage in R squared can be estimated by five different shrinkage formulas. The study dealt with the use of shrinkage formulas for various sample sizes, different R squared values, and different degrees of multicollinearity. (Author/JKS)

  14. Shrinkage behavior of low profile unsaturated polyester resins at low temperature and low pressure

    SciTech Connect

    Wen Li; Lee, L.J.

    1996-12-31

    In order to achieve excellent surface quality and dimension control of molded polymer composites, low profile additives (LPA) are widely used in low shrinkage unsaturated polyester (UPE) molding compound. Although the detailed LPA mechanism is still a subject of controversy, it is now generally agreed that the most important factor for the low profile behavior is the strong phase separation between LPA and UPE resin during curing. Among the extensive studies of LPA mechanism, most of the work focused on the reaction at high temperatures, since LPAs found most of their applications in high temperature and high pressure processes like sheet molding compound (SMC) and bulk molding compound (BMC). Recently, because of the growing interests of new processes such as low pressure SMC and vacuum infusion resin transfer molding, low shrinkage molding compound with the ability to be processed at low temperature and low pressure have attracted considerable attention from the composite industry. Therefore, further understanding of the low profile mechanism at low temperature and low pressure cure is necessary. Moreover, the relatively long reaction time at low temperature cure provides an opportunity to decouple the factors such as phase separation and microvoid formation, which occur almost at the same time in high temperature cure. The objective of this study is to determine LPA performance as well as to provide a better understanding of low profile mechanism at low temperature and low pressure.

  15. 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.

  16. Simulation of shrinkage and warpage of semi-crystalline thermoplastics

    NASA Astrophysics Data System (ADS)

    Hopmann, Ch.; Borchmann, N.; Spekowius, M.; Weber, M.; Schöngart, M.

    2015-05-01

    Today, the simulation of the injection molding process is state of the art. Besides the simulation of the manufacturing process, commercial simulation tools allow a prediction of the structural properties of the final part. Especially the complex shrinkage and warpage behavior is of interest as it significantly influences the part quality. Although modern simulation tools provide qualitatively correct results for several materials and processing conditions, significant deviations from the real component's behavior can occur for semi-crystalline thermoplastics. One underlying reason is the description on the macro scale used in these simulation tools. However, in semi-crystalline materials significant effects take place on the micro scale, e.g. crystalline superstructures that cannot be neglected. As part of a research project at IKV, investigations are carried out to improve the simulation accuracy of shrinkage and warpage. To point out differences in the accuracy of commercially available simulation tools, a reference part is computed for the materials polypropylene and polyoxymethylene. The results are validated by injection molding experiments. The shrinkage and warpage behavior is characterized by optical measuring technology. In future, models for the description of the pvT behavior of semi-crystalline thermoplastics will be implemented into the software package SphäroSim which was developed at IKV. With this software, crystallization kinetics for semi-crystalline thermoplastics can be calculated on the micro scale. With the newly implemented pvT models the calculation of shrinkage and warpage for semi-crystalline thermoplastics will be enabled on the micro scale.

  17. 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

  18. Shrinkage regression-based methods for microarray missing value imputation

    PubMed Central

    2013-01-01

    Background Missing values commonly occur in the microarray data, which usually contain more than 5% missing values with up to 90% of genes affected. Inaccurate missing value estimation results in reducing the power of downstream microarray data analyses. Many types of methods have been developed to estimate missing values. Among them, the regression-based methods are very popular and have been shown to perform better than the other types of methods in many testing microarray datasets. Results To further improve the performances of the regression-based methods, we propose shrinkage regression-based methods. Our methods take the advantage of the correlation structure in the microarray data and select similar genes for the target gene by Pearson correlation coefficients. Besides, our methods incorporate the least squares principle, utilize a shrinkage estimation approach to adjust the coefficients of the regression model, and then use the new coefficients to estimate missing values. Simulation results show that the proposed methods provide more accurate missing value estimation in six testing microarray datasets than the existing regression-based methods do. Conclusions Imputation of missing values is a very important aspect of microarray data analyses because most of the downstream analyses require a complete dataset. Therefore, exploring accurate and efficient methods for estimating missing values has become an essential issue. Since our proposed shrinkage regression-based methods can provide accurate missing value estimation, they are competitive alternatives to the existing regression-based methods. PMID:24565159

  19. Arthroscopic Thermal Capsular Shrinkage for Palmar Midcarpal Instability

    PubMed Central

    Hargreaves, David G.

    2014-01-01

    Background Arthroscopic capsular shrinkage has been previously used to stabilize major joints. This is the first series of its use in the wrist for palmar midcarpal instability (PMCI). Materials and Methods This is a medium-term retrospective review of 13 patients (15 wrists) at an average follow-up of 48 months postoperative. All patients were assessed with a functional questionnaire for instability and a Disabilities of the Arm, Shoulder, and Hand (DASH) score, as well as clinical examination. Description of Technique Arthroscopic capsular shrinkage was performed to the palmar and dorsal capsules of the radiocarpal and midcarpal joints using a bipolar thermal probe. All wrists were immobilized for 6 weeks post operation. Results 100% follow-up was achieved . All cases had an improvement in the frequency and severity of instability symptoms. The average DASH score was significantly reduced. There were no complications. The average loss of movement following the procedure was 15%. Conclusions The medium-term results show that wrist instability due to PMCI can be improved significantly by thermal capsular shrinkage with only a minimal amount of secondary stiffness. PMID:25097808

  20. 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

  1. Analysis of the Influence of Thermal Treatment on the Dry Turning of Al-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Salguero, J.; Carrilero, M. S.; Batista, M.; Álvarez, M.; Marcos, M.

    2009-11-01

    Manufacturing performance improvement must take into account economic, energetic and environmental considerations. Thus, when intermediate processes are avoided, manufacturing performance is improved from the three cited viewpoints. In the aerospace industry, pre-forms of UNS A92024 (Al-Cu) alloy-based structural elements are machined in T3 temper state previously to be thermally treated to reach O state, in order to facilitate its posterior plastic forming process. In this work, a comparative study of the dry turning of UNS A92024 alloy in both states has been carried out in order to eliminate the thermal treatment process. This study has been based on the finishing surface quality, cutting tool changes and chip arrangement. SOM/SEM/EDS analysis has shown that the main deviations are caused by secondary adhesion effects, which involve not only changes in the initial tool geometry but also a reduction of the chip shrinkage factor as a consequence of the lateral compression. However, the obtained results have revealed that alloy in O state can be dry-machined at cutting speeds higher than 120 m/min in order to reach similar quality levels as alloy in T3 state.

  2. Metallurgical factors on toughness in intercritically reheated HAZ of low-C low-alloy steel

    SciTech Connect

    Shiwaku, Toyoaki; Kobayashi, Yoichiro; Shimizu, Masato; Toyoda, Masao; Minami, Fumiyoshi

    1994-12-31

    Metallurgical factors on toughness in heat affected zone (HAZ) intercritically reheated between Ac1 and Ac3 were studied by welding thermal cycle simulation, because intercritically reheated HAZ has been, in general, recognized to be especially embrittled region in a multi-pass welded joint. The toughness of intercritical HAZ (ICHAZ) deteriorated with increasing cooling rate, while the toughness of intercritically reheated coarse grain HAZ (ICCGHAZ) deteriorated with decreasing cooling rate. It is found that the dominant metallurgical factor on toughness of ICHAZ is martensite-austenite (M-A) constituent, but those of ICCGHAZ are both M-A constituent and effective grain size depending on prior microstructure of ICCGHAZ.

  3. Optimal tumor shrinkage predicts long-term outcome in advanced nonsmall cell lung cancer (NSCLC) treated with target therapy

    PubMed Central

    He, Xiaobo; Zhang, Yang; Ma, Yuxiang; Zhou, Ting; Zhang, Jianwei; Hong, Shaodong; Sheng, Jin; Zhang, Zhonghan; Yang, Yunpeng; Huang, Yan; Zhang, Li; Zhao, Hongyun

    2016-01-01

    Abstract Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are used as standard therapies for advanced nonsmall cell lung cancer (NSCLC) patients with EGFR mutation positive. Because these targeted therapies could cause tumor necrosis and shrinkage, the purpose of the study is to search for a value of optimal tumor shrinkage as an appropriate indicator of outcome for advanced NSCLC. A total of 88 NSCLC enrollees of 3 clinical trials (IRESSA registration clinical trial, TRUST study and ZD6474 study), who received Gefitinib (250 mg, QD), Erlotinib (150 mg, QD), and ZD6474 (100 mg, QD), respectively, during December 2003 and October 2007, were retrospectively analyzed. The response evaluation criteria in solid tumors (RECIST) were used to identify responders, who had complete response (CR) or partial responses (PR) and nonresponders who had stable disease (SD) or progressive disease (PD). Receiver operating characteristics (ROC) analysis was used to find the optimal tumor shrinkage as an indicator for tumor therapeutic outcome. Univariate and multivariate Cox regression analyses were performed to compare the progression-free survival (PFS) and overall survival (OS) between responders and nonresponders stratified based on radiologic criteria. Among the 88 NSCLC patients, 26 were responders and 62 were nonresponders based on RECIST 1.0. ROC indicated that 8.32% tumor diameter shrinkage in the sum of the longest tumor diameter (SLD) was the cutoff point of tumor shrinkage outcomes, resulting in 46 responders (≤8.32%) and 42 nonresponders (≥8.32%). Univariate and multivariate Cox regression analyses indicated that (1) the responders (≤8.32%) and nonresponders (≥ −8.32%) were significantly different in median PFS (13.40 vs 1.17 months, P < 0.001) and OS (19.80 vs 7.90 months, P < 0.001) and (2) –8.32% in SLD could be used as the optimal threshold for PFS (hazard ratio [HR], 8.11, 95% CI, 3.75 to 17.51, P < 0.001) and OS

  4. 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. PMID:25039287

  5. Causal Factors of Weld Porosity in Gas Tungsten Arc Welding of Powder Metallurgy Produced Titanium Alloys

    SciTech Connect

    Muth, Thomas R; Yamamoto, Yukinori; Frederick, David Alan; Contescu, Cristian I; Chen, Wei; Lim, Yong Chae; Peter, William H; Feng, Zhili

    2013-01-01

    ORNL undertook an investigation using gas tungsten arc (GTA) welding on consolidated powder metallurgy (PM) titanium (Ti) plate, to identify the causal factors behind observed porosity in fusion welding. Tramp element compounds of sodium and magnesium, residual from the metallothermic reduction of titanium chloride used to produce the titanium, were remnant in the starting powder and were identified as gas forming species. PM-titanium made from revert scrap where sodium and magnesium were absent, showed fusion weld porosity, although to a lesser degree. We show that porosity was attributable to hydrogen from adsorbed water on the surface of the powders prior to consolidation. The removal / minimization of both adsorbed water on the surface of titanium powder and the residues from the reduction process prior to consolidation of titanium powders, are critical to achieve equivalent fusion welding success similar to that seen in wrought titanium produced via the Kroll process.

  6. Factors contributing to plastic strain amplification in slip dominated deformation of magnesium alloys

    NASA Astrophysics Data System (ADS)

    Sinclair, C. W.; Martin, G.; Lebensohn, R. A.

    2015-12-01

    While plastic strains are never distributed uniformly in polycrystals, it has recently been shown experimentally that the distribution can be extremely heterogeneous in magnesium polycrystals even when the deformation is dominated by slip. Here, we attempt to provide insight into the (macroscopic) factors that contribute to this strain amplification and to explain, from a local perspective, the origins of this strain amplification. To do this, full field VPFFT crystal plasticity simulations have been performed under the simplifying assumption that twinning is inoperative. It is shown that the experimentally observed heterogeneity can be reproduced when a sufficiently high anisotropy in slip system strength is assumed. This can be further accentuated by a weakening of the texture.

  7. Shrinkage and microstructural development during drying of organically modified silica xerogels

    SciTech Connect

    Raman, N.K.; Wallace, S.; Brinker, C.J. |

    1996-07-01

    We have studied the different driving forces behind syneresis in MTES/TEOS gels by aging them in different H{sub 2}O/EtOH pore fluids. We show using shrinkage, density, contact angle, and N{sub 2} sorption measurements, the influence of gel/solvent interactions on the microstructural evolution during drying. Competing effects of syneresis (that occurs during aging) and drying shrinkage resulted in the overall linear shrinkage of the organically modified gels to be constant at {approximately}50%. Increasing the hydrophobicity of the gels caused the driving force for syneresis to change from primarily condensation reactions to a combination of condensation and solid/liquid interfacial energy. In addition the condensation driven shrinkage was observed to be irreversible, whereas the interfacial free energy driven shrinkage was observed to be partially reversible. Nitrogen sorption experiments show that xerogels with the same overall extent of shrinkage can have vastly different microstructures due to the effects of microphase separation.

  8. Development of shrinkage resistant microfibre-reinforced cement-based composites

    NASA Astrophysics Data System (ADS)

    Hamedanimojarrad, P.; Adam, G.; Ray, A.; Thomas, P.; Vessalas, K.

    2012-06-01

    Different shrinkage types may cause serious durability dilemma on restrained concrete parts due to crack formation and propagation. Several classes of fibres are used by concrete industry in order to reduce crack size and crack number. In previous studies, most of these fibre types were found to be effective in reducing the number and sizes of the cracks, but not in shrinkage strain reduction. This study deals with the influence of a newly introduced type of polyethylene fibre on drying shrinkage reduction. The novel fibre is a polyethylene microfibre in a new geometry, which is proved to reduce the amount of total shrinkage in mortars. This special hydrophobic polyethylene microfibre also reduces moisture loss of mortar samples. The experimental results on short and long-term drying shrinkage as well as on several other properties are reported. The hydrophobic polyethylene microfibre showed promising improvement in shrinkage reduction even at very low concentrations (0.1% of cement weight).

  9. Effect of a weightlifting belt on spinal shrinkage.

    PubMed

    Bourne, N D; Reilly, T

    1991-12-01

    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. PMID:1810615

  10. Photoelastic study of shrinkage fitted components for a gasturbine engine

    NASA Astrophysics Data System (ADS)

    Govindaraju, T. V.; Maheshappa, H.; Govindaraju, N.; Gargesa, G.

    A 3D photoelastic model of shrink-fitted components of a gas turbine engine such as low-pressure main shaft and compressor adopter shaft (or hub) are used to perform a photo-elastic investigation of shrink-fitted components for different relative thickness ratio and different contact length ratio. The relative rigidity of the hub is found to increase as the relative thickness ratio increases, and the relative rigidity is found to increase as the contact length ratio decreases. An optimization of the geometry of the shrinkage-fitted components is also obtained.

  11. Dynamic Void Growth and Shrinkage in Mg under Electron Irradiation

    SciTech Connect

    Xu, W. Z.; Zhang, Y. F.; Cheng, G. M.; Jian, W. W.; Millett, P. C.; Koch, C. C.; Mathaudhu, S. N.; Zhu, Y. T.

    2014-04-30

    We report in-situ atomic-scale investigation of void evolution, including growth, coalescence and shrinkage, under electron irradiation. With increasing irradiation dose, the total volume of voids increased linearly, while nucleation rate of new voids decreased slightly, and the total number of voids decreased. Some voids continued to grow while others shrank to disappear, depending on the nature of their interactions with nearby self-interstitial loops. For the first time, surface diffusion of adatoms was observed largely responsible for the void coalescence and thickening. These findings provide fundamental understanding to help with the design and modeling of irradiation-resistant materials.

  12. 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. PMID:15790386

  13. 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.

  14. Controlling and understanding the polymerization shrinkage-induced stresses in light-cured composites.

    PubMed

    Suh, B I

    1999-01-01

    The shrinkage of composites induces stress in the final restoration when the composite is bonded to the tooth surface. The amount of stress can be controlled by the method of pulse-delay cure used. The development of new composites has changed the energy requirements for obtaining polymerization. The total energy required for optimal polymerization has been reduced and the rate at which the energy is delivered can have a strong effect on the final properties of the restoration. Newer composites may employ different photoinitiators, making the spectral emission from the curing light an important factor for properties of the final restoration. It is proposed that labels for composites carry: (1) indications for the total energy required; (2) specification of the pulse-delay cure if applicable; and (3) the required spectral bandwidth of the curing lamp light emission. PMID:11908394

  15. Shrinkage of the human core microbiome and a proposal for launching microbiome biobanks.

    PubMed

    Barzegari, Abolfazl; Saeedi, Nazli; Saei, Amir Ata

    2014-01-01

    The Human Microbiome Project (HMP) revealed the significance of the gut microbiome in promoting health. Disruptions in microbiome composition are associated with the pathogenesis of numerous diseases. The indigenous microflora has co-evolved with humans for millions of years and humans have preserved the inherited microbiomes through consumption of fermented foods and interactions with environmental microbes. Through modernization, traditional foods were abandoned, native food starters were substituted with industrial products, vaccines and antibiotics were used, extreme hygiene measures were taken, the rate of cesarean section increased, and breast feeding changed into formula. These factors have reduced human exposure to microbial symbionts and led to shrinkage of the core microbiome. Reduction in microbiome biodiversity can compromise the human immune system and predispose individuals to several modern diseases. This article suggests launching microbiome biobanks for archiving native microbiomes, supervising antibiotic use, probiotic design and native starter production, as well as advertising a revisit to native lifestyles. PMID:24957091

  16. Shrinkage Estimation of Varying Covariate Effects Based On Quantile Regression

    PubMed Central

    Peng, Limin; Xu, Jinfeng; Kutner, Nancy

    2013-01-01

    Varying covariate effects often manifest meaningful heterogeneity in covariate-response associations. In this paper, we adopt a quantile regression model that assumes linearity at a continuous range of quantile levels as a tool to explore such data dynamics. The consideration of potential non-constancy of covariate effects necessitates a new perspective for variable selection, which, under the assumed quantile regression model, is to retain variables that have effects on all quantiles of interest as well as those that influence only part of quantiles considered. Current work on l1-penalized quantile regression either does not concern varying covariate effects or may not produce consistent variable selection in the presence of covariates with partial effects, a practical scenario of interest. In this work, we propose a shrinkage approach by adopting a novel uniform adaptive LASSO penalty. The new approach enjoys easy implementation without requiring smoothing. Moreover, it can consistently identify the true model (uniformly across quantiles) and achieve the oracle estimation efficiency. We further extend the proposed shrinkage method to the case where responses are subject to random right censoring. Numerical studies confirm the theoretical results and support the utility of our proposals. PMID:25332515

  17. 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.

  18. Increasing the life of molds for casting copper and its alloys

    NASA Astrophysics Data System (ADS)

    Smirnov, A. N.; Spiridonov, D. V.

    2010-12-01

    The work of the molds intended for casting copper and copper alloys in semicontinuous casters for producing flat billets is considered. It is shown that, to increase the resistance of mold plates, the inner space of the mold should have a taper shape toward the casting direction and take into account the shrinkage of the linear dimensions of the ingot during its motion in the mold. The taper shape increases the intensity and uniformity of heat removal due to close contact between the ingot and the mold inner surface. Testing of new design molds under industrial conditions demonstrates that their resistance increases by a factor of 4.0-4.5. The taper effect of the mold plates is much more pronounced in their narrow faces.

  19. Shrinkage of renal tissue after impregnation via the cold Biodur plastination technique.

    PubMed

    Pereira-Sampaio, Marco A; Marques-Sampaio, Beatriz P S; Sampaio, Francisco J B; Henry, Robert W

    2011-08-01

    Thorough dehydration is a key for good plastination and invariably it leads to shrinkage. Shrinkage during plastination has been studied to lesser extent. Shrinkage was studied in 10 pig kidneys including regional shrinkage (cortex, medulla, sinus) and at which stages of the process (dehydration, impregnation, curing) shrinkage occurred. Kidneys were fixation by perfusion of 10% neutral buffered formalin solution via the renal artery. The vessels and ureter were filled with colored silicone (Dow Corning, Silastic E RTV Silicone Rubber) and the kidneys were cut into one centimeter transverse slices. Two slices of each kidney were plastinated via the classic von Hagens' method. Slices were photographed at the same focal length after preparation and at the end of each stage of plastination. Slice surface area was determined by a point-counting planimetry method. Post dehydration shrinkage of the kidney was 10.21% while post impregnation 10.11%. After completion of plastination, total area of kidney slice shrinkage was 19.72%. Cortical area shrunk 12.81% after dehydration and 13.16% after impregnation. After plastination, cortical area had shrunk 24.28%. No significant shrinkage occurred in the medulla and sinus. Results demonstrate that kidney shrinkage during impregnation is as intense as during dehydration. Significant shrinkage occurred in the renal cortex but not in the medulla and sinus. This demonstrates that different tissue types, even in the same specimen, have different rates of shrinkage during dehydration and impregnation. Therefore, plastinated specimens should be used carefully in research where obtaining measures is important. PMID:21714112

  20. The Effects of Metallurgical Factors on PWSCC Crack Growth Rates in TT Alloy 690 in Simulated PWR Primary Water

    NASA Astrophysics Data System (ADS)

    Yonezawa, Toshio; Watanabe, Masashi; Hashimoto, Atsushi

    2015-06-01

    Primary water stress corrosion cracking growth rates (PWSCCGRs) in highly cold-worked thermally treated (TT) Alloy 690 have been recently reported as exhibiting significant heat-to-heat variability. Authors hypothesized that these significant differences could be due to the metallurgical characteristics of each heat. In order to confirm this hypothesis, the effect of fundamental metallurgical characteristics on PWSCCGR measurements in cold-worked TT Alloy 690 has been investigated. The following new observations were made in this study: (1) Microcracks and voids were observed in or near eutectic crystals of grain boundary (GB) M23C6 carbides (primary carbides) after cold rolling, but were not observed before cold rolling. These primary carbides with microcracks and voids were observed in both lightly forged and as-cast and cold-rolled TT Alloy 690 (heat A) as well as in a cold-rolled TT Alloy 690 (heat Y) that simulated the chemical composition and carbide banded structure of the material previously tested by Paraventi and Moshier. However, this was not observed in precipitated (secondary) M23C6 GB carbides in heavily forged and cold-rolled TT Alloy 690 heat A and a cold-rolled commercial TT Alloy 690. (2) From microstructural analyses carried out on the various TT Alloy 690 test materials before and after cold rolling, the amount of eutectic crystals (primary carbides and nitrides) M23C6 and TiN depended on the chemical composition. In particular, the amount of M23C6 depended on the fabrication process. Microcracks and voids in or near the M23C6 and TiN precipitates were generated by the cold rolling process. (3) The PWSCCGRs observed in TT Alloy 690 were different for each heat and fabrication process. The PWSCCGR decreased with increasing Vickers hardness of each heat. However, for the same heats and fabrication processes, the PWSCCGR increased with increasing Vickers hardness due to cold work. Thus, the PWSCCGR must be affected not only by hardness (or

  1. 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.

  2. 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.

  3. Random effects and shrinkage estimation in capture-recapture models

    USGS Publications Warehouse

    Royle, J. Andrew; Link, W.A.

    2002-01-01

    We discuss the analysis of random effects in capture-recapture models, and outline Bayesian and frequentists approaches to their analysis. Under a normal model, random effects estimators derived from Bayesian or frequentist considerations have a common form as shrinkage estimators. We discuss some of the difficulties of analysing random effects using traditional methods, and argue that a Bayesian formulation provides a rigorous framework for dealing with these difficulties. In capture-recapture models, random effects may provide a parsimonious compromise between constant and completely time-dependent models for the parameters (e.g. survival probability). We consider application of random effects to band-recovery models, although the principles apply to more general situations, such as Cormack-Jolly-Seber models. We illustrate these ideas using a commonly analysed band recovery data set.

  4. BAYESIAN SHRINKAGE METHODS FOR PARTIALLY OBSERVED DATA WITH MANY PREDICTORS*

    PubMed Central

    Boonstra, Philip S.; Mukherjee, Bhramar; Taylor, Jeremy MG

    2013-01-01

    Motivated by the increasing use of and rapid changes in array technologies, we consider the prediction problem of fitting a linear regression relating a continuous outcome Y to a large number of covariates X, eg measurements from current, state-of-the-art technology. For most of the samples, only the outcome Y and surrogate covariates, W, are available. These surrogates may be data from prior studies using older technologies. Owing to the dimension of the problem and the large fraction of missing information, a critical issue is appropriate shrinkage of model parameters for an optimal bias-variance tradeoff. We discuss a variety of fully Bayesian and Empirical Bayes algorithms which account for uncertainty in the missing data and adaptively shrink parameter estimates for superior prediction. These methods are evaluated via a comprehensive simulation study. In addition, we apply our methods to a lung cancer dataset, predicting survival time (Y) using qRT-PCR (X) and microarray (W) measurements. PMID:24436727

  5. 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.

  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. PMID:24437766

  7. 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.

  8. Improvement in thermoelectric power factor of mechanically alloyed p-type SiGe by incorporation of TiB2

    NASA Astrophysics Data System (ADS)

    Ahmad, Sajid; Dubey, K.; Bhattacharya, Shovit; Basu, Ranita; Bhatt, Ranu; Bohra, A. K.; Singh, Ajay; Aswal, D. K.; Gupta, S. K.

    2016-05-01

    Nearly 60% of the world's useful energy is wasted as heat and recovering a fraction of this waste heat by converting it as useful electrical power is an important area of research[1]. Thermoelectric power generators (TEG) are solid state devices which converts heat into electricity. TEG consists of n and p-type thermoelements connected electrically in series and thermally in parallel[2]. Silicon germanium (SiGe) alloy is one of the conventional high temperature thermoelectric materials and is being used in radio-isotopes based thermoelectric power generators for deep space exploration programs.Temperature (T) dependence of thermoelectric (TE) properties of p-type SiGe and p-type SiGe-x wt.%TiB2 (x=6,8,10%) nanocomposite materials has been studied with in the temperature range of 300 K to 1100 K. It is observed that there is an improvement in the power factor (α2/ρ) of SiGe alloy on addition of TiB2 upto 8 wt.% that is mainly due to increase in the Seebeck coefficient (α) and electrical conductivity (σ) of the alloy.

  9. Ensemble Kalman filter implementations based on shrinkage covariance matrix estimation

    NASA Astrophysics Data System (ADS)

    Nino-Ruiz, Elias D.; Sandu, Adrian

    2015-11-01

    This paper develops efficient ensemble Kalman filter (EnKF) implementations based on shrinkage covariance estimation. The forecast ensemble members at each step are used to estimate the background error covariance matrix via the Rao-Blackwell Ledoit and Wolf estimator, which has been specifically developed to approximate high-dimensional covariance matrices using a small number of samples. Two implementations are considered: in the EnKF full-space (EnKF-FS) approach, the assimilation process is performed in the model space, while the EnKF reduce-space (EnKF-RS) formulation performs the analysis in the subspace spanned by the ensemble members. In the context of EnKF-RS, additional samples are taken from the normal distribution described by the background ensemble mean and the estimated background covariance matrix, in order to increase the size of the ensemble and reduce the sampling error of the filter. This increase in the size of the ensemble is obtained without running the forward model. After the assimilation step, the additional samples are discarded and only the model-based ensemble members are propagated further. Methodologies to reduce the impact of spurious correlations and under-estimation of sample variances in the context of the EnKF-FS and EnKF-RS implementations are discussed. An adjoint-free four-dimensional extension of EnKF-RS is also discussed. Numerical experiments carried out with the Lorenz-96 model and a quasi-geostrophic model show that the use of shrinkage covariance matrix estimation can mitigate the impact of spurious correlations during the assimilation process.

  10. Thermodynamic properties of La-Ga-Al and U-Ga-Al alloys and the separation factor of U/La couple in the molten salt-liquid metal system

    NASA Astrophysics Data System (ADS)

    Novoselova, A.; Smolenski, V.; Volkovich, V. A.; Ivanov, A. B.; Osipenko, A.; Griffiths, T. R.

    2015-11-01

    The electrochemical behaviour of lanthanum and uranium was studied in fused 3LiCl-2KCl eutectic and Ga-Al eutectic liquid metal alloy between 723 and 823 K. Electrode potentials were recorded vs. Cl-/Cl2 reference electrode and the temperature dependencies of the apparent standard potentials of La-(Ga-Al) and U-(Ga-Al) alloys were determined. Lanthanum and uranium activity coefficients and U/La couple separation factor were calculated. Partial excess free Gibbs energy, partial enthalpy of mixing and partial excess entropy of La-(Ga-Al) and U-(Ga-Al) alloys were estimated.

  11. Alloy materials

    DOEpatents

    Hans Thieme, Cornelis Leo; Thompson, Elliott D.; Fritzemeier, Leslie G.; Cameron, Robert D.; Siegal, Edward J.

    2002-01-01

    An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.

  12. Hot tearing evaluation for aluminium alloys

    NASA Astrophysics Data System (ADS)

    Brůna, Marek

    2016-06-01

    Hot tearing during solidification of aluminium alloys castings can be a serious problem. This phenomenon is well known but still insufficiently investigated. Hot tearing occurs in form of irregular cracks in metal castings that develop during solidification and cooling. The cause of hot tearing is generally attributed to the development of thermally induced tensile stresses and strains in a casting as the molten metal contracts during solidification and solid state shrinkage. Submited paper consists of two parts. The first part introduces the reader to the phenomenon of hot tearing. The second part describes newly developed method for assessing hot tearing susceptibility of aluminium alloys, and also gives the results on hot tearing for various aluminium alloys.

  13. 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. PMID:15265218

  14. Effect of light intensity on linear shrinkage of photo-activated composite resins during setting.

    PubMed

    Inoue, K; Howashi, G; Kanetou, T; Masumi, S; Ueno, O; Fujii, K

    2005-01-01

    The purpose of this investigation was to examine the effects of light intensity on linear shrinkage of photo-activated composite resins during setting. The materials used were four commercially available photo-activated composite resins. Three light-irradiation instruments were selected and prepared so as to obtain four light intensities (200, 480, 800 and 1600 mW cm(-2)). The linear shrinkage during setting was examined 10 min after light irradiation using a trial balance plastometer, and the specimen thickness was 2.0 mm for all materials. The depth of cure was examined according to the test method described in the International Organization for Standardization (ISO/FDIS 4049: 2000(E)). In measuring the linear shrinkage 60 s from the start of light irradiation for 10 s, there was a significant correlation (r = 0.89-0.94) between the amount of linear shrinkage and the light intensity: an increase in light intensity produced a greater linear shrinkage. Furthermore, there was a significant correlation (r = 0.92-1.0) between the linear shrinkage and the irradiation time: an increase in irradiation time resulted in a greater linear shrinkage. Values of the depth of cure ranged from 1.69 to 3.75 mm. PMID:15634297

  15. Cure shrinkage measurement of nonconductive adhesives by means of a thermomechanical analyzer

    NASA Astrophysics Data System (ADS)

    Yu, H.; Mhaisalkar, S. G.; Wong, E. H.

    2005-08-01

    The conductivity of a nonconductive adhesive (NCA) flip chip interconnect is completely dependent on the direct mechanical contact between the integrated circuit (IC) bump and substrate pad. Cure shrinkage of NCA is critical for the formation of the final contact force in the contacts. However, measurement of the cure shrinkage during cross-linking reaction is fairly difficult. This paper introduces a new, yet simple, approach to measure cure shrinkage of adhesives using a thermo-mechanical analyzer. Isothermal studies of shrinkage change as a function of curing show four distinct regions. First, the thickness of the epoxy decreases due to decreasing viscosity and applied load, followed by a stage where the dimension change is constant as the cross-linking reaction is yet to set in. Once cross-linking begins, the shrinkage reaches a maximum followed by a plateau where the cross-linking reaction has completed. Sharp changes of the slope of cure shrinkage versus degree of cure were observed to coincide with gelation and vitrification. After gelation, a linear relationship between the cure shrinkage and degree of cure was observed to extend until the occurrence of vitrification, which quenches the cross-linking reaction. Applied load in the range of 0.05 N was found to be optimal to minimize measurement errors.

  16. Numerical and experimental studies of drying and shrinkage induced microcracking in concrete

    NASA Astrophysics Data System (ADS)

    Jankovic, D.

    2007-12-01

    The aim of this research is to investigate moisture flow in cement paste and Interface Transition Zone, around aggregate, as well as associated shrinkage induced strains, and subsequent microcracking. Two coupled methods are used: numerical simulations and experiments. The moisture flow is numerically simulated by Lattice Gas Automata, while drying experiments are performed in Environmental Scanning Electron Microscope (ESEM) in order to determine drying deformations and shrinkage coefficient. The moisture movement simulation by Lattice Gas Automata, a type of cellular automata, involves different drying collision rules, which results in different density (moisture content) at each node. Special attention is given to the effect of the presence of aggregate particles on the moisture flow in concrete, which are considered rigid obstacles. The shrinkage deformation is considered a linear function of the moisture content if the relative humidity, RH does not exceed 40%. The calculated moisture gradient from the numerical analysis and an assumed shrinkage coefficient are used to calculate drying shrinkage induced strains and stresses using the basic equations. To determine the drying shrinkage coefficient for the RH range 100% to 20%, new experimental techniques of drying in ESEM are used. Small paste samples are cast in a specially developed mould with 2 mm thickness and afterwards carefully grounded and polished to a thickness of required 1 mm. The used variables in the tests are: various cement types, w/c ratio, sample age and curing conditions. Drying shrinkage displacements and strains are determined in order to calculate the drying shrinkage coefficient. These experimentally obtained values of the coefficient are compared with the literature data and used in numerical simulations of shrinkage induced strains, stresses and cracking in drying concrete.

  17. Modeling of the factors contributing to the initiation and propagation of the crevice corrosion of alloy 625

    SciTech Connect

    Lillard, R.S.; Scully, J.R. )

    1994-11-01

    Crevice corrosion of alloy 625 in both chlorinated and nonchlorinated American Society for Testing and Materials (ASTM) artificial ocean water was modeled. Secondary current and potential distributions as a function of crevice depth were obtained from the model using the following crevice initiation criteria (1) E < E[sub Flade], (2) i[sub diss] = 10 [mu]A/cm[sup 2], and (3) pH [approximately]0.46 at the site where the first two criteria are met. For alloy 625 in nonchlorinated ASTM artificial ocean water these criteria are satisfied at depths which are near the mouth of the crevice. These depths are incompatible with the mass-transport conditions governing the development of the critical crevice solution. In the chlorinated system the model predicts that initiation occurs at greater depths which are compatible with all the critical crevice solution. In the chlorinated system the model predicts that initiation occurs at greater depths which are compatible with all the criteria including mass-transport considerations. The model results are in agreement with remote crevice assembly experiments which show that crevice corrosion occurs more readily in the chlorinated ASTM artificial ocean water. Propagation of the crevice corrosion of alloy 625 is shown to be ohmically controlled by the resistance between the mouth of the crevice and the initiation site.

  18. Thermomechanical simulation of the selective laser melting process for PA12 including volumetric shrinkage

    NASA Astrophysics Data System (ADS)

    Riedlbauer, D.; Steinmann, P.; Mergheim, J.

    2015-05-01

    The present contribution is concerned with the finite element simulation of the thermomechanical material behavior in the selective laser melting process for PA12. In the process shrinkage of the powder material is observed when becoming melt, as the porous character of the powder vanishes due to the phase transition. A nonlinear thermomechanical finite element model is developed, which captures the shrinkage of the material and includes temperature dependent material parameters. The model is used to simulate the shrinkage of the material in the process, where an adaptive mesh refinement is applied for increasing the accuracy of the simulation. The results are qualitatively compared with experimental data and show a good agreement.

  19. 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.

  20. Obligate Insect Endosymbionts Exhibit Increased Ortholog Length Variation and Loss of Large Accessory Proteins Concurrent with Genome Shrinkage

    PubMed Central

    Kenyon, Laura J.; Sabree, Zakee L.

    2014-01-01

    Extreme genome reduction has been observed in obligate intracellular insect mutualists and is an assumed consequence of fixed, long-term host isolation. Rapid accumulation of mutations and pseudogenization of genes no longer vital for an intracellular lifestyle, followed by deletion of many genes, are factors that lead to genome reduction. Size reductions in individual genes due to small-scale deletions have also been implicated in contributing to overall genome shrinkage. Conserved protein functional domains are expected to exhibit low tolerance for mutations and therefore remain relatively unchanged throughout protein length reduction while nondomain regions, presumably under less selective pressures, would shorten. This hypothesis was tested using orthologous protein sets from the Flavobacteriaceae (phylum: Bacteroidetes) and Enterobacteriaceae (subphylum: Gammaproteobacteria) families, each of which includes some of the smallest known genomes. Upon examination of protein, functional domain, and nondomain region lengths, we found that proteins were not uniformly shrinking with genome reduction, but instead increased length variability and variability was observed in both the functional domain and nondomain regions. Additionally, as complete gene loss also contributes to overall genome shrinkage, we found that the largest proteins in the proteomes of nonhost-restricted bacteroidetial and gammaproteobacterial species often were inferred to be involved in secondary metabolic processes, extracellular sensing, or of unknown function. These proteins were absent in the proteomes of obligate insect endosymbionts. Therefore, loss of genes encoding large proteins not required for host-restricted lifestyles in obligate endosymbiont proteomes likely contributes to extreme genome reduction to a greater degree than gene shrinkage. PMID:24671745

  1. Stabilization of vacuum arc remelting of steels and alloys

    NASA Astrophysics Data System (ADS)

    Belyanchikov, L. N.

    2012-12-01

    The main cause of the electrode mass melting rate oscillations during vacuum arc remelting (VAR) of steels and alloys is shown to be the displacement of an arc into zones with different metallic vapor pressures. For the remelting process to be stabilized, the arc space length should be controlled as a function of the electrode melting rate and the shrinkage defects in cast electrodes should be removed by high-temperature gasostatic treatment.

  2. INTER-GROUP IMAGE REGISTRATION BY HIERARCHICAL GRAPH SHRINKAGE

    PubMed Central

    Ying, Shihui; Wu, Guorong; Liao, Shu; Shen, Dinggang

    2013-01-01

    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. PMID:24443692

  3. 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.

  4. 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

    2015-01-01

    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

  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. Study of the Effect of Shrinkage Porosity on Strength Low Carbon Cast Steel

    NASA Astrophysics Data System (ADS)

    Ol'khovik, E.

    2015-09-01

    Today there are many computer systems for modeling of the casting technology processes. All of them allow calculating the availability and distribution of the shrinkage porosity in the test casting, but this information allows only making changes in existing casting technology. In this paper you obtain the information about changes in the local and structural mechanical properties of the casting in the presence of its volume shrinkage porosity. Article presents the results of direct experimental studies of technological defects (shrinkage and gas porosity) impact on the mechanical properties of low carbon steel castings. Methods of investigation are also disclosed, including the methods for producing of molded samples obtained at different process conditions and the crystallization apparatus which is described for the measuring of the density of the samples. There are the mathematical relationship for the elastic modulus, yield stress, elongation and fatigue characteristics fracture cast steel with low carbon content in the presence of the volumetric shrinkage porosity.

  7. Increasing Item Complexity: A Possible Cause of Scale Shrinkage for Unidimensional Item Response Theory.

    ERIC Educational Resources Information Center

    Yen, Wendy M.

    1985-01-01

    An approximate relationship is devised between the unidimensional model used in data analysis and a multidimensional model hypothesized to be generating the item responses. Scale shrinkage is successfully predicted for several sets of simulated data. (Author/LMO)

  8. 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

  9. Electron-beam induced photoresist shrinkage influence on 2D profiles

    NASA Astrophysics Data System (ADS)

    Bunday, Benjamin; Cordes, Aaron; Allgair, John; Aguilar, Daniel Bellido; Tileli, Vasiliki; Thiel, Bradley; Avitan, Yohanan; Peltinov, Ram; Bar-Zvi, Mayaan; Adan, Ofer; Chirko, Konstantin

    2010-03-01

    For many years, lithographic resolution has been the main obstacle in keeping the pace of transistor densification to meet Moore's Law. For the 32 nm node and beyond, new lithography techniques will be used, including immersion ArF (iArF) lithography and extreme ultraviolet lithography (EUVL). As in the past, these techniques will use new types of photoresists with the capability to print smaller feature widths and pitches. Also, such smaller feature sizes will require thinner layers of photoresists, such as under 100 nm. In previous papers, we focused on ArF and iArF photoresist shrinkage. We evaluated the magnitude of shrinkage for both R&D and mature resists as a function of chemical formulation, lithographic sensitivity, scanning electron microscope (SEM) beam condition, and feature size. Shrinkage results were determined by the well accepted methodology described in ISMI's CD-SEM Unified Specification. A model for resist shrinkage, while derived elsewhere, was presented, that can be used to curve-fit to the shrinkage data resulting from multiple repeated measurements of resist features. Parameters in the curve-fit allow for metrics quantifying total shrinkage, shrinkage rate, and initial critical dimension (CD) before e-beam exposure. With these parameters and exhaustive measurements, a fundamental understanding of the phenomenology of the shrinkage trends was achieved, including how the shrinkage behaves differently for different sized features. This work was extended in yet another paper in which we presented a 1-D model for resist shrinkage that can be used to curve-fit to shrinkage curves. Calibration of parameters to describe the photoresist material and the electron beam were all that were required to fit the model to real shrinkage data, as long as the photoresist was thick enough that the beam could not penetrate the entire layer of resist. In this paper, we extend this work yet again to a 2-D model of a trapezoidal photoresist profile. This model thus

  10. 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. PMID:27251997

  11. The effect of solidification rate on the growth of small fatigue cracks in a cast 319-type aluminum alloy

    SciTech Connect

    Caton, M.J.; Jones, J.W.; Boileau, J.M.; Allison, J.E.

    1999-12-01

    A study was conducted to investigate the effect of solidification rate on the growth behavior of small fatigue cracks in a 319-type aluminum alloy, a common Al-Si-Cu alloy used in automotive castings. Fatigue specimens were taken from cast material that underwent a hot isostatic pressing (HIP) process in order to eliminate shrinkage pores and to facilitate the observation of surface-initiated cracks by replication. Naturally initiated surface cracks ranging in length from 17 {micro}m to 2 mm were measured using a replication technique. Growth rates of the small cracks were calculated as a function of the elastic stress-intensity-factor range ({Delta}K). Long-crack growth-rate data (10 mm {le} length {le} 25 mm) were obtained from compact-tension (CT) specimens, and comparison to the small-crack data indicates the existence of a significant small-crack effect in this alloy. The solidification rate is shown to have a significant influence on small-crack growth behavior, with faster solidification rates resulting in slower growth rates at equivalent {Delta}K levels. A stress-level effect is also observed for both solidification rates, with faster growth rates occurring at higher applied-stress amplitudes at a given {Delta}K. A crack-growth relation proposed by Nisitani and others is modified to give reasonable correlation of small-crack growth data to different solidification rates and stress levels.

  12. The effect of solidification rate on the growth of small fatigue cracks in a cast 319-type aluminum alloy

    NASA Astrophysics Data System (ADS)

    Caton, M. J.; Jones, J. Wayne; Boileau, J. M.; Allison, J. E.

    1999-12-01

    A study was conducted to investigate the effect of solidification rate on the growth behavior of small fatigue cracks in a 319-type aluminum alloy, a common Al-Si-Cu alloy used in automotive castings. Fatigue specimens were taken from cast material that underwent a hot isostatic pressing (HIP) process in order to eliminate shrinkage pores and to facilitate the observation of surface-initiated cracks by replication. Naturally initiated surface cracks ranging in length from 17 µm to 2 mm were measured using a replication technique. Growth rates of the small cracks were calculated as a function of the elastic stress-intensity-factor range (Δ K). Long-crack growth-rate data (10 mm≤length≤25 mm) were obtained from compact-tension (CT) specimens, and comparison to the small-crack data indicates the existence of a significant small-crack effect in this alloy. The solidification rate is shown to have a significant influence on small-crack growth behavior, with faster solidification rates resulting in slower growth rates at equivalent Δ K levels. A stress-level effect is also observed for both solidification rates, with faster growth rates occurring at higher applied-stress amplitudes at a given Δ K. A crack-growth relation proposed by Nisitani and others is modified to give reasonable correlation of small-crack growth data to different solidification rates and stress levels.

  13. Reducing the drying shrinkage of cement paste by admixture surface treatments

    SciTech Connect

    Xu, Y.; Chung, D.D.L.

    2000-02-01

    The drying shrinkage of concrete during curing is a source of residual stress and cracks. The problem is particularly severe for a large structure, such as a large concrete floor. Surface treatment of carbon fibers and/or silica fume by silane prior to using these admixtures in cement paste increases the effectiveness of these admixtures for reducing the drying shrinkage. Silane treatment of fibers is more effective than dichromate treatment or ozone treatment.

  14. 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.

  15. Shrinkage stress in concrete under dry-wet cycles: an example with concrete column

    NASA Astrophysics Data System (ADS)

    Gao, Yuan; Zhang, Jun; Luosun, Yiming

    2014-02-01

    This paper focuses on the simulation of shrinkage stress in concrete structures under dry-wet environments. In the modeling, an integrative model for autogenous and drying shrinkage predictions of concrete under dry-wet cycles is introduced first. Second, a model taking both cement hydration and moisture diffusion into account synchronously is used to calculate the distribution of interior humidity in concrete. Using the above two models, the distributions of shrinkage strain and stress in concrete columns made by normal and high strength concrete respectively under dry-wet cycles are calculated. The model results show that shrinkage gradient along the radial direction of the column from the center to outer surface increases with age as the outer circumference suffers to dry. The maximum and minimum shrinkage occur at the outer surface and the center of the column, respectively, under drying condition. As wetting starts, the shrinkage strain decreases with increase of interior humidity. The closer to the wetting face, the higher the humidity and the lower the shrinkage strain, as well as the lower the shrinkage stress. As results of the dry-wet cycles acting on the outer circumference of the column, cyclic stress status is developed within the area close to the outer surface of the column. The depth of the influencing zone of dry-wet cyclic action is influenced by concrete strength and dry-wet regime. For low strength concrete, relatively deeper influencing zone is expected compared with that of high strength concrete. The models are verified by concrete-steel composite ring tests and a good agreement between model and test results is found.

  16. 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. PMID:26132112

  17. 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.

  18. Development of a rapid cure polydimethylsiloxane replication process with near-zero shrinkage

    NASA Astrophysics Data System (ADS)

    Badshah, Mohsin Ali; Jang, Hyungjun; Kim, Young Kyu; Kim, Tae-Hyoung; Kim, Seok-min

    2014-07-01

    Replicated polydimethylsiloxane (PDMS) micro/nanostructures are widely used in various research fields due to their inexpensiveness, flexibility, low surface energy, good optical properties, biocompatibility, chemical inertness, high durability, and easy fabrication process. However, the application of PDMS micro/nanostructures is limited when an accurate pattern shape or position is required because of the shrinkage that occurs during the PDMS curing process. In this study, we analyzed the effects of processing parameters in the PDMS replication process on the shrinkage of the final structure. Although the shrinkage can be decreased by decreasing the curing temperature, this reduction also increases the unnecessary curing time. To minimize the inherent shrinkage in the PDMS replica without an accompanying curing time increase, we propose a PDMS replication process on a high modulus substrate (glass and polymer films) with compression pressure, in which the adhesion force between the substrate and the PDMS, and the compression pressure prevent shrinkage during the curing process. Using the proposed method, a PDMS replica with less than 0.1% in-plane and vertical shrinkage was obtained at a curing temperature of 150°C and a curing time of 10 min.

  19. Dental resins based on dimer acid dimethacrylates: a route to high conversion with low polymerization shrinkage.

    PubMed

    Lu, Hui; Trujillo-Lemon, Marianela; Ge, Junhao; Stansbury, Jeffrey W

    2010-05-01

    Incomplete polymerization, volumetric shrinkage, and shrinkage stress are among the primary disadvantages of current resin-based dental composites. Generally, any attempt to increase final double bond conversion only exacerbates polymerization shrinkage and stress. The use of dimer acid-derived dimethacrylate (DADMA) monomers in novel dental resin formulations is examined in this article as a potential means to address these disparate goals. A series of high molecular weight DADMA monomers with different functional groups used to connect the C36 dimer acid core and the methacrylates were formulated with urethane dimethacrylate (UDMA) and/or ethoxylated bisphenol A dimethacrylate (Bis-EMA) at various compositions to manipulate comonomer compatibility and polymeric mechanical properties. Along with reaction kinetics, dynamic polymerization shrinkage and shrinkage stress were assessed. Specific DADMA monomers demonstrated limited miscibility with either Bis-EMA or UDMA. Appropriate ternary resin formulations produced homogeneous monomeric mixtures capable of controlled polymerization-induced phase separation (PIPS) to yield heterogeneous final polymers. Reduced polymerization shrinkage and stress along with higher conversion was observed for DADMA ternary systems compared with a bisphenol A glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) resin control. The PIPS process resulted in a modest volume recovery and stress relaxation in the later stages of polymerization. These results indicate that certain dimer acid-derived dimethacrylates possess the potential to replace TEGDMA as a reactive diluent in dental resins that display a favorable and unique combination of properties. PMID:20521567

  20. Predominant factor determining wear properties of β-type and (α+β)-type titanium alloys in metal-to-metal contact for biomedical applications.

    PubMed

    Lee, Yoon-Seok; Niinomi, Mitsuo; Nakai, Masaaki; Narita, Kengo; Cho, Ken

    2015-01-01

    The predominant factor determining the wear properties of a new titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ) and a conventional titanium alloy, Ti-6Al-4V extra-low interstitial (Ti64) was investigated for TNTZ and Ti64 combinations in metal-to-metal contacting bio-implant applications. The worn surfaces, wear debris, and subsurface damages were analyzed using a scanning electron microscopy combined with energy-dispersive spectroscopy and electron-back scattered diffraction analysis. The volume loss of TNTZ is found to be larger than that of Ti64, regardless of the mating material. The wear track of TNTZ exhibits the galled regions and severe plastic deformation with large flake-like debris, indicative of delamination wear, which strongly suggests the occurrence of adhesive wear. Whereas, the wear track of Ti64 have a large number of regular grooves and microcuttings with cutting chip-like wear debris and microfragmentation of fine oxide debris, indicative of abrasive wear combined with oxidative wear. This difference in the wear type is caused by severe and mild subsurface deformations of TNTZ and Ti64, respectively. The lower resistance to plastic shearing for TNTZ compared to that of Ti64 induces delamination, resulting in a higher wear rate. PMID:25460417

  1. Evaluating the geochemically induced swelling/shrinkage of the near-field host clay rock using a THC model and the diffuse double layer theory

    NASA Astrophysics Data System (ADS)

    Zheng, L.; Liu, H.; Birkholzer, J. T.; Houseworth, J. E.; Sonnenthal, E. L.

    2011-12-01

    One advantage of emplacing nuclear waste in a clay formation is the potential self-sealing capability due to clay swelling. The swelling properties of the near-field host clay rock can be altered due to geochemical factors, including changes in groundwater geochemistry, proportions of exchangeable cations, and swelling clay mineral abundances. The clay host rock can also undergo geochemical changes due to the interaction with the engineered barrier system (EBS) materials. In this paper, coupled thermal, hydrological, and chemical (THC) models are linked with a swelling model based on diffuse double layer (DDL) theory and changes in the swelling properties of clay host rocks in the near field area are evaluated. Findings based on THC simulations using the reaction-transport code TOUGHREACT include: 1) Significant changes in the swelling pressure could be expected depending on various hydrogeologic and geochemical conditions. The change of hydration rate of the EBS (via the adjustment of tortuosity) could have significant effect on the swelling pressure. 2) Geochemically-induced swelling/shrinkage only occurs in the near-field area, within a few meters from the EBS interface. 3) Swelling/shrinkage induced porosity change is generally much smaller than that caused by mineral precipitation/dissolution. 4) The geochemically-induced swelling/shrinkage of host clay rock is the combined effect of variation in the pore water geochemistry, exchangeable cations, and smectite abundance. Neglecting any of these three latter factors might lead to a miscalculation of the geochemically-induced swelling pressure.

  2. Effectiveness of shrinkage and variable selection methods for the prediction of complex human traits using data from distantly related individuals.

    PubMed

    Berger, Swetlana; Pérez-Rodríguez, Paulino; Veturi, Yogasudha; Simianer, Henner; de los Campos, Gustavo

    2015-03-01

    Genome-wide association studies (GWAS) have detected large numbers of variants associated with complex human traits and diseases. However, the proportion of variance explained by GWAS-significant single nucleotide polymorphisms has been usually small. This brought interest in the use of whole-genome regression (WGR) methods. However, there has been limited research on the factors that affect prediction accuracy (PA) of WGRs when applied to human data of distantly related individuals. Here, we examine, using real human genotypes and simulated phenotypes, how trait complexity, marker-quantitative trait loci (QTL) linkage disequilibrium (LD), and the model used affect the performance of WGRs. Our results indicated that the estimated rate of missing heritability is dependent on the extent of marker-QTL LD. However, this parameter was not greatly affected by trait complexity. Regarding PA our results indicated that: (a) under perfect marker-QTL LD WGR can achieve moderately high prediction accuracy, and with simple genetic architectures variable selection methods outperform shrinkage procedures and (b) under imperfect marker-QTL LD, variable selection methods can achieved reasonably good PA with simple or moderately complex genetic architectures; however, the PA of these methods deteriorated as trait complexity increases and with highly complex traits variable selection and shrinkage methods both performed poorly. This was confirmed with an analysis of human height. PMID:25600682

  3. Effectiveness of Shrinkage and Variable Selection Methods for the Prediction of Complex Human Traits using Data from Distantly Related Individuals

    PubMed Central

    Pérez‐Rodríguez, Paulino; Veturi, Yogasudha; Simianer, Henner; de los Campos, Gustavo

    2015-01-01

    Summary Genome‐wide association studies (GWAS) have detected large numbers of variants associated with complex human traits and diseases. However, the proportion of variance explained by GWAS‐significant single nucleotide polymorphisms has been usually small. This brought interest in the use of whole‐genome regression (WGR) methods. However, there has been limited research on the factors that affect prediction accuracy (PA) of WGRs when applied to human data of distantly related individuals. Here, we examine, using real human genotypes and simulated phenotypes, how trait complexity, marker‐quantitative trait loci (QTL) linkage disequilibrium (LD), and the model used affect the performance of WGRs. Our results indicated that the estimated rate of missing heritability is dependent on the extent of marker‐QTL LD. However, this parameter was not greatly affected by trait complexity. Regarding PA our results indicated that: (a) under perfect marker‐QTL LD WGR can achieve moderately high prediction accuracy, and with simple genetic architectures variable selection methods outperform shrinkage procedures and (b) under imperfect marker‐QTL LD, variable selection methods can achieved reasonably good PA with simple or moderately complex genetic architectures; however, the PA of these methods deteriorated as trait complexity increases and with highly complex traits variable selection and shrinkage methods both performed poorly. This was confirmed with an analysis of human height. PMID:25600682

  4. Testing Departure from Additivity in Tukey’s Model using Shrinkage: Application to a Longitudinal Setting

    PubMed Central

    Ko, Yi-An; Mukherjee, Bhramar; Smith, Jennifer A.; Park, Sung Kyun; Kardia, Sharon L.R.; Allison, Matthew A.; Vokonas, Pantel S.; Chen, Jinbo; Diez-Roux, Ana V.

    2014-01-01

    While there has been extensive research developing gene-environment interaction (GEI) methods in case-control studies, little attention has been given to sparse and efficient modeling of GEI in longitudinal studies. In a two-way table for GEI with rows and columns as categorical variables, a conventional saturated interaction model involves estimation of a specific parameter for each cell, with constraints ensuring identifiability. The estimates are unbiased but are potentially inefficient because the number of parameters to be estimated can grow quickly with increasing categories of row/column factors. On the other hand, Tukey’s one degree of freedom (df) model for non-additivity treats the interaction term as a scaled product of row and column main effects. Due to the parsimonious form of interaction, the interaction estimate leads to enhanced efficiency and the corresponding test could lead to increased power. Unfortunately, Tukey’s model gives biased estimates and low power if the model is misspecified. When screening multiple GEIs where each genetic and environmental marker may exhibit a distinct interaction pattern, a robust estimator for interaction is important for GEI detection. We propose a shrinkage estimator for interaction effects that combines estimates from both Tukey’s and saturated interaction models and use the corresponding Wald test for testing interaction in a longitudinal setting. The proposed estimator is robust to misspecification of interaction structure. We illustrate the proposed methods using two longitudinal studies — the Normative Aging Study and the Multi-Ethnic Study of Atherosclerosis. PMID:25112650

  5. Modelling of micro- and macrosegregation for industrial multicomponent aluminium alloys

    NASA Astrophysics Data System (ADS)

    Ellingsen, K.; Mortensen, D.; M'Hamdi, M.

    2015-06-01

    Realistic predictions of macrosegregation formation during casting of aluminium alloys requires an accurate modeling of solute microsegregation accounting for multicomponent phase diagrams and secondary phase formation. In the present work, the stand alone Alstruc model, a microsegregation model for industrial multicomponent aluminium alloys, is coupled with the continuum model ALSIM which calculates the macroscopic transport of mass, enthalpy, momentum, and solutes as well as stresses and deformation during solidification of aluminium. Alstruc deals with multicomponent alloys accounting for temperature dependent partition coefficients, liquidus slopes and the precipitation of secondary phases. The challenge associated with computation of microsegregation for multicomponent alloys is solved in Alstruc by approximating the phase diagram data by simple, analytical expressions which allows for a CPU-time efficient coupling with the macroscopic transport model. In the present work, the coupled model has been applied in a study of macrosegregation including thermal and solutal convection, solidification shrinkage and surface exudation on an industrial DC-cast billet.

  6. 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

  7. 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

  8. Improving reliability of subject-level resting-state fMRI parcellation with shrinkage estimators.

    PubMed

    Mejia, Amanda F; Nebel, Mary Beth; Shou, Haochang; Crainiceanu, Ciprian M; Pekar, James J; Mostofsky, Stewart; Caffo, Brian; Lindquist, Martin A

    2015-05-15

    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 cortex by

  9. Ni{sub 3}Al aluminide alloys

    SciTech Connect

    Liu, C.T.

    1993-10-01

    This paper provides a brief review of the recent progress in research and development of Ni{sub 3}Al and its alloys. Emphasis has been placed on understanding low ductility and brittle fracture of Ni{sub 3}Al alloys at ambient and elevated temperatures. Recent studies have resulted in identifying both intrinsic and extrinsic factors governing the fracture behavior of Ni{sub 3}Al alloys. Parallel efforts on alloy design using physical metallurgy principles have led to properties for structural use. Industrial interest in these alloys is high, and examples of industrial involvement in processing and utilization of these alloys are briefly mentioned.

  10. Casting Characteristics of Aluminum Die Casting Alloys

    SciTech Connect

    Makhlouf M. Makhlouf; Diran Apelian

    2002-02-05

    The research program investigates the casting characteristics of selected aluminum die casting alloys. Specifically, the alloys' tendencies towards die soldering and sludge formation, and the alloys' fluidity and machinability are evaluated. It was found that: When the Fe and Mn contents of the alloy are low; caution has to be taken against possible die soldering. When the alloy has a high sludge factor, particularly a high level of Fe, measures must be taken to prevent the formation of large hardspots. For this kind of alloy, the Fe content should be kept at its lowest allowable level and the Mn content should be at its highest possible level. If there are problems in die filling, measures other than changing the alloy chemistry need to be considered first. In terms of alloy chemistry, the elements that form high temperature compounds must be kept at their lowest allowable levels. The alloys should not have machining problems when appropriate machining techniques and machining parameters are used.

  11. Correcting the Shrinkage Effects of Formalin Fixation and Tissue Processing for Renal Tumors: toward Standardization of Pathological Reporting of Tumor Size

    PubMed Central

    Tran, Thu; Sundaram, Chandru P.; Bahler, Clinton D.; Eble, John N.; Grignon, David J.; Monn, M. Francesca; Simper, Novae B.; Cheng, Liang

    2015-01-01

    Given the importance of correctly staging renal cell carcinomas, specific guidelines should be in place for tumor size measurement. While a standard means of renal tumor measurement has not been established, intuitively, tumor size should be based on fresh measurements. We sought to assess the accuracy of postfixation and microscopic measurements of renal tumor size, as compared to fresh measurements and radiographic size. Thirty-four nephrectomy cases performed by a single surgeon were prospectively measured at different time points. The study cases included 23 clear cell renal cell carcinomas, 6 papillary renal cell carcinomas, and 5 other renal tumors. Radiologic tumors were 12.1% larger in diameter than fresh tumors (P<0.01). Furthermore, fresh specimens were 4.6% larger than formalin-fixed specimens (P<0.01), and postfixation measurements were 7.1% greater than microscopic measurements (P<0.01). The overall mean percentage of shrinkage between fresh and histological specimens was 11.4% (P<0.01). Histological processing would cause a tumor stage shift from pT1b to pT1a for two tumors in this study. The shrinkage effects of formalin fixation and histological processing may result in understaging of renal cell carcinomas. The shrinkage factor should be considered when reporting tumor size. PMID:26185538

  12. Survival Outcome Assessed According to Tumor Response and Shrinkage Pattern in Patients with EGFR Mutation–Positive Non–Small-Cell Lung Cancer Treated with Gefitinib or Erlotinib

    PubMed Central

    Takeda, Masayuki; Nakagawa, Kazuhiko

    2014-01-01

    Introduction: Somatic mutations in the epidermal growth factor receptor gene (EGFR) are associated with a marked therapeutic response to EGFR–tyrosine kinase inhibitors (TKIs) in patients with advanced non–small cell lung cancer (NSCLC). Clinical indicators of the likely survival benefit of EGFR-TKI treatment in NSCLC patients with EGFR mutations have not been identified, however. We therefore evaluated progression-free survival (PFS) and overall survival (OS) according to tumor response and tumor shrinkage pattern in such patients. Methods: Among 145 EGFR mutation–positive NSCLC patients treated with EGFR-TKIs, 68 individuals were selected for analysis. Results: Of the 68 selected patients, 6 achieved a complete response (CR), 42 a partial response (PR), and 14 stable disease (SD). Both PFS and OS were significantly longer in patients who achieved a CR or PR than in those who experienced SD. Multivariate analysis showed that a response (CR or PR) to EGFR-TKIs was significantly associated with both PFS and OS. Among the CR/PR group, the median maximal tumor shrinkage relative to baseline was 56%, and the median time to response (TTR) was 4.2 weeks. The subsets of these patients who experienced rapid tumor regression (TTR of ≤4.2 weeks) or a high degree of tumor shrinkage (≥56%) did not show a more favorable PFS or OS compared with those who experienced slow tumor regression or a low degree of tumor shrinkage. Conclusion: Response (CR or PR) may represent the optimal surrogate for efficacy among EGFR mutation–positive NSCLC patients treated with EGFR-TKIs. PMID:24419417

  13. Method of fabricating thin-walled articles of tungsten-nickel-iron alloy

    DOEpatents

    Hovis, V.M. Jr.; Northcutt, W.G. Jr.

    The present invention relates to a method for fabricating thin-walled high-density structures of tungsten-nickel-iron alloys. A powdered blend of the selected alloy constituents is plasma sprayed onto a mandrel having the desired article configuration. The sprayed deposit is removed from the mandrel and subjected to liquid phase sintering to provide the alloyed structure. The formation of the thin-walled structure by plasma spraying significantly reduces shrinkage, and cracking while increasing physical properties of the structure over that obtainable by employing previously known powder metallurgical procedures.

  14. Method of fabricating thin-walled articles of tungsten-nickel-iron alloy

    DOEpatents

    Hovis, Jr., Victor M.; Northcutt, Jr., Walter G.

    1982-01-01

    The present invention relates to a method for fabricating thin-walled high-density structures oftungsten-nickel-iron alloys. A powdered blend of the selected alloy constituents is plasma sprayed onto a mandrel having the desired article configuration. The sprayed deposit is removed from the mandrel and subjected to liquid phase sintering to provide the alloyed structure. The formation of the thin-walled structure by plasma spraying significantly reduces shrinkage, and cracking while increasing physical properties of the structure over that obtainable by employing previously known powder metallurgical procedures.

  15. Non-Ionotropic NMDA Receptor Signaling Drives Activity-Induced Dendritic Spine Shrinkage

    PubMed Central

    Stein, Ivar S.; Gray, John A.

    2015-01-01

    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 Ca2+ 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 Ca2+ 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. SIGNIFICANCE STATEMENT 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 Ca2+ influx through NMDA-type glutamate receptors (NMDARs) in conjunction with long

  16. Concentration-dependent specimen shrinkage in iodine-enhanced microCT

    PubMed Central

    Vickerton, Paula; Jarvis, Jonathan; Jeffery, Nathan

    2013-01-01

    Iodine potassium iodide (I2KI) solution can be employed as a contrast agent for the visualisation of soft tissue structures in micro-computed tomography studies. This technique provides high resolution images of soft tissue non-destructively but initial studies suggest that the stain can cause substantial specimen shrinkage. The degree of specimen shrinkage, and potential deformation, is an important consideration when using the data for morphological studies. Here we quantify the macroscopic volume changes in mouse skeletal muscle, cardiac muscle and cerebellum as a result of immersion in the common fixatives 10% phosphate-buffered formal saline, 70% ethanol and 3% glutaraldehyde, compared with I2KI staining solution at concentrations of 2, 6, 10 and 20%. Immersion in the I2KI solution resulted in dramatic changes of tissue volume, which were far larger than the shrinkage from formalin fixation alone. The degree of macroscopic change was most dependent upon the I2KI concentration, with severe shrinkage of 70% seen in solutions of 20% I2KI after 14 days' incubation. When using this technique care needs to be taken to use the lowest concentration that will give adequate contrast to minimise artefacts due to shrinkage. PMID:23721431

  17. 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.

  18. 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

  19. 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.

  20. Effects of Prepolymerized Particle Size and Polymerization Kinetics on Volumetric Shrinkage of Dental Modeling Resins

    PubMed Central

    Ha, Jung-Yun; Chun, Ju-Na; Son, Jun Sik; Kim, Kyo-Han

    2014-01-01

    Dental modeling resins have been developed for use in areas where highly precise resin structures are needed. The manufacturers claim that these polymethyl methacrylate/methyl methacrylate (PMMA/MMA) resins show little or no shrinkage after polymerization. This study examined the polymerization shrinkage of five dental modeling resins as well as one temporary PMMA/MMA resin (control). The morphology and the particle size of the prepolymerized PMMA powders were investigated by scanning electron microscopy and laser diffraction particle size analysis, respectively. Linear polymerization shrinkage strains of the resins were monitored for 20 minutes using a custom-made linometer, and the final values (at 20 minutes) were converted into volumetric shrinkages. The final volumetric shrinkage values for the modeling resins were statistically similar (P > 0.05) or significantly larger (P < 0.05) than that of the control resin and were related to the polymerization kinetics (P < 0.05) rather than the PMMA bead size (P = 0.335). Therefore, the optimal control of the polymerization kinetics seems to be more important for producing high-precision resin structures rather than the use of dental modeling resins. PMID:24779020

  1. A Shrinkage Method for Testing the Hardy-Weinberg Equilibrium in Case-Control Studies

    PubMed Central

    Zang, Yong; Yuan, Ying

    2014-01-01

    Testing for the Hardy-Weinberg equilibrium (HWE) is often used as an initial step for checking the quality of genotyping. When testing the HWE for case-control data, the impact of a potential genetic association between the marker and the disease must be controlled for otherwise the results may be biased. Li and Li (2008) proposed a likelihood ratio test (LRT) that accounts for this potential genetic association and it is more powerful than the commonly used control-only χ2 test. However, the LRT is not efficient when the marker is independent of the disease, and also requires numerical optimization to calculate the test statistic. In this article, we propose a novel shrinkage test for assessing the HWE. The proposed shrinkage test yields higher statistical power than the LRT when the marker is independent of or weakly associated with the disease, and converges to the LRT when the marker is strongly associated with the disease. In addition, the proposed shrinkage test has a closed form and can be easily used to test the HWE for large datasets that result from genome-wide association studies. We compare the performance of the shrinkage test with existing methods using simulation studies, and apply the shrinkage test to a genome-wide association dataset for Alzheimer’s disease. PMID:23934751

  2. Perceptual shrinkage of a one-way motion path with high-speed motion.

    PubMed

    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

  3. 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

  4. Polymerization shrinkage stress measurement for a UV-curable resist in nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Amirsadeghi, Alborz; Jong Lee, Jae; Park, Sunggook

    2011-11-01

    A simple method was developed to obtain the polymerization shrinkage stress exerted on the sidewalls of resist/stamp interface in ultraviolet nanoimprint lithography. This method is based on the measurements of demolding force which is the sum of adhesion and friction forces. The mean polymerization shrinkage stress on the sidewalls can readily be decoupled from overall demolding force by independently measuring the friction coefficient, adhesion force and geometries of stamp structures. The polymerization shrinkage stress on the sidewalls is overall larger than adhesion and increases by adding more cross-linking agent to the resist composition. This indicates that in addition to lowering the adhesion at the resist/stamp interface, development of resists with low degrees of shrinkage during UV curing is critical to reducing demolding force. It was also found that the shrinkage stress depends not only on the resist composition but also the stamp structure. A pillar structured stamp leads to a larger stress than a stamp with gratings with identical depth and width.

  5. Photoresist cross-sectional shape change caused by scanning electron microscope-induced shrinkage

    NASA Astrophysics Data System (ADS)

    Ohashi, Takeyoshi; Sekiguchi, Tomoko; Yamaguchi, Atsuko; Tanaka, Junichi; Kawada, Hiroki

    2015-07-01

    Change in the cross-sectional profile of a photoresist (PR) pattern due to shrinkage was evaluated to investigate the mechanism of electron beam-induced shrinkage. A scanning transmission electron microscope (STEM) was used to observe the cross-sectional profiles of PR lines after atomic-layer deposition of metal oxide and carbon deposition on the sample surface. A HfO2 thin layer enhanced the profile contrast in the STEM measurements without blurring the edge, which enabled the precise cross-sectional measurement of the PR patterns. We found interesting features associated with shrinkage from the detailed profile change obtained using this method, such as a rounding of the pattern top, a necking of the sidewall profile, a rounding of the foot in the pattern on the organic underlying layer, and voltage-independent sidewall shrinkage under a large electron beam dose. These behaviors along with the results from a Monte Carlo simulation are discussed. Consequently, these observations experimentally clarified that the elastic deformation effect and the impact of the secondary electrons emitted from the spaces around the pattern into the sidewall are important to interpret the change in the shape of the pattern induced by shrinkage.

  6. In situ investigation of the shrinkage of photopolymerized micro/nanostructures: the effect of the drying process.

    PubMed

    Sun, Quan; Ueno, Kosei; Misawa, Hiroaki

    2012-02-15

    We report on experimental study of the shrinkage of photopolymerized micro/nanostructures fabricated by femtosecond direct laser writing in organic-inorganic resists. Blueshift of the stop-band positions of fabricated photonic crystals during the drying process, which follows the development and rinsing stages, indicates that the drying process plays an important role in the formation of the shrinkage. It is further confirmed that the shrinkage almost completely occurs during the drying process by in situ optical monitoring the structures. These findings will help to better understand, control, and even positively utilize the shrinkage in the applications of the photopolymerization-based direct laser writing technique. PMID:22344156

  7. Three-dimensional X-ray micro-computed tomography analysis of polymerization shrinkage vectors in flowable composite.

    PubMed

    Takemura, Yukihiko; Hanaoka, Koji; Kawamata, Ryota; Sakurai, Takashi; Teranaka, Toshio

    2014-01-01

    The polymerization shrinkage of flowable resin composites was evaluated using air bubbles as traceable markers. Three different surface treatments i.e. an adhesive silane coupling agent, a separating silane coupling agent, and a combination of both, were applied to standard cavities. Before and after polymerization, X-ray micro-computed tomography images were recorded. Their superimposition and comparison allowed position changes of the markers to be visualized as vectors. The movement of the markers in the resin composite was, therefore, quantitatively evaluated from the tomographic images. Adhesion was found to significantly influence shrinkage patterns. The method used here could be employed to visualize shrinkage vectors and shrinkage volume. PMID:24988881

  8. Measurement of polymerization-shrinkage evolution during curing in photopolymer with a white-light Fabry-Pérot interferometer.

    PubMed

    Kawana, Masaru; Takahashi, Jun-ichiro; Guo, Jinxin; Tomita, Yasuo

    2015-06-15

    We propose a simple method of measuring polymerization-shrinkage evolution during curing in photopolymer. The real-time spectral fringe analysis of a broadband beam transmitted through a Fabry-Pérot etalon supported by a photopolymer film provides the shrinkage evolution during curing. For the proof-of-principle demonstration a blue-sensitized nanoparticle-polymer composite material is used. It is shown that the measured shrinkage dynamics are well correlated with the photo-calorimetric conversion dynamics of monomer to polymer. We also discuss a discrepancy in steady-state shrinkage between our proposed and holographic Bragg-angle detuning measurements. PMID:26193515

  9. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1963-02-26

    A brazing alloy which, in the molten state, is characterized by excellent wettability and flowability, said alloy being capable of forming a corrosion resistant brazed joint wherein at least one component of said joint is graphite and the other component is a corrosion resistant refractory metal, said alloy consisting essentially of 20 to 50 per cent by weight of gold, 20 to 50 per cent by weight of nickel, and 15 to 45 per cent by weight of molybdenum. (AEC)

  10. VANADIUM ALLOYS

    DOEpatents

    Smith, K.F.; Van Thyne, R.J.

    1959-05-12

    This patent deals with vanadium based ternary alloys useful as fuel element jackets. According to the invention the ternary vanadium alloys, prepared in an arc furnace, contain from 2.5 to 15% by weight titanium and from 0.5 to 10% by weight niobium. Characteristics of these alloys are good thermal conductivity, low neutron capture cross section, good corrosion resistance, good welding and fabricating properties, low expansion coefficient, and high strength.

  11. Temperature dependence of band gap ratio and Q-factor defect mode in a semiconductor quaternary alloy hexagonal photonic-crystal hole slab

    NASA Astrophysics Data System (ADS)

    Sánchez-Cano, R.; Porras-Montenegro, N.

    2016-04-01

    We present numerical predictions for the photonic TE-like band gap ratio and the quality factors of symmetric localized defect as a function of the thickness slab and temperature by the use of plane wave expansion and the finite-difference time-domain methods. The photonic-crystal hole slab is composed of a 2D hexagonal array with identical air holes and a circular cross section, embedded in a non-dispersive III-V semiconductor quaternary alloy slab, which has a high value of dielectric function in the near-infrared region, and the symmetric defect is formed by increasing the radius of a single hole in the 2D hexagonal lattice. We show that the band gap ratio depends linearly on the temperature in the range 150-400 K. Our results show a strong temperature dependence of the quality factor Q, the maximum (Q = 7000) is reached at T = 350 hbox {K}, but if the temperature continues to increase, the efficiency drops sharply. Furthermore, we present numerical predictions for the electromagnetic field distribution at T = 350 hbox {K}.

  12. Treatment of ligament laxity by electrothermal shrinkage or surgical plication: a morphologic and mechanical comparison.

    PubMed

    Hill, Adam M; Jones, Ioan T; Hansen, Ulrich; Suri, Amrita; Sandison, Ann; Moss, Jill; Wallace, Andrew L

    2007-01-01

    Capsular plication or thermal shrinkage can be used to enhance surgical joint stabilization. We compared mechanical or morphologic properties of the medial collateral ligament of the rabbit knee treated by either bipolar radiofrequency electrothermal shrinkage or surgical plication. After 12 weeks, the medial collateral ligaments were procured from treated and contralateral knees to undergo viscoelastic (creep) testing, quantitative transmission electron microscopy, and immunohistochemistry. Creep strain in thermal (1.85% +/- 0.32%) and plicated (1.92% +/- 0.36%) ligaments was almost twice that of the control group (1.04% +/- 0.15%), although there was no difference between treatment modalities. The morphologic parameters of all 3 groups were significantly different (P < .001). The thermal ligaments demonstrated predominantly small fibrils, whereas the plicated group displayed an intermediate distribution of heterogeneous fibrils, suggesting a different pattern of remodeling. Viscoelastic properties are similar after thermal shrinkage or plication, though inferior to those of intact ligaments. PMID:17030129

  13. Ultra low-K shrinkage behavior when under electron beam in a scanning electron microscope

    SciTech Connect

    Lorut, F.; Imbert, G.; Roggero, A.

    2013-08-28

    In this paper, we investigate the tendency of porous low-K dielectrics (also named Ultra Low-K, ULK) behavior to shrink when exposed to the electron beam of a scanning electron microscope. Various experimental electron beam conditions have been used for irradiating ULK thin films, and the resulting shrinkage has been measured through use of an atomic force microscope tool. We report the shrinkage to be a fast, cumulative, and dose dependent effect. Correlation of the shrinkage with incident electron beam energy loss has also been evidenced. The chemical modification of the ULK films within the interaction volume has been demonstrated, with a densification of the layer and a loss of carbon and hydrogen elements being observed.

  14. Fast approach to infrared image restoration based on shrinkage functions calibration

    NASA Astrophysics Data System (ADS)

    Zhang, Chengshuo; Shi, Zelin; Xu, Baoshu; Feng, Bin

    2016-05-01

    High-quality image restoration in real time is a challenge for infrared imaging systems. We present a fast approach to infrared image restoration based on shrinkage functions calibration. Rather than directly modeling the prior of sharp images to obtain the shrinkage functions, we calibrate them for restoration directly by using the acquirable sharp and blurred image pairs from the same infrared imaging system. The calibration method is employed to minimize the sum of squared errors between sharp images and restored images from the blurred images. Our restoration algorithm is noniterative and its shrinkage functions are stored in the look-up tables, so an architecture solution of pipeline structure can work in real time. We demonstrate the effectiveness of our approach by testing its quantitative performance from simulation experiments and its qualitative performance from a developed wavefront coding infrared imaging system.

  15. Shrinkage of microstructures produced by two-photon polymerization of Zr-based hybrid photosensitive materials.

    PubMed

    Ovsianikov, Aleksandr; Shizhou, Xiao; Farsari, Maria; Vamvakaki, Maria; Fotakis, Costas; Chichkov, Boris N

    2009-02-16

    An investigation of the shrinking behaviour of a zirconium-based sol-gel composite micro-structured by two-photon polymerization is presented and a simple, straightforward methodology allowing the evaluation of shrinkage is suggested. It is shown that volume reduction is directly related to the average laser power (irradiation dose) used for the microfabrication and becomes a critical issue near the polymerization threshold. It is demonstrated that this shrinkage can be employed beneficially to improve the structural resolution. This is demonstrated by the presence of stopbands in the photonic crystal nanostructures fabricated with controlled volume reduction. Well above the polymerization threshold, the studied material exhibits remarkably low shrinkage. Therefore, no additional effort for the pre-compensation of distortion and for the improvement of structural stability is required. PMID:19219118

  16. Numerical evaluation of angular multiplexing in reflection-type holographic data storage in photopolymer with shrinkage.

    PubMed

    Yonetani, Yusuke; Nitta, Kouichi; Matoba, Osamu

    2010-02-01

    We evaluate numerically the effect of shrinkage of photopolymer on the bit error rate or signal-to-noise ratio in a reflection-type holographic data storage system with angular multiplexing. In the evaluation, we use a simple model where the material is divided into layered structures and then the shrinkage rate is proportional to the intensity in each layer. We present the effectiveness of the proposed model from the experimental results in the recording of the plane waves both in a transmission-type hologram and a reflection-type one. Several kinds of shrinkage rates are used to evaluate the characteristics of angular multiplexing in the reflection-type holographic memory. PMID:20119021

  17. Polymerization shrinkage and contraction force of composite resin restorative inserted with "Megafiller".

    PubMed

    Tani, Y; Nambu, T; Ishikawa, A; Katsuyama, S

    1993-12-01

    This study quantified the contraction force and polymerization shrinkage of composite resins with/without beta-Quartz Glass Ceramic Inserts (BQCI) as "Megafiller". The materials used for the determination included a chemically cured composite and five light-cured composites. The system for measuring contraction force consisted of a transparent teflon tube for preparing the specimen, a small load cell, a dynamic strain gauge and a pen-recorder. After the composite was packed into the teflon mold, a BQCI (Type R3) was inserted through the opening and the specimen was cured. Linear polymerization shrinkage of the composites was measured every 10 seconds from the start of mixing or irradiation to 90 minutes by the mercury bath method. Three pieces each of BQCI (Type T3) were inserted in each specimen. The results suggested that BQCI was markedly effective in reducing polymerization shrinkage, but was not always effective in reducing the contraction force during polymerization. PMID:8004912

  18. 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.

  19. Dental composite resins: measuring the polymerization shrinkage using optical fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Ottevaere, H.; Tabak, M.; Chah, K.; Mégret, P.; Thienpont, H.

    2012-04-01

    Polymerization shrinkage of dental composite materials is recognized as one of the main reasons for the development of marginal leakage between a tooth and filling material. As an alternative to conventional measurement methods, we propose optical fiber Bragg grating (FBG) based sensors to perform real-time strain and shrinkage measurements during the curing process of dental resin cements. We introduce a fully automated set-up to measure the Bragg wavelength shift of the FBG strain sensors and to accurately monitor the linear strain and shrinkage of dental resins during curing. Three different dental resin materials were studied in this work: matrix-filled BisGMA-based resins, glass ionomers and organic modified ceramics.

  20. Shrinkage control in a photopolymerizable hybrid solgel material for holographic recording.

    PubMed

    Ramos, Gonzalo; Alvarez-Herrero, Alberto; Belenguer, Tomas; del Monte, Francisco; Levy, David

    2004-07-10

    We report the correction of the shrinkage observed during UV postrecording curing in a holographic solgel material that was recently achieved by the use of various chemical formulations for the composition of the hybrid supporting matrix. We found that a chemical modification of the matrix noticeably attenuates the shrinkage (from 1.3% to 0.4% of the material's initial thickness with the inclusion of just 20% tetramethylorthosilicate), providing a material with improved stability for permanent data storage applications. The holographic properties of samples with different binders are also reported. In addition, a theoretical study has revealed the way by which to compensate for angular deviation in the Bragg condition during UV postrecording by tailoring the binder shrinkage (s), the maximum refractive-index modulation capability of the photosensitive mixture (deltan), or both. PMID:15285093

  1. Hormone-dependent shrinkage of a sphenoid wing meningioma after pregnancy: case report.

    PubMed

    Kerschbaumer, Johannes; Freyschlag, Christian F; Stockhammer, Günter; Taucher, Susanne; Maier, Hans; Thomé, Claudius; Seiz-Rosenhagen, Marcel

    2016-01-01

    Meningiomas are known to be associated with female sex hormones. Worsening neurological symptoms or newly diagnosed meningiomas have been described in the context of elevated levels of sex hormones, for example, in pregnancy. To the authors' knowledge, tumor shrinkage after the normalization of hormones has not been described, even if it is known that neurological deficits due to meningioma compression may improve after giving birth. A 32-year-old female patient presented with severe headache and vision disturbances at the end of her second pregnancy. Magnetic resonance imaging revealed an extended mass at the lateral left-sided sphenoid wing that was suspected to be a meningioma. After delivery, the patient's symptoms improved, and MRI obtained 2 months postpartum showed significant shrinkage of the lesion. Significant tumor shrinkage can occur after pregnancy. Thus, repeat imaging is indicated in these patients. PMID:26162042

  2. Shrinkage of polyurethane molecular stamp fixed on epoxy resin modified glass substrate

    NASA Astrophysics Data System (ADS)

    Liu, Zhengchun; He, Quanguo; Xiao, Pengfeng; Tang, Jianxin; He, Nongyue; Lu, Zuhong

    2003-01-01

    The shrinkage of polyurethane stamps used for the in situ synthesis of DNA microarrays via molecular stamping method was studied with Micron XYZ Scope. It was found that the polyurethane stamp fixed on the epoxy resin modified glass strongly and showed minimum linear shrinkage. The linear shrinkage of the whole polyurethane stamp and that of each feature of polyurethane stamp were controlled within 0.0341% and 0.309%, respectively, which were due to the strong van der Waals forces and hydrogen bonds between polyurethane and epoxy resin. It was also confirmed by scanning electron microscope that the polyurethane stamp fixed on the epoxy resin modified glass replicated the patterns of motherboard with a high fidelity. All these underlay the synthesis of DNA microarray through molecular stamping method.

  3. Shrinkage of freeze-dried cryosections of cells: Investigations by EFTEM and cryo-CLEM.

    PubMed

    Casanova, G; Nolin, F; Wortham, L; Ploton, D; Banchet, V; Michel, J

    2016-09-01

    Freeze-drying of cryosections of cells or tissues is considered to be the most efficient preparation for microanalysis purpose related to transmission electron microscopy. It allows the measurements of ions and water contents at the ultrastructural level. However an important drawback is associated to freeze-drying: the shrinkage of the cryosections. The aim of this paper is the investigation of this phenomenon by means of three different methods applied to both hydrated and dehydrated cryosections: direct distance measurements on fiducial points, thickness measurements by energy filtered transmission microscopy (EFTEM) and cryo-correlative light electron microscopy (cryo-CLEM). Measurements in our experimental conditions reveal a lateral shrinkage around 10% but the most important result concerns the lack of differential shrinkage between most of the cellular compartments. PMID:27428286

  4. Precise measurement of photoresist cross-sectional shape change caused by SEM-induced shrinkage

    NASA Astrophysics Data System (ADS)

    Ohashi, Takeyoshi; Sekiguchi, Tomoko; Yamaguchi, Atsuko; Tanaka, Junichi; Kawada, Hiroki

    2013-04-01

    The mechanism of photoresist shrinkage induced by electron-beam (EB) irradiation was studied. A precise cross-sectional profile of a photoresist pattern was obtained by a scanning transmission electron microscope (STEM) after atomic layer deposition of HfO2 on the sample patterns. Photoresist lines and spaces fabricated with positive-tone development and negative-tone development were exposed to an EB with much higher dose than a practical dose (to accelerate shrinkage intentionally). The obtained STEM images of the patterns before and after EB irradiation show that the shrinkage of the negative-tone-developed patterns is smaller than that of the positive-tone-developed patterns. This observation is explained by the fact that negative-tone-developed photoresist molecules do not contain protection groups, whose volatilization caused by EB irradiation is one of the origins of shrinkage. Another finding is that the EB irradiation causes top-rounding and necking of the pattern profile as well as linewidth slimming. The rounding of the pattern top profile suggests that the pattern's shape was elastically deformed. In addition, EB irradiation only onto the spaces caused sidewall shrinkage and a necking profile, although no electrons were irradiated directly onto the pattern. These phenomena are considered to be due to the electrons scattered from the spaces to the pattern sidewall. Finally, a Monte Carlo simulation of electron scattering showed that the distribution of the deposited EB energy on the pattern surface corresponds to the above-described change in pattern shape. Consequently, these observations and simulation results clarify the importance of the effect of elastic shape change and the impact of the electrons scattered from the underlying layer onto the sidewall in the mechanism of photoresist shrinkage.

  5. Band-gap shrinkage calculations and analytic model for strained bulk InGaAsP

    NASA Astrophysics Data System (ADS)

    Connelly, Michael J.

    2015-02-01

    Band-gap shrinkage is an important effect in semiconductor lasers and optical amplifiers. In the former it leads to an increase in the lasing wavelength and in the latter an increase in the gain peak wavelength as the bias current is increased. The most common model used for carrier-density dependent band-gap shrinkage is a cube root dependency on carrier density, which is strictly only true for high carrier densities and low temperatures. This simple model, involves a material constant which is treated as a fitting parameter. Strained InGaAsP material is commonly used to fabricate polarization insensitive semiconductor optical amplifiers (SOAs). Most mathematical models for SOAs use the cube root bandgap shrinkage model. However, because SOAs are often operated over a wide range of drive currents and input optical powers leading to large variations in carrier density along the amplifier length, for improved model accuracy it is preferable to use band-gap shrinkage calculated from knowledge of the material bandstructure. In this letter the carrier density dependent band-gap shrinkage for strained InGaAsP is calculated by using detailed non-parabolic conduction and valence band models. The shrinkage dependency on temperature and both tensile and compressive strain is investigated and compared to the cube root model, for which it shows significant deviation. A simple power model, showing an almost square-root dependency, is derived for carrier densities in the range usually encountered in InGaAsP laser diodes and SOAs.

  6. Regional Brain Shrinkage over Two Years: Individual Differences and Effects of Pro-Inflammatory Genetic Polymorphisms

    PubMed Central

    Persson, N.; Ghisletta, P.; Dahle, C.L.; Bender, A.R.; Yang, Y.; Yuan, P.; Daugherty, A.M.; Raz, N.

    2014-01-01

    We examined regional changes in brain volume in healthy adults (N = 167, age 19-79 years at baseline; N = 90 at follow-up) over approximately two years. With latent change score models, we evaluated mean change and individual differences in rates of change in 10 anatomically-defined and manually-traced regions of interest (ROIs): lateral prefrontal cortex (LPFC), orbital frontal cortex (OF), prefrontal white matter (PFw), hippocampus (HC), parahippocampal gyrus (PhG), caudate nucleus (Cd), putamen (Pt), insula (In), cerebellar hemispheres (CbH), and primary visual cortex (VC). Significant mean shrinkage was observed in the HC, CbH, In, OF, and the PhG, and individual differences in change were noted in all regions, except the OF. Pro-inflammatory genetic variants mediated shrinkage in PhG and CbH. Carriers of two T alleles of interleukin-1β (IL-1βC-511T, rs16944) and a T allele of methylenetetrahydrofolate reductase (MTHFRC677T, rs1801133) polymorphisms showed increased PhG shrinkage. No effects of a pro-inflammatory polymorphism for C-reactive protein (CRP-286C>A>T, rs3091244) or apolipoprotein (APOE) ε4 allele were noted. These results replicate the pattern of brain shrinkage observed in previous studies, with a notable exception of the LPFC thus casting doubt on the unique importance of prefrontal cortex in aging. Larger baseline volumes of CbH and In were associated with increased shrinkage, in conflict with the brain reserve hypothesis. Contrary to previous reports, we observed no significant linear effects of age and hypertension on regional brain shrinkage. Our findings warrant further investigation of the effects of neuroinflammation on structural brain change throughout the lifespan. PMID:25264227

  7. Shrinkage Study of Polypropylene Films Laminated on Steel-Influence of the Conformation Processes

    NASA Astrophysics Data System (ADS)

    Ponçot, Marc; Martin, Julien; Dahoun, Abdesselam; Hiver, Jean-Marie; Bourson, Patrice; Verchère, Didier

    2011-05-01

    Nowadays, thermoplastic polymers do not cease to attract the interest of the industrialists as steel / polymer composites for various applications in several domains, such as the automotive and the packaging. The ratio between their wide range of thermo-mechanical properties and their low weight density make these materials a real alternative for the current solutions for the lightening and the reinforcement of structural pieces. Likewise, their working facility is a major asset for performing parts of complex geometry. In this paper, we highlight the narrow relationship between the microstructure of a small impact isotactic polypropylene film, either filled or not by mineral particles (calcite), and its behaviour towards shrinkage which can occur during thermal treatments above its melting temperature. This phenomenon of shrinkage is characterized by dimensional instabilities which can in particular, affect the life cycle of the material. Indeed, they may induce the partial delamination of the steel sheet which is consequently exposed to various environmental aggressions. Corrosive behaviour can occur and cause early breakdown of the material. Influences of the extrusion and stamping processes on the microstructure and the shrinkage are presented. The macromolecular chains orientation of the crystalline phase, the volume damage and the heating parameters are studied, and show a real impact on the phenomenon magnitude. An experimental setup was developed at the laboratory to measure in real-time and with good precision, the displacements induced by shrinkage and the microstructural evolution of the polymer film during different thermal cycles. Finally, an empirical law allowing the shrinkage prediction is presented, taking into account the deformation value and the initial degree of chains orientation. These studies and their results have led to the determination of the optimal parameters settings for the different conformation processes with the aim of reducing

  8. Properties evaluation of silorane, low-shrinkage, non-flowable and flowable resin-based composites in dentistry

    PubMed Central

    Reis, Rodrigo S.; Moro, André F.V.; Perez, Cesar R.; Pessôa, Bárbara M.; Dias, Katia R.H.C.

    2015-01-01

    Purpose. This study tested the null hypothesis that different classes of direct restorative dental materials: silorane-based resin, low-shrinkage and conventional (non-flowable and flowable) resin-based composite (RBC) do not differ from each other with regard to polymerization shrinkage, depth of cure or microhardness. Methods. 140 RBC samples were fabricated and tested by one calibrated operator. Polymerization shrinkage was measured using a gas pycnometer both before and immediately after curing with 36 J/cm2 light energy density. Depth of cure was determined, using a penetrometer and the Knoop microhardness was tested from the top surface to a depth of 5 mm. Results. Considering polymerization shrinkage, the authors found significant differences (p < 0.05) between different materials: non-flowable RBCs showed lower values compared to flowable RBCs, with the silorane-based resin presenting the smallest shrinkage. The low shrinkage flowable composite performed similarly to non-flowable with significant statistical differences compared to the two other flowable RBCs. Regarding to depth of cure, low-shrinkage flowable RBC, were most effective compared to other groups. Microhardness was generally higher for the non-flowable vs. flowable RBCs (p < 0.05). However, the values for low-shrinkage flowable did not differ significantly from those of non-flowable, but were significantly higher than those of the other flowable RBCs. Clinical Significance. RBCs have undergone many modifications as they have evolved and represent the most relevant restorative materials in today’s dental practice. This study of low-shrinkage RBCs, conventional RBCs (non-flowable and flowable) and silorane-based composite—by in vitro evaluation of volumetric shrinkage, depth of cure and microhardness—reveals that although filler content is an important determinant of polymerization shrinkage, it is not the only variable that affects properties of materials that were tested in this study

  9. OPTIMAL SHRINKAGE ESTIMATION OF MEAN PARAMETERS IN FAMILY OF DISTRIBUTIONS WITH QUADRATIC VARIANCE

    PubMed Central

    Xie, Xianchao; Kou, S. C.; Brown, Lawrence

    2015-01-01

    This paper discusses the simultaneous inference of mean parameters in a family of distributions with quadratic variance function. We first introduce a class of semi-parametric/parametric shrinkage estimators and establish their asymptotic optimality properties. Two specific cases, the location-scale family and the natural exponential family with quadratic variance function, are then studied in detail. We conduct a comprehensive simulation study to compare the performance of the proposed methods with existing shrinkage estimators. We also apply the method to real data and obtain encouraging results. PMID:27041778

  10. Sparsity-based shrinkage approach for practicability improvement of H-LBP-based edge extraction

    NASA Astrophysics Data System (ADS)

    Zhao, Chenyi; Qiao, Shuang; Sun, Jianing; Zhao, Ruikun; Wu, Wei

    2016-07-01

    The local binary pattern with H function (H-LBP) technique enables fast and efficient edge extraction in digital radiography. In this paper, we reformulate the model of H-LBP and propose a novel sparsity-based shrinkage approach, in which the threshold can be adapted to the data sparsity. Using this model, we upgrade fast H-LBP framework and apply it to real digital radiography. The experiments show that the method improved using the new shrinkage approach can avoid elaborately artificial modulation of parameters and possess greater robustness in edge extraction compared with the other current methods without increasing processing time.

  11. Selected mechanical and physical properties and clinical application of a new low-shrinkage composite restoration.

    PubMed

    Duarte, Sillas; Botta, Ana Carolina; Phark, Jin-Ho; Sadan, Avishai

    2009-09-01

    Polymerization shrinkage is a major concern for bonded direct posterior restorations. Recently, a new low-shrinkage composite resin restorative material was developed. However, few data are available regarding clinical manipulation of this composite. Silorane-based composites represent an alternative to conventional methacrylate-based composites for direct posterior restorations. This article critically discusses the latest peer-reviewed reports related to polymerization, bonding, polishing, and color stability of silorane composite, focusing on its clinical application. Initial evaluation of this new category of composite material shows acceptable mechanical and physical properties. PMID:19639087

  12. Compressible cake filtration: monitoring cake formation and shrinkage using synchrotron X-rays

    SciTech Connect

    Bierck, B.R.; Wells, S.A.; Dick, R.I.

    1988-05-01

    High energy, highly collimated X-rays produced at the Cornell High Energy Synchrotron Sources (CHESS) enabled real-time suspended solids concentration measurements each second with 0.5 mm vertical separation in a kaolin filter cake. Suspended solids concentration profiles reflected expected effects of cumulative fluid drag forces. Shrinkage caused a significant increase in average cake suspended solids concentration after expiration of the slurry, and the saturated cake ultimately formed was virtually homogeneous. Shrinkage is consolidation under compressive forces created when capillary menisci form at air/liquid interfaces, and has a significant effect on cake structure in latter stages of compressible cake filtration.

  13. Visualization study of the shrinkage void distribution in thermal energy storage capsules of different geometry

    SciTech Connect

    Revankar, Shripad T.; Croy, Travis

    2007-01-15

    The presence of concentrated shrinkage voids in thermal energy storage systems employing encapsulated phase change material can cause serious problems when one attempts to melt the solidified phase change material for the next thermal cycle. Experiments were performed and void-formation phenomena with rectangular flat plate, spherical, and torus shape capsules were investigated. The initial void growth, distribution and the total void in the capsule were photographically studied from transparent capsules using cyclohexane, hexadecane, butanediol and octadecane as phase change materials. The observations on freezing process and the shrinkage void distribution are presented. (author)

  14. Determination of the dynamic stress intensity factors for 7075-T6 aluminum alloy using the reflected caustic method

    SciTech Connect

    Tsukagoshi, Seiji; Takahashi, Susumu; Shimamoto, Akira

    1996-12-31

    Dynamic fracture initiation and propagation in Al 7075-T6 was investigated experimentally using the optical method of reflected caustics combined with a simplified high speed photography. A crack propagation testing configuration consisting of a three point bending specimen loaded In a drop weighting was used. It was found that prior to crack initiation the stress intensity factor time record calculated using the dynamic impact load and a static formula disagrees with the actual stress Intensity factor measured by caustics. The impact fracture tests are performed. With use of Al 7075-T6 band plate test specimens with a V-notch on their one side. The dynamic stress intensity factor K{sub id} are given. With this, the authors experimentally calculated the dynamic fracture toughness K{sub ID}.

  15. ZIRCONIUM ALLOY

    DOEpatents

    Wilhelm, H.A.; Ames, D.P.

    1959-02-01

    A binary zirconiuin--antimony alloy is presented which is corrosion resistant and hard containing from 0.07% to 1.6% by weight of Sb. The alloys have good corrosion resistance and are useful in building equipment for the chemical industry.

  16. URANIUM ALLOYS

    DOEpatents

    Seybolt, A.U.

    1958-04-15

    Uranium alloys containing from 0.1 to 10% by weight, but preferably at least 5%, of either zirconium, niobium, or molybdenum exhibit highly desirable nuclear and structural properties which may be improved by heating the alloy to about 900 d C for an extended period of time and then rapidly quenching it.

  17. CD metrology for avoiding shrinkage of ArF resist patterns in 100 nm ArF lithography

    NASA Astrophysics Data System (ADS)

    You, Tae-Jun; Bok, Cheol-Kyu; Shin, Ki-Soo

    2002-07-01

    ML 4689-80 CD Metrology for Avoiding Shrinkage of ArF Resist Patterns in 100nm ArF Lithography Tae-Jun You, Cheolkyu Bok, Ki-Soo Shin Hynix Semiconductor, San 136-1 Amiri, Bubal-eub, Ichon-si, Kyongki-do 467-701, Korea We have observed CD(Critical Dimension) shrinkage of acrylate type ArF resist patterns during SEM measurement. CD change was 30% shrinkage for line pattern and 10% expansion for contact hole patterns after 30 times measurement. CD shrinkage was proportion to line pattern size but no relation with LER(Line Edge Roughness). We confirm that CD shrinkage different from resist to resist and SEM measurement condition. CD shrinkage was bigger for acrylate type resist than COMA(Cyclo Olefin Maleic Anhydride) type resist and smaller at lower electron voltage and current conditions. In order to get the improvement of CD shrinkage, we performed electron-beam curing before SEM measurement. Above (see paper for formula) electron-beam dose condition, CD shrinkage improved from 10% to 3%. However, this method caused OPC(Optical Proximity Correction) issue as CD also changed after electron-beam curing. Therefore, we tried to develop a new measurement method instead of applying additional process technique. In this paper, we will describe our CD measurement method, Off-Site measurement technique, for 100nm DRAM lithography. The Off-Site CD measurement repeatability (formula available in paper) was controlled below (see paper).

  18. Experimental evaluation and simulation of volumetric shrinkage and warpage on polymeric composite reinforced with short natural fibers

    NASA Astrophysics Data System (ADS)

    Santos, Jonnathan D.; Fajardo, Jorge I.; Cuji, Alvaro R.; García, Jaime A.; Garzón, Luis E.; López, Luis M.

    2015-09-01

    A polymeric natural fiber-reinforced composite is developed by extrusion and injection molding process. The shrinkage and warpage of high-density polyethylene reinforced with short natural fibers of Guadua angustifolia Kunth are analyzed by experimental measurements and computer simulations. Autodesk Moldflow® and Solid Works® are employed to simulate both volumetric shrinkage and warpage of injected parts at different configurations: 0 wt.%, 20 wt.%, 30 wt.% and 40 wt.% reinforcing on shrinkage and warpage behavior of polymer composite. Become evident the restrictive effect of reinforcing on the volumetric shrinkage and warpage of injected parts. The results indicate that volumetric shrinkage of natural composite is reduced up to 58% with fiber increasing, whereas the warpage shows a reduction form 79% to 86% with major fiber content. These results suggest that it is a highly beneficial use of natural fibers to improve the assembly properties of polymeric natural fiber-reinforced composites.

  19. 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

    ?'' To this end, we performed a crack propagation experiment under confining stress on an initially water-saturated bentonite clay layer that was exposed to pure ethanol on one surface and water on the other. We measured the rate of transport of ethanol across the clay layer and found that crack breakthrough across the clay layer was accompanied by a very large sudden increase in solvent flow through the layer. Although an experimental artifact prevented measurement of the exact breakthrough time, visual evidence indicates that the clay layer cracked rapidly in this experiment. Direct evidence of the cracks provided by X-ray tomographic images provide clear proof that an extensive array of cracks was created by the ethanol-induced shrinkage. Calculations based on measured fluid pressure and flow rates, and published permeabilities of unaltered calcium bentonite clays, show that the effective permeability of the clay layer increased by a factor of 10{sup 9}-10{sup 12}. Estimates of effective permeability based on crack dimensions measured from the X-ray tomographic images support these findings. Further detailed experiments and analyses are needed to develop a predictive theory and a quantitative design capability for this process. We have begun work on securing the necessary support for these studies, with the ultimate objective of developing and deploying this novel concept as a practical remediation technology in the field.

  20. Astrocytic Mechanisms Explaining Neural-Activity-Induced Shrinkage of Extraneuronal Space

    PubMed Central

    Einevoll, Gaute T.; Nagelhus, Erlend A.; Plahte, Erik; Zeuthen, Thomas; Lloyd, Catherine M.; Ottersen, Ole P.; Omholt, Stig W.

    2009-01-01

    Neuronal stimulation causes ∼30% shrinkage of the extracellular space (ECS) between neurons and surrounding astrocytes in grey and white matter under experimental conditions. Despite its possible implications for a proper understanding of basic aspects of potassium clearance and astrocyte function, the phenomenon remains unexplained. Here we present a dynamic model that accounts for current experimental data related to the shrinkage phenomenon in wild-type as well as in gene knockout individuals. We find that neuronal release of potassium and uptake of sodium during stimulation, astrocyte uptake of potassium, sodium, and chloride in passive channels, action of the Na/K/ATPase pump, and osmotically driven transport of water through the astrocyte membrane together seem sufficient for generating ECS shrinkage as such. However, when taking into account ECS and astrocyte ion concentrations observed in connection with neuronal stimulation, the actions of the Na+/K+/Cl− (NKCC1) and the Na+/HCO3− (NBC) cotransporters appear to be critical determinants for achieving observed quantitative levels of ECS shrinkage. Considering the current state of knowledge, the model framework appears sufficiently detailed and constrained to guide future key experiments and pave the way for more comprehensive astroglia–neuron interaction models for normal as well as pathophysiological situations. PMID:19165313

  1. Bayes and Empirical Bayes Shrinkage Estimation of Regression Coefficients: A Cross-Validation Study.

    ERIC Educational Resources Information Center

    Nebebe, Fassil; Stroud, T. W. F.

    1988-01-01

    Bayesian and empirical Bayes approaches to shrinkage estimation of regression coefficients and uses of these in prediction (i.e., analyzing intelligence test data of children with learning problems) are investigated. The two methods are consistently better at predicting response variables than are either least squares or least absolute deviations.…

  2. Use of Empirical Estimates of Shrinkage in Multiple Regression: A Caution.

    ERIC Educational Resources Information Center

    Kromrey, Jeffrey D.; Hines, Constance V.

    1995-01-01

    The accuracy of four empirical techniques to estimate shrinkage in multiple regression was studied through Monte Carlo simulation. None of the techniques provided unbiased estimates of the population squared multiple correlation coefficient, but the normalized jackknife and bootstrap techniques demonstrated marginally acceptable performance with…

  3. Estimating R-squared Shrinkage in Multiple Regression: A Comparison of Different Analytical Methods.

    ERIC Educational Resources Information Center

    Yin, Ping; Fan, Xitao

    2001-01-01

    Studied the effectiveness of various analytical formulas for estimating "R" squared shrinkage in multiple regression analysis, focusing on estimators of the squared population multiple correlation coefficient and the squared population cross validity coefficient. Simulation results suggest that the most widely used Wherry (R. Wherry, 1931) formula…

  4. [Shrinkage In the Squared Multiple Correlation Coefficient and Unbiased Estimates of Treatment Effects Using Omega Squared.

    ERIC Educational Resources Information Center

    Dalton, Starrett

    The amount of variance accounted for by treatment can be estimated with omega squared or with the squared multiple correlation coefficient. Monte Carlo methods were employed to compare omega squared, the squared multiple correlation coefficient, and the squared multiple correlation coefficient to which a shrinkage formula had been applied, in…

  5. Direct voxel-based comparisons between grey matter shrinkage and glucose hypometabolism in chronic alcoholism.

    PubMed

    Ritz, Ludivine; Segobin, Shailendra; Lannuzel, Coralie; Boudehent, Céline; Vabret, François; Eustache, Francis; Beaunieux, Hélène; Pitel, Anne L

    2016-09-01

    Alcoholism is associated with widespread brain structural abnormalities affecting mainly the frontocerebellar and the Papez's circuits. Brain glucose metabolism has received limited attention, and few studies used regions of interest approach and showed reduced global brain metabolism predominantly in the frontal and parietal lobes. Even though these studies have examined the relationship between grey matter shrinkage and hypometabolism, none has performed a direct voxel-by-voxel comparison between the degrees of structural and metabolic abnormalities. Seventeen alcoholic patients and 16 control subjects underwent both structural magnetic resonance imaging and (18)F-2-fluoro-deoxy-glucose-positron emission tomography examinations. Structural abnormalities and hypometabolism were examined in alcoholic patients compared with control subjects using two-sample t-tests. Then, these two patterns of brain damage were directly compared with a paired t-test. Compared to controls, alcoholic patients had grey matter shrinkage and hypometabolism in the fronto-cerebellar circuit and several nodes of Papez's circuit. The direct comparison revealed greater shrinkage than hypometabolism in the cerebellum, cingulate cortex, thalamus and hippocampus and parahippocampal gyrus. Conversely, hypometabolism was more severe than shrinkage in the dorsolateral, premotor and parietal cortices. The distinct profiles of abnormalities found within the Papez's circuit, the fronto-cerebellar circuit and the parietal gyrus in chronic alcoholism suggest the involvement of different pathological mechanisms. PMID:26661206

  6. Reducing Shrinkage in Convenience Stores by the Use of the PSI.

    ERIC Educational Resources Information Center

    Terris, William; Jones, John W.

    This bibliography contains over 1,200 behavioral and property is a rapidly growing problem. Successful strategies are needed to reduce employee theft; new loss prevention techniques need to be developed and evaluated. Two loss prevention programs aimed at reducing employees' theft were compared by the measures of shrinkage rates. Initially, a…

  7. Synthesis of a liquid-crystalline resin monomer with the property of low shrinkage polymerization.

    PubMed

    Liu, Wenwen; Chen, Su; Liu, Yiran; Ma, Yuanping; Wang, Na; Zhang, Zhenting; Yang, Yuzhe

    2013-01-01

    To reduce the polymerization shrinkage of the dental resin composites, a new liquid-crystalline resin monomer was developed. The acrylate liquid crystalline resin monomer (ALCRM), (4-3-(acryloyloxy)-2-hydroxypropoxy) phenyl 4-(3-(acryloyloxy)-2-hydroxypropoxy) benzoate, was synthesized by a three-step method. Using the ALCRM as the main monomer, the degree of conversion (DC) and the volume shrinkage of the resin matrix were compared with the traditional composite resin monomer (Bis-GMA), 2,2-bis[4-(2-hydroxy-3-methacryloyloxy-propoxy)-phenyl] propane. The new monomer showed liquid crystalline characteristics with a mesomorphic phasetransition temperature between 18ºC and 42ºC. When copolymerized with triethylene glycol dimethacrylate (TEGDMA) at a weight ratio of 7:3, the DC of ALCRM was higher and the volume shrinkage was 3.62±0.26%, which was less than that of the Bis-GMA. The ALCRM exhibits promising potential for the development of superior dental resins with low volume shrinkage. PMID:23903635

  8. Comparative evaluation of residual monomer content and polymerization shrinkage of a packable composite and an ormocer

    PubMed Central

    Sharma, Shalini; Padda, Bhupinder Kaur; Choudhary, Veena

    2012-01-01

    Aim: The aim of this study is to evaluate the residual monomer content and polymerization shrinkage of a packable composite (Surefil) and an ormocer (Admira). Materials and Methods: The study was conducted in two parts. In Part I, 10 samples of each material were prepared in a standardized split brass mould, using incremental curing technique. The residual monomer content was measured by observing change in weight before and after Soxhlet Extraction procedure. In part II, the volumetric polymerization shrinkage was calculated by measuring the difference in specific gravities of 10 uncured and 10 cured samples of each material using a modified version of ASTM D-792 method. The data obtained was put to statistical analysis using student's ‘t’ test. Results: Part I - The percentage change in weight for Surefil was 0.525% while that for Admira was 0.374%, which was found to be statistically significant. Part II - The volumetric percentage shrinkage for Surefil ranged between 1.04-3.42% and that for Admira between 1.01-2.31%, which was not found to be significant statistically. Conclusion: Admira may be considered more biocompatible than Surefil due to the lower residual monomer content in the former; however, both are comparable with regards to their polymerization shrinkage. PMID:22557816

  9. Low-shrinkage dental restorative composite: modeling viscoelastic behavior during setting.

    PubMed

    Dauvillier, Bibi S; Feilzer, Albert J

    2005-04-01

    Much attention has been directed toward developing dental direct restorative composites that generate less shrinkage stress during setting. The aim of this study was to explore the viscoelastic behavior of a new class of low-shrinkage dental restorative composite during setting. The setting behavior of an experimental oxirane composite has been investigated by analyzing stress-strain data with two-parametric mechanical models. Experimental data were obtained from a dynamic test method, in which the setting light-activated composite was continuously subjected to sinusoidal strain cycles. The material parameters and the model's predictive capacity were analyzed with validated modeling procedures. The light-activated oxirane composite exhibited shrinkage delay and low polymerization shrinkage strain and stresses when compared with conventional light-activated composite. Noise in the stress data restricted the predictive ability of the Maxwell model to the elastic modulus development of the composite only. Evaluation tests of their potential as restorative material are required, to examine if the biocompatibility and mechanical properties after setting of oxirane composites are acceptable for dental use. PMID:15685614

  10. Differential brain shrinkage over 6 months shows limited association with cognitive practice.

    PubMed

    Raz, Naftali; Schmiedek, Florian; Rodrigue, Karen M; Kennedy, Kristen M; Lindenberger, Ulman; Lövdén, Martin

    2013-07-01

    The brain shrinks with age, but the timing of this process and the extent of its malleability are unclear. We measured changes in regional brain volumes in younger (age 20-31) and older (age 65-80) adults twice over a 6 month period, and examined the association between changes in volume, history of hypertension, and cognitive training. Between two MRI scans, 49 participants underwent intensive practice in three cognitive domains for 100 consecutive days, whereas 23 control group members performed no laboratory cognitive tasks. Regional volumes of seven brain structures were measured manually and adjusted for intracranial volume. We observed significant mean shrinkage in the lateral prefrontal cortex, the hippocampus, the caudate nucleus, and the cerebellum, but no reliable mean change of the prefrontal white matter, orbital-frontal cortex, and the primary visual cortex. Individual differences in change were reliable in all regions. History of hypertension was associated with greater cerebellar shrinkage. The cerebellum was the only region in which significantly reduced shrinkage was apparent in the experimental group after completion of cognitive training. Thus, in healthy adults, differential brain shrinkage can be observed in a narrow time window, vascular risk may aggravate it, and intensive cognitive activity may have a limited effect on it. PMID:23665948

  11. Composite resin vs resin cement for luting of indirect restorations: comparison of solubility and shrinkage behavior.

    PubMed

    Bortolotto, Tissiana; Guillarme, Davy; Gutemberg, Daniel; Veuthey, Jean-Luc; Krejci, Ivo

    2013-01-01

    The aim of this study was to evaluate relationship between shrinkage development and early solubility of two commonly used luting materials, a self-adhesive cement (GCem chemical and light cured) and composite resin (Tetric). Linear displacement, shrinkage forces and leaching of UDMA from specimens immersed in 75% ethanol/25% water were measured. The least amount of linear shrinkage (33.0±2.9 µm) and polymerization force (4.1±0.3 kg) was observed in Tetric. UDMA leaching (% µg/mL) was the following: chemically cured GCem (4.2±0.2)>light cured GCem (1.5±0.1)>Tetric (0.1). Shrinkage development in the early stages of polymerization was much slower in the self-cured specimens in respect to light cured ones. With the chemically cured self-adhesive cement, incomplete materials' setting during the initial stages after polymerization favored monomer leaching from the cements' mass. PMID:24088842

  12. Shrinkage of bubbles and drops in the lattice Boltzmann equation method for nonideal gases.

    PubMed

    Zheng, Lin; Lee, Taehun; Guo, Zhaoli; Rumschitzki, David

    2014-03-01

    One characteristic of multiphase lattice Boltzmann equation (LBE) methods is that the interfacial region has a finite (i.e., noninfinitesimal) thickness known as a diffuse interface. In simulations of, e.g., bubble or drop dynamics, for problems involving nonideal gases, one frequently observes that the diffuse interface method produces a spontaneous, nonphysical shrinkage of the bubble or drop radius. In this paper, we analyze in detail a single-fluid two-phase model and use a LBE model for nonideal gases in order to explain this fundamental problem. For simplicity, we only investigate the static bubble or droplet problem. We find that the method indeed produces a density shift, bubble or droplet shrinkage, as well as a critical radius below which the bubble or droplet eventually vanishes. Assuming that the ratio between the interface thickness D and the initial bubble or droplet radius r0 is small, we analytically show the existence of this density shift, bubble or droplet radius shrinkage, and critical bubble or droplet survival radius. Numerical results confirm our analysis. We also consider droplets on a solid surface with different curvatures, contact angles, and initial droplet volumes. Numerical results show that the curvature, contact angle, and the initial droplet volume have an effect on this spontaneous shrinkage process, consistent with the survival criterion. PMID:24730962

  13. Urban shrinkage in Germany and the USA: a comparison of transformation patterns and local strategies.

    PubMed

    Wiechmann, Thorsten; Pallagst, Karina M

    2012-01-01

    Many American and European cities have to deal with demographic and economic trajectories leading to urban shrinkage. According to official data, 13% of urban regions in the US and 54% of those in the EU have lost population in recent years. However, the extent and spatial distribution of declining populations differ significantly between Europe and the US. In Germany, the situation is driven by falling birth rates and the effects of German reunification. In the US, shrinkage is basically related to long-term industrial transformation. But the challenges of shrinking cities seldom appeared on the agendas of politicians and urban planners until recently. This article provides a critical overview of the development paths and local strategies of four shrinking cities: Schwedt and Dresden in eastern Germany; Youngstown and Pittsburgh in the US. A typology of urban growth and shrinkage, from economic and demographic perspectives, enables four types of city to be differentiated and the differences between the US and eastern Germany to be discussed. The article suggests that a new transatlantic debate on policy and planning strategies for restructuring shrinking cities is needed to overcome the dominant growth orientation that in most cases intensifies the negative consequences of shrinkage. PMID:22518884

  14. Osmotic shrinkage elicits FAK- and Src phosphorylation and Src-dependent NKCC1 activation in NIH3T3 cells.

    PubMed

    Rasmussen, Line Jee Hartmann; Müller, Helene Steenkær Holm; Jørgensen, Bente; Pedersen, Stine Falsig; Hoffmann, Else Kay

    2015-01-15

    The mechanisms linking cell volume sensing to volume regulation in mammalian cells remain incompletely understood. Here, we test the hypothesis that activation of nonreceptor tyrosine kinases Src, focal adhesion kinase (FAK), and Janus kinase-2 (Jak2) occurs after osmotic shrinkage of NIH3T3 fibroblasts and contributes to volume regulation by activation of NKCC1. FAK phosphorylation at Tyr397, Tyr576/577, and Tyr861 was increased rapidly after exposure to hypertonic (575 mOsm) saline, peaking after 10 (Tyr397, Tyr576/577) and 10-30 min (Tyr861). Shrinkage-induced Src family kinase autophosphorylation (pTyr416-Src) was induced after 2-10 min, and immunoprecipitation indicated that this reflected phosphorylation of Src itself, rather than Fyn and Yes. Phosphorylated Src and FAK partly colocalized with vinculin, a focal adhesion marker, after hypertonic shrinkage. The Src inhibitor pyrazolopyrimidine-2 (PP2, 10 μM) essentially abolished shrinkage-induced FAK phosphorylation at Tyr576/577 and Tyr861, yet not at Tyr397, and inhibited shrinkage-induced NKCC1 activity by ∼50%. The FAK inhibitor PF-573,228 augmented shrinkage-induced Src phosphorylation, and inhibited shrinkage-induced NKCC1 activity by ∼15%. The apparent role of Src in NKCC1 activation did not reflect phosphorylation of myosin light chain kinase (MLC), which was unaffected by shrinkage and by PP2, but may involve Jak2, a known target of Src, which was rapidly activated by osmotic shrinkage and inhibited by PP2. Collectively, our findings suggest a major role for Src and possibly the Jak2 axis in shrinkage-activation of NKCC1 in NIH3T3 cells, whereas no evidence was found for major roles for FAK and MLC in this process. PMID:25377086

  15. Microstructural evolution and macroscopic shrinkage in the presence of density gradients and agglomeration

    NASA Astrophysics Data System (ADS)

    Lu, Peizhen

    X-ray computed tomography (CT) can characterize internal density gradients. An in-situ laser dilatometry has been constructed to track dimensional change at different positions of a sample during binder removal and sintering. This combination of tools not only allows us to better understand how microscopic change affects macroscopic dimensions, but also provides guidance for a variety of ceramic processes. Non-uniform agglomerate packing and deformation provide density gradients which drive binder migration during binder removal. Simultaneously, density undergoes a slight decrease accompanied by a 1.0% loss in dimensional tolerance. This and CT difference images suggest that capillary forces generated during binder melting can change the density distribution. During sintering, nonuniformities present in the green state persist into the fired state and become exaggerated. Regions of different initial density can occupy different stages sintering. At ˜88% sintered density, CT clearly showed that open porosity follows the distribution of low density areas. Mercury porosimetry detected three distinct levels of porosity. Microstructural examination correlated the porosity level with the coordination of (i) two to three or (ii) multiple grains around pores. Microstructural packing controls both the observed macroscopic expansion at T ≤ 1000°C and the onset of shrinkage. Neck formation initiates during expansion and not exclusively during shrinkage. Inter- and intra-agglomerate expansion/shrinkage proceed simultaneously but the effective 'transmission' of particle-level behavior to the macroscopic level appears to be controlled by the initial agglomerate bonding and internal agglomerate densities. Discrete element modeling provides corroborating evidence regarding the importance of compact continuity. Following the expansion-shrinkage transition, the higher the zone density the faster the initial shrinkage. The 25% RH sample shrank more rapidly than the same zone in

  16. Ge1-xSnx alloys synthesized by ion implantation and pulsed laser melting

    NASA Astrophysics Data System (ADS)

    Gao, Kun; Prucnal, S.; Huebner, R.; Baehtz, C.; Skorupa, I.; Wang, Yutian; Skorupa, W.; Helm, M.; Zhou, Shengqiang

    2014-07-01

    The tunable bandgap and the high carrier mobility of Ge1-xSnx alloys stimulate a large effort for bandgap and strain engineering for Ge based materials using silicon compatible technology. In this Letter, we present the fabrication of highly mismatched Ge1-xSnx alloys by ion implantation and pulsed laser melting with Sn concentration ranging from 0.5 at. % up to 1.5 at. %. According to the structural investigations, the formed Ge1-xSnx alloys are monocrystalline with high Sn-incorporation rate. The shrinkage of the bandgap of Ge1-xSnx alloys with increasing Sn content is proven by the red-shift of the E1 and E1 + Δ1 critical points in spectroscopic ellipsometry. Our investigation provides a chip technology compatible route to prepare high quality monocrystalline Ge1-xSnx alloys.

  17. 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

  18. Measurement, growth types and shrinkage of newly formed aerosol particles at an urban research platform

    NASA Astrophysics Data System (ADS)

    Salma, Imre; Németh, Zoltán; Weidinger, Tamás; Kovács, Boldizsár; Kristóf, Gergely

    2016-06-01

    Budapest platform for Aerosol Research and Training (BpART) was created for advancing long-term on-line atmospheric measurements and intensive aerosol sample collection campaigns in Budapest. A joint study including atmospheric chemistry or physics, meteorology, and fluid dynamics on several-year-long data sets obtained at the platform confirmed that the location represents a well-mixed, average atmospheric environment for the city centre. The air streamlines indicated that the host and neighbouring buildings together with the natural orography play an important role in the near-field dispersion processes. Details and features of the airflow structure were derived, and they can be readily utilised for further interpretations. An experimental method to determine particle diffusion losses in the differential mobility particle sizer (DMPS) system of the BpART facility was proposed. It is based on CPC-CPC (condensation particle counter) and DMPS-CPC comparisons. Growth types of nucleated particles observed in 4 years of measurements were presented and discussed specifically for cities. Arch-shaped size distribution surface plots consisting of a growth phase followed by a shrinkage phase were characterised separately since they supply information on nucleated particles. They were observed in 4.5 % of quantifiable nucleation events. The shrinkage phase took 1 h 34 min in general, and the mean shrinkage rate with standard deviation was -3.8 ± 1.0 nm h-1. The shrinkage of particles was mostly linked to changes in local atmospheric conditions, especially in global radiation and the gas-phase H2SO4 concentration through its proxy, or to atmospheric mixing in few cases. Some indirect results indicate that variations in the formation and growth rates of nucleated particles during their atmospheric transport could be a driving force of shrinkage for particles of very small sizes and on specific occasions.

  19. Shrinkage of dental composite in simulated cavity measured with digital image correlation.

    PubMed

    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

  20. Causal Factors of Weld Porosity in Gas Tungsten Arc Welding of Powder-Metallurgy-Produced Titanium Alloys

    NASA Astrophysics Data System (ADS)

    Muth, T. R.; Yamamoto, Y.; Frederick, D. A.; Contescu, C. I.; Chen, W.; Lim, Y. C.; Peter, W. H.; Feng, Z.

    2013-05-01

    An investigation was undertaken using gas tungsten arc (GTA) welding on consolidated powder metallurgy (PM) titanium (Ti) plate to identify the causal factors behind observed porosity in fusion welding. Tramp element compounds of sodium and magnesium, residual from the metallothermic reduction of titanium chloride used to produce the titanium, were remnant in the starting powder and were identified as gas-forming species. PM-titanium made from revert scrap, where sodium and magnesium were absent, showed fusion weld porosity, although to a lesser degree. We show that porosity was attributable to hydrogen from adsorbed water on the surface of the powders prior to consolidation. The removal and minimization of both adsorbed water on the surface of titanium powder and the residues from the reduction process prior to consolidation of titanium powders are critical for achieving equivalent fusion welding success similar to that seen in wrought titanium produced via the Kroll process.

  1. PLUTONIUM ALLOYS

    DOEpatents

    Chynoweth, W.

    1959-06-16

    The preparation of low-melting-point plutonium alloys is described. In a MgO crucible Pu is placed on top of the lighter alloying metal (Fe, Co, or Ni) and the temperature raised to 1000 or 1200 deg C. Upon cooling, the alloy slug is broke out of the crucible. With 14 at. % Ni the m.p. is 465 deg C; with 9.5 at. % Fe the m.p. is 410 deg C; and with 12.0 at. % Co the m.p. is 405 deg C. (T.R.H.) l6262 l6263 ((((((((Abstract unscannable))))))))

  2. Aluminum alloy

    NASA Technical Reports Server (NTRS)

    Blackburn, Linda B. (Inventor); Starke, Edgar A., Jr. (Inventor)

    1989-01-01

    This invention relates to aluminum alloys, particularly to aluminum-copper-lithium alloys containing at least about 0.1 percent by weight of indium as an essential component, which are suitable for applications in aircraft and aerospace vehicles. At least about 0.1 percent by weight of indium is added as an essential component to an alloy which precipitates a T1 phase (Al2CuLi). This addition enhances the nucleation of the precipitate T1 phase, producing a microstructure which provides excellent strength as indicated by Rockwell hardness values and confirmed by standard tensile tests.

  3. Assessment of murine brain tissue shrinkage caused by different histological fixatives using magnetic resonance and computed tomography imaging.

    PubMed

    Wehrl, Hans F; Bezrukov, Ilja; Wiehr, Stefan; Lehnhoff, Mareike; Fuchs, Kerstin; Mannheim, Julia G; Quintanilla-Martinez, Leticia; Kohlhofer, Ursula; Kneilling, Manfred; Pichler, Bernd J; Sauter, Alexander W

    2015-05-01

    Especially for neuroscience and the development of new biomarkers, a direct correlation between in vivo imaging and histology is essential. However, this comparison is hampered by deformation and shrinkage of tissue samples caused by fixation, dehydration and paraffin embedding. We used magnetic resonance (MR) imaging and computed tomography (CT) imaging to analyze the degree of shrinkage on murine brains for various fixatives. After in vivo imaging using 7 T MRI, animals were sacrificed and the brains were dissected and immediately placed in different fixatives, respectively: zinc-based fixative, neutral buffered formalin (NBF), paraformaldehyde (PFA), Bouin-Holland fixative and paraformaldehyde-lysine-periodate (PLP). The degree of shrinkage based on mouse brain volumes, radiodensity in Hounsfield units (HU), as well as non-linear deformations were obtained. The highest degree of shrinkage was observed for PLP (68.1%, P < 0.001), followed by PFA (60.2%, P<0.001) and NBF (58.6%, P<0.001). The zinc-based fixative revealed a low shrinkage with only 33.5% (P<0.001). Compared to NBF, the zinc-based fixative shows a slightly higher degree of deformations, but is still more homogenous than PFA. Tissue shrinkage can be monitored non-invasively with CT and MR. Zinc-based fixative causes the smallest degree of brain shrinkage and only small deformations and is therefore recommended for in vivo ex vivo comparison studies. PMID:25504583

  4. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1962-02-20

    A brazing alloy is described which, in the molten state, is characterized by excellent wettability and flowability and is capable of forming a corrosion-resistant brazed joint. At least one component of said joint is graphite and the other component is a corrosion-resistant refractory metal. The brazing alloy consists essentially of 40 to 90 wt % of gold, 5 to 35 wt% of nickel, and 1 to 45 wt% of tantalum. (AEC)

  5. COATED ALLOYS

    DOEpatents

    Harman, C.G.; O'Bannon, L.S.

    1958-07-15

    A coating is described for iron group metals and alloys, that is particularly suitable for use with nickel containing alloys. The coating is glassy in nature and consists of a mixture containing an alkali metal oxide, strontium oxide, and silicon oxide. When the glass coated nickel base metal is"fired'' at less than the melting point of the coating, it appears the nlckel diffuses into the vitreous coating, thus providing a closely adherent and protective cladding.

  6. The role of gravity on macrosegregation in alloys

    NASA Technical Reports Server (NTRS)

    Poirier, D. R.; Chen, C. F.; Heinrich, J. C.

    1991-01-01

    During dendritic solidification liquid flow is induced both by buoyancy forces and solidification shrinkage. There is strong evidence that the major reason for the liquid flow is the former, i.e., thermosolutal convection. In the microgravity environment, it is thought that the thermosolutal convection will be greatly diminished so that convection will be confined mainly to the flow of interdendritic liquid required to satisfy the solidification shrinkage. An attempt is made to provide improved models of dendritic solidification with emphasis on convection and macrosegregation. Macrosegregation is an extremely important subject to the commercial casting community. The simulation of thermosolutal convection in directionally solidified (DS) alloys is described. A linear stability analysis was used to predict marginal stability curves for a system that comprises a mushy zone underlying an all-liquid zone. The supercritical thermosolutal convection in directionally solidified dendritic alloys was also modeled. The model assumes a nonconvective initial state with planar and horizontal isotherms and isoconcentration that move upward at a constant solidification velocity. Results are presented for systems involving lead-tin alloys and show significant differences with results of plane-front solidification.

  7. Evaluation of shrinkage polymerization and temperature of different acrylic resins used to splinting transfer copings in indirect impression technique

    NASA Astrophysics Data System (ADS)

    Franco, Ana Paula G. O.; Karam, Leandro Z.; Galvão, José R.; Kalinowski, Hypolito J.

    2015-09-01

    The aim of the present study was evaluate the shrinkage polymerization and temperature of different acrylic resins used to splinting transfer copings in indirect impression technique. Two implants were placed in an artificial bone, with the two transfer copings joined with dental floss and acrylic resins; two dental resins are used. Measurements of deformation and temperature were performed with Fiber Braggs grating sensor for 17 minutes. The results revealed that one type of resin shows greater values of polymerization shrinkage than the other. Pattern resins did not present lower values of shrinkage, as usually reported by the manufacturer.

  8. Quantitative characterization of processing-microstructure-properties relationships in pressure die-cast magnesium alloys

    NASA Astrophysics Data System (ADS)

    Lee, Soon Gi

    The central goal of this research is to quantitatively characterize the relationships between processing, microstructure, and mechanical properties of important high-pressure die-cast (HPDC) Mg-alloys. For this purpose, a new digital image processing technique for automatic detection and segmentation of gas and shrinkage pores in the cast microstructure is developed and it is applied to quantitatively characterize the effects of HPDC process parameters on the size distribution and spatial arrangement of porosity. To get better insights into detailed geometry and distribution of porosity and other microstructural features, an efficient and unbiased montage based serial sectioning technique is applied for reconstruction of three-dimensional microstructures. The quantitative microstructural data have been correlated to the HPDC process parameters and the mechanical properties. The analysis has led to hypothesis of formation of new type of shrinkage porosity called, "gas induced shrinkage porosity" that has been substantiated via simple heat transfer simulations. The presence of inverse surface macrosegregation has been also shown for the first time in the HPDC Mg-alloys. An image analysis based technique has been proposed for simulations of realistic virtual microstructures that have realistic complex pore morphologies. These virtual microstructures can be implemented in the object oriented finite elements framework to model the variability in the fracture sensitive mechanical properties of the HPDC alloys.

  9. Carbon--silicon coating alloys for improved irradiation stability

    DOEpatents

    Bokros, J.C.

    1973-10-01

    For ceramic nuclear fuel particles, a fission product-retaining carbon-- silicon alloy coating is described that exhibits low shrinkage after exposure to fast neutron fluences of 1.4 to 4.8 x 10/sup 21/ n/cm/sup 2/ (E = 0.18 MeV) at irradiation temperatures from 950 to 1250 deg C. Isotropic pyrolytic carbon containing from 18 to 34 wt% silicon is co-deposited from a gaseous mixiure of propane, helium, and silane at a temperature of 1350 to 1450 deg C. (Official Gazette)

  10. Suspended, Shrinkage-Free, Electrospun PLGA Nanofibrous Scaffold for Skin Tissue Engineering.

    PubMed

    Ru, Changhai; Wang, Feilong; Pang, Ming; Sun, Lining; Chen, Ruihua; Sun, Yu

    2015-05-27

    Electrospinning is a technique for creating continuous nanofibrous networks that can architecturally be similar to the structure of extracellular matrix (ECM). However, the shrinkage of electrospun mats is unfavorable for the triggering of cell adhesion and further growth. In this work, electrospun PLGA nanofiber assemblies are utilized to create a scaffold. Aided by a polypropylene auxiliary supporter, the scaffold is able to maintain long-term integrity without dimensional shrinkage. This scaffold is also able to suspend in cell culture medium; hence, keratinocyte cells seeded on the scaffold are exposed to air as required in skin tissue engineering. Experiments also show that human skin keratinocytes can proliferate on the scaffold and infiltrate into the scaffold. PMID:25941905

  11. Modelling of shrinkage cavity defects during the wheel and belt casting process

    NASA Astrophysics Data System (ADS)

    Dablement, S.; Mortensen, D.; Fjaer, H.; Lee, M.; Grandfield, J.; Savage, G.; Nguyen, V.

    2012-07-01

    Properzi continuous casting is a wheel and belt casting process used for producing aluminium wire rod which is essential to the making of electrical cables and over head lines. One of the main concerns of Properzi process users is to ensure good quality of the final product and to avoid cast defects especially the presence of shrinkage cavity. Numerical models developed with the Alsim software, which allows an automatic calculation of gap dependent heat transfer coefficients at the metal-mould interface due to thermal deformation, are used in order to get a better understanding on the shrinkage cavity formation. Models show the effect of process parameters on the cavity defect development and provide initial guidance for users in order to avoid this kind of casting defect.

  12. Remarkable Lattice Shrinkage in Highly Oriented Crystalline Three-Dimensional Metal-Organic Framework Thin Films.

    PubMed

    Haraguchi, Tomoyuki; Otsubo, Kazuya; Sakata, Osami; Fujiwara, Akihiko; Kitagawa, Hiroshi

    2015-12-21

    Highly oriented crystalline thin films of metal-organic frameworks (MOFs) have promising practical applications, such as in gas separation, catalysis, and sensing. We report on the successful fabrication of highly oriented crystalline thin films of three-dimensional porous MOFs, Fe(pz)[M(CN)4] (M = Ni, Pd; pz = pyrazine). Synchrotron X-ray diffraction studies reveal not only the highly oriented crystalline nature but also the remarkable shrunken structure of the thin films (∼3-7% volume shrinkage) compared with bulk samples. Furthermore, because of lattice shrinkage, these films exhibit large lattice expansions upon guest adsorption, in marked contrast to the almost unchanged lattice in the bulk samples. PMID:26641131

  13. Inference of posterior inclusion probability of QTLs in Bayesian shrinkage analysis.

    PubMed

    Yang, Deguang; Han, Shanshan; Jiang, Dan; Yang, Runqing; Fang, Ming

    2015-01-01

    Bayesian shrinkage analysis estimates all QTLs effects simultaneously, which shrinks the effect of "insignificant" QTLs close to zero so that it does not need special model selection. Bayesian shrinkage estimation usually has an excellent performance on multiple QTLs mapping, but it could not give a probabilistic explanation of how often a QTLs is included in the model, also called posterior inclusion probability, which is important to assess the importance of a QTL. In this research, two methods, FitMix and SimMix, are proposed to approximate the posterior probabilities. Under the assumption of mixture distribution of the estimated QTL effect, FitMix and SimMix mathematically and intuitively fit mixture distribution, respectively. The simulation results showed that both methods gave very reasonable estimates for posterior probabilities. We also applied the two methods to map QTLs for the North American Barley Genome Mapping Project data. PMID:25857576

  14. 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.

  15. Oxidation behavior in reaction-bonded aluminum-silicon alloy/alumina powder compacts

    SciTech Connect

    Yokota, S.H.

    1992-12-01

    Goal of this research is to determine the feasibility of producing low-shrinkage mullite/alumina composites by applying the reaction-bonded alumina (RBAO) process to an aluminum-silicon alloy/alumina system. Mirostructural and compositional changes during heat treatment were studied by removing samples from the furnace at different steps in the heating schedule and then using optical and scanning electron microscopy, EDS and XRD to characterize the powder compacts. Results suggest that the oxidation behavior of the alloy compact is different from the model proposed for the pure Al/alumina system.

  16. Influence of raw materials composition on firing shrinkage, porosity, heat conductivity and microstructure of ceramic tiles

    NASA Astrophysics Data System (ADS)

    Kurovics, E.; Buzimov, A. Y.; Gömze, L. A.

    2016-04-01

    In this work some new raw material compositions from alumina, conventional brick-clays and sawdust were mixed, compacted and heat treated by the authors. Depending on raw material compositions and firing temperatures the specimens were examined on shrinkage, water absorption, heat conductivity and microstructures. The real raised experiments have shown the important role of firing temperature and raw material composition on color, heat conductivity and microstructure of the final product.

  17. Bayesian analysis of RNA sequencing data by estimating multiple shrinkage priors.

    PubMed

    Van De Wiel, Mark A; Leday, Gwenaël G R; Pardo, Luba; Rue, Håvard; Van Der Vaart, Aad W; Van Wieringen, Wessel N

    2013-01-01

    Next generation sequencing is quickly replacing microarrays as a technique to probe different molecular levels of the cell, such as DNA or RNA. The technology provides higher resolution, while reducing bias. RNA sequencing results in counts of RNA strands. This type of data imposes new statistical challenges. We present a novel, generic approach to model and analyze such data. Our approach aims at large flexibility of the likelihood (count) model and the regression model alike. Hence, a variety of count models is supported, such as the popular NB model, which accounts for overdispersion. In addition, complex, non-balanced designs and random effects are accommodated. Like some other methods, our method provides shrinkage of dispersion-related parameters. However, we extend it by enabling joint shrinkage of parameters, including those for which inference is desired. We argue that this is essential for Bayesian multiplicity correction. Shrinkage is effectuated by empirically estimating priors. We discuss several parametric (mixture) and non-parametric priors and develop procedures to estimate (parameters of) those. Inference is provided by means of local and Bayesian false discovery rates. We illustrate our method on several simulations and two data sets, also to compare it with other methods. Model- and data-based simulations show substantial improvements in the sensitivity at the given specificity. The data motivate the use of the ZI-NB as a powerful alternative to the NB, which results in higher detection rates for low-count data. Finally, compared with other methods, the results on small sample subsets are more reproducible when validated on their large sample complements, illustrating the importance of the type of shrinkage. PMID:22988280

  18. Influence of Shrinkage and Swelling Properties of Coal on Geologic Sequestration of Carbon Dioxide

    SciTech Connect

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

    2007-05-01

    The potential for enhanced methane production and geologic sequestration of carbon dioxide in coalbeds needs to be evaluated before large-scale sequestration projects are undertaken. Geologic sequestration of carbon dioxide in deep unmineable coal seams with the potential for enhanced coalbed methane production has become a viable option to reduce greenhouse gas emissions. The coal matrix is believed to shrink during methane production and swell during the injection of carbon dioxide, causing changes in tlie cleat porosity and permeability of the coal seam. However, the influence of swelling and shrinkage, and the geomechanical response during the process of carbon dioxide injection and methane recovery, are not well understood. A three-dimensional swelling and shrinkage model based on constitutive equations that account for the coupled fluid pressure-deformation behavior of a porous medium was developed and implemented in an existing reservoir model. Several reservoir simulations were performed at a field site located in the San Juan basin to investigate the influence of swelling and shrinkage, as well as other geomechanical parameters, using a modified compositional coalbed methane reservoir simulator (modified PSU-COALCOMP). The paper presents numerical results for interpretation of reservoir performance during injection of carbon dioxide at this site. Available measured data at the field site were compared with computed values. Results show that coal swelling and shrinkage during the process of enhanced coalbed methane recovery can have a significant influence on the reservoir performance. Results also show an increase in the gas production rate with an increase in the elastic modulus of the reservoir material and increase in cleat porosity. Further laboratory and field tests of the model are needed to furnish better estimates of petrophysical parameters, test the applicability of thee model, and determine the need for further refinements to the mathematical

  19. Lower prolactin levels during cabergoline treatment are associated to tumor shrinkage in prolactin secreting pituitary adenoma.

    PubMed

    Lombardi, M; Lupi, I; Cosottini, M; Rossi, G; Manetti, L; Raffaelli, V; Sardella, C; Martino, E; Bogazzi, F

    2014-12-01

    Dopamine agonists are considered as the first line therapy in prolactin (PRL) secreting pituitary adenomas inducing a normalization of serum PRL and reduction of tumor size. It is known that serum PRL levels, obtained during treatment, are a predictor of tumor shrinkage. Whether PRL suppression below the lower limit of the normal range is related to a greater chance of tumor shrinkage than just its normalization has not been established. This retrospective cohort study was carried out in a tertiary center. Clinical records of 151 patients with PRL-secreting pituitary adenomas (73 micro-, 78 macroadenomas) treated with cabergoline for at least 24 months were analyzed. The adenoma size was analyzed by MRI before and after 24 months of treatment. PRL levels were evaluated every 6 months, assigning a score at each time point (PRL 0 = suppressed; 1 = normal; 2 = above normal). The total score, after 24 months of treatment, was expressed as the sum of the score at each time point and ranged between 0 and 8. A tumor shrinkage was observed in 102/151 patients (67.5%) and it was significantly associated to a lower PRL total score (p = 0.021, OR = 0.85, CI = 0.73-0.97), being significantly more frequent in patients with suppressed PRL than in those with normal PRL (p = 0.045, OR = 0.42, CI = 0.18-0.98) at 24 months. Cabergoline therapy with the goal of achieving PRL levels below the lower limit of normal range can increase the chance to obtain tumor shrinkage of PRL-secreting pituitary adenomas. PMID:25230324

  20. Controlled Shrinkage and Re-expansion of a Single Aqueous Droplet Inside an Optical Vortex Trap

    PubMed Central

    Jeffries, Gavin D. M.; Kuo, Jason S.; Chiu, Daniel T.

    2008-01-01

    This paper describes the shrinkage and re-expansion of individual femtoliter-volume aqueous droplets that were suspended in an organic medium and held in an optical vortex trap. To elucidate the mechanism behind this phenomenon, we constructed a heat and mass transfer model and carried out experimental verifications of our model. From these studies, we conclude that an evaporation mechanism sufficiently describes the shrinkage of aqueous droplets held in a vortex trap, while a mechanism based on the supersaturation of the organic phase by water that surrounds the droplet adequately explains the re-expansion of the shrunk droplet. The proposed mechanisms correlate well with experimental observations using different organic media, when H2O was replaced with D2O, and when an optical tweezer was used to induce droplet shrinkage rather than an optical vortex trap. For H2O droplets, the temperature rise within the droplet during shrinkage was on the order of 1K or less, owing to the rapid thermal conduction of heat away from the droplet at the microscale and the sharp increase in solubility for water by the organic phase with slight elevations in temperature. Because most chemical species confined to droplets can be made impenetrable to the aqueous/organic interface, a change in the volume of aqueous droplets translates into a change in concentration of the dissolved species within the droplets. Therefore, this phenomenon should find use in the study of fundamental chemical processes that are sensitive to concentration, such as macromolecular crowding and protein nucleation and crystallization. PMID:17388431

  1. Controlled shrinkage and re-expansion of a single aqueous droplet inside an optical vortex trap.

    PubMed

    Jeffries, Gavin D M; Kuo, Jason S; Chiu, Daniel T

    2007-03-22

    This paper describes the shrinkage and re-expansion of individual femtoliter-volume aqueous droplets that were suspended in an organic medium and held in an optical vortex trap. To elucidate the mechanism behind this phenomenon, we constructed a heat- and mass-transfer model and carried out experimental verifications of our model. From these studies, we conclude that an evaporation mechanism sufficiently describes the shrinkage of aqueous droplets held in a vortex trap, whereas a mechanism based on the supersaturation of the organic phase by water that surrounds the droplet adequately explains the re-expansion of the shrunk droplet. The proposed mechanisms correlated well with experimental observations using different organic media, when H2O was replaced with D2O and when an optical tweezer was used to induce droplet shrinkage rather than an optical vortex trap. For H2O droplets, the temperature rise within the droplet during shrinkage was on the order of 1 K or less, owing to the rapid thermal conduction of heat away from the droplet at the microscale and the sharp increase in solubility for water by the organic phase with slight elevations in temperature. Because most chemical species confined to droplets can be made impenetrable to the aqueous/organic interface, a change in the volume of aqueous droplets translates into a change in concentration of the dissolved species within the droplets. Therefore, this phenomenon should find use in the study of fundamental chemical processes that are sensitive to concentration, such as macromolecular crowding and protein nucleation and crystallization. PMID:17388431

  2. Alloy softening in binary iron solid solutions

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1976-01-01

    An experimental study was conducted to determine whether alloy softening in Fe alloys is dependent on electron concentration and to provide a direct comparison of alloy softening and hardening in several binary Fe alloy systems having the same processing history. Alloy additions to Fe included the elements in the Periods 4-6 and the Groups IV-VIII with the exception of technetium. A total of 19 alloy systems was investigated, and hardness testing was the primary means of evaluation. Testing was carried out at four temperatures over a homologous temperature range of 0.043-0.227 times the absolute melting temperature of unalloyed Fe. Major conclusions are that the atomic radius ratio of solute-to-Fe is the key factor in controlling low-temperature hardness of the binary Fe alloys and that alloy softening rates at 77 K and alloy hardening rates at 411 K are correlated with this atomic radius ratio for 15 of the binary alloy systems. Mechanisms of alloy softening and hardening are proposed.

  3. Shrinkage and Sintering Behavior of a Low-Temperature Sinterable Nanosilver Die-Attach Paste

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Zhao, Meihua; Chen, Xu; Lu, Guo-Quan; Ngo, Khai; Luo, Shufang

    2012-09-01

    The drying and densification behavior of a nanosilver paste was studied by shrinkage and weight-loss measurements to provide fundamental understanding on the sintering behavior of the nanomaterial for packaging power devices and modules. The measured shrinkage behavior was found to be in good agreement with the weight-loss behavior of the paste as measured by thermogravitational analysis, and the comparison offered direct evidence of ~10% shrinkage contributed by late-stage densification of silver nanoparticles (NPs). It was found that sintered silver joints could be achieved without cracks or delamination under a ramp-soak temperature profile for bonding small-area chips, e.g., 3 mm × 3 mm or smaller. However, for bonding large-area chips, e.g., 5 mm × 5 mm or larger, rapid evaporation of the entrapped organic species caused the chips to delaminate, leading to large longitudinal cracks at the joint interface. Finally, examination of the microstructure evolution of the silver die-attach material revealed that binder molecules inhibited necking of the silver NPs and delayed densification during the sintering process of the nanosilver paste.

  4. Mal3 masks catastrophe events in Schizosaccharomyces pombe microtubules by inhibiting shrinkage and promoting rescue.

    PubMed

    Katsuki, Miho; Drummond, Douglas R; Osei, Michael; Cross, Robert A

    2009-10-23

    Schizosaccharomyces pombe Mal3 is a member of the EB family of proteins, which are proposed to be core elements in a tip-tracking network that regulates microtubule dynamics in cells. How Mal3 itself influences microtubule dynamics is unclear. We tested the effects of full-length recombinant Mal3 on dynamic microtubules assembled in vitro from purified S. pombe tubulin, using dark field video microscopy to avoid fluorescent tagging and data-averaging techniques to improve spatiotemporal resolution. We find that catastrophe occurs stochastically as a fast (<2.2 s) transition from constant speed growth to constant speed shrinkage with a constant probability that is independent of the Mal3 concentration. This implies that Mal3 neither stabilizes nor destabilizes microtubule tips. Mal3 does, however, stabilize the main part of the microtubule lattice, inhibiting shrinkage and increasing the frequency of rescues, consistent with recent models in which Mal3 on the lattice forms stabilizing lateral links between neighboring protofilaments. At high concentrations, Mal3 can entirely block shrinkage and induce very rapid rescue, making catastrophes impossible to detect, which may account for the apparent suppression of catastrophe by Mal3 and other EBs in vivo. Overall, we find that Mal3 stabilizes microtubules not by preventing catastrophe at the microtubule tip but by inhibiting lattice depolymerization and enhancing rescue. We argue that this implies that Mal3 binds microtubules in different modes at the tip and on the lattice. PMID:19740752

  5. Creep behavior of a rabbit model of ligament laxity after electrothermal shrinkage in vivo.

    PubMed

    Wallace, Andrew L; Hollinshead, Robert M; Frank, Cyril B

    2002-01-01

    Deformation of capsular tissue under constant load (creep) may lead to recurrent laxity after thermal shrinkage for shoulder instability. We investigated the effects of thermal shrinkage in a rabbit model in which the tibial insertion of the medial collateral ligament was elevated and shifted toward the joint line to create abnormal laxity. On the right side, radiofrequency electrothermal energy was applied to the shifted ligament, while the left side served as a control. Length, laxity, mass, cross-sectional area, water content, and creep behavior of the ligament were assessed at 0 (N = 8), 3 (N = 7), and 12 (N = 6) weeks postoperatively. Laxity was reduced with thermal treatment (0.65 +/- 0.31 compared with 3.33 +/- 0.25 mm). After 3 weeks, ligament mass, area, and water content were significantly increased in the thermally treated group compared with the untreated controls. At 12 weeks, cyclic creep strain remained greater than that in controls (1.25% +/- 0.65% compared with 0.93% +/- 0.22%). Although thermal shrinkage reduced laxity, there was increased potential to creep and failure at low physiologic stresses. These findings suggest that loading of thermally treated tissues should be carefully controlled during the early phase of rehabilitation after surgery. PMID:11799003

  6. Shrinkage activates a nonselective conductance: involvement of a Walker-motif protein and PKC.

    PubMed

    Nelson, D J; Tien, X Y; Xie, W; Brasitus, T A; Kaetzel, M A; Dedman, J R

    1996-01-01

    The ability of all cells to maintain their volume during an osmotic challenge is dependent on the regulated movement of salt and water across the plasma membrane. We demonstrate the phosphorylation-dependent gating of a nonselective conductance in Caco-2 cells during cellular shrinkage. Intracellular application of exogenous purified rat brain protein kinase C (PKC) resulted in the activation of a current similar to that activated during shrinkage with a Na(+)-to-Cl- permeability ratio of approximately 1.7:1. To prevent possible PKC- and/or shrinkage-dependent activation of cystic fibrosis transmembrane regulator (CFTR), which is expressed at high levels in Caco-2 cells, a functional anti-peptide antibody, anti-CFTR505-511, was introduced into the cells via the patch pipette. Anti-CFTR505-511, which is directed against the Walker motif in the first nucleotide binding fold of CFTR, prevented the PKC/shrink-age current activation. The peptide CFTR505-511 also induced current inhibition, suggesting the possible involvement of a regulatory element in close proximity to the channel that shares sequence homology with the first nucleotide binding fold of CFTR and whose binding to the channel is required for channel gating. PMID:8772443

  7. Glutaraldehyde crosslinking of collagen: effects of time, temperature, concentration and presoaking as measured by shrinkage temperature.

    PubMed

    Ruijgrok, J M; de Wijn, J R; Boon, M E

    1994-01-01

    Experiments were carried out to study the effect on the degree of crosslinking of: (a) short term (1 or 5 min) high (50 degrees C) temperature glutaraldehyde (GA) fixation of native collagen membrane, (b) a combination of GA presoaking at low temperature [0 degree C or room temperature (rt)] followed by short time (< 3 min) heating of synthetic collagen fleece in a multilayer diffusion model. As a measure for the degree of crosslinking the shrinkage temperature (Ts) was determined. Short time (1 or 5 min) high temperature (50 degrees C) fixation using 0.1% GA solution caused the shrinkage temperature to increase to 80% and 93% respectively, of the maximum attainable Ts employing GA crosslinking (ca 91 degrees C). Fixation with 0.01% GA for 5 min at 50 degrees C appeared equally as effective as 1 min with 0.1% GA. Although an elevated fixation temperature (from rt to 45 degrees C) was found to produce a substantial increase in Ts of the collagen sheets, a homogeneous distribution of cross links was not obtained by this method. Presoaking the samples at rt (1 h) or at 0 degree C (3 h) with subsequent short time heating to 45 degrees C caused an almost equal rise in shrinkage temperature in Ts throughout the collagen samples. PMID:10150174

  8. Heat-induced changes in the mechanics of a collagenous tissue: isothermal, isotonic shrinkage.

    PubMed

    Chen, S S; Wright, N T; Humphrey, J D

    1998-06-01

    We present data from isothermal, isotonic-shrinkage tests wherein bovine chordae tendineae were subjected to well-defined constant temperatures (from 65 to 90 degrees C), durations of heating (from 180 to 3600 s), and isotonic uniaxial stresses during heating (from 100 to 650 kPa). Tissue response during heating and "recovery" at 37 degrees C following heating was evaluated in terms of the axial shrinkage, a gross indicator of underlying heat-induced denaturation. There were three key findings. First, scaling the heating time via temperature and load-dependent characteristic times for the denaturation process collapsed all shrinkage data to a single curve, and thereby revealed a time-temperature-load equivalency. Second, the characteristic times exhibited an Arrhenius-type behavior with temperature wherein the slopes were nearly independent of applied load--this suggested that applied loads during heating affect the activation entropy, not energy. Third, all specimens exhibited a time-dependent, partial recovery when returned to 37 degrees C following heating, but the degree of recovery decreased with increases in the load imposed during heating. These new findings on heat-induced changes in tissue behavior will aid in the design of improved clinical heating protocols and provide guidance for the requisite constitutive formulations. PMID:10412406

  9. Shrinkage covariance matrix approach based on robust trimmed mean in gene sets detection

    NASA Astrophysics Data System (ADS)

    Karjanto, Suryaefiza; Ramli, Norazan Mohamed; Ghani, Nor Azura Md; Aripin, Rasimah; Yusop, Noorezatty Mohd

    2015-02-01

    Microarray involves of placing an orderly arrangement of thousands of gene sequences in a grid on a suitable surface. The technology has made a novelty discovery since its development and obtained an increasing attention among researchers. The widespread of microarray technology is largely due to its ability to perform simultaneous analysis of thousands of genes in a massively parallel manner in one experiment. Hence, it provides valuable knowledge on gene interaction and function. The microarray data set typically consists of tens of thousands of genes (variables) from just dozens of samples due to various constraints. Therefore, the sample covariance matrix in Hotelling's T2 statistic is not positive definite and become singular, thus it cannot be inverted. In this research, the Hotelling's T2 statistic is combined with a shrinkage approach as an alternative estimation to estimate the covariance matrix to detect significant gene sets. The use of shrinkage covariance matrix overcomes the singularity problem by converting an unbiased to an improved biased estimator of covariance matrix. Robust trimmed mean is integrated into the shrinkage matrix to reduce the influence of outliers and consequently increases its efficiency. The performance of the proposed method is measured using several simulation designs. The results are expected to outperform existing techniques in many tested conditions.

  10. Quantification of tissue shrinkage in canine small intestinal specimens after resection and fixation

    PubMed Central

    Clarke, Ben S.; Banks, Tania A.; Findji, Laurent

    2014-01-01

    The aim of this study was to quantify the longitudinal shrinkage of canine small intestinal specimens after resection and fixation in 10% formalin. Samples were obtained from 12 clinically normal dogs of medium to large breed via ventral midline coeliotomy and enterectomy. The length of each sample was measured before excision, immediately after excision, and after 24 h in 10% formalin. The results were interpreted with the use of single-sample t-tests of the average changes; P-values of less than 0.01 were considered significant. The samples indicated a significant decrease in length after resection and fixation. The mean shrinkage from the pre-excision state was 28.3% immediately after excision (P < 0.0001) and 26.3% after 24 h of fixation (P < 0.0001). There was a small but not significant increase in the length of the specimens between the 2nd and 3rd measurement points. Quantification of the longitudinal shrinkage of resected intestinal specimens may improve interpretation of the distance of surgical margins from abnormal tissue in histopathology reports and allow investigation of the margins required for the clearance of specific tumors. PMID:24396180

  11. Activity-Dependent Dendritic Spine Shrinkage and Growth Involve Downregulation of Cofilin via Distinct Mechanisms

    PubMed Central

    Calabrese, Barbara; Saffin, Jean-Michel; Halpain, Shelley

    2014-01-01

    A current model posits that cofilin-dependent actin severing negatively impacts dendritic spine volume. Studies suggested that increased cofilin activity underlies activity-dependent spine shrinkage, and that reduced cofilin activity induces activity-dependent spine growth. We suggest instead that both types of structural plasticity correlate with decreased cofilin activity. However, the mechanism of inhibition determines the outcome for spine morphology. RNAi in rat hippocampal cultures demonstrates that cofilin is essential for normal spine maintenance. Cofilin-F-actin binding and filament barbed-end production decrease during the early phase of activity-dependent spine shrinkage; cofilin concentration also decreases. Inhibition of the cathepsin B/L family of proteases prevents both cofilin loss and spine shrinkage. Conversely, during activity-dependent spine growth, LIM kinase stimulates cofilin phosphorylation, which activates phospholipase D-1 to promote actin polymerization. These results implicate novel molecular mechanisms and prompt a revision of the current model for how cofilin functions in activity-dependent structural plasticity. PMID:24740405

  12. Statistical Mechanics Provides Novel Insights into Microtubule Stability and Mechanism of Shrinkage

    PubMed Central

    Jain, Ishutesh; Inamdar, Mandar M.; Padinhateeri, Ranjith

    2015-01-01

    Microtubules are nano-machines that grow and shrink stochastically, making use of the coupling between chemical kinetics and mechanics of its constituent protofilaments (PFs). We investigate the stability and shrinkage of microtubules taking into account inter-protofilament interactions and bending interactions of intrinsically curved PFs. Computing the free energy as a function of PF tip position, we show that the competition between curvature energy, inter-PF interaction energy and entropy leads to a rich landscape with a series of minima that repeat over a length-scale determined by the intrinsic curvature. Computing Langevin dynamics of the tip through the landscape and accounting for depolymerization, we calculate the average unzippering and shrinkage velocities of GDP protofilaments and compare them with the experimentally known results. Our analysis predicts that the strength of the inter-PF interaction (Ems) has to be comparable to the strength of the curvature energy (Emb) such that Ems−Emb≈1kBT, and questions the prevalent notion that unzippering results from the domination of bending energy of curved GDP PFs. Our work demonstrates how the shape of the free energy landscape is crucial in explaining the mechanism of MT shrinkage where the unzippered PFs will fluctuate in a set of partially peeled off states and subunit dissociation will reduce the length. PMID:25692909

  13. Hygroscopic swelling and shrinkage of latewood cell wall micropillars reveal ultrastructural anisotropy

    PubMed Central

    Rafsanjani, Ahmad; Stiefel, Michael; Jefimovs, Konstantins; Mokso, Rajmund; Derome, Dominique; Carmeliet, Jan

    2014-01-01

    We document the hygroscopic swelling and shrinkage of the central and the thickest secondary cell wall layer of wood (named S2) in response to changes in environmental humidity using synchrotron radiation-based phase contrast X-ray tomographic nanoscopy. The S2 layer is a natural fibre-reinforced nano-composite polymer and is strongly reactive to water. Using focused ion beam, micropillars with a cross section of few micrometres are fabricated from the S2 layer of the latewood cell walls of Norway spruce softwood. The thin neighbouring cell wall layers are removed to prevent hindering or restraining of moisture-induced deformation during swelling or shrinkage. The proposed experiment intended to get further insights into the microscopic origin of the anisotropic hygro-expansion of wood. It is found that the swelling/shrinkage strains are highly anisotropic in the transverse plane of the cell wall, larger in the normal than in the direction parallel to the cell wall's thickness. This ultrastructural anisotropy may be due to the concentric lamellation of the cellulose microfibrils as the role of the cellulose microfibril angle in the transverse swelling anisotropy is negligible. The volumetric swelling of the cell wall material is found to be substantially larger than the one of wood tissues within the growth ring and wood samples made of several growth rings. The hierarchical configuration in wood optimally increases its dimensional stability in response to a humid environment with higher scales of complexity. PMID:24671938

  14. Using four-phase Eulerian volume averaging approach to model macrosegregation and shrinkage cavity

    NASA Astrophysics Data System (ADS)

    Wu, M.; Kharicha, A.; Ludwig, A.

    2015-06-01

    This work is to extend a previous 3-phase mixed columnar-equiaxed solidification model to treat the formation of shrinkage cavity by including an additional phase. In the previous model the mixed columnar and equiaxed solidification with consideration of multiphase transport phenomena (mass, momentum, species and enthalpy) is proposed to calculate the as- cast structure including columnar-to-equiaxed transition (CET) and formation of macrosegregation. In order to incorporate the formation of shrinkage cavity, an additional phase, i.e. gas phase or covering liquid slag phase, must be considered in addition to the previously introduced 3 phases (parent melt, solidifying columnar dendrite trunks and equiaxed grains). No mass and species transfer between the new and other 3 phases is necessary, but the treatment of the momentum and energy exchanges between them is crucially important for the formation of free surface and shrinkage cavity, which in turn influences the flow field and formation of segregation. A steel ingot is preliminarily calculated to exam the functionalities of the model.

  15. Multiple-Shrinkage Multinomial Probit Models with Applications to Simulating Geographies in Public Use Data

    PubMed Central

    Burgette, Lane F.; Reiter, Jerome P.

    2013-01-01

    Multinomial outcomes with many levels can be challenging to model. Information typically accrues slowly with increasing sample size, yet the parameter space expands rapidly with additional covariates. Shrinking all regression parameters towards zero, as often done in models of continuous or binary response variables, is unsatisfactory, since setting parameters equal to zero in multinomial models does not necessarily imply “no effect.” We propose an approach to modeling multinomial outcomes with many levels based on a Bayesian multinomial probit (MNP) model and a multiple shrinkage prior distribution for the regression parameters. The prior distribution encourages the MNP regression parameters to shrink toward a number of learned locations, thereby substantially reducing the dimension of the parameter space. Using simulated data, we compare the predictive performance of this model against two other recently-proposed methods for big multinomial models. The results suggest that the fully Bayesian, multiple shrinkage approach can outperform these other methods. We apply the multiple shrinkage MNP to simulating replacement values for areal identifiers, e.g., census tract indicators, in order to protect data confidentiality in public use datasets. PMID:24358073

  16. Hysteresis from Multiscale Porosity: Modeling Water Sorption and Shrinkage in Cement Paste

    NASA Astrophysics Data System (ADS)

    Pinson, Matthew B.; Masoero, Enrico; Bonnaud, Patrick A.; Manzano, Hegoi; Ji, Qing; Yip, Sidney; Thomas, Jeffrey J.; Bazant, Martin Z.; Van Vliet, Krystyn J.; Jennings, Hamlin M.

    2015-06-01

    Cement paste has a complex distribution of pores and molecular-scale spaces. This distribution controls the hysteresis of water sorption isotherms and associated bulk dimensional changes (shrinkage). We focus on two locations of evaporable water within the fine structure of pastes, each having unique properties, and we present applied physics models that capture the hysteresis by dividing drying and rewetting into two related regimes based on relative humidity (RH). We show that a continuum model, incorporating a pore-blocking mechanism for desorption and equilibrium thermodynamics for adsorption, explains well the sorption hysteresis for a paste that remains above approximately 20% RH. In addition, we show with molecular models and experiments that water in spaces of ≲1 nm width evaporates below approximately 20% RH but reenters throughout the entire RH range. This water is responsible for a drying shrinkage hysteresis similar to that of clays but opposite in direction to typical mesoporous glass. Combining the models of these two regimes allows the entire drying and rewetting hysteresis to be reproduced accurately and provides parameters to predict the corresponding dimensional changes. The resulting model can improve the engineering predictions of long-term drying shrinkage accounting also for the history dependence of strain induced by hysteresis. Alternative strategies for quantitative analyses of the microstructure of cement paste based on this mesoscale physical model of water content within porous spaces are discussed.

  17. Evaluation of polymerization shrinkage of dental composites by an optical method.

    PubMed

    Weig, K M; Magalhães Filho, T R; Costa Neto, C A; Costa, M F

    2015-02-01

    This study proposes an alternative methodology for evaluating polymerization shrinkage of dental composites using an advanced video extensometer (AVE) system. This equipment measures the displacement between two points drawn on a tooth's wall without requiring physical contact with the tooth. By doing so, the polymerization process was monitored by the cusp deflection. This technique was used in human and bovine teeth, where the cavities were prepared under controlled conditions so that the volume of the composite used was the same in both types of teeth. After the cavity preparation, the specimens were acid etched, washed and dried, and then the adhesive was applied and polymerized. The composite was then inserted into the cavity. Polymerization was performed with two different light polymerizing units (LD Max and Optilight Max - Gnatus do Brasil), and the displacement curve of the tooth cusp was recorded for a period of 400 s. After a statistical analysis, it was concluded that the technique was capable of evaluating shrinkage by the deflection from the cusps and that the human and bovine teeth do not react in a similar manner towards the polymerization shrinkage of composites. PMID:25492174

  18. The effect of resin shades on microhardness, polymerization shrinkage, and color change of dental composite resins.

    PubMed

    Jeong, Tae-Sung; Kang, Ho-Seung; Kim, Sung-Ki; Kim, Shin; Kim, Hyung-Il; Kwon, Yong Hoon

    2009-07-01

    The present study sought to evaluate the effect of resin shades on the degree of the polymerization. To this end, response variables affected by the degree of polymerization were examined in this study - namely, microhardness, polymerization shrinkage, and color change. Two commercial composite resins of four different shades were employed in this study: shades A3, A3.5, B3, and C3 of Z250 (Z2) and shades A3, A3.5, B3, and B4 of Solitaire 2 (S2). After light curing, the reflectance/absorbance, microhardness, polymerization shrinkage, and color change of the specimens were measured. On reflectance and absorbance, Z2 and S2 showed similar distribution curves regardless of the resin shade, with shade A3.5 of Z2 and shade A3 of S2 exhibiting the lowest/highest distributions. Similarly for attenuation coefficient and microhardness, the lowest/highest values were exhibited by shade A3.5 of Z2 and shade A3 of S2. On polymerization shrinkage, no statistically significant differences were observed among the different shades of Z2. Similarly for color change, Z2 specimens exhibited only a slight (DeltaE*=0.5-0.9) color change after immersion in distilled water for 10 days, except for shades A3 and A3.5. Taken together, results of the present study suggested that the degree of polymerization of the tested composite resins was minimally affected by resin shade. PMID:19721281

  19. Thoracoscopic CO laser coagulation shrinkage of blebs in treatment of spontaneous pneumothorax

    NASA Astrophysics Data System (ADS)

    Sensaki, Koji; Arai, Tsunenori; Kikuchi, Keiichi; Takagi, Keigo; Tanaka, Susumu; Kikuchi, Makoto

    1992-06-01

    Spontaneous pneumothorax is a common disease in young people. Operative intervention has been done in most of the recurrent cases. Recently thoracoscopic treatment has been tested as a less invasive treatment modarity. We adopted carbon monoxide (CO) laser for thoracoscopic treatment of recurrent spontaneous pneumothorax. CO laser (wavelength; 5.4 micrometers ) could be delivered by chalcogenide glass (As - S) covered with a teflon sheath and ZnSe fiber tip. The sterilized flexible bronchoscope was inserted through the thoracoscopic outer sheath under local anesthesia. Shrinkage of blebs was obtained by non-contact method of CO laser irradiation. Laser power at the tip was 2.5 - 5 W and irradiation duration was 0.5 s each. Excellent shrinkage of bleb and bulla could be obtained by CO laser without perforation complication. Advantages of CO laser as a thoracoscopic treatment were: (1) capability of fiber delivery (flexible thoracoscopy was easy to operate and clear to visualize the blebs which were frequently found at the apical portion of the lung, and (2) shallow extinction length (good shrinkage of blebs, low risk of perforation, and thin layer of carbonization). In conclusion, our new technique of thoracoscopic CO laser irradiation was found to be a safe and effective treatment of spontaneous pneumothorax.

  20. DH and ESPI laser interferometry applied to the restoration shrinkage assessment

    NASA Astrophysics Data System (ADS)

    Campos, L. M. P.; Parra, D. F.; Vasconcelos, M. R.; Vaz, M.; Monteiro, J.

    2014-01-01

    In dental restoration postoperative marginal leakage is commonly associated to polymerization shrinkage effects. In consequence the longevity and quality of restorative treatment depends on the shrinkage mechanisms of the composite filling during the polymerization. In this work the development of new techniques for evaluation of those effects under light-induced polymerization of dental nano composite fillings is reported. The composite resins activated by visible light, initiate the polymerization process by absorbing light in wavelengths at about 470 nm. The techniques employed in the contraction assessment were digital holography (DH) and Electronic Speckle Pattern Interferometry (ESPI) based on laser interferometry. A satisfactory resolution was achieved in the non-contact displacement field measurements on small objects concerning the experimental dental samples. According to a specific clinical protocol, natural teeth were used (human mandibular premolars). A class I cavity was drilled and restored with nano composite material, according to Black principles. The polymerization was monitored by DH and ESPI in real time during the cure reaction of the restoration. The total displacement reported for the material in relation of the tooth wall was 3.7 μm (natural tooth). The technique showed the entire tooth surface (wall) deforming during polymerization shrinkage.

  1. Multiple-Shrinkage Multinomial Probit Models with Applications to Simulating Geographies in Public Use Data.

    PubMed

    Burgette, Lane F; Reiter, Jerome P

    2013-06-01

    Multinomial outcomes with many levels can be challenging to model. Information typically accrues slowly with increasing sample size, yet the parameter space expands rapidly with additional covariates. Shrinking all regression parameters towards zero, as often done in models of continuous or binary response variables, is unsatisfactory, since setting parameters equal to zero in multinomial models does not necessarily imply "no effect." We propose an approach to modeling multinomial outcomes with many levels based on a Bayesian multinomial probit (MNP) model and a multiple shrinkage prior distribution for the regression parameters. The prior distribution encourages the MNP regression parameters to shrink toward a number of learned locations, thereby substantially reducing the dimension of the parameter space. Using simulated data, we compare the predictive performance of this model against two other recently-proposed methods for big multinomial models. The results suggest that the fully Bayesian, multiple shrinkage approach can outperform these other methods. We apply the multiple shrinkage MNP to simulating replacement values for areal identifiers, e.g., census tract indicators, in order to protect data confidentiality in public use datasets. PMID:24358073

  2. Large-proportional shrunken bio-replication of shark skin based on UV-curing shrinkage

    NASA Astrophysics Data System (ADS)

    Chen, Huawei; Che, Da; Zhang, Xin; Yue, Yue; Zhang, Deyuan

    2015-01-01

    The shark skin effect has attracted worldwide attention because of its superior drag reduction. As the product of natural selection, the maximum drag reduction of shark skin is found in its normal living environment. Large-proportional shrinkage of shark skin morphology is greatly anticipated for its adaptation to faster fluid flow. One novel approach, large-proportional shrunken bio-replication, is proposed as a method to adjust the optimal drag reduction region of shark skin based on the shrinkage of UV-cured material. The shark skin is taken as a replica template to allow large-proportional shrinking in the drag reduction morphology by taking advantage of the shrinkage of UV-curable material. The accuracy of the large-proportional shrunken bio-replication approach is verified by a comparison between original and shrunken bio-replicated shark skin, which shows that the shrinking ratio can reach 23% and the bio-replication accuracy is higher than 95%. In addition, the translation of the optimum drag reduction peak of natural surface function to various applications and environments is proved by drag reduction experiments.

  3. 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.

  4. Elevated temperature aluminum alloys

    NASA Technical Reports Server (NTRS)

    Meschter, Peter (Inventor); Lederich, Richard J. (Inventor); O'Neal, James E. (Inventor)

    1989-01-01

    Three aluminum-lithium alloys are provided for high performance aircraft structures and engines. All three alloys contain 3 wt % copper, 2 wt % lithium, 1 wt % magnesium, and 0.2 wt % zirconium. Alloy 1 has no further alloying elements. Alloy 2 has the addition of 1 wt % iron and 1 wt % nickel. Alloy 3 has the addition of 1.6 wt % chromium to the shared alloy composition of the three alloys. The balance of the three alloys, except for incidentql impurities, is aluminum. These alloys have low densities and improved strengths at temperatures up to 260.degree. C. for long periods of time.

  5. Superplasticity in aluminum alloys

    SciTech Connect

    Nieh, T. G.

    1997-12-01

    We have characterized in the Al-Mg system the microstructure and mechanical properties of a cold-rolled Al-6Mg-0.3Sc alloy. The alloy exhibited superplasticity at relatively high strain rates (about 10-2 s-1). At a strain rate of 10-2 s-1 there exists a wide temperature range (475-520`C) within which the tensile elongation is over 1000%. There also exists a wide strain rate range (10-3 - 10-1 s-1) within which the tensile elongation is over 500%. The presence of Sc in the alloy results in a uniform distribution of fine coherent Al3SC precipitates which effectively pin grain and subgrain boundaries during static and continuous recrystallization. As a result, the alloy retains its fine grain size (about 7 micron), even after extensive superplastic deformation (>1000%). During deformation, dislocations Mg with a high Schmidt factor slip across subgrains but are trapped by subgrain boundaries, as a result of the strong pining of Al3Sc. This process leads to the conversion of low-angled subgrain boundaries to high-angled grain boundaries and the subsequent grain boundary sliding, which produces superelasticity. A model is proposed to describe grain boundary sliding accommodated by dislocation glide across grains with a uniform distribution of coherent precipitates. The model predictions is consistent with experimental observations.

  6. Capturing heterogeneous nucleation of nanoscale pits and subsequent crystal shrinkage during Ostwald ripening of a metal phosphate.

    PubMed

    Chung, Sung-Yoon; Kim, Young-Min; Choi, Si-Young; Kim, Jin-Gyu

    2015-01-27

    It has been generally accepted that crystal shrinkage during Ostwald ripening can be understood simply as a reverse process of crystal growth, and as a result, little attention has been paid to shrinkage behavior. The entire microstructure of polycrystalline materials, however, forms as a consequence of both growing and shrinking crystals. Thus, scrutiny of shrinking characteristics in addition to growth aspects is essential for a complete understanding of the evolution of microstructure during Ostwald ripening. By capturing real-time in situ high-resolution electron micrographs at high temperature, we herein demonstrate the shrinkage behavior of nanocrystals embedded in a solid crystalline matrix during the ripening process of a metal phosphate. Unlike typical crystal growth behavior based on two-dimensional homogeneous nucleation, heterogeneous types of nucleation with nanoscale pits at solid-solid interfaces (or crystal edges) are observed to dominantly occur during shrinkage of the crystals. The findings of this study suggest that crystal shrinkage proceeds with a lower activation energy barrier than that of crystal growth, although both crystal growth and shrinkage take place at the same time during Ostwald ripening. PMID:25588182

  7. Partial shrinkage of venous tissues near valves using High Intensity Focused Ultrasound

    NASA Astrophysics Data System (ADS)

    Pichardo, Samuel; Curiel, Laura; Milleret, René; Pichot, Olivier; Lacoste, François; Chapelon, Jean-Yves

    2005-03-01

    The cross-section of a vein can be reduced by exposing the collagen of the vein wall to high temperature (85° C) for a few seconds. Partial shrinkage of the vein is appropriate for correcting deformations of valvular tissues that can cause the abnormal blood reflux which is the main cause of varicose veins and Superficial Venous Insufficiency. Due to its suitability for inducing localized heating, High Intensity Focused Ultrasound (HIFU) is a good method for correcting valvular tissue. In the present study, the feasibility of using HIFU for inducing partial shrinkage of the saphenous vein wall is demonstrated. The position and size of valvular deformations are well suited to being heated and, consequently, reduced with HIFU. The resulting shrinkage of deformations should restore normal function of the valve. An experimental protocol was used in which several in vitro segments of human saphenous vein were exposed with a monochromatic signal produced by a real-time imaging HIFU probe. The probe has a focal length of 45 mm, a diameter of 52.5 mm and operates at 3 MHz. Ultrasonic imaging, obtained with an 8-MHz 128-element linear array placed at the centre of the HIFU probe, was used to target the vein. The segment was inserted in a porcine muscle sample, and both were placed into a PVC cylinder. Individual sonications of the vein wall were performed for acoustic power values ranging between 8.75 and 35 W at a constant sonication duration of 5 s. Different durations ranging between 3 and 7 s at constant power were also tested. Finally, a long duration of 18 s was tested while the focal point was displaced along the vein wall at a speed of 0.5 mm/s. Results showed that shrinkage of the vein wall was observed using echographic and macroscopic analysis. In particular, the vein diameter was reduced by 15% for a sonication-duration of 18 s with continuous displacement of the focal point. Results showed that HIFU is suitable for partial shrinkage of the saphenous vein and

  8. Properties of tungsten heavy alloys, prepared by spark-plasma sintering

    NASA Astrophysics Data System (ADS)

    Ermakova, N. S.; Yurlova, M. S.; Grigoryev, E. G.

    2016-04-01

    In this paper the effect of spark-plasma sintering parameters on the microstructure and mechanical properties of tungsten heavy alloys VNZHK-90 and VNZHK-93 are studied. The basic dependences of the density and strength characteristics from the sintering temperature and velocity are shown. Conclusions about the dependence of the method of preparation of the starting powders on the microstructure of alloys are formulated. It was found that by spark-plasma sintering technique it is possible to achieve the theoretical density of compact heavy alloys during solid-phase sintering. It is shown that the maximum level of alloys mechanical properties is observed when sintering temperature 1300 ° C. It is found that the change in the rate of heating does not contribute to change in the density of the samples. At the same time, on the mechanical properties the shrinkage rate has a significant effect.

  9. Imparting passivity to vapor deposited magnesium alloys

    NASA Astrophysics Data System (ADS)

    Wolfe, Ryan C.

    Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread implementation of magnesium alloys is currently hindered by their relatively poor corrosion resistance. The objective of this research dissertation is to develop a scientific basis for the creation of a corrosion resistant magnesium alloy. The corrosion resistance of magnesium alloys is affected by several interrelated factors. Among these are alloying, microstructure, impurities, galvanic corrosion effects, and service conditions, among others. Alloying and modification of the microstructure are primary approaches to controlling corrosion. Furthermore, nonequilibrium alloying of magnesium via physical vapor deposition allows for the formation of single-phase magnesium alloys with supersaturated concentrations of passivity-enhancing elements. The microstructure and surface morphology is also modifiable during physical vapor deposition through the variation of evaporation power, pressure, temperature, ion bombardment, and the source-to-substrate distance. Aluminum, titanium, yttrium, and zirconium were initially chosen as candidates likely to impart passivity on vapor deposited magnesium alloys. Prior to this research, alloys of this type have never before been produced, much less studied. All of these metals were observed to afford some degree of corrosion resistance to magnesium. Due to the especially promising results from nonequilibrium alloying of magnesium with yttrium and titanium, the ternary magnesium-yttrium-titanium system was investigated in depth. While all of the alloys are lustrous, surface morphology is observed under the scanning

  10. Imparting passivity to vapor deposited magnesium alloys

    NASA Astrophysics Data System (ADS)

    Wolfe, Ryan C.

    Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread implementation of magnesium alloys is currently hindered by their relatively poor corrosion resistance. The objective of this research dissertation is to develop a scientific basis for the creation of a corrosion resistant magnesium alloy. The corrosion resistance of magnesium alloys is affected by several interrelated factors. Among these are alloying, microstructure, impurities, galvanic corrosion effects, and service conditions, among others. Alloying and modification of the microstructure are primary approaches to controlling corrosion. Furthermore, nonequilibrium alloying of magnesium via physical vapor deposition allows for the formation of single-phase magnesium alloys with supersaturated concentrations of passivity-enhancing elements. The microstructure and surface morphology is also modifiable during physical vapor deposition through the variation of evaporation power, pressure, temperature, ion bombardment, and the source-to-substrate distance. Aluminum, titanium, yttrium, and zirconium were initially chosen as candidates likely to impart passivity on vapor deposited magnesium alloys. Prior to this research, alloys of this type have never before been produced, much less studied. All of these metals were observed to afford some degree of corrosion resistance to magnesium. Due to the especially promising results from nonequilibrium alloying of magnesium with yttrium and titanium, the ternary magnesium-yttrium-titanium system was investigated in depth. While all of the alloys are lustrous, surface morphology is observed under the scanning

  11. Differential Tiam1/Rac1 activation in hippocampal and cortical neurons mediates differential spine shrinkage in response to oxygen/glucose deprivation

    PubMed Central

    Blanco-Suárez, Elena; Fiuza, Maria; Liu, Xun; Chakkarapani, Elavazhagan; Hanley, Jonathan G

    2014-01-01

    Distinct neuronal populations show differential sensitivity to global ischemia, with hippocampal CA1 neurons showing greater vulnerability compared to cortical neurons. The mechanisms that underlie differential vulnerability are unclear, and we hypothesize that intrinsic differences in neuronal cell biology are involved. Dendritic spine morphology changes in response to ischemic insults in vivo, but cell type-specific differences and the molecular mechanisms leading to such morphologic changes are unexplored. To directly compare changes in spine size in response to oxygen/glucose deprivation (OGD) in cortical and hippocampal neurons, we used separate and equivalent cultures of each cell type. We show that cortical neurons exhibit significantly greater spine shrinkage compared to hippocampal neurons. Rac1 is a Rho-family GTPase that regulates the actin cytoskeleton and is involved in spine dynamics. We show that Rac1 and the Rac guanine nucleotide exchange factor (GEF) Tiam1 are differentially activated by OGD in hippocampal and cortical neurons. Hippocampal neurons express more Tiam1 than cortical neurons, and reducing Tiam1 expression in hippocampal neurons by shRNA enhances OGD-induced spine shrinkage. Tiam1 knockdown also reduces hippocampal neuronal vulnerability to OGD. This work defines fundamental differences in signalling pathways that regulate spine morphology in distinct neuronal populations that may have a role in the differential vulnerability to ischemia. PMID:25248834

  12. Optimal tumor shrinkage predicts long-term outcome in advanced nonsmall cell lung cancer (NSCLC) treated with target therapy: Result from 3 clinical trials of advanced NSCLC by 1 institution.

    PubMed

    He, Xiaobo; Zhang, Yang; Ma, Yuxiang; Zhou, Ting; Zhang, Jianwei; Hong, Shaodong; Sheng, Jin; Zhang, Zhonghan; Yang, Yunpeng; Huang, Yan; Zhang, Li; Zhao, Hongyun

    2016-08-01

    Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are used as standard therapies for advanced nonsmall cell lung cancer (NSCLC) patients with EGFR mutation positive. Because these targeted therapies could cause tumor necrosis and shrinkage, the purpose of the study is to search for a value of optimal tumor shrinkage as an appropriate indicator of outcome for advanced NSCLC.A total of 88 NSCLC enrollees of 3 clinical trials (IRESSA registration clinical trial, TRUST study and ZD6474 study), who received Gefitinib (250 mg, QD), Erlotinib (150 mg, QD), and ZD6474 (100 mg, QD), respectively, during December 2003 and October 2007, were retrospectively analyzed. The response evaluation criteria in solid tumors (RECIST) were used to identify responders, who had complete response (CR) or partial responses (PR) and nonresponders who had stable disease (SD) or progressive disease (PD). Receiver operating characteristics (ROC) analysis was used to find the optimal tumor shrinkage as an indicator for tumor therapeutic outcome. Univariate and multivariate Cox regression analyses were performed to compare the progression-free survival (PFS) and overall survival (OS) between responders and nonresponders stratified based on radiologic criteria.Among the 88 NSCLC patients, 26 were responders and 62 were nonresponders based on RECIST 1.0. ROC indicated that 8.32% tumor diameter shrinkage in the sum of the longest tumor diameter (SLD) was the cutoff point of tumor shrinkage outcomes, resulting in 46 responders (≤8.32%) and 42 nonresponders (≥8.32%). Univariate and multivariate Cox regression analyses indicated that (1) the responders (≤8.32%) and nonresponders (≥ -8.32%) were significantly different in median PFS (13.40 vs 1.17 months, P < 0.001) and OS (19.80 vs 7.90 months, P < 0.001) and (2) -8.32% in SLD could be used as the optimal threshold for PFS (hazard ratio [HR], 8.11, 95% CI, 3.75 to 17.51, P < 0.001) and OS (HR, 2.36, 95

  13. Cryogenic Properties of a New Tough-Strong Iron Alloy

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1977-01-01

    A program was undertaken to develop an iron-base alloy having a fracture toughness of 220 MPa. m superscript 1/2 with a corresponding yield stress of 1.4 GPa (200 ksi) at-196 C. An Fe-12Ni alloy was selected as the base alloy. Factors considered included reactive metal additions, effects of interstitial impurities, strengthening mechanisms, and weldability. The goals were met in an Fe-12Ni-0.5Al alloy strengthened by thermomechanical processing or by precipitate strengthening with 2 percent Cu. The alloy is weldable with the weld metal and heat affected zone in the postweld annealed condition having toughness equivalent to the base alloy.

  14. Comparison of the Oxidation Rates of Some New Copper Alloys

    NASA Technical Reports Server (NTRS)

    Ogbuji, Linus U. J. Thomas; Humphrey, Donald L.

    2002-01-01

    Copper alloys were studied for oxidation resistance and mechanisms between 550 and 700 C, in reduced-oxygen environments expected in rocket engines, and their oxidation behaviors compared to that of pure copper. They included two dispersion-strengthened alloys (precipitation-strengthened and oxide-dispersion strengthened, respectively) and one solution-strengthened alloy. In all cases the main reaction was oxidation of Cu into Cu2O and CuO. The dispersion-strengthened alloys were superior to both Cu and the solution-strengthened alloy in oxidation resistance. However, factors retarding oxidation rates seemed to be different for the two dispersion-strengthened alloys.

  15. Striatal Iron Content Predicts Its Shrinkage and Changes in Verbal Working Memory after Two Years in Healthy Adults

    PubMed Central

    Haacke, E. Mark; Raz, Naftali

    2015-01-01

    The accumulation of non-heme iron in the brain has been proposed as a harbinger of neural and cognitive decline in aging and neurodegenerative disease, but support for this proposal has been drawn from cross-sectional studies, which do not provide valid estimates of change. Here, we present longitudinal evidence of subcortical iron accumulation in healthy human adults (age 19–77 at baseline). We used R2* relaxometry to estimate regional iron content twice within a 2 year period, measured volumes of the striatum and the hippocampus by manual segmentation, and assessed cognitive performance by working memory tasks. Two-year change and individual differences in the change of regional volumes, regional iron content, and working memory were examined by latent change score models while taking into account the age at baseline and metabolic risk indicators. Over the examined period, volume reduction occurred in the caudate nucleus and hippocampus, but iron content increased only in the striatum, where it explained shrinkage. Higher iron content in the caudate nucleus at baseline predicted lesser improvement in working memory after repeat testing. Although advanced age and elevated metabolic syndrome risk were associated with greater iron content in the putamen at baseline, neither age nor metabolic risk influenced change in any variable. Thus, longitudinal evidence supports the notion that accumulation of subcortical iron is a risk factor for neural and cognitive decline in normal aging. PMID:25926451

  16. Electron beam-assisted healing of nanopores in magnesium alloys

    PubMed Central

    Zheng, He; Liu, Yu; Cao, Fan; Wu, Shujing; Jia, Shuangfeng; Cao, Ajing; Zhao, Dongshan; Wang, Jianbo

    2013-01-01

    Nanopore-based sensing has emerged as a promising candidate for affordable and powerful DNA sequencing technologies. Herein, we demonstrate that nanopores can be successfully fabricated in Mg alloys via focused electron beam (e-beam) technology. Employing in situ high-resolution transmission electron microscopy techniques, we obtained unambiguous evidence that layer-by-layer growth of atomic planes at the nanopore periphery occurs when the e-beam is spread out, leading to the shrinkage and eventual disappearance of nanopores. The proposed healing process was attributed to the e-beam-induced anisotropic diffusion of Mg atoms in the vicinity of nanopore edges. A plausible diffusion mechanism that describes the observed phenomena is discussed. Our results constitute the first experimental investigation of nanopores in Mg alloys. Direct evidence of the healing process has advanced our fundamental understanding of surface science, which is of great practical importance for many technological applications, including thin film deposition and surface nanopatterning. PMID:23719630

  17. Electron beam-assisted healing of nanopores in magnesium alloys

    NASA Astrophysics Data System (ADS)

    Zheng, He; Liu, Yu; Cao, Fan; Wu, Shujing; Jia, Shuangfeng; Cao, Ajing; Zhao, Dongshan; Wang, Jianbo

    2013-05-01

    Nanopore-based sensing has emerged as a promising candidate for affordable and powerful DNA sequencing technologies. Herein, we demonstrate that nanopores can be successfully fabricated in Mg alloys via focused electron beam (e-beam) technology. Employing in situ high-resolution transmission electron microscopy techniques, we obtained unambiguous evidence that layer-by-layer growth of atomic planes at the nanopore periphery occurs when the e-beam is spread out, leading to the shrinkage and eventual disappearance of nanopores. The proposed healing process was attributed to the e-beam-induced anisotropic diffusion of Mg atoms in the vicinity of nanopore edges. A plausible diffusion mechanism that describes the observed phenomena is discussed. Our results constitute the first experimental investigation of nanopores in Mg alloys. Direct evidence of the healing process has advanced our fundamental understanding of surface science, which is of great practical importance for many technological applications, including thin film deposition and surface nanopatterning.

  18. Erythrocyte Shrinkage and Cell Membrane Scrambling after Exposure to the Ionophore Nonactin.

    PubMed

    Peter, Thomas; Bissinger, Rosi; Lang, Florian

    2016-02-01

    The ionophore antibiotic nonactin permeabilizes cell membranes to NH4+ and K(+) . Treatment of erythrocytes with nonactin is expected to trigger cellular K(+) loss with subsequent cell shrinkage, which in turn is known to trigger suicidal death of a wide variety of cells including erythrocytes. This study explored whether nonactin exposure induces eryptosis, the suicidal erythrocyte death characterized by cell shrinkage and translocation of cell membrane phosphatidylserine to the erythrocyte surface. Signalling of eryptosis includes increase in cytosolic Ca(2+) activity [(Ca(2+) )i ] and stimulation of protein kinase C (PKC) as well as p38 mitogen-activated protein kinase. Phosphatidylserine abundance at the cell surface was estimated from annexin-V-binding, cell volume from forward scatter (FSC) and (Ca(2+) )i from Fluo3-fluorescence. A 48-hr treatment of human erythrocytes with nonactin significantly decreased FSC (≥10 ng/ml) and significantly increased the percentage of annexin-V-binding cells (≥10 ng/ml), effects paralleled by increase in (Ca(2+) )i (≥50 ng/ml) and virtually abrogated by increase in extracellular K(+) concentration to 120 mM at the expense of Na(+) . The up-regulation of annexin-V-binding after nonactin treatment was significantly blunted but not abolished by the removal of extracellular Ca(2+) and by addition of either PKC inhibitor staurosporine (0.4 μM) or p38 kinase inhibitor SB203580 (2 μM). In conclusion, exposure of erythrocytes to the K(+) ionophore nonactin induces erythrocyte shrinkage and subsequent erythrocyte membrane scrambling, effects involving cellular K(+) loss, Ca(2+) entry and activation of staurosporine as well as SB203580-sensitive kinases. PMID:26280658

  19. Early daily trunk shrinkage is highly sensitive to water stress in nectarine trees

    NASA Astrophysics Data System (ADS)

    Pérez-Pastor, Alejandro; De la Rosa, Jose M.; Dodd, Ian C.; Conesa, María R.; Domingo, Rafael

    2014-05-01

    The sensitivity to water stress of different plant water status indicators was evaluated during two consecutive years in early nectarine trees grown in a semi-arid region. Measurements were made post-harvest and two irrigation treatments were applied: a control treatment (CTL), irrigated at 120% of crop evapotranspiration demand to achieve non-limiting water conditions, and a deficit irrigation treatment (DI), that applied around 37% less water than CTL during late postharvest. The plant water status indicators evaluated were midday stem water potential (Ψstem) and parameters derived from trunk diameter fluctuations (TDF): maximum daily shrinkage (MDS), trunk daily growth rate (TGR), early daily shrinkage measured between 0900 and 1200 h solar time (EDS), and late daily shrinkage (LDS) that occurred between 1200 h solar time and the moment that minimum trunk diameter was reached (typically 1600 h solar time). The most sensitive (highest ratio of signal intensity (SI) to noise) indicators to water stress were Ψstem together with EDS. The SI of EDS was greater than that of Ψstem, although with greater variability. EDS was a better indicator than MDS, with higher SI and similar variability. Although MDS was linearly related to Ψstem down to -1.5 MPa, thereafter MDS decreased with increasing water stress. In contrast, EDS was linearly related to Ψstem, although the slope of the regression decreased as the season progressed, as in the case of MDS. Further studies are needed to determine whether EDS is a sensitive indicator of water stress in a range of species.

  20. 10% Tumor Diameter Shrinkage on the First Follow-Up Computed Tomography Predicts Clinical Outcome in Patients With Advanced Renal Cell Carcinoma Treated With Angiogenesis Inhibitors: A Follow-Up Validation Study

    PubMed Central

    Franchetti, Yoko; Nishino, Mizuki; Fay, André P.; Ramaiya, Nikhil; Van den Abbeele, Annick D.; Choueiri, Toni K.

    2014-01-01

    Background. Vascular endothelial growth factor (VEGF)-targeted agents are standard therapies for metastatic renal cell carcinoma (mRCC), associated with variable tumor shrinkage. Response Evaluation Criteria in Solid Tumors (RECIST) is of limited utility in this setting, and other imaging changes are sought to reliably predict outcome early. We aim to validate 10% tumor shrinkage as the best early indicator of outcome. Methods. In this institutional review board-approved, Health Insurance Portability and Accountability Act-compliant study, 66 mRCC patients with 165 lesions on clinical trials of VEGF-targeted agents underwent thoracic and abdominal computed tomography at baseline and at first follow-up after therapy. Measurements were performed according to RECIST and tumor shrinkage of ≥10% decrease in sum of the longest diameter (−10%SLD). Correlation with time-to-treatment failure (TTF) and overall survival (OS) were compared and stratified by response to the radiologic criteria. Receiver-operating characteristics (ROC) analysis yielded the optimal threshold change in SLD, defining patients with prolonged survival. Results. More than −10%SLD significantly differentiated responders from nonresponders (median TTF 8.4 vs. 4.1 months, p = .001), whereas partial response by RECIST did not (median TTF 6.9 vs. 5.5 months in responders vs. nonresponders, p = .34). −10%SLD was also significantly predictive of OS (median OS 35.1 vs. 15.0 months in responders vs. nonresponders, p = .003). ROC curve analysis yielded −9.3% in SLD as the optimal threshold for response/no response. Conclusion. Ten percent tumor shrinkage is validated as a reliable early predictor of outcome in mRCC patients receiving VEGF-targeted therapies and may provide a practical measure to guide therapeutic decisions. PMID:24755461

  1. Effect of shrinkage and moisture content on the physical characteristics of blended cement mortars

    SciTech Connect

    Kanna, V.; Olson, R.A.; Jennings, H.M.

    1998-10-01

    The effects of drying on mortars containing Portland cement blended with fly ash or slag on the shrinkage, extent of surface cracking, pore size distribution as measured by mercury intrusion porosimetry, flexural strength, fracture toughness, and Young`s modulus are reported. Specimens were exposed to conditions of 100% relative humidity (RH), 50% RH, and/or oven-drying at 105 C. Drying coarsened the pore structure and increased the density of surface cracks, but surprisingly increased the flexural strength and the fracture toughness, and as anticipated lowered the Young`s modulus. This was regardless of the content of mineral admixture.

  2. On the Convergence of the Iterative Shrinkage/Thresholding Algorithm With a Weakly Convex Penalty

    NASA Astrophysics Data System (ADS)

    Bayram, Ilker

    2016-03-01

    We consider the iterative shrinkage/thresholding algorithm (ISTA) applied to a cost function composed of a data fidelity term and a penalty term. The penalty is non-convex but the concavity of the penalty is accounted for by the data fidelity term so that the overall cost function is convex. We provide a generalization of the convergence result for ISTA viewed as a forward-backward splitting algorithm. We also demonstrate experimentally that for the current setup, using large stepsizes in ISTA can accelerate convergence more than existing schemes proposed for the convex case, like TwIST or FISTA.

  3. Expansion and shrinkage of the sulfur composite electrode in rechargeable lithium batteries

    NASA Astrophysics Data System (ADS)

    He, Xiangming; Ren, Jianguo; Wang, Li; Pu, Weihua; Jiang, Changyin; Wan, Chunrong

    The expansion and shrinkage characteristics of sulfur composite cathode electrode in rechargeable lithium batteries have been investigated. It was found that the sulfur composites electrodes expanded when discharging and shrank when charging again. The thickness change of the electrode was measured to be about 22%. The thickness of lithium metal anodes was also changed when lithium deposition and dissolution, while the sulfur composites electrodes expanded and shrank conversely. The investigation showed that the thickness changes of lithium anode and sulfur composite cathode could be compensated with each other to keep the total thickness of the cell not to change so much.

  4. Alloy softening in binary molybdenum alloys

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1972-01-01

    An investigation was conducted to determine the effects of alloy additions of Hf, Ta, W, Re, Os, Ir, and Pt on the hardness of Mo. Special emphasis was placed on alloy softening in these binary Mo alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to Mo, while those elements having an equal number or fewer s+d electrons than Mo failed to produce alloy softening. Alloy softening and hardening can be correlated with the difference in number of s+d electrons of the solute element and Mo.

  5. Magnetic resonance imaging shrinkage patterns following neoadjuvant chemotherapy for breast carcinomas with an emphasis on the radiopathological correlations

    PubMed Central

    TOMIDA, KAORI; ISHIDA, MITSUAKI; UMEDA, TOMOKO; SAKAI, SACHIKO; KAWAI, YUKI; MORI, TSUYOSHI; KUBOTA, YOSHIHIRO; MEKATA, EIJI; NAKA, SHIGEYUKI; ABE, HAJIME; OKABE, HIDETOSHI; TANI, TOHRU

    2014-01-01

    Preoperative neoadjuvant chemotherapy (NAC) is considered to be the standard treatment for locally-advanced breast carcinomas. Obtaining precise information regarding the tumor extent and distribution by imaging modalities to assess the success of breast-conserving surgery following NAC is extremely important. Analysis of the detailed radiopathological correlation of magnetic resonance imaging (MRI) following NAC has not been reported previously. The MRI and histopathological shrinkage patterns of residual breast carcinomas in 27 consecutive cases were analyzed following NAC and classified into five categories: Types I and II (concentric shrinkage with and without surrounding lesions, respectively); type III (shrinkage with residual multinodular lesions); type IV (diffuse contrast enhancement in whole quadrant); and non-visualization. The present study clearly demonstrated that the most common MRI shrinkage pattern was type I (11 cases), followed by type II and non-visualization, and the most common histopathological shrinkage pattern was type II (11 cases), followed by type III (8 cases). The concordance rate between MRI and pathological patterns was 48% and the worst concordance MRI pattern was type I. MRI is considered to be a useful method for evaluation of the residual carcinoma following NAC. However, the concordance rate was low in the MRI pattern I cases and tiny foci of residual carcinoma were present in half of the non-visualization cases, as shown by MRI. Therefore, the tumor extent must be completely resected for patients who undergo NAC, and postoperative radiation may be important for preventing local recurrence of breast carcinoma. PMID:25054046

  6. Modeling and Analysis of Process Parameters for Evaluating Shrinkage Problems During Plastic Injection Molding of a DVD-ROM Cover

    NASA Astrophysics Data System (ADS)

    Öktem, H.

    2012-01-01

    Plastic injection molding plays a key role in the production of high-quality plastic parts. Shrinkage is one of the most significant problems of a plastic part in terms of quality in the plastic injection molding. This article focuses on the study of the modeling and analysis of the effects of process parameters on the shrinkage by evaluating the quality of the plastic part of a DVD-ROM cover made with Acrylonitrile Butadiene Styrene (ABS) polymer material. An effective regression model was developed to determine the mathematical relationship between the process parameters (mold temperature, melt temperature, injection pressure, injection time, and cooling time) and the volumetric shrinkage by utilizing the analysis data. Finite element (FE) analyses designed by Taguchi (L27) orthogonal arrays were run in the Moldflow simulation program. Analysis of variance (ANOVA) was then performed to check the adequacy of the regression model and to determine the effect of the process parameters on the shrinkage. Experiments were conducted to control the accuracy of the regression model with the FE analyses obtained from Moldflow. The results show that the regression model agrees very well with the FE analyses and the experiments. From this, it can be concluded that this study succeeded in modeling the shrinkage problem in our application.

  7. Investigation of the mechanical properties of a low-shrinkage liquid crystalline matrix combined with nano-hydroxyapatite.

    PubMed

    Liu, Wen Wen; He, Xiao Ping; Mo, An Chun; Yao, Qian Qian; Ye, Jun; Jing, Nie

    2011-01-01

    The objective of this study was to investigate the mechanical properties of a low-shrinkage acrylate liquid crystalline resin matrix (ALCRM), (4-3-(acryloyloxy)-2-hydroxypropoxy) phenyl 4-(3-(acryloyloxy)-2-hydroxypropoxy) benzoate, combined with nano-hydroxyapatite (na-HA). The ALCRM monomer and diluent monomer triethylene glycol dimethacrylate (TEGDMA) were mixed at a mass ratio of 7:3 to prepare the resin matrix. The volume shrinkage of the ALCRM/TEGDMA and the traditional resin matrix Bis-GMA (2, 2-bis [4-(3-methacryloxy-2-hydroxypropoxy) phenyl] propane)/TEGDMA were measured. Then 20%, 30%, and 40% na-HA were added to ALCRM/TEGDMA and Bis-GMA/TEGDMA, respectively. Compressive strength (CS) and Vickers hardness (VHN) were tested to identify mechanical properties of the composites. The volume shrinkage of the ALCRM/TEGDMA was 3.60% ± 0.36%, which was lower than that of the traditional resin matrix. Moreover, with the same amount of na-HA filler, the mechanical properties of the ALCRM-based composites were superior to those of Bis-GMA-based composites. ALCRM-based composites exhibited the highest CS and VHN values when the filler content was 30%. These results indicate that the low-shrinkage liquid crystalline resin matrix has strong mechanical properties after incorporating the na-HA. The experimental ALCRM-based composites have promising potential for the development of novel low-shrinkage dental resins with strong mechanical properties. PMID:21980241

  8. Does work stress make you shorter? An ambulatory field study of daily work stressors, job control, and spinal shrinkage.

    PubMed

    Igic, Ivana; Ryser, Samuel; Elfering, Achim

    2013-10-01

    Body height decreases throughout the day due to fluid loss from the intervertebral disk. This study investigated whether spinal shrinkage was greater during workdays compared with nonwork days, whether daily work stressors were positively related to spinal shrinkage, and whether job control was negatively related to spinal shrinkage. In a consecutive 2-week ambulatory field study, including 39 office employees and 512 days of observation, spinal shrinkage was measured by a stadiometer, and calculated as body height in the morning minus body height in the evening. Physical activity was monitored throughout the 14 days by accelerometry. Daily work stressors, daily job control, biomechanical workload, and recreational activities after work were measured with daily surveys. Multilevel regression analyses showed that spinal disks shrank more during workdays than during nonwork days. After adjustment for sex, age, body weight, smoking status, biomechanical work strain, and time spent on physical and low-effort activities during the day, lower levels of daily job control significantly predicted increased spinal shrinkage. Findings add to knowledge on how work redesign that increases job control may possibly contribute to preserving intervertebral disk function and preventing occupational back pain. PMID:24099165

  9. Electrothermal shrinkage reduces laxity but alters creep behavior in a lapine ligament model.

    PubMed

    Wallace, A L; Hollinshead, R M; Frank, C B

    2001-01-01

    Thermal denaturation of collagen in ligament tissue has the potential to enhance arthroscopic shoulder stabilization. Previous studies have shown that laser energy produces significant capsular shortening without alteration of viscoelastic properties, but little information is available on the effects of radio frequency electrothermal energy. We assessed the acute effects of radio frequency shrinkage with use of the lapine medial collateral ligament model, in which the tibial insertion was shifted proximally to produce abnormal laxity. Thermal treatment resulted in restoration of laxity from 3.33 +/- 0.25 mm to 0.66 +/- 0.31 mm, which was not significantly different from medial collateral ligaments replaced anatomically (0.50 +/- 0.34 mm). When tested at 4.1 megapascals, cyclic and static creep strains were increased twofold to threefold in thermally-treated ligaments (P <.01), and partial failure occurred in 2 of 8 cases. We conclude that radio frequency electrothermal shrinkage is effective at reducing laxity but significantly alters viscoelastic properties, posing a risk of recurrent stretching-out at "physiological" loads. PMID:11182728

  10. Recycling of rubble from building demolition for low-shrinkage concretes.

    PubMed

    Corinaldesi, Valeria; Moriconi, Giacomo

    2010-04-01

    In this project concrete mixtures were prepared that were characterized by low ductility due to desiccation by using debris from building demolition, which after a suitable treatment was used as aggregate for partial replacement of natural aggregates. The recycled aggregate used came from a recycling plant, in which rubble from building demolition was selected, crushed, cleaned, sieved, and graded. Such aggregates are known to be more porous as indicated by the Saturated Surface Dry (SSD) moisture content. The recycled concrete used as aggregates were added to the concrete mixture in order to study their influence on the fresh and hardened concrete properties. They were added either after water pre-soaking or in dry condition, in order to evaluate the influence of moisture in aggregates on the performance of concrete containing recycled aggregate. In particular, the effect of internal curing, due to the use of such aggregates, was studied. Concrete behavior due to desiccation under dehydration was studied by means of both drying shrinkage test and German angle test, through which shrinkage under the restrained condition of early age concrete can be evaluated. PMID:20022737

  11. 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.

  12. Characterization of a Low Shrinkage Dental Composite Containing Bismethylene Spiroorthocarbonate Expanding Monomer

    PubMed Central

    Fu, Jing; Liu, Wenjia; Hao, Zhichao; Wu, Xiangnan; Yin, Jian; Panjiyar, Anil; Liu, Xiaoqing; Shen, Jiefei; Wang, Hang

    2014-01-01

    In this study, a novel dental composite based on the unsaturated bismethylene spiroorthocarbonate expanding monomer 3,9-dimethylene-1,3,5,7-tetraoxa-spiro[5,5]undecane (BMSOC) and bisphenol-S-bis(3-meth acrylate-2-hydroxypropyl)ether (BisS-GMA) was prepared. CQ (camphorquinone) of 1 wt % and DMAEMA (2-(dimethylamino)ethyl methacrylate) of 2 wt % were used in a photoinitiation system to initiate the copolymerization of the matrix resins. Distilled water contact angle measurements were performed for the wettability measurement. Degree of conversion, volumetric shrinkage, contraction stress and compressive strength were measured using Fourier Transformation Infrared-FTIR spectroscopy, the AccuVol and a universal testing machine, respectively. Within the limitations of this study, it can be concluded that the resin composites modified by bismethylene spiroorthocarbonate and BisS-GMA showed a low volumetric shrinkage at 1.25% and a higher contact angle. The lower contraction stress, higher degree of conversion and compressive strength of the novel dental composites were also observed. PMID:24518683

  13. A bootstrapping soft shrinkage approach for variable selection in chemical modeling.

    PubMed

    Deng, Bai-Chuan; Yun, Yong-Huan; Cao, Dong-Sheng; Yin, Yu-Long; Wang, Wei-Ting; Lu, Hong-Mei; Luo, Qian-Yi; Liang, Yi-Zeng

    2016-02-18

    In this study, a new variable selection method called bootstrapping soft shrinkage (BOSS) method is developed. It is derived from the idea of weighted bootstrap sampling (WBS) and model population analysis (MPA). The weights of variables are determined based on the absolute values of regression coefficients. WBS is applied according to the weights to generate sub-models and MPA is used to analyze the sub-models to update weights for variables. The optimization procedure follows the rule of soft shrinkage, in which less important variables are not eliminated directly but are assigned smaller weights. The algorithm runs iteratively and terminates until the number of variables reaches one. The optimal variable set with the lowest root mean squared error of cross-validation (RMSECV) is selected. The method was tested on three groups of near infrared (NIR) spectroscopic datasets, i.e. corn datasets, diesel fuels datasets and soy datasets. Three high performing variable selection methods, i.e. Monte Carlo uninformative variable elimination (MCUVE), competitive adaptive reweighted sampling (CARS) and genetic algorithm partial least squares (GA-PLS) are used for comparison. The results show that BOSS is promising with improved prediction performance. The Matlab codes for implementing BOSS are freely available on the website: http://www.mathworks.com/matlabcentral/fileexchange/52770-boss. PMID:26826688

  14. Methodology for Registration of Shrinkage Tumors in Head-and-Neck CT Studies

    PubMed Central

    Wang, Jianhua; Dai, Jianrong; Jing, Yongjie; Huo, Yanan; Niu, Tianye

    2015-01-01

    Tumor shrinkage occurs in many patients undergoing radiotherapy for head-and-neck (H&N) cancer. However, one-to-one correspondence is not always available between voxels of two image sets. This makes intensity-based deformable registration difficult and inaccurate. In this paper, we describe a novel method to increase the performance of the registration in presence of tumor shrinkage. The method combines an image modification procedure and a fast symmetric Demons algorithm to register CT images acquired at planning and posttreatment fractions. The image modification procedure modifies the image intensities of the primary tumor by calculating tumor cell survival rate using the linear quadratic (LQ) model according to the dose delivered to the tumor. A scale operation is used to deal with uncertainties in biological parameters. The method was tested in 10 patients with nasopharyngeal cancer (NPC). Registration accuracy was improved compared with that achieved using the symmetric Demons algorithm. The average Dice similarity coefficient (DSC) increased by 21%. This novel method is suitable for H&N adaptive radiation therapy. PMID:26089960

  15. Consideration of the effects on fuel particle behavior from shrinkage cracks in the inner pyrocarbon layer

    NASA Astrophysics Data System (ADS)

    Miller, Gregory K.; Petti, David A.; Varacalle, Dominic J.; Maki, John T.

    2001-06-01

    The fundamental design for a gas-cooled pebble bed reactor relies on an understanding of the behavior of coated particle fuel. The coating layers surrounding the fuel kernels in these spherical particles consist of pyrolytic carbon layers and a silicon carbide (SiC) layer. These coating layers act as a pressure vessel that retains fission product gases. A small percentage of fuel particles may fail during irradiation in the mode of a traditional pressure vessel failure. Fuel performance models used to predict particle behavior have traditionally been one-dimensional models that focus on this failure mechanism. Results of irradiation experiments, however, show that many more fuel particles fail than would be predicted by this mechanism alone. Post-irradiation examinations indicate that multi-dimensional effects, such as the presence of shrinkage cracks in the inner pyrolytic carbon layer (IPyC), contribute to these unexplained failures. Results of a study performed to evaluate the significance of cracking in the IPyC layer on behavior of a fuel particle are presented herein, which indicate that shrinkage cracks could contribute significantly to fuel particle failures.

  16. Characterization of a low shrinkage dental composite containing bismethylene spiroorthocarbonate expanding monomer.

    PubMed

    Fu, Jing; Liu, Wenjia; Hao, Zhichao; Wu, Xiangnan; Yin, Jian; Panjiyar, Anil; Liu, Xiaoqing; Shen, Jiefei; Wang, Hang

    2014-01-01

    In this study, a novel dental composite based on the unsaturated bismethylene spiroorthocarbonate expanding monomer 3,9-dimethylene-1,3,5,7-tetraoxa-spiro[5,5]undecane (BMSOC) and bisphenol-S-bis(3-meth acrylate-2-hydroxypropyl)ether (BisS-GMA) was prepared. CQ (camphorquinone) of 1 wt % and DMAEMA (2-(dimethylamino)ethyl methacrylate) of 2 wt % were used in a photoinitiation system to initiate the copolymerization of the matrix resins. Distilled water contact angle measurements were performed for the wettability measurement. Degree of conversion, volumetric shrinkage, contraction stress and compressive strength were measured using Fourier Transformation Infrared-FTIR spectroscopy, the AccuVol and a universal testing machine, respectively. Within the limitations of this study, it can be concluded that the resin composites modified by bismethylene spiroorthocarbonate and BisS-GMA showed a low volumetric shrinkage at 1.25% and a higher contact angle. The lower contraction stress, higher degree of conversion and compressive strength of the novel dental composites were also observed. PMID:24518683

  17. Evaluation of polymerization shrinkage of resin cements through in vitro and in situ experiments

    NASA Astrophysics Data System (ADS)

    Franco, A. P. G. O.; Karam, L. Z.; Pulido, C. A.; Gomes, O. M. M.; Kalinowski, H. J.

    2014-08-01

    The aim of this study was to evaluate the behavior of two types of resin cements , conventional dual and dual self adhesive, through in vitro and in situ experiments. For the in vitro assay were selected two resin cements that were handled and dispensed over a mylar strip supported by a glass plate. The Bragg grating sensors were positioned and another portion of cement. was placed, covered by another mylar strip. For the in situ experiment 16 single-rooted teeth were selected who were divided into 2 groups: group 1 - conventional dual resin cement Relyx ARC and group 2 - dual self adhesive resin cement Relyx U200 ( 3M/ESPE ). The teeth were treated and prepared to receive the intracanal posts. Two Bragg grating sensors were recorded and introduced into the root canal at different apical and coronal positions. The results showed that the in vitro experiment presented similar values of polymerization shrinkage that the in situ experiment made in cervical position; whereas Relyx ARC resulted lower values compared to Relyx U200; and cervical position showed higher shrinkage than the apical.

  18. Incremental layer shear bond strength of low-shrinkage resin composites under different bonding conditions.

    PubMed

    Al Musa, A H; Al Nahedh, H N A

    2014-01-01

    The purpose of this study was to determine the incremental shear bond strength of a silorane-based composite (Filtek Silorane) repaired with silorane or a methacrylate-based composite (Filtek Z250) under various aging conditions. Also, the incremental bond strength of the silorane-based composite was compared with that of another low-shrinkage methacrylate-based composite (Aelite LS Posterior) under fresh and aged conditions, with and without the use of an adhesive resin between successive layers. The two brands of low-shrinkage composites were compared with a microhybrid, Filtek Z250, which served as the control. Substrate discs were fabricated and second layers were adhered to them immediately, after two weeks of aging, or after four weeks of aging and with and without an adhesive resin. Shear bond strengths were measured and failure modes were evaluated. The incremental bond strength of silorane to the silorane-based composite was not significantly different from that of the methacrylate-based composite. However, repairing a silorane-based composite with a methacrylate-based composite significantly reduced the bond strength. Aelite showed a lower incremental bond strength than Z250 and silorane, but the use of an adhesive significantly improved the bond strength. The absence of an oxygen-inhibited layer did not affect the bond strength of the consecutive layers of the silorane-based composite. PMID:24807812

  19. Methodology for Registration of Shrinkage Tumors in Head-and-Neck CT Studies.

    PubMed

    Wang, Jianhua; Dai, Jianrong; Jing, Yongjie; Huo, Yanan; Niu, Tianye

    2015-01-01

    Tumor shrinkage occurs in many patients undergoing radiotherapy for head-and-neck (H&N) cancer. However, one-to-one correspondence is not always available between voxels of two image sets. This makes intensity-based deformable registration difficult and inaccurate. In this paper, we describe a novel method to increase the performance of the registration in presence of tumor shrinkage. The method combines an image modification procedure and a fast symmetric Demons algorithm to register CT images acquired at planning and posttreatment fractions. The image modification procedure modifies the image intensities of the primary tumor by calculating tumor cell survival rate using the linear quadratic (LQ) model according to the dose delivered to the tumor. A scale operation is used to deal with uncertainties in biological parameters. The method was tested in 10 patients with nasopharyngeal cancer (NPC). Registration accuracy was improved compared with that achieved using the symmetric Demons algorithm. The average Dice similarity coefficient (DSC) increased by 21%. This novel method is suitable for H&N adaptive radiation therapy. PMID:26089960

  20. Effects of poison panel shrinkage and gaps on fuel storage rack reactivity

    SciTech Connect

    Boyd, W.A.; Mueller, D.E.

    1988-01-01

    Fixed poison panels are used in spent fuel rack designs to increase enrichment limits and reduce cell spacing; therefore, assurances that the maximum rack reactivity will meet the design limit (0.95) throughout the lifetime of the racks depend on the continued effectiveness of the poison with time. Industry data have shown that poison panels will shrink under irradiated conditions. From recent data, however, poison panels have been found to have gaps spanning their width after relatively short operating periods. This paper presents results of studies showing the fuel rack reactivity changes associated with poison panel shrinkage and formation of gaps. The discovery of gaps in the fuel rack poison panels at an operating plant raises concerns regarding the effectiveness of the poison over the lifetime of the fuel racks. Studies performed to evaluate the effect of the poison panel shrinkage on reactivity show that reactivity changes from zero to several percent are possible depending on the initial panel size. Results of recent studies show that some gaps can be accommodated in the fuel rack poison panels at the fuel midplane without causing the fuel rack K{sub eff} limit to be exceeded. With worst-case assumptions concerning gap size and the number of panels affected, other actions will likely be required to show that the rack K{sub eff} design limit will not be exceeded.

  1. Influence of irradiance on Knoop hardness, degree of conversion, and polymerization shrinkage of nanofilled and microhybrid composite resins.

    PubMed

    Fugolin, Ana Paula Piovezan; Correr-Sobrinho, Lourenço; Correr, Américo Bortolazzo; Sinhoreti, Mário Alexandre Coelho; Guiraldo, Ricardo Danil; Consani, Simonides

    2016-01-01

    The purpose of this study was to investigate the influence of the irradiance emitted by a light-curing unit on microhardness, degree of conversion (DC), and gaps resulting from shrinkage of 2 dental composite resins. Cylinders of nanofilled and microhybrid composites were fabricated and light cured. After 24 hours, the tops and bottoms of the specimens were evaluated via indentation testing and Fourier transform infrared spectroscopy to determine Knoop hardness number (KHN) and DC, respectively. Gap width (representing polymerization shrinkage) was measured under a scanning electron microscope. The nanofilled composite specimens presented significantly greater KHNs than did the microhybrid specimens (P < 0.05). The microhybrid composite resin exhibited significantly greater DC and gap width than the nanofilled material (P < 0.05). Irradiance had a mostly material-dependent influence on the hardness and DC, but not the polymerization shrinkage, of composite resins. PMID:26943085

  2. A proposed configuration for a stepped specimen to be used in the systematic evaluation of factors influencing warpage in metallic alloys being used for cryogenic wind tunnel models

    NASA Technical Reports Server (NTRS)

    Wigley, D. A.

    1982-01-01

    A proposed configuration for a stepped specimen to be used in the system evaluation of mechanisms that can introduce warpage or dimensional changes in metallic alloys used for cryogenic wind tunnel models is described. Considerations for selecting a standard specimen are presented along with results obtained from an investigation carried out for VASCOMAX 200 maraging steel. Details of the machining and measurement techniques utilized in the investigation are presented. Initial results from the sample of VASCOMAX 200 show that the configuration and measuring techniques are capable of giving quantitative results.

  3. Hygromorphic behaviour of cellular material: hysteretic swelling and shrinkage of wood probed by phase contrast X-ray tomography

    NASA Astrophysics Data System (ADS)

    Derome, Dominique; Rafsanjani, Ahmad; Patera, Alessandra; Guyer, Robert; Carmeliet, Jan

    2012-10-01

    Wood is a hygromorphic material, meaning it responds to changes in environmental humidity by changing its geometry. Its cellular biological structure swells during wetting and shrinks during drying. The origin of the moisture-induced deformation lies at the sub-cellular scale. The cell wall can be considered a composite material with stiff cellulose fibrils acting as reinforcement embedded in a hemicellulose/lignin matrix. The bulk of the cellulose fibrils, forming 50% of the cell wall, are oriented longitudinally, forming long-pitched helices. Both components of cell wall matrix are displaying swelling. Moisture sorption and, to a lesser degree, swelling/shrinkage are known to be hysteretic. We quantify the affine strains during the swelling and shrinkage using high resolution images obtained by phase contrast synchrotron X-ray tomography of wood samples of different porosities. The reversibility of the swelling/shrinkage is found for samples with controlled moisture sorption history. The deformation is more hysteretic for high than for low density samples. Swelling/shrinkage due to ad/desorption of water vapour displays also a non-affine component. The reversibility of the swelling/shrinkage indicates that the material has a structural capacity to show a persistent cellular geometry for a given moisture state and a structural composition that allows for moisture-induced transitional states. A collection of qualitative observations of small subsets of cells during swelling/shrinkage is further studied by simulating the observed behaviour. An anisotropic swelling coefficient of the cell wall is found to emerge and its origin is linked to the anisotropy of the cellulose fibrils arrangement in cell wall layers.

  4. Effects of preheating and precooling on the hardness and shrinkage of a composite resin cured with QTH and LED.

    PubMed

    Osternack, F H; Caldas, D B M; Almeida, J B; Souza, E M; Mazur, R F

    2013-01-01

    The aim of this study was to evaluate in vitro the hardness and shrinkage of a pre-cooled or preheated hybrid composite resin cured by a quartz-tungsten-halogen light (QTH) and light-emitting diode (LED) curing units. The temperature on the tip of the devices was also investigated. Specimens of Charisma resin composite were produced with a metal mold kept under 37°C. The syringes were submitted to 4°C, 23°C, and 60°C (n=20) before light-curing, which was carried out with the Optilux 501 VCL and Elipar FreeLight 2 units for 20 seconds. The specimens were kept under 37°C in a high humidity condition and darkness for 48 hours. The Knoop hardness test was carried out with a 50 gram-force (gf) load for 10 seconds, and the measurement of the shrinkage gap was carried out using an optical microscope. The data were subjected to analysis of variance and the Games-Howell test (α=0.05). The mean hardness of the groups were similar, irrespective of the temperatures (p>0.05). For 4°C and 60°C, the top surface light-cured by LED presented significantly reduced shrinkage when compared with the bottom and to both surfaces cured by QTH (p<0.05). It was concluded that the hardness was not affected by pre-cooling or preheating. However, polymerization shrinkage was slightly affected by different pre-polymerization temperatures. The QTH-curing generated greater shrinkage than LED-curing only when the composite was preheated. Different temperatures did not affect the composite hardness and shrinkage when cured by a LED curing unit. PMID:23088189

  5. Thermally stimulated current spectra of binder resin powders for copiers: Correction for thermal shrinkage of the sample powder compactions

    NASA Astrophysics Data System (ADS)

    Ikezakt, K.; Murata, Y.

    2008-12-01

    Thermally stimulated current (TSC) spectra observed under open- circuit condition for styrene- acrylic binder resin powder compactions for toners are corrected for their thermal shrinkage during TSC observation. For this binder resin, extrinsic current from motion of powder compactions with charges due to their thermal shrinkage was found to be much more effective than the sensitivity coefficient of a TSC measuring apparatus used. Particle size dependence of charge retention power of the resin powders was also examined by using this correction method and found that it decreased with decreasing their particle size.

  6. Order-of-magnitude polymerization-shrinkage suppression of volume gratings recorded in nanoparticle-polymer composites.

    PubMed

    Hata, Eiji; Tomita, Yasuo

    2010-02-01

    We demonstrate substantial shrinkage suppression of nanoparticle-polymer composite transmission gratings by use of the step-growth polymerization mechanism. It is shown that the polymerization shrinkage can be reduced as low as 0.3% at the nanoparticle concentration of 35 vol. % by which the refractive index modulation and the material sensitivity are maximized to be 8x10(-3) and 1014 cm/J, respectively, in the green. Our results offer a noticeable advance in the development of holographic data storage materials. PMID:20125733

  7. Mold deflection effects on the prediction of packing pressure decay and shrinkage of semi-crystalline polymers

    NASA Astrophysics Data System (ADS)

    Costa, Franco S.; Yuan, Zhongshuang

    2015-05-01

    The beneficial effect of considering mold deflection and mold spring-back on the prediction of packing pressure decay and part shrinkage of amorphous polymers has already been demonstrated. In this paper, a similar mold deflection effect is added to the recently developed flow-induced crystallization modeling of semi-crystalline materials during injection molding. The combined effect of improved solidification rate from the crystallization modeling and improved pressure decay due to the mold deflection effect results in improved part shrink and warp predictions. Simulation results are validated against molding data of cavity pressure and shrinkage for a range of polymers.

  8. Quantitative analysis of tumor shrinkage due to chemotherapy and its implication for radiation treatment planning in limited-stage small-cell lung cancer

    PubMed Central

    2013-01-01

    Background The optimal timing of chemoradiotherapy in limited-stage small-cell lung cancer (LS-SCLC) hasn’t been established, although evidence from studies supported that patients can benefit from early radiation therapy. The purpose of this study was to quantify tumor shrinkage in response to induction chemotherapy (IC), evaluate the impact of tumor shrinkage on radiation dosimetric parameters and determine its implication for the timing of radiation therapy for patients with LS-SCLC. Methods Twenty patients with LS-SCLC who were treated with IC followed by concomitant radiation therapy were investigated retrospectively. Ten patients received 1 cycle of IC, and 10 patients received 2 cycles of IC. Pre-IC CT imaging was coregistered with a simulation CT, and virtual radiation plans were created for pre- and post-IC thoracic disease in each case. The changes in the gross target volume (GTV), planning target volume (PTV) and dosimetric factors associated with the lungs, esophagus and heart were analyzed. Results The mean GTV and PTV for all of the patients decreased by 60.9% and 40.2%, respectively, which resulted in a significant reduction in the radiation exposure to the lungs, esophagus and heart. Changes in the PTV and radiation exposure of normal tissue were not significantly affected by the number of chemotherapy cycles delivered, although patients who received 2 cycles of IC had a greater decrease in GTV than those who received only 1 cycle of IC (69.6% vs. 52.1%, p = 0.273). Conclusions Our data showed that targeting the tumor post-IC may reduce the radiation dose to normal tissue in patients with LS-SCLC. However, the benefit to the normal tissue was not increased by an additional cycle of IC. These findings suggest that the first cycle of chemotherapy is very important for tumor shrinkage and that initiating thoracic radiation therapy at the second cycle of chemotherapy may be a reasonable strategy for timing of radiation therapy in LS

  9. An investigation into factors affecting the stability of carbons and carbon supported platinum and platinum/cobalt alloy catalysts during 1.2 V potentiostatic hold regimes at a range of temperatures

    NASA Astrophysics Data System (ADS)

    Ball, S. C.; Hudson, S. L.; Thompsett, D.; Theobald, B.

    To meet automotive targets for fuel cell operation and allow higher temperature operation an understanding of the factors affecting carbon and platinum stability is critical. The stability of both carbons and carbon supported platinum and platinum/cobalt alloy catalysts was studied during 1.2 V versus RHE potentiostatic hold tests using carbon and catalyst coated electrodes in a three-chamber wet electrolyte cell at a range of temperatures. At 80 °C the wt% of carbon corroded increases with increasing BET area. Surface oxidation was followed electrochemically using the quinone/hydroquinone redox couple. Increasing temperature, time at 1.2 V and wt% platinum on the carbon increases surface oxidation. Although increasing temperature was shown to increase the extent of carbon corrosion, catalysing the carbon did not significantly change how much carbon was corroded. Platinum stability was investigated by electrochemical metal area loss (ECA). Platinum catalysts on commercial carbons lost more ECA with increasing temperature. A platinum/cobalt alloy on a low surface area carbon was demonstrated to be more stable to both carbon corrosion and metal area loss at temperatures up to 80 °C than platinum catalysts on commercial carbons, making this material an excellent candidate for higher temperature automotive operation.

  10. Metal alloy identifier

    DOEpatents

    Riley, William D.; Brown, Jr., Robert D.

    1987-01-01

    To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.

  11. Design of experiment (DOE) study of biodegradable magnesium alloy synthesized by mechanical alloying using fractional factorial design

    NASA Astrophysics Data System (ADS)

    Salleh, Emee Marina; Ramakrishnan, Sivakumar; Hussain, Zuhailawati

    2014-06-01

    The biodegradable nature of magnesium (Mg) makes it a most highlighted and attractive to be used as implant materials. However, rapid corrosion rate of Mg alloys especially in electrolytic aqueous environment limits its performance. In this study, Mg alloy was mechanically milled by incorporating manganese (Mn) as alloying element. An attempt was made to study both effect of mechanical alloying and subsequent consolidation processes on the bulk properties of Mg-Mn alloys. 2k-2 factorial design was employed to determine the significant factors in producing Mg alloy which has properties closes to that of human bones. The design considered six factors (i.e. milling time, milling speed, weight percentage of Mn, compaction pressure, sintering temperature and sintering time). Density and hardness were chosen as the responses for assessing the most significant parameters that affected the bulk properties of Mg-Mn alloys. The experimental variables were evaluated using ANOVA and regression model. The main parameter investigated was compaction pressure.

  12. Accelerated glacier shrinkage in the Ak-Shyirak massif, Inner Tien Shan, during 2003-2013.

    PubMed

    Petrakov, Dmitry; Shpuntova, Alyona; Aleinikov, Alexandr; Kääb, Andreas; Kutuzov, Stanislav; Lavrentiev, Ivan; Stoffel, Markus; Tutubalina, Olga; Usubaliev, Ryskul

    2016-08-15

    The observed increase in summer temperatures and the related glacier downwasting has led to a noticeable decrease of frozen water resources in Central Asia, with possible future impacts on the economy of all downstream countries in the region. Glaciers in the Ak-Shyirak massif, located in the Inner Tien Shan, are not only affected by climate change, but also impacted by the open pit gold mining of the Kumtor Gold Company. In this study, glacier inventories referring to the years 2003 and 2013 were created for the Ak-Shyirak massif based on satellite imagery. The 193 glaciers had a total area of 351.2±5.6km(2) in 2013. Compared to 2003, the total glacier area decreased by 5.9±3.4%. During 2003-2013, the shrinkage rate of Ak-Shyirak glaciers was twice than that in 1977-2003 and similar to shrinkage rates in Tien Shan frontier ranges. We assessed glacier volume in 2013 using volume-area (VA) scaling and GlabTop modelling approaches. Resulting values for the whole massif differ strongly, the VA scaling derived volume is 30.0-26.4km(3) whereas the GlabTop derived volume accounts for 18.8-13.2km(3). Ice losses obtained from both approaches were compared to geodetically-derived volume change. VA scaling underestimates ice losses between 1943 and 2003 whereas GlabTop reveals a good match for eight glaciers for the period 2003-2012. In comparison to radio-echo soundings from three glaciers, the GlabTop model reveals a systematic underestimation of glacier thickness with a mean deviation of 16%. GlabTop tends to significantly underestimate ice thickness in accumulation areas, but tends to overestimate ice thickness in the lowermost parts of glacier snouts. Direct technogenic impact is responsible for about 7% of area and 5% of mass loss for glaciers in the Ak-Shyirak massif during 2003-2013. Therefore the increase of summer temperature seems to be the main driver of accelerated glacier shrinkage in the area. PMID:27100016

  13. The Future of Alumina-Forming Alloys: Challenges and Applications for Power Generation

    SciTech Connect

    Pint, Bruce A

    2011-01-01

    Alumina-forming alloys have been studied for over 50 years and are now needed for high efficiency power generation applications operating at higher temperatures. Especially in the presence of water vapor, alumina-forming alloys outperform conventional chromia-forming alloys above 1000 C. However, alloy mechanical behavior is a significant issue and alumina-forming alloy development has been limited. The opportunity for alloy development is discussed as well as the factors that limit oxidation resistance, including alloy thermal expansion and optimizing reactive element additions. Finally, lifetime modeling is discussed for thick section components together with the need to address performance in more complex environments.

  14. Electron g-factor in bulk Ga1-xInxAsySb1-y/GaSb quaternary alloy and in GaSb/Ga1-xInxAsySb1-y/GaSb Spherical quantum dots

    NASA Astrophysics Data System (ADS)

    Sánchez-Cano, R.; Porras-Montenegro, N.

    2011-12-01

    Secure quantum communications require an entanglement-preserving photo-detector in which quantum information is transmitted by photon polarization through an mid infrared optical fiber system and then transferred to electron spin in a optoelectronic semiconductor device. Using interpolation scheme we have investigated the electron g-factor in bulk Ga1-xInxAsySb1-y quaternary alloy matched to GaSb as a function of Indium and Arsenic concentration on the complete range 0≤x,y≤1. A specific g-factor as a function of the radius in a spherical GaSb/Ga1-xInxAsySb1-y/GaSb quantum dot heterostructure is calculated. Furthermore, we present calculations of the energy states including the Zeeman effect on the electrons confined in quaternary heterostructure quantum dots, with a parabolic confining potential under applied magnetic fields. Our calculations have been worked out by using interpolating methods to find the band gap as a function of the Indium concentration in order to determine the conduction band-offset at room temperature in GaSb/Ga1-xInxAsySb1-y/GaSb heterostructure, within the effective-mass approximation. Experimental or theoretical electron g-factor, spin-orbit splitting Δso, and coupling matrix elements Ep = (2/m0)||2 value between the states of the lowest conduction band Γ6 and the upper valence bands Γ8 for Ga1-xInxAsySb1-y/GaSb quaternary alloy are not readily available. Our predictions show that electron g-factor values are in the range between the electron g-factor measured in bulk GaSb when x→0 (g = -9.25) and that measured in InAs when x→1 (g = -18.08), but there is a remarkable minimum in the g-factor value (g≃-23.14) at x≃0.67.

  15. Impact of more detailed categorization of shrinkage or progression ratio at initial imaging response after sorafenib treatment in advanced hepatocellular carcinoma patients

    PubMed Central

    Wada, Yoshiyuki; Takami, Yuko; Tateishi, Masaki; Ryu, Tomoki; Mikagi, Kazuhiro; Saitsu, Hideki

    2015-01-01

    Background Sorafenib therapy improves survival in unresectable hepatocellular carcinoma (HCC) patients without an objective response. The present study investigated whether the initial imaging response might be a prognostic indicator after administration of sorafenib therapy in HCC patients. Patients and methods This retrospective study reviewed unresectable HCC patients undergoing sorafenib therapy. Patients evaluated without complete response, partial response (PR), or progressive disease (PD) at the initial imaging response evaluation by modified Response Evaluation Criteria in Solid Tumors were divided into three groups according to more detailed categorization of the shrinkage/progression ratio in initial imaging response. A comparison of progression-free and overall survival among these groups was performed. Results Of the 43 non-PR non-PD patients with target lesions, ten (23.3%) exhibited mild response (MR; −30% to −5%), 14 (32.6%) exhibited no change (NC; −5% to +5%), and 19 (44.2%) exhibited mild-PD (MPD; +5% to +20%). There was no statistical difference in progression-free or overall survival between MR and NC patients. The median progression-free survivals in NC+MR and mild-PD patients were 15.0 and 5.3 months, respectively (P<0.01), and the median survival times were 31.9 and 17.1 months, respectively (P<0.001). In multivariate analysis, etiology (hepatitis C virus) and initial imaging response (MR+NC) was identified as an independently good prognostic factor. Conclusion More detailed categorization of shrinkage or progression at the initial imaging response evaluation may be a useful marker for predicting sorafenib treatment outcomes in HCC patients. If the initial imaging response is not progression but stability, sorafenib may have a survival benefit. PMID:26586953

  16. The application of wavelet shrinkage denoising to magnetic Barkhausen noise measurements

    SciTech Connect

    Thomas, James

    2014-02-18

    The application of Magnetic Barkhausen Noise (MBN) as a non-destructive method of defect detection has proliferated throughout the manufacturing community. Instrument technology and measurement methodology have matured commensurately as applications have moved from the R and D labs to the fully automated manufacturing environment. These new applications present a new set of challenges including a bevy of error sources. A significant obstacle in many industrial applications is a decrease in signal to noise ratio due to (i) environmental EMI and (II) compromises in sensor design for the purposes of automation. The stochastic nature of MBN presents a challenge to any method of noise reduction. An application of wavelet shrinkage denoising is proposed as a method of decreasing extraneous noise in MBN measurements. The method is tested and yields marked improvement on measurements subject to EMI, grounding noise, and even measurements in ideal conditions.

  17. Anisotropic shrinkage of insect air sacs revealed in vivo by X-ray microtomography

    PubMed Central

    Xu, Liang; Chen, Rongchang; Du, Guohao; Yang, Yiming; Wang, Feixiang; Deng, Biao; Xie, Honglan; Xiao, Tiqiao

    2016-01-01

    Air sacs are thought to be the bellows for insect respiration. However, their exact mechanism of action as a bellows remains unclear. A direct way to investigate this problem is in vivo observation of the changes in their three-dimensional structures. Therefore, four-dimensional X-ray phase contrast microtomography is employed to solve this puzzle. Quantitative analysis of three-dimensional image series reveals that the compression of the air sac during respiration in bell crickets exhibits obvious anisotropic characteristics both longitudinally and transversely. Volumetric changes of the tracheal trunks in the prothorax further strengthen the evidence of this finding. As a result, we conclude that the shrinkage and expansion of the insect air sac is anisotropic, contrary to the hypothesis of isotropy, thereby providing new knowledge for further research on the insect respiratory system. PMID:27580585

  18. Emerging Applications of Polymersomes in Delivery: from Molecular Dynamics to Shrinkage of Tumors

    PubMed Central

    Discher, Dennis E.; Ortiz, Vanessa; Srinivas, Goundla; Klein, Michael L.; Kim, Younghoon; Christian, David; Cai, Shenshen; Photos, Peter; Ahmed, Fariyal

    2014-01-01

    Polymersomes are self-assembled shells of amphiphilic block copolymers that are currently being developed by many groups for fundamental insights into the nature of self-assembled states as well as for a variety of potential applications. While recent reviews have highlighted distinctive properties – particularly stability – that are strongly influenced by both copolymer type and polymer molecular weight, here we first review some of the more recent developments in computational molecular dynamics (MD) schemes that lend insight into assembly. We then review polymersome loading, in vivo stealthiness, degradation-based disassembly for controlled release, and even tumor-shrinkage in vivo. Comparisons of polymersomes with viral capsids are shown to encompass and inspire many aspects of current designs. PMID:24692840

  19. Characterization of field compaction using shrinkage analysis and visual soil examination

    NASA Astrophysics Data System (ADS)

    Johannes, Alice; Keller, Thomas; Weisskopf, Peter; Schulin, Rainer; Boivin, Pascal

    2016-04-01

    Visual field examination of soil structure can be very useful in extension work, because it is easy to perform, does not require equipment or lab analyses and the result is immediately available. The main limitations of visual methods are subjectivity and variation with field conditions. To provide reliable reference information, methods for objective and quantitative assessment of soil structure quality are still necessary. Soil shrinkage analysis (ShA) (Braudeau et al., 2004) provides relevant parameters for soil functions that allow precise and accurate assessment of soil compaction. To test it, we applied ShA to samples taken from a soil structure observatory (SSO) set up in 2014 on a loamy soil in Zurich, Switzerland to quantify the structural recovery of compacted agricultural soil. The objective in this presentation is to compare the ability of a visual examination method and ShA to assess soil compaction and structural recovery on the SSO field plots. Eighteen undisturbed soil samples were taken in the topsoil (5-10 cm) and 9 samples in the subsoil (30-35 cm) of compacted plots and control. Each sample went through ShA, followed by a visual examination of the sample and analysis of soil organic carbon and texture. ShA combines simultaneous shrinkage with water retention measurements and, in addition to soil properties such as bulk density, coarse and fine porosity, also provides information on hydrostructural stability and plasma and structural porosity. For visual examination the VESS method of Ball et al. (2007) was adapted to core samples previously equilibrated at -100 hPa matric potential. The samples were randomly and anonymously scored to avoid subjectivity and were equilibrated to insure comparable conditions. Compaction decreased the total specific volume, as well as air and water content at all matric potentials. Structural porosity was reduced, while plasma porosity remained unchanged. Compaction also changed the shape of the shrinkage curve: (i

  20. Smectic-A*-smectic-C* transition in a ferroelectric liquid crystal without smectic layer shrinkage.

    PubMed

    Giesselmann, F; Zugenmaier, P; Dierking, I; Lagerwall, S T; Stebler, B; Kaspar, M; Hamplová, V; Glogarová, M

    1999-07-01

    The smectic layer spacing of a nonfluorinated ferroelectric liquid crystal (FLC) compound with almost no shrinkage and only minor tendency to form zigzag defects was characterized by small angle x-ray diffraction. The material lacks a nematic phase. The smectic-A*-smectic-C* phase transition was studied by measuring the thermal and electric field response of the optical tilt and the electric polarization. These properties are described very well by a Landau expansion even without introduction of a higher-order Theta(6) term. This result suggests a pure second-order phase transition far from tricriticality and differs considerably from the typical behavior of the A*-C* transition in most FLC materials. PMID:11969798

  1. Bayesian Wavelet Shrinkage of the Haar-Fisz Transformed Wavelet Periodogram

    PubMed Central

    2015-01-01

    It is increasingly being realised that many real world time series are not stationary and exhibit evolving second-order autocovariance or spectral structure. This article introduces a Bayesian approach for modelling the evolving wavelet spectrum of a locally stationary wavelet time series. Our new method works by combining the advantages of a Haar-Fisz transformed spectrum with a simple, but powerful, Bayesian wavelet shrinkage method. Our new method produces excellent and stable spectral estimates and this is demonstrated via simulated data and on differenced infant electrocardiogram data. A major additional benefit of the Bayesian paradigm is that we obtain rigorous and useful credible intervals of the evolving spectral structure. We show how the Bayesian credible intervals provide extra insight into the infant electrocardiogram data. PMID:26381141

  2. On shrinkage and model extrapolation in the evaluation of clinical center performance

    PubMed Central

    Varewyck, Machteld; Goetghebeur, Els; Eriksson, Marie; Vansteelandt, Stijn

    2014-01-01

    We consider statistical methods for benchmarking clinical centers based on a dichotomous outcome indicator. Borrowing ideas from the causal inference literature, we aim to reveal how the entire study population would have fared under the current care level of each center. To this end, we evaluate direct standardization based on fixed versus random center effects outcome models that incorporate patient-specific baseline covariates to adjust for differential case-mix. We explore fixed effects (FE) regression with Firth correction and normal mixed effects (ME) regression to maintain convergence in the presence of very small centers. Moreover, we study doubly robust FE regression to avoid outcome model extrapolation. Simulation studies show that shrinkage following standard ME modeling can result in substantial power loss relative to the considered alternatives, especially for small centers. Results are consistent with findings in the analysis of 30-day mortality risk following acute stroke across 90 centers in the Swedish Stroke Register. PMID:24812420

  3. Slow and steady cell shrinkage reduces osmotic stress in bovine and murine oocyte and zygote vitrification

    PubMed Central

    Lai, D.; Ding, J.; Smith, G.W.; Smith, G.D.; Takayama, S.

    2015-01-01

    STUDY QUESTION Does the use of a new cryoprotectant agent (CPA) exchange protocol designed to minimize osmotic stress improve oocyte or zygote vitrification by reducing sublethal cryodamage? SUMMARY ANSWER The use of a new CPA exchange protocol made possible by automated microfluidics improved oocyte and zygote vitrification with superior morphology as indicated by a smoother cell surface, higher sphericity, higher cytoplasmic lipid retention, less cytoplasmic leakage and higher developmental competence compared with conventional methods. WHAT IS KNOWN ALREADY The use of more ‘steps’ of CPA exposure during the vitrification protocol increases cryosurvival and development in the bovine model. However, such an attempt to eliminate osmotic stress is limited by the practicality of performing numerous precise pipetting steps in a short amount of time. STUDY DESIGN, SIZE, DURATION Murine meiotically competent germinal vesicle intact oocytes and zygotes were harvested from the antral follicles in ovaries and ampulla, respectively. Bovine ovaries were obtained from a local abattoir at random stages of the estrous cycle. A total of 110 murine oocytes, 802 murine zygotes and 52 bovine oocytes were used in this study. PARTICIPANTS/MATERIALS, SETTING, METHODS Microfluidic devices were fabricated using conventional photo- and soft-lithography. CPAs used were 7.5% ethylene glycol (EG) and 7.5% dimethyl sulfoxide (DMSO) for equilibration solution and 15% EG, 15% DMSO and 0.5 M sucrose for vitrification solution. End-point analyses include mathematical modeling using Kedem–Katchalsky equations, morphometrics assessed by conventional and confocal microscopy, cytoplasmic lipid quantification by nile red staining, cytoplasmic leakage quantification by fluorescent dextran intercalation and developmental competence analysis by 96 h embryo culture and blastomere quantification. MAIN RESULTS AND THE ROLE OF CHANCE The automated microfluidics protocol decreased the shrinkage rate of

  4. Non uniform shrinkages of double-walled carbon nanotube as induced by electron beam irradiation

    SciTech Connect

    Zhu, Xianfang Li, Lunxiong; Gong, Huimin; Yang, Lan; Sun, Chenghua

    2014-09-01

    Electron beam-induced nanoinstabilities of pristine double-walled carbon nanotubes (DWCNTs) of two different configurations, one fixed at both ends and another fixed at only one end, were in-situ investigated in transmission electron microscope at room temperature. It was observed that the DWCNT fixed at both ends shrank in its diameter uniformly. Meanwhile, the DWCNT fixed at only one end intriguingly shrank preferentially from its free cap end along its axial direction whereas its diameter shrinkage was offset. A mechanism of “diffusion” along with “evaporation” at room temperature which is driven by the nanocurvature of the DWCNTs, and the athermal activation induced by the electron beam was proposed to elucidate the observed phenomena. The effect of the interlayer interaction of the DWCNTs was also discussed.

  5. Polymerization shrinkage of a dental resin composite determined by a fiber optic Fizeau interferometer

    NASA Astrophysics Data System (ADS)

    Arenas, Gustavo; Noriega, Sergio; Vallo, Claudia; Duchowicz, Ricardo

    2007-03-01

    A fiber optic sensing method based on a Fizeau-type interferometric scheme was employed for monitoring linear polymerization shrinkage in dental restoratives. This technique offers several advantages over the conventional methods of measuring polymerization contraction. This simple, compact, non-invasive and self-calibrating system competes with both conventional and other high-resolution bulk interferometric techniques. In this work, an analysis of the quality of interference signal and fringes visibility was performed in order to characterize their resolution and application range. The measurements of percent linear contraction as a function of the sample thickness were carried out in this study on two dental composites: Filtek P60 (3M ESPE) Posterior Restorer and Filtek Z250 (3M ESPE) Universal Restorer. The results were discussed with respect to others obtained employing alternative techniques.

  6. Spatio-Temporal Video Segmentation with Shape Growth or Shrinkage Constraint

    NASA Technical Reports Server (NTRS)

    Tarabalka, Yuliya; Charpiat, Guillaume; Brucker, Ludovic; Menze, Bjoern H.

    2014-01-01

    We propose a new method for joint segmentation of monotonously growing or shrinking shapes in a time sequence of noisy images. The task of segmenting the image time series is expressed as an optimization problem using the spatio-temporal graph of pixels, in which we are able to impose the constraint of shape growth or of shrinkage by introducing monodirectional infinite links connecting pixels at the same spatial locations in successive image frames. The globally optimal solution is computed with a graph cut. The performance of the proposed method is validated on three applications: segmentation of melting sea ice floes and of growing burned areas from time series of 2D satellite images, and segmentation of a growing brain tumor from sequences of 3D medical scans. In the latter application, we impose an additional intersequences inclusion constraint by adding directed infinite links between pixels of dependent image structures.

  7. Setting shrinkage and hygroscopic expansion of resin-modified glass-ionomer in experimental cylindrical cavities.

    PubMed

    Kim, Y G; Hirano, S

    1999-03-01

    The effects of the C-value (bonded surface area/unbonded surface area) and the volume of the cavity on the volumetric dimensional changes [volumetric setting shrinkage (VSS) and volumetric hygroscopic expansion (VHE)] of a resin-modified glass-ionomer (RMGI) filled in experimental cylindrical cavities were evaluated. The VSS and the VHE rate decreased with increasing C-value. There was a high inverse regression between the cavity C-value and volumetric dimensional changes, but a low regression between cavity volume and volumetric dimensional changes. Therefore, it was thought that greater contraction stress would remain in high C-value cavities than low C-value cavities during the setting process. It was also confirmed that the volumetric dimensional changes of RMGI in cavity were influenced primarily by the cavity C-value. PMID:10786149

  8. Bayesian Wavelet Shrinkage of the Haar-Fisz Transformed Wavelet Periodogram.

    PubMed

    Nason, Guy; Stevens, Kara

    2015-01-01

    It is increasingly being realised that many real world time series are not stationary and exhibit evolving second-order autocovariance or spectral structure. This article introduces a Bayesian approach for modelling the evolving wavelet spectrum of a locally stationary wavelet time series. Our new method works by combining the advantages of a Haar-Fisz transformed spectrum with a simple, but powerful, Bayesian wavelet shrinkage method. Our new method produces excellent and stable spectral estimates and this is demonstrated via simulated data and on differenced infant electrocardiogram data. A major additional benefit of the Bayesian paradigm is that we obtain rigorous and useful credible intervals of the evolving spectral structure. We show how the Bayesian credible intervals provide extra insight into the infant electrocardiogram data. PMID:26381141

  9. Body shrinkage due to Arctic warming reduces red knot fitness in tropical wintering range.

    PubMed

    van Gils, Jan A; Lisovski, Simeon; Lok, Tamar; Meissner, Włodzimierz; Ożarowska, Agnieszka; de Fouw, Jimmy; Rakhimberdiev, Eldar; Soloviev, Mikhail Y; Piersma, Theunis; Klaassen, Marcel

    2016-05-13

    Reductions in body size are increasingly being identified as a response to climate warming. Here we present evidence for a case of such body shrinkage, potentially due to malnutrition in early life. We show that an avian long-distance migrant (red knot, Calidris canutus canutus), which is experiencing globally unrivaled warming rates at its high-Arctic breeding grounds, produces smaller offspring with shorter bills during summers with early snowmelt. This has consequences half a world away at their tropical wintering grounds, where shorter-billed individuals have reduced survival rates. This is associated with these molluscivores eating fewer deeply buried bivalve prey and more shallowly buried seagrass rhizomes. We suggest that seasonal migrants can experience reduced fitness at one end of their range as a result of a changing climate at the other end. PMID:27174985

  10. Hessian Schatten-norm regularization for CBCT image reconstruction using fast iterative shrinkage-thresholding algorithm

    NASA Astrophysics Data System (ADS)

    Li, Xinxin; Wang, Jiang; Tan, Shan

    2015-03-01

    Statistical iterative reconstruction in Cone-beam computed tomography (CBCT) uses prior knowledge to form different kinds of regularization terms. The total variation (TV) regularization has shown state-of-the-art performance in suppressing noises and preserving edges. However, it produces the well-known staircase effect. In this paper, a method that involves second-order differential operators was employed to avoid the staircase effect. The ability to avoid staircase effect lies in that higher-order derivatives can avoid over-sharpening the regions of smooth intensity transitions. Meanwhile, a fast iterative shrinkage-thresholding algorithm was used for the corresponding optimization problem. The proposed Hessian Schatten norm-based regularization keeps lots of favorable properties of TV, such as translation and scale invariant, with getting rid of the staircase effect that appears in TV-based reconstructions. The experiments demonstrated the outstanding ability of the proposed algorithm over TV method especially in suppressing the staircase effect.

  11. Anisotropic shrinkage of insect air sacs revealed in vivo by X-ray microtomography.

    PubMed

    Xu, Liang; Chen, Rongchang; Du, Guohao; Yang, Yiming; Wang, Feixiang; Deng, Biao; Xie, Honglan; Xiao, Tiqiao

    2016-01-01

    Air sacs are thought to be the bellows for insect respiration. However, their exact mechanism of action as a bellows remains unclear. A direct way to investigate this problem is in vivo observation of the changes in their three-dimensional structures. Therefore, four-dimensional X-ray phase contrast microtomography is employed to solve this puzzle. Quantitative analysis of three-dimensional image series reveals that the compression of the air sac during respiration in bell crickets exhibits obvious anisotropic characteristics both longitudinally and transversely. Volumetric changes of the tracheal trunks in the prothorax further strengthen the evidence of this finding. As a result, we conclude that the shrinkage and expansion of the insect air sac is anisotropic, contrary to the hypothesis of isotropy, thereby providing new knowledge for further research on the insect respiratory system. PMID:27580585

  12. [Urban shrinkage and challenges for the public health-care service].

    PubMed

    Kabisch, S

    2007-10-01

    In the 21st century, urban development is facing new challenges caused by the simultaneous growing and shrinking of cities and urban regions. Whilst the development patterns and instruments of urban growth are well-known and widely accepted, the processes of shrinkage with its broad consequences, sphere of impact and speed need intensive investigation. In particular, urban restructuring including housing demolition brings about psychological stress situations for the affected inhabitants. Until the present time public services, including health-care, are poorly prepared to cope with the new situation. To take account of these new challenges, the adaptation of tasks, instruments and targets is urgently needed. To be successful, a continuous cooperation and communication between municipal institutions and housing enterprises responsible for urban and housing development is indispensable. Furthermore, appropriately focussed scientific research results can support the creation of adequate strategies and instruments. PMID:18040957

  13. Application of a Pore Fraction Hot Tearing Model to Directionally Solidified and Direct Chill Cast Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Dou, Ruifeng; Phillion, A. B.

    2016-06-01

    Hot tearing susceptibility is commonly assessed using a pressure drop equation in the mushy zone that includes the effects of both tensile deformation perpendicular to the thermal gradient as well as shrinkage feeding. In this study, a Pore Fraction hot tearing model, recently developed by Monroe and Beckermann (JOM 66:1439-1445, 2014), is extended to additionally include the effect of strain rate parallel to the thermal gradient. The deformation and shrinkage pore fractions are obtained on the basis of the dimensionless Niyama criterion and a scaling variable method. First, the model is applied to the binary Al-Cu system under conditions of directional solidification. It is shown that for the same Niyama criterion, a decrease in the cooling rate increases both the deformation and shrinkage pore fractions because of an increase in the time spent in the brittle temperature region. Second, the model is applied to the industrial aluminum alloy AA5182 as part of a finite element simulation of the Direct Chill (DC) casting process. It is shown that an increase in the casting speed during DC casting increases the deformation and shrinkage pore fractions, causing the maximum point of pore fraction to move towards the base of the casting. These results demonstrate that including the strain rate parallel to the thermal gradient significantly improves the predictive quality of hot tearing criteria based on the pressure drop equation.

  14. Application of a Pore Fraction Hot Tearing Model to Directionally Solidified and Direct Chill Cast Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Dou, Ruifeng; Phillion, A. B.

    2016-08-01

    Hot tearing susceptibility is commonly assessed using a pressure drop equation in the mushy zone that includes the effects of both tensile deformation perpendicular to the thermal gradient as well as shrinkage feeding. In this study, a Pore Fraction hot tearing model, recently developed by Monroe and Beckermann (JOM 66:1439-1445, 2014), is extended to additionally include the effect of strain rate parallel to the thermal gradient. The deformation and shrinkage pore fractions are obtained on the basis of the dimensionless Niyama criterion and a scaling variable method. First, the model is applied to the binary Al-Cu system under conditions of directional solidification. It is shown that for the same Niyama criterion, a decrease in the cooling rate increases both the deformation and shrinkage pore fractions because of an increase in the time spent in the brittle temperature region. Second, the model is applied to the industrial aluminum alloy AA5182 as part of a finite element simulation of the Direct Chill (DC) casting process. It is shown that an increase in the casting speed during DC casting increases the deformation and shrinkage pore fractions, causing the maximum point of pore fraction to move towards the base of the casting. These results demonstrate that including the strain rate parallel to the thermal gradient significantly improves the predictive quality of hot tearing criteria based on the pressure drop equation.

  15. Treatment effect heterogeneity for univariate subgroups in clinical trials: Shrinkage, standardization, or else.

    PubMed

    Varadhan, Ravi; Wang, Sue-Jane

    2016-01-01

    Treatment effect heterogeneity is a well-recognized phenomenon in randomized controlled clinical trials. In this paper, we discuss subgroup analyses with prespecified subgroups of clinical or biological importance. We explore various alternatives to the naive (the traditional univariate) subgroup analyses to address the issues of multiplicity and confounding. Specifically, we consider a model-based Bayesian shrinkage (Bayes-DS) and a nonparametric, empirical Bayes shrinkage approach (Emp-Bayes) to temper the optimism of traditional univariate subgroup analyses; a standardization approach (standardization) that accounts for correlation between baseline covariates; and a model-based maximum likelihood estimation (MLE) approach. The Bayes-DS and Emp-Bayes methods model the variation in subgroup-specific treatment effect rather than testing the null hypothesis of no difference between subgroups. The standardization approach addresses the issue of confounding in subgroup analyses. The MLE approach is considered only for comparison in simulation studies as the "truth" since the data were generated from the same model. Using the characteristics of a hypothetical large outcome trial, we perform simulation studies and articulate the utilities and potential limitations of these estimators. Simulation results indicate that Bayes-DS and Emp-Bayes can protect against optimism present in the naïve approach. Due to its simplicity, the naïve approach should be the reference for reporting univariate subgroup-specific treatment effect estimates from exploratory subgroup analyses. Standardization, although it tends to have a larger variance, is suggested when it is important to address the confounding of univariate subgroup effects due to correlation between baseline covariates. The Bayes-DS approach is available as an R package (DSBayes). PMID:26485117

  16. Gravitropism and phototropism of oat coleoptiles: Post-tropic autostraightening and tissue shrinkage during tropism

    NASA Astrophysics Data System (ADS)

    Tarui, Y.; Iino, M.

    1999-01-01

    We measured changes in length on the two opposite sides of the red-light-grown oat (Avena sativa L.) coleoptiles subjected to either gravitropic or phototropic stimulation and subsequently rotated on a horizontal clinostat. The length measurement was conducted using three 5 mm-long zones delimited by ink markers from the tip. Curvature of each zone was analyzed from the length difference between the two sides. Gravitropism was induced by displacing the seedling from the vertical by 30° or 90° for 25 min. Phototropism was induced by exposing the coleoptile to unilateral blue light for 30 s, which provided a fluence (1.0 μmol m-2) optimal for the pulse-induced positive phototropism or a lower, suboptimal fluence (0.03 μmol m-2). After negatively gravitropic bending, the upper two zones straightened rapidly at either displacement angle. After positively phototropic bending, straightening occurred, but only in the top zone and at the lower fluence. The upper two zones straightened rapidly, however, when bilateral blue light (30 s; 15 μmol m-2 from either direction) was applied 25 min after unilateral stimulation at the higher fluence. Bilateral blue light alone induced no curvature. These results confirm that the straightening of gravitropically bent coleoptiles is autonomic, and suggest that a similar autonomic response participates in the straightening of phototropically bent coleoptiles. Suppression of elongation on the concave side of the coleoptile mainly accounted for gravitropic and phototropic curvatures. The concave side of the top zone shrank during both tropisms. This shrinkage progressed at a high rate from the beginning of curvature response, suggesting that a drop in turgor pressure is the main and direct cause of the shrinkage.

  17. Aridification of the Sahara desert caused by Tethys Sea shrinkage during the Late Miocene.

    PubMed

    Zhang, Zhongshi; Ramstein, Gilles; Schuster, Mathieu; Li, Camille; Contoux, Camille; Yan, Qing

    2014-09-18

    It is widely believed that the Sahara desert is no more than ∼2-3 million years (Myr) old, with geological evidence showing a remarkable aridification of north Africa at the onset of the Quaternary ice ages. Before that time, north African aridity was mainly controlled by the African summer monsoon (ASM), which oscillated with Earth's orbital precession cycles. Afterwards, the Northern Hemisphere glaciation added an ice volume forcing on the ASM, which additionally oscillated with glacial-interglacial cycles. These findings led to the idea that the Sahara desert came into existence when the Northern Hemisphere glaciated ∼2-3 Myr ago. The later discovery, however, of aeolian dune deposits ∼7 Myr old suggested a much older age, although this interpretation is hotly challenged and there is no clear mechanism for aridification around this time. Here we use climate model simulations to identify the Tortonian stage (∼7-11 Myr ago) of the Late Miocene epoch as the pivotal period for triggering north African aridity and creating the Sahara desert. Through a set of experiments with the Norwegian Earth System Model and the Community Atmosphere Model, we demonstrate that the African summer monsoon was drastically weakened by the Tethys Sea shrinkage during the Tortonian, allowing arid, desert conditions to expand across north Africa. Not only did the Tethys shrinkage alter the mean climate of the region, it also enhanced the sensitivity of the African monsoon to orbital forcing, which subsequently became the major driver of Sahara extent fluctuations. These important climatic changes probably caused the shifts in Asian and African flora and fauna observed during the same period, with possible links to the emergence of early hominins in north Africa. PMID:25230661

  18. The engineering significance of shrinkage and swelling soils in blast damage investigations

    SciTech Connect

    Vitton, S.J.; Harris, W.W.

    1996-12-01

    In the US each year it has been estimated that expansive soils cause approximately $9.0 billion in damage to buildings, roads, airports, and other facilities. This figure alone exceeds the damage estimate for earthquakes, floods, tornadoes, and hurricanes combined. Unfortunately, some cases of expansive soil damage (swelling) are blamed on rock blasting operations if the blasting operations are located within the immediate area. While simple tests, such as the Atterberg limits test, can characterize a soil as expansive, it does not necessarily answer the question whether the foundation soils are causing distresses to a structure. In particular, it appears that once a soil has been labeled as nonexpansive it is no longer considered as a problem soil, in which case blast vibrations become the prime suspect. It should be emphasized, however, that even non-plastic soils, those soils with low to nonexistent plastic indexes, can exhibit significant shrinkage characteristics that can result in significant damage to structures. While expansive soil is a function of the mineralogy of the soil particles, i.e., swelling clay minerals, shrinkage is caused by the loss of moisture from soil as capillary pressures exceed the cohesion or tensile strength and is therefore a function of the soils particle size and its pore size distribution. This is a significant problem for all fine grained soils regardless of the soil`s mineralogy. It`s particularly important for regions of the US that typically have a positive water balance but experience significant drought periods when soil moisture is lost.

  19. Gravitropism and phototropism of oat coleoptiles: post-tropic autostraightening and tissue shrinkage during tropism.

    PubMed

    Tarui, Y; Iino, M

    1999-01-01

    We measured changes in length on the two opposite sides of the red-light-grown oat (Avena sativa L.) coleoptiles subjected to either gravitropic or phototropic stimulation and subsequently rotated on a horizontal clinostat. The length measurement was conducted using three 5 mm-long zones delimited by ink markers from the tip. Curvature of each zone was analyzed from the length difference between the two sides. Gravitropism was induced by displacing the seedling from the vertical by 30 degrees or 90 degrees for 25 min. Phototropism was induced by exposing the coleoptile to unilateral blue light for 30 s, which provided a fluence (1.0 micromoles m-2) optimal for the pulse-induced positive phototropism or a lower, suboptimal fluence (0.03 micromoles m-2). After negatively gravitropic bending, the upper two zones straightened rapidly at either displacement angle. After positively phototropic bending, straightening occurred, but only in the top zone and at the lower fluence. The upper two zones straightened rapidly, however, when bilateral blue light (30 s; 15 micromoles m-2 from either direction) was applied 25 min after unilateral stimulation at the higher fluence. Bilateral blue light alone induced no curvature. These results confirm that the straightening of gravitropically bent coleoptiles is autonomic, and suggest that a similar autonomic response participates in the straightening of phototropically bent coleoptiles. Suppression of elongation on the concave side of the coleoptile mainly accounted for gravitropic and phototropic curvatures. The concave side of the top zone shrank during both tropisms. This shrinkage progressed at a high rate from the beginning of curvature response, suggesting that a drop in turgor pressure is the main and direct cause of the shrinkage. PMID:11542618

  20. Degree of vinyl conversion, polymerization shrinkage and stress development in experimental endodontic composite

    PubMed Central

    O’Donnell, J.N.R.; Skrtic, D.

    2010-01-01

    This study explores degree of vinyl conversion (DVC), polymerization shrinkage (PS) and shrinkage stress (PSS) of the experimental amorphous calcium phosphate (ACP) composites intended for use as an endodontic sealer. Light-cure (LC), chemical cure (CC) or dual-cure (DC; combined light and chemical cure) resins comprised urethane dimethacrylate (UDMA), 2-hydroxyethyl methacrylate (HEMA), methacryloyloxyethyl phthalate (MEP) and a high molecular mass oligomeric co-monomer, poly(ethyleneglycol)-extended UDMA (PEG-U) (designated UPHM resin). To fabricate composites, a mass fraction of 60 % UPHM resin was blended with a mass fraction of 40 % as-made (am-ACP) or ground ACP (g-ACP). DVC values of copolymer (unfilled UPHM resin) and composite specimens were determined by infrared spectroscopy. Glass-filled composites were used as controls. PS and PSS of composites were determined by dilatometry and tensometry, respectively. LC copolymers attained extraordinary high DVC values at 24 h post-cure (95.7 %), compared to CC (52 %) and DC (79.3 %) copolymer specimens. While the DVC values of LC and DC am-ACP composites were reduced between 5 and 10 %, DVC values of DC g-ACP composites increased almost 8 % compared to the corresponding copolymers. High DVC attained in LC composites was, expectedly, accompanied with high PS values (on average 7 vol%). However, PSS developed in LC and especially DC composites did not exceed PSS values seen in other UDMA-based composites. Based on this initial evaluation, it is concluded that, DC, g-ACP filled UPHM composite shows promise as an endodontic sealer. However, further physicochemical evaluations, including water sorption, mechanical stability and ion release as well as a leachability studies need to be performed before this experimental material is tested for cellular responses and, eventually recommended for clinical utility. PMID:20411033

  1. 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).

  2. 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. PMID:24376382

  3. R Squared Shrinkage in Multiple Regression Research: An Empirical Evaluation of Use and Impact of Adjusted Effect Formulae.

    ERIC Educational Resources Information Center

    Thatcher, Greg W.; Henson, Robin K.

    This study examined research in training and development to determine effect size reporting practices. It focused on the reporting of corrected effect sizes in research articles using multiple regression analyses. When possible, researchers calculated corrected effect sizes and determine if the associated shrinkage could have impacted researcher…

  4. Determining Timing of Hepatectomy for Colorectal Cancer with Distant Metastasis According to Imaging-Based Tumor Shrinkage Ratio

    PubMed Central

    Sasaki, Yoshiyuki; Osada, Shinji; Mori, Ryuutarou; Imai, Hisashi; Tanaka, Yoshihiro; Matsuhashi, Nobuhiro; Okumura, Naoki; Nonaka, Kenichi; Takahashi, Takao; Yoshida, Kazuhiro

    2013-01-01

    Background: The optimal timing of surgical resection of liver metastasis remains controversial, and guidelines regarding the upper limits of operative indications have not yet been defined. Surgical indication for metastasis from colorectal cancer (CLM) based on results of preoperative chemotherapy and RNF8 was investigated. Methods: Differences in CLM size on CT were evaluated as shrinkage rate/day by dividing tumor shrinkage rates by the interval in days between CT. Levels of RNF8 of resected colorectal cancer and CLM frozen specimen were detected. Results: When the cut line for shrinkage rate at 12 weeks was set at 0.35%, disease-free survival was significantly better in patients with a shrinkage rate >0.35% vs. ≤0.35% (p=0.003). RNF8 expression was significantly higher in Tis (p=0.001). In liver metastasis, RNF8 expression level was significantly lower in patients with partial response to FOLFOX than with stable disease, (p=0.017). Conclusions: A strategy of FOLFOX administration for 12 weeks to patients with low RNF8 expression and hepatectomy planned after 4 weeks rest may be accepted as the best therapeutic option for treating CLM. PMID:23935401

  5. 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

  6. Shrinkage and Swelling of Coal Induced by Desorption and Sorption of Fluids: Theoretical Model and Interpretation of a Field Project

    SciTech Connect

    Siriwardane, H.J.; Gondle, R.K.; Smith, D.H.

    2009-01-01

    Geologic sequestration in deep unmineable coal seams and enhanced coalbed methane production is a promising choice, economically and environmentally, to reduce anthropogenic gases such as carbon dioxide in the atmosphere. Unmineable coal seams are typically known to adsorb large amounts of carbon dioxide in comparison to the sizeable amounts of sorbed methane, which raises the potential for large scale sequestration projects. During the process of sequestration, carbon dioxide is injected into the coalbed and desorbed methane is produced. The coal matrix is believed to shrink when a gas is desorbed and swell when a gas is sorbed, sometimes causing profound changes in the cleat porosity and permeability of the coal seam. These changes may have significant impact on the reservoir performance. Therefore, it is necessary to understand the combined influence of swelling and shrinkage, and geomechanical properties including elastic modulus, cleat porosity, and permeability of the reservoir. The present paper deals with the influence of swelling and shrinkage on the reservoir performance, and the geomechanical response of the reservoir system during the process of geologic sequestration of carbon dioxide and enhanced coalbed methane production in an actual field project located in northern New Mexico. A three-dimensional swelling and shrinkage model was developed and implemented into an existing reservoir model to understand the influence of geomechanical parameters, as well as swelling and shrinkage properties, on the reservoir performance. Numerical results obtained from the modified simulator were compared to available measured values from that site and previous studies. Results show that swelling and shrinkage, and the combination of geomechanical and operational parameters, have a significant influence on the performance of the reservoir system.

  7. Microstructure Formation during Solidification of Melt-Spun Co-Fe-Mn-Si Alloys

    NASA Astrophysics Data System (ADS)

    Zollinger, J.; Adam, O.; Daloz, D.

    2012-01-01

    Cobalt-based alloys ribbons for the fabrication of cored wires require high elongation, e.g. a good metallurgical quality associated with a fine grain structure. The melt-spinning process allows fabricating the 200 μm thick ribbons in a single casting step. However, the properties of such ribbon suffer from the presence of casting defects, leading to early fractures in the material. The present study investigates the microstructure and defect formation in melt-spun Co-6.5Fe-2.6Mn-(0-1.6)Si alloys (in wt.%). These alloys exhibit uncommon intrinsic behaviour and properties such as high nucleation undercoolings (up to 295K in DTA experiments) or reduced solidification interval (10 < T0 < 25 K). It is found that the main defect leading to fracture is micro-shrinkage due to the solutal dendrite growth at low nucleation undercooling. Low silicon additions (0.6 wt.%) are found to reduce the size and the occurrence of shrinkage and increase the elongation, whereas larger silicon additions (1.6 wt.%) are detrimental to the ribbon properties.

  8. Macrosegregation in Al-7Si alloy caused by abrupt cross-section change during directional solidification

    NASA Astrophysics Data System (ADS)

    Ghods, M.; Johnson, L.; Lauer, M.; Grugel, R. N.; Tewari, S. N.; Poirier, D. R.

    2016-09-01

    Hypoeutectic Al-7 wt .% Si alloys were directionally solidified vertically downward in cylindrical molds that incorporated an abrupt cross-section decrease (9.5 mm to 3.2 mm diameter) which, after 5 cm, reverted back to 9.5 mm diameter in a Bridgman furnace; two constant growth speeds and thermal gradients were investigated. Thermosolutal convection and cross-section-change-induced shrinkage flow effects on macrosegregation were investigated. Dendrite clustering and extensive radial macrosegregation was seen, particularly in the larger cross-sections, before contraction and after expansion, this more evident at the lower growth speed. This alloy shows positive longitudinal macrosegregation near cross-section decrease followed by negative macrosegregation right after it; the extent of macrosegregation, however, decreases with increasing growth speed. Primary dendrite steepling intensified as solidification proceeded into the narrower section and negative longitudinal macrosegregation was seen on the re-entrant shelves at expansion. A two-dimensional model accounting for both shrinkage and thermo-solutal convection was used to simulate solidification and the resulting mushy-zone steepling and macrosegregation. The experimentally observed longitudinal and radial macrosegregation associated with the cross-section changes during directional solidification of an Al-7Si alloy is well captured by the numerical simulations.

  9. A thermodynamic prediction for microporosity formation in aluminum-rich Al-Cu alloys

    NASA Technical Reports Server (NTRS)

    Poirier, D. R.; Yeum, K.; Maples, A. L.

    1987-01-01

    A computer model is used to predict the formation and degree of microporosity in a directionally solidified Al-4.5 wt pct Cu alloy, considering the interplay between solidification shrinkage and gas porosity. Macrosegregation theory is used to determine the local pressure within the interdendritic liquid. Results show interdendritic porosity for initial hydrogen contents in the 0.03-1 ppm range, and none below contents of 0.03. An increase in either the thermal gradient or the solidification rate is show to decrease the amount of interdendritic porosity.

  10. Radiation effects on the microstructure of a 9Cr-ODS alloy.

    SciTech Connect

    Gan, J.; Allen, T. R.; Birtcher, R. C.; Shutthanandan, S.; Thevothasan, S.; Materials Science Division; INL; Univ. of Wisconsin at Madison; PNNL

    2008-01-01

    Oxide dispersion strengthened (ODS) steels are prime candidates for high-temperature, high-dose cladding in advanced nuclear reactors. When a 9Cr-ODS alloy was irradiated with 5 MeV nickel ions at temperatures of 500-700 C to doses up to 150 dpa, there was no significant change in the dislocation arrangement. For oxide particles, there is a small shrinkage in size and increase in density with increasing irradiation dose. This work confirms that oxide particles and the microstructure of the 9Cr-ODS show minimal changes under irradiation at temperatures up to 700 C and doses up to 150 dpa.

  11. Substitution of Nickel by Combined Addition of Cobalt and Zirconium in Alloy A 332

    NASA Astrophysics Data System (ADS)

    Wüstenhagen, Andreas; Tonn, Babette

    2011-01-01

    Due to the increasing international competition and the resulting pricing pressure it is imperative to avoid the use of expensive alloying elements during the production of aluminium castings. The piston alloy A 332 shows an optimum combination of mechanical and casting properties and an attractive cost-performance ratio whereas nickel is the most expensive alloying element. A substitution of nickel by a combined addition of low contents of cobalt and zirconium has the potential capacitiy to increase the mechanical properties and reduce the costs of the alloy. At Clausthal University of Technology Thermo-Calc simulations and casting experiments were carried out to investigate the effect of the nickel subtitution. Thermo-Calc-simulations were made to analyze the intermetallic phases in these alloys. These simulations were evaluated by observations under optical microscope and SEM of specimens poured into permanent moulds. The size and morphology of the intermetallic phases and the primary silicon was analyzed by the use of image analysis software. The mechanical properties of the alloys were determined by tensile tests at room temperature, 250° C and 350° C. The tensile specimens were tested in as-cast and pre-aged condition. The effect on the castability was characterized by determining the flow length and the susceptibility to form shrinkages and hot cracks. The standard alloy A 332 and the new piston alloy with cobalt and zirconium were compared. The new alloy AlSi12,6Cu1Mg1CoZr exhibits a yield strength of 115 MPa and a tensile strength of 171 MPa at 250° C in pre-aged condition (250° C/100 h). At 350° C the new alloy displays a yield strength of 57 MPa and a tensile strength of 85 MPa in pre-aged condition (350° C/100h). Compared to the reference alloy AlSi12,6Cu1Ni1Mg1 the yield strength at 250° C was improved about 25% and the yield strength at 350° C about 7%. The favorable castability of the reference alloy is not affected by the substitution of

  12. Turbine Blade Alloy

    NASA Technical Reports Server (NTRS)

    MacKay, Rebecca

    2001-01-01

    The High Speed Research Airfoil Alloy Program developed a fourth-generation alloy with up to an +85 F increase in creep rupture capability over current production airfoil alloys. Since improved strength is typically obtained when the limits of microstructural stability are exceeded slightly, it is not surprising that this alloy has a tendency to exhibit microstructural instabilities after high temperature exposures. This presentation will discuss recent results obtained on coated fourth-generation alloys for subsonic turbine blade applications under the NASA Ultra-Efficient Engine Technology (UEET) Program. Progress made in reducing microstructural instabilities in these alloys will be presented. In addition, plans will be presented for advanced alloy development and for computational modeling, which will aid future alloy development efforts.

  13. The linear shrinkage and microhardness of packable composites polymerized by QTH or PAC unit.

    PubMed

    Park, Song-Ho; Noh, Byng-Duk; Cho, Yong-Sik; Kim, Su-Sun

    2006-01-01

    This study evaluated the effectiveness of a plasma arc curing (PAC) unit for packable resin composite curing. The amount and speed of polymerization shrinkage and the microhardness of packable composites were evaluated in order to compare the PAC unit's effectiveness with a quartz tungsten halogen (QTH) unit. Sure Fil (Dentsply Caulk), Pyramid (BISCO Inc) and Synergy Compact (Colténe/Whaledent) were used as the packable composites. In the case of curing with the PAC unit, the composites were light cured with Apollo 95E (DMD System Inc) for 1 second (Group 1), 2 seconds (Group 2), 3 seconds (Group 3), 6 seconds (Group 4) and 12 seconds (Group 5). For light curing with the QTH unit, the composites were light cured for 60 seconds using XL3000 (Group 6). The linear polymerization shrinkage of each composite was measured using a custom made linometer, and the data was stored in a computer every 0.5 to 0.55 seconds for a total of 60 seconds. For each composite, the amount of polymerization was compared using one-way ANOVA with Tukey at the 95% confidence level. In order to compare the speed of polymerization, the peak time (PT), showing the highest speed of polymerization and maximum speed of polymerization (Smax), were determined from the data and compared using one-way ANOVA with Tukey at the 95% confidence level for each material. Based on the statistical analysis among the PAC-cure groups (Groups 1 through 5), the group that was not statistically different from the QTH-cure group (Group 6) in the amount of linear polymerization shrinkage was determined for each material, and the corresponding curing time of the group was defined as the tentative minimum PAC-curing time (TMPT). For microhardness measurements, the samples were placed in a 2-mm thick Teflon plate. Twenty specimens, randomly divided into the PAC-cure group (Group 1) or the QTH-cure group (Group 2), were prepared for each material. In Group 1, each composite was light cured for TMPT with the PAC unit. In

  14. Leaf shrinkage: a predictive indicator of the potential variation of the surface area-to-volume ratio according to the leaf moisture content.

    PubMed

    Essaghi, Salaheddine; Hachmi, M'hamed; Yessef, Mohammed; Dehhaoui, Mohammed

    2016-01-01

    Leaf shrinkage provides insights into the potential variation of foliar SVR, within the same species, when leaf moisture content is changing in response to water deficit. Since SVR is among the most significant plant flammability features, leaf shrinkage would be a relevant component of fuel hazard assessment through its influence on SVR, enhancing-if it is taken into account-thereby the wildfire prediction accuracy. The purpose of this work is, first, to consider the leaf shrinkage by characterizing the plant species towards the shrinkability of their leaves, taking account the possible site effect, to characterize the behavior of shrinkage as a function of moisture content and finally to perform a classification for some dominant Mediterranean species based on the shrinkage levels. The assessment of the hierarchical relationships between the dimensional shrinkages is also aimed. Leaves and needles of thirteen tree and shrub species were harvested from six different sites in western Rif Mountains. Leaves dimensions and moisture content were measured regularly during a gradual drying at the laboratory. Dimensional shrinkages were calculated at each moisture content level. Dimensional shrinkages behaved similarly whether in leaf or timber and kept the same reporting relationships between each other. Among the species sampled in different sites, site effect is significant only in Pinus canariensis and Pistacia lentiscus. A classification of the plant species was carried out in three separate classes. Generally, shrinkage class of the plant species studied gave an idea on its flammability ranking reported in the literature, implying thus a cause-and-effect relationship between both parameters. PMID:27536513

  15. Grain Refinement of an Al-2 wt%Cu Alloy by Al3Ti1B Master Alloy and Ultrasonic Treatment

    NASA Astrophysics Data System (ADS)

    Wang, E. Q.; Wang, G.; Dargusch, M. S.; Qian, M.; Eskin, D. G.; StJohn, D. H.

    2016-03-01

    Both inoculation by AlTiB master alloys and Ultrasonic Treatment (UT) are effective methods of refining the grain size of aluminium alloys. The present study investigates the influence of UT on the grain refinement of an Al-2 wt% Cu alloy with a range of Al3TilB master alloy additions. When the alloy contains the smallest amount of added master alloy, UT caused significant additional grain refinement compared with that provided by the master alloy only. However, the influence of UT on grain size reduces with increasing addition of the master alloy. Plotting the grain size data versus the inverse of the growth restriction factor (Q) reveals that the application of UT causes both an increase in the number of potentially active nuclei and a decrease in the size of the nucleation free zone due to a reduction in the temperature gradient throughout the melt. Both these factors promote the formation of a fine equiaxed grain structure.

  16. A Comparative Evaluation of Microleakage of Two Low-Shrinkage Composites with a Conventional Resin Composite: an In Vitro Assessment

    PubMed Central

    Tavangar, Maryam; Tayefeh Davalloo, Reza; Darabi, Farideh; Karambin, Mahsa; Kazemi, Reza

    2016-01-01

    Statement of the Problem Polymerization shrinkage stress in composite restorations may lead to microleakage. Clinical methods such as using low-shrinkage composites have been suggested to overcome this problem; however, there are controversies about their efficiency in decreasing the microleakage. Purpose This in vitro study was conducted to compare the microleakage of two low-shrinkage resin composites with a conventional one. Materials and Method Fifty class V cavities of 2.5×3×2 mm (depth× length× width) were prepared in the buccal surfaces of intact bovine incisor teeth with the incisal margin on the enamel and gingival margin on the cementum. The teeth were randomly divided into 5 groups. In group 1, Clearfil APX (conventional) with SE Bond was used in 2 layers (Kuraray; Japan). In group 2, GC Kalore (low –shrinkage) with GC UniFil Bond was applied in one layer (GC Company). In group 3, the material of group 2 was applied in two layers. In group 4, FiltekP90 (low –shrinkage) with P90 System adhesive was applied in one layer (3M ESPE). In group 5, the materials of group 4 were applied in two layers. The samples were thermocycled and immersed in 0.5% fuchsin solution for 24h. The restorations were sectioned in buccolingual direction. Then they were evaluated for microleakage by using a stereomicroscope and scored as 0, 1, 2, and 3 and then Kruskal-Wallis test was used (p< 0.05). Results The groups were not significantly different regarding the microleakage in the coronal and cervical margins (p< 0.423 and p< 0.212, respectively); however, the Filtek P90 yielded the best results. In all groups, except group 5 (p= 0.018), the cervical margins had greater microleakage than the coronal margins. Conclusion The results suggested that low-shrinkage resin composites may not reduce the marginal microleakage. The proper use of conventional resin composites may offer comparable clinical results. PMID:26966710

  17. 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

  18. 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

  19. Impact of roots, mycorrhizas and earthworms on soil physical properties as assessed by shrinkage analysis

    NASA Astrophysics Data System (ADS)

    Milleret, R.; Le Bayon, R.-C.; Lamy, F.; Gobat, J.-M.; Boivin, P.

    2009-07-01

    SummarySoil biota such as earthworms, arbuscular mycorrhizal fungi (AMF) and plant roots are known to play a major role in engineering the belowground part of the terrestrial ecosystems, thus strongly influencing the water budget and quality on earth. However, the effect of soil organisms and their interactions on the numerous soil physical properties to be considered are still poorly understood. Shrinkage analysis allows quantifying a large spectrum of soil properties in a single experiment, with small standard errors. The objectives of the present study were, therefore, to assess the ability of the method to quantify changes in soil properties as induced by single or combined effects of leek roots ( Allium porrum), AMF ( Glomus intraradices) and earthworms ( Allolobophora chlorotica). The study was performed on homogenised soil microcosms and the experiments lasted 35 weeks. The volume of the root network and the external fungal hyphae was measured at the end, and undisturbed soil cores were collected. Shrinkage analysis allowed calculating the changes in soil hydro-structural stability, soil plasma and structural pore volumes, soil bulk density and plant available water, and structural pore size distributions. Data analysis revealed different impacts of the experimented soil biota on the soil physical properties. At any water content, the presence of A. chlorotica resulted in a decrease of the specific bulk volume and the hydro-structural stability around 25%, and in a significant increase in the bulk soil density. These changes went with a decrease of the structural pore volumes at any pore size, a disappearing of the thinnest structural pores, a decrease in plant available water, and a hardening of the plasma. On the contrary, leek roots decreased the bulk soil density up to 1.23 g cm -3 despite an initial bulk density of 1.15 g cm -3. This increase in volume was accompanied with a enhanced hydro-structural stability, a larger structural pore volume at any

  20. Model of curing shrinkage and kinetic parameters of an acrylate-based ultraviolet-embossing resist based on free volume theory

    NASA Astrophysics Data System (ADS)

    Liu, Nan; Liu, Jingbei; Lin, Jie; Davies, Graham; Jin, Peng; Zhang, Dou

    2013-04-01

    Free volume theory and a model of polymerization kinetics are introduced to predict and analyze the curing shrinkage and kinetic parameters of an acrylate-based ultraviolet-embossing resist. Curing shrinkage tests have been designed and performed to verify the accuracy of the model. The experimental results are in good agreement with the simulated results of the conversion behavior. The reaction coefficients of polymerization predicted by this model are essentially correct when compared to the classical experimental values. Moreover, the dynamic shrinkage during polymerization determined experimentally matches the simulated result predicted by our model.

  1. SUPERCONDUCTING VANADIUM BASE ALLOY

    DOEpatents

    Cleary, H.J.

    1958-10-21

    A new vanadium-base alloy which possesses remarkable superconducting properties is presented. The alloy consists of approximately one atomic percent of palladium, the balance being vanadium. The alloy is stated to be useful in a cryotron in digital computer circuits.

  2. Separation in Binary Alloys

    NASA Technical Reports Server (NTRS)

    Frazier, D. O.; Facemire, B. R.; Kaukler, W. F.; Witherow, W. K.; Fanning, U.

    1986-01-01

    Studies of monotectic alloys and alloy analogs reviewed. Report surveys research on liquid/liquid and solid/liquid separation in binary monotectic alloys. Emphasizes separation processes in low gravity, such as in outer space or in free fall in drop towers. Advances in methods of controlling separation in experiments highlighted.

  3. DELTA PHASE PLUTONIUM ALLOYS

    DOEpatents

    Cramer, E.M.; Ellinger, F.H.; Land. C.C.

    1960-03-22

    Delta-phase plutonium alloys were developed suitable for use as reactor fuels. The alloys consist of from 1 to 4 at.% zinc and the balance plutonium. The alloys have good neutronic, corrosion, and fabrication characteristics snd possess good dimensional characteristics throughout an operating temperature range from 300 to 490 deg C.

  4. PLUTONIUM-THORIUM ALLOYS

    DOEpatents

    Schonfeld, F.W.

    1959-09-15

    New plutonium-base binary alloys useful as liquid reactor fuel are described. The alloys consist of 50 to 98 at.% thorium with the remainder plutonium. The stated advantages of these alloys over unalloyed plutonium for reactor fuel use are easy fabrication, phase stability, and the accompanying advantuge of providing a means for converting Th/sup 232/ into U/sup 233/.

  5. Investigation on the Effect of Cooling Rate on Hot Tearing Susceptibility of Al2024 Alloy Using Thermal Analysis

    NASA Astrophysics Data System (ADS)

    Shabestari, S. G.; Ghoncheh, M. H.

    2015-12-01

    Effect of different cooling rates and Al-5Ti-1B grain refiner on hot tearing susceptibility of Al2024 alloy were studied using thermal analysis. Influence of cooling rates on microsegregation, and the amount of gas and shrinkage porosities was investigated. The cooling rates used in the present study range from 0.4 to 17.5 K s-1. To evaluate the hot tearing susceptibility, Clyne and Davies' criterion is used. To calculate solid fraction during solidification, solid fraction vs time is plotted based on Newtonian technique via thermal analysis. The results show that the hot tearing susceptibility reduces initially by increasing the cooling rate and then increases at higher cooling rates. Hot tearing susceptibility is decreased by grain refinement. Solidification characteristics of Al2024 e.g., microsegregation, gas, and shrinkage porosities are decreased by increasing cooling rate.

  6. Pressurized metallurgy for high performance special steels and alloys

    NASA Astrophysics Data System (ADS)

    Jiang, Z. H.; Zhu, H. C.; Li, H. B.; L1, Y.; Liu, F. B.

    2016-07-01

    The pressure is one of the basic parameters which greatly influences the metallurgical reaction process and solidification of steels and alloys. In this paper the history and present situation of research and application of pressurized metallurgy, especially pressurized metallurgy for special steels and alloys have been briefly reviewed. In the following part the physical chemistry of pressurized metallurgy is summarized. It is shown that pressurizing may change the conditions of chemical reaction in thermodynamics and kinetics due to the pressure effect on gas volume, solubility of gas and volatile element in metal melt, activity or activity coefficient of components, and change the physical and chemical properties of metal melt, heat transfer coefficient between mould and ingot, thus greatly influencing phase transformation during the solidification process and the solidification structure, such as increasing the solidification nucleation rate, reducing the critical nucleation radius, accelerating the solidification speed and significant macro/micro-structure refinement, and eliminating shrinkage, porosity and segregation and other casting defects. In the third part the research works of pressured metallurgy performed by the Northeastern University including establishment of pressurized induction melting (PIM) and pressurized electroslag remelting (PESR) equipments and development of high nitrogen steels under pressure are described in detail. Finally, it is considered in the paper that application of pressurized metallurgy in manufacture of high performance special steels and alloys is a relatively new research area, and its application prospects will be very broad and bright.

  7. Metallic alloy stability studies

    NASA Technical Reports Server (NTRS)

    Firth, G. C.

    1983-01-01

    The dimensional stability of candidate cryogenic wind tunnel model materials was investigated. Flat specimens of candidate materials were fabricated and cryo-cycled to assess relative dimensional stability. Existing 2-dimensional airfoil models as well as models in various stages of manufacture were also cryo-cycled. The tests indicate that 18 Ni maraging steel offers the greatest dimensional stability and that PH 13-8 Mo stainless steel is the most stable of the stainless steels. Dimensional stability is influenced primarily by metallurgical transformations (austenitic to martensitic) and manufacturing-induced stresses. These factors can be minimized by utilization of stable alloys, refinement of existing manufacturing techniques, and incorporation of new manufacturing technologies.

  8. Three-dimensional chemo-thermomechanically coupled simulation of curing adhesives including viscoplasticity and chemical shrinkage

    NASA Astrophysics Data System (ADS)

    Liebl, Christoph; Johlitz, Michael; Yagimli, Bülent; Lion, Alexander

    2012-05-01

    Based on the one-dimensional material model developed by Liebl et al. (Arch Appl Mech, 2011) a three-dimensional viscoelastic-viscoplastic material model for small deformations of curing adhesives on the basis of continuum mechanics is proposed in this contribution. The model describes the most relevant phenomena which occur during curing processes in the automotive industry and includes the effects of temperature and degree of cure on the mechanical properties of the material. Thermal expansion as well as chemical shrinkage are also contained. The yield stress for the viscoplastic part of the model goes back to the work of Schlimmer and Mahnken (Int J Numer Meth Eng 63:1461-1477, 2005), but is formulated in reference to the degree of cure and the temperature. Therefore this model considers chemo-thermomechanical coupling and extends the plasticity approach of Schlimmer and Mahnken, which is devised for cured adhesives, to the whole curing range, from the uncured to the fully cured adhesive. A peculiar focus is hereby laid on epoxy resins used in the automotive industry as structural adhesives.

  9. Neurodegenerative Disease Diagnosis using Incomplete Multi-Modality Data via Matrix Shrinkage and Completion

    PubMed Central

    Thung, Kim-Han; Wee, Chong-Yaw; Yap, Pew-Thian; Shen, Dinggang

    2014-01-01

    In this work, we are interested in predicting the diagnostic statuses of potentially neurodegenerated patients using feature values derived from multi-modality neuroimaging data and biological data, which might be incomplete. Collecting the feature values into a matrix, with each row containing a feature vector of a sample, we propose a framework to predict the corresponding associated multiple target outputs (e.g., diagnosis label and clinical scores) from this feature matrix by performing matrix shrinkage following by matrix completion. Specifically, we first combine the feature and target output matrices into a large matrix and then partition this large incomplete matrix into smaller submatrices, each consisting of samples with complete feature values (corresponding to a certain combination of modalities) and target outputs. Treating each target output as the outcome of a prediction task, we apply a 2-step multi-task learning algorithm to select the most discriminative features and samples in each submatrix. Features and samples that are not selected in any of the submatrices are discarded, resulting in a shrunk version of the original large matrix. The missing feature values and unknown target outputs of the shrunk matrix is then completed simultaneously. Experimental results using the ADNI dataset indicate that our proposed framework achieves higher classification accuracy at a greater speed when compared with conventional imputation-based classification methods and also yields competitive performance when compared with the state-of-the-art methods. PMID:24480301

  10. Long Lasting Protein Synthesis- and Activity-Dependent Spine Shrinkage and Elimination after Synaptic Depression

    PubMed Central

    Ramiro-Cortés, Yazmín; Israely, Inbal

    2013-01-01

    Neuronal circuits modify their response to synaptic inputs in an experience-dependent fashion. Increases in synaptic weights are accompanied by structural modifications, and activity dependent, long lasting growth of dendritic spines requires new protein synthesis. When multiple spines are potentiated within a dendritic domain, they show dynamic structural plasticity changes, indicating that spines can undergo bidirectional physical modifications. However, it is unclear whether protein synthesis dependent synaptic depression leads to long lasting structural changes. Here, we investigate the structural correlates of protein synthesis dependent long-term depression (LTD) mediated by metabotropic glutamate receptors (mGluRs) through two-photon imaging of dendritic spines on hippocampal pyramidal neurons. We find that induction of mGluR-LTD leads to robust and long lasting spine shrinkage and elimination that lasts for up to 24 hours. These effects depend on signaling through group I mGluRs, require protein synthesis, and activity. These data reveal a mechanism for long lasting remodeling of synaptic inputs, and offer potential insights into mental retardation. PMID:23951097

  11. eHUGS: Enhanced Hierarchical Unbiased Graph Shrinkage for Efficient Groupwise Registration

    PubMed Central

    Wu, Guorong; Peng, Xuewei; Ying, Shihui; Wang, Qian; Yap, Pew-Thian; Shen, Dan; Shen, Dinggang

    2016-01-01

    Effective and efficient spatial normalization of a large population of brain images is critical for many clinical and research studies, but it is technically very challenging. A commonly used approach is to choose a certain image as the template and then align all other images in the population to this template by applying pairwise registration. To avoid the potential bias induced by the inappropriate template selection, groupwise registration methods have been proposed to simultaneously register all images to a latent common space. However, current groupwise registration methods do not make full use of image distribution information for more accurate registration. In this paper, we present a novel groupwise registration method that harnesses the image distribution information by capturing the image distribution manifold using a hierarchical graph with its nodes representing the individual images. More specifically, a low-level graph describes the image distribution in each subgroup, and a high-level graph encodes the relationship between representative images of subgroups. Given the graph representation, we can register all images to the common space by dynamically shrinking the graph on the image manifold. The topology of the entire image distribution is always maintained during graph shrinkage. Evaluations on two datasets, one for 80 elderly individuals and one for 285 infants, indicate that our method can yield promising results. PMID:26800361

  12. Shrinkage prediction of seed-voxel brain connectivity using resting state fMRI

    PubMed Central

    Shou, Haochang; Eloyan, Ani; Nebel, Mary Beth; Mejia, Amanda; Pekar, James J.; Mostofsky, Stewart; Caffo, Brian; Lindquist, Martin A.; Crainiceanu, Ciprian M.

    2014-01-01

    Resting-state functional magnetic resonance imaging (rs-fMRI) is used to investigate synchronous activations in spatially distinct regions of the brain, which are thought to reflect functional systems supporting cognitive processes. Analyses are often performed using seed-based correlation analysis, allowing researchers to explore functional connectivity between data in a seed region and the rest of the brain. Using scan–rescan rs-fMRI data, we investigate how well the subject-specific seed-based correlation map from the second replication of the study can be predicted using data from the first replication. We show that one can dramatically improve prediction of subject-specific connectivity by borrowing strength from the group correlation map computed using all other subjects in the study. Even more surprisingly, we found that the group correlation map provided a better prediction of a subject's connectivity than the individual's own data. While further discussion and experimentation are required to understand how this can be used in practice, results indicate that shrinkage-based methods that borrow strength from the population mean should play a role in rs-fMRI data analysis. PMID:24879924

  13. A LEAST ABSOLUTE SHRINKAGE AND SELECTION OPERATOR (LASSO) FOR NONLINEAR SYSTEM IDENTIFICATION

    NASA Technical Reports Server (NTRS)

    Kukreja, Sunil L.; Lofberg, Johan; Brenner, Martin J.

    2006-01-01

    Identification of parametric nonlinear models involves estimating unknown parameters and detecting its underlying structure. Structure computation is concerned with selecting a subset of parameters to give a parsimonious description of the system which may afford greater insight into the functionality of the system or a simpler controller design. In this study, a least absolute shrinkage and selection operator (LASSO) technique is investigated for computing efficient model descriptions of nonlinear systems. The LASSO minimises the residual sum of squares by the addition of a 1 penalty term on the parameter vector of the traditional 2 minimisation problem. Its use for structure detection is a natural extension of this constrained minimisation approach to pseudolinear regression problems which produces some model parameters that are exactly zero and, therefore, yields a parsimonious system description. The performance of this LASSO structure detection method was evaluated by using it to estimate the structure of a nonlinear polynomial model. Applicability of the method to more complex systems such as those encountered in aerospace applications was shown by identifying a parsimonious system description of the F/A-18 Active Aeroelastic Wing using flight test data.

  14. α–blockade, apoptosis, and prostate shrinkage: how are they related?

    PubMed Central

    Chłosta, Piotr; Kaplan, Steven

    2013-01-01

    Purpose The α1–adrenoreceptor antagonists, such as terazosin and doxazosin, induce prostate programmed cell death (apoptosis) within prostate epithelial and stromal cells in vitro. This treatment should cause prostate volume decrease, However, this has never been observed in clinical conditions. The aim of this paper is to review the disconnect between these two processes. Methods PubMed and DOAJ were searched for papers related to prostate, apoptosis, and stem cell death. The following key words were used: prostate, benign prostate hyperplasia, programmed cell death, apoptosis, cell death, α1–adrenoreceptor antagonist, α–blockade, prostate epithelium, prostate stroma, stem cells, progenitors, and in vitro models. Results We have shown how discoveries related to stem cells can influence our understanding of α–blockade treatment for BPH patients. Prostate epithelial and mesenchymal compartments have stem (progenitors) and differentiating cells. These compartments are described in relation to experimental in vitro and in vivo settings. Conclusions Apoptosis is observed within prostate tissue, but this effect has no clinical significance and cannot lead to prostate shrinkage. In part, this is due to stem cells that are responsible for prostate tissue regeneration and are resistant to apoptosis triggered by α1–receptor antagonists. PMID:24579025

  15. Shrinkage and recyclability of poly(1,2-ethylene-bis(dimethylsiloxane))

    SciTech Connect

    Samara, M.; Loy, D.A.

    1998-08-01

    Non-shrinking polymers are desirable as encapsulants for strain-free packaging for electronics. Ring-opening polymerizations of cyclic monomers such as lactams, cyclic ethers, and cyclic oligosiloxanes have proven an effective strategy for reducing shrinkage. In this report the authors examined the loss of volume during the ring-opening polymerization of neat 2,2,5,5-tetramethyl-l-oxa-2,5-disilacyclopentane to give poly(1,2-ethylene-bis(dimethyl-siloxane)). Monomer 1 is under sufficient strain (8--12 kcal/mole) to permit its facile base-catalyzed polymerization to afford high molecular polymer. Monomer 1 was prepared by hydrolyzing and condensing either 1,2-bis(chlorodimethylsilyl)ethane or 1,m2-bis(dimethylethoxysilyl)ethane to give a low molecular weight oligomer. Pyrolysis of this oligomer with potassium hydroxide at 280 C afforded the cyclic monomer in good yield (60--70%). The ease with which the oligomer can be converted to monomer also led the authors to investigate the potential for recycling the high molecular weight polymer.

  16. Direct real-time measurement of shrinkage in photopolymer materials during recording of reflection gratings

    NASA Astrophysics Data System (ADS)

    Vojtíšek, Petr; Květoň, Milan

    2015-05-01

    Photopolymer recording materials aimed at a recording of holograms, diffraction elements for manipulation of light or storing of information received great deal of attention in recent years. For their optimal application it is desirable to characterize them and to know what to expect from them. During the recording of the diffraction gratings (or elements) into this photopolymer materials (but not exclusively) there can be some volume changes of the material itself (so-called shrinkage) which consequently alter the replay performance of such gratings, for example from a perspective of a color fidelity, reconstruction conditions, or diffraction efficiency (in case of a general hologram, the deformation of a holographic image is observed). The main aim is to characterize volume changes and to minimize them with application of some precompensation method in advance and so the resulting grating will have desired properties. In this contribution, we would like to present and discuss measurement method for direct and real-time detection of such volume changes for reflection gratings in low shrinkable photopolymer materials. This measurement method is based on a reconstruction of the grating with low intensity white light under slightly different angle than the angle of the recording is and the analysis on the idea of fringe plane rotation model. For a theoretical background the Kogelnik's Coupled Wave theory and Rigorous Coupled Wave Analysis are used. The recording of the diffraction gratings and measurement of their volume changes is experimentally done for a photopolymer material Bayfol HX101.

  17. Reduction of iron-oxide-carbon composites: part III. Shrinkage of composite pellets during reduction

    SciTech Connect

    Halder, S.; Fruehan, R.J.

    2008-12-15

    This article involves the evaluation of the volume change of iron-oxide-carbon composite pellets and its implications on reduction kinetics under conditions prevalent in a rotary hearth furnace (RHF) that were simulated in the laboratory. The pellets, in general, were found to shrink considerably during the reduction due to the loss of carbon and oxygen from the system, sintering of the iron-oxide, and formation of a molten slag phase at localized regions inside the pellets due to the presence of binder and coal/wood-charcoal ash at the reduction temperatures. One of the shortcomings of the RHF ironmaking process has been the inability to use multiple layers of composite pellets because of the impediment in heat transport to the lower layers of a multilayer bed. However, pellet shrinkage was found to have a strong effect on the reduction kinetics by virtue of enhancing the external heat transport to the lower layers. The volume change of the different kinds of composite pellets was studied as a function of reduction temperature and time. The estimation of the change in the amount of external heat transport with varying pellet sizes for a particular layer of a multilayer bed was obtained by conducting heat-transfer tests using inert low-carbon steel spheres. It was found that if the pellets of the top layer of the bed shrink by 30 pct, the external heat transfer to the second layer increases by nearly 6 times.

  18. A shrinkage approach for estimating a treatment effect using intermediate biomarker data in clinical trials.

    PubMed

    Li, Yun; Taylor, Jeremy M G; Little, Roderick J A

    2011-12-01

    In clinical trials, a biomarker (S ) that is measured after randomization and is strongly associated with the true endpoint (T) can often provide information about T and hence the effect of a treatment (Z ) on T. A useful biomarker can be measured earlier than T and cost less than T. In this article, we consider the use of S as an auxiliary variable and examine the information recovery from using S for estimating the treatment effect on T, when S is completely observed and T is partially observed. In an ideal but often unrealistic setting, when S satisfies Prentice's definition for perfect surrogacy, there is the potential for substantial gain in precision by using data from S to estimate the treatment effect on T. When S is not close to a perfect surrogate, it can provide substantial information only under particular circumstances. We propose to use a targeted shrinkage regression approach that data-adaptively takes advantage of the potential efficiency gain yet avoids the need to make a strong surrogacy assumption. Simulations show that this approach strikes a balance between bias and efficiency gain. Compared with competing methods, it has better mean squared error properties and can achieve substantial efficiency gain, particularly in a common practical setting when S captures much but not all of the treatment effect and the sample size is relatively small. We apply the proposed method to a glaucoma data example. PMID:21627627

  19. Reduction of Iron-Oxide-Carbon Composites: Part III. Shrinkage of Composite Pellets during Reduction

    NASA Astrophysics Data System (ADS)

    Halder, S.; Fruehan, R. J.

    2008-12-01

    This article involves the evaluation of the volume change of iron-oxide-carbon composite pellets and its implications on reduction kinetics under conditions prevalent in a rotary hearth furnace (RHF) that were simulated in the laboratory. The pellets, in general, were found to shrink considerably during the reduction due to the loss of carbon and oxygen from the system, sintering of the iron-oxide, and formation of a molten slag phase at localized regions inside the pellets due to the presence of binder and coal/wood-charcoal ash at the reduction temperatures. One of the shortcomings of the RHF ironmaking process has been the inability to use multiple layers of composite pellets because of the impediment in heat transport to the lower layers of a multilayer bed. However, pellet shrinkage was found to have a strong effect on the reduction kinetics by virtue of enhancing the external heat transport to the lower layers. The volume change of the different kinds of composite pellets was studied as a function of reduction temperature and time. The estimation of the change in the amount of external heat transport with varying pellet sizes for a particular layer of a multilayer bed was obtained by conducting heat-transfer tests using inert low-carbon steel spheres. It was found that if the pellets of the top layer of the bed shrink by 30 pct, the external heat transfer to the second layer increases by nearly 6 times.

  20. eHUGS: Enhanced Hierarchical Unbiased Graph Shrinkage for Efficient Groupwise Registration.

    PubMed

    Wu, Guorong; Peng, Xuewei; Ying, Shihui; Wang, Qian; Yap, Pew-Thian; Shen, Dan; Shen, Dinggang

    2016-01-01

    Effective and efficient spatial normalization of a large population of brain images is critical for many clinical and research studies, but it is technically very challenging. A commonly used approach is to choose a certain image as the template and then align all other images in the population to this template by applying pairwise registration. To avoid the potential bias induced by the inappropriate template selection, groupwise registration methods have been proposed to simultaneously register all images to a latent common space. However, current groupwise registration methods do not make full use of image distribution information for more accurate registration. In this paper, we present a novel groupwise registration method that harnesses the image distribution information by capturing the image distribution manifold using a hierarchical graph with its nodes representing the individual images. More specifically, a low-level graph describes the image distribution in each subgroup, and a high-level graph encodes the relationship between representative images of subgroups. Given the graph representation, we can register all images to the common space by dynamically shrinking the graph on the image manifold. The topology of the entire image distribution is always maintained during graph shrinkage. Evaluations on two datasets, one for 80 elderly individuals and one for 285 infants, indicate that our method can yield promising results. PMID:26800361

  1. Effect of treated filler loading on the photopolymerization inhibition and shrinkage of a dimethacrylate matrix.

    PubMed

    Nunes, T G; Pereira, S G; Kalachandra, S

    2008-05-01

    This study shows how treated filler loading influences the photopolymerization of a dimethacrylate comonomer mixture, regarding, in particular, shrinkage and inhibition under atmospheric oxygen, present in oral environment. Bis-GMA/TEGDMA (75/25 wt.%) resins were loaded with hybrid filler (Ba aluminosilicate glass and pyrogenic silica), treated with gamma-methacryloxy(propyl)trimethoxysilane, at 0-50 wt.% and light cured over a total of 30 s (45 mW/cm2). Degree of double-bond conversion (DC), obtained using FTIR, decreased with filler content. 1H MAS spectra (293-340 K) and STRAFI images (293 K) were obtained as a function of irradiation time and filler concentration. 1H signals of unreacted methacrylate groups were more intense for higher loaded resins and resonances from -CH2SiO2(OH) (T2) and -CH2SiO3- (T3) units, also observed by 29Si NMR, were resolved and suggest the presence of T2-resin bonds. 1D images show a reduction on polymerization contraction and reaction inhibition at the composite resin surface with filler loading. 2D resin images present a highly mobile surface layer, hence with lower DC. PMID:17914626

  2. Improved Accuracy of the Inherent Shrinkage Method for Fast and More Reliable Welding Distortion Calculations

    NASA Astrophysics Data System (ADS)

    Mendizabal, A.; González-Díaz, J. B.; San Sebastián, M.; Echeverría, A.

    2016-05-01

    This paper describes the implementation of a simple strategy adopted for the inherent shrinkage method (ISM) to predict welding-induced distortion. This strategy not only makes it possible for the ISM to reach accuracy levels similar to the detailed transient analysis method (considered the most reliable technique for calculating welding distortion) but also significantly reduces the time required for these types of calculations. This strategy is based on the sequential activation of welding blocks to account for welding direction and transient movement of the heat source. As a result, a significant improvement in distortion prediction is achieved. This is demonstrated by experimentally measuring and numerically analyzing distortions in two case studies: a vane segment subassembly of an aero-engine, represented with 3D-solid elements, and a car body component, represented with 3D-shell elements. The proposed strategy proves to be a good alternative for quickly estimating the correct behaviors of large welded components and may have important practical applications in the manufacturing industry.

  3. Improved Accuracy of the Inherent Shrinkage Method for Fast and More Reliable Welding Distortion Calculations

    NASA Astrophysics Data System (ADS)

    Mendizabal, A.; González-Díaz, J. B.; San Sebastián, M.; Echeverría, A.

    2016-07-01

    This paper describes the implementation of a simple strategy adopted for the inherent shrinkage method (ISM) to predict welding-induced distortion. This strategy not only makes it possible for the ISM to reach accuracy levels similar to the detailed transient analysis method (considered the most reliable technique for calculating welding distortion) but also significantly reduces the time required for these types of calculations. This strategy is based on the sequential activation of welding blocks to account for welding direction and transient movement of the heat source. As a result, a significant improvement in distortion prediction is achieved. This is demonstrated by experimentally measuring and numerically analyzing distortions in two case studies: a vane segment subassembly of an aero-engine, represented with 3D-solid elements, and a car body component, represented with 3D-shell elements. The proposed strategy proves to be a good alternative for quickly estimating the correct behaviors of large welded components and may have important practical applications in the manufacturing industry.

  4. Irradiation assisted stress corrosion cracking of HTH Alloy X-750 and Alloy 625

    SciTech Connect

    Mills, W.J.; Lebo, M.R.; Bajaj, R.; Kearns, J.J.; Hoffman, R.C.; Korinko, J.J.

    1994-06-01

    In-reactor testing of bolt-loaded precracked compact tension specimens was performed in 360{degree}C water to determine effect of irradiation on the SCC behavior of HTH Alloy X-750 and direct aged Alloy 625. Out-of-flux and autoclave control specimens provided baseline data. Primary test variables were stress intensity factor, fluence, chemistry, processing history, prestrain. Results for the first series of experiments were presented at a previous conference. Data from two more recent experiments are compared with previous results; they confirm that high irradiation levels significantly reduce SCC resistance in HTH Alloy X-750. Heat-to-heat differences in IASCC were related to differences in boron content, with low boron heats showing improved SCC resistance. The in-reactor SCC performance of Alloy 625 was superior to that for Alloy X-750, as no cracking was observed in any Alloy 625 specimens even though they were tested at very high K{sub 1} and fluence levels. A preliminary SCC usage model developed for Alloy X-750 indicates that in-reactor creep processes, which relax stresses but also increase crack tip strain rates, and radiolysis effects accelerate SCC. Hence, in-reactor SCC damage under high flux conditions may be more severe than that associated with postirradiation tests. In addition, preliminary mechanism studies were performed to determine the cause of IASCC In Alloy X-750.

  5. A Novel Compressed Sensing Method for Magnetic Resonance Imaging: Exponential Wavelet Iterative Shrinkage-Thresholding Algorithm with Random Shift.

    PubMed

    Zhang, Yudong; Yang, Jiquan; Yang, Jianfei; Liu, Aijun; Sun, Ping

    2016-01-01

    Aim. It can help improve the hospital throughput to accelerate magnetic resonance imaging (MRI) scanning. Patients will benefit from less waiting time. Task. In the last decade, various rapid MRI techniques on the basis of compressed sensing (CS) were proposed. However, both computation time and reconstruction quality of traditional CS-MRI did not meet the requirement of clinical use. Method. In this study, a novel method was proposed with the name of exponential wavelet iterative shrinkage-thresholding algorithm with random shift (abbreviated as EWISTARS). It is composed of three successful components: (i) exponential wavelet transform, (ii) iterative shrinkage-thresholding algorithm, and (iii) random shift. Results. Experimental results validated that, compared to state-of-the-art approaches, EWISTARS obtained the least mean absolute error, the least mean-squared error, and the highest peak signal-to-noise ratio. Conclusion. EWISTARS is superior to state-of-the-art approaches. PMID:27066068

  6. A Novel Compressed Sensing Method for Magnetic Resonance Imaging: Exponential Wavelet Iterative Shrinkage-Thresholding Algorithm with Random Shift

    PubMed Central

    Zhang, Yudong; Yang, Jiquan; Yang, Jianfei; Liu, Aijun; Sun, Ping

    2016-01-01

    Aim. It can help improve the hospital throughput to accelerate magnetic resonance imaging (MRI) scanning. Patients will benefit from less waiting time. Task. In the last decade, various rapid MRI techniques on the basis of compressed sensing (CS) were proposed. However, both computation time and reconstruction quality of traditional CS-MRI did not meet the requirement of clinical use. Method. In this study, a novel method was proposed with the name of exponential wavelet iterative shrinkage-thresholding algorithm with random shift (abbreviated as EWISTARS). It is composed of three successful components: (i) exponential wavelet transform, (ii) iterative shrinkage-thresholding algorithm, and (iii) random shift. Results. Experimental results validated that, compared to state-of-the-art approaches, EWISTARS obtained the least mean absolute error, the least mean-squared error, and the highest peak signal-to-noise ratio. Conclusion. EWISTARS is superior to state-of-the-art approaches. PMID:27066068

  7. High strength alloys

    SciTech Connect

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub

    2012-06-05

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.

  8. High strength alloys

    SciTech Connect

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J; John, Randy Carl; Kim, Dong Sub

    2010-08-31

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

  9. NiAl alloys for structural uses

    NASA Technical Reports Server (NTRS)

    Koss, D. A.

    1991-01-01

    conventional sense requires ductile powder particles which, through a cold welding and fracture process, can be dispersion strengthened by submicron-sized oxide particles. Using both the Ni-35Al-Fe alloys to contain approx. 1 v/o Y2O3. Preliminary results indicate that mechanically alloyed and extruded NiAl-Fe + Y2O3 alloys when heat treated to a grain-coarsened condition, exhibit improved creep resistance at 1000 C when compared to NiAl; oxidation resistance comparable to NiAl; and fracture toughness values a factor of three better than NiAl. As a result of the research initiated on this NASA program, a subsequent project with support from Inco Alloys International is underway.

  10. One-dimensional Stress Evaluation of a Ring Bulk HTS with Shrinkage Fit by an Iron Ring

    NASA Astrophysics Data System (ADS)

    Tsuchimoto, M.; Morita, M.

    The stress distributions of a ring bulk high-Tc superconductor are studied in the one-dimensional numerical analysis. Boundary condition is derivated under shrinkage fit by an iron ring. Convergences of the solutions are compared with the simple iteration method and the successive approximation method. Maximum hoop stresses are evaluated during the field-cooled magnetization. Differences of the solutions are also discussed between the present and the previous boundary conditions.

  11. Micro and Macro Segregation in Alloys Solidifying with Equiaxed Morphology

    NASA Technical Reports Server (NTRS)

    Stefanescu, Doru M.; Curreri, Peter A.; Leon-Torres, Jose; Sen, Subhayu

    1996-01-01

    To understand macro segregation formation in Al-Cu alloys, experiments were run under terrestrial gravity (1g) and under low gravity during parabolic flights (10(exp -2) g). Alloys of two different compositions (2% and 5% Cu) were solidified at two different cooling rates. Systematic microscopic and SEM observations produced microstructural and segregation maps for all samples. These maps may be used as benchmark experiments for validation of microstructure evolution and segregation models. As expected, the macro segregation maps are very complex. When segregation was measured along the central axis of the sample, the highest macro segregation for samples solidified at 1g was obtained for the lowest cooling rate. This behavior is attributed to the longer time available for natural convection and shrinkage flow to affect solute redistribution. In samples solidified under low-g, the highest macro-segregation was obtained at the highest cooling rate. In general, low-gravity solidification resulted in less segregation. To explain the experimental findings, an analytical (Flemings-Nereo) and a numerical model were used. For the numerical model, the continuum formulation was employed to describe the macroscopic transports of mass, energy, and momentum, associated with the microscopic transport phenomena, for a two-phase system. The model proposed considers that liquid flow is driven by thermal and solutal buoyancy, and by solidification shrinkage. The Flemings-Nereo model explains well macro segregation in the initial stages of low-gravity segregation. The numerical model can describe the complex macro segregation pattern and the differences between low- and high-gravity solidification.

  12. Room temperature creep in metals and alloys

    SciTech Connect

    Deibler, Lisa Anne

    2014-09-01

    Time dependent deformation in the form of creep and stress relaxation is not often considered a factor when designing structural alloy parts for use at room temperature. However, creep and stress relaxation do occur at room temperature (0.09-0.21 Tm for alloys in this report) in structural alloys. This report will summarize the available literature on room temperature creep, present creep data collected on various structural alloys, and finally compare the acquired data to equations used in the literature to model creep behavior. Based on evidence from the literature and fitting of various equations, the mechanism which causes room temperature creep is found to include dislocation generation as well as exhaustion.

  13. Spark alloying of an AL9 alloy by hard alloys

    NASA Astrophysics Data System (ADS)

    Kuptsov, S. G.; Fominykh, M. V.; Mukhinov, D. V.; Magomedova, R. S.; Nikonenko, E. A.

    2015-08-01

    The phase compositions of spark coatings of Kh12M steel with a VT1-0 (titanium) alloy and T15K6 and T30K4 hard alloys are studied. It is shown that the TiC titanium carbide forms in all cases and tungsten carbide decomposes with the formation of tungsten in a coating. These processes are intensified by increasing time, capacitance, and frequency. The surface hardness, the sample weight, and the white layer thickness increase monotonically.

  14. Creep Resistant Zinc Alloy

    SciTech Connect

    Frank E. Goodwin

    2002-12-31

    This report covers the development of Hot Chamber Die Castable Zinc Alloys with High Creep Strengths. This project commenced in 2000, with the primary objective of developing a hot chamber zinc die-casting alloy, capable of satisfactory service at 140 C. The core objectives of the development program were to: (1) fill in missing alloy data areas and develop a more complete empirical model of the influence of alloy composition on creep strength and other selected properties, and (2) based on the results from this model, examine promising alloy composition areas, for further development and for meeting the property combination targets, with the view to designing an optimized alloy composition. The target properties identified by ILZRO for an improved creep resistant zinc die-casting alloy were identified as follows: (1) temperature capability of 1470 C; (2) creep stress of 31 MPa (4500 psi); (3) exposure time of 1000 hours; and (4) maximum creep elongation under these conditions of 1%. The project was broadly divided into three tasks: (1) Task 1--General and Modeling, covering Experimental design of a first batch of alloys, alloy preparation and characterization. (2) Task 2--Refinement and Optimization, covering Experimental design of a second batch of alloys. (3) Task 3--Creep Testing and Technology transfer, covering the finalization of testing and the transfer of technology to the Zinc industry should have at least one improved alloy result from this work.

  15. [Casting of dental alloys with special reference to the bonding capacity of Ni-Cr alloys].

    PubMed

    Weber, H

    1979-07-01

    A short review on castability of dental alloys -- for which a definition is proposed -- reflects the different factors influencing the results of a casting. In this case solid sieves and plates are cast by use of one gold-base alloy (Type III) and two base metal alloys used for porcelain veneering. All three alloys filled the sieve pattern to a 100%, whereas they performed differently when cast as thin, solid squares. The most continuous results were achieved with a Ni-Cr-alloy whose melting temperature can be recognized since the ingots flow together when this point is reached. Since the plate pattern is most difficult to cast due to surface to bulk ratio it is assumed that a complete casting can only be achieved when the performance of the alloy is good and all required conditions match. Thus, this type of test seems to be suitable to determine the castability of a dental alloy. The sieve test should be used to investigate and to improve the influence of the different factors as for example burnout time and temperature of the mold and sprue size. PMID:380961

  16. Long-term nipple shrinkage following augmentation by an autologous rib cartilage transplant in free DIEP-flaps.

    PubMed

    Heitland, A; Markowicz, M; Koellensperger, E; Allen, R; Pallua, N

    2006-01-01

    Aesthetically pleasing nipple-areola reconstruction is a satisfying part of a two-stage breast reconstruction. The up to 50% [Banducci DR, Le TK, Hughes KC. Long-term follow-up of a modified Anton-Hartrampf nipple reconstruction. Ann Plast Surg 1999;43(5):467-9; discussion 469-70] postoperative shrinkage following a conventional nipple reconstruction is a well-known problem. Augmentation of the nipple with autologous banked cartilage seems to be a promising solution. From 2000-2003, 17 patients underwent a nipple-areola-complex reconstruction following secondary breast reconstruction using free perforator flaps. The rib cartilage harvested during the preparation of the internal thoracic vessels was banked subcutaneously and six months later replanted under the 'arrow flap' after contouring it in a 'mushroom' shape. One year later the shrinkage of the nipple in comparison to the intraoperative status was measured. In addition, patients were asked about their personal palpation impression and the aesthetic outcome. The average height decreased one year postoperatively about 25%. Thirteen of 17 patients judged the aesthetic outcome as very good, 16 nipples healed without cartilage protrusion and no patient felt discomfortable stiffness of the nipple. Our concept of a nipple augmentation with rib cartilage improves the projection and allows a more correct judgement of the later nipple shrinkage. We consider this technique to be an aesthetically satisfying and safe method, which could be used with any kind of breast reconstruction. PMID:16996429

  17. Relative shrinkage of adipocytes by paraffin in proportion to plastic embedding in human adipose tissue before and after weight loss.

    PubMed

    Verhoef, Sanne P M; van Dijk, Paul; Westerterp, Klaas R

    2013-01-01

    Adipocyte size is a major modulator of endocrine functioning of adipose tissue and methods allowing accurate determination of adipocyte size are important to study energy metabolism. The aim of this study was to assess the relative shrinkage of adipocytes before and after weight loss by comparing adipose tissue from the same subjects embedded in paraffin and plastic. 18 healthy subjects (5 males and 13 females) aged 20-50 y with a BMI of 28-38 kg/m² followed a very low energy diet for 8 weeks. Adipose tissue biopsies were taken prior to and after weight loss and were processed for paraffin and plastic sections. Parameters of adipocyte size were determined with computer image analysis. Mean adipocyte size was smaller in paraffin compared to plastic embedded tissue both before (66 ± 4 vs. 103 ± 5 μm, P < 0.001) as after weight loss (62 ± 4 vs. 91 ± 5 μm, P < 0.001). Relative shrinkage of adipocytes in paraffin embedded tissue in proportion to plastic embedded tissue was not significantly different before and after weight loss (73 and 69%, respectively). Shrinkage due to the type of embedding of the adipose tissue can be ignored when comparing before and after weight loss. Plastic embedding of adipose tissue provides more accurate and sensitive results. PMID:24331678

  18. [Cell shrinkage during apoptosis is not obligatory. Apoptosis of U937 cells induced by staurosporine and etoposide].

    PubMed

    Vereninov, A A; Goriachaia, T S; Matveev, V V; Moshkov, A V; Rozanov, Iu M; Sakuta, G A; Shirokova, A V; Iurinskaia, V E

    2004-01-01

    A study was made of apoptotic cell shrinkage, which is generally believed to be a hallmark of apoptosis. The two conventional models of apoptosis were used for examination of changes in cell water balance--one is apoptosis caused in human lymphoma cell line U937 by staurosporine, and the other by etoposide. Intracellular water was determined by measuring buoyant density of cells in continuous Percoll gradient. Apoptosis was recognized by microscopy and flow cytometry. Apoptosis caused by staurosporine (1 microM, 4 h) was found to be associated with a decrease in cell water content by almost 24%. In contrast, no decrease in cell water content was observed in U937 cells incubated with etoposide (50 microM, 4 h), in spite of the number of features suggesting the presence of apoptosis, such as the appearance of apoptotic bodies, chromatin condensation and fragmentation and disappearance of S-phase cells in DNA histogram. It is concluded that definition of apoptosis as "shrinkage-necrosis" (Kerr, 1971) needs correcting: the distinction of apoptotic cells involves the absence of swelling, rather than cell shrinkage. PMID:15473371

  19. Weldability of High Alloys

    SciTech Connect

    Maroef, I

    2003-01-22

    The purpose of this study was to investigate the effect of silicon and iron on the weldability of HAYNES HR-160{reg_sign} alloy. HR-I60 alloy is a solid solution strengthened Ni-Co-Cr-Si alloy. The alloy is designed to resist corrosion in sulfidizing and other aggressive high temperature environments. Silicon is added ({approx}2.75%) to promote the formation of a protective oxide scale in environments with low oxygen activity. HR-160 alloy has found applications in waste incinerators, calciners, pulp and paper recovery boilers, coal gasification systems, and fluidized bed combustion systems. HR-160 alloy has been successfully used in a wide range of welded applications. However, the alloy can be susceptible to solidification cracking under conditions of severe restraint. A previous study by DuPont, et al. [1] showed that silicon promoted solidification cracking in the commercial alloy. In earlier work conducted at Haynes, and also from published work by DuPont et al., it was recognized that silicon segregates to the terminal liquid, creating low melting point liquid films on solidification grain boundaries. Solidification cracking has been encountered when using the alloy as a weld overlay on steel, and when joining HR-160 plate in a thickness greater than19 millimeters (0.75 inches) with matching filler metal. The effect of silicon on the weldability of HR-160 alloy has been well documented, but the effect of iron is not well understood. Prior experience at Haynes has indicated that iron may be detrimental to the solidification cracking resistance of the alloy. Iron does not segregate to the terminal solidification product in nickel-base alloys, as does silicon [2], but iron may have an indirect or interactive influence on weldability. A set of alloys covering a range of silicon and iron contents was prepared and characterized to better understand the welding metallurgy of HR-160 alloy.

  20. 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

  1. Scale Rules for Macrosegregation during Direct-Chill Casting of Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Eskin, Dmitry G.; Du, Qiang; Katgerman, Laurens

    2008-05-01

    An analysis of published experimental and numerical results shows that there is a scaling relationship between the magnitude and direction of centerline segregation in direct-chill (DC) cast billets from aluminum alloys and the process parameters, i.e., billet diameter and casting speed. It seems that there is always a range of these process parameters where the centerline segregation is positive, and there is a threshold when the centerline segregation vanishes. Numerical simulations of macrosegregation during DC casting of a binary Al-Cu alloy were performed at different ratios of casting speed and billet diameter. The macrosegregation model takes into account only two mechanisms of macrosegregation, i.e., thermosolutal convection and shrinkage-induced flow. The results of these computer simulations fit well to the dependence obtained using numerous reference data. The results are discussed in terms of the contribution of different mechanisms of macrosegregation and the shape of the billet sump.

  2. Evaluating the Impact of Glacier Shrinkage on Water Supply at Volcán Chimborazo, Ecuador

    NASA Astrophysics Data System (ADS)

    La Frenierre, J.; Mark, B. G.

    2013-12-01

    Glaciers play a critical hydrologic role in mountain watersheds worldwide, and the potential effect of persistent glacier shrinkage on water supply is justly regarded as one of the key climate change impacts that the scientific and development communities must endeavor to understand. The relationship between glaciers and water supply is particularly acute in the tropical Andes, where irrigation is often essential for the sustainability of agricultural livelihoods. In Ecuador, the glaciers of Volcán Chimborazo (6267 m.a.s.l.) are a highly-visible component of the local hydrologic system and irrigators in the communities that surround the mountain are concerned about their potential vulnerability in the face of noticeable recent glacier retreat on the mountain. Here, I present results from an integrated study that quantifies the rate of glacier retreat at Chimborazo since the mid-1980s, estimates the present-day contribution of glacier melt to total discharge in the mountain's most glacierized watershed, and assays the implications of changing hydrologic conditions on water users in the region. Methods employed include direct hydrologic and glaciologic measurements, analysis of hydrologic tracers, remote sensing techniques, and social research activities such as household surveys and focus groups. Over the past quarter-century, increased water stress has been a key driver of shifting livelihood patterns in the agrarian communities below the mountain, with persistent glacier retreat one of multiple biophysical and socio-economic forcing mechanisms. Since 1986, Chimborazo has lost 20.5% of its glacier surface area (0.8%/yr). While station records indicate patterns of climate change consistent with those reported elsewhere in the tropical Andes (temperature increase of 1.1°C/decade; no statistically-significant changes in precipitation since 1985), there is a very strong local perception that surface water sources are diminishing and that rainfall patterns are

  3. Dosimetric verification of surface and superficial doses for head and neck IMRT with different PTV shrinkage margins

    SciTech Connect

    Shiau, An-Cheng; Lai, Pei-Ling; Liang, Ji-An; and others

    2011-03-15

    Purpose: Dosimetric uncertainty in the surface and superficial regions is still a major concern for radiation therapy and becomes more important when using the inverse planning algorithm for IMRT. The purpose of this study was to measure dose distributions and to evaluate the calculation accuracy in the superficial region for different planning target volume (PTV) shrinkage methods for head and neck IMRT plans. Methods: A spherical polystyrene phantom 160 mm in diameter (ball phantom) was used to simulate the shape of the head. Strips of superflab bolus with thicknesses of 3.5 and 7.0 mm were spread on the surface of the ball phantom. Three sets of CT images were acquired for the ball phantom without and with the bolus. The hypothetical clinical target volume (CTV) and critical structures (spinal cord and parotid glands) were outlined on each set of CT images. The PTVs were initially created by expanding an isotropic 3 mm margin from the CTV and then margins of 0, 3, and 5 mm were shrunk from the phantom surface for dosimetric analysis. Seven-field IMRT plans with a prescribed dose of 180 cGy and same dose constraints were designed using an Eclipse treatment planning system. Superficial doses at depths of 0, 3.5, and 7.0 mm and at seven beam axis positions (gantry angles of 0 deg., 30 deg., 60 deg., 80 deg., 330 deg., 300 deg., and 280 deg.) were measured for each PTV shrinkage margin using 0.1 mm ultrathin thermoluminescent dosimeters. For each plan, the measured doses were compared to the calculated doses. Results: The PTV without shrinkage had the highest intensity and the steepest dose gradient in the superficial region. The mean measured doses for different positions at depths of 0, 3.5, and 7.0 mm were 106{+-}18, 185{+-}16, and 188{+-}12 cGy, respectively. For a PTV with 3 mm shrinkage, the mean measured doses were 94{+-}13, 183{+-}8, and 191{+-}8 cGy. For a PTV with 5 mm shrinkage, the mean measured doses were 86{+-}11, 173{+-}8, and 187{+-}5 cGy. The

  4. Learning Iteration-wise Generalized Shrinkage-Thresholding Operators for Blind Deconvolution.

    PubMed

    Wangmeng Zuo; Dongwei Ren; Zhang, David; Shuhang Gu; Lei Zhang

    2016-04-01

    Salient edge selection and time-varying regularization are two crucial techniques to guarantee the success of maximum a posteriori (MAP)-based blind deconvolution. However, the existing approaches usually rely on carefully designed regularizers and handcrafted parameter tuning to obtain satisfactory estimation of the blur kernel. Many regularizers exhibit the structure-preserving smoothing capability, but fail to enhance salient edges. In this paper, under the MAP framework, we propose the iteration-wise ℓp-norm regularizers together with data-driven strategy to address these issues. First, we extend the generalized shrinkage-thresholding (GST) operator for ℓp-norm minimization with negative p value, which can sharpen salient edges while suppressing trivial details. Then, the iteration-wise GST parameters are specified to allow dynamical salient edge selection and time-varying regularization. Finally, instead of handcrafted tuning, a principled discriminative learning approach is proposed to learn the iterationwise GST operators from the training dataset. Furthermore, the multi-scale scheme is developed to improve the efficiency of the algorithm. Experimental results show that, negative p value is more effective in estimating the coarse shape of blur kernel at the early stage, and the learned GST operators can be well generalized to other dataset and real world blurry images. Compared with the state-of-the-art methods, our method achieves better deblurring results in terms of both quantitative metrics and visual quality, and it is much faster than the state-of-the-art patch-based blind deconvolution method. PMID:26915121

  5. Specific Shrinkage of Carotid Forks in Moyamoya Disease: A Novel Key Finding for Diagnosis

    PubMed Central

    KURODA, Satoshi; KASHIWAZAKI, Daina; AKIOKA, Naoki; KOH, Masaki; HORI, Emiko; NISHIKATA, Manabu; UMEMURA, Kimiko; HORIE, Yukio; NOGUCHI, Kyo; KUWAYAMA, Naoya

    2015-01-01

    This study was aimed to analyze the outer diameter of the involved arteries in moyamoya disease, using three-dimensional (3D) constructive interference in steady state (CISS) and direct surgical inspection. Radiological evaluation was performed in 64 patients with moyamoya disease. As the controls, six patients with severe middle cerebral artery (MCA) stenosis and 17 healthy subjects were also recruited. On 3D-CISS, the outer diameter was quantified in the supraclinoid portion of internal carotid artery (C1), the horizontal portions of MCA (M1) and anterior cerebral artery (A1), and basilar artery. The involved carotid fork was directly observed during surgery in another series of three adult patients with moyamoya disease. In 53 adult patients with moyamoya disease, the outer diameters of C1, M1, and A1 segments were 2.3 ± 0.7 mm, 1.3 ± 0.5 mm, and 1.0 ± 0.4 mm in the involved side (n = 91), being significantly smaller than the control (n = 17), severe M1 stenosis (n = 6), and non-involved side in moyamoya disease (n = 15, P < 0.01). There were significant correlations between Suzuki’s angiographical stage and the outer diameters of C1, M1, and A1 (P < 0.001). The laterality ratio of C1 and M1 was significantly smaller in unilateral moyamoya disease (n = 20) than the controls and severe MCA stenosis (P < 0.01). Direct observations revealed a marked decrease in the outer diameter of the carotid fork (n = 3). These findings strongly suggest specific shrinkage of the involved arteries in moyamoya disease, which may provide essential information to distinguish moyamoya disease from other intracranial arterial stenosis and shed light on the etiology and novel diagnosis cue of moyamoya disease. PMID:26369872

  6. Investigating filler morphology and mechanical properties of new low-shrinkage resin composite types.

    PubMed

    Leprince, J; Palin, W M; Mullier, T; Devaux, J; Vreven, J; Leloup, G

    2010-05-01

    Three types of low-shrinkage composites are today commercially available: Ormocers, cationic ring-opening curing systems and highly filled methacrylate-based materials, which cure via free-radical polymerization mechanisms. The aim of this study was to characterize the inorganic fraction of materials belonging to each type and to compare their mechanical properties. Two Ormocers (Admira and an experimental Ormocer V35694), one ring-opening composite (Filtek Silorane) and five methacrylate-based composites [Filtek Supreme XT, Tetric EvoCeram, Grandio, Synergy D6 (Coltène-Whaledent, Langenau, Germany) and an experimental material, V34930] were tested. Inorganic fillers were quantified by thermogravimetric analysis and morphologically characterized by scanning electron microscopy. Dynamic modulus was determined by an impulse excitation technique, static elastic moduli and flexural strength by a three-point bending method. The results were analyzed using ANOVA tests (P < 0.05) and linear correlations. Grandio, V34930 and V35694 exhibited significantly higher filler mass fractions. Both dynamic and static moduli of Grandio and V34930 were significantly higher than the other materials (P < 0.05), although no significant difference in flexural strength was observed between material type (P > 0.05). From the present findings, it was suggested that V35694 and Filtek Silorane exhibit comparable properties to conventional methacrylate-based composites, although clinically the cavity type and location must guide material choice. Under high occlusal load, the use of Grandio and V34930 might be favoured. For small cavities, alternative technologies could be preferred as the need for mechanical resistance is lower and the potential for stress generation is greater. PMID:20202096

  7. Genome-scale cluster analysis of replicated microarrays using shrinkage correlation coefficient

    PubMed Central

    Yao, Jianchao; Chang, Chunqi; Salmi, Mari L; Hung, Yeung Sam; Loraine, Ann; Roux, Stanley J

    2008-01-01

    Background Currently, clustering with some form of correlation coefficient as the gene similarity metric has become a popular method for profiling genomic data. The Pearson correlation coefficient and the standard deviation (SD)-weighted correlation coefficient are the two most widely-used correlations as the similarity metrics in clustering microarray data. However, these two correlations are not optimal for analyzing replicated microarray data generated by most laboratories. An effective correlation coefficient is needed to provide statistically sufficient analysis of replicated microarray data. Results In this study, we describe a novel correlation coefficient, shrinkage correlation coefficient (SCC), that fully exploits the similarity between the replicated microarray experimental samples. The methodology considers both the number of replicates and the variance within each experimental group in clustering expression data, and provides a robust statistical estimation of the error of replicated microarray data. The value of SCC is revealed by its comparison with two other correlation coefficients that are currently the most widely-used (Pearson correlation coefficient and SD-weighted correlation coefficient) using statistical measures on both synthetic expression data as well as real gene expression data from Saccharomyces cerevisiae. Two leading clustering methods, hierarchical and k-means clustering were applied for the comparison. The comparison indicated that using SCC achieves better clustering performance. Applying SCC-based hierarchical clustering to the replicated microarray data obtained from germinating spores of the fern Ceratopteris richardii, we discovered two clusters of genes with shared expression patterns during spore germination. Functional analysis suggested that some of the genetic mechanisms that control germination in such diverse plant lineages as mosses and angiosperms are also conserved among ferns. Conclusion This study shows that SCC is

  8. Corrosion of austenitic stainless steels and nickel-base alloys in supercritical water and novel control methods

    SciTech Connect

    Tan, Lizhen; Allen, Todd R.; Yang, Ying

    2012-01-01

    This chapter contains sections titled: (1) Introduction; (2) Thermodynamics of Alloy Oxidation; (3) Corrosion of Austenitic Stainless Steels and Ni-Base Alloys in SCW; (4) Novel Corrosion Control Methods; (5) Factors Influencing Corrosion; (6) Summary; and (7) References.

  9. Catalyst Alloys Processing

    NASA Astrophysics Data System (ADS)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  10. Composition control in laser surface alloying

    NASA Astrophysics Data System (ADS)

    Chande, T.; Mazumder, J.

    1983-06-01

    Laser surface alloying, a process of growing interest for local surface modification, relies upon a suitable composition and microstructure for satisfactory on-the-job performance. This paper reports the results of an initial systematic study of laser surface alloying nickel onto AISI 1020 steel substrates using a statistical experimental design technique. The objective was to relate processing conditions to dimensions, solute content, and microstructural refinement of the laser alloyed zones. Solute content was of principal concern as it is the single most important factor affecting the properties of laser surface alloys. The effects of varying the laser power, beam diameter, and speed on the width, depth, nickel content, and fluctuations in nickel content are reported. Interactions between process parameters are discussed, the reproducibility assessed, contour plots for solute content drawn. Dimensionless plots are developed that relate average solute content and microstructural refinement to process parameters. Previously published data for alloying chromium into 1018 steels are shown to contain similar trends. It is felt that such an approach would facilitate selection of processing conditions to obtain reproducibly the compositions and microstructures necessary for gainful utilization of laser surface alloys.

  11. Size and Sex-Dependent Shrinkage of Dutch Bees during One-and-a-Half Centuries of Land-Use Change.

    PubMed

    Oliveira, Mikail O; Freitas, Breno M; Scheper, Jeroen; Kleijn, David

    2016-01-01

    Land-use change and global warming are important factors driving bee decline, but it is largely unknown whether these drivers have resulted in changes in the life-history traits of bees. Recent studies have shown a stronger population decline of large- than small-bodied bee species, suggesting there may have been selective pressure on large, but not on small species to become smaller. Here we test this hypothesis by analyzing trends in bee body size of 18 Dutch species over a 147-year period using specimens from entomological collections. Large-bodied female bees shrank significantly faster than small-bodied female bees (6.5% and 0.5% respectively between 1900 and 2010). Changes in temperature during the flight period of bees did not influence the size-dependent shrinkage of female bees. Male bees did not shrink significantly over the same time period. Our results could imply that under conditions of declining habitat quantity and quality it is advantageous for individuals to be smaller. The size and sex-dependent responses of bees point towards an evolutionary response but genetic studies are required to confirm this. The declining body size of the large bee species that currently dominate flower visitation of both wild plants and insect-pollinated crops may have negative consequences for pollination service delivery. PMID:26863608

  12. Size and Sex-Dependent Shrinkage of Dutch Bees during One-and-a-Half Centuries of Land-Use Change

    PubMed Central

    Oliveira, Mikail O.; Freitas, Breno M.; Scheper, Jeroen; Kleijn, David

    2016-01-01

    Land-use change and global warming are important factors driving bee decline, but it is largely unknown whether these drivers have resulted in changes in the life-history traits of bees. Recent studies have shown a stronger population decline of large- than small-bodied bee species, suggesting there may have been selective pressure on large, but not on small species to become smaller. Here we test this hypothesis by analyzing trends in bee body size of 18 Dutch species over a 147-year period using specimens from entomological collections. Large-bodied female bees shrank significantly faster than small-bodied female bees (6.5% and 0.5% respectively between 1900 and 2010). Changes in temperature during the flight period of bees did not influence the size-dependent shrinkage of female bees. Male bees did not shrink significantly over the same time period. Our results could imply that under conditions of declining habitat quantity and quality it is advantageous for individuals to be smaller. The size and sex-dependent responses of bees point towards an evolutionary response but genetic studies are required to confirm this. The declining body size of the large bee species that currently dominate flower visitation of both wild plants and insect-pollinated crops may have negative consequences for pollination service delivery. PMID:26863608

  13. Analysis of small-sample clinical genomics studies using multi-parameter shrinkage: application to high-throughput RNA interference screening

    PubMed Central

    2013-01-01

    High-throughput (HT) RNA interference (RNAi) screens are increasingly used for reverse genetics and drug discovery. These experiments are laborious and costly, hence sample sizes are often very small. Powerful statistical techniques to detect siRNAs that potentially enhance treatment are currently lacking, because they do not optimally use the amount of data in the other dimension, the feature dimension. We introduce ShrinkHT, a Bayesian method for shrinking multiple parameters in a statistical model, where 'shrinkage' refers to borrowing information across features. ShrinkHT is very flexible in fitting the effect size distribution for the main parameter of interest, thereby accommodating skewness that naturally occurs when siRNAs are compared with controls. In addition, it naturally down-weights the impact of nuisance parameters (e.g. assay-specific effects) when these tend to have little effects across siRNAs. We show that these properties lead to better ROC-curves than with the popular limma software. Moreover, in a 3 + 3 treatment vs control experiment with 'assay' as an additional nuisance factor, ShrinkHT is able to detect three (out of 960) significant siRNAs with stronger enhancement effects than the positive control. These were not detected by limma. In the context of gene-targeted (conjugate) treatment, these are interesting candidates for further research. PMID:23819807

  14. PLUTONIUM-ZIRCONIUM ALLOYS

    DOEpatents

    Schonfeld, F.W.; Waber, J.T.

    1960-08-30

    A series of nuclear reactor fuel alloys consisting of from about 5 to about 50 at.% zirconium (or higher zirconium alloys such as Zircaloy), balance plutonium, and having the structural composition of a plutonium are described. Zirconium is a satisfactory diluent because it alloys readily with plutonium and has desirable nuclear properties. Additional advantages are corrosion resistance, excellent fabrication propenties, an isotropie structure, and initial softness.

  15. Amorphous metal alloy

    DOEpatents

    Wang, R.; Merz, M.D.

    1980-04-09

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  16. Low activation ferritic alloys

    DOEpatents

    Gelles, David S.; Ghoniem, Nasr M.; Powell, Roger W.

    1986-01-01

    Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

  17. Low activation ferritic alloys

    DOEpatents

    Gelles, D.S.; Ghoniem, N.M.; Powell, R.W.

    1985-02-07

    Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

  18. Technology status of tantalum alloys for space nuclear power applications

    NASA Technical Reports Server (NTRS)

    Hoffman, E. E.

    1985-01-01

    Tantalum alloys have a variety of properties which make them attractive candidates for application in nuclear power systems required to operate in space at elevated temperatures (1200 to 1600 K) for extended time periods. Most of the technology development on this class of alloys which is pertinent to space system application occurred during the 1960 to 1972 time period under NASA sponsorship. The most extensive data bases resulting from this earlier work were obtained on the alloys T-111 (Ta-8W-2Hf) and ASTAR 811C (Ta-8W-1Re-0.7Hf-0.025C). Emphasis in this paper is directed at the following technical factors: producibility, creep strength, weldability and compatibility. These factors are considered to be the most important elements in the selection of alloys for this application. Review of the available information indicates that alloys of this type are appropriate for application in many systems, particularly those utilizing alkali metals as the working fluid.

  19. NICKEL-BASE ALLOY

    DOEpatents

    Inouye, H.; Manly, W.D.; Roche, T.K.

    1960-01-19

    A nickel-base alloy was developed which is particularly useful for the containment of molten fluoride salts in reactors. The alloy is resistant to both salt corrosion and oxidation and may be used at temperatures as high as 1800 deg F. Basically, the alloy consists of 15 to 22 wt.% molybdenum, a small amount of carbon, and 6 to 8 wt.% chromium, the balance being nickel. Up to 4 wt.% of tungsten, tantalum, vanadium, or niobium may be added to strengthen the alloy.

  20. Rechargeable sodium alloy anode

    SciTech Connect

    Jow, T.R.

    1988-06-28

    A secondary battery is described comprising: (a) an anode which comprises an alloy of sodium and one or metals selected from the group consisting of tin, lead antimony, bismuth, selenium and tellerium, (b) an electrolyte comprising one or more organic solvents and one or more sodium salts dissolved therein forming dissolved sodium cations in solution; and (c) a cathode; the sodium cations from the electrolyte alloying with the one or more metals of the alloy in the anode during the charging of the battery and sodium in the alloy disoloving in the electrolyte during the discharging of the battery.

  1. The Prognostic Value of the Tumor Shrinkage Rate for Progression-Free Survival in Patients with Non-Small Cell Lung Cancer Receiving Gefitinib

    PubMed Central

    Park, Dong Il; Kim, Sun Young; Kim, Ju Ock; Jung, Sung Soo; Park, Hee Sun; Moon, Jae Young; Chung, Chae Uk; Kim, Song Soo; Seo, Jae Hee

    2015-01-01

    Background The efficacy of epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) therapy can be measured based on the rate of treatment response, based on the Response Evaluation Criteria in Solid Tumors (RECIST) criteria or progression-free survival (PFS). However, there are some patients harboring sensitive EGFR mutations who responded poorly to EGFR-TKI therapy. In addition, there is variability in the PFS after EGFR-TKI treatment. Methods We performed a retrospective analysis of the medical records of 85 patients with non-small cell lung cancer, who had achieved a stable disease or better response at the first evaluation of treatment response, after receiving a 2-month course of gefitinib. We calculated the tumor shrinkage rate (TSR) by measuring the longest and perpendicular diameter of the main mass on computed tomography before, and 2 months after, gefitinib therapy. Results There was a significant positive correlation between the TSR and PFS (R=0.373, p=0.010). In addition, a simple linear regression analysis showed that the TSR might be an indicator for the PFS (B±standard error, 244.54±66.79; p=0.001). On univariate analysis, the sex, histologic type, smoking history and the number of prior chemotherapy regimens, were significant prognostic factors. On multivariate regression analysis, both the TSR (β=0.257, p=0.029) and adenocarcinoma (β=0.323, p=0.005) were independent prognostic factors for PFS. Conclusion Our results showed that the TSR might be an early prognostic indicator for PFS in patients receiving EGFR-TKI therapy. PMID:26508917

  2. Microstructure Evolution of a Multifunctional Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Tian, Yu Xing; Hao, Yu Lin

    2016-03-01

    To optimize both mechanical and functional properties of multifunctional titanium alloys via grain refinement, an example of such alloys termed as Ti2448 is adopted to investigate its microstructure evolution and strain rate sensitivity by compression in the single β-phase field. The results show that flow stress and strain rate follow a bilinear relation, which is in sharp contrast with other metallic materials exhibiting a monotonic linearity. Below the critical strain of 1 s-1, the alloy has a normal strain rate sensitivity factor of 0.265. Above the critical value, its hardening rate is ultra-low with a factor of 0.03. Inspite of ultra-low hardening, the alloy is plastic stable under the tested conditions. With the aid of electron back-scattering diffraction and transmission electron microscopy analyses, microstructure evolution via several mechanisms such as dynamic recovery and recrystallization is evaluated by quantitative measurements of grain misorientation and its distribution, sub-grain formation, and localized grain refinement. These results are helpful to obtain the homogenous ultrafine-grained alloy by multi-step thermo-mechanical processing.

  3. Microstructure Evolution of a Multifunctional Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Tian, Yu Xing; Hao, Yu Lin

    2016-06-01

    To optimize both mechanical and functional properties of multifunctional titanium alloys via grain refinement, an example of such alloys termed as Ti2448 is adopted to investigate its microstructure evolution and strain rate sensitivity by compression in the single β-phase field. The results show that flow stress and strain rate follow a bilinear relation, which is in sharp contrast with other metallic materials exhibiting a monotonic linearity. Below the critical strain of 1 s-1, the alloy has a normal strain rate sensitivity factor of 0.265. Above the critical value, its hardening rate is ultra-low with a factor of 0.03. Inspite of ultra-low hardening, the alloy is plastic stable under the tested conditions. With the aid of electron back-scattering diffraction and transmission electron microscopy analyses, microstructure evolution via several mechanisms such as dynamic recovery and recrystallization is evaluated by quantitative measurements of grain misorientation and its distribution, sub-grain formation, and localized grain refinement. These results are helpful to obtain the homogenous ultrafine-grained alloy by multi-step thermo-mechanical processing.

  4. Geometric factors affecting dentin bonding in root canals: a theoretical modeling approach.

    PubMed

    Tay, Franklin R; Loushine, Robert J; Lambrechts, Paul; Weller, R Norman; Pashley, David H

    2005-08-01

    Cavity configuration factor (C-factor) is the ratio of the bonded surface area in a cavity to the unbonded surface area. In a box-like class I cavity, there may be five times more bonded surface area than the unbonded surface area. During polymerization, the volume of monomers is reduced, which creates sufficient shrinkage stresses to debond the material from dentin, thereby decreasing retention and increasing leakage. The important variables influencing bonding adhesive root-filling materials to canals was examined using a truncated inverted cone model. C-factors in bonded root canals exhibit a negative correlation with sealer thickness. For a 20 mm-long canal prepared with a size 25 file, calculated C-factors ranged from 46 to 23,461 with decreasing sealer thickness (500-1 microm), compared to a C-factor of 32 when the canal was filled only with sealer. As the thickness of the adhesive is reduced, the volummetric shrinkage is reduced, which results in a reduction in shrinkage stress (S-factor). C-factors above 954 calculated with sealer thickness smaller than 25 microm are partially compensated by increases in bonding area and decreases in shrinkage volume. However, the interaction of these two geometrically related factors (C- and S-factors) predicts that bonding of adhesive root-filling materials to root canals is highly unfavorable when compared with indirect intracoronal restorations with a similar resin film thickness. PMID:16044041

  5. Effect of urea and osmotic cell shrinkage on Ca2+ entry and contraction of vascular smooth muscle cells.

    PubMed

    Wagner, C A; Huber, S M; Wärntges, S; Zempel, G; Kaba, N K; Fux, R; Orth, N; Busch, G L; Waldegger, S; Lambert, I; Nilius, B; Heinle, H; Lang, F

    2000-06-01

    The present study was performed to elucidate the effects of urea on vascular smooth muscle cells (SMC). Addition of urea (20, 50, 100 mM) to physiological salt solution blunted the vasoconstrictory effect of phenylephrine (by 17, 25 and 30%, respectively) and of an increased extracellular K+ concentration (by 7, 14 and 19%, respectively) without affecting the basal tone of rabbit arterial rings. According to Fura-2 fluorescence in cultured SMC (A7r5), urea had no effect on basal intracellular calcium activity ([Ca2+]i), but significantly blunted the increase of [Ca2+]i following an increase of extracellular K+. Whole-cell patch-clamp studies revealed that the Ca2+ current through voltage-sensitive Ca2+ channels is significantly inhibited in the presence of urea. As evident from calcein fluorescence, addition of urea leads to sustained cell shrinkage. The effects of urea on vascular tone, [Ca2+]i activity, voltage-gated Ca2+ channels and cell volume are mimicked by addition of raffinose or NaCl. However, the cell shrinkage induced by urea is sustained, whereas the addition of equiosmolar NaCl is only transient and followed by a regulatory cell volume increase. Moreover, hypertonic NaCl increases, whereas urea decreases, the transcription of cell-volume-regulated kinase hsgk. In conclusion, urea leads to sustained shrinkage of vascular smooth muscle cells, which is followed by inhibition of voltage-gated Ca2+ channels, a decrease of [Ca2+]i and thus blunts the vasoconstrictory action of phenylephrine and increased extracellular K+ concentration. PMID:10898530

  6. The influence of shrinkage-cracking on the drying behaviour of White Portland cement using Single-Point Imaging (SPI).

    PubMed

    Beyea, S D; Balcom, B J; Bremner, T W; Prado, P J; Cross, A R; Armstrong, R L; Grattan-Bellew, P E

    1998-11-01

    The removal of water from pores in hardened cement paste smaller than 50 nm results in cracking of the cement matrix due to the tensile stresses induced by drying shrinkage. Cracks in the matrix fundamentally alter the permeability of the material, and therefore directly affect the drying behaviour. Using Single-Point Imaging (SPI), we obtain one-dimensional moisture profiles of hydrated White Portland cement cylinders as a function of drying time. The drying behaviour of White Portland cement, is distinctly different from the drying behaviour of related concrete materials containing aggregates. PMID:9875607

  7. The effect of weldability of alloy JBK-75 with various filler metal wire additions

    SciTech Connect

    Taylor, C.L.

    1991-04-01

    The purpose of this study was to investigate the compositional factors that affect the weldability of alloy JBK-75. This study was accomplished by using a variety of different commercial filler materials to systematically evaluate the weldability in the compositional range surrounding alloy JBK-75. The experimental design included varestraint testing, scanning electron microscopy, and phase diagram analysis. The varestraint testing demonstrated that the weldability of alloy JBK-75 could be improved with the use of other commercially available filler metals. The best improvement to weldability of alloy JBK-75 was with type 308L stainless steel and Hastelloy W filler metals. Adequate improvement to the weldability of alloy JBK-75 was obtained when utilizing types 309L and 310 stainless steel filler metals. Alloy 320LR, alloy 650 (NiCrFe-1), Incoloy 901, and Inconel 92 (NiCrFe-6) filler metals only marginally improved the weldability of alloy JBK-75. 59 refs., 27 figs., 24 tabs.

  8. Aluminum battery alloys

    DOEpatents

    Thompson, David S.; Scott, Darwin H.

    1985-01-01

    Aluminum alloys suitable for use as anode structures in electrochemical cs are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  9. Neutron Absorbing Alloys

    DOEpatents

    Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

    2004-05-04

    The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

  10. Copper-tantalum alloy

    DOEpatents

    Schmidt, Frederick A.; Verhoeven, John D.; Gibson, Edwin D.

    1986-07-15

    A tantalum-copper alloy can be made by preparing a consumable electrode consisting of an elongated copper billet containing at least two spaced apart tantalum rods extending longitudinally the length of the billet. The electrode is placed in a dc arc furnace and melted under conditions which co-melt the copper and tantalum to form the alloy.

  11. Cesium iodide alloys

    DOEpatents

    Kim, H.E.; Moorhead, A.J.

    1992-12-15

    A transparent, strong CsI alloy is described having additions of monovalent iodides. Although the preferred iodide is AgI, RbI and CuI additions also contribute to an improved polycrystalline CsI alloy with outstanding multispectral infrared transmittance properties. 6 figs.

  12. Surface composition of alloys

    NASA Astrophysics Data System (ADS)

    Sachtler, W. M. H.

    1984-11-01

    In equilibrium, the composition of the surface of an alloy will, in general, differ from that of the bulk. The broken-bond model is applicable to alloys with atoms of virtually equal size. If the heat of alloy formation is zero, the component of lower heat of atomization is found enriched in the surface. If both partners have equal heats of sublimination, the surface of a diluted alloy is enriched with the minority component. Size effects can enhance or weaken the electronic effects. In general, lattice strain can be relaxed by precipitating atoms of deviating size on the surface. Two-phase alloys are described by the "cherry model", i.e. one alloy phase, the "kernel" is surrounded by another alloy, the "flesh", and the surface of the outer phase, the "skin" displays a deviating surface composition as in monophasic alloys. In the presence of molecules capable of forming chemical bonds with individual metal atoms, "chemisorption induced surface segregation" can be observed at low temperatures, i.e. the surface becomes enriched with the metal forming the stronger chemisorption bonds.

  13. Aluminum battery alloys

    DOEpatents

    Thompson, D.S.; Scott, D.H.

    1984-09-28

    Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  14. Ductile transplutonium metal alloys

    DOEpatents

    Conner, W.V.

    1981-10-09

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as souces of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  15. PLUTONIUM-CERIUM ALLOY

    DOEpatents

    Coffinberry, A.S.

    1959-01-01

    An alloy is presented for use as a reactor fuel. The binary alloy consists essentially of from about 5 to 90 atomic per cent cerium and the balance being plutonium. A complete phase diagram for the cerium--plutonium system is given.

  16. Ductile transplutonium metal alloys

    DOEpatents

    Conner, William V.

    1983-01-01

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as sources of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  17. Modeling on the Solidification of 1J51 Fe-Ni-Based Alloy Ingot Under Vacuum Conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Lifeng; Gao, Chen; Li, Chongwei; Peng, Jie

    2014-07-01

    In this article, a numerical simulation model on the solidification of 1J51 Fe-Ni based alloy under vacuum conditions was established using ProCAST software (ESI Group, Paris, France). The calculated temperature profiles of the mold and the solidification profile of the ingot were compared with the measurement, showing a reasonable agreement. The validated model was then used to study the effects of the insulation condition, filling rate, and maximum filling fraction on the solidification state and porosity distribution of the ingot. It was indicated that the shrinkage cavity position of ingot with zirconia fiber was lower than that without zirconia fiber, and the likelihood of centerline shrinkage porosity was independent of the insulation method. The position of macroporosity varied little when the filling rate was from 2.17 kg/s to 5.17 kg/s, while serious solidification defects occurred in the body of ingot when the filling rate was lower than 4.17 kg/s. Increasing the maximum filling fraction had a positive impact on the rise of shrinkage cavity position, but it was hardly advisable because the metal yield decreased with the increase of the maximum filling fraction. Considering the above parameters discussed in this article, it was proposed to remove the zirconia fiber layer for the industrial practice.

  18. Ultrahigh temperature intermetallic alloys

    SciTech Connect

    Brady, M.P.; Zhu, J.H.; Liu, C.T.; Tortorelli, P.F.; Wright, J.L.; Carmichael, C.A.; Walker, L.R.

    1997-12-01

    A new family of Cr-Cr{sub 2}X based alloys with fabricability, mechanical properties, and oxidation resistance superior to previously developed Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys has been identified. The new alloys can be arc-melted/cast without cracking, and exhibit excellent room temperature and high-temperature tensile strengths. Preliminary evaluation of oxidation behavior at 1100 C in air indicates that the new Cr-Cr{sub 2}X based alloys form an adherent chromia-based scale. Under similar conditions, Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys suffer from extensive scale spallation.

  19. Alloys in energy development

    SciTech Connect

    Frost, B.R.T.

    1984-02-01

    The development of new and advanced energy systems often requires the tailoring of new alloys or alloy combinations to meet the novel and often stringent requirements of those systems. Longer life at higher temperatures and stresses in aggressive environments is the most common goal. Alloy theory helps in achieving this goal by suggesting uses of multiphase systems and intermediate phases, where solid solutions were traditionally used. However, the use of materials under non-equilibrium conditions is now quite common - as with rapidly solidified metals - and the application of alloy theory must be modified accordingly. Under certain conditions, as in a reactor core, the rate of approach to equilibrium will be modified; sometimes a quasi-equilibrium is established. Thus an alloy may exhibit enhanced general diffusion at the same time as precipitate particles are being dispersed and solute atoms are being carried to vacancy sinks. We are approaching an understanding of these processes and can begin to model these complex systems.

  20. Comparison of variation in the light curing cycle with a time gap and its effect on polymerization shrinkage, degree of conversion and microhardness of a nanohybrid composite

    PubMed Central

    Subbiya, Arunajatesan; Pearlin Mary, Newbegin Selvakumar Gold; Suresh, Malathi; Vivekanandhan, Paramasivam; Dhakshinamoorthy, Malarvizhi; Sukumaran, Vridhachalam Ganapathy

    2015-01-01

    Background: Giving a time gap and distance during curing can decrease the polymerization shrinkage. Aim: To evaluate the effect of time gap and distance between the curing tip and restoration on the polymerization shrinkage, degree of monomer conversion (DOC), and microhardness of a nanohybrid composite. Materials and Methods: A total of 50 standardized cylindrical specimens (Z350, 3M ESPE) were fabricated using a brass mould. The curing was done in contact with the sample surface for 20 seconds in the control group. In the four experimental groups, curing was initiated at 1-cm distance, followed by variation in the time gap and the curing cycle. The polymerization shrinkage, DOC, microhardness was calculated. Statistical Analysis: One-way analysis of variance (ANOVA) and post hoc-Dunnett test were used to analyze the data. Results: Curing at 1-cm distance for 10 seconds with a gap of 10 seconds and finishing the curing cycle with 20 seconds at 0 cm proved to be an appropriate technique to reduce the polymerization shrinkage without significantly affecting the DOC and microhardness. Conclusion: A simple innovative modification of varying the distance of curing and a time gap in the curing cycle can decrease the polymerization shrinkage without affecting the DOC and microhardness. PMID:25829697

  1. Centrosome repositioning in T cells is biphasic and driven by microtubule end-on capture-shrinkage

    PubMed Central

    Yi, Jason; Wu, Xufeng; Chung, Andrew H.; Chen, James K.; Kapoor, Tarun M.

    2013-01-01

    T cells rapidly reposition their centrosome to the center of the immunological synapse (IS) to drive polarized secretion in the direction of the bound target cell. Using an optical trap for spatial and temporal control over target presentation, we show that centrosome repositioning in Jurkat T cells exhibited kinetically distinct polarization and docking phases and required calcium flux and signaling through both the T cell receptor and integrin to be robust. In “frustrated” conjugates where the centrosome is stuck behind the nucleus, the center of the IS invaginated dramatically to approach the centrosome. Consistently, imaging of microtubules during normal repositioning revealed a microtubule end-on capture-shrinkage mechanism operating at the center of the IS. In agreement with this mechanism, centrosome repositioning was impaired by inhibiting microtubule depolymerization or dynein. We conclude that dynein drives centrosome repositioning in T cells via microtubule end-on capture-shrinkage operating at the center of the IS and not cortical sliding at the IS periphery, as previously thought. PMID:23979719

  2. Desiccation-Induced Volumetric Shrinkage of Compacted Metakaolin-Treated Black Cotton Soil for a Hydraulic Barriers System

    NASA Astrophysics Data System (ADS)

    Moses, George; Peter, Oriola F. O.; Osinubi, Kolawole J.

    2016-03-01

    Black cotton soil treated with up to 24% metakaolin (MCL) content was prepared by molding water contents of -2, 0, 2, 4 and 6% of optimum moisture content (OMC) and compacted with British Standard Light (BSL) and West African Standard (WAS) or `Intermediate' energies. The specimens were extruded from the compaction molds and allowed to air dry in a laboratory in order to assess the effect of desiccation-induced shrinkage on the compacted mix for use as a hydraulic barrier in a waste containment application. The results recorded show that the volumetric shrinkage strain (VSS) values were large within the first 10 days of drying; the VSS values increased with a higher molding of the water content, relative to the OMC. The VSS generally increased with a higher initial degree of saturation for the two compactive efforts, irrespective of the level of MCL treatment. Generally, the VSS decreased with an increasing MCL content. Only specimens treated with a minimum 20% MCL content and compacted with the WAS energy satisfied the regulatory maximum VSS of 4% for use as a hydraulic barrier.

  3. Kinetic studies of chemical shrinkage and residual stress formation in thermoset epoxy adhesives under confined curing conditions

    NASA Astrophysics Data System (ADS)

    Schumann, M.; Geiß, P. L.

    2015-05-01

    Faultless processing of thermoset polymers in demanding applications requires a profound mastering of the curing kinetics considering both the physico-chemical changes in the transition from the liquid to the solid state and the consolidation of the polymers network in the diffusion controlled curing regime past the gel point. Especially in adhesive joints shrinkage stress occurring at an early state of the curing process under confined conditions is likely to cause defects due to local debonding and thus reduce their strength and durability1. Rheometry is considered the method of choice to investigate the change of elastic and viscous properties in the progress of curing. Drawbacks however relate to experimental challenges in accessing the full range of kinetic parameters of thermoset resins with low initial viscosity from the very beginning of the curing reaction to the post-cure consolidation of the polymer due to the formation of secondary chemical bonds. Therefore the scope of this study was to interrelate rheological data with results from in-situ measurements of the shrinkage stress formation in adhesive joints and with the change of refractive index in the progress of curing. This combination of different methods has shown to be valuable in gaining advanced insight into the kinetics of the curing reaction. The experimental results are based on a multi component thermoset epoxy-amine adhesive.

  4. Detection of mouse liver cancer via a parallel iterative shrinkage method in hybrid optical/microcomputed tomography imaging

    NASA Astrophysics Data System (ADS)

    Wu, Ping; Liu, Kai; Zhang, Qian; Xue, Zhenwen; Li, Yongbao; Ning, Nannan; Yang, Xin; Li, Xingde; Tian, Jie

    2012-12-01

    Liver cancer is one of the most common malignant tumors worldwide. In order to enable the noninvasive detection of small liver tumors in mice, we present a parallel iterative shrinkage (PIS) algorithm for dual-modality tomography. It takes advantage of microcomputed tomography and multiview bioluminescence imaging, providing anatomical structure and bioluminescence intensity information to reconstruct the size and location of tumors. By incorporating prior knowledge of signal sparsity, we associate some mathematical strategies including specific smooth convex approximation, an iterative shrinkage operator, and affine subspace with the PIS method, which guarantees the accuracy, efficiency, and reliability for three-dimensional reconstruction. Then an in vivo experiment on the bead-implanted mouse has been performed to validate the feasibility of this method. The findings indicate that a tiny lesion less than 3 mm in diameter can be localized with a position bias no more than 1 mm the computational efficiency is one to three orders of magnitude faster than the existing algorithms; this approach is robust to the different regularization parameters and the lp norms. Finally, we have applied this algorithm to another in vivo experiment on an HCCLM3 orthotopic xenograft mouse model, which suggests the PIS method holds the promise for practical applications of whole-body cancer detection.

  5. Exploration of regularized covariance estimates with analytical shrinkage intensity for producing invertible covariance matrices in high dimensional hyperspectral data

    SciTech Connect

    Walsh, Stephen J.; Tardiff, Mark F.

    2007-10-01

    Removing background from hyperspectral scenes is a common step in the process of searching for materials of interest. Some approaches to background subtraction use spectral library data and require invertible covariance matrices for each member of the library. This is challenging because the covariance matrix can be calculated but standard methods for estimating the inverse requires that the data set for each library member have many more spectral measurements than spectral channels, which is rarely the case. An alternative approach is called shrinkage estimation. This method is investigated as an approach to providing an invertible covariance matrix estimate in the case where the number of spectral measurements is less than the number of spectral channels. The approach is an analytic method for arriving at a target matrix and the shrinkage parameter that modify the existing covariance matrix for the data to make it invertible. The theory is discussed to develop different estimates. The resulting estimates are computed and inspected on a set of hyperspectral data. This technique shows some promise for arriving at an invertible covariance estimate for small hyperspectral data sets.

  6. The influence of recycled expanded polystyrene (EPS) on concrete properties: Influence on flexural strength, water absorption and shrinkage

    NASA Astrophysics Data System (ADS)

    Elsalah, Jamaleddin; Al-Sahli, Yosra; Akish, Ahmed; Saad, Omar; Hakemi, Abdurrahman

    2013-12-01

    Expanded polystyrene waste in a granular form was used as a lightweight aggregate in order to produce lightweight concretë Lightweight EPS concrete composites were produced by replacing the coarse aggregate, either partially or fully with equal volume of EPS aggregates. The coarse aggregate replacements levels used were 25, 50, 75, and 100%, which corresponded to (9.20, 18.40, 27.60, and 36.8%) from total volume. The investigation is directed towards the development and performance evaluation of the concrete composites containing EPS aggregates, without addition of either bonding additives, or super-plasticizers on some concrete properties such as flexure strength, water absorption and change in length (or shrinkage). Experimental results showed that a density reduction of 12% caused flexure strength to decrease by 25.3% at a replacement level of 25% EPS. However, the reduction percentage strongly depends upon the replacement level of EPS granules. Moreover, the lower strength concretes showed a higher water absorption values compared to higher strength concrete, i.e., increasing the volume percentage of EPS increases the water absorption as well as the negative strain (shrinkage). The negative strain was higher at concretes of lower density (containing a high amount of EPS aggregate). The water to cement ratio of EPS aggregate concrete is found to be slightly lower than that of conventional concrete.

  7. Detection of mouse liver cancer via a parallel iterative shrinkage method in hybrid optical/microcomputed tomography imaging.

    PubMed

    Wu, Ping; Liu, Kai; Zhang, Qian; Xue, Zhenwen; Li, Yongbao; Ning, Nannan; Yang, Xin; Li, Xingde; Tian, Jie

    2012-12-01

    Liver cancer is one of the most common malignant tumors worldwide. In order to enable the noninvasive detection of small liver tumors in mice, we present a parallel iterative shrinkage (PIS) algorithm for dual-modality tomography. It takes advantage of microcomputed tomography and multiview bioluminescence imaging, providing anatomical structure and bioluminescence intensity information to reconstruct the size and location of tumors. By incorporating prior knowledge of signal sparsity, we associate some mathematical strategies including specific smooth convex approximation, an iterative shrinkage operator, and affine subspace with the PIS method, which guarantees the accuracy, efficiency, and reliability for three-dimensional reconstruction. Then an in vivo experiment on the bead-implanted mouse has been performed to validate the feasibility of this method. The findings indicate that a tiny lesion less than 3 mm in diameter can be localized with a position bias no more than 1 mm; the computational efficiency is one to three orders of magnitude faster than the existing algorithms; this approach is robust to the different regularization parameters and the lp norms. Finally, we have applied this algorithm to another in vivo experiment on an HCCLM3 orthotopic xenograft mouse model, which suggests the PIS method holds the promise for practical applications of whole-body cancer detection. PMID:23224049

  8. Using Multivariate Regression Model with Least Absolute Shrinkage and Selection Operator (LASSO) to Predict the Incidence of Xerostomia after Intensity-Modulated Radiotherapy for Head and Neck Cancer

    PubMed Central

    Ting, Hui-Min; Chang, Liyun; Huang, Yu-Jie; Wu, Jia-Ming; Wang, Hung-Yu; Horng, Mong-Fong; Chang, Chun-Ming; Lan, Jen-Hong; Huang, Ya-Yu; Fang, Fu-Min; Leung, Stephen Wan

    2014-01-01

    Purpose The aim of this study was to develop a multivariate logistic regression model with least absolute shrinkage and selection operator (LASSO) to make valid predictions about the incidence of moderate-to-severe patient-rated xerostomia among head and neck cancer (HNC) patients treated with IMRT. Methods and Materials Quality of life questionnaire datasets from 206 patients with HNC were analyzed. The European Organization for Research and Treatment of Cancer QLQ-H&N35 and QLQ-C30 questionnaires were used as the endpoint evaluation. The primary endpoint (grade 3+ xerostomia) was defined as moderate-to-severe xerostomia at 3 (XER3m) and 12 months (XER12m) after the completion of IMRT. Normal tissue complication probability (NTCP) models were developed. The optimal and suboptimal numbers of prognostic factors for a multivariate logistic regression model were determined using the LASSO with bootstrapping technique. Statistical analysis was performed using the scaled Brier score, Nagelkerke R2, chi-squared test, Omnibus, Hosmer-Lemeshow test, and the AUC. Results Eight prognostic factors were selected by LASSO for the 3-month time point: Dmean-c, Dmean-i, age, financial status, T stage, AJCC stage, smoking, and education. Nine prognostic factors were selected for the 12-month time point: Dmean-i, education, Dmean-c, smoking, T stage, baseline xerostomia, alcohol abuse, family history, and node classification. In the selection of the suboptimal number of prognostic factors by LASSO, three suboptimal prognostic factors were fine-tuned by Hosmer-Lemeshow test and AUC, i.e., Dmean-c, Dmean-i, and age for the 3-month time point. Five suboptimal prognostic factors were also selected for the 12-month time point, i.e., Dmean-i, education, Dmean-c, smoking, and T stage. The overall performance for both time points of the NTCP model in terms of scaled Brier score, Omnibus, and Nagelkerke R2 was satisfactory and corresponded well with the expected values. Conclusions

  9. Effect of Y Addition on the Mechanical Properties and Microstructure of Zn-Al Alloys

    NASA Astrophysics Data System (ADS)

    Li, Mingyang; Lu, Shujing; Long, Fang; Sheng, Meng; Geng, Haoran; Liu, Wendi

    2015-05-01

    This article will discuss the influence of the rare earth Y on the microstructure and mechanical properties of Zn-Al alloys (ZA27, ZA35, and ZA40), and it will provide reference to rare-earth microalloying through the cast ingot metallurgy process. The results also suggest that the microstructure can be refined and mechanical properties can be improved obviously when adding the right amount of Y, and its tensile strength and brinell hardness increased by 9.1% and 11.7% compared with the unmodified ZA27 alloys, respectively. Compared with non-Y addition, the alloys will form dispersed YZn12 phase, which can strongly pin dislocations and subgrain boundary, inhibiting further recrystallization. On this basis, the impacts of Y on the microstructure and mechanical properties of ZA27, ZA35, and ZA40 have been explored. After adding Y, the microstructures of as-cast Zn-Al alloys are refined at different degree. However, with the increase of Al content, the microstructure shows a certain coarsening and the segregation and shrinkage porosity occur. The most effective refining appears in ZA27-0.4%Y.

  10. Enhanced Shrinkage of Lanthanum Strontium Manganite (La0.90Sr0.10MnO3+δ) Resulting from Thermal and Oxygen Partial Pressure Cycling

    SciTech Connect

    McCarthy, Ben; Pederson, Larry R.; Anderson, Harlan U.; Zhou, Xiao Dong; Singh, Prabhakar; Coffey, Greg W.; Thomsen, Ed C.

    2007-10-01

    Exposure of La0.9Sr0.1MnO3+δ to repeated oxygen partial pressure cycles (air/10 ppm O2) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700 to 1000oC were orders of magnitude higher than Makipirtti-Meng model estimations based on stepwise isothermal dilatometry results at high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900oC. Shrinkage was greatest when LSM-10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygen vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria is re-established, whereas the latter condition does not lead to excess vacancy concentrations.

  11. THORIUM-SILICON-BERYLLIUM ALLOYS

    DOEpatents

    Foote, F.G.

    1959-02-10

    Th, Si, anol Bt alloys where Be and Si are each present in anmounts between 0.1 and 3.5% by weight and the total weight per cent of the minor alloying elements is between 1.5 and 4.5% are discussed. These ternary alloys show increased hardness and greater resistant to aqueous corrosion than is found in pure Th, Th-Si alloys, or Th-Be alloys.

  12. Wear response of a Zn-base alloy in the presence of SiC particle reinforcement: A comparative study with a copper-base alloy

    SciTech Connect

    Prasad, B.K.; Das, S.; Modi, O.P.; Jha, A.K.; Dasgupta, R.; Yegneswaran, A.H.

    1999-12-01

    An attempt has been made in this study to examine the effects produced by the reinforcement of (10 wt%) SiC particles on the sliding wear behavior of a Zn-base alloy. The matrix alloy was also subjected to identical test conditions to assess the influence of the SiC dispersoid phase. The wear characteristics of the (Zn-base alloy) composite and the matrix alloy were also compared with those of a Cu-base alloy (i.e., an aluminum bronze) in order to understand the scope of exploiting the Zn-base alloy matrix/composite as a substitute material for the latter (Cu-base) alloy. It has been observed that low frictional heat generated at the lower sliding speed (0.42 m/s) enabled the Zn-base (matrix) alloy to perform better than the composite material, while the Cu-base alloy showed intermediate wear resistance. On the contrary, the trend changed at a higher sliding speed (4.62 m/s) when high frictional heating caused the wear behavior of the Cu-base alloy to be superior to that of the Zn-base (matrix) alloy. The composite in this case performed better than the matrix alloy. The wear behavior of the specimens has been explained in terms of factors like microcracking tendency and thermal stability introduced by the SiC dispersoid phase and lubricating, load bearing, and low melting characteristics of microconstituents like {alpha} and {eta} in the (Zn-base) alloy system and the thermal stability of the Cu-base alloy. It seems that the predominance of one set of parameters over the other actually controls the overall performance of a material. Once again, it is the test conditions that ultimately allow a particular set of factors to govern the other and influence the response of the specimens accordingly. The observed wear behavior of the samples has been substantiated further with their wear surface characteristics.

  13. Hydrogen interactions in aluminum-lithium alloys

    NASA Technical Reports Server (NTRS)

    Smith, S. W.; Scully, J. R.

    1991-01-01

    A program is described which seeks to develop an understanding of the effects of dissolved and trapped hydrogen on the mechanical properties of selected Al-Li-Cu-X alloys. A proposal is made to distinguish hydrogen (H2) induced EAC from aqueous dissolution controlled EAC, to correlate H2 induced EAC with mobile and trapped concentrations, and to identify significant trap sites and hydride phases (if any) through use of model alloys and phases. A literature review shows three experimental factors which have impeded progress in the area of H2 EAC for this class of alloys. These are as listed: (1) inter-subgranular fracture in Al-Li alloys when tested in the S-T orientation in air or vacuum make it difficult to readily detect H2 induced fracture based on straight forward changes in fractography; (2) the inherently low H2 diffusivity and solubility in Al alloys is further compounded by a native oxide which acts as a H2 permeation barrier; and (3) H2 effects are masked by dissolution assisted processes when mechanical testing is performed in aqueous solutions.

  14. Magnesium silicide intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Li, Gh.; Gill, H. S.; Varin, R. A.

    1993-11-01

    Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not exceeding 1105 °C ± 5 °C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg2Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg2Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg2Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg2Si matrix were found in the Mg2Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.

  15. Alloy composition dependency of plastic deformation behavior in biaxial compressions of Ti-Nb alloys

    NASA Astrophysics Data System (ADS)

    Shimizu, Ichiro; Hisada, Kazuki; Ishikawa, Shinichi; Takemoto, Yoshito; Tada, Naoya

    2015-03-01

    Crystal structure of titanium alloy changes from alpha (hexagonal close-packed) to beta (body centered cubic) with increase of beta stabilizer content. This change of structure strongly influences on the plastic deformation behavior of titanium alloys, because it not only induces changes of slip systems but also activates martensitic transformation and deformation twinning. However, most of past studies on titanium alloys have been focused on the development of specific functionalities induced by alloy designing, and few research works have been reported on metal workability under multi-axial stress conditions, which is key factor to apply titanium alloys for engineering products. In this study, uniaxial and biaxial compression tests of titanium-niobium alloys with various niobium contents have been performed to clarify the influence of beta stabilizer content on the plastic behavior under compressive stress conditions. The titanium-niobium alloys were solution treated and then quenched from beta region to obtain metastable structures. The resultant stress-strain relations together with microscopic observations of texture revealed that the influence of niobium contents on the predominant plastic deformation mechanisms and thus on the hardening phenomena. The equi-plastic work contours obtained by uniaxial and biaxial compression tests also implied the crystal structure dependency of anisotropic hardening, which was evaluated quantitatively by means of Hill's anisotropic yield criterion. The results will provide information on the versatile constitutive relations of titanium alloys containing beta stabilizer elements, that is important to prove the performance of products manufactured by compressive metal working processes such as forging and extrusion.

  16. Aluminum Alloying Effects on Lattice Types, Microstructures, and Mechanical Behavior of High-Entropy Alloys Systems

    NASA Astrophysics Data System (ADS)

    Tang, Zhi; Gao, Michael C.; Diao, Haoyan; Yang, Tengfei; Liu, Junpeng; Zuo, Tingting; Zhang, Yong; Lu, Zhaoping; Cheng, Yongqiang; Zhang, Yanwen; Dahmen, Karin A.; Liaw, Peter K.; Egami, Takeshi

    2013-12-01

    The crystal lattice type is one of the dominant factors for controlling the mechanical behavior of high-entropy alloys (HEAs). For example, the yield strength at room temperature varies from 300 MPa for the face-centered-cubic (fcc) structured alloys, such as the CoCrCuFeNiTi x system, to about 3,000 MPa for the body-centered-cubic (bcc) structured alloys, such as the AlCoCrFeNiTi x system. The values of Vickers hardness range from 100 to 900, depending on lattice types and microstructures. As in conventional alloys with one or two principal elements, the addition of minor alloying elements to HEAs can further alter their mechanical properties, such as strength, plasticity, hardness, etc. Excessive alloying may even result in the change of lattice types of HEAs. In this report, we first review alloying effects on lattice types and properties of HEAs in five Al-containing HEA systems: Al x CoCrCuFeNi, Al x CoCrFeNi, Al x CrFe1.5MnNi0.5, Al x CoCrFeNiTi, and Al x CrCuFeNi2. It is found that Al acts as a strong bcc stabilizer, and its addition enhances the strength of the alloy at the cost of reduced ductility. The origins of such effects are then qualitatively discussed from the viewpoints of lattice-strain energies and electronic bonds. Quantification of the interaction between Al and 3 d transition metals in fcc, bcc, and intermetallic compounds is illustrated in the thermodynamic modeling using the CALculation of PHAse Diagram method.

  17. Permeation characteristics of some iron and nickel based alloys

    SciTech Connect

    Mitchell, D.J.; Edge, E.M.

    1985-06-15

    The permeation characteristics of deuterium in several iron and nickel based alloys were measured by the gas phase breakthrough technique in the temperature range 100 to 500 /sup 0/C with applied pressures ranging from 10 Pa to 100 kPa. The restriction of the gas flux imposed by surface oxides was modeled in order to evaluate the effects of surface oxide retardation of the gas flux on the effective values of the deuterium permeabilities and diffusivities in the alloys. The most permeable alloys were 430 and 431 stainless steels. The next most permeable alloy was Monel K-500, which exceeded the permeability of pure Ni by more than a factor of five at room temperature. The alloys with permeabilities less than pure Ni were, in order of decreasing permeability: the Inconels 625, 718, and 750, the Fe-Ni-Co glass-sealing alloys Kovar and Ceramvar, and the 300-series stainless steels. Deuterium trapping within the alloys appeared to influence the values of bulk diffusivities, which were not correlated with either the permeabilities or the chemical compositions of the alloys.

  18. [Evaluation of cervical gaps in complete metal crowns cast in alternative silver-tin alloys. Relationship to investing techniques].

    PubMed

    Vecchio, G M; Pretti, E; Vaz, R R; Zaniquelli, O

    1990-01-01

    The purpose of this study was to evaluate cervical mistifing of casting full metal crowns according to investment techniques using commercial available alloys made from silver stannum. Fifteen metal full crowns were obtained through stainless steel die with full crowns preparation, included into three groups as follows: conventional technique, vacuum technique and pressure technique. Readings of cervical disagreement were made through a comparing microscope increased 45 x and each crown was measured in 4 different regions (vestibular, lingual mesial and distal). This way it was verified which of the techniques proposed would balance the casting shrinkage for the silver-stannum alloy used. From the results obtained we conclude that the best cercical adaptation was the one got through pressure technique. PMID:2135769

  19. Physical properties of a nickel-base alloy prepared by isostatic pressing and sintering of the powdered metal.

    PubMed

    Fuys, R A; Craig, R G; Asger, K

    1976-04-01

    The physical and mechanical properties of samples of a nickel-base alloy fabricated by powder metallurgy were determined. The particle sizes of the powders used to make the samples varied from -80/ +200 mesh to -325 mesh. The compaction pressure varied from 138 to 414 MN/m2 and the sintering temperature varied from 1150 to 1250 degrees C. The shrinkage during processing, the porosity, tensile strength, yield strength, elongation, and elastic modulus were used to characterize the samples. The strength of the samples generally increased with decreasing particle size of the powder and increasing compaction pressure and sintering temperatures. The porosity and strength, therefore, could be varied over a wide range by controlling the various parameters. The properties of the samples prepared by powder metallurgy were compared with those of the cast alloy and compact bone. Conditions can be selected that will yield equivalent or better properties by powder metallurgy than by casting. PMID:1066448

  20. Investigation of the effects of cooling rate on the microstructure of investment cast biomedical grade Co alloys

    NASA Astrophysics Data System (ADS)

    Kaiser, R.; Browne, D. J.; Williamson, K.

    2012-01-01

    The objective of this work is to determine the microstructural characteristics of investment cast cobalt alloy as the cross-sectional area is varied, thus changing the local effective cooling rates and solidification times. The extent of published work on the as-cast properties of cobalt alloys is minimal. The primary aim of this work is therefore to extend knowledge of the behaviour of such alloys as they solidify, which will influence the design of new products as well as the industrial optimisation of the casting process. Wedge-shaped parts were cast from a biomedical grade cobalt alloy employing the method of lost wax investment casting. Analytical techniques such as optical microscopy, image analysis and microhardness testing were used to characterise the as-cast parts. Parameters studied include variations in grain structure, nature of the columnar and equiaxed zones and the spread of porosity (both shrinkage and gas). Changes in microstructure were compared to microhardness values obtained. The solidification profile of the alloy through the prototype cast component was investigated based on measurement of the dendrite arm spacings. A discussion on the physical phenomena controlling the microstructural variations is presented.