expansion cte values: Topics by Science.gov

Sample records for expansion cte values

Thermal Cycling of Thin and Thick Ply Composites

NASA Technical Reports Server (NTRS)

Tompkins, Stephen S.; Shen, James Y.; Lavoie, Andre J.

1994-01-01

An experimental study was conducted to determine the effects of ply thickness in composite laminates on thermally induced cracking and changes in the coefficient of thermal expansion (CTE). After a few thermal cycles, laminates with thick-plies cracked, resulting in large changes in CTE. CTE's of the thin-ply laminates were unaffected by microcracking during the first 500 thermal cycles, whereas, the CTE's of the thick-ply laminates changed significantly. After about 1500 cycles, microdamage had also reduced the CTE of the thin-ply laminates to a value of about half of their initial value.
High-precision thermal expansion measurements using small Fabry-Perot etalons

NASA Astrophysics Data System (ADS)

Davis, Mark J.; Hayden, Joseph S.; Farber, Daniel L.

2007-09-01

Coefficient of thermal expansion (CTE) measurements using small Fabry-Perot etalons were conducted on high and low thermal expansion materials differing in CTE by a factor of nearly 400. The smallest detectable change in length was ~10 -12 m. The sample consisted of a mm-sized Fabry-Perot etalon equipped with spherical mirrors; the material-under-test served as the 2.5 mm-thick spacer between the mirrors. A heterodyne optical setup was used with one laser locked to an ~780 nm hyperfine line of Rb gas and the other locked to a resonance of the sample etalon; changes in the beat frequency between the two lasers as a function of temperature directly provided a CTE value. The measurement system was tested using the high-CTE SCHOTT optical glass N-KF9 (CTE = 9.5 ppm/K at 23 °C). Measurements conducted under reproducibility conditions using five identically-prepared N-KF9 etalons demonstrate a precision of 0.1 ppm/K; absolute values (accuracy) are within 2-sigma errors with those made using mechanical dilatometers with 100-mm long sample rods. Etalon-based CTE measurements were also made on a high-CTE (~10.5 ppm/K), proprietary glass-ceramic used for high peak-pressure electrical feedthroughs and revealed statistically significant differences among parts made under what were assumed to be identical conditions. Finally, CTE measurements were made on etalons constructed from SCHOTT's ultra-low CTE Zerodur (R) glass-ceramic (CTE about -20 ppb/K at 50 °C for the material tested herein).
Thermal Cycling of Thin and Thick Ply Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tompkins, S.S.; Shen, J.Y.; Lavoie, A.J.

1994-01-01

An experimental study was conducted to determine the effects of ply thickness in composite laminates on thermally induced cracking and changes in the coefficient of thermal expansion (CTE). After a few thermal cycles, laminates with thick-plies cracked, resulting in large changes in CTE. CTE`s of the thin-ply laminates were unaffected by microcracking during the first 500 thermal cycles, whereas, the CTE`s of the thick-ply laminates changed significantly. After about 1500 cycles, microdamage had also reduced the CTE of the thin-ply laminates to a value of about half of their initial value.
Thermal Protection Supplement for Reducing Interface Thermal Mismatch

NASA Technical Reports Server (NTRS)

Stewart, David A. (Inventor); Leiser, Daniel B. (Inventor)

2017-01-01

A thermal protection system that reduces a mismatch of thermal expansion coefficients CTE between a first material layer (CTE1) and a second material layer (CTE2) at a first layer-second layer interface. A portion of aluminum borosilicate (abs) or another suitable additive (add), whose CTE value, CTE(add), satisfies (CTE(add)-CTE1)(CTE(add)-CTE2)<0, is distributed with variable additive density,.rho.(z;add), in the first material layer and/or in the second material layer, with.rho.(z;add) near the materials interface being relatively high (alternatively, relatively low) and.rho.(z;add) in a region spaced apart from the interface being relatively low (alternatively, relatively high).
Determination of Coefficient of Thermal Expansion (CTE) of 20MPa Mass Concrete Using Granite Aggregate

NASA Astrophysics Data System (ADS)

Chee Siang, GO

2017-07-01

Experimental test was carried out to determine the coefficient of thermal expansion (CTE) value of 20MPa mass concrete using granite aggregate. The CTE value was established using procedure proposed by Kada et al. 2002 in determining the magnitude of early-ages CTE through laboratory test which is a rather accurate way by eliminating any possible superimposed effect of others early-age thermal deformation shrinkages such as autogenous, carbonation, plastic and drying shrinkage. This was done by submitting granite concrete block samples instrumented with ST4 vibrating wire extensometers to thermal shocks. The response of the concrete samples to this shock results in a nearly instantaneous deformation, which are measured by the sensor. These deformations, as well as the temperature signal, are used to calculate the CTE. By repeating heat cycles, the variation in the early-ages of concrete CTE over time was monitored and assessed for a period of upto 7 days. The developed CTE value facilitating the verification and validation of actual maximum permissible critical temperature differential limit (rather than arbitrarily follow published value) of cracking potential. For thick sections, internal restraint is dominant and this is governed by differentials mainly. Of the required physical properties for thermal modelling, CTE is of paramount importance that with given appropriate internal restraint factor the condition of cracking due to internal restraint is governs by equation, ΔTmax= 3.663ɛctu / αc. Thus, it can be appreciated that an increase in CTE will lower the maximum allowable differential for cracking avoidance in mass concrete while an increase of tensile strain capacity will increase the maximum allowable temperature differential.
Space environmental effects: Construction and utilization of a system to measure low thermal strain in one meter graphite epoxy tubes

NASA Technical Reports Server (NTRS)

Davis, J. H.; Rives, C.

1982-01-01

A system for measuring the expansion of low coefficient of thermal expansion (CTE) materials was constructed around a H.P. 5526-A laser measuring system. The vacuum CTE measurements in the -150 F to +120 F range were made over a 6 month period on a graphite epoxy tube yielding CTE values of 2.5 to one fifty-millionth/F above ambient and 2 + or - one ten-millionth F below ambient temperature. To assure that the below ambient, approximately 10 microns high open loop nature of the delta L/L vs. T curves was not apparatus related, similar size quartz tubes (A and B) were checked and found to have only a 2 micron (negligable for quartz) open loop component. These two quartz tubes, A and B, had ambient CTE values 20% and 45% respectively higher than the average handbook value. The overnight microcreep diminished an order of magnitude during the first several cycles after the system had been reopened.
Effects of Isothermal Aging on the Thermal Expansion of Several Sn-Based Lead-Free Solder Alloys

NASA Astrophysics Data System (ADS)

Hasnine, M.; Bozack, M. J.

2018-03-01

In this paper, effects of high-temperature aging on the thermal expansion behavior of several lead-free alloys SAC305, SAC387, Sn-3.5Ag, SnCu, SN100C (SnCu-Ni-Ge) and SnCu-0.01Ge have been explored. The coefficients of thermal expansion (CTEs) of the alloys have been experimentally determined over the temperature range 30-150 °C after isothermal aging at 125 °C for up to 30 days (720 h). The CTE values of SAC305, SAC387 and Sn-3.5Ag increase by 8-16% after 30 days of aging, while the CTE values of SnCu, SnCu-Ge and SN100C solders increase by only 3-6%. The CTE evolution of lead-free solders can be explained by microstructural changes observed during isothermal aging, which causes coarsening of various phases of the solder. As the phases coarsen, dislocation movement proceeds with a consequent increase in the average interparticle distance. The observation of CTE increases during isothermal aging suggests potential reliability problems for lead-free solder joints subjected to long-term aging exposures at high temperatures.
Thermal expansion coefficient prediction of fuel-cell seal materials from silica sand

NASA Astrophysics Data System (ADS)

Hidayat, Nurul; Triwikantoro, Baqiya, Malik A.; Pratapa, Suminar

2013-09-01

This study is focused on the prediction of coefficient of thermal expansion (CTE) of silica-sand-based fuel-cell seal materials (FcSMs) which in principle require a CTE value in the range of 9.5-12 ppm/°C. A semi-quantitative theoretical method to predict the CTE value is proposed by applying the analyzed phase compositions from XRD data and characterized density-porosity behavior. A typical silica sand was milled at 150 rpm for 1 hour followed by heating at 1000 °C for another hour. The sand and heated samples were characterized by means of XRD to perceive the phase composition correlation between them. Rietveld refinement was executed to investigate the weight fraction of the phase contained in the samples, and then converted to volume fraction for composite CTE calculations. The result was applied to predict their potential physical properties for FcSM. Porosity was taken into account in the calculation after which it was directly measured by the Archimedes method.
Determination on the Coefficient of Thermal Expansion in High-Power InGaN-based Light-emitting Diodes by Optical Coherence Tomography.

PubMed

Lee, Ya-Ju; Chou, Chun-Yang; Huang, Chun-Ying; Yao, Yung-Chi; Haung, Yi-Kai; Tsai, Meng-Tsan

2017-10-31

The coefficient of thermal expansion (CTE) is a physical quantity that indicates the thermal expansion value of a material upon heating. For advanced thermal management, the accurate and immediate determination of the CTE of packaging materials is gaining importance because the demand for high-power lighting-emitting diodes (LEDs) is currently increasing. In this study, we used optical coherence tomography (OCT) to measure the CTE of an InGaN-based (λ = 450 nm) high-power LED encapsulated in polystyrene resin. The distances between individual interfaces of the OCT images were observed and recorded to derive the instantaneous CTE of the packaged LED under different injected currents. The LED junction temperature at different injected currents was established with the forward voltage method. Accordingly, the measured instantaneous CTE of polystyrene resin varied from 5.86 × 10 -5 °C -1 to 14.10 × 10 -5 °C -1 in the junction temperature range 25-225 °C and exhibited a uniform distribution in an OCT scanning area of 200 × 200 μm. Most importantly, this work validates the hypothesis that OCT can provide an alternative way to directly and nondestructively determine the spatially resolved CTE of the packaged LED device, which offers significant advantages over traditional CTE measurement techniques.
Coefficient of Thermal Expansion of Pressed PETN Pellets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, Darla Graff; DeLuca, Racci

2015-03-11

The PETN single crystal coefficient of thermal expansion (CTE) values were measured and reported by Cady in 1972 [1] over the temperature range of -160 to 100°C. Measurements were made in the (001) and (100) crystallographic directions, see Figure 1 (a replicate of Figure 1 from the Cady paper). Cady used his single-crystal data to calculate the linear CTE for a randomly-oriented multi-crystal pressing of PETN, and his values ranged from 76.5 με/°C (at 20°C) to 89.9 5 με/°C (at 90°C).
ZERODUR: progress in CTE characterization

NASA Astrophysics Data System (ADS)

Jedamzik, Ralf; Kunisch, Clemens; Westerhoff, Thomas

2013-09-01

In 2010, SCHOTT introduced a method for the modeling of the thermal expansion behavior of ZERODUR® under arbitrary temperature profiles for an optimized production of material for the upcoming Extremely Large Telescope (ELT) projects. In 2012 a new product was introduced based on this method called ZERODUR® TAILORED. ZERODUR® TAILORED provides an evolution in the specification of the absolute Coefficient of Thermal Expansion (CTE) value by including the individual customer requirements in this process. This paper presents examples showing the benefit of an application oriented approach in the design of specifications using ZERODUR®. Additionally it will be shown how the modeling approach has advanced during the last years to improve the prediction accuracy on long time scales. ZERODUR® is known not only for its lowest CTE but also for its excellent CTE homogeneity as shown in the past for disc shaped blanks typical for telescope mirror substrates. Additionally this paper presents recent results of CTE homogeneity measurements in the single digit ppb/K range for a rectangular cast plate proving that the excellent CTE homogeneity is independent of the production format.
Prototype of low thermal expansion materials: fabrication of mesoporous silica/polymer composites with densely filled polymer inside mesopore space.

PubMed

Kiba, Shosuke; Suzuki, Norihiro; Okawauchi, Yoshinori; Yamauchi, Yusuke

2010-09-03

A prototype of novel low thermal expansion materials using mesoporous silica particles is demonstrated. Mesoporous silica/polymer composites with densely filled polymer inside the mesopore space are fabricated by mechanically mixing both organically modified mesoporous silica and epoxy polymer. The mesopores are easily penetrated by polymers as a result of the capillary force during the mechanical composite processing. Furthermore, we propose a new model of polymer mobility restriction using mesoporous silica with a large pore space. The robust inorganic frameworks covering the polymer effectively restrict the polymer mobility against thermal energy. As a result, the degree of total thermal expansion of the composites is drastically decreased. From the mass-normalized thermal mechanical analysis (TMA) charts of various composites with different amounts of mesoporous silica particles, it is observed that the coefficient of thermal expansion (CTE) values gradually increase with an increase of the polymer amount outside the mesopores. It is proven that the CTE values in the range over the glass-transition temperatures (T(g)) are perfectly proportional to the outside polymer amounts. Importantly, the Y-intercept of the relation equation obtained by a least-square method is the CTE value and is almost zero. This means that thermal expansion does not occur if no polymers are outside the mesopores. Through such a quantative discussion, we clarify that only the outside polymer affects the thermal expansion of the composites, that is, the embedded polymers inside the mesopores do not expand at all during the thermal treatment.
Negative Thermal Expansion over a Wide Temperature Range in Fe-doped MnNiGe Composites

NASA Astrophysics Data System (ADS)

Zhao, Wenjun; Sun, Ying; Liu, Yufei; Shi, Kewen; Lu, Huiqing; Song, Ping; Wang, Lei; Han, Huimin; Yuan, Xiuliang; Wang, Cong

2018-02-01

Fe-doped MnNiGe alloys were successfully synthesized by solid-state reaction. Giant negative thermal expansion (NTE) behaviors with the coefficients of thermal expansion (CTE) of -285.23×10-6 K-1 (192-305 K) and -1167.09×10-6 K-1 (246-305 K) have been obtained in Mn0.90Fe0.10NiGe and MnNi0.90Fe0.10Ge, respectively. Furthermore, these materials were combined with Cu in order to control the NTE properties. The results indicate that the absolute value of CTE gradually decreases with increasing Cu contents. In Mn0.92Fe0.08NiGe/x%Cu, the CTE gradually changes from -64.92×10-6 K-1 (125-274 K) to -4.73×10-6 K-1 (173-229 K) with increasing value of x from 15 to 70. The magnetic measurements reveal that the NTE behaviors in this work are strongly correlated with the process of the magnetic phase transition and the introduction of Fe atoms could also change the spiral anti-ferromagnetic (s-AFM) state into ferromagnetic (FM) state at low temperature. Our study launches a new candidate for controlling thermal expansion properties of metal matrix materials which could have potential application in variable temperature environment.
Determination of coefficient of thermal expansion effects on Louisiana's PCC pavement design : research project capsule.

DOT National Transportation Integrated Search

2009-01-01

PROBLEM: The coefficient of thermal expansion (CTE) is a fundamental property of construction : materials such as steel and concrete. Although the CTE of steel is a well-defined : constant, the CTE of concrete varies substantially with aggregate type...
Space structures concepts and materials

NASA Technical Reports Server (NTRS)

Nowitzky, A. M.; Supan, E. C.

1988-01-01

An extension is preseted of the evaluation of graphite/aluminum metal matrix composites (MMC) for space structures application. A tubular DWG graphite/aluminum truss assembly was fabricated having the structural integrity and thermal stability needed for space application. DWG is a proprietary thin ply continuous graphite reinforced aluminum composite. The truss end fittings were constructed using the discontinuous ceramic particulate reinforced MMC DWAl 20 (trademark). Thermal stability was incorporated in the truss by utilizing high stiffness, negative coefficient of thermal expansion (CTE) P100 graphite fibers in a 6061 aluminum matrix, crossplied to provide minimized CTE in the assembled truss. Tube CTE was designed to be slightly negative to offset the effects of the end fitting and sleeve, CTE values of which are approx. 1/2 that of aluminum. In the design of the truss configuration, the CTE contribution of each component was evaluated to establish the component dimension and layup configuration required to provide a net zero CTE in the subassemblies which would then translate to a zero CTE for the entire truss bay produced.
Negative Thermal Expansion over a Wide Temperature Range in Fe-Doped MnNiGe Composites

PubMed Central

Zhao, Wenjun; Sun, Ying; Liu, Yufei; Shi, Kewen; Lu, Huiqing; Song, Ping; Wang, Lei; Han, Huimin; Yuan, Xiuliang; Wang, Cong

2018-01-01

Fe-doped MnNiGe alloys were successfully synthesized by solid-state reaction. Giant negative thermal expansion (NTE) behaviors with the coefficients of thermal expansion (CTE) of −285.23 × 10−6 K−1 (192–305 K) and −1167.09 × 10−6 K−1 (246–305 K) have been obtained in Mn0.90Fe0.10NiGe and MnNi0.90Fe0.10Ge, respectively. Furthermore, these materials were combined with Cu in order to control the NTE properties. The results indicate that the absolute value of CTE gradually decreases with increasing Cu contents. In Mn0.92Fe0.08NiGe/x%Cu, the CTE gradually changes from −64.92 × 10−6 K−1 (125–274 K) to −4.73 × 10−6 K−1 (173–229 K) with increasing value of x from 15 to 70. The magnetic measurements reveal that the NTE behaviors in this work are strongly correlated with the process of the magnetic phase transition and the introduction of Fe atoms could also change the spiral anti-ferromagnetic (s-AFM) state into ferromagnetic (FM) state at low temperature. Our study launches a new candidate for controlling thermal expansion properties of metal matrix materials which could have potential application in variable temperature environment. PMID:29468152
Evaluating the coefficient of thermal expansion using time periods of minimal thermal gradient for a temperature driven structural health monitoring

NASA Astrophysics Data System (ADS)

Reilly, J.; Abdel-Jaber, H.; Yarnold, M.; Glisic, B.

2017-04-01

Structural Health Monitoring aims to characterize the performance of a structure from a combination of recorded sensor data and analytic techniques. Many methods are concerned with quantifying the elastic response of the structure, treating temperature changes as noise in the analysis. While these elastic profiles do demonstrate a portion of structural behavior, thermal loads on a structure can induce comparable strains to elastic loads. Understanding this relationship between the temperature of the structure and the resultant strain and displacement can provide in depth knowledge of the structural condition. A necessary parameter for this form of analysis is the Coefficient of Thermal Expansion (CTE). The CTE of a material relates the amount of expansion or contraction a material undergoes per degree change in temperature, and can be determined from temperature-strain relationship given that the thermal strain can be isolated. Many times with concrete, the actual amount of expansion with temperature in situ varies from the given values for the CTE due to thermally generated elastic strain, which complicates evaluation of the CTE. To accurately characterize the relationship between temperature and strain on a structure, the actual thermal behavior of the structure needs to be analyzed. This rate can vary for different parts of a structure, depending on boundary conditions. In a case of unrestrained structures, the strain in the structure should be linearly related to the temperature change. Thermal gradients in a structure can affect this relationship, as they induce curvature and deplanations in the cross section. This paper proposes a method that addresses these challenges in evaluating the CTE.
Phase-Transformation-Induced Extra Thermal Expansion Behavior of (SrxBa1-x)TiO3/Cu Composite.

PubMed

Sheng, Jie; Wang, Lidong; Li, Shouwei; Yin, Benke; Liu, Xiangli; Fei, Wei-Dong

2016-06-03

The properties of metal matrix composites (MMCs) can be optimized effectively through adjusting the type or the volume fraction of reinforcement. Generally, the coefficient of thermal expansion (CTE) of MMCs can be reduced by increasing the volume fraction of the reinforcement with lower CTE than metal matrix. However, it is great challenge to fabricate low CTE MMCs with low reinforcement volume fraction because of the limitation of reinforcement CTEs. SrxBa1-xTiO3 (SBT) powder presents negative thermal expansion behavior during the phase transformation from tetragonal to cubic phase. Here, we demonstrate that the phase transformation of SBT can be utilized to reduce and design the thermal expansion properties of SBT particle-reinforced Cu (SBT/Cu) composite, and ultralow CTE can be obtained in SBT/Cu composite. The X-ray diffraction analysis on heating indicates that the temperature range of phase transformation is extended greatly, therefore, the low CTE can be achieved within wide temperature range. Landau-Devonshire theory study on the phase transformation behaviors of SBT particles in the composite indicates that thermal mismatch stress significantly affects the Curie temperature of SBT particles and the CTE of the composite. The results given in the present study provide a new approach to design the MMCs with low CTE.
Phase-Transformation-Induced Extra Thermal Expansion Behavior of (SrxBa1–x)TiO3/Cu Composite

PubMed Central

Sheng, Jie; Wang, Lidong; Li, Shouwei; Yin, Benke; Liu, Xiangli; Fei, Wei-Dong

2016-01-01

The properties of metal matrix composites (MMCs) can be optimized effectively through adjusting the type or the volume fraction of reinforcement. Generally, the coefficient of thermal expansion (CTE) of MMCs can be reduced by increasing the volume fraction of the reinforcement with lower CTE than metal matrix. However, it is great challenge to fabricate low CTE MMCs with low reinforcement volume fraction because of the limitation of reinforcement CTEs. SrxBa1−xTiO3 (SBT) powder presents negative thermal expansion behavior during the phase transformation from tetragonal to cubic phase. Here, we demonstrate that the phase transformation of SBT can be utilized to reduce and design the thermal expansion properties of SBT particle-reinforced Cu (SBT/Cu) composite, and ultralow CTE can be obtained in SBT/Cu composite. The X-ray diffraction analysis on heating indicates that the temperature range of phase transformation is extended greatly, therefore, the low CTE can be achieved within wide temperature range. Landau-Devonshire theory study on the phase transformation behaviors of SBT particles in the composite indicates that thermal mismatch stress significantly affects the Curie temperature of SBT particles and the CTE of the composite. The results given in the present study provide a new approach to design the MMCs with low CTE. PMID:27255420
Task 6 : material thermal input for Iowa materials.

DOT National Transportation Integrated Search

2008-02-01

The present research project was designed to determine thermal properties, such as coefficient of thermal expansion : (CTE) and thermal conductivity, of Iowa concrete pavement materials. These properties are required as input values by : the Mechanis...

Dilation Behavior of Thermal Spray Coatings

NASA Astrophysics Data System (ADS)

Bejarano Lopez, Miryan Lorena

Thermal Spray (TS) is a very versatile manufacturing process to deposit thick coatings on a variety of substrates. Coatings are used in protective (i.e. wear, chemical attack, high temperature, etc.) and functional (i.e. sensors) applications. TS coatings have a unique lamellar microstructure as a result of the overlapping of millions of molten and partially-molten particles. During processing, high deformation by impact, high temperature, and rapid solidification lead to a complex hierarchical material system that contains a high amount of microstructural defects. The presence of defects in the microstructure contribute to differences in property values in comparison to bulk materials. Thermal stresses and residual strains arise from processing, thermal gradients and thermal exposure. Evaluation of thermal properties, in this case, the coefficient of thermal expansion (CTE) is of vital importance to enhance coating performance. In this dissertation, expansion measurements of various metals, alloys, ceramics, and cermet coatings; were carried out using various techniques (push rod dilatometry, x-ray diffraction XRD, digital image correlation DIC, and curvature method) to determine the dilation behavior at the atomic, micro- and macro-scale levels. The main results were. 1) Mathematical models (Turner and Kerner) used for composite materials, successfully predicted the CTE property of a TS coating where the primary phase is the coating material and the secondary phases can be oxides, precipitates, etc. (formed as a byproduct of the spraying process). CTE was found not to be affected by porosity. 2) Despite the anisotropic behavior characteristic of TS coatings, the experimental results shown that CTE results to be reasonable isotropic within the scope of this study. 3) The curvature method was found to be an alternative technique to obtain the CTE, as well as the Young's modulus of coating in a bi-material strip, with good approximation. 4) An anomalous expansion behavior during the first heating exposure was exhibited by all coatings. The effect was named here, as "thermal shakedown", and is magnified in metals and alloys. 5) Non-isothermal rapid annealing of defects was correlated to this first irreversible contraction or expansion behavior. Although observed in most thermal spray materials, two material systems, pure Al and Ni-5Al were evaluated in-depth to quantify the mechanisms contributing to this behavior: vacancy formation, dislocation annealing, grain boundaries annihilation, residual stress relief, inelastic mechanical effects, etc. Correct determination of CTE values are important for design to assure integrity and functionality of coatings. Considerations of appropriate measurements are described in this dissertation.
Effects of thermal inhomogeneity on 4m class mirror substrates

NASA Astrophysics Data System (ADS)

Jedamzik, Ralf; Kunisch, Clemens; Westerhoff, Thomas

2016-07-01

The new ground based telescope generation is moving to a next stage of performance and resolution. Mirror substrate material properties tolerance and homogeneity are getting into focus. The coefficient of thermal expansion (CTE) homogeneity is even more important than the absolute CTE. The error in shape of a mirror, even one of ZERODUR, is affected by changes in temperature, and by gradients in temperature. Front to back gradients will change the radius of curvature R that in turn will change the focus. Some systems rely on passive athermalization and do not have means to focus. Similarly changes in soak temperature will result in surface changes to the extent there is a non-zero coefficient of thermal expansion. When there are in-homogeneities in CTE, the mirror will react accordingly. Results of numerical experiments are presented discussing the impact of CTE in-homogeneities on the optical performance of 4 m class mirror substrates. Latest improvements in 4 m class ZERODUR CTE homogeneity and the thermal expansion metrology are presented as well.
Thermomechanical Behavior of Developmental Thermal Barrier Coating Bond Coats

NASA Astrophysics Data System (ADS)

Pandey, Amit; Tolpygo, Vladimir K.; Hemker, Kevin J.

2013-04-01

Thermal expansion, microtensile, and stress relaxation experiments have been performed to contrast and compare the thermal and mechanical response of two experimental (L1 and H1) coatings provided by Honeywell Corporation (Morristown, NY). Thermal expansion experiments reveal that both coatings have coefficients of thermal expansion (CTE) that vary with temperature and that the CTE mismatch between the coatings and superalloy substrate is significant in the case of L1 as compared to H1. Values of the 0.2% offset yield stress (YS), Young's modulus ( E), and hardening exponent ( n) are reported. Room-temperature microtensile experiments show higher strain hardening and a very low value of failure strain for L1 as compared to H1. At elevated temperatures, there is a significant decrease in the YS of as-received L1 for (924 MPa at room temperature to 85 MPa at 1000°C) as compared to H1. Finally, a power law creep description for high-temperature stress relaxation is developed and the measured values of the stress exponent ( n = 3) and activation energies ( Q creep = 200-250 kJ/mol) are shown to be consistent with power law creep.
Next generation dilatometer for highest accuracy thermal expansion measurement of ZERODUR®

NASA Astrophysics Data System (ADS)

Jedamzik, Ralf; Engel, Axel; Kunisch, Clemens; Westenberger, Gerhard; Fischer, Peter; Westerhoff, Thomas

2015-09-01

In the recent years, the ever tighter tolerance for the Coefficient of thermal expansion (CTE) of IC Lithography component materials is requesting significant progress in the metrology accuracy to determine this property as requested. ZERODUR® is known for its extremely low CTE between 0°C to 50°C. The current measurement of the thermal expansion coefficient is done using push rod dilatometer measurement systems developed at SCHOTT. In recent years measurements have been published showing the excellent CTE homogeneity of ZERODUR® in the one-digit ppb/K range using these systems. The verifiable homogeneity was limited by the CTE(0°C, 50°C) measurement repeatability in the range of ± 1.2 ppb/K of the current improved push rod dilatometer setup using an optical interferometer as detector instead of an inductive coil. With ZERODUR® TAILORED, SCHOTT introduced a low thermal expansion material grade that can be adapted to individual customer application temperature profiles. The basis for this product is a model that has been developed in 2010 for better understanding of the thermal expansion behavior under given temperature versus time conditions. The CTE behavior predicted by the model has proven to be in very good alignment with the data determined in the thermal expansions measurements. The measurements to determine the data feeding the model require a dilatometer setup with excellent stability and accuracy for long measurement times of several days. In the past few years SCHOTT spent a lot of effort to drive a dilatometer measurement technology based on the push rod setup to its limit, to fulfill the continuously demand for higher CTE accuracy and deeper material knowledge of ZERODUR®. This paper reports on the status of the dilatometer technology development at SCHOTT.
Thermally induced changes in the focal distance of composite mirrors - Composites with a zero coefficient of thermal expansion of the radius of curvature

NASA Technical Reports Server (NTRS)

Dolgin, Benjamin P.

1992-01-01

Calculations are presented of the coefficient of thermal expansion (CTE) of the radius of curvature of the reflector face sheets made of a quasi-isotropic composite. It is shown that, upon cooling, the change of the CTE of the focal distance of the mirror is equal to that of the radius of the curvature of the reflector face sheet. The CTE of the radius of the curvature of a quasi-isotropic composite face sheet depends on both the in-plane and the out-of-plane CTEs. The zero in-plane CTE of a face sheet does not guarantee mirrors with no focal length changes.
Thermal properties and dynamic mechanical properties of ceramic fillers filled epoxy composites

NASA Astrophysics Data System (ADS)

Saidina, D. S.; Mariatti, M.; Juliewatty, J.

2015-07-01

This present study is aimed to enhance the thermal and dynamic mechanical properties of ceramic fillers such as Calcium Copper Titanate, CaCu3Ti4O12 (CCTO) and Barium Titanate (BaTiO3) filled epoxy thin film composites. As can be seen from the results, 20 vol% BaTiO3/epoxy thin film composite showed the lowest coefficient of thermal expansion (CTE) value, the highest decomposition temperature (T5 and Tonset) and weight of residue among the composites as the filler has low CTE value, distributed homogeneously throughout the composite and less voids can be seen between epoxy resin and BaTiO3 filler.
Homogeneity of the coefficient of linear thermal expansion of ZERODUR: a review of a decade of evaluations

NASA Astrophysics Data System (ADS)

Jedamzik, Ralf; Westerhoff, Thomas

2017-09-01

The coefficient of thermal expansion (CTE) and its spatial homogeneity from small to large formats is the most important property of ZERODUR. Since more than a decade SCHOTT has documented the excellent CTE homogeneity. It started with reviews of past astronomical telescope projects like the VLT, Keck and GTC mirror blanks and continued with dedicated evaluations of the production. In recent years, extensive CTE measurements on samples cut from randomly selected single ZERODUR parts in meter size and formats of arbitrary shape, large production boules and even 4 m sized blanks have demonstrated the excellent CTE homogeneity in production. The published homogeneity data shows single ppb/K peak to valley CTE variations on medium spatial scale of several cm down to small spatial scale of only a few mm mostly at the limit of the measurement reproducibility. This review paper summarizes the results also in respect to the increased CTE measurement accuracy over the last decade of ZERODUR production.
Thermal Expansion of Self-Organized and Shear-Oriented Cellulose Nanocrystal Films

Treesearch

Jairo A. Diaz; Xiawa Wu; Ashlie Martini; Jeffrey P. Youngblood; Robert J. Moon

2013-01-01

The coefficient of thermal expansion (CTE) of cellulose nanocrystal (CNC) films was characterized using novel experimental techniques complemented by molecular simulations. The characteristic birefringence exhibited by CNC films was utilized to calculate the in-plane CTE of selforganized and shear-oriented self-standing CNC films from room temperature to 100 °...
Zero expansion glass ceramic ZERODUR® roadmap for advanced lithography

NASA Astrophysics Data System (ADS)

Westerhoff, Thomas; Jedamzik, Ralf; Hartmann, Peter

2013-04-01

The zero expansion glass ceramic ZERODUR® is a well-established material in microlithography in critical components as wafer- and reticle-stages, mirrors and frames in the stepper positioning and alignment system. The very low coefficient of thermal expansion (CTE) and its extremely high CTE homogeneity are key properties to achieve the tight overlay requirements of advanced lithography processes. SCHOTT is continuously improving critical material properties of ZERODUR® essential for microlithography applications according to a roadmap driven by the ever tighter material specifications broken down from the customer roadmaps. This paper will present the SCHOTT Roadmap for ZERODUR® material property development. In the recent years SCHOTT established a physical model based on structural relaxation to describe the coefficient of thermal expansion's temperature dependence. The model is successfully applied for the new expansion grade ZERODUR® TAILORED introduced to the market in 2012. ZERODUR® TAILORED delivers the lowest thermal expansion of ZERODUR® products at microlithography tool application temperature allowing for higher thermal stability for tighter overlay control in IC production. Data will be reported demonstrating the unique CTE homogeneity of ZERODUR® and its very high reproducibility, a necessary precondition for serial production for microlithography equipment components. New data on the bending strength of ZERODUR® proves its capability to withstand much higher mechanical loads than previously reported. Utilizing a three parameter Weibull distribution it is possible to derive minimum strength values for a given ZERODUR® surface treatment. Consequently the statistical uncertainties of the earlier approach based on a two parameter Weibull distribution have been eliminated. Mechanical fatigue due to stress corrosion was included in a straightforward way. The derived formulae allows calculating life time of ZERODUR® components for a given stress load or the allowable maximum stress for a minimum required life time.
Development of Equivalent Material Properties of Microbump for Simulating Chip Stacking Packaging

PubMed Central

Lee, Chang-Chun; Tzeng, Tzai-Liang; Huang, Pei-Chen

2015-01-01

A three-dimensional integrated circuit (3D-IC) structure with a significant scale mismatch causes difficulty in analytic model construction. This paper proposes a simulation technique to introduce an equivalent material composed of microbumps and their surrounding wafer level underfill (WLUF). The mechanical properties of this equivalent material, including Young’s modulus (E), Poisson’s ratio, shear modulus, and coefficient of thermal expansion (CTE), are directly obtained by applying either a tensile load or a constant displacement, and by increasing the temperature during simulations, respectively. Analytic results indicate that at least eight microbumps at the outermost region of the chip stacking structure need to be considered as an accurate stress/strain contour in the concerned region. In addition, a factorial experimental design with analysis of variance is proposed to optimize chip stacking structure reliability with four factors: chip thickness, substrate thickness, CTE, and E-value. Analytic results show that the most significant factor is CTE of WLUF. This factor affects microbump reliability and structural warpage under a temperature cycling load and high-temperature bonding process. WLUF with low CTE and high E-value are recommended to enhance the assembly reliability of the 3D-IC architecture. PMID:28793495
Influence of sodalite zeolite infiltration on the coefficient of thermal expansion and bond strength of all-ceramic dental prostheses.

PubMed

Naji, Ghassan Abdul-Hamid; Omar, Ros Anita; Yahya, Rosiyah

2017-03-01

In all-ceramic systems, a high incidence of veneer chip-off has been reported in clinical studies. Coefficient of thermal expansion (CTE) behaviour is one of the factors that may increase residual stress in the interface and influence the veneer/core bond strength. Therefore, this study aimed to evaluate the effect of sodalite zeolite-infiltration on the CTE behaviour and bond strength of different all-ceramic prostheses. The case-study groups were synthesized sodalite zeolite-infiltrated alumina (IA-SOD) and synthesized sodalite zeolite-infiltrated zirconia-toughened alumina (ZTA) (IZ-SOD), while the control groups were glass-infiltrated alumina (IA-glass) and glass-infiltrated ZTA (IZ-glass). Forty cylindrical-shaped samples measuring 5 mm in diameter and 10 mm in height were tested for CTE using a thermo-mechanical analyser machine, and forty disc-shaped ceramic samples measuring 12 mm in diameter and 1.2 ± 0.2 mm in thickness were prepared using specially designed stainless steel split mould and veneered by cylinder-shaped (2 mm high × 2 mm diameter) low-fusing porcelain (Vita VM7). The veneer/core samples were sintered and tested for shear bond strength using a high precision universal testing machine. Scanning electron microscope, stereo microscope, atomic force microscope, and energy-dispersive X-ray spectroscopy were used to investigate the structural characteristics of samples at the fracture surface. The collected data were analyzed with a one-way ANOVA and Tukey HSD test (α=.05). IZ-SOD revealed highest CTE and shear bond strength values, while the IA-glass revealed the lowest values than the other groups. There was no significant difference in CTE and bond strength among IZ-SOD, IA-SOD and IZ-glass samples (p>0.05). The experimental SOD zeolite-infiltrated samples revealed higher CTE mismatch and bond strength along with a more favourable mode of failure than did the commercial glass-infiltrated samples. Sandblast technique is considered as effective conditioning procedure for enhancing the surface roughness of SOD zeolite-infiltrated frameworks which subsequently improving the bond strength. Copyright © 2016 Elsevier Ltd. All rights reserved.
Effect of sintering process and additives on the properties of cordierite based ceramics

NASA Astrophysics Data System (ADS)

Rundans, M.; Sperberga, I.; Sedmale, G.; Stinkulis, G.

2013-12-01

It is possible to obtain cordierite ceramics with high temperature synthesis using both synthetic and raw natural materials. This paper discusses the possibilities to obtain cordierite ceramics, replacing part of required oxides with raw materials from various Latvian deposits of dolomite and clay. The obtained raw cordierite powders were ground in two modes (3 and 12 hours) and fired at 1200 °C. Ceramic samples were characterized by hydrostatic weighting method; crystalline phase composition was studied by XRD. Obtained samples were evaluated by their mechanical (compressive) strength and linear coefficient of thermal expansion (CTE). Thermal shock resistance was tested using water quenching method and afterwards evaluated by using ultrasonic method to test changes in Young's modulus of elasticity. Results show that increase in grinding time causes samples to densify and promote formation of cordierite crystalline phase which corresponds to increase in total compressive strength and decrease of CTE values. CTE values of samples ground for 12 hours conform to that of obtained in other researches.
First-principles study on the thermal expansion of Ni-X binary alloys based on the quasi-harmonic Debye model

NASA Astrophysics Data System (ADS)

Shin, Yongjin; Jung, Woo-Sang; Lee, Young-Su

2016-11-01

In this study, we use the quasi-harmonic Debye model to predict the coefficient of thermal expansion of Ni- X binary alloys. The method bridges between the macroscopic elastic behavior and thermodynamic properties of materials without an expensive calculation of the volume dependence of the phonon density of states. Furthermore, the Grüneisen parameter is derived from the volume dependence of the Debye temperature, which is calculated from the first-principles elastic stiffness constants. The experimental coefficient of thermal expansion (CTE) of pure nickel is well reproduced, especially in the low temperature region. Among the few alloying elements tested, Al is predicted to slightly decrease the CTE whereas Mo and W are more effective in reducing the CTE. For the cases of Ni-X binary alloy systems, where the variation in the CTE is relatively small, the method used here appears to perform better than certain other formulations that rely entirely on the energy vs. volume relationship.
Evaluation of thermal expansion coefficient of carbon fiber reinforced composites using electronic speckle interferometry.

PubMed

Dong, Chengzhi; Li, Kai; Jiang, Yuxi; Arola, Dwayne; Zhang, Dongsheng

2018-01-08

An optical system for measuring the coefficient of thermal expansion (CTE) of materials has been developed based on electronic speckle interferometry. In this system, the temperature can be varied from -60°C to 180°C with a Peltier device. A specific specimen geometry and an optical arrangement based on the Michelson interferometer are proposed to measure the deformation along two orthogonal axes due to temperature changes. The advantages of the system include its high sensitivity and stability over the whole range of measurement. The experimental setup and approach for estimating the CTE was validated using an Aluminum alloy. Following this validation, the system was applied for characterizing the CTE of carbon fiber reinforced composite (CFRP) laminates. For the unidirectional fiber reinforced composites, the CTE varied with fiber orientation and exhibits anisotropic behavior. By stacking the plies with specific angles and order, the CTE of a specific CFRP was constrained to a low level with minimum variation temperature. The optical system developed in this study can be applied to CTE measurement for engineering and natural materials with high accuracy.
Glass ceramic ZERODUR enabling nanometer precision

NASA Astrophysics Data System (ADS)

Jedamzik, Ralf; Kunisch, Clemens; Nieder, Johannes; Westerhoff, Thomas

2014-03-01

The IC Lithography roadmap foresees manufacturing of devices with critical dimension of < 20 nm. Overlay specification of single digit nanometer asking for nanometer positioning accuracy requiring sub nanometer position measurement accuracy. The glass ceramic ZERODUR® is a well-established material in critical components of microlithography wafer stepper and offered with an extremely low coefficient of thermal expansion (CTE), the tightest tolerance available on market. SCHOTT is continuously improving manufacturing processes and it's method to measure and characterize the CTE behavior of ZERODUR® to full fill the ever tighter CTE specification for wafer stepper components. In this paper we present the ZERODUR® Lithography Roadmap on the CTE metrology and tolerance. Additionally, simulation calculations based on a physical model are presented predicting the long term CTE behavior of ZERODUR® components to optimize dimensional stability of precision positioning devices. CTE data of several low thermal expansion materials are compared regarding their temperature dependence between - 50°C and + 100°C. ZERODUR® TAILORED 22°C is full filling the tight CTE tolerance of +/- 10 ppb / K within the broadest temperature interval compared to all other materials of this investigation. The data presented in this paper explicitly demonstrates the capability of ZERODUR® to enable the nanometer precision required for future generation of lithography equipment and processes.
Multifunctional Lattices with Low Thermal Expansion and Low Thermal Conductivity

NASA Astrophysics Data System (ADS)

Xu, Hang; Liu, Lu; Pasini, Damiano

Systems in space are vulnerable to large temperature changes when travelling into and out of the Earth's shadow. Variations in temperature can lead to undesired geometric changes in susceptible applications requiring very fine precision. In addition, temperature-sensitive electronic equipment hosted in a satellite needs adequate thermal-control to guarantee a moderate ambient temperature. To address these specifications, materials with low coefficient of thermal expansion (CTE) and low coefficient of thermal conductivity (CTC) over a wide range of temperatures are often sought, especially for bearing components in satellites. Besides low CTE and low CTC, these materials should also provide desirable stiffness, strength and extraordinarily low mass. This work presents ultralightweight bi-material lattices with tunable CTE and CTC, besides high stiffness and strength. We show that the compensation of the thermal expansion and joint rotation at the lattice joints can be used as an effective strategy to tailor thermomechanical performance. Proof-of-concept lattices are fabricated from Al and Ti alloy sheets via a simple snap-fit technique and vacuum brazing, and their CTE and CTC are assessed via a combination of experiments and theory. Corresponding Author.
Dilatometer setup for low coefficient of thermal expansion materials measurements in the 140 K-250 K temperature range.

PubMed

Spannagel, Ruven; Hamann, Ines; Sanjuan, Josep; Schuldt, Thilo; Gohlke, Martin; Johann, Ulrich; Weise, Dennis; Braxmaier, Claus

2016-10-01

Space applications demand light weight materials with excellent dimensional stability for telescopes, optical benches, optical resonators, etc. Glass-ceramics and composite materials can be tuned to reach very low coefficient of thermal expansion (CTE) at different temperatures. In order to determine such CTEs, very accurate setups are needed. Here we present a dilatometer that is able to measure the CTE of a large variety of materials in the temperature range of 140 K to 250 K. The dilatometer is based on a heterodyne interferometer with nanometer noise levels to measure the expansion of a sample when applying small amplitude controlled temperature signals. In this article, the CTE of a carbon fiber reinforced polymer sample has been determined with an accuracy in the 10 -8 K -1 range.
ZERODUR TAILORED for cryogenic application

NASA Astrophysics Data System (ADS)

Jedamzik, R.; Westerhoff, T.

2014-07-01

ZERODUR® glass ceramic from SCHOTT is known for its very low thermal expansion coefficient (CTE) at room temperature and its excellent CTE homogeneity. It is widely used for ground-based astronomical mirrors but also for satellite applications. Many reference application demonstrate the excellent and long lasting performance of ZERODUR® components in orbit. For space application a low CTE of the mirror material is required at cryogenic temperatures together with a good match of the thermal expansion to the supporting structure material. It is possible to optimize the coefficient of thermal expansion of ZERODUR® for cryogenic applications. This paper reports on measurements of thermal expansion of ZERODUR® down to cryogenic temperatures of 10 K performed by the PTB (Physikalisch Technische Bundesanstallt, Braunschweig, Germany, the national metrology laboratory). The ZERODUR® TAILORED CRYO presented in this paper has a very low coefficient of thermal expansion down to 70 K. The maximum absolute integrated thermal expansion down to 10 K is only about 20 ppm. Mirror blanks made from ZERODUR® TAILORED CRYO can be light weighted to almost 90% with our modern processing technologies. With ZERODUR® TAILORED CRYO, SCHOTT offers the mirror blank material for the next generation of space telescope applications.
Low coefficient of thermal expansion polyimides containing metal ion additives

NASA Technical Reports Server (NTRS)

Stoakley, D. M.; St. Clair, A. K.

1992-01-01

Polyimides have become widely used as high performance polymers as a result of their excellent thermal stability and toughness. However, lowering their coefficient of thermal expansion (CTE) would increase their usefulness for aerospace and electronic applications where dimensional stability is a requirement. The incorporation of metal ion-containing additives into polyimides, resulting in significantly lowered CTE's, has been studied. Various metal ion additives have been added to both polyamic acid resins and soluble polyimide solutions in the concentration range of 4-23 weight percent. The incorporation of these metal ions has resulted in reductions in the CTE's of the control polyimides of 12 percent to over 100 percent depending on the choice of additive and its concentration.
Progress on glass ceramic ZERODUR enabling nanometer precision

NASA Astrophysics Data System (ADS)

Jedamzik, Ralf; Kunisch, Clemens; Nieder, Johannes; Weber, Peter; Westerhoff, Thomas

2016-03-01

The Semiconductor Industry is making continuous progress in shrinking feature size developing technologies and process to achieve < 10 nm feature size. The required Overlay specification for successful production is in the range one nanometer or even smaller. Consequently, materials designed into metrology systems of exposure or inspection tools need to fulfill ever tighter specification on the coefficient of thermal expansion (CTE). The glass ceramic ZERODUR® is a well-established material in critical components of microlithography wafer stepper and offered with an extremely low coefficient of thermal expansion, the tightest tolerance available on market. SCHOTT is continuously improving manufacturing processes and it's method to measure and characterize the CTE behavior of ZERODUR®. This paper is focusing on the "Advanced Dilatometer" for determination of the CTE developed at SCHOTT in the recent years and introduced into production in Q1 2015. The achievement for improving the absolute CTE measurement accuracy and the reproducibility are described in detail. Those achievements are compared to the CTE measurement accuracy reported by the Physikalische Technische Bundesanstalt (PTB), the National Metrology Institute of Germany. The CTE homogeneity is of highest importance to achieve nanometer precision on larger scales. Additionally, the paper presents data on the short scale CTE homogeneity and its improvement in the last two years. The data presented in this paper will explain the capability of ZERODUR® to enable the extreme precision required for future generation of lithography equipment and processes.

Composite Laminate With Coefficient of Thermal Expansion Matching D263 Glass

NASA Technical Reports Server (NTRS)

Robinson, David; Rodini, Benjamin

2012-01-01

The International X-ray Observatory project seeks to make an X-ray telescope assembly with 14,000 flexible glass segments. The glass used is commercially available SCHOTT D263 glass. Thermal expansion causes the mirror to distort out of alignment. A housing material is needed that has a matching coefficient of thermal expansion (CTE) so that when temperatures change in the X-ray mirror assembly, the glass and housing pieces expand equally, thus reducing or eliminating distortion. Desirable characteristics of this material include a high stiffness/weight ratio, and low density. Some metal alloys show promise in matching the CTE of D263 glass, but their density is high compared to aluminum, and their stiffness/weight ratio is not favorable. A laminate made from carbon fiber reinforced plastic (CFRP) should provide more favorable characteristics, but there has not been any made with the CTE matching D263 Glass. It is common to create CFRP laminates of various CTEs by stacking layers of prepreg material at various angles. However, the CTE of D263 glass is 6.3 ppm/ C at 20 C, which is quite high, and actually unachievable solely with carbon fiber and resin. A composite laminate has been developed that has a coefficient of thermal expansion identical to that of SCHOTT D263 glass. The laminate is made of a combination of T300 carbon fiber, Eglass, and RS3C resin. The laminate has 50% uni-T300 plies and 50% uni-E-glass plies, with each fiber-layer type laid up in a quasi-isotropic laminate for a total of 16 plies. The fiber volume (percent of fiber compared to the resin) controls the CTE to a great extent. Tests have confirmed that a fiber volume around 48% gives a CTE of 6.3 ppm/ C. This is a fairly simple composite laminate, following well established industry procedures. The unique feature of this laminate is a somewhat unusual combination of carbon fiber with E-glass (fiberglass). The advantage is that the resulting CTE comes out to 6.3 ppm/ C at 20 C, which matches D263 glass. The trick with this laminate is to establish the proper fiber volume to get the desired CTE. Laminates were made with several different fiber volumes and coupons were tested to establish the relationship between fiber volume and CTE. Testing proved that fiber volume should be about 48%.
Effect of the Different High Volume Fraction of SiC Particles on the Junction of Bismuthate Glass-SiCp/Al Composite

PubMed Central

Li, Xiaoqiang

2018-01-01

The in-house developed bismuthate glass and the SiCp/Al composites with different volume fractions of SiC particles (namely, 60 vol.%, 65 vol.%, 70 vol.%, and 75 vol.%) were jointed by vacuum hot-pressing process. The novel material can be used for the space mirror. The SiCp is an abbreviation for SiC particle. Firstly, the SiCp/Al composites with different vol.% of SiC particle were manufactured by using infiltration process. In order to obtain a stable bonding interface, the preoxide layers were fabricated on the surfaces of these composites for reacting with the bismuthate glass. The coefficient of thermal expansion (CTE) was carried out for characterizing the difference between the composites and bismuthate glass. The sealing quality of the composites and the bismuthate glass was quantified by using shear strength testing. The optical microstructures showed the particles were uniformly distributed in the Al matrix. The SEM image shows that a smooth oxidation layer was generated on the SiCp/Al composite. The CTE testing result indicated that the higher the vol.% of the particles in the composite, the lower the CTE value. The shear strength testing result disclosed that SiCp/Al composite with relatively low CTE value was favorable to obtain a bonding interface with high strength. PMID:29675118
Microstructure, Thermal, Mechanical, and Dielectric Properties of BaO-CaO-Al2O3-B2O3-SiO2 Glass-Ceramics

NASA Astrophysics Data System (ADS)

Li, Bo; Bian, Haibo; Fang, Yi

2017-12-01

BaO-CaO-Al2O3-B2O3-SiO2 (BCABS) glass-ceramics were prepared via the method of controlled crystallization. The effect of CaO modification on the microstructure, phase evolution, as well as thermal, mechanical, and dielectric properties was investigated. XRD identified that quartz is the major crystal phase; cristobalite and bazirite are the minor crystal phases. Moreover, the increase of CaO could inhibit the phase transformation from quartz to cristobalite, but excessive CaO would increase the porosity of the ceramics. Additionally, with increasing the amount of CaO, the thermal expansion curve tends to be linear, and subsequently the CTE value decreases gradually, which is attributed to the decrease of cristobalite with high CTE and the formation of CaSiO3 with low CTE. The results indicated that a moderate amount of CaO helps attaining excellent mechanical, thermal, and dielectric properties, that is, the specimen with 9 wt% CaO sintered at 950 °C has a high CTE value (11.5 × 10-6/°C), a high flexural strength (165.7 MPa), and good dielectric properties (ɛr = 6.2, tanδ = 1.8 × 10-4, ρ = 4.6 × 1011 Ω•cm).
Effect of the Different High Volume Fraction of SiC Particles on the Junction of Bismuthate Glass-SiCp/Al Composite.

PubMed

Wang, Bin; Qu, Shengguan; Li, Xiaoqiang

2018-01-01

The in-house developed bismuthate glass and the SiC p /Al composites with different volume fractions of SiC particles (namely, 60 vol.%, 65 vol.%, 70 vol.%, and 75 vol.%) were jointed by vacuum hot-pressing process. The novel material can be used for the space mirror. The SiCp is an abbreviation for SiC particle. Firstly, the SiC p /Al composites with different vol.% of SiC particle were manufactured by using infiltration process. In order to obtain a stable bonding interface, the preoxide layers were fabricated on the surfaces of these composites for reacting with the bismuthate glass. The coefficient of thermal expansion (CTE) was carried out for characterizing the difference between the composites and bismuthate glass. The sealing quality of the composites and the bismuthate glass was quantified by using shear strength testing. The optical microstructures showed the particles were uniformly distributed in the Al matrix. The SEM image shows that a smooth oxidation layer was generated on the SiC p /Al composite. The CTE testing result indicated that the higher the vol.% of the particles in the composite, the lower the CTE value. The shear strength testing result disclosed that SiC p /Al composite with relatively low CTE value was favorable to obtain a bonding interface with high strength.
Effect of space exposure of some epoxy matrix composites on their thermal expansion and mechanical properties (AO 138-8)

NASA Technical Reports Server (NTRS)

Jabs, Heinrich

1991-01-01

The experiment objectives are: to detect a variation of the coefficient of thermal expansion (CTE) of composite samples; to detect an evolution of mechanical properties; to compare the behavior of two epoxy resins. The CTE is measured by interferometric method in a vacuum chamber. The following mechanical tests are achieved on the samples: interlaminar shear strength; flexural strength; flatwise tensile strength. The results are reported.
Near zero coefficient of thermal expansion of beta-eucryptite without microcracking

DOEpatents

Reimanis, Ivar; Ramalingam, Subramanian

2015-06-16

The present invention is drawn to a lithia alumina silica material that exhibits a low CTE over a broad temperature range and a method of making the same. The low CTE of the material allows for a decrease in microcracking within the material.
Thermomechanical properties of zirconium tungstate/hydrogenated nitrile butadiene rubber (HNBR) composites for low-temperature applications

NASA Astrophysics Data System (ADS)

Akulichev, Anton G.; Alcock, Ben; Tiwari, Avinash; Echtermeyer, Andreas T.

2016-12-01

Rubber compounds for pressure sealing application typically have inferior dimensional stability with temperature fluctuations compared with their steel counterparts. This effect may result in seal leakage failures when subjected to decreases in temperature. Composites of hydrogenated nitrile butadiene rubber (HNBR) and zirconium tungstate as a negative thermal expansion filler were prepared in order to control the thermal expansivity of the material. The amount of zirconium tungstate (ZrW2O8) was varied in the range of 0 to about 40 vol%. The coefficient of thermal expansion (CTE), bulk modulus, uniaxial extension and compression set properties were measured. The CTE of the ZrW2O8-filled HNBR decreases with the filler content and it is reduced by a factor of 2 at the highest filler concentration used. The filler effect on CTE is found to be stronger when HNBR is below the glass transition temperature. The experimental thermal expansion data of the composites are compared with the theoretical estimates and predictions given by FEA. The effect of ZrW2O8 on the mechanical characteristics and compression set of these materials is also discussed.
Thermal expansion coefficient determination of polylactic acid using digital image correlation

NASA Astrophysics Data System (ADS)

Botean, Adrian-Ioan

2018-02-01

This paper aims determining the linear thermal expansion coefficient (CTE) of polylactic acid (PLA) using an optical method for measuring deformations called digital image correlation method (DIC). Because PLA is often used in making many pieces with 3D printing technology, it is opportune to know this coefficient to obtain a higher degree of precision in the construction of parts and to monitor deformations when these parts are subjected to a thermal gradient. Are used two PLA discs with 20 and 40% degree of filling. In parallel with this approach was determined the linear thermal expansion coefficient (CTE) for the copper cylinder on the surface of which are placed the two discs of PLA.
Lightweighted ZERODUR for telescopes

NASA Astrophysics Data System (ADS)

Westerhoff, T.; Davis, M.; Hartmann, P.; Hull, T.; Jedamzik, R.

2014-07-01

The glass ceramic ZERODUR® from SCHOTT has an excellent reputation as mirror blank material for earthbound and space telescope applications. It is known for its extremely low coefficient of thermal expansion (CTE) at room temperature and its excellent CTE homogeneity. Recent improvements in CNC machining at SCHOTT allow achieving extremely light weighted substrates up to 90% incorporating very thin ribs and face sheets. In 2012 new ZERODUR® grades EXPANSION CLASS 0 SPECIAL and EXTREME have been released that offer the tightest CTE grades ever. With ZERODUR® TAILORED it is even possible to offer ZERODUR® optimized for customer application temperature profiles. In 2013 SCHOTT started the development of a new dilatometer setup with the target to drive the industrial standard of high accuracy thermal expansion metrology to its limit. In recent years SCHOTT published several paper on improved bending strength of ZERODUR® and lifetime evaluation based on threshold values derived from 3 parameter Weibull distribution fitted to a multitude of stress data. ZERODUR® has been and is still being successfully used as mirror substrates for a large number of space missions. ZERODUR® was used for the secondary mirror in HST and for the Wolter mirrors in CHANDRA without any reported degradation of the optical image quality during the lifetime of the missions. Some years ago early studies on the compaction effects of electron radiation on ZERODUR® were re analyzed. Using a more relevant physical model based on a simplified bimetallic equation the expected deformation of samples exposed in laboratory and space could be predicted in a much more accurate way. The relevant ingredients for light weighted mirror substrates are discussed in this paper: substrate material with excellent homogeneity in its properties, sufficient bending strengths, space radiation hardness and CNC machining capabilities.
Mechanical, electrical, and thermal expansion properties of carbon nanotube-based silver and silver-palladium alloy composites

NASA Astrophysics Data System (ADS)

Pal, Hemant; Sharma, Vimal

2014-11-01

The mechanical, electrical, and thermal expansion properties of carbon nanotube (CNT)-based silver and silver-palladium (10:1, w/w) alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver-palladium nanocomposite with CNT resulted in increases in the hardness and Young's modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion (CTE). The hardness and Young's modulus of the nanocomposites were increased by 30%-40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver-palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.
Measurements of thermal conductivity and the coefficient of thermal expansion for polysilicon thin films by using double-clamped beams

NASA Astrophysics Data System (ADS)

Liu, Haiyun; Wang, Lei

2018-01-01

In this paper, a test structure for simultaneously determining thermal conductivity and the coefficient of thermal expansion (CTE) of polysilicon thin film is proposed. The test structure consists of two double-clamped beams with different lengths. A theoretical model for extracting thermal conductivity and CTE based on electrothermal analysis and resonance frequency approach is developed. Both flat and buckled beams are considered in the theoretical model. The model is confirmed by finite element software ANSYS. The test structures are fabricated by surface micromachined fabrication process. Experiments are carried out in our atmosphere. Thermal conductivity and CTE of polysilicon thin film are obtained to be (29.96 ± 0.92) W · m · K-1 and (2.65 ± 0.03) × 10-6 K-1, respectively, with temperature ranging from 300-400 K.
Thermal expansion and phase transitions of α-AlF{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morelock, Cody R.; Hancock, Justin C.; Wilkinson, Angus P., E-mail: angus.wilkinson@chemistry.gatech.edu

ReO{sub 3}-type materials are of interest for their potential low or negative thermal expansion. Many metal trifluorides MF{sub 3} adopt the cubic form of this structure at elevated temperatures, which rhombohedrally distorts upon cooling. The rhombohedral form displays strong positive volume thermal expansion, but cubic MF{sub 3} display much lower and sometimes negative thermal expansion. The expansion behavior of α-AlF{sub 3} was characterized via synchrotron powder diffraction between 323 and 1177 K. α-AlF{sub 3} is rhombohedral at ambient conditions and displays strongly anisotropic thermal expansion. The volume coefficient of thermal expansion (CTE), α{sub V}, at 500 K is ∼86 ppmmore » K{sup −1}, but the linear CTE along the c-axis, α{sub c}, is close to zero. α-AlF{sub 3} becomes cubic on heating to ∼713 K and continues to show positive thermal expansion above the phase transition (α{sub V}(900 K) ∼25 ppm K{sup −1}). - Graphical abstract: α-AlF{sub 3} has a rhombohedrally distorted ReO{sub 3}-type structure at ambient conditions and displays strongly positive volume thermal expansion that is highly anisotropic; the material becomes cubic on heating above ∼713 K and continues to show positive thermal expansion. - Highlights: • ReO{sub 3}-type α-AlF{sub 3} displays strongly anisotropic thermal expansion below 713 K. • α-AlF{sub 3} is cubic above 713 K and maintains positive (isotropic) thermal expansion. • The volume CTE changes from ∼86 to ∼25 ppm K{sup −1} on heating from 500 to 900 K. • The PTE of cubic α-AlF{sub 3} may be due to the presence of local octahedral tilts.« less
Elasto-plastic analysis of interface layers for fiber reinforced metal matrix composites

NASA Technical Reports Server (NTRS)

Doghri, I.; Leckie, F. A.

1991-01-01

The mismatch in coefficients of thermal expansion (CTE) of fiber and matrix in metal matrix composites reinforced with ceramic fibers induces high thermal stresses in the matrix. Elasto-plastic analyses - with different degrees of simplification and modelization - show that an interface layer with a sufficiently high CTE can reduce the tensile hoop stress in the matrix substantially.
The Effect of Compositional Tailoring on the Thermal Expansion and Tribological Properties of PS300: A Solid Lubricant Composite Coating

NASA Technical Reports Server (NTRS)

DellaCorte, C.; Fellenstein, J. A.

1996-01-01

This paper describes a research program in which the goal is to alter the thermal expansion coefficient of a composite solid lubricant coating, PS300, by compositional tailoring. PS300 is a plasma sprayed coating consisting of chrome oxide, silver and barium fluoride/calcium fluoride eutectic in NiCr binder. By adjusting the composition, the thermal expansion coefficient can be altered, and hence chosen, to more closely match a selected substrate preventing coating spallation at extreme temperatures. Thermal expansion coefficients (CTE) for a variety of compositions were measured from 25 to 800 C using a commercial dilatometer. The CTE's ranged from 7.0 to 13 x lO(exp -6)/deg C depending on the binder content. Subsequent tribological testing of a modified composition indicated that friction and wear properties were relatively insensitive to compositional tailoring.
Tunable thermal expansion and magnetism in Zr-doped ScF 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Tao; Xu, Jiale; Hu, Lei

The negative thermal expansion (NTE) behavior provides us an opportunity to design materials with controllable coefficient of thermal expansion (CTE). In this letter, we report a tunable isotropic thermal expansion in the cubic (Sc1-xZrx)F3+δ over a wide temperature and CTE range (αl = -4.0 to +16.8 x 10-6 K-1, 298–648 K). The thermal expansion can be well adjusted from strong negative to zero, and finally to large positive. Intriguingly, isotropic zero thermal expansion (αl = 2.6 x 10-7 K-1, 298–648 K) has been observed in the composition of (Sc0.8Zr0.2)F3+δ. The controllable thermal expansion in (Sc1-xZrx)F3+δ is correlated to the localmore » structural distortion. Interestingly, the ordered magnetic behavior has been found in the zero thermal expansion compound of (Sc0.8Zr0.2)F3+δ at room temperature, which presumably correlates with the unpaired electron of the lower chemical valence of Zr cation. The present study provides a useful reference to control the thermal expansion and explore the multi-functionalization for NTE materials.« less
The Community Must Work for CTE

ERIC Educational Resources Information Center

Green, Kimberly

2011-01-01

Funding threats have long loomed over career and technical education (CTE). However, congressional advocates have faithfully preserved investments in CTE--until fiscal year 2011. Global competition and a weak economy are game changers in terms of how policymakers perceive the value of CTE and education overall. And the CTE community must convince…
Carbon nanotube-copper exhibiting metal-like thermal conductivity and silicon-like thermal expansion for efficient cooling of electronics.

PubMed

Subramaniam, Chandramouli; Yasuda, Yuzuri; Takeya, Satoshi; Ata, Seisuke; Nishizawa, Ayumi; Futaba, Don; Yamada, Takeo; Hata, Kenji

2014-03-07

Increasing functional complexity and dimensional compactness of electronic devices have led to progressively higher power dissipation, mainly in the form of heat. Overheating of semiconductor-based electronics has been the primary reason for their failure. Such failures originate at the interface of the heat sink (commonly Cu and Al) and the substrate (silicon) due to the large mismatch in thermal expansion coefficients (∼300%) of metals and silicon. Therefore, the effective cooling of such electronics demands a material with both high thermal conductivity and a similar coefficient of thermal expansion (CTE) to silicon. Addressing this demand, we have developed a carbon nanotube-copper (CNT-Cu) composite with high metallic thermal conductivity (395 W m(-1) K(-1)) and a low, silicon-like CTE (5.0 ppm K(-1)). The thermal conductivity was identical to that of Cu (400 W m(-1) K(-1)) and higher than those of most metals (Ti, Al, Au). Importantly, the CTE mismatch between CNT-Cu and silicon was only ∼10%, meaning an excellent compatibility. The seamless integration of CNTs and Cu was achieved through a unique two-stage electrodeposition approach to create an extensive and continuous interface between the Cu and CNTs. This allowed for thermal contributions from both Cu and CNTs, resulting in high thermal conductivity. Simultaneously, the high volume fraction of CNTs balanced the thermal expansion of Cu, accounting for the low CTE of the CNT-Cu composite. The experimental observations were in good quantitative concurrence with the theoretically described 'matrix-bubble' model. Further, we demonstrated identical in-situ thermal strain behaviour of the CNT-Cu composite to Si-based dielectrics, thereby generating the least interfacial thermal strain. This unique combination of properties places CNT-Cu as an isolated spot in an Ashby map of thermal conductivity and CTE. Finally, the CNT-Cu composite exhibited the greatest stability to temperature as indicated by its low thermal distortion parameter (TDP). Thus, this material presents a viable and efficient alternative to existing materials for thermal management in electronics.
Advances in photonics thermal management and packaging materials

NASA Astrophysics Data System (ADS)

Zweben, Carl

2008-02-01

Heat dissipation, thermal stresses, and cost are key packaging design issues for virtually all semiconductors, including photonic applications such as diode lasers, light-emitting diodes (LEDs), solid state lighting, photovoltaics, displays, projectors, detectors, sensors and laser weapons. Heat dissipation and thermal stresses affect performance and reliability. Copper, aluminum and conventional polymeric printed circuit boards (PCBs) have high coefficients of thermal expansion, which can cause high thermal stresses. Most traditional low-coefficient-of-thermal-expansion (CTE) materials like tungsten/copper, which date from the mid 20 th century, have thermal conductivities that are no better than those of aluminum alloys, about 200 W/m-K. There are an increasing number of low-CTE materials with thermal conductivities ranging between that of copper (400 W/m-K) and 1700 W/m-K, and many other new low-CTE materials with lower thermal conductivities. An important benefit of low-CTE materials is that they allow use of hard solders. Some advanced materials are low cost. Others have the potential to be low cost in high-volume production. High-thermal-conductivity materials enable higher power levels, potentially reducing the number of required devices. Advanced thermal materials can constrain PCB CTE and greatly increase thermal conductivity. This paper reviews traditional packaging materials and advanced thermal management materials. The latter provide the packaging engineer with a greater range of options than in the past. Topics include properties, status, applications, cost, using advanced materials to fix manufacturing problems, and future directions, including composites reinforced with carbon nanotubes and other thermally conductive materials.
Determination of coefficient of thermal expansion effects on Louisiana's PCC pavement design.

DOT National Transportation Integrated Search

2011-12-01

With the development of the Mechanistic Empirical Pavement Design Guide (MEPDG) as a new pavement design tool, the : coefficient of thermal expansion (CTE) is now considered a more important design parameter in estimating pavement : performance inclu...
Chronic traumatic encephalopathy in contact sports: a systematic review of all reported pathological cases.

PubMed

Maroon, Joseph C; Winkelman, Robert; Bost, Jeffrey; Amos, Austin; Mathyssek, Christina; Miele, Vincent

2015-01-01

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with head trauma. Although initially believed to affect only boxers, the at-risk population has expanded to encompass a much wider demographic, including American football players, hockey players, wrestlers, and military veterans. This expansion has garnered considerable media attention and public concern for the potential neurodegenerative effects of head trauma. The main aim of this systematic review is to give a complete overview of the common findings and risk factors for CTE as well as the status quo regarding the incidence and prevalence of CTE. This systematic review was performed using PubMed and MEDLINE and includes all neuropathologically confirmed cases of CTE in the medical literature to date, from the first published case in 1954 to August 1, 2013 (n = 153). The demographics, including the primary source of mTBI (mild Traumatic Brain Injury), age and cause of death, ApoE genotype, and history of substance abuse, when listed, were obtained from each case report. The demographics of American football players found to have CTE are also presented separately in order to highlight the most prevalent group of CTE cases reported in recent years. These 153 case reports of CTE represent the largest collection to date. We found that a history of mTBI was the only risk factor consistently associated with CTE. In addition, we found no relationships between CTE and age of death or abnormal ApoE allele. Suicide and the presence of premorbid dementia was not strongly associated with CTE. We conclude that the incidence of CTE remains unknown due to the lack of large, longitudinal studies. Furthermore, the neuropathological and clinical findings related to CTE overlap with many common neurodegenerative diseases. Our review reveals significant limitations of the current CTE case reporting and questions the widespread existence of CTE in contact sports.

Chronic Traumatic Encephalopathy in Contact Sports: A Systematic Review of All Reported Pathological Cases

PubMed Central

Maroon, Joseph C.; Winkelman, Robert; Bost, Jeffrey; Amos, Austin; Mathyssek, Christina; Miele, Vincent

2015-01-01

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with head trauma. Although initially believed to affect only boxers, the at-risk population has expanded to encompass a much wider demographic, including American football players, hockey players, wrestlers, and military veterans. This expansion has garnered considerable media attention and public concern for the potential neurodegenerative effects of head trauma. The main aim of this systematic review is to give a complete overview of the common findings and risk factors for CTE as well as the status quo regarding the incidence and prevalence of CTE. This systematic review was performed using PubMed and MEDLINE and includes all neuropathologically confirmed cases of CTE in the medical literature to date, from the first published case in 1954 to August 1, 2013 (n = 153). The demographics, including the primary source of mTBI (mild Traumatic Brain Injury), age and cause of death, ApoE genotype, and history of substance abuse, when listed, were obtained from each case report. The demographics of American football players found to have CTE are also presented separately in order to highlight the most prevalent group of CTE cases reported in recent years. These 153 case reports of CTE represent the largest collection to date. We found that a history of mTBI was the only risk factor consistently associated with CTE. In addition, we found no relationships between CTE and age of death or abnormal ApoE allele. Suicide and the presence of premorbid dementia was not strongly associated with CTE. We conclude that the incidence of CTE remains unknown due to the lack of large, longitudinal studies. Furthermore, the neuropathological and clinical findings related to CTE overlap with many common neurodegenerative diseases. Our review reveals significant limitations of the current CTE case reporting and questions the widespread existence of CTE in contact sports. PMID:25671598
Pore size and concentration effect of mesoporous silica nanoparticles on the coefficient of thermal expansion and optical transparency of poly(ether sulfone) films.

PubMed

Vo, Nhat Tri; Patra, Astam K; Kim, Dukjoon

2017-01-18

Mesoporous silica nanoparticles (MSNs) with uniform size (<50 nm) yet with different pore diameters were synthesized, and used as fillers in poly(ether sulfone) (PES) films in order to decrease their coefficient of thermal expansion (CTE) without sacrificing optical transparency. Here, both CTE and optical transparency of the MSN/PES nanocomposite films gradually decreased with increasing MSN concentration. The PES films containing MSNs with larger pores showed the best performance in CTE and optical transparency. While the CTE decreased by 32.3% with increasing MSN content up to 0.5 wt%, the optical transparency decreased by only less than 6.9% because of the small and uniform particle size of less than 50 nm, which minimizes light scattering. This pore size effect is more clearly observed via an annealing process, which enables the polymer chains to slowly move and fill in the free volume in the pores of the MSN, and thus restricts the thermal motion. The effect of the silica nanoparticles was investigated not only on the thermal stability but also on the mechanical stability. We expect the MSNs synthesized in this study to be used as a promising filler to enhance the thermal and mechanical stability of the PES substrate without sacrificing its optical transparency.
Determination of coefficient of thermal expansion for Portland Cement Concrete pavements for MEPDG Implementation

DOT National Transportation Integrated Search

2012-10-01

The Coefficient of Thermal Expansion (CTE) is an important parameter in Portland Cement Concrete (PCC) pavement analysis and design as it is directly proportional to the magnitude of temperature-related pavement deformations throughout the pavement s...
Determination of coefficient of thermal expansion For Portland Cement Concrete pavements for MEPDG Implementation

DOT National Transportation Integrated Search

2012-10-01

The Coefficient of Thermal Expansion (CTE) is an important parameter in Portland Cement Concrete (PCC) pavement analysis and design as it is directly proportional to the magnitude of temperature-related pavement deformations throughout the pavement s...
Measurement of Linear Coefficient of Thermal Expansion and Temperature-Dependent Refractive Index Using Interferometric System

NASA Technical Reports Server (NTRS)

Corsetti, James A.; Green, William E.; Ellis, Jonathan D.; Schmidt, Greg R.; Moore, Duncan T.

2017-01-01

A system combining an interferometer with an environmental chamber for measuring both coefficient of thermal expansion (CTE) and temperature-dependent refractive index (dn/dT) simultaneously is presented. The operation and measurement results of this instrument are discussed.
Determination of coefficient of thermal expansion effects on Louisiana's PCC pavement design : technical summary report.

DOT National Transportation Integrated Search

2011-12-01

The coefficient of thermal expansion (CTE) has been widely considered as a fundamental property of : Portland cement concrete (PCC) pavement but has never played an important role in the thickness design : procedure for PCC pavement until recently. I...
Zirconium tungstate/epoxy nanocomposites: effect of nanoparticle morphology and negative thermal expansivity.

PubMed

Wu, Hongchao; Rogalski, Mark; Kessler, Michael R

2013-10-09

The ability to tailor the coefficient of thermal expansion (CTE) of a polymer is essential for mitigating thermal residual stress and reducing microcracks caused by CTE mismatch of different components in electronic applications. This work studies the effect of morphology and thermal expansivity of zirconium tungstate nanoparticles on the rheological, thermo-mechanical, dynamic-mechanical, and dielectric properties of ZrW2O8/epoxy nanocomposites. Three types of ZrW2O8 nanoparticles were synthesized under different hydrothermal conditions and their distinct properties were characterized, including morphology, particle size, aspect ratio, surface area, and CTE. Nanoparticles with a smaller particle size and larger surface area led to a more significant reduction in gel-time and glass transition temperature of the epoxy nanocomposites, while a higher initial viscosity and significant shear thinning behavior was found in prepolymer suspensions containing ZrW2O8 with larger particle sizes and aspect ratios. The thermo- and dynamic-mechanical properties of epoxy-based nanocomposites improved with increasing loadings of the three types of ZrW2O8 nanoparticles. In addition, the introduced ZrW2O8 nanoparticles did not negatively affect the dielectric constant or the breakdown strength of the epoxy resin, suggesting potential applications of ZrW2O8/epoxy nanocomposites in the microelectronic insulation industry.
Elevated temperature mechanical behavior of new low CTE superalloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowen, C.J.; Jablonski, P.D.

This paper presents the high temperature mechanical properties of several experimental low coefficient of thermal expansion (CTE) alloys. The use of such alloys facilitate the extension of advanced ferritic stainless steels to higher use temperature in advanced power generation systems. We find that one of these alloys, J5 appears to be favorable for bridging ferritic alloys (operating up to ~600°C) to traditional nickel based superalloys (operating at 750°C).
Mechanical and thermal properties of MoS2 reinforced epoxy nanocomposites

NASA Astrophysics Data System (ADS)

Madeshwaran, S. R.; Jayaganthan, R.; Velmurugan, R.; Gupta, N. K.; Manzhirov, A. V.

2018-04-01

The effects of molybdenum disulfide (MoS2) on thermal expansion and mechanical properties of epoxy composites were investigated. MoS2 nanosheets were exfoliated by ultra-sonication and reinforced into epoxy as nanofiller by mechanical stirring. Transmission electron microscopy observations demonstrated that MoS2 exhibited better dispersion in epoxy matrix. Thermal expansion measured by dilatometer has revealed that increasing MoS2 fractioninepoxy matrix significantly reduced the coefficient of thermal expansion (CTE). The 0.5wt% MoS2 incorporated epoxy composites shows 35.8% reduction in CTE as compared to neat epoxy. The addition of small fraction of MoS2(0.1wt%) in the composites increased the tensile and flexural strength 39.2% and 9.0% respectively. The glass transition temperature (Tg ) of 0.1wt% MoS2 incorporated epoxy composites shows 7.39% increase in Tg .
Effect of moisture content on the coefficient of thermal expansion of concrete.

DOT National Transportation Integrated Search

2007-09-01

The purpose of this report is to discuss a study conducted on twenty separate mix designs of concrete and the effects of : the aggregate type, moisture content, and temperature on the coefficient of thermal expansion(CTE). These results are to be use...
Educators' Perceptions and Value of Career and Technical Education Programs

ERIC Educational Resources Information Center

Shanklin, Stacey L.

2014-01-01

It is not known the extent to which CTE teachers compared to core teachers, student advisors, and administrators perceive the value of CTE programs in relationship to the 21st century skills needed for success in employment and postsecondary endeavors and the professional relationships needed to adequately support and grow CTE programs. The sample…
CORRELATION BETWEEN METAL-CERAMIC BOND STRENGTH AND COEFFICIENT OF LINEAR THERMAL EXPANSION DIFFERENCE

PubMed Central

Lopes, Stella Crosara; Pagnano, Valéria Oliveira; Rollo, João Manuel Domingos de Almeida; Leal, Mônica Barbosa; Bezzon, Osvaldo Luiz

2009-01-01

The purpose of this study was to evaluate the metal-ceramic bond strength (MCBS) of 6 metal-ceramic pairs (2 Ni-Cr alloys and 1 Pd-Ag alloy with 2 dental ceramics) and correlate the MCBS values with the differences between the coefficients of linear thermal expansion (CTEs) of the metals and ceramics. Verabond (VB) Ni-Cr-Be alloy, Verabond II (VB2), Ni-Cr alloy, Pors-on 4 (P), Pd-Ag alloy, and IPS (I) and Duceram (D) ceramics were used for the MCBS test and dilatometric test. Forty-eight ceramic rings were built around metallic rods (3.0 mm in diameter and 70.0 mm in length) made from the evaluated alloys. The rods were subsequently embedded in gypsum cast in order to perform a tensile load test, which enabled calculating the CMBS. Five specimens (2.0 mm in diameter and 12.0 mm in length) of each material were made for the dilatometric test. The chromel-alumel thermocouple required for the test was welded into the metal test specimens and inserted into the ceramics. ANOVA and Tukey's test revealed significant differences (p=0.01) for the MCBS test results (MPa), with PI showing higher MCBS (67.72) than the other pairs, which did not present any significant differences. The CTE (10-6 °C-1) differences were: VBI (0.54), VBD (1.33), VB2I (-0.14), VB2D (0.63), PI (1.84) and PD (2.62). Pearson's correlation test (r=0.17) was performed to evaluate of correlation between MCBS and CTE differences. Within the limitations of this study and based on the obtained results, there was no correlation between MCBS and CTE differences for the evaluated metal-ceramic pairs. PMID:19274398
Thermal Properties of Oxides With Magnetoplumbite Structure for Advanced Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Zhu, Dongming; Eslamloo-Grami, Maryam

2007-01-01

Oxides having magnetoplumbite structure are promising candidate materials for applications as high temperature thermal barrier coatings because of their high thermal stability, high thermal expansion, and low thermal conductivity. In this study, powders of LaMgAl11O19, GdMgAl11O19, SmMgAl11O19, and Gd0.7Yb0.3MgAl11O19 magnetoplumbite oxides were synthesized by citric acid sol-gel method and hot pressed into disk specimens. The thermal expansion coefficients (CTE) of these oxide materials were measured from room temperature to 1500 C. The average CTE value was found to be approx.9.6x10(exp -6)/C. Thermal conductivity of these magnetoplumbite-based oxide materials was also evaluated using steady-state laser heat flux test method. The effects of doping on thermal properties were also examined. Thermal conductivity of the doped Gd0.7Yb0.3MgAl11O19 composition was found to be lower than that of the undoped GdMgAl11O19. In contrast, thermal expansion coefficient was found to be independent of the oxide composition and appears to be controlled by the magnetoplumbite crystal structure. Thermal conductivity testing of LaMgAl11O19 and LaMnAl11O19 magnetoplumbite oxide coatings plasma sprayed on NiCrAlY/Rene N5 superalloy substrates indicated resistance of these coatings to sintering even at temperatures as high as 1600 C.
Recording and reading temperature tolerance in holographic data storage, in relation to the anisotropic thermal expansion of a photopolymer medium.

PubMed

Tanaka, Tomiji

2009-08-03

In holographic data storage, it is difficult to retrieve data if the temperature difference between recording and reading exceeds 2 K. To widen this tolerance, a compensation method--adjusting the wavelengths and incident directions of the recording and reading beams--has been proposed. In this paper, for the first time, a method for calculating the recording and reading temperature tolerance using this compensation is introduced. To widen the narrow tolerance, typically +/- 10 K, it is effective to increase the coefficient of thermal expansion (CTE) of the substrate or decrease the CTE of the photopolymer. Although reducing the Numerical aperture of the objective lens is also effective, it degrades the recording density.
Physical and Mechanical Properties of LoVAR: A New Lightweight Particle-Reinforced Fe-36Ni Alloy

NASA Technical Reports Server (NTRS)

Stephenson, Timothy; Tricker, David; Tarrant, Andrew; Michel, Robert; Clune, Jason

2015-01-01

Fe-36Ni is an alloy of choice for low thermal expansion coefficient (CTE) for optical, instrument and electrical applications in particular where dimensional stability is critical. This paper outlines the development of a particle-reinforced Fe-36Ni alloy that offers reduced density and lower CTE compared to the matrix alloy. A summary of processing capability will be given relating the composition and microstructure to mechanical and physical properties.
Advances in LED packaging and thermal management materials

NASA Astrophysics Data System (ADS)

Zweben, Carl

2008-02-01

Heat dissipation, thermal stresses and cost are key light-emitting diode (LED) packaging issues. Heat dissipation limits power levels. Thermal stresses affect performance and reliability. Copper, aluminum and conventional polymeric printed circuit boards (PCBs) have high coefficients of thermal expansion, which can cause high thermal stresses. Most traditional low-coefficient-of-thermal-expansion (CTE) materials like tungsten/copper, which date from the mid 20th century, have thermal conductivities that are no better than those of aluminum alloys, about 200 W/m-K. An OIDA LED workshop cited a need for better thermal materials. There are an increasing number of low-CTE materials with thermal conductivities ranging between that of copper (400 W/m-K) and 1700 W/m-K, and many other low-CTE materials with lower thermal conductivities. Some of these materials are low cost. Others have the potential to be low cost in high-volume production. High-thermal-conductivity materials enable higher power levels, potentially reducing the number of required LEDs. Advanced thermal materials can constrain PCB CTE and greatly increase thermal conductivity. This paper reviews traditional packaging materials and advanced thermal management materials. The latter provide the packaging engineer with a greater range of options than in the past. Topics include properties, status, applications, cost, using advanced materials to fix manufacturing problems, and future directions, including composites reinforced with carbon nanotubes and other thermally conductive materials.
CTE Month: ACTE and Schools Celebrate the Value of CTE

ERIC Educational Resources Information Center

Kidwai, Sabrina

2010-01-01

The Association for Career and Technical Education (ACTE) and Career and Technical Student Organizations DECA and FCCLA toured career and technical education (CTE) programs and academies at Falls Church High School in Arlington, Virginia, in February. Each year, to celebrate CTE Month, ACTE visits a local school to gain a better perspective of how…
The Electrical Properties for Phenolic Isocyanate-Modified Bisphenol-Based Epoxy Resins Comprising Benzoate Group.

PubMed

Lee, Eun Yong; Chae, Il Seok; Park, Dongkyung; Suh, Hongsuk; Kang, Sang Wook

2016-03-01

Epoxy resin has been required to have a low dielectric constant (D(k)), low dissipation factor (Df), low coefficient of thermal expansion (CTE), low water absorption, high mechanical, and high adhesion properties for various applications. A series of novel phenolic isocyanate-modified bisphenol-based epoxy resins comprising benzoate group were prepared for practical electronic packaging applications. The developed epoxy resins showed highly reduced dielectric constants (D(k)-3.00 at 1 GHz) and low dissipation values (Df-0.014 at 1 GHz) as well as enhanced thermal properties.
Investigation of low glass transition temperature on COTS PEMs reliability

NASA Technical Reports Server (NTRS)

Sandor, M.; Agarwal, S.

2002-01-01

Many factors influence PEM component reliability.One of the factors that can affect PEM performance and reliability is the glass transition temperature (Tg) and the coefficient of thermal expansion (CTE) of the encapsulant or underfill. JPL/NASA is investigating how the Tg and CTE for PEMs affect device reliability under different temperature and aging conditions. Other issues with Tg are also being investigated. Some preliminary data will be presented on glass transition temperature test results conducted at JPL.
Thermal-vacuum response of polymer matrix composites in space

NASA Technical Reports Server (NTRS)

Tennyson, R. C.; Matthews, R.

1993-01-01

This report describes a thermal-vacuum outgassing model and test protocol for predicting outgassing times and dimensional changes for polymer matrix composites. Experimental results derived from 'control' samples are used to provide the basis for analytical predictions to compare with the outgassing response of Long Duration Exposure Facility (LDEF) flight samples. Coefficient of thermal expansion (CTE) data are also presented. In addition, an example is given illustrating the dimensional change of a 'zero' CTE laminate due to moisture outgassing.

Stress analyses for the glass joints of contemporary sodium sulfur batteries

NASA Astrophysics Data System (ADS)

Jung, Keeyoung; Lee, Solki; Kim, Goun; Kim, Chang-Soo

2014-12-01

During the manufacturing and thermal cycles of advanced contemporary large sized sodium sulfur (NaS) batteries, thermally driven stresses can be applied to the glass sealing joints, which may result in catastrophic cell failure. To minimize the thermal stresses at the joints, there is a need to develop a method to properly estimate the maximum thermal stresses by varying the materials properties and shapes of the sealing area, and thereby determine the properties and shapes of sealing material at the joints. In the present study, the optimum coefficient of thermal expansion (CTE) of the glass sealant and end shape of the glass sealing area (i.e., concave, flat, and convex shapes) have been determined using the finite-element analysis (FEA) computation technique. The results showed that the CTE value of 7.8 × 10-6 K-1 with a convex end shape would have the lowest stress concentration in the vicinity of glass sealing joints for the prototype tubular NaS cell design adopted in this work.
Final Shape of Precision Molded Optics: Part 2 - Validation and Sensitivity to Material Properties and Process Parameters

DTIC Science & Technology

2012-06-27

of the critical contributors to deviation include structural relaxation of the glass, thermal expansion of the molds, TRS and viscoelastic behavior...the critical contributors to deviation include structural relaxation of the glass, thermal expansion of the molds, TRS and viscoelastic behavior of the...data. In that article glass was modeled as purely viscous and thermal expansion was accounted for with a constant coefficient of thermal expansion (CTE
Transverse Coefficient of Thermal Expansion Measurements of Carbon Fibers Using ESEM at High Temperatures

NASA Technical Reports Server (NTRS)

Ochoa, O.; Jiang, J.; Putnam, D.; Lo, Z.; Ellis, A.; Effinger, Michael

2003-01-01

The transverse coefficient of thermal expansion (CTE) of single IM7, T1000, and P55 carbon fibers are measured at elevated temperatures. The specimens are prepared by press-fitting fiber tows into 0.7mm-diameter cavity in a graphite disk of 5mm in diameter and 3mm high. The specimens are placed on a crucible in an ESEM, and images of the fiber cross section are taken as the fibers are heated up to 800 C. Holding time, heating and cool down cycles are also introduced. The geometrical changes are measured using a graphics tablet. The change in area/perimeter is calculated to determine the strain and transverse CTE for each fiber. In a complimentary computational effort, displacements and stresses are calculated with finite element models.
Development of New Generation of Perspireable Skin

DTIC Science & Technology

2015-02-20

Coefficient of Thermal Expansion (CTE) material simulating Reinforced Carbon - Carbon Composites (RCC). These tiles made of different materials...Very low thermal expansion coefficient materials, Annu. Rev. Mater. Sci., 1989, 19, 59-81 3. Mittal, R. and Chaplot S.L., Lattice dynamical...thermal expansion from0.3 to 1050 Kelvin in ZrW2O8, Science, 1996, 272, 90-92 6. G. Savage, Carbon - carbon composites, New York: Chapman & Hall, pp
CRE Solvability, Nonlocal Symmetry and Exact Interaction Solutions of the Fifth-Order Modified Korteweg-de Vries Equation

NASA Astrophysics Data System (ADS)

Cheng, Wen-Guang; Qiu, De-Qin; Yu, Bo

2017-06-01

This paper is concerned with the fifth-order modified Korteweg-de Vries (fmKdV) equation. It is proved that the fmKdV equation is consistent Riccati expansion (CRE) solvable. Three special form of soliton-cnoidal wave interaction solutions are discussed analytically and shown graphically. Furthermore, based on the consistent tanh expansion (CTE) method, the nonlocal symmetry related to the consistent tanh expansion (CTE) is investigated, we also give the relationship between this kind of nonlocal symmetry and the residual symmetry which can be obtained with the truncated Painlevé method. We further study the spectral function symmetry and derive the Lax pair of the fmKdV equation. The residual symmetry can be localized to the Lie point symmetry of an enlarged system and the corresponding finite transformation group is computed. Supported by National Natural Science Foundation of China under Grant No. 11505090, and Research Award Foundation for Outstanding Young Scientists of Shandong Province under Grant No. BS2015SF009
Theoretical modelling on thermal expansion of Al, Ag and Cu nanomaterials

NASA Astrophysics Data System (ADS)

Manu, Mehul; Dubey, Vikash

2018-05-01

A simple theoretical model is developed for the calculating the coefficient of volume thermal expansion (CTE) and volume thermal expansion (VTE) of Al, Ag and Cu nanomaterials by considering the cubo-octahedral structure with the change of temperature and the cluster size. At the room temperature, the coefficient of volume thermal expansion decreases sharply below 20-25 nm and the decrement of the coefficient of volume thermal expansion becomes slower above 20-25 nm. We also saw a variation in the volume thermal expansion with the variation of temperature and cluster size. At a fixed cluster size, the volume thermal expansion increases with an increase of temperature at below the melting temperature and show a linear relation of volume thermal expansion with the temperature. At a constant temperature, the volume thermal expansion decreases rapidly with an increase in cluster size below 20-25 nm and after 20-25 nm the decrement of volume thermal expansion becomes slower with the increase of the size of the cluster. Thermal expansion is due to the anharmonicity of the atom interaction. As the temperature rises the amplitude of crystal lattice vibration increases, but the equilibrium distance shifts as the atom spend more time at distance greater than the original spacing due as the repulsion at short distance greater than the corresponding attraction at farther distance. In considering the cubo- octahedral structure with the cluster order, the model prediction on the CTE and the VTE are in good agreement with the available experimental data which demonstrate the validity of our work.
Building Academic Skills in Context: Testing the Value of Enhanced Math Learning in CTE

ERIC Educational Resources Information Center

Stone, James R., III; Alfeld, Corinne; Pearson, Donna; Lewis, Morgan V.; Jensen, Susan

2006-01-01

An experimental study tested a model for enhancing mathematics instruction in five high school career and technical education (CTE) programs (agriculture, auto technology, business/marketing, health, and information technology). The model consisted of a pedagogy and intense teacher professional development. Volunteer CTE teachers were randomly…
Atomic Linkage Flexibility Tuned Isotropic Negative, Zero, and Positive Thermal Expansion in MZrF 6 (M = Ca, Mn, Fe, Co, Ni, and Zn)

DOE PAGES

Hu, Lei; Chen, Jun; Xu, Jiale; ...

2016-10-26

The controllable isotropic thermal expansion with a broad coefficient of thermal expansion (CTE) window is intriguing but remains challenge. Herein we report a cubic MZrF 6 series (M = Ca, Mn, Fe, Co, Ni and Zn), which exhibit controllable thermal expansion over a wide temperature range and with a broader CTE window (–6.69 to +18.23 × 10 –6/K). In particular, an isotropic zero thermal expansion (ZTE) is achieved in ZnZrF 6, which is one of the rarely documented hightemperature isotropic ZTE compounds. By utilizing temperature dependent high-energy synchrotron X-ray total scattering diffraction, it is found that the flexibility of metal···Fmore » atomic linkages in MZrF 6 plays a critical role in distinct thermal expansions. The flexible metal···F atomic linkages induce negative thermal expansion (NTE) for CaZrF 6, whereas the stiff ones bring positive thermal expansion (PTE) for 6. Thermal expansion could be transformed from striking negative, to zero, and finally to considerable positive though tuning the flexibility of metal···F atomic linkages by substitution with a series of cations on M sites of MZrF 6. In conclusion, the present study not only extends the scope of NTE families and rare high-temperature isotropic ZTE compounds but also proposes a new method to design systematically controllable isotropic thermal expansion frameworks from the perspective of atomic linkage flexibility.« less
Atomic Linkage Flexibility Tuned Isotropic Negative, Zero, and Positive Thermal Expansion in MZrF 6 (M = Ca, Mn, Fe, Co, Ni, and Zn)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Lei; Chen, Jun; Xu, Jiale

The controllable isotropic thermal expansion with a broad coefficient of thermal expansion (CTE) window is intriguing but remains challenge. Herein we report a cubic MZrF 6 series (M = Ca, Mn, Fe, Co, Ni and Zn), which exhibit controllable thermal expansion over a wide temperature range and with a broader CTE window (–6.69 to +18.23 × 10 –6/K). In particular, an isotropic zero thermal expansion (ZTE) is achieved in ZnZrF 6, which is one of the rarely documented hightemperature isotropic ZTE compounds. By utilizing temperature dependent high-energy synchrotron X-ray total scattering diffraction, it is found that the flexibility of metal···Fmore » atomic linkages in MZrF 6 plays a critical role in distinct thermal expansions. The flexible metal···F atomic linkages induce negative thermal expansion (NTE) for CaZrF 6, whereas the stiff ones bring positive thermal expansion (PTE) for 6. Thermal expansion could be transformed from striking negative, to zero, and finally to considerable positive though tuning the flexibility of metal···F atomic linkages by substitution with a series of cations on M sites of MZrF 6. In conclusion, the present study not only extends the scope of NTE families and rare high-temperature isotropic ZTE compounds but also proposes a new method to design systematically controllable isotropic thermal expansion frameworks from the perspective of atomic linkage flexibility.« less
Composition-Property Correlation in B2O3-SiO2 Preform Rods Produced Using Modified Chemical Vapor Deposition Technique

NASA Astrophysics Data System (ADS)

Islam, Mohammad; Saleem, Muhammad Rizwan

2012-02-01

Due to unique optical properties of high birefringent (Hi-Bi) fibers for sensing and coherent optical communications, there is a strong interest in process optimization at preform fabrication and fiber drawing stages. Boron-doped silica cladding acts as stress-applying part resulting in polarization properties of Hi-Bi fibers that are strongly dependent on chemical composition. Using modified chemical vapor deposition (MCVD) technique, B2O3-doped silica preform rods were synthesized under different precursor gas flow conditions. Qualitative information about B2O3-SiO2 system composition was derived from etching behavior in nonbuffered HF solution and subsequent microstructural examination using scanning electron microscope. Significant degree of B2O3 incorporation was seen in case of high BCl3:SiCl4 ratio and mild oxygen-deficient processing conditions. Increasing the B2O3 content to ~26 mol% led to a corresponding increase in coefficient of thermal expansion (CTE) to a maximum value of 2.35 ppm/K. The value of refractive index (RI), on the other hand, was found to decrease with increased B2O3 incorporation. A qualitative correlation between B2O3 and SiO2 system composition and physical properties such as CTE and RI was established.
Metal-Organic-Inorganic Nanocomposite Thermal Interface Materials with Ultralow Thermal Resistances.

PubMed

Yegin, Cengiz; Nagabandi, Nirup; Feng, Xuhui; King, Charles; Catalano, Massimo; Oh, Jun Kyun; Talib, Ansam J; Scholar, Ethan A; Verkhoturov, Stanislav V; Cagin, Tahir; Sokolov, Alexei V; Kim, Moon J; Matin, Kaiser; Narumanchi, Sreekant; Akbulut, Mustafa

2017-03-22

As electronic devices get smaller and more powerful, energy density of energy storage devices increases continuously, and moving components of machinery operate at higher speeds, the need for better thermal management strategies is becoming increasingly important. The removal of heat dissipated during the operation of electronic, electrochemical, and mechanical devices is facilitated by high-performance thermal interface materials (TIMs) which are utilized to couple devices to heat sinks. Herein, we report a new class of TIMs involving the chemical integration of boron nitride nanosheets (BNNS), soft organic linkers, and a copper matrix-which are prepared by the chemisorption-coupled electrodeposition approach. These hybrid nanocomposites demonstrate bulk thermal conductivities ranging from 211 to 277 W/(m K), which are very high considering their relatively low elastic modulus values on the order of 21.2-28.5 GPa. The synergistic combination of these properties led to the ultralow total thermal resistivity values in the range of 0.38-0.56 mm 2 K/W for a typical bond-line thickness of 30-50 μm, advancing the current state-of-art transformatively. Moreover, its coefficient of thermal expansion (CTE) is 11 ppm/K, forming a mediation zone with a low thermally induced axial stress due to its close proximity to the CTE of most coupling surfaces needing thermal management.
Continued Development of a Precision Cryogenic Dilatometer for the James Webb Space Telescope

NASA Technical Reports Server (NTRS)

Karlmann, Paul B.; Dudik, Matthew J.; Halverson, Peter G.; Levine, Marie; Marcin, Martin; Peters, Robert D.; Shaklan, Stuart; VanBuren, David

2004-01-01

As part of the James Webb Space Telescope (JWST) materials working group, a novel cryogenic dilatometer was designed and built at NASA Jet Propulsion Laboratory to help address stringent coefficient of thermal expansion (CTE) knowledge requirements. Previously reported results and error analysis have estimated a CTE measurement accuracy for ULE of 1.7 ppb/K with a 20K thermal load and 0.1 ppb/K with a 280K thermal load. Presented here is a further discussion of the cryogenic dilatometer system and a description of recent work including system modifications and investigations.
Building Academic Skills in Context: Testing the Value of Enhanced Math Learning in CTE. Pilot Study

ERIC Educational Resources Information Center

Stone, James R., III; Alfeld, Corinne; Pearson, Donna; Lewis, Morgan V.; Jensen, Susan

2005-01-01

This report describes the conduct and outcomes of an experimental pilot study conducted in Spring 2004 to develop and test a model that aimed to enhance career and technical education (CTE) instruction with the mathematics already embedded in the curricula of six occupational areas. Although present in the CTE curriculum, math is largely implicit…
Lightweight, Low-CTE Tubes Made From Biaxially Oriented LCPs

NASA Technical Reports Server (NTRS)

Rubin, Leslie; Federico, Frank; Formato, Richard; Larouco, John; Slager, William

2004-01-01

Tubes made from biaxially oriented liquid-crystal polymers (LCPs) have been developed for use as penetrations on cryogenic tanks. ( Penetrations in this context denotes feed lines, vent lines, and sensor tubes, all of which contribute to the undesired conduction of heat into the tanks.) In comparison with corresponding prior cryogenic-tank penetrations made from stainless steels and nickel alloys, the LCP penetrations offer advantages of less weight and less thermal conduction. An additional major advantage of LCP components is that one can tailor their coefficients of thermal expansion (CTEs). The estimated cost of continuous production of LCP tubes of typical sizes is about $1.27/ft ($4.17/m) [based on 1998 prices]. LCP tubes that are compatible with liquid oxygen and that feature tailored biaxial molecular orientation and quasi-isotropic properties (including quasi-isotropic CTE) have been fabricated by a combination of proprietary and patented techniques that involve the use of counterrotating dies (CRDs). Tailoring of the angle of molecular orientation is what makes it possible to tailor the CTE over a wide range to match the CTEs of adjacent penetrations of other tank components; this, in turn, makes it possible to minimize differential-thermal expansion stresses that arise during thermal cycling. The fabrication of biaxially oriented LCP tubes by use of CRDs is not new in itself. The novelty of the present development lies in tailoring the orientations and thus the CTEs and other mechanical properties of the LCPs for the intended cryogenic applications and in modifications of the CRDs for this purpose. The LCP tubes and the 304-stainless-steel tubes that the LCP tubes were intended to supplant were tested with respect to burst strength, permeability, thermal conductivity, and CTE.
Material thermal inputs of Iowa materials for MEPDG : tech transfer summary.

DOT National Transportation Integrated Search

2008-02-01

The thermal properties of concrete materials, such as coeffi cient of : thermal expansion (CTE), thermal conductivity, and heat capacity, are : required by the MEPDG program as the material inputs for pavement : design. However, a limited amount of t...
Modeling the Extremely Lightweight Zerodur Mirror (ELZM) Thermal Soak Test

NASA Technical Reports Server (NTRS)

Brooks, Thomas E.; Eng, Ron; Hull, Tony; Stahl, H. Philip

2017-01-01

Exoplanet science requires extreme wavefront stability (10 pm change/10 minutes), so every source of wavefront error (WFE) must be characterized in detail. This work illustrates the testing and characterization process that will be used to determine how much surface figure error (SFE) is produced by mirror substrate materials' CTE distributions. Schott's extremely lightweight Zerodur mirror (ELZM) was polished to a sphere, mounted, and tested at Marshall Space Flight Center (MSFC) in the X-Ray and Cryogenic Test Facility (XRCF). The test transitioned the mirror's temperature from an isothermal state at 292K to isothermal states at 275K, 250K and 230K to isolate the effects of the mirror's CTE distribution. The SFE was measured interferometrically at each temperature state and finite element analysis (FEA) has been completed to assess the predictability of the change in the mirror's surface due to a change in the mirror's temperature. The coefficient of thermal expansion (CTE) distribution in the ELZM is unknown, so the analysis has been correlated to the test data. The correlation process requires finding the sensitivity of SFE to a given CTE distribution in the mirror. A novel hand calculation is proposed to use these sensitivities to estimate thermally induced SFE. The correlation process was successful and is documented in this paper. The CTE map that produces the measured SFE is in line with the measured data of typical boules of Schott's Zerodur glass.
Modeling the Extremely Lightweight Zerodur Mirror (ELZM) thermal soak test

NASA Astrophysics Data System (ADS)

Brooks, Thomas E.; Eng, Ron; Hull, Tony; Stahl, H. Philip

2017-09-01

Exoplanet science requires extreme wavefront stability (10 pm change/10 minutes), so every source of wavefront error (WFE) must be characterized in detail. This work illustrates the testing and characterization process that will be used to determine how much surface figure error (SFE) is produced by mirror substrate materials' CTE distributions. Schott's extremely lightweight Zerodur mirror (ELZM) was polished to a sphere, mounted, and tested at Marshall Space Flight Center (MSFC) in the X-Ray and Cryogenic Test Facility (XRCF). The test transitioned the mirror's temperature from an isothermal state at 292K to isothermal states at 275K, 250K and 230K to isolate the effects of the mirror's CTE distribution. The SFE was measured interferometrically at each temperature state and finite element analysis (FEA) has been completed to assess the predictability of the change in the mirror's surface due to a change in the mirror's temperature. The coefficient of thermal expansion (CTE) distribution in the ELZM is unknown, so the analysis has been correlated to the test data. The correlation process requires finding the sensitivity of SFE to a given CTE distribution in the mirror. A novel hand calculation is proposed to use these sensitivities to estimate thermally induced SFE. The correlation process was successful and is documented in this paper. The CTE map that produces the measured SFE is in line with the measured data of typical boules of Schott's Zerodur glass.
Effects of ply thickness on thermal cycle induced damage and thermal strain

NASA Astrophysics Data System (ADS)

Tompkins, Stephen S.

1994-07-01

An experimental study was conducted to determine the effects of ply thickness in composite laminates on thermally induced cracking and changes in the coefficient of thermal expansion, CTE. A graphite-epoxy composite material, P75/ERL 1962, in thin (1 mil) and thick (5 mils) prepregs was used to make cross-ply laminates, ((0/90)(sub n))s, with equal total thickness (n=2, n=10) and cross-ply laminates with the same total number of plies (n=2). Specimens of each laminate configuration were cycled up to 1500 times between -250 and 250 F. Thermally induced microdamage was assessed as a function of the number of cycles as was the change in CTE. The results showed that laminates fabricated with thin-plies microcracked at significantly different rates and reached significantly different equilibrium crack densities than the laminate fabricated with thick-ply and n=2. The CTE of thin-ply laminates was less affected by thermal cycling and damage than the CTE of thick-ply laminates. These differences are attributed primarily to differences in interply constraints. Observed effects of ply thickness on crack density was qualitatively predicted by a combined shear-lag stress/energy method.
Effects of ply thickness on thermal cycle induced damage and thermal strain

NASA Technical Reports Server (NTRS)

Tompkins, Stephen S.

1994-01-01

An experimental study was conducted to determine the effects of ply thickness in composite laminates on thermally induced cracking and changes in the coefficient of thermal expansion, CTE. A graphite-epoxy composite material, P75/ERL 1962, in thin (1 mil) and thick (5 mils) prepregs was used to make cross-ply laminates, ((0/90)(sub n))s, with equal total thickness (n=2, n=10) and cross-ply laminates with the same total number of plies (n=2). Specimens of each laminate configuration were cycled up to 1500 times between -250 and 250 F. Thermally induced microdamage was assessed as a function of the number of cycles as was the change in CTE. The results showed that laminates fabricated with thin-plies microcracked at significantly different rates and reached significantly different equilibrium crack densities than the laminate fabricated with thick-ply and n=2. The CTE of thin-ply laminates was less affected by thermal cycling and damage than the CTE of thick-ply laminates. These differences are attributed primarily to differences in interply constraints. Observed effects of ply thickness on crack density was qualitatively predicted by a combined shear-lag stress/energy method.
Thermal Expansion Behavior of Hot-Pressed Engineered Matrices

NASA Technical Reports Server (NTRS)

Raj, S. V.

2016-01-01

Advanced engineered matrix composites (EMCs) require that the coefficient of thermal expansion (CTE) of the engineered matrix (EM) matches those of the fiber reinforcements as closely as possible in order to reduce thermal compatibility strains during heating and cooling of the composites. The present paper proposes a general concept for designing suitable matrices for long fiber reinforced composites using a rule of mixtures (ROM) approach to minimize the global differences in the thermal expansion mismatches between the fibers and the engineered matrix. Proof-of-concept studies were conducted to demonstrate the validity of the concept.

Picometer resolution interferometric characterization of the dimensional stability of zero CTE CFRP

NASA Astrophysics Data System (ADS)

Cordero Machado, Jorge; Heinrich, Thomas; Schuldt, Thilo; Gohlke, Martin; Lucarelli, Stefano; Weise, Dennis; Johann, Ulrich; Peters, Achim; Braxmaier, Claus

2008-07-01

Highly stable but lightweight structural materials are essential for the realization of spaceborne optical instruments, for example telescopes. In terms of optical performance, usually tight tolerances on the absolute spacing between telescope mirrors have to be maintained from integration on ground to operation in final orbit. Furthermore, a certain stability of the telescope structure must typically be ensured in the measurement band. Particular challenging requirements have to be met for the LISA Mission (Laser Interferometer Space Antenna), where the spacing between primary and secondary mirror must be stable to a few picometers. Only few materials offer sufficient thermal stability to provide such performance. Candidates are for example Zerodur and Carbon-Fiber Reinforced Plastic (CFRP), where the latter is preferred in terms of mechanical stiffness and robustness. We are currently investigating the suitability of CFRP with respect to the LISA requirements by characterization of its dimensional stability with heterodyne laser interferometry. The special, highly symmetric interferometer setup offers a noise level of 2 pm/√Hz at 0.1Hz and above, and therefore represents a unique tool for this purpose. Various procedures for the determination of the coefficient of thermal expansion (CTE) have been investigated, both on a test sample with negative CTE, as well as on a CFRP tube specifically tuned to provide a theoretical zero expansion in the axial dimension.
Evaluation of Ni-Cr-base alloys for SOFC interconnect applications

NASA Astrophysics Data System (ADS)

Yang, Zhenguo; Xia, Guan-Guang; Stevenson, Jeffry W.

To further understand the suitability of Ni-Cr-base alloys for solid oxide fuel cell (SOFC) interconnect applications, three commercial Ni-Cr-base alloys, Haynes 230, Hastelloy S and Haynes 242 were selected and evaluated for oxidation behavior under different exposure conditions, scale conductivity and thermal expansion. Haynes 230 and Hastelloy S, which have a relatively high Cr content, formed a thin scale mainly comprised of Cr 2O 3 and (Mn,Cr,Ni) 3O 4 spinels under SOFC operating conditions, demonstrating excellent oxidation resistance and a high scale electrical conductivity. In contrast, a thick double-layer scale with a NiO outer layer above a chromia-rich substrate was grown on Haynes 242 in moist air or at the air side of dual exposure samples, indicating limited oxidation resistance for the interconnect application. With a face-centered-cubic (FCC) substrate, all three alloys possess a coefficient of thermal expansion (CTE) that is higher than that of candidate ferritic stainless steels, e.g. Crofer22 APU. Among the three alloys, Haynes 242, which is heavily alloyed with W and Mo and contains a low Cr content, demonstrated the lowest average CTE at 13.1 × 10 -6 K -1 from room temperature to 800 °C, but it was also observed that the CTE behavior of Haynes 242 was very non-linear.
Anisotropic Thermal Behavior of Silicone Polymer, DC 745

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, Jillian Cathleen; Torres, Joseph Angelo; Volz, Heather Michelle

In material applications, it is important to understand how polymeric materials behave in the various environments they may encounter. One factor governing polymer behavior is processing history. Differences in fabrication will result in parts with varied or even unintended properties. In this work, the thermal expansion behavior of silicone DC 745 is studied. Thermomechanical analysis (TMA) is used to determine changes in sample dimension resulting from changes in temperature. This technique can measure thermal events such as the linear coefficient of thermal expansion (CTE), melting, glass transitions, cure shrinkage, and internal relaxations. Using a thermomechanical analyzer (Q400 TMA), it ismore » determined that DC 745 expands anisotropically when heated. This means that the material has a different CTE depending upon which direction is being measured. In this study, TMA experiments were designed in order to confirm anisotropic thermal behavior in multiple DC 745 samples of various ages and lots. TMA parameters such as temperature ramp rate, preload force, and temperature range were optimized in order to ensure the most accurate and useful data. A better understanding of the thermal expansion of DC 745 will allow for more accurate modeling of systems using this material.« less
Metal–Organic–Inorganic Nanocomposite Thermal Interface Materials with Ultralow Thermal Resistances

DOE PAGES

Yegin, Cengiz; Nagabandi, Nirup; Feng, Xuhui; ...

2017-02-27

As electronic devices get smaller and more powerful, energy density of energy storage devices increases continuously, and moving components of machinery operate at higher speeds, the need for better thermal management strategies is becoming increasingly important. The removal of heat dissipated during the operation of electronic, electrochemical, and mechanical devices is facilitated by high-performance thermal interface materials (TIMs) which are utilized to couple devices to heat sinks. Here in this paper, we report a new class of TIMs involving the chemical integration of boron nitride nanosheets (BNNS), soft organic linkers, and a copper matrix -- which are prepared by chemisorption-coupledmore » electrodeposition approach. These hybrid nanocomposites demonstrate bulk thermal conductivities ranging from 211 to 277 W/(m.K), which are very high considering their relatively low elastic modulus values on the order of 21.2 to 28.5 GPa. The synergistic combination of these properties lead to the ultra-low total thermal resistivity values in the range of 0.38 to 0.56 mm 2.K/W for a typical bondline thickness of 30-50 um, advancing the current state-of-art transformatively. Moreover, its coefficient of thermal expansion (CTE) is 11 ppm/K, forming a mediation zone with a low thermally-induced axial stress due to its close proximity to the CTE of most coupling surfaces needing thermal management.« less
Metal–Organic–Inorganic Nanocomposite Thermal Interface Materials with Ultralow Thermal Resistances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yegin, Cengiz; Nagabandi, Nirup; Feng, Xuhui

As electronic devices get smaller and more powerful, energy density of energy storage devices increases continuously, and moving components of machinery operate at higher speeds, the need for better thermal management strategies is becoming increasingly important. The removal of heat dissipated during the operation of electronic, electrochemical, and mechanical devices is facilitated by high-performance thermal interface materials (TIMs) which are utilized to couple devices to heat sinks. Here in this paper, we report a new class of TIMs involving the chemical integration of boron nitride nanosheets (BNNS), soft organic linkers, and a copper matrix -- which are prepared by chemisorption-coupledmore » electrodeposition approach. These hybrid nanocomposites demonstrate bulk thermal conductivities ranging from 211 to 277 W/(m.K), which are very high considering their relatively low elastic modulus values on the order of 21.2 to 28.5 GPa. The synergistic combination of these properties lead to the ultra-low total thermal resistivity values in the range of 0.38 to 0.56 mm 2.K/W for a typical bondline thickness of 30-50 um, advancing the current state-of-art transformatively. Moreover, its coefficient of thermal expansion (CTE) is 11 ppm/K, forming a mediation zone with a low thermally-induced axial stress due to its close proximity to the CTE of most coupling surfaces needing thermal management.« less
Thermal-mechanical properties of a graphitic-nanofibers reinforced epoxy.

PubMed

Salehi-Khojin, Amin; Jana, Soumen; Zhong, Wei-Hong

2007-03-01

We previously developed a series of reactive graphitic nanofibers (r-GNFs) reinforced epoxy (nano-epoxy) as composite matrices, which have shown good wetting and adhesion properties with continuous fiber. In this work, the thermal-mechanical properties of the nano-epoxy system containing EponTM Resin 828 and Epi-cure Curing Agent W were characterized. Results from three-point bending tests showed that the flexural strength and flexural modulus of this system with 0.30 wt% of reactive nanofibers were increased by 16%, and 21% respectively, over pure epoxy. Fracture toughness increased by ca. 40% for specimens with 0.50 wt% of r-GNFs. By dynamic mechanical analysis (DMA) test, specimens with 0.30 wt% of r-GNFs showed a significant increase in storage modulus E' (by ca. 122%) and loss modulus E" (by ca. 111%) with respect to that of pure epoxy. Also thermo-dilatometry analysis (TDA) was used to measure dimensional change of specimens as a function of temperature, and then, coefficients of thermal expansion (CTE) before and after glass transition temperature (Tg) were obtained. Results implied that nano-epoxy materials had good dimensional stability and reduced CTE values when compared to those of pure epoxy.
High Temperature Lightweight Self-Healing Ceramic Composites for Aircraft Engine Applications

NASA Technical Reports Server (NTRS)

Raj, Sai V.; Singh, Mrityunjay; Bhatt, Ramakrishna T.

2014-01-01

The present research effort was undertaken to develop a new generation of SiC fiber- reinforced engineered matrix composites (EMCs) with sufficient high temperature plasticity to reduce crack propagation and self-healing capabilities to fill surface-connected cracks to prevent the oxygen ingress to the fibers. A matrix engineered with these capabilities is expected to increase the load bearing capabilities of SiCSiC CMCs at high temperatures. Several matrix compositions were designed to match the coefficient of thermal expansion (CTE) of the SiC fibers using a rule of mixture (ROM) approach. The CTE values of these matrices were determined and it was demonstrated that they were generally in good agreement with that of monolithic SiC between room temperature and 1525 K. The parameters to hot press the powders were optimized, and specimens were fabricated for determining bend strength, CTE, oxidation and microstructural characteristics of the engineered matrices. The oxidation tests revealed that some of the matrices exhibited catastrophic oxidation, and therefore, these were eliminated from further consideration. Two promising compositions were down selected based on these results for further development. Four-point bend tests were conducted on these two promising matrices between room temperature and 1698 K. Although theses matrices were brittle and failed at low stresses at room temperature, they exhibited high temperature ductility and higher stresses at the higher temperatures. The effects of different additives on the self-healing capabilities of these matrices were investigated. The results of preliminary studies conducted to slurry and melt infiltration trials with CrSi2 are described.
Colossal Negative Thermal Expansion in Electron-Doped PbVO3 Perovskites.

PubMed

Yamamoto, Hajime; Imai, Takashi; Sakai, Yuki; Azuma, Masaki

2018-07-02

Colossal negative thermal expansion (NTE) with a volume contraction of about 8 %, the largest value reported so far for NTE materials, was observed in an electron-doped giant tetragonal perovskite compound Pb 1-x Bi x VO 3 (x=0.2 and 0.3). A polar tetragonal (P4mm) to non-polar cubic structural transition took place upon heating. The coefficient of thermal expansion (CTE) and the working temperature could be tuned by changing the Bi content, and La substitution decreased the transition temperature to room temperature. Pb 0.76 La 0.04 Bi 0.20 VO 3 exhibited a unit cell volume contraction of 6.7 % from 200 K to 420 K. Interestingly, further gigantic NTE of about 8.5 % was observed in a dilametric measurement of a Pb 0.76 La 0.04 Bi 0.20 VO 3 polycrystalline sample. The pronounced NTE in the sintered body should be attributed to an anisotropic lattice parameter change. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
CTE method and interaction solutions for the Kadomtsev-Petviashvili equation

NASA Astrophysics Data System (ADS)

Ren, Bo

2017-02-01

The consistent tanh expansion method is applied to the Kadomtsev-Petviashvili equation. The interaction solutions among one soliton and other types of solitary waves, such as multiple resonant soliton solutions and cnoidal waves, are explicitly given. Some special concrete interaction solutions are discussed both in analytical and graphical ways.
Ceramic matrix composite turbine engine vane

NASA Technical Reports Server (NTRS)

Schaff, Jeffery R. (Inventor); Shi, Jun (Inventor)

2012-01-01

A vane has an airfoil shell and a spar within the shell. The vane has an outboard shroud at an outboard end of the shell and an inboard platform at an inboard end of the shell. The shell includes a region having a coefficient of thermal expansion (CTE) varying with depth.
A Combined Experimental and Numerical Technique to Estimate Interfacial Bond Strength in MMC-Encapsulated Ceramic Systems

DTIC Science & Technology

2013-03-01

with density, Young’s modulus, coefficient of thermal expansion , and Poisson’s ratio, of 3.2 cm 3 , 449 GPa, 4.0 × 10 –6 o C –1 , and 0.16...considers the effect of hydrostatic pressure (confinement) on the strength of ceramics and was implemented using a user subroutine in ABAQUS . The...Due to the high temperature of the encapsulation casting process and the large differential in coefficients of thermal expansion (CTE) between the MMC
Nonlocal Symmetries, Consistent Riccati Expansion, and Analytical Solutions of the Variant Boussinesq System

NASA Astrophysics Data System (ADS)

Feng, Lian-Li; Tian, Shou-Fu; Zhang, Tian-Tian; Zhou, Jun

2017-07-01

Under investigation in this paper is the variant Boussinesq system, which describes the propagation of surface long wave towards two directions in a certain deep trough. With the help of the truncated Painlevé expansion, we construct its nonlocal symmetry, Bäcklund transformation, and Schwarzian form, respectively. The nonlocal symmetries can be localised to provide the corresponding nonlocal group, and finite symmetry transformations and similarity reductions are computed. Furthermore, we verify that the variant Boussinesq system is solvable via the consistent Riccati expansion (CRE). By considering the consistent tan-function expansion (CTE), which is a special form of CRE, the interaction solutions between soliton and cnoidal periodic wave are explicitly studied.
Minimizing the bimetallic bending for cryogenic metal optics based on electroless nickel

NASA Astrophysics Data System (ADS)

Kinast, Jan; Hilpert, Enrico; Lange, Nicolas; Gebhardt, Andreas; Rohloff, Ralf-Rainer; Risse, Stefan; Eberhardt, Ramona; Tünnermann, Andreas

2014-07-01

Ultra-precise metal optics are key components of sophisticated scientific instruments in astronomy and space applications. Especially for cryogenic applications, a detailed knowledge and the control of the coefficient of thermal expansion (CTE) of the used materials are essential. Reflective optical components in IR- and NIR-instruments primarily consist of the aluminum alloy Al6061. The achievable micro-roughness of diamond machined and directly polished Al6061 does not fulfill the requirements for applications in the visible spectral range. Electroless nickel enables the reduction of the mirror surface roughness to the sub-nm range by polishing. To minimize the associated disadvantageous bimetallic effect, a novel material combination for cryogenic mirrors based on electroless nickel and hypereutectic aluminum-silicon is investigated. An increasing silicon content of the aluminum material decreases the CTE in the temperature range to be considered. This paper shows the CTE for aluminum materials containing about 42 wt% silicon (AlSi42) and for electroless nickel with a phosphorous content ranging from 10.5 to 13 %. The CTE differ to about 0.5 × 10-6 K-1 in a temperature range from -185 °C (LN2) to 100 °C. Besides, the correlations between the chemical compositions of aluminum-silicon materials and electroless nickel are shown. A metrology setup for cryo-interferometry was developed to analyze the remaining and reversible shape deviation at cryogenic temperatures. Changes could be caused by different CTE, mounting forces and residual stress conditions. In the electroless nickel layer, the resulting shape deviation can be preshaped by deterministic correction processes such as magnetorheological finishing (MRF) at room temperature.
Solid solubility, phase transitions, thermal expansion, and compressibility in Sc{sub 1−x}Al{sub x}F{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morelock, Cody R.; Gallington, Leighanne C.; Wilkinson, Angus P., E-mail: angus.wilkinson@chemistry.gatech.edu

2015-02-15

With the goal of thermal expansion control, the synthesis and properties of Sc{sub 1−x}Al{sub x}F{sub 3} were investigated. The solubility limit of AlF{sub 3} in ScF{sub 3} at ∼1340 K is ∼50%. Solid solutions (x≤0.50) were characterized by synchrotron powder diffraction at ambient pressure between 100 and 900 K and at pressures <0.414 GPa while heating from 298 to 523 K. A phase transition from cubic to rhombohedral is observed. The transition temperature increases smoothly with Al{sup 3+} content, approaching 500 K at the solid solubility limit, and also upon compression at fixed Al{sup 3+} content. The slope of themore » pressure–temperature phase boundary is ∼0.5 K MPa{sup −1}, which is steep relative to that for most symmetry-lowering phase transitions in perovskites. The volume coefficient of thermal expansion (CTE) for the rhombohedral phase is strongly positive, but the cubic-phase CTE varies from negative (x<0.15) to near-zero (x=0.15) to positive (x>0.20) between ∼600 and 800 K. The cubic solid solutions elastically stiffen on heating, while Al{sup 3+} substitution causes softening at a given temperature. - Graphical abstract: The cubic-phase coefficient of thermal expansion for Sc{sub 1−x}Al{sub x}F{sub 3}(solubility limit ∼50% at ∼1340 K) becomes more positive with increased Al{sup 3+} substitution, but the average isothermal bulk modulus decreases (elastic softening). - Highlights: • The solubility limit of AlF{sub 3} in ScF{sub 3} at ∼1340 K is ∼50%. • The phase transition temperature of Sc{sub 1−x}Al{sub x}F{sub 3} increases smoothly with x. • The cubic-phase volume CTE varies from negative to positive with increasing x. • The cubic solid solutions elastically stiffen on heating. • Al{sup 3+} substitution causes softening at a given temperature.« less
Preliminary Study of Plasma Exosomal Tau as a Potential Biomarker for Chronic Traumatic Encephalopathy.

PubMed

Stern, Robert A; Tripodis, Yorghos; Baugh, Christine M; Fritts, Nathan G; Martin, Brett M; Chaisson, Christine; Cantu, Robert C; Joyce, James A; Shah, Sahil; Ikezu, Tsuneya; Zhang, Jing; Gercel-Taylor, Cicek; Taylor, Douglas D

2016-01-01

Chronic traumatic encephalopathy (CTE) is a tauopathy associated with prior exposure to repetitive head impacts, such as those incurred through American football and other collision sports. Diagnosis is made through neuropathological examination. Many of the clinical features of CTE are common in the general population, with and without a history of head impact exposure, making clinical diagnosis difficult. As is now common in the diagnosis of other neurodegenerative disorders, such as Alzheimer's disease, there is a need for methods to diagnose CTE during life through objective biomarkers. The aim of this study was to examine tau-positive exosomes in plasma as a potential CTE biomarker. Subjects were 78 former National Football League (NFL) players and 16 controls. Extracellular vesicles were isolated from plasma. Fluorescent nanoparticle tracking analysis was used to determine the number of vesicles staining positive for tau. The NFL group had higher exosomal tau than the control group (p < 0.0001). Exosomal tau discriminated between the groups, with 82% sensitivity, 100% specificity, 100% positive predictive value, and 53% negative predictive value. Within the NFL group, higher exosomal tau was associated with worse performance on tests of memory (p = 0.0126) and psychomotor speed (p = 0.0093). These preliminary findings suggest that exosomal tau in plasma may be an accurate, noninvasive CTE biomarker.
Cryogenic Refractive Index and Coefficient of Thermal Expansion for the S-TIH1 Glass

NASA Technical Reports Server (NTRS)

Quijada, Manuel A.; Leviton, Douglas; Content, David

2013-01-01

Using the CHARMS facility at NASA GSFC, we have measured the cryogenic refractive index of the Ohara S-TIH1 glass from 0.40 to 2.53 micrometers and from 120 to 300 K. We have also examined the spectral dispersion and thermo-optic coefficients (dn/dT). We also derived temperature-dependent Sellmeier models from which refractive index may be calculated for any wavelength and temperature within the stated ranges of each model. The S-TIH1 glass we tested exhibited unusual behavior in the thermo-optic coefficient. We found that for delta < 0.5 micrometers, the index of refraction decrease with a decrease in temperature (positive dn/dT). However, the situation was reversed for delta larger than 0.63 micrometers, where the index will increase with a decrease in temperature (negative dn/dT). We also measured the coefficient of thermal expansion (CTE) for the similar batch of S-TIH1 glass in order to understand its thermal properties. The CTE showed a monotonic change with a decrease in temperature.
Silica-Based and Borate-Based, Titania-Containing Bioactive Coatings Characterization: Critical Strain Energy Release Rate, Residual Stresses, Hardness, and Thermal Expansion.

PubMed

Rodriguez, Omar; Matinmanesh, Ali; Phull, Sunjeev; Schemitsch, Emil H; Zalzal, Paul; Clarkin, Owen M; Papini, Marcello; Towler, Mark R

2016-12-01

Silica-based and borate-based glass series, with increasing amounts of TiO₂ incorporated, are characterized in terms of their mechanical properties relevant to their use as metallic coating materials. It is observed that borate-based glasses exhibit CTE (Coefficient of Thermal Expansion) closer to the substrate's (Ti6Al4V) CTE, translating into higher mode I critical strain energy release rates of glasses and compressive residual stresses and strains at the coating/substrate interface, outperforming the silica-based glasses counterparts. An increase in the content of TiO₂ in the glasses results in an increase in the mode I critical strain energy release rate for both the bulk glass and for the coating/substrate system, proving that the addition of TiO₂ to the glass structure enhances its toughness, while decreasing its bulk hardness. Borate-based glass BRT3, with 15 mol % TiO₂ incorporated, exhibits superior properties overall compared to the other proposed glasses in this work, as well as 45S5 Bioglass ® and Pyrex.
Silica-Based and Borate-Based, Titania-Containing Bioactive Coatings Characterization: Critical Strain Energy Release Rate, Residual Stresses, Hardness, and Thermal Expansion

PubMed Central

Rodriguez, Omar; Matinmanesh, Ali; Phull, Sunjeev; Schemitsch, Emil H.; Zalzal, Paul; Clarkin, Owen M.; Papini, Marcello; Towler, Mark R.

2016-01-01

Silica-based and borate-based glass series, with increasing amounts of TiO2 incorporated, are characterized in terms of their mechanical properties relevant to their use as metallic coating materials. It is observed that borate-based glasses exhibit CTE (Coefficient of Thermal Expansion) closer to the substrate’s (Ti6Al4V) CTE, translating into higher mode I critical strain energy release rates of glasses and compressive residual stresses and strains at the coating/substrate interface, outperforming the silica-based glasses counterparts. An increase in the content of TiO2 in the glasses results in an increase in the mode I critical strain energy release rate for both the bulk glass and for the coating/substrate system, proving that the addition of TiO2 to the glass structure enhances its toughness, while decreasing its bulk hardness. Borate-based glass BRT3, with 15 mol % TiO2 incorporated, exhibits superior properties overall compared to the other proposed glasses in this work, as well as 45S5 Bioglass® and Pyrex. PMID:27916951
Hybrid Heat Exchangers

NASA Technical Reports Server (NTRS)

Tu, Jianping Gene; Shih, Wei

2010-01-01

A hybrid light-weight heat exchanger concept has been developed that uses high-conductivity carbon-carbon (C-C) composites as the heat-transfer fins and uses conventional high-temperature metals, such as Inconel, nickel, and titanium as the parting sheets to meet leakage and structural requirements. In order to maximize thermal conductivity, the majority of carbon fiber is aligned in the fin direction resulting in 300 W/m.K or higher conductivity in the fin directions. As a result of this fiber orientation, the coefficient of thermal expansion (CTE) of the C-C composite in both non-fiber directions matches well with the CTE of various high-temperature metal alloys. This allows the joining of fins and parting sheets by using high-temperature braze alloys.
Inhibitory effect of Clitoria ternatea flower petal extract on fructose-induced protein glycation and oxidation-dependent damages to albumin in vitro.

PubMed

Chayaratanasin, Poramin; Barbieri, Manuel Alejandro; Suanpairintr, Nipattra; Adisakwattana, Sirichai

2015-02-18

The accumulation of advanced glycation end products (AGEs) in body tissue has been implicated in the progression of age-related diseases. Inhibition of AGE formation is the imperative approach for alleviating diabetic complications. Clitoria ternatea extract (CTE) has been demonstrated to possess anti-diabetic activity. However, there is no scientific evidence supporting its anti-glycation activity. The objective of this study was to determine the inhibitory effect of CTE on fructose-induced formation of AGEs and protein oxidation. Antioxidant activity of CTE was also assessed by various methods. The aqueous extract of CTE (0.25-1.00 mg/ml) was measured for the content of total phenolic compounds, flavonoid, and anthocyanin by Folin-Ciocalteu assay, AlCl3 colorimetric method, and pH differential method, respectively. The various concentrations of CTE were incubated with BSA and fructose at 37°C for 28 days. The formation of fluorescent AGEs, the level of fructosamine, protein carbonyl content, and thiol group were measured. The in vitro antioxidant activity was measured by the 1,1-diphenyl 2-picrylhydrazyl (DPPH) scavenging activity, trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP), hydroxyl radical scavenging activity (HRSA), superoxide radical scavenging activity (SRSA), and ferrous ion chelating power (FICP). The results demonstrated that the content of total phenolics, flavonoids and total anthocyanins in CTE was 53 ± 0.34 mg gallic acid equivalents/g dried extract, 11.2 ± 0.33 mg catechin equivalents/g dried extract, and 1.46 ± 0.04 mg cyanidin-3-glucoside equivalents/g dried extract, respectively. Moreover, CTE (0.25-1.00 mg/ml) significantly inhibited the formation of AGEs in a concentration-dependent manner. CTE also markedly reduced the levels of fructosamine and the oxidation of protein by decreasing protein carbonyl content and preventing free thiol depletion. In the DPPH radical scavenging activity and SRSA, CTE had the IC50 values of 0.47 ± 0.01 mg/ml and 0.58 ± 0.04 mg/ml. Furthermore, the FRAP and TEAC values of CTE were 0.38 ± 0.01 mmol FeSO4 equivalents/mg dried extract and 0.17 ± 0.01 mg trolox equivalents/mg dried extract. However, CTE showed weak scavenging activity on hydroxyl radical and a weak antioxidant iron chelator. The results showed that CTE has strong antiglycation and antioxidant properties and might have therapeutic potentials in the prevention of AGE-mediated diabetic complications.

Comparative investigation of thermal and mechanical properties of cross-linked epoxy polymers with different curing agents by molecular dynamics simulation.

PubMed

Jeyranpour, F; Alahyarizadeh, Gh; Arab, B

2015-11-01

Molecular dynamics (MD) simulations were carried out to predict the thermal and mechanical properties of the cross-linked epoxy system composed of DGEBA resin and the curing agent TETA. To investigate the effects of curing agents, a comprehensive and comparative study was also performed on the thermal and mechanical properties of DGEBA/TETA and DGEBA/DETDA epoxy systems such as density, glass transition temperature (Tg), coefficient of thermal expansion (CTE) and elastic properties of different cross-linking densities and different temperatures. The results indicated that the glass transition temperature of DGEBA/TETA system calculated through density-temperature data, ∼ 385-395 °K, for the epoxy system with the cross-linking density of 62.5% has a better agreement with the experimental value (Tg, ∼ 400 °K) in comparison to the value calculated through the variation of cell volume in terms of temperature, 430-440 °K. They also indicated that CTE related parameters and elastic properties including Young, Bulk, and shear's moduli, and Poisson's ratio have a relative agreement with the experimental results. Comparison between the thermal and mechanical properties of epoxy systems of DGEBA/TETA and DGEBA/DETDA showed that the DGEBA/DETDA has a higher Tg in all cross linking densities than that of DGEBA/TETA, while higher mechanical properties was observed in the case of DGEBA/TETA in almost all cross linking densities. Copyright © 2015 Elsevier Inc. All rights reserved.
Emerging low-cost LED thermal management materials

NASA Astrophysics Data System (ADS)

Zweben, Carl H.

2004-10-01

As chip size and power levels continue to increase, thermal management, thermal stresses and cost have become key LED packaging issues. Until recently, low-coefficient-of-thermal-expansion (CTE) materials, which are needed to minimize thermal stresses, had thermal conductivities that are no better than those of aluminum alloys, about 200 W/m-K. Copper, which has a higher thermal conductivity (400 W/m-K), also has a high CTE, which can cause severe thermal stresses. We now have over a dozen low-CTE materials with thermal conductivities ranging between 400 and 1700 W/m-K, and almost a score with thermal conductivities at least 50% greater than that of aluminum. Some of these materials are low cost. Others have the potential to be low cost in high volume production. Emphasizing low cost, this paper reviews traditional packaging materials and the six categories of advanced materials: polymer matrix-, metal matrix-, ceramic matrix-, and carbon matrix composites; monolithic carbonaceous materials; and metal-metal composites/alloys. Topics include properties, status, applications, cost and likely future directions of new advanced materials, including carbon nanotubes and inexpensive graphite nanoplatelets.
Temperature induced distortions in space telescope mirrors

NASA Technical Reports Server (NTRS)

Nied, H. F.; Rudmann, A. A.

1993-01-01

In this paper, it is illustrated how measured instantaneous coefficients of thermal expansion (CTE) can be accurately taken into account when modeling the structural behavior of space based optical systems. In particular, the importance of including CTE spatial variations in the analysis of optical elements is emphasized. A comparison is made between the CTE's of three optical materials commonly used in the construction of space mirrors (ULE, Zerodur, and beryllium). The overall impact that selection of any one of these materials has on thermal distortions is briefly discussed. As an example of how temperature dependent spatial variations in thermal strain can be accurately incorporated in the thermo-structural analysis of a precision optical system, a finite element model is developed, which is used to estimate the thermally induced distortions in the Hubble Space Telescope's (HST) primary mirror. In addition to the structural analysis, the optical aberrations due to thermally induced distortions are also examined. These calculations indicate that thermal distortions in HST's primary mirror contribute mainly to defocus error with a relatively small contribution to spherical aberration.
CFRP composite mirrors for space telescopes and their micro-dimensional stability

NASA Astrophysics Data System (ADS)

Utsunomiya, Shin; Kamiya, Tomohiro; Shimizu, Ryuzo

2010-07-01

Ultra-lightweight and high-accuracy CFRP (carbon fiber reinforced plastics) mirrors for space telescopes were fabricated to demonstrate their feasibility for light wavelength applications. The CTE (coefficient of thermal expansion) of the all- CFRP sandwich panels was tailored to be smaller than 1×10-7/K. The surface accuracy of mirrors of 150 mm in diameter was 1.8 um RMS as fabricated and the surface smoothness was improved to 20 nm RMS by using a replica technique. Moisture expansion was considered the largest in un-predictable surface preciseness errors. The moisture expansion affected not only homologous shape change but also out-of-plane distortion especially in unsymmetrical compositions. Dimensional stability due to the moisture expansion was compared with a structural mathematical model.
Materials Properties Research at MSFC

NASA Technical Reports Server (NTRS)

Presson, Joan B.; Burdine, Robert (Technical Monitor)

2002-01-01

MSFC is currently planning, organizing and directing test coupon fabrication and subsequent CTE testing for two mirror materials of specific interest to the AMSD and NGST programs, Beryllium 0-30H (Be 0-30H) and Ultra Low Expansion glass (ULE). The ULE test coupons are being fabricated at MSFC from AMSD core residuals provided by Kodak, The Be 0-30H test coupons are being fabricated at Brush Wellman using residuals from the SBMD. Both sets of test coupons will be sent to a test vendor selected through the NASA competitive proposal process with the test results being provided by written report to MSFC by the end of the fiscal year. The test results will become model input data for the AMSD analysts, both MSFC and contractor, providing an enhancement to the historical CTE data currently available.
The JPL Cryogenic Dilatometer: Measuring the Thermal Expansion Coefficient of Aerospace Materials

NASA Technical Reports Server (NTRS)

Halverson, Peter G.; Dudick, Matthew J.; Karlmann, Paul; Klein, Kerry J.; Levine, Marie; Marcin, Martin; Parker, Tyler J.; Peters, Robert D.; Shaklan, Stuart; VanBuren, David

2007-01-01

This slide presentation details the cryogenic dilatometer, which is used by JPL to measure the thermal expansion coefficient of materials used in Aerospace. Included is a system diagram, a picture of the dilatometer chamber and the laser source, a description of the laser source, pictures of the interferometer, block diagrams of the electronics and software and a picture of the electronics, and software. Also there is a brief review of the accurace.error budget. The materials tested are also described, and the results are shown in strain curves, JPL measured strain fits are described, and the coefficient of thermal expansion (CTE) is also shown for the materials tested.
Microcracking of Materials for Space

NASA Technical Reports Server (NTRS)

Brown, Timothy L.

1998-01-01

The effect of thermal-cycling-induced microcracking in fiber-reinforced polymer matrix composites is studied. Specific attention is focused on microcrack density as a function of the number of thermal cycles, and the effect of microcracking on the dimensional stability of composite materials. Changes in laminate coefficient of thermal expansion (CTE) and laminate stiffness are of primary concern. Included in the study are materials containing four different Thornel fiber types: a PAN-based T50 fiber and three pitch-based fibers, P55, P75, and P120. The fiber stiffnesses range from 55 Msi to 120 Msi. The fiber CTE's range from -0.50 x 1O(exp -6)/degrees F to -0.80 x 10(exp -6)/degrees F. Also included are three matrix types: Fiberite's 934 epoxy, Amoco's ERL1962 toughened epoxy, and YLA's RS3 cyanate ester. The lamination sequences of the materials considered include a cross-ply configuration, [0/90](sub 2s), and two quasi-isotropic configurations, [0/+45/-45/90](sub s), and [0/+45/90/-45](sub s). The layer thickness of the materials range from a nominal 0.001 in. to 0.005 in. In addition to the variety of materials considered, three different thermal cycling temperature ranges are considered. These temperature ranges are +/-250 degrees F, +/-l5O degrees F, and +/-50 degrees F. The combination of these material and geometric parameters and temperature ranges, combined with thermal cycling to thousands of cycles, makes this one of the most comprehensive studies of thermal-cycling-induced microcracking to date. Experimental comparisons are presented by examining the effect of layer thickness, fiber type, matrix type, and thermal cycling temperature range on microcracking and its influence on the laminates. Results regarding layer thickness effects indicate that thin-layer laminates microcrack more severely than identical laminates with thick layers. For some specimens in this study, the number of microcracks in thin-layer specimens exceeds that in thick-layer specimens by more than a factor of two. Despite the higher number of microcracks in the thin-layer specimens, small changes in CTE after thousands of cycles indicate that the thin-layer specimens are relatively unaffected by the presence of these cracks compared to the thick-layer specimens. Results regarding fiber type indicate that the number of microcracks and the change in CTE after thousands of cycles in the specimens containing PAN-based fibers are less than in the specimens containing comparable stiffness pitch-based fibers. Results for specimens containing the different pitch-based fibers indicate that after thousands of cycles, the number of microcracks in the specimens does not depend on the modulus or CTE of the fiber. The change in laminate CTE does, however, depend highly on the stiffness and CTE of the fiber. Fibers with higher stiffness and more negative CTE exhibit the lowest change in laminate CTE as a result of thermal cycling. The overall CTE of these specimens is, however, more negative as a result of the more negative CTE of the fiber. Results regarding matrix type based on the +/-250 degree F temperature range indicate that the RS3 cyanate ester resin system exhibits the greatest resistance to microcracking and the least change in CTE, particularly for cycles numbering 3000 and less. Extrapolations to higher numbers of cycles indicate, however, that the margin of increased performance is expected to decrease with additional thermal cycling. Results regarding thermal cycling temperature range depend on the matrix type considered and the layer thickness of the specimens. For the ERL1962 resin system, microcrack saturation is expected to occur in all specimens, regardless of the temperature range to which the specimens are exposed. By contrast, the RS3 resin system demonstrates a threshold effect such that cycled to less severe temperature ranges, microcracking does not occur. For the RS3 specimens with 0.005 in. layer thickness, no microcracking or changes in CTE are observed in specimens cycled between +/-150 degree F or +/- 50 degree F. For the RS3 specimens with 0.002 in. layer thickness, no microcracking or changes in CTE are observed in specimens cycled between +/-50 degree F. Results regarding laminate stiffness indicate negligible change in laminate stiffness due to thermal cycling for the materials and geometries considered in this investigation. The study includes X-ray examination of the specimens, showing that cracks observed at the edge of the specimens penetrate the entire width of the specimen. Glass transition temperatures of the specimens are measured, showing that resin chemistry is not altered as a result of thermal cycling. Results are also presented based on a one-dimensional shear lag analysis developed in the literature. The analysis requires material property information that is difficult to obtain experimentally. Using limited data from the present investigation, material properties associated with the analysis are modified to obtain reasonable agreement with measured microcrack densities. Based on these derived material properties, the analysis generally overpredicts the change in laminate CTE. Predicted changes in laminate stiffness show reasonable correlation with experimentally measured values.
Fracture behavior of silica nanoparticle filled epoxy resin

NASA Astrophysics Data System (ADS)

Dittanet, Peerapan

This dissertation involves the addition of silica nanoparticles to a lightly crosslinked, model epoxy resin and investigates the effect of nanosilica content and particle size on glass transition temperature (Tg), coefficient of thermal expansion (CTE), Young's modulus (E), yield stress, and fracture toughness. This study aims to understand the influence of silica nanoparticle size, bimodal particle size distribution and silica content on the toughening behavior. The toughening mechanisms were determined using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and transmission optical microscopy (TOM). The approach identifies toughening mechanisms and develops a toughening model from unimodal-particle size systems first, then extends these concepts to various mixtures micron- and nanometer-size particles in a similar model epoxy. The experimental results revealed that the addition of nanosilica did not have a significant effect on Tg or the yield stress of epoxy resin, i.e. the yield stress and Tg remained constant regardless of nanosilica particle size. As expected, the addition of nanosilica had a significant impact on CTE, modulus and fracture toughness. The CTE values of nanosilica-filled epoxies were found to decrease with increasing nanosilica content, which can be attributed to the much lower CTE of the nanosilica fillers. Interestingly, the decreases in CTE showed strong particle size dependence. The Young's modulus was also found to significantly improve with addition of nanosilica and increase with increasing filler content. However, the particle size did not exhibit any effect on the Young's modulus. Finally, the fracture toughness and fracture energy showed significant improvements with the addition of nanosilica, and increased with increasing filler content. The effect of particle size on fracture toughness was negligible. Observation of the fracture surfaces using SEM and TOM showed evidence of debonding of nanosilica particles, matrix void growth, and matrix shear banding, which are credited for the increases in toughness for nanosilica-filled epoxy systems. Epoxy containing mixtures of two different size distributions of silica particles (42 micrometer and 23 nm-170nm particles) was explored for possible multiplicative toughening effect and to further understand the particle-epoxy interactions and toughening mechanisms of bimodal particle size distribution systems. The fracture toughness was improved by approximately 30% compared to that of the epoxy containing only one particle size of silica particles. The toughness improvement from the interaction of particle debonding from large particles and plastic void growth from small particles was clearly observed. The improvement in toughness occurred when the volume fraction ratio of the large and small particles was more than 50:50 ratios. The increased toughness was found to be additive not multiplicative effect.
A heterodyne interferometer for high-performance industrial metrology

NASA Astrophysics Data System (ADS)

Schuldt, Thilo; Gohlke, Martin; Weise, Dennis; Johann, Ulrich; Peters, Achim; Braxmaier, Claus

2008-11-01

We developed a compact, fiber-coupled heterodyne interferometer for translation and tilt metrology. Noise levels below 5 pm/√Hz in translation and below 10 nrad/√Hz in tilt measurement, both for frequencies above 10-2 Hz, were demonstrated in lab experiments. While this setup was developed with respect to the LISA (Laser Interferometer Space Antenna) space mission current activities focus on its adaptation for dimensional characterization of ultra-stable materials and industrial metrology. The interferometer is used in high-accuracy dilatometry measuring the coefficient of thermal expansion (CTE) of dimensionally highly stable materials such as carbon-fiber reinforced plastic (CFRP) and Zerodur. The facility offers the possibility to measure the CTE with an accuracy better 10-8/K. We also develop a very compact and quasi-monolithic sensor head utilizing ultra-low expansion glass material which is the basis for a future space-qualifiable interferometer setup and serves as a prototype for a sensor head used in industrial environment. For high resolution 3D profilometry and surface property measurements (i. e. roughness, evenness and roundness), a low-noise (<=1nm/√ Hz) actuator will be implemented which enables a scan of the measurement beam over the surface under investigation.
Crossover from band-like to thermally activated charge transport in organic transistors due to strain-induced traps

PubMed Central

Mei, Yaochuan; Diemer, Peter J.; Niazi, Muhammad R.; Hallani, Rawad K.; Jarolimek, Karol; Day, Cynthia S.; Risko, Chad; Anthony, John E.; Amassian, Aram

2017-01-01

The temperature dependence of the charge-carrier mobility provides essential insight into the charge transport mechanisms in organic semiconductors. Such knowledge imparts critical understanding of the electrical properties of these materials, leading to better design of high-performance materials for consumer applications. Here, we present experimental results that suggest that the inhomogeneous strain induced in organic semiconductor layers by the mismatch between the coefficients of thermal expansion (CTE) of the consecutive device layers of field-effect transistors generates trapping states that localize charge carriers. We observe a universal scaling between the activation energy of the transistors and the interfacial thermal expansion mismatch, in which band-like transport is observed for similar CTEs, and activated transport otherwise. Our results provide evidence that a high-quality semiconductor layer is necessary, but not sufficient, to obtain efficient charge-carrier transport in devices, and underline the importance of holistic device design to achieve the intrinsic performance limits of a given organic semiconductor. We go on to show that insertion of an ultrathin CTE buffer layer mitigates this problem and can help achieve band-like transport on a wide range of substrate platforms. PMID:28739934
Monitoring and Evaluation of a Long-Span Raiway Bridge Using SENTINEL-1 Data

NASA Astrophysics Data System (ADS)

Huang, Q.; Crosetto, M.; Monserrat, O.; Crippa, B.

2017-09-01

This paper is focused on displacement monitoring of a bridge, which is one of the key aspects of its structural health monitoring. A simplified Persistent Scatterer Interferometry (PSI) approach is used to monitor the displacements of the Nanjing Dashengguan Yangtze River High-speed Railway Bridge (China). This bridge is 1272 m long and hosts a total of 6 railway lines. The analysis was based on a set of twenty-nine Sentinel-1A images, acquired from April 2015 to August 2016. A dense set of measurement points were selected on the bridge. The PSI results show a maximum longitudinal displacement of 150 mm, on each side of the bridge. The displacements are strongly correlated with the temperature, showing that they are due to thermal expansion. Using the PSI results, the Coefficient of Thermal Expansion (CTE) of the whole bridge was estimated. The result agrees well with the CTE of the bridge materials. Using a regression model, the PSI-measured displacements were compared with in-situ measurements. The paper proposes a procedure to assess the performance of the movable bearings of the bridge, which is based on the PSI measurements.
Crossover from band-like to thermally activated charge transport in organic transistors due to strain-induced traps.

PubMed

Mei, Yaochuan; Diemer, Peter J; Niazi, Muhammad R; Hallani, Rawad K; Jarolimek, Karol; Day, Cynthia S; Risko, Chad; Anthony, John E; Amassian, Aram; Jurchescu, Oana D

2017-08-15

The temperature dependence of the charge-carrier mobility provides essential insight into the charge transport mechanisms in organic semiconductors. Such knowledge imparts critical understanding of the electrical properties of these materials, leading to better design of high-performance materials for consumer applications. Here, we present experimental results that suggest that the inhomogeneous strain induced in organic semiconductor layers by the mismatch between the coefficients of thermal expansion (CTE) of the consecutive device layers of field-effect transistors generates trapping states that localize charge carriers. We observe a universal scaling between the activation energy of the transistors and the interfacial thermal expansion mismatch, in which band-like transport is observed for similar CTEs, and activated transport otherwise. Our results provide evidence that a high-quality semiconductor layer is necessary, but not sufficient, to obtain efficient charge-carrier transport in devices, and underline the importance of holistic device design to achieve the intrinsic performance limits of a given organic semiconductor. We go on to show that insertion of an ultrathin CTE buffer layer mitigates this problem and can help achieve band-like transport on a wide range of substrate platforms.
Preparation of Functionally Graded Materials (FGMs) Using Coal Fly Ash and NiCr-Based Alloy Powder by Spark Plasma Sintering (SPS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaneko, Gen-yo; Kitagawa, Hiroyuki; Hasezaki, Kazuhiro

2008-02-15

Functionally Graded Materials (FGMs) were prepared by spark plasma sintering (SPS) using coal fly ash and NiCr alloy powder. The coal fly ash was produced by the Misumi Coal Thermal Power Station (Chugoku Electric Power Co., Inc.), with 80 wt% nickel and 20 wt% chromium (Fukuda Metal Foil and Powder Co., Ltd.) used as source materials. The sintering temperature in the graphite die was 1000 deg. C. X-ray diffraction patterns of the sintered coal fly ash materials indicated that mullite (3Al{sub 2}O{sub 3}{center_dot}2SiO{sub 2}) and silica (SiO{sub 2}) phases were predominant. Direct joining of coal fly ash and NiCr causesmore » fracture at the interface. This is due to the mismatch in the thermal expansion coefficients (CTE). A crack in the FGM was observed between the two layers with a CTE difference of over 4.86x10{sup -6} K{sup -1}, while a crack in the FGM was difficult to detect when the CTE difference was less than 2.77x10{sup -6} K{sup -1}.« less
[Preliminary study of bonding strength between diatomite-based dental ceramic and veneering porcelains].

PubMed

Lu, Xiao-li; Gao, Mei-qin; Cheng, Yu-ye; Zhang, Fei-min

2015-04-01

In order to choose the best veneering porcelain for diatomite-based dental ceramic substrate, the bonding strength between diatomite-based dental ceramics and veneering porcelains was measured, and the microstructure and elements distribution of interface were analyzed. The coefficient of thermal expansion (CTE) of diatomite-based dental ceramics was detected by dilatometry. Three veneering porcelain materials were selected with the best CTE matching including alumina veneering porcelain (group A), titanium porcelain veneering porcelain (group B), and E-max veneering porcelain (group C). Shear bonding strength was detected. SEM and EDS were used to observe the interface microstructure and element distribution. Statistical analysis was performed using SPSS 17.0 software package. The CTE of diatomite-based dental ceramics at 25-500 degrees centigrade was 8.85×10-6K-1. The diatomite-based substrate ceramics combined best with group C. Shear bonding strength between group A and C and group B and C both showed significant differences(P<0.05). SEM and EDS showed that the interface of group C sintered tightly and elements permeated on both sides of the interface. The diatomite-based substrate ceramics combines better with E-max porcelain veneer.
Thermal expansion and microstructural analysis of experimental metal-ceramic titanium alloys.

PubMed

Zinelis, Spiros; Tsetsekou, Athena; Papadopoulos, Triantafillos

2003-10-01

Statement of problem Low-fusing porcelains for titanium veneering have demonstrated inferior color stability and metal-ceramic longevity compared to conventional porcelains. This study evaluated the microstructure and thermal expansion coefficients of some experimental titanium alloys as alternative metallic substrates for low-fusing conventional porcelain. Commercially pure titanium (CP Ti) and various metallic elements (Al, Co, Sn, Ga, In, Mn) were used to prepare 8 titanium alloys using a commercial 2-chamber electric-arc vacuum/inert gas dental casting machine (Cyclarc). The nominal compositions of these alloys were the following (wt%): I: 80Ti-18Sn-1.5In-0.5Mn; II: 76Ti-12Ga-7Sn-4Al-1Co; III: 87Ti-13Ga; IV: 79Ti-13Ga-7Al-1Co; V: 82Ti-18In; VI: 75.5Ti-18In-5Al-1Co-0.5Mn; VII: 85Ti-10Sn-5Al; VIII: 78Ti-12Co-7Ga-3Sn. Six rectangular wax patterns for each test material (l = 25 mm, w = 3 mm, h = 1 mm) were invested with magnesia-based material and cast with grade II CP Ti (control) and the 8 experimental alloys. The porosity of each casting was evaluated radiographically, and defective specimens were discarded. Two cast specimens from CP Ti and alloys I-VIII were embedded in epoxy resin and, after metallographic grinding and polishing, were studied by means of scanning electron microscopy and wavelength dispersive electron probe microanalysis. One specimen of each material was utilized for the determination of coefficient of thermal expansion (CTE) with a dilatometer operating from room temperature up to 650 degrees C at a heating rate of 5 degrees C/minute. Secondary electron images (SEI) and compositional backscattered electron images (BEI-COMPO) revealed that all cast specimens consisted of a homogeneous matrix except Alloy VIII, which contained a second phase (possibly Ti(2)Co) along with the titanium matrix. The results showed that the coefficient of thermal expansion (CTE) varied from 10.1 to 13.1 x 10(-6)/ degrees C (25 degrees -500 degrees C), depending on the elemental composition. The CTE of titanium can be considerably changed by alloying. Two-phase alloys were developed when alloying elements were added in concentrations greater than the maximum solubility limit in alpha-titanium phase.
Theoretical analysis of compatibility of several reinforcement materials with NiAl and FeAl matrices

NASA Technical Reports Server (NTRS)

Misra, Ajay K.

1989-01-01

Several potential reinforcement materials were assessed for their chemical, coefficient of thermal expansion (CTE), and mechanical compatibility with the intermetallic matrices based on NiAl and FeAl. Among the ceramic reinforcement materials, Al2O3, TiC, and TiB2, appear to be the optimum choices for NiAl and FeAl matrices. However, the problem of CTE mismatch with the matrix needs to be solved for these three reinforcement materials. Beryllium-rich intermetallic compounds can be considered as potential reinforcement materials provided suitable reaction barrier coatings can be developed for these. Based on preliminary thermodynamic calculations, Sc2O3 and TiC appear to be suitable as reaction barrier coatings for the beryllides. Several reaction barrier coatings are also suggested for the currently available SiC fibers.
MoSi2-Base Composite for Engine Applications

NASA Technical Reports Server (NTRS)

Hebsur, Mohan G.; Nathal, Michael V.

1997-01-01

The intermetallic compound MoSi2 has long been known as a high temperature material that has excellent oxidation resistance and electrical/thermal conductivity. Also its low cost, high melting point (2023 C), relatively low density (6.2 g/cm versus 8 g/cm for current engine materials), and ease of machining make it an attractive structural material. However, the use of MoSi2 has been hindered because of the brittle nature of the material at low temperatures, inadequate creep resistance at high temperatures, accelerated oxidation (also known as 'pest' oxidation) at temperatures between approximately 400 and 500 C, and a coefficient of thermal expansion (CTE) that is relatively high in comparison to potential reinforcing fibers such as SiC. This CTE mismatch between the fiber and the matrix resulted in severe matrix cracking during thermal cycling.
Multiple thermal transitions and anisotropic thermal expansions of vertically aligned carbon nanotubes

NASA Astrophysics Data System (ADS)

Ya'akobovitz, Assaf

2016-10-01

Vertically aligned carbon nanotubes (VA-CNTs) hold the potential to play an instrumental role in a wide variety of applications in micro- and nano-devices and composites. However, their successful large-scale implementation in engineering systems requires a thorough understanding of their material properties, including their thermal behavior, which was the focus of the current study. Thus, the thermal expansion of as-grown VA-CNT microstructures was investigated while increasing the temperature from room temperature to 800 °C and then cooling it down. First thermal transition was observed at 191 ± 68 °C during heating, and an additional thermal transition was observed at 523 ± 138 °C during heating and at similar temperatures during cooling. Each thermal transition was characterized by a significant change in the coefficient of thermal expansion (CTE), which can be related to a morphological change in the VA-CNT microstructures. Measurements of the CTEs in the lateral directions revealed differences in the lateral thermal behaviors of the top, middle, and bottom portions of the VA-CNT microstructures, again indicating that their morphology dominates their thermal characteristics. A hysteretic behavior was observed, as the measured values of CTEs were altered due to the applied thermal loads and the height of the microstructures was slightly higher compared to its initial value. These findings provide an insight into the anisotropic thermal behavior of VA-CNT microstructures and shed light on the relationship between their morphology and thermal behavior.
Tailored benzoxazines as novel resin systems for printed circuit boards in high temperature e-mobility applications

NASA Astrophysics Data System (ADS)

Troeger, K.; Darka, R. Khanpour; Neumeyer, T.; Altstaedt, V.

2014-05-01

This study focuses on the development of Bisphenol-F-benzoxazine resins blended with different ratios of a trifunctional epoxy resin suitable as matrix for substrates for high temperature printed circuit board (HT-PCB) applications. With the benzoxazine blends glass transition temperatures of more than 190 °C could be achieved in combination with a coefficient of thermal expansion in thickness direction (z-CTE) of less than 60 ppm/K without adding any fillers. This shows the high potential of the benzoxazine-epoxy blend systems as substrate materials for HT-PCBs. To understand the thermal behavior of the different formulations, the apparent crosslink density was calculated based on data from Dynamic Mechanical Analysis. Laminates in laboratory scale were prepared and characterized to demonstrate the transformation of the neat resin properties into real electronic substrate properties. The produced laminates exhibit a z-CTE below 40 ppm/K.
Tailored benzoxazines as novel resin systems for printed circuit boards in high temperature e-mobility applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Troeger, K., E-mail: altstaedt@uni-bayreuth.de; Darka, R. Khanpour, E-mail: altstaedt@uni-bayreuth.de; Neumeyer, T., E-mail: altstaedt@uni-bayreuth.de

2014-05-15

This study focuses on the development of Bisphenol-F-benzoxazine resins blended with different ratios of a trifunctional epoxy resin suitable as matrix for substrates for high temperature printed circuit board (HT-PCB) applications. With the benzoxazine blends glass transition temperatures of more than 190 °C could be achieved in combination with a coefficient of thermal expansion in thickness direction (z-CTE) of less than 60 ppm/K without adding any fillers. This shows the high potential of the benzoxazine-epoxy blend systems as substrate materials for HT-PCBs. To understand the thermal behavior of the different formulations, the apparent crosslink density was calculated based on datamore » from Dynamic Mechanical Analysis. Laminates in laboratory scale were prepared and characterized to demonstrate the transformation of the neat resin properties into real electronic substrate properties. The produced laminates exhibit a z-CTE below 40 ppm/K.« less

Evaluation of ZnO:Al as a contact material to CdZnTe for radiation detector applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Roy, Utpal N.; Camarda, Giuseppe S.; Cui, Yonggang; Gul, Rubi; Hossain, Anwar; Yang, Ge; James, Ralph B.; Pradhan, Aswini K.; Mundle, Rajeh

2016-09-01

Aluminum (Al) doped ZnO with very high Al concentration acts as metal regarding its electrical conductivity. ZnO offers many advantages over the commonly-known metals being used today as electrode materials for nuclear detector fabrication. Often, the common metals show poor adhesion to CdZnTe or CdTe surfaces and have a tendency to peel off. In addition, there is a large mismatch of the coefficients of thermal expansion (CTE) between the metals and underlying CdZnTe, which is one of the reasons for mechanical degradation of the contact. In contrast ZnO has a close match of the CTE with CdZnTe and possesses 8-20 times higher hardness than the commonly-used metals. In this presentation, we will explore and discuss the properties of CdZnTe detectors with ZnO:Al contacts.
Mechanical Properties of Degraded PMR-15 Resin

NASA Technical Reports Server (NTRS)

Tsuji, Luis C.; McManus, Hugh L.; Bowles, Kenneth J.

1998-01-01

Thermo-oxidative aging produces a non-uniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hours. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and Coefficient of Thermal Expansion (CTE) of nitrogen aged specimens were measured directly. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.
Increasing the Thermal Stability of Aluminum Titanate for Solid Oxide Fuel Cell Anodes

NASA Technical Reports Server (NTRS)

Bender, Jeffrey B.

2004-01-01

Solid-oxide fuel cells (SOFCs) show great potential as a power source for future space exploration missions. Because SOFCs operate at temperatures significantly higher than other types of fuel cells, they can reach overall efficiencies of up to 60% and are able to utilize fossil fuels. The SOFC team at GRC is leading NASA's effort to develop a solid oxide fuel cell with a power density high enough to be used for aeronautics and space applications, which is approximately ten times higher than ground transport targets. layers must be able to operate as a single unit at temperatures upwards of 900'C for at least 40,000 hours with less than ten percent degradation. One key challenge to meeting this goal arises from the thermal expansion mismatch between different layers. The amount a material expands upon heating is expressed by its coefficient of thermal expansion (CTE). If the CTEs of adjacent layers are substantially different, thermal stresses will arise during the cell's fabrication and operation. These stresses, accompanied by thermal cycling, can fracture and destroy the cell. While this is not an issue at the electrolyte-cathode interface, it is a major concern at the electrolyte-anode interface, especially in high power anode-supported systems. electrolyte are nearly identical. Conventionally, this has been accomplished by varying the composition of the anode to match the CTE of the yittria-stabilized zirconia (YSZ) electrolyte (approx.10.8x10(exp -6/degC). A Ni/YSZ composite is typically used as a base material for the anode due to its excellent electrochemical properties, but its CTE is about 13.4x10(exp -6/degC). One potential way to lower the CTE of this anode is to add a small percentage of polycrystalline Al2TiO5, with a CTE of 0.68x10(exp -6/degC, to the Ni/YSZ base. However, Al2TiO5 is thermally unstable and loses its effectiveness as it decomposes to Al2O3 and TiO2 between 750 C and 1280 C. be used as additives to increase the thermal stability of Al2TiO5 in SOFC operating conditions without adversely affecting the electrochemical properties of the SOFC anode. Three candidate materials were chosen through an extensive literature review: MgO, Fe2O3, and ZrTiO4. Although all three have been shown to prevent Al2TiO5 decomposition under various conditions, their effectiveness in the temperature range and atmosphere of the SOFC has not yet been evaluated. Several batches of Al2TiO5 with varying amounts of additives were prepared, exposed to reducing and oxidizing atmospheres at elevated temperatures, and the resulting decomposition of Al2TiO5 was measured. The most promising additives were further evaluated with the goal of ultimately preparing low CTE anodes that are chemically compatible to current systems. Adding minor constituents to stabilize Al2TiO5 could ultimately preserve its low CTE for the life of the fuel cell and improve the cell's long-term performance without a drop in anode conductivity. Further, these low CTE filler additions could allow the use of new sulfur tolerant anode materials, improving the viability of SOFCs for future aeronautics and space applications. Every SOFC consists of a cathode and an anode separated by an electrolyte, These three One way to avoid this problem is to design the cell such that the CTEs of the anode and The objective of this summer research project was to evaluate several materials that could
Use of graphite epoxy composites in the Solar-A Soft X-Ray Telescope

NASA Technical Reports Server (NTRS)

Jurcevich, B. K.; Bruner, M. E.

1990-01-01

This paper describes the use of composite materials in the Soft X-Ray Telescope (SXT). One of the primary structural members of the telescope is a graphite epoxy metering tube. The metering tube maintains the structural stability of the telescope during launch as well as the focal length through various environmental conditions. The graphite epoxy metering tube is designed to have a negative coefficient of thermal expansion to compensate for the positive expansion of titanium structural supports. The focus is maintained to + or - 0.001 inch by matching the CTE of the composite tube to the remaining structural elements.
Thermomechanical properties of polymeric materials and related stresses

NASA Technical Reports Server (NTRS)

Lee, Sheng Yen

1990-01-01

The thermomechanical properties of a number of widely used polymeric materials were determined by thermomechanical analysis and dynamic mechanical analysis. A combined profile of the coefficient of thermal expansion and the modulus change over a wide temperature range obtained by the analyses shows clearly the drastic effect of the glass transition on both the CTE and the modulus of a polymer, and the damaging potential due to such effect.
Mechanical Properties of Steel Encapsulated Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Fudger, Sean; Klier, Eric; Karandikar, Prashant; McWilliams, Brandon; Ni, Chaoying

This research evaluates a coefficient of thermal expansion (CTE) mismatch induced residual compressive stress approach as a means of improving the ductility of metal matrix composites (MMCs). MMCs are frequently incorporated into advanced material systems due to their tailorable material properties. However, they often have insufficient strength and ductility for many structural applications. By combining MMCs with high strength steels in a hybridized, macro composite materials system that exploits the CTE mismatch, materials systems with improved strength, damage tolerance, and structural efficiency can be obtained. Macro hybridized systems consisting of steel encapsulated light metal MMCs were produced with the goal of creating a system which takes advantage of the high strength, modulus, and damage tolerance of steels and high specific stiffness and low density of MMCs while mitigating the high density of steels and the poor ductility of MMCs. Aluminum and magnesium based particulate reinforced MMCs combine many of the desirable characteristic of metals and ceramics, particularly the unique ability to tailor their CTE. This work aims to compare the performance of macro hybridized material systems consisting of aluminum or magnesium MMCs reinforced with Al2O3, SiC, or B4C particles and encapsulated by A36 steel, 304 stainless steel, or cold worked Nitronic® 50 stainless steels.
Multidetector-row computed tomography enterographic assessment of the ileal-anal pouch: descriptive radiologic analysis with endoscopic and pathologic correlation.

PubMed

Liszewski, Mark C; Sahni, V Anik; Shyn, Paul B; Friedman, Sonia; Hornick, Jason L; Erturk, Sukru M; Mortele, Koenraad J

2012-01-01

To describe the multidetector-row computed tomography enterographic (MD-CTE) features of the ileal-anal pouch after ileal pouch anal anastomosis (IPAA) surgery and correlate them with pouch endoscopy and histopathologic findings. All MD-CTE examinations performed on patients who underwent IPAA from July 1, 2005 to December 1, 2010 (n = 35; 16 [45.7%] men; mean age, 37.7 years; age range, 22-72 years) were retrospectively evaluated in consensus by 2 radiologists. All studies were evaluated for the presence of multiple imaging features. Two radiographic scores were then calculated: a total radiographic score and a radiographic active inflammation score. In patients who underwent MD-CTE, pouch endoscopy, and biopsy within 30 days (n = 13), both scores were correlated with findings on pouch endoscopy and histopathology. Of the 35 patients, 33 (94%) had at least one MD-CTE finding of active or chronic pouch inflammation and 27 patients (77%) had at least one MD-CTE finding of active pouch inflammation. Of the 13 patients who underwent endoscopy and biopsy, the total radiographic score demonstrated a strong positive correlation with endoscopic score (r = 0.81; P = 0.001) and a moderate positive correlation with histopathologic score (r = 0.56; P = 0.047). The radiographic active inflammation score demonstrated a strong positive correlation with endoscopic score (r = 0.83; P = 0.0004), but only a weak nonsignificant positive correlation with histopathologic score (r = 0.492, P = 0.087). In patients who had IPAA surgery, findings on MD-CTE correlate positively with findings on pouch endoscopy and histopathology and are sensitive measures for pouch inflammation with high positive predictive value. Thus, MD-CTE can be a useful noninvasive test in the early evaluation of symptomatic patients.
The effect of carbamic acid, (1,2,3-thiadiazole-4-ylcarbonyl)-hexyl ester on Peronophythora litchii infection, quality and physiology of postharvest litchi fruits.

PubMed

Liu, Hai; Jing, Guoxing; Jiang, Yueming; Luo, Fuying; Li, Zaifeng

2017-01-01

Litchi ( Litchi chinensis Sonn.) is a subtropical fruit with attractive characteristic of white to creamy semitranslucent flesh and red color in pericap, but it was easily subjected to the infection of Peronophythora litchii and lost its market values. Experiments were conducted to understand the effect of [Carbamic acid, (1,2,3-thiadiazole-4-ylcarbonyl)-hexyl ester, CTE] on the growth of P. litchi and quality properties in litchi fruits during postharvest storage. In vitro experiments, CTE with minimum inhibitory concentration (MIC, 5 mg/L) and minimum fungicidal concentration (MFC, 10 mg/L) were against the growth of P. litchi for 2 and 4 days, respectively, and SEM results showed that hyphae of P. litchii shrank, distorted and collapsed after CTE treatment. In vivo experiments, CTE treatment inhibited the increase of disease incidence, browning index, weight loss and PPO activity in non- P. litchii -inoculated fruits, meanwhile the treatment markedly inhibited the decrease of color characteristic (a*, b* and L*), anthocyanin content, phenolic contents, Vc content and POD activity, but TSS content was not significantly influenced during storage. In P. litchii -inoculated fruits, all these above mentioned parameters in CTE treated fruits were significantly higher than that in control fruits, but anthocyanin content, Vc, TSS and TA content did not have consistent differences between control and CTE treated fruits at the end of storage. CTE treatment reduced the disease incidence and browning index of litchi fruits, maintained the fruits quality and, thus, it could be an effective postharvest handling to extend the shelf life of litchi fruits during storage.
Cerebral [18 F]T807/AV1451 retention pattern in clinically probable CTE resembles pathognomonic distribution of CTE tauopathy

PubMed Central

Dickstein, D L; Pullman, M Y; Fernandez, C; Short, J A; Kostakoglu, L; Knesaurek, K; Soleimani, L; Jordan, B D; Gordon, W A; Dams-O'Connor, K; Delman, B N; Wong, E; Tang, C Y; DeKosky, S T; Stone, J R; Cantu, R C; Sano, M; Hof, P R; Gandy, S

2016-01-01

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disorder most commonly associated with repetitive traumatic brain injury (TBI) and characterized by the presence of neurofibrillary tangles of tau protein, known as a tauopathy. Currently, the diagnosis of CTE can only be definitively established postmortem. However, a new positron emission tomography (PET) ligand, [18F]T807/AV1451, may provide the antemortem detection of tau aggregates, and thus various tauopathies, including CTE. Our goal was to examine [18F]T807/AV1451 retention in athletes with neuropsychiatric symptoms associated with a history of multiple concussions. Here we report a 39-year-old retired National Football League player who suffered 22 concussions and manifested progressive neuropsychiatric symptoms. Emotional lability and irritability were the chief complaints. Serial neuropsychological exams revealed a decline in executive functioning, processing speed and fine motor skills. Naming was below average but other cognitive functions were preserved. Structural analysis of longitudinally acquired magenetic resonance imaging scans revealed cortical thinning in the left frontal and lateral temporal areas, as well as volume loss in the basal ganglia. PET with [18F]florbetapir was negative for amyloidosis. The [18F]T807/AV1451 PET showed multifocal areas of retention at the cortical gray matter–white matter junction, a distribution considered pathognomonic for CTE. [18F]T807/AV1451 standard uptake value (SUV) analysis showed increased uptake (SUVr⩾1.1) in bilateral cingulate, occipital, and orbitofrontal cortices, and several temporal areas. Although definitive identification of the neuropathological underpinnings basis for [18F]T807/AV1451 retention requires postmortem correlation, our data suggest that [18F]T807/AV1451 tauopathy imaging may be a promising tool to detect and diagnose CTE-related tauopathy in living subjects. PMID:27676441
CTE Teachers' Perspectives on the Process of CTE and Science Content Integration: A Grounded Theory

NASA Astrophysics Data System (ADS)

Spindler, Matthew Kenneth

The integration of career and technical education (CTE) and academic curricular content that capitalizes on natural and inherent connections represents a challenge for CTE professionals. The research question that was used to guide the current study was: What are CTE teachers' perspectives of and experiences with the process of CTE and science content integration? And more specifically, to generate a grounded theory which explicates the process of CTE and science content integration from the perspective of CTE teachers. The CTE teachers expressed that the process of CTE and science content integration was a process of evolutionizing. From the perspective of the CTE teachers involved integrating CTE and science content resulted in their programs of study being adapted into something different than they were before the process of integration was begun. The CTE teachers revealed that the evolutions in their programs of study and themselves were associated with three other categories within the grounded theory: (a) connecting; (b) enacting; and (c) futuring. The process of CTE and science content integration represents a deep and complex episode for CTE teachers. The process of CTE and science content integration requires connecting to others, putting ideas into action, and an orienting towards the future.
Multi-functional materials by powder processing for a thermal protection system with self-cooling capability: Perspirable skin

NASA Astrophysics Data System (ADS)

Sun, Li

Aerodynamic heating generated by the friction between the atmosphere and the space vehicle's surface at reentry can enhance the temperature on the surface as high as 1700°C. A Thermal Protection System (TPS) is needed to inhibit the heat entering into the vehicle. Presently, the completely passive thermal protection is used for TPS. The thermal ablation/erosion and oxidization reaction of the current TPS is the major threat to the safety of the space vehicle. Therefore, a new design for TPS with actively self-cooling capability was proposed by bio-mimicking the perspiration of the human body, henceforth called Perspirable skin. The design of Perspirable Skin consists of core material shrink-fitted into a skin panel such as Reinforced Carbon-Carbon (RCC) Composite. The core material contains a very small Coefficient of Thermal Expansion (CTE) compared to the panel material. As temperature increases, the gap between the core and the skin are produced due to the CTE difference. Compressed gas on board the space vehicle will blow out from the gap once the surface temperature reaches a critical value. The cold gas flows over the surface and mixes with the atmospheric air to compensate for the frictional heat. With Perspirable Skin, the highest temperature on the surface is expected to decrease, and we assumed it to be around half of the present temperature. This dissertation focuses on the selection of the core materials and their manufacturing by powder processing. Based on a series of experiments, several results were obtained: (1) the effect of powder mixing on the compaction capability and sintering capability was determined; (2) a flat 3-layered Al 2O3/ZrO2 Functionally Graded Material (FGM) without cracks was fabricated; (3) the factors contributing to the cracks in the multi-layered materials were investigated; (4) an isotropic negative thermal expansion material, ZrW2O8, as well as its composites with ZrO2 were processed by in-situ reaction of WO3 and ZrO2; (5) several CTE prediction models on composites containing ZrW2O 8 were studied and proposed as a better scheme for applying the contiguity of phase; (6) a novel processing technique to produce ZrW2O 8-ZrO2 continuous FGMs was developed; and (7) the thermal and mechanical properties of the various materials were measured. Finally, using finite element analysis (FEA), the complete design of Perspirable Skin has been accomplished.
Composite materials for space applications

NASA Technical Reports Server (NTRS)

Rawal, Suraj P.; Misra, Mohan S.; Wendt, Robert G.

1990-01-01

The objectives of the program were to: generate mechanical, thermal, and physical property test data for as-fabricated advanced materials; design and fabricate an accelerated thermal cycling chamber; and determine the effect of thermal cycling on thermomechanical properties and dimensional stability of composites. In the current program, extensive mechanical and thermophysical property tests of various organic matrix, metal matrix, glass matrix, and carbon-carbon composites were conducted, and a reliable database was constructed for spacecraft material selection. Material property results for the majority of the as-fabricated composites were consistent with the predicted values, providing a measure of consolidation integrity attained during fabrication. To determine the effect of thermal cycling on mechanical properties, microcracking, and thermal expansion behavior, approximately 500 composite specimens were exposed to 10,000 cycles between -150 and +150 F. These specimens were placed in a large (18 cu ft work space) thermal cycling chamber that was specially designed and fabricated to simulate one year low earth orbital (LEO) thermal cycling in 20 days. With this rate of thermal cycling, this is the largest thermal cycling unit in the country. Material property measurements of the thermal cycled organic matrix composite laminate specimens exhibited less than 24 percent decrease in strength, whereas, the remaining materials exhibited less than 8 percent decrease in strength. The thermal expansion response of each of the thermal cycled specimens revealed significant reduction in hysteresis and residual strain, and the average CTE values were close to the predicted values.
Diamond-Reinforced Matrix Composites

DTIC Science & Technology

1993-05-10

by chemical vapor deposition ( CVD ). 14 While preferable, scratching and oil- coating of substrate filaments 15 may not be absolutely necessary. For...composites. 25 13 Docket No.: N.C. 72,578 PATENT APPLICATION Inventor’s Name: Natishan et al. 1 4) Anti -oxidation coatings such as refractory oxides or 2...the mismatch in the 5 coefficients of thermal expansion (CTE). By coating the 6 reinforcement with diamond prior to the final 7 anti -oxidant coating
A fiber Bragg grating--bimetal temperature sensor for solar panel inverters.

PubMed

Ismail, Mohd Afiq; Tamchek, Nizam; Hassan, Muhammad Rosdi Abu; Dambul, Katrina D; Selvaraj, Jeyrai; Rahim, Nasrudin Abd; Sandoghchi, Reza; Adikan, Faisal Rafiq Mahamd

2011-01-01

This paper reports the design, characterization and implementation of a fiber Bragg grating (FBG)-based temperature sensor for an insulted-gate Bipolar transistor (IGBT) in a solar panel inverter. The FBG is bonded to the higher coefficient of thermal expansion (CTE) side of a bimetallic strip to increase its sensitivity. Characterization results show a linear relationship between increasing temperature and the wavelength shift. It is found that the sensitivity of the sensor can be categorized into three characterization temperature regions between 26 °C and 90 °C. The region from 41 °C to 90 °C shows the highest sensitivity, with a value of 14 pm/°C. A new empirical model that considers both temperature and strain effects has been developed for the sensor. Finally, the FBG-bimetal temperature sensor is placed in a solar panel inverter and results confirm that it can be used for real-time monitoring of the IGBT temperature.
An evaluation of plastic surgery resident selection factors.

PubMed

Liang, Fan; Rudnicki, Pamela A; Prince, Noah H; Lipsitz, Stuart; May, James W; Guo, Lifei

2015-01-01

Our purpose was to provide a metric by which evaluation criteria are prioritized during resident selection. In this study, we assessed which residency applicant qualities are deemed important by members of the American Association of Plastic Surgeons (AAPS). A survey was distributed to all 580 AAPS members, and 295 responded to rate the importance of resident metrics, including measures of competency and personal characteristics. Demographic information, background training, and interaction with residents were also noted. Using SAS v9.2 (SAS Institute, Cary, NC), outcomes were analyzed across demographic groups with column trend exact (CTE) test for ordinal variables, Mantel-Haenszel trend test for interval variables, and Fisher exact test for discrete variables. Regarding competency metrics, letters of recommendation from known sources is the most important factor, whereas letters from unknown sources ranks the lowest. Character evaluations identified honesty as the most desirable trait; dishonesty was the most despised. Across demographic groups, academic surgeons and program directors value letters from known sources more than nonacademicians or nonprogram directors (CTE p = 0.005 and 0.002, respectively). Academicians and current program directors regard research more highly than their counterparts do (CTE p = 0.022 and 0.022, respectively). Currently, practicing surgeons, academicians, and program directors value hard work more than others (CTE p = 0.008, 0.033, and 0.029, respectively). Program directors emphasize maturity and patient commitment and are less tolerant of narcissism (CTE p = 0.002, 0.005, and 0.003, respectively). Lastly, academic surgeons and program directors look more favorably upon strong team players (CTE p < 0.00001 and p = 0.008, respectively), but less so over time (Mantel-Haenszel trend p = 0.006). We have examined applicant metrics that were deemed important by AAPS members and assessed their demographic interpretation. We hope this article provides a framework for plastic surgery resident selection and a guide for applicants to ascertain which qualities are highly regarded by programs. Although these attributes are highly desirable, future studies could identify if they are predictive of successful and productive plastic surgery residencies and careers. Copyright © 2014 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.
A novel breast software phantom for biomechanical modeling of elastography.

PubMed

Bhatti, Syeda Naema; Sridhar-Keralapura, Mallika

2012-04-01

In developing breast imaging technologies, testing is done with phantoms. Physical phantoms are normally used but their size, shape, composition, and detail cannot be modified readily. These difficulties can be avoided by creating a software breast phantom. Researchers have created software breast phantoms using geometric and/or mathematical methods for applications like image fusion. The authors report a 3D software breast phantom that was built using a mechanical design tool, to investigate the biomechanics of elastography using finite element modeling (FEM). The authors propose this phantom as an intermediate assessment tool for elastography simulation; for use after testing with commonly used phantoms and before clinical testing. The authors design the phantom to be flexible in both, the breast geometry and biomechanical parameters, to make it a useful tool for elastography simulation. The authors develop the 3D software phantom using a mechanical design tool based on illustrations of normal breast anatomy. The software phantom does not use geometric primitives or imaging data. The authors discuss how to create this phantom and how to modify it. The authors demonstrate a typical elastography experiment of applying a static stress to the top surface of the breast just above a simulated tumor and calculate normal strains in 3D and in 2D with plane strain approximations with linear solvers. In particular, they investigate contrast transfer efficiency (CTE) by designing a parametric study based on location, shape, and stiffness of simulated tumors. The authors also compare their findings to a commonly used elastography phantom. The 3D breast software phantom is flexible in shape, size, and location of tumors, glandular to fatty content, and the ductal structure. Residual modulus, maps, and profiles, served as a guide to optimize meshing of this geometrically nonlinear phantom for biomechanical modeling of elastography. At best, low residues (around 1-5 KPa) were found within the phantom while errors were elevated (around 10-30 KPa) at tumor and lobule boundaries. From our FEM analysis, the breast phantom generated a superior CTE in both 2D and in 3D over the block phantom. It also showed differences in CTE values and strain contrast for deep and shallow tumors and showed significant change in CTE when 3D modeling was used. These changes were not significant in the block phantom. Both phantoms, however, showed worsened CTE values for increased input tumor-background modulus contrast. Block phantoms serve as a starting tool but a next level phantom, like the proposed breast phantom, will serve as a valuable intermediate for elastography simulation before clinical testing. Further, given the CTE metrics for the breast phantom are superior to the block phantom, and vary for tumor shape, location, and stiffness, these phantoms would enhance the study of elastography contrast. Further, the use of 2D phantoms with plane strain approximations overestimates the CTE value when compared to the true CTE achieved with 3D models. Thus, the use of 3D phantoms, like the breast phantom, with no approximations, will assist in more accurate estimation of modulus, especially valuable for 3D elastography systems.
Materials and structures

NASA Astrophysics Data System (ADS)

Saito, Theodore T.; Langenbeck, Sharon L.; Al-Jamily, Ghanim; Arnold, Joe; Barbee, Troy; Coulter, Dan; Dolgin, Ben; Fichter, Buck; George, Patricia; Gorenstein, Paul

1992-08-01

Materials and structures technology covers a wide range of technical areas. Some of the most pertinent issues for the Astrotech 21 missions include dimensionally stable structural materials, advanced composites, dielectric coatings, optical metallic coatings for low scattered light applications, low scattered light surfaces, deployable and inflatable structures (including optical), support structures in 0-g and 1-g environments, cryogenic optics, optical blacks, contamination hardened surfaces, radiation hardened glasses and crystals, mono-metallic telescopes and instruments, and materials characterization. Some specific examples include low coefficients of thermal expansion (CTE) structures (0.01 ppm/K), lightweight thermally stable mirror materials, thermally stable optical assemblies, high reliability/accuracy (1 micron) deployable structures, and characterization of nanometer level behavior of materials/structures for interferometry concepts. Large filled-aperture concepts will require materials with CTE's of 10(exp 9) at 80 K, anti-contamination coatings, deployable and erectable structures, composite materials with CTE's less than 0.01 ppm/K and thermal hysteresis, 0.001 ppm/K. Gravitational detection systems such as LAGOS will require rigid/deployable structures, dimensionally stable components, lightweight materials with low conductivity, and high stability optics. The Materials and Structures panel addressed these issues and the relevance of the Astrotech 21 mission requirements by dividing materials and structures technology into five categories. These categories, the necessary development, and applicable mission/program development phasing are summarized. For each of these areas, technology assessments were made and development plans were defined.
Investigation of abrupt degradation of drain current caused by under-gate crack in AlGaN/GaN high electron mobility transistors during high temperature operation stress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Chang; Liao, XueYang; Li, RuGuan

2015-09-28

In this paper, we investigate the degradation mode and mechanism of AlGaN/GaN based high electron mobility transistors (HEMTs) during high temperature operation (HTO) stress. It demonstrates that there was abrupt degradation mode of drain current during HTO stress. The abrupt degradation is ascribed to the formation of crack under the gate which was the result of the brittle fracture of epilayer based on failure analysis. The origin of the mechanical damage under the gate is further investigated and discussed based on top-down scanning electron microscope, cross section transmission electron microscope and energy dispersive x-ray spectroscopy analysis, and stress simulation. Basedmore » on the coupled analysis of the failure physical feature and stress simulation considering the coefficient of thermal expansion (CTE) mismatch in different materials in gate metals/semiconductor system, the mechanical damage under the gate is related to mechanical stress induced by CTE mismatch in Au/Ti/Mo/GaN system and stress concentration caused by the localized structural damage at the drain side of the gate edge. These results indicate that mechanical stress induced by CTE mismatch of materials inside the device plays great important role on the reliability of AlGaN/GaN HEMTs during HTO stress.« less
Laser welding of fused silica glass with sapphire using a non- stoichiometric, fresnoitic Ba2TiSi2O8·3 SiO2 thin film as an absorber

NASA Astrophysics Data System (ADS)

de Pablos-Martín, A.; Lorenz, M.; Grundmann, M.; Höche, Th.

2017-07-01

Laser welding of dissimilar materials is challenging, due to their difference in coefficients of thermal expansion (CTE). In this work, fused silica-to-sapphire joints were achieved by employment of a ns laser focused in the intermediate Si-enriched fresnoitic glass thin film sealant. The microstructure of the bonded interphase was analyzed down to the nanometer scale and related to the laser parameters used. The crystallization of fresnoite in the glass sealant upon laser process leads to an intense blue emission intensity under UV excitation. This crystallization is favored in the interphase with the silica glass substrate, rather than in the border with the sapphire. The formation of SiO2 particles was confirmed, as well. The bond quality was evaluated by scanning acoustic microscopy (SAM). The substrates remain bonded even after heat treatment at 100 °C for 30 min, despite the large CTE difference between both substrates.
Mechanical Properties of Degraded PMR-15 Resin

NASA Technical Reports Server (NTRS)

Tsuji, Luis C.

2000-01-01

Thermo-oxidative aging produces a nonuniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hr. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and coefficient of thermal expansion (CTE) of nitrogen aged specimens were measured directly. The nitrogen-aged specimens were assumed to have the same properties as the interior material in the air-aged specimens. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

Influence of engineered interfaces on residual stresses and mechanical response in metal matrix composites

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Wilt, Thomas E.

1992-01-01

Because of the inherent coefficient of thermal expansion (CTE) mismatch between fiber and matrix within metal and intermetallic matrix composite systems, high residual stresses can develop under various thermal loading conditions. These conditions include cooling from processing temperature to room temperature as well as subsequent thermal cycling. As a result of these stresses, within certain composite systems, radial, circumferential, and/or longitudinal cracks have been observed to form at the fiber matrix interface region. A number of potential solutions for reducing this thermally induced residual stress field have been proposed recently. Examples of some potential solutions are high CTE fibers, fiber preheating, thermal anneal treatments, and an engineered interface. Here the focus is on designing an interface (by using a compensating/compliant layer concept) to reduce or eliminate the thermal residual stress field and, therefore, the initiation and propagation of cracks developed during thermal loading. Furthermore, the impact of the engineered interface on the composite's mechanical response when subjected to isothermal mechanical load histories is examined.
Thermal Expansion Studies of Selected High Temperature Thermoelectric Materials

NASA Technical Reports Server (NTRS)

Ravi, Vilupanur; Firdosy, Samad; Caillat, Thierry; Brandon, Erik; Van Der Walde, Keith; Maricic, Lina; Sayir, Ali

2008-01-01

Radioisotope thermoelectric generators (RTGs) generate electrical power by converting the heat released from the nuclear decay of radioactive isotopes (typically plutonium-238) into electricity using a thermoelectric converter. RTGs have been successfully used to power a number of space missions and have demonstrated their reliability over an extended period of time (tens of years) and are compact, rugged, radiation resistant, scalable, and produce no noise, vibration or torque during operation. System conversion efficiency for state-of-practice RTGs is about 6% and specific power less than or equal to 5.1 W/kg. Higher specific power would result in more on-board power for the same RTG mass, or less RTG mass for the same on-board power. The Jet Propulsion Laboratory has been leading, under the advanced thermoelectric converter (ATEC) project, the development of new high-temperature thermoelectric materials and components for integration into advanced, more efficient RTGs. Thermoelectric materials investigated to date include skutterudites, the Yb14MnSb11 compound, and SiGe alloys. The development of long-lived thermoelectric couples based on some of these materials has been initiated and is assisted by a thermo-mechanical stress analysis to ensure that all stresses under both fabrication and operation conditions will be within yield limits for those materials. Several physical parameters are needed as input to this analysis. Among those parameters, the coefficient of thermal expansion (CTE) is critically important. Thermal expansion coefficient measurements of several thermoelectric materials under consideration for ATEC are described in this paper. The stress response at the interfaces in material stacks subjected to changes in temperature is discussed, drawing on work from the literature and project-specific tools developed here. The degree of CTE mismatch and the associated effect on the formation of stress is highlighted.
High-Temperature Oxidation-Resistant and Low Coefficient of Thermal Expansion NiAl-Base Bond Coat Developed for a Turbine Blade Application

NASA Technical Reports Server (NTRS)

2003-01-01

Many critical gas turbine engine components are currently made from Ni-base superalloys that are coated with a thermal barrier coating (TBC). The TBC consists of a ZrO2-based top coat and a bond coat that is used to enhance the bonding between the superalloy substrate and the top coat. MCrAlY alloys (CoCrAlY and NiCrAlY) are currently used as bond coats and are chosen for their very good oxidation resistance. TBC life is frequently limited by the oxidation resistance of the bond coat, along with a thermal expansion mismatch between the metallic bond coat and the ceramic top coat. The aim of this investigation at the NASA Glenn Research Center was to develop a new longer life, higher temperature bond coat by improving both the oxidation resistance and the thermal expansion characteristics of the bond coat. Nickel aluminide (NiAl) has excellent high-temperature oxidation resistance and can sustain a protective Al2O3 scale to longer times and higher temperatures in comparison to MCrAlY alloys. Cryomilling of NiAl results in aluminum nitride (AlN) formation that reduces the coefficient of thermal expansion (CTE) of the alloy and enhances creep strength. Thus, additions of cryomilled NiAl-AlN to CoCrAlY were examined as a potential bond coat. In this work, the composite alloy was investigated as a stand-alone substrate to demonstrate its feasibility prior to actual use as a coating. About 85 percent of prealloyed NiAl and 15 percent of standard commercial CoCrAlY alloys were mixed and cryomilled in an attritor with stainless steel balls used as grinding media. The milling was carried out in the presence of liquid nitrogen. The milled powder was consolidated by hot extrusion or by hot isostatic pressing. From the consolidated material, oxidation coupons, four-point bend, CTE, and tensile specimens were machined. The CTE measurements were made between room temperature and 1000 C in an argon atmosphere. It is shown that the CTE of the NiAl-AlN-CoCrAlY composite bond coat is lower than that of the commercially used coating alloy 16-6. To examine the potential of NiAl-AlN-CoCrAlY as a bond coat, we subjected two samples to cyclic furnace testing. The furnace cycle consisted of 45 min at 1163 C (2125 F ) followed by 15 min of cooling out of the furnace. The current NASA baseline TBC is a NiCrAlY bond coat below the 7YSZ top coat. The average TBC life for this baseline coating on Ren N5 is 188 plus or minus 19 cycles. NiAl-AlN-CoCrAlY specimens coated with the same 7YSZ top coat were still intact even after 1000 cycles. Therefore, the NiAl-AlN-CoCrAlY as a bulk substrate material, exhibits more than 5 times the life of the current state-of-the-art material. The next step is to evaluate this material as a coating on the same superalloy substrate.
Development and Characterization of SiC)/ MoSi2-Si3N4(p) Hybrid Composites

NASA Technical Reports Server (NTRS)

Hebsur, Mohan G.

1998-01-01

Intermetallic compound MoSi2 has long been known as a high temperature material that has excellent oxidation resistance and electrical/thermal conductivity. Also its low cost, high melting point (2023 C), relatively low density (6.2 g/cu cm versus 9 g/cu cm for current engine materials), and ease of machining, make it an attractive structural material. However, the use of MoSi2 has been hindered due to its poor toughness at low temperatures, poor creep resistance at high temperatures, and accelerated oxidation (also known as 'pest' oxidation) at temperatures between approximately 450 and 550 C. Continuous fiber reinforcing is very effective means of improving both toughness and strength. Unfortunately, MoSi2 has a relatively high coefficient of thermal expansion (CTE) compared to potential reinforcing fibers such as SiC. The large CTE mismatch between the fiber and the matrix resulted in severe matrix cracking during thermal cycling. Addition of about 30 to 50 vol % of Si3N4 particulate to MoSi2 improved resistance to low temperature accelerated oxidation by forming a Si2ON2 protective scale and thereby eliminating catastrophic 'pest failure'. The Si3N4 addition also improved the high temperature creep strength by nearly five orders of magnitude, doubled the room temperature toughness and significantly lowered the CTE of the MoSi2 and eliminated matrix cracking in SCS-6 reinforced composites even after thermal cycling. The SCS-6 fiber reinforcement improved the room temperature fracture toughness by seven times and impact resistance by five times. The composite exhibited excellent strength and toughness improvement up to 1400 C. More recently, tape casting was adopted as the preferred processing of MoSi2-base composites for improved fiber spacing, ability to use small diameter fibers, and for lower cost. Good strength and toughness values were also obtained with fine diameter Hi-Nicalon tow fibers. This hybrid composite remains competitive with ceramic matrix composites as a replacement for Ni-base superalloys in aircraft engine applications.
Nickel-Graphite Composite Compliant Interface and/or Hot Shoe Material

NASA Technical Reports Server (NTRS)

Firdosy, Samad A.; Chun-Yip Li, Billy; Ravi, Vilupanur A.; Fleurial, Jean-Pierre; Caillat, Thierry; Anjunyan, Harut

2013-01-01

Next-generation high-temperature thermoelectric-power-generating devices will employ segmented architectures and will have to reliably withstand thermally induced mechanical stresses produced during component fabrication, device assembly, and operation. Thermoelectric materials have typically poor mechanical strength, exhibit brittle behavior, and possess a wide range of coefficient of thermal expansion (CTE) values. As a result, the direct bonding at elevated temperatures of these materials to each other to produce segmented leg components is difficult, and often results in localized microcracking at interfaces and mec hanical failure due to the stresses that arise from the CTE mismatch between the various materials. Even in the absence of full mechanical failure, degraded interfaces can lead to increased electrical and thermal resistances, which adversely impact conversion efficiency and power output. The proposed solution is the insertion of a mechanically compliant layer, with high electrical and thermal conductivity, between the low- and high-temperature segments to relieve thermomechanical stresses during device fabrication and operation. This composite material can be used as a stress-relieving layer between the thermoelectric segments and/or between a thermoelectric segment and a hot- or cold-side interconnect material. The material also can be used as a compliant hot shoe. Nickel-coated graphite powders were hot-pressed to form a nickel-graphite composite material. A freestanding thermoelectric segmented leg was fabricated by brazing the compliant pad layer between the high-temperature p- Zintl and low-temperature p-SKD TE segments using Cu-Ag braze foils. The segmented leg stack was heated in vacuum under a compressive load to achieve bonding. The novelty of the innovation is the use of composite material that re duces the thermomechanical stresses en - countered in the construction of high-efficiency, high-temperature therm - o-electric devices. The compliant pad enables the bonding of dissimilar thermoelectric materials while maintaining the desired electrical and thermal properties essential for efficient device operation. The modulus, CTE, electrical, and thermal conductances of the composite can be controlled by varying the ratio of nickel to graphite.
Advanced Polymers for Practical Use

NASA Technical Reports Server (NTRS)

1999-01-01

Resulting from a SBIR contract with the Goddard Space Flight Center, Foster-Miller developed a high performance, low cost substrate for printed circuits with a coefficient of thermal expansion (CTE) matched to the surface mounted devices. The commercial product that resulted from the agreement between the two organizations was so successful that Foster-Miller created a spin-off company named Superex, Inc., devoted solely to the promotion of this particular substrate. The contract originated from NASA's need to develop better, more cost effective satellite and land based electronic applications.
LDEF-space environmental effects on materials: Composites and silicone coatings

NASA Technical Reports Server (NTRS)

Petrie, Brian C.

1992-01-01

The effects of long term low Earth orbit environments on thermal control coatings and organic matrix/fiber reinforced composites are discussed. Two diverse categories are reported here: silicone coatings and composites. For composites physical and structural properties were analyzed; results are reported on mass/dimensional loss, microcracking, short beam shear, coefficient of thermal expansion (CTE), and flexural properties. The changes in thermal control properties, mass, and surface chemistry and morphology are reported and analyzed for the silicone coatings.
Numerical Simulation and Experiments of Fatigue Crack Growth in Multi-Layer Structures of MEMS and Microelectronic Devices

DTIC Science & Technology

2006-12-01

ABAQUS by use of the UEL subroutine feature. The damage variable was defined on averaged variables per element (Roe and Siegmund, 2003). The location of... thermal expansion (CTE) which is similar to silicon. During the anodic bonding process, the stack of silicon and glass wafers is placed on a hot plate and...Brinckmann, T. Siegmund, "Modeling fatigue crack growth with ABAQUS ," 2005 ABAQUS Fracture Review Team Meeting, Providence, RI, (2005). 8. S
Simple optimized Brenner potential for thermodynamic properties of diamond

NASA Astrophysics Data System (ADS)

Liu, F.; Tang, Q. H.; Shang, B. S.; Wang, T. C.

2012-02-01

We have examined the commonly used Brenner potentials in the context of the thermodynamic properties of diamond. A simple optimized Brenner potential is proposed that provides very good predictions of the thermodynamic properties of diamond. It is shown that, compared to the experimental data, the lattice wave theory of molecular dynamics (LWT) with this optimized Brenner potential can accurately predict the temperature dependence of specific heat, lattice constant, Grüneisen parameters and coefficient of thermal expansion (CTE) of diamond.
Chronic traumatic encephalopathy in sports: a historical and narrative review.

PubMed

Solomon, Gary

2018-01-01

My objectives are to review: 1) a brief history of sport-related concussion (SRC) and chronic traumatic encephalopathy (CTE), 2) the evolution of CTE in American professional football, 3) the data regarding SRC/CTE as they relate to depression and suicide, 4) the data on the neurocognitive effects of subconcussion/repetitive head trauma (with emphases on heading the ball in soccer and early exposure to football), 5) the evidence related to SRC and neurodegenerative diseases, 6) the published studies of CTE, 7) the NINDS neuropathological criteria for CTE, 8) public beliefs about SRC/CTE, and 9) the scientific questions regarding CTE.
Larval susceptibility of Aloe barbadensis and Cannabis sativa against Culex quinquefasciatus, the filariasis vector.

PubMed

Maurya, Prejwltta; Mohan, Lalit; Sharma, Preeti; Srivastava, C N

2008-11-01

Larvicidal potential of petroleum ether, carbon tetrachloride and methanol extracts of Aloe barbadensis and Cannabis sativa has been investigated against Culex quinquefasciatus. Among the extracts examined, Carbon tetrachloride extract (Cte) of Aloe barbadensis was the most effective with LC50 values of 15.31 and 11.01 ppm after 24 and 48 hr of exposure, respectively followed by pertoleum ether extract (Pee) of A barbadensis, Cte of C. sativa, methanol extract (Mee) of A. barbadensis, methanol and petroleum ether of C. saliva, LC, being 25.97, 88.51, 144.44, 160.78 and 294.42 ppm affer 24hr and 16.60, 68.69, 108.38, 71.71 and 73.32 ppm after 48 hr of post treatment, respectively. Cte of both the plants exhibits potential larvicidal activity and can be used as ecofriendly alternative in the management of the filariasis vector, Culex quinquefasciatus.
Fabrication of Lanthanum Telluride 14-1-11 Zintl High-Temperature Thermoelectric Couple

NASA Technical Reports Server (NTRS)

Ravi, Vilupanur A.; Li, Billy Chun-Yip; Fleurial, Pierre; Star, Kurt

2010-01-01

The development of more efficient thermoelectric couple technology capable of operating with high-grade heat sources up to 1,275 K is key to improving the performance of radioisotope thermoelectric generators. Lanthanum telluride La3-xTe4 and 14-1-11 Zintls (Yb14MnSb11) have been identified as very promising materials. The fabrication of advanced high-temperature thermoelectric couples requires the joining of several dissimilar materials, typically including a number of diffusion bonding and brazing steps, to achieve a device capable of operating at elevated temperatures across a large temperature differential (up to 900 K). A thermoelectric couple typically comprises a heat collector/ exchanger, metallic interconnects on both hot and cold sides, n-type and ptype conductivity thermoelectric elements, and cold-side hardware to connect to the cold-side heat rejection and provide electrical connections. Differences in the physical, mechanical, and chemical properties of the materials that make up the thermoelectric couple, especially differences in the coefficients of thermal expansion (CTE), result in undesirable interfacial stresses that can lead to mechanical failure of the device. The problem is further complicated by the fact that the thermoelectric materials under consideration have large CTE values, are brittle, and cracks can propagate through them with minimal resistance. The inherent challenge of bonding brittle, high-thermal-expansion thermoelectric materials to a hot shoe material that is thick enough to carry the requisite electrical current was overcome. A critical advantage over prior art is that this device was constructed using all diffusion bonds and a minimum number of assembly steps. The fabrication process and the materials used are described in the following steps: (1) Applying a thin refractory metal foil to both sides of lanthanum telluride. To fabricate the n-type leg of the advanced thermoelectric couple, the pre-synthesized lanthanum telluride coupon was diffusion bonded to the metal foil using a thin adhesion layer. (2) Repeating a similar process for the 14-1-11 Zintl p-type leg of the advanced thermoelectric couple. (3) Bonding thick CTE-matched metal plates on the metallized lanthanum telluride and Yb14MnSb11 to form the hot and cold sides of the thermoelectric couple. The calculated conversion efficiency of such an advanced couple would be about 10.5 percent, about 35 percent better than heritage radioisotope thermoelectric technology that relies on Si-Ge alloys. In addition, unlike Si-Ge alloys, these materials can be combined with many other thermoelectric materials optimized for operation at lower temperatures to achieve conversion efficiency in excess of 15 percent (a factor of 2 increase over heritage technology).
Career and Technical Education (CTE) Directors' Experiences with CTE's Contributions to Science, Technology, Engineering, and Math (STEM) Education Implementation

ERIC Educational Resources Information Center

Nkhata, Bentry

2013-01-01

In spite of the large overlap in the goals of CTE and STEM education, there is little evidence of the role(s) CTE delivery systems, programs, curricula, or pedagogical strategies can play in advancing STEM education. Because of their responsibilities, especially for organizational and instructional leadership, school district CTE directors could…
Chronic traumatic encephalopathy-integration of canonical traumatic brain injury secondary injury mechanisms with tau pathology.

PubMed

Kulbe, Jacqueline R; Hall, Edward D

2017-11-01

In recent years, a new neurodegenerative tauopathy labeled Chronic Traumatic Encephalopathy (CTE), has been identified that is believed to be primarily a sequela of repeated mild traumatic brain injury (TBI), often referred to as concussion, that occurs in athletes participating in contact sports (e.g. boxing, American football, Australian football, rugby, soccer, ice hockey) or in military combatants, especially after blast-induced injuries. Since the identification of CTE, and its neuropathological finding of deposits of hyperphosphorylated tau protein, mechanistic attention has been on lumping the disorder together with various other non-traumatic neurodegenerative tauopathies. Indeed, brains from suspected CTE cases that have come to autopsy have been confirmed to have deposits of hyperphosphorylated tau in locations that make its anatomical distribution distinct for other tauopathies. The fact that these individuals experienced repetitive TBI episodes during their athletic or military careers suggests that the secondary injury mechanisms that have been extensively characterized in acute TBI preclinical models, and in TBI patients, including glutamate excitotoxicity, intracellular calcium overload, mitochondrial dysfunction, free radical-induced oxidative damage and neuroinflammation, may contribute to the brain damage associated with CTE. Thus, the current review begins with an in depth analysis of what is known about the tau protein and its functions and dysfunctions followed by a discussion of the major TBI secondary injury mechanisms, and how the latter have been shown to contribute to tau pathology. The value of this review is that it might lead to improved neuroprotective strategies for either prophylactically attenuating the development of CTE or slowing its progression. Copyright © 2017 Elsevier Ltd. All rights reserved.
Increasing the doping efficiency by surface energy control for ultra-transparent graphene conductors.

PubMed

Chang, Kai-Wen; Hsieh, Ya-Ping; Ting, Chu-Chi; Su, Yen-Hsun; Hofmann, Mario

2017-08-22

Graphene's attractiveness in many applications is limited by its high resistance. Extrinsic doping has shown promise to overcome this challenge but graphene's performance remains below industry requirements. This issue is caused by a limited charge transfer efficiency (CTE) between dopant and graphene. Using AuCl 3 as a model system, we measure CTE as low as 5% of the expected values due to the geometrical capacitance of small adsorbate clusters. We here demonstrate a strategy for enhancing the CTE by a two-step optimization of graphene's surface energy prior to AuCl 3 doping. First, exposure to UV ozone modified the hydrophilicity of graphene and was found to decrease the cluster's geometric capacitance, which had a direct effect on the CTE. Occurrence of lattice defects at high UV exposure, however, deteriorated graphene's transport characteristics and limited the effectiveness of this pretreatment step. Thus, prior to UV exposure, a functionalized polymer layer was introduced that could further enhance graphene's surface energy while protecting it from damage. Combination of these treatment steps were found to increase the AuCl 3 charge transfer efficiency to 70% and lower the sheet resistance to 106 Ω/γ at 97% transmittance which represents the highest reported performance for doped single layer graphene and is on par with commercially available transparent conductors.
CarbAl Heat Transfer Material

NASA Technical Reports Server (NTRS)

Fink, Richard

2015-01-01

The increasing use of power electronics, such as high-current semiconductor devices and modules, within space vehicles is driving the need to develop specialty thermal management materials in both the packaging of these discrete devices and the packaging of modules consisting of these device arrays. Developed by Applied Nanotech, Inc. (ANI), CarbAl heat transfer material is uniquely characterized by its low density, high thermal diffusivity, and high thermal conductivity. Its coefficient of thermal expansion (CTE) is similar to most power electronic materials, making it an effective base plate substrate for state-of-the-art silicon carbide (SiC) super junction transistors. The material currently is being used to optimize hybrid vehicle inverter packaging. Adapting CarbAl-based substrates to space applications was a major focus of the SBIR project work. In Phase I, ANI completed modeling and experimentation to validate its deployment in a space environment. Key parameters related to cryogenic temperature scaling of CTE, thermal conductivity, and mechanical strength. In Phase II, the company concentrated on improving heat sinks and thermally conductive circuit boards for power electronic applications.
Repetitive Head Impacts and Chronic Traumatic Encephalopathy

PubMed Central

McKee, Ann C.; Alosco, Michael; Huber, Bertrand R.

2016-01-01

There are growing concerns that cumulative repetitive head impact exposure through routine participation in contact and collision sports is associated with increased risk of long-term problems in memory and cognition, including the development of chronic traumatic encephalopathy (CTE). CTE is a distinctive neurodegenerative disease that occurs as a result of repetitive head impacts (RHI) including concussion and subconcussion. Like most neurodegenerative diseases, CTE can only be diagnosed by postmortem neuropathologic examination of brain tissue. Recently a panel of exerts concluded that CTE is a unique disorder with a pathognomonic lesion that can be reliably distinguished from other neurodegenerative diseases, such as Alzheimer’s disease and frontotemporal lobar degeneration. The pathognomonic lesion of CTE consists of a perivascular accumulation of hyperphosphorylated tau protein in neurons and astrocytes in an irregular pattern, and is typically most prominent at the depths of the cerebral sulci. Clinically CTE is associated with violent behaviors, explosivity, a loss of control, depression, suicide, memory loss and cognitive changes. While the exact incidence and prevalence of CTE remain unknown, there is increasing evidence that CTE affects amateur atheletes as well as professional athletes and military veterans. Given the millions of contact sport athletes and military service members who are exposed to RHI each year, CTE has become a major public health concern. There is a critical need for identification of CTE during life, improved understanding of the epidemiology and pathobiology, and the development of effective prevention and treatment strategies for CTE. PMID:27637402
Thermophysical ESEM and TEM Characterization of Carbon Fibers CTE, Spectroscopy and Roughness Studies at High Temperatures

NASA Technical Reports Server (NTRS)

Ochoa, Ozden O.

2004-01-01

Accurate determination of the transverse properties of carbon fibers is important for assessment and prediction of local material as well as global structural response of composite components. However the measurements are extremely difficult due to the very small diameters of the fibers (few microns only) and must be conducted within a microscope. In this work, environmental scanning electron microscope (ESEM) and transmission electron microscope (TEM) are used to determine the transverse coefficient of thermal expansion of different carbon fibers as a function of temperature.
PROPULSION AND POWER RAPID RESPONSE RESEARCH AND DEVELOPMENT (R&D) SUPPORT. Deliver Order 0002: Power-Dense, Solid Oxide Fuel Cell Systems: High-Performance, High-Power-Density Solid Oxide Fuel Cells - Materials and Load Control

DTIC Science & Technology

2010-04-01

aluminum titanate has evolved from a coefficient of thermal expansion (CTE) lowering additive in traditional nickel/YSZ cermets to an anchoring...provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently...volumetric concentrations well below percolation for traditional cermets . The coarsening of nickel after high temperature thermal treatment poses
Is phosphorylated tau unique to chronic traumatic encephalopathy? Phosphorylated tau in epileptic brain and chronic traumatic encephalopathy.

PubMed

Puvenna, Vikram; Engeler, Madeline; Banjara, Manoj; Brennan, Chanda; Schreiber, Peter; Dadas, Aaron; Bahrami, Ashkon; Solanki, Jesal; Bandyopadhyay, Anasua; Morris, Jacqueline K; Bernick, Charles; Ghosh, Chaitali; Rapp, Edward; Bazarian, Jeffrey J; Janigro, Damir

2016-01-01

Repetitive traumatic brain injury (rTBI) is one of the major risk factors for the abnormal deposition of phosphorylated tau (PT) in the brain and chronic traumatic encephalopathy (CTE). CTE and temporal lobe epilepsy (TLE) affect the limbic system, but no comparative studies on PT distribution in TLE and CTE are available. It is also unclear whether PT pathology results from repeated head hits (rTBI). These gaps prevent a thorough understanding of the pathogenesis and clinical significance of PT, limiting our ability to develop preventative and therapeutic interventions. We quantified PT in TLE and CTE to unveil whether a history of rTBI is a prerequisite for PT accumulation in the brain. Six postmortem CTE (mean 73.3 years) and age matched control samples were compared to 19 surgically resected TLE brain specimens (4 months-58 years; mean 27.6 years). No history of TBI was present in TLE or control; all CTE patients had a history of rTBI. TLE and CTE brain displayed increased levels of PT as revealed by immunohistochemistry. No age-dependent changes were noted, as PT was present as early as 4 months after birth. In TLE and CTE, cortical neurons, perivascular regions around penetrating pial vessels and meninges were immunopositive for PT; white matter tracts also displayed robust expression of extracellular PT organized in bundles parallel to venules. Microscopically, there were extensive tau-immunoreactive neuronal, astrocytic and degenerating neurites throughout the brain. In CTE perivascular tangles were most prominent. Overall, significant differences in staining intensities were found between CTE and control (P<0.01) but not between CTE and TLE (P=0.08). pS199 tau analysis showed that CTE had the most high molecular weight tangle-associated tau, whereas epileptic brain contained low molecular weight tau. Tau deposition may not be specific to rTBI since TLE recapitulated most of the pathological features of CTE. Copyright © 2015 Elsevier B.V. All rights reserved.

Is phosphorylated tau unique to chronic traumatic encephalopathy? Phosphorylated tau in epileptic brain and chronic traumatic encephalopathy

PubMed Central

Puvenna, Vikram; Engeler, Madeline; Banjara, Manoj; Brennan, Chanda; Schreiber, Peter; Dadas, Aaron; Bahrami, Ashkon; Solanki, Jesal; Bandyopadhyay, Anasua; Morris, Jacqueline K.; Bernick, Charles; Ghosh, Chaitali; Bazarian, Jeffrey J.; Janigro, Damir

2016-01-01

Repetitive traumatic brain injury (rTBI) is one of the major risk factors for the abnormal deposition of phosphorylated tau (PT) in the brain and chronic traumatic encephalopathy (CTE). CTE and temporal lobe epilepsy (TLE) affect the limbic system, but no comparative studies on PT distribution in TLE and CTE are available. It is also unclear whether PT pathology results from repeated head hits (rTBI). These gaps prevent a thorough understanding of the pathogenesis and clinical significance of PT, limiting our ability to develop preventative and therapeutic interventions. We quantified PT in TLE and CTE to unveil whether a history of rTBI is a prerequisite for PT accumulation in the brain. Six post mortem CTE (mean 73.3 years) and age matched control samples were compared to 19 surgically resected TLE brain specimens (4 months-58 years; mean 27.6 years). No history of TBI was present in TLE or control; all CTE patients had a history of rTBI. TLE and CTE brain displayed increased levels of PT as revealed by immunohistochemistry. No age-dependent changes were noted, as PT was present as early as 4 months after birth. In TLE and CTE, cortical neurons, perivascular regions around penetrating pial vessels and meninges were immunopositive for PT; white matter tracts also displayed robust expression of extracellular PT organized in bundles parallel to venules. Microscopically, there were extensive tau-immunoreactive neuronal, astrocytic and degenerating neurites throughout the brain. In CTE perivascular tangles were most prominent. Overall, significant differences in staining intensities were found between CTE and control (P<0.01) but not between CTE and TLE (P=0.08). pS199 tau analysis showed that CTE had the most high molecular weight tangle-associated tau, whereas epileptic brain contained low molecular weight tau. Tau deposition may not be specific to rTBI since TLE recapitulated most of the pathological features of CTE. PMID:26556772
The neuropathology of chronic traumatic encephalopathy.

PubMed

McKee, Ann C; Stein, Thor D; Kiernan, Patrick T; Alvarez, Victor E

2015-05-01

Repetitive brain trauma is associated with a progressive neurological deterioration, now termed as chronic traumatic encephalopathy (CTE). Most instances of CTE occur in association with the play of sports, but CTE has also been reported in association with blast injuries and other neurotrauma. Symptoms of CTE include behavioral and mood changes, memory loss, cognitive impairment and dementia. Like many other neurodegenerative diseases, CTE is diagnosed with certainty only by neuropathological examination of brain tissue. CTE is a tauopathy characterized by the deposition of hyperphosphorylated tau (p-tau) protein as neurofibrillary tangles, astrocytic tangles and neurites in striking clusters around small blood vessels of the cortex, typically at the sulcal depths. Severely affected cases show p-tau pathology throughout the brain. Abnormalities in phosphorylated 43 kDa TAR DNA-binding protein are found in most cases of CTE; beta-amyloid is identified in 43%, associated with age. Given the importance of sports participation and physical exercise to physical and psychological health as well as disease resilience, it is critical to identify the genetic risk factors for CTE as well as to understand how other variables, such as stress, age at exposure, gender, substance abuse and other exposures, contribute to the development of CTE. © 2015 International Society of Neuropathology.
The Neuropathology of Chronic Traumatic Encephalopathy

PubMed Central

McKee, Ann C.; Stein, Thor D.; Kiernan, Patrick T.; Alvarez, Victor E.

2015-01-01

Repetitive brain trauma is associated with a progressive neurological deterioration, now termed as chronic traumatic encephalopathy (CTE). Most instances of CTE occur in association with the play of sports, but CTE has also been reported in association with blast injuries and other neurotrauma. Symptoms of CTE include behavioral and mood changes, memory loss, cognitive impairment and dementia. Like many other neurodegenerative diseases, CTE is diagnosed with certainty only by neuropathological examination of brain tissue. CTE is a tauopathy characterized by the deposition of hyperphosphorylated tau (p-tau) protein as neurofibrillary tangles, astrocytic tangles and neurites in striking clusters around small blood vessels of the cortex, typically at the sulcal depths. Severely affected cases show p-tau pathology throughout the brain. Abnormalities in phosphorylated 43 kDa TAR DNA-binding protein are found in most cases of CTE; beta-amyloid is identified in 43%, associated with age. Given the importance of sports participation and physical exercise to physical and psychological health as well as disease resilience, it is critical to identify the genetic risk factors for CTE as well as to understand how other variables, such as stress, age at exposure, gender, substance abuse and other exposures, contribute to the development of CTE. PMID:25904048
UVIS CTE Monitor: Star Clusters

NASA Astrophysics Data System (ADS)

Noeske, Kai

2010-09-01

*** NOTE 2: 2ND CHANGE MAR 26 2011: VISIT 13 HAD FAILED. APPROVED FOR REPETITION. ****** NEW VISIT 14 IS IDENTICAL TO FORMER VISIT 13, WITH EXCEPTIONS THAT SOME SUBEXPOSURES ARE REMOVED. ****** SEE OBSERVING DESCRIPTION FOR DETAILS. ****** NOTE: THIS IS A CHANGED PHASE II PROPOSAL AFTER VISITS 1,2,7 HAD BEEN EXECUTED ****** CHANGES BECAME NECESSARY AFTER ANALYSIS OF INCOMING CALIBRATION DATA FROM 12379 AND 12348 ****** THIS REVISED PHASE II {submission 14FEB2011} ADDS THE EVALUATION OF CHARGE INJECTION***The changes amount to:1} dropping the 3rd epoch {August 2011} of external CTE monitoring {3 orbits}2} simplifying the CTE monitor observations in the second epoch {March 2011}, freeing up 1 orbit3} using the freed up orbits from 1} and 2}, together with two additional external orbits that we were granted, to thoroughly assess the data quality of charge - injected data under realistic observing setups.These charge-injected observations will be obtained during the 2nd epoch of the CTE monitor program, in the March 2011 window.------ Original Text prior to 14 Feb 2011 below this line -----------This program extends the Cycle 17 external CTE calibration {CAL/WFC3 ID 11924} program for WFC3/UVIS over Cycle 18. Targets are {i} the sparse cluster NGC 6791 observed in Cycle 17, to continue a consistent set of observations that allows to isolate the time evolution of the CTE, and {ii} a denser field in 47 Tuc {NGC 104}. The latter will provide data to measure the dependence of the CTE on field crowding. It will also provide a consistent comparison between the CTE evolution of WFC3/UVIS and that of ACS/WFC at the same time into the flight {1 year}, because ACS/WFC CTE data were based on 47 Tuc observations. Additional observations of 47 Tuc in the CVZ will provide a wide range of background levels to measure the background dependence of the UVIS CTE.Goals are {i} the continued monitoring of the time evolution of the WFC3/UVIS CTE, {ii} establishing the detector X,Y dependence of the CTE, {iii} CTE dependence of the background level and {iv} an improved CTE correction model based on these measurements. These goals include CTE effects on both photometry and astrometry.
Endorsements, Electives & More: CTE & State Graduation Requirements

ERIC Educational Resources Information Center

National Association of State Directors of Career Technical Education Consortium, 2015

2015-01-01

The past few years have seen a persistent and consistent focus on Career Technical Education (CTE), including a particular focus on graduation requirements. This brief from Advance CTE highlights a few ways in which states are exploring embedding and elevating CTE programs, assessments and experiences within their statewide graduation…
A Profile of School-Based Enterprises within CTE Disciplines

ERIC Educational Resources Information Center

Haltinner, Urs; Mooney, Carol; Stanislawski, Debbie

2012-01-01

It is imperative that career and technical education (CTE) utilize research-proven pedagogy. Pushing on relevance to arrive at rigor provides an opportunity for "limited" and "perpetual duration" real-world learning experiences to be implemented within every contemporary CTE program. This study describes how secondary CTE programs are currently…
Specifications for Developing Secondary Program Proposals.

ERIC Educational Resources Information Center

Maryland State Dept. of Education, Baltimore. Div. of Career Technology and Adult Learning.

This document, which is designed for individuals developing local career and technology education (CTE) program proposals and/or designing new CTE facilities in Maryland, presents the CTE program specifications that were developed to ensure the quality of CTE programs in public schools in Maryland. The document is divided into four sections. The…
The Status of Preservice Education in Career and Technology Education.

ERIC Educational Resources Information Center

Bruening, Thomas H.; Scanlon, Dennis C.; Hodes, Carol L.

A study collected baseline data about the status of teacher preservice Career and Technology Education (CTE) from program chairs at colleges and universities in the United Status. The survey had six sections: pedagogical competencies for CTE teachers, CTE certification process, course delivery, recent program revisions, CTE program demographics,…
Design and manufacture of a lightweight piezo-composite curved actuator

NASA Astrophysics Data System (ADS)

Yoon, K. Joon; Shin, Seokjun; Park, Hoon C.; Goo, Nam Seo

2002-02-01

In this paper we are concerned with the design, manufacture and performance test of a lightweight piezo-composite curved actuator (called LIPCA) using a top carbon fiber composite layer with near-zero coefficient of thermal expansion (CTE), a middle PZT ceramic wafer, and a bottom glass/epoxy layer with a high CTE. The main point of the design for LIPCA is to replace the heavy metal layers of THUNDERTM by lightweight fiber reinforced plastic layers without losing the capabilities for generating high force and large displacement. It is possible to save up to about 40% of the weight if we replace the metallic backing material by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use an epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a carbon prepreg were simply stacked and cured at an elevated temperature (177 °C) after following an autoclave bagging process. We found that the manufactured composite laminate device had a sufficient curvature after being detached from a flat mould. An analysis method using the classical lamination theory is presented to predict the curvature of LIPCA after curing at an elevated temperature. The predicted curvatures are in quite good agreement with the experimental values. In order to investigate the merits of LIPCA, performance tests of both LIPCA and THUNDERTM have been conducted under the same boundary conditions. From the experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDERTM.
Influence of firing time and framework thickness on veneered Y-TZP discs curvature.

PubMed

Jakubowicz-Kohen, Boris D; Sadoun, Michaël J; Douillard, Thierry; Mainjot, Amélie K

2014-02-01

The objective of the present work was to study the curvature of very thinly, veneered Y-TZP discs of different framework thicknesses submitted to different firing times. Fifteen 20-mm-wide Y-TZP discs were produced in three different thicknesses: 0.75, 1, 1.5mm. One disc from each group was left unveneered while the others were layered with a 0.1mm veneering ceramic layer. All discs underwent five firing cycles for a total cumulative firing time of 30 min, 1, 2, 5 and 10h at 900°C. The curvature profile was measured using a profilometer after the veneering process and after each firing cycle respectively. A fitted curve was then used to estimate the, curvature radius. The coefficient of thermal expansion (CTE) measurements were taken on veneering, ceramic and Y-TZP beam samples that underwent the same firing schedule. Those data were used to calculate the curvature generated by CTE variations over firing time. All bilayered samples exhibited a curvature that increased over firing time inversely to framework thickness. However non-veneered samples did not exhibit any curvature modification. The results of the present study reveal that even a very thin veneer layer (0.1mm) can induce a significant curvature of Y-TZP discs. The dilatometric results showed that Tg and CTE, variations are not sufficient to explain this curvature. A chemical-induced zirconia volume, augmentation located at the framework sub-surface near the interface could explain the sample, curvature and its increase with firing time. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Trends in CTE Coursetaking. Data Point. NCES 2014-901

ERIC Educational Resources Information Center

Hudson, Lisa

2013-01-01

This NCES Data Point shows changes in high school students' participation in career and technical education (CTE) between 1990 and 2009. The Data Point documents an overall decline in CTE participation during this period, although participation increased in some CTE occupational areas, such as communications and health care. (Contains 2 figures.)
Maryland's Library Public Awareness Campaign for CTE

ERIC Educational Resources Information Center

Gilli, Lynne M.; Lohnes, Marjorie R.

2011-01-01

Career and technical education (CTE) has grown and changed tremendously over the past 20 years. While great strides have been made in upgrading CTE in Maryland, many parents, students, policymakers and community members were not familiar with the "new and improved" CTE. In a bid to spread the word about the "new and improved"…
Chronic traumatic encephalopathy: contributions from the Boston University Center for the Study of Traumatic Encephalopathy.

PubMed

Riley, David O; Robbins, Clifford A; Cantu, Robert C; Stern, Robert A

2015-01-01

Chronic Traumatic Encephalopathy (CTE) is a neurodegenerative disease associated with repetitive brain trauma (RBT). Initially described in boxers, CTE has now been found in other contact sport athletes with a history of RBT. In recent years, there has been tremendous media attention regarding CTE, primarily because of the deaths of high profile American football players who were found to have CTE upon neuropathological examination. However, the study of CTE remains in its infancy. This review focuses on research from the Centre for the Study of Traumatic Encephalopathy (CSTE) at Boston University. This study reviews the formation of the CSTE, major CSTE publications and current ongoing research projects at the CSTE. The neuropathology of CTE has been well-described. Current research focuses on: methods of diagnosing the disease during life (including the development of biomarkers), examination of CTE risk factors (including genetic susceptibility and head impact exposure variables); description of the clinical presentation of CTE; development of research diagnostic criteria for Traumatic Encephalopathy Syndrome; and assessment of mechanism and pathogenesis. Current research at the BU CSTE is aimed at increasing understanding of the long-term consequences of repetitive head impacts and attempting to begin to answer several of the unanswered questions regarding CTE.
WFC3/UVIS External CTE Monitor: Single-Chip CTE Measurements

NASA Astrophysics Data System (ADS)

Gosmeyer, C. M.; Baggett, S.

2016-12-01

We present the first results of single-chip measurements of charge transfer efficiency (CTE) in the UVIS channel of the Hubble Space Telescope Wide Field Camera 3 (HST/WFC3). This test was performed in Cycle 20 in two visits. In the first visit a field in the star cluster NGC 6583 was observed. In a second visit, the telescope returned to the field, but rotated by 180 degrees and with a shift in pointing that allowed the same stars to be imaged, near and far from the amplifiers, on the same chip of the two-chip UVIS field of-view. This dataset enables a measurement of CTE loss on each separate chip. The current CTE monitor measures CTE loss as an average of the two chips because it dithers by a chip-height to obtain observations of the same sources near and far from the amplifiers, instead of the more difficult to-schedule 180-degree rotation. We find that CTE loss is worse on Chip 1 than on Chip 2 across all cases for which we had data: short and long exposures and w! ith and without the pixel-based CTE correction. In the best case, for long exposures with the CTE correction applied, the max difference between the two chip's flux losses is 3%/2048 pixels. This case should apply for most science observations where the background is 12 e-/pixel. In the worst case of low-background short exposures, e.g. those without post-flash, the max difference between the two chips is 17% flux loss/2048 pixels. Uncertainties are <0.01% flux loss/2048 pixels. Because of the two chips' different CTE loss rates, we will consider adding this test as part of the routine yearly monitor and creating a chip-specific CTE correction software.
From Shock to Action: Pathway to Success

ERIC Educational Resources Information Center

Stone, Michael R.

2012-01-01

Career and technical education (CTE) is forced to be reactive. A good example is the fact that CTE cannot prepare students for jobs that do not exist. Outside forces create the demand for occupations and workers: CTE has to react to the demand. CTE must also respond and react to changes created by legislative mandates and administrative order. Due…
Exploring the Technical Expression of Academic Knowledge: The Science-in-CTE Pilot Study

ERIC Educational Resources Information Center

Pearson, Donna; Young, R. Brent; Richardson, George B.

2013-01-01

The Science-in-CTE pilot study tested a curriculum integration model that enhanced the science that oc-curs in CTE curricula. The study replicated the National Research Center for Career and Technical Ed-ucation's (NRCCTE) Math-in-CTE experimental research design (Stone, Alfeld, & Pearson, 2008) with applied science in secondary agricultural…
Gender, Career and Technical Education (CTE) Nontraditional Coursetaking, and Wage Gap

ERIC Educational Resources Information Center

Fluhr, Stephanie A.; Choi, Namok; Herd, Ann; Woo, Hongryun; Alagaraja, Meera

2017-01-01

The two main objectives of this study were to examine the relationship between high school student (9th-12th) gender and nontraditional career and technical education (CTE) course taking, and the combined effects of gender and program area on estimated future wage earnings for male and female CTE completers. A Midwestern state CTE database…
CTE's Role in Energy and Environmental Sustainability

ERIC Educational Resources Information Center

Hyslop, Alisha

2009-01-01

ACTE Issue Briefs are designed to highlight the role of career and technical education (CTE) in a broader issue of national interest. Each Brief is designed to strengthen the voice of CTE related to the specific issue and to draw more attention to CTE activities and best practices around the country. The Briefs provide background information,…
Mapping the Chapter: One Way to Tackle the CTE Textbook

ERIC Educational Resources Information Center

Laverick DeFelice, Catherine

2010-01-01

This reading specialist has come up with a strategy to help other CTE instructors map the CTE textbook, so that students can better comprehend the information in them and discover a joy of reading. CTE textbooks present a particular challenge because they are packed with information and can be quite different in structure than texts student have…
Measuring the Return on Investment for CTE

ERIC Educational Resources Information Center

Kotamraju, Pradeep

2011-01-01

Career and technical education (CTE) is increasingly being seen as a major contributor to the recovery of the U.S. economy. However, questions exist as to the effectiveness and impact of CTE. One is whether the federal investment (Carl D. Perkins Act) in CTE is paying off. To answer this, there is a need to establish the "internal…

CT enterography for Crohn's disease: accurate preoperative diagnostic imaging.

PubMed

Vogel, Jon; da Luz Moreira, Andre; Baker, Mark; Hammel, Jeffery; Einstein, David; Stocchi, Luca; Fazio, Victor

2007-11-01

CT enterography (CTE) is a technique that provides detailed images of the small bowel by using a low Hounsfield unit oral contrast media. This study was designed to correlate CTE findings with operative findings in patients with Crohn's disease. We performed a retrospective study of all patients with Crohn's disease of the small bowel or colon, who had CTE and subsequent small bowel or colon surgery within three months after the CT examination. CTE findings of stricture, fistula, inflammatory mass, abscess, and combinations of these abnormalities were compared with operative findings. Specialist radiologists and fellowship-trained colorectal surgeons participated in the study. The Fisher's exact test or chi-squared tests were used with respect to categorical data, and the Wilcoxon's rank-sum test was used for quantitative data. In 36 patients, the presence or absence of stricture, fistula, abscess, or inflammatory mass was correctly determined by CTE in 100, 94, 100, and 97 percent, respectively. The accuracy for stricture or fistula number was 83 and 86 percent, respectively. There were nine patients with multiple disease phenotypes identified on CTE of which eight were confirmed at surgery. CTE overestimated or underestimated the extent of disease in 11 patients (31 percent). CTE is an accurate preoperative diagnostic imaging study for small-bowel Crohn's disease. The ability of this imaging study to detect both luminal and extraluminal pathology is a distinct advantage of CTE compared with small-bowel contrast studies.
Why Are You Here? CTE Students' Enrollment Motivations and Career Aspirations

ERIC Educational Resources Information Center

DeFeo, Dayna Jean

2015-01-01

This is a study of 1,134 high school students enrolled in career and technical education (CTE) classes for which they could receive articulated credit at a local community college. We sought to understand why students take CTE classes, what their career aspirations are, whether or not they know about career opportunities in CTE fields, and whether…
New Directions for High School Career and Technical Education in Wyoming: A Strategic Plan

ERIC Educational Resources Information Center

Hoachlander, Gary; Klein, Steven; Studier, Carol

2007-01-01

This report offers a plan for improving career and technical education (CTE) in Wyoming, but it is about more than just technical education. Realizing the potential of CTE to contribute to students' mastery of both academic and technical knowledge depends not only on strengthening the CTE curriculum, but also on embedding CTE in a larger program…
Transcriptome analyses of chronic traumatic encephalopathy show alterations in protein phosphatase expression associated with tauopathy

PubMed Central

Seo, Jeong-Sun; Lee, Seungbok; Shin, Jong-Yeon; Hwang, Yu Jin; Cho, Hyesun; Yoo, Seong-Keun; Kim, Yunha; Lim, Sungsu; Kim, Yun Kyung; Hwang, Eun Mi; Kim, Su Hyun; Kim, Chong-Hyun; Hyeon, Seung Jae; Yun, Ji-Young; Kim, Jihye; Kim, Yona; Alvarez, Victor E; Stein, Thor D; Lee, Junghee; Kim, Dong Jin; Kim, Jong-Il; Kowall, Neil W; Ryu, Hoon; McKee, Ann C

2017-01-01

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disorder that is associated with repetitive head injury and has distinctive neuropathological features that differentiate this disease from other neurodegenerative diseases. Intraneuronal tau aggregates, although they occur in different patterns, are diagnostic neuropathological features of CTE, but the precise mechanism of tauopathy is not known in CTE. We performed whole RNA sequencing analysis of post-mortem brain tissue from patients with CTE and compared the results to normal controls to determine the transcriptome signature changes associated with CTE. The results showed that the genes related to the MAP kinase and calcium-signaling pathways were significantly downregulated in CTE. The altered expression of protein phosphatases (PPs) in these networks further suggested that the tauopathy observed in CTE involves common pathological mechanisms similar to Alzheimer's disease (AD). Using cell lines and animal models, we also showed that reduced PPP3CA/PP2B phosphatase activity is directly associated with increases in phosphorylated (p)-tau proteins. These findings provide important insights into PP-dependent neurodegeneration and may lead to novel therapeutic approaches to reduce the tauopathy associated with CTE. PMID:28524178
Chronic traumatic encephalopathy.

PubMed

Omalu, Bennet

2014-01-01

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative syndrome, which is caused by single, episodic, or repetitive blunt force impacts to the head and transfer of acceleration-deceleration forces to the brain. CTE presents clinically as a composite syndrome of mood disorders and behavioral and cognitive impairment, with or without sensorimotor impairment. Symptoms of CTE may begin with persistent symptoms of acute traumatic brain injury (TBI) following a documented episode of brain trauma or after a latent period that may range from days to weeks to months and years, up to 40 years following a documented episode of brain trauma or cessation of repetitive TBI. Posttraumatic encephalopathy is distinct from CTE, can be comorbid with CTE, and is a clinicopathologic syndrome induced by focal and/or diffuse, gross and/or microscopic destruction of brain tissue following brain trauma. The brain of a CTE sufferer may appear grossly unremarkable, but shows microscopic evidence of primary and secondary proteinopathies. The primary proteinopathy of CTE is tauopathy, while secondary proteinopathies may include, but are not limited to, amyloidopathy and TDP proteinopathy. Reported prevalence rates of CTE in cohorts exposed to TBI ranges from 3 to 80% across age groups. © 2014 S. Karger AG, Basel.
76 FR 48822 - Applications for New Awards; Technical Assistance and Dissemination To Improve Services and...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-09

... improved student performance on standardized measures of math and literacy achievement (Pearson, Sawyer... skills in context: Testing the value of enhanced math learning in CTE (Final study). St. Paul, Minnesota...
The Influence of Career-Focused Education on Student Career Planning and Development: A Comparison of CTE and Non-CTE Students

ERIC Educational Resources Information Center

Mobley, Catherine; Sharp, Julia L.; Hammond, Cathy; Withington, Cairen; Stipanovic, Natalie

2017-01-01

Our study is part of a broader longitudinal study of a state-mandated career-focused school reform policy. We investigate whether career and technical education (CTE) and non-CTE students differed in interactions with guidance counselors, level of participation in career planning and development, and beliefs about the relevance of having a career…
The Biological Basis of Chronic Traumatic Encephalopathy following Blast Injury: A Literature Review.

PubMed

Aldag, Matt; Armstrong, Regina C; Bandak, Faris; Bellgowan, Patrick S F; Bentley, Timothy; Biggerstaff, Sean; Caravelli, Katrina; Cmarik, Joan; Crowder, Alicia; DeGraba, Thomas J; Dittmer, Travis A; Ellenbogen, Richard G; Greene, Colin; Gupta, Raj K; Hicks, Ramona; Hoffman, Stuart; Latta, Robert C; Leggieri, Michael J; Marion, Donald; Mazzoli, Robert; McCrea, Michael; O'Donnell, John; Packer, Mark; Petro, James B; Rasmussen, Todd E; Sammons-Jackson, Wendy; Shoge, Richard; Tepe, Victoria; Tremaine, Ladd A; Zheng, James

2017-09-01

The United States Department of Defense Blast Injury Research Program Coordinating Office organized the 2015 International State-of-the-Science meeting to explore links between blast-related head injury and the development of chronic traumatic encephalopathy (CTE). Before the meeting, the planning committee examined articles published between 2005 and October 2015 and prepared this literature review, which summarized broadly CTE research and addressed questions about the pathophysiological basis of CTE and its relationship to blast- and nonblast-related head injury. It served to inform participants objectively and help focus meeting discussion on identifying knowledge gaps and priority research areas. CTE is described generally as a progressive neurodegenerative disorder affecting persons exposed to head injury. Affected individuals have been participants primarily in contact sports and military personnel, some of whom were exposed to blast. The symptomatology of CTE overlaps with Alzheimer's disease and includes neurological and cognitive deficits, psychiatric and behavioral problems, and dementia. There are no validated diagnostic criteria, and neuropathological evidence of CTE has come exclusively from autopsy examination of subjects with histories of exposure to head injury. The perivascular accumulation of hyperphosphorylated tau (p-tau) at the depths of cortical sulci is thought to be unique to CTE and has been proposed as a diagnostic requirement, although the contribution of p-tau and other reported pathologies to the development of clinical symptoms of CTE are unknown. The literature on CTE is limited and is focused predominantly on head injuries unrelated to blast exposure (e.g., football players and boxers). In addition, comparative analyses of clinical case reports has been challenging because of small case numbers, selection biases, methodological differences, and lack of matched controls, particularly for blast-exposed individuals. Consequently, the existing literature is not sufficient to determine whether the development of CTE is associated with head injury frequency (e.g., single vs. multiple exposures) or head injury type (e.g., impact, nonimpact, blast-related). Moreover, the incidence and prevalence of CTE in at-risk populations is unknown. Future research priorities should include identifying additional risk factors, pursuing population-based longitudinal studies, and developing the ability to detect and diagnose CTE in living persons using validated criteria.
Thermal Properties and Structural Stability of LaCoO3 in Reducing and Oxidizing Environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radovic, Miladin; Speakman, Scott A; Allard Jr, Lawrence Frederick

2008-09-01

Thermal expansion of LaCoO3 perovskite in air and 4% H2/96% Ar reducing atmosphere has been studied by Thermal Mechanical Analysis (TMA). The thermal behavior of LaCoO3 in air exhibits a non-linear expansion in 100 400 C temperature range. A significant increase of CTE measured in air both during heating and cooling experiments occurs in the 200 250 C temperature range, corresponding to a known spin state transition. LaCoO3 is found to be unstable in a reducing atmosphere. It undergoes a series of expansion and contractions due to phase transformations beginning around 500 C with very intensive chemical/phase changes at 850oCmore » and above. These expansions and contractions are directly related to the formation of La3Co3O8, La2CoO4, La4Co3O10, La2O3, CoO, and other Co compounds due to the reducing atmosphere. Although LaCoO3 is a good ionic and electronic conductor and catalyst, its high thermal expansion as well structural instability in reducing environments presents a serious restriction for its application in solid oxide fuel cells, sensors or gas separation membranes.« less
Unwelcoming Classroom Climates: The Role of Gender Microaggressions in CTE

ERIC Educational Resources Information Center

Lester, Jaime; Struthers, Brice; Yamanaka, Aoi

2017-01-01

This chapter reviews the literature, gender and CTE, classroom climate, and faculty-student interactions and presents results of a qualitative study on gender microaggressions in community college CTE classrooms.
Gene Profiling of Nucleus Basalis Tau Containing Neurons in Chronic Traumatic Encephalopathy: A Chronic Effects of Neurotrauma Consortium Study.

PubMed

Mufson, Elliott J; He, Bin; Ginsberg, Stephen D; Carper, Benjamin A; Bieler, Gayle S; Crawford, Fiona; Alvarez, Victor E; Huber, Bertrand R; Stein, Thor D; McKee, Ann C; Perez, Sylvia E

2018-06-01

Military personnel and athletes exposed to traumatic brain injury may develop chronic traumatic encephalopathy (CTE). Brain pathology in CTE includes intracellular accumulation of abnormally phosphorylated tau proteins (p-tau), the main constituent of neurofibrillary tangles (NFTs). Recently, we found that cholinergic basal forebrain (CBF) neurons within the nucleus basalis of Meynert (nbM), which provide the major cholinergic innervation to the cortex, display an increased number of NFTs across the pathological stages of CTE. However, molecular mechanisms underlying nbM neurodegeneration in the context of CTE pathology remain unknown. Here, we assessed the genetic signature of nbM neurons containing the p-tau pretangle maker pS422 from CTE subjects who came to autopsy and received a neuropathological CTE staging assessment (Stages II, III, and IV) using laser capture microdissection and custom-designed microarray analysis. Quantitative analysis revealed dysregulation of key genes in several gene ontology groups between CTE stages. Specifically, downregulation of the nicotinic cholinergic receptor subunit β-2 gene (CHRNB2), monoaminergic enzymes catechol-O-methyltransferase (COMT) and dopa decarboxylase (DDC), chloride channels CLCN4 and CLCN5, scaffolding protein caveolin 1 (CAV1), cortical development/cytoskeleton element lissencephaly 1 (LIS1), and intracellular signaling cascade member adenylate cyclase 3 (ADCY3) was observed in pS422-immunreactive nbM neurons in CTE patients. By contrast, upregulation of calpain 2 (CAPN2) and microtubule-associated protein 2 (MAP2) transcript levels was found in Stage IV CTE patients. These single-population data in vulnerable neurons indicate alterations in gene expression associated with neurotransmission, signal transduction, the cytoskeleton, cell survival/death signaling, and microtubule dynamics, suggesting novel molecular pathways to target for drug discovery in CTE.
Chronic traumatic encephalopathy: a potential late and under recognized consequence of rugby union?

PubMed

Stewart, W; McNamara, P H; Lawlor, B; Hutchinson, S; Farrell, M

2016-01-01

The association between exposure to head injury and increased risk of neurodegenerative disease, specifically chronic traumatic encephalopathy (CTE), is widely recognized. Historically, this was largely considered a phenomenon restricted to boxers, with more recent case series identifying further 'high risk' individuals, such as former American footballers, or military personnel. However, in all cases thus far reported, it is clear that it is the exposure to head injury which is associated with increased dementia risk, and not the circumstances or environment of exposure. As such, there is considerable potential for under-recognition of CTE in patients presenting with neurodegenerative disease, particularly where head injury exposure might have been historical and through sport. This article reviews current understanding of CTE and, via an illustrative case in rugby union, highlights the value of a detailed history on head injury and also draws attention to imaging studies in assessing patients with neurodegenerative disease. © The Author 2015. Published by Oxford University Press on behalf of the Association of Physicians. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Electrical behavior of aluminosilicate glass-ceramic sealants and their interaction with metallic solid oxide fuel cell interconnects

NASA Astrophysics Data System (ADS)

Goel, Ashutosh; Tulyaganov, Dilshat U.; Kharton, Vladislav V.; Yaremchenko, Aleksey A.; Ferreira, José M. F.

A series of alkaline-earth aluminosilicate glass-ceramics (GCs) were appraised with respect to their suitability as sealants for solid oxide fuel cells (SOFCs). The parent composition with general formula Ca 0.9MgAl 0.1La 0.1Si 1.9O 6 was modified with Cr 2O 3 and BaO. The addition of BaO led to a substantial decrease in the total electrical conductivity of the GCs, thus improving their insulating properties. BaO-containing GCs exhibited higher coefficient of thermal expansion (CTE) in comparison to BaO-free GCs. An extensive segregation of oxides of Ti and Mn, components of the Crofer22 APU interconnect alloy, along with negligible formation of BaCrO 4 was observed at the interface between GC/interconnects diffusion couples. Thermal shock resistance and gas-tightness of GC sealants in contact with yttria-stabilized zirconia electrolyte (8YSZ) was evaluated in air and water. Good matching of CTE and strong, but not reactive, adhesion to the solid electrolyte and interconnect, in conjunction with a high level of electrical resistivity, are all advantageous for potential SOFC applications.
Mechanisms of the micro-crack generation in an ultra-thin AlN/GaN superlattice structure grown on Si(110) substrates by metalorganic chemical vapor deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, X. Q., E-mail: xq-shen@aist.go.jp; Takahashi, T.; Ide, T.

2015-09-28

We investigate the generation mechanisms of micro-cracks (MCs) in an ultra-thin AlN/GaN superlattice (SL) structure grown on Si(110) substrates by metalorganic chemical vapor deposition. The SL is intended to be used as an interlayer (IL) for relaxing tensile stress and obtaining high-quality crack-free GaN grown on Si substrates. It is found that the MCs can be generated by two different mechanisms, where large mismatches of the lattice constant (LC) and the coefficient of thermal expansion (CTE) play key roles in the issue. Different MC configurations (low-density and high-density MCs) are observed, which are considered to be formed during the differentmore » growth stages (SL growth and cooling down processes) due to the LC and the CTE effects. In-situ and ex-situ experimental results support the mechanism interpretations of the MCs generation. The mechanism understanding makes it possible to optimize the SL IL structure for growing high-quality crack-free GaN films on Si substrates for optical and electronic device applications.« less
Vertically aligned CNT-Cu nano-composite material for stacked through-silicon-via interconnects.

PubMed

Sun, Shuangxi; Mu, Wei; Edwards, Michael; Mencarelli, Davide; Pierantoni, Luca; Fu, Yifeng; Jeppson, Kjell; Liu, Johan

2016-08-19

For future miniaturization of electronic systems using 3D chip stacking, new fine-pitch materials for through-silicon-via (TSV) applications are likely required. In this paper, we propose a novel carbon nanotube (CNT)/copper nanocomposite material consisting of high aspect ratio, vertically aligned CNT bundles coated with copper. These bundles, consisting of hundreds of tiny CNTs, were uniformly coated by copper through electroplating, and aspect ratios as high as 300:1 were obtained. The resistivity of this nanomaterial was found to be as low as ∼10(-8) Ω m, which is of the same order of magnitude as the resistivity of copper, and its temperature coefficient was found to be only half of that of pure copper. The main advantage of the composite TSV nanomaterial is that its coefficient of thermal expansion (CTE) is similar to that of silicon, a key reliability factor. A finite element model was set up to demonstrate the reliability of this composite material and thermal cycle simulations predicted very promising results. In conclusion, this composite nanomaterial appears to be a very promising material for future 3D TSV applications offering both a low resistivity and a low CTE similar to that of silicon.
High School Students' Perception of Career Technical Education and Factors that Influence Enrollment in Programs at a Regional Occupational Center

ERIC Educational Resources Information Center

St. Gean, Laurie M.

2010-01-01

The purpose of this study was to learn about the demographic profile of South Bay-area high school Career Technical Education (CTE) students (those who enroll in CTE courses outside the school day), their perceptions related to CTE, the people and other factors that influence them to enroll in CTE courses, and students' opinions on which…
Protection of Clitoria ternatea flower petal extract against free radical-induced hemolysis and oxidative damage in canine erythrocytes.

PubMed

Phrueksanan, Wathuwan; Yibchok-anun, Sirinthorn; Adisakwattana, Sirichai

2014-10-01

The present study assessed the antioxidant activity and protective ability of Clitoria ternatea flower petal extract (CTE) against in vitro 2,2'-azobis-2-methyl-propanimidamide dihydrochloride (AAPH)-induced hemolysis and oxidative damage of canine erythrocytes. From the phytochemical analysis, CTE contained phenolic compounds, flavonoids, and anthocyanins. In addition, CTE showed antioxidant activity as measured by oxygen radical absorbance capacity (ORAC) method and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. CTE (400 µg/ml) remarkably protected erythrocytes against AAPH-induced hemolysis at 4 h of incubation. Moreover, CTE (400 µg/ml) reduced membrane lipid peroxidation and protein carbonyl group formation and prevented the reduction of glutathione concentration in AAPH-induced oxidation of erythrocytes. The AAPH-induced morphological alteration of erythrocytes from a smooth discoid to an echinocytic form was effectively protected by CTE. The present results contribute important insights that CTE may have the potential to act as a natural antioxidant to prevent free radical-induced hemolysis, protein oxidation and lipid peroxidation in erythrocytes. Copyright © 2014 Elsevier Ltd. All rights reserved.
Productive HIV-1 Infection of Human Cervical Tissue Ex Vivo is Associated with the Secretory Phase of the Menstrual Cycle

PubMed Central

Saba, Elisa; Origoni, Massimo; Taccagni, Gianluca; Ferrari, Davide; Doglioni, Claudio; Nava, Alice; Lisco, Andrea; Grivel, Jean-Charles; Margolis, Leonid; Poli, Guido

2013-01-01

Cervical tissue explants (CTE) from 22 HIV-1 seronegative women were exposed to R5 HIV-1 ex vivo. Eight CTE were productively infected in terms of HIV-1 p24Gag release in culture supernatants whereas 14 were not. Nonetheless, both accumulation of HIV-1gag DNA and of p24Gag+ CD4+ T cells and macrophages occurred in both productive and, at lower levels, in nonproductive CTE. Nonproductive CTE differed from productive CTE for higher secretion of CCL3 and CCL5. A post-hoc analysis revealed that all productive CTE were established from women in their secretory phase of the menstrual cycle, whereas nonproductive CTE derived from women either in their secretory (28%) or proliferative (36%) menstrual cycle phases or with an atrophic endometrium (36%). Thus, our results support the epidemiological observation that sexual HIV-1 transmission from males to women as well as from women to men is more efficient during their secretory phase of the menstrual cycle. PMID:23385427
Thermomechanical Fatigue Damage/Failure Mechanisms in SCS-6/Timetal 21S [0/90](Sub S) Composite

NASA Technical Reports Server (NTRS)

Castelli, Michael G.

1994-01-01

The thermomechanical fatigue (TMF) deformation, damage, and life behaviors of SCS6/Timetal 21S (0/90)s were investigated under zero-tension conditions. In-phase (IP) and out-of-phase (OP) loadings were investigated with a temperature cycle from 150 to 650 deg C. An advanced TMF test technique was used to quantify mechanically damage progression. The technique incorporated explicit measurements of the macroscopic (1) isothermal static moduli at the temperature extremes of the TMF cycle and (2) coefficient of thermal expansion (CTE) as functions of the TMF cycles. The importance of thermal property degradation and its relevance to accurate post-test data analysis and interpretation is briefly addressed. Extensive fractography and metallography were conducted on specimens from failed and interrupted tests to characterize the extent of damage at the microstructure level. Fatigue life results indicated trends analogous to those established for similar unidirectional(0) reinforced titanium matrix composite systems. High stress IP and mid to low stress OP loading conditions were life-limiting in comparison to maximum temperature isothermal conditions. Dominant damage mechanisms changed with cycle type. Damage resulting from IP TMF conditions produced measurable decreases in static moduli but only minimal changes in the CTE. Metallography on interrupted and failed specimens revealed extensive (0) fiber cracking with sparse matrix damage. No surface initiated matrix cracks were present. Comparable OP TMF conditions initiated environment enhanced surface cracking and matrix cracking initiated at (90) fiber/matrix (F/M) interfaces. Notable static moduli and CTE degradations were measured. Fractography and metallography revealed that the transverse cracks originating from the surface and (90) F/M interfaces tended to converge and coalesce at the (0) fibers.
Hygrothermal properties of composites

NASA Technical Reports Server (NTRS)

Arsenovic, Petar

1996-01-01

The testing procedure and acceptance criteria for outgassing selection of materials to be used in spacecraft has been reviewed. Outgassing testing should be conducted according to ASTM Standard E 595-90. In general, materials with CVCM less than or equal to 0.10% and TML less than or equal to 1.00% are acceptable for space applications. Next, test data on several types of graphite-epoxy composite materials are presented over time at various relative humidity levels at room temperature for moisture absorption, and under vacuum at several temperatures for moisture desorption (outgassing). The data can be accurately represented by simple equations which are useful for materials characterization. Finally, a laser dilatometer systems of extremely high sensitivity and accuracy was assembled and used to measure the coefficient of thermal expansion (CTE) of several types of graphite-epoxy structures, culminating in the ability to perform loading and thermal expansion tests on a prototype optical bench.

Characterization of microstructural, mechanical and thermophysical properties of Th-52U alloy

NASA Astrophysics Data System (ADS)

Das, Santanu; Kaity, S.; Kumar, R.; Banerjee, J.; Roy, S. B.; Chaudhari, G. P.; Daniel, B. S. S.

2016-11-01

Th-52 wt.% U alloy has a microstructure featuring interspersed networks of uranium rich and thorium rich phases. Room temperature hardness of the alloy is more than twice that of unalloyed thorium. The alloy age hardens (550 °C) only slightly (peak hardness/hardness of solution heated and quenched = 1.05). Room temperature thermal conductivity (25.6 W m-1 °C-1) is close to that of uranium and most of the binary and ternary metallic alloy fuel materials. Average linear coefficient of thermal expansion (CTE) of Th-52 wt.% U alloy [11.2 × 10-06 °C-1 (27-290 °C) and 16.75 × 10-06 °C-1 (27-600 °C)] are comparable with that of many metallic alloy fuel candidates. Th-52 wt.% U alloy with non-age hardenable microstructure, appreciable thermal conductivity, moderate thermal expansion may find metallic fuel applications in nuclear reactors.
Dr. Omalu Talks Childhood, Concussions, and CTE | Poster

Cancer.gov

Dr. Bennet Omalu, the famed forensic pathologist who discovered Chronic Traumatic Encephalopathy (CTE), recently spoke at NCI at Frederick about his upbringing as well as the trials he faced while working to educate the NFL about CTE.
CTE: Education for a Strong Economy

ERIC Educational Resources Information Center

Conneely, Nancy; Hyslop, Alisha

2018-01-01

For nearly a century, career and technical education (CTE) programs across the United States have focused on equipping students with technical and life skills to help them become productive citizens. This brief report presents the benefits of CTE.
Using Return on Investment (ROI) and Other Related Tools: Guidelines for Measuring Career and Technical Education (CTE) Internal Efficiency and External Effectiveness

ERIC Educational Resources Information Center

Kotamraju, Pradeep; Mettille, John L., III

2012-01-01

Career and technical education (CTE) is increasingly seen as a major potential contributor to the recovery of the U.S. economy. However, the effectiveness and impact of the current Carl D. Perkins Act (otherwise known as Perkins IV) that governs CTE are unclear. Is the federal investment in CTE paying off? To answer this, we need to establish the…
Pixel-based CTE Correction of ACS/WFC: Modifications To The ACS Calibration Pipeline (CALACS)

NASA Astrophysics Data System (ADS)

Smith, Linda J.; Anderson, J.; Armstrong, A.; Avila, R.; Bedin, L.; Chiaberge, M.; Davis, M.; Ferguson, B.; Fruchter, A.; Golimowski, D.; Grogin, N.; Hack, W.; Lim, P. L.; Lucas, R.; Maybhate, A.; McMaster, M.; Ogaz, S.; Suchkov, A.; Ubeda, L.

2012-01-01

The Advanced Camera for Surveys (ACS) was installed on the Hubble Space Telescope (HST) nearly ten years ago. Over the last decade, continuous exposure to the harsh radiation environment has degraded the charge transfer efficiency (CTE) of the CCDs. The worsening CTE impacts the science that can be obtained by altering the photometric, astrometric and morphological characteristics of sources, particularly those farthest from the readout amplifiers. To ameliorate these effects, Anderson & Bedin (2010, PASP, 122, 1035) developed a pixel-based empirical approach to correcting ACS data by characterizing the CTE profiles of trails behind warm pixels in dark exposures. The success of this technique means that it is now possible to correct full-frame ACS/WFC images for CTE degradation in the standard data calibration and reduction pipeline CALACS. Over the past year, the ACS team at STScI has developed, refined and tested the new software. The details of this work are described in separate posters. The new code is more effective at low flux levels (< 50 electrons) than the original Anderson & Bedin code, and employs a more accurate time and temperature dependence for CTE. The new CALACS includes the automatic removal of low-level bias stripes (produced by the post-repair ACS electronics) and pixel-based CTE correction. In addition to the standard cosmic ray corrected, flat-fielded and drizzled data products (crj, flt and drz files) there are three new equivalent files (crc, flc and drc) which contain the CTE-corrected data products. The user community will be able to choose whether to use the standard or CTE-corrected products.
Absence of chronic traumatic encephalopathy in retired football players with multiple concussions and neurological symptomatology.

PubMed

Hazrati, Lili-Naz; Tartaglia, Maria C; Diamandis, Phedias; Davis, Karen D; Green, Robin E; Wennberg, Richard; Wong, Janice C; Ezerins, Leo; Tator, Charles H

2013-01-01

Chronic traumatic encephalopathy (CTE) is the term coined for the neurodegenerative disease often suspected in athletes with histories of repeated concussion and progressive dementia. Histologically, CTE is defined as a tauopathy with a distribution of tau-positive neurofibrillary tangles (NFTs) that is distinct from other tauopathies, and usually shows an absence of beta-amyloid deposits, in contrast to Alzheimer's disease (AD). Although the connection between repeated concussions and CTE-type neurodegeneration has been recently proposed, this causal relationship has not yet been firmly established. Also, the prevalence of CTE among athletes with multiple concussions is unknown. We performed a consecutive case series brain autopsy study on six retired professional football players from the Canadian Football League (CFL) with histories of multiple concussions and significant neurological decline. All participants had progressive neurocognitive decline prior to death; however, only 3 cases had post-mortem neuropathological findings consistent with CTE. The other 3 participants had pathological diagnoses of AD, amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Moreover, the CTE cases showed co-morbid pathology of cancer, vascular disease, and AD. Our case studies highlight that not all athletes with history of repeated concussions and neurological symptomology present neuropathological changes of CTE. These preliminary findings support the need for further research into the link between concussion and CTE as well as the need to expand the research to other possible causes of taupathy in athletes. They point to a critical need for prospective studies with good sampling methods to allow us to understand the relationship between multiple concussions and the development of CTE.
Concussion in Chronic Traumatic Encephalopathy

PubMed Central

Stein, Thor D.; Alvarez, Victor E.; McKee, Ann C.

2015-01-01

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease that occurs in association with repetitive mild traumatic brain injury. It is associated with a variety of clinical symptoms in multiple domains, and there is a distinct pattern of pathological changes. The abnormal tau pathology in CTE occurs uniquely in those regions of the brain that are likely most susceptible to stress concentration during trauma. CTE has been associated with a variety of types of repetitive head trauma, most frequently contact sports. In cases published to date, the mean length of exposure to repetitive head trauma was 15.4 years. The clinical symptoms of the disease began after a mean latency of 14.5 years with a mean age of death of 59.3 years. Most subjects had a reported history of concussions with a mean of 20.3. However, 16 % of published CTE subjects did not have a history of concussion suggesting that subconcussive hits are sufficient to lead to the development of CTE. Overall, the number of years of exposure, not the number of concussions, was significantly associated with worse tau pathology in CTE. This suggests that it is the chronic and repetitive nature of head trauma, irrespective of concussive symptoms, that is the most important driver of disease. CTE and exposure to repetitive head trauma is also associated with a variety of other neurodegenerations, including Alzheimer disease. In fact, amyloid β peptide deposition is altered and accelerated in CTE and is associated with worse disease. Here, we review the current exposure, clinical, and pathological associations of CTE. PMID:26260277
Structural-Thermal-Optical-Performance (STOP) Model Development and Analysis of a Field-widened Michelson Interferometer

NASA Technical Reports Server (NTRS)

Scola, Salvatore J.; Osmundsen, James F.; Murchison, Luke S.; Davis, Warren T.; Fody, Joshua M.; Boyer, Charles M.; Cook, Anthony L.; Hostetler, Chris A.; Seaman, Shane T.; Miller, Ian J.;

2014-01-01

An integrated Structural-Thermal-Optical-Performance (STOP) model was developed for a field-widened Michelson interferometer which is being built and tested for the High Spectral Resolution Lidar (HSRL) project at NASA Langley Research Center (LaRC). The performance of the interferometer is highly sensitive to thermal expansion, changes in refractive index with temperature, temperature gradients, and deformation due to mounting stresses. Hand calculations can only predict system performance for uniform temperature changes, under the assumption that coefficient of thermal expansion (CTE) mismatch effects are negligible. An integrated STOP model was developed to investigate the effects of design modifications on the performance of the interferometer in detail, including CTE mismatch, and other three- dimensional effects. The model will be used to improve the design for a future spaceflight version of the interferometer. The STOP model was developed using the Comet SimApp'TM' Authoring Workspace which performs automated integration between Pro-Engineer®, Thermal Desktop®, MSC Nastran'TM', SigFit'TM', Code V'TM', and MATLAB®. This is the first flight project for which LaRC has utilized Comet, and it allows a larger trade space to be studied in a shorter time than would be possible in a traditional STOP analysis. This paper describes the development of the STOP model, presents a comparison of STOP results for simple cases with hand calculations, and presents results of the correlation effort to bench-top testing of the interferometer. A trade study conducted with the STOP model which demonstrates a few simple design changes that can improve the performance seen in the lab is also presented.

Identification, cloning, and characterization of a major cat flea salivary allergen (Cte f 1).

PubMed

McDermott, M J; Weber, E; Hunter, S; Stedman, K E; Best, E; Frank, G R; Wang, R; Escudero, J; Kuner, J; McCall, C

2000-05-01

An 18 kDa protein isolated from saliva of the cat flea, Ctenocephalides felis, elicits a positive intradermal skin test (IDST) in 100 and 80% of experimental and clinical flea allergic dogs, respectively. Using solid-phase enzyme-linked immuno assay (ELISA), this protein detected IgE in 100 and 80% of experimental and clinical flea allergic dogs, respectively. A cDNA (pFSI) encoding a full-length Cte f 1 protein was isolated from a C. felis salivary gland cDNA library, using a combination of PCR and hybridization screening. This cDNA is 658 bp in length, and contains an open reading frame of 528 bp. The open reading frame encodes a protein of 176 amino acids, consisting of an 18 amino acid signal sequence and a 158 amino acid mature protein. The calculated molecular weight and pI of the mature protein are 18106 Da and 9.3, respectively. The protein, named Cte f 1, is the first novel major allergen described for canine flea allergy. Recombinant Cte f 1 (rCte f 1) was expressed in Escherichia coli, Pichia pastoris and baculovirus infected Trichoplusia ni cells. Approximately, 90% of the rCte f 1 expressed in E. coli accumulated in insoluble inclusion bodies, which could be refolded to a soluble mixture of disulfide isomers with partial IgE binding activity. Small quantities of an apparently correctly refolded form of rCte f 1, which had IgE binding activity equal to the native antigen, was isolated from the soluble fraction of E. coli cells. However, P. pastoris and baculovirus infected insect cells expressed and secreted a fully processed, correctly refolded and fully active form of rCte f 1. Mass spectrometry analysis of the active forms of rCte f 1confirmed that eight intact disulfide bonds were present, matching the number observed in the native allergen. The relative ability of rCte f 1 to bind IgE in the serum of flea allergic animals, produced in these three expression systems, matched that of the native allergen. Competition ELISA demonstrated that approximately 90% of the specific IgE binding to native Cte f 1 could be blocked by the different forms of rCte f 1.
The multi-factorial origins of Chronic Traumatic Encephalopathy (CTE) symptomology in post-career athletes: The athlete post-career adjustment (AP-CA) model.

PubMed

Gaetz, Michael

2017-05-01

CTE has two prominent components: the pathophysiology that is detected in the brain postmortem and the symptomology that is present in the interval between retirement and end of life. CTE symptomology has been noted to include memory difficulties, aggression, depression, explosivity, and executive dysfunction at early stages progressing to problems with attention, mood swings, visuospatial difficulties, confusion, progressive dementia, and suicidality (e.g. McKee et al. (2012), Omalu et al. (2010a-c), McKee et al. (2009)). There are a number of assumptions embedded within the current CTE literature: The first is the assumption that CTE symptomology reported by athletes and their families is the product of the pathophysiology change detected post-mortem (e.g. McKee et al. (2009)). At present, there is little scientific evidence to suggest that all CTE symptomology is the product of CTE pathophysiology. It has been assumed that CTE pathophysiology causes CTE symptomology (Meehan et al. (2015), Iverson et al. (2016)) but this link has never been scientifically validated. The purpose of the present work is to provide a multi-factorial theoretical framework to account for the symptomology reported by some athletes who sustain neurotrauma during their careers that will lead to a more systematic approach to understanding post-career symptomology. There is significant overlap between the case reports of athletes with post-mortem diagnoses of CTE, and symptom profiles of those with a history of substance use, chronic pain, and athlete career transition stress. The athlete post-career adjustment (AP-CA) model is intended to explain some of the symptoms that athletes experience at the end of their careers or during retirement. The AP-CA model consists of four elements: neurotrauma, chronic pain, substance use, and career transition stress. Based on the existing literature, it is clear that any one of the four elements of the AP-CA model can account for a significant number of CTE symptoms. In addition, depression can be a chronic lifelong co-morbid condition that may be present prior to an athletic career, or may be developed secondary to any of the model elements as shown in Fig. 1. Notably, neurotrauma is a necessary, but not a sufficient condition, for the development of CTE symptomology. Copyright © 2017 Elsevier Ltd. All rights reserved.
Synthesis and Characterization of Nano Boron Nitride Reinforced Magnesium Composites Produced by the Microwave Sintering Method

PubMed Central

Seetharaman, Sankaranarayanan; Subramanian, Jayalakshmi; Tun, Khin Sandar; Hamouda, Abdelmagid S.; Gupta, Manoj

2013-01-01

In this study, magnesium composites with nano-size boron nitride (BN) particulates of varying contents were synthesized using the powder metallurgy (PM) technique incorporating microwave-assisted two-directional sintering followed by hot extrusion. The effect of nano-BN addition on the microstructural and the mechanical behavior of the developed Mg/BN composites were studied in comparison with pure Mg using the structure-property correlation. Microstructural characterization revealed uniform distribution of nano-BN particulates and marginal grain refinement. The coefficient of thermal expansion (CTE) value of the magnesium matrix was improved with the addition of nano-sized BN particulates. The results of XRD studies indicate basal texture weakening with an increase in nano-BN addition. The composites showed improved mechanical properties measured under micro-indentation, tension and compression loading. While the tensile yield strength improvement was marginal, a significant increase in compressive yield strength was observed. This resulted in the reduction of tension-compression yield asymmetry and can be attributed to the weakening of the strong basal texture. PMID:28809252
Fluorinated graphite fibers as a new engineering material: Promises and challenges

NASA Technical Reports Server (NTRS)

Hung, Ching-Cheh; Long, Martin

1989-01-01

Pitch based graphitized carbon fibers with electrical resistivity of 300 micro-Ohm/cm were brominated and partially debrominated to 18 percent bromine at room temperature, and then fluorinated at 300 to 450 C, either continuously or intermittently for several cycles. In addition, on fluorine and titanium fluoride intercalated fiber sample was fluorinated at 270 C from the same fiber source. The mass and conductivity of the brominated-debrominated then fluorinated fibers (with fluorine-to-carbon atom ratio of 0.54 or higher) stabilized at room temperature air in a few days. However, at 200 C, these values decreased rapidly and then more slowly, throughout a 2-week test period. The electrically insulative or semiconductive fibers were found to be compatible with epoxy and have the fluorine-to-carbon atom ratio of 0.65 to 0.68, thermal conductivity of 5 to 24 W/m-K, electrical resistivity of 10(exp 4) to 10(exp 11) Ohm/cm, tensile strength of 70 to 150 ksi, Young's modulus of 20 to 30 msi, and CTE (coefficient of thermal expansion) values of 7 ppm/deg C. Data of these physical property values are preliminary. However, it is concluded that these physical properties can be tailor-made. They depend largely on the fluorine content of the final products and the intercalant in the fibers before fluorination, and, to a smaller extent, on the fluorination temperature histogram.
Exploring the thermal expansion of fluorides and oxyfluorides with rhenium trioxide-type structures: From negative to positive thermal expansion

NASA Astrophysics Data System (ADS)

Greve, Benjamin K.

This thesis explores the thermal expansion and high pressure behavior of some materials with the ReO3 structure type. This structure is simple and has, in principle, all of the features necessary for negative thermal expansion (NTE) arising from the transverse thermal motion of the bridging anions and the coupled rotation of rigid units; however, ReO 3 itself only exhibits mild NTE across a narrow temperature range at low temperatures. ReO3 is metallic because of a delocalized d-electron, and this may contribute to the lack of NTE in this material. The materials examined in this thesis are all based on d 0 metal ions so that the observed thermal expansion behavior should arise from vibrational, rather than electronic, effects. In Chapter 2, the thermal expansion of scandium fluoride, ScF3 , is examined using a combination of in situ synchrotron X-ray and neutron variable temperature diffraction. ScF3 retains the cubic ReO3 structure across the entire temperature range examined (10 - 1600 K) and exhibits pronounced negative thermal expansion at low temperatures. The magnitude of NTE in this material is comparable to that of cubic ZrW2O8, which is perhaps the most widely studied NTE material, at room temperature and below. This is the first report of NTE in an ReO3 type structure across a wide temperature range. Chapter 3 presents a comparison between titanium oxyfluoride, TiOF 2, and a vacancy-containing titanium hydroxyoxyfluoride, Ti x(O/OH/F)3. TiOF2 was originally reported to adopt the cubic ReO3 structure type under ambient conditions, therefore the initial goal for this study was to examine the thermal expansion of this material and determine if it displayed interesting behavior such as NTE. During the course of the study, it was discovered that the original synthetic method resulted in Tix(O/OH/F)3, which does adopt the cubic ReO3 structure type. The chemical composition of the hydroxyoxyfluoride is highly dependent upon synthesis conditions and subsequent heat treatments. This material readily pyrohydrolyizes at low temperatures (≈350 K). It was also observed that TiOF does not adopt the cubic ReO 3 structure; at room temperature it adopts a rhombohedrally distorted variant of the ReO3 structure. Positive thermal expansion was observed for TiOF2 from 120 K through decomposition into TiO2. At ≈400 K, TiOF2 undergoes a structural phase transition from rhombohedral to cubic symmetry. High pressure diffraction studies revealed a cubic to rhombohedral phase transition for Tix(O/OH/F) 3 between 0.5-1 GPa. No phase transitions were observed for TiOF 2 on compression. In Chapter 4, an in situ variable pressure-temperature diffraction experiment examining the effects of pressure on the coefficients of thermal expansion (CTE) for ScF3 and TaO2F is presented. In the manufacture and use of composites, which is a possible application for low and NTE materials, stresses may be experienced. Pressure was observed to have a negligible effect on cubic ScF3's CTE; however, for TaO 2F the application of modest pressures, such as those that might be experienced in the manufacture or use of composites, has a major effect on its CTE. This effect is associated with a pressure-induced phase transition from cubic to rhombohedral symmetry upon compression. TaO2F was prepared from the direct reaction of Ta2O5 with TaF 5 and from the digestion of Ta2O5 in hot hydrofluoric acid. The effects of pressure on the two samples of TaO2F were qualitatively similar. The slightly different properties for the samples are likely due to differences in their thermal history leading to differing arrangements of oxide and fluoride in these disordered materials. In Chapter 5, the local structures of TiOF2 and TaO2 F are examined using pair distribution functions (PDFs) obtained from X-ray total scattering experiments. In these materials, the anions (O/F) are disordered over the available anion positions. While traditional X-ray diffraction provides detailed information about the average structures of these materials, it is not sufficient to fully understand their thermal expansion. Fits of simple structural models to the low r portions of PDFs for these materials indicate the presence of geometrically distinct M -X-M (M = Ti, Ta; X = O, F) linkages, and a simple analysis of the TaO2F variable temperature PDFs indicates that these distinct links respond differently to temperature.
Acute effect of Clitoria ternatea flower beverage on glycemic response and antioxidant capacity in healthy subjects: a randomized crossover trial.

PubMed

Chusak, Charoonsri; Thilavech, Thavaree; Henry, Christiani Jeyakumar; Adisakwattana, Sirichai

2018-01-08

Clitoria ternatea L., a natural food-colorant containing anthocyanin, demonstrated antioxidant and antihyperglycemic activity. The aim of this study was to determine the effects of Clitoria ternatea flower extract (CTE) on postprandial plasma glycemia response and antioxidant status in healthy men. In a randomized, crossover study, 15 healthy men (ages 22.53 ± 0.30 years; with body mass index of 21.57 ± 0.54 kg/m 2 ) consumed five beverages: (1) 50 g sucrose in 400 mL water; (2) 1 g CTE in 400 mL of water; (3) 2 g CTE in 400 mL of water; (4) 50 g sucrose and 1 g CTE in 400 mL of water; and (5) 50 g sucrose and 2 g CTE in 400 mL of water. Incremental postprandial plasma glucose, insulin, uric acid, antioxidant capacities and lipid peroxidation were measured during 3 h of administration. After 30 min ingestion, the postprandial plasma glucose and insulin levels were suppressed when consuming sucrose plus 1 g and 2 g CTE. In addition, consumption of CTE alone did not alter plasma glucose and insulin concentration in the fasting state. The significant increase in plasma antioxidant capacity (ferric reducing ability of plasma (FRAP), oxygen radical absorbance capacity (ORAC), trolox equivalent antioxidant capacity (TEAC), and protein thiol) and the decrease in malondialdehyde (MDA) level were observed in the subjects who received 1 g and 2 g CTE. Furthermore, consumption of CTE protected sucrose-induced reduction in ORAC and TEAC and increase in plasma MDA. These findings suggest that an acute ingestion of CTE increases plasma antioxidant capacity without hypoglycemia in the fasting state. It also improves postprandial glucose, insulin and antioxidant status when consumed with sucrose. Thai Clinical Trials Registry: TCTR20170609003 . Registered 09 September 2017. 'retrospectively registered'.
Chronic Traumatic Encephalopathy in Athletes: Progressive Tauopathy following Repetitive Head Injury

PubMed Central

McKee, Ann C.; Cantu, Robert C.; Nowinski, Christopher J.; Hedley-Whyte, E. Tessa; Gavett, Brandon E.; Budson, Andrew E.; Santini, Veronica E.; Lee, Hyo-Soon; Kubilus, Caroline A.; Stern, Robert A.

2009-01-01

Since the 1920s, it has been known that the repetitive brain trauma associated with boxing may produce a progressive neurological deterioration, originally termed “dementia pugilistica” and more recently, chronic traumatic encephalopathy (CTE). We review the 47 cases of neuropathologically verified CTE recorded in the literature and document the detailed findings of CTE in 3 professional athletes: one football player and 2 boxers. Clinically, CTE is associated with memory disturbances, behavioral and personality changes, Parkinsonism, and speech and gait abnormalities. Neuropathologically, CTE is characterized by atrophy of the cerebral hemispheres, medial temporal lobe, thalamus, mammillary bodies, and brainstem, with ventricular dilatation and a fenestrated cavum septum pellucidum. Microscopically, there are extensive tau-immunoreactive neurofibrillary tangles, astrocytic tangles, and spindle-shaped and threadlike neurites throughout the brain. The neurofibrillary degeneration of CTE is distinguished from other tauopathies by preferential involvement of the superficial cortical layers, irregular, patchy distribution in the frontal and temporal cortices, propensity for sulcal depths, prominent perivascular, periventricular and subpial distribution, and marked accumulation of tau-immunoreactive astrocytes. Deposition of beta amyloid, most commonly as diffuse plaques, occurs in fewer than half the cases. CTE is a neuropathologically distinct, slowly progressive tauopathy with a clear environmental etiology. PMID:19535999
Negative Thermal Expansion and Ferroelectric Oxides in Electronic Device Composites

NASA Astrophysics Data System (ADS)

Trujillo, Joy Elizabeth

Electronic devices increasingly pervade our daily lives, driving the need to develop components which have material properties that can be designed to target a specific need. The principle motive of this thesis is to investigate the effects of particle size and composition on three oxides which possess electronic and thermal properties essential to designing improved ceramic composites for more efficient, high energy storage devices. A metal matrix composite project used the negative thermal expansion oxide, ZrW2O 8, to offset the high thermal expansion of the metal matrix without sacrificing high thermal conductivity. Composite preparation employed a powder mixing technique to achieve easy composition control and homogenous phase distribution in order to build composites which target a specific coefficient of thermal expansion (CTE). A tailorable CTE material is desirable for overcoming thermomechanical failure in heat sinks or device casings. This thesis also considers the particle size effect on dielectric properties in a common ferroelectric perovskite, Ba1-xSrxTiO 3. By varying the Ba:Sr ratio, the Curie temperature can be adjusted and by reducing the particle size, the dielectric constant can be increased and hysteresis decreased. These conditions could yield anonymously large dielectric constants near room temperature. However, the ferroelectric behavior has been observed to cease below a minimum size of a few tens of nanometers in bulk or thin film materials. Using a new particle slurry approach, electrochemical impedance spectroscopy allows dielectric properties to be determined for nanoparticles, as opposed to conventional methods which measure only bulk or thin film dielectric properties. In this manner, Ba1-xSrxTiO3 was investigated in a new size regime, extending the theory on the ferroelectric behavior to < 10 nm diameter. This knowledge will improve the potential to incorporate high dielectric constant, low loss ferroelectric nanoparticles in many complex composites. Finally, powder composite processing and impedance spectroscopy techniques were combined to investigate the SrTiO3/(Y2O3) x(ZrO2)1-x (STO/YSZ) oxide system. Thin film heterostructures of STO/YSZ are used in electrochemical energy devices due to their enhanced interfacial ionic conductivity. This work investigated whether this ionic conductivity enhancement could be observed in bulk sintered architectures, which may lead to new device designs for energy storage needs.
Absence of chronic traumatic encephalopathy in retired football players with multiple concussions and neurological symptomatology

PubMed Central

Hazrati, Lili-Naz; Tartaglia, Maria C.; Diamandis, Phedias; Davis, Karen D.; Green, Robin E.; Wennberg, Richard; Wong, Janice C.; Ezerins, Leo; Tator, Charles H.

2013-01-01

Background: Chronic traumatic encephalopathy (CTE) is the term coined for the neurodegenerative disease often suspected in athletes with histories of repeated concussion and progressive dementia. Histologically, CTE is defined as a tauopathy with a distribution of tau-positive neurofibrillary tangles (NFTs) that is distinct from other tauopathies, and usually shows an absence of beta-amyloid deposits, in contrast to Alzheimer's disease (AD). Although the connection between repeated concussions and CTE-type neurodegeneration has been recently proposed, this causal relationship has not yet been firmly established. Also, the prevalence of CTE among athletes with multiple concussions is unknown. Methods: We performed a consecutive case series brain autopsy study on six retired professional football players from the Canadian Football League (CFL) with histories of multiple concussions and significant neurological decline. Results: All participants had progressive neurocognitive decline prior to death; however, only 3 cases had post-mortem neuropathological findings consistent with CTE. The other 3 participants had pathological diagnoses of AD, amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Moreover, the CTE cases showed co-morbid pathology of cancer, vascular disease, and AD. Discussion: Our case studies highlight that not all athletes with history of repeated concussions and neurological symptomology present neuropathological changes of CTE. These preliminary findings support the need for further research into the link between concussion and CTE as well as the need to expand the research to other possible causes of taupathy in athletes. They point to a critical need for prospective studies with good sampling methods to allow us to understand the relationship between multiple concussions and the development of CTE. PMID:23745112
Teaching, Connecting & Empowering Today's Learners

ERIC Educational Resources Information Center

Jones, Virginia R.

2013-01-01

Since career and technical education (CTE) is based historically on promoting technical, hands-on, real-world applications in numerous vocations, CTE educators are uniquely poised to offer more use of instructional technology in their classrooms. Many CTE educators have remarkable connections with industry partnerships, internships and learning…
Correcting STIS CCD Point-Source Spectra for CTE Loss

NASA Technical Reports Server (NTRS)

Goudfrooij, Paul; Bohlin, Ralph C.; Maiz-Apellaniz, Jesus

2006-01-01

We review the on-orbit spectroscopic observations that are being used to characterize the Charge Transfer Efficiency (CTE) of the STIS CCD in spectroscopic mode. We parameterize the CTE-related loss for spectrophotometry of point sources in terms of dependencies on the brightness of the source, the background level, the signal in the PSF outside the standard extraction box, and the time of observation. Primary constraints on our correction algorithm are provided by measurements of the CTE loss rates for simulated spectra (images of a tungsten lamp taken through slits oriented along the dispersion axis) combined with estimates of CTE losses for actual spectra of spectrophotometric standard stars in the first order CCD modes. For point-source spectra at the standard reference position at the CCD center, CTE losses as large as 30% are corrected to within approx.1% RMS after application of the algorithm presented here, rendering the Poisson noise associated with the source detection itself to be the dominant contributor to the total flux calibration uncertainty.
Preparation of Ultraviolet Curing Type Silicone Rubbers Containing Mesoporous Silica Fillers.

PubMed

Abdullah, Nawfel; Hossain, Md Shahriar A; Fatehmulla, Amanullah; Farooq, Wazirzada Aslam; Islam, Md Tofazzal; Miyamoto, Nobuyoshi; Bando, Yoshio; Kamachi, Yuichiro; Malgras, Victor; Yamauchi, Yusuke; Suzuki, Norihiro

2018-01-01

Here we have been focusing on mesoporous silica (MPS) as inorganic filler material to improve the mechanical strength of silicone rubbers. The MPS particles are more effective in reducing the coefficient of thermal expansion (CTE) and hardening silicone rubber composites when compared to commercially available nonporous silica particles. In this study, we utilize ultraviolet curing type silicone rubbers and prepare MPS composites according to a simple single-step method. From an industrial viewpoint, simplifying the fabrication processes is critical. The thermal stability and mechanical strength are examined in detail in order to showcase the effectiveness of MPS particles as filler materials.

A Method for Characterizing Thermoset Polyimides

NASA Technical Reports Server (NTRS)

Ranganathaiah, C.; Sprinkle, D. R.; Pater, R. H.; Eftekhari, A.

1996-01-01

Thermoset polyimides have great potential for successfully meeting tough stress and temperature challenges in the advanced aircraft development program. However, studies of structure-property relationships in these materials have not been very successful so far. Positron lifetime spectroscopy (PLS) has been used to investigate free volumes and associated parameters in a series of variable, segmental molecular weight samples. The free volume correlates well with the molecular weight M(sub c), the cross-link density v, and the coefficient of thermal expansion (CTE) of these materials. Currently, no other techniques are available for direct measurement of these parameters, particularly for polymers in solid phase. Experimental results and their interpretations are presented.
Oracle Academy: Four Success Stories Model the Competitive Edge of CTE

ERIC Educational Resources Information Center

Techniques: Connecting Education and Careers, 2004

2004-01-01

"Vocational Education's" transformation to "Career and Technical Education" (CTE) is clearly underway as evidenced by the increased number of advanced topics and knowledge depth being taught in courses today. Technology advances across all industry sectors impact all CTE departments--from Agricultural Science to Business and Marketing. Building…
Practical Literacy Matters: Teacher Confidence Is Key

ERIC Educational Resources Information Center

Santamaria, Laura A.; Taylor, Marissa K.; Park, Travis D.; Keene, Barrett L.; van der Mandele, Elizabeth

2010-01-01

Literacy is important to career and technical education (CTE) teachers, who strive to integrate core academic and cognitive skills and knowledge into their classrooms. There is little question that educators need to continually address literacy within CTE. Rather, the issue for many CTE teachers and administrators becomes how to effectively…
State Leadership for Career Technical Education.

ERIC Educational Resources Information Center

Kister, Joanna

This document is comprised of two main parts: (1) Role and Nature of State Leadership; and (2) Developing Leaders. Issues related to state leadership for career and technical education (CTE) were studied. CTE-related research, policy, and practice were reviewed. State directors of CTE were surveyed, and 39 individuals considered opinion leaders in…
Changing Approaches--Changing Perspectives

ERIC Educational Resources Information Center

Park, Travis; Pearson, Donna; Sawyer, Jennifer

2011-01-01

Over the past seven years, research teams from the National Research Center for Career and Technical Education (NRCCTE) have been at work testing curriculum integration models. Each of three studies--Math-in-CTE, Authentic Literacy-in-CTE, and Science-in-CTE--has focused on the development of pedagogic frameworks and delivery of professional…
Chronic traumatic encephalopathy: historical origins and current perspective.

PubMed

Montenigro, Philip H; Corp, Daniel T; Stein, Thor D; Cantu, Robert C; Stern, Robert A

2015-01-01

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease that is most often identified in postmortem autopsies of individuals exposed to repetitive head impacts, such as boxers and football players. The neuropathology of CTE is characterized by the accumulation of hyperphosphorylated tau protein in a pattern that is unique from that of other neurodegenerative diseases, including Alzheimer's disease. The clinical features of CTE are often progressive, leading to dramatic changes in mood, behavior, and cognition, frequently resulting in debilitating dementia. In some cases, motor features, including parkinsonism, can also be present. In this review, the historical origins of CTE are revealed and an overview of the current state of knowledge of CTE is provided, including the neuropathology, clinical features, proposed clinical and pathological diagnostic criteria, potential in vivo biomarkers, known risk factors, and treatment options.
Hair growth-promoting effect of Carthamus tinctorius floret extract.

PubMed

Junlatat, Jintana; Sripanidkulchai, Bungorn

2014-07-01

The florets of Carthamus tinctorius L. have traditionally been used for hair growth promotion. This study aimed to examine the potential of hydroxysafflor yellow A-rich C. tinctorius extract (CTE) on hair growth both in vitro and in vivo. The effect of CTE on cell proliferation and hair growth-associated gene expression in dermal papilla cells and keratinocytes (HaCaT) was determined. In addition, hair follicles from mouse neonates were isolated and cultured in media supplemented with CTE. Moreover, CTE was applied topically on the hair-shaved skin of female C57BL/6 mice, and the histological profile of the skin was investigated. C. tinctorius floret ethanolic extract promoted the proliferation of both dermal papilla cells and HaCaT and significantly stimulated hair growth-promoting genes, including vascular endothelial growth factor and keratinocyte growth factor. In contrast, CTE suppressed the expression of transforming growth factor-β1 that is the hair loss-related gene. Furthermore, CTE treatment resulted in a significant increase in the length of cultured hair follicles and stimulated the growth of hair with local effects in mice. The results provided the preclinical data to support the potential use of CTE as a hair growth-promoting agent. Copyright © 2013 John Wiley & Sons, Ltd.
Epidemiology of mild traumatic brain injury and neurodegenerative disease

PubMed Central

Gardner, Raquel C.; Yaffe, Kristine

2015-01-01

Every year an estimated 42 million people worldwide suffer a mild traumatic brain injury (MTBI) or concussion. More severe traumatic brain injury (TBI) is a well-established risk factor for a variety of neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS). Recently, large epidemiological studies have additionally identified MTBI as a risk factor for dementia. The role of MTBI in risk of PD or ALS is less well established. Repetitive MTBI and repetitive sub-concussive head trauma has been linked to increased risk for a variety of neurodegenerative diseases including chronic traumatic encephalopathy (CTE). CTE is a unique neurodegenerative tauopathy first described in boxers but more recently described in a variety of contact sport athletes, military veterans, and civilians exposed to repetitive MTBI. Studies of repetitive MTBI and CTE have been limited by referral bias, lack of consensus clinical criteria for CTE, challenges of quantifying MTBI exposure, and potential for confounding. The prevalence of CTE is unknown and the amount of MTBI or sub-concussive trauma exposure necessary to produce CTE is unclear. This review will summarize the current literature regarding the epidemiology of MTBI, post-TBI dementia and Parkinson's disease, and CTE while highlighting methodological challenges and critical future directions of research in this field. PMID:25748121
In-situ monitoring of curing and ageing effects in FRP plates using embedded FBG sensors

NASA Astrophysics Data System (ADS)

Xian, Guijun; Wang, Chuan; Li, Hui

2010-04-01

In recent years, fiber reinforced polymer (FRP) composites have been widely applied in civil engineering for retrofitting or renewal of existing structures. Since FRP composite may degrade when exposed to severe outdoor environments, a serious concern has been raised on its long term durability. In the present study, fiber Bragg grating (FBG) sensors were embedded in glass-, carbon- and basalt-fiber reinforced epoxy based FRP plates with wet lay-up technology, to in-situ monitor the stain changes in FRPs during the curing, and water immersion and freeze-thaw ageing processes. The study demonstrates that the curing of epoxy resin brings in a slight tension strain (e.g., 10 ~ 30 μɛ) along the fiber direction and a high contraction (e.g., ~ 1100μɛ) in the direction perpendicular to the fibers, mainly due to the resin shrinkage. The cured FRP strips were then subjected to distilled water immersion at 80oC and freeze-thaw cycles from -30°C to 30°C. Remarkable strain changes of FRPs due to the variation of the temperatures during freeze-thaw cycles indicate the potential property degradation from fatigue. The maximum strain change is dependent on the fiber types and directions to the fiber. Based on the monitored strain values with temperature change and water uptake content, CTE (coefficient of thermal expansion) and CME (coefficient of moisture expansion) are exactly determined for the FRPs.
Clinicopathological Evaluation of Chronic Traumatic Encephalopathy in Players of American Football.

PubMed

Mez, Jesse; Daneshvar, Daniel H; Kiernan, Patrick T; Abdolmohammadi, Bobak; Alvarez, Victor E; Huber, Bertrand R; Alosco, Michael L; Solomon, Todd M; Nowinski, Christopher J; McHale, Lisa; Cormier, Kerry A; Kubilus, Caroline A; Martin, Brett M; Murphy, Lauren; Baugh, Christine M; Montenigro, Phillip H; Chaisson, Christine E; Tripodis, Yorghos; Kowall, Neil W; Weuve, Jennifer; McClean, Michael D; Cantu, Robert C; Goldstein, Lee E; Katz, Douglas I; Stern, Robert A; Stein, Thor D; McKee, Ann C

2017-07-25

Players of American football may be at increased risk of long-term neurological conditions, particularly chronic traumatic encephalopathy (CTE). To determine the neuropathological and clinical features of deceased football players with CTE. Case series of 202 football players whose brains were donated for research. Neuropathological evaluations and retrospective telephone clinical assessments (including head trauma history) with informants were performed blinded. Online questionnaires ascertained athletic and military history. Participation in American football at any level of play. Neuropathological diagnoses of neurodegenerative diseases, including CTE, based on defined diagnostic criteria; CTE neuropathological severity (stages I to IV or dichotomized into mild [stages I and II] and severe [stages III and IV]); informant-reported athletic history and, for players who died in 2014 or later, clinical presentation, including behavior, mood, and cognitive symptoms and dementia. Among 202 deceased former football players (median age at death, 66 years [interquartile range, 47-76 years]), CTE was neuropathologically diagnosed in 177 players (87%; median age at death, 67 years [interquartile range, 52-77 years]; mean years of football participation, 15.1 [SD, 5.2]), including 0 of 2 pre-high school, 3 of 14 high school (21%), 48 of 53 college (91%), 9 of 14 semiprofessional (64%), 7 of 8 Canadian Football League (88%), and 110 of 111 National Football League (99%) players. Neuropathological severity of CTE was distributed across the highest level of play, with all 3 former high school players having mild pathology and the majority of former college (27 [56%]), semiprofessional (5 [56%]), and professional (101 [86%]) players having severe pathology. Among 27 participants with mild CTE pathology, 26 (96%) had behavioral or mood symptoms or both, 23 (85%) had cognitive symptoms, and 9 (33%) had signs of dementia. Among 84 participants with severe CTE pathology, 75 (89%) had behavioral or mood symptoms or both, 80 (95%) had cognitive symptoms, and 71 (85%) had signs of dementia. In a convenience sample of deceased football players who donated their brains for research, a high proportion had neuropathological evidence of CTE, suggesting that CTE may be related to prior participation in football.
Modeling FBG sensors sensitivity from cryogenic temperatures to room temperature as a function of metal coating thickness

NASA Astrophysics Data System (ADS)

Vendittozzi, Cristian; Felli, Ferdinando; Lupi, Carla

2018-05-01

Fiber optics with photo-imprinted Bragg grating have been studied in order to be used as temperature sensors in cryogenic applications. The main disadvantage presented by Fiber Bragg Grating (FBG) sensors is the significant drop in sensitivity as temperature decreases, mainly due to the critical lowering of the thermo-optic coefficient of the fiber and the very low thermal expansion coefficient (CTE) of fused silica at cryogenic temperatures. Thus, especially for the latter, it is important to enhance sensitivity to temperature by depositing a metal coating presenting higher CTE. In this work the thermal sensitivity of metal-coated FBG sensors has been evaluated by considering their elongation within temperature variations in the cryogenic range, as compared to bare fiber sensors. To this purpose, a theoretical model simulating elongation of metal-coated sensors has been developed. The model has been used to evaluate the behaviour of different metals which can be used as coating (Ni, Cu, Al, Zn, Pb and In). The optimal coating thickness has been calculated at different fixed temperature (from 5 K to 100 K) for each metal. It has been found that the metal coating effectiveness depends on thickness and operating temperature in accordance to our previous experimental work and theory suggest.
Warpage of QFN Package in Post Mold Cure Process of integrated circuit packaging

NASA Astrophysics Data System (ADS)

Sriwithoon, Nattha; Ugsornrat, Kessararat; Srisuwitthanon, Warayoot; Thonglor, Panakamon

2017-09-01

This research studied about warpage of QFN package in post mold cure process of integrated circuit (IC) packages using pre-plated (PPF) leadframe. For IC package, epoxy molding compound (EMC) are molded by cross linking of compound stiffness but incomplete crosslinked network and leading the fully cured thermoset by post mold cure (PMC) process. The cure temperature of PMC can change microstructure of EMC in term of stress inside the package and effect to warpage of the package due to coefficient of thermal expansion (CTE) between EMC and leadframe. In experiment, cure temperatures were varied to check the effect of internal stress due to different cure temperature after completed post mold cure for TDFN 2×3 8L. The cure temperature were varied with 180 °C, 170 °C, 160 °C, and 150°C with cure time 4 and 6 hours, respectively. For analysis, the TDFN 2×3 8L packages were analyzed the warpage by thickness gauge and scanning acoustic microscope (SAM) after take the test samples out from the oven cure. The results confirmed that effect of different CTE between EMC and leadframe due to different cure temperature resulting to warpage of the TDFN 2×3 8L packages.
Reinforced carbon fiber laminates with oriented carbon nanotube epoxy nanocomposites: Magnetic field assisted alignment and cryogenic temperature mechanical properties.

PubMed

He, Yuxin; Yang, Song; Liu, Hu; Shao, Qian; Chen, Qiuyu; Lu, Chang; Jiang, Yuanli; Liu, Chuntai; Guo, Zhanhu

2018-05-01

The epoxy nanocomposites with ordered multi-walled carbon nanotubes (MWCNTs) were used to influence the micro-cracks resistance of carbon fiber reinforced epoxy (CF/EP) laminate at 77 K, Oxidized MWCNTs functionalized with Fe 3 O 4 (Fe 3 O 4 /O-MWCNTs) with good magnetic properties were prepared by co-precipitation method and used to modify epoxy (EP) for cryogenic applications. Fe 3 O 4 /O-MWCNTs reinforced carbon fiber epoxy composites were also prepared through vacuum-assisted resin transfer molding (VARTM). The ordered Fe 3 O 4 /O-MWCNTs were observed to have effectively improved the mechanical properties of epoxy (EP) matrix at 77 K and reduce the coefficient of thermal expansion (CTE) of EP matrix. The ordered Fe 3 O 4 /O-MWCNTs also obviously improved the micro-cracks resistance of CF/EP composites at 77 K. Compared to neat EP, the CTE of ordered Fe 3 O 4 /O-MWCNTs modified CF/EP composites was decreased 37.6%. Compared to CF/EP composites, the micro-cracks density of ordered Fe 3 O 4 /O-MWCNTs modified CF/EP composites at 77 K was decreased 37.2%. Copyright © 2018 Elsevier Inc. All rights reserved.
A high sensitivity heterodyne interferometer as a possible optical readout for the LISA gravitational reference sensor and its application to technology verification

NASA Astrophysics Data System (ADS)

Gohlke, Martin; Schuldt, Thilo; Weise, Dennis; Cordero, Jorge; Peters, Achim; Johann, Ulrich; Braxmaier, Claus

2017-11-01

The gravitational wave detector LISA utilizes as current baseline a high sensitivity Optical Readout (ORO) for measuring the relative position and tilt of a free flying proof mass with respect to the satellite housing. The required sensitivities in the frequency band from 30 μHz to 1Hz are ˜ pm/ √ Hz for the translation√ and nrad/√ Hz for the tilt measurement. EADS Astrium, in collaboration with the Humboldt University Berlin and the University of Applied Sciences Konstanz, has realized a prototype ORO over the past years. The interferometer is based on a highly symmetric design where both, measurement and reference beam have a similar optical pathlength, and the same frequency and polarization. The technique of differential wavefront sensing (DWS) for tilt measurement is implemented. With our setup noise levels below 5pm/ √Hz for translation and below 10nrad/ √Hz for tilt measurements - both for frequencies above 10mHz - were demonstrated. We give an overview over the experimental setup, its current performance and the planned improvements. We also discuss the application to first verification of critical LISA aspects. As example we present measurements of the coefficient of thermal expansion (CTE) of various carbon fiber reinforced plastic (CFRP) including a "near-zero-CTE" tube.
High-Temperature Mechanical Properties of the P/M Extruded Mg -SiCp Composites

NASA Astrophysics Data System (ADS)

Labib, F.; Mahmudi, R.; Ghasemi, H. M.

2018-03-01

In the present study, pure magnesium reinforced with 0, 5, 10 and 15 vol.% SiC particulates was successfully prepared by powder metallurgy technique before being hot extruded. The average 14 μm grain size of the composite specimens remained almost unchanged after addition of SiC particles, while their dimensional stability was improved because of the reduction in the coefficient of thermal expansion (CTE) from 28.6 × 10-6 K-1 in pure Mg to 27.3, 25.3 and 23.4 × 10-6 K-1 in the Mg-5% SiC, Mg-10% SiC and Mg-15% SiC composites, respectively. Mechanical properties of the specimens were investigated in the temperature range of 298-498 K, implementing shear punch testing and hot hardness techniques. Depending on the test temperature, addition of SiC particles to the pure Mg matrix increased shear yield stress and ultimate shear strength of the materials by 5-25 and 6-23 MPa, respectively. The shear strength improvement was mainly attributed to the CTE mismatch strengthening mechanism (9.5-25.5 MPa), and to a lesser extent (1-4.5 MPa), to the load transfer mechanism. Finally, using the modified Clyne model, the contribution of different strengthening mechanisms to the total shear strength improvement in the composites was evaluated.
Enhancing Corrosion and Wear Resistance of AA6061 by Friction Stir Processing with Fe78Si9B13 Glass Particles

PubMed Central

Guo, Lingyu; Liu, Yan; Shen, Kechang; Song, Chaoqun; Yang, Min; Kim, Kibuem; Wang, Weimin

2015-01-01

The AA6061-T6 aluminum alloy samples including annealed Fe78Si9B13 particles were prepared by friction stir processing (FSP) and investigated by various techniques. The Fe78Si9B13-reinforced particles are uniformly dispersed in the aluminum alloy matrix. The XRD results indicated that the lattice parameter of α-Al increases and the preferred orientation factors F of (200) plane of α-Al reduces after friction stir processing. The coefficient of thermal expansion (CTE) for FSP samples increases at first with the temperature but then decreases as the temperature further increased, which can be explained by the dissolving of Mg and Si from β phase and Fe78Si9B13 particles. The corrosion and wear resistance of FSP samples have been improved compared with that of base metal, which can be attributed to the reduction of grain size and the CTE mismatch between the base metal and reinforced particles by FSP, and the lubrication effect of Fe78Si9B13 particles also plays a role in improving wear resistance. In particular, the FSP sample with reinforced particles in amorphous state exhibited superior corrosion and wear resistance due to the unique metastable structure. PMID:28793492
Modeling of twisted and coiled polymer (TCP) muscle based on phenomenological approach

NASA Astrophysics Data System (ADS)

Karami, Farzad; Tadesse, Yonas

2017-12-01

Twisted and coiled polymers (TCP) muscles are linear actuators that respond to change in temperature. Exploiting high negative coefficient of thermal expansion (CTE) and helical geometry give them a significant ability to change length in a limited temperature range. Several applications and experimental data of these materials have been demonstrated in the last few years. To use these actuators in robotics and control system applications, a mathematical model for predicting their behavior is essential. In this work, a practical and accurate phenomenological model for estimating the displacement of TCP muscles, as a function of the load as well as input electrical current, is proposed. The problem is broken down into two parts, i.e. modeling of the electro-thermal and then the thermo-elastic behavior of the muscles. For the first part, a differential equation, with changing electrical resistance term, is derived. Next, by using a temperature-dependent modulus of elasticity and CTE as well as taking the geometry of the muscles into account, an expression for displacement is derived. Experimental data for different loads and actuation current levels are used for verifying the model and investigating its accuracy. The result shows a good agreement between the simulation and experimental results for all loads.
Control wafer bow of InGaP on 200 mm Si by strain engineering

NASA Astrophysics Data System (ADS)

Wang, Bing; Bao, Shuyu; Made, Riko I.; Lee, Kwang Hong; Wang, Cong; Eng Kian Lee, Kenneth; Fitzgerald, Eugene A.; Michel, Jurgen

2017-12-01

When epitaxially growing III-V compound semiconductors on Si substrates the mismatch of coefficients of thermal expansion (CTEs) between III-V and Si causes stress and wafer bow. The wafer bow is deleterious for some wafer-scale processing especially when the wafer size is large. Strain engineering was applied in the epitaxy of InGaP films on 200 mm silicon wafers having high quality germanium buffers. By applying compressive strain in the InGaP films to compensate the tensile strain induced by CTE mismatch, wafer bow was decreased from about 100 μm to less than 50 μm. X-ray diffraction studies show a clear trend between the decrease of wafer bow and the compensation of CTE mismatch induced tensile strain in the InGaP layers. In addition, the anisotropic strain relaxation in InGaP films resulted in anisotropic wafer bow along two perpendicular (110) directions. Etch pit density and plane-view transmission electron microscopy characterizations indicate that threading dislocation densities did not change significantly due to the lattice-mismatch applied in the InGaP films. This study shows that strain engineering is an effective method to control wafer bow when growing III-V semiconductors on large size Si substrates.
Industrial Applications of Graphite Fluoride Fibers

NASA Technical Reports Server (NTRS)

Hung, Ching-Cheh; Kucera, Donald

1991-01-01

Based on fluorination technology developed during 1934 to 1959, and the fiber technology developed during the 1970s, a new process was developed to produce graphite fluoride fibers. In the process, pitch based graphitized carbon fibers are at first intercalated and deintercalated several times by bromine and iodine, followed by several cycles of nitrogen heating and fluorination at 350 to 370 C. Electrical, mechanical, and thermal properties of this fiber depend on the fluorination process and the fluorine content of the graphite fluoride product. However, these properties are between those of graphite and those of PTFE (Teflon). Therefore, it is considered to be a semiplastic. The physical properties suggest that this new material may have many new and unexplored applications. For example, it can be a thermally conductive electrical insulator. Its coefficient of thermal expansion (CTE) can be adjusted to match that of silicon, and therefore, it can be a heat sinking printed circuit board which is CTE compatible with silicon. Using these fibers in printed circuit boards may provide improved electrical performance and reliability of the electronics on the board over existing designs. Also, since it releases fluorine at 300 C or higher, it can be used as a material to store fluorine and to conduct fluorination. This application may simplify the fluorination process and reduce the risk of handling fluorine.
A small graphene oxide sheet/polyvinylidene fluoride bilayer actuator with large and rapid responses to multiple stimuli.

PubMed

Xu, Guochuang; Zhang, Miao; Zhou, Qinqin; Chen, Hongwu; Gao, Tiantian; Li, Chun; Shi, Gaoquan

2017-11-16

A high-performance actuator should be able to deliver large-shape deformations, fast actuations and sensitive responses to multiple stimuli. Here, we report such an actuator constructed from one layer of polyvinylidene fluoride (PVDF) with a high coefficient of thermal expansion (CTE), and another layer of small sheets of graphene oxide (SGO) with a negative CTE. The opposite deformations of both actuation layers make the SGO/PVDF bilayer actuator highly sensitive to the temperature stimulus with a large bending sensitivity of 1.5 cm -1 °C -1 . Upon irradiation with 60 mW cm -2 infrared light, this SGO/PVDF bilayer actuator displayed an extremely rapid tip displacement rate of 140 mm s -1 . Furthermore, this actuator can also sensitively respond to moisture because of its SGO layer, showing a curvature change from -22 to 13 cm -1 upon changing the relative humidity (RH) from 11% to 86%. This actuator can generate a contractile or relaxed stress 18 times that of mammalian skeletal muscle, under light irradiation or moisture with a response time as short as 1 s, being capable of lifting an object with a weight 80 times that of itself. Furthermore, it also showed excellent stability and repeatability.

High power vertical stacked and horizontal arrayed diode laser bar development based on insulation micro-channel cooling (IMCC) and hard solder bonding technology

NASA Astrophysics Data System (ADS)

Wang, Boxue; Jia, Yangtao; Zhang, Haoyu; Jia, Shiyin; Liu, Jindou; Wang, Weifeng; Liu, Xingsheng

2018-02-01

An insulation micro-channel cooling (IMCC) has been developed for packaging high power bar-based vertical stack and horizontal array diode lasers, which eliminates many issues caused in its congener packaged by commercial copper formed micro-channel cooler(MCC), such as coefficient of thermal expansion (CTE) mismatch between cooler and diode laser bar, high coolant quality requirement (DI water) and channel corrosion and electro-corrosion induced by DI water if the DI-water quality is not well maintained The IMCC cooler separates water flow route and electrical route, which allows tap-water as coolant without electro-corrosion and therefore prolongs cooler lifetime dramatically and escalated the reliability of these diode lasers. The thickness of ceramic and copper in an IMCC cooler is well designed to minimize the CTE mismatch between laser bar and cooler, consequently, a very low "SMILE" of the laser bar can be achieved for small fast axis divergence after collimation. In additional, gold-tin hard solder bonding technology was also developed to minimize the risk of solder electromigration at high current density and thermal fatigue under hard-pulse operation mode. Testing results of IMCC packaged diode lasers are presented in this report.
Analytical design model for a piezo-composite unimorph actuator and its verification using lightweight piezo-composite curved actuators

NASA Astrophysics Data System (ADS)

Yoon, K. J.; Park, K. H.; Lee, S. K.; Goo, N. S.; Park, H. C.

2004-06-01

This paper describes an analytical design model for a layered piezo-composite unimorph actuator and its numerical and experimental verification using a LIPCA (lightweight piezo-composite curved actuator) that is lighter than other conventional piezo-composite type actuators. The LIPCA is composed of top fiber composite layers with high modulus and low CTE (coefficient of thermal expansion), a middle PZT ceramic wafer, and base layers with low modulus and high CTE. The advantages of the LIPCA design are to replace the heavy metal layer of THUNDER by lightweight fiber-reinforced plastic layers without compromising the generation of high force and large displacement and to have design flexibility by selecting the fiber direction and the number of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use a resin prepreg system. A piezo-actuation model for a laminate with piezo-electric material layers and fiber composite layers is proposed to predict the curvature and residual stress of the LIPCA. To predict the actuation displacement of the LIPCA with curvature, a finite element analysis method using the proposed piezo-actuation model is introduced. The predicted deformations are in good agreement with the experimental ones.
Learning and Serving through CTE

ERIC Educational Resources Information Center

Reese, Susan

2010-01-01

Across the country, career and technical (CTE) students are learning skills that will help them make a living, while also learning the meaning of giving that will help them, as Churchill put it, "make a life." Service-learning is an integral component of American education that goes on every day in CTE classes and career and technical…
Idaho Secondary Principals Perceptions of CTE Teachers' Professional Development Needs

ERIC Educational Resources Information Center

Cannon, John G.; Tenuto, Penny; Kitchel, Allen

2013-01-01

The purpose of this research was to identify secondary principals' perceptions of Career and Technical Education (CTE) teacher's professional development needs. A descriptive instrument based on Borich's (1980) Needs Assessment Model was completed by 128 respondents (N = 256). Items related to teaching in a CTE program were used to rate the…
A Missing Link for California's Pathways Movement: CTE Instructional Staff

ERIC Educational Resources Information Center

Lundy-Wagner, Valerie

2016-01-01

Recently, the State of California committed nearly one billion dollars to the development of career and technical education (CTE) pathways that lead to locally relevant, high-growth, high-demand careers. This investment represents a pivot from relatively disjointed approaches to CTE in high schools and community colleges, and reflects an…
Leader-Member Exchange, Cognitive Style, and Student Achievement

ERIC Educational Resources Information Center

Mosley, Chaney; Broyles, Thomas; Kaufman, Eric

2014-01-01

The purpose of this study is to explain how the quality of teacher-student relationships and the gap of cognitive styles between teachers and students impact student achievement. The population for the study was comprised of 11 career and technical education (CTE) teachers and 210 CTE students, representing six disciplines within CTE. The study…
Now Is the Time to Advocate for CTE

ERIC Educational Resources Information Center

Baxter, Jamie

2011-01-01

This year has been a very frustrating year for career and technical education (CTE) advocates across the country. They have experienced significant funding reductions for the Carl D. Perkins Career and Technical Education Act (Perkins), not to mention the cuts in state and local CTE funding. The Association for Career and Technical Education…
Preparing Students for Careers, Not Just Jobs

ERIC Educational Resources Information Center

Ciccolo, Joseph A.

2008-01-01

Massachusetts, home to some of the most prestigious institutions of higher education, has also been a leader for decades in the delivery of career and technical education (CTE). Across the state of 351 cities and towns, there are 26 regional CTE school districts and dozens more technical wings in comprehensive high schools. CTE institutions such…
Send Students Anywhere without Leaving the Classroom: Virtual Reality in CTE

ERIC Educational Resources Information Center

Ausburn, Floyd B.; Ausburn, Lynna J.

2008-01-01

Students in career and technical education (CTE) programs have many environments they need to discover, explore, and understand. For CTE teachers, transporting their students to these environments can be difficult, dangerous, or even impossible. However, there is now a way to take students on location anywhere without leaving the classroom.…
Kentucky Career and Technical Teacher Education Programs/Ongoing Issues

ERIC Educational Resources Information Center

Workman, Ed; Stubbs, Joyce

2012-01-01

What is Career and Technical Education (CTE)? How does one identify and recognized strong CTE educational programs? And after one has answers to the first two questions, how does one successfully align CTE teacher education (CTTE) programs across large institutions such as colleges within universities, or in Kentucky's endeavor within universities…
CareerTech VISION 2012--Transforming CTE Together

ERIC Educational Resources Information Center

Bray, Janet B.

2012-01-01

As the leader in career and technical education (CTE), the Association for Career and Technical Education (ACTE) understands the ongoing challenges faced by the CTE community. That is why ACTE has created CareerTech VISION 2012, a bold and visionary event that addresses the evolving needs of the global society and meets all individual and…
2012 National Policy Seminar Wrap-Up

ERIC Educational Resources Information Center

Blandford, Ayoka

2012-01-01

CTE works! That was the recurring theme that attendees heard at the 2012 National Policy Seminar (NPS) hosted by ACTE. For those new to the event and lobbying, a pre-conference workshop, "Learning the Ropes of Washington CTE Advocacy," laid out the basics of Hill advocacy. Veteran CTE advocates were offered a basics-plus session,…
Career and Technical Education (CTE) Student Success in Community Colleges: A Conceptual Model

ERIC Educational Resources Information Center

Hirschy, Amy S.; Bremer, Christine D.; Castellano, Marisa

2011-01-01

Career and technical education (CTE) students pursuing occupational associate's degrees or certificates differ from students seeking academic majors at 2-year institutions in several ways. This article examines several theoretical models of student persistence and offers a conceptual model of student success focused on CTE students in community…
The evidence for chronic traumatic encephalopathy in boxing.

PubMed

McCrory, Paul; Zazryn, Tsharni; Cameron, Peter

2007-01-01

The sport of boxing has been the source of much debate, with concerns about the neurological risks of participating having led to many calls to ban the sport. This review seeks to establish an evidence base for the development of boxing-related chronic traumatic encephalopathy (CTE) and to determine the relevance of this information to the modern day sport.The clinical features of CTE include various symptoms affecting the pyramidal and extrapyramidal systems, which manifest most often as disturbed gait and coordination, slurred speech and tremors, as well as cerebral dysfunction causing cognitive impairments and neurobehavioural disturbances. Both amateur and professional boxers are potentially at risk of developing CTE. No current epidemiological evidence exists to determine the prevalence of this condition in modern day boxing, despite 17% of professional boxers in Britain with careers in the 1930-50s having clinical evidence of CTE. As medical presence within the sport increases and with modern boxers likely to have shorter careers, a reduced exposure to repetitive head trauma, and improved treatment and understanding of the development of CTE will occur. This should lead to the incidence of CTE diminishing in boxing populations.
Numerical simulation of CTE mismatch and thermal-structural stresses in the design of interconnects

NASA Astrophysics Data System (ADS)

Peter, Geoffrey John M.

With the ever-increasing chip complexity, interconnects have to be designed to meet the new challenges. Advances in optical lithography have made chip feature sizes available today at 70 nm dimensions. With advances in Extreme Ultraviolet Lithography, X-ray Lithography, and Ion Projection Lithography it is expected that the line width will further decrease to 20 nm or less. With the decrease in feature size, the number of active devices on the chip increases. With higher levels of circuit integration, the challenge is to dissipate the increased heat flux from the chip surface area. Thermal management considerations include coefficient of thermal expansion (CTE) matching to prevent failure between the chip and the board. This in turn calls for improved system performance and reliability of the electronic structural systems. Experience has shown that in most electronic systems, failures are mostly due to CTE mismatch between the chip, board, and the solder joint (solder interconnect). The resulting high thermal-structural stress and strain due to CTE mismatch produces cracks in the solder joints with eventual failure of the electronic component. In order to reduce the thermal stress between the chip, board, and the solder joint, this dissertation examines the effect of inserting wire bundle (wire interconnect) between the chip and the board. The flexibility of the wires or fibers would reduce the stress at the rigid joints. Numerical simulations of two, and three-dimensional models of the solder and wire interconnects are examined. The numerical simulation is linear in nature and is based on linear isotropic material properties. The effect of different wire material properties is examined. The effect of varying the wire diameter is studied by changing the wire diameter. A major cause of electronic equipment failure is due to fatigue failure caused by thermal cycling, and vibrations. A two-dimensional modal and harmonic analysis was simulated for the wire interconnect and the solder interconnect. The numerical model simulated using ANSYS program was validated with the numerical/experimental results of other published researchers. In addition the results were cross-checked by IDEAS program. A prototype non-working wire interconnect is proposed to emphasize practical application. The numerical analysis, in this dissertation is based on a U.S. Patent granted to G. Peter(42).
Chronic Traumatic Encephalopathy in Athletes Involved with High-impact Sports

PubMed Central

Safinia, Cyrus; Bershad, Eric M.; Clark, H. Brent; SantaCruz, Karen; Alakbarova, Naila; Suarez, Jose I.; Divani, Afshin A.

2016-01-01

Background and purpose Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease occurring most commonly in athletes and is caused by repeated concussive or subconcussive blows to the head. The main purpose of this review is to evaluate the published literature on chronic traumatic encephalopathy (CTE) in athletes participating in high-impact sports. In particular, we highlight the significance of concussive and subconcussive impacts in multiple sports, elucidate the differences between clinical/pathological features of CTE and related neurodegenerative diseases, and provide an explanation for the variation in clinical presentation between athletes of different sports. Methods A review targeting relevant publications to CTE was performed. The PubMed/MEDLINE index was searched for keywords such as “chronic traumatic encephalopathy,” “repetitive traumatic brain injury,” “mild traumatic brain injury,” and “concussion” from year 1924 through March 1, 2016. Results A consensus panel’s recent identification of a pathognomonic pathology in CTE, characterized by an irregular distribution of phosphorylated tau deposits, is an important step in developing consensus diagnostic criteria and clinicopathological studies. After review of major clinical studies, evidence suggests that there are clear differences in neuropathological features, clinical progression, and manifestation of symptoms between CTE and other neurodegenerative diseases. The literature suggests boxers tend to have more severe symptoms than other athletes due to more frequent rotational and shearing impacts. Data regarding genetic predispositions of CTE have been inconsistent in part due to low subject populations. Positron emission tomography imaging involving tau-binding ligands has recently proven effective in differentiating CTE from control groups and other neurodegenerative diseases. Conclusions Further longitudinal studies should be conducted to correlate the number of suffered concussive/subconcussive forces to the likelihood of developing chronic traumatic brain injury symptoms. Research striving for a reliable antemortem CTE diagnosis would be immensely beneficial, leading to more accurate estimates of prevalence, allowing clinicians to assess future risk of athletes’ continued participation in sports, and enabling clinicians to make appropriate preventive recommendations. PMID:27829969
Iron deficiency in female pattern hair loss, chronic telogen effluvium, and control groups.

PubMed

Olsen, Elise A; Reed, Katherine B; Cacchio, Patrick B; Caudill, Leslie

2010-12-01

The literature suggests that iron deficiency (ID) may play a role in female pattern hair loss (FPHL) or in chronic telogen effluvium (CTE). We sought to determine if ID is more common in women with FPHL and/or CTE than in control subjects without hair loss. This was a controlled study of 381 Caucasian women aged 18 years or older with FPHL or CTE seen in the Duke University Hair Disorders Clinic, Durham, NC, and 76 Caucasian women aged 18 years or older from the university environs who had no history or physical findings of hair loss (control subjects). All participants had to have at least a serum ferritin and hemoglobin reading and history of menopausal status. When ferritin less than or equal to 15 μg/L was used as the definition, ID occurred in 12.4%, 12.1%, and 29.8% of premenopausal women with FPHL (n = 170), CTE (n = 58), and control subjects (n = 47), respectively, and in 1.7%, 10.5%, and 6.9% of postmenopausal women with FPHL (n = 115), CTE (n = 38), and control subjects (n = 29), respectively. When ferritin less than or equal to 40 μg/L was used as the definition, ID occurred in 58.8%, 63.8%, and 72.3% of premenopausal women with FPHL, CTE, and control subjects, respectively, and in 26.1%, 36.8%, and 20.7% of postmenopausal women with FPHL, CTE, and control subjects, respectively. There was no statistically significant increase in the incidence of ID in premenopausal or postmenopausal women with FPHL or CTE versus control subjects. The effect of correction of ID on hair loss is unknown. ID is common in women but not increased in patients with FPHL or CTE compared with control subjects. Copyright © 2010 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.
Pixel-based CTE Correction of ACS/WFC: New Constraints from Short Darks

NASA Astrophysics Data System (ADS)

Anderson, Jay; ACS Team

2012-01-01

The original Anderson & Bedin (2010) pixel-based correction for imperfect charge-transfer efficiency (CTE) in HST's ACS was based on a study of Warm Pixels (WPs) in a series of 1000s dark exposures. WPs with more than about 25 electrons were sufficiently isolated in these images that we could examine and model their trails. However, WPs with fewer electrons than this were more plentiful and suffered from significant crowding. To remedy this, we have taken a series of shorter dark exposures: 30s, 100s, and 339s. These supplemental exposures have two benefits. The first is that in the shorter exposures, 10 electron WPs are more sparse and their trails can be measured in isolation. The second benefit is that we can now get a handle on the absolute CTE losses, since the long-dark exposures can be used to accurately predict how many counts the WPs in the short-dark exposures should see. Any missing counts are a reflection of imperfect CTE. This new absolute handle on the CTE losses allows us to probe CTE even for very low charge packets. We find that CTE losses reach a nearly pathological level for charge packets with fewer than 20 electrons. Most ACS observations have backgrounds that are higher than this, so this does not have a large impact on science. Nevertheless, understanding CTE losses at all charge-packet levels is still important, as biases and darks often have low backgrounds. We note that these WP-based approaches to understanding CTE losses could be used in laboratory studies, as well. At present, many laboratory studies focus on Iron-55 sources, which all have 1620 electrons. Astronomical sources of interest are often fainter than this. By varying the dark exposure time, a wide diversity of WP intensities can be generated and cross-checked.
Hepatoprotective effect of 10% ethanolic extract from Curdrania tricuspidata leaves against ethanol-induced oxidative stress through suppression of CYP2E1.

PubMed

You, Yanghee; Min, Seoyoung; Lee, Yoo-Hyun; Hwang, Kwontack; Jun, Woojin

2017-10-01

The hepatoprotective effect of 10% ethanolic extract of Curdrania tricuspidata (CTE) was investigated in HepG2/2E1 cells and C57BL/6 J mice. When compared ethanol-only treated HepG2/2E1 cells, pretreatment of CTE prevented increased intra-cellular reactive oxygen species levels and decreased antioxidant activities by ethanol-induced oxidative stress. In C57BL/6 J mice, CTE at a dose of 250 mg/kg/day was administered for 10 days, with ethanol (5 g/kg/day) administered for the final 3 days. Pretreatment with CTE prevented the elevated activities of serum aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase caused by ethanol-induced hepatic damage. CTE-treated mice displayed a reduced level of malondialdehyde and increased antioxidant activities of catalase, glutathione S-transferase, glutathione peroxidase, and superoxide dismutase, as well as a reduced level of glutathione as compared with ethanol-only-treated mice. CTE-treated mice exhibited significant inhibition of CYP2E1 activities and expression. These results suggest that CTE could be a useful agent for the prevention of ethanol-induced oxidative damage in the liver, elevating antioxidative potentials and alleviating oxidative stress by suppressing CYP2El. Copyright © 2017 Elsevier Ltd. All rights reserved.
Time to Give CTE What It Deserves -- R-E-S-P-E-C-T

ERIC Educational Resources Information Center

Gammill, Deidra M.

2015-01-01

A former English teacher becomes a Teacher Academy instructor in a high school career and technical education department and learns of the bias against CTE [career-technical education] programs and students, which are stigmatized for supposedly lacking rigor and strong students. Such perceptions are outmoded, the author says, because CTE is much…

Conducting Return on Investment Analyses for Secondary and Postsecondary CTE: A Framework

ERIC Educational Resources Information Center

Hollenbeck, Kevin M.

2011-01-01

In recent work, the author has estimated the rate of return for several workforce development programs in the State of Washington, including secondary and postsecondary career and technical education (CTE; Hollenbeck, 2008). The returns are based on estimates of the net impact of CTE on individuals' labor market experiences and government income…
Literacy and Numeracy among Job Corps Students: Opportunities for Targeted Academic Infusion in CTE

ERIC Educational Resources Information Center

Mellard, Daryl F.; Woods, Kari L.; Desa, Deana Md.

2012-01-01

High literacy and numeracy demands in career and technical education (CTE) compared to low skill levels among many students prompted calls for academic infusion into training curricula. Research on CTE academic curriculum integration implicitly assumes that students' reading and math skills are like those described by models of typical academic…
CTE Funding: An Uphill Battle

ERIC Educational Resources Information Center

Baxter, Jamie

2012-01-01

For the last decade, career and technical education (CTE) funding has seen some ups, but mostly downs. While it received a modest increase in 2002, that increase was swept away in 2008 due to across-the-board cuts. It was difficult for CTE to receive another increase in the early 2000s because every year the Bush Administration proposed to either…
State Secondary CTE Standards: Developing a Framework out of a Patchwork of Policies

ERIC Educational Resources Information Center

Castellano, Marisa; Harrison, Linda; Schneider, Sherrie

2007-01-01

Many state educational administrators are currently working to define secondary career and technical education (CTE) content standards that specify the knowledge and skills students are expected to master in CTE program areas. The two-phase project on which this report is based explored (a) the progress and status of states in developing statewide…
Are There Academic CTE Cluster Pipelines? Linking High School CTE Coursetaking and Postsecondary Credentials

ERIC Educational Resources Information Center

Plasman, Jay S.; Gottfried, Michael; Sublett, Cameron

2017-01-01

Career and technical education (CTE) has become a key focus of stakeholders across the political spectrum. It has been shown to be an effective means of promoting many desired outcomes, including increased chances of high school graduation, improved opportunities of enrolling in advanced math and science courses, and increased earnings after high…
Meta-Analysis Research: A Potential Choice for CTE Researchers and Consumers

ERIC Educational Resources Information Center

Gordon, Howard R. D.

2007-01-01

A search of the ERIC database, Academic Search Premier, and a review of literature suggests that meta-analysis is ignored by career and technical education (CTE) researchers, a situation that is regrettable but remediable. The purpose of this paper was to provide CTE researchers and consumers with selected procedures and guidelines for conducting…
The Neglected Majority--Revisited

ERIC Educational Resources Information Center

Stone, James R., III

2005-01-01

nation moves into the 6th year of the No Child Left Behind (NCLB) school reform era. The demand for skilled labor in many occupational sectors is strong and growing. Studies have shown CTE helps increase students outcomes and achievements. This ought to be good news for CTE. However, due in large part to NCLB, secondary CTE is increasingly under…
CTE Policy Past, Present, and Future: Driving Forces behind the Evolution of Federal Priorities

ERIC Educational Resources Information Center

Imperatore, Catherine; Hyslop, Alisha

2017-01-01

Federal legislation has driven and been receptive to the vision of a rigorous, relevant career and technical education (CTE) system integrated with academics and aligned across middle school, secondary school, and postsecondary education. This article uses a social policy analysis approach to trace the history of federal CTE policy throughout the…
The Future of CTE: Programs of Study

ERIC Educational Resources Information Center

Shumer, Rob; Digby, Cynthia

2012-01-01

Education in today's world is very challenging. From concerns over the funding of career and technical education (CTE) to discussions about the achievement gap and dropout prevention, to debates about what it means to be college- and career-ready, the role of CTE in educational reform paradoxically is both at the forefront and on the backburner of…
Demand, Supply and Results for Secondary Career and Technical Education.

ERIC Educational Resources Information Center

Washington State Workforce Training and Education Coordinating Board, Olympia.

The benefits of offering high school students career and technical education (CTE) in addition to training in basic academic skills and the cost-effectiveness of CTE were examined by reviewing available data on demand, supply, and results for CTE. The analysis confirmed that the market and demand for workers with only a high school education still…
The neuropathology of sport.

PubMed

McKee, Ann C; Daneshvar, Daniel H; Alvarez, Victor E; Stein, Thor D

2014-01-01

The benefits of regular exercise, physical fitness and sports participation on cardiovascular and brain health are undeniable. Physical activity reduces the risk for cardiovascular disease, type 2 diabetes, hypertension, obesity, and stroke, and produces beneficial effects on cholesterol levels, antioxidant systems, inflammation, and vascular function. Exercise also enhances psychological health, reduces age-related loss of brain volume, improves cognition, reduces the risk of developing dementia, and impedes neurodegeneration. Nonetheless, the play of sports is associated with risks, including a risk for mild TBI (mTBI) and, rarely, catastrophic traumatic injury and death. There is also growing awareness that repetitive mTBIs, such as concussion and subconcussion, can occasionally produce persistent cognitive, behavioral, and psychiatric problems as well as lead to the development of a neurodegeneration, chronic traumatic encephalopathy (CTE). In this review, we summarize the beneficial aspects of sports participation on psychological, emotional, physical and cognitive health, and specifically analyze some of the less common adverse neuropathological outcomes, including concussion, second-impact syndrome, juvenile head trauma syndrome, catastrophic sudden death, and CTE. CTE is a latent neurodegeneration clinically associated with behavioral changes, executive dysfunction and cognitive impairments, and pathologically characterized by frontal and temporal lobe atrophy, neuronal and axonal loss, and abnormal deposits of paired helical filament (PHF)-tau and 43 kDa TAR deoxyribonucleic acid (DNA)-binding protein (TDP-43). CTE often occurs as a sole diagnosis, but may be associated with other neurodegenerative disorders, including motor neuron disease (CTE-MND). Although the incidence and prevalence of CTE are not known, CTE has been reported most frequently in American football players and boxers. Other sports associated with CTE include ice hockey, professional wrestling, soccer, rugby, and baseball.
The neuropathology of sport

PubMed Central

Daneshvar, Daniel H.; Alvarez, Victor E.; Stein, Thor D.

2014-01-01

The benefits of regular exercise, physical fitness and sports participation on cardiovascular and brain health are undeniable. Physical activity reduces the risk for cardiovascular disease, type 2 diabetes, hypertension, obesity, and stroke, and produces beneficial effects on cholesterol levels, antioxidant systems, inflammation, and vascular function. Exercise also enhances psychological health, reduces age-related loss of brain volume, improves cognition, reduces the risk of developing dementia, and impedes neurodegeneration. Nonetheless, the play of sports is associated with risks, including a risk for mild TBI (mTBI) and, rarely, catastrophic traumatic injury and death. There is also growing awareness that repetitive mTBIs, such as concussion and subconcussion, can occasionally produce persistent cognitive, behavioral, and psychiatric problems as well as lead to the development of a neurodegeneration, chronic traumatic encephalopathy (CTE). In this review, we summarize the beneficial aspects of sports participation on psychological, emotional, physical and cognitive health, and specifically analyze some of the less common adverse neuropathological outcomes, including concussion, second-impact syndrome, juvenile head trauma syndrome, catastrophic sudden death, and CTE. CTE is a latent neurodegeneration clinically associated with behavioral changes, executive dysfunction and cognitive impairments, and pathologically characterized by frontal and temporal lobe atrophy, neuronal and axonal loss, and abnormal deposits of paired helical filament (PHF)-tau and 43 kDa TAR deoxyribonucleic acid (DNA)-binding protein (TDP-43). CTE often occurs as a sole diagnosis, but may be associated with other neurodegenerative disorders, including motor neuron disease (CTE-MND). Although the incidence and prevalence of CTE are not known, CTE has been reported most frequently in American football players and boxers. Other sports associated with CTE include ice hockey, professional wrestling, soccer, rugby, and baseball. PMID:24366527
Commonly Used Theories in CTE Research: Toward a Core Theory Base for CTE

ERIC Educational Resources Information Center

Schmidtke, Carsten

2017-01-01

Presently, there is no widespread agreement on foundational theories for Career and Technical Education (CTE) as a discipline, nor is there much discussion and debate in the literature on what a theory foundation might look like. The case has been made that theory helps scholars and practitioners look at data from different angles, offer different…
Alignment of CTE Centers with the Baldrige Quality Award in Education Criteria: Perceptions of Leaders and Faculty

ERIC Educational Resources Information Center

Crum-Allen, Patricia; Palmer, Louann Bierlein

2016-01-01

This study examined career and technical education (CTE) centers in Michigan and their potential alignment with the Malcolm Baldrige Quality Award in Education. CTE center leaders and their faculty were asked to provide their perceptions of how well their organizations meet Baldrige quality elements, using a version of the Baldrige Assessment…
Predictors of Instructional Strategy Use of Faculty in Career and Technical Education Programs: Signature Pedagogies of the Field

ERIC Educational Resources Information Center

Fletcher, Edward C., Jr.; Djajalaksana, Yenni

2014-01-01

The purpose of this research study was to identify potential signature pedagogies in the field of CTE as well as specific disciplines within CTE, and to explain instructional strategy use by faculty's demographic characteristics, course delivery modes, and academic discipline. Based on a national survey of CTE faculty teaching at the postsecondary…
Public High School Teachers of Career and Technical Education in 2007-08. Web Tables. NCES 2011-235

ERIC Educational Resources Information Center

Bersudskaya, Vera; Cataldi, Emily Forrest

2011-01-01

These Web Tables focus on public school teachers in grades 9-12 who taught primarily career and technical education (CTE), academic, or other subjects during the 2007-08 school year. CTE teachers are grouped based on their main subject area: nonoccupational CTE, including family and consumer sciences education and general labor market preparation,…
The CTE Teacher Selection and Hiring Decision: Practices and Perceptions from Select Pennsylvania CTE Directors

ERIC Educational Resources Information Center

Haas, Beth Ann

2012-01-01

Unlike the academic teacher who has years of teacher training at a university, a teaching practicum, and experiences that lead to the acquisition of a teaching credential, a career and technical education (CTE) teacher typically is hired and placed in the classroom with no pre-service experience or training. Career and technical administrators are…
The Labor Market Imperative for CTE: Changes and Challenges for the 21st Century

ERIC Educational Resources Information Center

Stringfield, Sam; Stone, James R., III.

2017-01-01

The labor market in the United States is evolving in unexpected ways following the 2007 recession. Career and technical education (CTE) has historically linked young people to the workplace. In this article we examine the U.S. labor market and provide multiple perspectives on its growth and direction and implications for future directions for CTE.…
Expanding Opportunities: Postsecondary Career and Technical Education and Preparing Tomorrow's Workforce. A Position Paper

ERIC Educational Resources Information Center

Visger, Brett

2007-01-01

With nearly a third of all students in for-credit postsecondary education enrolled in career and technical education (CTE) programs, CTE is a valuable partner in moving reform efforts forward at the postsecondary level by providing leadership in pedagogy as well as systems-building and economic development. This enables CTE to play the role of…
Chronic Traumatic Encephalopathy: Known Causes, Unknown Effects.

PubMed

Iacono, Diego; Shively, Sharon B; Edlow, Brian L; Perl, Daniel P

2017-05-01

Chronic traumatic encephalopathy (CTE) is a neuropathologic diagnosis typically made in human brains with a history of repetitive traumatic brain injury (rTBI). It remains unknown whether CTE occurs exclusively after rTBI, or whether a single TBI (sTBI) can cause CTE. Similarly, it is unclear whether impact (eg, motor vehicle accidents) and non-impact (eg, blasts) types of energy transfer trigger divergent or common pathologies. While it is established that a history of rTBI increases the risk of multiple neurodegenerative diseases (eg, dementia, parkinsonism, and CTE), the possible pathophysiologic and molecular mechanisms underlying these risks have yet to be elucidated. Published by Elsevier Inc.

A Review of Neuroimaging Findings in Repetitive Brain Trauma

PubMed Central

Koerte, Inga K.; Lin, Alexander P.; Willems, Anna; Muehlmann, Marc; Hufschmidt, Jakob; Coleman, Michael J.; Green, Isobel; Liao, Huijun; Tate, David F.; Wilde, Elisabeth A.; Pasternak, Ofer; Bouix, Sylvain; Rathi, Yogesh; Bigler, Erin D.; Stern, Robert A.; Shenton, Martha E.

2017-01-01

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease confirmed at post-mortem. Those at highest risk are professional athletes who participate in contact sports and military personnel who are exposed to repetitive blast events. All neuropathologically-confirmed CTE cases, to date, have had a history of repetitive head impacts. This suggests that repetitive head impacts may be necessary for the initiation of the pathogenetic cascade that, in some cases, leads to CTE. Importantly, while all CTE appears to result from repetitive brain trauma, not all repetitive brain trauma results in CTE. Magnetic resonance imaging has great potential for understanding better the underlying mechanisms of repetitive brain trauma. In this review we provide an overview of advanced imaging techniques currently used to investigate brain anomalies. We also provide an overview of neuroimaging findings in those exposed to repetitive head impacts in the acute/subacute and chronic phase of injury and in more neurodegenerative phases of injury, as well as in military personnel exposed to repetitive head impacts. Finally, we discuss future directions for research that will likely lead to a better understanding of the underlying mechanisms separating those who recover from repetitive brain trauma versus those who go on to develop CTE. PMID:25904047
Modeling Chronic Traumatic Encephalopathy: The Way Forward for Future Discovery.

PubMed

Turner, Ryan C; Lucke-Wold, Brandon P; Logsdon, Aric F; Robson, Matthew J; Lee, John M; Bailes, Julian E; Dashnaw, Matthew L; Huber, Jason D; Petraglia, Anthony L; Rosen, Charles L

2015-01-01

Despite the extensive media coverage associated with the diagnosis of chronic traumatic encephalopathy (CTE), our fundamental understanding of the disease pathophysiology remains in its infancy. Only recently have scientific laboratories and personnel begun to explore CTE pathophysiology through the use of preclinical models of neurotrauma. Some studies have shown the ability to recapitulate some aspects of CTE in rodent models, through the use of various neuropathological, biochemical, and/or behavioral assays. Many questions related to CTE development, however, remain unanswered. These include the role of impact severity, the time interval between impacts, the age at which impacts occur, and the total number of impacts sustained. Other important variables such as the location of impacts, character of impacts, and effect of environment/lifestyle and genetics also warrant further study. In this work, we attempt to address some of these questions by exploring work previously completed using single- and repetitive-injury paradigms. Despite some models producing some deficits similar to CTE symptoms, it is clear that further studies are required to understand the development of neuropathological and neurobehavioral features consistent with CTE-like features in rodents. Specifically, acute and chronic studies are needed that characterize the development of tau-based pathology.
Chronic Traumatic Encephalopathy: Where Are We and Where Are We Going?

PubMed Central

Mez, Jesse; Stern, Robert A.; McKee, Ann C.

2015-01-01

Chronic traumatic encephalopathy (CTE, previously called punch drunk and dementia pugilistica) has a rich history in the medical literature in association with boxing, but has only recently been recognized with other contact sports, such as football and ice hockey, as well as with military blast injuries. CTE is thought to be a neurodegenerative disease associated with repeated concussive and subconcussive blows to the head. There is characteristic gross and microscopic pathology found in the brain, including frontal and temporal atrophy, axonal degeneration, and hyperphosphorylated tau and TAR DNA-binding protein 43 pathology. Clinically, there are characteristic progressive deficits in cognition (memory, executive dysfunction), behavior (explosivity, aggression), mood (depression, suicidality), and motor function (parkinsonism), which correlate with the anatomic distribution of brain pathology. While CTE shares clinical and neuropathological traits with other neurodegenerative diseases, the clinical syndrome and the neuropathology as a whole are distinct from other neurodegenerative diseases. Here we review the CTE literature to date. We also draw on the literature from mild traumatic brain injury and other neurodegenerative dementias, particularly when these studies provide guidance for future CTE research. We conclude by suggesting seven essential areas for future CTE research. PMID:24136455
Modeling Chronic Traumatic Encephalopathy: The Way Forward for Future Discovery

PubMed Central

Turner, Ryan C.; Lucke-Wold, Brandon P.; Logsdon, Aric F.; Robson, Matthew J.; Lee, John M.; Bailes, Julian E.; Dashnaw, Matthew L.; Huber, Jason D.; Petraglia, Anthony L.; Rosen, Charles L.

2015-01-01

Despite the extensive media coverage associated with the diagnosis of chronic traumatic encephalopathy (CTE), our fundamental understanding of the disease pathophysiology remains in its infancy. Only recently have scientific laboratories and personnel begun to explore CTE pathophysiology through the use of preclinical models of neurotrauma. Some studies have shown the ability to recapitulate some aspects of CTE in rodent models, through the use of various neuropathological, biochemical, and/or behavioral assays. Many questions related to CTE development, however, remain unanswered. These include the role of impact severity, the time interval between impacts, the age at which impacts occur, and the total number of impacts sustained. Other important variables such as the location of impacts, character of impacts, and effect of environment/lifestyle and genetics also warrant further study. In this work, we attempt to address some of these questions by exploring work previously completed using single- and repetitive-injury paradigms. Despite some models producing some deficits similar to CTE symptoms, it is clear that further studies are required to understand the development of neuropathological and neurobehavioral features consistent with CTE-like features in rodents. Specifically, acute and chronic studies are needed that characterize the development of tau-based pathology. PMID:26579067
Clinicopathological Evaluation of Chronic Traumatic Encephalopathy in Players of American Football

PubMed Central

Mez, Jesse; Daneshvar, Daniel H.; Kiernan, Patrick T.; Abdolmohammadi, Bobak; Alvarez, Victor E.; Huber, Bertrand R.; Alosco, Michael L.; Solomon, Todd M.; Nowinski, Christopher J.; McHale, Lisa; Cormier, Kerry A.; Kubilus, Caroline A.; Martin, Brett M.; Murphy, Lauren; Baugh, Christine M.; Montenigro, Phillip H.; Chaisson, Christine E.; Tripodis, Yorghos; Kowall, Neil W.; Weuve, Jennifer; McClean, Michael D.; Cantu, Robert C.; Goldstein, Lee E.; Katz, Douglas I.; Stern, Robert A.; Stein, Thor D.; McKee, Ann C.

2018-01-01

IMPORTANCE Players of American football may be at increased risk of long-term neurological conditions, particularly chronic traumatic encephalopathy (CTE). OBJECTIVE To determine the neuropathological and clinical features of deceased football players with CTE. DESIGN, SETTING, AND PARTICIPANTS Case series of 202 football players whose brains were donated for research. Neuropathological evaluations and retrospective telephone clinical assessments (including head trauma history) with informants were performed blinded. Online questionnaires ascertained athletic and military history. EXPOSURES Participation in American football at any level of play. MAIN OUTCOMES AND MEASURES Neuropathological diagnoses of neurodegenerative diseases, including CTE, based on defined diagnostic criteria; CTE neuropathological severity (stages I to IV or dichotomized into mild [stages I and II] and severe [stages III and IV]); informant-reported athletic history and, for players who died in 2014 or later, clinical presentation, including behavior, mood, and cognitive symptoms and dementia. RESULTS Among 202 deceased former football players (median age at death, 66 years [interquartile range, 47–76 years]), CTE was neuropathologically diagnosed in 177 players (87%; median age at death, 67 years [interquartile range, 52–77 years]; mean years of football participation, 15.1 [SD, 5.2]), including 0 of 2 pre–high school, 3 of 14 high school (21%), 48 of 53 college (91%), 9 of 14 semiprofessional (64%), 7 of 8 Canadian Football League (88%), and 110 of 111 National Football League (99%) players. Neuropathological severity of CTE was distributed across the highest level of play, with all 3 former high school players having mild pathology and the majority of former college (27 [56%]), semiprofessional (5 [56%]), and professional (101 [86%]) players having severe pathology. Among 27 participants with mild CTE pathology, 26 (96%) had behavioral or mood symptoms or both, 23 (85%) had cognitive symptoms, and 9 (33%) had signs of dementia. Among 84 participants with severe CTE pathology, 75 (89%) had behavioral or mood symptoms or both, 80 (95%) had cognitive symptoms, and 71 (85%) had signs of dementia. CONCLUSIONS AND RELEVANCE In a convenience sample of deceased football players who donated their brains for research, a high proportion had neuropathological evidence of CTE, suggesting that CTE may be related to prior participation in football. PMID:28742910
Graphite fluoride fibers and their applications in the space industry

NASA Technical Reports Server (NTRS)

Hung, Ching-Chen; Long, Martin; Dever, Therese

1990-01-01

Characterization and potential space applications of graphite fluoride fibers from commercially available graphitized carbon fibers are presented. Graphite fluoride fibers with fluorine to carbon ratios of 0.65 and 0.68 were found to have electrical resistivity values of 10(exp 4) and 10(exp 11) Ohms-cm, respectively, and thermal conductivity values of 24 and 5 W/m-K, respectively. At this fluorine content range, the fibers have tensile strength of 0.25 + or - 0.10 GPa (36 + or - 14 ksi), Young's modulus of 170 + or - 30 GPa (25 + or - 5 Msi). The coefficient of thermal expansion value of a sample with fluorine to carbon ratio of 0.61 was found to be 7 ppm/C. These properties change and approach the graphite value as the fluorine content approach 0. Electrically insulative graphite fluoride fiber is at least five times more thermally conductive than fiberglass. Therefore, it can be used as a heat sinking printed circuit board material for low temperature, long life power electronics in spacecraft. Also, partially fluorinated fiber with tailor-made physical properties to meet the requirements of certain engineering design can be produced. For example, a partially fluorinated fiber could have a predetermined CTE value in -1.5 to 7 ppm/C range and would be suitable for use in solar concentrators in solar dynamic power systems. It could also have a predetermined electrical resistivity value suitable for use as a low observable material. Experimental data indicate that slightly fluorinated graphite fibers are more durable in the atomic oxygen environment than pristine graphite. Therefore, fluorination of graphite used in the construction of spacecraft that would be exposed to the low Earth orbit atomic oxygen may protect defect sites in atomic oxygen protective coatings and therefore decrease the rate of degradation of graphite.
Materials property definition and generation for carbon-carbon and carbon phenolic materials

NASA Technical Reports Server (NTRS)

Canfield, A. R.; Mathis, J. R.; Starrett, H. S.; Koenig, J. R.

1987-01-01

A data base program to generate statistically significant material-property data for carbon-carbon and carbon phenolic materials to be used in designs of Space Shuttle is described. The program, which will provide data necessary for thermal and stress modeling of Shuttle nozzle and exit cone structures, includes evaluation of tension, compression, shear strength, shear modulus, thermal expansion, thermal conductivity, permeability, and emittance for both materials; the testing of carbon phenolic materials also includes CTE, off-gassing, pyrolysis, and RTG. Materials to be tested will be excised from Space Shuttle inlet, throat, and exit cone billets and modified involute carbon-carbon exit cones; coprocessed blocks, panels, and cylinders will also be tested.
A lightweight thermal heat switch for redundant cryocooling on satellites

NASA Astrophysics Data System (ADS)

Dietrich, M.; Euler, A.; Thummes, G.

2017-04-01

A previously designed cryogenic thermal heat switch for space applications has been optimized for low mass, high structural stability, and reliability. The heat switch makes use of the large linear thermal expansion coefficient (CTE) of the thermoplastic UHMW-PE for actuation. A structure model, which includes the temperature dependent properties of the actuator, is derived to be able to predict the contact pressure between the switch parts. This pressure was used in a thermal model in order to predict the switch performance under different heat loads and operating temperatures. The two models were used to optimize the mass and stability of the switch. Its reliability was proven by cyclic actuation of the switch and by shaker tests.
Recent Development of SOFC Metallic Interconnect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu JW, Liu XB

2010-04-01

Interest in solid oxide fuel cells (SOFC) stems from their higher e±ciencies and lower levels of emitted pollu- tants, compared to traditional power production methods. Interconnects are a critical part in SOFC stacks, which connect cells in series electrically, and also separate air or oxygen at the cathode side from fuel at the anode side. Therefore, the requirements of interconnects are the most demanding, i:e:, to maintain high elec- trical conductivity, good stability in both reducing and oxidizing atmospheres, and close coe±cient of thermal expansion (CTE) match and good compatibility with other SOFC ceramic components. The paper reviewed the interconnectmore » materials, and coatings for metallic interconnect materials.« less
Understanding Participation in Secondary Career and Technical Education in the 21st Century: Implications for Policy and Practice

ERIC Educational Resources Information Center

Aliaga, Oscar A.; Kotamraju, Pradeep; Stone, James R., III

2014-01-01

We examine participation in Career and Technical Education (CTE) using a typology that better reflects the CTE credit-taking experience of all public high school students, and it is based on the several changes in academic requirements that all students need to meet in order to graduate, including those considered CTE students. We argue that the…
High Temperature Mechanical Behavior of UHTC Coatings for Thermal Protection of Re-Entry Vehicles

NASA Astrophysics Data System (ADS)

Pulci, G.; Tului, M.; Tirillò, J.; Marra, F.; Lionetti, S.; Valente, T.

2011-01-01

In this work, the high temperature mechanical properties of ultra high temperature ceramics (UHTC) coatings deposited by plasma spraying have been investigated; particularly the stress-strain relationship of ZrB2-based thick films has been evaluated by means of 4-point bending tests up to 1500 °C in air. Results show that at each investigated temperature (500, 1000, and 1500 °C) modulus of rupture (MOR) values are higher than the ones obtained at room temperature (RT); moreover at 1500 °C the UHTC coatings exhibit a marked plastic behavior, maintaining a flexural strength 25% higher compared to RT tested samples. The coefficient of linear thermal expansion (CTE) has been evaluated up to 1500 °C: obtained data are of primary importance for substrate selection, interface design and to analyze the thermo-mechanical behavior of coating-substrate coupled system. Finally, SEM-EDS analyses have been carried out on as-sprayed and tested materials in order to understand the mechanisms of reinforcement activated by high temperature exposure and to identify the microstructural modifications induced by the combination of mechanical loads and temperature in an oxidizing environment.
Military Blast Injury and Chronic Neurodegeneration: Research Presentations from the 2015 International State-of-the-Science Meeting.

PubMed

Agoston, Denes; Arun, Peethambaran; Bellgowan, Patrick; Broglio, Steven; Cantu, Robert; Cook, David; da Silva, Uade Olaghere; Dickstein, Dara; Elder, Gregory; Fudge, Elizabeth; Gandy, Sam; Gill, Jessica; Glenn, John F; Gupta, Raj K; Hinds, Sidney; Hoffman, Stuart; Lattimore, Theresa; Lin, Alexander; Lu, Kun Ping; Maroon, Joseph; Okonkwo, David; Perl, Daniel; Robinson, Meghan; Rosen, Charles; Smith, Douglas

2017-09-01

Blast-related traumatic brain injury (TBI) is a signature injury of recent military conflicts, leading to increased Department of Defense (DoD) interest in its potential long-term effects, such as chronic traumatic encephalopathy (CTE). The DoD Blast Injury Research Program Coordinating Office convened the 2015 International State-of-the-Science Meeting to discuss the existing evidence regarding a causal relationship between TBI and CTE. Over the course of the meeting, experts across government, academia, and the sports community presented cutting edge research on the unique pathological characteristics of blast-related TBI, blast-related neurodegenerative mechanisms, risk factors for CTE, potential biomarkers for CTE, and treatment strategies for chronic neurodegeneration. The current paper summarizes these presentations. Although many advances have been made to address these topics, more research is needed to establish the existence of links between the long-term effects of single or multiple blast-related TBI and CTE.
Chronic traumatic encephalopathy and other neurodegenerative proteinopathies

PubMed Central

Tartaglia, Maria Carmela; Hazrati, Lili-Naz; Davis, Karen D.; Green, Robin E. A.; Wennberg, Richard; Mikulis, David; Ezerins, Leo J.; Keightley, Michelle; Tator, Charles

2014-01-01

“Chronic traumatic encephalopathy” (CTE) is described as a slowly progressive neurodegenerative disease believed to result from multiple concussions. Traditionally, concussions were considered benign events and although most people recover fully, about 10% develop a post-concussive syndrome with persisting neurological, cognitive and neuropsychiatric symptoms. CTE was once thought to be unique to boxers, but it has now been observed in many different athletes having suffered multiple concussions as well as in military personal after repeated blast injuries. Much remains unknown about the development of CTE but its pathological substrate is usually tau, similar to that seen in Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD). The aim of this “perspective” is to compare and contrast clinical and pathological CTE with the other neurodegenerative proteinopathies and highlight that there is an urgent need for understanding the relationship between concussion and the development of CTE as it may provide a window into the development of a proteinopathy and thus new avenues for treatment. PMID:24550810
Postsecondary and Labor Force Transitions among Public High School Career and Technical Education Participants. Issue Tables. NCES 2011-234

ERIC Educational Resources Information Center

Bersudskaya, Vera; Chen, Xianglei

2011-01-01

Career and technical education (CTE) is a significant component of high school education. For the last several decades, more than 90 percent of public high school graduates have earned at least some credits in CTE, with graduates from the class of 2005 earning an average of 4.0 CTE credits (Hudson and Laird 2009; Levesque 2003; Levesque et al.…
A Comparative Study of the Trends in Career and Technical Education Among European Countries, the United States, and the Republic of China.

ERIC Educational Resources Information Center

Wu, Robert T. Y.

Theories influencing the development of trends in career and technical education (CTE) in Europe, the United States, and the Republic of China (Taiwan)were examined. The analysis established that, when determining the goals of CTE and areas of focus of efforts to improve CTE curricula and delivery, European countries focus on theories related to…
Chondracanthus tenellus (Harvey) hommersand extract protects the human keratinocyte cell line by blocking free radicals and UVB radiation-induced cell damage.

PubMed

Piao, Mei Jing; Hyun, Yu Jae; Oh, Tae-Heon; Kang, Hee Kyoung; Yoo, Eun Sook; Koh, Young Sang; Lee, Nam Ho; Suh, In Soo; Hyun, Jin Won

2012-12-01

The aim of this study was to investigate the protective effects of the ethanol extract of the red algae Chondracanthus tenellus (Harvey) Hommersand (CTE) on cultured human keratinocyte cell line. The cellular protection conferred by CTE was evidenced by the ability of the extract to absorb ultraviolet B (UVB; 280-320 nm) and to scavenge the radical 1,1-diphenyl-2-picrylhydrazyl, as well as intracellular reactive oxygen species (ROS), induced by either hydrogen peroxide (H(2)O(2)) or UVB radiation. In addition, both superoxide anion generated by the xanthine/xanthine oxidase system and hydroxyl radical generated by the Fenton reaction (FeSO(4) + H(2)O(2)) were scavenged by CTE, as confirmed using electron spin resonance spectrometry. In the human keratinocyte cell line, CTE decreased the degree of injury resulting from UVB-induced oxidative stress to lipids, proteins, and DNA. CTE-treated cells also showed a reduction in UVB-induced apoptosis, as exemplified by fewer apoptotic bodies and less DNA fragmentation. Taken together, these results suggest that CTE confers protection on the human keratinocyte cell line against UVB-induced oxidative stress by absorbing UVB ray and scavenging ROS, thereby reducing injury to cellular constituents.
Antiobesity and Antidiabetes Effects of a Cudrania tricuspidata Hydrophilic Extract Presenting PTP1B Inhibitory Potential

PubMed Central

Kim, Dae Hoon; Lee, Sooung; Chung, Youn Wook; Kim, Byeong Mo; Kim, Hanseul; Kim, Kunhong; Yang, Kyung Mi

2016-01-01

Diabetes and obesity represent the major health problems and the most age-related metabolic diseases. Protein-tyrosine phosphatase 1B (PTP1B) has emerged as an important regulator of insulin signal transduction and is regarded as a pharmaceutical target for metabolic disorders. To find novel natural materials presenting therapeutic activities against diabetes and obesity, we screened various herb extracts using a chip screening allowing the determination of PTP1B inhibitory effects of the tested compounds using insulin receptor (IR) as the substrate. Cudrania tricuspidata leaves (CTe) had a strong inhibitory effect on PTP1B activity and substantially inhibited fat accumulation in 3T3-L1 cells. CTe was orally administrated to diet-induced obesity (DIO) mice once daily for 3 weeks after which changes in glucose, insulin metabolism, and fat accumulation were examined. Hepatic enzyme markers (aspartate aminotransferase, AST, and alanine aminotransferase, ALT) and total fat mass and triglyceride levels decreased in CTe-treated mice, whereas body weight and total cholesterol concentration slightly decreased. CTe increased the phosphorylation of IRS-1 and Akt in liver tissue. Furthermore, CTe treatment significantly lowered blood glucose levels and improved insulin secretion in DIO mice. Our results strongly suggest that CTe may represent a promising therapeutic substance against diabetes and obesity. PMID:26989693
Elevated specific peripheral cytokines found in major depressive disorder patients with childhood trauma exposure: a cytokine antibody array analysis.

PubMed

Lu, Shaojia; Peng, Hongjun; Wang, Lifeng; Vasish, Seewoobudul; Zhang, Yan; Gao, Weijia; Wu, Weiwei; Liao, Mei; Wang, Mi; Tang, Hao; Li, Wenping; Li, Weihui; Li, Zexuan; Zhou, Jiansong; Zhang, Zhijun; Li, Lingjiang

2013-10-01

Taking into consideration the previous evidence of revealing the relationship of early life adversity, major depressive disorder (MDD), and stress-linked immunological changes, we recruited 22 MDD patients with childhood trauma exposures (CTE), 21 MDD patients without CTE, and 22 healthy controls without CTE, and then utilized a novel cytokine antibody array methodology to detect potential biomarkers underlying MDD in 120 peripheral cytokines and to evaluate the effect of CTE on cytokine changes in MDD patients. Although 13 cytokines were identified with highly significant differences in expressions between MDD patients and normal controls, this relationship was significantly attenuated and no longer significant after consideration of the effect of CTE in MDD patients. Depressed individuals with CTE (TD patients) were more likely to have higher peripheral levels of those cytokines. Severity of depression was associated with plasma levels of certain increased cytokines; meanwhile, the increased cytokines led to a proper separation of TD patients from normal controls during clustering analyses. Our research outcomes add great strength to the relationship between depression and cytokine changes and suggest that childhood trauma may play a vital role in the co-appearance of cytokine changes and depression. Copyright © 2013 Elsevier Inc. All rights reserved.
ACS Internal CTE Monitor and Short Darks

NASA Astrophysics Data System (ADS)

Ogaz, Sara

2013-10-01

This is a continuation of Program 13156 and is to be executed once a cycle for internal CTE and short darks, respectively.INTERNAL CTE MONITOR:The charge transfer efficiency {CTE} of the ACS CCD detectors will decline as damage due to on-orbit radiation exposure accumulates. This degradation will be monitored once a cycle to determine the useful lifetime of the CCDs. All the data for this program is acquired using internal targets {lamps} only, so all of the exposures should be taken during Earth occultation time {but not during SAA passages}. This program emulates the ACS pre-flight ground calibration and post-launch SMOV testing {program 8948}, so that results from each epoch can be directly compared. Extended Pixel Edge Response {EPER} data will be obtained over a range of signal levels for the Wide Field Channel {WFC}. The signal levels are 125, 500, 1620, 5000, 10000, and 60000 electrons at gain 2.Since Cycle 18, this monitoring program was reduced {compared to 11881} considering that there is also an external CTE monitoring program.SHORT DARKS:To improve the pixel-based CTE model at signals below 10 DN, short dark frames are needed to obtain a statistically useful sample of clean, warm pixel trails. This program obtains a set of dark frames for each of the following exposure times: 66 s {60 s for some subarrays} and 339 s. These short darks and the 1040 s darks obtained from the CCD Daily Monitor will sample warm and hot pixels over logarithmically increasing brightness. Subarray short darks were added in Cycle 19 to study CTE tails in different subarray readout modes.
Endoscopic Complete Remission of Crohn Disease After Anti-Tumor Necrosis Factor-α Therapy: CT Enterographic Findings and Their Clinical Implications.

PubMed

Kim, Cherry; Park, Seong Ho; Yang, Suk-Kyun; Ye, Byong Duk; Park, Sang Hyoung; Lee, Jong Seok; Kim, Hyun Jin; Kim, Ah Young; Ha, Hyun Kwon

2016-06-01

The purpose of this study was to describe the CT enterographic (CTE) findings after endoscopic complete remission (CR) of Crohn disease in patients treated with anti-tumor necrosis factor-α (anti-TNF-α) and the clinical implications of these findings. The records of 27 patients with Crohn disease (14 men, 13 women; mean age, 28.4 ± 8.6 [SD] years) who achieved endoscopic (ileocolonoscopic) CR after anti-TNF-α therapy and underwent CTE both before therapy and at endoscopic CR were identified. Two readers independently assessed the frequencies and severities of mural and perienteric CTE abnormalities, generally regarded as active inflammatory findings, in the terminal ileum and colorectum in the endoscopic CR state and compared them with the corresponding findings before anti-TNF-α therapy. The association between the presence of CTE abnormalities in the face of endoscopic CR and patient outcome during subsequent follow-up was investigated. CTE abnormalities were present in the face of endoscopic CR in 11-18 (26-42%) of 43 bowel sections (18 terminal ileum, 25 colorectum), the most frequent being mural hyperenhancement (21-40%) followed by mural thickening (12-16%). Both findings were mild and unaccompanied by other findings. The frequency and severity of mural and perienteric CTE abnormalities were statistically significantly reduced at endoscopic CR compared with the pre-treatment state. Patients with (n = 10) and without (n = 17) CTE abnormalities at endoscopic CR did not significantly differ with respect to Crohn disease aggravation during subsequent follow-up periods averaging 27.4 and 28.5 months (0/10 versus 2/17, p = 0.516). More than one-fourth of bowel sections in endoscopic CR after anti-TNF-α therapy had residual CTE abnormalities, predominantly mild mural thickening or hyperenhancement. These findings may not have any clinical significance.

The combination of a reduction in contrast agent dose with low tube voltage and an adaptive statistical iterative reconstruction algorithm in CT enterography: Effects on image quality and radiation dose.

PubMed

Feng, Cui; Zhu, Di; Zou, Xianlun; Li, Anqin; Hu, Xuemei; Li, Zhen; Hu, Daoyu

2018-03-01

To investigate the subjective and quantitative image quality and radiation exposure of CT enterography (CTE) examination performed at low tube voltage and low concentration of contrast agent with adaptive statistical iterative reconstruction (ASIR) algorithm, compared with conventional CTE.One hundred thirty-seven patients with suspected or proved gastrointestinal diseases underwent contrast enhanced CTE in a multidetector computed tomography (MDCT) scanner. All cases were assigned to 2 groups. Group A (n = 79) underwent CT with low tube voltage based on patient body mass index (BMI) (BMI < 23 kg/m, 80 kVp; BMI ≥ 23 kg/m, 100 kVp) and low concentration of contrast agent (270 mg I/mL), the images were reconstructed with standard filtered back projection (FBP) algorithm and 50% ASIR algorithm. Group B (n = 58) underwent conventional CTE with 120 kVp and 350 mg I/mL contrast agent, the images were reconstructed with FBP algorithm. The computed tomography dose index volume (CTDIvol), dose length product (DLP), effective dose (ED), and total iodine dosage were calculated and compared. The CT values, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) of the normal bowel wall, gastrointestinal lesions, and mesenteric vessels were assessed and compared. The subjective image quality was assessed independently and blindly by 2 radiologists using a 5-point Likert scale.The differences of values for CTDIvol (8.64 ± 2.72 vs 11.55 ± 3.95, P < .001), ED (6.34 ± 2.24 vs 8.52 ± 3.02, P < .001), and DLP (422.6 ± 149.40 vs 568.30 ± 213.90, P < .001) were significant between group A and group B, with a reduction of 25.2%, 25.7%, and 25.7% in group A, respectively. The total iodine dosage in group A was reduced by 26.1%. The subjective image quality did not differ between the 2 groups (P > .05) and all image quality scores were greater than or equal to 3 (moderate). Fifty percent ASIR-A group images provided lower image noise, but similar or higher quantitative image quality in comparison with FBP-B group images.Compared with the conventional protocol, CTE performed at low tube voltage, low concentration of contrast agent with 50% ASIR algorithm produce a diagnostically acceptable image quality with a mean ED of 6.34 mSv and a total iodine dose reduction of 26.1%.
Mesocarbon microbead based graphite for spherical fuel element to inhibit the infiltration of liquid fluoride salt in molten salt reactor

NASA Astrophysics Data System (ADS)

Zhong, Yajuan; Zhang, Junpeng; Lin, Jun; Xu, Liujun; Zhang, Feng; Xu, Hongxia; Chen, Yu; Jiang, Haitao; Li, Ziwei; Zhu, Zhiyong; Guo, Quangui

2017-07-01

Mesocarbon microbeads (MCMB) and quasi-isostatic pressing method were used to prepare MCMB based graphite (MG) for spherical fuel element to inhibit the infiltration of liquid fluoride salt in molten salt reactor (MSR). Characteristics of mercury infiltration and molten salt infiltration in MG were investigated and compared with A3-3 (graphite for spherical fuel element in high temperature gas cooled reactor) to identify the infiltration behaviors. The results indicated that MG had a low porosity about 14%, and an average pore diameter of 96 nm. Fluoride salt occupation of A3-3 (average pore diameter was 760 nm) was 10 wt% under 6.5 atm, whereas salt gain did not infiltrate in MG even up to 6.5 atm. It demonstrated that MG could inhibit the infiltration of liquid fluoride salt effectively. Coefficient of thermal expansion (CTE) of MG lies in 6.01 × 10-6 K-1 (α∥) and 6.15 × 10-6 K-1 (α⊥) at the temperature range of 25-700 °C. The anisotropy factor of MG calculated by CTE maintained below 1.02, which could meet the requirement of the spherical fuel element (below 1.30). The constant isotropic property of MG is beneficial for the integrity and safety of the graphite used in the spherical fuel element for a MSR.
Alternatives for joining Si wafers to strain-accommodating Cu for high-power electronics

NASA Astrophysics Data System (ADS)

Faust, Nicholas; Messler, Robert W.; Khatri, Subhash

2001-10-01

Differences in the coefficients of thermal expansion (CTE) between silicon wafers and underlying copper electrodes have led to the use of purely mechanical dry pressure contacts for primary electrical and thermal connections in high-power solid-state electronic devices. These contacts are limited by their ability to dissipate I2R heat from within the device and by their thermal fatigue life. To increase heat dissipation and effectively deal with the CTE mismatch, metallurgical bonding of the silicon to a specially-structured, strain-accommodating copper electrode has been proposed. This study was intended to seek alternative methods for and demonstrate the feasibility of bonding Si to structured Cu in high-power solid-state devices. Three different but fundamentally related fluxless approaches identified and preliminarily assessed were: (1) conventional Sn-Ag eutectic solder; (2) a new, commercially-available active solder based on the Sn-Ag eutectic; and (3) solid-liquid interdiffusion bonding using the Au-In system. Metallurgical joints were made with varying quality levels (according to nonde-structive ultrasonic C-scan mapping, SEM, and electron microprobe) using each approach. Mechanical shear testing resulted in cohesive failure within the Si or the filler alloys. The best approach, in which eutectic Sn-Ag solder in pre-alloyed foil form was employed on Si and Cu substrates metallized (from the substrate outward) with Ti, Ni and Au, exhibited joint thermal conduction 74% better than dry pressure contacts.
Failure Mechanisms of SAC/Fe-Ni Solder Joints During Thermal Cycling

NASA Astrophysics Data System (ADS)

Gao, Li-Yin; Liu, Zhi-Quan; Li, Cai-Fu

2017-08-01

Thermal cycling tests have been conducted on Sn-Ag-Cu/Fe- xNi ( x = 73 wt.% or 45 wt.%) and Sn-Ag-Cu/Cu solder joints according to the Joint Electron Device Engineering Council industrial standard to study their interfacial reliability under thermal stress. The interfacial intermetallic compounds formed for solder joints on Cu, Fe-73Ni, and Fe-45Ni were 4.5 μm, 1.7 μm, and 1.4 μm thick, respectively, after 3000 cycles, demonstrating excellent diffusion barrier effect of Fe-Ni under bump metallization (UBM). Also, two deformation modes, viz. solder extrusion and fatigue crack formation, were observed by scanning electron microscopy and three-dimensional x-ray microscopy. Solder extrusion dominated for solder joints on Cu, while fatigue cracks dominated for solder joints on Fe-45Ni and both modes were detected for those on Fe-73Ni. Solder joints on Fe-Ni presented inferior reliability during thermal cycling compared with those on Cu, with characteristic lifetime of 3441 h, 3190 h, and 1247 h for Cu, Fe-73Ni, and Fe-45Ni UBM, respectively. This degradation of the interfacial reliability for solder joints on Fe-Ni is attributed to the mismatch in coefficient of thermal expansion (CTE) at interconnection level. The CTE mismatch at microstructure level was also analyzed by electron backscatter diffraction for clearer identification of recrystallization-related deformation mechanisms.
ZERODUR thermo-mechanical modelling and advanced dilatometry for the ELT generation

NASA Astrophysics Data System (ADS)

Jedamzik, Ralf; Kunisch, Clemens; Westerhoff, Thomas

2016-07-01

Large amounts of low thermal expansion material are required for the upcoming ELT projects. The main mirror is designed using several hundreds of hexagonal 1.4 m sized mirror blanks. The M2 and M3 are monolithic 4 m class mirror blanks. The mirror blank material needs to fulfill tight requirements regarding CTE specification and homogeneity. Additionally the mirror blanks need to be dimensionally stable for more than 30 years. In particular, stress effects due to the changes in the environment shall not entail shape variation of more than 0.5 μm PV within 30 years. In 2010 SCHOTT developed a physically based model to describe the thermal and mechanical long time behavior of ZERODUR. The model enables simulation of the long time behavior of ZERODUR mirror blanks under realistic mechanical and thermal constraints. This presentation shows FEM simulation results on the long time behavior of the ELT M1, M2 and M3 mirror blanks under different loading conditions. Additionally the model results will be compared to an already 15 years lasting long time measurement of a ZERODUR sample at the German federal physical standardization institute (PTB). In recent years SCHOTT pushed the push rod dilatometer measurement technology to its limit. With the new Advanced Dilatometer CTE measurement accuracies of +- 3 ppb/K and reproducibilities of better 1 ppb/K have been achieved. The new Advanced Dilatometer exhibits excellent long time stability.
Evaluating the Impacts of Technology Education on Military Maintenance Students

ERIC Educational Resources Information Center

Jordan, Jeremy D.; Curtis, Christopher

2010-01-01

The United States Air Force (USAF) provides career and technical education (CTE) to a wide variety of specialty career fields. Training airmen to carry out the mission while honoring the USAF core values of integrity first, service before self, and excellence in all we do is the top priority of military leaders and trainers. Vehicle maintenance is…
A Conserved C-terminal Element in the Yeast Doa10 and Human MARCH6 Ubiquitin Ligases Required for Selective Substrate Degradation*

PubMed Central

Zattas, Dimitrios; Berk, Jason M.; Kreft, Stefan G.; Hochstrasser, Mark

2016-01-01

Specific proteins are modified by ubiquitin at the endoplasmic reticulum (ER) and are degraded by the proteasome, a process referred to as ER-associated protein degradation. In Saccharomyces cerevisiae, two principal ER-associated protein degradation ubiquitin ligases (E3s) reside in the ER membrane, Doa10 and Hrd1. The membrane-embedded Doa10 functions in the degradation of substrates in the ER membrane, nuclear envelope, cytoplasm, and nucleoplasm. How most E3 ligases, including Doa10, recognize their protein substrates remains poorly understood. Here we describe a previously unappreciated but highly conserved C-terminal element (CTE) in Doa10; this cytosolically disposed 16-residue motif follows the final transmembrane helix. A conserved CTE asparagine residue is required for ubiquitylation and degradation of a subset of Doa10 substrates. Such selectivity suggests that the Doa10 CTE is involved in substrate discrimination and not general ligase function. Functional conservation of the CTE was investigated in the human ortholog of Doa10, MARCH6 (TEB4), by analyzing MARCH6 autoregulation of its own degradation. Mutation of the conserved Asn residue (N890A) in the MARCH6 CTE stabilized the normally short lived enzyme to the same degree as a catalytically inactivating mutation (C9A). We also report the localization of endogenous MARCH6 to the ER using epitope tagging of the genomic MARCH6 locus by clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated genome editing. These localization and CTE analyses support the inference that MARCH6 and Doa10 are functionally similar. Moreover, our results with the yeast enzyme suggest that the CTE is involved in the recognition and/or ubiquitylation of specific protein substrates. PMID:27068744
HST/WFC3: Understanding and Mitigating Radiation Damage Effects in the CCD Detectors

NASA Astrophysics Data System (ADS)

Baggett, S.; Anderson, J.; Sosey, M.; MacKenty, J.; Gosmeyer, C.; Noeske, K.; Gunning, H.; Bourque, M.

2015-09-01

At the heart of the Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) UVIS channel resides a 4096x4096 pixel e2v CCD array. While these detectors are performing extremely well after more than 5 years in low-earth orbit, the cumulative effects of radiation damage cause a continual growth in the hot pixel population and a progressive loss in charge transfer efficiency (CTE) over time. The decline in CTE has two effects: (1) it reduces the detected source flux as the defects trap charge during readout and (2) it systematically shifts source centroids as the trapped charge is later released. The flux losses can be significant, particularly for faint sources in low background images. Several mitigation options exist, including target placement within the field of view, empirical stellar photometric corrections, post-flash mode and an empirical pixel-based CTE correction. The application of a post-flash has been remarkably effective in WFC3 at reducing CTE losses in low background images for a relatively small noise penalty. Currently all WFC3 observers are encouraged to post-flash images with low backgrounds. Another powerful option in mitigating CTE losses is the pixel-based CTE correction. Analagous to the CTE correction software currently in use in the HST Advanced Camera for Surveys (ACS) pipeline, the algorithm employs an empirical observationally-constrained model of how much charge is captured and released in order to reconstruct the image. Applied to images (with or without post-flash) after they are acquired, the software is currently available as a standalone routine. The correction will be incorporated into the standard WFC3 calibration pipeline.
Chronic traumatic encephalopathy: a spectrum of neuropathological changes following repetitive brain trauma in athletes and military personnel

PubMed Central

2014-01-01

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease that occurs in association with repetitive traumatic brain injury experienced in sport and military service. In most instances, the clinical symptoms of the disease begin after a long period of latency ranging from several years to several decades. The initial symptoms are typically insidious, consisting of irritability, impulsivity, aggression, depression, short-term memory loss and heightened suicidality. The symptoms progress slowly over decades to include cognitive deficits and dementia. The pathology of CTE is characterized by the accumulation of phosphorylated tau protein in neurons and astrocytes in a pattern that is unique from other tauopathies, including Alzheimer’s disease. The hyperphosphorylated tau abnormalities begin focally, as perivascular neurofibrillary tangles and neurites at the depths of the cerebral sulci, and then spread to involve superficial layers of adjacent cortex before becoming a widespread degeneration affecting medial temporal lobe structures, diencephalon and brainstem. Most instances of CTE (>85% of cases) show abnormal accumulations of phosphorylated 43 kDa TAR DNA binding protein that are partially colocalized with phosphorylated tau protein. As CTE is characterized pathologically by frontal and temporal lobe atrophy, by abnormal deposits of phosphorylated tau and by 43 kDa TAR DNA binding protein and is associated clinically with behavioral and personality changes, as well as cognitive impairments, CTE is increasingly categorized as an acquired frontotemporal lobar degeneration. Currently, some of the greatest challenges are that CTE cannot be diagnosed during life and the incidence and prevalence of the disorder remain uncertain. Furthermore, the contribution of age, gender, genetics, stress, alcohol and substance abuse to the development of CTE remains to be determined. PMID:24423082
BACTERICIDAL COATINGS ON TEXTILES FOR REMEDIATION OF INTERMICROBE ACTIVITY (BaCTeRIA) SUMMARY REPORT

DTIC Science & Technology

2017-07-07

Activity by Bacillus sp. P11” Food Bioprocess Technol. 4:822- 828. (2011) Levy, S.B and Marshal,l B.; “ Antibacterial resistance worldwide: causes...TEXTILES FOR REMEDIATION OF INTERMICROBE ACTIVITY (BaCTeRIA) SUMMARY REPORT by Tobyn A. Branck Courtney M. Cowell Jennifer M. Rego and...October 2011 – September 2015 4. TITLE AND SUBTITLE BACTERICIDAL COATINGS ON TEXTILES FOR REMEDIATION OF INTERMICROBE ACTIVITY (BaCTeRIA) SUMMARY REPORT
Building a Vision for the Future of Career and Technical Education in Maine. A Report on the CTE Visioning Conference (Portland, Maine, June 15-17, 2004)

ERIC Educational Resources Information Center

Maine Department of Education, 2004

2004-01-01

This report documents the three-day conference held on June 15-17, 2004, in which approximately 80 stakeholders in Maine's Career and Technical Education system (CTE) gathered at the Portland Arts and Technology High School to begin a process intended to produce a strategic plan for CTE by the fall of 2004. Over the summer, the statewide CTE…
Characterization of Early Pathological Tau Conformations and Phosphorylation in Chronic Traumatic Encephalopathy

PubMed Central

Kanaan, Nicholas M.; Cox, Kristine; Alvarez, Victor E.; Stein, Thor D.; Poncil, Sharra; McKee, Ann C.

2016-01-01

Chronic traumatic encephalopathy (CTE) is a neurodegenerative tauopathy that develops after repetitive head injury. Several lines of evidence in other tauopathies suggest that tau oligomer formation induces neurotoxicity and that tau oligomer-mediated neurotoxicity involves induction of axonal dysfunction through exposure of an N-terminal motif in tau, the phosphatase-activating domain (PAD). Additionally, phosphorylation at serine 422 in tau occurs early and correlates with cognitive decline in patients with Alzheimer disease (AD). We performed immunohistochemistry and immunofluorescence on fixed brain sections and biochemical analysis of fresh brain extracts to characterize the presence of PAD-exposed tau (TNT1 antibody), tau oligomers (TOC1 antibody), tau phosphorylated at S422 (pS422 antibody), and tau truncated at D421 (TauC3 antibody) in the brains of 9-11 cases with CTE and cases of nondemented aged controls and AD (Braak VI) (n = 6, each). All 3 early tau markers (ie, TNT1, TOC1, and pS422) were present in CTE and displayed extensive colocalization in perivascular tau lesions that are considered diagnostic for CTE. Notably, the TauC3 epitope, which is abundant in AD, was relatively sparse in CTE. Together, these results provide the first description of PAD exposure, TOC1 reactive oligomers, phosphorylation of S422, and TauC3 truncation in the tau pathology of CTE. PMID:26671985
Linking traumatic brain injury to chronic traumatic encephalopathy: identification of potential mechanisms leading to neurofibrillary tangle development.

PubMed

Lucke-Wold, Brandon Peter; Turner, Ryan Coddington; Logsdon, Aric Flint; Bailes, Julian Edwin; Huber, Jason Delwyn; Rosen, Charles Lee

2014-07-01

Significant attention has recently been drawn to the potential link between head trauma and the development of neurodegenerative disease, namely chronic traumatic encephalopathy (CTE). The acute neurotrauma associated with sports-related concussions in athletes and blast-induced traumatic brain injury in soldiers elevates the risk for future development of chronic neurodegenerative diseases such as CTE. CTE is a progressive disease distinguished by characteristic tau neurofibrillary tangles (NFTs) and, occasionally, transactive response DNA binding protein 43 (TDP43) oligomers, both of which have a predilection for perivascular and subcortical areas near reactive astrocytes and microglia. The disease is currently only diagnosed postmortem by neuropathological identification of NFTs. A recent workshop sponsored by National Institute of Neurological Disorders and Stroke emphasized the need for premortem diagnosis, to better understand disease pathophysiology and to develop targeted treatments. In order to accomplish this objective, it is necessary to discover the mechanistic link between acute neurotrauma and the development of chronic neurodegenerative and neuropsychiatric disorders such as CTE. In this review, we briefly summarize what is currently known about CTE development and pathophysiology, and subsequently discuss injury-induced pathways that warrant further investigation. Understanding the mechanistic link between acute brain injury and chronic neurodegeneration will facilitate the development of appropriate diagnostic and therapeutic options for CTE and other related disorders.
Joining Carbon-Carbon Composites and High-Temperature Materials with High Energy Electron Beams

NASA Technical Reports Server (NTRS)

Goodman, Daniel; Singler, Robert

1998-01-01

1. Program goals addressed during this period. Experimental work was directed at formation of a low-stress bond between carbon- carbon and aluminum, with the objective of minimizing the heating of the aluminum substrate, thereby minimizing stresses resulting from the coefficient of thermal expansion (CTE) difference between the aluminum and carbon-carbon. A second objective was to form a bond between carbon-carbon and aluminum with good thermal conductivity for electronic thermal management (SEM-E) application. 2. Substrates and joining materials selected during this period. Carbon-Carbon Composite (CCC) to Aluminum. CCC (Cu coated) to Aluminum. Soldering compounds based on Sn/Pb and Sn/Ag/Cu/Bi compositions. 3. Soldering experiments performed. Conventional techniques. High Energy Electron Beam (HEEB) process.
Enhanced vbasis laser diode package

DOEpatents

Deri, Robert J.; Chen, Diana; Bayramian, Andy; Freitas, Barry; Kotovsky, Jack

2014-08-19

A substrate having an upper surface and a lower surface is provided. The substrate includes a plurality of v-grooves formed in the upper surface. Each v-groove includes a first side and a second side perpendicular to the first side. A laser diode bar assembly is disposed within each of the v-grooves and attached to the first side. The laser diode bar assembly includes a first adhesion layer disposed on the first side of the v-groove, a metal plate attached to the first adhesion layer, a second adhesion layer disposed over the metal plate, and a laser diode bar attached to the second adhesion layer. The laser diode bar has a coefficient of thermal expansion (CTE) substantially similar to that of the metal plate.
Interferometric phase measurement of zerodur, aluminum and SXA mirrors at cryogenic temperatures

NASA Technical Reports Server (NTRS)

Magner, Thomas J.; Barney, Richard D.

1988-01-01

A research program was undertaken to determine the surface figure error of several different types of mirrors at cryogenic temperatures. Two-inch diameter parabolic, spherical and flat mirrors were fabricated from zerodur, aluminum and a metal matrix composite of silicon carbide reinforced aluminum (SXA). The ratio of silicon carbide to aluminum was selected so that the coefficient of thermal expansion (CTE) of the metal matrix matched electroless nickel. A liquuid helium dewar was modified to add an interferometric grade window, a cold electronic shutter and a strain-free copper mirror mount. Interferometric phase measurements on each mirror mounted in the dewar were made without the window, with the window, under vacuum, at around 80K and between 10K and 24K.
Chronic Traumatic Encephalopathy

MedlinePlus

... trauma is likely the cause of CTE. Football players have been the focus of most CTE studies. However, athletes participating in other sports, including soccer, ice hockey, rugby, boxing, wrestling, basketball, field hockey, ...
Combined Effects of Temperature and Irradiation on Concrete Damage

DOE PAGES

Le Pape, Yann; Giorla, Alain; Sanahuja, Julien

2016-01-01

Aggregate radiation-induced volumetric expansion (RIVE) is a predominant mechanism in the formation of mechanical damage in the hardened cement paste (hcp) of irradiated concrete under fast-neutron flux (Giorla et al. 2015). Among the operating conditions difference between test reactors and light water reactors (LWRs), the difference of irradiation flux and temperature is significant. While a temperature increase is quite generally associated with a direct, or indirect (e.g., by dehydration) loss of mechanical properties (Maruyama et al. 2014), we found that it causes a partial annealing of irradiation amorphization of α-quartz, hence, reducing RIVE rate. Based on data collected by Bykovmore » et al. (1981), an incremental RIVE model coupling neutron fluence and temperature is developed. The elastic properties and coefficient of thermal expansion (CTE) of irradiated polycrystalline quartz are interpreted through analytical homogenization of experimental data on irradiated α-quartz published by Mayer and Lecomte (1960). Moreover, the proposed model, implemented in the meso-scale simulation code AMIE, is compared to experimental data obtained on ordinary concrete made of quartz/quartzite aggregate (Dubrovskii et al. 1967). Substantial discrepancy, in terms of damage and volumetric expansion developments, is found when comparing irradiation scenarios assuming constant flux and temperature, as opposed to more realistic test reactor operation conditions.« less
Determination of the linear coefficient of thermal expansion in polymer films at the nanoscale: influence of the composition of EVA copolymers and the molecular weight of PMMA.

PubMed

González-Benito, J; Castillo, E; Cruz-Caldito, J F

2015-07-28

Nanothermal-expansion of poly(ethylene-co-vinylacetate), EVA, and poly(methyl methacrylate), PMMA, in the form of films was measured to finally obtain linear coefficients of thermal expansion, CTEs. The simple deflection of a cantilever in an atomic force microscope, AFM, was used to monitor thermal expansions at the nanoscale. The influences of: (a) the structure of EVA in terms of its composition (vinylacetate content) and (b) the size of PMMA chains in terms of the molecular weight were studied. To carry out this, several polymer samples were used, EVA copolymers with different weight percents of the vinylacetate comonomer (12, 18, 25 and 40%) and PMMA polymers with different weight average molecular weights (33.9, 64.8, 75.600 and 360.0 kg mol(-1)). The dependencies of the vinyl acetate weight fraction of EVA and the molecular weight of PMMA on their corresponding CTEs were analyzed to finally explain them using new, intuitive and very simple models based on the rule of mixtures. In the case of EVA copolymers a simple equation considering the weighted contributions of each comonomer was enough to estimate the final CTE above the glass transition temperature. On the other hand, when the molecular weight dependence is considered the free volume concept was used as novelty. The expansion of PMMA, at least at the nanoscale, was well and easily described by the sum of the weighted contributions of the occupied and free volumes, respectively.
Multi Frequency Phase Fluorimetry (MFPF) for Oxygen Partial Pressure Measurement: Ex Vivo Validation by Polarographic Clark-Type Electrode

PubMed Central

Boehme, Stefan; Duenges, Bastian; Klein, Klaus U.; Hartwich, Volker; Mayr, Beate; Consiglio, Jolanda; Baumgardner, James E.; Markstaller, Klaus; Basciani, Reto; Vogt, Andreas

2013-01-01

Background Measurement of partial pressure of oxygen (PO2) at high temporal resolution remains a technological challenge. This study introduces a novel PO2 sensing technology based on Multi-Frequency Phase Fluorimetry (MFPF). The aim was to validate MFPF against polarographic Clark-type electrode (CTE) PO2 measurements. Methodology/Principal Findings MFPF technology was first investigated in N = 8 anaesthetised pigs at FIO2 of 0.21, 0.4, 0.6, 0.8 and 1.0. At each FIO2 level, blood samples were withdrawn and PO2 was measured in vitro with MFPF using two FOXY-AL300 probes immediately followed by CTE measurement. Secondly, MFPF-PO2 readings were compared to CTE in an artificial circulatory setup (human packed red blood cells, haematocrit of 30%). The impacts of temperature (20, 30, 40°C) and blood flow (0.8, 1.6, 2.4, 3.2, 4.0 L min−1) on MFPF-PO2 measurements were assessed. MFPF response time in the gas- and blood-phase was determined. Porcine MFPF-PO2 ranged from 63 to 749 mmHg; the corresponding CTE samples from 43 to 712 mmHg. Linear regression: CTE = 15.59+1.18*MFPF (R2 = 0.93; P<0.0001). Bland Altman analysis: meandiff 69.2 mmHg, rangediff -50.1/215.6 mmHg, 1.96-SD limits -56.3/194.8 mmHg. In artificial circulatory setup, MFPF-PO2 ranged from 20 to 567 mmHg and CTE samples from 11 to 575 mmHg. Linear regression: CTE = −8.73+1.05*MFPF (R2 = 0.99; P<0.0001). Bland-Altman analysis: meandiff 6.6 mmHg, rangediff -9.7/20.5 mmHg, 1.96-SD limits -12.7/25.8 mmHg. Differences between MFPF and CTE-PO2 due to variations of temperature were less than 6 mmHg (range 0–140 mmHg) and less than 35 mmHg (range 140–750 mmHg); differences due to variations in blood flow were less than 15 mmHg (all P-values>0.05). MFPF response-time (monoexponential) was 1.48±0.26 s for the gas-phase and 1.51±0.20 s for the blood-phase. Conclusions/Significance MFPF-derived PO2 readings were reproducible and showed excellent correlation and good agreement with Clark-type electrode-based PO2 measurements. There was no relevant impact of temperature and blood flow upon MFPF-PO2 measurements. The response time of the MFPF FOXY-AL300 probe was adequate for real-time sensing in the blood phase. PMID:23565259

Multi frequency phase fluorimetry (MFPF) for oxygen partial pressure measurement: ex vivo validation by polarographic clark-type electrode.

PubMed

Boehme, Stefan; Duenges, Bastian; Klein, Klaus U; Hartwich, Volker; Mayr, Beate; Consiglio, Jolanda; Baumgardner, James E; Markstaller, Klaus; Basciani, Reto; Vogt, Andreas

2013-01-01

Measurement of partial pressure of oxygen (PO2) at high temporal resolution remains a technological challenge. This study introduces a novel PO2 sensing technology based on Multi-Frequency Phase Fluorimetry (MFPF). The aim was to validate MFPF against polarographic Clark-type electrode (CTE) PO2 measurements. MFPF technology was first investigated in N = 8 anaesthetised pigs at FIO2 of 0.21, 0.4, 0.6, 0.8 and 1.0. At each FIO2 level, blood samples were withdrawn and PO2 was measured in vitro with MFPF using two FOXY-AL300 probes immediately followed by CTE measurement. Secondly, MFPF-PO2 readings were compared to CTE in an artificial circulatory setup (human packed red blood cells, haematocrit of 30%). The impacts of temperature (20, 30, 40°C) and blood flow (0.8, 1.6, 2.4, 3.2, 4.0 L min(-1)) on MFPF-PO2 measurements were assessed. MFPF response time in the gas- and blood-phase was determined. Porcine MFPF-PO2 ranged from 63 to 749 mmHg; the corresponding CTE samples from 43 to 712 mmHg. Linear regression: CTE = 15.59+1.18*MFPF (R(2) = 0.93; P<0.0001). Bland Altman analysis: meandiff 69.2 mmHg, rangediff -50.1/215.6 mmHg, 1.96-SD limits -56.3/194.8 mmHg. In artificial circulatory setup, MFPF-PO2 ranged from 20 to 567 mmHg and CTE samples from 11 to 575 mmHg. Linear regression: CTE = -8.73+1.05*MFPF (R(2) = 0.99; P<0.0001). Bland-Altman analysis: meandiff 6.6 mmHg, rangediff -9.7/20.5 mmHg, 1.96-SD limits -12.7/25.8 mmHg. Differences between MFPF and CTE-PO2 due to variations of temperature were less than 6 mmHg (range 0-140 mmHg) and less than 35 mmHg (range 140-750 mmHg); differences due to variations in blood flow were less than 15 mmHg (all P-values>0.05). MFPF response-time (monoexponential) was 1.48±0.26 s for the gas-phase and 1.51±0.20 s for the blood-phase. MFPF-derived PO2 readings were reproducible and showed excellent correlation and good agreement with Clark-type electrode-based PO2 measurements. There was no relevant impact of temperature and blood flow upon MFPF-PO2 measurements. The response time of the MFPF FOXY-AL300 probe was adequate for real-time sensing in the blood phase.
The STEM and CTE Pipeline for Community College Students with Learning Disabilities

NASA Astrophysics Data System (ADS)

Morgan, Micaela Victoria Cesario

The technological nature of the world we live in has produced a need for a workforce that is technologically savvy and possesses 21st century skills and abilities. Given that students with a learning disability (LD) may be an untapped source of science, technology, engineering, and mathematics (STEM) or career and technical education (CTE) potential, it is important to understand 1) whether LD students are capable of pursuing STEM and CTE fields and 2) what will aid them in successfully pursuing those fields. The two studies presented aim to answer those questions through a latent profile and latent class analysis. The results from the first study indicated that there are two STEM capable profiles of LD students: High-STEM and CTE Capability or Low-STEM Capability. It was found that female LD students were significantly more likely to be in the High-STEM and CTE Capability profile (.75, p < .05) by 2.11 times and that African-American LD students were significantly more likely to be found in the Low-STEM Capability profile (-1.31, p < .10). It was also more prevalent for LD students to pursue either STEM or CTE at the 2-year college regardless of what profile they resided in. Understanding a students' STEM or CTE capability can play a role in how they prepare and plan for their future. For the second study it was found that LD students could be categorized into three engagement classes: Highly Engaged LD Students, Moderately Engaged LD Students, and Poorly Engaged LD Students. Again, gender played a role in students' classification and it was found that female students were significantly more likely to be in the Moderately Engaged class (.22, p < .05). Results from this study also indicate that the 2-year pathway is the most traversed by LD students. LD students who were engaged in their IEP process, possess self-determination, and are able to utilize accommodations were more successful in pursuing a STEM and CTE field. Implications for postsecondary institutions will be discussed.
Progression of tau pathology within cholinergic nucleus basalis neurons in chronic traumatic encephalopathy: A Chronic Effects of Neurotrauma Consortium Study

PubMed Central

Mufson, Elliott J.; Perez, Sylvia E.; Nadeem, Muhammad; Mahady, Laura; Kanaan, Nicholas M.; Abrahamson, Eric E.; Ikonomovic, Milos D.; Crawford, Fiona; Alvarez, Victor; Stein, Thor; McKee, Ann C.

2017-01-01

Objective To test the hypothesis that the nucleus basalis of Meynert (nbM), a cholinergic basal forebrain (CBF) cortical projection system, develops neurofibrillary tangles (NFTs) during the progressive pathological stages of chronic traumatic encephalopathy (CTE) in the brain of athletes. Method To characterize NFT pathology we used tau- antibodies marking early, intermediate, and late stages of NFT development in cholinergic basal forebrain tissue obtained at autopsy from eighteen former athletes and veterans with a history of repetitive mild traumatic brain injury (TBI). Results We found evidence that cholinergic nbM neurons develop intracellular tau-immunoreactive changes progressively across the pathological stages of CTE. In particular, there was an increase in pretangle (phosphorylated pS422) and oligomeric (TOC1 and TNT1) forms of tau in stage IV compared to stage II CTE cases. The nbM neurons also displayed pathologic TDP-43 inclusions and diffuse extracellular and vascular amyloid-β (Aβ) deposits in CTE. A higher percent of pS422/p75NTR, pS422 and TNT1 labeled neurons were significantly correlated with age at symptom onset, interval between symptom onset and death and age at death. Conclusion The development of NFTs within the nbM neurons could contribute to the basal forebrain cortical cholinergic disconnection in CTE. Further studies are needed to determine the mechanism driving NFT formation in the nbM neurons and its relation to chronic cognitive dysfunction in CTE. PMID:27834536
Chronic traumatic encephalopathy: the dangers of getting "dinged"

PubMed Central

2012-01-01

Chronic traumatic encephalopathy (CTE) is a form of neurodegeneration that results from repetitive brain trauma. Not surprisingly, CTE has been linked to participation in contact sports such as boxing, hockey and American football. In American football getting "dinged" equates to moments of dizziness, confusion, or grogginess that can follow a blow to the head. There are approximately 100,000 to 300,000 concussive episodes occurring in the game of American football alone each year. It is believed that repetitive brain trauma, with or possibly without symptomatic concussion, sets off a cascade of events that result in neurodegenerative changes highlighted by accumulations of hyperphosphorylated tau and neuronal TAR DNA-binding protein-43 (TDP-43). Symptoms of CTE may begin years or decades later and include a progressive decline of memory, as well as depression, poor impulse control, suicidal behavior, and, eventually, dementia similar to Alzheimer's disease. In some individuals, CTE is also associated with motor neuron disease similar to amyotrophic lateral sclerosis. Given the millions of athletes participating in contact sports that involve repetitive brain trauma, CTE represents an important public health issue. In this review, we discuss recent advances in understanding the etiology of CTE. It is now known that those instances of mild concussion or "dings" that we may have previously not noticed could very well be causing progressive neurodegenerative damage to a player's brain. In the future, focused and intensive study of the risk factors could potentially uncover methods to prevent and treat this disease. PMID:23984220
Mutation of EpCAM leads to intestinal barrier and ion transport dysfunction.

PubMed

Kozan, Philip A; McGeough, Matthew D; Peña, Carla A; Mueller, James L; Barrett, Kim E; Marchelletta, Ronald R; Sivagnanam, Mamata

2015-05-01

Congenital tufting enteropathy (CTE) is a devastating diarrheal disease seen in infancy that is typically associated with villous changes and the appearance of epithelial tufts. We previously found mutations in epithelial cell adhesion molecule (EpCAM) to be causative in CTE. We developed a knock-down cell model of CTE through transfection of an EpCAM shRNA construct into T84 colonic epithelial cells to elucidate the in vitro role of EpCAM in barrier function and ion transport. Cells with EpCAM deficiency exhibited decreased electrical resistance, increased permeability, and decreased ion transport. Based on mutations in CTE patients, an in vivo mouse model was developed, with tamoxifen-inducible deletion of exon 4 in Epcam resulting in mutant protein with decreased expression. Tamoxifen treatment of Epcam (Δ4/Δ4) mice resulted in pathological features of villous atrophy and epithelial tufts, similar to those in human CTE patients, within 4 days post induction. Epcam (Δ4/Δ4) mice also showed decreased expression of tight junctional proteins, increased permeability, and decreased ion transport in the intestines. Taken together, these findings reveal mechanisms that may underlie disease in CTE. Knock-down EpCAM cell model of congenital tufting enteropathy was developed. In vivo inducible mouse model was developed resulting in mutant EpCAM protein. Cells with EpCAM deficiency demonstrated barrier and ion transport dysfunction. Tamoxifen-treated Epcam (Δ4/Δ4) mice demonstrated pathological features. Epcam (Δ4/Δ4) mice showed improper barrier function and ion transport.
Human reductive halothane metabolism in vitro is catalyzed by cytochrome P450 2A6 and 3A4.

PubMed

Spracklin, D K; Thummel, K E; Kharasch, E D

1996-09-01

The anesthetic halothane undergoes extensive oxidative and reductive biotransformation, resulting in metabolites that cause hepatotoxicity. Halothane is reduced anaerobically by cytochrome P450 (P450) to the volatile metabolites 2-chloro-1,1-difluoroethene (CDE) and 2-chloro-1,1,1-trifluoroethane (CTE). The purpose of this investigation was to identify the human P450 isoform(s) responsible for reductive halothane metabolism. CDE and CTE formation from halothane metabolism by human liver microsomes was determined by GC/MS analysis. Halothane metabolism to CDE and CTE under reductive conditions was completely inhibited by carbon monoxide, which implicates exclusively P450 in this reaction. Eadie-Hofstee plots of both CDE and CTE formation were nonlinear, suggesting multiple P450 isoform involvement. Microsomal CDE and CTE formation were each inhibited 40-50% by P450 2A6-selective inhibitors (coumarin and 8-methoxypsoralen) and 55-60% by P450 3A4-selective inhibitors (ketoconazole and troleandomycin). P450 1A-, 2B6-, 2C9/10-, and 2D6-selective inhibitors (7,8-benzoflavone, furafylline, orphenadrine, sulfaphenazole, and quinidine) had no significant effect on reductive halothane metabolism. Measurement of product formation catalyzed by a panel of cDNA-expressed P450 isoforms revealed that maximal rates of CDE formation occurred with P450 2A6, followed by P450 3A4. P450 3A4 was the most effective catalyst of CTE formation. Among a panel of 11 different human livers, there were significant linear correlations between the rate of CDE formation and both 2A6 activity (r = 0.64, p < 0.04) and 3A4 activity (r = 0.64, p < 0.03). Similarly, there were significant linear correlations between CTE formation and both 2A6 activity (r = 0.55, p < 0.08) and 3A4 activity (r = 0.77, p < 0.005). The P450 2E1 inhibitors 4-methylpyrazole and diethyldithiocarbamate inhibited CDE and CTE formation by 20-45% and 40-50%, respectively; however, cDNA-expressed P450 2E1 did not catalyze significant amounts of CDE or CTE production, and microsomal metabolite formation was not correlated with P450 2E1 activity. This investigation demonstrated that human liver microsomal reductive halothane metabolism is catalyzed predominantly by P450 2A6 and 3A4. This isoform selectivity for anaerobic halothane metabolism contrasts with that for oxidative human halothane metabolism, which is catalyzed predominantly by P450 2E1.
Junior Seau: An Illustrative Case of Chronic Traumatic Encephalopathy and Update on Chronic Sports-Related Head Injury.

PubMed

Azad, Tej D; Li, Amy; Pendharkar, Arjun V; Veeravagu, Anand; Grant, Gerald A

2016-02-01

Few neurologic diseases have captured the nation's attention more completely than chronic traumatic encephalopathy (CTE), which has been discovered in the autopsies of professional athletes, most notably professional football players. The tragic case of Junior Seau, a Hall of Fame, National Football League linebacker, has been the most high-profile confirmed case of CTE. Here we describe Seau's case, which concludes an autopsy conducted at the National Institutes of Health that confirmed the diagnosis. Since 1990, Junior Seau had a highly distinguished 20-year career playing for the National Football League as a linebacker, from which he sustained multiple concussions. He committed suicide on May 2, 2012, at age 43, after which an autopsy confirmed a diagnosis of CTE. His clinical history was significant for a series of behavioral disturbances. Seau's history and neuropathologic findings were used to better understand the pathophysiology, diagnosis, and possible risk factors for CTE. This high-profile case reflects an increasing awareness of CTE as a long-term consequence of multiple traumatic brain injuries. The previously unforeseen neurologic risks of American football have begun to cast doubt on the safety of the sport. Copyright © 2016 Elsevier Inc. All rights reserved.
The SnRK2-APC/CTE regulatory module mediates the antagonistic action of gibberellic acid and abscisic acid pathways

PubMed Central

Lin, Qibing; Wu, Fuqing; Sheng, Peike; Zhang, Zhe; Zhang, Xin; Guo, Xiuping; Wang, Jiulin; Cheng, Zhijun; Wang, Jie; Wang, Haiyang; Wan, Jianmin

2015-01-01

Abscisic acid (ABA) and gibberellic acid (GA) antagonistically regulate many developmental processes and responses to biotic or abiotic stresses in higher plants. However, the molecular mechanism underlying this antagonism is still poorly understood. Here, we show that loss-of-function mutation in rice Tiller Enhancer (TE), an activator of the APC/CTE complex, causes hypersensitivity and hyposensitivity to ABA and GA, respectively. We find that TE physically interacts with ABA receptor OsPYL/RCARs and promotes their degradation by the proteasome. Genetic analysis also shows OsPYL/RCARs act downstream of TE in mediating ABA responses. Conversely, ABA inhibits APC/CTE activity by phosphorylating TE through activating the SNF1-related protein kinases (SnRK2s), which may interrupt the interaction between TE and OsPYL/RCARs and subsequently stabilize OsPYL/RCARs. In contrast, GA can reduce the level of SnRK2s and may promote APC/CTE-mediated degradation of OsPYL/RCARs. Thus, we propose that the SnRK2-APC/CTE regulatory module represents a regulatory hub underlying the antagonistic action of GA and ABA in plants. PMID:26272249
The science and questions surrounding chronic traumatic encephalopathy.

PubMed

Ban, Vin Shen; Madden, Christopher J; Bailes, Julian E; Hunt Batjer, H; Lonser, Russell R

2016-04-01

Recently, the pathobiology, causes, associated factors, incidence and prevalence, and natural history of chronic traumatic encephalopathy (CTE) have been debated. Data from retrospective case series and high-profile media reports have fueled public fear and affected the medical community's understanding of the role of sports-related traumatic brain injury (TBI) in the development of CTE. There are a number of limitations posed by the current evidence that can lead to confusion within the public and scientific community. In this paper, the authors address common questions surrounding the science of CTE and propose future research directions.
A Conserved C-terminal Element in the Yeast Doa10 and Human MARCH6 Ubiquitin Ligases Required for Selective Substrate Degradation.

PubMed

Zattas, Dimitrios; Berk, Jason M; Kreft, Stefan G; Hochstrasser, Mark

2016-06-03

Specific proteins are modified by ubiquitin at the endoplasmic reticulum (ER) and are degraded by the proteasome, a process referred to as ER-associated protein degradation. In Saccharomyces cerevisiae, two principal ER-associated protein degradation ubiquitin ligases (E3s) reside in the ER membrane, Doa10 and Hrd1. The membrane-embedded Doa10 functions in the degradation of substrates in the ER membrane, nuclear envelope, cytoplasm, and nucleoplasm. How most E3 ligases, including Doa10, recognize their protein substrates remains poorly understood. Here we describe a previously unappreciated but highly conserved C-terminal element (CTE) in Doa10; this cytosolically disposed 16-residue motif follows the final transmembrane helix. A conserved CTE asparagine residue is required for ubiquitylation and degradation of a subset of Doa10 substrates. Such selectivity suggests that the Doa10 CTE is involved in substrate discrimination and not general ligase function. Functional conservation of the CTE was investigated in the human ortholog of Doa10, MARCH6 (TEB4), by analyzing MARCH6 autoregulation of its own degradation. Mutation of the conserved Asn residue (N890A) in the MARCH6 CTE stabilized the normally short lived enzyme to the same degree as a catalytically inactivating mutation (C9A). We also report the localization of endogenous MARCH6 to the ER using epitope tagging of the genomic MARCH6 locus by clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated genome editing. These localization and CTE analyses support the inference that MARCH6 and Doa10 are functionally similar. Moreover, our results with the yeast enzyme suggest that the CTE is involved in the recognition and/or ubiquitylation of specific protein substrates. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.
HST/WFC3: understanding and mitigating radiation damage effects in the CCD detectors

NASA Astrophysics Data System (ADS)

Baggett, S. M.; Anderson, J.; Sosey, M.; Gosmeyer, C.; Bourque, M.; Bajaj, V.; Khandrika, H.; Martlin, C.

2016-07-01

At the heart of the Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) UVIS channel is a 4096x4096 pixel e2v CCD array. While these detectors continue to perform extremely well after more than 7 years in low-earth orbit, the cumulative effects of radiation damage are becoming increasingly evident. The result is a continual increase of the hotpixel population and the progressive loss in charge-transfer efficiency (CTE) over time. The decline in CTE has two effects: (1) it reduces the detected source flux as the defects trap charge during readout and (2) it systematically shifts source centroids as the trapped charge is later released. The flux losses can be significant, particularly for faint sources in low background images. In this report, we summarize the radiation damage effects seen in WFC3/UVIS and the evolution of the CTE losses as a function of time, source brightness, and image-background level. In addition, we discuss the available mitigation options, including target placement within the field of view, empirical stellar photometric corrections, post-flash mode and an empirical pixel-based CTE correction. The application of a post-flash has been remarkably effective in WFC3 at reducing CTE losses in low-background images for a relatively small noise penalty. Currently, all WFC3 observers are encouraged to consider post-flash for images with low backgrounds. Finally, a pixel-based CTE correction is available for use after the images have been acquired. Similar to the software in use in the HST Advanced Camera for Surveys (ACS) pipeline, the algorithm employs an observationally-defined model of how much charge is captured and released in order to reconstruct the image. As of Feb 2016, the pixel-based CTE correction is part of the automated WFC3 calibration pipeline. Observers with pre-existing data may request their images from MAST (Mikulski Archive for Space Telescopes) to obtain the improved products.
STS-55 Pilot Henricks uses CTE equipment mounted on SL-D2 aft end cone

NASA Technical Reports Server (NTRS)

1993-01-01

STS-55 Pilot Terence T. Henricks, positioned in front of an adjustable workstation mounted on the Spacelab Deutsche 2 (SL-D2) science module aft end cone, conducts Crew Telesupport Experiment (CTE). The STS-55 crew portrait (STS055(S)002) appears on the screen of the Macintosh portable computer. CTE will demonstrate real-time communication between the shuttle crew and the ground via a computer-based multimedia documentation file that includes text, graphics, and photos. CTE is expected to improve the effectiveness of on-orbit payload operations, returns from scientific investigations, crew interaction with the ground, and contingency maintenance tasks for systems and payloads. Also in the view and attached to the end cone are a fire extinguisher, a checklist, and an STS-37 extravehicular activity (EVA) photo of Mission Specialist (MS1) and Payload Commander (PLC) Jerry L. Ross (STS037-18-032).
Diverse mechanisms of antidiabetic effects of the different procyanidin oligomer types of two different cinnamon species on db/db mice.

PubMed

Chen, Liang; Sun, Peng; Wang, Ting; Chen, Kaixian; Jia, Qi; Wang, Heyao; Li, Yiming

2012-09-12

The procyanidin oligomers are thought to be responsible for the antidiabetic activity of cinnamon. To investigate the hypoglycemic effects of different procyanidin oligomer types, the procyanidin oligomer-rich extracts were prepared from two different cinnamon species. Using high-performance liquid chromatography with purified procyanidin oligomers as reference compounds, we found that the Cinnamomum cassia extract (CC-E) and Cinnamomum tamala extract (CT-E) were rich in B- and A-type procyanidin oligomers, respectively. In the experiment, 8-week-old diabetic (db/db) mice were gavaged with CC-E and CT-E (both 200 mg/kg per day) for 4 weeks. Both CC-E and CT-E exhibited antidiabetic effects. Moreover, histopathological studies of the pancreas, liver, and adipose tissue showed that CC-E promoted lipid accumulation in the adipose tissue and liver, whereas CT-E mainly improved the insulin concentration in the blood and pancreas.
Preparation and thermal shock resistance of high emissivity molybdenum disilicide- aluminoborosilicate glass hybrid coating on fiber reinforced aerogel composite

NASA Astrophysics Data System (ADS)

Shao, Gaofeng; Lu, Yucao; Wu, Xiaodong; Wu, Jun; Cui, Sheng; Jiao, Jian; Shen, Xiaodong

2017-09-01

To develop a flexible reusable surface insulation for thermal protection system, MoSi2-aluminoborosilicate glass hybrid coatings have been prepared on Al2O3 fiber reinforced Al2O3-SiO2 aerogel composite by slurry dipping and rapid sintering method. The effect of MoSi2 content on radiative property and thermal shock behavior was investigated. The total emissivity values of all the coatings exceeded 0.85 in the wavelength of 0.8-2.5 μm. The M10 and M50 coatings were up to 0.9, which was due to the highest amorphous glass content of the M10 coating and the largest surface roughness of the M50 coating. The M30 coated composite showed the best thermal shock resistance with only 0.023% weight loss after 20 thermal shock cycles between 1473 K and room temperature, which was attributed to the similar thermal expansion coefficients between the coating and the substrate and the appropriate viscosity of aluminoborosilicate glass at 1473 K. The cracks resulted from CTE mismatch stress with different sizes formed and grew on the surface of M10, M40 and M50 coated samples, leading to the failure of the composites.
Unusually sharp paramagnetic phase transition in thin film Fe3Pt invar

NASA Astrophysics Data System (ADS)

Drisko, Jasper; Cumings, John

2013-03-01

Invar alloys, typically 3d transition metal rich systems, are most commonly known for their extremely low coefficients of thermal expansion (CTE) over a wide range of temperatures close to room temperature. This anomalous behavior in the CTE lends Invar to a variety of important applications in precision mechanical devices, scientific instruments, and sensors, among others. Many theoretical models of Invar have been proposed over the years, the most promising of which is a system described by two coexisting phases, one high-spin high-volume and the other low-spin low-volume, that compete to stabilize the volume of the material as the temperature is changed. However, no theory has yet been able to explain all experimental observations across the range of Invar alloys, especially at finite temperature. We have fabricated thin films of a Fe3Pt Invar alloy and investigate them using Lorentz Transmission Electron Microscopy (TEM). 23nm films are deposited onto SiN membrane substrates via radio-frequency magnetron sputtering from a pure Fe target decorated with Pt pieces. We observe novel magnetic domain structures and an unusually sharp phase transition between ferromagnetic (FM) and paramagnetic (PM) regions of the film under a temperature gradient. This sharp transition suggests that the FM-to-PM transition may be first order, perhaps containing a structural-elastic component to the order parameter. However, electron diffraction reveals that both the FM and PM regions have the same FCC crystal structure.
Natural Silica Sand/Alumina Ceramic Composites: Promising Candidates for Fuel-Cell Sealants

NASA Astrophysics Data System (ADS)

Hidayat, N.; Istiqomah; Widianto, M. Y. H.; Taufiq, A.; Sunaryono; Triwikantoro; Zainuri, M.; Baqiya, M. A.; Aristia, G.; Pratapa, S.

2017-05-01

An attempt has been developed to establish the prospect of the useful application of Indonesian natural silica sand, instead of commercially expensive materials, as a future fuel-cell sealant. The sand was initially washed and ball-milled at 150 rpm for 60 minutes and then heated at 1000 °C for the same duration. The resulting powder was then mixed with alumina powder at various amounts and shaped into discs before sintering at 1150 °C and 1250 °C to produce compact ceramics. The diameter shrinkage, porosity, and density of the ceramics were evaluated by Archimedes method. Their crystalline phase composition was quantified by Rietveld refinement analysis on the X-ray diffraction (XRD) data and the phase weight fraction was then used for coefficient of thermal expansion (CTE) evaluation. It was observed that the bulk density increased while the porosity decreased with alumina addition. The XRD data analysis revealed that the prepared silica sand contains a very high purity of quartz-SiO2, i.e. 97.8(18)%. The sintering temperatures of 1150 °C and 1250 °C transformed some quartz-SiO2 to crystobalite-SiO2. All the calcite-CaCO3 exhibited reaction sintering with SiO2 forming wollastonite-CaSiO3. Therefore, the ceramic composites contained SiO2/Al2O3/CaSiO3. Regarding CTE, all of the composites meet the criteria for fuel-cell sealants, in the range of 9-12 ppm/°C.
Dimensional stability performance of a CFRP sandwich optical bench for microsatellite payload

NASA Astrophysics Data System (ADS)

Desnoyers, N.; Goyette, P.; Leduc, B.; Boucher, M.-A.

2017-09-01

Microsatellite market requires high performance while minimizing mass, volume and cost. Telescopes are specifically targeted by these trade-offs. One of these is to use the optomechanical structure of the telescope to mount electronic devices that may dissipate heat. However, such approach may be problematic in terms of distortions due to the presence of high thermal gradients throughout the telescope structure. To prevent thermal distortions, Carbon Fiber Reinforced Polymer (CFRP) technology can be used for the optomechanical telescope material structure. CFRP is typically about 100 times less sensitive to thermal gradients and its coefficient of thermal expansion (CTE) is about 200 to 600 times lower than standard aluminum alloys according to inhouse measurements. Unfortunately, designing with CFRP material is not as straightforward as with metallic materials. There are many parameters to consider in order to reach the desired dimensional stability under thermal, moisture and vibration exposures. Designing optomechanical structures using CFRP involves many challenges such as interfacing with optics and sometimes dealing with high CTE mounting interface structures like aluminum spacecraft buses. INO has designed a CFRP sandwich telescope structure to demonstrate the achievable performances of such technology. Critical parameters have been optimized to maximize the dimensional stability while meeting the stringent environmental requirements that microsatellite payloads have to comply with. The telescope structure has been tested in vacuum from -40°C to +50°C and has shown a good fit with finite element analysis predictions.
Ultra-thin multilayer capacitors.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renk, Timothy Jerome; Monson, Todd C.

2009-06-01

The fabrication of ultra-thin lanthanum-doped lead zirconium titanate (PLZT) multilayer ceramic capacitors (MLCCs) using a high-power pulsed ion beam was studied. The deposition experiments were conducted on the RHEPP-1 facility at Sandia National Laboratories. The goal of this work was to increase the energy density of ceramic capacitors through the formation of a multilayer device with excellent materials properties, dielectric constant, and standoff voltage. For successful device construction, there are a number of challenging requirements including achieving correct stoichiometric and crystallographic composition of the deposited PLZT, as well as the creation of a defect free homogenous film. This report detailsmore » some success in satisfying these requirements, although 900 C temperatures were necessary for PLZT perovskite phase formation. These temperatures were applied to a previously deposited multi-layer film which was then post-annealed to this temperature. The film exhibited mechanical distress attributable to differences in the coefficient of thermal expansion (CTE) of the various layers. This caused significant defects in the deposited films that led to shorts across devices. A follow-on single layer deposition without post-anneal produced smooth layers with good interface behavior, but without the perovskite phase formation. These issues will need to be addressed in order for ion beam deposited MLCCs to become a viable technology. It is possible that future in-situ heating during deposition may address both the CTE issue, and result in lowered processing temperatures, which in turn could raise the probability of successful MLCC formation.« less
Structural and Chemical Analysis of the Zirconia-Veneering Ceramic Interface.

PubMed

Inokoshi, M; Yoshihara, K; Nagaoka, N; Nakanishi, M; De Munck, J; Minakuchi, S; Vanmeensel, K; Zhang, F; Yoshida, Y; Vleugels, J; Naert, I; Van Meerbeek, B

2016-01-01

The interfacial interaction of veneering ceramic with zirconia is still not fully understood. This study aimed to characterize morphologically and chemically the zirconia-veneering ceramic interface. Three zirconia-veneering conditions were investigated: 1) zirconia-veneering ceramic fired on sandblasted zirconia, 2) zirconia-veneering ceramic on as-sintered zirconia, and 3) alumina-veneering ceramic (lower coefficient of thermal expansion [CTE]) on as-sintered zirconia. Polished cross-sectioned ceramic-veneered zirconia specimens were examined using field emission gun scanning electron microscopy (Feg-SEM). In addition, argon-ion thinned zirconia-veneering ceramic interface cross sections were examined using scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectrometry (EDS) at high resolution. Finally, the zirconia-veneering ceramic interface was quantitatively analyzed for tetragonal-to-monoclinic phase transformation and residual stress using micro-Raman spectroscopy (µRaman). Feg-SEM revealed tight interfaces for all 3 veneering conditions. High-resolution transmission electron microscopy (HRTEM) disclosed an approximately 1.0-µm transformed zone at sandblasted zirconia, in which distinct zirconia grains were no longer observable. Straight grain boundaries and angular grain corners were detected up to the interface of zirconia- and alumina-veneering ceramic with as-sintered zirconia. EDS mapping disclosed within the zirconia-veneering ceramic a few nanometers thick calcium/aluminum-rich layer, touching the as-sintered zirconia base, with an equally thick silicon-rich/aluminum-poor layer on top. µRaman revealed t-ZrO2-to-m-ZrO2 phase transformation and residual compressive stress at the sandblasted zirconia surface. The difference in CTE between zirconia- and the alumina-veneering ceramic resulted in residual tensile stress within the zirconia immediately adjacent to its interface with the veneering ceramic. The rather minor chemical elemental shifts recorded in the veneering ceramic did not suffice to draw definitive conclusions regarding potential chemical interaction of the veneering ceramic with zirconia. Sandblasting damaged the zirconia surface and induced phase transformation that also resulted in residual compressive stress. Difference in CTE of zirconia versus that of the veneering ceramic resulted in an unfavorable residual tensile stress at the zirconia-veneering ceramic interface. © International & American Associations for Dental Research 2015.
CCL11 is increased in the CNS in chronic traumatic encephalopathy but not in Alzheimer's disease.

PubMed

Cherry, Jonathan D; Stein, Thor D; Tripodis, Yorghos; Alvarez, Victor E; Huber, Bertrand R; Au, Rhoda; Kiernan, Patrick T; Daneshvar, Daniel H; Mez, Jesse; Solomon, Todd M; Alosco, Michael L; McKee, Ann C

2017-01-01

CCL11, a protein previously associated with age-associated cognitive decline, is observed to be increased in the brain and cerebrospinal fluid (CSF) in chronic traumatic encephalopathy (CTE) compared to Alzheimer's disease (AD). Using a cohort of 23 deceased American football players with neuropathologically verified CTE, 50 subjects with neuropathologically diagnosed AD, and 18 non-athlete controls, CCL11 was measured with ELISA in the dorsolateral frontal cortex (DLFC) and CSF. CCL11 levels were significantly increased in the DLFC in subjects with CTE (fold change = 1.234, p < 0.050) compared to non-athlete controls and AD subjects with out a history of head trauma. This increase was also seen to correlate with years of exposure to American football (β = 0.426, p = 0.048) independent of age (β = -0.046, p = 0.824). Preliminary analyses of a subset of subjects with available post-mortem CSF showed a trend for increased CCL11 among individuals with CTE (p = 0.069) mirroring the increase in the DLFC. Furthermore, an association between CSF CCL11 levels and the number of years exposed to football (β = 0.685, p = 0.040) was observed independent of age (β = -0.103, p = 0.716). Finally, a receiver operating characteristic (ROC) curve analysis demonstrated CSF CCL11 accurately distinguished CTE subjects from non-athlete controls and AD subjects (AUC = 0.839, 95% CI 0.62-1.058, p = 0.028). Overall, the current findings provide preliminary evidence that CCL11 may be a novel target for future CTE biomarker studies.

CCL11 is increased in the CNS in chronic traumatic encephalopathy but not in Alzheimer’s disease

PubMed Central

Stein, Thor D.; Tripodis, Yorghos; Alvarez, Victor E.; Huber, Bertrand R.; Au, Rhoda; Kiernan, Patrick T.; Daneshvar, Daniel H.; Mez, Jesse; Solomon, Todd M.; Alosco, Michael L.; McKee, Ann C.

2017-01-01

CCL11, a protein previously associated with age-associated cognitive decline, is observed to be increased in the brain and cerebrospinal fluid (CSF) in chronic traumatic encephalopathy (CTE) compared to Alzheimer’s disease (AD). Using a cohort of 23 deceased American football players with neuropathologically verified CTE, 50 subjects with neuropathologically diagnosed AD, and 18 non-athlete controls, CCL11 was measured with ELISA in the dorsolateral frontal cortex (DLFC) and CSF. CCL11 levels were significantly increased in the DLFC in subjects with CTE (fold change = 1.234, p < 0.050) compared to non-athlete controls and AD subjects with out a history of head trauma. This increase was also seen to correlate with years of exposure to American football (β = 0.426, p = 0.048) independent of age (β = -0.046, p = 0.824). Preliminary analyses of a subset of subjects with available post-mortem CSF showed a trend for increased CCL11 among individuals with CTE (p = 0.069) mirroring the increase in the DLFC. Furthermore, an association between CSF CCL11 levels and the number of years exposed to football (β = 0.685, p = 0.040) was observed independent of age (β = -0.103, p = 0.716). Finally, a receiver operating characteristic (ROC) curve analysis demonstrated CSF CCL11 accurately distinguished CTE subjects from non-athlete controls and AD subjects (AUC = 0.839, 95% CI 0.62–1.058, p = 0.028). Overall, the current findings provide preliminary evidence that CCL11 may be a novel target for future CTE biomarker studies. PMID:28950005
Chronic traumatic encephalopathy: how serious a sports problem is it?

PubMed

Tator, Charles H

2014-01-01

It is now recognised that there is a spectrum of concussion disorders ranging from acute concussion at one end to various forms of brain degeneration at the other end. The spectrum includes acute concussion, second impact syndrome or acute cerebral swelling, postconcussion syndrome, depression or anxiety, chronic traumatic encephalopathy (CTE) and possibly other forms of central nervous system degeneration. It is essential to carefully evaluate the clinical and neuropathological correlations of CTE that have been published. This has been accomplished in an excellent paper on this subject by Gardner and colleagues in this issue. There have been significant advances in our knowledge of the clinical and neuropathological features of CTE in athletes in the past 10 years. However, we are just at the beginning of our appreciation of this entity due to the paucity of research and the inability to diagnose CTE during life. At present, it is not possible to assess the validity of the proposed methods of classification and grading of the severity of the disease. Additional studies of large numbers of at-risk athletes are essential, especially prospective longitudinal studies. Obviously, such studies would be even more effective if reliable in vivo biomarkers were discovered, especially non-invasive ones such as advanced MRI or MR spectroscopy or invasive ones such as blood or cerebrospinal fluid tests. The major questions that remain unanswered include the frequency of CTE in various collision sports, the causal or otherwise relationship between concussions and CTE, the number of concussions that need to be involved and their management.
Looking inside the Black Box: The Value Added by Career and Technical Student Organizations to Students' High School Experience

ERIC Educational Resources Information Center

Alfeld, Corinne; Stone, James R., III; Aragon, Steven R.; Hansen, David M.; Zirkle, Christopher; Connors, James; Spindler, Matt; Romine, Rebecca Swinburne; Woo, Hui-Jeong

2007-01-01

In addition to hands-on learning in classrooms and work-related activities such as co-op, many CTE programs offer a career-focused student organization, known as a Career and Technical Student Organization, or CTSO. CTSOs have been touted as developing such characteristics as leadership and employability skills in students; however, there is…
Advanced mirror technology development (AMTD): year five status

NASA Astrophysics Data System (ADS)

Stahl, H. Philip

2017-09-01

The Advanced Mirror Technology Development (AMTD) project is in Phase 2 of a multiyear effort initiated in Fiscal Year (FY) 2012, to mature the Technology Readiness Level (TRL) of critical technologies required to enable 4-m-orlarger monolithic or segmented ultraviolet, optical, and infrared (UVOIR) space telescope primary-mirror assemblies for general astrophysics, ultra-high-contrast observations of exoplanets, and National Interest missions. Key accomplishments of 2016/17 include the completion of the Harris Corp 150 Hz 1.5-meter Ultra-Low Expansion (ULE) mirror substrate using stacked core method to demonstrate lateral stability of the stacked core technology, as well as the characterization and validation by test of the mechanical and thermal performance of the 1.2-meter Zerodur mirror using the STOP model prediction and verification of CTE homogeneity.
Graphite/Cyanate Ester Face Sheets for Adaptive Optics

NASA Technical Reports Server (NTRS)

Bennett, Harold; Shaffer, Joseph; Romeo, Robert

2008-01-01

It has been proposed that thin face sheets of wide-aperture deformable mirrors in adaptive-optics systems be made from a composite material consisting of cyanate ester filled with graphite. This composite material appears to offer an attractive alternative to low-thermal-expansion glasses that are used in some conventional optics and have been considered for adaptive-optics face sheets. Adaptive-optics face sheets are required to have maximum linear dimensions of the order of meters or even tens of meters for some astronomical applications. If the face sheets were to be made from low-thermal-expansion glasses, then they would also be required to have thicknesses of the order of a millimeter so as to obtain the optimum compromise between the stiffness needed for support and the flexibility needed to enable deformation to controlled shapes by use of actuators. It is difficult to make large glass sheets having thicknesses less than 3 mm, and 3-mm-thick glass sheets are too stiff to be deformable to the shapes typically required for correction of wavefronts of light that has traversed the terrestrial atmosphere. Moreover, the primary commercially produced candidate low-thermal-expansion glass is easily fractured when in the form of thin face sheets. Graphite-filled cyanate ester has relevant properties similar to those of the low-expansion glasses. These properties include a coefficient of thermal expansion (CTE) of the order of a hundredth of the CTEs of other typical mirror materials. The Young s modulus (which quantifies stiffness in tension and compression) of graphite-filled cyanate ester is also similar to the Young's moduli of low-thermal-expansion glasses. However, the fracture toughness of graphite-filled cyanate ester is much greater than that of the primary candidate low-thermal-expansion glass. Therefore, graphite-filled cyanate ester could be made into nearly unbreakable face sheets, having maximum linear dimensions greater than a meter and thicknesses of the order of a millimeter, that would satisfy the requirements for use in adaptive optics.
Education Industry, 2006

DTIC Science & Technology

2006-01-01

resulted in the U.S. Department of Education referring to it as Career and Technical Education (CTE). Minuteman High School, a highly successful...whole, and ultimately the students and the nation, will suffer the consequences. 7 Vocational Education The challenge for Career and Technical Education (CTE
ASTP video tape recorder ground support equipment (audio/CTE splitter/interleaver). Operations manual

NASA Technical Reports Server (NTRS)

1974-01-01

A descriptive handbook for the audio/CTE splitter/interleaver (RCA part No. 8673734-502) was presented. This unit is designed to perform two major functions: extract audio and time data from an interleaved video/audio signal (splitter section), and provide a test interleaved video/audio/CTE signal for the system (interleaver section). It is a rack mounting unit 7 inches high, 19 inches wide, 20 inches deep, mounted on slides for retracting from the rack, and weighs approximately 40 pounds. The following information is provided: installation, operation, principles of operation, maintenance, schematics and parts lists.
Factors Influencing Clinical Correlates of Chronic Traumatic Encephalopathy (CTE): A Review

PubMed Central

Asken, Breton M.; Sullan, Molly J.; Snyder, Aliyah R.; Houck, Zachary M.; Bryant, Vaughn E.; Hizel, Loren P.; McLaren, Molly E.; Dede, Duane E.; Jaffee, Michael S.; DeKosky, Steven T.; Bauer, Russell M.

2017-01-01

Chronic traumatic encephalopathy (CTE) is a neuropathologically defined disease reportedly linked to a history of repetitive brain trauma. As such, retired collision sport athletes are likely at heightened risk for developing CTE. Researchers have described distinct pathological features of CTE as well a wide range of clinical symptom presentations, recently termed traumatic encephalopathy syndrome (TES). These clinical symptoms are highly variable, non-specific to individuals described as having CTE pathology in case reports, and are often associated with many other factors. This review describes the cognitive, emotional, and behavioral changes associated with 1) developmental and demographic factors, 2) neurodevelopmental disorders, 3) normal aging, 4) adjusting to retirement, 5) drug and alcohol abuse, 6) surgeries and anesthesia, and 7) sleep difficulties, as well as the relationship between these factors and risk for developing dementia-related neurodegenerative disease. We discuss why some professional athletes may be particularly susceptible to many of these effects and the importance of choosing appropriate controls groups when designing research protocols. We conclude that these factors should be considered as modifiers predominantly of the clinical outcomes associated with repetitive brain trauma within a broader biopsychosocial framework when interpreting and attributing symptom development, though also note potential effects on neuropathological outcomes. Importantly, this could have significant treatment implications for improving quality of life. PMID:27561662
CTE's Role in Urban Education. Issue Brief

ERIC Educational Resources Information Center

Association for Career and Technical Education (ACTE), 2012

2012-01-01

This Issue Brief explores the promising role that career and technical education programs play in addressing key student achievement issues facing urban schools. CTE programs engage urban students by providing rigorous and relevant coursework, fostering positive relationships, establishing clear pathways and connecting education and…
Unions, Contractors and CTE

ERIC Educational Resources Information Center

Jarosz, Francesca

2006-01-01

Across Illinois, in places where unions thrive, construction industry professionals and career and technical education (CTE) teachers are working together in promoting work-based learning program to students. Likewise, the outreach program provides union-supported contractors with qualified candidates for future employment. Programs such as the…
Criteria for solvent-induced chronic toxic encephalopathy: a systematic review.

PubMed

van der Hoek, J A; Verberk, M M; Hageman, G

2000-08-01

In 1985, a WHO Working Group presented diagnostic criteria and a classification for solvent-induced chronic toxic encephalopathy (CTE). In the same year, the "Workshop on neurobehavioral effects of solvents" in Raleigh, N.C., USA introduced a somewhat different classification for CTE. The objective of this review is to study the diagnostic procedures that are used to establish the diagnosis of CTE, and the extent to which the diagnostic criteria and classification of the WHO, and the classification of the Raleigh Working Group, are applied. A systematic search of studies on CTE was performed, and the diagnostic criteria and use of the WHO and Raleigh classifications were listed. We retrieved 30 original articles published in English from 1985 to 1998, in which CTE was diagnosed. Only two articles did not report the duration of solvent exposure. The type of solvent(s) involved was described in detail in four articles, poorly in 17 articles, and not at all in nine articles. Tests of general intelligence were used in 19 articles, and tests of both attention and mental flexibility and of learning and memory were used in 18 articles. Exclusion, by interview, of potentially confounding conditions, such as somatic diseases with central nervous effects and psychiatric diseases, was reported in 21 and 16 articles, respectively. In only six of the articles were both the WHO diagnostic criteria and the WHO or Raleigh classifications used. In the future, parameters of exposure, psychological test results, and use of medication that possibly affects psychological test results should always be described. We list some advantages and disadvantages of the Raleigh and WHO classifications. To aid inter-study comparisons, the diagnosis of CTE should be categorized and reported according to an internationally accepted classification.
The design and modeling of periodic materials with novel properties

NASA Astrophysics Data System (ADS)

Berger, Jonathan Bernard

Cellular materials are ubiquitous in our world being found in natural and engineered systems as structural materials, sound and energy absorbers, heat insulators and more. Stochastic foams made of polymers, metals and even ceramics find wide use due to their novel properties when compared to monolithic materials. Properties of these so called hybrid materials, those that combine materials or materials and space, are derived from the localization of thermomechanical stresses and strains on the mesoscale as a function of cell topology. The effects of localization can only be generalized in stochastic materials arising from their inherent potential complexity, possessing variations in local chemistry, microstructural inhomogeneity and topological variations. Ordered cellular materials on the other hand, such as lattices and honeycombs, make for much easier study, often requiring analysis of only a single unit-cell. Theoretical bounds predict that hybrid materials have the potential to push design envelopes offering lighter stiffer and stronger materials. Hybrid materials can achieve very low and even negative coefficients of thermal expansion (CTE) while retaining a relatively high stiffness -- properties completely unmatched by monolithic materials. In the first chapter of this thesis a two-dimensional lattice is detailed that possess near maximum stiffness, relative to the tightest theoretical bound, and low, zero and even appreciably negative thermal expansion. Its CTE and stiffness are given in closed form as a function of geometric parameters and the material properties. This result is confirmed with finite elements (FE) and experiment. In the second chapter the compressive stiffness of three-dimensional ordered foams, both closed and open cell, are predicted with FE and the results placed in property space in terms of stiffness and density. A novel structure is identified that effectively achieves theoretical bounds for Young's, shear and bulk modulus simultaneously, over a wide range of relative densities, greatly expanding the property space of available materials with a pragmatic manufacturable structure. A variety of other novel and previously studied ordered foam topologies are also presented that are largely representative of the spectrum of performance of such materials, shedding insight into the behavior of all cellular materials.
Online CTE in the Community College

ERIC Educational Resources Information Center

Garza Mitchell, Regina L.; Etshim, Rachal; Dietz, Brian T.

2016-01-01

This single-site case study explored how one community college integrated online education into CTE courses and programs. Through semi-structured interviews and document analysis, the study explores how one college integrated online education (fully online, hybrid, and web-enhanced) into areas typically considered "hands-on".…
Acute and chronic traumatic encephalopathies: pathogenesis and biomarkers

PubMed Central

DeKosky, Steven T.; Blennow, Kaj; Ikonomovic, Milos D.; Gandy, Sam

2014-01-01

Over the past decade, public awareness of the long-term pathological consequences of traumatic brain injury (TBI) has increased. Such awareness has been stimulated mainly by reports of progressive neurological dysfunction in athletes exposed to repetitive concussions in high-impact sports such as boxing and American football, and by the rising number of TBIs in war veterans who are now more likely to survive explosive blasts owing to improved treatment. Moreover, the entity of chronic traumatic encephalopathy (CTE)—which is marked by prominent neuropsychiatric features including dementia, parkinsonism, depression, agitation, psychosis, and aggression—has become increasingly recognized as a potential late outcome of repetitive TBI. Annually, about 1% of the population in developed countries experiences a clinically relevant TBI. The goal of this Review is to provide an overview of the latest understanding of CTE pathophysiology, and to delineate the key issues that are challenging clinical and research communities, such as accurate quantification of the risk of CTE, and development of reliable biomarkers for single-incident TBI and CTE. PMID:23558985
Acute and chronic traumatic encephalopathies: pathogenesis and biomarkers.

PubMed

DeKosky, Steven T; Blennow, Kaj; Ikonomovic, Milos D; Gandy, Sam

2013-04-01

Over the past decade, public awareness of the long-term pathological consequences of traumatic brain injury (TBI) has increased. Such awareness has been stimulated mainly by reports of progressive neurological dysfunction in athletes exposed to repetitive concussions in high-impact sports such as boxing and American football, and by the rising number of TBIs in war veterans who are now more likely to survive explosive blasts owing to improved treatment. Moreover, the entity of chronic traumatic encephalopathy (CTE)--which is marked by prominent neuropsychiatric features including dementia, parkinsonism, depression, agitation, psychosis, and aggression--has become increasingly recognized as a potential late outcome of repetitive TBI. Annually, about 1% of the population in developed countries experiences a clinically relevant TBI. The goal of this Review is to provide an overview of the latest understanding of CTE pathophysiology, and to delineate the key issues that are challenging clinical and research communities, such as accurate quantification of the risk of CTE, and development of reliable biomarkers for single-incident TBI and CTE.
Cognitive Reserve as a Modifier of Clinical Expression in Chronic Traumatic Encephalopathy: A Preliminary Examination.

PubMed

Alosco, Michael L; Mez, Jesse; Kowall, Neil W; Stein, Thor D; Goldstein, Lee E; Cantu, Robert C; Katz, Douglas I; Solomon, Todd M; Kiernan, Patrick T; Murphy, Lauren; Abdolmohammadi, Bobak; Daneshvar, Daniel; Montenigro, Philip H; Nowinski, Christopher J; Stern, Robert A; McKee, Ann C

2017-01-01

This study conducted a preliminary examination on cognitive reserve (CR) as a modifier of symptom expression in subjects with autopsy-confirmed chronic traumatic encephalopathy (CTE). The sample included 25 former professional football players neuropathologically diagnosed with CTE stage III or IV. Next of kin interviews ascertained age at cognitive and behavioral/mood symptom onset and demographic/athletic characteristics. Years of education and occupational attainment defined CR. High occupational achievement predicted later age at cognitive (p=0.02) and behavioral/mood (p=0.02) onset. Education was not an individual predictor. These preliminary findings suggest that CR may forestall the clinical manifestation of CTE.
Tau prions from Alzheimer’s disease and chronic traumatic encephalopathy patients propagate in cultured cells

PubMed Central

Woerman, Amanda L.; Aoyagi, Atsushi; Patel, Smita; Kazmi, Sabeen A.; Lobach, Iryna; Grinberg, Lea T.; McKee, Ann C.; Seeley, William W.; Olson, Steven H.; Prusiner, Stanley B.

2016-01-01

Tau prions are thought to aggregate in the central nervous system, resulting in neurodegeneration. Among the tauopathies, Alzheimer’s disease (AD) is the most common, whereas argyrophilic grain disease (AGD), corticobasal degeneration (CBD), chronic traumatic encephalopathy (CTE), Pick’s disease (PiD), and progressive supranuclear palsy (PSP) are less prevalent. Brain extracts from deceased individuals with PiD, a neurodegenerative disorder characterized by three-repeat (3R) tau prions, were used to infect HEK293T cells expressing 3R tau fused to yellow fluorescent protein (YFP). Extracts from AGD, CBD, and PSP patient samples, which contain four-repeat (4R) tau prions, were transmitted to HEK293 cells expressing 4R tau fused to YFP. These studies demonstrated that prion propagation in HEK cells requires isoform pairing between the infecting prion and the recipient substrate. Interestingly, tau aggregates in AD and CTE, containing both 3R and 4R isoforms, were unable to robustly infect either 3R- or 4R-expressing cells. However, AD and CTE prions were able to replicate in HEK293T cells expressing both 3R and 4R tau. Unexpectedly, increasing the level of 4R isoform expression alone supported the propagation of both AD and CTE prions. These results allowed us to determine the levels of tau prions in AD and CTE brain extracts. PMID:27911827
In vivo characterization of chronic traumatic encephalopathy using [F-18]FDDNP PET brain imaging.

PubMed

Barrio, Jorge R; Small, Gary W; Wong, Koon-Pong; Huang, Sung-Cheng; Liu, Jie; Merrill, David A; Giza, Christopher C; Fitzsimmons, Robert P; Omalu, Bennet; Bailes, Julian; Kepe, Vladimir

2015-04-21

Chronic traumatic encephalopathy (CTE) is an acquired primary tauopathy with a variety of cognitive, behavioral, and motor symptoms linked to cumulative brain damage sustained from single, episodic, or repetitive traumatic brain injury (TBI). No definitive clinical diagnosis for this condition exists. In this work, we used [F-18]FDDNP PET to detect brain patterns of neuropathology distribution in retired professional American football players with suspected CTE (n = 14) and compared results with those of cognitively intact controls (n = 28) and patients with Alzheimer's dementia (AD) (n = 24), a disease that has been cognitively associated with CTE. [F-18]FDDNP PET imaging results in the retired players suggested the presence of neuropathological patterns consistent with models of concussion wherein brainstem white matter tracts undergo early axonal damage and cumulative axonal injuries along subcortical, limbic, and cortical brain circuitries supporting mood, emotions, and behavior. This deposition pattern is distinctively different from the progressive pattern of neuropathology [paired helical filament (PHF)-tau and amyloid-β] in AD, which typically begins in the medial temporal lobe progressing along the cortical default mode network, with no or minimal involvement of subcortical structures. This particular [F-18]FDDNP PET imaging pattern in cases of suspected CTE also is primarily consistent with PHF-tau distribution observed at autopsy in subjects with a history of mild TBI and autopsy-confirmed diagnosis of CTE.
In vivo characterization of chronic traumatic encephalopathy using [F-18]FDDNP PET brain imaging

PubMed Central

Barrio, Jorge R.; Small, Gary W.; Wong, Koon-Pong; Huang, Sung-Cheng; Liu, Jie; Merrill, David A.; Giza, Christopher C.; Fitzsimmons, Robert P.; Omalu, Bennet; Bailes, Julian; Kepe, Vladimir

2015-01-01

Chronic traumatic encephalopathy (CTE) is an acquired primary tauopathy with a variety of cognitive, behavioral, and motor symptoms linked to cumulative brain damage sustained from single, episodic, or repetitive traumatic brain injury (TBI). No definitive clinical diagnosis for this condition exists. In this work, we used [F-18]FDDNP PET to detect brain patterns of neuropathology distribution in retired professional American football players with suspected CTE (n = 14) and compared results with those of cognitively intact controls (n = 28) and patients with Alzheimer’s dementia (AD) (n = 24), a disease that has been cognitively associated with CTE. [F-18]FDDNP PET imaging results in the retired players suggested the presence of neuropathological patterns consistent with models of concussion wherein brainstem white matter tracts undergo early axonal damage and cumulative axonal injuries along subcortical, limbic, and cortical brain circuitries supporting mood, emotions, and behavior. This deposition pattern is distinctively different from the progressive pattern of neuropathology [paired helical filament (PHF)-tau and amyloid-β] in AD, which typically begins in the medial temporal lobe progressing along the cortical default mode network, with no or minimal involvement of subcortical structures. This particular [F-18]FDDNP PET imaging pattern in cases of suspected CTE also is primarily consistent with PHF-tau distribution observed at autopsy in subjects with a history of mild TBI and autopsy-confirmed diagnosis of CTE. PMID:25848027
Long-term consequences of repetitive brain trauma: chronic traumatic encephalopathy.

PubMed

Stern, Robert A; Riley, David O; Daneshvar, Daniel H; Nowinski, Christopher J; Cantu, Robert C; McKee, Ann C

2011-10-01

Chronic traumatic encephalopathy (CTE) has been linked to participation in contact sports such as boxing and American football. CTE results in a progressive decline of memory and cognition, as well as depression, suicidal behavior, poor impulse control, aggressiveness, parkinsonism, and, eventually, dementia. In some individuals, it is associated with motor neuron disease, referred to as chronic traumatic encephalomyelopathy, which appears clinically similar to amyotrophic lateral sclerosis. Results of neuropathologic research has shown that CTE may be more common in former contact sports athletes than previously believed. It is believed that repetitive brain trauma, with or possibly without symptomatic concussion, is responsible for neurodegenerative changes highlighted by accumulations of hyperphosphorylated tau and TDP-43 proteins. Given the millions of youth, high school, collegiate, and professional athletes participating in contact sports that involve repetitive brain trauma, as well as military personnel exposed to repeated brain trauma from blast and other injuries in the military, CTE represents an important public health issue. Focused and intensive study of the risk factors and in vivo diagnosis of CTE will potentially allow for methods to prevent and treat these diseases. Research also will provide policy makers with the scientific knowledge to make appropriate guidelines regarding the prevention and treatment of brain trauma in all levels of athletic involvement as well as the military theater. Copyright © 2011 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Neuroimaging in repetitive brain trauma

PubMed Central

2014-01-01

Sports-related concussions are one of the major causes of mild traumatic brain injury. Although most patients recover completely within days to weeks, those who experience repetitive brain trauma (RBT) may be at risk for developing a condition known as chronic traumatic encephalopathy (CTE). While this condition is most commonly observed in athletes who experience repetitive concussive and/or subconcussive blows to the head, such as boxers, football players, or hockey players, CTE may also affect soldiers on active duty. Currently, the only means by which to diagnose CTE is by the presence of phosphorylated tau aggregations post-mortem. Non-invasive neuroimaging, however, may allow early diagnosis as well as improve our understanding of the underlying pathophysiology of RBT. The purpose of this article is to review advanced neuroimaging methods used to investigate RBT, including diffusion tensor imaging, magnetic resonance spectroscopy, functional magnetic resonance imaging, susceptibility weighted imaging, and positron emission tomography. While there is a considerable literature using these methods in brain injury in general, the focus of this review is on RBT and those subject populations currently known to be susceptible to RBT, namely athletes and soldiers. Further, while direct detection of CTE in vivo has not yet been achieved, all of the methods described in this review provide insight into RBT and will likely lead to a better characterization (diagnosis), in vivo, of CTE than measures of self-report. PMID:25031630
The Oregon Career and Technical Education Study

ERIC Educational Resources Information Center

Klein, Steven; Richards, Amanda

2008-01-01

Oregon educators, policymakers, and business people are working together to increase the number and quality of Career and Technical Education (CTE) programs in secondary and postsecondary institutions. CTE is an integral component of Oregon's education and workforce development system and prepares students for careers in areas ranging from the…
Developing Technical Skill Assessments

ERIC Educational Resources Information Center

Hyslop, Alisha

2009-01-01

One of the biggest challenges facing the career and technical education (CTE) community as it works to implement the 2006 Perkins Act is responding to more rigorous requirements for reporting on CTE students' technical skill attainment. The U.S. Department of Education suggested in non-regulatory guidance that states and locals use the number of…
Career Technical Education and Labor Market Demand

ERIC Educational Resources Information Center

National Association of State Directors of Career Technical Education Consortium, 2012

2012-01-01

Current data indicates that Career Technical Education (CTE) graduates with high school diplomas or postsecondary skills are preparing for careers in fields that are growing or in high-demand. Matching employability skills with workforce demand has been an issue among industries across the nation. CTE provides relevant academic and technical…
Research Needs: Career and Technical Education

ERIC Educational Resources Information Center

Kosloski, Michael F., Jr.; Ritz, John M.

2016-01-01

Research is an important component of each professional field. This study sought to determine topics that needed further research in the school subjects known as career and technical education. It determined topics that needed to be researched related to high school career and technical education (CTE) and the preparation for teaching CTE in…
Learning in Context

ERIC Educational Resources Information Center

Burke, Scott; Moore, Tom

2009-01-01

When geometry and career and technical education (CTE) are cotaught in the process of building a house, learning is enhanced, test scores improve, and there's a waiting list of students wanting in. Geometry in Construction is a class instructed by the authors--a CTE teacher (Scott Burke) and a mathematics teacher (Tom Moore). While Moore instructs…
The Benefits of Career and Technical Education. Trends and Issues Alert.

ERIC Educational Resources Information Center

Brown, Bettina Lankard

Career and technical education (CTE) can benefit students directly by providing earning advantages before and after graduation. It can benefit them indirectly by increasing engagement, retention, and persistence and by directing them to postsecondary education and pursuit of lifelong learning. CTE programs motivate students to get involved in…
Team-Teaching a Digital Senior Capstone Project in CTE

ERIC Educational Resources Information Center

Ryan, Melanie D.; Tews, Nichole M.; Washer, Barton A.

2012-01-01

Secondary career and technical education (CTE) students are faced with the unique challenge of learning not only specific content-related knowledge and skills, but also postsecondary preparation, 21st century technology, employability and self-marketing skills. At Cass Career Center in Harrisonville, Missouri, a senior capstone project was…
Clicking Your Way to Student Success!

ERIC Educational Resources Information Center

Bostwick, Dianna; Foster, John; Bloomfield, Amie; Rutledge, Paul

2013-01-01

According to the authors, their field has been in a constant state of change and evolution, from manual arts to vocational education to career and technical education (CTE). In a recent effort to increase academic and occupational achievement and success for all CTE students through targeted improvement plans, the state of Pennsylvania implemented…
South Tahoe: A Model for Career Tech

ERIC Educational Resources Information Center

Kisel, James

2012-01-01

With the help of close to $30 million in grant monies from Career Technical Education (CTE) and Overcrowding Relief grants, and Joint-Use and High Performance grants, Lake Tahoe Unified School District and architect LPA, Inc., have already completed a CTE "Green" Construction and Transportation Academy, a new classroom building and the…
Parallels in Arts Education and CTE: Some Guiding Reflections

ERIC Educational Resources Information Center

Hull, Bradley J.

2010-01-01

Many forces shape the current national conversation regarding career and technical education (CTE). Perkins IV guides the discussion through concepts such as challenging academic and technical standards; high skill, high wage, or high demand occupations; and programs of study. Workforce development and training, the economic recession,…
NPS Draws CTE Educators from around the Country

ERIC Educational Resources Information Center

Emeagwali, N. Susan

2010-01-01

In this article, the author describes the Association for Career and Technical Education's (ACTE) National Policy Seminar (NPS) which successfully brought hundreds of career and technical educators to Arlington, Virginia. The event, which was held March 8-10, provided career and technical education (CTE) professionals with an opportunity to keep…
State Policies Impacting CTE: 2015 Year in Review

ERIC Educational Resources Information Center

Association for Career and Technical Education (ACTE), 2016

2016-01-01

In 2015, states continued to invest heavily in career and technical education (CTE), as leaders and policymakers sought to strengthen their state economies, fill the talent pipeline with well-prepared workers in key industries, and provide meaningful educational and career opportunities for citizens at every learner level. More than 125…
Implications of Distance Education for CTE. ERIC Digest No. 227.

ERIC Educational Resources Information Center

Wonacott, Michael E.

Distance education (DE) is increasingly seen as a powerful vehicle for delivering various types of education, including career and technical education (CTE). Fast-paced, pervasive changes in the economic, social, and technological foundations of education and educational delivery, including the increasing use of information and communications…
Critical Success Factors in a High School Healthcare Education Program

ERIC Educational Resources Information Center

Thessin, Rebecca A.; Scully-Russ, Ellen; Lieberman, Daina S.

2017-01-01

Research has demonstrated career and technical education (CTE) programs have a strong positive influence on secondary students' behavior, attendance, academic achievement, and college persistence. Critical success factors common to career academies, small schools, and CTE programs include socio-emotional support and community, along with a culture…
Aligning Career and Technical Education

ERIC Educational Resources Information Center

Workman, Ed; Stubbs, Joyce

2011-01-01

The issues and concerns facing Kentucky Career and Technical Teacher Education (KY CTTE), university teacher educators and state department Career and Technical Education (CTE) leaders in providing and preparing the best CTE teachers possible are not unique to Kentucky. In an effort to better understand these issues and concerns a team of state…
Aligning K-12 and Postsecondary Career Pathways with Workforce Needs

ERIC Educational Resources Information Center

Zinth, Jennifer

2015-01-01

Since 2013, states have witnessed significant legislative activity related to secondary- and postsecondary-level career/technical education (CTE). One key goal of much recent policymaking activity has been to improve alignment between high school and postsecondary CTE programs, including by developing state or regional structures to design career…
Process for preparing an assembly of an article and a polyimide which resists dimensional change, delamination and debonding when exposed to changes in temperature

NASA Technical Reports Server (NTRS)

Stoakley, Diane M. (Inventor); St.clair, Anne K. (Inventor)

1994-01-01

An assembly of an article and a polyimide composition is prepared. The assembly resists dimensional change, delamination, or debonding when exposed to changes in temperature. An article is provided. A polyamic acid solution which yields a polyimide having a low coefficient of thermal expansion (CTE) was prepared. Equimolar quantities of an aromatic diamine and an aromatic dianhydride were reacted in a solvent medium to form a polyamic acid solution. A metal ion-containing additive was added to the solution. Examples of this additive are: TbCl3, DyCl3, ErCl3, TmCl3, Al(C5H7O2)3, and Er2S3. The polyamic acid solution was imidized and is combined with the article to form the assembly.
Carbon-carbon mirrors for exoatmospheric and space applications

NASA Astrophysics Data System (ADS)

Krumweide, Duane E.; Wonacott, Gary D.; Woida, Patrick M.; Woida, Rigel Q.; Shih, Wei

2007-09-01

The cost and leadtime associated with beryllium has forced the MDA and other defense agencies to look for alternative materials with similar structural and thermal properties. The use of carbon-carbon material, specifically in optical components has been demonstrated analytically in prior SBIR work at San Diego Composites. Carbon-carbon material was chosen for its low in-plane and through-thickness CTE (athermal design), high specific stiffness, near-zero coefficient of moisture expansion, availability of material (specifically c-c honeycomb for lightweight substrates), and compatibility with silicon monoxide (SiO) and silicon dioxide (SiO II) coatings. Subsequent development work has produced shaped carbon-carbon sandwich substrates which have been ground, polished, coated and figured using traditional optical processing. Further development has also been done on machined monolithic carbon-carbon mirror substrates which have also been processed using standard optical finishing techniques.
Advanced Mirror Technology Development (AMTD): Year Five Status

NASA Technical Reports Server (NTRS)

Stahl, H Philip

2017-01-01

The Advanced Mirror Technology Development (AMTD) project is in Phase 2 of a multiyear effort initiated in Fiscal Year (FY) 2012, to mature the Technology Readiness Level (TRL) of critical technologies required to enable 4-m-or-larger monolithic or segmented ultraviolet, optical, and infrared (UVOIR) space telescope primary-mirror assemblies for general astrophysics, ultra-high-contrast observations of exoplanets, and National Interest missions. Key accomplishments of 2016/17 include the completion of the Harris Corp approximately 150 Hz 1.5-meter Ultra-Low Expansion (ULE Registered trademark) mirror substrate using stacked core method to demonstrate lateral stability of the stacked core technology, as well as the characterization and validation by test of the mechanical and thermal performance of the 1.2-meter Zerodur (Registered trademark) mirror using the STOP model prediction and verification of CTE homogeneity.

Next-generation hollow retroreflectors for lunar laser ranging.

PubMed

Preston, Alix; Merkowitz, Stephen

2013-12-20

The three retroreflector arrays put on the Moon 40 years ago by the Apollo astronauts and the French-built arrays on the Soviet Lunokhod rovers continue to be useful targets, and have provided the most stringent tests of the Strong Equivalence Principle and the time variation of Newton's gravitational constant, as well as valuable insight into the Moon's interior. However, the precision of the ranging measurements are now being limited by the physical size of the arrays and a new generation of retroreflectors is required to make significant advances over current capabilities. Large single-cube retroreflectors represent the most promising approach to overcoming current limitations, and hollow retroreflectors in particular have the potential to maintain their good optical performance over the nearly 300 K temperature swing that occurs during the lunar cycle. Typically, epoxies are used for aligning and bonding hollow retroreflectors, but their thermal stability will predominantly be limited by the difference of the coefficient of thermal expansion (CTE) between the epoxy and the glass. A relatively new bonding method known as hydroxide catalysis bonding (HCB) has been used to adhere complex optical components for space-based missions. HCB has an extremely thin bond, a low CTE, and a high breaking strength that makes it an ideal candidate for bonding hollow retroreflectors for lunar laser ranging (LLR). In this work, we present results of a feasibility study of bonded Pyrex and fused silica hollow retroreflectors using both epoxy and HCB methods, including the results of thermally cycling the hollow retroreflectors from 295 to 185 K. Finally, we discuss the potential for using these retroreflectors for future LLR.
Study on Subgrain Rotation Behavior at Different Interfaces of a Solder Joint During Thermal Shock

NASA Astrophysics Data System (ADS)

Han, Jing; Tan, Shihai; Guo, Fu

2016-12-01

In order to investigate subgrain rotation behavior in the recrystallized region of lead-free solder joints, a ball grid array (BGA) specimen with a cross-sectioned edge row was thermally shocked. Electron backscattered diffraction (EBSD) was used to obtain the microstructure and orientations of Sn grains or subgrains in as-reflowed and thermally shocked conditions. Orientation imaging microscopy (OIM) showed that several subgrains were formed at the tilted twin grain boundaries, near the chip side and near the printed circuit board (PCB) side after 200 thermal shocks due to a highly mismatched coefficient of thermal expansion (CTE) of twin grains. Also, subgrains formed at the chip side and PCB side in the solder joint were selected to research the grain rotation behavior in lead-free solder joints. The analysis of subgrain rotation also indicated that the rotation behavior of subgrains was different between the chip side and PCB side. It was closely related with the large different crystal orientations between the chip side and PCB side. Furthermore, electron backscattered patterns (EBSPs) at several parts of the joint were not obtained after 300 thermal shocks due to the serious deformation caused by mismatched CTE during thermal shock. But 4 subgrains were selected and compared with that of the initial state and 200-thermal shock conditions. The results showed that the subgrains at the chip side were also rotated around the Sn [101] and [001] axes and the subgrains at the PCB side were also rotated around the Sn [100] axis, which indicated a continuous process of subgrain rotation.
CTE Solvability, Exact Solutions and Nonlocal Symmetries of the Sharma-Tasso-Olver Equation

NASA Astrophysics Data System (ADS)

Pu, Huan; Jia, Man

2015-12-01

In this letter, we prove that the STO equation is CTE solvable and obtain the exact solutions of solitons fission and fusion. We also provide the nonlocal symmetries of the STO equation related to CTE. The nonlocal symmetries are localized by prolonging the related enlarged system. Supported by National Natural Science Foundation of China under Grant Nos. 11205092, 11175092 and 11435005, Ningbo Natural Science Foundation under Grant Nos. 2015A610159 and 2012A610178 and by the Opening Project of Zhejiang Provincial Top Key Discipline of Physics Sciences in Ningbo University under Grant No. xkzw11502. And the authors were sponsored by K. C. Wong Magna Fund in Ningbo University
Increasing Student Achievement: Educators' Guide to Secondary Career & Technical Education Assessment

ERIC Educational Resources Information Center

National Occupational Competency Testing Institute, 2012

2012-01-01

This guide attempts to address an aspect of secondary CTE (Career and Technical Education) that has received little attention; the assessment literacy of educators. School leaders need to go beyond ensuring routine compliance with external and internal regulatory forces to identify ways in which CTE program teachers might better understand…
A National Effort to Integrate Math and Science with CTE

ERIC Educational Resources Information Center

Hyslop, Alisha

2008-01-01

National activities focus on priority areas and are often designed to develop, improve and identify the most successful methods and techniques for providing career and technical education (CTE) programs under Perkins. One of these priority areas under the 2006 Perkins Act is the integration of academic and technical education. Since the early…
Online Career and Technical Education in the Community College

ERIC Educational Resources Information Center

Garza Mitchell, Regina L.

2017-01-01

Very little empirical research has been conducted about online career and technical education (CTE). Despite the continuing enrollment growth in online education (Lokken, 2016) and the national emphasis on CTE as a means of boosting the economy (D'Amico, Morgan, Katsinas, & Friedel, 2014), relatively little is understood about the scope and…
Connecting CTE to Labor Market Information. Practice Application Brief.

ERIC Educational Resources Information Center

Brown, Bettina Lankard

The use of up-to-date labor market information (LMI) provided by a variety of state, federal, and local agencies and organizations can help program planners and policy makers design effective career and technical education (CTE) programs to prepare students for occupations and careers in demand. LMI includes information about labor market…
Availability of Data on Noncredit Education and Postsecondary Certifications: An Analysis of Selected State-Level Data Systems

ERIC Educational Resources Information Center

Sykes, Andrea R.; Szuplat, Mary A.; Decker, Cynthia G.

2014-01-01

Federal policymakers have interest in three specific areas of postsecondary career and technical education (CTE): associate degrees and certificates awarded in CTE, skills and training obtained through noncredit courses, and industry-recognized certifications. Research and data are readily available on students earning degrees and certificates in…
Promoting Work-Based Learning: Efforts in Connecticut and Kentucky

ERIC Educational Resources Information Center

Alliance for Excellent Education, 2012

2012-01-01

In the summer of 2012, the National Association of State Directors of Career Technical Education Consortium (NASDCTEc) and the Alliance for Excellent Education conducted a survey of State Directors of Career Technical Education (CTE) to gauge state efforts to better connect CTE with a larger college- and career-readiness agenda. Survey questions…
The Implication of Student Voice on Career and Technical Education Career Academy Retention

ERIC Educational Resources Information Center

Conti, Erin Michelle

2014-01-01

Career and Technical Education (CTE) contains not only the "traditional" trade programs such as cosmetology, and carpentry, but also career academies, which marry hands on learning with an academically rigorous curriculum that prepares students for a post-secondary education. My district, like many other CTE districts with academies,…
Preparing Workers for Successful Careers

ERIC Educational Resources Information Center

Reese, Susan

2010-01-01

No doubt career and technical education (CTE) is integral in preparing a skilled workforce for today's jobs. Hands-on training is an important element of the CTE classroom, and when that occurs in an actual workplace setting, it may be called internship, apprenticeship or cooperative education. Whatever term is applied, it is another way in which…
CTE: Educating Tomorrow's Workforce Today. Maryland Classroom. Vol. 13, No.2

ERIC Educational Resources Information Center

Mulqueen, Nan, Ed.

2008-01-01

Maryland redesigned its CTE (career and technical education) program a dozen years ago to prepare students for the 21st Century's global economy and its rapidly changing workforce needs. With 350 business and industry representatives, the state created a program whose emphasis is problem-solving and critical thinking, rather than narrow,…
Career and Technical Education. 2015 Annual Report

ERIC Educational Resources Information Center

Utah System of Higher Education, 2015

2015-01-01

Career and Technical Education (CTE) is a key ingredient to meet the needs of Utah's economy. Utah System of Higher Education (USHE) institutions offer CTE programs in all regions of the state, working closely with local business and industry leaders to develop and deliver programs specifically tailored to local workforce development needs. This…
Stating the Case for CTE in Arizona

ERIC Educational Resources Information Center

Reese, Susan

2006-01-01

This article discusses the academic success of CTE students in Arizona which is making a solid case for the role of career and technical education in America's high schools. When the Association for Career and Technical Education (ACTE) issued its position paper, "Reinventing the American High School for the 21st Century," it contained…
Access Barriers to Distance Education Perceived by Inservice and Preservice Career and Technical Education Majors.

ERIC Educational Resources Information Center

Zirkle, Chris

The access barriers to distance education faced by inservice and preservice career and technical education (CTE) majors were examined through a survey of 76 students enrolled in undergraduate- and graduate-level CTE education programs. Completed questionnaires were received from 60 students (response rate, 78.9%). Forty respondents worked…
CTE Alignment with 21st Century Skills

ERIC Educational Resources Information Center

Drysielski, Robert

2015-01-01

Career and technical education generally has focused on helping people to understand the relationship between education and work to acquire employment skills. There is a need for action to ensure that the programs being offered in Career and Technical Education (CTE) align with the needs of the 21st century workforce. This research will attempted…
How Community Colleges Are Closing the Skills Gap through CTE and STEM Funding Innovations

ERIC Educational Resources Information Center

Lowry, Kimberly; Thomas-Anderson, Tricia

2017-01-01

This chapter summarizes funding trends to support career and technical education (CTE) and science, technology, engineering, and math (STEM) programs at community colleges compared to funding for similar programs at 4-year colleges and universities. Examples of intramural and extramural funding strategies as well as lessons learned and…
Career and Technical Education (CTE) Transfer Research Project: Improving Transfer Pathways for California Community College Students in CTE Programs

ERIC Educational Resources Information Center

Karandjeff, Kelley; Schiorring, Eva

2011-01-01

Despite the current economic downturn, workforce projections indicate that California will experience shortages in its supply of baccalaureate-trained workers in the decades to come, particularly engineers, accountants, nurses, teachers and law enforcement professionals. Students often start their journey toward these occupations in community…
A Bridge to the Future

ERIC Educational Resources Information Center

Anderson, Richard

2008-01-01

Career and technical education (CTE) has a promising future at Darlington (WI) High School. In this article, the author describes how a class bridge project became a real-world, project-based learning opportunity involving higher-level thinking skills that are at the core of CTE at his school. It began when a local citizen approached him at the…
Raising the Bar: Technical Assessments for Secondary CTE Programs

ERIC Educational Resources Information Center

Uy, Erin; Green, Kimberly

2009-01-01

Having a strong connection to the employer community, career technical education (CTE) has long understood the importance of students being armed with industry recognized credentials and certificates as they enter the workplace. The enactment of the Carl D. Perkins Career and Technical Education Act in 2006, commonly referred to as Perkins IV,…

Real Integration--Where the Rubber Meets the Road

ERIC Educational Resources Information Center

Moye, Johnny J.

2011-01-01

Integration of core academics into career and technical education (CTE) is not new. Putting core academics into context, CTE courses provide an excellent platform for students to learn the relevance of science, technology, engineering, and mathematics (STEM) as well as literature, arts, and social studies. Students learn to use this information by…
Planning and Designing Today's Career Tech Facility

ERIC Educational Resources Information Center

Seaman, James

2010-01-01

During the past 20 years, career and technical education (CTE) has gone through significant changes. CTE has evolved in response to the changes technology has had on the job market. Preparing students for high-tech, high-skill job opportunities is the new focus. The facilities that house these programs, however, have not kept pace with these…
Lack of Sleep Could Be Trouble for CTE Students

ERIC Educational Resources Information Center

Scarpello, Gary

2010-01-01

Career and technical education (CTE) students find themselves in school environments using equipment and tools that could cause injury if mishandled. It is imperative that these students be wide awake and alert when operating these tools. But many adolescents are not getting the sleep they need to be refreshed and alert. Sleep restores brain…
TSA and Standards-Based Learning through TECH-Know

ERIC Educational Resources Information Center

Taylor, Jerianne S.; Peterson, Richard E.; Ernst, Jeremy

2005-01-01

Career and technical student organizations (CTSOs) serve as an integral part of many career and technical education (CTE) programs across the country. Their activities and competitions make up many of the strongest CTE programs due to their co-curricular nature. With memberships ranging from tens of thousands to almost a half million, it is hard…
Gender Equity Issues in CTE and STEM Education: Economic and Social Implications

ERIC Educational Resources Information Center

Toglia, Thomas V.

2013-01-01

Title IX of the Educational Amendments of 1972 has significant implications for gender equity in career and technical education (CTE) and science, technology, engineering, and mathematics (STEM) programs--and the relatively low number of women and girls pursuing nontraditional careers has significant economic and social implications. From an…
Career and Technical Education. 2016 Annual Report

ERIC Educational Resources Information Center

Utah System of Higher Education, 2016

2016-01-01

Career and Technical Education (CTE) is a key ingredient to meet the needs of Utah's economy. Utah System of Higher Education (USHE) institutions offer CTE programs in all regions of the state, working closely with local business and industry leaders to develop and deliver programs specifically tailored to local workforce development needs. This…
21st Century Business Education: Predictions from Oklahoma CTE Business Educators

ERIC Educational Resources Information Center

McAnally, Beverly

2012-01-01

This study described the predictions of 146 (n = 146) full-time CTE BMITE teachers about the greatest influences on the future of Business, Marketing and Information Technology Education. A quantitative descriptive survey research design was implemented for the study using a sample of teachers in middle schools, high schools and career and…
Positive and Negative Experiences of Career Technical Secondary Students in Online Courses

ERIC Educational Resources Information Center

Harms, David Mathew

2016-01-01

Research indicates that secondary students who are successful in online classes share common traits. However, many secondary career technical education (CTE) students taking online courses do not demonstrate the traits identified for success. CTE students may not benefit from online classes unless they are designed with their needs in mind. The…
The Impact of Special Education Law on Career and Technical Education

ERIC Educational Resources Information Center

Dieterich, Cynthia A.; Smith, Kristian J.

2015-01-01

Career and technical education (CTE) provides students of all ability levels the opportunity to develop skills for a post-secondary career. When students with disabilities are included in CTE, educators are legally required to provide an appropriate program that meets each student's unique needs. There are, however, few discussions in the…
Developing Knowledge Creating Technical Education Institutions through the Voice of Teachers: Content Analysis Approach

ERIC Educational Resources Information Center

Song, Ji Hoon; Kim, Hye Kyoung; Park, Sunyoung; Bae, Sang Hoon

2014-01-01

The purpose of this study was to develop an empirical data-driven model for a knowledge creation school system in career technical education (CTE) by identifying supportive and hindering factors influencing knowledge creation practices in CTE schools. Nonaka and colleagues' (Nonaka & Konno, 1998; Nonaka & Takeuchi, 1995) knowledge…
Emerging Careers Come into Focus

ERIC Educational Resources Information Center

Reese, Susan

2010-01-01

When career and technological education (CTE) began, known then as vocational technical education, only those with the most vivid imaginations and creative minds could envision it as it is today. Many of today's jobs didn't even exist when the baby boomers entered the workforce. Over the decades, CTE has maintained its commitment to preparing a…
CTE homogeneity, isotropy and reproducibility in large parts made of sintered SiC

NASA Astrophysics Data System (ADS)

Bougoin, Michel; Castel, Didier; Levallois, Franck

2017-11-01

For Herschel SiC primary mirror purpose, a new approach of comparative CTE measurement has been developed; it is based on the well known bimetallic effect ("biceramic" in this case) and also optical measurements. This method offers a good CTE comparison capability in the range of 170-420K (extensible to 5-420K) depending of the thermal test facilities performance, with a resolution of only 0.001 μm/m.K. The Herschel primary mirror is made of 12 SiC segments which are brazed together. The CTE of each segment has been compared with the one of a witness sample and no visible change, higher than the measurement accuracy, has been observed. Furthermore, a lot of samples have been cut out from a spare segment, from different places and also from all X, Y and Z direction of the reference frame. No deviation was seen in all of these tests, thus demonstrating the very good homogeneity, reproducibility and isotropy of the Boostec® SiC material. Some recent literature about SiC material measurements at cryogenic temperature shows a better behaviour of Boostec® SiC material in comparison with other kind of SiC which are also candidate for space optics, in particular for isotropy purpose. After a review of the available literature, this paper describes the comparative CTE measurement method and details the results obtained during the measurement campaigns related to Herschel project.
Clinical subtypes of chronic traumatic encephalopathy: literature review and proposed research diagnostic criteria for traumatic encephalopathy syndrome.

PubMed

Montenigro, Philip H; Baugh, Christine M; Daneshvar, Daniel H; Mez, Jesse; Budson, Andrew E; Au, Rhoda; Katz, Douglas I; Cantu, Robert C; Stern, Robert A

2014-01-01

The long-term consequences of repetitive head impacts have been described since the early 20th century. Terms such as punch drunk and dementia pugilistica were first used to describe the clinical syndromes experienced by boxers. A more generic designation, chronic traumatic encephalopathy (CTE), has been employed since the mid-1900s and has been used in recent years to describe a neurodegenerative disease found not just in boxers but in American football players, other contact sport athletes, military veterans, and others with histories of repetitive brain trauma, including concussions and subconcussive trauma. This article reviews the literature of the clinical manifestations of CTE from 202 published cases. The clinical features include impairments in mood (for example, depression and hopelessness), behavior (for example, explosivity and violence), cognition (for example, impaired memory, executive functioning, attention, and dementia), and, less commonly, motor functioning (for example, parkinsonism, ataxia, and dysarthria). We present proposed research criteria for traumatic encephalopathy syndrome (TES) which consist of four variants or subtypes (TES behavioral/mood variant, TES cognitive variant, TES mixed variant, and TES dementia) as well as classifications of 'probable CTE' and 'possible CTE'. These proposed criteria are expected to be modified and updated as new research findings become available. They are not meant to be used for a clinical diagnosis. Rather, they should be viewed as research criteria that can be employed in studies of the underlying causes, risk factors, differential diagnosis, prevention, and treatment of CTE and related disorders.
Limbic system structure volumes and associated neurocognitive functioning in former NFL players.

PubMed

Lepage, Christian; Muehlmann, Marc; Tripodis, Yorghos; Hufschmidt, Jakob; Stamm, Julie; Green, Katie; Wrobel, Pawel; Schultz, Vivian; Weir, Isabelle; Alosco, Michael L; Baugh, Christine M; Fritts, Nathan G; Martin, Brett M; Chaisson, Christine; Coleman, Michael J; Lin, Alexander P; Pasternak, Ofer; Makris, Nikos; Stern, Robert A; Shenton, Martha E; Koerte, Inga K

2018-05-19

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with exposure to repetitive head impacts. CTE has been linked to disruptions in cognition, mood, and behavior. Unfortunately, the diagnosis of CTE can only be made post-mortem. Neuropathological evidence suggests limbic structures may provide an opportunity to characterize CTE in the living. Using 3 T magnetic resonance imaging, we compared select limbic brain regional volumes - the amygdala, hippocampus, and cingulate gyrus - between symptomatic former National Football League (NFL) players (n = 86) and controls (n = 22). Moreover, within the group of former NFL players, we examined the relationship between those limbic structures and neurobehavioral functioning (n = 75). The former NFL group comprised eighty-six men (mean age = 55.2 ± 8.0 years) with at least 12 years of organized football experience, at least 2 years of active participation in the NFL, and self-reported declines in cognition, mood, and behavior within the last 6 months. The control group consisted of men (mean age = 57.0 ± 6.6 years) with no history of contact-sport involvement or traumatic brain injury. All control participants provided neurobehavioral data. Compared to controls, former NFL players exhibited reduced volumes of the amygdala, hippocampus, and cingulate gyrus. Within the NFL group, reduced bilateral cingulate gyrus volume was associated with worse attention and psychomotor speed (r = 0.4 (right), r = 0.42 (left); both p < 0.001), while decreased right hippocampal volume was associated with worse visual memory (r = 0.25, p = 0.027). Reduced volumes of limbic system structures in former NFL players are associated with neurocognitive features of CTE. Volume reductions in the amygdala, hippocampus, and cingulate gyrus may be potential biomarkers of neurodegeneration in those at risk for CTE.
Chronic traumatic encephalopathy in an Iraqi war veteran with posttraumatic stress disorder who committed suicide.

PubMed

Omalu, Bennet; Hammers, Jennifer L; Bailes, Julian; Hamilton, Ronald L; Kamboh, M Ilyas; Webster, Garrett; Fitzsimmons, Robert P

2011-11-01

Following his discovery of chronic traumatic encephalopathy (CTE) in football players in 2002, Dr. Bennet Omalu hypothesized that posttraumatic stress disorder (PTSD) in military veterans may belong to the CTE spectrum of diseases. The CTE surveillance at the Brain Injury Research Institute was therefore expanded to include deceased military veterans diagnosed with PTSD. The authors report the case of a 27-year-old United States Marine Corps (USMC) Iraqi war veteran, an amphibious assault vehicle crewman, who committed suicide by hanging after two deployments to Fallujah and Ramadi. He experienced combat and was exposed to mortar blasts and improvised explosive device blasts less than 50 m away. Following his second deployment he developed a progressive history of cognitive impairment, impaired memory, behavioral and mood disorders, and alcohol abuse. Neuropsychiatric assessment revealed a diagnosis of PTSD with hyperarousal (irritability and insomnia) and numbing. He committed suicide approximately 8 months after his honorable discharge from the USMC. His brain at autopsy appeared grossly unremarkable except for congestive brain swelling. There was no atrophy or remote focal traumatic brain injury such as contusional necrosis or hemorrhage. Histochemical and immunohistochemical brain tissue analysis revealed CTE changes comprising multifocal, neocortical, and subcortical neurofibrillary tangles and neuritic threads (ranging from none, to sparse, to frequent) with the skip phenomenon, accentuated in the depths of sulci and in the frontal cortex. The subcortical white matter showed mild rarefaction, sparse perivascular and neuropil infiltration by histiocytes, and mild fibrillary astrogliosis. Apolipoprotein E genotype was 3/4. The authors report this case as a sentinel case of CTE in an Iraqi war veteran diagnosed with PTSD to possibly stimulate new lines of thought and research in the possible pathoetiology and pathogenesis of PTSD in military veterans as part of the CTE spectrum of diseases, and as chronic sequelae and outcomes of repetitive traumatic brain injuries.
Clinical correlates to assist with chronic traumatic encephalopathy diagnosis: Insights from a novel rodent repeat concussion model.

PubMed

Thomsen, Gretchen M; Ko, Ara; Harada, Megan Y; Ma, Annie; Wyss, Livia; Haro, Patricia; Vit, Jean-Philippe; Avalos, Pablo; Dhillon, Navpreet K; Cho, Noell; Shelest, Oksana; Ley, Eric J

2017-06-01

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease linked to repetitive head injuries. Chronic traumatic encephalopathy symptoms include changes in mood, behavior, cognition, and motor function; however, CTE is currently diagnosed only postmortem. Using a rat model of recurrent traumatic brain injury (TBI), we demonstrate rodent deficits that predict the severity of CTE-like brain pathology. Bilateral, closed-skull, mild TBI was administered once per week to 35 wild-type rats; eight rats received two injuries (2×TBI), 27 rats received five injuries (5×TBI), and 13 rats were sham controls. To determine clinical correlates for CTE diagnosis, TBI rats were separated based on the severity of rotarod deficits and classified as "mild" or "severe" and further separated into "acute," "short," and "long" based on age at euthanasia (90, 144, and 235 days, respectively). Brain atrophy, phosphorylated tau, and inflammation were assessed. All eight 2×TBI cases had mild rotarod deficiency, 11 5×TBI cases had mild deficiency, and 16 cases had severe deficiency. In one cohort of rats, tested at approximately 235 days of age, balance, rearing, and grip strength were significantly worse in the severe group relative to both sham and mild groups. At the acute time period, cortical thinning, phosphorylated tau, and inflammation were not observed in either TBI group, whereas corpus callosum thinning was observed in both TBI groups. At later time points, atrophy, tau pathology, and inflammation were increased in mild and severe TBI groups in the cortex and corpus callosum, relative to sham controls. These injury effects were exacerbated over time in the severe TBI group in the corpus callosum. Our model of repeat mild TBI suggests that permanent deficits in specific motor function tests correlate with CTE-like brain pathology. Assessing balance and motor coordination over time may predict CTE diagnosis.
Designing mid-wave infrared (MWIR) thermo-optic coefficient (dn/dT) in chalcogenide glasses

NASA Astrophysics Data System (ADS)

Gleason, Benn; Sisken, Laura; Smith, Charmayne; Richardson, Kathleen

2016-05-01

Seventeen infrared-transmitting GeAsSe chalcogenide glasses were fabricated to determine the role of chemistry and structure on mid-wave infrared (MWIR) optical properties. The refractive index and thermoptic coefficients of samples were measured at λ = 4.515 μm using an IR-modified Metricon prism coupler, located at University of Central Florida. Thermo-optic coefficient (dn/dT) values were shown to range from approximately -40 ppm/°C to +65 ppm/°C, and refractive index was shown to vary between approximately 2.5000 and 2.8000. Trends in refractive index and dn/dT were found to be related to the atomic structures present within the glassy network, as opposed to the atomic percentage of any individual constituent. A linear correlation was found between the quantity (n-3•dn/dT) and the coefficient of thermal expansion (CTE) of the glass, suggesting the ability to compositionally design chalcogenide glass compositions with zero dn/dT, regardless of refractive index or dispersion performance. The tunability of these novel glasses offer increased thermal and mechanical stability as compared to the current commercial zero dn/dT options such as AMTIR-5 from Amorphous Materials Inc. For IR imaging systems designed to achieve passive athermalization, utilizing chalcogenide glasses with their tunable ranges of dn/dT (including zero) can be key to addressing system size, weight, and power (SWaP) limitations.
Understanding the Reliability of Solder Joints Used in Advanced Structural and Electronics Applications: Part 2 - Reliability Performance.

DOE PAGES

Vianco, Paul T.

2017-03-01

Whether structural or electronic, all solder joints must provide the necessary level of reliability for the application. The Part 1 report examined the effects of filler metal properties and the soldering process on joint reliability. Filler metal solderability and mechanical properties, as well as the extents of base material dissolution and interface reaction that occur during the soldering process, were shown to affect reliability performance. The continuation of this discussion is presented in this Part 2 report, which highlights those factors that directly affect solder joint reliability. There is the growth of an intermetallic compound (IMC) reaction layer at themore » solder/base material interface by means of solid-state diffusion processes. In terms of mechanical response by the solder joint, fatigue remains as the foremost concern for long-term performance. Thermal mechanical fatigue (TMF), a form of low-cycle fatigue (LCF), occurs when temperature cycling is combined with mismatched values of the coefficient of thermal expansion (CTE) between materials comprising the solder joint “system.” Vibration environments give rise to high-cycle fatigue (HCF) degradation. Although accelerated aging studies provide valuable empirical data, too many variants of filler metals, base materials, joint geometries, and service environments are forcing design engineers to embrace computational modeling to predict the long-term reliability of solder joints.« less
Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnan, N. M. Anoop; Wang, Bu; Falzone, Gabriel

Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development,more » and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C–S–H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C–S–H shows a sudden increase when the CaO/SiO 2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C–S–H’s nanostructure. We identify that confinement is dictated by the topology of the C–S–H’s atomic network. Altogether, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.« less
Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates.

PubMed

Krishnan, N M Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan; Pilon, Laurent; Bauchy, Mathieu; Sant, Gaurav

2016-12-28

Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO 2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H's nanostructure. We identify that confinement is dictated by the topology of the C-S-H's atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

Fabrication of Silicon Nitride Dental Core Ceramics with Borosilicate Veneering material

NASA Astrophysics Data System (ADS)

Wananuruksawong, R.; Jinawath, S.; Padipatvuthikul, P.; Wasanapiarnpong, T.

2011-10-01

Silicon nitride (Si3N4) ceramic is a great candidate for clinical applications due to its high fracture toughness, strength, hardness and bio-inertness. This study has focused on the Si3N4 ceramic as a dental core material. The white Si3N4 was prepared by pressureless sintering at relative low sintering temperature of 1650 °C in nitrogen atmosphere. The coefficient of thermal expansion (CTE) of Si3N4 ceramic is lower than that of Zirconia and Alumina ceramic which are popular in this field. The borosilicate glass veneering was employed due to its compatibility in thermal expansion. The sintered Si3N4 specimens represented the synthetic dental core were paintbrush coated by a veneer paste composed of borosilicate glass powder (<150 micrometer, Pyrex) with 5 wt% of zirconia powder (3 wt% Y2O3 - partial stabilized zirconia) and 30 wt% of polyvinyl alcohol (5 wt% solution). After coating the veneer on the Si3N4 specimens, the firing was performed in electric tube furnace between 1000-1200°C. The veneered specimens fired at 1100°C for 15 mins show good bonding, smooth and glossy without defect and crazing. The veneer has thermal expansion coefficient as 3.98×10-6 °C-1, rather white and semi opaque, due to zirconia addition, the Vickers hardness as 4.0 GPa which is closely to the human teeth.
Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates

DOE PAGES

Krishnan, N. M. Anoop; Wang, Bu; Falzone, Gabriel; ...

2016-12-06

Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development,more » and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C–S–H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C–S–H shows a sudden increase when the CaO/SiO 2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C–S–H’s nanostructure. We identify that confinement is dictated by the topology of the C–S–H’s atomic network. Altogether, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.« less
Racial/Ethnic and Gender Equity Patterns in Illinois High School Career and Technical Education Coursework

ERIC Educational Resources Information Center

Hamilton, Asia Fuller; Malin, Joel; Hackmann, Donald

2015-01-01

This study analyzed high school Career and Technical Education (CTE) enrollments in Illinois, with comparisons to national data when possible, by career cluster and pathway and with respect to gender and racial/ethnic makeup of students. Enrollment patterns in Science, Technology, Engineering, and Math (STEM) CTE programming were emphasized.…
Business-Industry Relationships and CTE. In Brief: Fast Facts for Policy and Practice No. 12.

ERIC Educational Resources Information Center

Imel, Susan

Developing and maintaining effective partnerships with employers has always been an important part of career and technical education (CTE). Recently, however, the need for and nature of these relationships have changed. Effective partnerships are no longer focused on specific activities and programs or employers merely donating resources or money;…
A Cooperative Learning Group Procedure for Improving CTE and Science Integration

ERIC Educational Resources Information Center

Spindler, Matt

2016-01-01

The purpose of this case study was to create information about the employment of Cooperative Learning Groups (CLG) to enhance the science integrating learning objectives utilized in secondary CTE courses. The objectives of the study were to determine if CLGs were an effective means for increasing the number of: a) science integrating learning…
Revamped NPS Brings More Focus to CTE Issues

ERIC Educational Resources Information Center

Techniques: Connecting Education and Careers (J3), 2008

2008-01-01

In March, attendees at the annual ACTE National Policy Seminar (NPS) got more than they bargained for. With a new hotel and a completely reorganized agenda, career and technical educators were more than energized to bring the career and technical education (CTE) message to Capitol Hill. This year marked the first time ACTE held a special briefing…
Causal Effects of Career-Technical Education on Postsecondary Work Outcomes of Individuals with High-Incidence Disabilities

ERIC Educational Resources Information Center

Lee, Heok In; Rojewski, Jay W.; Gregg, Noel

2016-01-01

Using data from the National Longitudinal Transition Study-2, a propensity score analysis revealed significant causal effects for a secondary career and technical education (CTE) concentration on the postsecondary work outcomes of adolescents with high-incidence disabilities. High school students identified as CTE concentrators (three or more high…
Career and Technical Education: The Impact of Program Investment on Accountability Ratings

ERIC Educational Resources Information Center

Hersperger, Susan L.

2012-01-01

Purpose: The purpose of this study was to examine the extent to which Career and Technical Education (CTE) enrollment and expenditure differed as a function of the accountability ratings of Texas public high schools. The extent to which CTE enrollment and expenditure influences accountability ratings is not clear. Accordingly, in this study, CTE…
Gender Microaggressions and Learning Environments: The Role of Physical Space in Teaching Pedagogy and Communication

ERIC Educational Resources Information Center

Lester, Jaime; Yamanaka, Aoi; Struthers, Brice

2016-01-01

Career and technical education (CTE) programs account for a large proportion of student enrollments in community colleges each year. While women tend to dominate CTE enrollments overall, they remain concentrated in historically feminized fields contrary to nontraditional occupations in which less than 25% of workers are females. Drawing on the…
Teachers' Use of Test-Item Banks for Student Assessment in North Carolina Secondary Agricultural Education Programs

ERIC Educational Resources Information Center

Marshall, Joy Morgan

2014-01-01

Higher expectations are on all parties to ensure students successfully perform on standardized tests. Specifically in North Carolina agriculture classes, students are given a CTE Post Assessment to measure knowledge gained and proficiency. Prior to students taking the CTE Post Assessment, teachers have access to a test item bank system that…
Meta-Analysis as a Choice to Improve Research in Career and Technical Education

ERIC Educational Resources Information Center

Gordon, Howard R. D.; McClain, Clifford R.; Kim, Yeonsoo; Maldonado, Cecilia

2010-01-01

A search of the ERIC and Academic Search Premier data bases, and a comprehensive review of literature suggest that meta-analysis is ignored by career and technical education (CTE) researchers, a situation that is regrettable but remediable. The purpose of this theoretical paper is to provide CTE researchers and consumers with procedures for…
Advocacy on the Front Lines of CTE

ERIC Educational Resources Information Center

Reese, Susan

2011-01-01

Career and technical education (CTE) in the 21st century is more relevant and rigorous than ever before. It prepares students to compete in the global workplace, it inspires lifelong learning, and it helps prevent at-risk students from dropping out of school because it keeps them engaged in the learning process. Those who work on the front lines…
Analysis of the Integration of Skill Standards into Community College Curriculum

ERIC Educational Resources Information Center

Aragon, Steven R.; Woo, Hui-Jeong; Marvel, Matthew R.

2005-01-01

The utilization of skill standards in the curriculum development process has become an increasingly prominent aspect of the reform movement in career and technical education (CTE) over the past 10 years. Data were collected across 10 CTE program areas from a nationally representative sample of community colleges. The authors discuss the extent to…
Career and Technical Education Administrators' Perceptions of Secondary Teachers' Attire as Indicated by Selected Professional Attributes

ERIC Educational Resources Information Center

Gordon, Howard R. D.

2010-01-01

The purpose of this study was to assess the perceptions of career and technical education (CTE) administrators toward secondary teachers' attire as indicated by 10 occupational attributes. The population consisted of CTE administrators employed by West Virginia Department of Education during 2006-2007 academic school year. The top three attributes…
Definitive Readings in the History, Philosophy, Theories and Practice of Career and Technical Education

ERIC Educational Resources Information Center

Wang, Victor C. X., Ed.

2010-01-01

In this information age, career and technical education (CTE) has become a multibillion dollar training enterprise. To make the students more competitive in the labor force and to make the nation economically strong and firms internationally competitive, everyone has to depend on CTE to train today's workers of various kinds. This book brings…
The Professional Educator: Notes from New York City

ERIC Educational Resources Information Center

Mulgrew, Michael

2014-01-01

In New York City, as in many places across the country, there is much discussion about strengthening career and technical education (CTE). New York City's approach to Career and Technical Education (CTE) is held up as a model for getting this type of education right. A recent conference highlighted six schools that represented only a fraction of…
"They're Not Keeping a Journal of Feelings": Literacy Initiatives and Career and Technical Education

ERIC Educational Resources Information Center

Kohnen, Angela M.

2015-01-01

Career and Technical Education (CTE) centers offer an opportunity for students to engage in authentic reading and writing activities. In many states, "embedding" English and math credits (i.e., allowing students to earn traditional core subject credits in the context of their CTE programs) has become a popular trend. This article reports…
Evolving Partnerships to Enhance Transition: Meeting POS Expectations

ERIC Educational Resources Information Center

Morelock, Kristy

2012-01-01

Finding the best way for students to learn and achieve success is of utmost importance to the State of Illinois and the nation as a whole. College and career success is critical to the national and state economy. Career and technical education (CTE) has been central to this call for greater college completion, and the credentials that CTE provides…
Deans of Career and Technical Education: Charting the Course to Senior Administration

ERIC Educational Resources Information Center

Levin, Shelley Zarovsky

2010-01-01

The purpose of this study was to explore the essential leadership practices, abilities, and experiences of Deans of Career and Technical Education (CTE) and to consider how these Deans of CTE fit into the succession process of the community college. A qualitative case study was conducted with three dyads of career Deans and their supervising…
Law and Justice CTE Program Offers a Hands-On Approach to Learning

ERIC Educational Resources Information Center

Klein, Jennifer

2013-01-01

Tom Washburn, founder of the Law and Justice Program in Fulton County Schools in Atlanta, Georgia, sees career and technical education (CTE) as a framework for gains in reading comprehension, public speaking, math and science. "It's a holistic approach to learning, framed by law and justice. Behind the scenes we're reading novels, improving…

What is CTE? Practitioners Struggle to Define Their Field in the United States

ERIC Educational Resources Information Center

Fletcher, Edward C.; Lasonen, Johanna L.; Hernandez-Gantes, Victor M.

2013-01-01

The purpose of this phenomenological study was to capture the perspectives of 13 masters' students, who are also practitioners in Career and Technical Education (CTE), regarding how they conceive of the field. A few recurring themes emerged: (a) transitional identity as the field tries to distance itself from the stigma of vocational education;…
Factors Influencing the Retention of Secondary Family and Consumer Sciences Teachers

ERIC Educational Resources Information Center

Dainty, Julie D.; Sandford, Brian A.; Su, Sho-Hsien; Belcher, Gregory G.

2011-01-01

The impact of teacher retention on quality education has inspired a great deal of research. Although many factors have been identified as contributors, few have been specific to the career and technical education (CTE) area and the diversity of CTE programs demands a more specific approach. The purpose of this study was to identify specific…
This Little Piggy Went to MARKET!

ERIC Educational Resources Information Center

Gorton, Carolyn

2012-01-01

Career and technical education (CTE) in Charlotte County, Florida, has a new identity thanks to the creativity and marketing by the K-12 CTE teachers who decided to make a difference. When one walks into any of the elementary or middle school STEM labs, or high school Career and Professional Education (CAPE) Academies, he/she sees a packed house…
Celebrating CTE Month 2008: ACTE Tours McKinley Technical High School

ERIC Educational Resources Information Center

Kidwai, Sabrina

2008-01-01

A delegation of visitors descended on McKinley Technical High School in Washington, D.C., on February 19 for Career and Technical Education (CTE) Month. ACTE staff, several congressional staffers, staff from SkillsUSA, FCCLA and the District of Columbia Department of Career and Technical Education visited the school--a public charter which offers…
The Effect of Career and Technical Education on Human Capital Accumulation: Causal Evidence from Massachusetts

ERIC Educational Resources Information Center

Dougherty, Shaun M.

2018-01-01

Earlier work demonstrates that career and technical education (CTE) can provide long-term financial benefits to participants, yet few have explored potential academic impacts, with none in the era of high-stakes accountability. This paper investigates the causal impact of participating in a specialized high school-based CTE delivery system on high…
Strengthening Career and Technical Education and 21st Century Skills in Philadelphia

ERIC Educational Resources Information Center

Philadelphia Youth Network, 2009

2009-01-01

In Spring 2007, the John S. and James L. Knight Foundation awarded funds to the Philadelphia Youth Network (PYN) to undertake an analysis of Career and Technical Education (CTE) in Philadelphia, and to make recommendations on how CTE and other forms of career-connected education could better align with Philadelphia standards for college and career…
Software Technology Readiness Assessment. Defense Acquisition Guidance with Space Examples

DTIC Science & Technology

2010-04-01

are never Software CTE candidates 19 Algorithm Example: Filters • Definitions – Filters in Signal Processing • A filter is a mathematical algorithm...Segment Segment • SOA as a CTE? – Google produced 40 million (!) hits in 0.2 sec for “SOA”. Even if we discount hits on the Society of Actuaries and
Rigor "and" Relevance: Enhancing High School Students' Math Skills through Career and Technical Education

ERIC Educational Resources Information Center

Stone, James R., III; Alfeld, Corinne; Pearson, Donna

2008-01-01

Numerous high school students, including many who are enrolled in career and technical education (CTE) courses, do not have the math skills necessary for today's high-skill workplace or college entrance requirements. This study tests a model for enhancing mathematics instruction in five high school CTE programs (agriculture, auto technology,…
Composite Technology for Exploration

NASA Technical Reports Server (NTRS)

Fikes, John

2017-01-01

The CTE (Composite Technology for Exploration) Project will develop and demonstrate critical composites technologies with a focus on joints that utilize NASA expertise and capabilities. The project will advance composite technologies providing lightweight structures to support future NASA exploration missions. The CTE project will demonstrate weight-saving, performance-enhancing bonded joint technology for Space Launch System (SLS)-scale composite hardware.
The Status of Career and Technical Education Undergraduate and Graduate Programs in the United States

ERIC Educational Resources Information Center

Fletcher, Edward C.; Gordon, Howard R. D.

2017-01-01

The purpose of this study was to examine undergraduate and graduate student enrollments, course delivery modes, and curricular trends and issues of CTE programs. Based on findings from 139 program/department coordinators, results emphasized that although CTE programs within institutions of higher education have declined in number (Fletcher,…
On-Time Graduation of Career and Technical Education Concentrators in Arizona

ERIC Educational Resources Information Center

Jaime, Laura Eileen

2017-01-01

The purpose of this quantitative causal-comparative study was to examine the effect that Career and Technical Education (CTE) concentrators, non-CTE concentrators and academic concentrators have on the on-time graduation of 1035 high school students in 7 high schools in Arizona for the 2015--2016 school year. There were three research questions…
The Image of Career and Technical Education. Practice Application Brief.

ERIC Educational Resources Information Center

Brown, Bettina Lankard

Career and technical education (CTE) instructors can use four strategies to present a new image of CTE as a viable strategy for education and work. Strategy 1 is to give students something to brag about. Three ways to help students see their vocational studies as unique and special opportunities for satisfying and rich experiences are to provide…
Standards for Technological Literacy and STEM Education Delivery through Career and Technical Education Programs

ERIC Educational Resources Information Center

Asunda, Paul A.

2012-01-01

At a minimum, employers rely on career and technical education (CTE) and workforce training systems to supply workers able to perform in their jobs. In CTE classes that seek to integrate science, technology, engineering, and mathematics (STEM) concepts, it falls to the instructors to design and sequence the learning experiences that will promote…
Balancing Career and Technical Education with Academic Coursework: The Consequences for Mathematics Achievement in High School

ERIC Educational Resources Information Center

Bozick, Robert; Dalton, Benjamin

2013-01-01

Federal legislation has attempted to move career and technical education (CTE) from a segregated component of the high school curriculum to an integrated element that jointly improves both academic and career readiness. However, concerns remain about the ability of CTE to improve academic learning. Using a nationally representative sample of high…
21st Century Educators: Developing and Supporting Great Career and Technical Education Teachers. Special Issues Brief. Revised Edition

ERIC Educational Resources Information Center

Jacques, Catherine; Potemski, Amy

2014-01-01

This Special Issues Brief from the Center on Great Teachers and Leaders (GTL Center) offers insight into three human capital management policies that are critical for career and technical education (CTE) teachers: certification, performance evaluation, and professional development. CTE teachers are uniquely positioned to improve college and career…
Ripples and Breaks: Reflecting on Learning Ecologies in Career and Technical Education

ERIC Educational Resources Information Center

Jocson, Korina M.

2016-01-01

In this paper, the author reflects on a year-long ethnography to point out contextual factors situated in career and technical education (CTE) and specifically how a CTE teacher and a university researcher shaped learning opportunities to support students' interests in the arts, technology, and multimedia communications. The discussion arched by a…
Career and Technical Education in the Crossroads of Change

ERIC Educational Resources Information Center

Quailey, Janice

2012-01-01

Career and technical education (CTE) is faced with numerous forces that may impact its future. A variety of forces directly or indirectly affect CTE, ranging from the persisting stigma or negative image of career and technical education, the schools' curricular structure and requirements, along with federal laws such as No Child Left Behind (NCLB)…
CTE's Role in Urban Education

ERIC Educational Resources Information Center

Hyslop, Alisha; Imperatore, Catherine

2013-01-01

Education in the United States is facing a crisis of completion and performance, both at the secondary and postsecondary levels, with high dropout rates and a significant number of students ill-prepared for further education and careers. These problems are even more acute in America's urban schools. Today's CTE is on the cutting edge of…
Career and Technical Education Pathway Programs, Academic Performance, and the Transition to College and Career

ERIC Educational Resources Information Center

Lekes, Natasha; Bragg, Debra. D.; Loeb, Jane W.; Oleksiw, Catherine A.; Marszalek, Jacob; Brooks-LaRaviere, Margaret; Zhu, Rongchun; Kremidas, Chloe C.; Akukwe, Grace; Lee, Hyeong-Jong; Hood, Lisa K.

2007-01-01

This mixed method study examined secondary student matriculation to two selected community colleges offering career and technical education (CTE) transition programs through partnerships with K-12 and secondary districts having numerous high schools. The study had two distinct components: (1) a secondary study that compared CTE and non-CTE…
MDRC's Career and Technical Education Projects. Issue Focus

ERIC Educational Resources Information Center

MDRC, 2017

2017-01-01

The past decade has seen a resurgence of interest in career and technical education (CTE) as a way to engage students, help people build the skills necessary to succeed in a technologically advanced economy, and meet employer demand for workers. MDRC--which has a two-decade history of developing and evaluating CTE programs, including their…

Residual Stress Induced Mechanical Property Enhancement in Steel Encapsulated Light Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Fudger, Sean James

Macro hybridized systems consisting of steel encapsulated light metal matrix composites (MMCs) were produced with the goal of creating a low cost/light weight composite system with enhanced mechanical properties. MMCs are frequently incorporated into advanced material systems due to their tailorable material properties. However, they often have insufficient ductility for many structural applications. The macro hybridized systems take advantage of the high strength, modulus, and damage tolerance of steels and high specific stiffness and low density of MMCs while mitigating the high density of steels and the poor ductility of MMCs. Furthermore, a coefficient of thermal expansion (CTE) mismatch induced residual compressive stress method is utilized as a means of improving the ductility of the MMCs and overall efficiency of the macro hybridized systems. Systems consisting of an A36, 304 stainless steel, or NitronicRTM 50 stainless steel shell filled with an Al-SiC, Al-Al2O3, or Mg-B4C MMC are evaluated in this work. Upon cooling from processing temperatures, residual strains are generated due to a CTE mismatch between each of the phases. The resulting systems offer higher specific properties and a more structurally efficient system can be attained. Mechanical testing was performed and improvements in yield stress, ultimate tensile stress, and ductility were observed. However, the combination of these dissimilar materials often results in the formation of intermetallic compounds. In certain loading situations, these typically brittle intermetallic layers can result in degraded performance. X-ray Diffraction (XRD), X-ray Energy Dispersive Spectroscopy (EDS), and Electron Backscatter Diffraction (EBSD) are utilized to characterize the intermetallic layer formation at the interface between the steel and MMC. As the residual stress condition in each phase has a large impact on the mechanical property improvement, accurate quantification of these strains/stresses is paramount. X-ray Diffraction Residual Stress Analysis (XRD-RSA) or Neutron diffraction was performed on numerous systems in multiple steel shell thickness variations. The analysis shows variation in the measured strain and stress results due to outer steel thickness, difference in CTE between materials, and relative position within the composite. Improvements in mechanical properties, namely ductility and yield stress, are a direct result of these measured strains.
Charge transfer efficiency in HST WFC3/UVIS: monitoring and mitigation

NASA Astrophysics Data System (ADS)

Baggett, Sylvia M.; Anderson, Jay; Sosey, Megan L.; Bourque, Matthew; Martlin, Catherine; Kurtz, Heather; Shanahan, Clare; Kozhurina-Platais, Vera; Sabbi, Elena; WFC3 Team

2017-01-01

The UVIS channel of the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) contains a 4096x4096 pixel e2v CCD array. The detectors have been performing well on-orbit but as expected, are exhibiting the cumulative effects of radiation damage. The result is a growing hot pixel population and declining charge transfer efficiency. We summarize the progression of the CTE losses, their effects on science data, and discuss two of the primary mitigation options: post-flash and a pixel-based CTE correction. The latter is now part of the automated WFC3 calibration pipeline in the Mikulski Archive for Space Telescopes (MAST), providing observers with both standard and CTE-corrected data products.
Career and Technical Education, Inclusion, and Postsecondary Outcomes for Students With Learning Disabilities.

PubMed

Theobald, Roddy J; Goldhaber, Dan D; Gratz, Trevor M; Holden, Kristian L

2018-05-01

We used longitudinal data from Washington State to investigate the relationships among career and technical education (CTE) enrollment, inclusion in general education, and high school and postsecondary outcomes for students with learning disabilities. We replicated earlier findings that students with learning disabilities who were enrolled in a "concentration" of CTE courses had higher rates of employment after graduation than observably similar students with learning disabilities who were enrolled in fewer CTE courses. We also found that students with learning disabilities who spent more time in general education classrooms in high school had higher rates of on-time graduation, college attendance, and employment than observably similar students with learning disabilities who spent less time in general education classrooms in these grades.
Mount Protects Thin-Walled Glass or Ceramic Tubes from Large Thermal and Vibration Loads

NASA Technical Reports Server (NTRS)

Amato, Michael; Schmidt, Stephen; Marsh. James; Dahya, Kevin

2011-01-01

The design allows for the low-stress mounting of fragile objects, like thin walled glass, by using particular ways of compensating, isolating, or releasing the coefficient of thermal expansion (CTE) differences between the mounted object and the mount itself. This mount profile is lower than true full kinematic mounting. Also, this approach enables accurate positioning of the component for electrical and optical interfaces. It avoids the higher and unpredictable stress issues that often result from potting the object. The mount has been built and tested to space-flight specifications, and has been used for fiber-optic, optical, and electrical interfaces for a spaceflight mission. This mount design is often metal and is slightly larger than the object to be mounted. The objects are optical or optical/electrical, and optical and/or electrical interfaces are required from the top and bottom. This requires the mount to be open at both ends, and for the object s position to be controlled. Thin inside inserts at the top and bottom contact the housing at defined lips, or edges, and hold the fragile object in the mount. The inserts can be customized to mimic the outer surface of the object, which further reduces stress. The inserts have the opposite CTE of the housing material, partially compensating for the CTE difference that causes thermal stress. A spring washer is inserted at one end to compensate for more CTE difference and to hold the object against the location edge of the mount for any optical position requirements. The spring also ensures that any fiber-optic or optic interface, which often requires some pressure to ensure a good interface, does not overstress the fragile object. The insert thickness, material, and spring washer size can be traded against each other to optimize the mount and stresses for various thermal and vibration load ranges and other mounting requirements. The alternate design uses two separate, unique features to reduce stress and hold the object. A release agent is applied to the inside surface of the mount just before the binding potting material is injected in the mount. This prevents the potting material from bonding to the mount, and thus prevents stress from being applied, at very low temperatures, to the fragile object being mounted. The potting material mixing and curing is temperature- and humidity-controlled. The mount has radial grooves cut in it that the potting material fills, thus controlling the vertical position of the mounted object. The design can easily be used for long and thin objects, short and wide objects, and any shape in between. The design s advantages are amplified for long and thin fragile objects. The general testing range was 45 to +45 C, but multiple mounts were successfully tested down to 60 and up to 50 C and the design can be adjusted for larger ranges.
Application of a Fuzzy Neural Network Model in Predicting Polycyclic Aromatic Hydrocarbon- Mediated Perturbations of the Cyp1b1 Transcriptional Regulatory Network in Mouse Skin

PubMed Central

Larkin, Andrew; Siddens, Lisbeth K.; Krueger, Sharon K.; Tilton, Susan C.; Waters, Katrina M.; Williams, David E.; Baird, William M.

2013-01-01

Polycyclic aromatic hydrocarbons (PAHs) are present in the environment as complex mixtures with components that have diverse carcinogenic potencies and mostly unknown interactive effects. Non-additive PAH interactions have been observed in regulation of cytochrome P450 (CYP) gene expression in the CYP1 family. To better understand and predict biological effects of complex mixtures, such as environmental PAHs, an 11 gene input-1 gene output fuzzy neural network (FNN) was developed for predicting PAH-mediated perturbations of dermal Cyp1b1 transcription in mice. Input values were generalized using fuzzy logic into low, medium, and high fuzzy subsets, and sorted using k-means clustering to create Mamdani logic functions for predicting Cyp1b1 mRNA expression. Model testing was performed with data from microarray analysis of skin samples from FVB/N mice treated with toluene (vehicle control), dibenzo[def,p]chrysene (DBC), benzo[a]pyrene (BaP), or 1 of 3 combinations of diesel particulate extract (DPE), coal tar extract (CTE) and cigarette smoke condensate (CSC) using leave one out cross-validation. Predictions were within 1 log2 fold change unit of microarray data, with the exception of the DBC treatment group, where the unexpected down-regulation of Cyp1b1 expression was predicted but did not reach statistical significance on the microarrays. Adding CTE to DPE was predicted to increase Cyp1b1 expression, whereas adding CSC to CTE and DPE was predicted to have no effect, in agreement with microarray results. The aryl hydrocarbon receptor repressor (Ahrr) was determined to be the most significant input variable for model predictions using back-propagation and normalization of FNN weights. PMID:23274566
Characteristics of thermally-induced transverse cracks in graphite epoxy composite laminates

NASA Technical Reports Server (NTRS)

Adams, D. S.; Bowles, D. E.; Herakovich, C. T.

1983-01-01

The characteristics of thermally induced transverse cracks in T300/5208 graphite-epoxy cross-ply and quasi-isotropic laminates were investigated both experimentally and analytically. The formation of transverse cracks and the subsequent crack spacing present during cool down to -250 F (116K) and thermal cycling between 250 and -250 F (116 and 394K) was investigated. The state of stress in the vicinity of a transverse crack and the influence of transverse cracking on the laminate coefficient of thermal expansion (CTE) was predicted using a generalized plane strain finite element analysis and a modified shear lag analysis. A majority of the cross-ply laminates experienced transverse cracking during the initial cool down to -250 F whereas the quasi-isotropic laminates remained uncracked. The in situ transverse strength of the 90 degree layers was more than 1.9 times greater than the transverse strength of the unidirectional 90 degree material for all laminates investigated.
Fiber-Reinforced Reactive Nano-Epoxy Composites

NASA Technical Reports Server (NTRS)

Zhong, Wei-Hong

2011-01-01

An ultra-high-molecular-weight polyethylene/ matrix interface based on the fabrication of a reactive nano-epoxy matrix with lower surface energy has been improved. Enhanced mechanical properties versus pure epoxy on a three-point bend test include: strength (25 percent), modulus (20 percent), and toughness (30 percent). Increased thermal properties include higher Tg (glass transition temperature) and stable CTE (coefficient of thermal expansion). Improved processability for manufacturing composites includes faster wetting rates on macro-fiber surfaces, lower viscosity, better resin infusion rates, and improved rheological properties. Improved interfacial adhesion properties with Spectra fibers by pullout tests include initial debonding force of 35 percent, a maximum pullout force of 25 percent, and energy to debond at 65 percent. Improved mechanical properties of Spectra fiber composites (tensile) aging resistance properties include hygrothermal effects. With this innovation, high-performance composites have been created, including carbon fibers/nano-epoxy, glass fibers/nano-epoxy, aramid fibers/ nano-epoxy, and ultra-high-molecularweight polyethylene fiber (UHMWPE).
Application of Thermo-Mechanical Measurements of Plastic Packages for Reliability Evaluation of PEMS

NASA Technical Reports Server (NTRS)

Sharma, Ashok K.; Teverovsky, Alexander

2004-01-01

Thermo-mechanical analysis (TMA) is typically employed for measurements of the glass transition temperature (Tg) and coefficients of thermal expansion (CTE) in molding compounds used in plastic encapsulated microcircuits (PEMs). Application of TMA measurements directly to PEMs allows anomalies to be revealed in deformation of packages with temperature, and thus indicates possible reliability concerns related to thermo-mechanical integrity and stability of the devices. In this work, temperature dependencies of package deformation were measured in several types of PEMs that failed environmental stress testing including temperature cycling, highly accelerated stress testing (HAST) in humid environments, and bum-in (BI) testing. Comparison of thermo-mechanical characteristics of packages and molding compounds in the failed parts allowed for explanation of the observed failures. The results indicate that TMA of plastic packages might be used for quality evaluation of PEMs intended for high-reliability applications.
Enhancing Cognitive Training Through Aerobic Exercise After a First Schizophrenia Episode: Theoretical Conception and Pilot Study

PubMed Central

Nuechterlein, Keith H.; Ventura, Joseph; McEwen, Sarah C.; Gretchen-Doorly, Denise; Vinogradov, Sophia; Subotnik, Kenneth L.

2016-01-01

Cognitive training (CT) and aerobic exercise have separately shown promise for improving cognitive deficits in schizophrenia. Aerobic exercise releases brain-derived neurotrophic factor, which promotes synaptic plasticity and neurogenesis. Thus, aerobic exercise provides a neurotrophic platform for neuroplasticity-based CT. The combination of aerobic exercise and CT may yield more robust effects than CT alone, particularly in the initial course of schizophrenia. In a pilot study, 7 patients with a recent onset of schizophrenia were assigned to Cognitive Training & Exercise (CT&E) and 9 to CT alone for a 10-week period. Posit Science programs were used for CT. Neurocognitive training focused on tuning neural circuits related to perceptual processing and verbal learning and memory. Social cognitive training used the same learning principles with social and affective stimuli. Both groups participated in these training sessions 2d/wk, 2h/d. The CT&E group also participated in an aerobic conditioning program for 30 minutes at our clinic 2d/wk and at home 2d/wk. The effect size for improvement in the MATRICS Consensus Cognitive Battery Overall Composite score for CT&E patients relative to CT patients was large. Functional outcome, particularly independent living skills, also tended to improve more in the CT&E than in the CT group. Muscular endurance, cardiovascular fitness, and diastolic blood pressure also showed relative improvement in the CT&E compared to the CT group. These encouraging pilot study findings support the promise of combining CT and aerobic exercise to improve the early course of schizophrenia. PMID:27460618
Chronic traumatic encephalopathy (CTE) in a National Football League Player: Case report and emerging medicolegal practice questions.

PubMed

Omalu, Bennet I; Hamilton, Ronald L; Kamboh, M Ilyas; DeKosky, Steven T; Bailes, Julian

2010-01-01

We present a case of chronic traumatic encephalopathy (CTE) in a retired National Football League (NFL) Player with autopsy findings, apolipoprotein E genotype, and brain tissue evidence of chronic brain damage. This 44-year-old retired NFL player manifested a premortem history of cognitive and neuropsychiatric impairment, which included in part, chronic depression, suicide attempts, insomnia, paranoia, and impaired memory before he finally committed suicide. A full autopsy was performed with Polymerase Chain Reaction-based analyses of his blood to determine the apolipoprotein genotype. Histochemical and immunohistochemical analyses were performed on topographical gross sections of the brain. Autopsy confirmed a fatal gunshot wound of the head. The apolipoprotein E genotype was E3/E3 and the brain tissue revealed diffuse cerebral taupathy (Neurofibrillary Tangles and Neuritic Threads). This will be the third case of CTE in a national football player, which has been reported in the medical literature. Omalu et al., reported the first two cases in 2005 and 2006. This case series manifested similar premortem history of neuropsychiatric impairment with autopsy evidence of cerebral taupathy without any neuritic amyloidopathy. For a definitive diagnosis of CTE to be made, and for medicolegal purposes, a full autopsy must be performed with histochemical and immunohistochemical analyses of the brain to identify the presence of Neurofibrillary Tangles (NFTs) and Neuritic Threads (NTs). Further longitudinal prospective studies are required to confirm the common denominators and epidemiology of CTE in professional American football players, which have been identified by this case series.
Chronic Traumatic Encephalopathy in Blast-Exposed Military Veterans and a Blast Neurotrauma Mouse Model

PubMed Central

Goldstein, Lee E.; Fisher, Andrew M.; Tagge, Chad A.; Zhang, Xiao-Lei; Velisek, Libor; Sullivan, John A.; Upreti, Chirag; Kracht, Jonathan M.; Ericsson, Maria; Wojnarowicz, Mark W.; Goletiani, Cezar J.; Maglakelidze, Giorgi M.; Casey, Noel; Moncaster, Juliet A.; Minaeva, Olga; Moir, Robert D.; Nowinski, Christopher J.; Stern, Robert A.; Cantu, Robert C.; Geiling, James; Blusztajn, Jan K.; Wolozin, Benjamin L.; Ikezu, Tsuneya; Stein, Thor D.; Budson, Andrew E.; Kowall, Neil W.; Chargin, David; Sharon, Andre; Saman, Sudad; Hall, Garth F.; Moss, William C.; Cleveland, Robin O.; Tanzi, Rudolph E.; Stanton, Patric K.; McKee, Ann C.

2013-01-01

Blast exposure is associated with traumatic brain injury (TBI), neuropsychiatric symptoms, and long-term cognitive disability. We examined a case series of postmortem brains from U.S. military veterans exposed to blast and/or concussive injury. We found evidence of chronic traumatic encephalopathy (CTE), a tau protein–linked neurodegenerative disease, that was similar to the CTE neuropathology observed in young amateur American football players and a professional wrestler with histories of concussive injuries. We developed a blast neurotrauma mouse model that recapitulated CTE-linked neuropathology in wild-type C57BL/6 mice 2 weeks after exposure to a single blast. Blast-exposed mice demonstrated phosphorylated tauopathy, myelinated axonopathy, microvasculopathy, chronic neuroinflammation, and neurodegeneration in the absence of macroscopic tissue damage or hemorrhage. Blast exposure induced persistent hippocampal-dependent learning and memory deficits that persisted for at least 1 month and correlated with impaired axonal conduction and defective activity-dependent long-term potentiation of synaptic transmission. Intracerebral pressure recordings demonstrated that shock waves traversed the mouse brain with minimal change and without thoracic contributions. Kinematic analysis revealed blast-induced head oscillation at accelerations sufficient to cause brain injury. Head immobilization during blast exposure prevented blast-induced learning and memory deficits. The contribution of blast wind to injurious head acceleration may be a primary injury mechanism leading to blast-related TBI and CTE. These results identify common pathogenic determinants leading to CTE in blast-exposed military veterans and head-injured athletes and additionally provide mechanistic evidence linking blast exposure to persistent impairments in neurophysiological function, learning, and memory. PMID:22593173
Contact sport-related chronic traumatic encephalopathy in the elderly: clinical expression and structural substrates

PubMed Central

Costanza, Alessandra; Weber, Kerstin; Gandy, Samuel; Bouras, Constantin; Hof, Patrick R.; Canuto, Alessandra

2011-01-01

Professional boxers and other contact sport athletes are exposed to repetitive brain trauma that may affect motor functions, cognitive performance, emotional regulation and social awareness. The term of chronic traumatic encephalopathy (CTE) was recently introduced to regroup a wide spectrum of symptoms such as cerebellar, pyramidal, and extrapyramidal syndromes, impairments in orientation, memory, language, attention, information processing and frontal executive functions, as well as personality changes and behavioural and psychiatric symptoms. Magnetic resonance imaging (MRI) usually reveals hippocampal and vermis atrophy, a cavum septum pellucidum (CSP), signs of diffuse axonal injury, pituitary gland atrophy, dilated perivascular spaces, and periventricular white matter disease. Given the partial overlapping of the clinical expression, epidemiology, and pathogenesis of CTE and Alzheimer’s disease (AD), as well as the close association between traumatic brain injuries (TBIs) and neurofibrillary tangle formation, a mixed pathology promoted by pathogenetic cascades resulting in either CTE or AD has been postulated. Molecular studies suggested that TBIs increase the neurotoxicity of the TAR DNA-binding protein 43 (TDP-43) that is a key pathological marker of ubiquitin-positive forms of frontotemporal dementia (FTLD-TDP) associated or not with motor neuron disease/amyotrophic lateral sclerosis (MND/ALS). Similar patterns of immunoreactivity for TDP-43 in CTE, FTLD-TDP, and ALS as well as epidemiological correlations support the presence of common pathogenetic mechanisms. The present review provides a critical update of the evolution of the concept of CTE with reference to its neuropathological definition together with an in depth discussion of the differential diagnosis between this entity, AD and frontotemporal dementia. PMID:21696410
Chronic traumatic encephalopathy in blast-exposed military veterans and a blast neurotrauma mouse model.

PubMed

Goldstein, Lee E; Fisher, Andrew M; Tagge, Chad A; Zhang, Xiao-Lei; Velisek, Libor; Sullivan, John A; Upreti, Chirag; Kracht, Jonathan M; Ericsson, Maria; Wojnarowicz, Mark W; Goletiani, Cezar J; Maglakelidze, Giorgi M; Casey, Noel; Moncaster, Juliet A; Minaeva, Olga; Moir, Robert D; Nowinski, Christopher J; Stern, Robert A; Cantu, Robert C; Geiling, James; Blusztajn, Jan K; Wolozin, Benjamin L; Ikezu, Tsuneya; Stein, Thor D; Budson, Andrew E; Kowall, Neil W; Chargin, David; Sharon, Andre; Saman, Sudad; Hall, Garth F; Moss, William C; Cleveland, Robin O; Tanzi, Rudolph E; Stanton, Patric K; McKee, Ann C

2012-05-16

Blast exposure is associated with traumatic brain injury (TBI), neuropsychiatric symptoms, and long-term cognitive disability. We examined a case series of postmortem brains from U.S. military veterans exposed to blast and/or concussive injury. We found evidence of chronic traumatic encephalopathy (CTE), a tau protein-linked neurodegenerative disease, that was similar to the CTE neuropathology observed in young amateur American football players and a professional wrestler with histories of concussive injuries. We developed a blast neurotrauma mouse model that recapitulated CTE-linked neuropathology in wild-type C57BL/6 mice 2 weeks after exposure to a single blast. Blast-exposed mice demonstrated phosphorylated tauopathy, myelinated axonopathy, microvasculopathy, chronic neuroinflammation, and neurodegeneration in the absence of macroscopic tissue damage or hemorrhage. Blast exposure induced persistent hippocampal-dependent learning and memory deficits that persisted for at least 1 month and correlated with impaired axonal conduction and defective activity-dependent long-term potentiation of synaptic transmission. Intracerebral pressure recordings demonstrated that shock waves traversed the mouse brain with minimal change and without thoracic contributions. Kinematic analysis revealed blast-induced head oscillation at accelerations sufficient to cause brain injury. Head immobilization during blast exposure prevented blast-induced learning and memory deficits. The contribution of blast wind to injurious head acceleration may be a primary injury mechanism leading to blast-related TBI and CTE. These results identify common pathogenic determinants leading to CTE in blast-exposed military veterans and head-injured athletes and additionally provide mechanistic evidence linking blast exposure to persistent impairments in neurophysiological function, learning, and memory.
Career and Technical Education and Academic Progress at the End of High School: Evidence from the Education Longitudinal Study of 2002

ERIC Educational Resources Information Center

Bozick, Robert; Dalton, Ben

2013-01-01

This report examines the role of career and technical education (CTE) for assessing students in learning mathematics and preventing students from dropping out of high school. CTE is a wide field of educational practice that includes occupational training and career preparation offered in formats ranging from individual courses to comprehensive…
CTE and the Economy--Finding the Upside in the Downside

ERIC Educational Resources Information Center

Reese, Susan

2009-01-01

The economic news has been dire--from growing unemployment numbers to the slashing of state and local budgets. Schools have been forced to look at cost cutting measures--from larger classes to the elimination of some programs. Yet, amid all the bad news, there is some good news to be found for career and technical education (CTE)--and some…
Aligning Classroom Instruction with Workplace Skills: Equipping CTE Students with the Math Skills Necessary for Entry-Level Carpentry

ERIC Educational Resources Information Center

Mohr, Cory

2008-01-01

With approximately 2,500 students dropping out of U.S. high schools every day, there exists a need to align classroom instruction with corresponding "real world" applications. In order to keep students' motivation high and help ensure high levels of validity in instruction, core curriculum instructors and career and technical education (CTE)…
Motivating Students to Complete High School through Career and Technical Education

ERIC Educational Resources Information Center

McDuffie, Kimberly Sabrina

2013-01-01

Since the 1980s, stakeholders have perceived Career and Technical Education (CTE) as a dumping ground for underachieving students who will not attend a 4-year college or university. Thus, the stigma has been created that CTE only serves low-performing students. The problem addressed in this study was that students were dropping out of high school…
On the Rise: The Role of Career and Technical Education in Arizona's Future. 21st Century Career and Technical Education Pathways

ERIC Educational Resources Information Center

Gupta, Sapna

2013-01-01

This report examines the potential of Career and Technical Education (CTE) in Arizona in terms of providing employers certified skills need to compete regionally, nationally and internationally and students avenues for higher education, quality of life and job satisfaction. An appendix on "Estimating the Effect of CTE on High School…
The Road Less Traveled: Realizing the Potential of Career Technical Education in the California Community Colleges

ERIC Educational Resources Information Center

Shulock, Nancy; Moore, Colleen; Offenstein, Jeremy

2011-01-01

The Career Technical Education (CTE) mission of California's community colleges is not well understood by policymakers in comparison to the transfer mission of the colleges. This exploratory study, to be followed by a more comprehensive research agenda, is motivated by the belief that CTE is a vital piece of the college completion agenda but is…
Strengthening Career and Technical Education and 21st Century Skills in Philadelphia. Executive Summary

ERIC Educational Resources Information Center

Philadelphia Youth Network, 2009

2009-01-01

In Spring 2007, the John S. and James L. Knight Foundation awarded funds to the Philadelphia Youth Network (PYN) to undertake an analysis of Career and Technical Education (CTE) in Philadelphia, and to make recommendations on how CTE and other forms of career-connected education could better align with high-wage/high-demand jobs in the regional…

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