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Sample records for structural response properties

  1. Marsh Soil Responses to Nutrients: Belowground Structural and Organic Properties

    EPA Science Inventory

    Coastal marsh responses to nutrient enrichment apparently depend upon soil matrix and whether the system is primarily biogenic or minerogenic. Deteriorating organic rich marshes (Jamaica Bay, NY) receiving wastewater effluent had lower belowground biomass, organic matter, and soi...

  2. Marsh Soil Responses to Nutrients: Belowground Structural and Organic Properties.

    EPA Science Inventory

    Coastal marsh responses to nutrient enrichment apparently depend upon soil matrix and whether the system is primarily biogenic or minerogenic. Deteriorating organic rich marshes (Jamaica Bay, NY) receiving wastewater effluent had lower belowground biomass, organic matter, and soi...

  3. Mechanical properties and fire response of geopolymer structural composites

    SciTech Connect

    Foden, A.J.; Balaguru, P.; Lyon, R.E.

    1996-12-31

    One of the major concerns in using Fiber Reinforced Composites in applications that might be subjected to fire is their resistance to high temperature. Some of the fabrics used in FRC, such as carbon, are fire resistant. However, almost all the resins used cannot withstand temperatures higher than 200{degrees}C. This paper deals with the development and use of a potassium aluminosilicate (GEOPOLYNER) that is inorganic and can easily sustain more than 1000{degrees}. The results presented include the composite behavior in tension, flexure, and shear. Tests have been conducted on the virgin samples and samples exposed to temperatures from 200 to 1000{degrees}. The results indicate that the composite can withstand 327, 245, and 14 MPa in tension, flexure, and shear respectively. It retains about 63 percent of its original flexural Strength at 800{degrees}. The fire response of the carbon fiber composite was measured and the results compared to organic matrix composites being used for infrastructure and transportation applications. At irradiance levels of 50 kW/m{sup 2} typical of the heat flux in a well developed fire, glass- or carbon-reinforced polyester, vinylester, epoxy, bismaleimde cyanate ester, polyimide, phenolic, and engineered thermoplastic laminates ignited readily and released appreciable heat and smoke, while carbon-fiber reinforced GEOPOLYNER composites did not ignite, bum, or release any smoke even after extended heat flux exposure.

  4. Synthesis, crystal structure, electronic structure, and photoelectric response properties of KCu2SbS3.

    PubMed

    Wang, Ruiqi; Zhang, Xian; He, Jianqiao; Zheng, Chong; Lin, Jianhua; Huang, Fuqiang

    2016-02-28

    Copper thioantimonates have received enormous attention due to their potential for applications in photovoltaic devices. In this work, a new layered compound KCu2SbS3 was synthesized via a reactive flux method using thiourea as a reactive flux. The compound crystallizes in the triclinic space group P1[combining macron]. The structure features two-dimensional [Cu2SbS3](-) layers stacking along the c axis with K(+) ions intercalated between the layers. Each [Cu2SbS3](-) layer is composed of two single graphene-like layers connected via interlayer Cu-S bonds and CuSb contacts. The optical measurements indicate that the compound has a band gap of 1.7 eV. The Hall effect measurement shows that KCu2SbS3 is a p-type semiconductor with a carrier concentration of 7 × 10(16) cm(-3). First-principles calculations reveal that the direct transition occurs between Cu-3d-S-3p orbitals (VBM) to Sb-5p-S-3p orbitals (CBM). The photoelectric response properties of KCu2SbS3 under visible light irradiation were analyzed. The photocurrent is 3.7 μA cm(-2) at 10 V bias, demonstrating its potential for applications in photoelectric devices. PMID:26794832

  5. Simple Cell Response Properties Imply Receptive Field Structure: Balanced Gabor and/or Bandlimited Field Functions

    PubMed Central

    Cope, Davis; Blakeslee, Barbara; McCourt, Mark E.

    2011-01-01

    The classical receptive fields of simple cells in mammalian primary visual cortex demonstrate three cardinal response properties: 1) they do not respond to stimuli which are spatially homogeneous; 2) they respond best to stimuli in a preferred orientation (direction); and 3) they do not respond to stimuli in other, non-preferred orientations (directions). We refer to these as the Balanced Field Property, the Maximum Response Direction Property, and the Zero Response Direction Property, respectively. These empirically-determined response properties are used to derive a complete characterization of elementary receptive field functions (of cosine- and mixed-type) defined as products of a circularly symmetric weight function and a simple periodic carrier. Two disjoint classes of elementary receptive field functions result: the balanced Gabor class, a generalization of the traditional Gabor filter, and a bandlimited class whose Fourier transforms have compact support (i.e., are zero-valued outside of a bounded range). The detailed specification of these two classes of receptive field functions from empirically-based postulates may prove useful to neurophysiologists seeking to test alternative theories of simple cell receptive field structure, and to computational neuroscientists seeking basis functions with which to model human vision. PMID:19721693

  6. Response of Simulated Drinking Water Biofilm Mechanical and Structural Properties to Long-Term Disinfectant Exposure.

    PubMed

    Shen, Yun; Huang, Conghui; Monroy, Guillermo L; Janjaroen, Dao; Derlon, Nicolas; Lin, Jie; Espinosa-Marzal, Rosa; Morgenroth, Eberhard; Boppart, Stephen A; Ashbolt, Nicholas J; Liu, Wen-Tso; Nguyen, Thanh H

    2016-02-16

    Mechanical and structural properties of biofilms influence the accumulation and release of pathogens in drinking water distribution systems (DWDS). Thus, understanding how long-term residual disinfectants exposure affects biofilm mechanical and structural properties is a necessary aspect for pathogen risk assessment and control. In this study, elastic modulus and structure of groundwater biofilms was monitored by atomic force microscopy (AFM) and optical coherence tomography (OCT) during three months of exposure to monochloramine or free chlorine. After the first month of disinfectant exposure, the mean stiffness of monochloramine- or free-chlorine-treated biofilms was 4 to 9 times higher than those before treatment. Meanwhile, the biofilm thickness decreased from 120 ± 8 μm to 93 ± 6-107 ± 11 μm. The increased surface stiffness and decreased biofilm thickness within the first month of disinfectant exposure was presumably due to the consumption of biomass. However, by the second to third month during disinfectant exposure, the biofilm mean stiffness showed a 2- to 4-fold decrease, and the biofilm thickness increased to 110 ± 7-129 ± 8 μm, suggesting that the biofilms adapted to disinfectant exposure. After three months of the disinfectant exposure process, the disinfected biofilms showed 2-5 times higher mean stiffness (as determined by AFM) and 6-13-fold higher ratios of protein over polysaccharide, as determined by differential staining and confocal laser scanning microscopy (CLSM), than the nondisinfected groundwater biofilms. However, the disinfected biofilms and nondisinfected biofilms showed statistically similar thicknesses (t test, p > 0.05), suggesting that long-term disinfection may not significantly remove net biomass. This study showed how biofilm mechanical and structural properties vary in response to a complex DWDS environment, which will contribute to further research on the risk assessment and control of biofilm-associated-pathogens in DWDS

  7. Structural building response review

    SciTech Connect

    Not Available

    1980-01-15

    The integrity of a nuclear power plant during a postulated seismic event is required to protect the public against radiation. Therefore, a detailed set of seismic analyses of various structures and equipment is performed while designing a nuclear power plant. This report describes the structural response analysis method, including the structural model, soil-structure interaction as it relates to structural models, methods for seismic structural analysis, numerical integration methods, methods for non-seismic response analysis approaches for various response combinations, structural damping values, nonlinear response, uncertainties in structural properties, and structural response analysis using random properties. The report describes the state-of-the-art in these areas for nuclear power plants. It also details the past studies made at Sargent and Lundy to evaluate different alternatives and the conclusions reached for the specific purposes that those studies were intended. These results were incorporated here because they fall into the general scope of this report. The scope of the present task does not include performing new calculations.

  8. Transient response of structures with uncertain properties to nonlinear shock loading

    NASA Astrophysics Data System (ADS)

    Caresta, Mauro; Langley, Robin S.; Woodhouse, Jim

    2013-10-01

    A method is presented to predict the transient response of a structure at the driving point following an impact or a shock loading. The displacement and the contact force are calculated solving the discrete convolution between the impulse response and the contact force itself, expressed in terms of a nonlinear Hertzian contact stiffness. Application of random point process theory allows the calculation of the impulse response function from knowledge of the modal density and the geometric characteristics of the structure only. The theory is applied to a wide range of structures and results are experimentally verified for the case of a rigid object hitting a beam, a plate, a thin and a thick cylinder and for the impact between two cylinders. The modal density of the flexural modes for a thick slender cylinder is derived analytically. Good agreement is found between experimental, simulated and published results, showing the reliability of the method for a wide range of situations including impacts and pyroshock applications.

  9. Regional Variation in the Structural Response and Geometrical Properties of Human Ribs

    PubMed Central

    Cormier, Joseph M.; Stitzel, Joel D.; Duma, Stefan M.; Matsuoka, Fumio

    2005-01-01

    By incorporating material and geometrical properties into a model of the human thorax one can develop an injury criterion that is a function of stress and strain of the material and not a function of the global response of the thorax. Previous research on the mechanical properties of ribs has focused on a limited set of specific ribs. For this study a total of 52 rib specimens were removed from four cadaver subjects. Variation in peak moment by thoracic region was significant (p < 0.01) with average values of 2, 2.9 and 3.9 N-m for the anterior, lateral and posterior regions respectively. Two geometrical properties, radius of gyration and distance from the neutral axis, showed significant variation by region (p < 0.0001) as well as by rib level (p = < 0.01, 0.05). The results of this study can be used to update current models of the human thorax to account for the variation in strength and geometrical properties throughout the rib cage. Accounting for the variation in rib properties by region will improve injury predictive measures and, therefore, the ability to design systems to prevent thoracic injury. PMID:16179146

  10. Structure, innervation and response properties of integumentary sensory organs in crocodilians

    PubMed Central

    Leitch, Duncan B.; Catania, Kenneth C.

    2012-01-01

    SUMMARY Integumentary sensory organs (ISOs) are densely distributed on the jaws of crocodilians and on body scales of members of the families Crocodilidae and Gavialidae. We examined the distribution, anatomy, innervation and response properties of ISOs on the face and body of crocodilians and documented related behaviors for an alligatorid (Alligator mississippiensis) and a crocodylid (Crocodylus niloticus). Each of the ISOs (roughly 4000 in A. mississippiensis and 9000 in C. niloticus) was innervated by networks of afferents supplying multiple different mechanoreceptors. Electrophysiological recordings from the trigeminal ganglion and peripheral nerves were made to isolate single-unit receptive fields and to test possible osmoreceptive and electroreceptive functions. Multiple small (<0.1 mm2) receptive fields, often from a single ISO, were recorded from the premaxilla, the rostral dentary, the gingivae and the distal digits. These responded to a median threshold of 0.08 mN. The less densely innervated caudal margins of the jaws had larger receptive fields (>100 mm2) and higher thresholds (13.725 mN). Rapidly adapting, slowly adapting type I and slowly adapting type II responses were identified based on neuronal responses. Several rapidly adapting units responded maximally to vibrations at 20–35 Hz, consistent with reports of the ISOs' role in detecting prey-generated water surface ripples. Despite crocodilians' armored bodies, the ISOs imparted a mechanical sensitivity exceeding that of primate fingertips. We conclude that crocodilian ISOs have diverse functions, including detection of water movements, indicating when to bite based on direct contact of pursued prey, and fine tactile discrimination of items held in the jaws. PMID:23136155

  11. Structure, innervation and response properties of integumentary sensory organs in crocodilians.

    PubMed

    Leitch, Duncan B; Catania, Kenneth C

    2012-12-01

    Integumentary sensory organs (ISOs) are densely distributed on the jaws of crocodilians and on body scales of members of the families Crocodilidae and Gavialidae. We examined the distribution, anatomy, innervation and response properties of ISOs on the face and body of crocodilians and documented related behaviors for an alligatorid (Alligator mississippiensis) and a crocodylid (Crocodylus niloticus). Each of the ISOs (roughly 4000 in A. mississippiensis and 9000 in C. niloticus) was innervated by networks of afferents supplying multiple different mechanoreceptors. Electrophysiological recordings from the trigeminal ganglion and peripheral nerves were made to isolate single-unit receptive fields and to test possible osmoreceptive and electroreceptive functions. Multiple small (<0.1 mm(2)) receptive fields, often from a single ISO, were recorded from the premaxilla, the rostral dentary, the gingivae and the distal digits. These responded to a median threshold of 0.08 mN. The less densely innervated caudal margins of the jaws had larger receptive fields (>100 mm(2)) and higher thresholds (13.725 mN). Rapidly adapting, slowly adapting type I and slowly adapting type II responses were identified based on neuronal responses. Several rapidly adapting units responded maximally to vibrations at 20-35 Hz, consistent with reports of the ISOs' role in detecting prey-generated water surface ripples. Despite crocodilians' armored bodies, the ISOs imparted a mechanical sensitivity exceeding that of primate fingertips. We conclude that crocodilian ISOs have diverse functions, including detection of water movements, indicating when to bite based on direct contact of pursued prey, and fine tactile discrimination of items held in the jaws. PMID:23136155

  12. Using the structure of natural scenes and sounds to predict neural response properties in the brain

    NASA Astrophysics Data System (ADS)

    Deweese, Michael

    2014-03-01

    The natural scenes and sounds we encounter in the world are highly structured. The fact that animals and humans are so efficient at processing these sensory signals compared with the latest algorithms running on the fastest modern computers suggests that our brains can exploit this structure. We have developed a sparse mathematical representation of speech that minimizes the number of active model neurons needed to represent typical speech sounds. The model learns several well-known acoustic features of speech such as harmonic stacks, formants, onsets and terminations, but we also find more exotic structures in the spectrogra representation of sound such as localized checkerboard patterns and frequency-modulated excitatory subregions flanked by suppressive sidebands. Moreover, several of these novel features resemble neuronal receptive fields reported in the Inferior Colliculus (IC), as well as auditory thalamus (MGBv) and primary auditory cortex (A1), and our model neurons exhibit the same tradeoff in spectrotemporal resolution as has been observed in IC. To our knowledge, this is the first demonstration that receptive fields of neurons in the ascending mammalian auditory pathway beyond the auditory nerve can be predicted based on coding principles and the statistical properties of recorded sounds. We have also developed a biologically-inspired neural network model of primary visual cortex (V1) that can learn a sparse representation of natural scenes using spiking neurons and strictly local plasticity rules. The representation learned by our model is in good agreement with measured receptive fields in V1, demonstrating that sparse sensory coding can be achieved in a realistic biological setting.

  13. Different behavioral effect dose–response profiles in mice exposed to two-carbon chlorinated hydrocarbons: Influence of structural and physical properties

    SciTech Connect

    Umezu, Toyoshi Shibata, Yasuyuki

    2014-09-01

    The present study aimed to clarify whether dose–response profiles of acute behavioral effects of 1,2-dichloroethane (DCE), 1,1,1-trichloroethane (TCE), trichloroethylene (TRIC), and tetrachloroethylene (PERC) differ. A test battery involving 6 behavioral endpoints was applied to evaluate the effects of DCE, TCE, TRIC, and PERC in male ICR strain mice under the same experimental conditions. The behavioral effect dose–response profiles of these compounds differed. Regression analysis was used to evaluate the relationship between the dose–response profiles and structural and physical properties of the compounds. Dose–response profile differences correlated significantly with differences in specific structural and physical properties. These results suggest that differences in specific structural and physical properties of DCE, TCE, TRIC, and PERC are responsible for differences in behavioral effects that lead to a variety of dose–response profiles. - Highlights: • We examine effects of 4 chlorinated hydrocarbons on 6 behavioral endpoints in mice. • The behavioral effect dose–response profiles for the 4 compounds are different. • We utilize regression analysis to clarify probable causes of the different profiles. • The compound's physicochemical properties probably produce the different profiles.

  14. Magnetically Responsive Nanostructures with Tunable Optical Properties.

    PubMed

    Wang, Mingsheng; Yin, Yadong

    2016-05-25

    Stimuli-responsive materials can sense specific environmental changes and adjust their physical properties in a predictable manner, making them highly desired components for designing novel sensors, intelligent systems, and adaptive structures. Magnetically responsive structures have unique advantages in applications, as external magnetic stimuli can be applied in a contactless manner and cause rapid and reversible responses. In this Perspective, we discuss our recent progress in the design and fabrication of nanostructured materials with various optical responses to externally applied magnetic fields. We demonstrate tuning of the optical properties by taking advantage of the magnetic fields' abilities to induce magnetic dipole-dipole interactions or control the orientation of the colloidal magnetic nanostructures. The design strategies are expected to be extendable to the fabrication of novel responsive materials with new optical effects and many other physical properties. PMID:27115174

  15. Response of Mg Addition on the Dendritic Structures and Mechanical Properties of Hypoeutectic Al-10Si (Wt Pct) Alloys

    NASA Astrophysics Data System (ADS)

    Karaköse, Ercan; Yildiz, Mehmet; Keskin, Mustafa

    2016-08-01

    Rapidly solidified hypoeutectic Al-10Si- xMg ( x = 0, 5, 10 wt pct) alloys were produced by the melt-spinning method. The phase composition was identified by X-ray diffractometry, and the microstructures of the alloys were characterized by scanning electron microscopy. The melting characteristics were studied by differential scanning calorimetry and differential thermal analysis under an Ar atmosphere. The mechanical properties of the melt-spun and conventionally solidified alloys were tested by tensile-strength and Vickers microhardness tests. The results illustrate that the cooling rate and solidification time of 89 μm thick melt-spun ribbon were estimated to be 2.97 × 107 K s-1 and 9.31 × 10-6 s, respectively. Nanoscale Si spot particles were observed growing on the surface of the dendritic α-Al matrix and the average sizes of these spots ranged from 10 to 50 nm. The improvement in the tensile properties and microhardness was related to structural refinement and the supersaturated α-Al solid solution; the nanoscale-dispersed Si spot particles made a significant improvement to the mechanical properties of the melt-spun ribbon. Detailed electrical resistivity tests of the ribbons were carried out at temperatures of 300 K to 800 K (27 °C to 527 °C).

  16. Response of Mg Addition on the Dendritic Structures and Mechanical Properties of Hypoeutectic Al-10Si (Wt Pct) Alloys

    NASA Astrophysics Data System (ADS)

    Karaköse, Ercan; Yildiz, Mehmet; Keskin, Mustafa

    2016-05-01

    Rapidly solidified hypoeutectic Al-10Si-xMg (x = 0, 5, 10 wt pct) alloys were produced by the melt-spinning method. The phase composition was identified by X-ray diffractometry, and the microstructures of the alloys were characterized by scanning electron microscopy. The melting characteristics were studied by differential scanning calorimetry and differential thermal analysis under an Ar atmosphere. The mechanical properties of the melt-spun and conventionally solidified alloys were tested by tensile-strength and Vickers microhardness tests. The results illustrate that the cooling rate and solidification time of 89 μm thick melt-spun ribbon were estimated to be 2.97 × 107 K s-1 and 9.31 × 10-6 s, respectively. Nanoscale Si spot particles were observed growing on the surface of the dendritic α-Al matrix and the average sizes of these spots ranged from 10 to 50 nm. The improvement in the tensile properties and microhardness was related to structural refinement and the supersaturated α-Al solid solution; the nanoscale-dispersed Si spot particles made a significant improvement to the mechanical properties of the melt-spun ribbon. Detailed electrical resistivity tests of the ribbons were carried out at temperatures of 300 K to 800 K (27 °C to 527 °C).

  17. Electrochemical and structural properties of the electrical double layer of two-component electrolytes in response to varied electrode potential

    NASA Astrophysics Data System (ADS)

    Kiyohara, Kenji; Yamagata, Masaki; Ishikawa, Masashi

    2016-04-01

    The electrochemical and structural properties of the electrical double layers for two-component electrolytes were studied by Monte Carlo simulations using simple models. When the electrolyte contains two species of cations that have different diameters, the capacitance on the cathode dramatically increases as a large negative potential is applied. This behavior is qualitatively similar to the one reported in an experimental work that has used Li-containing ionic liquid as the electrolyte [M. Yamagata et al., Electrochim. Acta 110, 181-190 (2013)], in which it has also been reported that addition of Li ions to the electrolyte enhances the potential window to the negative side. The analysis of the ionic structure showed that the electrical double layer on the cathode is dominantly formed by the larger cations under small negative potentials, while they are replaced by the smaller cations under large negative potentials. This transition of the ionic structure with electrode potential is also consistent with the enhancement of the potential window that was found in the experimental work, which suggests that the organic cations are expelled from the electrical double layer under large negative potentials and the chance of decomposition is reduced.

  18. Optimizing and modeling of effective parameters on the structural and magnetic properties of Fe3O4 nanoparticles synthesized by coprecipitation technique using response surface methodology

    NASA Astrophysics Data System (ADS)

    Ghazanfari, Mohammad Reza; Kashefi, Mehrdad; Jaafari, Mahmoud Reza

    2016-07-01

    In present work, the Fe3O4 magnetic nanoparticles were successfully synthesized by coprecipitation method. In order to study the effects of influential factors on the structural and magnetic properties of particles, the experimental runs were designed using response surface methodology (RSM) based on central composite design (CCD), while the reaction temperature, Fe2+/Fe3+ cation ratio, and pH of reaction were defined as effective factors on the two responses include the amounts of crystallinity degree and saturation magnetization (Ms). The investigation of structural, magnetic, and microstructural properties of particles were carried out by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. As a result, the predictive quadratic models were fitted on the both responses while the R2 values were more than 0.97 for both models. The highest amounts of both responses (crystallinity degree: 88.07% and Ms: 65.801 emu/g) are presented when the reaction temperature, cation ratio, and pH amounts are equal to 90 °C, 0.60, and 10.5, respectively. Finally, the TEM results show the particles with size of about 10 nm and narrow size distribution.

  19. Structural Properties of Cruciferin and Napin of Brassica napus (Canola) Show Distinct Responses to Changes in pH and Temperature.

    PubMed

    Perera, Suneru P; McIntosh, Tara C; Wanasundara, Janitha P D

    2016-01-01

    The two major storage proteins identified in Brassica napus (canola) were isolated and studied for their molecular composition, structural characteristics and the responses of structural features to the changes in pH and temperature. Cruciferin, a complex of six monomers, has a predominantly β-sheet-containing secondary structure. This protein showed low pH unstable tertiary structure, and distinctly different solubility behaviour with pH when intact in the seed cellular matrix. Cruciferin structure unfolds at pH 3 even at ambient temperature. Temperature-induced structure unfolding was observed above the maximum denaturation temperature of cruciferin. Napin was soluble in a wider pH range than cruciferin and has α-helices dominating secondary structure. Structural features of napin showed less sensitivity to the changes in medium pH and temperature. The surface hydrophobicity (S₀) and intrinsic fluorescence of tryptophan residue appear to be good indicators of cruciferin unfolding, however they were not the best to demonstrate structural changes of napin. These two storage proteins of B. napus have distinct molecular characteristics, therefore properties and functionalities they provide are contrasting rather than complementary. PMID:27618118

  20. Influence of shock loading on the structure/property response of Ti-48Al-2Cr-2Nb and Ti-24Al-11Nb

    SciTech Connect

    Gray, R.T. III

    1994-02-01

    Intermetallics are receiving increasing attention for applications requiring high-leverage materials possessing potentially high pay-offs such as in gas-turbine engines. While the quasi-static deformation response of a broad range of intermetallics is receiving intense scientific and engineering study, increased utilization of intermetallics under dynamic loading requires an understanding of their high-rate/shock-wave behavior. In this paper the influence of shock loading on structure/property behavior of Ti-48Al-2Cr-2Nb and Ti-24Al-11Nb is presented. The reload constitutive response of both shock-loaded intermetallics supports the dynamic deformation of both intermetallics being controlled by a Peierls mechanism. Defect generation and storage in intermetallics is compared and contrasted to that typical to conventional disordered metals and alloys.

  1. The Structures & Properties of Carbon

    ERIC Educational Resources Information Center

    Castellini, Olivia M.; Lisensky, George C.; Ehrlich, Jennifer; Zenner, Greta M.; Crone, Wendy C.

    2006-01-01

    The four main forms of carbon--diamond, graphite, buckyballs, and carbon nanotubes (CNTs)--are an excellent vehicle for teaching fundamental principles of chemical bonding, material structure, and properties. Carbon atoms form a variety of structures that are intrinsically connected to the properties they exhibit. Educators can take advantage of…

  2. Phospholipids fatty acids of drinking water reservoir sedimentary microbial community: Structure and function responses to hydrostatic pressure and other physico-chemical properties.

    PubMed

    Chai, Bei-Bei; Huang, Ting-Lin; Zhao, Xiao-Guang; Li, Ya-Jiao

    2015-07-01

    Microbial communities in three drinking water reservoirs, with different depth in Xi'an city, were quantified by phospholipids fatty acids analysis and multivariate statistical analysis was employed to interpret their response to different hydrostatic pressure and other physico-chemical properties of sediment and overlying water. Principle component analyses of sediment characteristics parameters showed that hydrostatic pressure was the most important effect factor to differentiate the overlying water quality from three drinking water reservoirs from each other. NH4+ content in overlying water was positive by related to hydrostatic pressure, while DO in water-sediment interface and sediment OC in sediment were negative by related with it. Three drinking water reservoir sediments were characterized by microbial communities dominated by common and facultative anaerobic Gram-positive bacteria, as well as, by sulfur oxidizing bacteria. Hydrostatic pressure and physico-chemical properties of sediments (such as sediment OC, sediment TN and sediment TP) were important effect factors to microbial community structure, especially hydrostatic pressure. It is also suggested that high hydrostatic pressure and low dissolved oxygen concentration stimulated Gram-positive and sulfate-reducing bacteria (SRB) bacterial population in drinking water reservoir sediment. This research supplied a successful application of phospholipids fatty acids and multivariate analysis to investigate microbial community composition response to different environmental factors. Thus, few physico-chemical factors can be used to estimate composition microbial of community as reflected by phospholipids fatty acids, which is difficult to detect. PMID:26387360

  3. Research on structures, mechanical properties, and mechanical responses of TKX-50 and TKX-50 based PBX with molecular dynamics.

    PubMed

    Ma, Song; Li, Yajin; Li, Yang; Luo, Yunjun

    2016-02-01

    To improve the practicality and safety of a novel explosive dihydroxylamm onium 5,5'-bis (tetrazole)-1,1'-diolate (TKX-50), polyvinylidene difluoride (PVDF) and polychlorotrifluoroe-thylene (PCTFE) were respectively added to the TKX-50, forming the polymer-bonded explosives (PBX). Interfacial and mechanical properties of PBX were investigated through molecular dynamics (MD) method, desensitizing mechanisms of fluorine-polymers for TKX-50 were researched by compression and bulk shear simulations. Results show that the binding energies (E bind ) between polymers (PVDF or PCTFE) and TKX-50 surfaces all rank in order of (011) > (100) > (010), shorter interatomic distance and the resulted higher potentials lead to higher E bind on TKX-50/PVDF interfaces than that on PCTFE/TKX-50 interfaces. Compared with TKX-50, the ductility of PBX is improved due to the isotropic mechanical property and flexibility of fluorine-polymers especially the PCTFE. Desensitizing effect of fluorine-polymers for TKX-50 is found under loading condition, which is attributed to the enhanced compressibility and buffer capacity against external pressure in compression, as well as the improved lubricity to reduce the sliding potentials in bulk shear process. Graphical Abstract Comparisons of the internal stress and slide potentials of the novel explosive,TKX-50 and its based PBX. Desensitizing effects can be found by the adding of fluorine-polymers, it owes to their better flexibility and lubricity as well as the amorphous nature. PMID:26809515

  4. Celotex Structural Properties Tests

    SciTech Connect

    Smith, A.C.

    2001-01-26

    In the course of regulatory review of the 9975 packaging, the question of the effects environmental conditions on performance of the packaging was raised. The results of previous tests of the Celotex material, used for impact absorption and thermal insulation, indicated that the effect of temperature variation was small. Accordingly, performance under ambient conditions was judged to be representative of performance under temperature extremes. To extend the database to include other effects, and in response to the questions, a series of materials tests were performed on the Celotex brand cellulose fiberboard material.

  5. Structural response synthesis

    SciTech Connect

    Ozisik, H.; Keltie, R.F.

    1988-12-01

    The open loop control technique of predicting a conditioned input signal based on a specified output response for a second order system has been analyzed both analytically and numerically to gain a firm understanding of the method. Differences between this method of control and digital closed loop control using pole cancellation were investigated as a follow up to previous experimental work. Application of the technique to diamond turning using a fast tool is also discussed.

  6. Finite Element Estimation of Meteorite Structural Properties

    NASA Technical Reports Server (NTRS)

    Hart, Kenneth Arthur

    2015-01-01

    The goal of the project titled Asteroid Threat Assessment at NASA Ames Research Center is to develop risk assessment tools. The expertise in atmospheric entry in the Entry Systems and Technology Division is being used to describe the complex physics of meteor breakup in the atmosphere. The breakup of a meteor is dependent on its structural properties, including homogeneity of the material. The present work describes an 11-week effort in which a literature survey was carried for structural properties of meteoritic material. In addition, the effect of scale on homogeneity isotropy was studied using a Monte Carlo approach in Nastran. The properties were then in a static structural response simulation of an irregularly-shape meteor (138-scale version of Asteroid Itokawa). Finally, an early plan was developed for doctoral research work at Georgia Tech. in the structural failure fragmentation of meteors.

  7. Studies and correlation among the structural, electrical and gas response properties of aerosol spray deposited self assembled nanocrystalline CuO

    NASA Astrophysics Data System (ADS)

    Singh, Iqbal; Bedi, R. K.

    2011-06-01

    Nanostructured CuO films have been grown on to the glass substrate by varying the deposition time from 10 to 30 min and substrate temperature from 300 to 400 °C by a simple ultrasonic spray pyrolysis technique, using aqueous a cupric nitrate solution as precursor. The effect of the substrate temperature on the textural, structural, electrical, and gas sensing properties of CuO films was studied and correlated. Thermal analysis of the dried precursor shows the elimination of physisorbed and chemisorbed water. It suggests the formation of CuO phase on substrate at temperature of 300 °C. X-ray diffractograms of the films indicate the formation of polycrystalline monoclinic CuO having monoclinic with crystallite size around 18 nm. The texture coefficient finds the (0 0 2) plane as the preferred orientation in films. The microstrain and dislocation densities have been calculated and found to decreases with increase in substrate temperature. The scanning electron micrographs indicate the formation of trapezium like facet structures on the film surface. AFM analysis shows uniform deposition of the CuO film over the entire substrate surface. Observations reveal that the film deposited at 300 °C show comparatively higher activation energy and appreciable response to ammonia at room temperature. The use of aqueous cupric nitrate as precursor results in the deposition of single phase copper oxide films.

  8. Structural bases for mechano-responsive properties in molecular gels of (R)-12-hydroxy-N-(ω-hydroxyalkyl)octadecanamides. Rates of formation and responses to destructive strain.

    PubMed

    Mallia, V Ajay; Weiss, Richard G

    2015-07-01

    The self-assembly and gelation behavior of a series of (R)-12-hydroxy-N-(ω-hydroxyalkyl)octadecanamides (HS-n-OH, where n = 2, 3, 4 and 5 is the length of the alkyl chain on nitrogen), as well as those of two ‘model’ compounds, N-(3-hydroxypropyl)octadecanamide (S-3-OH) and (R)-12-hydroxy-N-propyloctadecanamide (HS-3), have been investigated in a wide range of liquids. A unique aspect of some of the HS-n-OH gels is the degree and velocity of their recovery of viscoelasticity after the cessation of destructive shear. The recovery times vary from less than one second to hundreds of seconds, depending on the length of the ω-hydroxyalkyl group on nitrogen. The data indicate that the modes and dynamics of aggregation of the gelator molecules from incubation of a sol phase below the gel melting temperature, as analyzed by Avrami and fractal equations, cannot be used to explain the degree and dynamics of the thixotropy: sol-to-gel transformations involve assembly of 0-dimensional objects (i.e., individual gelator molecules) into 1-dimensional fibrils and then into 3-dimensional networks; recovery after mechano-destruction of gels requires only 1-dimensional to 3-dimensional re-assembly or re-association of 3-dimensional spherulitic objects. A model to understand the extreme sensitivity of the thixotropy on the length of the ω-hydroxyalkyl group in the HS-n-OH (which is based upon detailed comparisons among the dynamic properties of the gels, the morphologies of the neat gelators, and the fibrillar networks of the gels) invokes the importance of the cleavage and reformation of H-bonds between fibers at ‘junction zones’ or between spherulitic objects. PMID:26007154

  9. Semiconductor alloys - Structural property engineering

    NASA Technical Reports Server (NTRS)

    Sher, A.; Van Schilfgaarde, M.; Berding, M.; Chen, A.-B.

    1987-01-01

    Semiconductor alloys have been used for years to tune band gaps and average bond lengths to specific applications. Other selection criteria for alloy composition, and a growth technique designed to modify their structural properties, are presently considered. The alloys Zn(1-y)Cd(y)Te and CdSe(y)Te(1-y) are treated as examples.

  10. Dynamic response of aircraft structure

    NASA Technical Reports Server (NTRS)

    1975-01-01

    The physical and mathematical problems associated with the response of elastic structures to random excitations such as occurs during buffeting and other transonic phenomena were discussed. The following subjects were covered: (1) general dynamic system consisting of the aircraft structure, the aerodynamic driving forces due to separated flow, and the aerodynamic forces due to aircraft structural motion, (2) structural and aerodynamic quantities of the dynamic system with special emphasis given to the description of the aerodynamic forces, and including a treatment of similarity laws, scaling effects, and wind tunnel testing, and (3) methods for data processing of fluctuating pressure recordings and techniques for response analysis for random excitation. A general buffeting flutter model, which takes into account the interactions between the separated and motion induced flows was presented. Relaxations of this model leading to the forced vibration model were explained.

  11. Vibration Response of Airplane Structures

    NASA Technical Reports Server (NTRS)

    Theodorsen, Theodore; Gelalles, A G

    1935-01-01

    This report presents test results of experiments on the vibration-response characteristics of airplane structures on the ground and in flight. It also gives details regarding the construction and operation of vibration instruments developed by the National Advisory Committee for Aeronautics.

  12. The Effect of Response Format on the Psychometric Properties of the Narcissistic Personality Inventory: Consequences for Item Meaning and Factor Structure.

    PubMed

    Ackerman, Robert A; Donnellan, M Brent; Roberts, Brent W; Fraley, R Chris

    2016-04-01

    The Narcissistic Personality Inventory (NPI) is currently the most widely used measure of narcissism in social/personality psychology. It is also relatively unique because it uses a forced-choice response format. We investigate the consequences of changing the NPI's response format for item meaning and factor structure. Participants were randomly assigned to one of three conditions: 40 forced-choice items (n = 2,754), 80 single-stimulus dichotomous items (i.e., separate true/false responses for each item; n = 2,275), or 80 single-stimulus rating scale items (i.e., 5-point Likert-type response scales for each item; n = 2,156). Analyses suggested that the "narcissistic" and "nonnarcissistic" response options from the Entitlement and Superiority subscales refer to independent personality dimensions rather than high and low levels of the same attribute. In addition, factor analyses revealed that although the Leadership dimension was evident across formats, dimensions with entitlement and superiority were not as robust. Implications for continued use of the NPI are discussed. PMID:25616401

  13. Three dimensional responsive structure of tough hydrogels

    NASA Astrophysics Data System (ADS)

    Yang, Xuxu; Ma, Chunxin; Li, Chi; Xie, Yuhan; Huang, Xiaoqiang; Jin, Yongbin; Zhu, Ziqi; Liu, Junjie; Li, Tiefeng

    2015-04-01

    Three dimensional responsive structures have high value for the application of responsive hydrogels in various fields such as micro fluid control, tissue engineering and micro robot. Whereas various hydrogels with stimuli-responsive behaviors have been developed, designing and fabricating of the three dimensional responsive structures remain challenging. We develop a temperature responsive double network hydrogel with novel fabrication methods to assemble the complex three dimensional responsive structures. The shape changing behavior of the structures can be significantly increased by building blocks with various responsiveness. Mechanical instability is built into the structure with the proper design and enhance the performance of the structure. Finite element simulation are conducted to guide the design and investigate the responsive behavior of the hydrogel structures

  14. Nonlinear absorption properties of 5,10-A2B2 porphyrins--correlation of molecular structure with the nonlinear responses.

    PubMed

    Zawadzka, Monika; Wang, Jun; Blau, Werner J; Senge, Mathias O

    2013-06-01

    The nonlinear absorption properties of two series of novel free base and metalated meso 5,10-A2B2 substituted porphyrins, both bearing p-tolyl as an A substituent and TMS-ethynyl or bromine as a B substituent, were investigated with the open Z-scan technique at 532 nm in the ns time regime. Most of the compounds exhibited a transmission drop with increasing input fluence. This behavior is desirable for their applications in optical limiting. More complex responses: a drop in transmission followed by an increase in transmission or an increase in transmission followed by a transmission drop, with increasing input fluence, were detected for certain compounds. All of the recorded responses were successfully fitted with a four-level model with simultaneous two-photon absorption arising from the higher excited states (consecutive one- + one- + two-photon absorption). The TMS-ethynyl group was found to be a more efficient meso substituent in optical limiting than the bromine atom. Indium, lead and zinc complexes with TMS-ethynyl substituents were the strongest positive nonlinear absorbers amongst compounds studied which makes them the most interesting candidates for optical limiting application. PMID:23503655

  15. Probabilistic methods for structural response analysis

    NASA Technical Reports Server (NTRS)

    Wu, Y.-T.; Burnside, O. H.; Cruse, T. A.

    1988-01-01

    This paper addresses current work to develop probabilistic structural analysis methods for integration with a specially developed probabilistic finite element code. The goal is to establish distribution functions for the structural responses of stochastic structures under uncertain loadings. Several probabilistic analysis methods are proposed covering efficient structural probabilistic analysis methods, correlated random variables, and response of linear system under stationary random loading.

  16. Structural properties, electric response and magnetic behaviour of La2SrFe2CoO9 triple complex perovskite

    NASA Astrophysics Data System (ADS)

    Casallas, F.; Vera, E.; Landínez, D.; Parra, C.; Roa, J.

    2016-02-01

    The triple perovskite La2SrFe2CoO9 was prepared by the solid state reaction method from the high purity precursor powders La2O3, SrCO3, Fe2O3, Co2O3 (99.9%). The crystalline structure was studied by X-ray diffraction experiments and Rietveld refinement analysis. Results reveal that this material crystallizes in an orthorhombic triple perovskite belonging to the space group Pnma (#62) with lattice constants a=5.491978(2)Ǻ, b=7.719842(2)Ǻ and c=5.436260(3)Ǻ. The granular surface morphology was studied from images of Scanning Electron Microscopy. The electric response was studied by the Impedance Spectroscopy technique from 10.0mHz up to 0.1MHz, at different temperatures (77-300K). Measurements of magnetization as a function of temperature permitted to determine the occurrence of a paramagnetic - ferromagnetic transition for a Curie temperature of 280K, which suggests it application in nanoelectronic devices. From the fit of the magnetic response with the Curie- Weiss equation it was concluded that the effective magnetic moment is particularly large due to the contribution of La, Fe and Co cations.

  17. Correctness properties for iterated hardware structures

    NASA Technical Reports Server (NTRS)

    Windley, Phillip J.

    1993-01-01

    Iterated structures occur frequently in hardware. This paper describes properties required of mathematical relations that can be implemented iteratively and demonstrates the use of these properties on a generalized class of adders. This work provides a theoretical basis for the correct synthesis of iterated arithmetic structures.

  18. Structure, processing, and properties of potatoes

    NASA Technical Reports Server (NTRS)

    Lloyd, Isabel K.; Kolos, Kimberly R.; Menegaux, Edmond C.; Luo, Huy; Mccuen, Richard H.; Regan, Thomas M.

    1992-01-01

    The objective of this experiment and lesson intended for high school students in an engineering or materials science course or college freshmen is to demonstrate the relation between processing, structure, and thermodynamic and physical properties. The specific objectives are to show the effect of structure and structural changes on thermodynamic properties (specific heat) and physical properties (compressive strength); to illustrate the first law of thermodynamics; to compare boiling a potato in water with cooking it in a microwave in terms of the rate of structural change and the energy consumed to 'process' the potato; and to demonstrate compression testing.

  19. Structure-property evolution during polymer crystallization

    NASA Astrophysics Data System (ADS)

    Arora, Deepak

    The main theme of this research is to understand the structure-property evolution during crystallization of a semicrystalline thermoplastic polymer. A combination of techniques including rheology, small angle light scattering, differential scanning calorimetry and optical microscopy are applied to follow the mechanical and optical properties along with crystallinity and the morphology. Isothermal crystallization experiments on isotactic poly-1-butene at early stages of spherulite growth provide quantitative information about nucleation density, volume fraction of spherulites and their crystallinity, and the mechanism of connecting into a sample spanning structure. Optical microscopy near the fluid-to-solid transition suggests that the transition, as determined by time-resolved mechanical spectroscopy, is not caused by packing/jamming of spherulites but by the formation of a percolating network structure. The effect of strain, Weissenberg number (We ) and specific mechanical work (w) on rate of crystallization (nucleation followed by growth) and on growth of anisotropy was studied for shear-induced crystallization of isotactic poly-1-butene. The samples were sheared for a finite strain at the beginning of the experiment and then crystallized without further flow (Janeschitz-Kriegl protocol). Strain requirements to attain steady state/leveling off of the rate of crystallization were found to be much larger than the strain needed to achieve steady state of flow. The large strain and We>1 criteria were also observed for morphological transition from spherulitic growth to oriented growth. An apparatus for small angle light scattering (SALS) and light transmission measurements under shear was built and tested at the University of Massachusetts Amherst. As a new development, the polarization direction can be rotated by a liquid crystal polarization rotator (LCPR) with a short response time of 20 ms. The experiments were controlled and analyzed with a LabVIEW(TM) based

  20. Localized sclerotic bone response demonstrated reduced nanomechanical creep properties.

    PubMed

    Chen, Xiuli; Goh, James Cho Hong; Teoh, Swee Hin; De, Shamal Das; Soong, Richie; Lee, Taeyong

    2013-01-01

    Sclerosis (tissue hardening) development is a common occurrence in slow growing or benign osteolytic lesions. However, there is lack of knowledge on the mechanical and material property changes associated with sclerotic bone response. The immune system is postulated to play a relevant role in evoking sclerotic bone responses. In this study, localized sclerotic response in an immunocompetent model of Walker 256 breast carcinoma in SD rats showed an apparent increase in new reactive bone formation. Sclerotic rat femurs had significant increases in bone mineral density (BMD), bone mineral content (BMC), bone volume fraction (BV/TV), bone surface density (BS/TV), trabecular number (Tb.N) and a significant decrease in trabecular separation (Tb.Sp) and structural model index (SMI) as compared to control rat femurs. Significantly reduced creep responses (increased η) were observed for both trabecular and cortical bone in sclerotic bones while no significant difference was observed in elastic modulus (E) and hardness (H) values. Therefore, we conclude that viscoelastic creep property using nanoindentation would serve as a more sensitive indicator of localized bone modeling than elastic properties. Moreover, reduced viscoelasticity can contribute towards increased microcrack propagation and therefore reduced toughness. Since significant positive correlations between elastic properties (E) and (H) with viscosity (η) were also observed, our results indicate that sclerotic response of bone metastasis would cause reduced toughness (increased η) with stiffening of material (increased E and H). PMID:23127639

  1. Structure and physical properties of silkworm cocoons

    PubMed Central

    Chen, Fujia; Porter, David; Vollrath, Fritz

    2012-01-01

    Silkworm cocoons have evolved a wide range of different structures and combinations of physical and chemical properties in order to cope with different threats and environmental conditions. We present our observations and measurements on 25 diverse types of cocoons in a first attempt to correlate physical properties with the structure and morphology of the cocoons. These two architectural parameters appear to be far more important than the material properties of the silk fibres themselves. We consider tensile and compressive mechanical properties and gas permeation of the cocoon walls, and in each case identify mechanisms or models that relate these properties to cocoon structure, usually based upon non-woven fibre composites. These properties are of relevance also for synthetic non-woven composite materials and our studies will help formulate bio-inspired design principles for new materials. PMID:22552916

  2. The effects of bolted joints on dynamic response of structures

    NASA Astrophysics Data System (ADS)

    Zaman, I.; Khalid, A.; Manshoor, B.; Araby, S.; Ghazali, M. I.

    2013-12-01

    Joint is an universal fastening technology for structural members; in particular bolted joints are extensively used in mechanical structures due to their simple maintenance and low cost. However, the components of bolted joints are imperative because failure could be catastrophic and endanger lives. Hence, in this study, the effects of bolted joints on vibrating structures are investigated by determining the structural dynamic properties, such as mode shapes, damping ratios and natural frequencies, and these are compared with the monolithic structures (welding). Two approaches of experimental rigs are developed: a beam and a frame where both are subjected to dynamic loading. The analysis reveals the importance of bolted joints in increasing the damping properties and minimizing the vibration magnitude of structures, this indicates the significant influence of bolted joints on the dynamic behaviour of assembled structures. The outcome of this study provides a good model for predicting the experimental variable response in different types of structural joints.

  3. Relaxation, Structure, and Properties of Semicoherent Interfaces

    NASA Astrophysics Data System (ADS)

    Shao, S.; Wang, J.

    2016-01-01

    Materials containing a high density of interfaces are promising candidates for future energy technologies because interfaces acting as sources, sinks, and barriers for defects can improve mechanical and irradiation properties of materials. A semicoherent interface widely occurring in various materials is composed of a network of misfit dislocations and coherent regions separated by misfit dislocations. In this article, we review the relaxation mechanisms, structure, and properties of (111) semicoherent interfaces in face-centered cubic structures.

  4. Structural properties of compact groups

    NASA Technical Reports Server (NTRS)

    De Carvalho, R. R.; Ribeiro, A. L. B.; Zepf, Stephen E.

    1994-01-01

    We report the results of a systematic study of galaxies in the regions of Hickson compact groups. Our sample is composed of the 22 Hickson groups which are located in the southern hemisphere and have cz less than 9000 km/s. Making use of digitized images of IIIa-J plates that cover an area of 0.5 x 0.5 deg around each group, we were able to detect and classify images down to a magnitude limit of 19.5 in the B band. This limit is typically three magnitudes fainter than previous studies. Most groups show a statistically significant excess of fainter galaxies compared to the background. These fainter galaxies typically have a somewhat more extended spatial distribution than the brighter galaxies originally classified by Hickson. Our data suggest that Hickson groups have a wide range in density and radius, ranging from very compact structures with overdensities of the order of 10(exp 2) and crossing times of roughly 0.01 H(sub 0 sup -1), to much more diffuse structures, similar to loose groups, with overdensities of about 3 and crossing times of roughly 0.5 H(sub 0 sup -1).

  5. Structural Properties of Mismatched Alloys

    NASA Astrophysics Data System (ADS)

    Mousseau, Normand

    The problem of understanding the local structure of disordered alloys has been around for a long time. In this thesis, I look more specifically at the effect of size-mismatch disorder in binary alloys under many forms: metallic and semiconductor alloys, bulk and surfaces, two and three dimensional systems. I have studied the limitations of a central-force model (CFM) and an embedded-atom potential (EAM) in describing the local structure of binary metallic alloys composed of Ag, Au, Cu, Ni, Pd, or Pt. Although an analytical model developed using the CFM explains qualitatively well the experimental and numerical results, in many cases, it is important to add electronic density effects through a more sophisticated potential like EAM in order to agree quantitatively with experiment. I have also looked at amorphous and crystalline silicon-germanium alloys. It turns out that the effect of size-mismatch is the same on a crystalline and an amorphous lattice. In the latter case, it can be seen as a perturbation of the much larger disorder due to the amorphisation process. However, the analytical predictions differ, for both the crystalline and amorphous alloys, from the experimental results. If one is to believe the data, there is only one possible explanation for this inconsistency: large amounts of hydrogen are present in the samples used for the measurements. Since the data analysis of EXAFS results is not always straightforward, I have proposed some experiments that could shed light on this problem. One of these experiments would be to look at the (111) surface of a Si-Ge alloy with a scanning tunneling microscope. I also present in this thesis the theoretical predictions for the height distribution at the surface as well as some more general structural information about the relaxation in the network as one goes away from the surface. Finally, I have studied the effect of size -mismatch in a purely two dimensional lattice, looking for mismatch-driven phase transitions

  6. Response of structural and magnetic properties of ultra-thin FeCo-V foils to high-energy beam welding processes

    NASA Astrophysics Data System (ADS)

    Mostaan, H.; Shamanian, M.; Hasani, S.; Szpunar, J. A.

    2015-11-01

    Microstructural evolutions and grain-boundary-character distribution during high-energy-beam welding of ultra-thin FeCo-V foils were studied. Detailed data about the boundaries, coincidence site lattice (CSL) relationships, grain sizes, and microstructural features were acquired from electron-backscatter diffraction (EBSD) maps. Moreover, the evolution of the magnetic properties during high-energy-beam welding was studied using vibrating sample magnetometry (VSM). The fraction of low-angle boundaries was observed to increase in the fusion zones of both electron- and laser-beam-welded foils. The results showed that the fractions of low-Ʃ CSL boundaries (particularly twin boundaries, Ʃ3) in the fusion zones of the welded foils are higher than those in the base metal. Because the strain rates produced during high-energy-beam welding are very high (because of the extremely high cooling rate), grain deformation by a slip mechanism is limited; therefore, deformation by grain twinning is dominant. VSM analysis showed that the magnetic properties of the welded foils, i.e., their remanence, coercive force, and energy product, changed significantly. The formation of large grains with preferred orientation parallel to the easy axis of magnetization was the main reason for the diminished magnetic properties.

  7. Interior Structure and Tidal Response of Mercury

    NASA Astrophysics Data System (ADS)

    Steinke, Teresa; Sohl, Frank; Hussmann, Hauke; Knapmeyer, Martin; Wagner, Frank Walter

    2013-04-01

    Recent determinations of Mercury's mean density, polar moment of inertia factor, and the inertia of its solid outer shell provide strong constraints on the radius of its liquid core. We present an ensemble of spherically symmetric interior structure models that all satisfy the observational constraints. The models consist of a pure iron solid inner core, a liquid Fe-FeS outer core, a peridotite mantle and a crust predominantly composed of plagioclase. The sulfur content in the outer core, the iron and magnesium content of the mantle, and the crustal thickness vary throughout the ensemble. Comparison of observed and predicted moments of inertia yields admissible ranges for the outer core radius and the mantle density. From this model ensemble we derive geophysical observables that would allow further constraining the interior structure of Mercury in future experiments. The moment of inertia constraints allow for both forsterite and fayalite rich mantle compositions. Variations of mantle density trade off with crustal thickness and core composition. This non-uniqueness could be resolved using seismic travel time observations: since the P wave velocity of a fayalite mantle is significantly lower than that of the plagioclase-rich crust, a shadow zone arises as a clear discriminant between the two end-member compositions. The planet's response to solar tidal forcing strongly depends on its interior structure and rheological properties and can be parameterized in terms of the surface body tide Love numbers k2 and h2, respectively. We employ the frequency-dependent Maxwell rheology to calculate the body tide Love numbers for the main tidal period (87.97 days) using the density, rigidity and viscosity profiles of our structural models. We obtain values between 0.38 and 0.65 for k2 and between 0.70 and 1.12 for h2, respectively, thereby indicating the substantial tidal response of Mercury's interior. Furthermore we find that, via viscosity and rigidity, both k2 and h2 are

  8. Autoclave foam concrete: Structure and properties

    NASA Astrophysics Data System (ADS)

    Mestnikov, Alexei; Semenov, Semen; Strokova, Valeria; Nelubova, Viktoria

    2016-01-01

    This paper describes the technology and properties of autoclaved foam concrete taking into account practical experience and laboratory studies. The results of study of raw materials and analysis of structure and properties of foam-concrete before and after autoclave treatment are basic in this work. Experimental studies of structure and properties of foam concrete are carried out according to up-to-date methods and equipment on the base of the shared knowledge centers. Results of experimental studies give a deep understanding of properties of raw materials, possible changes and new formations in inner layers of porous material providing the improvement of constructional and operational properties of autoclaved foam concrete. Principal directions of technology enhancement as well as developing of production of autoclave foam concretes under cold-weather conditions in Russia climate are justified.

  9. Tribological properties of structural ceramics

    NASA Technical Reports Server (NTRS)

    Buckley, Donald H.; Miyoshi, Kazuhisa

    1989-01-01

    The tribological and lubricated behavior of both oxide and nonoxide ceramics are reviewed in this chapter. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as has been observed with metals. Grit size effects in two and three body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing. Ceramics compositions both as coatings and in composites are described for the high temperature lubrication of both alloys and ceramics.

  10. Tribological properties of structural ceramics

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Miyoshi, K.

    1985-01-01

    The tribological and lubricated behavior of both oxide and nonoxide ceramics are reviewed in this chapter. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as has been observed with metals. Grit size effects in two and three body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing. Ceramics compositions both as coatings and in composites are described for the high temperature lubrication of both alloys and ceramics.

  11. Structural Properties of Barred Galaxies

    NASA Astrophysics Data System (ADS)

    Kim, Taehyun; Gadotti, D. A.; Sheth, K.; Lee, M.; S4G Team

    2014-01-01

    We have performed two-dimensional multicomponent decomposition of 144 local barred spiral galaxies using 3.6 micron images from the Spitzer Survey of Stellar Structure in Galaxies. Our model fit includes up to four components (bulge, disk, bar, and a point source) and, most importantly, takes into account disk breaks. We present that ignoring the disk break and using a single disk scale length in the model fit for Type II (down- bending) disk galaxies can lead to differences of 40% in the disk scale length, 10% in bulge-to-total luminosity ratio (B/T), and 25% in bar-to-total luminosity ratios. We show that for galaxies with B/T > 0.1, the break radius to bar radius, r_br/R_bar, varies between 1 and 3, but as a function of B/T the ratio remains roughly constant. This suggests that in bulge-dominated galaxies the disk break is likely related to the outer Lindblad Resonance (OLR) of the bar, and thus the OLR also moves outwards at the same rate as the bar grows. For galaxies with B/T < 0.1, r_br/R_bar, spans a wide range from 1 to 6. This suggests that the mechanism that produces the break in these galaxies may be different from that in galaxies with more massive bulges. Consistent with previous studies, we conclude that disk breaks in galaxies with small bulges may originate from bar resonances that may be also coupled with the spiral arms, or be related to star formation thresholds. We quantifiy shapes of bar radial surface brightness profiles by measuring their Sersic indices and show that bars in higher B/T galaxies have flatter radial surface brightness profile than bulgeless galaxies do. In particular, bulgeless galaxies mostly have bars with steep profiles. We show that the normalized bar length is correlated with B/T, which is consistent with bars growing longer with time.

  12. Peak structural response to nonstationary random excitations

    NASA Technical Reports Server (NTRS)

    Shinozuka, M.; Yang, J.-N.

    1971-01-01

    Study establishes distribution function of peak response values, based on frequency interpretation. Excitations considered include impact loading on landing gears and aircraft gust loading. Because of relative severity of excitations, prediction of fatigue and maximum response characteristics is important part of task of structural analysis and design.

  13. Effect of Gd3+ doping on structural, optical and frequency-dependent dielectric response properties of pseudo-cubic BaTiO3 nanostructures

    NASA Astrophysics Data System (ADS)

    Borah, Manjit; Mohanta, Dambarudhar

    2014-06-01

    We report on the structural, optical and dielectric characterization of solid state derived, pseudo-cubic nanoscale barium titanates (BTs) with gadolinium (Gd3+) as substitutional dopant. Referring to X-ray diffractograms, apart from the BT peaks related to perovskite structure, the non-existence of any additional peaks due to byproducts has revealed that Gd3+ has undergone substitutional doping into the BT host lattice. The well-separated BT nanoparticles of typical size ˜10-15 nm were observed through electron microscopy studies. Following a direct, allowed type carrier transition ( n=1/2), a reduction in the optical band gap value (from 3.28 to 3.255 eV) was observed when the Gd-doping level was varied within 0-7 %. Conversely, the Urbach energy followed an increasing trend, from a value of 0.741 to 1.879 eV. Furthermore, the dielectric constant showed a decreasing tendency with doping content and with increasing frequency. However, in the low-frequency region, the loss tangent (tan δ), which is the combined result of orientational polarization and electrical conduction, was found to be quite high in the doped samples as compared to their un-doped counterpart. The frequency-dependent electrical data were also analyzed in the framework of conductivity and impedance formalisms. In particular, the ac conductivity which varies as ˜ ω s approaches ideal Debye behavior ( s→1) for a low Gd level and a higher doping concentration did not show improved dielectric feature of the host. The incorporation of rare-earth (Gd3+) ions into the BT host system could greatly manifest dielectric relaxation and carrier conduction mechanisms, in a given frequency range, and thus can find immense scope in miniaturized nanoelectronic elements including ceramic capacitors and transducers.

  14. Structure Defect Property Relationships in Binary Intermetallics

    NASA Astrophysics Data System (ADS)

    Medasani, Bharat; Ding, Hong; Chen, Wei; Persson, Kristin; Canning, Andrew; Haranczyk, Maciej; Asta, Mark

    2015-03-01

    Ordered intermetallics are light weight materials with technologically useful high temperature properties such as creep resistance. Knowledge of constitutional and thermal defects is required to understand these properties. Vacancies and antisites are the dominant defects in the intermetallics and their concentrations and formation enthalpies could be computed by using first principles density functional theory and thermodynamic formalisms such as dilute solution method. Previously many properties of the intermetallics such as melting temperatures and formation enthalpies were statistically analyzed for large number of intermetallics using structure maps and data mining approaches. We undertook a similar exercise to establish the dependence of the defect properties in binary intermetallics on the underlying structural and chemical composition. For more than 200 binary intermetallics comprising of AB, AB2 and AB3 structures, we computed the concentrations and formation enthalpies of vacancies and antisites in a small range of stoichiometries deviating from ideal stoichiometry. The calculated defect properties were datamined to gain predictive capabilities of defect properties as well as to classify the intermetallics for their suitability in high-T applications. Supported by the US DOE under Contract No. DEAC02-05CH11231 under the Materials Project Center grant (Award No. EDCBEE).

  15. Identifying the Hamiltonian structure in linear response theory

    NASA Astrophysics Data System (ADS)

    List, Nanna Holmgaard; Coriani, Sonia; Christiansen, Ove; Kongsted, Jacob

    2014-06-01

    We present a unifying framework for linear response eigenvalue equations that encompasses both variational Hartree-Fock and Kohn-Sham density functional theory as well as non-variational coupled-cluster theory. The joint description is rooted in the so-called Hamiltonian structure of the response kernel matrices, whose properties permit an immediate identification of the well-known paired eigenvalue spectrum describing a molecule in the isolated state. Recognizing the Hamiltonian structure underlying the equations further enables a generalization to the case of a polarizable-embedded molecule treated in variational and, in particular, in non-variational theories.

  16. Structural and electronic properties of dense liquid and amorphous nitrogen

    SciTech Connect

    Boates, B; Bonev, S A

    2011-02-11

    We present first-principles calculations of the structural and electronic properties of liquid nitrogen in the pressure-temperature range of 0-200 GPa and 2000-6000 K. The molecular-polymerization and molecular-atomic liquid phase boundaries have been mapped over this region. We find the polymeric liquid to be metallic, similar to what has been reported for the higher-temperature atomic fluid. An explanation of the electronic properties is given based on the structure and bonding character of the transformed liquids. We discuss the structural and bonding differences between the polymeric liquid and insulating solid cubic-gauche nitrogen to explain the differences in their electronic properties. Furthermore, we discuss the mechanism responsible for charge transport in polymeric nitrogen systems to explain the conductivity of the polymeric fluid and the semi-conducting nature of low-temperature amorphous nitrogen.

  17. Algorithms for Determining Physical Responses of Structures Under Load

    NASA Technical Reports Server (NTRS)

    Richards, W. Lance; Ko, William L.

    2012-01-01

    Ultra-efficient real-time structural monitoring algorithms have been developed to provide extensive information about the physical response of structures under load. These algorithms are driven by actual strain data to measure accurately local strains at multiple locations on the surface of a structure. Through a single point load calibration test, these structural strains are then used to calculate key physical properties of the structure at each measurement location. Such properties include the structure s flexural rigidity (the product of the structure's modulus of elasticity, and its moment of inertia) and the section modulus (the moment of inertia divided by the structure s half-depth). The resulting structural properties at each location can be used to determine the structure s bending moment, shear, and structural loads in real time while the structure is in service. The amount of structural information can be maximized through the use of highly multiplexed fiber Bragg grating technology using optical time domain reflectometry and optical frequency domain reflectometry, which can provide a local strain measurement every 10 mm on a single hair-sized optical fiber. Since local strain is used as input to the algorithms, this system serves multiple purposes of measuring strains and displacements, as well as determining structural bending moment, shear, and loads for assessing real-time structural health. The first step is to install a series of strain sensors on the structure s surface in such a way as to measure bending strains at desired locations. The next step is to perform a simple ground test calibration. For a beam of length l (see example), discretized into n sections and subjected to a tip load of P that places the beam in bending, the flexural rigidity of the beam can be experimentally determined at each measurement location x. The bending moment at each station can then be determined for any general set of loads applied during operation.

  18. Structural characteristic responses for finite element model updating of structures

    NASA Astrophysics Data System (ADS)

    Zhou, Linren; Wang, Lei; Ou, Jinping

    2014-04-01

    The field measurements of structures are very important to the structural finite element (FE) model updating because the errors and uncertainties of a FE model are corrected directly through closing the discrepancies between the analytical responses from FE model and the measurements from field testing of a structure. Usually, the accurate and reliable field measurements are very limited. Therefore, it is very important to make full use of the limited and valuable field measurements in structural model updating to achieve a best result with the lowest cost. In this paper, structural FE model updating is investigated in the point of view of solving a mathematical problem, and different amount and category of structural dynamic responses and static responses are considered as constraints to explore their effects on the updated results of different degree and types of structural damages. The numerical studies are carried out on a space truss. Accounting for the numerical results, some inherent phenomena and connections taking account of the updating parameters, output responses and the updated results are revealed and discussed. Some useful and practicable suggestions about using the field measurements for FE model updating are provided to achieve efficient and reliable results.

  19. Structure, chemistry, and properties of mineral nanoparticles

    SciTech Connect

    Waychunas, G.A.; Zhang, H.; Gilbert, B.

    2008-12-02

    Nanoparticle properties can depart markedly from their bulk analog materials, including large differences in chemical reactivity, molecular and electronic structure, and mechanical behavior. The greatest changes are expected at the smallest sizes, e.g. 10 nm and below, where surface effects are expected to dominate bonding, shape and energy considerations. The precise chemistry at nanoparticle interfaces can have a profound effect on structure, phase transformations, strain, and reactivity. Certain phases may exist only as nanoparticles, requiring transformations in chemistry, stoichiometry and structure with evolution to larger sizes. In general, mineralogical nanoparticles have been little studied.

  20. Mechanical properties of carbon nanotube ropes with hierarchical helical structures

    NASA Astrophysics Data System (ADS)

    Zhao, Zi-Long; Zhao, Hong-Ping; Wang, Jian-Shan; Zhang, Zhong; Feng, Xi-Qiao

    2014-11-01

    Hierarchical helical structures widely exist in both artificial and biological materials. Such nanomaterials as carbon nanotube ropes with hierarchical helical structures hold a promise for potential applications, for instance, in aerospace and medical engineering. In the present paper, a bottom-up theoretical model is established to investigate the mechanical properties of this kind of novel nanomaterials. The geometry of a rope with a hierarchy of chirality is first formulated. On the basis of the analysis of the internal forces and deformations of a single helical ply, a theoretical model is provided to predict the mechanical responses of multi-level helical materials. The effect of hierarchical helical structures is revealed by comparing the properties between a carbon nanotube rope with two-level helical structure and its counterpart bundle consisting of straight carbon nanotubes. The dependence of the mechanical properties of materials on the initial helical angles, fiber numbers, and handednesses at different structural levels are examined. Carbon nanotube ropes are found with higher deformation ability and elastic property which can be easily tuned via their microstructural parameters. This work helps understand the behavior of chiral materials and also provides inspirations for optimal design of advanced nanomaterials with hierarchical helical structures.

  1. MASPROP- MASS PROPERTIES OF A RIGID STRUCTURE

    NASA Technical Reports Server (NTRS)

    Hull, R. A.

    1994-01-01

    The computer program MASPROP was developed to rapidly calculate the mass properties of complex rigid structural systems. This program's basic premise is that complex systems can be adequately described by a combination of basic elementary structural shapes. Thirteen widely used basic structural shapes are available in this program. They are as follows: Discrete Mass, Cylinder, Truncated Cone, Torus, Beam (arbitrary cross section), Circular Rod (arbitrary cross section), Spherical Segment, Sphere, Hemisphere, Parallelepiped, Swept Trapezoidal Panel, Symmetric Trapezoidal Panels, and a Curved Rectangular Panel. MASPROP provides a designer with a simple technique that requires minimal input to calculate the mass properties of a complex rigid structure and should be useful in any situation where one needs to calculate the center of gravity and moments of inertia of a complex structure. Rigid body analysis is used to calculate mass properties. Mass properties are calculated about component axes that have been rotated to be parallel to the system coordinate axes. Then the system center of gravity is calculated and the mass properties are transferred to axes through the system center of gravity by using the parallel axis theorem. System weight, moments of inertia about the system origin, and the products of inertia about the system center of mass are calculated and printed. From the information about the system center of mass the principal axes of the system and the moments of inertia about them are calculated and printed. The only input required is simple geometric data describing the size and location of each element and the respective material density or weight of each element. This program is written in FORTRAN for execution on a CDC 6000 series computer with a central memory requirement of approximately 62K (octal) of 60 bit words. The development of this program was completed in 1978.

  2. Structure Property Relationships of Carboxylic Acid Isosteres

    PubMed Central

    2016-01-01

    The replacement of a carboxylic acid with a surrogate structure, or (bio)-isostere, is a classical strategy in medicinal chemistry. The general underlying principle is that by maintaining the features of the carboxylic acid critical for biological activity, but appropriately modifying the physicochemical properties, improved analogs may result. In this context, a systematic assessment of the physicochemical properties of carboxylic acid isosteres would be desirable to enable more informed decisions of potential replacements to be used for analog design. Herein we report the structure–property relationships (SPR) of 35 phenylpropionic acid derivatives, in which the carboxylic acid moiety is replaced with a series of known isosteres. The data set generated provides an assessment of the relative impact on the physicochemical properties that these replacements may have compared to the carboxylic acid analog. As such, this study presents a framework for how to rationally apply isosteric replacements of the carboxylic acid functional group. PMID:26967507

  3. Final disposal room structural response calculations

    SciTech Connect

    Stone, C.M.

    1997-08-01

    Finite element calculations have been performed to determine the structural response of waste-filled disposal rooms at the WIPP for a period of 10,000 years after emplacement of the waste. The calculations were performed to generate the porosity surface data for the final set of compliance calculations. The most recent reference data for the stratigraphy, waste characterization, gas generation potential, and nonlinear material response have been brought together for this final set of calculations.

  4. Input estimation from measured structural response

    SciTech Connect

    Harvey, Dustin; Cross, Elizabeth; Silva, Ramon A; Farrar, Charles R; Bement, Matt

    2009-01-01

    This report will focus on the estimation of unmeasured dynamic inputs to a structure given a numerical model of the structure and measured response acquired at discrete locations. While the estimation of inputs has not received as much attention historically as state estimation, there are many applications where an improved understanding of the immeasurable input to a structure is vital (e.g. validating temporally varying and spatially-varying load models for large structures such as buildings and ships). In this paper, the introduction contains a brief summary of previous input estimation studies. Next, an adjoint-based optimization method is used to estimate dynamic inputs to two experimental structures. The technique is evaluated in simulation and with experimental data both on a cantilever beam and on a three-story frame structure. The performance and limitations of the adjoint-based input estimation technique are discussed.

  5. Composition-Structure-Property Relations of Compressed Borosilicate Glasses

    NASA Astrophysics Data System (ADS)

    Svenson, Mouritz N.; Bechgaard, Tobias K.; Fuglsang, Søren D.; Pedersen, Rune H.; Tjell, Anders Ø.; Østergaard, Martin B.; Youngman, Randall E.; Mauro, John C.; Rzoska, Sylwester J.; Bockowski, Michal; Smedskjaer, Morten M.

    2014-08-01

    Hot isostatic compression is an interesting method for modifying the structure and properties of bulk inorganic glasses. However, the structural and topological origins of the pressure-induced changes in macroscopic properties are not yet well understood. In this study, we report on the pressure and composition dependences of density and micromechanical properties (hardness, crack resistance, and brittleness) of five soda-lime borosilicate glasses with constant modifier content, covering the extremes from Na-Ca borate to Na-Ca silicate end members. Compression experiments are performed at pressures ≤1.0 GPa at the glass transition temperature in order to allow processing of large samples with relevance for industrial applications. In line with previous reports, we find an increasing fraction of tetrahedral boron, density, and hardness but a decreasing crack resistance and brittleness upon isostatic compression. Interestingly, a strong linear correlation between plastic (irreversible) compressibility and initial trigonal boron content is demonstrated, as the trigonal boron units are the ones most disposed for structural and topological rearrangements upon network compaction. A linear correlation is also found between plastic compressibility and the relative change in hardness with pressure, which could indicate that the overall network densification is responsible for the increase in hardness. Finally, we find that the micromechanical properties exhibit significantly different composition dependences before and after pressurization. The findings have important implications for tailoring microscopic and macroscopic structures of glassy materials and thus their properties through the hot isostatic compression method.

  6. Structural properties of small rhodium clusters

    SciTech Connect

    Soon, Yee Yeen; Yoon, Tiem Leong; Lim, Thong Leng

    2015-04-24

    We report a systematic study of the structural properties of rhodium clusters at the atomistic level. A novel global-minimum search algorithm, known as parallel tempering multicanonical basin hopping plus genetic algorithm (PTMBHGA), is used to obtain the geometrical structures with lowest minima at the semi-empirical level where Gupta potential is used to describe the atomic interaction among the rhodium atoms. These structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The structures are optimized for different spin multiplicities. The ones with lowest energies will be taken as ground-state structures. In most cases, we observe only minor changes in the geometry and bond length of the clusters as a result of DFT-level re-optimization. Only in some limited cases, the initial geometries obtained from the PTMBHGA are modified by the re-optimization. The variation of structural properties, such as ground-state geometry, symmetry and binding energy, with respect to the cluster size is studied and agreed well with other results available in the literature.

  7. Multifunctional composites and structures with integrated mechanical and electromagnetic properties

    NASA Astrophysics Data System (ADS)

    Amirkhizi, Alireza Vakil

    Composite materials are used for their excellent structural performance. Load-bearing properties are traditionally the only aspects for which a composite structure is designed. Recent technological advances have made it possible to reach beyond this limited view. Inspired by biological systems, we seek to develop engineering materials that exhibit multiple functionalities in addition to providing structural integrity. Composites are a natural host for embedding elements that can enhance their nonstructural response. The present work is focused on embedding periodic arrays of scattering elements within composites to modify and tune their overall electromagnetic properties. A number of techniques for numerical and analytical modeling of the periodic media are discussed. Based on these methods we have designed and fabricated composites with tuned electromagnetic properties. Examples include fiber-reinforced polymer composites with embedded arrays of straight wires or coils. In both cases, the overall dielectric constant of the medium is reduced and can even be rendered negative within microwave frequencies. The coil medium can exhibit chiral response. Solutions for eliminating this behavior as well as a method for calculation of the bianisotropic material parameters are presented. One can achieve similar response at higher frequencies by reducing the length scale. For example, we show that a polymer film with embedded nano-strips of gold can demonstrate negative dielectric constant in infrared regime. An example of a structural composite is presented for which the magnetic permeability is altered and is turned negative within a microwave band. Finally, a general method for homogenization of the electromagnetic properties of periodic media based on the microstructure is developed. Two independent chapters complete this dissertation. In Chapter 8 the response of a soft hypo-elastic material in a pressure---shear experiment is studied. A nonlinear pressure- and

  8. Explorations of molecular structure-property relationships.

    PubMed

    Seybold, P G

    1999-01-01

    The problem of the relationship between the structure of a molecule and its physical, chemical, and biological properties is one of the most fundamental in chemistry. Three molecular structure-property studies are discussed as illustrations of different approaches to this problem. In the first study the carcinogenic activities of polycyclic aromatic hydrocarbons and their derivatives are examined. Molecular orbital calculations of the presumptive activation steps and species for these compounds (based on the "bay region" theory of activation) are seen to yield a surprisingly good guide to the observed carcinogenic activities. Both activation and deactivation steps are considered. The second study reviews structure-property work on the tissue solubilities of halogenated hydrocarbons. Relatively simple structural descriptors give a good account of the solubilities of these compounds in blood, muscle, fat, and liver tissue. With the aid of principal components analysis it is shown that there are two dominant dimensions to this problem, which can be interpreted in terms of solubilities of the compounds in lipid and saline environments. The final study, which examines the boiling points of aliphatic alcohols, illustrates the value of using more than one descriptor set. The (perhaps surprising) conclusion is that a theoretical model can sometimes be more accurate than the data upon which it is based. Moreover, two models are better than one. PMID:10491848

  9. Response of joint dominated space structures

    NASA Technical Reports Server (NTRS)

    1987-01-01

    An efficient linearization method is presented for calculating the transient response of nonlinear systems due to initial disturbances. The method is an extension of the describing function approach in which the steady state response of the system is calculated by representing the nonlinear element, typically joints in the case of space structures, by impedances which are functions of the amplitude of response. Thus, the problem of solving the differential equation for the steady state response becomes one of solving a set of nonlinear algebraic equations involving the steady state amplitudes and phases of the system. It is shown that for the transient case the steady state impedances can be averaged over the range of responses in order to provide equivalent values of stiffness and damping that, for a given set of initial displacements, may be treated as being constant for purposes of calculating system response. Single degree of freedom system are used to demonstrate the method and to develop an approach for optimizing the joint's characteristics so as to minimize transient response times. The use of this method for response estimation and optimization in multiple degree of freedom systems is investigated.

  10. Lattice Truss Structural Response Using Energy Methods

    NASA Technical Reports Server (NTRS)

    Kenner, Winfred Scottson

    1996-01-01

    A deterministic methodology is presented for developing closed-form deflection equations for two-dimensional and three-dimensional lattice structures. Four types of lattice structures are studied: beams, plates, shells and soft lattices. Castigliano's second theorem, which entails the total strain energy of a structure, is utilized to generate highly accurate results. Derived deflection equations provide new insight into the bending and shear behavior of the four types of lattices, in contrast to classic solutions of similar structures. Lattice derivations utilizing kinetic energy are also presented, and used to examine the free vibration response of simple lattice structures. Derivations utilizing finite element theory for unique lattice behavior are also presented and validated using the finite element analysis code EAL.

  11. Electrooptical properties and structural features of amorphous ITO

    SciTech Connect

    Amosova, L. P.

    2015-03-15

    Thin indium-tin oxide (ITO) films are deposited onto cold substrates by magnetron-assisted sputtering. The dependences of the structural, electrical, and optical properties of the films on the oxygen content in the atmosphere of sputtering and the growth rate are studied. It is shown that, if the substrate temperature is no higher than the ITO crystallization temperature and the conditions of growth deviate from the optimal relationship between the oxygen pressure and the growth rate, the resistance of the layers can be six or seven orders of magnitude higher than the resistance of conducting amorphous layers and reach hundreds of megaohms. At the same time, the optical properties of insulating layers in the visible spectral region are completely identical to the properties of the conducing amorphous modification. A conceptual model of defects responsible for the insulating properties of amorphous ITO is proposed.

  12. Analysis of Crushing Response of Composite Crashworthy Structures

    NASA Astrophysics Data System (ADS)

    David, Matthew; Johnson, Alastair F.; Voggenreiter, H.

    2013-10-01

    The paper describes quasi-static and dynamic tests to characterise the energy absorption properties of polymer composite crash energy absorbing segment elements under axial loads. Detailed computer tomography scans of failed specimens are used to identify local compression crush failure mechanisms at the crush front. The varied crushing morphology between the compression strain rates identified in this paper is observed to be due to the differences in the response modes and mechanical properties of the strain dependent epoxy matrix. The importance of understanding the role of strain rate effects in composite crash energy absorbing structures is highlighted in this paper.

  13. Structural and electronic properties of thallium compounds

    NASA Astrophysics Data System (ADS)

    Paliwal, Neetu; Srivastava, Vipul

    2016-05-01

    The tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA has been used to calculate structural and electronic properties of thallium pnictides TlX (X=Sb, Bi) at high pressure. As a function of volume, the total energy is evaluated. Apart from this, the lattice parameter (a0), bulk modulus (B0), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed metallic behaviour in TlSb and TlBi compounds. The values of equilibrium lattice constants and bulk modulus are agreed well with the available data.

  14. Acoustical properties of nonwoven fiber network structures

    NASA Astrophysics Data System (ADS)

    Tascan, Mevlut

    Sound insulation is one of the most important issues for the automotive and building industries. Because they are porous fibrous structures, textile materials can be used as sound insulating and sound absorbing materials. Very high-density materials such as steel can insulate sound very effectively but these rigid materials reflect most of the sound back to the environment, causing sound pollution. Additionally, because high-density, rigid materials are also heavy and high cost, they cannot be used for sound insulation for the automotive and building industries. Nonwoven materials are more suitable for these industries, and they can also absorb sound in order to decrease sound pollution in the environment. Therefore, nonwoven materials are one of the most important materials for sound insulation and absorption applications materials. Insulation and absorption properties of nonwoven fabrics depend on fiber geometry and fiber arrangement within the fabric structure. Because of their complex structure, it is very difficult to define the microstructure of nonwovens. The structure of nonwovens only has fibers and voids that are filled by air. Because of the complexity of fiber-void geometry, there is still not a very accurate theory or model that defines the structural arrangement. A considerable amount of modeling has been reported in literature [1--19], but most models are not accurate due to the assumptions made. Voids that are covered by fibers are called pores in nonwoven structures and their geometry is very important, especially for the absorption properties of nonwovens. In order to define the sound absorption properties of nonwoven fabrics, individual pore structure and the number of pores per unit thickness of the fabric should be determined. In this research, instead of trying to define pores, the properties of the fibers are investigated and the number of fibers per volume of fabric is taken as a parameter in the theory. Then the effect of the nonwoven

  15. Structure-property Relationships of Layered Oxypnictides

    NASA Astrophysics Data System (ADS)

    Muir, Sean W.

    Investigating the structure-property relationships of solid state materials can help improve many of the materials we use each day in life. It can also lead to the discovery of materials with interesting and unforeseen properties. In this work the structure property relationships of newly discovered layered oxypnictide phases are presented and discussed. There has generally been worldwide interest in layered oxypnictide materials following the discovery of superconductivity up to 55 K for iron arsenides such as LnFeAsO 1-xFx (where Ln = Lanthanoid). This work presents efforts to understand the structure and physical property changes which occur to LnFeAsO materials when Fe is replaced with Rh or Ir and when As is replaced with Sb. As part of this work the solid solution between LaFeAsO and LaRhAsO was examined and superconductivity is observed for low Rh content with a maximum critical temperature of 16 K. Ln RhAsO and LnIrAsO compositions are found to be metallic; however Ce based compositions display a resistivity temperature dependence which is typical of Kondo lattice materials. At low temperatures a sudden drop in resistivity occurs for both CeRhAsO and CeIrAsO compositions and this drop coincides with an antiferromagnetic transition. The Kondo scattering temperatures and magnetic transition temperatures observed for these materials can be rationalized by considering the expected difference in N(EF) J parameters between them, where N(EF) is the density of states at the Fermi level and J represents the exchange interaction between the Ce 4f1 electrons and the conduction electrons. In addition to studying these 4d and 5d substituted systems the LaFeSbO compositional system was investigated. While LaFeSbO has not been successfully synthesized the transition metal free layered oxypnictide composition La2SbO 2 was discovered and its structural and physical properties have been examined along with the properties of La2BiO2. Density functional theory was used to

  16. The Structure and Properties of Parachute Cloths

    NASA Technical Reports Server (NTRS)

    Mcnicholas, H J; Hedrick, F

    1930-01-01

    The requisite properties of a parachute cloth are discussed and the methods for measuring these properties described. In addition to the structural analysis of the cloths, the properties measured were weight, breaking strength, tear resistance, elasticity, and air permeability. Thirty-six silk cloths of domestic manufacture, not previously used in parachute construction are compared with some silk cloths of foreign manufacture. These foreign cloths were ones proven by trial and extended use to be suitable materials for parachute construction. Contrary to the belief that domestic woven cloths were not suitable materials for parachute construction, it is shown that many domestic silk cloths are satisfactory and in some respects superior to the foreign products. Based on a comparative study of all the cloths, specifications are drawn for the manufacture of silk parachute cloth.

  17. A global approach for the identification of structural connection properties

    NASA Technical Reports Server (NTRS)

    Lawrence, Charles; Huckelbridge, Arthur A.

    1990-01-01

    A general procedure is developed for identifying properties of structural joints. The procedure, which uses experimental response data, is considered general because it is applicable to any size or type of structural system. The present procedure, which identifies characteristics such as damping and stiffness, accommodates both linear and nonlinear joint properties and may process test data measured at arbitrary stations on the structural system. The method identifies joint characteristics by performing a global fit between predicted and measured data. It overcomes limitations of previous methods in that it can better deal with parameter-dependent constraints (e.g., gaps). The method is demonstrated with a simplified model of a bladed disk assembly having friction damping and mistuning.

  18. Structure and Electronic Properties of Polycrystalline Dielectrics

    SciTech Connect

    Mckenna, Keith P.; Shluger, AL

    2013-07-07

    We present an overview of the theoretical approaches that can be employed to model polycrystalline oxides along with a discussion of their limitations and associated challenges. We then present results for two metal oxide materials, MgO and HfO2, where theory and experiment have come together to provide insight into the structure and electronic properties of grain boundaries. Finally, we conclude with a discussion and outlook.

  19. Structural properties of hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Ooi, N.; Rajan, V.; Gottlieb, J.; Catherine, Y.; Adams, J. B.

    2006-04-01

    The electronic and structural properties of hexagonal boron nitride (BN) were studied using density functional theory calculations. Three different approximations for the exchange—correlation energy (the local density and two forms of the generalized gradient)—were used to calculate properties such as the bulk modulus, cohesive energy and lattice constants to determine their relative predictive abilities for this system. In general, calculations using the local density approximation produced properties slightly closer to experimental values than calculations with either generalized gradient approximations. Different stackings, or arrangements of one basal plane with respect to another, were examined to determine the equilibrium stacking(s) and it was found that the different stackings have similar cohesive energies and bulk moduli. Energy versus volume curves were calculated for each stacking using two different methods to determine their relative efficacy. Bulk moduli values obtained assuming no pressure dependence were closer to experimental values than those obtained from three common equations of state. Comparisons between the cohesive energies of hexagonal BN and cubic BN show that the cubic phase is more stable. The pressure/volume dependence of the band structure was studied for several different stackings and all showed similar behaviour, specifically a 3-4.5 eV band gap that was nearly independent of pressure in the -500 to +500 kb regime. These calculated results of the pressure/volume dependence of the band structure are the first reports for this system.

  20. Effective structural properties in polycrystalline graphene

    NASA Astrophysics Data System (ADS)

    Hossain, Zubaer

    This talk will discuss effective structural properties in polycrystalline graphene under the presence of atomic scale heterogeneity. Polycrystallinity is ubiquitous in solids, but theories describing their effective behavior remain limited, particularly when heterogeneity is present in the form of nonuniform deformation or composition. Over the decades, exploration of the effective transport and strength properties of heterogeneous systems has been carried out mostly with random distribution of grains or regular periodic structures under various approximations, in translating the underlying physics into a single representative volume element. Although heterogeneity can play a critical role in modulating the basic behavior of low-dimensional materials, it is difficult to capture the local characteristics accurately by these approximations. Taking polycrystalline graphene as an example material, we study the effective structural properties (such as Young's Modulus, Poisson's ratio and Toughness) by using a combination of density functional theory and molecular dynamic simulations. We identify the key mechanisms that govern their effective behavior and exploit the understanding to engineer the behavior by doping with a carefully selected choice of chemical elements.

  1. Landscape structure and climate influences on hydrologic response

    NASA Astrophysics Data System (ADS)

    Nippgen, Fabian; McGlynn, Brian L.; Marshall, Lucy A.; Emanuel, Ryan E.

    2011-12-01

    Climate variability and catchment structure (topography, geology, vegetation) have a significant influence on the timing and quantity of water discharged from mountainous catchments. How these factors combine to influence runoff dynamics is poorly understood. In this study we linked differences in hydrologic response across catchments and across years to metrics of landscape structure and climate using a simple transfer function rainfall-runoff modeling approach. A transfer function represents the internal catchment properties that convert a measured input (rainfall/snowmelt) into an output (streamflow). We examined modeled mean response time, defined as the average time that it takes for a water input to leave the catchment outlet from the moment it reaches the ground surface. We combined 12 years of precipitation and streamflow data from seven catchments in the Tenderfoot Creek Experimental Forest (Little Belt Mountains, southwestern Montana) with landscape analyses to quantify the first-order controls on mean response times. Differences between responses across the seven catchments were related to the spatial variability in catchment structure (e.g., slope, flowpath lengths, tree height). Annual variability was largely a function of maximum snow water equivalent. Catchment averaged runoff ratios exhibited strong correlations with mean response time while annually averaged runoff ratios were not related to climatic metrics. These results suggest that runoff ratios in snowmelt dominated systems are mainly controlled by topography and not by climatic variability. This approach provides a simple tool for assessing differences in hydrologic response across diverse watersheds and climate conditions.

  2. Structural and dynamical properties of complex networks

    NASA Astrophysics Data System (ADS)

    Ghoshal, Gourab

    Recent years have witnessed a substantial amount of interest within the physics community in the properties of networks. Techniques from statistical physics coupled with the widespread availability of computing resources have facilitated studies ranging from large scale empirical analysis of the worldwide web, social networks, biological systems, to the development of theoretical models and tools to explore the various properties of these systems. Following these developments, in this dissertation, we present and solve for a diverse set of new problems, investigating the structural and dynamical properties of both model and real world networks. We start by defining a new metric to measure the stability of network structure to disruptions, and then using a combination of theory and simulation study its properties in detail on artificially generated networks; we then compare our results to a selection of networks from the real world and find good agreement in most cases. In the following chapter, we propose a mathematical model that mimics the structure of popular file-sharing websites such as Flickr and CiteULike and demonstrate that many of its properties can solved exactly in the limit of large network size. The remaining part of the dissertation primarily focuses on the dynamical properties of networks. We first formulate a model of a network that evolves under the addition and deletion of vertices and edges, and solve for the equilibrium degree distribution for a variety of cases of interest. We then consider networks whose structure can be manipulated by adjusting the rules by which vertices enter and leave the network. We focus in particular on degree distributions and show that, with some mild constraints, it is possible by a suitable choice of rules to arrange for the network to have any degree distribution we desire. In addition we define a simple local algorithm by which appropriate rules can be implemented in practice. Finally, we conclude our

  3. Structural Properties of Defects in Glassy Liquids.

    PubMed

    Cubuk, Ekin D; Schoenholz, Samuel S; Kaxiras, Efthimios; Liu, Andrea J

    2016-07-01

    At zero temperature a disordered solid corresponds to a local minimum in the energy landscape. As the temperature is raised or the system is driven with a mechanical load, the system explores different minima via dynamical events in which particles rearrange their relative positions. We have shown recently that the dynamics of particle rearrangements are strongly correlated with a structural quantity associated with each particle, "softness", which we can identify using supervised machine learning. Particles of a given softness have a well-defined energy scale that governs local rearrangements; because of this property, softness greatly simplifies our understanding of glassy dynamics. Here we investigate the correlation of softness with other commonly used structural quantities, such as coordination number and local potential energy. We show that although softness strongly correlates with these properties, its predictive power for rearrangement dynamics is much higher. We introduce a useful metric for quantifying the quality of structural quantities as predictors of dynamics. We hope that, in the future, authors introducing new structural measures of dynamics will compare their proposals quantitatively to softness using this metric. We also show how softness correlations give insight into rearrangements. Finally, we explore the physical meaning of softness using unsupervised dimensionality reduction and reduced curve-fitting models, and show that softness can be recast in a form that is amenable to analytical treatment. PMID:27092716

  4. Acoustic scattering response of hierarchic honeycomb structures for cylindrical and spherical structures

    NASA Astrophysics Data System (ADS)

    Mor, Arun

    Sandwich panels with honeycomb core are often employed in structures for improved mechanical properties with lightweight. Honeycombs are defined by non-overlapping and periodic unit cells. Most research conducted on these sandwich panels focuses on stiffness and strength properties. The acoustic aspect of these panels has been focused on sound transmission loss. For acoustics, previous studies used effective honeycomb orthotropic elastic moduli based on Cartesian unit cell geometry to model the core as a homogeneous structure. While efficient, this modeling approach loses accuracy at higher frequencies. Furthermore, when used for curved panels, the effective moduli are only approximate. In this work, mechanical and acoustic characteristics of cylindrical and spherical honeycomb panels are studied using finite element analysis. The unit cell geometry core is oriented both radially and in the transverse direction. The models are analyzed for sound scattering measured by target strength with interactions between structure and the acoustic medium through coupling between the domains. Both air and water are compared for the acoustic region. Different honeycomb core geometries varying in the hexagon arrangement, number of unit cells and level of hierarchy are studied. The structures developed are constrained to have the same total mass allowing for comparisons based on only changes in stiffness properties. The effect of face sheet thickness on the mechanical and acoustic properties of the curved sandwich structures is also studied. The vibration and acoustic scattering behavior of these structures have been investigated for natural frequencies between 1-1000 Hz to predict and understand the different responses near and at resonances. The target strength response of the structures has been studied in the near field at both front and back of the structures. The effect of acoustic coupling is observed clearly on varying the outer domains properties between air and water. It

  5. Structural Properties of the Native Ligamentum Teres

    PubMed Central

    Philippon, Marc J.; Rasmussen, Matthew T.; Turnbull, Travis Lee; Trindade, Christiano A.C.; Hamming, Mark G.; Ellman, Michael B.; Harris, Matthew; LaPrade, Robert F.; Wijdicks, Coen A.

    2014-01-01

    Background: A majority of studies investigating the role of the ligamentum teres (LT) have focused primarily on anatomical and histological descriptions. To date, however, the structural properties of the LT have yet to be fully elucidated. Purpose: To investigate the structural properties of the native LT in a human cadaveric model. Study Design: Descriptive laboratory study. Methods: A total of 12 human cadaveric hemipelvises (mean age, 53.6 years; range, 34-63 years) were dissected free of all extra-articular soft tissues to isolate the LT and its acetabular and femoral attachments. A dynamic tensile testing machine distracted each femur in line with the fibers of the LT at a displacement-controlled rate of 0.5 mm/s. The anatomic dimensions, structural properties, and modes of failure were recorded. Results: The LT achieved a mean yield load of 75 N and ultimate failure load of 204 N. The LT had mean lengths of 38.0 and 53.0 mm at its yield and failure points, respectively. The most common (75% of specimens) mechanism of failure was tearing at the fovea capitis. On average, the LT had a linear stiffness of 16 N/mm and elastic modulus of 9.24 MPa. The mean initial length and cross-sectional area were 32 mm and 59 mm2, respectively. Conclusion: The human LT had a mean ultimate failure load of 204 N. Therefore, the results of this investigation, combined with recent biomechanical and outcomes studies, suggest that special consideration should be given to preserving the structural and corresponding biomechanical integrity of the LT during surgical intervention. Clinical Relevance: The LT may be more important as a static stabilizer of the hip joint than previously recognized. Further studies are recommended to investigate the appropriate indications to perform surgical repair or reconstruction of the LT for preservation of hip stability and function. PMID:26535290

  6. Magnetic response properties of gaudiene - a cavernous and aromatic carbocage.

    PubMed

    Rauhalahti, M; Muñoz-Castro, A; Sundholm, D

    2016-07-28

    A spherical and cavernous carbocage molecule exhibiting faces with larger ring sizes than regular fullerenes is a suitable species for investigating how molecular magnetic properties depend on the structure of the molecular framework. The studied all-carbon gaudiene (C72) is a highly symmetrical molecule with three- and four-fold faces formed by twelve membered rings. Here, we attempt to unravel the magnetic response properties of C72 by performing magnetic shielding and current density calculations with the external magnetic field applied in different directions. The obtained results indicate that the induced current density flows mainly along the chemical bonds that are largely perpendicular to the magnetic field direction. However, the overall current strength for different directions of the magnetic field is nearly isotropic differing by only 10% indicating that C72 can to some extent be considered to be a spherical aromatic molecule, whose current density and magnetic shielding are ideally completely isotropic. The induced magnetic field is found to exhibit long-range shielding cones in the field direction with a small deshielding region located perpendicularly to the field outside the molecule. The magnetic shielding is isotropic inside the molecular framework of C72, whereas an orientation-dependent magnetic response appears mainly at the exterior of the molecular cage. PMID:27352814

  7. PROBABILISTIC STRUCTURAL RESPONSE OF STRUCTURE UNDER COLLAPSE LOADING

    SciTech Connect

    J. PEPIN; E. RODRIGUEZ; ET AL

    2001-01-05

    Engineers at Los Alamos National Laboratory (LANL) are currently developing the capability to provide a reliability-based structural evaluation technique for performing weapon reliability assessments. To enhance the analyst's confidence with these new methods, an integrated experiment and analysis project has been developed. The uncertainty associated with the collapse response of commercially available spherical marine float is evaluated with the aid of the non-linear explicit dynamics code DYNA3D (Whirley and Engelmann 1988) coupled with the probabilistic code NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) (Thacker et al. 1998). Variations in geometric shape parameters and uncertainties in material parameters are characterized and included in the probabilistic model.

  8. Property-optimized Gaussian basis sets for molecular response calculations

    NASA Astrophysics Data System (ADS)

    Rappoport, Dmitrij; Furche, Filipp

    2010-10-01

    With recent advances in electronic structure methods, first-principles calculations of electronic response properties, such as linear and nonlinear polarizabilities, have become possible for molecules with more than 100 atoms. Basis set incompleteness is typically the main source of error in such calculations since traditional diffuse augmented basis sets are too costly to use or suffer from near linear dependence. To address this problem, we construct the first comprehensive set of property-optimized augmented basis sets for elements H-Rn except lanthanides. The new basis sets build on the Karlsruhe segmented contracted basis sets of split-valence to quadruple-zeta valence quality and add a small number of moderately diffuse basis functions. The exponents are determined variationally by maximization of atomic Hartree-Fock polarizabilities using analytical derivative methods. The performance of the resulting basis sets is assessed using a set of 313 molecular static Hartree-Fock polarizabilities. The mean absolute basis set errors are 3.6%, 1.1%, and 0.3% for property-optimized basis sets of split-valence, triple-zeta, and quadruple-zeta valence quality, respectively. Density functional and second-order Møller-Plesset polarizabilities show similar basis set convergence. We demonstrate the efficiency of our basis sets by computing static polarizabilities of icosahedral fullerenes up to C720 using hybrid density functional theory.

  9. Optimum structural sizing for gust induced response

    NASA Technical Reports Server (NTRS)

    Hajela, P.; Bach, C. T.

    1988-01-01

    The present paper describes an optimization capability for sizing airframe structures that are subjected to a combination of deterministic and random loads. Design constraints are implemented to prevent structural failure in fatigue and due to a single exceedance of the allowable stress. The random load is treated as a stationary, homogeneous process with a Gaussian probability distribution, and a frequency domain method is used for the computation of dynamic response parameters. An equal-probability-of-load-combination criterion is proposed in the formulation of strength constraints. This alleviates problems associated with the incomplete phase information available when using power spectral density methods. The optimization procedure is illustrated by examples using typical built-up structures.

  10. Structure-property relationships of bismaleimides

    NASA Astrophysics Data System (ADS)

    Tenteris-Noebe, Anita Diane

    The purpose of this research was to control and systematically vary the network topology of bismaleimides through cure temperature and chemistry (addition of various coreactants) and subsequently attempt to determine structure-mechanical property relationships. Characterization of the bismaleimide structures by dielectric, rheological, and thermal analyses, and density measurements was subsequently correlated with mechanical properties such as modulus, yield strength, fracture energy, and stress relaxation. The model material used in this investigation was 4,4sp'-bismaleimidodiphenyl methane (BMI). BMI was coreacted with either 4,4sp'-methylene dianiline (MDA), o,osp'-diallyl bisphenol A (DABA) from Ciba Geigy, or diamino diphenyl sulfone (DDS). Three cure paths were employed: a low-temperature cure of 140sp°C where chain extension should predominate, a high-temperature cure of 220sp°C where both chain extension and crosslinking should occur simultaneously, and a low-temperature (140sp°C) cure followed immediately by a high-temperature (220sp°C) cure where the chain extension reaction or amine addition precedes BMI homopolymerization or crosslinking. Samples of cured and postcured PMR-15 were also tested to determine the effects of postcuring on the mechanical properties. The low-temperature cure condition of BMI/MDA exhibited the highest modulus values for a given mole fraction of BMI with the modulus decreasing with decreasing concentration of BMI. The higher elastic modulus is the result of steric hindrance by unreacted BMI molecules in the glassy state. The moduli values for the high- and low/high-temperature cure conditions of BMI/MDA decreased as the amount of diamine increased. All the moduli values mimic the yield strength and density trends. For the high-temperature cure condition, the room-temperature modulus remained constant with decreasing mole fraction of BMI for the BMI/DABA and BMI/DDS systems. Postcuring PMR-15 increases the modulus over that

  11. Structure-Property Relationships of Bismaleimides

    NASA Technical Reports Server (NTRS)

    Tenteris-Noebe, Anita D.

    1997-01-01

    The purpose of this research was to control and systematically vary the network topology of bismaleimides through cure temperature and chemistry (addition of various coreactants) and subsequently attempt to determine structure-mechanical property relationships. Characterization of the bismaleimide structures by dielectric, rheological, and thermal analyses, and density measurements was subsequently correlated with mechanical properties such as modulus, yield strength, fracture energy, and stress relaxation. The model material used in this investigation was 4,4'-BismaleiMidodIphenyl methane (BMI). BMI was coreacted with either 4,4'-Methylene Dianiline (MDA), o,o'-diallyl bisphenol A (DABA) from Ciba Geigy, or Diamino Diphenyl Sulfone (DDS). Three cure paths were employed: a low- temperature cure of 140 C where chain extension should predominate, a high-temperature cure of 220 C where both chain extension and crosslinking should occur simultaneously, and a low-temperature (140 C) cure followed immediately by a high-temperature (220 C) cure where the chain extension reaction or amine addition precedes BMI homopolymerization or crosslinking. Samples of cured and postcured PMR-15 were also tested to determine the effects of postcuring on the mechanical properties. The low-temperature cure condition of BMI/MDA exhibited the highest modulus values for a given mole fraction of BMI with the modulus decreasing with decreasing concentration of BMI. The higher elastic modulus is the result of steric hindrance by unreacted BMI molecules in the glassy state. The moduli values for the high- and low/high-temperature cure conditions of BMI/MDA decreased as the amount of diamine increased. All the moduli values mimic the yield strength and density trends. For the high-temperature cure condition, the room- temperature modulus remained constant with decreasing mole fraction of BMT for the BMI/DABA and BMI/DDS systems. Postcuring PMR-15 increases the modulus over that of the cured

  12. Structural properties of impact ices accreted on aircraft structures

    NASA Technical Reports Server (NTRS)

    Scavuzzo, R. J.; Chu, M. L.

    1987-01-01

    The structural properties of ice accretions formed on aircraft surfaces are studied. The overall objectives are to measure basic structural properties of impact ices and to develop finite element analytical procedures for use in the design of all deicing systems. The Icing Research Tunnel (IRT) was used to produce simulated natural ice accretion over a wide range of icing conditions. Two different test apparatus were used to measure each of the three basic mechanical properties: tensile, shear, and peeling. Data was obtained on both adhesive shear strength of impact ices and peeling forces for various icing conditions. The influences of various icing parameters such as tunnel air temperature and velocity, icing cloud drop size, material substrate, surface temperature at ice/material interface, and ice thickness were studied. A finite element analysis of the shear test apparatus was developed in order to gain more insight in the evaluation of the test data. A comparison with other investigators was made. The result shows that the adhesive shear strength of impact ice typically varies between 40 and 50 psi, with peak strength reaching 120 psi and is not dependent on the kind of substrate used, the thickness of accreted ice, and tunnel temperature below 4 C.

  13. Electronic structure and optical properties of resin

    NASA Astrophysics Data System (ADS)

    Rao, Zhi-Fan; Zhou, Rong-Feng

    2013-03-01

    We used the density of functional theory (DFT) to study the electronic structure and density of states of resin by ab initio calculation. The results show the band gap of resin is 1.7 eV. The covalent bond is combined C/O atoms with H atoms. The O 2p orbital is the biggest effect near the Fermi level. The results of optical properties show the reflectivity is low, and the refractive index is 1.7 in visible light range. The highest absorption coefficient peak is in 490 nm and the value is 75,000.

  14. Nanostructured lead sulfide: synthesis, structure and properties

    NASA Astrophysics Data System (ADS)

    Sadovnikov, S. I.; Gusev, A. I.; Rempel, A. A.

    2016-07-01

    The theoretical and experimental results of recent studies dealing with nanostructured lead sulfide are summarized and analyzed. The key methods for the synthesis of nanostructured lead sulfide are described. The crystal structure of PbS in nanopowders and nanofilms is discussed. The influence of the size of nanostructure elements on the optical and thermal properties of lead sulfide is considered. The dependence of the band gap of PbS on the nanoparticle (crystallite) size for powders and films is illustrated. The bibliography includes 222 references.

  15. Structure and properties of a beryllium dilayer

    SciTech Connect

    Boettger, J.C.; Trickey, S.B.

    1985-07-15

    All-electron, density-functional calculations on an hcp Be dilayer find c/a at equilibrium to be 1.69 +- 0.03, a = 4.20 +- 0.02 a.u. (Kohn, Sham, Gaspar) or c/a = 1.69 +- 0.02, a = 4.10 +- 0.03 a.u. (Hedin and Lundqvist). In either case there is very weak interplanar bonding. While these structural properties are noticeably different from those of the bulk crystal, the dilayer work function (Hedin and Lundqvist) is essentially identical to the experimental bulk value.

  16. Structure and properties of a beryllium dilayer

    NASA Astrophysics Data System (ADS)

    Boettger, J. C.; Trickey, S. B.

    1985-07-01

    All-electron, density-functional calculations on an hcp Be dilayer find c/a at equilibrium to be 1.69+/-0.03, a=4.20+/-0.02 a.u. (Kohn, Sham, Gaspar) or c/a=1.69+/-0.02, a=4.10+/-0.03 a.u. (Hedin and Lundqvist). In either case there is very weak interplanar bonding. While these structural properties are noticeably different from those of the bulk crystal, the dilayer work function (Hedin and Lundqvist) is essentially identical to the experimental bulk value.

  17. Structural and optical properties of nanostructured nickel

    NASA Astrophysics Data System (ADS)

    Singh, J.; Pandey, J.; Gupta, R.; Kaurav, N.; Tripathi, J.

    2016-05-01

    Metal nanoparticles are attractive because of their special structure and better optical properties. Nickel nanoparticles (Ni-Np) have been synthesized successfully by thermal decomposition method in the presence of trioctyl phosphine (TOP) and oleylamine (OAm). The samples were characterized by X-ray diffraction (XRD), Zetapotential measurement and Fourier transforms infrared (FTIR) spectroscopy. The size of Ni nanoparticles can be readily tuned from 13.86 nm. As-synthesized Ni nanoparticles have hexagonal closed pack (hcp) cubic structure as characterized by power X-ray diffraction (XRD) prepared at 280°C. The possible formation mechanism has also been phenomenological proposed for as synthesized Ni-Np. The value of Zeta potential was found 12.25 mV.

  18. Properties of multilayer nonuniform holographic structures

    SciTech Connect

    Pen, E F; Rodionov, Mikhail Yu

    2010-12-09

    Experimental results and analysis of properties of multilayer nonuniform holographic structures formed in photopolymer materials are presented. The theoretical hypotheses is proved that the characteristics of angular selectivity for the considered structures have a set of local maxima, whose number and width are determined by the thicknesses of intermediate layers and deep holograms and that the envelope of the maxima coincides with the selectivity contour of a single holographic array. It is also experimentally shown that hologram nonuniformities substantially distort shapes of selectivity characteristics: they become asymmetric, the local maxima differ in size and the depths of local minima reduce. The modelling results are made similar to experimental data by appropriately choosing the nonuniformity parameters. (imaging and image processing. holography)

  19. Extraordinary electronic properties in uncommon structure types

    NASA Astrophysics Data System (ADS)

    Ali, Mazhar Nawaz

    In this thesis I present the results of explorations into several uncommon structure types. In Chapter 1 I go through the underlying idea of how we search for new compounds with exotic properties in solid state chemistry. The ideas of exploring uncommon structure types, building up from the simple to the complex, using chemical intuition and thinking by analogy are discussed. Also, the history and basic concepts of superconductivity, Dirac semimetals, and magnetoresistance are briefly reviewed. In chapter 2, the 1s-InTaS2 structural family is introduced along with the discovery of a new member of the family, Ag0:79VS2; the synthesis, structure, and physical properties of two different polymorphs of the material are detailed. Also in this chapter, we report the observation of superconductivity in another 1s structure, PbTaSe2. This material is especially interesting due to it being very heavy (resulting in very strong spin orbit coulping (SOC)), layered, and noncentrosymmetric. Electronic structure calculations reveal the presence of a bulk 3D Dirac cone (very similar to graphene) that is gapped by SOC originating from the hexagonal Pb layer. In Chapter 3 we show the re-investigation of the crystal structure of the 3D Dirac semimetal, Cd3As2. It is found to be centrosymmetric, rather than noncentrosymmetric, and as such all bands are spin degenerate and there is a 4-fold degenerate bulk Dirac point at the Fermi level, making Cd3As2 a 3D electronic analog to graphene. Also, for the first time, scanning tunneling microscopy experiments identify a 2x2 surface reconstruction in what we identify as the (112) cleavage plane of single crystals; needle crystals grow with a [110] long axis direction. Lastly, in chapter 4 we report the discovery of "titanic" (sadly dubbed ⪉rge, nonsaturating" by Nature editors and given the acronym XMR) magnetoresistance (MR) in the non-magnetic, noncentrosymmetric, layered transition metal dichalcogenide WTe2; over 13 million% at 0.53 K in

  20. Structure and shear response of lipid monolayers

    SciTech Connect

    Dutta, P.; Ketterson, J.B.

    1990-02-01

    Organic monolayers and multilayers are both scientifically fascinating and technologically promising; they are, however, both complex systems and relatively inaccessible to experimental probes. In this Progress Report, we describe our X-ray diffraction studies, which have given us substantial new information about the structures and phase transitions in monolayers on the surface of water; our use of these monolayers as a unique probe of the dynamics of wetting and spreading; and our studies of monolayer mechanical properties using a simple but effective technique available to anyone using the Wilhelmy method to measure surface tension.

  1. Synthesis, structure, and properties of glasses under extreme conditions

    NASA Astrophysics Data System (ADS)

    Guerette, Michael J.

    Anomalous mechanical properties of silica glass include stiffening upon heating, initially softening under pressure, and non-linear elastic response to strains. Through understanding structural changes in silica glass under a broad range of temperature, pressure, and strain conditions and how they influence the mechanical properties, insight was gained for how to change the silica glass network to better suit specific uses in extreme conditions. In this dissertation, pressure-quenching routes were used to effectively change the glass atomic packing and to make densified glass. Applied in the non-rigid state near the glass transition temperature, quench pressures up to 8 GPa have been used to achieve density increase of 25% in silica glass. The resulting structure and properties of as-quenched samples have been investigated using XRD, Raman and Brillouin spectroscopy. In-situ Raman and Brillouin light scattering techniques were developed to study the structure, elastic and dynamic properties of silica glass under high temperature, high pressure and high strain conditions. High temperature measurements were carried out in an optical furnace up to 1500°C, a diamond anvil cell was used to carry out high pressure experiments up to 25 GPa, and a two-point bender was used for measuring glasses in excess of 6% strain in both tensile and compressive regions. Pressure-quenching from the non-rigid state near the glass transition temperature imparts structural signatures to densified silica glass that cannot be accomplished through cold compression at room temperature. The unique structures of pressure-quenched silica glass are reflected in decreased anomalous response of silica glass to external stimuli of high temperature or high pressure, and therefore greater thermo-mechanical stability. The nonlinear elastic behavior of silica glass has been directly probed from the compressive to the tensile side of silica fibers in bend by using in-situ Brillouin light scattering. This

  2. Structural properties of reduced Upton montmorillonite

    NASA Astrophysics Data System (ADS)

    Gates, W. P.; Stucki, J. W.; Kirkpatrick, R. J.

    1996-12-01

    Reduction of octahedral Fe in the crystalline structure of smectites influences, possibly controls, surface-sensitive physical and chemical properties. The purpose of this study was to investigate if reduction of structural Fe by Na-dithionite or bacteria affects the chemical environment of constituent cations in montmorillonite, employing solid state multinuclear (29Si and 27Al) magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Reduction of structural Fe resulted in a positive (down field) chemical shift of the main Si Q3 (Q3(0Al)) site which was strongly correlated with Fe(II) content and inferred that distortions in Si-OT (T=Si, Al) bond angles and Si-O bond lengths occur with increasing layer charge. The line width (W) of the 29Si Q3 signal also increased with increasing levels of reduction. No change occurred in the position of the peak maximum for the octahedral Al (27AlVI) signal; however, an increased W was observed for this peak with increasing Fe(II) content. These results are attributed to decreases in Si-O-T bond angles and Si-O bond distances, corresponding to a better fit between the tetrahedral and octahedral sheets brought about by the presence of Fe(II) in the clay structure. The increased 27AlVI signal width (W) may also be due to a lessening of the paramagnetic influence of Fe(III) nuclei and enhancement of 27AlVI signals with different quadrupole coupling constants (QCC). Multinuclear MAS NMR analyses of dithioniteand microbially-reduced montmorillonite indicate that reduction of structural Fe caused reversible changes in the smectite structure, at least as far as this method could discern.

  3. Structural properties of autoclaved aerated concrete masonry

    SciTech Connect

    Matthys, J.H.; Nelson, R.L.

    1999-07-01

    Autoclaved aerated concrete masonry units are manufactured from portland cement, quartz sand, water, lime, gypsum and a gas forming agent. The units are steam cured under pressure in an autoclave transforming the material into a hard calcium silicate. The autoclaved aerated concrete masonry units are large-size solid rectangular prisms which are laid using thin-bed mortar layers into masonry assemblages. The system and product are not new--patented in 1924 by Swedish architect Johan Eriksson. Over a period of 60 years this product has been used in all areas of residential and industrial construction and in virtually all climates. However, the principal locations of application have been generally outside the US Little information in the US is available on the structural properties of this product. Due to the interest in use of this product in the construction industry and the construction of production plants in the US, the Construction Research Center at the University of Texas at Arlington and Robert L. Nelson & Associates conducted a series of tests to determine some of the basic structural properties of this product. This paper presents the findings of those investigations.

  4. Repair material properties for effective structural application

    SciTech Connect

    Mangat, P.S.; Limbachiya, M.C.

    1997-04-01

    Strength and engineering properties of three generic repair materials which are likely to influence long-term performance of repaired concrete structures were studied. Measured properties include strength, stiffness, shrinkage and creep deformations, together with the complete compressive stress-strain characteristics including post-cracking behavior. The repair materials considered in this investigation are commercially available and widely used. These included a high performance non-shrinkable concrete, a mineral based cementitious material with no additives or coarse aggregate size particles, and a cementitious mortar containing styrene acrylic copolymer with fiber additives. Performance comparisons are also made between these materials and plain concrete mixes of similar strength and stiffness, suitable for repair applications. The results show that shrinkage of the repair materials was significantly greater than the shrinkage of normal concrete. Moreover, the shrinkage of those modified with a polymer admixture was found to be very sensitive to the relative humidity of the exposure compared to normal concrete. The post-peak strain capacity of the material modified with a polymer admixture was markedly improved leading to a more pronounced falling branch of stress-strain curve. The ultimate stress level (at a maximum load) of specially formulated repair materials varies significantly, the lowest ultimate stress being recorded for the porous mineral-based material. The inclusion of aggregates improves the mechanical properties and dimensional stability of repair materials.

  5. Broadband multiple responses of surface modes in quasicrystalline plasmonic structure

    PubMed Central

    Yuan, Haiming; Jiang, Xiangqian; Huang, Feng; Sun, Xiudong

    2016-01-01

    We numerically study the multiple excitation of surface modes in 2D photonic quasicrystal/metal/substrate structure. An improved rigorous coupled wave analysis method that can handle the quasicrystalline structure is presented. The quasicrystalline lattice, which refers to Penrose tiling in this paper, is generated by the cut-and-project method. The normal incidence spectrum presents a broadband multiple responses property. We find that the phase matching condition determines the excitation frequency for a given incident angle, while the depth of the reflection valley depends on the incident polarization. The modes will split into several sub-modes at oblique incidence, which give rise to the appearance of more responses on the spectrum. PMID:27492782

  6. Broadband multiple responses of surface modes in quasicrystalline plasmonic structure

    NASA Astrophysics Data System (ADS)

    Yuan, Haiming; Jiang, Xiangqian; Huang, Feng; Sun, Xiudong

    2016-08-01

    We numerically study the multiple excitation of surface modes in 2D photonic quasicrystal/metal/substrate structure. An improved rigorous coupled wave analysis method that can handle the quasicrystalline structure is presented. The quasicrystalline lattice, which refers to Penrose tiling in this paper, is generated by the cut-and-project method. The normal incidence spectrum presents a broadband multiple responses property. We find that the phase matching condition determines the excitation frequency for a given incident angle, while the depth of the reflection valley depends on the incident polarization. The modes will split into several sub-modes at oblique incidence, which give rise to the appearance of more responses on the spectrum.

  7. Broadband multiple responses of surface modes in quasicrystalline plasmonic structure.

    PubMed

    Yuan, Haiming; Jiang, Xiangqian; Huang, Feng; Sun, Xiudong

    2016-01-01

    We numerically study the multiple excitation of surface modes in 2D photonic quasicrystal/metal/substrate structure. An improved rigorous coupled wave analysis method that can handle the quasicrystalline structure is presented. The quasicrystalline lattice, which refers to Penrose tiling in this paper, is generated by the cut-and-project method. The normal incidence spectrum presents a broadband multiple responses property. We find that the phase matching condition determines the excitation frequency for a given incident angle, while the depth of the reflection valley depends on the incident polarization. The modes will split into several sub-modes at oblique incidence, which give rise to the appearance of more responses on the spectrum. PMID:27492782

  8. Structural, biological and biophysical properties of glycated and glycoxidized phosphatidylethanolamines.

    PubMed

    Annibal, Andrea; Riemer, Thomas; Jovanovic, Olga; Westphal, Dennis; Griesser, Eva; Pohl, Elena E; Schiller, Jürgen; Hoffmann, Ralf; Fedorova, Maria

    2016-06-01

    Glycation and glycoxidation of proteins and peptides have been intensively studied and are considered as reliable diagnostic biomarkers of hyperglycemia and early stages of type II diabetes. However, glucose can also react with primary amino groups present in other cellular components, such as aminophospholipids (aminoPLs). Although it is proposed that glycated aminoPLs can induce many cellular responses and contribute to the development and progression of diabetes, the routes of their formation and their biological roles are only partially revealed. The same is true for the influence of glucose-derived modifications on the biophysical properties of PLs. Here we studied structural, signaling, and biophysical properties of glycated and glycoxidized phosphatidylethanolamines (PEs). By combining high resolution mass spectrometry and nuclear magnetic resonance spectroscopy it was possible to deduce the structures of several intermediates indicating an oxidative cleavage of the Amadori product yielding glycoxidized PEs including advanced glycation end products, such as carboxyethyl- and carboxymethyl-ethanolamines. The pro-oxidative role of glycated PEs was demonstrated and further associated with several cellular responses including activation of NFκB signaling pathways. Label free proteomics indicated significant alterations in proteins regulating cellular metabolisms. Finally, the biophysical properties of PL membranes changed significantly upon PE glycation, such as melting temperature (Tm), membrane surface charge, and ion transport across the phospholipid bilayer. PMID:27012418

  9. Spectral Response of Multilayer Optical Structures to Dynamic Loading

    NASA Astrophysics Data System (ADS)

    Scripka, David; Lecroy, Garrett; Lee, Gyuhyon; Sun, Changyan; Kang, Zhitao; Summers, Christopher J.; Thadhani, Naresh N.

    2015-06-01

    Distributed Bragg Reflectors and optical microcavities are multilayer optical structures with spectral properties that are intrinsically sensitive to external perturbations. With nanometer to micrometer dimensions and near instantaneous optical response, these structures show significant potential as the basis for mesoscale time-resolved diagnostics that can be used to probe the dynamic behavior of mesoscale heterogeneous materials. In order to characterize the optical and mechanical behavior of the multilayer structures, a coupled computational-experimental study is underway. A mechanistic analysis of the spectral response of the structures to dynamic loading will be presented, along with computational simulations illustrating the observable spectral effects of 1D shock compression. Results from fabrication of specific multilayer designs and initial laser-driven shock loading experiments will be shown and compared to the simulation results. Preliminary results indicate that the magnitude of dynamic loading can be directly correlated to the altered spectral response. Potential applications of the theoretical diagnostics and challenges associated with spatially resolved data collection methodology will also be discussed. DTRA grant HDTRA-1-12-1-0052 is acknowledged. David Scripka is supported by the Department of Defense through the National Defense Science and Engineering Graduate Fellowship Program.

  10. Mechanical Properties and Shock Response of PMMA

    NASA Astrophysics Data System (ADS)

    Jordan, Jennifer; Casem, Daniel; Moy, Paul; Walter, Timothy

    2015-06-01

    Polymethylmethacrylate (PMMA) is used widely in shock experiments as a window material and in explosive characterization tests, e.g. gap tests, as a shock mitigation material. In order to simulate the complex loading present in a gap test, the constitutive response of the PMMA must be well understood. However, it is not clear what characterization must be done when the PMMA material is changed, e.g. changing supplier, and the Rohm and Haas Type II UVA PMMA, which was used for many of the calibration experiments, is no longer available. In this paper, we will present characterization results on legacy Rohm and Haas Type II UVA in comparison with new PMMA grades proposed for use in gap tests. The materials are characterized in compression quasi-statically and dynamically. The quasi-static tests include simultaneous digital image correlation to determine local strain and temperature measurements. Planar shock experiments are performed to determine the compression and release response.

  11. Structure, properties, and dynamic behavior of Earth's inner core

    NASA Astrophysics Data System (ADS)

    Reaman, Daniel Marcus

    Long-standing debate has persisted regarding the nature of the Earth's inner core, from its age and composition to its structure and dynamic high-pressure, high-temperature behavior. The equation of state of the alloy which comprises the inner core, the material transport properties of inner-core materials and the mechanism responsible for its structure are all required to gain further insight into the current and past state of the Earth's deep interior. Experimental work in the diamond-anvil cell (DAC) coupled with theoretical calculations are reported here to constrain these aspects of the Earth's inner core. Use of the DAC has allowed us to determine an equation of state of a planetary-core representative Fe64Ni36 alloy to 95 GP and ˜ 3000 K. Increasing the Ni content in these experiments relative to the estimated abundance in the inner core (˜5--10%) provides a critical investigation on the effects of increasing Ni content on the equation of state of FeNi alloys, thereby providing insight in to the behavior of these alloys at high pressures and temperatures with applications to other planetary cores. The use of micro-fabricated samples in the DAC is a novel new way of measuring material transport properties under high-pressure and temperature conditions. Using micro-fabricated samples in these experiments, with a controlled geometry of Fe and Ni, has allowed the measurement of interdiffusion coefficients in FeNi alloys and extended the previous pressure range of these experiments by a factor of three. The resulting data has been extrapolated to inner-core conditions to place constraints on material transport properties at those conditions while providing insight into some of the other physical properties of inner-core material, such as the solid-state viscosity. The seismically-anisotropic structure of the inner core remains a point of contention amongst geophysicists. Though many viable hypotheses have been put forth regarding the nature of this structure

  12. Response properties of self-improving systems

    NASA Astrophysics Data System (ADS)

    Krakovsky, Andrey

    2016-04-01

    We observe that a sustained positivity (or negativity) of a system's second-order response will result in a directional change of the system's characteristics under the corresponding random exposure. We identify these changes with improvement (or decline) in the state of a system and introduce the concept of self-improving systems as systems which characteristics can sustainably improve under a random exposure. The resulting framework is of a general phenomenological nature and can be applied to complex systems across different areas of knowledge.

  13. Response properties of self-improving systems.

    PubMed

    Krakovsky, Andrey

    2016-04-01

    We observe that a sustained positivity (or negativity) of a system's second-order response will result in a directional change of the system's characteristics under the corresponding random exposure. We identify these changes with improvement (or decline) in the state of a system and introduce the concept of self-improving systems as systems which characteristics can sustainably improve under a random exposure. The resulting framework is of a general phenomenological nature and can be applied to complex systems across different areas of knowledge. PMID:27059562

  14. Structure and Properties of Tactic Hydrogenated Polynorbornenes

    NASA Astrophysics Data System (ADS)

    Burns, Adam B.; Register, Richard A.

    Tacticity is one of the most important structural parameters for determining the physical properties of a polymer. A high degree of steroregularity typically promotes crystallization, with different tacticities giving rise to differences in crystal structure, melting point, and degree of crystallinity. In polynorbornene (PN) made by ring-opening metathesis polymerization (ROMP), tacticity is determined by the relative configuration of the nonplanar cyclopentylene rings enchained in the backbone. Traditional ROMP initiators yield atactic polymers (aPN); however, recent advances in catalyst design have produced both isotactic and syndiotactic PN. Newly reported cis,isotactic- and cis,syndiotactic-PNs were catalytically hydrogenated (abbreviated ihPN and shPN, respectively) without altering the tacticity. The thermal and structural characteristics of ihPN and shPN were studied by differential scanning calorimetry (DSC) and wide-angle x-ray scattering (WAXS) and compared to that of ahPN. Remarkably, all three polymers are semicrystalline, each with a distinct crystal structure. ihPN has a nominal melting point of 165 C, more than 20 C above that of ahPN. WAXS patterns of melt-drawn fibers of ihPN show few strong reflections indicative of either a highly symmetric unit cell or poor long-range order. ihPN fibers also exhibit a crystal-crystal transition near 130 C, which is not fully reversible on subsequent cooling. On the other hand, shPN has a nominal melting point some 15 C below that of ahPN, and shPN fibers show no evidence of polymorphism.

  15. Structural response of fiber composite fan blades

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Minich, M. D.

    1975-01-01

    A fiber composite airfoil, typical for high-tip speed compressor applications, is subjected to load conditions anticipated to be encountered in such applications, and its structural response is theoretically investigated. The analysis method used consists of composite mechanics embedded in pre- and post-processors and coupled with NASTRAN. The load conditions examined include thermal due to aerodynamic heating, pressure due to aerodynamic forces, centrifugal, and combinations of these. The various responses investigated include root reactions due to various load conditions, average composite and ply stresses, ply delaminations, and the fundamental modes and the corresponding reactions. The results show that the thermal and pressure stresses are negligible compared to those caused by the centrifugal forces. Also, the core-shell concept for composite blades is an inefficient design (core plies not highly stressed) and appears to be sensitive to interply delaminations. The results are presented in graphical and tabular forms to illustrate the types and amount of data required for such an analysis, and to provide quantitative data of the various responses which can be helpful in designing such composite blades.

  16. Melt Structure and Properties: Progress and Prognoses

    NASA Astrophysics Data System (ADS)

    Stebbins, J. F.

    2004-12-01

    Recent advances in quantitative determinations of silicate glass structure are beginning to place important constraints on models of the physical and chemical properties of melts, but much remains to be done before such models can become entirely based on structure. For example, models of free energy and major component activities generally assume (lacking better constraints) that network species (e.g. Al, Si, "Qn" groups) and network modifiers (e.g. Na, Ca, K, Mg) each mix randomly. However, recent spectroscopic studies demonstrate strong ordering in the network (significant if incomplete Al avoidance; preference of Al for "Q4" groups, etc.) and between modifier cations differing greatly in field strength (e.g. K+, Mg2+). Solution models thus may need substantial revision, unless new studies of temperature effects on such ordering indicate approach to randomness at magmatic temperatures. Such studies are ongoing, facilitated by recent developments in hyper-quenching technology. On the other hand, discovery of such low-T ordering provides a likely (and long-suspected) mechanism for at least some of the configurational entropy in multicomponent melts, which in turn is a critical part of models of viscosity: at least in systems with high Al/Si ratios, for example, increase in Al/Si disorder with increasing T will a major part of this term. In many systems, however, the structural origins of Sconf remain mysterious. For both major and minor components, considerable information now exists to constrain models both of activity and of transport processes, but progress awaits development of useful model forms. Examples include new information on the local coordination of anions such as fluoride and chloride, which again show strong chemical ordering. Similarly, we now know a great deal about the concentration of minor "defect" species, that have been considered to be important to viscosity and diffusion (e.g. AlO5, SiO5, "excess" NBO). However, going from speculative

  17. Structure-property relationships of carbon aerogels

    SciTech Connect

    Pekala, R.W.; Alviso, C.T.; Kong, F.M.

    1993-12-01

    Of the organic reactions in sol-gel polymerizations, the most studied reaction is the aqueous polycondensation of resorcinol with formaldehyde; the resulting crosslinked gels are supercritically dried from CO{sub 2} to give resorcinol-formaldehyde (RF) aerogels. These aerogels can be pyrolyzed to form vitreous carbon monoliths with black color, high porosity, ultrafine cell/pore size, high surface area, and interconnected particles of the organic precursor. The structure and properties of the carbon aerogels depend on R/C (resorcinol/catalyst) ratio of starting solution, pyrolysis temperature, and chemical activation. Each variable is discussed. Carbon aerogels provide an almost ideal electrode material (in double-layer capacitors) owing to low electrical resistivity (<40 mohm-cm), controllable pore size distribution (5--500 {angstrom}), and high volumetric surface areas ({approximately}500 m{sup 2}/cm{sup 3}).

  18. Geometrical, response, and gap properties of Lindbladians

    NASA Astrophysics Data System (ADS)

    Albert, Victor V.; Bradlyn, Barry; Fraas, Martin; Jiang, Liang

    We study Lindbladians admitting multi-dimensional steady-state subspaces (SSS) which can be used to store, protect, and process quantum information. We derive an analytical formula for the left eigenmatrices of such Lindbladians corresponding to purely imaginary eigenvalues. This formula resolves how Lindbladian evolution affects perturbative response and geometrical features of the SSS and allows us to generalize recent work to all types of SSS. We show that Hamiltonian and certain jump operator perturbations induce, to first order, exclusively unitary evolution on the SSS. Similarly, the holonomy (generalization of geometric phase) induced on the SSS after adiabatic traversal of a closed path in parameter space is unitary. We derive a new Riemannian metric tensor in parameter space induced by one type of SSS, generalizing the Fubini-Study metric to Lindbladians possessing one or more mixed steady states. We derive a Kubo formula governing linear response of the SSS to Hamiltonian perturbations. Finally, we show that the energy scale governing leakage out of the SSS is different from the conventional Lindbladian dissipative gap.

  19. Structure Property Studies for Additively Manufactured Parts

    SciTech Connect

    Milenski, Helen M; Schmalzer, Andrew Michael; Kelly, Daniel

    2015-08-17

    Since the invention of modern Additive Manufacturing (AM) processes engineers and designers have worked hard to capitalize on the unique building capabilities that AM allows. By being able to customize the interior fill of parts it is now possible to design components with a controlled density and customized internal structure. The creation of new polymers and polymer composites allow for even greater control over the mechanical properties of AM parts. One of the key reasons to explore AM, is to bring about a new paradigm in part design, where materials can be strategically optimized in a way that conventional subtractive methods cannot achieve. The two processes investigated in my research were the Fused Deposition Modeling (FDM) process and the Direct Ink Write (DIW) process. The objectives of the research were to determine the impact of in-fill density and morphology on the mechanical properties of FDM parts, and to determine if DIW printed samples could be produced where the filament diameter was varied while the overall density remained constant.

  20. Structural properties of spatially embedded networks

    NASA Astrophysics Data System (ADS)

    Kosmidis, K.; Havlin, S.; Bunde, A.

    2008-05-01

    We study the effects of spatial constraints on the structural properties of networks embedded in one- or two-dimensional space. When nodes are embedded in space, they have a well-defined Euclidean distance r between any pair. We assume that nodes at distance r have a link with probability p(r)~r-δ. We study the mean topological distance l and the clustering coefficient C of these networks and find that they both exhibit phase transitions for some critical value of the control parameter δ depending on the dimensionality d of the embedding space. We have identified three regimes. When δ2d the networks are "large" worlds l~N1/d with high clustering. Our results indicate that spatial constrains have a significant impact on the network properties, a fact that should be taken into account when modeling complex networks.

  1. High-pressure structural properties of tetramethylsilane

    NASA Astrophysics Data System (ADS)

    Zhen-Xing, Qin; Xiao-Jia, Chen

    2016-02-01

    High-pressure structural properties of tetramethylsilane are investigated by synchrotron powder x-ray diffraction at pressures up to 31.1 GPa and room temperature. A phase with the space group of Pnma is found to appear at 4.2 GPa. Upon compression, the compound transforms to two following phases: the phase with space groups of P21/c at 9.9 GPa and the phase with P2/m at 18.2 GPa successively via a transitional phase. The unique structural character of P21/c supports the phase stability of tetramethylsilane without possible decomposition upon heavy compression. The appearance of the P2/m phase suggests the possible realization of metallization for this material at higher pressure. Project supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project from Ministry of Education of China (Grant No. 708070), the Fundamental Research Funds for the Central Universities, South China University of Technology (Grant No. 2014ZZ0069), the National Natural Science Foundation of China (Grant No. 51502189), and the Doctoral Project of Taiyuan University of Science and Technology, China (Grant No. 20132010).

  2. Structural Properties of Amorphous Indium-Based Oxides

    NASA Astrophysics Data System (ADS)

    Khanal, Rabi; Medvedeva, Julia

    2014-03-01

    Amorphous transparent conducting and semiconducting oxides exhibit similar or even superior properties to those observed in their crystalline counterparts. To understand how the structural properties change upon amorphization and how chemical composition affects the local and long-range structure of the amorphous oxides, we employ first-principles molecular dynamics to generate amorphous In-X-O with X =Zn, Ga, Sn, Ge, Y, or Sc, and compare their local structure features to those obtained for amorphous and crystalline indium oxide. The results reveal that the short-range structure of the Metal-O polyhedra is generally preserved in the amorphous oxides; however, different metals (In and X) show quantitatively or qualitatively different behavior. Some of the metals retain their natural distances and/or coordination; while others allow for a highly distorted environment and thus favor ``defect'' formation under variable oxygen conditions. At the same time, we find that the presence of X increases both the average In-O coordination and the number of the 6-coordinated In atoms as compared to those in IO. The improved In coordination may be responsible for the observed reduction in the carrier concentration as the substitution level in In-X-O increases.

  3. Thin films of tetrafluorosubstituted cobalt phthalocyanine: Structure and sensor properties

    NASA Astrophysics Data System (ADS)

    Klyamer, Darya D.; Sukhikh, Aleksandr S.; Krasnov, Pavel O.; Gromilov, Sergey A.; Morozova, Natalya B.; Basova, Tamara V.

    2016-05-01

    In this work, thin films of tetrafluorosubstituted cobalt phthalocyanine (CoPcF4) were prepared by organic molecular beam deposition and their structure was studied using UV-vis, polarization dependent Raman spectroscopy, XRD and atomic force microscopy. Quantum chemical calculations (DFT) have been employed in order to determine the detailed assignment of the bands in the CoPcF4 IR and Raman spectra. The electrical sensor response of CoPcF4 films to ammonia vapours was investigated and compared with that of unsubstituted cobalt phthalocyanine films. In order to explain the difference in sensitivity of the unsubstituted and fluorinated phthalocyanines to ammonia, the nature and properties of chemical binding between CoPc derivatives and NH3 were described by quantum-chemical calculations utilizing DFT method. The effect of post-deposition annealing on surface morphology and gas sensing properties of CoPcF4 films was also studied.

  4. Melt Structure and Properties: a Spectroscopic Perspective

    NASA Astrophysics Data System (ADS)

    Stebbins, J.

    2006-12-01

    Entropy, volume, and their P/T derivatives are at the heart of models of the thermodynamics of silicate melts and magmas. Quantitative characterization of glass structure is leading to important new insights into the links from "Microscopic to Macroscopic" that can at least guide interpretations of data and in some cases even have predictive power. A few recent examples will be discussed here. The often-large configurational components to heat capacities, thermal expansivities, and compressibilities of melts strongly indicate that structural changes with temperature and pressure are of key importance. At least some aspects of thermal increases in configurational (as opposed to vibrational) disorder are amenable to spectroscopic detection, either with in situ methods or on glasses with varying quench rates and thus varying fictive temperatures. In some systems, such changes are now clear, and can be shown to make significant contributions to properties. These include network cation coordination in systems such as borate liquids (BO4 to BO3 at higher T), and Al-Si disordering in aluminosilicates. In general, however, progress in this rich problem has only begun. It has long been suspected from thermodynamic analyses (and theoretical simulations) that configurational changes in melts play a key role in volume compression at high pressure, over and above that which can be expressed in "normal" equations of state or from those expected from bond compression and bending. Scattering and spectroscopic studies have revealed some of the important aspects of pressure-induced structural changes, but again we are just at the beginning of full understanding. For example, binary silicate glasses quenched from high-P melts clearly record some systematic increases in Si coordination, while aluminosilicates record systematic pressure and compositional (modifier cation field strength) effects on Al coordination in recovered samples with large, quenched-in density increases

  5. Structural properties, phase stability, elastic properties and electronic structures of Cu-Ti intermetallics

    NASA Astrophysics Data System (ADS)

    Chen, Shuai; Duan, Yong-Hua; Huang, Bo; Hu, Wen-Cheng

    2015-11-01

    The structural properties, phase stabilities, anisotropic elastic properties and electronic structures of Cu-Ti intermetallics have been systematically investigated using first principles based on the density functional theory. The calculated equilibrium structural parameters agree well with available experimental data. The ground-state convex hull of formation enthalpies as a function of Cu content is slightly symmetrical at CuTi with a minimal formation enthalpy (-13.861 kJ/mol of atoms), which indicates that CuTi is the most stable phase. The mechanical properties, including elastic constants, polycrystalline moduli and anisotropic indexes, were evaluated. G/B is more pertinent to hardness than to the shear modulus G due to the high power indexes of 1.137 for G/B. The mechanical anisotropy was also characterized by describing the three-dimensional (3D) surface constructions. The order of elastic anisotropy is Cu4Ti3 > Cu3Ti2 > α-Cu4Ti > Cu2Ti > CuTi > β-Cu4Ti > CuTi2. Finally, the electronic structures were discussed and Cu2Ti is a semiconductor.

  6. Structure-Property Study of Piezoelectricity in Polyimides

    NASA Technical Reports Server (NTRS)

    Ounaies, Zoubeida; Park, Cheol; Harrison, Joycelyn S.; Smith, Joseph G.; Hinkley, Jeffrey

    1999-01-01

    High performance piezoelectric polymers are of interest to NASA as they may be useful for a variety of sensor applications. Over the past few years research on piezoelectric polymers has led to the development of promising high temperature piezoelectric responses in some novel polyimides. In this study, a series of polyimides have been studied with systematic variations in the diamine monomers that comprise the polyimide while holding the dianhydride constant. The effect of structural changes, including variations in the nature and concentration of dipolar groups, on the remanent polarization and piezoelectric coefficient is examined. Fundamental structure-piezoelectric property insight will enable the molecular design of polymers possessing distinct improvements over state-of-the-art piezoelectric polymers including enhanced polarization, polarization stability at elevated temperatures, and improved processability.

  7. Extended structures and physicochemical properties of uranyl-organic compounds.

    PubMed

    Wang, Kai-Xue; Chen, Jie-Sheng

    2011-07-19

    The ability of uranium to undergo nuclear fission has been exploited primarily to manufacture nuclear weapons and to generate nuclear power. Outside of its nuclear physics, uranium also exhibits rich chemistry, and it forms various compounds with other elements. Among the uranium-bearing compounds, those with a uranium oxidation state of +6 are most common and a particular structural unit, uranyl UO(2)(2+) is usually involved in these hexavalent uranium compounds. Apart from forming solids with inorganic ions, the uranyl unit also bonds to organic molecules to generate uranyl-organic coordination materials. If appropriate reaction conditions are employed, uranyl-organic extended structures (1-D chains, 2-D layers, and 3-D frameworks) can be obtained. Research on uranyl-organic compounds with extended structures allows for the exploration of their rich structural chemistry, and such studies also point to potential applications such as in materials that could facilitate nuclear waste disposal. In this Account, we describe the structural features of uranyl-organic compounds and efforts to synthesize uranyl-organic compounds with desired structures. We address strategies to construct 3-D uranyl-organic frameworks through rational selection of organic ligands and the incorporation of heteroatoms. The UO(2)(2+) species with inactive U═O double bonds usually form bipyramidal polyhedral structures with ligands coordinated at the equatorial positions, and these polyhedra act as primary building units (PBUs) for the construction of uranyl-organic compounds. The geometry of the uranyl ions and the steric arrangements and functionalities of organic ligands can be exploited in the the design of uranyl--organic extended structures, We also focus on the investigation of the promising physicochemical properties of uranyl-organic compounds. Uranyl-organic materials with an extended structure may exhibit attractive properties, such as photoluminescence, photocatalysis

  8. Structure dependent elastic properties of supergraphene

    NASA Astrophysics Data System (ADS)

    Hou, Juan; Yin, Zhengnan; Zhang, Yingyan; Chang, Tien-Chong

    2016-04-01

    Complete replacement of aromatic carbon bonds in graphene by carbyne chains gives rise to supergraphene whose mechanical properties are expected to depend on its structure. However, this dependence is to date unclear. In this paper, explicit expressions for the in-plane stiffness and Poisson's ratio of supergraphene are obtained using a molecular mechanics model. The theoretical results show that the in-plane stiffness of supergraphene is drastically (at least one order) smaller than that of graphene, whereas its Poisson's ratio is higher than 0.5. As the index number increases (i.e., the length of carbyne chains increases and the bond density decreases), the in-plane stiffness of supergraphene decreases while the Poisson's ratio increases. By analyzing the relation among the layer modulus, in-plane stiffness and Poisson's ratio, it is revealed that the mechanism of the faster decrease in the in-plane stiffness than the bond density is due to the increase of Poisson's ratio. These findings are useful for future applications of supergraphene in nanomechanical systems.

  9. Crystalline mesophases: Structure, mobility, and pharmaceutical properties.

    PubMed

    Shalaev, Evgenyi; Wu, Ke; Shamblin, Sheri; Krzyzaniak, Joseph F; Descamps, Marc

    2016-05-01

    Crystalline mesophases, which are commonly classified according to their translational, orientational, and conformational order as liquid crystals, plastic crystals, and conformationally disordered crystals, represent a common state of condensed matter. As an intermediate state between crystalline and amorphous materials, crystalline mesophases resemble amorphous materials in relation to their molecular mobility, with the glass transition being their common property, and at the same time possessing a certain degree of translational periodicity (with the exception of nematic phase), with corresponding narrow peaks in X-ray diffraction patterns. For example, plastic crystals, which can be formed both by near-spherical molecules and molecules of lower symmetry, such as planar or chain molecules, can have both extremely sharp X-ray diffraction lines and exhibit glass transition. Fundamentals of structural arrangements in mesophases are compared with several types of disorder in crystalline materials, as well as with short-range ordering in amorphous solids. Main features of the molecular mobility in crystalline mesophases are found to be generally similar to amorphous materials, although some important differences do exist, depending on a particular type of mobility modes involved in relaxation processes. In several case studies reviewed, chemical stability appears to follow the extent of disorder, with the stability of crystalline mesophase found to be intermediate between amorphous (least stable) and crystalline (most stable) materials. Finally, detection of crystalline mesophases during manufacturing of two different types of dosage forms is discussed. PMID:27067607

  10. Record breaking properties for typical autocorrelation structures

    NASA Astrophysics Data System (ADS)

    Anagnostopoulou, Eirini; Galani, Andriani; Dimas, Panagiotis; Karanasios, Alexandros; Mastrotheodoros, Theodoros; Michaelidi, Eleni-Maria; Nikolopoulos, Dionisios; Pontikos, Stamatis; Sourla, Fani; Chazapi, Anna; Papalexiou, Simon Michael; Koutsoyiannis, Demetris

    2013-04-01

    Record-breaking occurrences in hydrometeorological processes are often used particularly in communicating information to the public and their analysis offers the possibility of better comprehending extreme events. However, the typical comprehension depends on prototypes characterized by pure randomness. In fact the occurrence of record breaking depends on the marginal distribution and the autocorrelation function of the process as well the length of available record. Here we study the influence of the process autocorrelation structure on the statistics of record-breaking occurrences giving emphasis on the differences with those of a purely random process. The particular stochastic processes, which we examine, are the AR(1), AR(2) and ARMA(1,1), as well as the Hurst-Kolmogorov process. The necessary properties are calculated using either analytical methods when possible or Monte Carlo simulation. We also compare the model results with observed hydrometeorological time series. Acknowledgement: This research is conducted within the frame of the undergraduate course "Stochastic Methods in Water Resources" of the National Technical University of Athens (NTUA). The School of Civil Engineering of NTUA provided moral support for the participation of the students in the Assembly.

  11. Atmospheric structure and cloud properties on Venus

    NASA Astrophysics Data System (ADS)

    Zasova, L. V.

    We discuss the structure of the Venus atmosphere from the surface to 100 km and properties of the clouds. The solar energy deposited on Venus is the same as that on the Earth. However, because of the greenhouse effect in the thick atmosphere the surface temperature is of 735K. Thermal structure of troposphere (below 58-60 km) is characterized by the temperature rate of 7.7K/km, and small negative equator-pole temperature gradient. Two connective zones are observed in the troposphere: in the middle clouds (50-56 km) and below 30 km. Middle atmosphere above 60 km (mesosphere) is stable. In the upper clouds (58-68 km) 50 % of the solar energy is absorbed by `unknown UV absorber'. This leads to generation of the thermal tides, which influence the thermal structure of the mesosphere. Dissipation of the tides may produce energy to support the superrotation - dynamic state of the Venus atmosphere. Local time variation of temperature of the mesosphere, upper boundary of the clouds and zonal wind is defined by the tides. Strongest thermal tides are observed in the cold collar near 100 mb level. Temperature of the atmosphere decreases from equator to pole below 70 km and increases above the clouds, in a way that the polar region is of 20 K warmer than low latitudes. Air masses, which ascend in equatorial region move to the polar region above the clouds against the temperature gradient and descend in the near polar region. The main component of the clouds from 48 to 70 km is sulfuric acid at all latitudes, which is produced by photochemistry from the SO2 and H2O. Being conservative scattering, the clouds allow investigation on the night side of the atmosphere below the clouds and the surface in the windows between the CO2 bands. The altitude of the upper boundary of the clouds decreases from equator to high latitudes and it has the lowest position at polar region in the hot dipole (below 60 km). The haze of submicron particles, which may be found from 30 to 90 km, is strongly

  12. Consensus structure elucidation combining GC/EI-MS, structure generation, and calculated properties.

    PubMed

    Schymanski, Emma L; Gallampois, Christine M J; Krauss, Martin; Meringer, Markus; Neumann, Steffen; Schulze, Tobias; Wolf, Sebastian; Brack, Werner

    2012-04-01

    This article explores consensus structure elucidation on the basis of GC/EI-MS, structure generation, and calculated properties for unknown compounds. Candidate structures were generated using the molecular formula and substructure information obtained from GC/EI-MS spectra. Calculated properties were then used to score candidates according to a consensus approach, rather than filtering or exclusion. Two mass spectral match calculations (MOLGEN-MS and MetFrag), retention behavior (Lee retention index/boiling point correlation, NIST Kovat's retention index), octanol-water partitioning behavior (log K(ow)), and finally steric energy calculations were used to select candidates. A simple consensus scoring function was developed and tested on two unknown spectra detected in a mutagenic subfraction of a water sample from the Elbe River using GC/EI-MS. The top candidates proposed using the consensus scoring technique were purchased and confirmed analytically using GC/EI-MS and LC/MS/MS. Although the compounds identified were not responsible for the sample mutagenicity, the structure-generation-based identification for GC/EI-MS using calculated properties and consensus scoring was demonstrated to be applicable to real-world unknowns and suggests that the development of a similar strategy for multidimensional high-resolution MS could improve the outcomes of environmental and metabolomics studies. PMID:22414024

  13. Seismic Safety Margins Research Program (Phase I). Project IV. Structural building response; Structural Building Response Review

    SciTech Connect

    Healey, J.J.; Wu, S.T.; Murga, M.

    1980-02-01

    As part of the Phase I effort of the Seismic Safety Margins Research Program (SSMRP) being performed by the University of California Lawrence Livermore Laboratory for the US Nuclear Regulatory Commission, the basic objective of Subtask IV.1 (Structural Building Response Review) is to review and summarize current methods and data pertaining to seismic response calculations particularly as they relate to the objectives of the SSMRP. This material forms one component in the development of the overall computational methodology involving state of the art computations including explicit consideration of uncertainty and aimed at ultimately deriving estimates of the probability of radioactive releases due to seismic effects on nuclear power plant facilities.

  14. Superprotonic solid acids: Structure, properties, and applications

    NASA Astrophysics Data System (ADS)

    Boysen, Dane Andrew

    In this work, the structure and properties of superprotonic MH nXO4-type solid acids (where M = monovalent cation, X = S, Se, P, As, and n = 1, 2) have been investigated and, for the first time, applied in fuel cell devices. Several MH nXO4-type solid acids are known to undergo a "superprotonic" solid-state phase transition upon heating, in which the proton conductivity increases by several orders of magnitude and takes on values of ˜10 -2O-1cm-1. The presence of superprotonic conductivity in fully hydrogen bonded solid acids, such as CsH2PO4, has long been disputed. In these investigations, through the use of pressure, the unequivocal identification of superprotonic behavior in both RbH2PO4 and CsH2PO 4 has been demonstrated, whereas for chemically analogous compounds with smaller cations, such as KH2PO4 and NaH2PO 4, superprotonic conductivity was notably absent. Such observations have led to the adoption of radius ratio rules, in an attempt to identify a critical ion size effect on the presence of superprotonic conductivity in solid acids. It has been found that, while ionic size does play a prominent role in the presence of superprotonic behavior in solid acids, equally important are the effects of ionic and hydrogen bonding. Next, the properties of superprotonic phase transition have been investigated from a thermodynamic standpoint. With contributions from this work, a formulation has been developed that accounts for the entropy resulting from both the disordering of both hydrogen bonds and oxy-anion librations in the superprotonic phase of solid acids. This formulation, fundamentally derived from Linus Pauling's entropy rules for ice, accurately accounts for the change in entropy through a superprotonic phase transition. Lastly, the first proof-of-priniciple fuel cells based upon solid acid electrolytes have been demonstrated. Initial results based upon a sulfate electrolyte, CsHSO4, demonstrated the viability of solid acids, but poor chemical stability

  15. Structure and Early Soot Oxidation Properties of Laminar Diffusion Flames

    NASA Technical Reports Server (NTRS)

    El-Leathy, A. M.; Xu, F.; Faeth, G. M.

    2001-01-01

    Soot is an important unsolved problem of combustion science because it is present in most hydrocarbon-fueled flames and current understanding of the reactive and physical properties of soot in flame environments is limited. This lack of understanding affects progress toward developing reliable predictions of flame radiation properties, reliable predictions of flame pollutant emission properties and reliable methods of computational combustion, among others. Motivated by these observations, the present investigation extended past studies of soot formation in this laboratory, to consider soot oxidation in laminar diffusion flames using similar methods. Early work showed that O2 was responsible for soot oxidation in high temperature O2-rich environments. Subsequent work in high temperature flame environments having small O2 concentrations, however, showed that soot oxidation rates substantially exceeded estimates based on the classical O2 oxidation rates of Nagle and Strickland-Constable and suggests that radicals such as O and OH might be strong contributors to soot oxidation for such conditions. Neoh et al. subsequently made observations in premixed flames, supported by later work, that showed that OH was responsible for soot oxidation at these conditions with a very reasonable collision efficiency of 0.13. Subsequent studies in diffusion flames, however, were not in agreement with the premixed flame studies: they agreed that OH played a dominant role in soot oxidation in flames, but found collision efficiencies that varied with flame conditions and were not in good agreement with each other or with Neoh et al. One explanation for these discrepancies is that optical scattering and extinction properties were used to infer soot structure properties for the studies that have not been very successful for representing the optical properties of soot. Whatever the source of the problem, however, these differences among observations of soot oxidation in premixed and

  16. Processing-structure-property relationships in oriented polymers

    NASA Astrophysics Data System (ADS)

    Xia, Zhiyong

    The Processing-Structure-Property (P-S-P) relationships in oriented polymers have been studied in this dissertation. Controlled polymer orientation has been achieved through the equal channel angular extrusion (ECAE) process. The structure of the ECAE-oriented polymers have been investigated from all dimensional levels, i.e., from spherulitical scale (micrometer scale), lamellar scale (nanometer scale) to crystallographic scale (angstrom scale). The results indicate that the polymer spherulites are deformed into macrofibrils after one ECAE process. Within the macrofibrils, a "V-type" lamellar orientation has been formed to accommodate the overall straining of spherulites. The molecular chains in the crystalline lamellae are found to be tilted at a small angle with respect to the lamellar surface. Whereas, the molecular chains between the macrofibrils and crystalline lamellae are highly stretched. Property characterization indicates that ECAE-induced microstructure is responsible for the improved physical and mechanical properties. The improved physical and mechanical properties include high tensile modulus, higher impact fracture toughness and better scratch resistance. This research has also clarified several controversies in the research of semicrystalline polymers. First, this research gives an unambiguous account on the lamellar evolution during large-scale plastic deformation. The crystalline lamellae in the ECAE-oriented samples have been found to be evolved from the original crystalline lamellae. Secondly, the shifting of the primary relaxation peak in ECAE-oriented PET has been found to be due to the increase in molecular orientation. Thirdly, the transmission electron microscopy (TEM) indicates that in low crystallinity semicrystalline polymers, the larger value of the two characteristic lengths from small angle X-ray scattering (SAXS) correlation function analysis should be assigned to the crystalline lamellar thickness.

  17. Seismic Response Analysis and Design of Structure with Base Isolation

    SciTech Connect

    Rosko, Peter

    2010-05-21

    The paper reports the study on seismic response and energy distribution of a multi-story civil structure. The nonlinear analysis used the 2003 Bam earthquake acceleration record as the excitation input to the structural model. The displacement response was analyzed in time domain and in frequency domain. The displacement and its derivatives result energy components. The energy distribution in each story provides useful information for the structural upgrade with help of added devices. The objective is the structural displacement response minimization. The application of the structural seismic response research is presented in base-isolation example.

  18. Carbon fiber reinforced composites: their structural and thermal properties

    NASA Astrophysics Data System (ADS)

    Cheng, Jingquan; Yang, Dehua

    2010-07-01

    More and more astronomical telescopes use carbon fiber reinforced composites (CFRP). CFRP has high stiffness, high strength, and low thermal expansion. However, they are not isotropic in performance. Their properties are direction dependent. This paper discusses, in detail, the structural and thermal properties of carbon fiber structure members, such as tubes, plates, and honeycomb sandwich structures. Comparisons are provided both from the structural point of view and from the thermal point of view.

  19. Structure-function properties of anticorrosive exopolyaccharides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nanoscale biobased exopolymer films were shown that provide protection to metal substrates under corrosive environments and that the films could be self-repairing in aqueous environments. This work describes the fundamental properties of thin exopolymer films including thermodynamic properties, film...

  20. Graph theory in structure-property correlations

    NASA Astrophysics Data System (ADS)

    Vinogradova, M. G.; Fedina, Yu. A.; Papulov, Yu. G.

    2016-02-01

    The possibilities of the theoretical graph approach to the construction and interpretation of additive schemes for calculation and prediction are discussed. Working formulas are derived for calculating the thermodynamic properties of alkanes and their substitutes. The obtained algorithms are used to calculate thermodynamic properties of chloroalkanes that correspond to experimental values.

  1. Statistical energy analysis response prediction methods for structural systems

    NASA Technical Reports Server (NTRS)

    Davis, R. F.

    1979-01-01

    The results of an effort to document methods for accomplishing response predictions for commonly encountered aerospace structural configurations is presented. Application of these methods to specified aerospace structure to provide sample analyses is included. An applications manual, with the structural analyses appended as example problems is given. Comparisons of the response predictions with measured data are provided for three of the example problems.

  2. A primer for structural response to random pressure fluctuations

    NASA Technical Reports Server (NTRS)

    Dowell, E. H.; Vaicaitis, R.

    1975-01-01

    A review was made of power spectral methods for determining linear response of structures to random pressure fluctuations. Various simplifying assumptions are made for the purpose of obtaining useful formula for structural response. The transmission of sound through a flexible structure into an interior cavity was also treated.

  3. A simple auxetic tubular structure with tuneable mechanical properties

    NASA Astrophysics Data System (ADS)

    Ren, Xin; Shen, Jianhu; Ghaedizadeh, Arash; Tian, Hongqi; Xie, Yi Min

    2016-06-01

    Auxetic materials and structures are increasingly used in various fields because of their unusual properties. Auxetic tubular structures have been fabricated and studied due to their potential to be adopted as oesophageal stents where only tensile auxetic performance is required. However, studies on compressive mechanical properties of auxetic tubular structures are limited in the current literature. In this paper, we developed a simple tubular structure which exhibits auxetic behaviour in both compression and tension. This was achieved by extending a design concept recently proposed by the authors for generating 3D metallic auxetic metamaterials. Both compressive and tensile mechanical properties of the auxetic tubular structure were investigated. It was found that the methodology for generating 3D auxetic metamaterials could be effectively used to create auxetic tubular structures as well. By properly adjusting certain parameters, the mechanical properties of the designed auxetic tubular structure could be easily tuned.

  4. Design of Hybrid Solid Polymer Electrolytes: Structure and Properties

    NASA Technical Reports Server (NTRS)

    Bronstein, Lyudmila M.; Karlinsey, Robert L.; Ritter, Kyle; Joo, Chan Gyu; Stein, Barry; Zwanziger, Josef W.

    2003-01-01

    This paper reports synthesis, structure, and properties of novel hybrid solid polymer electrolytes (SPE's) consisting of organically modified aluminosilica (OM-ALSi), formed within a poly(ethylene oxide)-in-salt (Li triflate) phase. To alter the structure and properties we fused functionalized silanes containing poly(ethylene oxide) (PEO) tails or CN groups.

  5. Structure and Thermal Properties of Porous Geological Materials

    NASA Astrophysics Data System (ADS)

    Kirk, Simon; Williamson, David

    2011-06-01

    Understanding the behaviour of porous geological materials is important for developing models of the explosive loading of rock in mining applications. To this end it is essential to first characterise its complex internal structure. Knowing the structure shows how the properties of the component materials relate to the overall properties of rock. The structure and mineralogy of Gosford sandstone was investigated and this information was used to predict its thermal properties. The thermal properties of the material were measured experimentally and compared against these predictions.

  6. Personality Research Form: Factor Structure and Response Style Involvement

    ERIC Educational Resources Information Center

    Stricker, Lawrence J.

    1974-01-01

    Explores factor structure of the Personality Research Form (PRF) and examines the inventory's relations with response styles. In general, the PRF content scales correlate moderately with each other and with measures of acquiescence, social desirability, and defensiveness response biases. (Author)

  7. Chitosan/halloysite nanotubes bionanocomposites: structure, mechanical properties and biocompatibility.

    PubMed

    Liu, Mingxian; Zhang, Yun; Wu, Chongchao; Xiong, Sheng; Zhou, Changren

    2012-11-01

    Incorporation of nanosized reinforcements into chitosan usually results in improved properties and changed microstructures. Naturally occurred halloysite nanotubes (HNTs) are incorporated into chitosan for forming bionanocomposite films via solution casting. The electrostatic attraction and hydrogen bonding interactions between HNTs and chitosan are confirmed. HNTs are uniformly dispersed in chitosan matrix. The tensile strength and Young's modulus of chitosan are enhanced by HNTs. The storage modulus and glass transition temperature of chitosan/HNTs films also increase significantly. Blending with HNTs induces changes in surface nanotopography and increase of roughness of chitosan films. In vitro fibroblasts response demonstrates that both chitosan and chitosan/HNTs nanocomposite films are cytocompatibility even when the loading of HNTs is 10%. In summary, these results provide insights into understanding of the structural relationships of chitosan/HNTs bionanocomposite films in potential applications, such as scaffold materials in tissue engineering. PMID:22743347

  8. Optical properties of structurally modified glasses doped with gold ions.

    PubMed

    Qiu, Jianrong; Jiang, Xiongwei; Zhu, Congshan; Inouye, Hideyuki; Si, Jinhai; Hirao, Kazuyuki

    2004-02-15

    We report on the optical properties of a structurally modified silicate glass doped with Au ions. The area in the vicinity of the focal point of an 800-nm femtosecond laser in a glass sample became gray as a result of the formation of color centers after laser irradiation and turned red because of precipitation of Au nanoparticles after further annealing at 550 degrees C for 30 min. When the glass was excited by UV light at 365 nm, yellowish-white and orange-yellow emissions were observed in the laser-irradiated and the Au-nanoparticle-precipitated area, respectively. An optical Kerr shutter experiment showed that the Au nanoparticle-precipitated glass had an ultrafast nonlinear optical response, and the third-order nonlinear susceptibility was estimated to be approximately 10(-11) esu. PMID:14971756

  9. Optical properties of structurally modified glasses doped with gold ions

    NASA Astrophysics Data System (ADS)

    Qiu, Jianrong; Jiang, Xiongwei; Zhu, Congshan; Inouye, Hideyuki; Si, Jinhai; Hirao, Kazuyuki

    2004-02-01

    We report on the optical properties of a structurally modified silicate glass doped with Au ions. The area in the vicinity of the focal point of an 800-nm femtosecond laser in a glass sample became gray as a result of the formation of color centers after laser irradiation and turned red because of precipitation of Au nanoparticles after further annealing at 550 °C for 30 min. When the glass was excited by UV light at 365 nm, yellowish-white and orange-yellow emissions were observed in the laser-irradiated and the Au-nanoparticle-precipitated area, respectively. An optical Kerr shutter experiment showed that the Au nanoparticle-precipitated glass had an ultrafast nonlinear optical response, and the third-order nonlinear susceptibility was estimated to be ~10-11 esu.

  10. Computing Response Of A Structure To Random Transient Pressures

    NASA Technical Reports Server (NTRS)

    Sepcenko, Valentin; Margasahayam, Ravi

    1994-01-01

    Improved method of computing vibrational response of structure to transient random acoustic excitation at predominantly low frequencies devised, called "deterministic". Motivated by need to analyze more accurately vibro/acoustic responses of structures at spacecraft-launching facilities and determine whether need for reinforcement or redesign to withstand launch environment. Also used to study such phenomena as earthquake motions, ocean waves, aircraft pressure gusts, responses of bridges to winds, and effects to jet-engine noise on aircraft structures.

  11. Evaluating structural deterioration of ceramic candle filters using dynamic response

    SciTech Connect

    Chen, R.H.L.; Parthasarathy, B.

    1996-12-31

    Ceramic candle filters used in the recent demonstration plant have experienced degradation and fracturing. Preliminary examination of these ceramic filters indicated that damage of the filters may have resulted from strength degradation. This study proposes a nondestructive evaluation of the structural properties of the ceramic candle filters. A virgin Refraction filter and twelve Schumacher filters which were previously tested under high pressure and high temperature at the demonstration power plant were evaluated. The vibration signatures of the ceramic filters at different degradation levels are established using transient impact response technique. Results from this study indicate that the natural frequencies of the filters can be used as an index to quantify the damage condition of the filters. The results of this study also indicate the feasibility of using the vibration mode shapes to predict the damage location of the filters.

  12. Structure and physical properties of transparent ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Krumin', A. E.; Shternberg, A. R.

    1987-10-01

    Transparent ferroelectric ceramics (TFCs) are currently being used in the design of various solid-state optoelectronic devices. This paper examines the composition and structure of TFCs as well as requirements on the preparation of TFCs and criteria for the search for new TFC compositions. The properties of TFCs are examined, including the electrooptical effect, optical and electrooptical properties in the infrared, nonlinear-optical properties, the effect of radiation on the physical properties of TFCs, and phase-transition characteristics.

  13. Dendritic Cell Responses to Surface Properties of Clinical Titanium Surfaces

    PubMed Central

    Kou, Peng Meng; Schwartz, Zvi; Boyan, Barbara D.

    2010-01-01

    Dendritic cells (DCs) play pivotal roles in responding to foreign entities during an innate immune response and initiating effective adaptive immunity as well as maintaining immune tolerance. The sensitivity of DCs to foreign stimuli also makes them useful cells to assess the inflammatory response to biomaterials. Elucidating the material property-DC phenotype relationships using a well-defined biomaterial system is expected to provide criteria for immuno-modulatory biomaterial design. Clinical titanium (Ti) substrates, including pretreatment (PT), sand-blasted and acid-etched (SLA), and modified SLA (modSLA), with different roughness and surface energy were used to treat DCs and resulted in differential DC responses. PT and SLA induced a mature DC (mDC) phenotype, while modSLA promoted a non-inflammatory environment by supporting an immature DC (iDC) phenotype based on surface marker expression, cytokine production profiles and cell morphology. Principal component analysis (PCA) confirmed these experimental results, and it also indicated that the non-stimulating property of modSLA covaried with certain surface properties, such as high surface hydrophilicity, % oxygen and % Ti of the substrates. In addition to the previous research that demonstrated the superior osteogenic property of modSLA compared to PT and SLA, the result reported herein indicates that modSLA may further benefit implant osteo-integration by reducing local inflammation and its associated osteoclastogenesis. PMID:20977948

  14. GH11 xylanases: Structure/function/properties relationships and applications.

    PubMed

    Paës, Gabriel; Berrin, Jean-Guy; Beaugrand, Johnny

    2012-01-01

    For technical, environmental and economical reasons, industrial demands for process-fitted enzymes have evolved drastically in the last decade. Therefore, continuous efforts are made in order to get insights into enzyme structure/function relationships to create improved biocatalysts. Xylanases are hemicellulolytic enzymes, which are responsible for the degradation of the heteroxylans constituting the lignocellulosic plant cell wall. Due to their variety, xylanases have been classified in glycoside hydrolase families GH5, GH8, GH10, GH11, GH30 and GH43 in the CAZy database. In this review, we focus on GH11 family, which is one of the best characterized GH families with bacterial and fungal members considered as true xylanases compared to the other families because of their high substrate specificity. Based on an exhaustive analysis of the sequences and 3D structures available so far, in relation with biochemical properties, we assess biochemical aspects of GH11 xylanases: structure, catalytic machinery, focus on their "thumb" loop of major importance in catalytic efficiency and substrate selectivity, inhibition, stability to pH and temperature. GH11 xylanases have for a long time been used as biotechnological tools in various industrial applications and represent in addition promising candidates for future other uses. PMID:22067746

  15. Structure-Property Relationships of Architectural Coatings by Neutron Methods

    NASA Astrophysics Data System (ADS)

    Nakatani, Alan

    2015-03-01

    Architectural coatings formulations are multi-component mixtures containing latex polymer binder, pigment, rheology modifiers, surfactants, and colorants. In order to achieve the desired flow properties for these formulations, measures of the underlying structure of the components as a function of shear rate and the impact of formulation variables on the structure is necessary. We have conducted detailed measurements to understand the evolution under shear of local microstructure and larger scale mesostructure in model architectural coatings formulations by small angle neutron scattering (SANS) and ultra small angle neutron scattering (USANS), respectively. The SANS results show an adsorbed layer of rheology modifier molecules exist on the surface of the latex particles. However, the additional hydrodynamic volume occupied by the adsorbed surface layer is insufficient to account for the observed viscosity by standard hard sphere suspension models (Krieger-Dougherty). The USANS results show the presence of latex aggregates, which are fractal in nature. These fractal aggregates are the primary structures responsible for coatings formulation viscosity. Based on these results, a new model for the viscosity of coatings formulations has been developed, which is capable of reproducing the observed viscosity behavior.

  16. Transport properties of pancreatic cancer describe gemcitabine delivery and response

    PubMed Central

    Koay, Eugene J.; Truty, Mark J.; Cristini, Vittorio; Thomas, Ryan M.; Chen, Rong; Chatterjee, Deyali; Kang, Ya’an; Bhosale, Priya R.; Tamm, Eric P.; Crane, Christopher H.; Javle, Milind; Katz, Matthew H.; Gottumukkala, Vijaya N.; Rozner, Marc A.; Shen, Haifa; Lee, Jeffery E.; Wang, Huamin; Chen, Yuling; Plunkett, William; Abbruzzese, James L.; Wolff, Robert A.; Varadhachary, Gauri R.; Ferrari, Mauro; Fleming, Jason B.

    2014-01-01

    Background. The therapeutic resistance of pancreatic ductal adenocarcinoma (PDAC) is partly ascribed to ineffective delivery of chemotherapy to cancer cells. We hypothesized that physical properties at vascular, extracellular, and cellular scales influence delivery of and response to gemcitabine-based therapy. Methods. We developed a method to measure mass transport properties during routine contrast-enhanced CT scans of individual human PDAC tumors. Additionally, we evaluated gemcitabine infusion during PDAC resection in 12 patients, measuring gemcitabine incorporation into tumor DNA and correlating its uptake with human equilibrative nucleoside transporter (hENT1) levels, stromal reaction, and CT-derived mass transport properties. We also studied associations between CT-derived transport properties and clinical outcomes in patients who received preoperative gemcitabine-based chemoradiotherapy for resectable PDAC. Results. Transport modeling of 176 CT scans illustrated striking differences in transport properties between normal pancreas and tumor, with a wide array of enhancement profiles. Reflecting the interpatient differences in contrast enhancement, resected tumors exhibited dramatic differences in gemcitabine DNA incorporation, despite similar intravascular pharmacokinetics. Gemcitabine incorporation into tumor DNA was inversely related to CT-derived transport parameters and PDAC stromal score, after accounting for hENT1 levels. Moreover, stromal score directly correlated with CT-derived parameters. Among 110 patients who received preoperative gemcitabine-based chemoradiotherapy, CT-derived parameters correlated with pathological response and survival. Conclusion. Gemcitabine incorporation into tumor DNA is highly variable and correlates with multiscale transport properties that can be derived from routine CT scans. Furthermore, pretherapy CT-derived properties correlate with clinically relevant endpoints. Trial registration. Clinicaltrials.gov NCT01276613

  17. Response of joint dominated space structures

    NASA Technical Reports Server (NTRS)

    1987-01-01

    An approximate method is developed for estimating the transient response of nonlinear systems in terms of linearized modes of response. Its advantages are that it is computationally more efficient than the time integration method and that it is possible to view the design problem in the more traditional physical terms of modal response. The major drawback of the approximate method is loss of accuracy. It seems that both approximate methods and time integration have their roles in design. Approximate methods provide efficient tools for performing parametric studies and they supply physical insights into how to optimize system performance that are not easily inferred from strictly numerical methods. Time integration provides a method for assessing the accuracy of the approximate solution for key simulations and for fine tuning the final design. In the procedure presented the nonlinear system is approximated by an equivalent linear system in which the system parameters are constant over the range of transient response.

  18. Structure and properties of "nematically ordered" aerogels

    NASA Astrophysics Data System (ADS)

    Asadchikov, V. E.; Askhadullin, R. Sh.; Volkov, V. V.; Dmitriev, V. V.; Kitaeva, N. K.; Martynov, P. N.; Osipov, A. A.; Senin, A. A.; Soldatov, A. A.; Chekrygina, D. I.; Yudin, A. N.

    2015-04-01

    The microstructure, specific area, and mechanical properties of various samples of "nematically ordered" aerogels whose strands are almost parallel to each other at macroscopic distances have been studied. The strong anisotropy of such aerogels distinguishes them from standard aerogels, which are synthesized by solgel technology, and opens new possibilities for physical experiments.

  19. Structural and mechanical properties of thorium carbide

    SciTech Connect

    Aynyas, Mahendra; Pataiya, Jagdeesh; Arya, B. S.; Singh, A.; Sanyal, S. P.

    2015-06-24

    We have investigated the cohesive energies, equilibrium lattice constants, pressure-volume relationship, phase transition pressure and elastic constant for thorium carbide using an interionic potential theory with modified ionic charge, which includes Coulomb screening effect due to d-electrons. This compound undergoes structural phase transition from NaCl (B{sub 1}) to CsCl (B{sub 2}) structure at high pressure 40 GPa. We have also calculated bulk, Young, and shear moduli, Poisson ratio and anisotropic ratio in NaCl (B{sub 1}) structure and compared them with other experimental and theoretical results which show a good agreement.

  20. Design sensitivity analysis of nonlinear structural response

    NASA Technical Reports Server (NTRS)

    Cardoso, J. B.; Arora, J. S.

    1987-01-01

    A unified theory is described of design sensitivity analysis of linear and nonlinear structures for shape, nonshape and material selection problems. The concepts of reference volume and adjoint structure are used to develop the unified viewpoint. A general formula for design sensitivity analysis is derived. Simple analytical linear and nonlinear examples are used to interpret various terms of the formula and demonstrate its use.

  1. Inferring Earth structure from the response to ocean tidal loads

    NASA Astrophysics Data System (ADS)

    Martens, H. R.; Simons, M.; Ito, T.

    2012-12-01

    Tidal forces, generated primarily by gravitational interactions with the moon and Sun, distort the shape of Earth's solid interior (body tides) and redistribute the mass of the oceans (ocean tides). The periodic shifting of ocean mass places cyclic loads on Earth, with the response to these loads observable as spatial displacements in Global Positioning System (GPS) data. Gravitational and elastic responses of the solid Earth to ocean tidal loads (OTLs) are controlled by the material properties of Earth's interior and may hence be used to constrain independently the absolute values of density and the elastic moduli down to c. 300km depth. Previous analysis of this type focused on structure in the western United States. We present observational results and modeled predictions for OTL-induced surface displacements at nearly 100 GPS stations across Brazil, Argentina, and Uruguay. Relative to the earlier study region, eastern South America is an ideal geographic location to study the effects of OTLs because it is composed primarily of stable shield and platform provinces, implying less structural complexity. Furthermore, the region is bounded to the north and east by large amplitude ocean tides. Obtaining absolute values for material properties in the crust and upper mantle beneath South America could provide valuable insight into the structure of the Amazonian craton and hence knowledge about its long-term stability against tectonic deformation. We extract the amplitude and phase of several main tidal constituents from the GPS data using classical harmonic analysis. We then compare our observations with theoretical predictions drawn from a variety of Earth models. Predicted surface displacements derived from radially symmetric Earth models, such as PREM and ad hoc perturbations to PREM, exhibit spatially correlated residuals, suggesting a need to explore a wider family of models, including those with lateral heterogeneity. Initially we have relied on one

  2. Structures and physical properties of R2TX3 compounds

    NASA Astrophysics Data System (ADS)

    Pan, Zhi-Yan; Cao, Chong-De; Bai, Xiao-Jun; Song, Rui-Bo; Zheng, Jian-Bang; Duan, Li-Bing

    2013-05-01

    Rare-earth compounds have been an attractive subject based on the unique electronic structures of the rare-earth elements. Novel ternary intermetallic compounds R2TX3 (R = rare-earth element or U, T = transition-metal element, X = Si, Ge, Ga, In) are a significant branch of this research field due to their complex and intriguing physical properties, such as magnetic order at low temperature, spin-glass behavior, Kondo effect, heavy fermion behavior, and so on. The unique physical properties of R2TX3 compounds are related to distinctive electronic structures, crystal structures, microinteraction, and external environment. Most R2TX3 compounds crystallize in AlB2-type or derived AlB2-type structures and exhibit many similar properties. This paper gives a concise review of the structures and physical properties of these compounds. Spin glass, magnetic susceptibility, resistivity, and specific heat of R2TX3 compounds are discussed.

  3. Electronic structure and photophysical properties of polyimides

    SciTech Connect

    LaFemina, J.P.; Kafafi, S.A.

    1992-04-01

    The quantum mechanical AM1 and CNDO/S3 models were used to examine the effect of isoelectronic substitutions on the conformation, electronic structure, and optical absorption spectra for a series of aromatic polyimides. An analysis of the geometric changes at the substitution site and its effect on the electronic structure allowed for the prediction of changes in the ICT band of the optical absorption spectra.

  4. Structure-Function-Property-Design Interplay in Biopolymers: Spider Silk

    PubMed Central

    Tokareva, Olena; Jacobsen, Matthew; Buehler, Markus; Wong, Joyce; Kaplan, David L.

    2013-01-01

    Spider silks have been a focus of research for almost two decades due to their outstanding mechanical and biophysical properties. Recent advances in genetic engineering have led to the synthesis of recombinant spider silks, thus helping to unravel a fundamental understanding of structure-function-property relationships. The relationships between molecular composition, secondary structures, and mechanical properties found in different types of spider silks are described, along with a discussion of artificial spinning of these proteins and their bioapplications, including the role of silks in biomineralization and fabrication of biomaterials with controlled properties. PMID:23962644

  5. Status of geometry effects on structural nuclear composite properties

    SciTech Connect

    Will Windes; Y. Katoh; L.L. Snead; E. Lara-Curzio; C. Henagar, Jr.

    2005-09-01

    structural ceramic composites being considered for control rod applications within the VHTR design. While standard sized (i.e. 150-mm long or longer) test specimens can be used for baseline non-irradiated thermal creep studies, very small, compact, tensile specimens will be required for the irradiated creep studies. Traditionally, it is standard practice to use small, representative test samples in place of full-size components for an irradiated study. However, a real problem exists for scale-up of composite materials. Unlike monolithic materials, these composites are engineered from two distinct materials using complicated infiltration techniques to provide full density and maximum mechanical properties. The material properties may be significantly affected when the component geometry or size is changed. It must be demonstrated that the smaller test samples used in an irradiated study will adequately represent larger composite tubes used for control rod applications. To accomplish this, two different test programs are being implemented to establish that small, flat test specimens are representative of the mechanical response for large, cylindrical composite tubes: a size effect study and a geometry effect study.

  6. Structure and properties of diamond and diamond-like films

    SciTech Connect

    Clausing, R.E.

    1993-01-01

    This section is broken into four parts: (1) introduction, (2) natural IIa diamond, (3) importance of structure and composition, and (4) control of structure and properties. Conclusions of this discussion are that properties of chemical vapor deposited diamond films can compare favorably with natural diamond, that properties are anisotropic and are a strong function of structure and crystal perfection, that crystal perfection and morphology are functions of growth conditions and can be controlled, and that the manipulation of texture and thereby surface morphology and internal crystal perfection is an important step in optimizing chemically deposited diamond films for applications.

  7. Factor structure, reliability, and validity of the Therapist Response Questionnaire.

    PubMed

    Tanzilli, Annalisa; Colli, Antonello; Del Corno, Franco; Lingiardi, Vittorio

    2016-04-01

    The aim of this study was to examine the stability of the factor structure and psychometric properties of the Therapist Response Questionnaire (Betan, Heim, Zittel Conklin, & Westen, 2005; Zittel Conklin & Westen, 2003), a clinician report instrument able to measure the clinician's emotional reactions to the patient in psychotherapy. A national sample of psychiatrists and clinical psychologists (N = 332) of psychodynamic and cognitive-behavioral orientation completed the Therapist Response Questionnaire, as well as the Shedler-Westen Assessment Procedure-200 (Westen & Shedler, 1999a, 1999b), to assess personality disorders and level of psychological functioning, regarding a patient currently in their care. They also administered the Symptom Checklist-90-Revised (Derogatis, 1994) to the patients. Exploratory and confirmatory factor analyses revealed 9 distinct countertransference factors that were similar to 8 dimensions identified in the original version of the measure: (a) helpless/inadequate, (b) overwhelmed/disorganized, (c) positive/satisfying, (d) hostile/angry, (e) criticized/devalued, (f) parental/protective, (g) special/overinvolved, (h) sexualized, and (i) disengaged. These scales showed excellent internal consistencies and good validity. They were especially able to capture the quality and intensity of emotional states that therapists experience while treating personality-disordered patients, as well as to better differentiate them; additionally, they tapped into the complexity of clinicians' reactions toward patients experiencing severe psychiatric symptomatology. Results seem to confirm that Therapist Response Questionnaire is a valid and reliable instrument that allows to evaluate patterns of countertransference responses in clinically sensitive and psychometrically robust ways, regardless of therapists' orientations. The clinical and research implications of these findings are addressed. (PsycINFO Database Record PMID:26389623

  8. Fiber: composition, structures, and functional properties.

    PubMed

    Sims, Ian M; Monro, John A

    2013-01-01

    Kiwifruit dietary fiber consists of cell-wall polysaccharides that are typical of the cell walls of many dicotyledonous fruits, being composed of pectic polysaccharides, hemicelluloses, and cellulose. The kiwifruit pectic polysaccharides consist of homo- and rhamnogalacturonans with various neutral, (arabino)-galactan side chains, while the hemicelluloses are mostly xyloglucan and xylan. The proportions of pectic polysaccharide, hemicellulose, and cellulose in both green 'Hayward' and 'Zespri® Gold' are similar and are little affected by in vitro exposure to gastric and small intestinal digestion. The hydration properties of the kiwifruit-swelling and water retention capacity-are also unaffected by foregut digestion, indicating that the functional properties of kiwifruit fiber survive in the foregut. However, in the hindgut, kiwifruit fiber is fermented, but whole kiwifruit consumed in association with slowly fermented fiber leads to distal displacement of fermentation, indicating that hindgut benefits of kiwifruit may result from its interaction with other dietary sources of fiber. PMID:23394983

  9. Structural response of rectilinear containment to overpressurization

    SciTech Connect

    Pfeiffer, P.A.; Kulak, R.F.

    1995-07-01

    Containment structures for nuclear reactors are the final barrier between released radionuclides and the public. Containment structures are constructed from steel, reinforced concrete, or prestressed concrete. US nuclear reactor containment geometries tend to be cylindrical with elliptical or hemispherical heads. The older Soviet designed reactors do not use a containment building to mitigate the effects of accidents. Instead, they employ a sealed set of rectilinear, interconnected compartments, collectively called the accident localization system (ALS), to reduce the release of radionuclides to the atmosphere during accidents. The purpose of this paper is to present a methodology that can be used to find the structural capacity of reinforced concrete structures. The method is applicable to both cylindrical and rectilinear geometries. As an illustrative example, the methodology is applied to a generic VVER-440/V213 design.

  10. MPOD: A Material Property Open Database linked to structural information

    NASA Astrophysics Data System (ADS)

    Pepponi, Giancarlo; Gražulis, Saulius; Chateigner, Daniel

    2012-08-01

    Inspired by the Crystallography Open Database (COD), the Material Properties Open Database (MPOD) was given birth. MPOD aims at collecting and making publicly available at no charge tensorial properties (including scalar properties) of phases and linking such properties to structural information of the COD when available. MPOD files are written with the STAR file syntax, used and developed for the Crystallographic Information Files. A dictionary containing new definitions has been written according to the Dictionary Definition Language 1, although some tricks were adopted to allow for multiple entries still avoiding ambiguousness. The initial set includes mechanical properties, elastic stiffness and compliance, internal friction; electrical properties, resistivity, dielectric permittivity and stiffness, thermodynamic properties, heat capacity, thermal conductivity, diffusivity and expansion; electromechanical properties, piezoelectricity, electrostriction, electromechanical coupling; optical properties; piezooptic and photoelastic properties; superconducting properties, critical fields, penetration and coherence lengths. Properties are reported in MPOD files where the original published paper containing the data is cited and structural and experimental information is also given. One MPOD file contains information relative to only one publication and one phase. The files and the information contained therein can also be consulted on-line at http://www.materialproperties.org.

  11. Engineering Property Prediction Tools for Tailored Polymer Composite Structures

    SciTech Connect

    Nguyen, Ba Nghiep; Foss, Peter; Wyzgoski, Michael; Trantina, Gerry; Kunc, Vlastimil; Schutte, Carol; Smith, Mark T.

    2009-12-23

    This report summarizes our FY 2009 research activities for the project titled:"Engineering Property Prediction Tools for Tailored Polymer Composite Structures." These activities include (i) the completion of the development of a fiber length attrition model for injection-molded long-fiber thermoplastics (LFTs), (ii) development of the a fatigue damage model for LFTs and its implementation in ABAQUS, (iii) development of an impact damage model for LFTs and its implementation in ABAQUS, (iv) development of characterization methods for fatigue testing, (v) characterization of creep and fatigue responses of glass-fiber/polyamide (PA6,6) and glass-fiber/polypropylene (PP), (vi) characterization of fiber length distribution along the flow length of glass/PA6,6 and glass-fiber/PP, and (vii) characterization of impact responses of glass-fiber/PA6,6. The fiber length attrition model accurately captures the fiber length distribution along the flow length of the studied glass-fiber/PP material. The fatigue damage model is able to predict the S-N and stiffness reduction data which are valuable to the fatigue design of LFTs. The impact damage model correctly captures damage accumulation observed in experiments of glass-fiber/PA6,6 plaques.Further work includes validations of these models for representative LFT materials and a complex LFT part.

  12. SSI response of a typical shear wall structure. Appendix B. In-structure response spectra comparisons. Volume 2

    SciTech Connect

    Johnson, J.J.; Schewe, E.C.; Maslenikov, O.R.

    1984-04-01

    The objectives of this study were two-fold: (1) develop building response calibration factors, i.e., factors which relate best estimate or median level response to responses calculated by selected design procedures. Soil-structure interaction was the phenomenon of interest because significant simplifications are frequently introduced in its treatment; and (2) the second objective can be viewed in the context of a question: what effect does placing an identical structure on different sites and with different foundation conditions have on structure response. The structure selected for this study is a part of the Zion AFT complex. Only the auxiliary, fuel-handling, and diesel generator buildings were studied. This structure is a connected group of shear-wall buildings constructed of reinforced concrete, typical of nuclear power plant structures. The bases of comparison for this study were structure responses: peak in-structure accelerations (27 components), and peak wall forces and moments (111 components). In-structure response spectra were also considered. This appendix contains in-structure response spectra comparisons in detail.

  13. Structural and plasmonic properties of gold nanocrystals

    NASA Astrophysics Data System (ADS)

    Sivapalan, Sean T.

    the nanoparticles. The nanoparticles were then tilted such that were oriented so that the electron beam was parallel to a major zone axis and the diffraction pattern recorded. We observed streaks at each Bragg reflection that changed depending on the shape of the nanoparticle. This is in contrast to the spots for the Bragg reflections observed for normal small area diffraction patterns of gold nanoparticles. The angles between the streaks were compared using vector analysis to theoretical simulated three dimensional models and showed good correlation. These studies indicate such a platform can be used to elucidate the structure of high-index gold nanoparticle shapes such as trisoctahedra. The as-synthesized gold nanoparticles had surface plasmon resonances that incrementally spanned the spectral region of 500-900 nm. The reporter molecules used all have an absorption maximum far from the excitation wavelength. This ensures that chemical resonant based effects are minimized and plasmonic electromagnetic effects dominate the observed signal enhancement. For gold nanorods, the highest SERS signal from six different aspect ratios was observed with absorption maxima blue-shifted from the laser excitation wavelength. This finding is in contrast to substrate measurements where the maximum observed signal is red-shifted from the laser excitation wavelength. A similar platform was used to compare the effects of changing the nanoparticle shape on the observed SERS enhancement. We synthesized trisoctahedral, cubic and spherical geometries with electronic absorption maxima that overlapped within 3 nm. The relative SERS enhancement with 785 nm excitation was compared to theoretical simulations using finite element analysis. The observed signal intensities correlated well to the theory, suggesting the electromagnetic fields focused towards sharp edges and corners dominated the spectral response. The final chapters of this thesis are tailored towards understanding the distance

  14. Aeroelastic Stability and Response of Rotating Structures

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.; Reddy, T. S. R.

    1998-01-01

    A summary of the work performed from 1996 to 1997 is presented. More details can be found in the cited references. This grant led to the development of aeroelastic analyses methods for predicting flutter and forced response in fans, compressors, and turbines using computational

  15. Aeroelastic Stability & Response of Rotating Structures

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.; Reddy, T. S. R.

    2001-01-01

    A summary of the work performed under NASA grant NCC3-605 is presented. More details can be found in the cited references. This grant led to the development of relatively faster aeroelastic analyses methods for predicting flutter and forced response in fans, compressors, and turbines using computational fluid dynamic (CFD) methods.

  16. Electronic structure and optical properties of graphene/stanene heterobilayer.

    PubMed

    Chen, Xianping; Meng, Ruishen; Jiang, Junke; Liang, Qiuhua; Yang, Qun; Tan, Chunjian; Sun, Xiang; Zhang, Shengli; Ren, Tianling

    2016-06-28

    The structural, electronic and optical properties of the graphene hybrid with stanene, the tin counterpart of graphene, are investigated by means of density functional calculation with the observation of band gap opening and enhanced visible light response. The lattice mismatch between graphene and stanene is taken into consideration and several stacking methods for model construction are proposed to study the possible effects. The Dirac feature can be observed in this bilayer system with relatively stronger interlayer interaction than weak van der Waals forces, which is ascribed to the unsaturated p orbital of stanene. Despite the mutual semi-metal nature of graphene and stanene, it is significant to note a band gap opening and the electrical neutrality of the bilayer. The combination of high carrier mobility of graphene and the excellent spin Hall effect of stanene is expected to coexist in the bilayer structure. In addition, we found that the stanene monolayer has a relatively lower work function than graphene and more importantly, it exhibits more pronounced optical absorption than graphene. The results indicate that a graphene/stanene heterobilayer will facilitate the performance of stanene related spintronic devices and is therefore a good candidate for photoelectronic devices. PMID:27253913

  17. Handling properties of diverse automobiles and correlation with full scale response data. [driver/vehicle response to aerodynamic disturbances

    NASA Technical Reports Server (NTRS)

    Hoh, R. H.; Weir, D. H.

    1973-01-01

    Driver/vehicle response and performance of a variety of vehicles in the presence of aerodynamic disturbances are discussed. Steering control is emphasized. The vehicles include full size station wagon, sedan, compact sedan, van, pickup truck/camper, and wagon towing trailer. Driver/vehicle analyses are used to estimate response and performance. These estimates are correlated with full scale data with test drivers and the results are used to refine the driver/vehicle models, control structure, and loop closure criteria. The analyses and data indicate that the driver adjusts his steering control properties (when he can) to achieve roughly the same level of performance despite vehicle variations. For the more disturbance susceptible vehicles, such as the van, the driver tightens up his control. Other vehicles have handling dynamics which cause him to loosen his control response, even though performance degrades.

  18. Effect of processing on Polymer/Composite structure and properties

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Advances in the vitality and economic health of the field of polymer forecasting are discussed. A consistent and rational point of view which considers processing as a participant in the underlying triad of relationships which comprise materials science and engineering is outlined. This triad includes processing as it influences material structure, and ultimately properties. Methods in processing structure properties, polymer science and engineering, polymer chemistry and synthesis, structure and modification and optimization through processing, and methods of melt flow modeling in processing structure property relations of polymer were developed. Mechanical properties of composites are considered, and biomedical materials research to include polymer processing effects are studied. An analysis of the design technology of advances graphite/epoxy composites is also reported.

  19. Relating Dynamic Properties to Atomic Structure in Metallic Glasses

    SciTech Connect

    Sheng, H.W.; Ma, E.; Kramer, Matthew J.

    2012-07-18

    Atomic packing in metallic glasses is not completely random but displays various degrees of structural ordering. While it is believed that local structures profoundly affect the properties of glasses, a fundamental understanding of the structure–property relationship has been lacking. In this article, we provide a microscopic picture to uncover the intricate interplay between structural defects and dynamic properties of metallic glasses, from the perspective of computational modeling. Computational methodologies for such realistic modeling are introduced. Exploiting the concept of quasi-equivalent cluster packing, we quantify the structural ordering of a prototype metallic glass during its formation process, with a new focus on geometric measures of subatomic “voids.” Atomic sites connected with the voids are found to be crucial in terms of understanding the dynamic, including vibrational and atomic transport, properties. Normal mode analysis is performed to reveal the structural origin of the anomalous boson peak (BP) in the vibration spectrum of the glass, and its correlation with atomic packing cavities. Through transition-state search on the energy landscape of the system, such structural disorder is found to be a facilitating factor for atomic diffusion, with diffusion energy barriers and diffusion pathways significantly varying with the degree of structural relaxation/ordering. The implications of structural defects for the mechanical properties of metallic glasses are also discussed.

  20. Bio-inspired fabrication of stimuli-responsive photonic crystals with hierarchical structures and their applications

    NASA Astrophysics Data System (ADS)

    Lu, Tao; Peng, Wenhong; Zhu, Shenmin; Zhang, Di

    2016-03-01

    When the constitutive materials of photonic crystals (PCs) are stimuli-responsive, the resultant PCs exhibit optical properties that can be tuned by the stimuli. This can be exploited for promising applications in colour displays, biological and chemical sensors, inks and paints, and many optically active components. However, the preparation of the required photonic structures is the first issue to be solved. In the past two decades, approaches such as microfabrication and self-assembly have been developed to incorporate stimuli-responsive materials into existing periodic structures for the fabrication of PCs, either as the initial building blocks or as the surrounding matrix. Generally, the materials that respond to thermal, pH, chemical, optical, electrical, or magnetic stimuli are either soft or aggregate, which is why the manufacture of three-dimensional hierarchical photonic structures with responsive properties is a great challenge. Recently, inspired by biological PCs in nature which exhibit both flexible and responsive properties, researchers have developed various methods to synthesize metals and metal oxides with hierarchical structures by using a biological PC as the template. This review will focus on the recent developments in this field. In particular, PCs with biological hierarchical structures that can be tuned by external stimuli have recently been successfully fabricated. These findings offer innovative insights into the design of responsive PCs and should be of great importance for future applications of these materials.

  1. Hierarchical photonic structured stimuli-responsive materials as high-performance colorimetric sensors

    NASA Astrophysics Data System (ADS)

    Lu, Tao; Zhu, Shenmin; Chen, Zhixin; Wang, Wanlin; Zhang, Wang; Zhang, Di

    2016-05-01

    Hierarchical photonic structures in nature are of special interest because they can be used as templates for fabrication of stimuli-responsive photonic crystals (PCs) with unique structures beyond man-made synthesis. The current stimuli-responsive PCs templated directly from natural PCs showed a very weak external stimuli response and poor durability due to the limitations of natural templates. Herein, we tackle this problem by chemically coating functional polymers, polyacrylamide, on butterfly wing scales which have hierarchical photonic structures. As a result of the combination of the strong water absorption properties of the polyacrylamide and the PC structures of the butterfly wing scales, the designed materials demonstrated excellent humidity responsive properties and a tremendous colour change. The colour change is induced by the refractive index change which is in turn due to the swollen nature of the polymer when the relative humidity changes. The butterfly wing scales also showed an excellent durability which is due to the chemical bonds formed between the polymer and wing scales. The synthesis strategy provides an avenue for the promising applications of stimuli-responsive PCs with hierarchical structures.Hierarchical photonic structures in nature are of special interest because they can be used as templates for fabrication of stimuli-responsive photonic crystals (PCs) with unique structures beyond man-made synthesis. The current stimuli-responsive PCs templated directly from natural PCs showed a very weak external stimuli response and poor durability due to the limitations of natural templates. Herein, we tackle this problem by chemically coating functional polymers, polyacrylamide, on butterfly wing scales which have hierarchical photonic structures. As a result of the combination of the strong water absorption properties of the polyacrylamide and the PC structures of the butterfly wing scales, the designed materials demonstrated excellent humidity

  2. Structural and electronic properties of sodium nanoclusters

    NASA Astrophysics Data System (ADS)

    Perez, Luis A.; Reyes-Nava, Juan A.; Garzon, Ignacio L.

    2006-03-01

    Recent advances on mass selection of sodium nanoclusters and their characterization by photoemission electron spectroscopy [1] have given useful data for a variety of clusters sizes. These data may lead to assignments of the relevant structures by comparing the measured photoelectron spectra (PES) with the electronic density of states (DOS) obtained from DFT calculations. In this work, the lowest energy structures modeled by the many-body Gupta potential, are obtained by using molecular dynamics simulations for Nan (n= 178, 204, 271, 298-300, 309). DFT calculations were then performed for neutral, positively- and negatively-charged Nan clusters. A comparison between the DOS of clusters of the same size but different charge will be presented, as well as between the available experimental PES and the theoretical obtained DOS.[1] H. Haberland, T. Hippler, J. Donges, O. Kostko, M. Schmidt, B. von Issendorff, Phys. Rev. Lett. 94, 035701 (2005).

  3. Processing, structure, and properties of nanostructured multifunctional tribological coatings.

    PubMed

    Lin, Jianliang; Park, In-Wook; Mishra, Brajendra; Pinkas, Malki; Moore, John J; Anton, Jennifer M; Kim, Kwang Ho; Voevodin, Andrey A; Levashov, Evgeny A

    2009-07-01

    . Applying higher pulse frequency and longer reverse time (lower duty cycle) will result in higher ion energy and ion flux in the plasma, which can be utilized to improve the film structure and properties. For example, optimum properties of the TiC-a:C coating were a hardness of 35 to 40 GPa and a COF of 0.2 to 0.22 for moderate maximum ion energies of 70 to 100 eV, and a super high hardness of 41 GPa and low wear rate of 3.41 x 10(-6) mm3N(-1) m(-1) was obtained for Cr-Al-N coatings deposited with a maximum ion energy of 122 eV. These conditions can be achieved by adjusting the pulsing parameters and target voltages. However, the pulsed ion energy together with the applied substrate bias are need to be carefully controlled in order to avoid excessive ion bombardment (e.g., the maximum ion energy is larger than 180 eV in the current study), which will responsible for an increase in point and line defects, and high residual stress in the crystalline structure. PMID:19916411

  4. Response properties of pigeon otolith afferents to linear acceleration

    NASA Technical Reports Server (NTRS)

    Si, X.; Angelaki, D. E.; Dickman, J. D.

    1997-01-01

    In the present study, the sensitivity to sinusoidal linear accelerations in the plane of the utricular macula was tested in afferents. The head orientation relative to the translation axis was varied in order to determine the head position that elicited the maximal and minimal responses for each afferent. The response gain and phase values obtained to 0.5-Hz and 2-Hz linear acceleration stimuli were then plotted as a function of head orientation and a modified cosine function was fit to the data. From the best-fit cosine function, the predicted head orientations that would produce the maximal and minimal response gains were estimated. The estimated maximum response gains to linear acceleration in the utricular plane for the afferents varied between 75 and 1420 spikes s-1 g-1. The mean maximal gains for all afferents to 0.5-Hz and 2-Hz sinusoidal linear acceleration stimuli were 282 and 367 spikes s-1 g-1, respectively. The minimal response gains were essentially zero for most units. The response phases always led linear acceleration and remained constant for each afferent, regardless of head orientation. These response characteristics indicate that otolith afferents are cosine tuned and behave as one-dimensional linear accelerometers. The directions of maximal sensitivity to linear acceleration for the afferents varied throughout the plane of the utricle; however, most vectors were directed out of the opposite ear near the interaural axis. The response dynamics of the afferents were tested using stimulus frequencies ranging between 0.25 Hz and 10 Hz (0.1 g peak acceleration). Across stimulus frequencies, most afferents had increasing gains and constant phase values. These dynamic properties for individual afferents were fit with a simple transfer function that included three parameters: a mechanical time constant, a gain constant, and a fractional order distributed adaptation operator.

  5. Structure, (governance) and health: an unsolicited response

    PubMed Central

    Reidpath, Daniel D; Allotey, Pascale

    2006-01-01

    Background In a recently published article, it was suggested that governance was the significant structural factor affecting the epidemiology of HIV. This suggestion was made notwithstanding the observed weak correlation between governance and HIV prevalence (r = .2). Unfortunately, the paper raised but left unexamined the potentially more important questions about the relationship between the broader health of populations and structural factors such as the national economy and physical infrastructure. Methods Utilizing substantially the same data sources as the original article, the relationship between population health (healthy life expectancy) and three structural factors (access to improved water, GDP per capita, and governance) were examined in each of 176 countries. Results Governance was found to be significantly correlated with population health, as were GDP per capita, and access to improved water. They were also found to be significantly correlated with each other. Conclusion The findings are discussed with reference to the growing interest in structural factors as an explanation for population health outcomes, and the relatively weak relationship between governance and HIV prevalence. PMID:16978401

  6. Structure-property study of keto-ether polyimides

    NASA Technical Reports Server (NTRS)

    Dezern, James F.; Croall, Catharine I.

    1991-01-01

    As part of an on-going effort to develop an understanding of how changes in the chemical structure affect polymer properties, an empirical study was performed on polyimides containing only ether and/or carbonyl connecting groups in the polymer backbone. During the past two decades the structure-property relationships in linear aromatic polyimides have been extensively investigated. More recently, work has been performed to study the effect of isomeric attachment of keto-ether polyimides on properties such as glass transition temperature and solubility. However, little work has been reported on the relation of polyimide structure to mechanical properties. The purpose of this study was to determine the effect of structural changes in the backbone of keto-ether polyimides on their mechanical properties, specifically, unoriented thin film tensile properties. This study was conducted in two stages. The purpose of the initial stage was to examine the physical and mechanical properties of a representative group (four) of polyimide systems to determine the optimum solvent and cure cycle requirements. These optimum conditions were then utilized in the second stage to prepare films of keto-ether polyimides which were evaluated for mechanical and physical properties. All of the polyimides were prepared using isomers of oxydianiline (ODA) and diaminobenzophenone (DABP) in combination with 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-oxydiphthalic anhydride (ODPA).

  7. Structural properties of rare earth chalcogenides

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Ramakant; Bhardwaj, Purvee; Singh, Sadhna

    2016-05-01

    The pressure induced NaCl (B1) to CsCl (B2) structural phase transition of rare earth mono-chalcogenide (PuTe) has been investigated in this paper. A modified interaction potential model (MIPM) (including the covalency effect) has been developed. Phase transition pressures are associated with a sudden collapse in volume. The phase transition pressures and associated volume collapses obtained from present potential model show a generally good agreement with available experimental data than others.

  8. Structure and properties of detonation soot particles

    SciTech Connect

    MalKOV, I.Y.; Titiov, V.M.

    1996-05-01

    The influence of TNT/RDX (50/50) detonation parameters and conservation conditions of detonation products during their expansion in hermetic detonation chamber on structure and phase composition of the detonation carbon has been considered. Systematic studies made it possible to establish the real structure of detonation carbon depending on experimental conditions. It has been shown that both during explosion in a chamber and thermal annealing in vacuum the nanoparticles of diamond have the tendency to transform not into graphite particles, as was assumed earlier, but into onionlike structures of fullerene series, composed of closed concentric carbon shells, the so-called carbon onions. The nanometer carbon particles have been obtained which comprise a diamond nucleus surrounded by a graphite-like mantle composed of quasi-spherical carbon shells which are the intermediate products of annealing of nanodiamond. The influence of initial sizes of the diamond particles and temperature on the annealing of diamond has been studied. {copyright} {ital 1996 American Institute of Physics.}

  9. Structure and Soot Formation Properties of Laminar Flames

    NASA Technical Reports Server (NTRS)

    El-Leathy, A. M.; Xu, F.; Faeth, G. M.

    2001-01-01

    Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science for several reasons: soot emissions are responsible for more deaths than any other combustion-generated pollutant, thermal loads due to continuum radiation from soot limit the durability of combustors, thermal radiation from soot is mainly responsible for the growth and spread of unwanted fires, carbon monoxide emissions associated with soot emissions are responsible for most fire deaths, and limited understanding of soot processes in flames is a major impediment to the development of computational combustion. Motivated by these observations, soot processes within laminar premixed and nonpremixed (diffusion) flames are being studied during this investigation. The study is limited to laminar flames due to their experimental and computational tractability, noting the relevance of these results to practical flames through laminar flamelet concepts. Nonbuoyant flames are emphasized because buoyancy affects soot processes in laminar diffusion flames whereas effects of buoyancy are small for most practical flames. This study involves both ground- and space-based experiments, however, the following discussion will be limited to ground-based experiments because no space-based experiments were carried out during the report period. The objective of this work was to complete measurements in both premixed and nonpremixed flames in order to gain a better understanding of the structure of the soot-containing region and processes of soot nucleation and surface growth in these environments, with the latter information to be used to develop reliable ways of predicting soot properties in practical flames. The present discussion is brief, more details about the portions of the investigation considered here can be found in refs. 8-13.

  10. 41 CFR 102-37.90 - What are GSA's responsibilities in the donation of surplus property?

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... responsibilities in the donation of surplus property? 102-37.90 Section 102-37.90 Public Contracts and Property... PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY General Services Administration (GSA) § 102-37.90 What are GSA's responsibilities in the donation of surplus property? The General Services...

  11. 41 CFR 102-37.90 - What are GSA's responsibilities in the donation of surplus property?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... responsibilities in the donation of surplus property? 102-37.90 Section 102-37.90 Public Contracts and Property... PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY General Services Administration (GSA) § 102-37.90 What are GSA's responsibilities in the donation of surplus property? The General Services...

  12. 41 CFR 102-37.90 - What are GSA's responsibilities in the donation of surplus property?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... responsibilities in the donation of surplus property? 102-37.90 Section 102-37.90 Public Contracts and Property... PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY General Services Administration (GSA) § 102-37.90 What are GSA's responsibilities in the donation of surplus property? The General Services...

  13. 41 CFR 102-37.90 - What are GSA's responsibilities in the donation of surplus property?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... responsibilities in the donation of surplus property? 102-37.90 Section 102-37.90 Public Contracts and Property... PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY General Services Administration (GSA) § 102-37.90 What are GSA's responsibilities in the donation of surplus property? The General Services...

  14. 41 CFR 102-37.90 - What are GSA's responsibilities in the donation of surplus property?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... responsibilities in the donation of surplus property? 102-37.90 Section 102-37.90 Public Contracts and Property... PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY General Services Administration (GSA) § 102-37.90 What are GSA's responsibilities in the donation of surplus property? The General Services...

  15. Acid-responsive properties of fibrils from heat-induced whey protein concentrate.

    PubMed

    Xu, Hong-Hua; Wang, Jing; Dong, Shi-Rong; Cheng, Wen; Kong, Bao-Hua; Tan, Jun-Yan

    2016-08-01

    The heat-induced fibrils of whey protein concentrate (WPC) have demonstrated an acid-responsive property; that is, the fibrils went through formation-depolymerization-reformation as pH was adjusted to 1.8, 6.5, and back to 1.8. We investigated the microstructure, driving force, and thermal stability of 3.0% (wt) WPC nanofibrils adjusted between pH 6.5 and 1.8 twice. The results showed that the nanofibrils had acid-responsive properties and good thermal stability after reheating for 10h at 90°C and adjusting pH from 1.8 to 6.5 to 1.8. The content of WPC fibril aggregates was not much different with the prolongation of heating times during pH variation. Although the nanofibrils' structure could be destroyed only by changing the pH, the essence of this destruction might only form fiber fragments, polymers that would restore a fibrous structure upon returning to pH 1.8. A described model for the acid-responsive assembly of fibrils of WPC was proposed. The fibrils went through formation-depolymerization-reformation by weaker noncovalent interactions (surface hydrophobicity) as pH changed from 1.8 to 6.5 back to 1.8. However, the fibrils lost the acid-responsive properties because much more S-S (disulfide) formation occurred when the solution was adjusted to pH 6.5 and reheated. Meanwhile, fibrils still possessed acid-responsive properties when reheated at pH 1.8, and the content of fibrils slightly increased with a further reduction of α-helix structure. PMID:27265171

  16. Starch: Structure, Properties, Chemistry, and Enzymology

    NASA Astrophysics Data System (ADS)

    Robyt, John F.

    Starch is a very important and widely distributed natural product, occurring in the leaves of green plants, seeds, fruits, stems, roots, and tubers. It serves as the chemical storage form of the energy of the sun and is the primary source of energy for the organisms on the Earth. Starch is composed of two kinds of polysaccharides, amylose and amylopectin, exclusively composed of D-glucose residues with α-(1→4) linkages in a linear amylose and α-(1→4) linkages and ˜5% α-(1→6) branch linkages in amylopectin, both combined in a water-insoluble granule that is partially crystalline and whose size, shape, and morphology are dependent on its biological source. The properties, isolation, fractionation, enzymatic degradation, biosynthesis, chemical modification, and specific methods of analysis of starch are presented.

  17. Determining the Mechanical Properties of Lattice Block Structures

    NASA Technical Reports Server (NTRS)

    Wilmoth, Nathan

    2013-01-01

    Lattice block structures and shape memory alloys possess several traits ideal for solving intriguing new engineering problems in industries such as aerospace, military, and transportation. Recent testing at the NASA Glenn Research Center has investigated the material properties of lattice block structures cast from a conventional aerospace titanium alloy as well as lattice block structures cast from nickel-titanium shape memory alloy. The lattice block structures for both materials were sectioned into smaller subelements for tension and compression testing. The results from the cast conventional titanium material showed that the expected mechanical properties were maintained. The shape memory alloy material was found to be extremely brittle from the casting process and only compression testing was completed. Future shape memory alloy lattice block structures will utilize an adjusted material composition that will provide a better quality casting. The testing effort resulted in baseline mechanical property data from the conventional titanium material for comparison to shape memory alloy materials once suitable castings are available.

  18. Interply layer degradation effects on composite structural response

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Williams, G. C.

    1983-01-01

    Recent research activities at NASA Lewis Research Center to computationally evaluate the effects of interply layer progressive weakening (degradation) on the structural response of a composite beam are summarized. The structural responses of interest include: (1) bending, (2) buckling, (3) free vibrations, (4) periodic excitation, and (5) impact. Finite element analysis was used for the computational evaluations. The interply layer degradation effects on the various structural responses were determined and assessed as a function of the interply layer modulus varying from 1 million psi down to 1000 psi and even lower for some limiting cases. The results obtained show that the interply layer degradation has generally negligible effects on composite structural response and, therefore, structural integrity, unless the interply layer modulus degrades to about 10,000 psi or less.

  19. Material properties from acoustic radiation force step response

    PubMed Central

    Orescanin, Marko; Toohey, Kathleen S.; Insana, Michael F.

    2009-01-01

    An ultrasonic technique for estimating viscoelastic properties of hydrogels, including engineered biological tissues, is being developed. An acoustic radiation force is applied to deform the gel locally while Doppler pulses track the induced movement. The system efficiently couples radiation force to the medium through an embedded scattering sphere. A single-element, spherically-focused, circular piston element transmits a continuous-wave burst to suddenly apply and remove a radiation force to the sphere. Simultaneously, a linear array and spectral Doppler technique are applied to track the position of the sphere over time. The complex shear modulus of the gel was estimated by applying a harmonic oscillator model to measurements of time-varying sphere displacement. Assuming that the stress-strain response of the surrounding gel is linear, this model yields an impulse response function for the gel system that may be used to estimate material properties for other load functions. The method is designed to explore the force-frequency landscape of cell-matrix viscoelasticity. Reported measurements of the shear modulus of gelatin gels at two concentrations are in close agreement with independent rheometer measurements of the same gels. Accurate modulus measurements require that the rate of Doppler-pulse transmission be matched to a priori estimates of gel properties. PMID:19425636

  20. Structure and properties of solid surfaces

    NASA Technical Reports Server (NTRS)

    Gatos, H. C.

    1974-01-01

    Difficulties in experimental studies of crystalline surfaces are related to the fact that surface atoms have an intrinsic tendency to react with their environment. A second problem is connected with the effective thickness of surfaces, which ranges from one to several atom layers. The phenomenology of surface interactions with gases are considered, taking into account physical adsorption, chemisorption, and the oxidation of surfaces. Studies of the surface structure are discussed, giving attention to field emission microscopy, field-ion microscopy, electron diffraction techniques, Auger spectroscopy, scanning electron microscopy, electron probe microanalysis, ion microprobe methods, and low-energy backscattering spectroscopy. Investigations of semiconductor surfaces are also described.

  1. Surface structure and electronic properties of materials

    NASA Technical Reports Server (NTRS)

    Siekhaus, W. J.; Somorjai, G. A.

    1975-01-01

    A surface potential model is developed to explain dopant effects on chemical vapor deposition. Auger analysis of the interaction between allotropic forms of carbon and silicon films has shown Si-C formation for all forms by glassy carbon. LEED intensity measurements have been used to determine the mean square displacement of surface atoms of silicon single crystals, and electron loss spectroscopy has shown the effect of structure and impurities on surface states located within the band gap. A thin film of Al has been used to enhance film crystallinity at low temperature.

  2. Aeroelastic Stability and Response of Rotating Structures

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.; Reddy, Tondapu

    2004-01-01

    A summary of the work performed under NASA grant is presented. More details can be found in the cited references. This grant led to the development of relatively faster aeroelastic analysis methods for predicting flutter and forced response in fans, compressors, and turbines using computational fluid dynamic (CFD) methods. These methods are based on linearized two- and three-dimensional, unsteady, nonlinear aerodynamic equations. During the period of the grant, aeroelastic analysis that includes the effects of uncertainties in the design variables has also been developed.

  3. The structural origin of anomalous properties of liquid water

    PubMed Central

    Nilsson, Anders; Pettersson, Lars G. M.

    2015-01-01

    Water is unique in its number of unusual, often called anomalous, properties. When hot it is a normal simple liquid; however, close to ambient temperatures properties, such as the compressibility, begin to deviate and do so increasingly on further cooling. Clearly, these emerging properties are connected to its ability to form up to four well-defined hydrogen bonds allowing for different local structural arrangements. A wealth of new data from various experiments and simulations has recently become available. When taken together they point to a heterogeneous picture with fluctuations between two classes of local structural environments developing on temperature-dependent length scales. PMID:26643439

  4. Radar response from vegetation with nodal structure

    NASA Technical Reports Server (NTRS)

    Blanchard, B. J.; Oneill, P. E.

    1984-01-01

    Radar images from the SEASAT synthetic aperture radar (SAR) produced unusually high returns from corn and sorghum fields, which seem to indicate a correlation between nodal separation in the stalk and the wavelength of the radar. These images also show no difference in return from standing or harvested corn. Further investigation using images from the Shuttle Imaging Radar (SIR-A) substantiated these observations and showed a degradation of the high return with time after harvest. From portions of corn and sweet sorghum stalks that were sampled to measure stalk water content, it was determined that near and after maturity the water becomes more concentrated in the stalk nodes. The stalk then becomes a linear sequence of alternating dielectrics as opposed to a long slender cylinder with uniform dielectric properties.

  5. Auxetic oesophageal stents: structure and mechanical properties.

    PubMed

    Ali, Murtaza Najabat; Busfield, James J C; Rehman, Ihtesham U

    2014-02-01

    Oesophageal cancer is the ninth leading cause of malignant cancer death and its prognosis remains poor, ranking as the sixth most frequent cause of death in the world. This research work aims to adopt an Auxetic (rotating-squares) geometry device, that had previously been examined theoretically and analysed by Grima and Evans (J Mater Sci Lett 19(17):1563-1565, 2000), to produce a novel Auxetic oesophageal stent and stent-grafts relevant to the palliative treatment of oesophageal cancer and also for the prevention of dysphagia. This paper discusses the manufacture of a small diameter Auxetic oesophageal stent and stent-graft. The oral deployment of such an Auxetic stent would be simplest if a commercial balloon dilatational catheter was used as this obviates the need for an expensive dedicated delivery system. A novel manufacturing route was employed in this research to develop both Auxetic films and Auxetic oesophageal stents, which ranged from conventional subtractive techniques to a new additive manufacturing method. Polyurethane was selected as a material for the fabrication of Auxetic films and Auxetic oesophageal stents because of its good biocompatibility and non-toxicological properties. The Auxetic films were later used for the fabrication of seamed Auxetic oesophageal stents. The flexible polyurethane tubular grafts were also attached to the inner luminal side of the seamless Auxetic oesophageal stents, in order to prevent tumour in-growth. Scanning electron microscopy was used to conduct surface morphology study by using different Auxetic specimens developed from different conventional and new additive manufacturing techniques. Tensile testing of the Auxetic films was performed to characterise their mechanical properties. The stent expansion tests of the Auxetic stents were done to analyse the longitudinal extension and radial expansion of the Auxetic stent at a range of radial pressures applied by the balloon catheter, and to also identify the pressure

  6. Engineering the Structure and Properties of DNA-Nanoparticle Superstructures Using Polyvalent Counterions.

    PubMed

    Chou, Leo Y T; Song, Fayi; Chan, Warren C W

    2016-04-01

    DNA assembly of nanoparticles is a powerful approach to control their properties and prototype new materials. However, the structure and properties of DNA-assembled nanoparticles are labile and sensitive to interactions with counterions, which vary with processing and application environment. Here we show that substituting polyamines in place of elemental counterions significantly enhanced the structural rigidity and plasmonic properties of DNA-assembled metal nanoparticles. These effects arose from the ability of polyamines to condense DNA and cross-link DNA-coated nanoparticles. We further used polyamine wrapped DNA nanostructures as structural templates to seed the growth of polymer multilayers via layer-by-layer assembly, and controlled the degree of DNA condensation, plasmon coupling efficiency, and material responsiveness to environmental stimuli by varying polyelectrolyte composition. These results highlight counterion engineering as a versatile strategy to tailor the properties of DNA-nanoparticle assemblies for various applications, and should be applicable to other classes of DNA nanostructures. PMID:26942662

  7. Response of structural materials to radiation environments

    SciTech Connect

    Czajkowski, C.J.

    1997-12-01

    An evaluation of proton and neutron damage to aluminum, stainless steel, nickel alloys, and various aluminum alloys has been performed. The proton studies were conducted at energies of 200 MeV, 800 MeV, and 23.5 GeV. The proton studies consisted of evaluation and characterization of proton-irradiated window/target materials from accelerators and comparison to nonirradiated archival materials. The materials evaluated for the proton irradiations included 99.9999 wt% aluminum, 1100 aluminum, 5052 aluminum, 304 stainless steel, and inconel 718. The neutron damage research centered on 6061 T-6 aluminum which was obtained from a control-rod follower from the Brookhaven National Laboratory`s (BNL) High Flux Beam Reactor (HFBR). This material had received thermal neutron fluence up to {approximately}4 {times} 10{sup 23} n/cm{sup 2}. The possible effects of thermal-to-fast neutron flux ratios are discussed. The increases in tensile strength in the proton-irradiated materials is shown to be the result of atomic displacements. These displacements cause interstitials and vacancies which aggregate into defect clusters which result in radiation hardening of the materials. Production of gas (helium) in the grain boundaries of proton irradiated 99.9999 wt% aluminum is also discussed. The major factor contributing to the mechanical-property changes in the neutron-irradiated 6061 T-6 aluminum is the production of transmutation products formed by interactions of the aluminum with thermal neutrons. The metallurgical and mechanical-property evaluations for the research consisted of electron microscopy (both scanning and transmission), tensile testing, and microhardness testing.

  8. Gogny HFB prediction of nuclear structure properties

    SciTech Connect

    Goriely, S.; Hilaire, S.; Girod, M.

    2011-10-28

    Large scale mean field calculations from proton to neutron drip lines have been performed using the Hartree-Fock-Bogoliubov method based on the Gogny nucleon-nucleon effective interaction. This extensive study has shown the ability of the method to reproduce bulk nuclear structure data available experimentally. This includes nuclear masses, radii, matter densities, deformations, moment of inertia as well as collective mode (low energy and giant resonances). In particular, the first mass table based on a Gogny-Hartree-Fock-Bogolyubov calculation including an explicit and coherent account of all the quadrupole correlation energies is presented. The rms deviation with respect to essentially all the available mass data is 798 keV. Nearly 8000 nuclei have been studied under the axial symmetry hypothesis and going beyond the mean-field approach.

  9. Analysis of waveguiding properties of VCSEL structures

    SciTech Connect

    Erteza, I.A.

    1996-09-01

    In this paper, the authors explore the feasibility of using the distributed Bragg reflector, grown on the substrate for a VCSEL (Vertical Cavity Surface Emitting Laser), to provide waveguiding within the substrate. This waveguiding could serve as an interconnection among VCSELs in an array. Before determining the feasibility of waveguide interconnected VCSELs, two analysis methods are presented and evaluated for their applicability to this problem. The implementations in Mathematica of both these methods are included. Results of the analysis show that waveguiding in VCSEL structures is feasible. Some of the many possible uses of waveguide interconnected VCSELs are also briefly discussed. The tools and analysis presented in this report can be used to evaluate such system concepts and to do detailed design calculations.

  10. Structure property relations in glassy-semicrystalline block copolymers

    NASA Astrophysics Data System (ADS)

    Khanna, Vikram

    The ability of block copolymers to segregate into nanoscale morphologies makes them a versatile class of engineering materials. This work investigates the relation between the block copolymer structure and its mechanical properties, film dynamics and diffusion kinetics. The first part investigates the influence of structure on the mechanical properties of poly(cyclohexylethylene)-poly(ethylene) (PCHE-PE) block copolymer films. For lamellar block copolymers the mechanical properties depend significantly on the chain architecture (diblock, triblock and pentablock). Diblock copolymer films show complete failure at small strains and pentablock copolymer films show the toughest, response. Moreover, the orientation of the cylinders in a cylinder forming pentablock copolymer affects the toughness of the block copolymer films. In the second part, the effect of surface energy and chain architecture on the orientation of microdomains in the same block copolymer films is investigated. Cylindrical and lamellar triblock copolymers with a PE midblock orient their microdomains normal to the surface. However, a lamellar diblock copolymer prefers a parallel orientation of the sheets with an E surface. Moreover, a cylindrical triblock copolymer with a reduced surface energy poly(ethylene-butylene) midblock orders with the cylinder domains oriented parallel to the surface. Self-consistent field theory calculations suggest that the entropic cost of forming a wetting layer comprised entirely of looping blocks for the triblock architecture, a constraint absent in diblock copolymers, stabilizes the perpendicular orientation. Thus in triblock copolymers, parallel orientations are only stabilized when the surface energy of the midblock is small enough to compensate for this conformational penalty. Finally, a study of the diffusion kinetics of cylinder forming poly(styrene)-poly(ethylene) triblock (SES) and pentablock (SESES) copolymers suggests that for similar molecular weights SESES

  11. Electronic and structural properties of metallic microclusters

    SciTech Connect

    Maiti, A.

    1992-04-01

    The first part of this thesis presents a first-order pseudopotential calculation at T=O of the total energy of small sodium clusters of size N<800. The calculation is based on a local-pseudopotential scheme and local-density correlation and exchange. A temperature-size (T-N) phase-diagram is then derived using the T=O results and Lindemann`s criterion for melting. The phase-diagram contains three regions of stability: (1) a liquid (jellium) phase at temperatures above the melting line T{sub M}(N) where cluster-stability occurs at electronic magic numbers: (2) a phase related to complete geometrical shells of body-centered-cubic structure at temperatures below the melting line; and (3) a close-packed structure at very low temperatures and sufficiently large N. The melting line drops to T{sub M}(N)=O for N<65, where electronic magic numbers are stable even at T=O. The phase diagram reduces asymptotically to the known phases of sodium as N{yields}{infinity}, including the known martensitic transformation at T{approximately}5 K. The second and the last part of this thesis consists of a study of small-cluster many-body systems by means of an on-site ``local`` chemical potential which allows the continuous variation of local electron-density. This method yields a criterion to distinguish particular features of a small cluster that are likely to survive in the large-N thermodynamic limit from those discontinuities that arise only from finite-size effects.

  12. Electronic and structural properties of metallic microclusters

    SciTech Connect

    Maiti, A.

    1992-04-01

    The first part of this thesis presents a first-order pseudopotential calculation at T=O of the total energy of small sodium clusters of size N<800. The calculation is based on a local-pseudopotential scheme and local-density correlation and exchange. A temperature-size (T-N) phase-diagram is then derived using the T=O results and Lindemann's criterion for melting. The phase-diagram contains three regions of stability: (1) a liquid (jellium) phase at temperatures above the melting line T{sub M}(N) where cluster-stability occurs at electronic magic numbers: (2) a phase related to complete geometrical shells of body-centered-cubic structure at temperatures below the melting line; and (3) a close-packed structure at very low temperatures and sufficiently large N. The melting line drops to T{sub M}(N)=O for N<65, where electronic magic numbers are stable even at T=O. The phase diagram reduces asymptotically to the known phases of sodium as N{yields}{infinity}, including the known martensitic transformation at T{approximately}5 K. The second and the last part of this thesis consists of a study of small-cluster many-body systems by means of an on-site local'' chemical potential which allows the continuous variation of local electron-density. This method yields a criterion to distinguish particular features of a small cluster that are likely to survive in the large-N thermodynamic limit from those discontinuities that arise only from finite-size effects.

  13. Determination of HART I Blade Structural Properties by Laboratory Testing

    NASA Technical Reports Server (NTRS)

    Jung, Sung N.; Lau, Benton H.

    2012-01-01

    The structural properties of higher harmonic Aeroacoustic Rotor Test (HART I) blades were measured using the original set of blades tested in the German-dutch wind tunnel (DNW) in 1994. the measurements include bending and torsion stiffness, geometric offsets, and mass and inertia properties of the blade. the measured properties were compared to the estimated values obtained initially from the blade manufacturer. The previously estimated blade properties showed consistently higher stiffness, up to 30 percent for the flap bending in the blade inboard root section.

  14. An Analytical Solution for Transient Thermal Response of an Insulated Structure

    NASA Technical Reports Server (NTRS)

    Blosser, Max L.

    2012-01-01

    An analytical solution was derived for the transient response of an insulated aerospace vehicle structure subjected to a simplified heat pulse. This simplified problem approximates the thermal response of a thermal protection system of an atmospheric entry vehicle. The exact analytical solution is solely a function of two non-dimensional parameters. A simpler function of these two parameters was developed to approximate the maximum structural temperature over a wide range of parameter values. Techniques were developed to choose constant, effective properties to represent the relevant temperature and pressure-dependent properties for the insulator and structure. A technique was also developed to map a time-varying surface temperature history to an equivalent square heat pulse. Using these techniques, the maximum structural temperature rise was calculated using the analytical solutions and shown to typically agree with finite element simulations within 10 to 20 percent over the relevant range of parameters studied.

  15. Effect of wet grinding on structural properties of ball clay

    SciTech Connect

    Purohit, A. Chander, S.; Dhaka, M. S.; Hameed, A.; Singh, P.; Nehra, S. P.

    2015-05-15

    In this paper, the effect of wet grinding on structural properties of ball clay is undertaken. The wet grinding treatment was performed employing ball and vibro mills for different time spells of 2, 4, 8 and 16 hours. The structural properties were carried out using X-ray diffraction (XRD). The structure of ground samples is found to be simple cubic. The crystallographic parameters are calculated and slight change in lattice constant, inter planner spacing and particle size is observed with grinding treatment. The results are in agreement with the available literature.

  16. Spectral response of multilayer optical structures to dynamic mechanical loading

    NASA Astrophysics Data System (ADS)

    Scripka, David; LeCroy, Garrett; Summers, Christopher J.; Thadhani, Naresh N.

    2015-05-01

    A computational study of Distributed Bragg Reflectors (DBR) and Optical Microcavities (OMC) was conducted to ascertain their potential as time-resolved mesoscale sensors due to their unique structure-driven spectral characteristics. Shock wave propagation simulations of polymer-based DBRs and glass/ceramic-based OMCs were coupled with spectral response calculations to demonstrate the combined dynamic mechanical and spectral response of the structures. Clear spectral shifts in both structures are predicted as a function of dynamic loading magnitude. Potential applications of the structures include high spatial and temporal resolution surface maps of material states, and in-situ probing of material interfaces during dynamic loading.

  17. Growth, structure, morphology, and magnetic properties of Ni ferrite films

    PubMed Central

    2013-01-01

    The morphology, structure, and magnetic properties of nickel ferrite (NiFe2O4) films fabricated by radio frequency magnetron sputtering on Si(111) substrate have been investigated as functions of film thickness. Prepared films that have not undergone post-annealing show the better spinel crystal structure with increasing growth time. Meanwhile, the size of grain also increases, which induces the change of magnetic properties: saturation magnetization increased and coercivity increased at first and then decreased. Note that the sample of 10-nm thickness is the superparamagnetic property. Transmission electron microscopy displays that the film grew with a disorder structure at initial growth, then forms spinel crystal structure as its thickness increases, which is relative to lattice matching between substrate Si and NiFe2O4. PMID:23622034

  18. Cement-aggregate compatibility and structure property relationships including modelling

    SciTech Connect

    Jennings, H.M.; Xi, Y.

    1993-07-15

    The role of aggregate, and its interface with cement paste, is discussed with a view toward establishing models that relate structure to properties. Both short (nm) and long (mm) range structure must be considered. The short range structure of the interface depends not only on the physical distribution of the various phases, but also on moisture content and reactivity of aggregate. Changes that occur on drying, i.e. shrinkage, may alter the structure which, in turn, feeds back to alter further drying and shrinkage. The interaction is dynamic, even without further hydration of cement paste, and the dynamic characteristic must be considered in order to fully understand and model its contribution to properties. Microstructure and properties are two subjects which have been pursued somewhat separately. This review discusses both disciplines with a view toward finding common research goals in the future. Finally, comment is made on possible chemical reactions which may occur between aggregate and cement paste.

  19. Preliminary investigation of the frequency response and distortion properties of nonlinear image processing algorithms

    NASA Astrophysics Data System (ADS)

    Wells, Jered R.; Dobbins, James T.

    2013-03-01

    Assessment of the resolution properties of nonlinear imaging systems is a useful but challenging task. While the modulation transfer function (MTF) fully describes contrast resolution as a function of spatial frequency for linear systems, an equivalent metric does not exist for systems with significant nonlinearity. Therefore, this preliminary investigation attempts to classify and quantify the amount of scaling and distortion imposed on a given image signal as the result of a nonlinear process (nonlinear image processing algorithm). As a proof-of-concept, a median filter is assessed in terms of its principle frequency response (PFR) and distortion response (DR) functions. These metrics are derived in frequency space using a sinusoidal basis function, and it is shown that, for a narrow-band sinusoidal input signal, the scaling and distortion properties of the nonlinear filter are described exactly by PFR and DR, respectively. The use of matched sinusoidal basis and input functions accurately reveals the frequency response to long linear structures of different scale. However, when more complex (multi-band) input signals are considered, PFR and DR fail to adequately characterize the frequency response due to nonlinear interaction effects between different frequency components during processing. Overall, the results reveal the context-dependent nature of nonlinear image processing algorithm performance, and they emphasize the importance of the basis function choice in algorithm assessment. In the future, more complex forms of nonlinear systems analysis may be necessary to fully characterize the frequency response properties of nonlinear algorithms in a context-dependent manner.

  20. The structural response of a rail accelerator

    NASA Technical Reports Server (NTRS)

    Wang, S. Y.

    1983-01-01

    The transient response of a 0.4 by 0.6 cm rectangular bore rail accelerator was analyzed by a three dimensional finite element code. The copper rail deflected to a peak value of 0.08 mm in compression and then oscillated at an amplitude of 0.02 mm. Simultaneously the insulating side wall of glass fabric base, epoxy resin laminate (G-1o) was compressed to a peak value of 0.13 mm and rebounded to a steady state in extension. Projectile pinch or blowby due to the rail extension or compression, respectively, can be identified by examining the time history of the rail displacement. The effect of blowby was most significant at the side wall characterized by mm size displacement in compression. Dynamic stress calculations indicate that the G-10 supporting material behind the rail is subjected to over 21 MPa at which the G-10 could fail if the laminate was not carefully oriented. Results for a polycarbonate resin (Lexan) side wall show much larger displacements and stresses than for G-10. The tradeoff between the transparency of Lexan and the mechanical strength of G-10 for sidewall material is obvious. Displacement calculations from the modal method are smaller than the results from the direct integration method by almost an order of magnitude, because the high frequency effect is neglected.

  1. The structural response of a rail acceleration

    NASA Technical Reports Server (NTRS)

    Wang, S. Y.

    1984-01-01

    The transient response of a 0.4 by 0.6 cm rectangular bore rail accelerator was analyzed by a three dimensional finite element code. The copper rail deflected to a peak value of 0.08 mm in compression and then oscillated at an amplitude of 0.02 mm. Simultaneously the insulating side wall of glass fabric base, epoxy resin laminate (G-10) was compressed to a peak value of 0.13 mm and rebounded to a steady state in extension. Projectile pinch or blowby due to the rail extension or compression, respectively, can be identified by examining the time history of the rail displacement. The effect of blowby was most significant at the side wall characterized by mm size displacement in compression. Dynamic stress calculations indicate that the G-10 supporting material behind the rail is subjected to over 21 MPa at which the G-10 could fail if the laminate was not carefully oriented. Results for a polycarbonate resin (Lexan) side wall show much larger displacements and stresses than for G-10. The tradeoff between the transparency of Lexan and the mechanical strength of G-10 for sidewall material is obvious. Displacement calculations from the modal method are smaller than the results from the direct integration method by almost an order of magnitude, because the high frequency effect is neglected. Previously announced in STAR as N83-35412

  2. Structure-Property-Function Relationship in Humic Substances to Explain the Biological Activity in Plants

    PubMed Central

    García, Andrés Calderín; de Souza, Luiz Gilberto Ambrosio; Pereira, Marcos Gervasio; Castro, Rosane Nora; García-Mina, José María; Zonta, Everaldo; Lisboa, Francy Junior Gonçalves; Berbara, Ricardo Luis Louro

    2016-01-01

    Knowledge of the structure-property-function relationship of humic substances (HSs) is key for understanding their role in soil. Despite progress, studies on this topic are still under discussion. We analyzed 37 humic fractions with respect to their isotopic composition, structural characteristics, and properties responsible for stimulating plant root parameters. We showed that regardless of the source of origin of the carbon (C3 or C4), soil-extracted HSs and humic acids (HAs) are structurally similar to each other. The more labile and functionalized HS fraction is responsible for root emission, whereas the more recalcitrant and less functionalized HA fraction is related to root growth. Labile structures promote root stimulation at lower concentrations, while recalcitrant structures require higher concentrations to promote a similar stimulus. These findings show that lability and recalcitrance, which are derived properties of humic fractions, are related to the type and intensity of their bioactivity. In summary, the comparison of humic fractions allowed a better understanding of the relationship between the source of origin of plant carbon and the structure, properties, and type and intensity of the bioactivity of HSs in plants. In this study, scientific concepts are unified and the basis for the agronomic use of HSs is established. PMID:26862010

  3. Structure-Property-Function Relationship in Humic Substances to Explain the Biological Activity in Plants.

    PubMed

    García, Andrés Calderín; de Souza, Luiz Gilberto Ambrosio; Pereira, Marcos Gervasio; Castro, Rosane Nora; García-Mina, José María; Zonta, Everaldo; Lisboa, Francy Junior Gonçalves; Berbara, Ricardo Luis Louro

    2016-01-01

    Knowledge of the structure-property-function relationship of humic substances (HSs) is key for understanding their role in soil. Despite progress, studies on this topic are still under discussion. We analyzed 37 humic fractions with respect to their isotopic composition, structural characteristics, and properties responsible for stimulating plant root parameters. We showed that regardless of the source of origin of the carbon (C3 or C4), soil-extracted HSs and humic acids (HAs) are structurally similar to each other. The more labile and functionalized HS fraction is responsible for root emission, whereas the more recalcitrant and less functionalized HA fraction is related to root growth. Labile structures promote root stimulation at lower concentrations, while recalcitrant structures require higher concentrations to promote a similar stimulus. These findings show that lability and recalcitrance, which are derived properties of humic fractions, are related to the type and intensity of their bioactivity. In summary, the comparison of humic fractions allowed a better understanding of the relationship between the source of origin of plant carbon and the structure, properties, and type and intensity of the bioactivity of HSs in plants. In this study, scientific concepts are unified and the basis for the agronomic use of HSs is established. PMID:26862010

  4. Structure-Property-Function Relationship in Humic Substances to Explain the Biological Activity in Plants

    NASA Astrophysics Data System (ADS)

    García, Andrés Calderín; de Souza, Luiz Gilberto Ambrosio; Pereira, Marcos Gervasio; Castro, Rosane Nora; García-Mina, José María; Zonta, Everaldo; Lisboa, Francy Junior Gonçalves; Berbara, Ricardo Luis Louro

    2016-02-01

    Knowledge of the structure-property-function relationship of humic substances (HSs) is key for understanding their role in soil. Despite progress, studies on this topic are still under discussion. We analyzed 37 humic fractions with respect to their isotopic composition, structural characteristics, and properties responsible for stimulating plant root parameters. We showed that regardless of the source of origin of the carbon (C3 or C4), soil-extracted HSs and humic acids (HAs) are structurally similar to each other. The more labile and functionalized HS fraction is responsible for root emission, whereas the more recalcitrant and less functionalized HA fraction is related to root growth. Labile structures promote root stimulation at lower concentrations, while recalcitrant structures require higher concentrations to promote a similar stimulus. These findings show that lability and recalcitrance, which are derived properties of humic fractions, are related to the type and intensity of their bioactivity. In summary, the comparison of humic fractions allowed a better understanding of the relationship between the source of origin of plant carbon and the structure, properties, and type and intensity of the bioactivity of HSs in plants. In this study, scientific concepts are unified and the basis for the agronomic use of HSs is established.

  5. Photovoltaic properties of ZnO nanorods/p-type Si heterojunction structures.

    PubMed

    Pietruszka, Rafal; Witkowski, Bartlomiej Slawomir; Luka, Grzegorz; Wachnicki, Lukasz; Gieraltowska, Sylwia; Kopalko, Krzysztof; Zielony, Eunika; Bieganski, Piotr; Placzek-Popko, Ewa; Godlewski, Marek

    2014-01-01

    Selected properties of photovoltaic (PV) structures based on n-type zinc oxide nanorods grown by a low temperature hydrothermal method on p-type silicon substrates (100) are investigated. PV structures were covered with thin films of Al doped ZnO grown by atomic layer deposition acting as transparent electrodes. The investigated PV structures differ in terms of the shapes and densities of their nanorods. The best response is observed for the structure containing closely-spaced nanorods, which show light conversion efficiency of 3.6%. PMID:24605282

  6. Seismic response analysis of an instrumented building structure

    USGS Publications Warehouse

    Li, H.-J.; Zhu, S.-Y.; Celebi, M.

    2003-01-01

    The Sheraton - Universal hotel, an instrumented building lying in North Hollywood, USA is selected for case study in this paper. The finite element method is used to produce a linear time - invariant structural model, and the SAP2000 program is employed for the time history analysis of the instrumented structure under the base excitation of strong motions recorded in the basement during the Northridge, California earthquake of 17 January 1994. The calculated structural responses are compared with the recorded data in both time domain and frequency domain, and the effects of structural parameters evaluation and indeterminate factors are discussed. Some features of structural response, such as the reason why the peak responses of acceleration in the ninth floor are larger than those in the sixteenth floor, are also explained.

  7. Freshwater ecosystems--structure and response.

    PubMed

    Jones, J G

    2001-10-01

    Before it is possible to predict the impact of human activities on the natural environment it is necessary to understand the forces that drive and, therefore, control that environment. This paper is concerned with the freshwater component of the aquatic environment. The driving forces involved (some of which are under man's control) can be divided into the physical and the chemical, but the response is, almost entirely, biological. Although most impacts of the food processing industry might be perceived to be on running waters, this is not always the case, but we can apply the same basic rules to both static and running waters. The physical forces that determine how a lake functions are as follows. In early spring, in the temperate zone, the temperature of the surface water in lakes rises and the sunlight input increases. This results in stratification of the water body. The cooler, deeper water is separated, physically, by gravity. This isolated water plays a very different role in the function of the lake and is analogous to how a river works. Man's activities drive these systems by our input of inorganic and organic substances. The inorganic inputs, particularly of phosphorous, stimulate undesirable algal growths, some of which may produce particularly dangerous toxins. We must now accept that climate change, driven by man, will exacerbate these problems. Organic inputs from the food industry, i.e., carbohydrates, lipids, and proteins, will all impact lakes and rivers by increasing the biological oxygen demand. The worst case scenario is total loss of oxygen from the water as a result of microbial activity. Lipids create the greatest oxygen demand but carbohydrates (more easily biodegradable) also result in unsightly "sewage fungus." Protein waste can be degraded to produce ammonia and sulfide, both of which produce toxicity problems. Bioremediation processes, particularly phytoremediation, can alleviate these problems in a cost-effective manner and this paper

  8. Nano-structured magnetic metamaterial with enhanced nonlinear properties

    PubMed Central

    Kobljanskyj, Yuri; Melkov, Gennady; Guslienko, Konstantin; Novosad, Valentyn; Bader, Samuel D.; Kostylev, Michael; Slavin, Andrei

    2012-01-01

    Nano-structuring can significantly modify the properties of materials. We demonstrate that size-dependent modification of the spin-wave spectra in magnetic nano-particles can affect not only linear, but also nonlinear magnetic response. The discretization of the spectrum removes the frequency degeneracy between the main excitation mode of a nano-particle and the higher spin-wave modes, having the lowest magnetic damping, and reduces the strength of multi-magnon relaxation processes. This reduction of magnon-magnon relaxation for the main excitation mode leads to a dramatic increase of its lifetime and amplitude, resulting in the intensification of all the nonlinear processes involving this mode. We demonstrate this experimentally on a two-dimensional array of permalloy nano-dots for the example of parametric generation of a sub-harmonic of an external microwave signal. The characteristic lifetime of this sub-harmonic is increased by two orders of magnitude compared to the case of a continuous magnetic film, where magnon-magnon relaxation limits the lifetime. PMID:22745899

  9. High temperature structural and magnetic properties of cobalt nanorods

    SciTech Connect

    Ait Atmane, Kahina; Zighem, Fatih; Soumare, Yaghoub; Ibrahim, Mona; Boubekri, Rym; Maurer, Thomas; Margueritat, Jeremie; Piquemal, Jean-Yves; Ott, Frederic; Chaboussant, Gregory; Schoenstein, Frederic; Jouini, Noureddine; Viau, Guillaume

    2013-01-15

    We present in this paper the structural and magnetic properties of high aspect ratio Co nanoparticles ({approx}10) at high temperatures (up to 623 K) using in-situ X ray diffraction (XRD) and SQUID characterizations. We show that the anisotropic shapes, the structural and texture properties are preserved up to 500 K. The coercivity can be modelled by {mu}{sub 0}H{sub C}=2(K{sub MC}+K{sub shape})/M{sub S} with K{sub MC} the magnetocrystalline anisotropy constant, K{sub shape} the shape anisotropy constant and M{sub S} the saturation magnetization. H{sub C} decreases linearly when the temperature is increased due to the loss of the Co magnetocrystalline anisotropy contribution. At 500 K, 50% of the room temperature coercivity is preserved corresponding to the shape anisotropy contribution only. We show that the coercivity drop is reversible in the range 300-500 K in good agreement with the absence of particle alteration. Above 525 K, the magnetic properties are irreversibly altered either by sintering or by oxidation. - Graphical abstract: We present in this paper the structural and magnetic properties of high aspect ratio Co nanorods ({approx}10) at high temperatures (up to 623 K) using in-situ X-ray diffraction and SQUID characterizations. We show that the anisotropic shapes, the structural and texture properties are preserved up to 500 K. Above 525 K, the magnetic properties are irreversibly altered either by sintering or by oxidation. Highlights: Black-Right-Pointing-Pointer Ferromagnetic Co nanorods are prepared using the polyol process. Black-Right-Pointing-Pointer The structural and texture properties of the Co nanorods are preserved up to 500 K. Black-Right-Pointing-Pointer The magnetic properties of the Co nanorods are irreversibly altered above 525 K.

  10. Personality Research Form: Factor Structure and Response Style Involvement.

    ERIC Educational Resources Information Center

    Stricker, Lawrence J.

    The aims of this study were (1) to explore the factor structure of the Personality Research Form (PRF) and (2) to examine the inventory's relations with response styles. In general the PRF content scales correlated moderately with each other and with measures of acquiesence, social desirability, and defensiveness response Biases. Six oblique…

  11. Relationship of the optical absorption and scattering properties with mechanical and structural properties of apple tissue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optical absorption and scattering properties of fruit change with the physiological and biochemical activities in the tissue during ripening and postharvest storage. But it has not been well understood on how these changes are related to the structural and mechanical properties of fruit. This resear...

  12. Hierarchical photonic structured stimuli-responsive materials as high-performance colorimetric sensors.

    PubMed

    Lu, Tao; Zhu, Shenmin; Chen, Zhixin; Wang, Wanlin; Zhang, Wang; Zhang, Di

    2016-05-21

    Hierarchical photonic structures in nature are of special interest because they can be used as templates for fabrication of stimuli-responsive photonic crystals (PCs) with unique structures beyond man-made synthesis. The current stimuli-responsive PCs templated directly from natural PCs showed a very weak external stimuli response and poor durability due to the limitations of natural templates. Herein, we tackle this problem by chemically coating functional polymers, polyacrylamide, on butterfly wing scales which have hierarchical photonic structures. As a result of the combination of the strong water absorption properties of the polyacrylamide and the PC structures of the butterfly wing scales, the designed materials demonstrated excellent humidity responsive properties and a tremendous colour change. The colour change is induced by the refractive index change which is in turn due to the swollen nature of the polymer when the relative humidity changes. The butterfly wing scales also showed an excellent durability which is due to the chemical bonds formed between the polymer and wing scales. The synthesis strategy provides an avenue for the promising applications of stimuli-responsive PCs with hierarchical structures. PMID:27128843

  13. Tensile properties of helical auxetic structures: A numerical study

    NASA Astrophysics Data System (ADS)

    Wright, J. R.; Sloan, M. R.; Evans, K. E.

    2010-08-01

    This paper discusses a helical auxetic structure which has a diverse range of practical applications. The mechanical properties of the system can be determined by particular combinations of geometry and component material properties; finite element analysis is used to investigate the static behavior of these structures under tension. Modeling criteria are determined and design issues are discussed. A description of the different strain-dependent mechanical phases is provided. It is shown that the stiffnesses of the component fibers and the initial helical wrap angle are critical design parameters, and that strain-dependent changes in cross-section must be taken into consideration: we observe that the structures exhibit nonlinear behavior due to nonzero component Poisson's ratios. Negative Poisson's ratios for the helical structures as low as -5 are shown. While we focus here on the structure as a yarn our findings are, in principle, scaleable.

  14. Structure and physical properties of Hydrogrossular mineral series

    NASA Astrophysics Data System (ADS)

    Adhikari, Puja

    The mineral hydrogrossular series (Ca3Al2(SiO 4)3-x(OH)4x; 0 ≤ x ≤ 3) are important water bearing minerals found in the upper and lower part of the Earth's mantle. They are vital to the planet's hydrosphere under different hydrothermal conditions. The composition and structure of this mineral series are important in geoscience and share many commonalities with cement and clay materials. Other than the end members of the series x = 0 (grossular) and x = 3 (katoite) which have a cubic garnet structure, the structure of the series is totally unknown. We used large-scale ab initio modeling to investigate the structures and properties for hydrogrossular series for x = 0, 0.5, 1, 1.5, 2, 2.5, 3. Results indicate that for x > 0 and x < 3, the structures are tetragonal. This shows that there is structural change related to the lowering of overall symmetry associated with the composition of SiO4 tetrahedra and AlO6 octahedra. Total Bond order also explains the reason behind the change in the compressibility of the series. The electronic structure, mechanical and optical properties of the hydrogrossular series are calculated and the results for grossular and katoite are in good agreement with the available experimental data. The x--dependence of these physical properties for the series supports the notion of the aforementioned structural transition from cubic to tetragonal.

  15. From insect scales to sensor design: modelling the mechanochromic properties of bicontinuous cubic structures.

    PubMed

    Wu, Xia; Ma, Duancheng; Eisenlohr, Philip; Raabe, Dierk; Fabritius, Helge-Otto

    2016-01-01

    Many of the three-dimensional photonic crystals occurring in the scales of insects have bicontinuous cubic structures. Their optical properties have been studied extensively, however little is known about their mechanical properties and their optical response under deformation. We demonstrated a mechanochromic effect by deforming the scales of a weevil and calculated the elastic, optical and mechanochromic (assuming homogeneous deformation) properties of the three types of bicontinuous cubic structures occurring in nature: P-structure (primitive), G-structure (gyroid) and D-structure (diamond). The results show that all investigated properties of these three structure types strongly depend on their geometry, structural parameters such as volume fractions of the two constituting phases and the directions of the incident light or applied stress, respectively. Interestingly, the mechanochromic simulation results predict that these structures may show blue-shift or even red-shift under compression along certain directions. Our results provide design guidelines for mechanochromic sensing materials operating in the elastic regime, including parameters such as sensitivity and direction of spectral shift. PMID:27301299

  16. Spatiotemporal properties of sensory responses in vivo are strongly dependent on network context.

    PubMed

    Civillico, Eugene F; Contreras, Diego

    2012-01-01

    Sensory responses in neocortex are strongly modulated by changes in brain state, such as those observed between sleep stages or attentional levels. However, the specific effects of network state changes on the spatiotemporal properties of sensory responses are poorly understood. The slow oscillation, which is observed in neocortex under ketamine-xylazine anesthesia and is characterized by alternating depolarizing (up-states) and hyperpolarizing (down-states) phases, provides an opportunity to study the state-dependence of primary sensory responses in large networks. Here we used voltage sensitive dye (VSD) imaging to record the spatiotemporal properties of sensory responses and local field potential (LFP) and multiunit activity (MUA) recordings to monitor the ongoing brain state in which the sensory responses occurred. Despite a rich variability of slow oscillation patterns, sensory responses showed a consistent relationship with the ongoing oscillation and triggered a new up-state only after the termination of the refractory period that followed the preceding oscillatory cycle. We show that spatiotemporal properties of whisker-evoked responses are highly dependent on their timing with regard to the ongoing oscillation. In both the up- and down-states, responses spread across large portions of the barrel field, although the up-state responses were reduced in total area due to their sparseness. The depolarizing response in the up-state showed a tendency to propagate along the rows, with an amplitude and slope favoring the higher-numbered arcs. In the up-state, but not in the down-state, the depolarizing response was followed by a hyperpolarizing wave with a consistent spatial structure. We measured the suppression of whisker-evoked responses by a preceding response at 100 ms, and found that suppression showed the same spatial asymmetry as the depolarization. Because the resting level of cells in the up-state is likely to be closer to that in the awake animal, we

  17. Structures and Mechanical Properties of Natural and Synthetic Diamonds

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1998-01-01

    A revolution in the diamond technology is in progress, as the low-pressure process becomes an industrial reality. It will soon be possible to take advantage of the demanding properties of diamond to develop a myriad of new applications, particularly for self-lubricating, wear-resistant, and superhard coatings. The production of large diamond films or sheets at low cost, a distinct possibility in the not-too-distant future, may drastically change tribology technology, particularly regarding solid lubricants and lubricating materials and systems. This paper reviews the structures and properties of natural and synthetic diamonds to gain a better understanding of the tribological properties of diamond and related materials. Atomic and crystal structure, impurities, mechanical properties, and indentation hardness of diamond are described.

  18. Transmission properties of frequency selective structures with air gaps

    NASA Astrophysics Data System (ADS)

    Meng, Zhi-Jun; Wang, Li-Feng; Lü, Ming-Yun; Wu, Zhe

    2010-12-01

    The transmission properties of compound frequency selective structures with dielectric slab and air gaps were investigated by computation and experimentation. Mechanism analyses were also carried out. Results show that the air gaps have a distinct influence on the transmission properties. Resonant frequency of the structure would increase rapidly when the air gap appears. After the gap gets larger to a specific value, generally 1/5 wavelength corresponding to the resonant frequency, the transmission properties would change periodically with the gap thickness. The change of transmission properties in one period has a close relationship with the dielectric thickness. These results provide a new method for designing a bandpass radome of large incidence angle and low loss with the concept of stealth shield radome.

  19. Structural and oxidation properties of CoNi nanowires

    NASA Astrophysics Data System (ADS)

    Aguilera-Granja, Faustino; Montejano-Carrizales, Juan Martin; Vogel, Eugenio E.

    2016-06-01

    Nanocylinders made out of CoNi alloys offer interesting properties which are dependent on the proportion of the constituent elements, the preparation methods and the thermal history of the sample. In the present paper we calculate the structural and electronic properties of Co1- x Ni x alloys at subnanoscopic level. SIESTA program is used to relax the structures following standard protocols. Relative positions of the minority atoms (Ni) are varied aiming to find the lowest energy configurations. It is found that Ni atoms minimize energy at surface positions mainly at the ends of the cylinders. The implications of this result in the magnetic properties of the systems are discussed. The work is continued to study the oxidation properties of the different possible surface compositions. It is found that surfaces of Ni are more resistant to oxidation than Co ones. The combination of the two previous results can lead to cylinders with high magnetic coercivity and relatively high resistance to oxidation.

  20. Electronic, Thermal and Structural Properties of Graphene Oxide Frameworks

    SciTech Connect

    Zhu, Pan; Sumpter, Bobby G; Meunier, V.

    2013-01-01

    We report a theoretical study of the electronic, thermal, and structural properties of a series of graphene oxide frameworks (GOFs) using first-principles calculations based on density functional theory. The molecular structure of GOFs is systematically studied by varying the nature and concentration of linear boronic acid pillars and the thermal stability is assessed using ab initio molecular dynamics. The results demonstrate that GOFs are thermally stable up to 550 K and that electronic properties, such as their band gap, can be modified controllably by an appropriate choice of pillaring unit and pillar concentration. The tunability of the electronic structure using non-chemical means, e.g., mechanical strain, is also quantified. Overall, this class of materials is predicted to offer highly tunable materials electronic properties ranging from metallic to semiconducting.

  1. Electronic, Thermal, and Structural Properties of Graphene Oxide Frameworks

    SciTech Connect

    Zhu, Pan; Sumpter, Bobby G; Meunier, V.

    2013-01-01

    We report a theoretical study of the electronic, thermal, and structural properties of a series of graphene oxide frameworks (GOFs) using first-principles calculations based on density functional theory. The molecular structure of GOFs is systematically studied by varying the nature and concentration of linear boronic acid pillars, and the thermal stability is assessed using ab initio molecular dynamics. The results demonstrate that GOFs are thermally stable up to 550 K and that electronic properties, such as their band gap, can be modified controllably by an appropriate choice of pillaring unit and pillar concentration. The tunability of the electronic structure using nonchemical means, e.g., mechanical strain, is also quantified. Overall, this class of materials is predicted to offer highly tunable materials electronic properties ranging from metallic to semiconducting.

  2. The structural, elastic and thermodynamic properties of thorium tetraboride

    NASA Astrophysics Data System (ADS)

    Aydin, Sezgin; Tatar, Aynur

    2011-04-01

    The structural, elastic and thermodynamic properties of thorium tetraboride (ThB 4) have been investigated by using first-principles plane-wave pseudopotential density functional theory with generalized gradient approximation. The behaviors of structural parameters under 0-70 GPa hydrostatic pressure are studied by means of Broyden, Fletcher, Goldfarb, and Shanno (BFGS) geometry optimization scheme. By using the stress-strain method, single crystal elastic constants are calculated to test the mechanical stability of the crystal structure and to determine mechanical properties such as bulk modulus at each pressure. However, in order to study the thermodynamic properties of ThB 4, the quasi-harmonic Debye model is used. Then, the dependencies of bulk modulus, heat capacities, thermal expansions, Grüneisen parameters and Debye temperatures on the temperature and pressure are obtained in the whole pressure range 0-70 GPa and temperature range 0-1500 K.

  3. Solar Sail Material Performance Property Response to Space Environmental Effects

    NASA Technical Reports Server (NTRS)

    Edwards, David L.; Semmel, Charles; Hovater, Mary; Nehls, Mary; Gray, Perry; Hubbs, Whitney; Wertz, George

    2004-01-01

    The National Aeronautics and Space Administration's (NASA) Marshall Space Flight Center (MSFC) continues research into the utilization of photonic materials for spacecraft propulsion. Spacecraft propulsion, using photonic materials, will be achieved using a solar sail. A solar sail operates on the principle that photons, originating from the sun, impart pressure to the sail and therefore provide a source for spacecraft propulsion. The pressure imparted to a solar sail can be increased, up to a factor of two, if the sun-facing surface is perfectly reflective. Therefore, these solar sails are generally composed of a highly reflective metallic sun-facing layer, a thin polymeric substrate and occasionally a highly emissive back surface. Near term solar sail propelled science missions are targeting the Lagrange point 1 (Ll) as well as locations sunward of L1 as destinations. These near term missions include the Solar Polar Imager and the L1 Diamond. The Environmental Effects Group at NASA s Marshall Space Flight Center (MSFC) continues to actively characterize solar sail material in preparation for these near term solar sail missions. Previous investigations indicated that space environmental effects on sail material thermo-optical properties were minimal and would not significantly affect the propulsion efficiency of the sail. These investigations also indicated that the sail material mechanical stability degrades with increasing radiation exposure. This paper will further quantify the effect of space environmental exposure on the mechanical properties of candidate sail materials. Candidate sail materials for these missions include Aluminum coated Mylar[TM], Teonex[TM], and CPl (Colorless Polyimide). These materials were subjected to uniform radiation doses of electrons and protons in individual exposures sequences. Dose values ranged from 100 Mrads to over 5 Grads. The engineering performance property responses of thermo-optical and mechanical properties were

  4. Structure, mechanical properties, and fracture of 20GL cast steel

    NASA Astrophysics Data System (ADS)

    Schastlivtsev, V. M.; Tabatchikova, T. I.; Yakovleva, I. L.; Klyueva, S. Yu.

    2014-04-01

    The structure and mechanical properties of 20GL steel are studied. It is shown that a significant decrease in the ductility and impact toughness of the steel is caused by intercrystalline fracture, which is induced by a weakening of the intercrystallite bonds due to the existence of coarse lamellar pearlite and nonmetallic inclusions, namely, film inclusions and eutectic-type oxysulfides, at the boundaries of primary crystals. Annealing from a temperature in the intercritical range is found to improve the mechanical properties.

  5. Formation, Structure and Properties of Amorphous Carbon Char from Polymer Materials in Extreme Atmospheric Reentry Environments

    NASA Technical Reports Server (NTRS)

    Lawson, John W.

    2010-01-01

    Amorphous carbonaceous char produced from the pyrolysis of polymer solids has many desirable properties for ablative heat shields for space vehicles. Molecular dynamics simulations are presented to study the transformation of the local atomic structure from virgin polymer to a dense, disordered char [1]. Release of polymer hydrogen is found to be critical to allow the system to collapse into a highly coordinated char structure. Mechanisms of the char formation process and the morphology of the resulting structures are elucidated. Thermal conductivity and mechanical response of the resulting char are evaluated [2]. During reenty, the optical response and oxidative reactivity of char are also important properties. Results of ab initio computations of char optical functions [3] and char reactivity [4] are also presented.

  6. Simulating the Structural Response of a Preloaded Bolted Joint

    NASA Technical Reports Server (NTRS)

    Knight, Norman F., Jr.; Phillips, Dawn R.; Raju, Ivatury S.

    2008-01-01

    The present paper describes the structural analyses performed on a preloaded bolted-joint configuration. The joint modeled was comprised of two L-shaped structures connected together using a single bolt. Each L-shaped structure involved a vertical flat segment (or shell wall) welded to a horizontal segment (or flange). Parametric studies were performed using elasto-plastic, large-deformation nonlinear finite element analyses to determine the influence of several factors on the bolted-joint response. The factors considered included bolt preload, washer-surface-bearing size, edge boundary conditions, joint segment length, and loading history. Joint response is reported in terms of displacements, gap opening, and surface strains. Most of the factors studied were determined to have minimal effect on the bolted-joint response; however, the washer-bearing-surface size affected the response significantly.

  7. Nonstationary Transient Vibroacoustic Response of a Beam Structure

    NASA Technical Reports Server (NTRS)

    Caimi, R. E.; Margasahayam, R. N.; Nayfeh, Jamal F.

    1997-01-01

    This study consists of an investigation into the nonstationary transient response of the Verification Test Article (VETA) when subjected to random acoustic excitation. The goal is to assess excitation models that can be used in the design of structures and equipment when knowledge of the structure and the excitation is limited. The VETA is an instrumented cantilever beam that was exposed to acoustic loading during five Space Shuttle launches. The VETA analytical structural model response is estimated using the direct averaged power spectral density and the normalized pressure spectra methods. The estimated responses are compared to the measured response of the VETA. These comparisons are discussed with a focus on prediction conservatism and current design practice.

  8. The influence of structural response on sympathetic detonation

    NASA Technical Reports Server (NTRS)

    Watson, J. L.

    1980-01-01

    The role that a munition's structural response plays in the ignition process and the development of violent reactions and detonations is explored. The munition's structural response is identified as one of the factors that influences reaction violence. If the structural response of a round is known, this knowledge can be used to redstruce the probability that a large explosion would result from the sequential detonation of individual rounds within a large storage array. The response of an acceptor round was studied. The castings fail in the same manner regardless of whether or not there is a fill material present in the round. These failures are caused by stress waves which are transformed from compressive waves to tensile waves by reflection as the impact energy moves around the casting. Since these waves move in opposite directions around the projectile circumference and collide opposite the point of impact, very high tensile forces are developed which can crack the casing.

  9. Structure and mechanical properties of liquid crystalline filaments

    SciTech Connect

    Eremin, Alexey; Nemes, Alexandru; Stannarius, Ralf; Schulz, Mario; Nadasi, Hajnalka; Weissflog, Wolfgang

    2005-03-01

    The formation of stable freely suspended filaments is an interesting peculiarity of some liquid crystal phases. So far, little is known about their structure and stability. Similarly to free-standing smectic films, an internal molecular structure of the mesophase stabilizes these macroscopically well-ordered objects with length to diameter ratios of 10{sup 3} and above. In this paper, we report observations of smectic liquid crystal fibers formed by bent-shaped molecules in different mesophases. Our study, employing several experimental techniques, focuses on mechanical and structural aspects of fiber formation such as internal structure, stability, and mechanical and optical properties.

  10. Structural phase transition and electronic properties of NdBi

    SciTech Connect

    Sahu, Ashvini K.; Patiya, Jagdish; Sanyal, Sankar P.

    2015-06-24

    The structural and electronic properties of NdBi from an electronic structure calculation have been presented. The calculation is performed using self-consistent tight binding linear muffin tin orbital (TB-LMTO) method within the local density approximation (LDA). The calculated equilibrium structural parameters are in good agreement with the available experimental results. It is found that this compound shows metallic behavior under ambient condition and undergoes a structural phase transition from the NaCl structure to the CsCl structure at the pressure 20.1 GPa. The electronic structures of NdBi under pressure are investigated. It is found that NdBi have metallization and the hybridizations of atoms in NdBi under pressure become stronger.

  11. Frequency response modeling and control of flexible structures: Computational methods

    NASA Technical Reports Server (NTRS)

    Bennett, William H.

    1989-01-01

    The dynamics of vibrations in flexible structures can be conventiently modeled in terms of frequency response models. For structural control such models capture the distributed parameter dynamics of the elastic structural response as an irrational transfer function. For most flexible structures arising in aerospace applications the irrational transfer functions which arise are of a special class of pseudo-meromorphic functions which have only a finite number of right half place poles. Computational algorithms are demonstrated for design of multiloop control laws for such models based on optimal Wiener-Hopf control of the frequency responses. The algorithms employ a sampled-data representation of irrational transfer functions which is particularly attractive for numerical computation. One key algorithm for the solution of the optimal control problem is the spectral factorization of an irrational transfer function. The basis for the spectral factorization algorithm is highlighted together with associated computational issues arising in optimal regulator design. Options for implementation of wide band vibration control for flexible structures based on the sampled-data frequency response models is also highlighted. A simple flexible structure control example is considered to demonstrate the combined frequency response modeling and control algorithms.

  12. Nanostructured ferroelectrics: fabrication and structure-property relations.

    PubMed

    Han, Hee; Kim, Yunseok; Alexe, Marin; Hesse, Dietrich; Lee, Woo

    2011-10-25

    With the continued demand for ultrahigh density ferroelectric data storage applications, it is becoming increasingly important to scale the dimension of ferroelectrics down to the nanometer-scale region and to thoroughly understand the effects of miniaturization on the materials properties. Upon reduction of the physical dimension of the material, the change in physical properties associated with size reduction becomes extremely difficult to characterize and to understand because of a complicated interplay between structures, surface properties, strain effects from substrates, domain nucleation, and wall motions. In this Review, the recent progress in fabrication and structure-property relations of nanostructured ferroelectric oxides is summarized. Various fabrication approaches are reviewed, with special emphasis on a newly developed stencil-based method for fabricating ferroelectric nanocapacitors, and advantages and limitations of the processes are discussed. Stress-induced evolutions of domain structures upon reduction of the dimension of the material and their implications on the electrical properties are discussed in detail. Distinct domain nucleation, growth, and propagation behaviors in nanometer-scale ferroelectric capacitors are discussed and compared to those of micrometer-scale counterparts. The structural effect of ferroelectric nanocapacitors on the domain switching behavior and cross-talk between neighboring capacitors under external electric field is reviewed. PMID:21919083

  13. An Integrated Theory for Predicting the Hydrothermomechanical Response of Advanced Composite Structural Components

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    An integrated theory is developed for predicting the hydrothermomechanical (HDTM) response of fiber composite components. The integrated theory is based on a combined theoretical and experimental investigation. In addition to predicting the HDTM response of components, the theory is structured to assess the combined hydrothermal effects on the mechanical properties of unidirectional composites loaded along the material axis and off-axis, and those of angleplied laminates. The theory developed predicts values which are in good agreement with measured data at the micromechanics, macromechanics, laminate analysis and structural analysis levels.

  14. Influence of Mn on crystal structure and thermoelectric properties of GeTe compounds

    NASA Astrophysics Data System (ADS)

    Lee, J. K.; Oh, M. W.; Kim, B. S.; Min, B. K.; Lee, H. W.; Park, S. D.

    2014-07-01

    The thermoelectric properties of the Ge1- x Mn x Te compounds were investigated in the temperature range from 300 K to 773 K. The crystal structure of the compound was gradually changed with Mn, changing from a rhombohedral to a cubic-like cell. The Seebeck coefficient and the electrical resistivity were increased with Mn. From the Hall coefficient measurement, the reduction of the carrier concentration was confirmed and was responsible for the change of the electrical properties. The thermal conductivity was also reduced with Mn. The maximum dimensionless figure of merit, ZT, was obtained for x = 0.05 composition, where the value was ZT = 1.3 at 773 K. The evolution of the crystal structure with Mn attributed to the change of the thermoelectric properties. The Mn-doped compound which has a more cubic phase than a rhombohedral exhibited superior thermoelectric properties to the pure rhombohedral phase. [Figure not available: see fulltext.

  15. The Structure, Functions, and Mechanical Properties of Keratin

    NASA Astrophysics Data System (ADS)

    McKittrick, J.; Chen, P.-Y.; Bodde, S. G.; Yang, W.; Novitskaya, E. E.; Meyers, M. A.

    2012-04-01

    Keratin is one of the most important structural proteins in nature and is widely found in the integument in vertebrates. It is classified into two types: α-helices and β-pleated sheets. Keratinized materials can be considered as fiber-reinforced composites consisting of crystalline intermediate filaments embedded in an amorphous protein matrix. They have a wide variety of morphologies and properties depending on different functions. Here, we review selected keratin-based materials, such as skin, hair, wool, quill, horn, hoof, feather, and beak, focusing on the structure-mechanical property-function relationships and finally give some insights on bioinspired composite design based on keratinized materials.

  16. Structural and luminescent properties of electron-irradiated silicon

    SciTech Connect

    Sobolev, N. A.; Loshachenko, A. S.; Aruev, P. N.; Kalyadin, A. E.; Shek, E. I.; Zabrodskiy, V. V.; Shtel'makh, K. F.; Vdovin, V. I.; Xiang, Luelue; Yang, Deren

    2014-02-21

    Structural defects induced by electron irradiation of p-Cz-Si wafers were identified. The influence of the annealing conditions in a chlorine-containing atmosphere on the structural and luminescent properties of the samples was examined. Light-emitting diodes based on electron-irradiated and high-temperature-annealed wafers were fabricated by a vapour-phase epitaxy technique and their luminescence properties were studied. A high-intensity dislocation-related D1 line was observed at 1.6 μm in the room-temperature electroluminescence spectrum.

  17. Electrical properties and applications of carbon nanotube structures.

    PubMed

    Bandaru, Prabhakar R

    2007-01-01

    The experimentally verified electrical properties of carbon nanotube structures and manifestations in related phenomena such as thermoelectricity, superconductivity, electroluminescence, and photoconductivity are reviewed. The possibility of using naturally formed complex nanotube morphologies, such as Y-junctions, for new device architectures are then considered. Technological applications of the electrical properties of nanotube derived structures in transistor applications, high frequency nanoelectronics, field emission, and biological sensing are then outlined. The review concludes with an outlook on the technological potential of nanotubes and the need for new device architectures for nanotube systems integration. PMID:17450889

  18. Bioinformatics and variability in drug response: a protein structural perspective

    PubMed Central

    Lahti, Jennifer L.; Tang, Grace W.; Capriotti, Emidio; Liu, Tianyun; Altman, Russ B.

    2012-01-01

    Marketed drugs frequently perform worse in clinical practice than in the clinical trials on which their approval is based. Many therapeutic compounds are ineffective for a large subpopulation of patients to whom they are prescribed; worse, a significant fraction of patients experience adverse effects more severe than anticipated. The unacceptable risk–benefit profile for many drugs mandates a paradigm shift towards personalized medicine. However, prior to adoption of patient-specific approaches, it is useful to understand the molecular details underlying variable drug response among diverse patient populations. Over the past decade, progress in structural genomics led to an explosion of available three-dimensional structures of drug target proteins while efforts in pharmacogenetics offered insights into polymorphisms correlated with differential therapeutic outcomes. Together these advances provide the opportunity to examine how altered protein structures arising from genetic differences affect protein–drug interactions and, ultimately, drug response. In this review, we first summarize structural characteristics of protein targets and common mechanisms of drug interactions. Next, we describe the impact of coding mutations on protein structures and drug response. Finally, we highlight tools for analysing protein structures and protein–drug interactions and discuss their application for understanding altered drug responses associated with protein structural variants. PMID:22552919

  19. Structure-Property Relationships of Solids in Pharmaceutical Processing

    NASA Astrophysics Data System (ADS)

    Chattoraj, Sayantan

    Pharmaceutical development and manufacturing of solid dosage forms is witnessing a seismic shift in the recent years. In contrast to the earlier days when drug development was empirical, now there is a significant emphasis on a more scientific and structured development process, primarily driven by the Quality-by-Design (QbD) initiatives of US Food and Drug Administration (US-FDA). Central to such an approach is the enhanced understanding of solid materials using the concept of Materials Science Tetrahedron (MST) that probes the interplay between four elements, viz., the structure, properties, processing, and performance of materials. In this thesis work, we have investigated the relationships between the structure and those properties of pharmaceutical solids that influence their processing behavior. In all cases, we have used material-sparing approaches to facilitate property assessment using very small sample size of materials, which is a pre-requisite in the early stages of drug development when the availability of materials, drugs in particular, is limited. The influence of solid structure, either at the molecular or bulk powder levels, on crystal plasticity and powder compaction, powder flow, and solid-state amorphization during milling, has been investigated in this study. Through such a systematic evaluation, we have captured the involvement of structure-property correlations within a wide spectrum of relevant processing behaviors of pharmaceutical solids. Such a holistic analysis will be beneficial for addressing both regulatory and scientific issues in drug development.

  20. Hierarchical structure and mechanical properties of remineralized dentin.

    PubMed

    Chen, Yi; Wang, Jianming; Sun, Jian; Mao, Caiyun; Wang, Wei; Pan, Haihua; Tang, Ruikang; Gu, Xinhua

    2014-12-01

    It is widely accepted that the mechanical properties of dentin are significantly determined by its hierarchical structure. The current correlation between the mechanical properties and the hierarchical structure was mainly established by studying altered forms of dentin, which limits the potential outcome of the research. In this study, dentins with three different hierarchical structures were obtained via two different remineralization procedures and at different remineralization stages: (1) a dentin structure with amorphous minerals incorporated into the collagen fibrils, (2) a dentin with crystallized nanominerals incorporated into the collagen fibrils, and (3) a dentin with an out-of-order mineral layer filling the collagen fibrils matrix. Nanoindentation tests were performed to investigate the mechanical behavior of the remineralized dentin slides. The results showed that the incorporation of the crystallized nanominerals into the acid-etched demineralized organic fibrils resulted in a remarkable improvement of the mechanical properties of the dentin. In contrast, for the other two structures, i.e. the amorphous minerals inside the collagen fibrils and the out-of-order mineral layer within the collagen fibrils matrix, the excellent mechanical properties of dentin could not be restored. PMID:25259668

  1. Spatially localized structure-function relations in the elastic properties of sheared articular cartilage

    NASA Astrophysics Data System (ADS)

    Silverberg, Jesse; Bonassar, Lawrence; Cohen, Itai

    2013-03-01

    Contemporary developments in therapeutic tissue engineering have been enabled by basic research efforts in the field of biomechanics. Further integration of technology in medicine requires a deeper understanding of the mechanical properties of soft biological materials and the structural origins of their response under extreme stresses and strains. Drawing on the science generated by the ``Extreme Mechanics'' community, we present experimental results on the mechanical properties of articular cartilage, a hierarchically structured soft biomaterial found in the joints of mammalian long bones. Measurements of the spatially localized structure and mechanical properties will be compared with theoretical descriptions based on networks of deformed rods, poro-visco-elasticity, and standard continuum models. Discrepancies between experiment and theory will be highlighted, and suggestions for how models can be improved will be given.

  2. Probabilistic structural response of a valve assembly to high impact loading

    SciTech Connect

    Rodriguez, E.A.; Thacker, B.H.

    2000-10-01

    Engineers at Los Alamos National Laboratory (LANL) are currently developing capabilities, in cooperation with Southwest Research Institute, to provide reliability-based structural evaluation techniques for performing weapon component and system reliability assessments. The development and applications of Probabilistic Structural Analysis Methods (PSAM) is an important ingredient in the overall weapon reliability assessments. Focus, herein, is placed on the uncertainty associated with the structural response of an explosive actuated valve-piston assembly. The probabilistic dynamic response of the piston upon impact is evaluated through the coupling of the probabilistic code NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) [1] with the non-linear structural dynamics code, ABAQUS/Explicit [2]. The probabilistic model includes variations in piston mass and geometry, and mechanical properties, such as Young's Modulus, yield strength, and flow characteristics. Finally, the probability of exceeding a specified strain limit, which is related to piston fracture, is determined.

  3. Structural Properties of Liquid SiC during Rapid Solidification

    PubMed Central

    Yan, WanJun; Gao, TingHong; Guo, XiaoTian; Qin, YunXiang; Xie, Quan

    2013-01-01

    The rapid solidification of liquid silicon carbide (SiC) is studied by molecular dynamic simulation using the Tersoff potential. The structural properties of liquid and amorphous SiC are analyzed by the radial distribution function, angular distribution function, coordination number, and visualization technology. Results show that both heteronuclear and homonuclear bonds exist and no atomic segregation occurs during solidification. The bond angles of silicon and carbon atoms are distributed at around 109° and 120°, respectively, and the average coordination number is <4. Threefold carbon atoms and fourfold silicon atoms are linked together by six typical structures and ultimately form a random network of amorphous structure. The simulated results help understand the structural properties of liquid and amorphous SiC, as well as other similar semiconductor alloys. PMID:24288474

  4. Structural properties of liquid SiC during rapid solidification.

    PubMed

    Yan, WanJun; Gao, TingHong; Guo, XiaoTian; Qin, YunXiang; Xie, Quan

    2013-01-01

    The rapid solidification of liquid silicon carbide (SiC) is studied by molecular dynamic simulation using the Tersoff potential. The structural properties of liquid and amorphous SiC are analyzed by the radial distribution function, angular distribution function, coordination number, and visualization technology. Results show that both heteronuclear and homonuclear bonds exist and no atomic segregation occurs during solidification. The bond angles of silicon and carbon atoms are distributed at around 109° and 120°, respectively, and the average coordination number is <4. Threefold carbon atoms and fourfold silicon atoms are linked together by six typical structures and ultimately form a random network of amorphous structure. The simulated results help understand the structural properties of liquid and amorphous SiC, as well as other similar semiconductor alloys. PMID:24288474

  5. Micro- and nanosized boron carbide: synthesis, structure and properties

    NASA Astrophysics Data System (ADS)

    Andrievski, Rostislav A.

    2012-06-01

    Methods of synthesis of powder particles, fibres (wires), tubes, films, coatings and bulk materials based on micro- and nanocrystalline and amorphous boron carbide are considered. Specific features of the electronic structure, material structure and physicochemical and mechanical properties of boron carbide and boron carbide-based composites are discussed. Their existing and potential applications are highlighted. The little studied aspects of the research area in question are specified. The bibliography includes 105 references.

  6. Level set based structural topology optimization for minimizing frequency response

    NASA Astrophysics Data System (ADS)

    Shu, Lei; Wang, Michael Yu; Fang, Zongde; Ma, Zhengdong; Wei, Peng

    2011-11-01

    For the purpose of structure vibration reduction, a structural topology optimization for minimizing frequency response is proposed based on the level set method. The objective of the present study is to minimize the frequency response at the specified points or surfaces on the structure with an excitation frequency or a frequency range, subject to the given amount of the material over the admissible design domain. The sensitivity analysis with respect to the structural boundaries is carried out, while the Extended finite element method (X-FEM) is employed for solving the state equation and the adjoint equation. The optimal structure with smooth boundaries is obtained by the level set evolution with advection velocity, derived from the sensitivity analysis and the optimization algorithm. A number of numerical examples, in the frameworks of two-dimension (2D) and three-dimension (3D), are presented to demonstrate the feasibility and effectiveness of the proposed approach.

  7. Structure response and damage produced by airblast from surface mining

    SciTech Connect

    Siskind, D.E.; Stachura, V.J.; Stagg, M.S.; Kopp, J.W.

    1980-01-01

    The Bureau of Mines studied airblast from surface mining to assess its damage and annoyance potential, and to determine safe levels and appropriate measurement techniques. Research results obtained from direct measurements of airblast-produced structure responses, damage, and analysis of instrument characteristics were combined with studies of sonic booms and human response to transient overpressures. Safe levels of airblast were found to be 134 db (0.1 Hz), 133 db (2 Hz), 129 db (6 Hz), and 105 db C-slow. These four airblast levels and measurement methods are equivalent in terms of structure response, and any one could be used as a safe-level criterion. Of the four methods, only the 0.1-Hz high-pass linear method accurately measures the total airblast energy present; however, the other three were found to adequately quantify the structure response and also represent techniques that are readily available to industry. Where a single airblast measuring system must be used, the 2-Hz linear peak response is the best overall compromise. The human response and annoyance problem from airblast is probably caused primarily by wall rattling and the resulting secondary noises. Although these will not entirely be precluded by the recommended levels, they are low enough to preclude damage to residential structures and any possible human injury over the long term.

  8. Nano-structured smart hydrogels with rapid response and high elasticity

    PubMed Central

    Xia, Lie-Wen; Xie, Rui; Ju, Xiao-Jie; Wang, Wei; Chen, Qianming; Chu, Liang-Yin

    2013-01-01

    Smart hydrogels, or stimuli-responsive hydrogels, are three-dimensional networks composed of crosslinked hydrophilic polymer chains that are able to dramatically change their volume and other properties in response to environmental stimuli such as temperature, pH and certain chemicals. Rapid and significant response to environmental stimuli and high elasticity are critical for the versatility of such smart hydrogels. Here we report the synthesis of smart hydrogels which are rapidly responsive, highly swellable and stretchable, by constructing a nano-structured architecture with activated nanogels as nano-crosslinkers. The nano-structured smart hydrogels show very significant and rapid stimuli-responsive characteristics, as well as highly elastic properties to sustain high compressions, resist slicing and withstand high level of deformation, such as bending, twisting and extensive stretching. Because of the concurrent rapid and significant stimuli-response and high elasticity, these nano-structured smart hydrogels may expand the scope of hydrogel applications, and provide enhanced performance in their applications. PMID:23900497

  9. Structure and physical properties of biomembranes and model membranes

    NASA Astrophysics Data System (ADS)

    Hianik, T.

    2006-12-01

    Biomembranes belong to the most important structures of the cell and the cell organels. They play not only structural role of the barrier separating the external and internal part of the membrane but contain also various functional molecules, like receptors, ionic channels, carriers and enzymes. The cell membrane also preserves non-equillibrium state in a cell which is crucial for maintaining its excitability and other signaling functions. The growing interest to the biomembranes is also due to their unique physical properties. From physical point of view the biomembranes, that are composed of lipid bilayer into which are incorporated integral proteins and on their surface are anchored peripheral proteins and polysaccharides, represent liquid scrystal of smectic type. The biomembranes are characterized by anisotropy of structural and physical properties. The complex structure of biomembranes makes the study of their physical properties rather difficult. Therefore several model systems that mimic the structure of biomembranes were developed. Among them the lipid monolayers at an air-water interphase, bilayer lipid membranes (BLM), supported bilayer lipid membranes (sBLM) and liposomes are most known. This work is focused on the introduction into the "physical word" of the biomembranes and their models. After introduction to the membrane structure and the history of its establishment, the physical properties of the biomembranes and their models areare stepwise presented. The most focus is on the properties of lipid monolayers, BLM, sBLM and liposomes that were most detailed studied. This contribution has tutorial character that may be usefull for undergraduate and graduate students in the area of biophysics, biochemistry, molecular biology and bioengineering, however it contains also original work of the author and his co-worker and PhD students, that may be usefull also for specialists working in the field of biomembranes and model membranes.

  10. Synthesis and surface properties of environmentally responsive segmented polyurethanes.

    PubMed

    Vaidya, Ashish; Chaudhury, Manoj K

    2002-05-01

    Polyurethanes, containing well-defined assemblies of perfluoro-polyether (PFPE or hexafluoropropene oxide oligomer), polydimethylsiloxane (PDMS), and polyethylene glycol (PEG) segments, exhibit oleophobic, hydrophobic, and hydrophilic properties in response to the polarity of the contacting medium. These polymers were prepared by reacting hydroxy(polyethyleneoxy)-propylether-terminated PDMS block copolymer (HO-PEG-PDMS-PEG-OH) with 4,4'-methylene-bis(phenylene isocyanate) (MDI) in the presence of dibutyltin dilaurate catalyst, followed by reaction with 1,2-diol functional PFPE and chain extension with 2,2,3,3-tetrafluoro-1,4-butanediol (FB). The oleophobic and hydrophobic properties of the segmented polyurethanes (SPU) are due to the segregation of PFPE segments at the polymer-air interface. Wettability studies revealed that the same surface becomes hydrophilic, presumably due to the segregation of the PEG segments at the polymer-water interface. This hydrophobic-to-hydrophilic transformation of the surface prevails not only when the polymer is in contact with liquid water but with water vapor as well. The understanding of the reconstruction mechanism of this novel family of SPU surfaces would furnish valuable information for various applications where dynamic transformation of surface activity is desired. PMID:16290591

  11. Modeling vibration response and damping of cables and cabled structures

    NASA Astrophysics Data System (ADS)

    Spak, Kaitlin S.; Agnes, Gregory S.; Inman, Daniel J.

    2015-02-01

    In an effort to model the vibration response of cabled structures, the distributed transfer function method is developed to model cables and a simple cabled structure. The model includes shear effects, tension, and hysteretic damping for modeling of helical stranded cables, and includes a method for modeling cable attachment points using both linear and rotational damping and stiffness. The damped cable model shows agreement with experimental data for four types of stranded cables, and the damped cabled beam model shows agreement with experimental data for the cables attached to a beam structure, as well as improvement over the distributed mass method for cabled structure modeling.

  12. Topologically nontrivial Fermi regions and their novel electromagnetic response properties

    NASA Astrophysics Data System (ADS)

    Lee, Ching Hua; Zhang, Xiao

    In the last decade, there has been a surge of interest in the application of topology to condensed matter physics. So far, most studies have been concerned with the novel properties that arise due to nontrivial band topology, i.e Quantum Anomalous Hall and Z2 topological insulators (TIs). In this talk, I shall describe another context where nontrivial topology also leads to interesting, measurable effects. Within the semi-classical Boltzmann approach, it can be shown that a topologically nontrivial Fermi sea region generically exhibits a non-monotonic nonlinear electromagnetic response in the limit of low chemical potential. Such topologically nontrivial regions of filled states can arise in experimentally realized TI heterostructures or materials with large Rashba splitting, i.e. BiTeI, where the Fermi sea is not simply connected. A non-monotonic electromagnetic response implies regimes of negative differential resistance, which have important applications in technologies involving microwave generation, like motion sensing and radio astronomy. We hope that nontrivial Fermi sea topology will hence provide another route for the realization of such technologies.

  13. Bacterial community structure and soil properties of a subarctic tundra soil in Council, Alaska

    PubMed Central

    Kim, Hye Min; Jung, Ji Young; Yergeau, Etienne; Hwang, Chung Yeon; Hinzman, Larry; Nam, Sungjin; Hong, Soon Gyu; Kim, Ok-Sun; Chun, Jongsik; Lee, Yoo Kyung

    2014-01-01

    The subarctic region is highly responsive and vulnerable to climate change. Understanding the structure of subarctic soil microbial communities is essential for predicting the response of the subarctic soil environment to climate change. To determine the composition of the bacterial community and its relationship with soil properties, we investigated the bacterial community structure and properties of surface soil from the moist acidic tussock tundra in Council, Alaska. We collected 70 soil samples with 25-m intervals between sampling points from 0–10 cm to 10–20 cm depths. The bacterial community was analyzed by pyrosequencing of 16S rRNA genes, and the following soil properties were analyzed: soil moisture content (MC), pH, total carbon (TC), total nitrogen (TN), and inorganic nitrogen ( and ). The community compositions of the two different depths showed that Alphaproteobacteria decreased with soil depth. Among the soil properties measured, soil pH was the most significant factor correlating with bacterial community in both upper and lower-layer soils. Bacterial community similarity based on jackknifed unweighted unifrac distance showed greater similarity across horizontal layers than through the vertical depth. This study showed that soil depth and pH were the most important soil properties determining bacterial community structure of the subarctic tundra soil in Council, Alaska. PMID:24893754

  14. Carbon aerogels: An update on structure, properties, and applications

    SciTech Connect

    Pekala, R.W.; Mayer, S.T.; Kaschmitter, J.L.; Kong, F.M.

    1993-07-01

    Aerogels are unique porous materials whose composition, structure, and properties can be controlled at the nanometer scale. This paper examines the synthesis of organic aerogels and their carbonized derivatives. Carbon aerogels have low electrical resistivity, high surface area, and a tunable pore size. These materials are finding applications as electrodes in double layer capacitors.

  15. Structure-property considerations in the development of biolubricants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetable oils and their derivatives such as alkyl esters of various fatty acids are good candidates for the development of biolubricants. These materials possess structures that gives them certain highly desirable properties for lubricant applications than that found in petroleum-based oil. Among s...

  16. Elastic properties of inhomogeneous media with chaotic structure.

    PubMed

    Novikov, V V; Wojciechowski, K W; Belov, D V; Privalko, V P

    2001-03-01

    The elastic properties of an inhomogeneous medium with chaotic structure were derived within the framework of a fractal model using the iterative averaging approach. The predicted values of a critical index for the bulk elastic modulus and of the Poisson ratio in the vicinity of a percolation threshold were in fair agreement with the available experimental data for inhomogeneous composites. PMID:11308722

  17. Biobased oil structure on amphiphilic and tribological properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biobased oils are those derived from farm-based renewable raw materials. Most are vegetable oils (such as soybean, canola, corn, etc.) or chemical modifications of vegetable oils. They have a number of interesting structural features that impact their amphiphilic and lubrication properties. The basi...

  18. Study of wound dressing structure and hydration/dehydration properties

    NASA Astrophysics Data System (ADS)

    Lugão, A. B.; Machado, L. D. B.; Miranda, L. F.; Alvarez, M. R.; Rosiak, J. M.

    1998-06-01

    Hydrogels manufactured by radio-induced crosslinking and simultaneous sterilisation of hydrogels of PVP, PEG and agar, according to the Rosiak method, have many desirable properties for using as wound dressings. However, some properties need to be improved or better controlled. The membranes need to be strong enough to be freely used. Another important property to be controlled is the capacity of absorption of exudate and the kinetics of drying. Therefore, it was necessary to understand the role of main parameters (agar, PVP, PEG concentration and dose) in the structure of the net and in the hydration and dehydration properties. The structure of the membranes was studied by sol analysis and the hydrating/dehydrating properties were studied by isothermal thermogravimetric analysis. The gel content for all samples were always in agreement with expected values considering that only PVP undergoes crosslinking. The hydrating and dehydration results did not show variation with the tested parameters. It was concluded that the network was solely composed of crosslinked PVP plasticezed by the other compounds. The properties of hydration/dehydration is related rather to diffusion than to capillarity or osmose and to the chemical retention of water in the polymeric matrix.

  19. Modelling of the structure-property relationships in the α-quartz structures

    NASA Astrophysics Data System (ADS)

    Yao, Yongtao; Alderson, Kim; Alderson, Andrew; Leng, Jinsong

    2013-04-01

    The molecular mechanism has been employed to model the structure-property relationships of auxetic material with tetrahedral framework at the atomistic level. The germania α-quartz subject uniaxial stress loading in z direction will be investigated. The strain-dependent structure and mechanical properties will be predicted from the force field based simulations, including the transformation from positive-to-negative Poisson's ratio behaviour and vice versa.

  20. Sonic-boom-induced building structure responses including damage.

    NASA Technical Reports Server (NTRS)

    Clarkson, B. L.; Mayes, W. H.

    1972-01-01

    Concepts of sonic-boom pressure loading of building structures and the associated responses are reviewed, and results of pertinent theoretical and experimental research programs are summarized. The significance of sonic-boom load time histories, including waveshape effects, are illustrated with the aid of simple structural elements such as beams and plates. Also included are discussions of the significance of such other phenomena as three-dimensional loading effects, air cavity coupling, multimodal responses, and structural nonlinearities. Measured deflection, acceleration, and strain data from laboratory models and full-scale building tests are summarized, and these data are compared, where possible, with predicted values. Damage complaint and claim experience due both to controlled and uncontrolled supersonic flights over communities are summarized with particular reference to residential, commercial, and historic buildings. Sonic-boom-induced building responses are compared with those from other impulsive loadings due to natural and cultural events and from laboratory simulation tests.

  1. Advanced probabilistic methods for quantifying the effects of various uncertainties in structural response

    NASA Technical Reports Server (NTRS)

    Nagpal, Vinod K.

    1988-01-01

    The effects of actual variations, also called uncertainties, in geometry and material properties on the structural response of a space shuttle main engine turbopump blade are evaluated. A normal distribution was assumed to represent the uncertainties statistically. Uncertainties were assumed to be totally random, partially correlated, and fully correlated. The magnitude of these uncertainties were represented in terms of mean and variance. Blade responses, recorded in terms of displacements, natural frequencies, and maximum stress, was evaluated and plotted in the form of probabilistic distributions under combined uncertainties. These distributions provide an estimate of the range of magnitudes of the response and probability of occurrence of a given response. Most importantly, these distributions provide the information needed to estimate quantitatively the risk in a structural design.

  2. Three Dimensional Response Spectrum Soil Structure Modeling Versus Conceptual Understanding To Illustrate Seismic Response Of Structures

    SciTech Connect

    Touqan, Abdul Razzaq

    2008-07-08

    Present methods of analysis and mathematical modeling contain so many assumptions that separate them from reality and thus represent a defect in design which makes it difficult to analyze reasons of failure. Three dimensional (3D) modeling is so superior to 1D or 2D modeling, static analysis deviates from the true nature of earthquake load which is 'a dynamic punch', and conflicting assumptions exist between structural engineers (who assume flexible structures on rigid block foundations) and geotechnical engineers (who assume flexible foundations supporting rigid structures). Thus a 3D dynamic soil-structure interaction is a step that removes many of the assumptions and thus clears reality to a greater extent. However such a model cannot be analytically analyzed. We need to anatomize and analogize it. The paper will represent a conceptual (analogical) 1D model for soil structure interaction and clarifies it by comparing its outcome with 3D dynamic soil-structure finite element analysis of two structures. The aim is to focus on how to calculate the period of the structure and to investigate effect of variation of stiffness on soil-structure interaction.

  3. Postnatal development of auditory central evoked responses and thalamic cellular properties.

    PubMed

    Venkataraman, Yamini; Bartlett, Edward L

    2014-05-01

    During development, the sense of hearing changes rapidly with age, especially around hearing onset. During this period, auditory structures are highly sensitive to alterations of the acoustic environment, such as hearing loss or background noise. This sensitivity includes auditory temporal processing, which is important for processing complex sounds, and for acquiring reading and language skills. Developmental changes can be observed at multiple levels of brain organization-from behavioral responses to cellular responses, and at every auditory nucleus. Neuronal properties and sound processing change dramatically in auditory cortex neurons after hearing onset. However, development of its primary source, the auditory thalamus, or medial geniculate body (MGB), has not been well studied over this critical time window. Furthermore, to understand how temporal processing develops, it is important to determine the relative maturation of temporal processing not only in the MGB, but also in its inputs. Cellular properties of rat MGB neurons were studied using in vitro whole-cell patch-clamp recordings, at ages postnatal day (P) 7-9; P15-17, and P22-32. Auditory evoked potentials were measured in P14-17 and P22-32 rats. MGB action potentials became about five times faster, and the ability to generate spike trains increased with age, particularly at frequencies of 50 Hz and higher. Evoked potential responses, including auditory brainstem responses (ABR), middle latency responses (MLR), and amplitude modulation following responses, showed increased amplitudes with age, and ABRs and MLRs additionally showed decreased latencies with age. Overall, temporal processing at subthalamic nuclei is concurrently maturing with MGB cellular properties. PMID:24214269

  4. Advanced composites structural concepts and materials technologies for primary aircraft structures: Structural response and failure analysis

    NASA Technical Reports Server (NTRS)

    Dorris, William J.; Hairr, John W.; Huang, Jui-Tien; Ingram, J. Edward; Shah, Bharat M.

    1992-01-01

    Non-linear analysis methods were adapted and incorporated in a finite element based DIAL code. These methods are necessary to evaluate the global response of a stiffened structure under combined in-plane and out-of-plane loading. These methods include the Arc Length method and target point analysis procedure. A new interface material model was implemented that can model elastic-plastic behavior of the bond adhesive. Direct application of this method is in skin/stiffener interface failure assessment. Addition of the AML (angle minus longitudinal or load) failure procedure and Hasin's failure criteria provides added capability in the failure predictions. Interactive Stiffened Panel Analysis modules were developed as interactive pre-and post-processors. Each module provides the means of performing self-initiated finite elements based analysis of primary structures such as a flat or curved stiffened panel; a corrugated flat sandwich panel; and a curved geodesic fuselage panel. This module brings finite element analysis into the design of composite structures without the requirement for the user to know much about the techniques and procedures needed to actually perform a finite element analysis from scratch. An interactive finite element code was developed to predict bolted joint strength considering material and geometrical non-linearity. The developed method conducts an ultimate strength failure analysis using a set of material degradation models.

  5. RNA intrusions change DNA elastic properties and structure

    NASA Astrophysics Data System (ADS)

    Chiu, Hsiang-Chih; Koh, Kyung Duk; Evich, Marina; Lesiak, Annie L.; Germann, Markus W.; Bongiorno, Angelo; Riedo, Elisa; Storici, Francesca

    2014-08-01

    The units of RNA, termed ribonucleoside monophosphates (rNMPs), have been recently found as the most abundant defects present in DNA. Despite the relevance, it is largely unknown if and how rNMPs embedded in DNA can change the DNA structure and mechanical properties. Here, we report that rNMPs incorporated in DNA can change the elastic properties of DNA. Atomic force microscopy (AFM)-based single molecule elasticity measurements show that rNMP intrusions in short DNA duplexes can decrease - by 32% - or slightly increase the stretch modulus of DNA molecules for two sequences reported in this study. Molecular dynamics simulations and nuclear magnetic resonance spectroscopy identify a series of significant local structural alterations of DNA containing embedded rNMPs, especially at the rNMPs and nucleotide 3' to the rNMP sites. The demonstrated ability of rNMPs to locally alter DNA mechanical properties and structure may help in understanding how such intrusions impact DNA biological functions and find applications in structural DNA and RNA nanotechnology.The units of RNA, termed ribonucleoside monophosphates (rNMPs), have been recently found as the most abundant defects present in DNA. Despite the relevance, it is largely unknown if and how rNMPs embedded in DNA can change the DNA structure and mechanical properties. Here, we report that rNMPs incorporated in DNA can change the elastic properties of DNA. Atomic force microscopy (AFM)-based single molecule elasticity measurements show that rNMP intrusions in short DNA duplexes can decrease - by 32% - or slightly increase the stretch modulus of DNA molecules for two sequences reported in this study. Molecular dynamics simulations and nuclear magnetic resonance spectroscopy identify a series of significant local structural alterations of DNA containing embedded rNMPs, especially at the rNMPs and nucleotide 3' to the rNMP sites. The demonstrated ability of rNMPs to locally alter DNA mechanical properties and structure

  6. Solar Sail Material Performance Property Response to Space Environmental Effects

    NASA Technical Reports Server (NTRS)

    Edwards, David L.; Semmel, Charles; Hovater, Mary; Nehls, Mary; Gray, Perry; Hubbs, Whitney; Wertz, George

    2004-01-01

    The National Aeronautics and Space Administration's (NASA) Marshall Space Flight Center (MSFC) continues research into the utilization of photonic materials for spacecraft propulsion. Spacecraft propulsion, using photonic materials, will be achieved using a solar sail. A solar sail operates on the principle that photons, originating from the sun, impart pressure to the sail and therefore provide a source for spacecraft propulsion. The pressure imparted to a solar sail can be increased, up to a factor of two if the sun-facing surface is perfectly reflective. Therefore, these solar sails are generally composed of a highly reflective metallic sun-facing layer, a thin polymeric substrate and occasionally a highly emissive back surface. Near term solar sail propelled science missions are targeting the Lagrange point 1 (L1) as well as locations sunward of L1 as destinations. These near term missions include the Solar Polar Imager' and the L1 Diamond '. The Environmental Effects Group at NASA's Marshall Space Fliglit Center (MSFC) continues to actively characterize solar sail material in preparation for these near term solar sail missions. Previous investigations indicated that space environmental effects on sail material thermo-optical properties were minimal and would not significantly affect the propulsion efficiency of the sail3-'. These investigations also indicated that the sail material mechanical stability degrades with increasing radiation exposure. This paper will further quantify the effect of space environmental exposure on the mechanical properties of candidate sail materials. Candidate sail materials for these missions include Aluminum coated Mylar TM, Teonexm, and CP1 (Colorless Polyimide). These materials were subjected to uniform radiation doses of electrons and protons in individual exposures sequences. Dose values ranged from 100 Mrads to over 5 Grads. The engineering performance property responses of thermo-optical and mechanical properties were

  7. Calculating nonlocal optical properties of structures with arbitrary shape.

    SciTech Connect

    McMahon, J. M.; Gray, S. K.; Schatz, G. C.; Northwestern Univ.

    2010-07-16

    In a recent Letter [J. M. McMahon, S. K. Gray, and G. C. Schatz, Phys. Rev. Lett. 103, 097403 (2009)], we outlined a computational method to calculate the optical properties of structures with a spatially nonlocal dielectric function. In this paper, we detail the full method and verify it against analytical results for cylindrical nanowires. Then, as examples of our method, we calculate the optical properties of Au nanostructures in one, two, and three dimensions. We first calculate the transmission, reflection, and absorption spectra of thin films. Because of their simplicity, these systems demonstrate clearly the longitudinal (or volume) plasmons characteristic of nonlocal effects, which result in anomalous absorption and plasmon blueshifting. We then study the optical properties of spherical nanoparticles, which also exhibit such nonlocal effects. Finally, we compare the maximum and average electric field enhancements around nanowires of various shapes to local theory predictions. We demonstrate that when nonlocal effects are included, significant decreases in such properties can occur.

  8. Structure and electronic properties of (+)-catechin: aqueous solvent effects.

    PubMed

    Bentz, Erika N; Pomilio, Alicia B; Lobayan, Rosana M

    2014-02-01

    We report a study of the structure of (+)-catechin, which belongs to the family of the flavan-3-ols-one of the five most widely distributed phenolic groups. The biological activities and pharmaceutical utility of these compounds are related to antioxidant activity due to their ability to scavenge free radicals. A breakthrough in the study of the conformational space of this compound, so far absent in the literature, is presented herein. A detailed analysis of the electronic distribution, charge delocalization effects, and stereoelectronic effects is presented following application of the theory of atoms in molecules (AIM) and natural bond orbital analysis. The stability order, and the effects of electron delocalization in the structures were analyzed in depth. The molecular electrostatic potential (MEP) was also obtained, assessing changes in the electronic distribution in aqueous solution, the effects of the solvent on the intrinsic electronic properties, and molecular geometry. The effect of the aqueous solvent on MEP was also quantified, and rationalized by charge delocalization mechanisms, relating them to structural changes and topological properties of the electronic charge density. To further analyze the effects of the aqueous solvent, as well as investigating the molecular and structural properties of these compounds in a biological environment, the polarizabilities for all conformers characterized were also calculated. All results were interpreted on the basis of our accumulated knowledge on (4α→6", 2α→O→1")-phenylflavans in previous reports, thus enriching and deepening the analysis of both types of structure. PMID:24526380

  9. Properties of Air Traffic Conflicts for Free and Structured Routing

    NASA Technical Reports Server (NTRS)

    Bilimoria, Karl D.; Lee, Hilda Q.

    2001-01-01

    This paper analyzes the properties of air traffic conflicts in a future free routing system against those in the current structured routing system. Simulation of en route air traffic operations (above 18,000 ft) over the contiguous United States for a 24-hour period, constructed with initial conditions from actual air traffic data, were conducted using the Future ATM Concepts Evaluation Tool (FACET). Free routes were modeled as great circle (direct) routes from origin to destination, and structured routes were derived from actual flight plans along the current system of air routes. The conflict properties analyzed in this study include: (1) Total number of conflicts; (2) Distributions of key conflict parameters; and, (3) Categorization of conflicts into independent conflicts and two types of interacting conflicts. Preliminary results (for Denver Center traffic) indicate that conflict properties in a free routing system are different from those in the current structured routing system. In particular, a free routing system has significantly fewer conflicts, involving a correspondingly smaller number of aircraft, compared to the current structured routing system. Additionally, the conflict parameter distributions indicate that free routing conflicts are less intrusive than structured routing conflicts, and would therefore require small trajectory deviations for resolution.

  10. Structural property of regulatory elements in human promoters

    NASA Astrophysics Data System (ADS)

    Cao, Xiao-Qin; Zeng, Jia; Yan, Hong

    2008-04-01

    The capacity of transcription factors to activate gene expression is encoded in the promoter sequences, which are composed of short regulatory motifs that function as transcription factor binding sites (TFBSs) for specific proteins. To the best of our knowledge, the structural property of TFBSs that controls transcription is still poorly understood. Rigidity is one of the important structural properties of DNA, and plays an important role in guiding DNA-binding proteins to the target sites efficiently. After analyzing the rigidity of 2897 TFBSs in 1871 human promoters, we show that TFBSs are generally more flexible than other genomic regions such as exons, introns, 3' untranslated regions, and TFBS-poor promoter regions. Furthermore, we find that the density of TFBSs is consistent with the average rigidity profile of human promoters upstream of the transcription start site, which implies that TFBSs directly influence the promoter structure. We also examine the local rigid regions probably caused by specific TFBSs such as the DNA sequence TATA(A/T)A(A/T) box, which may inhibit nucleosomes and thereby facilitate the access of transcription factors bound nearby. Our results suggest that the structural property of TFBSs accounts for the promoter structure as well as promoter activity.

  11. Seismic Safety Program: Ground motion and structural response

    SciTech Connect

    Not Available

    1993-05-01

    In 1964, John A. Blume & Associates Research Division (Blume) began a broad-range structural response program to assist the Nevada Operations Office of the US Atomic Energy Commission (AEC) in ensuring the continued safe conduct of underground nuclear detonation testing at the Nevada Test Site (NTS) and elsewhere. Blume`s long experience in earthquake engineering provided a general basis for the program, but much more specialized knowledge was required for the AEC`s purposes. Over the next 24 years Blume conducted a major research program to provide essential understanding of the detailed nature of the response of structures to dynamic loads such as those imposed by seismic wave propagation. The program`s results have been embodied in a prediction technology which has served to provide reliable advanced knowledge of the probable effects of seismic ground motion on all kinds of structures, for use in earthquake engineering and in building codes as well as for the continuing needs of the US Department of Energy`s Nevada Operations Office (DOE/NV). This report is primarily an accounting of the Blume work, beginning with the setting in 1964 and the perception of the program needs as envisioned by Dr. John A. Blume. Subsequent chapters describe the structural response program in detail and the structural prediction procedures which resulted; the intensive data acquisition program which, as is discussed at some length, relied heavily on the contributions of other consultant-contractors in the DOE/NV Seismic Safety Support Program; laboratory and field studies to provide data on building elements and structures subjected to dynamic loads from sources ranging from testing machines to earthquakes; structural response activities undertaken for testing at the NTS and for off-NTS underground nuclear detonations; and concluding with an account of corollary studies including effects of natural forces and of related studies on building response.

  12. Defective graphene and nanoribbons: electronic, magnetic and structural properties

    NASA Astrophysics Data System (ADS)

    Guerra, Thiago; Azevedo, Sérgio; Machado, Marcelo

    2016-03-01

    We make use of first-principles calculations, based on the density functional theory (DFT), to investigate the alterations at the structural, energetic, electronic and magnetic properties of graphene and zigzag graphene nanoribbons (ZGNRs) due to the inclusion of different types of line and punctual defects. For the graphene it is found that the inclusion of defects breaks the translational symmetry of the crystal with drastic changes at its electronic structure, going from semimetallic to semiconductor and metallic. Regarding the magnetic properties, no magnetization is observed for the defective graphene. We also show that the inclusion of defects at ZGNRs is a good way to create and control pronounced peaks at the Fermi level. Furthermore, defective ZGNRs structures show magnetic moment by supercell up to 2.0 μ B . For the non defective ZGNRs is observed a switch of the magnetic coupling between opposite ribbon edges from the antiferromagnetic to the ferrimagnetic and ferromagnetic configurations.

  13. The Structure and Properties of Amorphous Indium Oxide

    PubMed Central

    2015-01-01

    A series of In2O3 thin films, ranging from X-ray diffraction amorphous to highly crystalline, were grown on amorphous silica substrates using pulsed laser deposition by varying the film growth temperature. The amorphous-to-crystalline transition and the structure of amorphous In2O3 were investigated by grazing angle X-ray diffraction (GIXRD), Hall transport measurement, high resolution transmission electron microscopy (HRTEM), electron diffraction, extended X-ray absorption fine structure (EXAFS), and ab initio molecular dynamics (MD) liquid-quench simulation. On the basis of excellent agreement between the EXAFS and MD results, a model of the amorphous oxide structure as a network of InOx polyhedra was constructed. Mechanisms for the transport properties observed in the crystalline, amorphous-to-crystalline, and amorphous deposition regions are presented, highlighting a unique structure–property relationship. PMID:25678743

  14. Optical properties and structure of beryllium lead silicate glasses

    SciTech Connect

    Zhidkov, I. S.; Zatsepin, A. F.; Cholakh, S. O.; Kuznetsova, Yu. A.

    2014-10-21

    Luminescence and optical properties and structural features of (BeO){sub x}(PbO⋅SiO{sub 2}){sub 1−x} glasses (x = 0 ÷ 0.3) are investigated by means of optical absorption and photoluminescence spectroscopy and X-ray diffraction. The regularities of the formation of the optical absorption edge and static disorder are studied. It is shown that the optical absorption and luminescence are determined by transitions between localized states of lead ions. The impact of beryllium oxide on optical and luminescence properties and electronic structure of bands tails is discussed. The presence of two different concentration ranges with various short-range order structure and band tails nature has been established.

  15. Correlation of Local Structure and Electronic Properties of Glass Materials

    NASA Astrophysics Data System (ADS)

    Lordi, Vincenzo; Adelstein, Nicole

    2015-03-01

    Wide band gap glasses such as silica and its derivatives are typically considered insulators. However, electronic transport in glasses can be important for certain applications, such as when used as the host material for a scintillator radiation detector. Here we explore the relationship between local structure in glass materials and the corresponding electronic properties of carrier transport and charge trapping. We present a novel analysis that decomposes the distribution of localized band tail states in terms of specific local structural features in the glass. Comparison of the structure-related transport properties of different glass compositions is given, using silica and sodium silicate as prototypes. Prepared by LLNL under Contract DE-AC52-07NA27344.

  16. Harnessing data structure for recovery of randomly missing structural vibration responses time history: Sparse representation versus low-rank structure

    NASA Astrophysics Data System (ADS)

    Yang, Yongchao; Nagarajaiah, Satish

    2016-06-01

    Randomly missing data of structural vibration responses time history often occurs in structural dynamics and health monitoring. For example, structural vibration responses are often corrupted by outliers or erroneous measurements due to sensor malfunction; in wireless sensing platforms, data loss during wireless communication is a common issue. Besides, to alleviate the wireless data sampling or communication burden, certain accounts of data are often discarded during sampling or before transmission. In these and other applications, recovery of the randomly missing structural vibration responses from the available, incomplete data, is essential for system identification and structural health monitoring; it is an ill-posed inverse problem, however. This paper explicitly harnesses the data structure itself-of the structural vibration responses-to address this (inverse) problem. What is relevant is an empirical, but often practically true, observation, that is, typically there are only few modes active in the structural vibration responses; hence a sparse representation (in frequency domain) of the single-channel data vector, or, a low-rank structure (by singular value decomposition) of the multi-channel data matrix. Exploiting such prior knowledge of data structure (intra-channel sparse or inter-channel low-rank), the new theories of ℓ1-minimization sparse recovery and nuclear-norm-minimization low-rank matrix completion enable recovery of the randomly missing or corrupted structural vibration response data. The performance of these two alternatives, in terms of recovery accuracy and computational time under different data missing rates, is investigated on a few structural vibration response data sets-the seismic responses of the super high-rise Canton Tower and the structural health monitoring accelerations of a real large-scale cable-stayed bridge. Encouraging results are obtained and the applicability and limitation of the presented methods are discussed.

  17. Solvent-responsive properties of octadecyltrichlorosiloxane nanostructures investigated using atomic force microscopy in liquid.

    PubMed

    Kulkarni, Shalaka A; Lyles, Venetia D; Serem, Wilson K; Lu, Lu; Kumar, Revati; Garno, Jayne C

    2014-05-20

    An emerging challenge for nanoscale measurements is to capture and quantify the magnitude of structural changes in response to environmental changes. Certain environmental parameters can affect the nanoscale morphology of samples, such as changing the pH, solvent polarity, ionic strength, and temperature. We prepared test platforms of n-octadecyltrichlorosilane ring nanostructures to study surface morphology changes at the nanoscale in selected liquid media compared to dry conditions in air. Particle lithography combined with organosilane vapor deposition was used to fabricate nanostructures of regular dimensions. Multilayer nanostructures of OTS were used as a test platform for scanning probe studies of solvent-responsive properties where the sides of designed ring structures expose a 3D interface for studying the interaction of solvents with molecular side groups. In dry, ambient conditions, nanostructures of OTS were first imaged using contact mode atomic force microscopy (AFM). Next, ethanol or buffer was introduced to the sample cell, and images were acquired using the same probe. We observed substantial changes in the lateral and vertical dimensions of the ring nanostructures in AFM topography frames; the sizes of the rings were observed to swell by tens of nanometers. Even after heat treatment of samples to promote cross-linking, the samples still evidenced swelling in liquid media. This research will have consequences for studies of the properties of nanomaterials, such as solvent-responsive organic films and polymers. PMID:24788214

  18. Nickel-aluminum alloy clusters -- structural and dynamical properties

    SciTech Connect

    Jellinek, J.; Krissinel, E.B.

    1997-08-01

    Structural and dynamical properties of mixed Ni{sub n}Al{sub m} alloy clusters mimicked by a many-body potential are studied computationally for all the possible compositions n and m such that n + m = 13. It is shown that the manifold of the usually very large number of the different possible structural forms can be systematized by introducing classes of structures corresponding to the same concentration of the components, geometry and type of the central atom. General definitions of mixing energy and mixing coefficient are introduced, and it is shown that the energy ordering of the structural forms within each class is governed by the mixing coefficient. The peculiarities of the solid-to-liquid-like transition are described as a function of the concentration of the two types of atoms. These peculiarities are correlated with and explained in terms of the energy spectra of the structural forms. Class-dependent features of the dynamics are described and analyzed.

  19. Development of a satellite structural architecture for operationally responsive space

    NASA Astrophysics Data System (ADS)

    Arritt, Brandon J.; Buckley, Steven J.; Ganley, Jeffrey M.; Welsh, Jeffry S.; Henderson, Benjamin K.; Lyall, M. Eric; Williams, Andrew D.; Preble, Jeffrey C.; DiPalma, John; Mehle, Greg; Roopnarine, R.

    2008-03-01

    The Air Force Research Laboratory/Space Vehicles Directorate (AFRL/RV) is developing a satellite structural architecture in support of the Department of Defense's Operationally Responsive Space (ORS) initiative. Such a structural architecture must enable rapid Assembly, Integration, and Test (AI&T) of the satellite, accommodate multiple configurations (to include structural configurations, components, and payloads), and incorporate structurally integrated thermal management and electronics, while providing sufficient strength, stiffness, and alignment accuracy. The chosen approach will allow a wide range of satellite structures to be assembled from a relatively small set of structural components. This paper details the efforts of AFRL, and its contractors, to develop the technology necessary to realize these goals.

  20. Response of launch pad structures to random acoustic excitation

    NASA Technical Reports Server (NTRS)

    Margasahayam, Ravi; Sepcenko, Valentin; Caimi, Raoul

    1992-01-01

    Two solutions (probabilistic and deterministic) for the random vibration problem are presented in this paper from the standpoint of their applicability to predict the response of ground structures subjected to acoustic loading during the launch of a Space Shuttle. Deficiencies of the probabilistic method, especially to predict response in the low-frequency regime, prompted the development of the deterministic analysis, which offers a valid alternative. Challenges associated with the implementation of these response solutions in a commercially available Finite Element Method (FEM) code are briefly addressed.

  1. Influence of cure via network structure on mechanical properties of a free-radical polymerizing thermoset

    NASA Astrophysics Data System (ADS)

    Ganglani, Manisha Sachin

    The matrix of a composite material exerts influence over composite properties. The hypothesis is that control of molecular architecture of the matrix allows for the control of resin properties and therefore impacts composite properties. The objective of this research is to define the relationship between cure chemistry, network structure, and final physical properties of vinyl ester-styrene (VE/S) resin, a free-radical polymerizing thermoset polymer often used as the matrix of fiber reinforced polymers. Tensile and fracture properties of the polymer are found to depend on both cure schedule and cure formulation. The possibilities of phase separation and microgel formation being the cause for the differences in mechanical properties are examined. This research shows that the VE/S system does not phase separate under the conditions studied. This proven, the research examines changes in network architecture under different cure conditions. It is found that though bulk properties of the resin are unaffected by the details of the cure, the microscopic morphology, in particular the type of crosslink formed (intermolecular bond or intramolecular bond), is sensitive to both cure temperature and initiation mechanism as determined by cure formulation. Thus, the molecular architecture of the network is responsible for the bulk mechanical properties of the resin. A kinetic analysis shows that both temperature and initiation mechanism affect the apparent "reaction order" of the VE/S system as determined by the autoacceleration equation. This apparent reaction order is interpreted as being an indication of the degree of heterogeneity in the resin. By controlling cure temperature and cure formulation, it is possible to minimize the apparent reaction order and thereby optimize physical properties. Finally, a theory is adapted from other non-network polymer systems to describe qualitatively how cure temperature and initiation mechanism may alter the heterogeneity in network

  2. Key parameters governing the dynamic response of long-period structures

    NASA Astrophysics Data System (ADS)

    Fukuwa, N.; Tobita, J.

    2008-04-01

    The present study describes the important factors (period, duration, and intensity) involved in evaluating input ground motion and structural response for the design of long-period structures such as high-rise buildings and base-isolated buildings. First, the fundamental dynamic properties of high-rise buildings are explained based on the results of newly introduced vibration observations programs. Next, the distribution of the predominant period and duration of seismic ground motion within the Nobi Plain, one of the largest sedimentary plains in Japan, is discussed with respect to the possibility of resonance of long-period structures. Finally, we introduce a recently developed long-stroke shaking table that is intended to convince structural engineers and building owners to take adequate countermeasures against large floor response in high-rise buildings because of resonance.

  3. Quantitative structure property relationship modeling of excipient properties for prediction of formulation characteristics.

    PubMed

    Gaikwad, Vinod L; Bhatia, Neela M; Desai, Sujit A; Bhatia, Manish S

    2016-10-20

    Quantitative structure property relationship (QSPR) is used to relate the excipient descriptors with the formulation properties. A QSPR model is developed by regression analysis of selected descriptors contributing towards the targeted formulation properties. Developed QSPR model is validated by the true external method where it showed good accuracy and precision in predicting the formulation composition as experimental t90% (61.35min) is observed very close to predicted t90% (67.37min). Hence, QSPR approach saves resources by predicting drug release from an unformulated formulation; avoiding repetitive trials in the development of a new formulation and/or optimization of existing one. PMID:27474604

  4. Structural and electrical properties of silicon hyperdoped with gold

    NASA Astrophysics Data System (ADS)

    Mathews, Jay; Liu, Yining; Malladi, Girish; Efstathiadis, Harry; Warrender, Jeffrey

    Recent advances in the field of laser hyperdoping have produced a new class of materials that could lead the way to silicon-based, CMOS-compatible infrared detectors. Using the method of ion implantation followed by pulsed laser melting (II-PLM), silicon films with impurities at concentrations well above the solid solubility limit can be fabricated. Recent work has centered around Si:Au, from which prototype IR detectors have been successfully fabricated, but there are still many questions about the structural, electrical, and optical properties of this material. In order to enhance the infrared absorption and achieve high-efficiency devices, a thorough understanding of these properties is necessary, and the processes for device fabrication must be optimized. In this work, we explore the structural and electrical properties of Si:Au hyperdoped films. Si:Au films were annealed at various temperatures, and RBS channeling was used to measure the fraction of Au atoms sitting at substitutional sites. Additionally, transmission line method (TLM) and van der Pauw (VDP) test structures were fabricated in order to investigate formation of Ohmic contacts on the hyperdoped films and to study the electrical properties of Si:Au.

  5. An efficient modeling methodology of structural systems containing viscoelastic dampers based on frequency response function substructuring

    NASA Astrophysics Data System (ADS)

    de Lima, A. M. G.; Rade, D. A.; Lépore Neto, F. P.

    2009-05-01

    In this paper it is suggested a modeling methodology of structural systems supported by translational and rotational viscoelastic mounts or joints based on a frequency response function coupling technique. Such strategy enables to predict the dynamic behaviour of the composite systems given a set of frequency response functions of the main structure and a driving point frequency response function of the viscoelastic support. These frequency response functions can be obtained either experimentally or by finite element modeling. Both cases are considered in the study. After presenting the underlying theoretical aspects, the results of numerical simulations of two-dimensional structures are presented, emphasizing the procedure conceived to compute the frequency response functions of the viscoelastic mounts or joints from a detailed finite element model using commercial packages and material properties provided by manufacturers. The dependency of the viscoelastic behaviour on frequency and temperature is accounted for by using the complex modulus approach and the concepts of reduced frequency and shift factor. An investigation using experimentally acquired frequency response functions of a frame structure with a translational viscoelastic damper is presented. Based on the obtained results, the main features of the modeling methodology are highlighted.

  6. Structure and Properties of Amorphous Transparent Conducting Oxides

    NASA Astrophysics Data System (ADS)

    Medvedeva, Julia

    Driven by technological appeal, the research area of amorphous oxide semiconductors has grown tremendously since the first demonstration of the unique properties of amorphous indium oxide more than a decade ago. Today, amorphous oxides, such as a-ITO, a-IZO, a-IGZO, or a-ZITO, exhibit the optical, electrical, thermal, and mechanical properties that are comparable or even superior to those possessed by their crystalline counterparts, pushing the latter out of the market. Large-area uniformity, low-cost low-temperature deposition, high carrier mobility, optical transparency, and mechanical flexibility make these materials appealing for next-generation thin-film electronics. Yet, the structural variations associated with crystalline-to-amorphous transition as well as their role in carrier generation and transport properties of these oxides are far from being understood. Although amorphous oxides lack grain boundaries, factors like (i) size and distribution of nanocrystalline inclusions; (ii) spatial distribution and clustering of incorporated cations in multicomponent oxides; (iii) formation of trap defects; and (iv) piezoelectric effects associated with internal strains, will contribute to electron scattering. In this work, ab-initio molecular dynamics (MD) and accurate density-functional approaches are employed to understand how the properties of amorphous ternary and quaternary oxides depend on quench rates, cation compositions, and oxygen stoichiometries. The MD results, combined with thorough experimental characterization, reveal that interplay between the local and long-range structural preferences of the constituent oxides gives rise to a complex composition-dependent structural behavior in the amorphous oxides. The proposed network models of metal-oxygen polyhedra help explain the observed intriguing electrical and optical properties in In-based oxides and suggest ways to broaden the phase space of amorphous oxide semiconductors with tunable properties. The

  7. Graph Theoretic Foundations of Multibody Dynamics Part I: Structural Properties.

    PubMed

    Jain, Abhinandan

    2011-06-21

    This is the first part of two papers that use concepts from graph theory to obtain a deeper understanding of the mathematical foundations of multibody dynamics. The key contribution is the development of a unifying framework that shows that key analytical results and computational algorithms in multibody dynamics are a direct consequence of structural properties and require minimal assumptions about the specific nature of the underlying multibody system. This first part focuses on identifying the abstract graph theoretic structural properties of spatial operator techniques in multibody dynamics. The second part paper exploits these structural properties to develop a broad spectrum of analytical results and computational algorithms.Towards this, we begin with the notion of graph adjacency matrices and generalize it to define block-weighted adjacency (BWA) matrices and their 1-resolvents. Previously developed spatial operators are shown to be special cases of such BWA matrices and their 1-resolvents. These properties are shown to hold broadly for serial and tree topology multibody systems. Specializations of the BWA and 1-resolvent matrices are referred to as spatial kernel operators (SKO) and spatial propagation operators (SPO). These operators and their special properties provide the foundation for the analytical and algorithmic techniques developed in the companion paper.We also use the graph theory concepts to study the topology induced sparsity structure of these operators and the system mass matrix. Similarity transformations of these operators are also studied. While the detailed development is done for the case of rigid-link multibody systems, the extension of these techniques to a broader class of systems (e.g. deformable links) are illustrated. PMID:22102790

  8. Structure and luminescence properties of tellurium(IV) complex compounds

    NASA Astrophysics Data System (ADS)

    Sedakova, T. V.; Mirochnik, A. G.; Karasev, V. E.

    2011-05-01

    Using the tellurium(IV) complex compounds as an example, we study the interrelation between the geometric structure and spectral luminescence properties. We find that, in the series of compounds of Te(IV), which are characterized by the island octahedral coordination of Te(IV) ions, the luminescence intensity depends on the degree of distortion of the Te(IV) coordination polyhedron, the Stokes shift, and the energy of the luminescence transition. We revealed that the considered series of Te(IV) compounds possess reversible thermochromic properties.

  9. Structure property relationships of carbonaceous films grown under ion enhancement

    SciTech Connect

    Weissmantel, C.; Ackermann, E.; Bewilogua, K.; Hecht, G.; Kupfer, H.; Rau, B.

    1986-11-01

    Based on our own results and in comparison with data published by other groups the structure property relationships of carbon and carbon/metal films prepared by sputtering and deposition of partially ionized species are discussed. Films grown by ion beam sputtering are dark brownish and amorphous with a small fraction of microcrystals. However, a transition to transparent and insulating layers can be effected by ion bombardment. C/Me coatings, where Me stands for Ti or Sn, were obtained by magnetron sputtering of composite targets. The films proved to be amorphous up to metal concentrations of more than 10 at. %, but metal and carbide crystals grow upon annealing. Measurements of the hardness, the electrical conductivity, and the contact behavior in dependence on the composition provided interesting information. For carbon films prepared by deposition of partially ionized benzene species it has been found that the properties depend characteristically on the ion energy; typical ''diamondlike'' i-C films are obtained by applying a bias voltage from 1--3 keV. The thermal stability of the amorphous coatings is discussed in conjunction with their electrical conductivity. Summarizing extensive structure investigations, a structure model based on tetrahedrally interlinked carbon rings is proposed. Composites of the type i-C/Me (Me: Al, Ti, Cr), which were prepared by simultaneous metal evaporation, exhibit a wide range of structure property relations.

  10. Effect of dielectrophoretic structuring on piezoelectric and pyroelectric properties of lead titanate-epoxy composites

    NASA Astrophysics Data System (ADS)

    Khanbareh, H.; van der Zwaag, S.; Groen, W. A.

    2014-10-01

    Functional granular composites of lead titanate particles in an epoxy matrix prepared by dielectrophoresis show enhanced dielectric, piezoelectric and pyroelectric properties compared to 0-3 composites for different ceramic volume content from 10% to 50%. Two structuring parameters, the interparticle distance and the percentage of 1-3 connectivity are used based on the Bowen model and the mixed connectivity model respectively. The degree of structuring calculated according to both models correlate well with the increase in piezoelectric and pyroelectric sensitivities of the composites. Higher sensitivity of the electroactive properties are observed at higher ceramic volume fractions. The effect of electrical conductivity of the matrix on the pyroelectric responsivity of the composites has been demonstrated to be a key parameter in governing the pyroelectric properties of the composites.

  11. Noise transmission properties and control strategies for composite structures

    NASA Technical Reports Server (NTRS)

    Silcox, Richard J.; Beyer, Todd B.; Lester, Harold C.

    1991-01-01

    A study of several component technologies required to apply active control techniques to reduce interior noise in composite aircraft structures is described. The mechanisms of noise transmission in an all composite, large-scale, fuselage model are studied in an experimental program and found similar to mechanisms found in conventional aircraft construction. Two primary conditions of structural acoustic response are found to account for the dominant interior acoustic response. A preliminary study of active noise control in cylinders used piezoceramic actuators as force inputs for a simple aluminum fuselage model. These actuators provided effective control for the same two conditions of noise transmission found in the composite fuselage structure. The use of piezoceramic actuators to apply force inputs overcomes the weight and structural requirements of conventional shaker actuators. Finally, in order to accurately simulate these types of actuators in a cylindrical shell, two analytical models are investigated that apply either in-plane forces or bending moments along the boundaries of a finite patch. It is shown that the bending model may not be as effective as the force model for exciting the low order azimuthal modes that typically dominate the structural acoustic response in these systems. This result will affect the arrangement and distribution of actuators required for effective active control systems.

  12. Lanthanide coordination polymers: Synthesis, diverse structure and luminescence properties

    SciTech Connect

    Song, Xue-Qin Lei, Yao-Kun; Wang, Xiao-Run; Zhao, Meng-Meng; Peng, Yun-Qiao; Cheng, Guo-Quan

    2014-10-15

    The new semirigid exo-bidentate ligand incorporating furfurysalicylamide terminal groups, namely, 1,4-bis([(2′-furfurylaminoformyl)phenoxyl]methyl)-2,5-bismethylbenzene (L) was synthesized and used as building blocks for constructing lanthanide coordination polymers with luminescent properties. The series of lanthanide nitrate complexes have been characterized by elemental analysis, IR spectroscopy, and X-ray diffraction analysis. The semirigid ligand L, as a bridging ligand, reacts with lanthanide nitrates forming three distinct structure types: chiral noninterpenetrated two-dimensional (2D) honeycomblike (6,3) (hcb, Schläfli symbol 6{sup 3}, vertex symbol 6 6 6) topological network as type I, 1D zigzag chain as type II and 1D trapezoid ladder-like chain as type III. The structural diversities indicate that lanthanide contraction effect played significant roles in the structural self-assembled process. The luminescent properties of Eu{sup III}, Tb{sup III} and Dy{sup III} complexes are discussed in detail. Due to the good match between the lowest triplet state of the ligand and the resonant energy level of the lanthanide ion, the lanthanide ions in Eu{sup III}, Tb{sup III} and Dy{sup III} complexes can be efficiently sensitized by the ligand. - Graphical abstract: We present herein six lanthanide coordination polymers of a new semirigid exo-bidentate ligand which not only display diverse structures but also possess strong luminescence properties. - Highlights: • We present lanthanide coordination polymers of a new semirigid exo-bidentate ligand. • The lanthanide coordination polymers exhibit diverse structures. • The luminescent properties of Tb{sup III}, Eu{sup III} and Dy{sup III} complexes are discussed in detail.

  13. SEISMIC RESPONSE OF DAM WITH SOIL-STRUCTURE INTERACTION.

    USGS Publications Warehouse

    Bycroft, G.N.; Mork, P.N.

    1987-01-01

    An analytical solution to the response of a long trapezoidal-section dam on a foundation consisting of an elastic half-space and subjected to simulated earthquake motion is developed. An optimum seismic design is achieved when the cross section of the dam is triangular. The effect of soil structure interaction is to lower the strain occurring in the dam.

  14. Non-dimensional response surfaces for structural optimization with uncertainty

    NASA Astrophysics Data System (ADS)

    Venter, Gerhardus

    Approximation concepts are an effective approach for alleviating some of the problems associated with the direct use of modern computerized analysis techniques in an optimization environment. Recently, response surface approximations have gained popularity as polynomial approximations that are global in nature. Response surface approximations shift the computational burden from the optimization problem to the problem of constructing the approximations, and accommodate the use of detailed analysis techniques without the need of derivative information. Additionally, response surface approximations filter out numerical noise inherent to most numerical analysis procedures, by providing a smooth approximate response function, and simplify the integration of the analysis and the optimization codes. The present dissertation investigates the use of response surface approximations in expensive structural optimization problems and aims to suggest techniques for improving both the accuracy of response surface approximations as well as the efficiency with which they are constructed. A stepped plate design problem is considered and response surface approximations are constructed for different failure mechanisms using numerical experiments conducted with a finite element analysis. Both an isotropic and a composite laminated plate, where the change in thickness is a result of internal ply drop off, are considered. The proposed methodology uses a combination of dimensional analysis, higher order response surface approximations, stepwise regression, a detailed error analysis and statistical design of experiments to improve both accuracy and efficiency. Dimensional analysis identifies variables intrinsic to the problem, and thus reduces the number of variables in the resulting response surface approximation. Stepwise regression is used to eliminate insignificant parameters from a response surface approximation and statistical design of experiments is used to identify a small set of

  15. An integrated theory for predicting the hydrothermomechanical response of advanced composite structural components

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    A theory is developed for predicting the hydrothermomechanical response of advanced composite structural components. The combined hydrothermal effects on the mechanical properties of unidirectional composites loaded along the material axis and off-axis, and of angleplied laminates are also evaluated. The materials investigated consist of neat PR-288 epoxy matrix resin and an AS-type graphite fiber/PR-288 resin unidirectional composite.

  16. Effect of the aerated structure on selected properties of freeze-dried hydrocolloid gels

    NASA Astrophysics Data System (ADS)

    Ciurzyńska, Agnieszka; Lenart, Andrzej

    2016-01-01

    The ability to create diverse structures and studies on the effect of the aerated structure on selected properties with the use of freeze-dried gels may provide knowledge about the properties of dried foods. Such gels can be a basis for obtaining innovative food products. For the gel preparation, 3 types of hydrocolloids were used: low-methoxyl pectin, a mixture of xanthan gum and locust-bean gum, and a mixture of xanthan gum and guar gum. Gels were aerated for 3 and 7 min, frozen at a temperature of -45°C 2 h-1, and freeze-dried at a temperature of 30°C. For the samples obtained, structure, porosity, shrinkage, rehydration, and colour were investigated. It was shown that the type of the hydrocolloid and aeration time influence the structure of freeze-dried gels, which determines such properties of samples as porosity, shrinkage, density, rehydration, and colour. The bigger pores of low-methoxyl pectin gels undergo rehydration in the highest degree. The delicate and aerated structure of gels with the mixture of xanthan gum and locust-bean gum was damaged during freeze-drying and shrinkage exhibited the highest value. Small pores of samples with the mixture of xanthan gum and guar gum were responsible for the lower rehydration properties, but the highest porosity value contributed to the highest lightness value.

  17. Designing structures for dynamical properties via natural frequencies separation. Application to tensegrity structures design

    NASA Astrophysics Data System (ADS)

    Sultan, Cornel

    2009-05-01

    The design of structures for dynamic properties is addressed by placing conditions on the separation between natural frequencies. Additional constraints, like lower and upper bounds on the natural frequencies, are also included. A fast numerical algorithm that exploits the mathematical structure of the resulting problem is developed. Examples of the algorithm's application to tensegrity structures design are presented and the connection between natural frequencies separation and proportional damping approximation is analyzed.

  18. Atomic structures and electronic properties of phosphorene grain boundaries

    NASA Astrophysics Data System (ADS)

    Guo, Yu; Zhou, Si; Zhang, Junfeng; Bai, Yizhen; Zhao, Jijun

    2016-06-01

    Grain boundary (GB) is one main type of defects in two-dimensional (2D) crystals, and has significant impact on the physical properties of 2D materials. Phosphorene, a recently synthesized 2D semiconductor, possesses a puckered honeycomb lattice and outstanding electronic properties. It is very interesting to know the possible GBs present in this novel material, and how their properties differ from those in the other 2D materials. Based on first-principles calculations, we explore the atomic structure, thermodynamic stability, and electronic properties of phosphorene GBs. A total of 19 GBs are predicted and found to be energetically stable with formation energies much lower than those in graphene. These GBs do not severely affect the electronic properties of phosphorene: the band gap of perfect phosphorene is preserved, and the electron mobilities are only moderately reduced in these defective systems. Our theoretical results provide vital guidance for experimental tailoring the electronic properties of phosphorene as well as the device applications using phosphorene materials.

  19. On the dimension of complex responses in nonlinear structural vibrations

    NASA Astrophysics Data System (ADS)

    Wiebe, R.; Spottswood, S. M.

    2016-07-01

    The ability to accurately model engineering systems under extreme dynamic loads would prove a major breakthrough in many aspects of aerospace, mechanical, and civil engineering. Extreme loads frequently induce both nonlinearities and coupling which increase the complexity of the response and the computational cost of finite element models. Dimension reduction has recently gained traction and promises the ability to distill dynamic responses down to a minimal dimension without sacrificing accuracy. In this context, the dimensionality of a response is related to the number of modes needed in a reduced order model to accurately simulate the response. Thus, an important step is characterizing the dimensionality of complex nonlinear responses of structures. In this work, the dimensionality of the nonlinear response of a post-buckled beam is investigated. Significant detail is dedicated to carefully introducing the experiment, the verification of a finite element model, and the dimensionality estimation algorithm as it is hoped that this system may help serve as a benchmark test case. It is shown that with minor modifications, the method of false nearest neighbors can quantitatively distinguish between the response dimension of various snap-through, non-snap-through, random, and deterministic loads. The state-space dimension of the nonlinear system in question increased from 2-to-10 as the system response moved from simple, low-level harmonic to chaotic snap-through. Beyond the problem studied herein, the techniques developed will serve as a prescriptive guide in developing fast and accurate dimensionally reduced models of nonlinear systems, and eventually as a tool for adaptive dimension-reduction in numerical modeling. The results are especially relevant in the aerospace industry for the design of thin structures such as beams, panels, and shells, which are all capable of spatio-temporally complex dynamic responses that are difficult and computationally expensive to

  20. Responsive satellites and the need for structural health monitoring

    NASA Astrophysics Data System (ADS)

    Arritt, Brandon J.; Kumar, Amrita; Buckley, Steven; Hannum, Robert; Welsh, Jeffry; Beard, Shawn; Qin, Xinlin; Wegner, Peter

    2007-04-01

    The United States is striving to develop an Operationally Responsive Space capability. The goal is to be able to deliver tailored spacecraft capabilities to the warfighter as needs arise. This places a premium on the timespan between generating that requirement and having a functioning satellite performing its mission on orbit. Although there is lively debate regarding how to achieve this responsive space capability, one thing remains undeniable; the satellite flight qualification and launch vehicle integration process needs to be dramatically truncated. This paper describes the Air Force Research Laboratory's attempts to validate the use of Structural Health Monitoring (SHM) in lieu of traditional structural flight qualification testing schemes (static and shock loads, random vibration, coupled loads analysis, thermal vacuum testing, etc.) for potential Responsive Space (RS) satellites.

  1. Magnetic and structural properties of amorphous CoTi soft ferromagnetic thin films. II. Structural properties

    NASA Astrophysics Data System (ADS)

    Machizaud, F.; Ounadjela, K.; Suran, G.

    1989-07-01

    The structure of amorphous Co1-xTix thin films prepared by rf sputtering was studied by electron microscopy as a function of the deposition parameters and the concentration of the layers. We tried to simulate the experimental diffraction spectra by a structural model which took into account the short-range order observed in the corresponding crystalline alloy. The model which gave the best agreement with the experimental results is a random continuous network built up of clusters with trigonal, octahedral, and icosahedral symmetry. The size and the structural correlations between the various clusters were also determined. By changing the respective amount of the clusters we could simulate the slight variations of the characteristics of the diffused intensities obtained on samples deposited under a different pressure of the sputtering gas PAr. This structural model provided an explanation of the variations of the induced anisotropy Ku with PAr with thermomagnetic annealing, and as a function of the concentration of the films. These results are reported in paper I.

  2. Humic acids: Structural properties and multiple functionalities for novel technological developments.

    PubMed

    de Melo, Bruna Alice Gomes; Motta, Fernanda Lopes; Santana, Maria Helena Andrade

    2016-05-01

    Humic acids (HAs) are macromolecules that comprise humic substances (HS), which are organic matter distributed in terrestrial soil, natural water, and sediment. HAs differ from the other HS fractions (fulvic acid and humins) in that they are soluble in alkaline media, partially soluble in water, and insoluble in acidic media. Due to their amphiphilic character, HAs form micelle-like structures in neutral to acidic conditions, which are useful in agriculture, pollution remediation, medicine and pharmaceuticals. HAs have undefined compositions that vary according to the origin, process of obtainment, and functional groups present in their structures, such as quinones, phenols, and carboxylic acids. Quinones are responsible for the formation of reactive oxygen species (ROS) in HAs, which are useful for wound healing and have fungicidal/bactericidal properties. Phenols and carboxylic acids deprotonate in neutral and alkaline media and are responsible for various other functions, such as the antioxidant and anti-inflammatory properties of HAs. In particular, the presence of phenolic groups in HAs provides antioxidant properties due to their free radical scavenging capacity. This paper describes the main multifunctionalities of HAs associated with their structures and properties, focusing on human health applications, and we note perspectives that may lead to novel technological developments. To the best of our knowledge, this is the first review to address this topic from this approach. PMID:26952503

  3. Predicting olfactory receptor neuron responses from odorant structure

    PubMed Central

    Schmuker, Michael; de Bruyne, Marien; Hähnel, Melanie; Schneider, Gisbert

    2007-01-01

    Background Olfactory receptors work at the interface between the chemical world of volatile molecules and the perception of scent in the brain. Their main purpose is to translate chemical space into information that can be processed by neural circuits. Assuming that these receptors have evolved to cope with this task, the analysis of their coding strategy promises to yield valuable insight in how to encode chemical information in an efficient way. Results We mimicked olfactory coding by modeling responses of primary olfactory neurons to small molecules using a large set of physicochemical molecular descriptors and artificial neural networks. We then tested these models by recording in vivo receptor neuron responses to a new set of odorants and successfully predicted the responses of five out of seven receptor neurons. Correlation coefficients ranged from 0.66 to 0.85, demonstrating the applicability of our approach for the analysis of olfactory receptor activation data. The molecular descriptors that are best-suited for response prediction vary for different receptor neurons, implying that each receptor neuron detects a different aspect of chemical space. Finally, we demonstrate that receptor responses themselves can be used as descriptors in a predictive model of neuron activation. Conclusion The chemical meaning of molecular descriptors helps understand structure-response relationships for olfactory receptors and their "receptive fields". Moreover, it is possible to predict receptor neuron activation from chemical structure using machine-learning techniques, although this is still complicated by a lack of training data. PMID:17880742

  4. Mechanisms Responsible for Microwave Properties in High Performance Dielectric Materials

    NASA Astrophysics Data System (ADS)

    Zhang, Shengke

    Microwave properties of low-loss commercial dielectric materials are optimized by adding transition-metal dopants or alloying agents (i.e. Ni, Co, Mn) to tune the temperature coefficient of resonant frequency (tau f) to zero. This occurs as a result of the temperature dependence of dielectric constant offsetting the thermal expansion. At cryogenic temperatures, the microwave loss in these dielectric materials is dominated by electron paramagnetic resonance (EPR) loss, which results from the spin-excitations of d-shell electron spins in exchange-coupled clusters. We show that the origin of the observed magnetically-induced shifts in the dielectric resonator frequency originates from the same mechanism, as described by the Kramers-Kronig relations. The temperature coefficient of resonator frequency, tauf, is related to three material parameters according to the equation, tau f = - (½ tauepsilon + ½ taumu + alphaL), where tauepsilon, taumu , and alphaL are the temperature coefficient of dielectric constant, magnetic permeability, and lattice constant, respectively. Each of these parameters for dielectric materials of interest are measured experimentally. These results, in combination with density functional simulations, developed a much improved understanding of the fundamental mechanisms responsible for tau f. The same experimental methods have been used to characterize in-situ the physical nature and concentration of performance-degrading point defects in the dielectrics of superconducting planar microwave resonators.

  5. Meeting Report: Structural Determination of Environmentally Responsive Proteins

    PubMed Central

    Reinlib, Leslie

    2005-01-01

    The three-dimensional structure of gene products continues to be a missing lynchpin between linear genome sequences and our understanding of the normal and abnormal function of proteins and pathways. Enhanced activity in this area is likely to lead to better understanding of how discrete changes in molecular patterns and conformation underlie functional changes in protein complexes and, with it, sensitivity of an individual to an exposure. The National Institute of Environmental Health Sciences convened a workshop of experts in structural determination and environmental health to solicit advice for future research in structural resolution relative to environmentally responsive proteins and pathways. The highest priorities recommended by the workshop were to support studies of structure, analysis, control, and design of conformational and functional states at molecular resolution for environmentally responsive molecules and complexes; promote understanding of dynamics, kinetics, and ligand responses; investigate the mechanisms and steps in posttranslational modifications, protein partnering, impact of genetic polymorphisms on structure/function, and ligand interactions; and encourage integrated experimental and computational approaches. The workshop participants also saw value in improving the throughput and purity of protein samples and macromolecular assemblies; developing optimal processes for design, production, and assembly of macromolecular complexes; encouraging studies on protein–protein and macromolecular interactions; and examining assemblies of individual proteins and their functions in pathways of interest for environmental health. PMID:16263521

  6. The role of penetrant structure in the transport and mechanical properties of a thermoset adhesive

    NASA Astrophysics Data System (ADS)

    Kwan, Kermit S.

    In this work the relationships between penetrant structure, its transport properties, and its effects on the mechanical properties of a polymer matrix were investigated. Although there is a vast amount of data on the diffusion of low molecular weight molecules into polymeric materials and on the mechanical properties of various polymer-penetrant systems, no attempts have been made to inter-relate the two properties with respect to the chemical structure of the diffusant. Therefore, two series of penetrants---n-alkanes and esters---were examined in this context, with the goal of correlating molecular size, shape, and chemical nature of the penetrant to its final transport and matrix mechanical properties. These correlations have been demonstrated to allow quantitative prediction of one property, given a reasonable set of data on the other parameters. A series of n-alkanes (C6--C17) and esters (C5--C17) have been used to separate the effects of penetrant size and shape, from those due to polymer-penetrant interactions, in the diffusion through a polyamide polymeric adhesive. These effects have been taken into account in order to yield a qualitative relationship that allows for prediction of diffusivity based upon penetrant structural information. Transport properties have been analyzed using mass uptake experiments as well as an in-situ FTIR-ATR technique to provide detailed kinetic as well as thermodynamic information on this process. The phenomenon of diffusion and its effects on the resulting dynamic mechanical response of a matrix polymeric adhesive have been studied in great detail using the method of reduced variables. The concept of a diffusion-time shift factor (log aDt) has been introduced to create doubly-reduced master curves, taking into account the effects of temperature and the variations in the polymer mechanical response due to the existence of a low molecular weight penetrant.

  7. Structural and electrical properties of In-implanted Ge

    SciTech Connect

    Feng, R. Kremer, F.; Mirzaei, S.; Medling, S. A.; Ridgway, M. C.; Sprouster, D. J.; Decoster, S.; Glover, C. J.; Russo, S. P.

    2015-10-28

    We report on the effects of dopant concentration on the structural and electrical properties of In-implanted Ge. For In concentrations of ≤ 0.2 at. %, extended x-ray absorption fine structure and x-ray absorption near-edge structure measurements demonstrate that all In atoms occupy a substitutional lattice site while metallic In precipitates are apparent in transmission electron micrographs for In concentrations ≥0.6 at. %. Evidence of the formation of In-vacancy complexes deduced from extended x-ray absorption fine structure measurements is complimented by density functional theory simulations. Hall effect measurements of the conductivity, carrier density, and carrier mobility are then correlated with the substitutional In fraction.

  8. Chiral phosphorus nanotubes: structure, bonding, and electronic properties.

    PubMed

    Fernández-Escamilla, H N; Quijano-Briones, J J; Tlahuice-Flores, A

    2016-05-14

    The study of black phosphorus nanotubes (PNTs) had been devoted to zigzag and armchair structures, with no consideration of chiral structures to date. In this communication, we studied the structural and electronic (band structure) properties of chiral nanotubes using a periodic plane wave-pseudopotential approach. We found that some chiral nanotubes display similar bandgaps and binding energies per atom (BEA) as armchair PNTs and Born-Oppenheimer molecular dynamics (BOMD) calculations attest their thermal stability. Interestingly, we determined that the bandgap is tuned by varying the PNTs chirality and it is not related to their diameters. This feature can be exploited in optical and electronic applications wherein a direct and sizable bandgap is required. PMID:27094567

  9. Quality assessment of modeled protein structure using physicochemical properties.

    PubMed

    Rana, Prashant Singh; Sharma, Harish; Bhattacharya, Mahua; Shukla, Anupam

    2015-04-01

    Physicochemical properties of proteins always guide to determine the quality of the protein structure, therefore it has been rigorously used to distinguish native or native-like structure from other predicted structures. In this work, we explore nine machine learning methods with six physicochemical properties to predict the Root Mean Square Deviation (RMSD), Template Modeling (TM-score), and Global Distance Test (GDT_TS-score) of modeled protein structure in the absence of its true native state. Physicochemical properties namely total surface area, euclidean distance (ED), total empirical energy, secondary structure penalty (SS), sequence length (SL), and pair number (PN) are used. There are a total of 95,091 modeled structures of 4896 native targets. A real coded Self-adaptive Differential Evolution algorithm (SaDE) is used to determine the feature importance. The K-fold cross validation is used to measure the robustness of the best predictive method. Through the intensive experiments, it is found that Random Forest method outperforms over other machine learning methods. This work makes the prediction faster and inexpensive. The performance result shows the prediction of RMSD, TM-score, and GDT_TS-score on Root Mean Square Error (RMSE) as 1.20, 0.06, and 0.06 respectively; correlation scores are 0.96, 0.92, and 0.91 respectively; R(2) are 0.92, 0.85, and 0.84 respectively; and accuracy are 78.82% (with ± 0.1 err), 86.56% (with ± 0.1 err), and 87.37% (with ± 0.1 err) respectively on the testing data set. The data set used in the study is available as supplement at http://bit.ly/RF-PCP-DataSets. PMID:25524475

  10. Study on the Response Coefficient of Setback Structures Compared to Regular Moment Frame Structures

    SciTech Connect

    Mirghaderi, S. Rasoul; Khafaf, Bardia; Epackachi, Siamak

    2008-07-08

    In design practice of many countries, seismic analysis and proportioning of structures are usually based upon linear elastic analysis due to reduced seismic forces by response coefficient; R. Setback structures are one of the most popular shapes of the constructed buildings. In setback structures, the shape and proportions of the building have a major effect on distribution of earthquake forces as they work their way through the building. On the other hand, geometric configuration has a profound effect on the structural-dynamic response of a building. Therefore, when a building has irregular features, such as asymmetric in height or vertical discontinuity, the traditional assumptions used in development of seismic criteria for regular buildings may not be applicable. Inelastic seismic behavior of these types of structures seems to be quite different from the regular steel moment resisting structures in which the overall ductility is localized at beam-ends.In order to investigate the seismic behavior and estimate the Response Coefficient of those structures, nonlinear static analysis (pushover) are used for three categories of setback structures namely low rise, medium rise and high rise buildings with different setbacks in their height. The Response Coefficient are calculated and compared with those taken from regular type of moment frame structures.

  11. Structural response measurements to insure penetrator data integrity

    SciTech Connect

    Bateman, V.I.; Mayes, R.L.; James, G.H. III

    1993-09-01

    Measurements made by a penetrator structure penetration of some medium may not measure the penetration environment directly. In general, the measurements quantify the penetrator`s structural response to the penetrator force environment. This paper reports laboratory testing and analysis techniques that have been used to identify and/or remove highly nonlinear responses which can mask the penetration environments one desires to measure. Results for two penetrator structures are presented. For the first penetrator, shock testing was conducted to determine the cause of accelerometer failure during field tests. For a second penetrator, shock testing was conducted to assist with the interpretation of accelerometer measurements made during field tests for which the penetrator was instrumented with one axial accelerometer. Very high acceleration levels for a data bandwidth of DC to 70 kHz were recorded in these field tests. The laboratory test results for these two penetrators are presented and discussed.

  12. Bioinspired Cellular Structures: Additive Manufacturing and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Stampfl, J.; Pettermann, H. E.; Liska, R.

    Biological materials (e.g., wood, trabecular bone, marine skeletons) rely heavily on the use of cellular architecture, which provides several advantages. (1) The resulting structures can bear the variety of "real life" load spectra using a minimum of a given bulk material, featuring engineering lightweight design principles. (2) The inside of the structures is accessible to body fluids which deliver the required nutrients. (3) Furthermore, cellular architectures can grow organically by adding or removing individual struts or by changing the shape of the constituting elements. All these facts make the use of cellular architectures a reasonable choice for nature. Using additive manufacturing technologies (AMT), it is now possible to fabricate such structures for applications in engineering and biomedicine. In this chapter, we present methods that allow the 3D computational analysis of the mechanical properties of cellular structures with open porosity. Various different cellular architectures including disorder are studied. In order to quantify the influence of architecture, the apparent density is always kept constant. Furthermore, it is shown that how new advanced photopolymers can be used to tailor the mechanical and functional properties of the fabricated structures.

  13. Properties and structure of raised bog peat humic acids

    NASA Astrophysics Data System (ADS)

    Klavins, Maris; Purmalis, Oskars

    2013-10-01

    Humic substances form most of the organic components of soil, peat and natural waters, and their structure and properties differ very much depending on their source. The aims of this study are to characterize humic acids (HAs) from raised bog peat, to evaluate the homogeneity of peat HAs within peat profiles, and to study peat humification impact on properties of HAs. A major impact on the structure of peat HAs have lignin-free raised bog biota (dominantly represented by bryophytes of different origin). On diagenesis scale, peat HAs have an intermediate position between the living organic matter and coal organic matter, and their structure is formed in a process in which more labile structures (carbohydrates, amino acids, etc.) are destroyed, while thermodynamically more stable aromatic and polyaromatic structures emerge as a result of abiotic synthesis. However, in comparison with soil, aquatic and other HAs, aromaticity of peat HAs is much lower. Comparatively, the raised bog peat HAs are at the beginning of the transformation process of living organic matter. Concentrations of carboxyl and phenolic hydroxyl groups change depending on the peat age and decomposition degree from where HAs have been isolated, and carboxylic acidity of peat HAs increases with peat depth and humification degree.

  14. Dielectric and structural properties of ferroelectric betaine arsenate films

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Zaitseva, N. V.; Yurko, E. I.; Svinarev, F. B.

    2014-12-01

    Ferroelectric films of betaine arsenate and partially deuterated betaine arsenate have been grown by evaporation on LiNbO3, α-Al2O3, and NdGaO3 substrates with a preliminarily deposited structure of interdigitated electrodes, as well as on the Al/glass substrate. This paper presents the results of the examination of the block structure of the films in a polarizing microscope, the X-ray diffraction analysis of their crystal structure, and the investigation of the dielectric properties in a measuring field oriented both parallel and perpendicular to the plane of the film. The transition of the films to the ferroelectric state at T = T c is accompanied by anomalies of the capacitance of the structure, an increase in the dielectric loss, and the appearance of dielectric hysteresis loops. The growth of the films from a solution of betaine arsenate in a heavy water leads to an increase in the ferroelectric transition temperature from T c = 119 K in the films without deuterium to T c = 149 K, which corresponds to the degree of deuteration of approximately 60-70%. The dielectric and structural properties of the films are compared with those of the betaine arsenate single crystals and the previously studied films of betaine phosphite and glycine phosphite.

  15. RaptorX-Property: a web server for protein structure property prediction

    PubMed Central

    Wang, Sheng; Li, Wei; Liu, Shiwang; Xu, Jinbo

    2016-01-01

    RaptorX Property (http://raptorx2.uchicago.edu/StructurePropertyPred/predict/) is a web server predicting structure property of a protein sequence without using any templates. It outperforms other servers, especially for proteins without close homologs in PDB or with very sparse sequence profile (i.e. carries little evolutionary information). This server employs a powerful in-house deep learning model DeepCNF (Deep Convolutional Neural Fields) to predict secondary structure (SS), solvent accessibility (ACC) and disorder regions (DISO). DeepCNF not only models complex sequence–structure relationship by a deep hierarchical architecture, but also interdependency between adjacent property labels. Our experimental results show that, tested on CASP10, CASP11 and the other benchmarks, this server can obtain ∼84% Q3 accuracy for 3-state SS, ∼72% Q8 accuracy for 8-state SS, ∼66% Q3 accuracy for 3-state solvent accessibility, and ∼0.89 area under the ROC curve (AUC) for disorder prediction. PMID:27112573

  16. RaptorX-Property: a web server for protein structure property prediction.

    PubMed

    Wang, Sheng; Li, Wei; Liu, Shiwang; Xu, Jinbo

    2016-07-01

    RaptorX Property (http://raptorx2.uchicago.edu/StructurePropertyPred/predict/) is a web server predicting structure property of a protein sequence without using any templates. It outperforms other servers, especially for proteins without close homologs in PDB or with very sparse sequence profile (i.e. carries little evolutionary information). This server employs a powerful in-house deep learning model DeepCNF (Deep Convolutional Neural Fields) to predict secondary structure (SS), solvent accessibility (ACC) and disorder regions (DISO). DeepCNF not only models complex sequence-structure relationship by a deep hierarchical architecture, but also interdependency between adjacent property labels. Our experimental results show that, tested on CASP10, CASP11 and the other benchmarks, this server can obtain ∼84% Q3 accuracy for 3-state SS, ∼72% Q8 accuracy for 8-state SS, ∼66% Q3 accuracy for 3-state solvent accessibility, and ∼0.89 area under the ROC curve (AUC) for disorder prediction. PMID:27112573

  17. Density Functional Study of the structural properties in Tamoxifen

    NASA Astrophysics Data System (ADS)

    de Coss-Martinez, Romeo; Tapia, Jorge A.; Quijano-Quiñones, Ramiro F.; Canto, Gabriel I.

    2013-03-01

    Using the density functional theory, we have studied the structural properties of Tamoxifen. The calculations were performed with two methodological approaches, which were implemented in SIESTA and Spartan codes. For SIESTA, we considerate a linear combination of atomic orbitals method, using pseudopotentials and the van der Waals approximation for the exchange-correlation potential. Here we analyzed and compared the atomic structure between our results and other theoretical study. We found differences in the bond lengths between the results, that could be attributed to code approaches in each one. This work was supported under Grant FOMIX 2011-09 N: 170297 of Ph.D. A. Tapia.

  18. Structure and spectral properties of truxene dye S5

    NASA Astrophysics Data System (ADS)

    Baryshnikov, G. V.; Minaev, B. F.; Minaeva, V. A.; Ning, Z.; Zhang, Q.

    2012-02-01

    On the ground of functional theory with the B3LYP and BMK functionals, we have studied the structure and optical properties of a truxene dye sensitizer S5 for photoelectric transducers. Based on the calculations of the vertical excitations energy of the dye molecule and accounting the influence of the solvent, we have revealed a positive solvatochromic effect that is weak compared to results obtained in the vacuum approximation. We have studied new features describing stabilization of the planar structure of the cyanothiophene-acrylic fragment of the S5 dye.

  19. Structural and magnetic properties of Mg substituted Co nanoferrites

    NASA Astrophysics Data System (ADS)

    Sharma, Jyoti; Sharma, Neha; Yadav, Premlata; Parashar, Jyoti; Jadoun, Priya; Saxena, V. K.; Bhatnagar, D.; Sharma, K. B.

    2016-05-01

    The structural and magnetic properties of magnesium substituted cobalt nano ferrites CoxMg1-xFe2O4 (x= 0.2, 0.4 and 1.0) have been investigated. The structural characterization has been done by X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). The magnetic studies indicate that the samples show ferromagnetic behaviour at room temperature as well as at low temperature. The magnetization decreases with Mg content in both the cases due to the less magnetic nature of Mg ions than that of the Co ions.

  20. Structure-Dependent Viscoelastic Properties of C(9)-Alkanethiol Monolayers

    SciTech Connect

    Mayer, Thomas M.; Michalske, Terry A.; Shinn, Neal D.

    1999-08-10

    Quartz crystal microbalance techniques and in situ spectroscopic ellipsometry are used to probe the structure-dependent intrinsic viscoelastic properties of self-assembled CH{sub 3}(CH{sub 2}){sub 8}SH alkanethiol monolayer adsorbed from the gas phase onto Au(111)-textured substrates. Physisorbed molecules, mixed chemisorbed-fluid/solid phases and solid-phase domain boundaries make sequentially dominant contributions to the measured energy dissipation in the growing monolayer. Deviations from Langmuir adsorption kinetics reveal a precursor-mediated adsorption channel. These studies reveal the impact of structural heterogeneity in tribological studies of monolayer lubricants.

  1. Structure-Property Relationship in High Tg Thermosetting Polyimides

    NASA Technical Reports Server (NTRS)

    Chuang, Kathy C.; Meador, Mary Ann B.; HardyGreen, DeNise

    2000-01-01

    This viewgraph presentation gives an overview of the structure-property relationship in high glass transition temperatures (T(sub g)) thermosetting polyimides. The objectives of this work are to replace MDA in PMR-15 with 2,2-substituted benzidine and to evaluate the thermo-oxidative stability and mechanical properties of DMBZ-15 against PMR-15. Details are given on the T(sub g) of polyimide resins, the x-ray crystal structure of 2,2-Bis(trifluoro)benzidine (BFBZ), the isothermal aging of polyimide resins at 288 C under 1 atm of circulating air, the compressive strength of polyimide composites, and a gas evaluation profile of DMBZ-15 polyimide resins.

  2. Structure and Electronic Properties of Cerium Orthophosphate: Theory and Experiment

    SciTech Connect

    Adelstein, Nicole; Mun, B. Simon; Ray, Hannah; Ross Jr, Phillip; Neaton, Jeffrey; De Jonghe, Lutgard

    2010-07-27

    Structural and electronic properties of cerium orthophosphate (CePO{sub 4}) are calculated using density functional theory (DFT) with the local spin-density approximation (LSDA+U), with and without gradient corrections (GGA-(PBE)+U), and compared to X-ray diffraction and photoemission spectroscopy measurements. The density of states is found to change significantly as the Hubbard parameter U, which is applied to the Ce 4f states, is varied from 0 to 5 eV. The calculated structural properties are in good agreement with experiment and do not change significantly with U. Choosing U = 3 eV for LDSA provides the best agreement between the calculated density of states and the experimental photoemission spectra.

  3. Structures and Properties of Polymers Important to Their Wear Behavior

    NASA Technical Reports Server (NTRS)

    Tanaka, K.

    1984-01-01

    The wear and transfer of various semicrystalline polymers sliding against smooth steel or glass surfaces were examined. The effects of structures, and properties of polymers on their wear behavior are discussed. It is found that the high wear characteristics of PTFE is due to the easy destruction of the banded structure of PTFE. The size of spherulites and the molecular profile are closely related to the magnitude of wear rates of typical semicrystalline polymers. The effects of these factors on the wear rate on the basis of the destruction or melting of spherulites at the frictional surface are discussed. Although the fatigue theory of wear indicates that some mechanical properties are important to wear behavior, it is shown that the theory does not always explain the experimental result obtained on a smooth surface.

  4. Chirality-Mediated Mechanical and Structural Properties of Oligopeptide Hydrogels

    SciTech Connect

    Taraban, Marc B.; Feng, Yue; Hammouda, Boualem; Hyland, Laura L.; Yu, Y. Bruce

    2012-10-29

    The origin and the effects of homochirality in the biological world continuously stimulate numerous hypotheses and much debate. This work attempts to look at the biohomochirality issue from a different angle - the mechanical properties of the bulk biomaterial and their relation to nanoscale structures. Using a pair of oppositely charged peptides that co-assemble into hydrogels, we systematically investigated the effect of chirality on the mechanical properties of these hydrogels through different combinations of syndiotactic and isotactic peptides. It was found that homochirality confers mechanical advantage, resulting in a higher elastic modulus and strain yield value. Yet, heterochirality confers kinetic advantage, resulting in faster gelation. Structurally, both homochiral and heterochiral hydrogels are made of fibers interconnected by lappet-like webs, but the homochiral peptide fibers are thicker and denser. These results highlight the possible role of biohomochirality in the evolution and/or natural selection of biomaterials.

  5. Computer program for determining mass properties of a rigid structure

    NASA Technical Reports Server (NTRS)

    Hull, R. A.; Gilbert, J. L.; Klich, P. J.

    1978-01-01

    A computer program was developed for the rapid computation of the mass properties of complex structural systems. The program uses rigid body analyses and permits differences in structural material throughout the total system. It is based on the premise that complex systems can be adequately described by a combination of basic elemental shapes. Simple geometric data describing size and location of each element and the respective material density or weight of each element were the only required input data. From this minimum input, the program yields system weight, center of gravity, moments of inertia and products of inertia with respect to mutually perpendicular axes through the system center of gravity. The program also yields mass properties of the individual shapes relative to component axes.

  6. Structural and optical properties for typical solid mirror shapes

    NASA Technical Reports Server (NTRS)

    Cho, Myung K.; Richard, Ralph M.

    1990-01-01

    A method is developed to determine the weight, center of gravity, areal properties, and mass inertial properties for typical mirrors. A number of support conditions were considered to examine optical surface deflections, surface quality, and fundamental natural frequency for single- and double-arch mirror shapes. Structural performance estimates were made with the NASTRAN program, and optical performances were evaluated with the FRINGE program, using an SXA 40-in mirror. To show the behavior of element types from the NASTRAN program, finite element validity and sensitivity studies were performed in optical model applications. Material parameters, contoured back shapes, and support locations are shown to have significant effects on structural and optical performances. Optimal support locations and support points are given. Fundamental natural frequencies for some shapes are found with the closed-form solution. The plate models results may not be acceptable for determining real mirror optical performances.

  7. Optical properties of a multibarrier structure under intense laser fields

    NASA Astrophysics Data System (ADS)

    Ospina, D. A.; Akimov, V.; Mora-Ramos, M. E.; Morales, A. L.; Tulupenko, V.; Duque, C. A.

    2015-11-01

    Using the diagonalization method and within the effective mass and parabolic band approximations, the energy spectrum and the wave functions are investigated in biased multibarrier structure taking into account the effects of nonresonant intense laser fields. We calculated the optical properties from the susceptibility using a nonperturbative formalism recently reported. We study the changes in the intersubband optical absorption coefficients and refraction index for several values of the dressing laser parameter and for some specific values of the electric field applied along the growth direction of the heterostructure. It is concluded from our study that the peaks in the optical absorption spectrum have redshifts or blueshifts as a function of the laser parameter and the electric field. These parameters could be suitable tools for tuning the electronic and optical properties of the multibarrier structure.

  8. Thermal Properties of Structural Materials Used in LWR Vessels

    SciTech Connect

    J. E. Daw; J. L. Rempe; D. L. Knudson

    2011-01-01

    High temperature material property data for structural materials used in existing Light Water Reactors (LWRs) are limited. Often, extrapolated values recommended in the literature differ significantly. To reduce uncertainties in predictions relying upon extrapolated data for LWR vessel and penetration materials, high temperature tests were completed on SA533 Grade B, Class 1 (SA533B1) low alloy steel, Stainless Steel 304 (SS304), and Inconel 600 using material property measurement systems available in the High Temperature Test Laboratory (HTTL) at the Idaho National Laboratory (INL). Properties measured include thermal expansion, specific heat capacity, and thermal diffusivity for temperatures up to 1200 °C. From these results, thermal conductivity and density were calculated. Results show that, in some cases, previously recommended values for these materials differ significantly from measured values at high temperatures.

  9. 41 CFR 102-75.955 - Who is responsible for decontaminating excess and surplus real property?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... PROPERTY 75-REAL PROPERTY DISPOSAL Management of Excess and Surplus Real Property Decontamination § 102-75... responsible for all expenses to the Government and for the supervision of the decontamination of excess and... be exercised in the decontamination, management, and disposal of contaminated property in order...

  10. 41 CFR 102-75.955 - Who is responsible for decontaminating excess and surplus real property?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... PROPERTY 75-REAL PROPERTY DISPOSAL Management of Excess and Surplus Real Property Decontamination § 102-75... responsible for all expenses to the Government and for the supervision of the decontamination of excess and... be exercised in the decontamination, management, and disposal of contaminated property in order...

  11. 41 CFR 102-75.955 - Who is responsible for decontaminating excess and surplus real property?

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... PROPERTY 75-REAL PROPERTY DISPOSAL Management of Excess and Surplus Real Property Decontamination § 102-75... responsible for all expenses to the Government and for the supervision of the decontamination of excess and... be exercised in the decontamination, management, and disposal of contaminated property in order...

  12. 41 CFR 102-75.955 - Who is responsible for decontaminating excess and surplus real property?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... PROPERTY 75-REAL PROPERTY DISPOSAL Management of Excess and Surplus Real Property Decontamination § 102-75... responsible for all expenses to the Government and for the supervision of the decontamination of excess and... be exercised in the decontamination, management, and disposal of contaminated property in order...

  13. 41 CFR 102-75.955 - Who is responsible for decontaminating excess and surplus real property?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... PROPERTY 75-REAL PROPERTY DISPOSAL Management of Excess and Surplus Real Property Decontamination § 102-75... responsible for all expenses to the Government and for the supervision of the decontamination of excess and... be exercised in the decontamination, management, and disposal of contaminated property in order...

  14. Material Properties Analysis of Structural Members in Pumpkin Balloons

    NASA Technical Reports Server (NTRS)

    Sterling, W. J.

    2003-01-01

    The efficient design, service-life qualification, and reliability predictions for lightweight aerospace structures require careful mechanical properties analysis of candidate structural materials. The demand for high-quality laboratory data is particularly acute when the candidate material or the structural design has little history. The pumpkin-shaped super-pressure balloon presents both challenges. Its design utilizes load members (tendons) extending from apex to base around the gas envelope to achieve a lightweight structure. The candidate tendon material is highly weight-efficient braided HM cord. Previous mechanical properties studies of Zylon have focused on fiber and yarn, and industrial use of the material in tensile applications is limited. For high-performance polymers, a carefully plamed and executed properties analysis scheme is required to ensure the data are relevant to the desired application. Because no directly-applicable testing standard was available, a protocol was developed based on guidelines fiom professional and industry organizations. Due to the liquid-crystalline nature of the polymer, the cord is very stiff, creeps very little, and does not yield. Therefore, the key material property for this application is the breaking strength. The pretension load and gauge length were found to have negligible effect on the measured breaking strength over the ranges investigated. Strain rate was found to have no effect on breaking strength, within the range of rates suggested by the standards organizations. However, at the lower rate more similar to ULDB operations, the strength was reduced. The breaking strength increased when the experiment temperature was decreased from ambient to 183K which is the lowest temperature ULDB is expected to experience. The measured strength under all test conditions was well below that resulting from direct scale-up of fiber strength based on the manufacturers data. This expected result is due to the effects of the

  15. Ground State Properties and Bubble Structure of Synthesized Superheavy Nuclei

    NASA Astrophysics Data System (ADS)

    Singh, S. K.; Ikram, M.; Patra, S. K.

    2013-01-01

    We calculate the ground state properties of recently synthesized superheavy elements (SHEs) from Z = 105-118 along with the predicted proton magic Z = 120. The relativistic and nonrelativistic mean field formalisms are used to evaluate the binding energy (BE), charge radius, quadrupole deformation parameter and the density distribution of nucleons. We analyzed the stability of the nuclei based on BE and neutron to proton ratio. We also studied the bubble structure which reveals the special features of the superheavy nuclei.

  16. Computational study of hydroxyapatite structures, properties and defects

    NASA Astrophysics Data System (ADS)

    Bystrov, V. S.; Coutinho, J.; Bystrova, A. V.; Dekhtyar, Yu D.; Pullar, R. C.; Poronin, A.; Palcevskis, E.; Dindune, A.; Alkan, B.; Durucan, C.; Paramonova, E. V.

    2015-03-01

    Hydroxyapatite (HAp) was studied from a first principle approach using the local density approximation (LDA) method in AIMPRO code, in combination with various quantum mechanical (QM) and molecular mechanical (MM) methods from HypemChem 7.5/8.0. The data obtained were used for studies of HAp structures, the physical properties of HAp (density of electronic states—DOS, bulk modulus etc) and defects in HAp. Computed data confirmed that HAp can co-exist in different phases—hexagonal and monoclinic. Ordered monoclinic structures, which could reveal piezoelectric properties, are of special interest. The data obtained allow us to characterize the properties of the following defects in HAp: O, H and OH vacancies; H and OH interstitials; substitutions of Ca by Mg, Sr, Mn or Se, and P by Si. These properties reveal the appearance of additional energy levels inside the forbidden zone, shifts of the top of the valence band or the bottom of the conduction band, and subsequent changes in the width of the forbidden zone. The data computed are compared with other known data, both calculated and experimental, such as alteration of the electron work functions under different influences of various defects and treatments, obtained by photoelectron emission. The obtained data are very useful, and there is an urgent need for such analysis of modified HAp interactions with living cells and tissues, improvement of implant techniques and development of new nanomedical applications.

  17. Structure for Storing Properties of Particles (PoP)

    SciTech Connect

    Patel, N. R.; Mattoon, C. M.; Beck, B. R.; Summers, N. C.; Brown, D. A.

    2014-06-01

    Some evaluated nuclear databases are critical for applications such as nuclear energy, nuclear medicine, homeland security, and stockpile stewardship. Particle masses, nuclear excitation levels, and other “Properties of Particles” are essential for making evaluated nuclear databases. Currently, these properties are obtained from various databases that are stored in outdated formats. Moreover, the “Properties of Particles” (PoP) structure is being designed that will allow storing all information for one or more particles in a single place, so that each evaluation, simulation, model calculation, etc. can link to the same data. Information provided in PoP will include properties of nuclei, gammas and electrons (along with other particles such as pions, as evaluations extend to higher energies). Presently, PoP includes masses from the Atomic Mass Evaluation version 2003 (AME2003), and level schemes and gamma decays from the Reference Input Parameter Library (RIPL-3). The data are stored in a hierarchical structure. An example of how PoP stores nuclear masses and energy levels will be presented here.

  18. Structure for Storing Properties of Particles (PoP)

    SciTech Connect

    Patel, N.R.; Mattoon, C.M.; Beck, B.R.; Summers, N.C.; Brown, D.A.

    2014-06-15

    Evaluated nuclear databases are critical for applications such as nuclear energy, nuclear medicine, homeland security, and stockpile stewardship. Particle masses, nuclear excitation levels, and other “Properties of Particles” are essential for making evaluated nuclear databases. Currently, these properties are obtained from various databases that are stored in outdated formats. A “Properties of Particles” (PoP) structure is being designed that will allow storing all information for one or more particles in a single place, so that each evaluation, simulation, model calculation, etc. can link to the same data. Information provided in PoP will include properties of nuclei, gammas and electrons (along with other particles such as pions, as evaluations extend to higher energies). Presently, PoP includes masses from the Atomic Mass Evaluation version 2003 (AME2003), and level schemes and gamma decays from the Reference Input Parameter Library (RIPL-3). The data are stored in a hierarchical structure. An example of how PoP stores nuclear masses and energy levels will be presented here.

  19. Dielectric properties modelling of cellular structures with PDMS for micro-sensor applications

    NASA Astrophysics Data System (ADS)

    Kachroudi, Achraf; Basrour, Skandar; Rufer, Libor; Sylvestre, Alain; Jomni, Fathi

    2015-12-01

    Electro-active polymers are emerging in the fields of actuators and micro-sensors because their good dielectric and mechanical properties makes them suitable for such applications. In this work, we focus on micro-structured (cellular) polymer materials (referred as piezoelectrets or ferroelectrets) that need prior charging to attain piezoelectric behaviour. The development of such applications requires an in-depth knowledge of the intrinsic dielectric properties of such structures and models to enable the accurate prediction of a given micro-structured material’s dielectric properties. Various polymers including polypropylene, polytetrafluoroethylene, fluoroethylenepropylene, cyclo-olefines and poly(ethylene terephthalate) in a cellular form have been studied by researchers over the last fifteen years. However, there is still a lack of information on the intrinsic dielectric properties of the most recently used dielectric polymer (polydimethylsiloxane, PDMS) over wide frequency and temperature ranges. In this work, we shall propose an exhaustive equivalent electrical circuit model and explain how it can be used to predict the micro-structured PDMS complex permittivity versus frequency and temperature. The results obtained from the model were found to be in good agreement with experimental data for various micro-structured PDMS materials. Typically, for micro-sensor applications, the dielectric constant and dielectric losses are key factors which need to be minimized. We have developed a configuration which enables both to be strongly reduced with a reduction of 16% in the dielectric constant of a micro-structured PDMS compared with the bulk material. In addition, the phenomena responsible for dielectric losses variations with frequency and temperature are discussed and correlated with the theoretical model. Our model is thus proved to be a powerful tool for the control of the dielectric properties of micro-structured PDMS material for micro-sensor applications.

  20. Crystal structure and physical properties of Mo{sub 2}B: First-principle calculations

    SciTech Connect

    Zhou, Dan; Cui, Qiliang E-mail: liquan777@jlu.edu.cn; Li, Quan E-mail: liquan777@jlu.edu.cn; Wang, Jingshu

    2014-03-21

    Several decades ago, Mo{sub 2}B was assumed to have an Al{sub 2}Cu-type structure with I4/mcm space group. Using ab initio phonon calculations, we identify the earlier proposed Al{sub 2}Cu-type structure is dynamically unstable at ambient pressure. An energetically more favorable phase with the tetragonal I4/m structure was then predicted by employing frozen-phonon technique. The currently predicted I4/m phase is mechanically and dynamically stable and energetically more favorable than that of the earlier proposed Al{sub 2}Cu-type structure. The electronic structures calculations indicate that Mo{sub 2}B is a metal with several bands crossing the Fermi level. Our analysis indicates that the three-dimensional network of the covalent Mo-B bond is responsible for the ultra-incompressible property of Mo{sub 2}B.

  1. Designing the Structure of Carbon Fibers for Optimal Mechanical Properties

    SciTech Connect

    Ozcan, Soydan; Vautard, Frederic; Naskar, Amit K

    2014-01-01

    Carbon fiber manufacturing follows generic processing steps: formation of thermoplastic fibers, stabilization, and carbonization. The final structures and end properties of the carbon fiber can differ significantly depending on the precursor chemistry and the associated processing sciences. Polyacrylonitrile (PAN) and mesophase pitch are the predominant precursors used in the production of carbon fibers. PAN-based carbon fibers consist of nanocrystalline graphitic domains typically 1.5 5 nm in size surrounded by amorphous carbon; in contrast, pitch-based carbon fibers are 10 50 nm crystallites with the graphitic (002) planes mostly aligned parallel to the fiber axis. It has been seen that the skin core structure of PAN-based carbon fibers plays a significant role in their mechanical properties. Designing a more homogenous carbon fiber microstructure by controlling the starting polymer and process parameters results in a different set of tensile strengths and elastic moduli. In this study the microstructural defect distribution (0.1 200 nm), measured by small-angle X-ray scattering, was shown to be directly related to the tensile strength of the carbon fibers. Here the formation of carbon structures from various polymer precursors is reviewed. Such a comprehensive understanding offers the opportunity to design carbon fiber microstructures with improved properties and to ultimately create new types of carbon fibers from alternative precursors at reduced cost.

  2. Elastic properties and electronic structures of lanthanide hexaborides

    NASA Astrophysics Data System (ADS)

    Duan, Jie; Zhou, Tong; Zhang, Li; Du, Ji-Guang; Jiang, Gang; Wang, Hong-Bin

    2015-09-01

    The structural, elastic, and electronic properties of a series of lanthanide hexaborides (LnB6) have been investigated by performing ab initio calculations based on the density functional theory using the Vienna ab initio simulation package. The calculated lattice and elastic constants of LnB6 are in good agreement with the available experimental data and other theoretical results. The polycrystalline Young’s modulus, shear modulus, the ratio of bulk to shear modulus B/G, Poisson’s ratios, Zener anisotropy factors, as well as the Debye temperature are calculated, and all of the properties display some regularity with increasing atomic number of lanthanide atoms, whereas anomalies are observed for EuB6 and YbB6. In addition, detailed electronic structure calculations are carried out to shed light on the peculiar elastic properties of LnB6. The total density of states demonstrates the existence of a pseudogap and indicates lower structure stability of EuB6 and YbB6 compared with others.

  3. Aircraft Structural Mass Property Prediction Using Conceptual-Level Structural Analysis

    NASA Technical Reports Server (NTRS)

    Sexstone, Matthew G.

    1998-01-01

    This paper describes a methodology that extends the use of the Equivalent LAminated Plate Solution (ELAPS) structural analysis code from conceptual-level aircraft structural analysis to conceptual-level aircraft mass property analysis. Mass property analysis in aircraft structures has historically depended upon parametric weight equations at the conceptual design level and Finite Element Analysis (FEA) at the detailed design level. ELAPS allows for the modeling of detailed geometry, metallic and composite materials, and non-structural mass coupled with analytical structural sizing to produce high-fidelity mass property analyses representing fully configured vehicles early in the design process. This capability is especially valuable for unusual configuration and advanced concept development where existing parametric weight equations are inapplicable and FEA is too time consuming for conceptual design. This paper contrasts the use of ELAPS relative to empirical weight equations and FEA. ELAPS modeling techniques are described and the ELAPS-based mass property analysis process is detailed. Examples of mass property stochastic calculations produced during a recent systems study are provided. This study involved the analysis of three remotely piloted aircraft required to carry scientific payloads to very high altitudes at subsonic speeds. Due to the extreme nature of this high-altitude flight regime, few existing vehicle designs are available for use in performance and weight prediction. ELAPS was employed within a concurrent engineering analysis process that simultaneously produces aerodynamic, structural, and static aeroelastic results for input to aircraft performance analyses. The ELAPS models produced for each concept were also used to provide stochastic analyses of wing structural mass properties. The results of this effort indicate that ELAPS is an efficient means to conduct multidisciplinary trade studies at the conceptual design level.

  4. Aircraft Structural Mass Property Prediction Using Conceptual-Level Structural Analysis

    NASA Technical Reports Server (NTRS)

    Sexstone, Matthew G.

    1998-01-01

    This paper describes a methodology that extends the use of the Equivalent LAminated Plate Solution (ELAPS) structural analysis code from conceptual-level aircraft structural analysis to conceptual-level aircraft mass property analysis. Mass property analysis in aircraft structures has historically depended upon parametric weight equations at the conceptual design level and Finite Element Analysis (FEA) at the detailed design level ELAPS allows for the modeling of detailed geometry, metallic and composite materials, and non-structural mass coupled with analytical structural sizing to produce high-fidelity mass property analyses representing fully configured vehicles early in the design process. This capability is especially valuable for unusual configuration and advanced concept development where existing parametric weight equations are inapplicable and FEA is too time consuming for conceptual design. This paper contrasts the use of ELAPS relative to empirical weight equations and FEA. ELAPS modeling techniques are described and the ELAPS-based mass property analysis process is detailed Examples of mass property stochastic calculations produced during a recent systems study are provided This study involved the analysis of three remotely piloted aircraft required to carry scientific payloads to very high altitudes at subsonic speeds. Due to the extreme nature of this high-altitude flight regime,few existing vehicle designs are available for use in performance and weight prediction. ELAPS was employed within a concurrent engineering analysis process that simultaneously produces aerodynamic, structural, and static aeroelastic results for input to aircraft performance analyses. The ELAPS models produced for each concept were also used to provide stochastic analyses of wing structural mass properties. The results of this effort indicate that ELAPS is an efficient means to conduct multidisciplinary trade studies at the conceptual design level.

  5. Self-diagnosis of smart structures based on dynamical properties

    NASA Astrophysics Data System (ADS)

    Fritzen, C.-P.; Kraemer, P.

    2009-08-01

    When we talk about "smart structures" we can think about different properties and capabilities which make a structure "intelligent" in a certain sense. Originally, the expression "smart" was used in the context that a structure can react and adapt to certain environmental conditions, such as change of shape, compensation of deformations, active vibration damping, etc. Over the last year, the expression "smart" has been extended to the field of structural health monitoring (SHM), where sensor networks, actuators and computational capabilities are used to enable a structure to perform a self-diagnosis with the goal that this structure can release early warnings about a critical health state, locate and classify damage or even to forecast the remaining life-time. This paper intends to give an overview and point out recent developments of vibration-based methods for SHM. All these methods have in common that a structural change due to a damage results in a more or less significant change of the dynamic behavior. For the diagnosis an inverse problem has to be solved. We discuss the use of modal information as well as the direct use of forced and ambient vibrations in the time and frequency domain. Examples from civil and aerospace engineering as well as off-shore wind energy plants show the applicability of these methods.

  6. Strain properties analysis and wireless collection system of PVDF for structural local health monitoring of civil engineering structures

    NASA Astrophysics Data System (ADS)

    Yu, Yan; Wang, Yang; Dong, Weijie; Jin, Yajing; Ou, Jinping

    2009-07-01

    For large civil engineering structures and base establishments, for example, bridges, super-high buildings, long-span space structures, offshore platforms and pipe systems of water & gas supply, their lives are up to a few decades or centuries. Damaged by environmental loads, fatigue effects, corrosion effects and material aging, these structures experience inevitably such side effects as damage accumulation, resistance reduction and even accidents. The traditional civil structure is a kind of passive one, whose performance and status are unpredictable to a great extent, but the informatics' introduction breaks a new path to obtain the status of the structure, thus it is an important research direction to evaluate and improve reliability of civil structures by the use of monitoring and health diagnosis technique, and this also assures the security of service for civil engineering structures. Smart material structure, originated from the aerospace sector, has been a research hotspot in civil engineering, medicine, shipping, and so on. For structural health monitoring of civil engineering, the research about high-performance sensing unit of smart material structure is very important, and this will possibly push further the development and application of monitoring and health diagnosis techniques. At present, piezoelectric materials are one of the most widely used sensing materials among the research of smart material structures. As one of the piezoelectric materials, PVDF(Polyvinylidene Fluoride)film is widely considered for the advantages of low cost, good mechanical ability, high sensibility, the ability of being easily placed and resistance of corrosion. However, only a few studies exit about building a mature monitoring system using PVDF. In this paper, for the sake of using PVDF for sensing unit for structural local monitoring of civil engineering, the strain sensing properties of PVDF are studied in detail. Firstly, the operating mechanism of PVDF is analyzed

  7. Probabilistic SSME blades structural response under random pulse loading

    NASA Technical Reports Server (NTRS)

    Shiao, Michael; Rubinstein, Robert; Nagpal, Vinod K.

    1987-01-01

    The purpose is to develop models of random impacts on a Space Shuttle Main Engine (SSME) turbopump blade and to predict the probabilistic structural response of the blade to these impacts. The random loading is caused by the impact of debris. The probabilistic structural response is characterized by distribution functions for stress and displacements as functions of the loading parameters which determine the random pulse model. These parameters include pulse arrival, amplitude, and location. The analysis can be extended to predict level crossing rates. This requires knowledge of the joint distribution of the response and its derivative. The model of random impacts chosen allows the pulse arrivals, pulse amplitudes, and pulse locations to be random. Specifically, the pulse arrivals are assumed to be governed by a Poisson process, which is characterized by a mean arrival rate. The pulse intensity is modelled as a normally distributed random variable with a zero mean chosen independently at each arrival. The standard deviation of the distribution is a measure of pulse intensity. Several different models were used for the pulse locations. For example, three points near the blade tip were chosen at which pulses were allowed to arrive with equal probability. Again, the locations were chosen independently at each arrival. The structural response was analyzed both by direct Monte Carlo simulation and by a semi-analytical method.

  8. Optical properties of vanadium dioxide thin film in nanoparticle structure

    NASA Astrophysics Data System (ADS)

    Fang, Baoying; Li, Yi; Tong, Guoxiang; Wang, Xiaohua; Yan, Meng; Liang, Qian; Wang, Feng; Qin, Yuan; Ding, Jie; Chen, Shaojuan; Chen, Jiankun; Zheng, Hongzhu; Yuan, Wenrui

    2015-09-01

    The thermo-optic effect and infrared optical properties of VO2 nanoparticles were studied to obtain an optical material with special property that can be used in smart windows. The reflectance and transmittance spectra of the VO2 nanoparticles with different duty cycles at different temperatures were simulated with a specific dispersion relation. Vanadium metal nanoparticles were deposited on glass substrate by magnetic reactive sputtering with porous alumina template (AAO) mask, and the VO2 nanoparticles were prepared by thermal oxidation. The nanostructure and optical properties of the VO2 nanoparticles were characterized by atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and spectrophotometry. The method of preparation of the sample is economical and the phase transition temperature is observed to drop to 43 °C. The transmission at 1700 nm exhibits a variation of 29% between the metallic and semiconducting states. The VO2 nanoparticles exhibit a significant thermochromic property. The transmittance of the VO2 nanoparticles is improved compared with the VO2 film. The decrease in phase transition temperature and the enhancement of optical properties demonstrate that VO2 film in nanoparticle structure is a viable candidate material for smart windows.

  9. Structural and optical properties of axial silicon-germanium nanowire heterojunctions

    NASA Astrophysics Data System (ADS)

    Wang, X.; Tsybeskov, L.; Kamins, T. I.; Wu, X.; Lockwood, D. J.

    2015-12-01

    Detailed studies of the structural and optical properties of axial silicon-germanium nanowire heterojunctions show that despite the 4.2% lattice mismatch between Si and Ge they can be grown without a significant density of structural defects. The lattice mismatch induced strain is partially relieved due to spontaneous SiGe intermixing at the heterointerface during growth and lateral expansion of the Ge segment of the nanowire. The mismatch in Ge and Si coefficients of thermal expansion and low thermal conductivity of Si/Ge nanowire heterojunctions are proposed to be responsible for the thermally induced stress detected under intense laser radiation in photoluminescence and Raman scattering measurements.

  10. Structural and optical properties of axial silicon-germanium nanowire heterojunctions

    SciTech Connect

    Wang, X.; Tsybeskov, L.; Kamins, T. I.; Wu, X.; Lockwood, D. J.

    2015-12-21

    Detailed studies of the structural and optical properties of axial silicon-germanium nanowire heterojunctions show that despite the 4.2% lattice mismatch between Si and Ge they can be grown without a significant density of structural defects. The lattice mismatch induced strain is partially relieved due to spontaneous SiGe intermixing at the heterointerface during growth and lateral expansion of the Ge segment of the nanowire. The mismatch in Ge and Si coefficients of thermal expansion and low thermal conductivity of Si/Ge nanowire heterojunctions are proposed to be responsible for the thermally induced stress detected under intense laser radiation in photoluminescence and Raman scattering measurements.

  11. Structural properties of ultrafine Ba-hexaferrite nanoparticles

    SciTech Connect

    Makovec, Darko; Primc, Darinka; Sturm, Saso; Kodre, Alojz; Jozef Stefan Institute, Jamova ulica 39, SI-1000 Ljubljana ; Hanzel, Darko; Drofenik, Miha; Jozef Stefan Institute, Jamova ulica 39, SI-1000 Ljubljana

    2012-12-15

    Crystal structure of ultrafine Ba-hexaferrite (BaFe{sub 12}O{sub 19}) nanoparticles was studied using X-ray diffractometry (XRD), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDXS), X-ray absorption fine structure (XAFS), and Moessbauer spectroscopy (MS), to be compared to the structure of larger nanoparticles and the bulk. The nanoparticles were synthesized with hydrothermal treatment of an appropriate suspension of Ba and Fe hydroxides in the presence of a large excess of OH{sup -}. The ultrafine nanoparticles were formed in a discoid shape, {approx}10 nm wide and only {approx}3 nm thick, comparable to the size of the hexagonal unit cell in the c-direction. The HRTEM image analysis confirmed the hexaferrite structure, whereas EDXS showed the composition matching the BaFe{sub 12}O{sub 19} formula. XAFS and MS analyses showed considerable disorder of the structure, most probably responsible for the low magnetization. - Graphical abstract: Left: HREM image of an ultrafine Ba-hexaferrite nanoparticle (inset: TEM image of the nanoparticles); Right: the experimental HRTEM image is compared with calculated image and corresponding atomic model. Highlights: Black-Right-Pointing-Pointer Crystal structure of ultrafine Ba-hexaferrite (BaFe{sub 12}O{sub 19}) nanoparticles was compared to the structure of the bulk. Black-Right-Pointing-Pointer Thickness the discoid nanoparticles was comparable to the size of the hexagonal unit cell in the c-direction. Black-Right-Pointing-Pointer Considerable disorder of the nanoparticles' structure is most probably responsible for their low magnetization.

  12. Correlation of Structural and Macroscopic Properties of Starches with Their Tabletability Using the SM(2) Approach.

    PubMed

    Dave, Vivek S; Chanda, Monica; Sayles, Matt; Popielarczyk, Michael; Boyce, Heather; Bompelliwar, Sai Krishna; Bates, Simon; Morris, Ken R; Haware, Rahul V

    2015-11-01

    The effects of PURE-DENT® and SPRESS® starch properties on their compression behavior was characterized using "SM(2) " approach (structural properties, macroscopic properties, and multivariate analysis). Moisture sorption rate constants, moisture content, amylose and amylopectin degradation enthalpy, percent crystallinity, amylose-amylopectin ratio, and cross-linking degree were used to profile starch structural properties. Particle density, particle size distribution, and Heckel compression descriptors [yield pressure (YP) of plastic deformation, and elastic recovery] were used as macroscopic descriptors. The structural and macroscopic properties were correlated qualitatively [principal component analysis (PCA)] and quantitatively [standard least square regression (SLSR)] with the tablet mechanical strength (TMS). These analyses revealed that the differences correlated with amylose-amylopectin content, particle density, compression mechanisms, and TMS between the starch grades. Univariate analysis proved lacking; however, PCA identified the particle size, moisture content, percent crystallinity, amylose-amylopectin ratio, and YP of plastic deformation and elastic recovery as the main factors influencing the starch TMS. SLSR quantified the positive influence of Fourier transform infrared spectra absorbance ratio at 1022-1003 and YP of the immediate elastic recovery, and the negative contribution of amylopectin content on the TMS. Therefore, starch amylose and amylopectin content, crystallinity, and lower elastic recovery are mainly responsible for better TMS. PMID:26235472

  13. Polymer layered silicate nanocomposites: Structure, morphology, and properties

    NASA Astrophysics Data System (ADS)

    Nawani, Pranav

    Layered silicates are important fillers for improving various mechanical, flame retardant, and barrier properties of polymers, which can be attributed to their sheet-like morphology. Layered silicates can be modified with organic surfactants to render them compatible with polymer matrices. Organically modified silicates (organoclays) having large surface areas are very cost-efficient non-toxic nanofillers effective at very low loads and are readily available. Upon amalgamation of organoclays with polymer matrix nanocomposites, polymer chains can penetrate in between the silicate layers and result in an intercalated structure where the clay stack remains intact but the interlayer spacing is increased. When penetration becomes more severe, disintegration of clay stacks can occur, resulting in an exfoliated structure. It has often been observed that exfoliation is not complete down to the level of isolated silicate layers; rather, the large clay stacks are broken up into shorter stacks termed 'tactoids' together with a few individual silicate layers, resulting in a kind of mixed intercalated-exfoliated structure. Organoclay particles are mostly intercalated, having a preferred orientation with the clay gallery planes being preferentially parallel to the plane of the pressed film. Preferential orientation of organoclays affects the barrier properties of polymer membranes. Additional fillers like carbon black can induce a change in the orientation of organoclays. The effect of carbon black on the orientation of organoclays was elucidated and a relationship between orientation and permeability of air through such membranes was established. We have also investigated the flammability properties of a series of polymer nanocomposites, containing various Transition Metal Ion (TMI) modified organoclays. The improved fire retardation in nanocomposites with TMI-modified organoclays can be attributed to enhanced carbonaceous char formation during combustion, i.e., charring

  14. Sound and structural vibration: Radiation, transmission and response

    NASA Astrophysics Data System (ADS)

    Fahy, F.

    The physical process of vibrational interaction between fluids and solid structures, and models and analyses of the behavior of coupled fluid-structure systems are described. The temporal and spatial distributions of wave field variables, the characteristics of waves in beam, plate, and shell structures, the dispersion relationships between wave speed and frequency forms, the natural frequencies and modes of bounded elastic systems, and the functions of outgoing and returning waves are discussed. The mechanics of sound radiation from vibratory surfaces and the use of far-field evaluation of the Rayleigh integral and traveling wave Fourier component synthesis for analysis of sound radiation for planar surfaces are studied. Fluid loading or vibrating structures, the wave impediance or structures and fluids, and the effects of fluid loading on the radiation of plates are investigated. Sound transmission through various plane partitions, flexural wave propagation in a circular cylindrical shell, and the coupling between shell modes and acoustic duct modes are considered. The analysis of the vibrational response of thin-plate and shell structures to incident sound, acoustic-coupling between structures and enclosed volumes of fluid, and analyses of fluid-structure interaction are examined.

  15. Temperature-sensitive PVA/PNIPAAm semi-IPN hydrogels with enhanced responsive properties.

    PubMed

    Zhang, Jian-Tao; Bhat, Rahila; Jandt, Klaus D

    2009-01-01

    A series of temperature-sensitive hydrogels of semi-interpenetrating polymeric networks (semi-IPN) composed of poly(N-isopropylacrylamide) (PNIPAAm) and poly(vinyl alcohol) (PVA) were prepared by radical polymerization. The PNIPAAm networks were cross-linked by N,N'-methylenebisacrylamide in the presence of linear PVA. The reaction processes were investigated by rheometry using oscillatory deformation tests. It was found that gelations were very fast and the modulus reached equilibrium within about 12.5min. The prepared semi-IPN hydrogels were characterized for their morphologies and thermal behaviors by scanning electron microscopy and differential scanning calorimetry, respectively. The interior network structures of the semi-IPN matrix became more porous with increasing PVA. In comparison to the conventional PNIPAAm gel, the newly reported semi-IPN hydrogels exhibited the same lower critical solution temperature. Their swelling properties, such as temperature dependence of equilibrium swelling ratio, shrinking kinetics and reswelling kinetics in water, were also studied. Experimental data indicated that the shrinking and reswelling rates of the semi-IPN hydrogels were much faster than those of the conventional PNIPAAm hydrogels. With this novel approach, water absorption and response properties could be adjusted by tuning the feed ratio of NIPAAm and PVA. These fast responsive hydrogels exhibited improved temperature sensitivity and swelling properties compared to the conventional PNIPAAm hydrogel, which would be critical and desirable for a gel to find potential applications in biomedical fields, such as drug delivery systems and sensors. PMID:18656431

  16. The cortical analysis of speech-specific temporal structure revealed by responses to sound quilts.

    PubMed

    Overath, Tobias; McDermott, Josh H; Zarate, Jean Mary; Poeppel, David

    2015-06-01

    Speech contains temporal structure that the brain must analyze to enable linguistic processing. To investigate the neural basis of this analysis, we used sound quilts, stimuli constructed by shuffling segments of a natural sound, approximately preserving its properties on short timescales while disrupting them on longer scales. We generated quilts from foreign speech to eliminate language cues and manipulated the extent of natural acoustic structure by varying the segment length. Using functional magnetic resonance imaging, we identified bilateral regions of the superior temporal sulcus (STS) whose responses varied with segment length. This effect was absent in primary auditory cortex and did not occur for quilts made from other natural sounds or acoustically matched synthetic sounds, suggesting tuning to speech-specific spectrotemporal structure. When examined parametrically, the STS response increased with segment length up to ∼500 ms. Our results identify a locus of speech analysis in human auditory cortex that is distinct from lexical, semantic or syntactic processes. PMID:25984889

  17. The cortical analysis of speech-specific temporal structure revealed by responses to sound quilts

    PubMed Central

    Overath, Tobias; McDermott, Josh H; Zarate, Jean Mary; Poeppel, David

    2016-01-01

    Speech contains temporal structure that the brain must analyze to enable linguistic processing. To investigate the neural basis of this analysis, we used sound quilts, stimuli constructed by shuffling segments of a natural sound, approximately preserving its properties on short timescales while disrupting them on longer scales. We generated quilts from foreign speech to eliminate language cues and manipulated the extent of natural acoustic structure by varying the segment length. Using functional magnetic resonance imaging, we identified bilateral regions of the superior temporal sulcus (STS) whose responses varied with segment length. This effect was absent in primary auditory cortex and did not occur for quilts made from other natural sounds or acoustically matched synthetic sounds, suggesting tuning to speech-specific spectrotemporal structure. When examined parametrically, the STS response increased with segment length up to ~500 ms. Our results identify a locus of speech analysis in human auditory cortex that is distinct from lexical, semantic or syntactic processes. PMID:25984889

  18. The Synthesis of Structural Responses Using Experimentally Measured Frequency Response Functions and Field Test Data

    SciTech Connect

    CAP,JEROME S.; NELSON,CURTIS F.

    2000-11-17

    This paper presents an analysis technique used to generate the structural response at locations not measured during the ejection of a captive-carried store. The ejection shock event is complicated by the fact that forces may be imparted to the store at eight distinct locations. The technique derives forcing functions by combining the initial field test data for a limited number of measurement locations with Frequency Response Functions (FRFs) measured using a traditional modal-type impact (tap) test at the same locations. The derived forcing functions were then used with tap test FRFs measured at additional locations of interest to produce the desired response data.

  19. Circulating Microparticles Alter Formation, Structure, and Properties of Fibrin Clots

    PubMed Central

    Zubairova, Laily D.; Nabiullina, Roza M.; Nagaswami, Chandrasekaran; Zuev, Yuriy F.; Mustafin, Ilshat G.; Litvinov, Rustem I.; Weisel, John W.

    2015-01-01

    Despite the importance of circulating microparticles in haemostasis and thrombosis, there is limited evidence for potential causative effects of naturally produced cell-derived microparticles on fibrin clot formation and its properties. We studied the significance of blood microparticles for fibrin formation, structure, and susceptibility to fibrinolysis by removing them from platelet-free plasma using filtration. Clots made in platelet-free and microparticle-depleted plasma samples from the same healthy donors were analyzed in parallel. Microparticles accelerate fibrin polymerisation and support formation of more compact clots that resist internal and external fibrinolysis. These variations correlate with faster thrombin generation, suggesting thrombin-mediated kinetic effects of microparticles on fibrin formation, structure, and properties. In addition, clots formed in the presence of microparticles, unlike clots from the microparticle-depleted plasma, contain 0.1–0.5-μm size granular and CD61-positive material on fibres, suggesting that platelet-derived microparticles attach to fibrin. Therefore, the blood of healthy individuals contains functional microparticles at the levels that have a procoagulant potential. They affect the structure and stability of fibrin clots indirectly through acceleration of thrombin generation and through direct physical incorporation into the fibrin network. Both mechanisms underlie a potential role of microparticles in haemostasis and thrombosis as modulators of fibrin formation, structure, and resistance to fibrinolysis. PMID:26635081

  20. Hierarchical structure and physicochemical properties of plasticized chitosan.

    PubMed

    Meng, Qingkai; Heuzey, Marie-Claude; Carreau, Pierre J

    2014-04-14

    Plasticized chitosan with hierarchical structure, including multiple length scale structural units, was prepared by a "melt"-based method, that is, thermomechanical mixing, as opposed to the usual casting-evaporation procedure. Chitosan was successfully plasticized by thermomechanical mixing in the presence of concentrated lactic acid and glycerol using a batch mixer. Different plasticization formulations were compared in this study, in which concentrated lactic acid was used as protonation agent as well as plasticizer. The microstructure of thermomechanically plasticized chitosan was investigated by X-ray diffraction, scanning electron microscopy, and optical microscopy. With increasing amount of additional plasticizers (glycerol or water), the crystallinity of the plasticized chitosan decreased from 63.7% for the original chitosan powder to almost zero for the sample plasticized with additional water. Salt linkage between lactic acid molecules and amino side chains of chitosan was confirmed by FTIR spectroscopy: the lactic acid molecules expanded the space between the chitosan molecules of the crystalline phase. In the presence of other plasticizers (glycerol and water), various levels of structural units including an amorphous phase, nanofibrils, nanofibril clusters, and microfibers were produced under mechanical shear and thermal energy and identified for the first time. The thermal and thermomechanical properties of the plasticized chitosan were measured by thermogravimetric analysis, differential scanning calorimetric, and DMA. These properties were correlated with the different levels of microstructure, including multiple structural units. PMID:24564751

  1. Biological glass fibers: Correlation between optical and structural properties

    PubMed Central

    Aizenberg, Joanna; Sundar, Vikram C.; Yablon, Andrew D.; Weaver, James C.; Chen, Gang

    2004-01-01

    Biological systems have, through the course of time, evolved unique solutions for complex optical problems. These solutions are often achieved through a sophisticated control of fine structural features. Here we present a detailed study of the optical properties of basalia spicules from the glass sponge Euplectella aspergillum and reconcile them with structural characteristics. We show these biosilica fibers to have a distinctive layered design with specific compositional variations in the glass/organic composite and a corresponding nonuniform refractive index profile with a high-index core and a low-index cladding. The spicules can function as single-mode, few-mode, or multimode fibers, with spines serving as illumination points along the spicule shaft. The presence of a lens-like structure at the end of the fiber increases its light-collecting efficiency. Although free-space coupling experiments emphasize the similarity of these spicules to commercial optical fibers, the absence of any birefringence, the presence of technologically inaccessible dopants in the fibers, and their improved mechanical properties highlight the advantages of the low-temperature synthesis used by biology to construct these remarkable structures. PMID:14993612

  2. A novel self-assembling peptide with UV-responsive properties.

    PubMed

    Wei, Ran; Jin, Cheng-Cheng; Quan, Jing; Nie, Hua-li; Zhu, Li-Min

    2014-03-01

    A novel heptapeptide comprising Ile-Gln-Ser-Pro-His-Phe-Phe (IQSPHFF) identified and found to undergo self-assembly into microparticles in solution. To understand the effects of ultraviolet (UV) irradiation on the self-assembly process, IQSPHFF solutions were exposed to the UV light of 365 nm at room temperature. This exposure was found to have a profound effect on the morphology of the self-assembled aggregates, converting the microparticles to nanorod shapes. Circular dichroism and FTIR studies indicated distinct structural differences in the arrangements of the peptide moieties before and after UV irradiation. However, Mass spectrum analysis and high performance liquid chromatography of the peptide molecules before and after UV irradiation demonstrated that the chemical structure of IQSPHFF was not changed. UV-visible spectroscopy and fluorescence spectroscopy studies showed that the absorption peak both increased after UV irradiation. Overall, our data show that the heptapeptide with UV-responsive properties. PMID:23828220

  3. Structural neighboring property for identifying protein-protein binding sites

    PubMed Central

    2015-01-01

    Background The protein-protein interaction plays a key role in the control of many biological functions, such as drug design and functional analysis. Determination of binding sites is widely applied in molecular biology research. Therefore, many efficient methods have been developed for identifying binding sites. In this paper, we calculate structural neighboring property through Voronoi diagram. Using 6,438 complexes, we study local biases of structural neighboring property on interface. Results We propose a novel statistical method to extract interacting residues, and interacting patches can be clustered as predicted interface residues. In addition, structural neighboring property can be adopted to construct a new energy function, for evaluating docking solutions. It includes new statistical property as well as existing energy items. Comparing to existing methods, our approach improves overall Fnat value by at least 3%. On Benchmark v4.0, our method has average Irmsd value of 3.31Å and overall Fnat value of 63%, which improves upon Irmsd of 3.89 Å and Fnat of 49% for ZRANK, and Irmsd of 3.99Å and Fnat of 46% for ClusPro. On the CAPRI targets, our method has average Irmsd value of 3.46 Å and overall Fnat value of 45%, which improves upon Irmsd of 4.18 Å and Fnat of 40% for ZRANK, and Irmsd of 5.12 Å and Fnat of 32% for ClusPro. Conclusions Experiments show that our method achieves better results than some state-of-the-art methods for identifying protein-protein binding sites, with the prediction quality improved in terms of CAPRI evaluation criteria. PMID:26356630

  4. Planetary Rings: An Update on Structure and Properties

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeff; DeVincenzi, Donald (Technical Monitor)

    2002-01-01

    Over the last several years there has been steady progress in several areas related to the structure and composition of planetary rings. Much of the progress was related to Saturn's rings: new observations by Hubble Space Telescope (HST) and NASA's Infrared Telescope Facility (IRTF), theoretical modeling of the vertical structure of, and particle properties in the rings, discovery of intriguing structural/spectral variations on small spatial scales, new observations and analysis of thermal emission from the rings, theoretical and observational constraints on the quadrupole brightness asymmetry at visual and microwave wavelengths, and new studies of "clumps" in and near the F ring. In addition, new observations were obtained of Jupiter's rings by Cassini, and new models were put forth to explain the narrow edges and apse alignment of the Uranian rings (and presumably other narrow eccentric rings).

  5. Optical and electrical properties of nanolaminate dielectric structures

    NASA Astrophysics Data System (ADS)

    Dikov, Hr; Vitanov, P.; Ivanova, T.; Stavrov, V.

    2016-03-01

    The aim of this study was formation of a multilayered transparent conductive nanolaminate structure with optimized conductivity vs. transparency parameters. The nanolayered structure comprised one or two thin layers of dielectric materials. The overall electrical conductivity was modified by tuning the size of the planar metal granules. Magnetron sputtering system with three different targets was used for layers deposition. The advantages are: the good reproducibility of a low-temperature process allows for effective process control and, optionally, selective formation of conductive areas in a dielectric structure. Our studies revealed that the relation between the sheet resistance and the maximum transparency in the visible spectral range depends on the size of the metal granules and the film thickness of the dielectric coating. The technology provides transparent conductive coatings with well-controlled optical and electrical properties.

  6. Production, structure, texture, and mechanical properties of severely deformed magnesium

    NASA Astrophysics Data System (ADS)

    Volkov, A. Yu.; Antonova, O. V.; Kamenetskii, B. I.; Klyukin, I. V.; Komkova, D. A.; Antonov, B. D.

    2016-05-01

    Methods of the severe plastic deformation (SPD) of pure magnesium at room temperature, namely, transverse extrusion and hydroextrusion in a self-destroyed shell, have been developed. The maximum true strain of the samples after the hydroextrusion was e ~ 3.2; in the course of transverse extrusion and subsequent cold rolling, a true strain of e ~ 6.0 was achieved. The structure and mechanical properties of the magnesium samples have been studied in different structural states. It has been shown that the SPD led to a decrease in the grain size d to ~2 μm; the relative elongation at fracture δ increased to ~20%. No active twinning has been revealed. The reasons for the high plasticity of magnesium after SPD according to the deformation modes suggested are discussed from the viewpoint of the hierarchy of the observed structural states.

  7. TECHNIQUES FOR THE STUDY OF THE STRUCTURAL PROPERTIES.

    SciTech Connect

    FERNANDEZ-GARCIA, M.; RODRIGUEZ, J.A.; MARTINEZ-ARIAS, A.; HANSON, J.C.

    2006-06-30

    The evolution of our understanding of the behavior of oxide nanostructures depends heavily on the structural information obtained from a wide range of physical methods traditionally used in solid state physics, surface science and inorganic chemistry. In this chapter, we describe several techniques that are useful for the characterization of the structural properties of oxide nanostructures: X-ray diffraction (XRD) and scattering, X-ray absorption fine structure (XAFS), Raman spectroscopy, transmission electron microscopy (TEM), scanning tunneling microscopy (STM) and atomic force microscopy (AFM). The ultimate goal is to obtain information about the spatial arrangement of atoms in the nanostructures with precise interatomic distances and bond angles. This may not be possible for complex systems and one may get only partial information about the local geometry or morphology.

  8. Surface structure, crystallographic and ice-nucleating properties of cellulose

    NASA Astrophysics Data System (ADS)

    Hiranuma, Naruki; Möhler, Ottmar; Kiselev, Alexei; Saathoff, Harald; Weidler, Peter; Shutthanandan, Shuttha; Kulkarni, Gourihar; Jantsch, Evelyn; Koop, Thomas

    2015-04-01

    Increasing evidence of the high diversity and efficient freezing ability of biological ice-nucleating particles is driving a reevaluation of their impact upon climate. Despite their potential importance, little is known about their atmospheric abundance and ice nucleation efficiency, especially non-proteinaceous ones, in comparison to non-biological materials (e.g., mineral dust). Recently, microcrystalline cellulose (MCC; non-proteinaceous plant structural polymer) has been identified as a potential biological ice-nucleating particle. However, it is still uncertain if the ice-nucleating activity is specific to the MCC structure or generally relevant to all cellulose materials, such that the results of MCC can be representatively scaled up to the total cellulose content in the atmosphere to address its role in clouds and the climate system. Here we use the helium ion microscopy (HIM) imaging and the X-ray diffraction (XRD) technique to characterize the nanoscale surface structure and crystalline properties of the two different types of cellulose (MCC and fibrous cellulose extracted from natural wood pulp) as model proxies for atmospheric cellulose particles and to assess their potential accessibility for water molecules. To complement these structural characterizations, we also present the results of immersion freezing experiments using the cold stage-based droplet freezing BINARY (Bielefeld Ice Nucleation ARaY) technique. The HIM results suggest that both cellulose types have a complex porous morphology with capillary spaces between the nanoscale fibrils over the microfiber surface. These surface structures may make cellulose accessible to water. The XRD results suggest that the structural properties of both cellulose materials are in agreement (i.e., P21 space group; a=7.96 Å, b=8.35 Å, c=10.28 Å) and comparable to the crystallographic properties of general monoclinic cellulose (i.e., Cellulose Iβ). The results obtained from the BINARY measurements suggest

  9. An Unstructured Finite Volume Approach for Structural Dynamics in Response to Fluid Motions

    PubMed Central

    Xia, Guohua; Lin, Ching-Long

    2008-01-01

    A new cell-vortex unstructured finite volume method for structural dynamics is assessed for simulations of structural dynamics in response to fluid motions. A robust implicit dual-time stepping method is employed to obtain time accurate solutions. The resulting system of algebraic equations is matrix-free and allows solid elements to include structure thickness, inertia, and structural stresses for accurate predictions of structural responses and stress distributions. The method is coupled with a fluid dynamics solver for fluid-structure interaction, providing a viable alternative to the finite element method for structural dynamics calculations. A mesh sensitivity test indicates that the finite volume method is at least of second-order accuracy. The method is validated by the problem of vortex-induced vibration of an elastic plate with different initial conditions and material properties. The results are in good agreement with existing numerical data and analytical solutions. The method is then applied to simulate a channel flow with an elastic wall. The effects of wall inertia and structural stresses on the fluid flow are investigated. PMID:18496602

  10. Note on dynamic response of large space structures

    NASA Astrophysics Data System (ADS)

    Elishakoff, I.; Abramovich, H.

    1992-07-01

    The dynamic behavior of large space structures, modeled as a Bresse-Timoshenko beam, was analyzed using the Bresse-Timoshenko beam model, but with the 4th-order derivative of the beam deflection with respect to time not included in the dynamical equations. In particular, the forced vibration response of symmetric large space structures was calculated for various parameters of the system. It is shown that a direct modal analysis yielding an exact solution is applicable due to the absence of the 4th-order time derivative in the Bresse-Timoshenko beam equations.

  11. Structural phase transition and electronic properties in samarium chalcogenides

    NASA Astrophysics Data System (ADS)

    Panwar, Y. S.; Aynyas, Mahendra; Pataiya, J.; Sanyal, Sankar P.

    2016-05-01

    The electronic structure and high pressure properties of samarium monochalcogenides SmS, SmSe and SmTe have been reported by using tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA). The total energy as a function of volume is evaluated. It is found that these monochalcogenides are stable in NaCl-type structure under ambient pressure. We predict a structural phase transition from NaCl-type (B1-phase) structure to CsCl-type (B2-type) structure for these compounds. Phase transition pressures were found to be 1.7, 4.4 and 6.6 GPa, for SmS, SmSe and SmTe respectively. Apart from this, the lattice parameter (a0), bulk modulus (B0), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed that these compounds exhibit metallic character. The calculated values of equilibrium lattice parameter and phase transition pressure are in general good agreement with available data.

  12. Structure-topology-property correlations of sodium phosphosilicate glasses

    SciTech Connect

    Hermansen, Christian; Smedskjaer, Morten M.; Guo, Xiaoju; Youngman, Randall E.; Mauro, John C.; Yue, Yuanzheng

    2015-08-14

    In this work, we investigate the correlations among structure, topology, and properties in a series of sodium phosphosilicate glasses with [SiO{sub 2}]/[SiO{sub 2} + P{sub 2}O{sub 5}] ranging from 0 to 1. The network structure is characterized by {sup 29}Si and {sup 31}P magic-angle spinning nuclear magnetic resonance and Raman spectroscopy. The results show the formation of six-fold coordinated silicon species in phosphorous-rich glasses. Based on the structural data, we propose a formation mechanism of the six-fold coordinated silicon, which is used to develop a quantitative structural model for predicting the speciation of the network forming units as a function of chemical composition. The structural model is then used to establish a temperature-dependent constraint description of phosphosilicate glass topology that enables prediction of glass transition temperature, liquid fragility, and indentation hardness. The topological constraint model provides insight into structural origin of the mixed network former effect in phosphosilicate glasses.

  13. Structure and Properties of Infrared Transmitting Chalcohalide Glasses.

    NASA Astrophysics Data System (ADS)

    Heo, Jong

    There have been a great deal of demands placed on the materials which show high transmittance in the mid -IR region compared to oxide glasses. Halide and chalcogenide glasses have long been studied as candidates for this purpose. There is yet a third family of glasses made by the mixture of halide and chalcogenide glasses which will be referred to here as "chalcohalide glasses". The purpose of the present work is to investigate the structure and properties of new chalcohalide glasses in the Ge-S-Br and Ge-S-I systems. The role of halogen atoms on the structure of GeS_2 and GeS_3 glasses has been discussed in detail based on the results obtained from IR, Raman and x-ray photoelectron spectroscopy. Effect of halogen addition on such properties as IR-transmittance, density, glass transition temperature and refractive index has also been studied. As the halogen components were added to binary Ge-S glasses, there would be a formation of Ge-Br bonds substituting sulfur atoms in the GeS_4 tetrahedra. Sulfur atoms removed from the GeS _4 tetrahedra would then form S_8 rings and chains. In general, the structure of Ge-S-Br(or I) glasses can best be described as a solid solution of S_8 rings dispersed throughout the network structure formed by GeBr _{rm x}S_ {4-rm x}(or GeI_ {rm x}S_{4- rm x}) groups and thereby forming a molecular phase separation. It could be expected that the network connectivity of Ge-S glasses decreases with the formation of Ge-Br (or I) bonds due to the network terminating role of monovalent halogen atoms. Consequently, structure of these glasses would become more open and eventually lead to the formation of chain-like structures. The observed changes in the properties of chalcohalide glasses in the Ge-S-Br and Ge -S-I systems support the proposed structural model.

  14. Xylonucleic acid: synthesis, structure, and orthogonal pairing properties

    PubMed Central

    Maiti, Mohitosh; Maiti, Munmun; Knies, Christine; Dumbre, Shrinivas; Lescrinier, Eveline; Rosemeyer, Helmut; Ceulemans, Arnout; Herdewijn, Piet

    2015-01-01

    There is a common interest for studying xeno-nucleic acid systems in the fields of synthetic biology and the origin of life, in particular, those with an engineered backbone and possessing novel properties. Along this line, we have investigated xylonucleic acid (XyloNA) containing a potentially prebiotic xylose sugar (a 3′-epimer of ribose) in its backbone. Herein, we report for the first time the synthesis of four XyloNA nucleotide building blocks and the assembly of XyloNA oligonucleotides containing all the natural nucleobases. A detailed investigation of pairing and structural properties of XyloNAs in comparison to DNA/RNA has been performed by thermal UV-melting, CD, and solution state NMR spectroscopic studies. XyloNA has been shown to be an orthogonal self-pairing system which adopts a slightly right-handed extended helical geometry. Our study on one hand, provides understanding for superior structure-function (-pairing) properties of DNA/RNA over XyloNA for selection as an informational polymer in the prebiotic context, while on the other hand, finds potential of XyloNA as an orthogonal genetic system for application in synthetic biology. PMID:26175047

  15. Structure properties relationship in electrospun thermoset butyl rubber

    NASA Astrophysics Data System (ADS)

    Viriyabanthorn, Nantiya

    Development of breathable elastomeric membranes based upon butyl rubber (IIR) compounds was investigated. These semi-permeable membranes were produced by electrospinning the compounded butyl rubber under appropriate conditions. They were designed to be selectively permeable. Specifically, these elastomeric membranes allowed moisture vapor transport, while maintaining a barrier against liquid water. Additionally, the conductive nature of carbon black in the compounds was shown to allow greater control over membrane thickness than generally observed in electrospun fabrics. Data were presented to show that the excellent chemical resistance of butyl rubber to organic solvents and toxic agents was maintained despite the porous nature of the membranes. Air flow resistance could also be adjusted as functions of processing conditions which related to fiber diameter and porosity of the membrane. Mechanical properties, in addition to various transport properties, are compared to a butyl rubber baseline. The moisture vapor transport properties are compared to expanded PTFE films. The results demonstrate the effectiveness of thermoset elastomeric membranes for producing flexible, selectively permeable barriers. Moreover, It also shows the capability to produce nonwoven materials for applications requiring high elongation (stretch) and porosity. In most elastomer formulations, carbon black is used as filler because of its reinforcing properties. The addition of carbon was also found to be important in the electrospinning of butyl rubber. Carbon black typically results in improved mechanical properties for rubber compounds, however, its conductive properties can also play a role in the resulting fiber structure during the electrospinning process. Carbon black loadings were varied from 0, 25, 50, and 75 parts per hundred rubber (phr). Increased carbon black loading resulted in a larger process window and reduced density and bead formation. Tensile modulus (corrected for changes

  16. Effects of skeleton structure on necrosis targeting and clearance properties of radioiodinated dianthrones.

    PubMed

    Zhang, Dongjian; Jiang, Cuihua; Yang, Shengwei; Gao, Meng; Huang, Dejian; Wang, Xiaoning; Shao, Haibo; Feng, Yuanbo; Sun, Ziping; Ni, Yicheng; Zhang, Jian; Yin, Zhiqi

    2016-07-01

    Necrosis avid agents (NAAs) can be used for diagnose of necrosis-related diseases, evaluation of therapeutic responses and targeted therapeutics of tumor. In order to probe into the effects of molecular skeleton structure on necrosis targeting and clearance properties of radioiodinated dianthrones, four dianthrone compounds with the same substituents but different skeletal structures, namely Hypericin (Hyp), protohypericin (ProHyp), emodin dianthrone mesomer (ED-1) and emodin dianthrone raceme (ED-2) were synthesized and radioiodinated. Then radioiodinated dianthrones were evaluated in vitro for their necrosis avidity in A549 lung cancer cells untreated and treated with H2O2. Their biodistribution and pharmacokinetic properties were determined in rat models of induced necrosis. In vitro cell assay revealed that destruction of rigid skeleton structure dramatically reduced their necrosis targeting ability. Animal studies demonstrated that destruction of rigid skeleton structure dramatically reduced the necrotic tissue uptake and speed up the clearance from the most normal tissues for the studied compounds. Among these (131)I-dianthrones, (131)I-Hyp exhibited the highest uptake and persistent retention in necrotic tissues. Hepatic infarction could be clearly visualized by SPECT/CT using (131)I-Hyp as an imaging probe. The results suggest that the skeleton structure of Hyp is the lead structure for further structure optimization of this class of NAAs. PMID:26586010

  17. Response of fiber reinforced sandwich structures subjected to explosive loading

    SciTech Connect

    Perotti, Luigi E.; El Sayed, Tamer; Deiterding, Ralf; Ortiz, Michael

    2011-01-01

    The capability to numerically simulate the response of sandwich structures to explosive loading constitutes a powerful tool to analyze and optimize their design by investigating the influence of different parameters. In order to achieve this objective, the necessary models for foam core and fiber reinforced materials in finite kinematics have been developed together with a finite element scheme which includes C1 finite elements for shells and cohesive elements able to capture the fracture propagation in composite fiber reinforced materials. This computational capability has been used to investigate the response of fiber reinforced sandwich shells to explosive loading. Based on the dissipated fracture energy resulting from these simulations, a factorial design has been carried out to assess the effect of different parameters on the sandwich shell response creating a tool for its optimization.

  18. Dynamic response of heavy duty diesel engine structures

    SciTech Connect

    Anderton, D.; Ghazy, M.R.

    1987-01-01

    The paper describes an investigation to identify the sources of forces which cause the vibration of different parts of the engine structure in a turbocharged heavy duty diesel engine of 2 litres/cylinder capacity. The differences in vibration response at the main bearings and on the engine outer surfaces is shown. Results of overall dynamic stiffness measurements at the main bearings indicate that the oil film has a negligible effect on the behaviour of the major vibration response. A model is put forward for an absolute prediction of the engine outer surface vibration. The model can be seen as an alternative or complement to current F.E. techniques. A comparison between predicted and measured vibration on the crankcase is presented. Predicted vibration response spectra are used to show the relative contribution of liner and bearing forces to the overall crankcase and cylinder block vibration of the engine.

  19. Structural health monitoring in composite materials using frequency response methods

    NASA Astrophysics Data System (ADS)

    Kessler, Seth S.; Spearing, S. Mark; Atalla, Mauro J.; Cesnik, Carlos E. S.; Soutis, Constantinos

    2001-08-01

    Cost effective and reliable damage detection is critical for the utilization of composite materials in structural applications. Non-destructive evaluation techniques (e.g. ultrasound, radiography, infra-red imaging) are available for use during standard repair and maintenance cycles, however by comparison to the techniques used for metals these are relatively expensive and time consuming. This paper presents part of an experimental and analytical survey of candidate methods for the detection of damage in composite materials. The experimental results are presented for the application of modal analysis techniques applied to rectangular laminated graphite/epoxy specimens containing representative damage modes, including delamination, transverse ply cracks and through-holes. Changes in natural frequencies and modes were then found using a scanning laser vibrometer, and 2-D finite element models were created for comparison with the experimental results. The models accurately predicted the response of the specimems at low frequencies, but the local excitation and coalescence of higher frequency modes make mode-dependent damage detection difficult and most likely impractical for structural applications. The frequency response method was found to be reliable for detecting even small amounts of damage in a simple composite structure, however the potentially important information about damage type, size, location and orientation were lost using this method since several combinations of these variables can yield identical response signatures.

  20. Characterization of structural response to hypersonic boundary-layer transition

    DOE PAGESBeta

    Riley, Zachary B.; Deshmukh, Rohit; Miller, Brent A.; McNamara, Jack J.; Casper, Katya M.

    2016-05-24

    The inherent relationship between boundary-layer stability, aerodynamic heating, and surface conditions makes the potential for interaction between the structural response and boundary-layer transition an important and challenging area of study in high-speed flows. This paper phenomenologically explores this interaction using a fundamental two-dimensional aerothermoelastic model under the assumption of an aluminum panel with simple supports. Specifically, an existing model is extended to examine the impact of transition onset location, transition length, and transitional overshoot in heat flux and fluctuating pressure on the structural response of surface panels. Transitional flow conditions are found to yield significantly increased thermal gradients, and theymore » can result in higher maximum panel temperatures compared to turbulent flow. Results indicate that overshoot in heat flux and fluctuating pressure reduces the flutter onset time and increases the strain energy accumulated in the panel. Furthermore, overshoot occurring near the midchord can yield average temperatures and peak displacements exceeding those experienced by the panel subject to turbulent flow. Lastly, these results suggest that fully turbulent flow does not always conservatively predict the thermo-structural response of surface panels.« less

  1. Modelling benthic biophysical drivers of ecosystem structure and biogeochemical response

    NASA Astrophysics Data System (ADS)

    Stephens, Nicholas; Bruggeman, Jorn; Lessin, Gennadi; Allen, Icarus

    2016-04-01

    The fate of carbon deposited at the sea floor is ultimately decided by biophysical drivers that control the efficiency of remineralisation and timescale of carbon burial in sediments. Specifically, these drivers include bioturbation through ingestion and movement, burrow-flushing and sediment reworking, which enhance vertical particulate transport and solute diffusion. Unfortunately, these processes are rarely satisfactorily resolved in models. To address this, a benthic model that explicitly describes the vertical position of biology (e.g., habitats) and biogeochemical processes is presented that includes biological functionality and biogeochemical response capturing changes in ecosystem structure, benthic-pelagic fluxes and biodiversity on inter-annual timescales. This is demonstrated by the model's ability to reproduce temporal variability in benthic infauna, vertical pore water nutrients and pelagic-benthic solute fluxes compared to in-situ data. A key advance is the replacement of bulk parameterisation of bioturbation by explicit description of the bio-physical processes responsible. This permits direct comparison with observations and determination of key parameters in experiments. Crucially, the model resolves the two-way interaction between sediment biogeochemistry and ecology, allowing exploration of the benthic response to changing environmental conditions, the importance of infaunal functional traits in shaping benthic ecological structure and the feedback the resulting bio-physical processes exert on pore water nutrient profiles. The model is actively being used to understand shelf sea carbon cycling, the response of the benthos to climatic change, food provision and other societal benefits.

  2. 41 CFR 102-37.130 - What are a SASP's responsibilities in the donation of surplus property?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... responsibilities in the donation of surplus property? 102-37.130 Section 102-37.130 Public Contracts and Property... PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY State Agency for Surplus Property (SASP) § 102-37.130 What are a SASP's responsibilities in the donation of surplus property? As a SASP,...

  3. 41 CFR 102-37.130 - What are a SASP's responsibilities in the donation of surplus property?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... responsibilities in the donation of surplus property? 102-37.130 Section 102-37.130 Public Contracts and Property... PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY State Agency for Surplus Property (SASP) § 102-37.130 What are a SASP's responsibilities in the donation of surplus property? As a SASP,...

  4. 41 CFR 102-37.130 - What are a SASP's responsibilities in the donation of surplus property?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... responsibilities in the donation of surplus property? 102-37.130 Section 102-37.130 Public Contracts and Property... PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY State Agency for Surplus Property (SASP) § 102-37.130 What are a SASP's responsibilities in the donation of surplus property? As a SASP,...

  5. 41 CFR 102-37.130 - What are a SASP's responsibilities in the donation of surplus property?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... responsibilities in the donation of surplus property? 102-37.130 Section 102-37.130 Public Contracts and Property... PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY State Agency for Surplus Property (SASP) § 102-37.130 What are a SASP's responsibilities in the donation of surplus property? As a SASP,...

  6. 41 CFR 102-37.130 - What are a SASP's responsibilities in the donation of surplus property?

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... responsibilities in the donation of surplus property? 102-37.130 Section 102-37.130 Public Contracts and Property... PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY State Agency for Surplus Property (SASP) § 102-37.130 What are a SASP's responsibilities in the donation of surplus property? As a SASP,...

  7. Structure-mechanics property relationship of waste derived biochars.

    PubMed

    Das, Oisik; Sarmah, Ajit K; Bhattacharyya, Debes

    2015-12-15

    The widespread applications of biochar in agriculture and environmental remediation made the scientific community ignore its mechanical properties. Hence, to examine the scope of biochar's structural applications, its mechanical properties have been investigated in this paper through nanoindentation technique. Seven waste derived biochars, made under different pyrolysis conditions and from diverse feedstocks, were studied via nanoindentation, infrared spectroscopy, X-ray crystallography, thermogravimetry, and electron microscopy. Following this, an attempt was made to correlate the biochars' hardness/modulus with reaction conditions and their chemical properties. The pine wood biochar made at 900°C and 60min residence time was found to have the highest hardness and elastic modulus of 4.29 and 25.01GPa, respectively. It was shown that a combination of higher heat treatment (≥500°C) temperature and longer residence time (~60min) increases the values of hardness and modulus. It was further realized that pyrolysis temperature was a more dominant factor than residence time in determining the final mechanical properties of biochar particles. The degree of aromaticity and crystallinity of the biochar were also correlated with higher values of hardness and modulus. PMID:26322726

  8. Quantum chemistry structures and properties of 134 kilo molecules.

    PubMed

    Ramakrishnan, Raghunathan; Dral, Pavlo O; Rupp, Matthias; von Lilienfeld, O Anatole

    2014-01-01

    Computational de novo design of new drugs and materials requires rigorous and unbiased exploration of chemical compound space. However, large uncharted territories persist due to its size scaling combinatorially with molecular size. We report computed geometric, energetic, electronic, and thermodynamic properties for 134k stable small organic molecules made up of CHONF. These molecules correspond to the subset of all 133,885 species with up to nine heavy atoms (CONF) out of the GDB-17 chemical universe of 166 billion organic molecules. We report geometries minimal in energy, corresponding harmonic frequencies, dipole moments, polarizabilities, along with energies, enthalpies, and free energies of atomization. All properties were calculated at the B3LYP/6-31G(2df,p) level of quantum chemistry. Furthermore, for the predominant stoichiometry, C7H10O2, there are 6,095 constitutional isomers among the 134k molecules. We report energies, enthalpies, and free energies of atomization at the more accurate G4MP2 level of theory for all of them. As such, this data set provides quantum chemical properties for a relevant, consistent, and comprehensive chemical space of small organic molecules. This database may serve the benchmarking of existing methods, development of new methods, such as hybrid quantum mechanics/machine learning, and systematic identification of structure-property relationships. PMID:25977779

  9. Geometry, electronic structures and optical properties of phosphorus nanotubes.

    PubMed

    Hu, Tao; Hashmi, Arqum; Hong, Jisang

    2015-10-16

    Using a first principles approach, we investigated the geometry, electronic structures, and optical properties of phosphorus nanotubes (PNTs). Two possible 1D configurations, the so-called α-PNTs and β-PNTs, are proposed, which are structurally related to blue and black phosphorus monolayers, respectively. Hereby, we predict that both armchair and zigzag geometries can be synthesized in α-PNTs, but the zigzag form of β-PNT is highly unfavorable because of large strain and conformation energies. The band gap of α-PNTs is expected to be ∼2.67 eV, and this is insensitive to the chirality when the tube's inner diameter is larger than 1.3 nm, while the armchair β-PNTs have a much smaller band gap. Interestingly, we find nearly flat band structures in the zigzag α-PNT system. This may indicate that an excited particle-hole pair has a huge effective mass. We also find asymmetric optical properties with respect to the polarization direction. The armchair α-PNT for parallel polarization shows a large refractive index of 2.6 near the ultraviolet wavelength, and also we find that the refractive index can be even smaller than 1 in certain frequency ranges. The zigzag tubes show very weak reflectivity for parallel polarization, while the armchair tube displays high reflectivity. PMID:26391069

  10. High intensity ultrasound modified ovalbumin: Structure, interface and gelation properties.

    PubMed

    Xiong, Wenfei; Wang, Yuntao; Zhang, Chunlan; Wan, Jiawei; Shah, Bakht Ramin; Pei, Yaqiong; Zhou, Bin; Li, Jin; Li, Bin

    2016-07-01

    Influence of high intensity ultrasound (HIUS) on the structure and properties of ovalbumin (OVA) were investigated. It was found that the subunits and secondary structure of OVA did not change significantly with HIUS treatment from the electrophoretic patterns and circular dichroism (CD) spectrum. The amount of free sulfhydryl groups increased and intrinsic fluorescence spectra analysis indicated changes in the tertiary structure and partial unfold of OVA after sonication increased. Compared with the untreated OVA, HIUS treatment increased the emulsifying activity and foaming ability, and decreased interface tension (oil-water and air-water interface), which due to the increased surface hydrophobicity and decreased the surface net charge in OVA, while the emulsifying and foaming stability had no remarkable differences. The increased particle size may be attributed to formation of protein aggregates. Moreover, the gelation temperatures of HIUS-treated samples were higher than the untreated OVA according to the temperature sweep model rheology, and this effect was consistent with the increased in surface hydrophobicity for ultrasound treated OVA. These changes in functional properties of OVA would promote its application in food industry. PMID:26964953

  11. Magnetic and structural properties of Mn-Ga thin films

    NASA Astrophysics Data System (ADS)

    Zhao, Siqian; Suzuki, Takao

    2016-05-01

    A systematic experimental work has been conducted to understand the magnetic properties of Mn-Ga thin films. Multilayer structured thin films of [MnGa 2 nm/Mn x nm]×25 (x = 0.2˜3.5, which corresponds to Mn at%56˜86) were sputter-deposited onto silica glass substrates, followed by annealing in vacuum. It is found that the magnetic properties strongly depend on x. For x = 0.5, the high magnetization values are found, where the nanocrystalline L10 structure is present. The samples with x = 2.0-3.0 exhibit the coercivity Hc higher than 10 kOe at room temperature where the nanocrystalline D022 structures are found to form. The correlation between the magnetic anisotropy constant K and saturation magnetization Ms is also discussed. The nth power dependence of magnetic anisotropy constant K on Ms is found, where the values of n are 7.8 and 1.9 for x = 0.5 and 2.5, respectively. The present result of the power dependence of n equals about 8 for the L10 MnGa suggests that the magnetic anisotropy in a nanocrystalline L10 MnGa phase is much different from the ordered FePt phase. On the other hand, the power dependence of the D022 nanocrystalline phase suggests the two-ion mechanism.

  12. Structural Properties of Finite MoS2 Nanowires

    NASA Astrophysics Data System (ADS)

    Clark, Shaylyn; Salgado, Andres; Fernandez-Seivane, Lucas; Lopez-Lozano, Xochitl

    2015-03-01

    Molybdenum disulfide (MoS2) has been one of the most important catalysts used in refineries worldwide for hydrodesulfurization over the past century. In the last decade, and with the advent of nanotechnology, there has been a special interest in MoS2 nanostructures due to their high potential as novel nanocatalysts. The study of the properties of these systems is of fundamental interest for the experimental design of their catalytic activity and efficiency. In this work, we have performed ab initio density-functional calculations (DFT) to investigate the structural properties of finite MoS2 nanostrutures. All the models here presented were based on newly experimentally observed morphologies in MoS2 industrial catalysts using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images. We simulated STEM images of the theoretical models to compare it with the experimental ones. In contrast with infinite models, the finite models prefer a rippled/twisted structure morphology over the planar or helical ones. The rippled/twisted models appear to be structurally more stable.

  13. Oxide Thermoelectric Materials: A Structure-Property Relationship

    NASA Astrophysics Data System (ADS)

    Nag, Abanti; Shubha, V.

    2014-04-01

    Recent demand for thermoelectric materials for power harvesting from automobile and industrial waste heat requires oxide materials because of their potential advantages over intermetallic alloys in terms of chemical and thermal stability at high temperatures. Achievement of thermoelectric figure of merit equivalent to unity ( ZT ≈ 1) for transition-metal oxides necessitates a second look at the fundamental theory on the basis of the structure-property relationship giving rise to electron correlation accompanied by spin fluctuation. Promising transition-metal oxides based on wide-bandgap semiconductors, perovskite and layered oxides have been studied as potential candidate n- and p-type materials. This paper reviews the correlation between the crystal structure and thermoelectric properties of transition-metal oxides. The crystal-site-dependent electronic configuration and spin degeneracy to control the thermopower and electron-phonon interaction leading to polaron hopping to control electrical conductivity is discussed. Crystal structure tailoring leading to phonon scattering at interfaces and nanograin domains to achieve low thermal conductivity is also highlighted.

  14. Structural and magnetic properties of chromium doped zinc ferrite

    SciTech Connect

    Sebastian, Rintu Mary; Thankachan, Smitha; Xavier, Sheena; Mohammed, E. M.; Joseph, Shaji

    2014-01-28

    Zinc chromium ferrites with chemical formula ZnCr{sub x}Fe{sub 2−x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by Sol - Gel technique. The structural as well as magnetic properties of the synthesized samples have been studied and reported here. The structural characterizations of the samples were analyzed by using X – Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The single phase spinel cubic structure of all the prepared samples was tested by XRD and FTIR. The particle size was observed to decrease from 18.636 nm to 6.125 nm by chromium doping and induced a tensile strain in all the zinc chromium mixed ferrites. The magnetic properties of few samples (x = 0.0, 0.4, 1.0) were investigated using Vibrating Sample Magnetometer (VSM)

  15. Electronic structure and magnetic properties of zigzag blue phosphorene nanoribbons

    SciTech Connect

    Hu, Tao; Hong, Jisang

    2015-08-07

    We investigated the electronic structure and magnetism of zigzag blue phosphorene nanoribbons (ZBPNRs) using first principles density functional theory calculations by changing the widths of ZBPNRs from 1.5 to 5 nm. In addition, the effect of H and O passivation was explored as well. The ZBPNRs displayed intra-edge antiferromagnetic ground state with a semiconducting band gap of ∼0.35 eV; and this was insensitive to the edge structure relaxation effect. However, the edge magnetism of ZBPNRs disappeared with H-passivation. Moreover, the band gap of H-passivated ZBPNRs was greatly enhanced because the calculated band gap was ∼1.77 eV, and this was almost the same as that of two-dimensional blue phosphorene layer. For O-passivated ZBPNRs, we also found an intra-edge antiferromagnetic state. Besides, both unpassivated and O-passivated ZBPNRs preserved almost the same band gap. We predict that the electronic band structure and magnetic properties can be controlled by means of passivation. Moreover, the edge magnetism can be also modulated by the strain. Nonetheless, the intrinsic physical properties are size independent. This feature can be an advantage for device applications because it may not be necessary to precisely control the width of the nanoribbon.

  16. Lanthanide coordination polymers: Synthesis, diverse structure and luminescence properties

    NASA Astrophysics Data System (ADS)

    Song, Xue-Qin; Lei, Yao-Kun; Wang, Xiao-Run; Zhao, Meng-Meng; Peng, Yun-Qiao; Cheng, Guo-Quan

    2014-10-01

    The new semirigid exo-bidentate ligand incorporating furfurysalicylamide terminal groups, namely, 1,4-bis{[(2‧-furfurylaminoformyl)phenoxyl]methyl}-2,5-bismethylbenzene (L) was synthesized and used as building blocks for constructing lanthanide coordination polymers with luminescent properties. The series of lanthanide nitrate complexes have been characterized by elemental analysis, IR spectroscopy, and X-ray diffraction analysis. The semirigid ligand L, as a bridging ligand, reacts with lanthanide nitrates forming three distinct structure types: chiral noninterpenetrated two-dimensional (2D) honeycomblike (6,3) (hcb, Schläfli symbol 63, vertex symbol 6 6 6) topological network as type I, 1D zigzag chain as type II and 1D trapezoid ladder-like chain as type III. The structural diversities indicate that lanthanide contraction effect played significant roles in the structural self-assembled process. The luminescent properties of EuIII, TbIII and DyIII complexes are discussed in detail. Due to the good match between the lowest triplet state of the ligand and the resonant energy level of the lanthanide ion, the lanthanide ions in EuIII, TbIII and DyIII complexes can be efficiently sensitized by the ligand.

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

    PubMed

    Dayal, Manmeet Singh; Catchmark, Jeffrey M

    2016-06-25

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

  18. Structural characterization and magnetic properties of steels subjected to fatigue

    NASA Astrophysics Data System (ADS)

    Lo, C. C. H.; Tang, F.; Biner, S. B.; Jiles, D. C.

    2000-05-01

    Studies have been made on the effects of residual stress and microstructure on the variations of magnetic properties of steels during fatigue. Strain-controlled fatigue tests have been conducted on 0.2wt% C steel samples which were (1) cold-worked, (2) cold-worked and annealed at 500 °C to relieve residual stress, and (3) annealed at 905 °C to produce a ferrite/pearlite structure. The changes of surface microstructure were studied by SEM replica technique. The dislocation structures of samples fatigued for different numbers of cycle were studied by TEM. In the initial stage of fatigue coercivity was found to behave differently for samples which have different residual stress levels. In the intermediate stage the magnetic hysteresis parameters became stable as the dislocation cell structure developed in the samples. In the final stage the magnetic parameters decreased dramatically. The decrease rate is related to the propagation rate of fatigue cracks observed in the SEM study, which was found to be dependent on the sample microstructure. The present results indicate that the magnetic inspection technique is able to differentiate the residual stress effects from the fatigue damage induced by cyclic loading, and therefore it is possible to detect the onset of fatigue failure in steel components via measurements of the changes in magnetic properties.—This work was sponsored by the National Science Foundation, under grant number CMS-9532056.

  19. Structure-property relations in amorphous carbon for photovoltaics

    NASA Astrophysics Data System (ADS)

    Risplendi, Francesca; Bernardi, Marco; Cicero, Giancarlo; Grossman, Jeffrey C.

    2014-07-01

    Carbon is emerging as a material with great potential for photovoltaics (PV). However, the amorphous form (a-C) has not been studied in detail as a PV material, even though it holds similarities with amorphous Silicon (a-Si) that is widely employed in efficient solar cells. In this work, we correlate the structure, bonding, stoichiometry, and hydrogen content of a-C with properties linked to PV performance such as the electronic structure and optical absorption. We employ first-principles molecular dynamics and density functional theory calculations to generate and analyze a set of a-C structures with a range of densities and hydrogen concentrations. We demonstrate that optical and electronic properties of interest in PV can be widely tuned by varying the density and hydrogen content. For example, sunlight absorption in a-C films can significantly exceed that of a same thickness of a-Si for a range of densities and H contents in a-C. Our results highlight promising features of a-C as the active layer material of thin-film solar cells.

  20. Structure-property relations in amorphous carbon for photovoltaics

    SciTech Connect

    Risplendi, Francesca; Cicero, Giancarlo; Bernardi, Marco; Grossman, Jeffrey C.

    2014-07-28

    Carbon is emerging as a material with great potential for photovoltaics (PV). However, the amorphous form (a-C) has not been studied in detail as a PV material, even though it holds similarities with amorphous Silicon (a-Si) that is widely employed in efficient solar cells. In this work, we correlate the structure, bonding, stoichiometry, and hydrogen content of a-C with properties linked to PV performance such as the electronic structure and optical absorption. We employ first-principles molecular dynamics and density functional theory calculations to generate and analyze a set of a-C structures with a range of densities and hydrogen concentrations. We demonstrate that optical and electronic properties of interest in PV can be widely tuned by varying the density and hydrogen content. For example, sunlight absorption in a-C films can significantly exceed that of a same thickness of a-Si for a range of densities and H contents in a-C. Our results highlight promising features of a-C as the active layer material of thin-film solar cells.

  1. Structural and Dielectric Properties of Subnanometric Laminates of Binary Oxides.

    PubMed

    Kahouli, Abdelkader; Lebedev, Oleg; Ben Elbahri, Marwa; Mercey, Bernard; Prellier, Wilfrid; Riedel, Stefan; Czernohorsky, Malte; Lallemand, Florent; Bunel, Catherine; Lüders, Ulrike

    2015-11-25

    Capacitors with a dielectric material consisting of amorphous laminates of Al2O3 and TiO2 with subnanometer individual layer thicknesses can show strongly enhanced capacitance densities compared to the bulk or laminates with nanometer layer thickness. In this study, the structural and dielectric properties of such subnanometer laminates grown on silicon by state-of-the-art atomic layer deposition are investigated with varying electrode materials. The laminates show a dielectric constant reaching 95 combined with a dielectric loss (tan δ) of about 0.2. The differences of the observed dielectric properties in capacitors with varying electrodes indicate that chemical effects at the interface with the TiN electrode play a major role, while the influence of the local roughness of the individual layers is rather limited. PMID:26523935

  2. The Structure and Properties of Cast Iron Alloyed with Copper

    NASA Astrophysics Data System (ADS)

    Razumakov, A. A.; Stepanova, N. V.; Bataev, I. A.; Lenivtseva, O. G.; Riapolova, Iu Iu; Emurlaev, K. I.

    2016-04-01

    Cast iron with 3 wt. % Cu was prepared by induction melting and casting in sand molds. The structure of the samples was studied using light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The addition of Cu promoted formation of pearlite and slightiy decreased the volume fraction of graphite. No Cu inclusions were found by LM and SEM. The nanoprecipitations of ε-Cu in lamellar pearlite were observed by TEM. The properties of the Cu-alloyed cast iron were compared with the properties of cast iron not alloyed with Cu. The hardness of cast iron after alloying with Cu increased and the friction coefficient decreased in comparison with the reference sample.

  3. Structure-property relationships in silica-siloxane nanocomposite materials

    SciTech Connect

    Ulibarri, T.A.; Derzon, D.K.; Wang, L.C.

    1997-03-01

    The simultaneous formation of a filler phase and a polymer matrix via in situ sol-gel techniques provides silica-siloxane nanocomposite materials of high strength. This study concentrates on the effects of temperature and relative humidity on a trimodal polymer system in an attempt to accelerate the reaction as well as evaluate subtle process- structure-property relations. It was found that successful process acceleration is only viable for high humidity systems when using the tin(IV) catalyst dibutyltin dilaurate. Processes involving low humidity were found to be very temperature and time dependent. Bimodal systems were investigated and demonstrated that the presence of a short-chain component led to enhanced material strength. This part of the study also revealed a link between the particle size and population density and the optimization of material properties.

  4. Structure and properties of water film adsorbed on mica surfaces

    NASA Astrophysics Data System (ADS)

    Zhao, Gutian; Tan, Qiyan; Xiang, Li; Cai, Di; Zeng, Hongbo; Yi, Hong; Ni, Zhonghua; Chen, Yunfei

    2015-09-01

    The structure profiles and physical properties of the adsorbed water film on a mica surface under conditions with different degrees of relative humidity are investigated by a surface force apparatus. The first layer of the adsorbed water film shows ice-like properties, including a lattice constant similar with ice crystal, a high bearing capacity that can support normal pressure as high as 4 MPa, a creep behavior under the action of even a small normal load, and a character of hydrogen bond. Adjacent to the first layer of the adsorbed water film, the water molecules in the outer layer are liquid-like that can flow freely under the action of external loads. Experimental results demonstrate that the adsorbed water layer makes the mica surface change from hydrophilic to weak hydrophobic. The weak hydrophobic surface may induce the latter adsorbed water molecules to form water islands on a mica sheet.

  5. Structural and electronic properties of GaAsBi

    NASA Astrophysics Data System (ADS)

    Achour, H.; Louhibi, S.; Amrani, B.; Tebboune, A.; Sekkal, N.

    2008-08-01

    The structural and electronic properties of the GaAs 1- xBi x ternary alloy are investigated by means of two first principles and full potential methods, the linear augmented plane waves (FPLAPW) method and a recent version of the full potential linear muffin-tin orbitals method (FPLMTO) which enables an accurate treatment of the interstitial regions. In particular, we have found that the maximal GaBi mole fraction x for which GaBi xAs 1- x remains a semiconductor is probably around x=0.5. The electronic properties of (GaAs) m/(GaBi) n quantum well superlattices (SLs) have also been calculated and it is found that such SLs are semiconductors when m is larger or equal to n.

  6. Lanthanides caged by the organic chelates; structural properties

    NASA Astrophysics Data System (ADS)

    Smentek, Lidia

    2011-04-01

    The structure, in particular symmetry, geometry and morphology of organic chelates coordinated with the lanthanide ions are analyzed in the present review. This is the first part of a complete presentation of a theoretical description of the properties of systems, which are widely used in technology, but most of all, in molecular biology and medicine. The discussion is focused on the symmetry and geometry of the cages, since these features play a dominant role in the spectroscopic activity of the lanthanides caged by organic chelates. At the same time, the spectroscopic properties require more formal presentation in the language of Racah algebra, and deserve a separate analysis. In addition to the parent systems of DOTA, DOTP, EDTMP and CDTMP presented here, their modifications by various antennas are analyzed. The conclusions that have a strong impact upon the theory of the energy transfer and the sensitized luminescence of these systems are based on the results of numerical density functional theory calculations.

  7. Synthetic melanin thin films: Structural and electrical properties

    NASA Astrophysics Data System (ADS)

    da Silva, M. I. N.; Dezidério, S. N.; Gonzalez, J. C.; Graeff, C. F. O.; Cotta, M. A.

    2004-11-01

    Scanning probe microscopy was used to investigate the structural and electrical organization at the nanoscopic level of hydrated melanin thin films synthesized by oxidizing L-3-(3,4-dihydroxyphenyl)-alanine (L-dopa) in dimethyl sulfoxide. Atomic force microscopy (AFM) provided the morphologies of the L-dopa melanin films. Electrostatic force microscopy and conductive-AFM were used to spatially resolve the electrical properties of the material. Using a simple parallel plate capacitor model a method to measure the charge distribution on the sample was developed. The correlations between topography, electric charge, and current images of the sample demonstrated that the hydration process produces a restructuring of melanin observed not only through topographic variations, but also through the creation of areas with different electrical properties.

  8. Structure Formation Mechanisms and Electrical Properties of PVD Fluoropolymer Films

    NASA Astrophysics Data System (ADS)

    Luchnikov, P. A.

    2015-01-01

    The mechanisms of forming fluoropolymer coatings on silicon substrates via condensation from an active gas phase using directed flows of accelerated electrons and ions are studied. It is demonstrated that electrical properties of the resulting fluoropolymer films strongly depend on the technological parameters of the deposition process. Their most optimal properties are reported when condensation takes place at the temperatures within ~373-386 K. It is shown that thermal annealing of the films in vacuum at 430-470 K improves their electrophysical parameters by re-evaporating the low-molecular complexes from the structure and decreasing the concentration of defects and spin-radicals, while annealing in air gives rise to formation of additional polar groups.

  9. Properties of strained structures and topological defects in graphene.

    PubMed

    Lu, Jiong; Bao, Yang; Su, Chen Liang; Loh, Kian Ping

    2013-10-22

    Strain and defect engineering of graphene can modify the topological features of electronic states, leading to novel properties such as pseudomagnetism in bubbles and metallicity in extended topological defects. A consequence of graphene being a soft membrane is that it can be strain-engineered to become highly corrugated by modifying its adhesion to the substrate. Extended grain boundaries in graphene can be constructed from periodic combinations of nonhexagonal rings (5-7 pairs). However, a controlled method of producing these defects is not currently available. In this Perspective, we discuss some of the recent advances in studying the properties and formation mechanisms of strained structures and defects in graphene, extending across both physics and chemistry. PMID:24143926

  10. Structure and electronic properties of nanodiamond and its fluorination effect

    NASA Astrophysics Data System (ADS)

    Takai, Kazuyuki; Kogane, Kenta; Touhara, Hidekazu; Hattori, Yoshiyuki

    2015-03-01

    Fluorination of nano-sized diamond (ND) is expected not only to stabilize the surface structure, but also to introduce functional groups on the surface, the conduction carriers, and so on. In this study, we evaluate the structure and magnetic properties of ND and fluorinated ND (FND) in order to consider the change in the electronic state and the surface structure by fluorination. Fluorination of ND was carried out by the direct reaction between gaseous fluorine (1 atm) and commercially available detonation diamond at 623 - 873 K. X-ray Diffraction study reveals the structural stability of core part of ND during fluorination. X-ray photoemission spectroscopy exhibits F1s peak at the lower binding energy region than that for physisorbed molecular fluorine, indicating the formation of the chemical bonding between C and F in the sample. The Electron Paramagnetic Resonance results suggest that fluorination induces not only changes in the surface structure but also relaxation of defects in the core part.

  11. Physico-chemical properties and cytotoxic effects of sugar-based surfactants: Impact of structural variations.

    PubMed

    Lu, Biao; Vayssade, Muriel; Miao, Yong; Chagnault, Vincent; Grand, Eric; Wadouachi, Anne; Postel, Denis; Drelich, Audrey; Egles, Christophe; Pezron, Isabelle

    2016-09-01

    Surfactants derived from the biorefinery process can present interesting surface-active properties, low cytotoxicity, high biocompatibility and biodegradability. They are therefore considered as potential sustainable substitutes to currently used petroleum-based surfactants. To better understand and anticipate their performances, structure-property relationships need to be carefully investigated. For this reason, we applied a multidisciplinary approach to systematically explore the effect of subtle structural variations on both physico-chemical properties and biological effects. Four sugar-based surfactants, each with an eight carbon alkyl chain bound to a glucose or maltose head group by an amide linkage, were synthesized and evaluated together along with two commercially available standard surfactants. Physico-chemical properties including solubility, Krafft point, surface-tension lowering and critical micellar concentration (CMC) in water and biological medium were explored. Cytotoxicity evaluation by measuring proliferation index and metabolic activity against dermal fibroblasts showed that all surfactants studied may induce cell death at low concentrations (below their CMC). Results revealed significant differences in both physico-chemical properties and cytotoxic effects depending on molecule structural features, such as the position of the linkage on the sugar head-group, or the orientation of the amide linkage. Furthermore, the cytotoxic response increased with the reduction of surfactant CMC. This study underscores the relevance of a methodical and multidisciplinary approach that enables the consideration of surfactant solution properties when applied to biological materials. Overall, our results will contribute to a better understanding of the concomitant impact of surfactant structure at physico-chemical and biological levels. PMID:27137806

  12. Attitude error response of structures to actuator/sensor noise

    NASA Technical Reports Server (NTRS)

    Balakrishnan, A. V.

    1991-01-01

    Explicit closed-form formulas are presented for the RMS attitude-error response to sensor and actuator noise for co-located actuators/sensors as a function of both control-gain parameters and structure parameters. The main point of departure is the use of continuum models. In particular the anisotropic Timoshenko model is used for lattice trusses typified by the NASA EPS Structure Model and the Evolutionary Model. One conclusion is that the maximum attainable improvement in the attitude error varying either structure parameters or control gains is 3 dB for the axial and torsion modes, the bending being essentially insensitive. The results are similar whether the Bernoulli model or the anisotropic Timoshenko model is used.

  13. Structural response of transport airplanes in crash situations

    NASA Technical Reports Server (NTRS)

    Thomson, R. G.; Caiafa, C.

    1983-01-01

    This report highlights the results of contractural studies of transport accident data undertaken in a joint research program sponsored by the FAA and NASA. From these accident data studies it was concluded that the greatest potential for improved transport crashworthiness is in the reduction of fire related fatalities. Accident data pertaining to fuselage integrity, main landing gear collapse, fuel tank rupture, wing breaks, tearing of tank lower surfaces, and engine pod scrubbing are discussed. In those accidents where the energy absorbing protective capability of the fuselage structure is expended and the airplane experiences major structural damage, trauma caused fatalities are also discussed. The dynamic performance of current seat/restraint systems are examined but it is concluded that the accident data does not adequately define the relationship between occupant response and the dynamic interaction with the seat, floor and fuselage structure.

  14. FAST Mast Structural Response to Axial Loading: Modeling and Verification

    NASA Technical Reports Server (NTRS)

    Knight, Norman F., Jr.; Elliott, Kenny B.; Templeton, Justin D.; Song, Kyongchan; Rayburn, Jeffery T.

    2012-01-01

    The International Space Station s solar array wing mast shadowing problem is the focus of this paper. A building-block approach to modeling and analysis is pursued for the primary structural components of the solar array wing mast structure. Starting with an ANSYS (Registered Trademark) finite element model, a verified MSC.Nastran (Trademark) model is established for a single longeron. This finite element model translation requires the conversion of several modeling and analysis features for the two structural analysis tools to produce comparable results for the single-longeron configuration. The model is then reconciled using test data. The resulting MSC.Nastran (Trademark) model is then extended to a single-bay configuration and verified using single-bay test data. Conversion of the MSC. Nastran (Trademark) single-bay model to Abaqus (Trademark) is also performed to simulate the elastic-plastic longeron buckling response of the single bay prior to folding.

  15. Characterization of structural connections using free and forced response test data

    NASA Technical Reports Server (NTRS)

    Lawrence, Charles; Huckelbridge, Arthur A.

    1989-01-01

    The accurate prediction of system dynamic response often has been limited by deficiencies in existing capabilities to characterize connections adequately. Connections between structural components often are complex mechanically, and difficult to accurately model analytically. Improved analytical models for connections are needed to improve system dynamic preditions. A procedure for identifying physical connection properties from free and forced response test data is developed, then verified utilizing a system having both a linear and nonlinear connection. Connection properties are computed in terms of physical parameters so that the physical characteristics of the connections can better be understood, in addition to providing improved input for the system model. The identification procedure is applicable to multi-degree of freedom systems, and does not require that the test data be measured directly at the connection locations.

  16. 41 CFR 102-78.55 - For which properties must Federal agencies assume historic preservation responsibilities?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... must Federal agencies assume historic preservation responsibilities? 102-78.55 Section 102-78.55 Public... MANAGEMENT REGULATION REAL PROPERTY 78-HISTORIC PRESERVATION Historic Preservation § 102-78.55 For which properties must Federal agencies assume historic preservation responsibilities? Federal agencies must...

  17. 41 CFR 102-78.55 - For which properties must Federal agencies assume historic preservation responsibilities?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... must Federal agencies assume historic preservation responsibilities? 102-78.55 Section 102-78.55 Public... MANAGEMENT REGULATION REAL PROPERTY 78-HISTORIC PRESERVATION Historic Preservation § 102-78.55 For which properties must Federal agencies assume historic preservation responsibilities? Federal agencies must...

  18. 41 CFR 102-78.55 - For which properties must Federal agencies assume historic preservation responsibilities?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... must Federal agencies assume historic preservation responsibilities? 102-78.55 Section 102-78.55 Public... MANAGEMENT REGULATION REAL PROPERTY 78-HISTORIC PRESERVATION Historic Preservation § 102-78.55 For which properties must Federal agencies assume historic preservation responsibilities? Federal agencies must...

  19. 41 CFR 102-78.55 - For which properties must Federal agencies assume historic preservation responsibilities?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... must Federal agencies assume historic preservation responsibilities? 102-78.55 Section 102-78.55 Public... MANAGEMENT REGULATION REAL PROPERTY 78-HISTORIC PRESERVATION Historic Preservation § 102-78.55 For which properties must Federal agencies assume historic preservation responsibilities? Federal agencies must...

  20. 41 CFR 102-78.55 - For which properties must Federal agencies assume historic preservation responsibilities?

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... must Federal agencies assume historic preservation responsibilities? 102-78.55 Section 102-78.55 Public... MANAGEMENT REGULATION REAL PROPERTY 78-HISTORIC PRESERVATION Historic Preservation § 102-78.55 For which properties must Federal agencies assume historic preservation responsibilities? Federal agencies must...

  1. Ground/Flight Correlation of Aerodynamic Loads with Structural Response

    NASA Technical Reports Server (NTRS)

    Mangalam, Arun S.; Davis, Mark C.

    2009-01-01

    Ground and flight tests provide a basis and methodology for in-flight characterization of the aerodynamic and structural performance through the monitoring of the fluid-structure interaction. The NF-15B flight tests of the Intelligent Flight Control System program provided a unique opportunity to test the correlation of aerodynamic loads with points of flow attaching and detaching from the surface, which are also known as flow bifurcation points, as observed in a previous wind tunnel test performed at the U.S. Air Force Academy (Colorado Springs, Colorado). Moreover, flight tests, along with the subsequent unsteady aerodynamic tests in the NASA Transonic Dynamics Tunnel (TDT), provide a basis using surface flow sensors as means of assessing the aeroelastic performance of flight vehicles. For the flight tests, the NF-15B tail was instrumented with hot-film sensors and strain gages for measuring root-bending strains. This data were gathered via selected sideslip maneuvers performed at level flight and subsonic speeds. The aerodynamic loads generated by the sideslip maneuver resulted in a structural response, which were then compared with the hot-film sensor signals. The hot-film sensor signals near the stagnation region were found to be highly correlated with the root-bending strains. For the TDT tests, a flexible wing section developed under the U.S. Air Force Research Lab SensorCraft program was instrumented with strain gages, accelerometers, and hot-film sensors at two span stations. The TDT tests confirmed the correlation between flow bifurcation points and the wing structural response to tunnel-generated gusts. Furthermore, as the wings structural modes were excited by the gusts, a gradual phase change between the flow bifurcation point and the structural mode occurred during a resonant condition.

  2. Structural and physical properties of sanxan polysaccharide from Sphingomonas sanxanigenens.

    PubMed

    Huang, Haidong; Wu, Mengmeng; Yang, Hongpeng; Li, Xiaoyan; Ren, Mengnan; Li, Guoqiang; Ma, Ting

    2016-06-25

    Sphingomonas sanxanigenens, a new species of the genus Sphingomonas, synthesizes extracellular biopolymer termed sanxan. Sanxan polysaccharide was purified from the fermentation broth by Sephacryl S-400 column chromatography. The molecular weight of sanxan polysaccharide was 408kDa by the method of size-exclusion chromatography combined with laser light scattering. Based on FT-IR, periodate oxidation, Smith degradation, composition analysis and nuclear magnetic resonance experiments, the structure of sanxan polysaccharide was elucidated as follows: The solution of sanxan polysaccharide showed properties of high viscosity and shear-thinning. By cooling hot solutions, sanxan polysaccharide could form elastic thermoreversible gel. PMID:27083833

  3. Structural properties of amorphous silicon produced by electron irradiation

    SciTech Connect

    Yamasaki, J.; Takeda, S.

    1999-07-01

    The structural properties of the amorphous Si (a-Si), which was created from crystalline silicon by 2 MeV electron irradiation at low temperatures about 25 K, are examined in detail by means of transmission electron microscopy and transmission electron diffraction. The peak positions in the radial distribution function (RDF) of the a-Si correspond well to those of a-Si fabricated by other techniques. The electron-irradiation-induced a-Si returns to crystalline Si after annealing at 550 C.

  4. Electronic structure and properties of layered gallium telluride

    NASA Astrophysics Data System (ADS)

    Shenoy, U. Sandhya; Gupta, Uttam; Narang, Deepa S.; Late, Dattatray J.; Waghmare, Umesh V.; Rao, C. N. R.

    2016-05-01

    Layer-dependent electronic structure and properties of gallium monochalcogenides, GaX where X = S, Se, Te, have been investigated using first-principles calculations based on various functionals, with a motivation to assess their use in photocatalytic water splitting. Since hydrogen evolution by water splitting using visible light provides a promising way for solar energy conversion, both theoretical and experimental studies have been carried out on the photochemical hydrogen evolution by GaTe. We also present the Raman spectra of GaTe examined by both theory and experiment.

  5. Structural, anisotropic and electronic properties of C96 under pressure

    NASA Astrophysics Data System (ADS)

    Xing, Mengjiang; Li, Binhua; Yu, Zhengtao; Chen, Qi

    2016-01-01

    An investigation of the structural, elastic, electronic and anisotropic properties of C96 under high pressure has been calculated using first-principles calculations based on density functional theory, as implemented in the Cambridge Serial Total Energy Package code. At elevated pressures, the elastic constants and shear modulus, Young's modulus and Poisson's ratio for C96 increase with pressure increasing. The anisotropy studies of Young's modulus, shear modulus, Poisson's ratio, Zener anisotropy index, the universal elastic anisotropy index AU and hardness show that C96 exhibits a small anisotropy. The sound velocities, Debye temperature and band gap of C96 under high pressure are also calculated.

  6. Electronic Structure and Optical Properties of Twisted Bilayer Black Phosphorus

    NASA Astrophysics Data System (ADS)

    Cao, Ting; Li, Zhenglu; Qiu, Diana Y.; Louie, Steven G.

    Using first-principles calculations, we find that the electronic structure and optical properties of bilayer black phosphorus can be modified significantly through changing the interlayer twist angle. We demonstrate the origin of these twist angle dependent effects, and connect our predicted results to experimental measurements. This work was supported by NSF Grant No. DMR15-1508412, and the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Computational resources have been provided by DOE at Lawrence Berkeley National Laboratory's NERSC facility.

  7. Structural characteristics and radiative properties of tropical cloud clusters

    SciTech Connect

    Machado, L.A.T.; Rossow, W.B.

    1993-12-01

    By identifying individual tropical cloud clusters in eight months of the International Satellite Cloud Climatology Project data, the size distribution, average cloud properties, and their variation with system size in tropical convective systems (CS) is examined. The geographic distribution of CS shows a concentration over land areas in the summer hemisphere with little seasonal variation except for the major shift of location into the summer hemisphere. When the tropics are considered as a whole or a region is considered over a whole season, CS of all sizes form a continuous size distribution where the area covered by the clouds in each size range is approximately the same. Land CS show a small excess of the smallest CS and a small deficit of the largest CS in comparison to ocean CS. Average CS cloud properties suggest two major cloud types: One with lower cloud-top pressures and much higher optical thicknesses, associated with deep convection, and one with higher cloud-top pressures and some evidence of a further division into optically thicker and thinner parts. The average properties of these clouds vary in a correlated fashion such that a larger horizontal extent of the convective system cloud is accompanied by a lower convective cloud-top pressure, larger anvil cloud size, and larger anvil cloud optical thickness. These structural properties and their diurnal variation also suggest that the smallest CS may represent a mixture of the formative and dissipative stages of CS, while the medium and large sizes are, principally, the mature stage. A radiative transfer model is used to evaluate the local radiative effects of CS with average cloud properties. The results imply that the mesoscale anvil cloud reinforces the diabatic heating of the atmosphere by the convection and may help sustain these systems at night. The radiative effects of the convective clouds may reinforce the diurnal variation of convection. 80 refs., 17 figs., 3 tabs.

  8. Structural Properties of the Caenorhabditis elegans Neuronal Network

    PubMed Central

    Varshney, Lav R.; Chen, Beth L.; Paniagua, Eric; Hall, David H.; Chklovskii, Dmitri B.

    2011-01-01

    Despite recent interest in reconstructing neuronal networks, complete wiring diagrams on the level of individual synapses remain scarce and the insights into function they can provide remain unclear. Even for Caenorhabditis elegans, whose neuronal network is relatively small and stereotypical from animal to animal, published wiring diagrams are neither accurate nor complete and self-consistent. Using materials from White et al. and new electron micrographs we assemble whole, self-consistent gap junction and chemical synapse networks of hermaphrodite C. elegans. We propose a method to visualize the wiring diagram, which reflects network signal flow. We calculate statistical and topological properties of the network, such as degree distributions, synaptic multiplicities, and small-world properties, that help in understanding network signal propagation. We identify neurons that may play central roles in information processing, and network motifs that could serve as functional modules of the network. We explore propagation of neuronal activity in response to sensory or artificial stimulation using linear systems theory and find several activity patterns that could serve as substrates of previously described behaviors. Finally, we analyze the interaction between the gap junction and the chemical synapse networks. Since several statistical properties of the C. elegans network, such as multiplicity and motif distributions are similar to those found in mammalian neocortex, they likely point to general principles of neuronal networks. The wiring diagram reported here can help in understanding the mechanistic basis of behavior by generating predictions about future experiments involving genetic perturbations, laser ablations, or monitoring propagation of neuronal activity in response to stimulation. PMID:21304930

  9. Structure and other properties of Jupiter's distant magnetotail

    NASA Technical Reports Server (NTRS)

    Lepping, R. P.; Desch, M. D.; Klein, L. W.; Sittler, E. C., Jr.; Sullivan, J. D.; Kurth, W. S.; Behannon, K. W.

    1983-01-01

    Analyses of data from Voyager 2 experiments provide evidence for, and characteristics of, a Jovian magnetotail extending at least to 9,000 Jovian radii from the planet. During approximately (25 day) periodic sightings of the tail, the magnetic field tended to point radially towards or away from Jupiter, indicating preservation to large distances of the bipolar, lobe like structure observed near the planet. This periodicity, along with various properties of the solar wind at this time, indicates that the tail is apparently influenced by recurrent solar wind features. Anomalous magnetic fields, not aligned with the nominal tail axis, also exist within the tail, especially in the low density, central (core) region, indicating some complexity of internal structure.

  10. Investigation of structural and electrical properties of mixed ferrite system

    SciTech Connect

    Astik, Nidhi M. Jha, Prafulla K.

    2015-05-15

    In the present work, structural and electrical properties of mixed ferrite systems are studied. As prepared compound of Co{sub 0.85}Ca{sub 0.15-y}Cd{sub y}Fe{sub 2}O{sub 4} (y=0.10, 0.15) is synthesized in polycrystalline form, using the stoichiometric mixture of oxides with conventional standard ceramic route with double sintering at 950°C and 1100°C and characterized by X-ray diffraction. The X-ray diffraction pattern confirms the presence of cubic (FCC) structure. The sharp intensified peaks in X-ray diffraction pattern clearly indicate the completeness of reaction.

  11. Structures and Properties of Naturally Occurring Polyether Antibiotics

    PubMed Central

    Rutkowski, Jacek; Brzezinski, Bogumil

    2013-01-01

    Polyether ionophores represent a large group of natural, biologically active substances produced by Streptomyces spp. They are lipid soluble and able to transport metal cations across cell membranes. Several of polyether ionophores are widely used as growth promoters in veterinary. Polyether antibiotics show a broad spectrum of bioactivity ranging from antibacterial, antifungal, antiparasitic, antiviral, and tumour cell cytotoxicity. Recently, it has been shown that some of these compounds are able to selectively kill cancer stem cells and multidrug-resistant cancer cells. Thus, they are recognized as new potential anticancer drugs. The biological activity of polyether ionophores is strictly connected with their molecular structure; therefore, the purpose of this paper is to present an overview of their formula, molecular structure, and properties. PMID:23586016

  12. N-doped graphene: Polarization effects and structural properties

    NASA Astrophysics Data System (ADS)

    Ghorbanfekr-Kalashami, Hossein; Neek-Amal, M.; Peeters, F. M.

    2016-05-01

    The structural and mechanical properties of N-doped graphene (NG) are investigated using reactive force field (ReaxFF) potentials in large-scale molecular dynamics simulations. We found that ripples, which are induced by the dopants, change the roughness of NG, which depends on the number of dopants and their local arrangement. For any doping ratio N/C, the NG becomes ferroelectric with a net dipole moment. The formation energy increases nonlinearly with N/C ratio, while the Young's modulus, tensile strength, and intrinsic strain decrease with the number of dopants. Our results for the structural deformation and the thermoelectricity of the NG sheet are in good agreement with recent experiments and ab initio calculations.

  13. Characterization of structure and thermophysical properties of three ESR slags

    NASA Astrophysics Data System (ADS)

    Plotkowski, A.; deBarbadillo, J.; Krane, Matthew J. M.

    2016-07-01

    The structure and properties of electroslag remelting (ESR) slags were characterized. Slags samples of three compositions were obtained from industrial remelting processes at Special Metals Corporation and from casting in a laboratory vacuum induction melter. The structure of the slag samples was observed using optical and electron microscopy, and phases were identified and their relative amounts quantified using X-ray diffraction. Laser flash thermal diffusivity, density, and differential scanning calorimetry measurements for specific heat were performed to determine the bulk thermal conductivity of the samples. Sample porosity was measured as a function of depth using a serial sectioning technique, and a onedimensional computational model was developed to estimate the thermal conductivity of the fully dense slags. These results are discussed in context with previous studies, and opportunities for future research are identified. AFRL Case Number: 88ABW-2015-1871.

  14. Community structure from spectral properties in complex networks

    NASA Astrophysics Data System (ADS)

    Servedio, V. D. P.; Colaiori, F.; Capocci, A.; Caldarelli, G.

    2005-06-01

    We analyze the spectral properties of complex networks focusing on their relation to the community structure, and develop an algorithm based on correlations among components of different eigenvectors. The algorithm applies to general weighted networks, and, in a suitably modified version, to the case of directed networks. Our method allows to correctly detect communities in sharply partitioned graphs, however it is useful to the analysis of more complex networks, without a well defined cluster structure, as social and information networks. As an example, we test the algorithm on a large scale data-set from a psychological experiment of free word association, where it proves to be successful both in clustering words, and in uncovering mental association patterns.

  15. Small magnetic structures in the photosphere, radiative properties

    NASA Astrophysics Data System (ADS)

    Palacios, Judith; Domingo, Vicente; Cabello, Iballa; Bonet, José Antonio; Sánchez Almeida, Jorge

    The three dimensional structure of small magnetic field features in the photosphere, their dynamic behavior and their radiative properties are studied. We analyze data obtained in simultaneous observations made on Sept 29 and 30, 2007 with the HINODE spacecraft and the Swedish Solar Telescope (SST) in La Palma in different wavelengths, such as CaII (396.85 nm) and CN (388.35 nm) and other with Hinode data; and Gband (430.56 nm) with SST. Tha analysis is completed with high resolution Gband and Gcontinuum (436.39 nm) images from SST obtained on 2005 and 2006. Magnetograms have been obtained from both observatories. SST images have been processed with MOMFB code. Ribbon-like structures and "flowers" are studied in detail. Comparisons with solar atmospheric models are presented.

  16. Structural, optical, and magnetic properties of FeVO3

    NASA Astrophysics Data System (ADS)

    Singh, Pooja; Gupta, Anurag; Dogra, Anjana

    2016-05-01

    We report the structural, optical, and magnetic properties of polycrystalline FeVO3 synthesized by solid state reaction technique.While FeVO3 has rhombohedral crystal structure with space group R-3c (167) identical to the parentα-Fe2O3, the lattice volume reduces due to the replacement of Fe3+ with V3+ having smaller ionic radii. The most remarkable outcome of doping is reduction in band gap from 2.1 (α-Fe2O3) to 1.5 eV (FeVO3), which is favorable for photo-electrochemical applications. Although the canted ferromagnetism persists in FeVO3, an enhancement in magnetic moment is observed as compared to the parent compound.

  17. Structural stability and elastic properties of prototypical covalent organic frameworks

    NASA Astrophysics Data System (ADS)

    Zhou, Wei; Wu, Hui; Yildirim, Taner

    2010-10-01

    We report the first investigation of the structural stabilities and elastic properties of covalent organic frameworks (COFs), a new class of porous crystalline materials. Representative 2D COFs were found to prefer shifted AA stacking, somewhat similar to graphite. The shear moduli of 2D COFs are exceedingly small, suggesting that the layer-layer coupling in 2D COFs is rather weak, and stacking faults may widely exist. Representative 3D COFs were found to exhibit relatively low elastic stiffness overall. In particular, COF-108, the least dense crystal known, exhibits rather low bulk and shear moduli. Our findings provide important structural and physical details to be considered in the further development of COF materials.

  18. Structure-property relationships of nanoscale engineered perovskite oxides

    NASA Astrophysics Data System (ADS)

    Tian, Wei

    Recent advances in the synthesis of nanoscale customized structure have demonstrated that reactive molecular beam epitaxy (MBE) can be used to construct nanostructure of oxides with atomic control. The ability to engineer the structure and chemistry of oxides at the nanometer scale makes possible for the creation of new functional materials that can be designed to have exceptional properties. This thesis focused on understanding structure-property relationships of such nanoscale customized oxides utilizing state-of-the-art transmission electron microscopy (TEM). Epitaxial thin films of n = 1--5 members of Ruddlesden-Popper homologous series Srn+1Ti nO3n+1 were synthesized by reactive MBE. We investigated the structure and microstructure of these thin films by x-ray diffraction along with high-resolution transmission electron microscopy (HRTEM) in combination with computer image simulations. We found that the thin films of n = 1--3 members are nearly free of intergrowths, e.g. phase-pure, while n = 4 and 5 thin films contain noticeably more intergrowth defects and anti-phase boundaries in their perovskite sheets. We show that these results are consistent with what is known about the thermodynamics of Sr n+1TinO3 n+1 phases. We also investigated the atomic structure and interfacial structure of artificial PbTiO3/SrTiO3 and BaTiO3/SrTiO 3 superlattices grown by MBE both with and without digital compositional grading. Both of these systems form a solid solution over their entire composition range. Thus, these layered heterostructures are metastable. We demonstrated, however, that the thermodynamically metastable superlattices can be kinetically stabilized via layer-by-layer growth. In addition, we found that the interfaces between two constituents in the heterostructures are atomically-abrupt. The superlattice thin films were made fully coherent with the substrates, resulting in a homogeneous large strain in the BaTiO3 layers due to the lattice mismatch between BaTiO3

  19. Structural and functional properties of hemp seed protein products.

    PubMed

    Malomo, Sunday A; He, Rong; Aluko, Rotimi E

    2014-08-01

    The effects of pH and protein concentration on some structural and functional properties of hemp seed protein isolate (HPI, 84.15% protein content) and defatted hemp seed protein meal (HPM, 44.32% protein content) were determined. The HPI had minimum protein solubility (PS) at pH 4.0, which increased as pH was decreased or increased. In contrast, the HPM had minimum PS at pH 3.0, which increased at higher pH values. Gel electrophoresis showed that some of the high molecular weight proteins (>45 kDa) present in HPM were not well extracted by the alkali and were absent or present in low ratio in the HPI polypeptide profile. The amino acid composition showed that the isolation process increased the Arg/Lys ratio of HPI (5.52%) when compared to HPM (3.35%). Intrinsic fluorescence and circular dichroism data indicate that the HPI proteins had a well-defined structure at pH 3.0, which was lost as pH value increased. The differences in structural conformation of HPI at different pH values were reflected as better foaming capacity at pH 3.0 when compared to pH 5.0, 7.0, and 9.0. At 10 and 25 mg/mL protein concentrations, emulsions formed by the HPM had smaller oil droplet sizes (higher quality), when compared to the HPI-formed emulsions. In contrast at 50 mg/mL protein concentration, the HPI-formed emulsions had smaller oil droplet sizes (except at pH 3.0). We conclude that the functional properties of hemp seed protein products are dependent on structural conformations as well as protein concentration and pH. PMID:25048774

  20. Structural, magnetic and dielectric properties of NiZnFe2O4 nanocrystals

    NASA Astrophysics Data System (ADS)

    Datt, Gopal; Abhyankar, A. C.

    2016-04-01

    In this paper we report the structural, magnetic and dielectric properties of hydrothermally synthesised NiZnFe2O4 nanocrystals. The Rietveld refinement of XRD data reveals that nanoparticles are crystallized in spinel structure with Fd-3m space group and the lattice parameter is found to be 8.413 (2) Ȧ. The FESEM microstructures reveal that the particles are in the spherical shape with a size lying between 20-25 nm. The magnetic data analysis shows that the coercivity of the nanoparticles is almost zero at room temperature and the magnetization value is Ms = 45 emu/g. The dielectric relaxation of the NiZnFe2O4 nanocrystals obeys the modified Debye model which considers the more than one ion contributing to the relaxation. The ac-conductivity of these nanocrystals is governed by the universal dielectric response (UDR) model, where the variable-range hopping of localized polarons is responsible for conduction.

  1. Structural and internal acoustic response of cylinders with applications to rocket payload fairings

    NASA Astrophysics Data System (ADS)

    Niezrecki, Christopher

    In this work the internal acoustic response of a closed simply-supported (SS) cylinder actuated by piezoelectric (PZT) actuators is presented. A research-grade SS cylinder is created and the modal properties are analyzed experimentally. The experimental modal properties are compared to finite element analysis (FEA) and to results predicted by Love shell theory. The experimental results indicate that the created cylinder has dynamic properties that are similar to the analytical and FEA results. The validated model is used to extrapolate results for a SS cylinder that emulates a Minotaur payload fairing. The internal cylinder acoustic levels are investigated for PZT actuation between 35 and 400 Hz. It is found that changes in cylinder parameters (stiffness and material density) do not have a large effect on the magnitude of the structural response. Likewise the interior acoustic response is not greatly affected by changes to the cylinder parameters. As the applied voltage increases linearly, the internal sound pressure level (SPL) varies logarithmically. This behavior is a limiting factor in using a PZT actuator to generate high internal SPLs. Significant reductions in the structural response due to increased damping do not equate to similar reductions in the acoustic SPLs for the cylinder. The sound levels at the acoustic resonant frequencies are essentially unaffected by the significant increase in structural damping while the acoustic levels at the structural resonant frequencies are mildly reduced. The interior acoustic response of the cylinder is dominated by the acoustic modes and therefore significant reductions in the overall interior acoustic levels will not be achieved if only the structural resonances are controlled. The model indicates that the maximum acoustic levels generated by the baseline PZT actuator are sufficient at the higher frequency range but are not commensurate with the levels found in a typical fairing in the lower frequency range (below

  2. Structural, elastic and thermodynamic properties of the tetragonal structure of germanium carbonitride

    NASA Astrophysics Data System (ADS)

    Xing, Mengjiang; Li, Binhua; Yu, Zhengtao; Chen, Qi

    2016-04-01

    The structural, mechanical, electronic and thermodynamic properties of the tetragonal structure germanium carbonitride (t-GeCN) were first investigated using the density function theory with the ultrasoft psedopotential scheme in the frame of the generalized gradient approximation and the local density approximation. The elastic constants have confirmed that the t-GeCN is mechanically stable and phonon spectra have confirmed that the t-GeCN is dynamically stable. The anisotropy studies show that t-GeCN exhibits a larger anisotropy in its Poisson's ratio, Young's modulus, shear modulus, sound velocities and universal elastic anisotropy index. Electronic structure study shows that t-GeCN is an indirect semiconductor with band gap of 0.628 eV. The thermodynamic properties of t-GeCN, including Debye temperature, heat capacity, Grüneisen parameter and thermal expansion coefficient are investigated utilizing the quasi-harmonic Debye model.

  3. Analysis of community properties and node properties to understand the structure of the bus transport network

    NASA Astrophysics Data System (ADS)

    Sun, Yeran; Mburu, Lucy; Wang, Shaohua

    2016-05-01

    Akin to most infrastructures, intraurban bus networks are large and highly complex. Understanding the composition of such networks requires an intricate decomposition of the network into modules, taking into account the manner in which network links are distributed among the nodes. There exists for each set of highly interlinked nodes little connectivity with the next set of highly interlinked nodes. This inherent property of nodes makes community detection a popular approach for analyzing the structure of complex networks. In this study, we attempt to understand the structure of the intraurban bus network of Ireland's capital city, Dublin in a two-step approach. We first analyze the modular structure of the network by identifying potential communities. Secondly, we assess the prominence of each network node by examining the module-based topological properties of the nodes. Results of this empirical study reveal a clear pattern of independent communities, indicating thus, an implicit multi-community structure of the intraurban bus network. Examination of the geographic characteristics of the identified communities shows a degree of socio-economic divisions of the Dublin city. Furthermore, a large majority of the important nodes (vital transportation hubs) are located at the city center, implying that most of the bus lines in Dublin city tend to intersect the city's core.

  4. Tuning transport properties on graphene multiterminal structures by mechanical deformations

    NASA Astrophysics Data System (ADS)

    Latge, Andrea; Torres, Vanessa; Faria, Daiara

    The realization of mechanical strain on graphene structures is viewed as a promise route to tune electronic and transport properties such as changing energy band-gaps and promoting localization of states. Using continuum models, mechanical deformations are described by effective gauge fields, mirrored as pseudomagnetic fields that may reach quite high values. Interesting symmetry features are developed due to out of plane deformations on graphene; lift sublattice symmetry was predicted and observed in centrosymmetric bumps and strained nanobubbles. Here we discuss the effects of Gaussian-like strain on a hexagonal graphene flake connected to three leads, modeled as perfect graphene nanoribbons. The Green function formalism is used within a tight-binding approximation. For this particular deformation sharp resonant states are achieved depending on the strained structure details. We also study a fold-strained structure in which the three leads are deformed extending up to the very center of the hexagonal flake. We show that conductance suppressions can be controlled by the strain intensity and important transport features are modeled by the electronic band structure of the leads.

  5. Harnessing the Unique Structural Properties of Isolated α-Helices*

    PubMed Central

    Swanson, Carter J.; Sivaramakrishnan, Sivaraj

    2014-01-01

    The α-helix is a ubiquitous secondary structural element that is almost exclusively observed in proteins when stabilized by tertiary or quaternary interactions. However, beginning with the unexpected observations of α-helix formation in the isolated C-peptide in ribonuclease A, there is growing evidence that a significant percentage (0.2%) of all proteins contain isolated stable single α-helical domains (SAH). These SAH domains provide unique structural features essential for normal protein function. A subset of SAH domains contain a characteristic ER/K motif, composed of a repeating sequence of ∼4 consecutive glutamic acids followed by ∼4 consecutive basic arginine or lysine (R/K) residues. The ER/K α-helix, also termed the ER/K linker, has been extensively characterized in the context of the myosin family of molecular motors and is emerging as a versatile structural element for protein and cellular engineering applications. Here, we review the structure and function of SAH domains, as well as the tools to identify them in natural proteins. We conclude with a discussion of recent studies that have successfully used the modular ER/K linker for engineering chimeric myosin proteins with altered mechanical properties, as well as synthetic polypeptides that can be used to monitor and systematically modulate protein interactions within cells. PMID:25059657

  6. Synthetic melanin films: Assembling mechanisms, scaling behavior, and structural properties

    NASA Astrophysics Data System (ADS)

    Lorite, Gabriela S.; Coluci, Vitor R.; da Silva, Maria Ivonete N.; Dezidério, Shirlei N.; Graeff, Carlos Frederico O.; Galva~O, Douglas S.; Cotta, Mônica A.

    2006-06-01

    In this work we report on the surface characterization of melanin thin films prepared using both water-based and organic solvent-based melanin syntheses. Atomic force microscopy (AFM) analysis of these films suggests that the organic solvent synthesis provides relatively planar basic melanin structures; these basic structures generate surface steps with height in the range of 2-3 nm and small tendency to form larger aggregates. The scaling properties obtained from the AFM data were used to infer the assembling mechanisms of these thin films which depend on the solvent used for melanin synthesis. The behavior observed in organic solvent-based melanin suggests a diffusion-limited aggregation process. Thus films with good adhesion to the substrate and smoother morphologies than water-prepared melanin films are obtained. Electronic structure calculations using a conductorlike screening model were also performed in order to elucidate the microscopic processes of thin film formation. Our results suggest that the agglomerates observed in hydrated samples originate from reaction with water at specific locations on the surface most likely defects on the planar structure.

  7. Plant Coilin: Structural Characteristics and RNA-Binding Properties

    PubMed Central

    Protopopova, Anna; Yaminsky, Igor; Arutiunian, Alexander; Love, Andrew J.; Taliansky, Michael; Kalinina, Natalia

    2013-01-01

    Cajal bodies (CBs) are dynamic subnuclear compartments involved in the biogenesis of ribonucleoproteins. Coilin is a major structural scaffolding protein necessary for CB formation, composition and activity. The predicted secondary structure of Arabidopsis thaliana coilin (Atcoilin) suggests that the protein is composed of three main domains. Analysis of the physical properties of deletion mutants indicates that Atcoilin might consist of an N-terminal globular domain, a central highly disordered domain and a C-terminal domain containing a presumable Tudor-like structure adjacent to a disordered C terminus. Despite the low homology in amino acid sequences, a similar type of domain organization is likely shared by human and animal coilin proteins and coilin-like proteins of various plant species. Atcoilin is able to bind RNA effectively and in a non-specific manner. This activity is provided by three RNA-binding sites: two sets of basic amino acids in the N-terminal domain and one set in the central domain. Interaction with RNA induces the multimerization of the Atcoilin molecule, a consequence of the structural alterations in the N-terminal domain. The interaction with RNA and subsequent multimerization may facilitate coilin’s function as a scaffolding protein. A model of the N-terminal domain is also proposed. PMID:23320094

  8. Thermoluminescence properties of gamma-irradiated nano-structure hydroxyapatite.

    PubMed

    Shafaei, M; Ziaie, F; Sardari, D; Larijani, M M

    2016-02-01

    The suitability of nano-structured hydroxyapatite (HAP) for use as a thermoluminescence dosimeter was investigated. HAP samples were synthesized using a hydrolysis method. The formation of nanoparticles was confirmed by X-ray diffraction and average particle size was estimated to be ~30 nm. The glow curve exhibited a peak centered at around 200 °C. The additive dose method was applied and this showed that the thermoluminescence (TL) glow curves follow first-order kinetics due to the non-shifting nature of Tm after different doses. The numbers of overlapping peaks and related kinetic parameters were identified from Tm -Tstop through computerized glow curve deconvolution methods. The dependence of the TL responses on radiation dose was studied and a linear dose response up to 1000 Gy was observed for the samples. PMID:26015169

  9. Impact of Acoustic Standing Waves on Structural Responses

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.

    2014-01-01

    For several decades large reverberant chambers and most recently direct field acoustic testing have been used in the aerospace industry to test larger structures with low surface densities such as solar arrays and reflectors to qualify them and to detect faults in the design and fabrication. It has been reported that in reverberant chamber and direct acoustic testing, standing acoustic modes may strongly couple with the fundamental structural modes of the test hardware (Reference 1). In this paper results from a recent reverberant chamber acoustic test of a composite reflector are discussed. These results provide further convincing evidence of the acoustic standing wave and structural modes coupling phenomenon. The purpose of this paper is to alert test organizations to this phenomenon so that they can account for the potential increase in structural responses and ensure that flight hardware undergoes safe testing. An understanding of the coupling phenomenon may also help minimize the over and/or under testing that could pose un-anticipated structural and flight qualification issues.

  10. Structure and properties of sodium bismuth titanate ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Aksel, Elena

    Piezoelectric materials are commonly used in sensor and actuator technologies due to their unique ability to couple electrical and mechanical displacements. Applications of piezoelectric materials range from diesel engine fuel injectors, sonar, ultrasound, and nanopositioners in scanning microscopes. Changing environmental regulations and policies have led to a recent surge in the research of lead-free piezoelectric materials. One such system currently under investigation is sodium bismuth titanate (Na0.5Bi0.5 TiO3) or NBT. It has recently been investigated with the addition of chemical modifiers as well as part of various solid solutions with other compounds. However, research into the structure and properties of NBT is still in its infancy. The aim of this dissertation was to develop a comprehensive understanding of the crystal structure and property relationships in NBT. First, the formation of the NBT phase during solid state processing was examined using in situ X-ray diffraction. It was determined that NBT forms through a particle conversion mechanism of the Bi2O 3 particle. The average and local room temperature structure of calcined and sintered NBT were examined using both high resolution synchrotron X-ray diffraction and neutron diffraction techniques. It was determined that the room temperature average structure of this material is best modeled using the monoclinic Cc space group rather than the previously accepted rhombohedral R3c space group. A combined high resolution XRD and neutron diffraction Rietveld refinement provided refined lattice parameters, atomic positions, and displacement parameters. The departure of the local structure of NBT from the average structure was examined through the Pair Distribution Function analysis. It was determined that Na+ and Bi3+, which share the A-site, have differing bonding environments with their surrounding O2- ions. In order to understand the origin of the piezoelectric depolarization behavior of NBT, crystal

  11. Biochemical and Structural Properties of Mouse Kynurenine Aminotransferase III

    SciTech Connect

    Han, Q.; Robinson, H; Cai, T; Tagle, D; Li, J

    2009-01-01

    Kynurenine aminotransferase III (KAT III) has been considered to be involved in the production of mammalian brain kynurenic acid (KYNA), which plays an important role in protecting neurons from overstimulation by excitatory neurotransmitters. The enzyme was identified based on its high sequence identity with mammalian KAT I, but its activity toward kynurenine and its structural characteristics have not been established. In this study, the biochemical and structural properties of mouse KAT III (mKAT III) were determined. Specifically, mKAT III cDNA was amplified from a mouse brain cDNA library, and its recombinant protein was expressed in an insect cell protein expression system. We established that mKAT III is able to efficiently catalyze the transamination of kynurenine to KYNA and has optimum activity at relatively basic conditions of around pH 9.0 and at relatively high temperatures of 50 to 60C. In addition, mKAT III is active toward a number of other amino acids. Its activity toward kynurenine is significantly decreased in the presence of methionine, histidine, glutamine, leucine, cysteine, and 3-hydroxykynurenine. Through macromolecular crystallography, we determined the mKAT III crystal structure and its structures in complex with kynurenine and glutamine. Structural analysis revealed the overall architecture of mKAT III and its cofactor binding site and active center residues. This is the first report concerning the biochemical characteristics and crystal structures of KAT III enzymes and provides a basis toward understanding the overall physiological role of mammalian KAT III in vivo and insight into regulating the levels of endogenous KYNA through modulation of the enzyme in the mouse brain.

  12. Structure and mechanical properties of Saxidomus purpuratus biological shells.

    PubMed

    Yang, W; Zhang, G P; Zhu, X F; Li, X W; Meyers, M A

    2011-10-01

    The strength and fracture behavior of Saxidomus purpuratus shells were investigated and correlated with the structure. The shells show a crossed lamellar structure in the inner and middle layers and a fibrous/blocky and porous structure composed of nanoscaled particulates (~100 nm diameter) in the outer layer. It was found that the flexure strength and fracture mode are a function of lamellar organization and orientation. The crossed lamellar structure of this shell is composed of domains of parallel lamellae with approximate thickness of 200-600 nm. These domains have approximate lateral dimensions of 10-70 μm with a minimum of two orientations of lamellae in the inner and middle layers. Neighboring domains are oriented at specific angles and thus the structure forms a crossed lamellar pattern. The microhardness across the thickness was lower in the outer layer because of the porosity and the absence of lamellae. The tensile (from flexure tests) and compressive strengths were analyzed by means of Weibull statistics. The mean tensile (flexure) strength at probability of 50%, 80-105 MPa, is on the same order as the compressive strength (~50-150 MPa) and the Weibull moduli vary from 3.0 to 7.6. These values are significantly lower than abalone nacre, in spite of having the same aragonite structure. The lower strength can be attributed to a smaller fraction of the organic interlayer. The fracture path in the specimens is dominated by the orientation of the domains and proceeds preferentially along lamella boundaries. It also correlates with the color changes in the cross section of the shell. The cracks tend to undergo a considerable change in orientation when the color changes abruptly. The distributions of strengths, cracking paths, and fracture surfaces indicate that the mechanical properties of the shell are anisotropic with a hierarchical nature. PMID:21783161

  13. Correlating microemulsion fuel composition, structure, and combustion properties

    SciTech Connect

    Griffith, W.L.; Compere, A.L.

    1989-01-01

    Microemulsion fuels provide a method for increasing the use of byproduct and biomass materials, including alcohols, in diesel fuels. The ability to replace 50% of diesel fuel with byproduct and biomass-derived materials microemulsion fuels could significantly decrease petroleum consumption. However, it is likely that the low particulate and NO{sub x} emissions characteristic of these fuels will drive the adoption of this technology. This report is concerned with the development of a series of short experiments to determine the fuel composition changes required to support development of microemulsion fuels which have combustion properties acceptable to the public and adequate to support widespread use in current diesel engines. The goal is delineation of microemulsion diesel fuel compositions which have acceptable compression ignition and emissions properties and which permit the replacement of one-third to one-half of current diesel fuel petroleum. A review of the literature on cetane enhancers for conventional and alternative diesel fuels was performed and a small number of enhancers likely to be effective with high-alcohol fuels selected. Based on linear regression analysis of emissions from a passenger diesel engine using alcohol and aqueous microemulsion fuels, correlation between microemulsion solution structure as determined by small-angle neutron scattering and actual NO{sub x} and particulate emissions was determined. The analysis indicates that solution structure and microemulsion composition play major roles in emissions modification. 223 refs., 5 figs., 9 tabs.

  14. Structural properties of particle deposits at heterogeneous surfaces

    NASA Astrophysics Data System (ADS)

    Stojiljković, D.; Šćepanović, J. R.; Vrhovac, S. B.; Švrakić, N. M.

    2015-06-01

    The random sequential adsorption (RSA) approach is used to analyze adsorption of spherical particles of a fixed radius on nonuniform flat surfaces covered by rectangular cells. The configuration of the cells (heterogeneities) was produced by performing RSA simulations to a prescribed coverage fraction θ_0{(cell)} . Adsorption was assumed to occur if the particle (projected) center lies within a rectangular cell area, i.e. if sphere touches the cells. The jammed-state properties of the model were studied for different values of cell size α (comparable with the adsorbing particle size) and density θ_0{(cell)} . Numerical simulations were carried out to investigate adsorption kinetics, jamming coverage, and structure of coverings. Structural properties of the jammed-state coverings were analyzed in terms of the radial distribution function g(r) and distribution of the Delaunay ‘free’ volumes P(v). It was demonstrated that adsorption kinetics and the jamming coverage decreased significantly, at a fixed density θ_0{(cell)} , when the cell size α increased. The predictions following from our calculation suggest that the porosity (pore volumes) of deposited monolayer can be controlled by the size and shape of landing cells, and by anisotropy of the cell deposition procedure.

  15. Lanthanide Ion Doped Upconverting Nanoparticles: Synthesis, Structure and Properties.

    PubMed

    Yan, Chenglin; Zhao, Haiguang; Perepichka, Dmitrii F; Rosei, Federico

    2016-08-01

    Lanthanide doped upconverting nanoparticles (UCNPs) have emerged as a new class of luminescent materials, with major discoveries and overall significant progress during the last decade. Unlike multiphoton absorption in organic dyes or semiconductor quantum dots, lanthanide doped UCNPs involve real intermediate quantum states and convert infrared (IR) into visible light via sequential electronic excitation. The relatively high efficiency of this process even at low radiation flux makes UCNPs particularly attractive for many current and emerging areas of technology. The aim of this article is to highlight several recent advances in this rapidly growing field, emphasizing the relationships between structure and properties of UCNPs. Additionally, various strategies developed for the synthesis of UCNPs with a focus on the various synthetic approaches that yield high-quality monodisperse samples with controlled size, shape and crystalline phase are reviewed. Emerging synthetic approaches towards designed structure to improve the optical and electronic properties of UCNPs are discussed. Finally, recent examples of applications of UCNPs in biomedical and optoelectronics research, giving our own perspectives on future directions and emerging possibilities of the field are described. PMID:27345736

  16. Structural and electrical properties of polymorphic pentacene thin films

    NASA Astrophysics Data System (ADS)

    Stadlober, Barbara; Satzinger, Valentin; Maresch, Hannes; Somitsch, Dieter; Haase, Anja; Pichler, Heinz; Rom, Werner; Jakopic, Georg

    2003-11-01

    Due to its outstanding carrier transport capabilities the aromatic hydrocarbon pentacene is still one of the most promising out of all organic semiconducting materials investigated so far. Pentacene appears in several polymorphic structures that significantly differ with respect to the d(001) spacing. It is shown, that precise control of the epitaxial growth process of thin films enables not only to adjust the formation of the polymorphic phases, but also to influence grain size and shape. The relative volume fraction of the pentacene polymorphs is determined by several parameters which are substrate material, deposition rate, film thickness and substrate temperature. A comparison of X-ray diffraction and Raman measurements reveals that the phase with the smaller layer-by-layer spacing grows on top of the other]. Moreover, there is a strict correlation between evaporation rate and maximum grain size. In addition to structural we also investigated the electrical properties of pentacene thin films focussing on polymorphism and its influence on the transport properties. Apart from the fact that the charge carrier mobility is strongly influenced by the grain size it turned out that the bulk phase is related to a lower intrinisic mobility than the thin film phase.

  17. Structure and mechanical properties of irradiated magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Devanathan, R.; Yu, N.; Sickafus, K. E.; Nastasi, M.

    1996-09-01

    The relationship between structure and mechanical properties of MgAl 2O 4 spinel single crystals following 400 keV Xe 2+ irradiation at 100 K to doses up to 1 × 10 20 ions/m 2 was examined. The structural changes in the irradiated layer were studied using electron diffraction from cross-sectional samples. The nano-indentation technique was used to determine the mechanical properties. At low doses, the material transformed into a metastable crystalline phase characterized by the rearrangement of cations. At the onset of this transformation, the Young's modulus and hardness rose to values about 10 and 15% higher, respectively, than those of the unirradiated crystal. Upon further irradiation, the metastable crystal became amorphous. The Young's modulus and hardness of the amorphous state were about 30 and 60% less, respectively, than the corresponding values of unirradiated spinel. These results, in conjunction with the findings of a recent computer simulation study, provide important insights into the exceptional radiation resistance of magnesium aluminate spinel.

  18. Structure and rheological properties in alkali aluminosilicate melts

    NASA Astrophysics Data System (ADS)

    Le Losq, Charles; Neuville, Daniel

    2010-05-01

    Rheological properties of silicate melts govern both magma ascension from the mantle to the surface of the earth and volcanological eruptions styles and behaviors. In this mind, it is very important to understand which parameters influence these properties. Up to now, we know for example that viscosity of silicate melts is dependent of temperature, pressure and chemical composition. In this work, we will focus on the Na2O-K2O-Al2O3-SiO2 system, which is of a prime importance because it deals with a non-negligible part of natural melts like haplogranitic rhyolitic alkali magmas. We will first present our viscosity measurements and some modelisation concepts based on the Adam and Gibbs theory. From configurational entropy theory we obtain some macroscopic information's that we can link to the structure of glasses and melts. In this mind, we have investigated them with Raman and NMR spectroscopies. These spectroscopies provide information on speciation and polymerization of glasses and melts. We will present and discuss structural and rheological variations as a function of temperature and chemical change.

  19. Elastic properties of nanostructured materials with layered grain boundary structure

    NASA Astrophysics Data System (ADS)

    Karakasidis, T. E.; Charitidis, C. A.; Skarakis, D.; Chouliaras, F.

    2007-08-01

    Atomistic calculations of the elastic constants for a bulk nanostructured material that consists of a layered structure where alternating layers meet along high angle grain boundaries and where atoms interact via a Lennard-Jones potential are presented. The calculations of the elastic constants were performed in the frame of homogeneous deformations for a wide range of layer widths ranging from 2.24 up to 74.62 nm. The results showed that the relaxation of the atomic structure affects the elastic constants for the cases where more than 5% of atoms are located in the GB region. Also it was found that the way that external stresses are applied on the system affects the values of the obtained elastic properties, with the elastic constants related to the characteristic directions of the grain boundary being the most affected ones. The findings of this work are of interest for the fabrication methods of nanostructured materials, the measurement methods of their elastic properties as well as multiscale modeling schemes of nanostructured materials.

  20. Structure and flow properties of block copolyelectrolyte hydrogels

    NASA Astrophysics Data System (ADS)

    Srivastava, Samanvaya; Tirrell, Matthew

    2015-03-01

    Polyelectrolyte complexes (PEC) are dense, polymer-rich phases that form when oppositely charged polyelectrolyte chains spontaneously associate and phase separate in aqueous mediums. Bulk phase separation of the PECs can be evaded by combining one or both of the polyelectrolytes with a neutral polymer, thus engineering pathways for self-assembly of PEC based micelles and hydrogels with large-scale ordering of the nanoscale PEC domains. The PEC domains in these assemblies can encapsulate both hydrophobic and hydrophilic therapeutics and thus have tremendous potential in drug delivery, diagnostic and tissue engineering applications. This study will present insights on the equilibrium structure and self-assembly kinetics of PEC hybrid hydrogels through detailed rheology studies of self-assembled materials comprising of functionalized polyallyl glycidyl ethers (PAGE) connected to either single poly(ethylene glycol) (PEG) chain to form diblock copolymers or as functionalized end-groups on a triblock copolymer with a PEG midblock. The effect of key parameters such as polymer concentration, polymer block lengths, salt, ionic strength, and degree of charge mismatch on the equilibrium materials properties will be discussed, with a special emphasis on the temporal evolution of flow properties, and will lead to comparisons with the rheology models for associating polymers. Complementary studies with extensive static and dynamic light, X-ray and neutron scattering investigations will also be presented, thus providing a comprehensive structural description of these materials.

  1. Bridged bis-BODIPYs: their synthesis, structures and properties.

    PubMed

    Kesavan, Praseetha E; Das, Sudipta; Lone, Mohsin Y; Jha, Prakash C; Mori, Shigeki; Gupta, Iti

    2015-10-21

    A series of bis-BODIPYs 1-6 bridged via thiophene, furan, N-alkylcarbazole, triphenyl-amine, para- and meta-phenylene groups have been synthesized and characterized by various spectroscopic techniques. The change in the spectroscopic properties of bis-BODIPYs upon varying the size of spacers was studied. X-ray crystal structures of three bis-BODIPYs containing triphenylamine, para- and meta-phenylene bridges were solved. Intermolecular C(H)π and ππ stacking interactions were observed in solid state structures of three bis-BODIPYs. The dihedral angles between the spacer unit and two boron-dipyrrin units were lower in all three compounds as compared to their corresponding monomers. This suggests increased interactions between the two boron-dipyrrin units in molecules which are in turn reflected in the anodic shifts in their reduction potentials. DFT studies indicated effective electronic interactions between spacers and two boron dipyrrin units in all the bis-BODIPYs. The calculated HOMO-LUMO gap was found to be lower for bis-BODIPY having bulky carbazole spacers and higher for bis-BODIPY having smaller furan spacers. Changing the spacer size clearly affected the spectroscopic properties of the bis-BODIPYs and red shifted absorption and emission maxima were observed for bis-BODIPYs with furan and thiophene spacers as compared to bis-BODIPYs with phenylene or bulky aromatic spacers. PMID:26373792

  2. Structure and mechanical properties of Octopus vulgaris suckers.

    PubMed

    Tramacere, Francesca; Kovalev, Alexander; Kleinteich, Thomas; Gorb, Stanislav N; Mazzolai, Barbara

    2014-02-01

    In this study, we investigate the morphology and mechanical features of Octopus vulgaris suckers, which may serve as a model for the creation of a new generation of attachment devices. Octopus suckers attach to a wide range of substrates in wet conditions, including rough surfaces. This amazing feature is made possible by the sucker's tissues, which are pliable to the substrate profile. Previous studies have described a peculiar internal structure that plays a fundamental role in the attachment and detachment processes of the sucker. In this work, we present a mechanical characterization of the tissues involved in the attachment process, which was performed using microindentation tests. We evaluated the elasticity modulus and viscoelastic parameters of the natural tissues (E ∼ 10 kPa) and measured the mechanical properties of some artificial materials that have previously been used in soft robotics. Such a comparison of biological prototypes and artificial material that mimics octopus-sucker tissue is crucial for the design of innovative artificial suction cups for use in wet environments. We conclude that the properties of the common elastomers that are generally used in soft robotics are quite dissimilar to the properties of biological suckers. PMID:24284894

  3. Surface, structural and tensile properties of proton beam irradiated zirconium

    NASA Astrophysics Data System (ADS)

    Rafique, Mohsin; Chae, San; Kim, Yong-Soo

    2016-02-01

    This paper reports the surface, structural and tensile properties of proton beam irradiated pure zirconium (99.8%). The Zr samples were irradiated by 3.5 MeV protons using MC-50 cyclotron accelerator at different doses ranging from 1 × 1013 to 1 × 1016 protons/cm2. Both un-irradiated and irradiated samples were characterized using Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction (XRD) and Universal Testing Machine (UTM). The average surface roughness of the specimens was determined by using Nanotech WSxM 5.0 develop 7.0 software. The FESEM results revealed the formation of bubbles, cracks and black spots on the samples' surface at different doses whereas the XRD results indicated the presence of residual stresses in the irradiated specimens. Williamson-Hall analysis of the diffraction peaks was carried out to investigate changes in crystallite size and lattice strain in the irradiated specimens. The tensile properties such as the yield stress, ultimate tensile stress and percentage elongation exhibited a decreasing trend after irradiation in general, however, an inconsistent behavior was observed in their dependence on proton dose. The changes in tensile properties of Zr were associated with the production of radiation-induced defects including bubbles, cracks, precipitates and simultaneous recovery by the thermal energy generated with the increase of irradiation dose.

  4. Unusual structural properties of polymers confined in a nanocylinder

    NASA Astrophysics Data System (ADS)

    Jiang, Zhi-Bin; Peng, Meng-Jie; Li, Lin-Ling; Zhou, Dong-Shan; Wang, Rong; Xue, Gi

    2015-07-01

    Structural properties of polymers confined in nanocylinders are investigated by Monte Carlo simulation, which is successfully used to consider the conformational property of constrained polymers. The conformational properties of the polymers close to the walls exhibit different features. The density profiles of polymers are enhanced near the wall of the nanocylinder, which shows that the packing densities differ near the wall and far from the wall. The highest densities near the wall of the nanocylinder decrease with increasing radius of the nanocylinder. Furthermore, the density excess is not only near the wall of the nanocylinder, but also shifts to the center of the nanocylinder at lower temperatures. The radius of gyration and the bond length of polymers in the nanocylinder show that the polymer chains tend to extend along the axis of the nanocylinder in highly confined nanocylinder and contract at lower temperature. Our results are very helpful in understanding the packing induced physical behaviors of polymers in nanocylinders, such as glass transition, crystallization, etc. Project supported by the National Natural Science Foundation of China (Grant Nos. 21474051, 21074053, and 51133002), the National Basic Research Program of China (Grant No. 2012CB821503), and the Program for Changjiang Scholars and Innovative Research Team in University, China.

  5. Tooth and bone deformation: structure and material properties by ESPI

    NASA Astrophysics Data System (ADS)

    Zaslansky, Paul; Shahar, Ron; Barak, Meir M.; Friesem, Asher A.; Weiner, Steve

    2006-08-01

    In order to understand complex-hierarchical biomaterials such as bones and teeth, it is necessary to relate their structure and mechanical-properties. We have adapted electronic speckle pattern-correlation interferometry (ESPI) to make measurements of deformation of small water-immersed specimens of teeth and bones. By combining full-field ESPI with precision mechanical loading we mapped sub-micron displacements and determined material-properties of the samples. By gradually and elastically compressing the samples, we compensate for poor S/N-ratios and displacement differences of about 100nm were reliably determined along samples just 2~3mm long. We produced stress-strain curves well within the elastic performance range of these materials under biologically relevant conditions. For human tooth-dentin, Young's modulus in inter-dental areas of the root is 40% higher than on the outer sides. For cubic equine bone samples the compression modulus of axial orientations is about double the modulus of radial and tangential orientations (20 GPa versus 10 GPa respectively). Furthermore, we measured and reproduced a surprisingly low Poisson's ratio, which averaged about 0.1. Thus the non-contact and non-destructive measurements by ESPI produce high sensitivity analyses of mechanical properties of mineralized tissues. This paves the way for mapping deformation-differences of various regions of bones, teeth and other biomaterials.

  6. Structure and mechanical properties of Octopus vulgaris suckers

    PubMed Central

    Tramacere, Francesca; Kovalev, Alexander; Kleinteich, Thomas; Gorb, Stanislav N.; Mazzolai, Barbara

    2014-01-01

    In this study, we investigate the morphology and mechanical features of Octopus vulgaris suckers, which may serve as a model for the creation of a new generation of attachment devices. Octopus suckers attach to a wide range of substrates in wet conditions, including rough surfaces. This amazing feature is made possible by the sucker's tissues, which are pliable to the substrate profile. Previous studies have described a peculiar internal structure that plays a fundamental role in the attachment and detachment processes of the sucker. In this work, we present a mechanical characterization of the tissues involved in the attachment process, which was performed using microindentation tests. We evaluated the elasticity modulus and viscoelastic parameters of the natural tissues (E ∼ 10 kPa) and measured the mechanical properties of some artificial materials that have previously been used in soft robotics. Such a comparison of biological prototypes and artificial material that mimics octopus-sucker tissue is crucial for the design of innovative artificial suction cups for use in wet environments. We conclude that the properties of the common elastomers that are generally used in soft robotics are quite dissimilar to the properties of biological suckers. PMID:24284894

  7. Structure and Thermoelectric Properties of Zinc Oxide Based Materials

    NASA Astrophysics Data System (ADS)

    Liang, Xin

    The present dissertation investigates the relationship between the structure and thermoelectric properties of ZnO based materials, with a focus on trivalent element doping on engineering the microstructure and altering the electrical and thermal transport properties. Within the solubility range, the addition of trivalent elements, such as In3+, Fe 3+ and Ga3+, is observed to increase the electrical conductivity of ZnO and decrease the thermal conductivity. As the solubility is exceeded, the consequent structure and thermoelectric properties varies with dopant species. The ZnO-In2O3 binary system, which we have chosen as one of the model systems, is of particular interests as it contains a variety of phase equilibria and microstructures. The In2O3(ZnO)k superlattice structures, which form as the indium solubility is reached, are observed to strongly scatter phonons while relatively permissive to electrons, resulting in a low thermal conductivity of about 2 W/mK and improved electrical conductivity. The thermal (Kapitza) resistance of In2O3(ZnO)k superlattice interfaces is found to be 5.0 +/- 0.6 x 10-10 m 2K/W by fitting the modified Klemens-Callaway's thermal conductivity model to the experimental data. Across the phase diagram, the materials behave as n-type free-electron semiconductors at high temperatures. An effective medium approximation model is for the first time successfully tested on the thermoelectrics of two-phase regions. Both Fe2O3-ZnO and Ga2O3-ZnO binary systems are also investigated. In the Fe doped ZnO system, a highly Fe concentrated ZnO solid solution phase as well as the significant grain refinement are observed after high temperature annealing. The Ga2O 3(ZnO)9 homologous superlattices in Ga2O 3-ZnO system is also found to strongly scatter phonons and induces a drastic reduction in thermal conductivity. Thermal conductivity, as one of the key factors in thermoelectrics, is highly sensitive to material defects. In this dissertation, I also

  8. Preparation and properties on hollow nano-structured smoke material

    NASA Astrophysics Data System (ADS)

    Liu, Xiang-cui; Dai, Meng-yan; Fang, Guo-feng; Shi, Wei-dong; Cheng, Xiang; Liu, Hai-feng; Zhang, Tong

    2013-09-01

    In recent years, the weapon systems of laser guidance and infrared (IR) imaging guidance have been widely used in modern warfare because of their high precision and strong anti-interference. Notwithstanding, military smoke, as a rapid and effective passive jamming means, can effectively counteract the attack of enemy precision-guided weapons by scattering and absorbability. Conventional smoke has good attenuation capability only to visible light (0.4-0.76 μm), but hardly any effect to other electromagnetic wave band. The weapon systems of laser guidance and IR imaging guidance usually work in broad band, including near IR (1-3 μm), middle IR (3-5 μm), far IR (8-14 μm), and so on. Accordingly, exploiting and using new efficient obscurant materials, which is one of the important factors that develop smoke technology, have become a focus and attracted more interests around the world. Then nano-structured materials that are developing very quickly have turned into our new choice. Hollow nano-structured materials (HNSM) have many special properties because of their nano-size wall-thickness and sub-micron grain-size. After a lot of HNSM were synthesized in this paper, their physical and chemical properties, including grain size, phase composition, microstructure, optical properties and resistivity were tested and analysed. Then the experimental results of the optical properties showed that HNSM exhibit excellent wave-absorbing ability in ultraviolet, visible and infrared regions. On the basis of the physicochemmical properties, HNSM are firstly applied in smoke technology field. And the obscuration performance of HNSM smoke was tested in smoke chamber. The testing waveband included 1.06μm and 10.6μm laser, 3-5μm and 8-14μm IR radiation. Then the main parameters were obtained, including the attenuation rate, the transmission rate, the mass extinction coefficient, the efficiency obscuring time, and the sedimentation rate, etc. The main parameters of HNSM smoke were

  9. Frequency response characteristics and response spectra of base-isolated and un-isolated structures

    SciTech Connect

    Mok, G.C.; Namba, H.

    1995-07-06

    The transmissibility of seismic loads through a linear base-isolation system is analyzed using an impedance method. The results show that the system acts like a {open_quotes}low-pass{close_quotes} filter. It attenuates high-frequency loads but passes through low-frequency ones. The filtering effect depends on the vibration frequencies and damping of the isolated structure and the isolation system. This paper demonstrates the benefits and design principles of base isolation by comparing the transmissibilities and response spectra of isolated and un-isolated structures. Parameters of typical isolated buildings and ground motions of the 1994 Northridge earthquake are used for the demonstration.

  10. Hippocampal structural and functional changes associated with electroconvulsive therapy response

    PubMed Central

    Abbott, C C; Jones, T; Lemke, N T; Gallegos, P; McClintock, S M; Mayer, A R; Bustillo, J; Calhoun, V D

    2014-01-01

    Previous animal models and structural imaging investigations have linked hippocampal neuroplasticity to electroconvulsive therapy (ECT) response, but the relationship between changes in hippocampal volume and temporal coherence in the context of ECT response is unknown. We hypothesized that ECT response would increase both hippocampal resting-state functional magnetic resonance imaging connectivity and hippocampal volumes. Patients with major depressive disorder (n=19) were scanned before and after the ECT series. Healthy, demographically matched comparisons (n=20) were scanned at one-time interval. Longitudinal changes in functional connectivity of hippocampal regions and volumes of hippocampal subfields were compared with reductions in ratings of depressive symptoms. Right hippocampal connectivity increased (normalized) after the ECT series and correlated with depressive symptom reduction. Similarly, the volumes of the right hippocampal cornu ammonis (CA2/3), dentate gyrus and subiculum regions increased, but the hippocampal subfields were unchanged relative to the comparison group. Connectivity changes were not evident in the left hippocampus, and volume changes were limited to the left CA2/3 subfields. The laterality of the right hippocampal functional connectivity and volume increases may be related to stimulus delivery method, which was predominately right unilateral in this investigation. The findings suggested that increased hippocampal functional connectivity and volumes may be biomarkers for ECT response. PMID:25405780

  11. The structural and property evolution of cellulose during carbonization

    NASA Astrophysics Data System (ADS)

    Rhim, Yo-Rhin

    The understanding of the structure and related property evolution during carbonization is imperative in engineering carbon materials for specific functionalities. High purity cellulose was used as a model precursor to help understand the conversion of organic compounds to hard carbons. Several characterization techniques were employed to follow the structural, compositional and property changes during the thermal transformation of microcrystalline cellulose to carbon over the temperature range of 250°C to 2000°C. These studies revealed several stages of composition and microstructure evolution during carbonization supported by the observation of five distinct regions of electrical and thermal properties. In Region I, from 250°C to 400°C, depolymerisation of cellulose molecules caused the evolution of volatile gases and decrease in dipole polarization. This also led to the reduction of overall AC electrical conductivity and specific heat. In Region II, from 450°C to 500°C, the formation and growth of conducting sp 2 carbon clusters resulted in increases in overall AC electrical conductivity and thermal diffusivity with rising temperature. For heat treatment temperatures of 550°C and 600°C, Region III, carbon clusters grew into aggregates of curved carbon layers leading to interfacial polarization and onset of percolation. AC electrical and thermal conductivities are enhanced due to electron hopping and improved phonon transport among carbon clusters. With temperatures rising from 650°C to 1000°C, Region IV, DC conductivity began to emerge and increased sharply along with thermal conductivity with further percolation of carbon clusters as lateral growth of carbon layers continued. Lastly, from 1200°C to 2000°C, Region V, DC electrical conductivity remained constant due to a fully percolated system.

  12. The structural response of gadolinium phosphate to pressure

    DOE PAGESBeta

    Heffernan, Karina M.; Ross, Nancy L.; Spencer, Elinor C.; Boatner, Lynn A.

    2016-06-16

    In this study, accurate elastic constants for gadolinium phosphate (GdPO4) have been measured by single-crystal high-pressure diffraction methods. The bulk modulus of GdPO4 determined under hydrostatic conditions, 128.1(8) GPa (K'=5.8(2)), is markedly different from that obtained with GdPO4 under non-hydrostatic conditions (160(2) GPa), which indicates the importance of shear stresses on the elastic response of this phosphate. Finally, high pressure Raman and diffraction analysis indicate that the PO4 tetrahedra behave as rigid units in response to pressure and that contraction of the GdPO4 structure is facilitated by bending/twisting of the Gd–O–P links that result in increased distortion in the GdO9more » polyhedra.« less

  13. The structural response of gadolinium phosphate to pressure

    NASA Astrophysics Data System (ADS)

    Heffernan, Karina M.; Ross, Nancy L.; Spencer, Elinor C.; Boatner, Lynn A.

    2016-09-01

    Accurate elastic constants for gadolinium phosphate (GdPO4) have been measured by single-crystal high-pressure diffraction methods. The bulk modulus of GdPO4 determined under hydrostatic conditions, 128.1(8) GPa (Kʹ=5.8(2)), is markedly different from that obtained with GdPO4 under non-hydrostatic conditions (160(2) GPa), which indicates the importance of shear stresses on the elastic response of this phosphate. High pressure Raman and diffraction analysis indicate that the PO4 tetrahedra behave as rigid units in response to pressure and that contraction of the GdPO4 structure is facilitated by bending/twisting of the Gd-O-P links that result in increased distortion in the GdO9 polyhedra.

  14. Molecular response properties in equation of motion coupled cluster theory: A time-dependent perspective

    NASA Astrophysics Data System (ADS)

    Coriani, Sonia; Pawłowski, Filip; Olsen, Jeppe; Jørgensen, Poul

    2016-01-01

    Molecular response properties for ground and excited states and for transitions between these states are defined by solving the time-dependent Schrödinger equation for a molecular system in a field of a time-periodic perturbation. In equation of motion coupled cluster (EOM-CC) theory, molecular response properties are commonly obtained by replacing, in configuration interaction (CI) molecular response property expressions, the energies and eigenstates of the CI eigenvalue equation with the energies and eigenstates of the EOM-CC eigenvalue equation. We show here that EOM-CC molecular response properties are identical to the molecular response properties that are obtained in the coupled cluster-configuration interaction (CC-CI) model, where the time-dependent Schrödinger equation is solved using an exponential (coupled cluster) parametrization to describe the unperturbed system and a linear (configuration interaction) parametrization to describe the time evolution of the unperturbed system. The equivalence between EOM-CC and CC-CI molecular response properties only holds when the CI molecular response property expressions—from which the EOM-CC expressions are derived—are determined using projection and not using the variational principle. In a previous article [F. Pawłowski, J. Olsen, and P. Jørgensen, J. Chem. Phys. 142, 114109 (2015)], it was stated that the equivalence between EOM-CC and CC-CI molecular response properties only held for a linear response function, whereas quadratic and higher order response functions were mistakenly said to differ in the two approaches. Proving the general equivalence between EOM-CC and CC-CI molecular response properties is a challenging task, that is undertaken in this article. Proving this equivalence not only corrects the previous incorrect statement but also first and foremost leads to a new, time-dependent, perspective for understanding the basic assumptions on which the EOM-CC molecular response property expressions

  15. Molecular response properties in equation of motion coupled cluster theory: A time-dependent perspective.

    PubMed

    Coriani, Sonia; Pawłowski, Filip; Olsen, Jeppe; Jørgensen, Poul

    2016-01-14

    Molecular response properties for ground and excited states and for transitions between these states are defined by solving the time-dependent Schrödinger equation for a molecular system in a field of a time-periodic perturbation. In equation of motion coupled cluster (EOM-CC) theory, molecular response properties are commonly obtained by replacing, in configuration interaction (CI) molecular response property expressions, the energies and eigenstates of the CI eigenvalue equation with the energies and eigenstates of the EOM-CC eigenvalue equation. We show here that EOM-CC molecular response properties are identical to the molecular response properties that are obtained in the coupled cluster-configuration interaction (CC-CI) model, where the time-dependent Schrödinger equation is solved using an exponential (coupled cluster) parametrization to describe the unperturbed system and a linear (configuration interaction) parametrization to describe the time evolution of the unperturbed system. The equivalence between EOM-CC and CC-CI molecular response properties only holds when the CI molecular response property expressions-from which the EOM-CC expressions are derived-are determined using projection and not using the variational principle. In a previous article [F. Pawłowski, J. Olsen, and P. Jørgensen, J. Chem. Phys. 142, 114109 (2015)], it was stated that the equivalence between EOM-CC and CC-CI molecular response properties only held for a linear response function, whereas quadratic and higher order response functions were mistakenly said to differ in the two approaches. Proving the general equivalence between EOM-CC and CC-CI molecular response properties is a challenging task, that is undertaken in this article. Proving this equivalence not only corrects the previous incorrect statement but also first and foremost leads to a new, time-dependent, perspective for understanding the basic assumptions on which the EOM-CC molecular response property expressions are

  16. Structural Basis of Response Regulator Dephosphorylation by Rap Phosphatases

    SciTech Connect

    V Parashar; N Mirouze; D Dubnau; M Neiditch

    2011-12-31

    Bacterial Rap family proteins have been most extensively studied in Bacillus subtilis, where they regulate activities including sporulation, genetic competence, antibiotic expression, and the movement of the ICEBs1 transposon. One subset of Rap proteins consists of phosphatases that control B. subtilis and B. anthracis sporulation by dephosphorylating the response regulator Spo0F. The mechanistic basis of Rap phosphatase activity was unknown. Here we present the RapH-Spo0F X-ray crystal structure, which shows that Rap proteins consist of a 3-helix bundle and a tetratricopeptide repeat domain. Extensive biochemical and genetic functional studies reveal the importance of the observed RapH-Spo0F interactions, including the catalytic role of a glutamine in the RapH 3-helix bundle that inserts into the Spo0F active site. We show that in addition to dephosphorylating Spo0F, RapH can antagonize sporulation by sterically blocking phosphoryl transfer to and from Spo0F. Our structure-function analysis of the RapH-Spo0F interaction identified Rap protein residues critical for Spo0F phosphatase activity. This information enabled us to assign Spo0F phosphatase activity to a Rap protein based on sequence alone, which was not previously possible. Finally, as the ultimate test of our newfound understanding of the structural requirements for Rap phosphatase function, a non-phosphatase Rap protein that inhibits the binding of the response regulator ComA to DNA was rationally engineered to dephosphorylate Spo0F. In addition to revealing the mechanistic basis of response regulator dephosphorylation by Rap proteins, our studies support the previously proposed T-loop-Y allostery model of receiver domain regulation that restricts the aromatic 'switch' residue to an internal position when the {beta}4-{alpha}4 loop adopts an active-site proximal conformation.

  17. Development and Validation of the Implicit Information from Lewis Structures Instrument(IILSI): Do Students Connect Structures with Properties?

    ERIC Educational Resources Information Center

    Cooper, Melanie M.; Underwood, Sonia M.; Hilley, Caleb Z.

    2012-01-01

    Lewis structures are a simplified two dimensional "cartoon" of molecular structure that allow a knowledgeable user to predict the types of properties a particular substance may exhibit. However, prior research shows that many students fail to recognize these structure-property connections and are unable to decode the information contained in the…

  18. Effect of Shear on Physiochemical Properties of Matrix Metalloproteinase Responsive Silk-Elastinlike Hydrogels

    PubMed Central

    Price, Robert; Poursaid, Azadeh; Cappello, Joseph; Ghandehari, Hamidreza

    2014-01-01

    Silk-elastinlike protein polymers (SELPs) have been fabricated as matrices for controlled delivery of bioactive agents. In this application the need for an environmentally responsive, degradable polymer has risen to improve treatment outcomes. To satisfy this need, we have designed, synthesized, and expressed SELPs with matrix metalloproteinase (MMP) degradable sequences inserted in distinct regions of the polymer backbone. Upon characterization of the physiochemical properties of newly synthesized analogues, it was determined that conditioning of the polymers was necessary for normalization of batch properties, and to generate a more robust polymer network suitable for delivery. In this report we have examined the use of shear stress to condition synthesized material prior to application as a controlled release matrix. The application of high shear to SELPs results in significant changes in physiochemical properties as assayed by swelling ratio, soluble fraction release, rate of gel formation, stiffness of hydrogels, and nanoparticle release from matrices. These observed changes in material characteristics may be caused by the removal of semi-stable secondary and tertiary structure from single polymer strands leading to a more robust hydrogel with greater intermolecular interaction. PMID:25094031

  19. Thermo-responsive and compression properties of TEMPO-oxidized cellulose nanofiber-modified PNIPAm hydrogels.

    PubMed

    Wei, Jinguang; Chen, Yufei; Liu, Hongzhi; Du, Chungui; Yu, Huilong; Zhou, Zhongxi

    2016-08-20

    In this study, TEMPO-oxidized bamboo cellulose nanofibers (TO-CNF) with anionic carboxylate groups on the surfaces were in-situ incorporated into poly(N-isopropylacrylamide) (PNIPAm) matrix to improve its thermo-responsive and mechanical properties during the polymerization. The microstructure, swelling behaviors, and compressive strength of resultant PNIPAm composite hydrogels with varying contents of TO-CNFs (0-10wt%) were then examined, respectively. Modified hydrogels exhibited the similar light transparency to pure PNIPAm one due to the formation of semi-IPN structure between PNIPAm and TO-CNF. FT-IR spectra demonstrated that the presence of TO-CNF did not alter the position of characteristic peaks associated with PNIPAm. SEM observation suggested that the pore size of PNIPAm hydrogels was markedly increased after the incorporation of TO-CNF. Also, the composite hydrogels showed superior swelling behavior and much improved compression properties with respect to pure PNIPAm one. Thus, TO-CNF appeared to be a "green" nanofiller that can simultaneously improve swelling and mechanical properties of PNIPAm hydrogel. PMID:27178925

  20. Charge carrier transport properties in layer structured hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2014-10-01

    Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of μ ∝ (T/T0)-α with α = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ħω = 192 meV (or 1546 cm-1), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.