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1

A Model of the Fatigue Life Distribution of Composite Laminates Based on Their Static Strength Distribution  

Microsoft Academic Search

The reasons of the static strength dispersion and the fatigue life dispersion of composite laminates are analyzed in this article. It is concluded that the inner original defects, which derived from the manufacturing process of composite laminates, are the common and major reason of causing the random distributions of the static strength and the fatigue life. And there is a

Wu Fuqiang; Yao Weixing

2008-01-01

2

Assuring Life in Composite Systems  

NASA Technical Reports Server (NTRS)

A computational simulation method is presented to assure life in composite systems by using dynamic buckling of smart composite shells as an example. The combined use of composite mechanics, finite element computer codes, and probabilistic analysis enable the effective assessment of the dynamic buckling load of smart composite shells. A universal plot is generated to estimate the dynamic buckling load of composite shells at various load rates and probabilities. The shell structure is also evaluated with smart fibers embedded in the plies right below the outer plies. The results show that, on the average, the use of smart fibers improved the shell buckling resistance by about 9% at different probabilities and delayed the buckling occurrence time. The probabilistic sensitivities results indicate that uncertainties in the fiber volume ratio and ply thickness have major effects on the buckling load. The uncertainties in the electric field strength and smart material volume fraction have moderate effects and thereby in the assured life of the shell.

Chamis, Christos c.

2008-01-01

3

SPECIES COMPOSITION, DISTRIBUTION, LIFE FORMS AND FOLK NOMENCLATURE OF FOREST AND COMMON LAND PLANTS OF WESTERN CHITWAN, NEPAL  

PubMed Central

This paper enumerates 349 plant species belonging to 77 families of vascular plants collected in the winter seasons of 1996 and 2000 by the flora teams of the Population and Ecology Research Laboratory, Nepal. Of the total species, 249 species belong to dicotyledons, 87 species to monocotyledons and 13 species to pteridophytes. Among the families, dicotyledons contributed the highest number of families (55 in number) followed by monocotyledons and pteridophytes. In the study areas, species composition varies with the type of habitats in the study plots. Some species are unique in distribution. The highest unique species are contributed by common lands (87 spp.), followed by the Chitwan National Park forest (36 spp.) and Tikauli forest (32 spp.). Ageratum houstonianum Mill., Cynodon dactylon (L.) Pers., Imperata cylindrica (L.) Beauv., Rungia parviflora (Retz.) Nees, Saccharum spontaneum L. and Thelypteris auriculata (J. Sm.) K. Iwats are the most common species across all the research blocks. Of the listed plants, many plants have local names either in Nepalese or other tribal languages. Plants are named in different ways on the basis of habit, habitat, smell, taste, and morphological characters of the plants, which are also the basis of nomenclature in plant taxonomy. PMID:22962539

Dangol, D. R.

2012-01-01

4

Effect of Individual Component Life Distribution on Engine Life Prediction  

NASA Technical Reports Server (NTRS)

The effect of individual engine component life distributions on engine life prediction was determined. A Weibull-based life and reliability analysis of the NASA Energy Efficient Engine was conducted. The engine s life at a 95 and 99.9 percent probability of survival was determined based upon the engine manufacturer s original life calculations and assumed values of each of the component s cumulative life distributions as represented by a Weibull slope. The lives of the high-pressure turbine (HPT) disks and blades were also evaluated individually and as a system in a similar manner. Knowing the statistical cumulative distribution of each engine component with reasonable engineering certainty is a condition precedent to predicting the life and reliability of an entire engine. The life of a system at a given reliability will be less than the lowest-lived component in the system at the same reliability (probability of survival). Where Weibull slopes of all the engine components are equal, the Weibull slope had a minimal effect on engine L(sub 0.1) life prediction. However, at a probability of survival of 95 percent (L(sub 5) life), life decreased with increasing Weibull slope.

Zaretsky, Erwin V.; Hendricks, Robert C.; Soditus, Sherry M.

2003-01-01

5

Multiscale Fatigue Life Prediction for Composite Panels  

NASA Technical Reports Server (NTRS)

Fatigue life prediction capabilities have been incorporated into the HyperSizer Composite Analysis and Structural Sizing Software. The fatigue damage model is introduced at the fiber/matrix constituent scale through HyperSizer s coupling with NASA s MAC/GMC micromechanics software. This enables prediction of the micro scale damage progression throughout stiffened and sandwich panels as a function of cycles leading ultimately to simulated panel failure. The fatigue model implementation uses a cycle jumping technique such that, rather than applying a specified number of additional cycles, a specified local damage increment is specified and the number of additional cycles to reach this damage increment is calculated. In this way, the effect of stress redistribution due to damage-induced stiffness change is captured, but the fatigue simulations remain computationally efficient. The model is compared to experimental fatigue life data for two composite facesheet/foam core sandwich panels, demonstrating very good agreement.

Bednarcyk, Brett A.; Yarrington, Phillip W.; Arnold, Steven M.

2012-01-01

6

A distributed program composition system  

NASA Technical Reports Server (NTRS)

A graphical technique for creating distributed computer programs is investigated and a prototype implementation is described which serves as a testbed for the concepts. The type of programs under examination is restricted to those comprising relatively heavyweight parts that intercommunicate by passing messages of typed objects. Such programs are often presented visually as a directed graph with computer program parts as the nodes and communication channels as the edges. This class of programs, called parts-based programs, is not well supported by existing computer systems; much manual work is required to describe the program to the system, establish the communication paths, accommodate the heterogeneity of data types, and to locate the parts of the program on the various systems involved. The work described solves most of these problems by providing an interface for describing parts-based programs in this class in a way that closely models the way programmers think about them: using sketches of diagraphs. Program parts, the computational modes of the larger program system are categorized in libraries and are accessed with browsers. The process of programming has the programmer draw the program graph interactively. Heterogeneity is automatically accommodated by the insertion of type translators where necessary between the parts. Many decisions are necessary in the creation of a comprehensive tool for interactive creation of programs in this class. Possibilities are explored and the issues behind such decisions are presented. An approach to program composition is described, not a carefully implemented programming environment. However, a prototype implementation is described that can demonstrate the ideas presented.

Brown, Robert L.

1989-01-01

7

A distributed interactive composition tool  

Microsoft Academic Search

As an interactive, computerized, network oriented musical composition tool, Rabisco allows users to create stream of MIDI data in real-time by drawing simple sketches using a simple 2-D graphical tablet (pad). Utilizing a client-server architecture, Rabisco allows virtual joint compositions where several musicians interact over the network or the internet, each using a Rabisco client. Current applications includes Distance Learning,

Márcio O. Costa; Jônatas Manzolli; Dan Sharoni

2002-01-01

8

PROBABILISTIC FATIGUE LIFE EVALUATION OF COMPOSITE STRUCTURES  

Microsoft Academic Search

Methods and corresponding computer codes are discussed for probabilistically evaluating composite structural fracture under cyclic fatigue. The progressive fracture of a composite structure under cyclic fatigue is simulated via an innovative approach independent of stress intensity factors and fracture toughness parameters. A computer code is utilized for the simulation of composite structural damage and fracture. Structural degradation response is assessed

Levon Minnetyan; Dade Huang; Christos C. Chamis

2002-01-01

9

Probability distribution of fatigue life controlled by defects  

Microsoft Academic Search

An equation is derived for determining the cumulative probability distribution of fatigue life controlled by the defects in the material, and a method is proposed to determine the most deleterious to the fatigue life group of defects. The equation avoids some serious drawbacks of the classical approach to determine the fatigue life distribution, which are revealed on the basis of

M. T. Todinov

2001-01-01

10

Assessment of fatigue life for small composite wind turbine blades  

Microsoft Academic Search

The present design and assessment of fatigue life for the small composite wind turbine blades (SCWTBs) can be certified by IEC 61400-2 “Wind Turbines - Part2: Design requirements of small wind turbines”. The paper will establish an analytical method on the fatigue life analysis of SCWTBs. Using the Microsoft Office EXCEL to calculate the maximum stress, minimum stress and stress

Jia-Hroung Wu

2010-01-01

11

Fatigue Life Methodology for Bonded Composite Skin/Stringer Configurations  

NASA Technical Reports Server (NTRS)

A methodology is presented for determining the fatigue life of composite structures based on fatigue characterization data and geometric nonlinear finite element (FE) analyses. To demonstrate the approach, predicted results were compared to fatigue tests performed on specimens which represented a tapered composite flange bonded onto a composite skin. In a first step, tension tests were performed to evaluate the debonding mechanisms between the flange and the skin. In a second step, a 2D FE model was developed to analyze the tests. To predict matrix cracking onset, the relationship between the tension load and the maximum principal stresses transverse to the fiber direction was determined through FE analysis. Transverse tension fatigue life data were used to -enerate an onset fatigue life P-N curve for matrix cracking. The resulting prediction was in good agreement with data from the fatigue tests. In a third step, a fracture mechanics approach based on FE analysis was used to determine the relationship between the tension load and the critical energy release rate. Mixed mode energy release rate fatigue life data were used to create a fatigue life onset G-N curve for delamination. The resulting prediction was in good agreement with data from the fatigue tests. Further, the prediction curve for cumulative life to failure was generated from the previous onset fatigue life curves. The results showed that the methodology offers a significant potential to Predict cumulative fatigue life of composite structures.

Krueger, Ronald; Paris, Isabelle L.; OBrien, T. Kevin; Minguet, Pierre J.

2001-01-01

12

Considerations concerning fatigue life of metal matrix composites  

Microsoft Academic Search

Since metal matrix composites (MMC) are composed from two very distinct materials each having their own physical and mechanical properties, it is feasible that the fatigue resistance depends on the strength of the weaker constituent. Based on this assumption, isothermal fatigue lives of several MMC's were analyzed utilizing a fatigue life diagram approach. For each MMC, the fatigue life diagram

V. M. Radhakrishnan; Paul A. Bartolotta

1993-01-01

13

Sex differences in body composition early in life  

Microsoft Academic Search

Background: Early development of the percentage of fat and muscle is rarely considered, but is important because excessive fat is related to the development of diabetes and other morbidities later in life. In pediatric medicine, there are few to no data comparing sex differences in body composition in the first months of life despite the fact that males are typically

David A. Fields; Sowmya Krishnan; Amy B. Wisniewski

2009-01-01

14

Life form composition and stratification of montane humid forests in Meghalaya, northeast India  

Microsoft Academic Search

Life form composition and stratification was studied in five protected patches of humid montane forest in Jaintia hills of Meghalaya, northeast India. A total of 546 vascular plants recorded from the five stands were distributed in five major life-forms, exhibited dominance of phanerophytes (44-51%) in the community followed by chamaephytes (11-17%), epiphytes (11-16%), lianas (7-16%), geophytes (4-12%) and therophytes (2-9%).

S. ALEMMEREN JAMIR; K. UPADHAYA; H. N. PANDEY

15

Fatigue Life Analysis of Small Composite Sandwich Wind Tuebine Blades  

Microsoft Academic Search

The present fatigue life analysis of the small composite sandwich wind turbine blades (SCSWTBs) can be certified by IEC 61400-2:Wind Turbines - Part2: Design requirements of small wind turbines (IEC 61400-2 2006). The paper will establish an analytical method for the fatigue life analysis of SCSWTBs. Microsoft Office EXCEL is used to calculate the maximum stress, minimum stress, and stress

J. H. Wu; F. M. Lai

2011-01-01

16

Tension fatigue analysis and life prediction for composite laminates  

NASA Technical Reports Server (NTRS)

A methodology is presented for the tension fatigue analysis and life prediction of composite laminates subjected to tension fatigue loading. The methodology incorporates both the generic fracture mechanics characterization of delamination and the assessment of the infuence of damage on laminate fatigue life. Tension fatigue tests were conducted on quasi-isotropic and orthotropic glass epoxy, graphite epoxy, and glass/graphite epoxy hybrid laminates, demonstrating good agreement between measured and predicted lives.

O'Brien, T. K.; Rigamonti, M.; Zanotti, C.

1989-01-01

17

Life-span distributions of supermarket products  

NASA Astrophysics Data System (ADS)

We have analyzed the lifetime distributions of more than 0.7 million products sold across approximately 400 Japanese supermarkets. The distributions are well approximated by an exponential function for products with lifetimes longer than 1000 days, implying that the manufacturers' decisions about whether to continue production are purely random. However, the distributions tend to deviate from an exponential distribution for products with lifetimes shorter than 1000 days. Specifically, the distributions for food products exhibit a quicker decay in a short time scale, suggesting the existence of competing products during the initial stages of the product lifecycle. On the other hand, the distributions for toiletry products exhibit a slower decay in a short time scale.

Ueno, Hiromichi; Watanabe, Tsutomu; Takayasu, Misako

2010-04-01

18

Fatigue Life Methodology for Bonded Composite Skin/Stringer Configurations  

NASA Technical Reports Server (NTRS)

A methodology is presented for determining the fatigue life of bonded composite skin/stringer structures based on delamination fatigue characterization data and geometric nonlinear finite element analyses. Results were compared to fatigue tests on stringer flange/skin specimens to verify the approach.

Krueger, Ronald; Paris, Isabelle L.; OBrien, T. Kevin

2000-01-01

19

Fatigue Life Methodology for Bonded Composite Skin\\/Stringer Configurations  

Microsoft Academic Search

A methodology is presented for determining the fatigue life of bonded composite skin\\/stringer structures based on delamination fatigue characterization data and geometric nonlinear finite element analyses. Results were compared to fatigue tests on stringer flange\\/skin specimens to verify the approach.

Ronald Krueger; Isabelle L. Paris; T. Kevin O'Brien; Pierre J. Minguet

2000-01-01

20

Durability/life of fiber composites in hygrothermomechanical environments  

NASA Technical Reports Server (NTRS)

Statistical analysis and multiple regression were used to determine and quantify the significant hygrothermomechanical variables which influence the tensile durability/life (cycle loading, fatigue) of boron-fiber/epoxy-matrix (B/E) and high-modulus-fiber/epoxy-matrix (HMS/E) composites. The use of the multiple regression analysis reduced the variables from fifteen, assumed initially, to six or less with a probability of greater than 0.999. The reduced variables were used to derive predictive models for compression and intralaminar shear durability/life of B/E and HMS/E composites assuming isoparametric fatigue behavior. The predictive models were subsequently generalized to predict the durability/life of graphite/fiber-r generalized model is of simple form, predicts conservative values compared with measured data and should be adequate for use in preliminary designs. Previously announced in STAR as N82-14287

Chamis, C. C.; Sinclair, J. H.

1982-01-01

21

Probabilistic fatigue life prediction of metallic and composite materials  

NASA Astrophysics Data System (ADS)

Fatigue is one of the most common failure modes for engineering structures, such as aircrafts, rotorcrafts and aviation transports. Both metallic materials and composite materials are widely used and affected by fatigue damage. Huge uncertainties arise from material properties, measurement noise, imperfect models, future anticipated loads and environmental conditions. These uncertainties are critical issues for accurate remaining useful life (RUL) prediction for engineering structures in service. Probabilistic fatigue prognosis considering various uncertainties is of great importance for structural safety. The objective of this study is to develop probabilistic fatigue life prediction models for metallic materials and composite materials. A fatigue model based on crack growth analysis and equivalent initial flaw size concept is proposed for metallic materials. Following this, the developed model is extended to include structural geometry effects (notch effect), environmental effects (corroded specimens) and manufacturing effects (shot peening effects). Due to the inhomogeneity and anisotropy, the fatigue model suitable for metallic materials cannot be directly applied to composite materials. A composite fatigue model life prediction is proposed based on a mixed-mode delamination growth model and a stiffness degradation law. After the development of deterministic fatigue models of metallic and composite materials, a general probabilistic life prediction methodology is developed. The proposed methodology combines an efficient Inverse First-Order Reliability Method (IFORM) for the uncertainty propogation in fatigue life prediction. An equivalent stresstransformation has been developed to enhance the computational efficiency under realistic random amplitude loading. A systematical reliability-based maintenance optimization framework is proposed for fatigue risk management and mitigation of engineering structures.

Xiang, Yibing

22

12 CFR 2.3 - Distribution of credit life insurance income.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 false Distribution of credit life insurance income. 2.3 Section 2.3...DEPARTMENT OF THE TREASURY SALES OF CREDIT LIFE INSURANCE § 2.3 Distribution of credit life insurance income. (a) Distribution of...

2011-01-01

23

12 CFR 2.3 - Distribution of credit life insurance income.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Distribution of credit life insurance income. 2.3 Section 2.3...DEPARTMENT OF THE TREASURY SALES OF CREDIT LIFE INSURANCE § 2.3 Distribution of credit life insurance income. (a) Distribution of...

2010-01-01

24

12 CFR 2.3 - Distribution of credit life insurance income.  

...2014-01-01 false Distribution of credit life insurance income. 2.3 Section 2.3...DEPARTMENT OF THE TREASURY SALES OF CREDIT LIFE INSURANCE § 2.3 Distribution of credit life insurance income. (a) Distribution of...

2014-01-01

25

12 CFR 2.3 - Distribution of credit life insurance income.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 false Distribution of credit life insurance income. 2.3 Section 2.3...DEPARTMENT OF THE TREASURY SALES OF CREDIT LIFE INSURANCE § 2.3 Distribution of credit life insurance income. (a) Distribution of...

2012-01-01

26

12 CFR 2.3 - Distribution of credit life insurance income.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Distribution of credit life insurance income. 2.3 Section 2.3...DEPARTMENT OF THE TREASURY SALES OF CREDIT LIFE INSURANCE § 2.3 Distribution of credit life insurance income. (a) Distribution of...

2013-01-01

27

Dramatic increase in fatigue life in hierarchical graphene composites.  

PubMed

We report the synthesis and fatigue characterization of fiberglass/epoxy composites with various weight fractions of graphene platelets infiltrated into the epoxy resin as well as directly spray-coated on to the glass microfibers. Remarkably only ?0.2% (with respect to the epoxy resin weight and ?0.02% with respect to the entire laminate weight) of graphene additives enhanced the fatigue life of the composite in the flexural bending mode by up to 1200-fold. By contrast, under uniaxial tensile fatigue conditions, the graphene fillers resulted in ?3-5-fold increase in fatigue life. The fatigue life increase (in the flexural bending mode) with graphene additives was ?1-2 orders of magnitude superior to those obtained using carbon nanotubes. In situ ultrasound analysis of the nanocomposite during the cyclic fatigue test suggests that the graphene network toughens the fiberglass/epoxy-matrix interface and prevents the delamination/buckling of the glass microfibers under compressive stress. Such fatigue-resistant hierarchical materials show potential to improve the safety, reliability, and cost effectiveness of fiber-reinforced composites that are increasingly the material of choice in the aerospace, automotive, marine, sports, biomedical, and wind energy industries. PMID:20863061

Yavari, F; Rafiee, M A; Rafiee, J; Yu, Z-Z; Koratkar, N

2010-10-01

28

Progressive Failure And Life Prediction of Ceramic and Textile Composites  

NASA Technical Reports Server (NTRS)

An engineering approach to predict the fatigue life and progressive failure of multilayered composite and textile laminates is presented. Analytical models which account for matrix cracking, statistical fiber failures and nonlinear stress-strain behavior have been developed for both composites and textiles. The analysis method is based on a combined micromechanics, fracture mechanics and failure statistics analysis. Experimentally derived empirical coefficients are used to account for the interface of fiber and matrix, fiber strength, and fiber-matrix stiffness reductions. Similar approaches were applied to textiles using Repeating Unit Cells. In composite fatigue analysis, Walker's equation is applied for matrix fatigue cracking and Heywood's formulation is used for fiber strength fatigue degradation. The analysis has been compared with experiment with good agreement. Comparisons were made with Graphite-Epoxy, C/SiC and Nicalon/CAS composite materials. For textile materials, comparisons were made with triaxial braided and plain weave materials under biaxial or uniaxial tension. Fatigue predictions were compared with test data obtained from plain weave C/SiC materials tested at AS&M. Computer codes were developed to perform the analysis. Composite Progressive Failure Analysis for Laminates is contained in the code CPFail. Micromechanics Analysis for Textile Composites is contained in the code MicroTex. Both codes were adapted to run as subroutines for the finite element code ABAQUS and CPFail-ABAQUS and MicroTex-ABAQUS. Graphic user interface (GUI) was developed to connect CPFail and MicroTex with ABAQUS.

Xue, David Y.; Shi, Yucheng; Katikala, Madhu; Johnston, William M., Jr.; Card, Michael F.

1998-01-01

29

Development of a Composite Delamination Fatigue Life Prediction Methodology  

NASA Technical Reports Server (NTRS)

Delamination is one of the most significant and unique failure modes in composite structures. Because of a lack of understanding of the consequences of delamination and the inability to predict delamination onset and growth, many composite parts are unnecessarily rejected upon inspection, both immediately after manufacture and while in service. NASA Langley is leading the efforts in the U.S. to develop a fatigue life prediction methodology for composite delamination using fracture mechanics. Research being performed to this end will be reviewed. Emphasis will be placed on the development of test standards for delamination characterization, incorporation of approaches for modeling delamination in commercial finite element codes, and efforts to mature the technology for use in design handbooks and certification documents.

OBrien, Thomas K.

2009-01-01

30

ORIGINAL PAPER Floristic composition and spatial distribution of germinable  

E-print Network

of seeds in the soil and the changes of the seed bank composition during the regeneration processORIGINAL PAPER Floristic composition and spatial distribution of germinable seeds in a spruce these impacts, it is crucial to investigate the species composition and functional diversity of the buried

Paris-Sud XI, Université de

31

Computational micromechanics of composites: The effect of particle spatial distribution  

Microsoft Academic Search

The effect of the reinforcement spatial distribution on the tensile deformation was investigated in a sphere-reinforced ductile-matrix composite through the finite element simulation of a representative volume element of the material. Composites with four different random and isotropic particle spatial distributions were considered: a homogeneous one and three heterogeneous ones, where the particles were clustered in spherical regions with increasing

Javier Segurado; Javier LLorca

2006-01-01

32

Isothermal life prediction of composite lamina using a damage mechanics approach  

Microsoft Academic Search

A method for predicting isothermal plastic fatigue life of a composite lamina is presented in which both fibers and matrix are isotropic materials. In general, the fatigue resistances of the matrix, fibers, and interfacial material must be known in order to predict composite fatigue life. Composite fatigue life is predicted using only the matrix fatigue resistance due to inelasticity micromechanisms.

N. M. Abuelfoutouh; M. J. Verrilli; G. R. Halford

1989-01-01

33

Maximum likelihood estimation for life distributions with competing failure modes  

NASA Technical Reports Server (NTRS)

Systems which are placed on test at time zero, function for a period and die at some random time were studied. Failure may be due to one of several causes or modes. The parameters of the life distribution may depend upon the levels of various stress variables the item is subject to. Maximum likelihood estimation methods are discussed. Specific methods are reported for the smallest extreme-value distributions of life. Monte-Carlo results indicate the methods to be promising. Under appropriate conditions, the location parameters are nearly unbiased, the scale parameter is slight biased, and the asymptotic covariances are rapidly approached.

Sidik, S. M.

1979-01-01

34

Life Cycle Assessment of Carbon Fiber-Reinforced Polymer Composites  

SciTech Connect

Carbon fiber-reinforced polymer matrix composites is gaining momentum with the pressure to lightweight vehicles, however energy-intensity and cost remain some of the major barriers before this material could be used in large-scale automotive applications. A representative automotive part, i.e., a 30.8 kg steel floor pan having a 17% weight reduction potential with stringent cash performance requirements has been considered for the life cycle energy and emissions analysis based on the latest developments occurring in the precursor type (conventional textile-based PAN vs. renewable-based lignin), part manufacturing (conventional SMC vs. P4) and fiber recycling technologies. Carbon fiber production is estimated to be about 14 times more energy-intensive than conventional steel production, however life cycle primary energy use is estimated to be quite similar to the conventional part, i.e., 18,500 MJ/part, especially when considering the uncertainty in LCI data that exists from using numerous sources in the literature. Lignin P4 technology offers the most life cycle energy and CO2 emissions benefits compared to a conventional stamped steel technology. With a 20% reduction in energy use in the lignin conversion to carbon fiber and free availability of lignin as a by-product of ethanol and wood production, a 30% reduction in life cycle energy use could be obtained. A similar level of life cycle energy savings could also be obtained with a higher part weight reduction potential of 43%.

Das, Sujit [ORNL

2011-01-01

35

Proposed framework for thermomechanical life modeling of metal matrix composites  

NASA Technical Reports Server (NTRS)

The framework of a mechanics of materials model is proposed for thermomechanical fatigue (TMF) life prediction of unidirectional, continuous-fiber metal matrix composites (MMC's). Axially loaded MMC test samples are analyzed as structural components whose fatigue lives are governed by local stress-strain conditions resulting from combined interactions of the matrix, interfacial layer, and fiber constituents. The metallic matrix is identified as the vehicle for tracking fatigue crack initiation and propagation. The proposed framework has three major elements. First, TMF flow and failure characteristics of in situ matrix material are approximated from tests of unreinforced matrix material, and matrix TMF life prediction equations are numerically calibrated. The macrocrack initiation fatigue life of the matrix material is divided into microcrack initiation and microcrack propagation phases. Second, the influencing factors created by the presence of fibers and interfaces are analyzed, characterized, and documented in equation form. Some of the influences act on the microcrack initiation portion of the matrix fatigue life, others on the microcrack propagation life, while some affect both. Influencing factors include coefficient of thermal expansion mismatch strains, residual (mean) stresses, multiaxial stress states, off-axis fibers, internal stress concentrations, multiple initiation sites, nonuniform fiber spacing, fiber debonding, interfacial layers and cracking, fractured fibers, fiber deflections of crack fronts, fiber bridging of matrix cracks, and internal oxidation along internal interfaces. Equations exist for some, but not all, of the currently identified influencing factors. The third element is the inclusion of overriding influences such as maximum tensile strain limits of brittle fibers that could cause local fractures and ensuing catastrophic failure of surrounding matrix material. Some experimental data exist for assessing the plausibility of the proposed framework.

Halford, Gary R.; Lerch, Bradley A.; Saltsman, James F.

1993-01-01

36

Tensile properties of short fiber composites with fiber strength distribution  

Microsoft Academic Search

The influence of fiber rupture, fiber pull-out and fiber tensile strength distribution on the post-cracking behavior of short-randomly-distributed fiber reinforced brittle-matrix composites has been analyzed using an approach based on the Weibull weakest-link statistics. The analysis led to the development of a predicting model for the composite bridging stress-crack opening displacement (sc - d) law—a fundamental material property necessary for

M. Maalej

2001-01-01

37

Life Modeling and Design Analysis for Ceramic Matrix Composite Materials  

NASA Technical Reports Server (NTRS)

The primary research efforts focused on characterizing and modeling static failure, environmental durability, and creep-rupture behavior of two classes of ceramic matrix composites (CMC), silicon carbide fibers in a silicon carbide matrix (SiC/SiC) and carbon fibers in a silicon carbide matrix (C/SiC). An engineering life prediction model (Probabilistic Residual Strength model) has been developed specifically for CMCs. The model uses residual strength as the damage metric for evaluating remaining life and is posed probabilistically in order to account for the stochastic nature of the material s response. In support of the modeling effort, extensive testing of C/SiC in partial pressures of oxygen has been performed. This includes creep testing, tensile testing, half life and residual tensile strength testing. C/SiC is proposed for airframe and propulsion applications in advanced reusable launch vehicles. Figures 1 and 2 illustrate the models predictive capabilities as well as the manner in which experimental tests are being selected in such a manner as to ensure sufficient data is available to aid in model validation.

2005-01-01

38

Ceramic Matrix Composites (CMC) Life Prediction Method Development  

NASA Technical Reports Server (NTRS)

Advanced launch systems (e.g., Reusable Launch Vehicle and other Shuttle Class concepts, Rocket-Based Combine Cycle, etc.), and interplanetary vehicles will very likely incorporate fiber reinforced ceramic matrix composites (CMC) in critical propulsion components. The use of CMC is highly desirable to save weight, to improve reuse capability, and to increase performance. CMC candidate applications are mission and cycle dependent and may include turbopump rotors, housings, combustors, nozzle injectors, exit cones or ramps, and throats. For reusable and single mission uses, accurate prediction of life is critical to mission success. The tools to accomplish life prediction are very immature and not oriented toward the behavior of carbon fiber reinforced silicon carbide (C/SiC), the primary system of interest for a variety of space propulsion applications. This paper describes an approach to satisfy the need to develop an integrated life prediction system for CMC that addresses mechanical durability due to cyclic and steady thermomechanical loads, and takes into account the impact of environmental degradation.

Levine, Stanley R.; Calomino, Anthony M.; Ellis, John R.; Halbig, Michael C.; Mital, Subodh K.; Murthy, Pappu L.; Opila, Elizabeth J.; Thomas, David J.; Thomas-Ogbuji, Linus U.; Verrilli, Michael J.

2000-01-01

39

An overview of computational simulation methods for composite structures failure and life analysis  

NASA Technical Reports Server (NTRS)

Three parallel computational simulation methods are being developed at the LeRC Structural Mechanics Branch (SMB) for composite structures failure and life analysis: progressive fracture CODSTRAN; hierarchical methods for high-temperature composites; and probabilistic evaluation. Results to date demonstrate that these methods are effective in simulating composite structures failure/life/reliability.

Chamis, Christos C.

1993-01-01

40

An overview of computational simulation methods for composite structures failure and life analysis  

SciTech Connect

Three parallel computational simulation methods are being developed at the LeRC Structural Mechanics Branch (SMB) for composite structures failure and life analysis: progressive fracture CODSTRAN; hierarchical methods for high-temperature composites; and probabilistic evaluation. Results to date demonstrate that these methods are effective in simulating composite structures failure/life/reliability.

Chamis, C.C.

1993-10-01

41

Distributed Workflow Service Composition Based on CTR Technology  

NASA Astrophysics Data System (ADS)

Recently, WS-BPEL has gradually become the basis of a standard for web service description and composition. However, WS-BPEL cannot efficiently describe distributed workflow services for lacking of special expressive power and formal semantics. This paper presents a novel method for modeling distributed workflow service composition with Concurrent TRansaction logic (CTR). The syntactic structure of WS-BPEL and CTR are analyzed, and new rules of mapping WS-BPEL into CTR are given. A case study is put forward to show that the proposed method is appropriate for modeling workflow business services under distributed environments.

Feng, Zhilin; Ye, Yanming

42

Fatigue Life Prediction of an Intermetallic Matrix Composite at Elevated Temperatures.  

National Technical Information Service (NTIS)

A strain-based fatigue life prediction method is proposed for an intermetallic matrix composite (IMC) under tensile cyclic loadings at elevated temperatures. Styled after the Universal Slopes method, the model utilizes the composite's tensile properties t...

P. A. Bartolotta

1991-01-01

43

Barium distributions in teeth reveal early life dietary transitions in primates  

PubMed Central

Early life dietary transitions reflect fundamental aspects of primate evolution and are important determinants of health in contemporary human populations1,2. Weaning is critical to developmental and reproductive rates; early weaning can have detrimental health effects but enables shorter inter-birth intervals, which influences population growth3. Uncovering early life dietary history in fossils is hampered by the absence of prospectively-validated biomarkers that are not modified during fossilisation4. Here we show that major dietary shifts in early life manifest as compositional variations in dental tissues. Teeth from human children and captive macaques, with prospectively-recorded diet histories, demonstrate that barium (Ba) distributions accurately reflect dietary transitions from the introduction of mother’s milk and through the weaning process. We also document transitions in a Middle Palaeolithic juvenile Neanderthal, which shows a pattern of exclusive breastfeeding for seven months, followed by seven months of supplementation. After this point, Ba levels in enamel returned to baseline prenatal levels, suggesting an abrupt cessation of breastfeeding at 1.2 years of age. Integration of Ba spatial distributions and histological mapping of tooth formation enables novel studies of the evolution of human life history, dietary ontogeny in wild primates, and human health investigations through accurate reconstructions of breastfeeding history. PMID:23698370

Austin, Christine; Smith, Tanya M.; Bradman, Asa; Hinde, Katie; Joannes-Boyau, Renaud; Bishop, David; Hare, Dominic J.; Doble, Philip; Eskenazi, Brenda; Arora, Manish

2013-01-01

44

Fatigue Life Methodology for Tapered Hybrid Composite Flexbeams  

NASA Technical Reports Server (NTRS)

Nonlinear-tapered flexbeam specimens from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. Two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) associated with simulated delamination growth in the flexbeams are presented from both codes. These results compare well with each other and suggest that the initial delamination growth from the tip of the ply-drop toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves for comparison with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared well with the test results.

urri, Gretchen B.; Schaff, Jeffery R.

2006-01-01

45

Tension fatigue analysis and life prediction for composite laminates  

NASA Technical Reports Server (NTRS)

A tension fatigue life prediction methodology for composite laminates is presented. Tension fatigue tests were conducted on quasi-isotropic and orthotropic glass epoxy, graphite epoxy, and glass/graphite epoxy hybrid laminates. Edge delamination onset data were used to generate plots of strain energy release rate as a function of cycles to delamination onset. These plots were then used along with strain energy release rate analyses of delaminations initiating at matrix cracks to predict local delamination onset. Stiffness loss was measured experimentally to account for the accumulation of matrix cracks and for delamination growth. Fatigue failure was predicted by comparing the increase in global strain resulting from stiffness loss to the decrease in laminate failure strain resulting from delaminations forming at matrix cracks through the laminate thickness. Good agreement between measured and predicted lives indicated that the through-thickness damage accumulation model can accurately describe fatigue failure for laminates where the delamination onset behavior in fatigue is well characterized, and stiffness loss can be monitored in real time to account for damage growth.

Obrien, T. K.; Rigamonti, M.; Zanotti, C.

1988-01-01

46

Composition of Autonomous Services with Distributed Data Flows and Computations  

Microsoft Academic Search

This paper presents a Flow-based Infrastructure for Composing Autonomous Services (FICAS) that supports a software composition paradigm, where software components are linked together through an integration framework to form composed software applications called megaservices. The software components are provided as processes managed by independent service providers; we call these components autonomous services. FICAS employs a distributed data-flow approach that differs

David Liu; Jun Peng; Kincho H. Law; Gio Wiederhold; Ram D. Sriram

2003-01-01

47

Cosmic Rays 8.1 Composition and energy distribution  

E-print Network

Chapter 8 Cosmic Rays 8.1 Composition and energy distribution Cosmic rays can be broadly defined, and exotics (WIMPS, axions,...) striking the earth. The primary cosmic rays are those entering the upper atmosphere, the cosmic rays of the interstellar medium. Secondary cosmic rays are those produced

Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group

48

Compositional Semantics for Real-time Distributed Computing  

Microsoft Academic Search

We give a compositional denotational semantics for a real-time distributed language, based on the linear history semantics for CSP of Francez et al. Concurrent execution is not modelled by interleaving but by an extension of the maximal parallelism model of Salwicki, that allows the modelling of transmission time for communications. The importance of constructing a semantics (and in general a

Ron Koymans; R. K. Shyamasundar; Willem P. De Roever; Rob Gerth; S. Arun-kumar

1985-01-01

49

Composition and Distribution of Beach Debris in Orange County, California  

Microsoft Academic Search

Many studies have quantified debris collected on beaches around the world. Only a few of those studies have been conducted in the United States, and they are largely limited to semi-quantitative efforts performed as part of volunteer clean-up activities. This study quantifies the distribution and composition of beach debris by sampling 43 stratified random sites on the Orange County, California

Shelly L. Moore; Dominic Gregorio; Michael Carreon; Stephen B. Weisberg; Molly K. Leecaster

2001-01-01

50

Composition distributions of particles in a gelling mixture.  

PubMed

Gelation in a two component disperse system wherein binary coagulation governs the temporal changes of particle composition spectra is studied for the crossproduct coagulation kernel proportional to m1n2+m2n1, with m,n being the numbers of monomers of the first and the second component in the coalescing pair of particles. This model reveals the sol-gel transition, i.e., after a finite interval of time the conservation of the total particle mass concentration violates because of the formation of giant particles (the gel). This paper reports on the exact solution of this model for arbitrary initial particle composition spectra. Exact expressions for the particle composition spectrum, the gel mass, and the second moments of the composition distribution are derived. Two scenarios of gelation, where the gel is either active or passive, are considered. PMID:24730804

Lushnikov, A A

2014-03-01

51

Fatigue Life Methodology for Tapered Composite Flexbeam Laminates  

NASA Technical Reports Server (NTRS)

The viability of a method for determining the fatigue life of composite rotor hub flexbeam laminates using delamination fatigue characterization data and a geometric non-linear finite element (FE) analysis was studied. Combined tension and bending loading was applied to non-linear tapered flexbeam laminates with internal ply drops. These laminates, consisting of coupon specimens cut from a full-size S2/E7T1 glass-epoxy flexbeam were tested in a hydraulic load frame under combined axial-tension and transverse cyclic bending. The magnitude of the axial load remained constant and the direction of the load rotated with the specimen as the cyclic bending load was applied. The first delamination damage observed in the specimens occurred at the area around the tip of the outermost ply-drop group. Subsequently, unstable delamination occurred by complete delamination along the length of the specimen. Continued cycling resulted in multiple delaminations. A 2D finite element model of the flexbeam was developed and a geometrically non-linear analysis was performed. The global responses of the model and test specimens agreed very well in terms of the transverse displacement. The FE model was used to calculate strain energy release rates (G) for delaminations initiating at the tip of the outer ply-drop area and growing toward the thick or thin regions of the flexbeam, as was observed in the specimens. The delamination growth toward the thick region was primarily mode 2, whereas delamination growth toward the thin region was almost completely mode 1. Material characterization data from cyclic double-cantilevered beam tests was used with the peak calculated G values to generate a curve predicting fatigue failure by unstable delamination as a function of the number of loading cycles. The calculated fatigue lives compared well with the test data.

Murri, Gretchen B.; OBrien, T. Kevin; Rousseau, Carl Q.

1997-01-01

52

Size and composition distribution of atmospheric particles in southern California  

SciTech Connect

Continuous measurements of single particle size and chemical composition in the atmosphere are made using aerosol time-of-flight mass spectrometers (ATOFMS) operated alongside more conventional reference air sampling instruments at a network of three urban air monitoring sites in southern California. Electrical aerosol analyzers and optical particle counters are employed to acquire continuous particle size distribution data, and inertial impactor and bulk filter samples with 4-h resolution are taken for determination of particle size and chemical composition. Filter and impactor samples also are taken upwind of the air basin at Santa Catalina Island in order to characterize background air quality. The airborne particle size and composition distribution as measured by the cascade impactors at inland sites differ from that over the ocean principally due to depletion of sea salt particles accompanied by the addition of fine carbon-containing particles and secondary aerosol nitrate. Data from the ATOFMS systems create a continuous time series of sodium-, ammonium-, nitrate-, and carbon-containing particle counts that provide a high-resolution view of differences in particle composition as a function of location in the air basin. Results show that the characteristic peak in the Los Angeles area aerosol mass distribution in the 0.2--0.3-{micro}m size range observed during the 1987 SCAQS experiments has been reduced, consistent with reductions in diesel soot and elemental carbon emissions since that time.

Hughes, L.S.; Allen, J.O.; Kleeman, M.J. [and others] [and others

1999-10-15

53

Using pseudo amino acid composition to predict protein subcellular location: approached with amino acid composition distribution  

Microsoft Academic Search

Summary.  In the Post Genome Age, there is an urgent need to develop the reliable and effective computational methods to predict the\\u000a subcellular localization for the explosion of newly found proteins. Here, a novel method of pseudo amino acid (PseAA) composition,\\u000a the so-called “amino acid composition distribution” (AACD), is introduced. First, a protein sequence is divided equally into\\u000a multiple segments. Then,

J.-Y. Shi; S.-W. Zhang; Q. Pan; G.-P. Zhou

2008-01-01

54

26 CFR 1.401(a)(9)-9 - Life expectancy and distribution period tables.  

...2014-04-01 2014-04-01falseLife expectancy and distribution period tables...Plans, Etc.§ 1.401(a)(9)-9Life expectancy and distribution period tables. Q-1. What is the life expectancy for an individual for...

2014-04-01

55

41 CFR 101-27.209 - Utilization and distribution of shelf-life items.  

...Utilization and distribution of shelf-life items. 101-27.209 Section 101-27...MANAGEMENT 27.2-Management of Shelf-Life Materials § 101-27.209 Utilization and distribution of shelf-life items. Where it is determined...

2014-07-01

56

41 CFR 101-27.209 - Utilization and distribution of shelf-life items.  

Code of Federal Regulations, 2013 CFR

...Utilization and distribution of shelf-life items. 101-27.209 Section 101-27...MANAGEMENT 27.2-Management of Shelf-Life Materials § 101-27.209 Utilization and distribution of shelf-life items. Where it is determined...

2013-07-01

57

41 CFR 101-27.209 - Utilization and distribution of shelf-life items.  

Code of Federal Regulations, 2011 CFR

...Utilization and distribution of shelf-life items. 101-27.209 Section 101-27...MANAGEMENT 27.2-Management of Shelf-Life Materials § 101-27.209 Utilization and distribution of shelf-life items. Where it is determined...

2011-07-01

58

41 CFR 101-27.209 - Utilization and distribution of shelf-life items.  

Code of Federal Regulations, 2012 CFR

...Utilization and distribution of shelf-life items. 101-27.209 Section 101-27...MANAGEMENT 27.2-Management of Shelf-Life Materials § 101-27.209 Utilization and distribution of shelf-life items. Where it is determined...

2012-07-01

59

Stressed Oxidation Life Prediction for C/SiC Composites  

NASA Technical Reports Server (NTRS)

The residual strength and life of C/SiC is dominated by carbon interface and fiber oxidation if seal coat and matrix cracks are open to allow oxygen ingress. Crack opening is determined by the combination of thermal, mechanical and thermal expansion mismatch induced stresses. When cracks are open, life can be predicted by simple oxidation based models with reaction controlled kinetics at low temperature, and by gas phase diffusion controlled kinetics at high temperatures. Key life governing variables in these models include temperature, stress, initial strength, oxygen partial pressure, and total pressure. These models are described in this paper.

Levine, Stanley R.

2004-01-01

60

MAE: An Integrated Design Tool for Failure and Life Prediction of Composites  

Microsoft Academic Search

An advanced strength and life prediction tool, MAE, was developed for the analysis and design of composite structures and components. The MAE integrates three theories and methods: micromechanics of failure (MMF), an accelerated testing method (ATM), and an evolution of damage (EOD). The MAE can serve as a useful tool to predict damage initiation, progression and life under various durability

Sangwook Sihn; Jin Woo Park

2008-01-01

61

Changes in the Lipid Composition of Thalassiosira pseudonana during Its Life Cycle  

Microsoft Academic Search

The lipid and fatty acid (FA) compositions of a marine diatom alga Thalassiosira pseudonana grown in culture were investigated. The relative content of separate lipid classes and their FA composition varied during of the life cycle. During the periods of active cell division and resting cell production, the proportion of polar lipids, as the structural components of cell membranes, increased.

N. V. Zhukova

2004-01-01

62

A Component-based Programming Model for Composite, Distributed Applications  

NASA Technical Reports Server (NTRS)

The nature of scientific programming is evolving to larger, composite applications that are composed of smaller element applications. These composite applications are more frequently being targeted for distributed, heterogeneous networks of computers. They are most likely programmed by a group of developers. Software component technology and computational frameworks are being proposed and developed to meet the programming requirements of these new applications. Historically, programming systems have had a hard time being accepted by the scientific programming community. In this paper, a programming model is outlined that attempts to organize the software component concepts and fundamental programming entities into programming abstractions that will be better understood by the application developers. The programming model is designed to support computational frameworks that manage many of the tedious programming details, but also that allow sufficient programmer control to design an accurate, high-performance application.

Eidson, Thomas M.; Bushnell, Dennis M. (Technical Monitor)

2001-01-01

63

Influence of Material Distribution on Impact Resistance of Hybrid Composites  

NASA Technical Reports Server (NTRS)

Impact events occur in a wide variety of circumstances. A typical example is a bullet impacting a target made of composite material. These impact events produce time-varying loads on a structure that can result in damage. As a first step to understanding the damage resistance issue in composite laminates, an accurate prediction of the transient response during an impact event is necessary. The analysis of dynamic loadings on laminated composite plates has undergone considerable development recently. Rayleigh-Ritz energy method was used to determine the impact response of laminated plates. The impact response of composite plates using shear deformation plate theory was analyzed. In recent work a closed-form solution was obtained for a rectangular plate with four edges simply supported subjected to a center impact load using classical plate theory. The problem was further investigated and the analysis results compared of both classical plate theory and shear deformation theory, and found that classical plate theory predicts very accurate results for the range of small deformations considered. In this study, the influence of cross sectional material distribution on the comparative impact responses of hybrid metal laminates subjected to low and medium velocity impacts is investigated. A simple linear model to evaluate the magnitude of the impact load is proposed first, and it establishes a relation between the impact velocity and the impact force. Then a closed-form solution for impact problem is presented. The results were compared with the finite element analysis results. For an 11 layer-hybrid laminate, the impact response as a function of material distribution in cross-section is presented. With equal areal weight, the effect of the number of laminate layers on the impact resistance is also investigated. Finally, the significance of the presented results is discussed.

Abatan, Ayu; Hu, Hurang

1998-01-01

64

Remaining service life diagnostic technology of phenol insulators for power distribution equipment  

Microsoft Academic Search

We have applied a remaining service life diagnostic technology to phenol insulators of power distribution equipment. Application of chemical evaluation and the Mahalanobis-Taguchi (MT) method enabled us to diagnose the insulators' degree of deterioration with great accuracy and nondestructively on-site. Time was defined as the end of service life when electrical discharge was initiated and a remaining service life was

S. Miki; T. Hasegawa; S. Umemura; H. Okazawa; Y. Otsuka; H. Inujima

2007-01-01

65

Particle distribution in a polymer nano-composite  

SciTech Connect

We use the hybrid particle-Self Consistent Field calculation (hybrid particle-SCF) to study the distribution of particles in a multi-block copolymer nano-composite. Using the static approach, we first find the effective interaction potential between the nano-particles and the polymer. The interaction has an entropic and an enthalpic component. The dynamical simulation confirms that the distribution of particles has a maximum at the minima of the interaction potential. We also study the situation where the nano-particles are distributed in a blend of AB diblock and A homopolymer. In this case, for large homopolymer concentration (larger than 20%), an interface is created between components that are identical, but they come from different types of polymer chains (i.e. the AB diblock or the A homopolymer). We find that the interaction potential has a minimum in this A/A interface which is of pure entropic origin. Furthermore the dynamical simulation reveals that the distribution of nano-particles has a maximum in the area around this interface.

Maniadis, Panagiotis [Los Alamos National Laboratory; Kober, Edward M [Los Alamos National Laboratory; Lookman, Turab [Los Alamos National Laboratory; Tsimpanogiannis, I [NCSR, GREECE

2009-01-01

66

Fatigue life methodology for tapered hybrid composite flexbeams  

Microsoft Academic Search

Nonlinear-tapered flexbeam specimens from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. Two different graphite\\/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two

Gretchen B. Murri; Jeffery R. Schaff

2006-01-01

67

FATIGUE LIFE ANALYSIS OF TAPERED HYBRID COMPOSITE FLEXBEAMS  

Microsoft Academic Search

Nonlinear-tapered flexbeam laminates from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. The two different graphite\\/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from

Gretchen B. Murri; Jeffery R. Schaff; Alan L. Dobyns

68

Stress distribution in composite flatwise tension test specimens  

NASA Technical Reports Server (NTRS)

A finite element analysis was conducted to determine the stress distribution in typical graphite/epoxy composite flat wise tension (FWT) specimens under normal loading conditions. The purpose of the analysis was to determine the relationship between the applied load and the stress in the sample to evaluate the validity of the test as a means of measuring the out-of-plane strength of a composite laminate. Three different test geometries and three different material lay ups were modeled. In all cases, the out-of-plane component of stress in the test section was found to be uniform, with no stress concentrations, and very close to the nominal applied stress. The stress in the sample was found to be three-dimensional, and the magnitude of in-plane normal and shear stresses varied with the anisotropy of the test specimen. However, in the cases considered here, these components of stress were much smaller than the out-of-plane normal stress. The geometry of the test specimen had little influence on the results. It was concluded that the flat wise tension test provides a good measure of the out-of-plane strength for the representative materials that were studied.

Scott, Curtis A.; Pereira, J. Michael

1993-01-01

69

A simulation of corrosion fatigue life distribution in low alloy steel  

NASA Astrophysics Data System (ADS)

A Monte Carlo simulation of corrosion fatigue life distributions was conducted in a low alloy steel, SNCM439, by assuming that the scatter of fatigue life resulted from the variation in the growth characteristics of corrosion pits and fatigue cracks. The parameters used in the simulation were obtained experimentally. The results showed that the experimental distributions were expressed satisfactorily by the simulation in which the parameters obtained from fatigue tests at the same stress were used. Therefore, it is concluded that corrosion fatigue life distribution can be predicted by a Monte Carlo simulation taking account of the statistical properties in the growth processes of corrosion pits and fatigue cracks.

Nakajima, Masaki; Kunieda, Hisashi; Tokaji, Keiro

1992-07-01

70

Probabilistic Distribution of Fatigue Crack Growth Life Considering Effect of Crack Coalescence  

NASA Astrophysics Data System (ADS)

The studies of probabilistic distribution of fatigue crack growth life (or the fatigue fracture probability) have been reported. However, some studies have concluded that each crack grows independently, without crack coalescence; while others indicate the defects should be treated as 2-dimensional cracks. In this study, a method to predict the probabilistic distribution of fatigue crack growth life that considers crack coalescence of the surface crack at the welded line is presented, and the influence of several parameters on the life distribution is discussed.

Yoon, Han-Yong; Lee, Sang-Chan

71

Spatial distribution and life-history aspects of blackspot seabream Pagellus bogaraveo (Osteichthyes: Sparidae).  

PubMed

Spatial distribution and life history aspects of Pagellus bogaraveo in the eastern Ionian Sea were investigated using the data from 13 different studies carried out in the area from 1983 to 2010. The spatial patterns of the abundance, biomass and mean size showed that the species inhabits the shallow waters of the shelf (<170?m depth) as juveniles up to a certain size (<180?mm total length, LT ), moving to deeper waters of the slope (mainly 400-500?m depth) as adults. The spatial pattern of abundance indicated a continuous distribution of the species in deep waters, with hot-spot areas of high values, whereas in shallow waters distribution was more discontinuous, with higher concentrations of juveniles in estuaries and brackish waters. The study of biological aspects of the species revealed (1) a difference in the increase in mass between males and females, (2) protandrous hermaphroditism, accompanied by the presence of primary females and males that do not change sex, (3) a sex ratio in favour of females >250?mm LT , (4) the presence of hermaphrodites between 200 and 370?mm, (5) a long reproduction period from June to March, (6) a size at first maturity around 300?mm and (7) a diet composition of adults based mainly on fishes, and also on opportunistic behaviour in the food scarce environment of deep waters. The results suggest that the species' distribution and feeding strategies are the most appropriate for the oligotrophic eastern Ionian waters and that these conditions result in smaller sizes of the species in the east Mediterranean Sea compared to the west basin and the east Atlantic Ocean, with implications for the growth and reproductive biology of the species. PMID:24298951

Mytilineou, Ch; Tsagarakis, K; Bekas, P; Anastasopoulou, A; Kavadas, S; Machias, A; Haralabous, J; Smith, C J; Petrakis, G; Dokos, J; Kapandagakis, A

2013-12-01

72

Asteroid taxonomy and the distribution of the compositional types  

NASA Technical Reports Server (NTRS)

Physical observations of minor planets documented in the TRIAD computer file are used to classify 752 objects into the broad compositional types C, S, M, E, R, and U (unclassifiable) according to the prescriptions adopted by Bowell et al. (1978). Diameters are computed from the photometric magnitude using radiometric and/or polarimetric data where available, or else from albedos characteristic of the indicated type. An analysis of the observational selection effects leads to tabulation of the actual number of asteroids, as a function of type and diameter, in each of 15 orbital element zones. For the whole main belt the population is 75% of type C, 15% of type S, and 10% of other types, with no belt-wide dependence of the mixing ratios on diameter. In some zones the logarithmic diameter-frequency relations are decidedly nonlinear. The relative frequency of S-type objects decreases smoothly outward through the main belt, with exponential scale length 0.5 AU. The rarer types show a more chaotic, but generally flatter, distribution over distance. Characteristic type distributions, contrasting with the background population, are found for the Eos, Koronis, Nysa and Themis families.

Zellner, B.

1979-01-01

73

Durability and Life of Ceramic Matrix Composites in Combustion Environment  

NASA Technical Reports Server (NTRS)

It is now generally recognized that the next frontier in the commercial air travel will be achieved by an optimum combination of the concepts being used for the air and space transports. It will depend upon the new engines specifically designed to meet the demanding strength, temperature, environment and economy requirements. The successful development of an advanced propulsion system for a 21st Century High Speed Civil Transport will require key advances in the combustor system. Minimizing nitrous oxide (NO(x)) emission is critical, since the deleterious interaction within the ozone layer would occur at the proposed vehicle cruise level of about 75,000 feet. In order to achieve the low NOx levels an efficient combustor operating at controlled equivalence ratios and high combustion temperatures are required. This requires a combustor, whose one portion will be operating in an oxidizing environment while the other portion will operate in a reducing environment. This rather unusual requirement has introduced considerable challenge to the materials scientists and engineers, the development of material systems capable of long-life at high temperatures (up to 3000 F) in an oxidizing and/or reducing environment.

Tewari, Surendra

1997-01-01

74

25 CFR 179.101 - How does the Secretary distribute principal and income to the holder of a life estate?  

Code of Federal Regulations, 2013 CFR

...distribute principal and income to the holder of a life estate? 179.101 Section 179.101 Indians...DEPARTMENT OF THE INTERIOR LAND AND WATER LIFE ESTATES AND FUTURE INTERESTS Life Estates Not Created Under AIPRA §...

2013-04-01

75

25 CFR 179.101 - How does the Secretary distribute principal and income to the holder of a life estate?  

Code of Federal Regulations, 2011 CFR

...distribute principal and income to the holder of a life estate? 179.101 Section 179.101 Indians...DEPARTMENT OF THE INTERIOR LAND AND WATER LIFE ESTATES AND FUTURE INTERESTS Life Estates Not Created Under AIPRA §...

2011-04-01

76

25 CFR 179.101 - How does the Secretary distribute principal and income to the holder of a life estate?  

Code of Federal Regulations, 2012 CFR

...distribute principal and income to the holder of a life estate? 179.101 Section 179.101 Indians...DEPARTMENT OF THE INTERIOR LAND AND WATER LIFE ESTATES AND FUTURE INTERESTS Life Estates Not Created Under AIPRA §...

2012-04-01

77

25 CFR 179.101 - How does the Secretary distribute principal and income to the holder of a life estate?  

Code of Federal Regulations, 2010 CFR

...distribute principal and income to the holder of a life estate? 179.101 Section 179.101 Indians...DEPARTMENT OF THE INTERIOR LAND AND WATER LIFE ESTATES AND FUTURE INTERESTS Life Estates Not Created Under AIPRA §...

2010-04-01

78

25 CFR 179.101 - How does the Secretary distribute principal and income to the holder of a life estate?  

...distribute principal and income to the holder of a life estate? 179.101 Section 179.101 Indians...DEPARTMENT OF THE INTERIOR LAND AND WATER LIFE ESTATES AND FUTURE INTERESTS Life Estates Not Created Under AIPRA §...

2014-04-01

79

Fatigue Life Prediction of a Hoop-Wrapped Composite CNG Cylinder Containing Surface Flaw  

E-print Network

Abstract — In recent years many experimental and numerical studies have been conducted on the fatigue behaviour of CNG storage pressure vessels. The main objective of these studies is to estimate the total fatigue life, which consists of two parts: i) Life till crack nucleation and ii) Crack growth life. Although fatigue evaluation methods for metal cylinders are widely covered in literature including the ASME Boiler and Pressure Vessel Code, comprehensive approaches for fatigue evaluation of composite-reinforced pressure vessels are very few. This paper calculates the fatigue life till crack nucleation for a steel-lined hoop wrapped composite pressure vessel containing a surface flaw (notch) using strain-life approach. Firstly, static stress analysis taking into account the non-linear material behaviour of steel liner was performed using finite element method to provide input for the fatigue analysis. Then fatigue analysis was carried out by applying a cyclic pressure inside the pre-stressed cylinder using strain-life approach, and the results obtained by the numerical simulations are discussed. The approach associated with these calculations can be used to study the effect of various material and geometry parameters on the fatigue life of the pressure vessel.

Kumar Agrawal; Surendra Kumar

80

Remaining Service Life Diagnostic Technology of Insulators for Power Distribution Equipment  

Microsoft Academic Search

We have developed a remaining service life diagnostic technology for insulators, which are important parts involved in determining the service life of power distribution equipment. Application of chemical evaluation and the Mahalanobis-Taguchi method enabled us to diagnose the insulators' degree of deterioration with great accuracy and nondestructively on-site. The theory, which derives the threshold value of surface resistivity for electric

Shinsuke Miki; Hiroshi Okazawa; Taketoshi Hasegawa; Sei Tsunoda; Hiroshi Inujima

2007-01-01

81

Comparative life-cycle analysis of steel-concrete composite bridges  

Microsoft Academic Search

Competitiveness of steel construction and, in particular, steel and composite bridges, requires a broader view that encompasses the concepts of sustainability and life-cycle assessment in parallel with the classical structural and geotechnical issues. Also, from the economical viewpoint, the progressive transfer of operational duties from the National Road Authorities to private companies in the context of design, build and operate

Helena Gervásio; Luís Simões da Silva

2008-01-01

82

Using atmospheric composition as a metric for detecting life on habitable planets  

Microsoft Academic Search

The extent to which a planet's atmospheric composition is in chemical disequilibrium is a possible diagnostic tool for detecting life on habitable exoplanets. It is generally recognized that departure from chemical equilibrium of the Earth's atmosphere reflects the prodigious release and uptake of gases by the biosphere (1). But abiotic free energy sources can promote disequilibrium too, e.g., through photochemistry

D. C. Catling; D. Bergsman

2009-01-01

83

Modeling and life prediction methodology for Titanium Matrix Composites subjected to mission profiles  

Microsoft Academic Search

Titanium matrix composites (TMC) are being evaluated as structural materials for elevated temperature applications in future generation hypersonic vehicles. In such applications, TMC components are subjected to complex thermomechanical loading profiles at various elevated temperatures. Therefore, thermomechanical fatigue (TMF) testing, using a simulated mission profile, is essential for evaluation and development of life prediction methodologies. The objective of the research

M. Mirdamadi; W. S. Johnson

1994-01-01

84

Strength and fatigue life evaluation of composite laminate with embedded sensors  

NASA Astrophysics Data System (ADS)

Prognosis regarding durability of composite structures using various Structural Health Monitoring (SHM) techniques is an important and challenging topic of research. Ultrasonic SHM systems with embedded transducers have potential application here due to their instant monitoring capability, compact packaging potential toward unobtrusiveness and noninvasiveness as compared to non-contact ultrasonic and eddy current techniques which require disassembly of the structure. However, embedded sensors pose a risk to the structure by acting as a flaw thereby reducing life. The present paper focuses on the determination of strength and fatigue life of the composite laminate with embedded film sensors like CNT nanocomposite, PVDF thin films and piezoceramic films. First, the techniques of embedding these sensors in composite laminates is described followed by the determination of static strength and fatigue life at coupon level testing in Universal Testing Machine (UTM). Failure mechanisms of the composite laminate with embedded sensors are studied for static and dynamic loading cases. The coupons are monitored for loading and failure using the embedded sensors. A comparison of the performance of these three types of embedded sensors is made to study their suitability in various applications. These three types of embedded sensors cover a wide variety of applications, and prove to be viable in embedded sensor based SHM of composite structures.

Rathod, Vivek T.; Hiremath, S. R.; Roy Mahapatra, D.

2014-04-01

85

The distribution of stars most likely to harbor intelligent life.  

PubMed

Simple heuristic models and recent numerical simulations show that the probability of habitable planet formation increases with stellar mass. We combine those results with the distribution of main-sequence stellar masses to obtain the distribution of stars most likely to possess habitable planets as a function of stellar lifetime. We then impose the self-selection condition that intelligent observers can only find themselves around a star with a lifetime greater than the time required for that observer to have evolved, T(i). This allows us to obtain the stellar timescale number distribution for a given value of T(i). Our results show that for habitable planets with a civilization that evolved at time T(i) = 4.5 Gyr the median stellar lifetime is 13 Gyr, corresponding approximately to a stellar type of G5, with two-thirds of the stars having lifetimes between 7 and 30 Gyr, corresponding approximately to spectral types G0-K5. For other values of T(i) the median stellar lifetime changes by less than 50%. PMID:19778273

Whitmire, Daniel P; Matese, John J

2009-09-01

86

Environmental Factors Related to the Distribution, Abundance, and Life History Characteristics of Mountain Whitefish in Idaho  

Microsoft Academic Search

Mountain whitefish Prosopium williamsoni are a broadly distributed native salmonid in western North America, but comparatively little investigation has been made regarding their population characteristics. We surveyed 2,043 study sites to assess whether physiochemical stream conditions affected mountain whitefish distribution and abundance in southern Idaho, and at 20 of these sites life history characteristics were also estimated. A total of

Kevin A. Meyer; F. Steven Elle; James A. Lamansky Jr

2009-01-01

87

Accelerated Life Testing Model for a Generalized Birnbaum-Saunders Distribution  

E-print Network

of the distribution, is the failure threshold level, is the standard deviation of the failure time dataAccelerated Life Testing Model for a Generalized Birnbaum-Saunders Distribution Yao Cheng and E. A@gmail.com, elsayed@rci.rutgers.edu Abstract--Fatigue failures caused by cyclic stresses are commonly

Boyer, Edmond

88

Maximum likelihood estimation for life distributions with competing failure modes  

NASA Technical Reports Server (NTRS)

The general model for the competing failure modes assuming that location parameters for each mode are expressible as linear functions of the stress variables and the failure modes act independently is presented. The general form of the likelihood function and the likelihood equations are derived for the extreme value distributions, and solving these equations using nonlinear least squares techniques provides an estimate of the asymptotic covariance matrix of the estimators. Monte-Carlo results indicate that, under appropriate conditions, the location parameters are nearly unbiased, the scale parameter is slightly biased, and the asymptotic covariances are rapidly approached.

Sidik, S. M.

1979-01-01

89

Energy, ecology and the distribution of microbial life  

PubMed Central

Mechanisms that govern the coexistence of multiple biological species have been studied intensively by ecologists since the turn of the nineteenth century. Microbial ecologists in the meantime have faced many fundamental challenges, such as the lack of an ecologically coherent species definition, lack of adequate methods for evaluating population sizes and community composition in nature, and enormous taxonomic and functional diversity. The accessibility of powerful, culture-independent molecular microbiology methods offers an opportunity to close the gap between microbial science and the main stream of ecological theory, with the promise of new insights and tools needed to meet the grand challenges humans face as planetary engineers and galactic explorers. We focus specifically on resources related to energy metabolism because of their direct links to elemental cycling in the Earth's history, engineering applications and astrobiology. To what extent does the availability of energy resources structure microbial communities in nature? Our recent work on sulfur- and iron-oxidizing autotrophs suggests that apparently subtle variations in the concentration ratios of external electron donors and acceptors select for different microbial populations. We show that quantitative knowledge of microbial energy niches (population-specific patterns of energy resource use) can be used to predict variations in the abundance of specific taxa in microbial communities. Furthermore, we propose that resource ratio theory applied to micro-organisms will provide a useful framework for identifying how environmental communities are organized in space and time. PMID:23754819

Macalady, Jennifer L.; Hamilton, Trinity L.; Grettenberger, Christen L.; Jones, Daniel S.; Tsao, Leah E.; Burgos, William D.

2013-01-01

90

The cosmic ray primary composition at the knee region from lateral distributions of atmospheric C  

E-print Network

The cosmic ray primary composition at the knee region from lateral distributions of atmospheric C.40.De 96.40.Pq Keywords: Cosmic rays Extensive air showers Atmospheric C erenkov Chemical composition associated with extensive air showers to study the chemical composition of the primary cosmic rays

91

Inferences from the vertical distribution of Fe isotopic compositions1 on pedogenetic processes in soils2  

E-print Network

.geoderma.2013.06.007 #12;2 ABSTRACT1 The isotopic compositions of major elements in soils can help understand compositions combined with classical soil parameters, such as granulometry, pH,5 and C and N concentrations. We1 Inferences from the vertical distribution of Fe isotopic compositions1 on pedogenetic processes

Boyer, Edmond

92

Agent-based semantic composition of Web services using distributed description logics  

E-print Network

of ontology is the key to improve Web services with semantics and interoperability. Ontologies enrich WebAgent-based semantic composition of Web services using distributed description logics Mourad Ouziri Distributed Description Logics (DDL) to achieve the semantic composition of web services. DDL allows one

Paris-Sud XI, Université de

93

Biogenic aerosols from Amazonia: Composition, size distributions and optical properties  

NASA Astrophysics Data System (ADS)

Amazonia is an excellent laboratory to study atmospheric processes that are characteristic of natural conditions, as they existed prior to the impact of industrialization on the regional and global atmosphere. Biogenic aerosols dominate the particle population in Amazonia, showing a strong link between forest biology and atmospheric composition. In the fine fraction, aerosols are mostly secondary organic particles formed from biogenic emissions of trace gases, with a contribution of primary particles. In the coarse mode, primary biogenic particles dominates the picture. Aerosols have been continuously measured at the TT34 LBA tower at the ZF2 ecological station about 55 Km North of Manaus since January 2008. Fine mode aerosol mass concentration is very low in Amazonia, with PM2.5 of about 1.3×0.7 ?g m-3 and 3.4×2.0 ?g m-3 in the wet and dry seasons, respectively. In terms of particle number concentrations a median value of 220 cm-3 in the wet season and 2,200 cm-3 in the dry season were observed. An aerosol chemical speciation monitor (ACSM) was deployed in 2013, and it shows that organic aerosol account to 81% to the non-refractory PM1 aerosol loading at TT34, while in the dry season, a high 93% content of organic particles was observed. Size distribution shows the occurrence of bursts of particles with about 20 nanometers at night time, possibly associated with biological process. Very few events of new particle formation are observed. Aerosol light scattering and absorption coefficients at the TT34 site were low during the wet season, increasing by a factor of 5, approximately, in the dry season due to long range transport of biomass burning aerosols reaching the forest site. Aerosol single scattering albedo (SSA) ranged from 0.84 in the wet season up to 0.91 in the dry, indicating a surprising high absorption in the wet season, associated with biogenic particles.

Rizzo, L. V.; Artaxo, P. P.; Brito, J. F.; Barbosa, H. M.; Andreae, M. O.; Martin, S. T.

2013-12-01

94

Phosphorylation alters tau distribution and elongates life span in Drosophila.  

PubMed

The microtubule-associated tau protein has long been considered an axon-specific protein. Although many articles describe the subcellular localization of tau as regulated by post-modification in cultured cells, the intracellular regulation of its distribution in living animals has yet to be elucidated. In the present study, we demonstrate that phosphorylation alters tau polarity in Drosophila melanogaster. Interestingly, it was observed that expression of phosphorylation-incompetent tau impaired neurite growth more severely than either hyperphosphorylated or pseudophosphorylated tau. We also found that inducible expression of hyper- or pseudo-phosphorylated tau in adult flies strikingly prolonged their lifespan. This study offers an alternative tauopathic model by demonstrating that hyperphosphorylated tau has a beneficial effect on the nervous system. This is also corroborated by common effects seen in a variety of organisms in response to various stresses. We hope that this important animal model leads to a paradigm shift in thinking about hyperphosphorylated tau, which plays a protective role in nervous systems rather than the toxic role that many have historically been given to it. PMID:20555141

Yeh, Po-An; Chang, Ching-Jin; Tu, Pong-Hsien; Wilson, Harry Iain; Chien, Ju-Yi; Tang, Chiou-Yang; Su, Ming-Tsan

2010-01-01

95

Fatigue life prediction of an intermetallic matrix composite at elevated temperatures  

NASA Technical Reports Server (NTRS)

A strain-based fatigue life prediction method is proposed for an intermetallic matrix composite (IMC) under tensile cyclic loadings at elevated temperatures. Styled after the Universal Slopes method, the model utilizes the composite's tensile properties to estimate fatigue life. Factors such as fiber volume ratio, number of plys and temperature dependence are implicitly incorporated into the model through these properties. The model constants are determined by using unidirectional fatigue data at temperatures of 425 and 815 C. Fatigue lives from two independent sources are used to verify the model at temperatures of 650 and 760 C. Cross-ply lives at 760 C are also predicted. It is demonstrated that the correlation between experimental and predicted lives is within a factor of two.

Bartolotta, Paul A.

1991-01-01

96

Erosion Coatings Developed to Increase the Life and Durability of Composites  

NASA Technical Reports Server (NTRS)

Both the NASA Glenn Research Center and the Allison Advanced Development Company (AADC) have worked to develop and demonstrate erosion-resistant coatings that would increase the life and durability of composite materials used in commercial aircraft engines. These composite materials reduce component weight by 20 to 30 percent and result in less fuel burn and emissions and more fuel savings. Previously, however, their use was limited because of poor erosion resistance, which causes concerns about safety and leads to high maintenance costs. The coatings were tested by the University of Cincinnati, and the composites were manufactured by Texas Composites and coated by Engelhard and NASA Glenn. Rolls-Royce Corporation uses composite materials, which are stronger and less dense than steel or titanium, to make bypass vanes for their AE3007 engines. These engines are widely used in regional jet aircraft (Embraer) and unmanned air vehicles such as the Northrop Grumman Global Hawk. Coatings developed by NASA/Rolls-Royce can reduce erosion from abrasive materials and from impurities in the air that pass over these vanes, allowing Rolls-Royce to take advantage of the benefits of composite materials over titanium without the added costs of increased maintenance and/or engine failure. The Higher Operating Temperature Propulsion Components (HOTPC) Project developed cost-effective, durable coatings as part of NASA's goal to increase aviation system capacity growth. These erosion coatings will reduce the number of special inspections or instances of discontinued service due to erosion, allowing aircraft capacity to be maintained without inconveniencing the traveling public. A specific example of extending component life showed that these coatings increased the life of graphite fiber and polymer composite bypass vanes up to 8 times over that of the uncoated vanes. This increased durability allows components to operate to full design life without the fear of wear or failure. Recently, Rolls-Royce completed over 2000 hr of engine testing with the coated fan exit bypass vanes. There was no loss of coating after nearly 5000 typical engine cycles. Midway through the engine tests, the coated vanes were removed from the engine during a scheduled maintenance and inspection period. The vanes were shipped back to Glenn, where they underwent further stress testing in the Structural Dynamics Lab, mimicking more extreme conditions than those typical of the AE3007 engine cycle. These vanes were then replaced in the AE3007 and subjected to another 1000 hr of engine tests. Once again, there was no loss of coating and only a minimal appearance of cracking.

Sutter, James K.; Naik, Subhash K.; Bowman, Cheryl L.; Siefker, Robert; Miyoshi, Kazuhisa; Perusek, Gail P.

2004-01-01

97

Ultrasonic attenuation as an indicator of fatigue life of graphite/epoxy fiber composite  

NASA Technical Reports Server (NTRS)

The narrow band ultrasonic longitudinal wave velocity and attenuation were measured as a function of the transfiber compression-compression fatigue of unidirectional graphite/epoxy composites. No change in velocity was detected at any point in fatigue life. For specimens fatigued at 80% of static strength, there was generally a 5% to 10% increase in attenuation, however, this increase does not appear to be a satisfactory indicator of fatigue life. On the other hand, there appears to be a correlation between initial attenuation (measured prior to cycling) and cycles to fracture. Initial attenuation as measured at 1.5 MHz and 2.0 MHz appears to be a good indicator of relative fatigue life.

Williams, J. H., Jr.; Doll, B.

1979-01-01

98

Fatigue Life Recovery in Corroded Aluminium Alloys Using Bonded Composite Reinforcements  

NASA Astrophysics Data System (ADS)

Bonded composite reinforcements, such as boron/epoxy or carbon/epoxy, are becoming widely used to repair fatigue or stress corrosion cracks in aluminium alloy aircraft components. They also have considerable potential as repairs for corrosion damage, although the non-discrete nature of corrosion damage is a considerable complication. This paper describes studies on bonded repairs of two types of typical corrosion damage, both of which cause a dramatic reduction in fatigue life: a) relatively severe exfoliation and b) relatively minor pitting. Both studies are based on earlier Australian experimental studies on the structural significance of corrosion. In the studies described in this paper, other than the standard surface treatment used to attach the reinforcement no attempt was made to remove the corrosion damage. It is concluded that bonded repairs can provide useful fatigue life recovery even with serious exfoliation damage; however, such repairs should be regarded only as a temporary measure. For permanent and far more effective repairs most of the damage should be removed (ground-out) prior to reinforcement. In contrast, with minor pitting, greater than full life recovery is feasible. This observation also leads to the conclusion that bonded repairs will be tolerant of minor pitting inadvertently left after grind-out. Strain reduction by the reinforcement, as expected, is the major contributor to life extension. However, in the case of minor pitting environmental isolation by the adhesive is probably highly beneficial. Residual stresses in the metal resulting from the composite reinforcement causes some loss in patching efficiency.

Baker, Alan A.

2006-05-01

99

Remaining Service Life Diagnostic Technology of Insulators for Power Distribution Equipment  

NASA Astrophysics Data System (ADS)

We have developed a remaining service life diagnostic technology for insulators, which are important parts involved in determining the service life of power distribution equipment. Application of chemical evaluation and the Mahalanobis-Taguchi method enabled us to diagnose the insulators' degree of deterioration with great accuracy and nondestructively on-site. The theory, which derives the threshold value of surface resistivity for electric discharge initiation calculated from rated voltage, the form of an insulator, etc., was established and a remaining service life was presumed from the diagnostic results by the MT method and the year in which the master curve of service life and the threshold value intersect. It was clarified that a remaining service life could be presumed by this technology because there was a good relationship between the check examination results of electric discharge initiation in the laboratory and the presumption results.

Miki, Shinsuke; Okazawa, Hiroshi; Hasegawa, Taketoshi; Tsunoda, Sei; Inujima, Hiroshi

100

Validation of Framework Code Approach to a Life Prediction System for Fiber Reinforced Composites  

NASA Technical Reports Server (NTRS)

The grant was conducted by the MMC Life Prediction Cooperative, an industry/government collaborative team, Ohio Aerospace Institute (OAI) acted as the prime contractor on behalf of the Cooperative for this grant effort. See Figure I for the organization and responsibilities of team members. The technical effort was conducted during the period August 7, 1995 to June 30, 1996 in cooperation with Erwin Zaretsky, the LERC Program Monitor. Phil Gravett of Pratt & Whitney was the principal technical investigator. Table I documents all meeting-related coordination memos during this period. The effort under this grant was closely coordinated with an existing USAF sponsored program focused on putting into practice a life prediction system for turbine engine components made of metal matrix composites (MMC). The overall architecture of the NMC life prediction system was defined in the USAF sponsored program (prior to this grant). The efforts of this grant were focussed on implementing and tailoring of the life prediction system, the framework code within it and the damage modules within it to meet the specific requirements of the Cooperative. T'he tailoring of the life prediction system provides the basis for pervasive and continued use of this capability by the industry/government cooperative. The outputs of this grant are: 1. Definition of the framework code to analysis modules interfaces, 2. Definition of the interface between the materials database and the finite element model, and 3. Definition of the integration of the framework code into an FEM design tool.

Gravett, Phillip

1997-01-01

101

Effect of carbide distribution on rolling-element fatigue life of AMS 5749  

NASA Technical Reports Server (NTRS)

Endurance tests with ball bearings made of corrosion resistant bearing steel which resulted in fatigue lives much lower than were predicted are discussed. Metallurgical analysis revealed an undesirable carbide distribution in the races. It was shown in accelerated fatigue tests in the RC rig that large, banded carbides can reduce rolling element fatigue life by a factor of approximately four. The early spalling failures on the bearing raceways are attributed to the large carbide size and banded distribution.

Parker, R. J.; Bamberger, E. N.

1983-01-01

102

Mechanisms Controlling Particle Distribution in Infusion Molded Composites  

Microsoft Academic Search

This article presents results from an experimental investigation in which two grades of aluminatrihydroxide (ATH) particles are added to liquid resin and used in infusion molding experiments. Based on the results, potential key mechanisms controlling resin flow and hence also the final particle distribution are proposed. A pore doublet model is proposed to explain the seemingly random spatial distribution of

S. P. Fernberg; E. J. SANDLUND; T. S. LUNDSTROM

2006-01-01

103

Residual Strain Distribution in Bent Composite Boiler Tubes  

SciTech Connect

Kraft recovery boilers are typically constructed of carbon steel boiler tubes clad with a corrosion resistant layer, and these composite tubes are bent and welded together to form air port panels which enable the combustion air to enter the boiler. In this paper, the through-thickness residual strain in the carbon steel layer of non-heat-treated and heat-treated composite bent tubes were measured by neutron diffraction techniques and modeled by finite element modeling. The results can be used to optimize material selection and manufacturing processes to prevent stress corrosion and corrosion fatigue cracking in the boiler tubes.

Hubbard, Camden R [ORNL; Gorti, Sarma B [ORNL; Tang, Fei [ORNL; Keiser, James R [ORNL

2006-01-01

104

DISTRIBUTION AND DURATION OF PELAGIC LIFE OF LARVAE OF DOVER SOLE, MICROSTOMUS PACIFICUS,. REX SOLE,  

E-print Network

DISTRIBUTION AND DURATION OF PELAGIC LIFE OF LARVAE OF DOVER SOLE, MICROSTOMUS PACIFICUS,. REX SOLE. HOSIE,2 AND SALLY L. RICHARDSONI ABSTRACT Dover and rex sole larvae attain an exceptionally large size the continental slope and in the upper 50 m of the water column. The rex sole larvae captured were 5-89 mm long

105

Aspects of Chub Shiner Notropis potteri Life History with Comments on Native Distribution and Conservation Status  

E-print Network

Aspects of Chub Shiner Notropis potteri Life History with Comments on Native Distribution/Aquatic Station, Texas State University-San Marcos, San Marcos 78666 ABSTRACT.--Chub shiner Notropis potteri, to the Red River Drainage. INTRODUCTION Chub shiner Notropis potteri was first discovered by Potter (1938

Aspbury, Andrea S. - Department of Biology, Texas State University

106

Surface composition and barium evaporation rate of ``pedigreed'' impregnated tungsten dispenser cathodes during accelerated life testing  

NASA Astrophysics Data System (ADS)

A study has been made of the surface composition and barium evaporation rate of "pedigreed" impregnated tungsten dispenser cathodes. The effect of air exposure on coated cathodes was examined and was found to have no significant effect on barium evaporation rate although in some cases longer reactivation times were required. No changes in surface topography were apparent following air exposure and reactivation. Life testing was done at 100°C above the typical operating temperature for the cathode, where the typical operating temperature was taken to be 950°C for coated cathodes and 1050°C for uncoated cathodes. The cathodes were examined at different stages of life testing, up to 1200 h. Significant decreases in barium evaporation rates were found after as few as 500 h of life testing. After 1000 h the evaporation rate had decreased more than an order of magnitude. Changes in surface composition were also found. The effects of tungsten particle size, used in manufacture of the billet, on barium evaporation rate were also studied but no correlation was found.

Tomich, D. H.; Mescher, J. A.; Grant, J. T.

1987-03-01

107

Litter sex composition affects life-history traits in yellow-bellied marmots.  

PubMed

1. The presence of siblings might have long-lasting fitness consequences because they influence the early environment in which an animal develops. Several studies under laboratory conditions have shown long-lasting consequences from the presence of male siblings in utero on morphology and life-history traits. However, in wild animals, such effects of litter sex composition are unexplored. 2. We capitalized on a long-term study of individually marked yellow-bellied marmots (Marmota flaviventris) and documented the effects of weaned litter sex composition and anogenital distance on several life-history and fitness traits. 3. First, we demonstrated that the number of males in a litter influenced anogenital distance. Then, we found that masculinized females, those with larger anogenital distances, were less likely to survive their first hibernation, were more likely to disperse and were less likely to become pregnant and wean young. Males from male-biased litters had lower growth rates, but we failed to detect longer-term consequences. 4. Taken together, our results show profound sex-dependent effects of litter sex composition, probably due to differential prenatal exposure to androgens, in free-living animals. We conclude that masculinization might constitute an alternative mechanism explaining variation in different demographic traits. This finding highlights the importance of studying these maternal effects, and they enhance our concern over the widespread use of endocrine disrupting compounds. PMID:21801175

Monclús, Raquel; Blumstein, Daniel T

2012-01-01

108

Distributed multifunctional sensor network for composite structural state sensing  

NASA Astrophysics Data System (ADS)

Advanced fiber reinforced composite materials are becoming the main structural materials of next generation of aircraft because of their high strength and stiffness to weight ratios, and strong designability. In order to take full advantages of composite materials, there is a need to develop an embeddable multifunctional sensing system to allow a structure to "feel" and "think" its structural state. In this paper, the concept of multifunctional sensor network integrated with a structure, similar to the human nervous system, has been developed. Different types of network sensors are permanently integrated within a composite structure to sense structural strain, temperature, moisture, aerodynamic pressure; monitor external impact on the structure; and detect structural damages. Utilizing this revolutionary concept, future composite structures can be designed and manufactured to provide multiple modes of information, so that the structures have the capabilities for intelligent sensing, environmental adaptation and multi-functionality. The challenges for building such a structural state sensing system and some solutions to address the challenges are also discussed in the paper.

Qing, Xinlin P.; Wang, Yishou; Gao, Limin; Kumar, Amrita

2012-04-01

109

Moment distributions around holes in symmetric composite laminates subjected to bending moments  

NASA Technical Reports Server (NTRS)

An analytical investigation of the effects of holes on the moment distribution of symmetric composite laminates subjected to bending moments is described. A general, closed-form solution for the moment distribution of an infinite anisotropic plate is derived, and this solution is used to determine stress distributions both on the hole boundary and throughout the plate. Results are presented for several composite laminates that have holes and are subjected to either pure bending or cylindrical bending. Laminates with a circular hole or with an elliptical hole are studied. Laminate moment distributions are discussed, and ply stresses are described.

Prasad, C. B.; Shuart, M. J.

1989-01-01

110

Composite bridge behavior and load distribution influenced by shakedown and diaphragms  

E-print Network

-load distribution were analyzed in the composite bridge. Most shnnkage and creep strains due to prestress losses, predicted with the theoretical time-step method presented by ACI, agreed with the measured data from the model bndge study. Additional concrete... strains due to differential creep in the composite structure were impossible to measure during the constant live- load testing. However, permanent deflections in the bridge girders before the Overload tests were larger than predicted by the composite...

Gilstrap, Christopher Max

2012-06-07

111

Particle size distribution and compositional effects on textural properties and appearance of dark chocolates  

Microsoft Academic Search

Particle size distribution (PSD) and composition in dark chocolate were varied and their effects on textural properties of molten and tempered chocolates determined using a TA.HD Plus Texture Analyzer. Surface colour was evaluated in terms of CIELAB parameters L*, C* and h° using a HunterLab Miniscan Colorimeter. Compositional parameters for particle size distribution were [D90 (>90% finer) of 18?m, 25?m,

Emmanuel Ohene Afoakwa; Alistair Paterson; Mark Fowler; Joselio Vieira

2008-01-01

112

Simulations of Fiber Distribution Effects in Fiber-Reinforced Cement Composites  

Microsoft Academic Search

This paper describes a lattice model for coupled moisture transport?stress analyses of fiber-reinforced cement composites (FRCC). Each fiber, and its interface with the matrix material, is explicitly represented within the three-dimensional material volume. This enables the direct study of fiber orientation and distribution effects on composite performance. Realistic, nonuniform fiber distributions can be specified as model input. Basic applications of

John E. Bolander; Yun Mook Lim

2008-01-01

113

Simulations of Fiber Distribution Effects in Fiber-Reinforced Cement Composites  

Microsoft Academic Search

This paper describes a lattice model for coupled moisture transport\\/stress analyses of fiber-reinforced cement composites (FRCC). Each fiber, and its interface with the matrix material, is explicitly represented within the three-dimensional material volume. This enables the direct study of fiber orientation and distribution effects on composite performance. Realistic, nonuniform fiber distributions can be specified as model input. Basic applications of

John E. Bolander; Yun Mook Lim

2008-01-01

114

Amino Acid Composition Distribution: a Novel Sequence Representation for Prediction of Protein Subcellular Localization  

Microsoft Academic Search

A novel representation of protein sequence, amino acid composition distribution (AACD), is introduced to perform prediction of subcellular localization in this paper. First, a protein sequence is divided equally into multiple segments. Then, amino acid composition of each segment is calculated in series. After that, each protein sequence can be represented a feature vector. Finally, feature vectors of all sequences

Jianyu Shi; Shaowu Zhang; Quan Pan; Guo-Ping Zhou

2007-01-01

115

Distribution and composition of particulate organic matter in the Ross Sea (Antarctica)  

Microsoft Academic Search

The biochemical composition and spatial distribution of particulate organic matter (POM) were studied in the Ross Sea (Antarctica) in summer 1989 to assess the quantitative role of organic carbon fractions in the cycling of organic matter in the water column. Large differences in chemical composition were observed between surface and deep layers. The results indicated that, despite large geographical differences,

Mauro Fabiano; Paolo Povero; Roberto Danovaro

1993-01-01

116

Bayesian Analysis of Step-Stress Accelerated Life Test with Exponential Distribution  

SciTech Connect

In this article, we propose a general Bayesian inference approach to the step-stress accelerated life test with type II censoring. We assume that the failure times at each stress level are exponentially distributed and the test units are tested in an increasing order of stress levels. We formulate the prior distribution of the parameters of life-stress function and integrate the engineering knowledge of product failure rate and acceleration factor into the prior. The posterior distribution and the point estimates for the parameters of interest are provided. Through the Markov chain Monte Carlo technique, we demonstrate a nonconjugate prior case using an industrial example. It is shown that with the Bayesian approach, the statistical precision of parameter estimation is improved and, consequently, the required number of failures could be reduced.

Lee, J.; Pan, R.

2012-04-01

117

Ion composition and energy distribution during 10 magnetic storms  

Microsoft Academic Search

Data from the plasma composition experiment on ISEE 1 were used to investigate the relative quantities and energy characteristics of H\\/sup +\\/, He\\/sup + +\\/, and O\\/sup +\\/ in the near-equatorial magnetosphere at R< or =15 R\\/sub E\\/ during magnetic storms, principally during the early main phase. The ions included in this study had energies in the range of 0.1<

W. Lennartsson; R. D. Sharp; E. G. Shelley; R. G. Johnson; H. Balsiger

1981-01-01

118

Creep Cavity Growth Model for Creep-Fatigue Life Prediction of a Unidirectional W/Cu Composite.  

National Technical Information Service (NTIS)

A microstructural model was developed to predict creep-fatigue life in a (0)(sub 4), 9 volume percent tungsten fiber-reinforced copper matrix composite at the temperature of 833 K. The mechanism of failure of the composite is assumed to be governed by the...

Y. Kim, M. J. Verrilli, G. R. Halford

1992-01-01

119

Modeling and life prediction methodology for titanium matrix composites subjected to mission profiles  

SciTech Connect

Titanium matrix composites (TMCs) are being evaluated as structural materials for elevated temperature applications in future generation hypersonic vehicles. In such applications, TMC components are subjected to complex thermomechanical loading profiles at various elevated temperatures. Therefore, thermomechanical fatigue (TMF) testing, using a simulated mission profile, is essential for evaluation and development of life prediction methodologies. The objective of the research presented in this paper was to evaluate the TMF response of the [0/90]{sub 2s} SCS-6/TIMETAL-21S subjected to a generic hypersonic flight profile and its portions with a temperature ranging from {minus}130 to 816 C. It was found that the composite modulus, prior to rapid degradation, had consistent values for all the profiles tested. The accumulated minimum strain was also found to be the same for all the profiles tested. A micromechanics-based analysis was used to predict the stress-strain response of the laminate and of the constituents in each ply during thermomechanical loading conditions by using only constituent properties as input. The fiber was modeled as elastic with transverse orthotropic and temperature-dependent properties. The matrix was modeled using a thermoviscoplastic constitutive relationship. In the analysis, the composite modulus degradation was assumed to result from matrix cracking and was modeled by reducing the matrix modulus. Fatigue lives of the composite subjected to the complex generic hypersonic flight profiles were well correlated using the predicted stress in 0{degree} fibers.

Mirdamadi, M. [Analytical Services and Materials Inc., Hampton, VA (United States); Johnson, W.S. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Engineering

1996-12-31

120

Modeling and life prediction methodology for Titanium Matrix Composites subjected to mission profiles  

SciTech Connect

Titanium matrix composites (TMC) are being evaluated as structural materials for elevated temperature applications in future generation hypersonic vehicles. In such applications, TMC components are subjected to complex thermomechanical loading profiles at various elevated temperatures. Therefore, thermomechanical fatigue (TMF) testing, using a simulated mission profile, is essential for evaluation and development of life prediction methodologies. The objective of the research presented in this paper was to evaluate the TMF response of the (0/90)2s SCS-6/Timetal-21S subjected to a generic hypersonic flight profile and its portions with a temperature ranging from -130 C to 816 C. It was found that the composite modulus, prior to rapid degradation, had consistent values for all the profiles tested. A micromechanics based analysis was used to predict the stress-strain response of the laminate and of the constituents in each ply during thermomechanical loading conditions by using only constituent properties as input. The fiber was modeled as elastic with transverse orthotropic and temperature dependent properties. The matrix was modeled using a thermoviscoplastic constitutive relation. In the analysis, the composite modulus degradation was assumed to result from matrix cracking and was modeled by reducing the matrix modulus. Fatigue lives of the composite subjected to the complex generic hypersonic flight profile were well correlated using the predicted stress in 0 degree fibers.

Mirdamadi, M.; Johnson, W.S.

1994-08-01

121

Modeling and life prediction methodology for Titanium Matrix Composites subjected to mission profiles  

NASA Technical Reports Server (NTRS)

Titanium matrix composites (TMC) are being evaluated as structural materials for elevated temperature applications in future generation hypersonic vehicles. In such applications, TMC components are subjected to complex thermomechanical loading profiles at various elevated temperatures. Therefore, thermomechanical fatigue (TMF) testing, using a simulated mission profile, is essential for evaluation and development of life prediction methodologies. The objective of the research presented in this paper was to evaluate the TMF response of the (0/90)2s SCS-6/Timetal-21S subjected to a generic hypersonic flight profile and its portions with a temperature ranging from -130 C to 816 C. It was found that the composite modulus, prior to rapid degradation, had consistent values for all the profiles tested. A micromechanics based analysis was used to predict the stress-strain response of the laminate and of the constituents in each ply during thermomechanical loading conditions by using only constituent properties as input. The fiber was modeled as elastic with transverse orthotropic and temperature dependent properties. The matrix was modeled using a thermoviscoplastic constitutive relation. In the analysis, the composite modulus degradation was assumed to result from matrix cracking and was modeled by reducing the matrix modulus. Fatigue lives of the composite subjected to the complex generic hypersonic flight profile were well correlated using the predicted stress in 0 degree fibers.

Mirdamadi, M.; Johnson, W. S.

1994-01-01

122

Study on Composition Distribution and Ferromagnetism of Monodisperse FePt Nanoparticles  

PubMed Central

Monodisperse FePt nanoparticles with size of 4.5 and 6.0 nm were prepared by simultaneous reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl in benzylether. The crystallography structure, size, and composition of the FePt nanoparticles were examined by X-ray diffraction and transmission electron microscopy. Energy dispersive X-ray spectrometry measurements of individual particles indicate a broad compositional distribution in both the 4.5 and 6 nm FePt nanoparticles. The effects of compositional distribution on the phase-transition and magnetic properties of the FePt nanoparticles were investigated. PMID:20672087

2010-01-01

123

Study on Composition Distribution and Ferromagnetism of Monodisperse FePt Nanoparticles.  

PubMed

Monodisperse FePt nanoparticles with size of 4.5 and 6.0 nm were prepared by simultaneous reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl in benzylether. The crystallography structure, size, and composition of the FePt nanoparticles were examined by X-ray diffraction and transmission electron microscopy. Energy dispersive X-ray spectrometry measurements of individual particles indicate a broad compositional distribution in both the 4.5 and 6 nm FePt nanoparticles. The effects of compositional distribution on the phase-transition and magnetic properties of the FePt nanoparticles were investigated. PMID:20672087

Wang, Hb; Wang, H; Zhang, J; Yang, Fj; Xu, Ym; Li, Q

2010-01-01

124

Dynamis: Dynamic Overlay Service Composition for Distributed Stream Processing  

Microsoft Academic Search

Advanced Internet services, such as those for processing data streams from sensor networks, often need to support complex operations to meet the needs of multiple user groups. Exploiting resources of distributed nodes to compose services in an overlay network is one approach to addressing this problem. To compose services, an overlay infrastructure needs to support dynamic adaptation to varying conditions

Farshad A. Samimi; Philip K. Mckinley

2008-01-01

125

DISTRIBUTION AND CATCH COMPOSITION OF JONAH CRAB, CANCER BOREALIS, AND ROCK CRAB, CANCER IRRORATUS,  

E-print Network

DISTRIBUTION AND CATCH COMPOSITION OF JONAH CRAB, CANCER BOREALIS, AND ROCK CRAB, CANCER IRRORATUS ofJonah crab, Cancer borealis, and rock crab, C. irroratus, collected near Boothbay Harbor, Maine, revealed dissimilarities in the distribution of the two species. Jonah crabs were more numerous

126

Application of reliability and fiber probabilistic strength distribution concepts to composite vessel burst strength design  

Microsoft Academic Search

A composite pressure vessel design approach that is based on reliability and probabilistic fiber strength distribution concepts is discussed. The method is based on the fiber strain-strength interference reliability theory. The way in which fiber strength distribution parameters generated by two tensile tests of impregnated carbon fiber strands can be used in pressure vessel strength design is examined. It is

David Cohen

1992-01-01

127

Composition and distribution of surfactants around Lake Chini, Malaysia.  

PubMed

This study aims to determine the composition of surfactants in the lake surface microlayer, rainwater, and atmospheric aerosols in the area surrounding Lake Chini, Pahang. Surfactants in the lake surface microlayer were taken from seven different stations around the lake, while samples of rainwater were taken from five different sampling stations. The samples of atmospheric aerosols were collected from the Lake Chini Research Centre which is in close proximity to the lake. The colorimetric analysis method was used to determine the composition and concentration of anionic surfactants as methylene blue active substances (MBAS) and cationic surfactants as disulphine blue active substances (DBAS). The concentration of anionic surfactants, as MBAS, in the surface microlayer ranged between 0.08 to 0.23 ?mol L(-1), while the range of concentration of cationic surfactants as DBAS ranged from 0.09 to 0.11 ?mol L(-1). The concentration of MBAS was higher in rainwater when compared to surfactants in the lake surface microlayer. The high concentration of surfactants in the fine mode of atmospheric aerosols suggests that natural and anthropogenic sources of surfactants contribute to the atmospheric surfactants. PMID:21472384

Latif, Mohd Talib; Wanfi, Lim; Hanif, Norfazrin Mohd; Roslan, Razarul Naim; Ali, Masni Mohd; Mushrifah, Idris

2012-03-01

128

Constituent-Based Life Models Being Developed for SiC/SiC Composites  

NASA Technical Reports Server (NTRS)

For the successful utilization of ceramic matrix composites (CMC) as hot-section components in advanced aeropropulsion engines, the CMC constituents will need to be tailored and optimized to meet all the critical property demands of each component. Under the High-Speed Research (HSR) and Advanced High-Temperature Engine Materials Technology (HITEMP) Programs, the NASA Glenn Research Center at Lewis Field initiated research to develop mechanistic models for key CMC thermostructural properties. These models would describe the effects of different constituent factors (composition, geometry, and volume fraction) and of potential application conditions (stress, time, temperature, and environment) on these properties. Particular focus was placed on both analytical and numerical modeling of state-of-the-art SiC/SiC composites where the primary load-bearing constituents are stoichiometric SiC fibers in a complex multiphase SiC matrix produced by chemical vapor infiltration and melt infiltration. Recent studies have resulted in computer-based numerical models for the elastic modulus, thermal expansion, and thermal conductivity properties of the SiC/SiC system. Additional studies have generated analytical and empirical models for the time dependence of composite rupture strength at temperatures above 2200 F (1200 C), where CMC's have an important thermostructural advantage over current nickel-based superalloys. These life models utilize thermal activation theory and fiber stress-rupture results measured at Glenn to generate Larson-Miller (L M) plots of fiber rupture strength versus q, a single time- and temperature-dependent parameter. Assuming a worse case in which the SiC matrix is cracked, rupture is then controlled by the time-dependent fracture characteristics of the fiber bundles bridging the matrix cracks. With this as the controlling mechanism, one can then use simple composite theory and the fiber L M plots to predict CMC rupture strength versus the q parameter. The dashed line shows the predicted rupture strength of a SiC/SiC composite that is reinforced by a state-of-the-art stoichiometric SiC fiber. For the q parameter, time is in hours and temperature in degrees kelvin. To generate these predictions, a two-dimensional 0 /90 composite with approximately 16 percent fiber in the applied stress direction and an air test environment were assumed. As such, it is possible to compare the model predictions against limited stress-rupture data for this CMC as shown by the data points. The good agreement confirms the rupture model at least for the selected CMC and test conditions. Thus for this particular SiC/SiC composite, one can estimate a 1000-hr rupture strength of approximately 12 ksi at 2400 F (T = 1588 K and q = 39 700 K). At lower CMC application stresses, the SiC matrix is typically uncracked, so both the fiber and matrix constituents share the composite load. In this case, CMC rupture is controlled by the constituent with the longest rupture time based on the creep rate of the composite. Measured Monkman-Grant plots of rupture time versus creep rate for the two SiC constituents have been used to develop CMC life models for this important application condition. NASA and DOD are currently using this information to establish application and material goals for more advanced CMC's that can be used at even higher temperatures.

DiCarlo, James A.; Yun, Hee Mann

2000-01-01

129

Composite Weibull-Inverse Transformed Gamma distribution and its actuarial application  

NASA Astrophysics Data System (ADS)

This paper introduces a new composite model, namely, composite Weibull-Inverse Transformed Gamma distribution which assumes Weibull distribution for the head up to a specified threshold and inverse transformed gamma distribution beyond it. The closed form of probability density function (pdf) as well as the estimation of parameters by maximum likelihood method is presented. The model is compared with several benchmark distributions and their performances are measured. A well-known data set, Danish fire loss data, is used for this purpose and it's Value at Risk (VaR) using the new model is computed. In comparison to several standard models, the composite Weibull- Inverse Transformed Gamma model proved to be a competitor candidate.

Maghsoudi, Mastoureh; Bakar, Shaiful Anuar Abu; Hamzah, Nor Aishah

2014-07-01

130

Evaluation of the probability distribution of pitting corrosion fatigue life in aircraft materials  

NASA Astrophysics Data System (ADS)

Corrosion and fatigue properties of aircraft materials are known to have a considerable scatter due to the random nature of materials, loading, and environmental conditions. A probabilistic approach for predicting the pitting corrosion fatigue life has been investigated which captures the effect of the interaction of the cyclic load and corrosive environment and all stages of the corrosion fatigue process (i.e. the pit nucleation and growth, pit-crack transition, short- and long-crack propagation). The probabilistic model investigated considers the uncertainties in the initial pit size, corrosion pitting current, and material properties due to the scatter found in the experimental data. Monte Carlo simulations were performed to define the failure probability distribution. Predicted cumulative distribution functions of fatigue life agreed reasonably well with the existing experimental data.

Qingyuan, Wang; Kawagoishi, N.; Chen, Q.; Pidaparti, R. M.

2003-06-01

131

Kinetics of Formation of Molecular Weight Distribution of Epoxy Composite  

NASA Astrophysics Data System (ADS)

Curing of epoxy matrix prepreg in free space environment is a complex problem. A simulation of the chemical reaction, evaporation and radiation effects in the matrix is a way to understand and predict the curing process. We have developed a mathematical apparatus of the epoxy resin kinetics in term of molecular weight distribution (MWD), which includes the polymerization mechanism of bifunctional epoxy and sixfunctional triethylenetetraamine (TETA) molecules. The mathematical model for a number of molecules with the mass m at time t is based on the following equation $ beta(t,m)=m_{am} / m sum(6}_{i=0) alpha(am) _i (t,m)+ m_{ep} / m sum(2}_{i=0) alpha(ep) _i (t,m), where m_{am} and m_{ep} are the masses of one amine block and one epoxy block, respectively; alpha^{am}_i (t,m) is the MWD near the TETA blocks with the chemical bonds i at time t for the mass values m>0; alpha_i^{ep}(t,m) is the MWD parameters of the epoxy blocks with chemical bonds i at time t for the mass values m>0. For the distribution densities alpha^{am}_i (t,m) and alpha_i^{ep}(t,m), we propose the differential system of equations, which has been solved by applying boundary conditions which are based on the results of chromatography and infrared spectroscopy measurements of the epoxy matrix having different concentration of the hardener. For the initial MWD we accept a Gaussian distribution with parameters alpha^{am}_0 (t,m_1) =146 amu, alpha_0^{ep}(t,m_1) =340 amu and alpha_1^{ep}(t,m_1) =624 amu. Dispersion of the molecular weight for the initial distribution equals to 25 amu. A portion of TETA molecules in the fraction was 25%, and the portion of epoxy molecules with i=0 and i=1 was 67.5% and 7.5%$, respectively. Solutions were obtained at mass step equals to 5 amu and at time step equals to 0.25 min over the interval from 0 to 500 min. The model gives a full kinetic of MWD during the curing reaction. The study is supported by the RFBR (grants N 12-08-00970-a and N 14-08-96011-r-ural-a).

Komar, Lyudmila A.; Kondyurin, Alexey; Svistkov, Alexander L.

132

Ion composition and energy distribution during 10 magnetic storms  

NASA Technical Reports Server (NTRS)

Data from the plasma composition experiment of ISEE 1 are used to investigate the relative quantities and energy characteristics of H(+), He(++), He(+), and O(+) ions in the near-equatorial magnetosphere during magnetic storm conditions. The ions in the study had energies between 0.1 and 17 keV/e and pitch angles between 45 and 135 deg. The data were obtained during 10 storms, for the most part at or immediately following the peak Dst, covering all major local time sectors and geocentric distances between 2 and 15 earth radii. The ion fluxes are averaged over the spacecraft spin angle and over time for periods ranging from about 20 min close to the earth to more than an hour in most distant regions. The inferred 'isotropic' number densities are characterized by a large to dominant fraction of terrestrial ions throughout the energy range covered. The data are found to be consistent with a terrestrial origin for all of the O(+), most of the He(+), and a large but varying fraction of the H(+), whereas the He(++) and part of the H(+) appear to be of solar wind origin.

Lennartsson, W.; Sharp, R. D.; Shelley, E. G.; Johnson, R. G.; Balsiger, H.

1981-01-01

133

Multi-scale mechanism based life prediction of polymer matrix composites for high temperature airframe applications  

NASA Astrophysics Data System (ADS)

A multi-scale mechanism-based life prediction model is developed for high-temperature polymer matrix composites (HTPMC) for high temperature airframe applications. In the first part of this dissertation the effect of Cloisite 20A (C20A) nano-clay compounding on the thermo-oxidative weight loss and the residual stresses due to thermal oxidation for a thermoset polymer bismaleimide (BMI) are investigated. A three-dimensional (3-D) micro-mechanics based finite element analysis (FEA) was conducted to investigate the residual stresses due to thermal oxidation using an in-house FEA code (NOVA-3D). In the second part of this dissertation, a novel numerical-experimental methodology is outlined to determine cohesive stress and damage evolution parameters for pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic cohesive layer model was implemented in an in-house FEA code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. Double cantilever beam (DCB) experiments were conducted (at UT-Dallas) on both pristine and isothermally aged IM-7/BMI composite specimens to determine the model parameters. The J-Integral based approach was adapted to extract cohesive stresses near the crack tip. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic cohesive layer model to numerically simulate the DCB experiment. FEA simulation accurately captures the macro-scale behavior (load-displacement history) simultaneously with the micro-scale behavior (crack-growth history).

Upadhyaya, Priyank

134

Spatial distribution of total, ammonia-oxidizing, and denitrifying bacteria in biological wastewater treatment reactors for bioregenerative life support.  

PubMed

Bioregenerative life support systems may be necessary for long-term space missions due to the high cost of lifting supplies and equipment into orbit. In this study, we investigated two biological wastewater treatment reactors designed to recover potable water for a spacefaring crew being tested at Johnson Space Center. The experiment (Lunar-Mars Life Support Test Project-Phase III) consisted of four crew members confined in a test chamber for 91 days. In order to recycle all water during the experiment, an immobilized cell bioreactor (ICB) was employed for organic carbon removal and a trickling filter bioreactor (TFB) was utilized for ammonia removal, followed by physical-chemical treatment. In this study, the spatial distribution of various microorganisms within each bioreactor was analyzed by using biofilm samples taken from four locations in the ICB and three locations in the TFB. Three target genes were used for characterization of bacteria: the 16S rRNA gene for the total bacterial community, the ammonia monooxygenase (amoA) gene for ammonia-oxidizing bacteria, and the nitrous oxide reductase (nosZ) gene for denitrifying bacteria. A combination of terminal restriction fragment length polymorphism (T-RFLP), sequence, and phylogenetic analyses indicated that the microbial community composition in the ICB and the TFB consisted mainly of Proteobacteria, low-G+C gram-positive bacteria, and a Cytophaga-Flexibacter-Bacteroides group. Fifty-seven novel 16S rRNA genes, 8 novel amoA genes, and 12 new nosZ genes were identified in this study. Temporal shifts in the species composition of total bacteria in both the ICB and the TFB and ammonia-oxidizing and denitrifying bacteria in the TFB were also detected when the biofilms were compared with the inocula after 91 days. This result suggests that specific microbial populations were either brought in by the crew or enriched in the reactors during the course of operation. PMID:11976099

Sakano, Yuko; Pickering, Karen D; Strom, Peter F; Kerkhof, Lee J

2002-05-01

135

Optimizing Powder Distribution in Production of Surface Nano-Composite via Friction Stir Processing  

NASA Astrophysics Data System (ADS)

Notwithstanding the extensive interest in using friction stir processing (FSP) for producing metal matrix composite (MMC), more uniform powder distribution along the composite zone is still needed. In most studies, one groove is machined out of the specimen, filled with powder, and then processed by identical passes. In this investigation, an innovative technique was used that involved machining out of three gradient grooves with increasing depth from the advancing side to the retreating side instead of using a conventional sample with just a groove. Macro, optical, and scanning electron microscopy (SEM) images and microhardness test were used to evaluate the powder distribution. The images indicated that the most uniform distribution of SiC particles in the whole composite zone was related to a three-gradient grooves sample. Microohardness measurement of a three-gradient grooves sample, carried out along the cross section and perpendicular to the traverse direction of FSP, experiences less fluctuation in hardness compared with other techniques.

Heydarian, Arash; Dehghani, Kamran; Slamkish, Taymor

2014-06-01

136

Composition of engineering web services with distributed data-flows and computations  

Microsoft Academic Search

This paper describes an experimental Flow-based Infrastructure for Composing Autonomous Services (FICAS), which supports a service-composition paradi gm that integrates loosely- coupled software components. For traditional software service composition frameworks, the data-flows and control-flows are centrally coordinated, and the co mposed service operates as the hub for all data communications. FICAS, on the other hand, employs a distributed data flow

David Liu; Jun Peng; Kincho H. Law; Gio Wiederhold; Ram D. Sriram

2005-01-01

137

Effects of particle size distribution and composition on rheological properties of dark chocolate  

Microsoft Academic Search

Control of chocolate viscosity is vital to its quality and production cost, and directly influenced by solids particle size\\u000a distribution (PSD) and composition. Effects of PSD and composition on rheological properties of molten dark chocolate were\\u000a investigated by varying PSD [D90 (90% finer than this size) of 18, 25, 35 and 50 ?m], fat 25, 30 and 35% and lecithin (0.3

Emmanuel Ohene Afoakwa; Alistair Paterson; Mark Fowler

2008-01-01

138

Probability distributions for the strength of composite materials. III: The effect of fiber arrangement  

Microsoft Academic Search

This paper continues the study of the chain-of-bundles model for the statistical strength of composite materials. The focus is onthree-dimensional composites where the fibers in a cross-section form atwo-dimensional array. In particular, two-layer tapes and hexagonal arrays are considered, and bounding distributions are obtained based on the occurrence of at least two adjacent fiber fractures in the material. As in

R. E. Pitt; S. L. Phoenix

1982-01-01

139

Application of a Fiber Optic Distributed Strain Sensor System to Woven E-Glass Composite  

NASA Technical Reports Server (NTRS)

A distributed strain sensing system utilizing a series of identically written Bragg gratings along an optical fiber is examined for potential application to Composite Armored Vehicle health monitoring. A vacuum assisted resin transfer molding process was used to fabricate a woven fabric E-glass/composite panel with an embedded fiber optic strain sensor. Test samples machined from the panel were mechanically tested in 4-point bending. Experimental results are presented that show the mechanical strain from foil strain gages comparing well to optical strain from the embedded sensors. Also, it was found that the distributed strain along the sample length was consistent with the loading configuration.

Anastasi, Robert F.; Lopatin, Craig

2001-01-01

140

Simulations of Fiber Distribution Effects in Fiber-Reinforced Cement Composites  

SciTech Connect

This paper describes a lattice model for coupled moisture transport/stress analyses of fiber-reinforced cement composites (FRCC). Each fiber, and its interface with the matrix material, is explicitly represented within the three-dimensional material volume. This enables the direct study of fiber orientation and distribution effects on composite performance. Realistic, nonuniform fiber distributions can be specified as model input. Basic applications of the model are presented, with emphasis toward simulating the durability mechanics of FRCC exposed to drying environments. The modeling of functionally graded FRCC is an obvious potential extension of this work.

Bolander, John E. [Department of Civil and Environmental Engineering, University of California, Davis Davis, CA 95616-5294 (United States); Lim, Yun Mook [School of Civil and Environmental Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

2008-02-15

141

Minimum life-cycle cost heat losses for shallow-trench underground heat distribution systems  

SciTech Connect

The rates of heat loss from two underground insulated pipes installed in a shallow trench were calculated using a computer program based on the application of the finite-element method to solution of two-dimensional steady heat-conduction problems. The calculated results of pipe heat loss under a specified ground-temperature condition are summarized for a range of pipe-insulation thickness, different sizes of shallow trench, and various pipe fluid temperatures. Methods of determining the minimum life-cycle cost heat loss and the corresponding economic insulation thickness for shallow-trench heat distribution systems are presented. Life-cycle-costing analysis was performed for two insulated pipes in a concrete trench to determine the cost of construction, annual energy cost associated with pipe heat loss, and yearly operating and maintenance costs.

Fang, J.B.

1986-05-01

142

Determinants of Change in Stroke-Specific Quality of Life After Distributed Constraint-Induced Therapy  

PubMed Central

OBJECTIVE. We identified the predictive factors of change in quality of life (QOL) after a distributed form of constraint-induced therapy (dCIT) among stroke survivors. METHOD. Seventy-four participants were treated with dCIT. We identified eight potential determinants of change: age, gender, side of lesion, time since stroke, cognitive status, motor impairment of the upper extremity, activities of daily living (ADLs), and instrumental ADLs (IADLs). The Stroke-Specific Quality of Life Scale (SS–QOL) was used to assess QOL. RESULTS. Right-sided lesion and onset >17 mo earlier determined greater improvement in the SS–QOL Energy domain. Onset >10 mo earlier, poorer IADL performance, and age >68 yr predicted improvement in the Family Role, Mobility, and Mood domains, respectively. CONCLUSION. Side of lesion, time since stroke, IADL performance, and age were the most important determinants of QOL in patients receiving stroke motor rehabilitation. PMID:23245783

Huang, Yan-Hua; Wu, Ching-Yi; Hsieh, Yu-Wei; Snow, Wilaiwan M.; Wang, Tien-Ni

2013-01-01

143

25 CFR 179.201 - How does the Secretary distribute principal and income to the holder of a life estate without...  

Code of Federal Regulations, 2012 CFR

...distribute principal and income to the holder of a life estate without regard to waste? 179.201 ...DEPARTMENT OF THE INTERIOR LAND AND WATER LIFE ESTATES AND FUTURE INTERESTS Life Estates Created Under AIPRA § 179.201...

2012-04-01

144

25 CFR 179.201 - How does the Secretary distribute principal and income to the holder of a life estate without...  

Code of Federal Regulations, 2010 CFR

...distribute principal and income to the holder of a life estate without regard to waste? 179.201 ...DEPARTMENT OF THE INTERIOR LAND AND WATER LIFE ESTATES AND FUTURE INTERESTS Life Estates Created Under AIPRA § 179.201...

2010-04-01

145

25 CFR 179.201 - How does the Secretary distribute principal and income to the holder of a life estate without...  

Code of Federal Regulations, 2011 CFR

...distribute principal and income to the holder of a life estate without regard to waste? 179.201 ...DEPARTMENT OF THE INTERIOR LAND AND WATER LIFE ESTATES AND FUTURE INTERESTS Life Estates Created Under AIPRA § 179.201...

2011-04-01

146

25 CFR 179.201 - How does the Secretary distribute principal and income to the holder of a life estate without...  

Code of Federal Regulations, 2013 CFR

...distribute principal and income to the holder of a life estate without regard to waste? 179.201 ...DEPARTMENT OF THE INTERIOR LAND AND WATER LIFE ESTATES AND FUTURE INTERESTS Life Estates Created Under AIPRA § 179.201...

2013-04-01

147

Synergy: Sharing-Aware Component Composition for Distributed Stream Processing Systems  

Microsoft Academic Search

Many emerging on-line data analysis applications require applying continuous query operations such as correlation, aggregation, and filtering to data streams in real-time. Distributed stream processing s ystems allow in-network stream processing to achieve better scalability and qualit y-of-service (QoS) pro- vision. In this paper we present Synergy, a distributed stream processing mid- dleware that provides sharing-aware component composition. Synergy enables

Thomas Repantis; Xiaohui Gu; Vana Kalogeraki

2006-01-01

148

QoS-Aware Shared Component Composition for Distributed Stream Processing Systems  

Microsoft Academic Search

Many emerging online data analysis applications require applying continuous query operations such as correlation, aggregation, and filtering to data streams in real time. Distributed stream processing systems allow in-network stream processing to achieve better scalability and quality-of-service (QoS) provision. In this paper, we present Synergy, a novel distributed stream processing middleware that provides automatic sharing-aware component composition capability. Synergy enables

Thomas Repantis; Xiaohui Gu; Vana Kalogeraki

2009-01-01

149

Development of Elderly Quality of Life Index - Eqoli: Item Reduction and Distribution into Dimensions  

PubMed Central

OBJECTIVE To describe item reduction and its distribution into dimensions in the construction process of a quality of life evaluation instrument for the elderly. METHODS The sampling method was chosen by convenience through quotas, with selection of elderly subjects from four programs to achieve heterogeneity in the “health status”, “functional capacity”, “gender”, and “age” variables. The Clinical Impact Method was used, consisting of the spontaneous and elicited selection by the respondents of relevant items to the construct Quality of Life in Old Age from a previously elaborated item pool. The respondents rated each item’s importance using a 5-point Likert scale. The product of the proportion of elderly selecting the item as relevant (frequency) and the mean importance score they attributed to it (importance) represented the overall impact of that item in their quality of life (impact). The items were ordered according to their impact scores and the top 46 scoring items were grouped in dimensions by three experts. A review of the negative items was performed. RESULTS One hundred and ninety three people (122 women and 71 men) were interviewed. Experts distributed the 46 items into eight dimensions. Closely related items were grouped and dimensions not reaching the minimum expected number of items received additional items resulting in eight dimensions and 43 items. DISCUSSION The sample was heterogeneous and similar to what was expected. The dimensions and items demonstrated the multidimensionality of the construct. The Clinical Impact Method was appropriate to construct the instrument, which was named Elderly Quality of Life Index - EQoLI. An accuracy process will be examined in the future. PMID:18438571

Paschoal, Sergio Marcio Pacheco; Filho, Wilson Jacob; Litvoc, Julio

2008-01-01

150

Waste prevention in liquid detergent distribution: A comparison based on life cycle assessment.  

PubMed

The distribution of liquid detergents through self-dispensing systems has been adopted in some Italian retail stores over the last few years. By enabling the consumer to refill several times the same container, it is proposed as a less waste-generating and more environmentally friendly alternative to the traditional distribution with single-use plastic containers. For this reason, its implementation is encouraged by the national waste prevention programme recently adopted in Italy. In order to assess such claims, a life cycle assessment was carried out to evaluate whether detergent distribution through self-dispensing systems actually allows to achieve the expected reduction in waste generation and environmental impacts. The focus was on the distribution within the large-scale retail trade and on the categories of laundry detergents, fabric softeners and hand dishwashing detergents. For each of them, a set of baseline single-use scenarios were compared with two alternative waste prevention scenarios, where the detergent is distributed through self-dispensing systems. Beyond waste generation, also the Cumulative Energy Demand and thirteen midpoint-level potential impact indicators were calculated for the comparison. Results showed that a reduction in waste generation up to 98% can be achieved, depending on the category of detergent, on the baseline scenario of comparison and on the number of times the refillable container is used. A progressive reduction in the energy demand and in most of the potential impacts was also observed, starting from a minimum number of uses of the refillable container. PMID:25209251

Nessi, Simone; Rigamonti, Lucia; Grosso, Mario

2014-11-15

151

Nonparametric Fine Tuning of Mixtures: Application to Non-Life Insurance Claims Distribution Estimation  

NASA Astrophysics Data System (ADS)

When pricing a specific insurance premium, actuary needs to evaluate the claims cost distribution for the warranty. Traditional actuarial methods use parametric specifications to model claims distribution, like lognormal, Weibull and Pareto laws. Mixtures of such distributions allow to improve the flexibility of the parametric approach and seem to be quite well-adapted to capture the skewness, the long tails as well as the unobserved heterogeneity among the claims. In this paper, instead of looking for a finely tuned mixture with many components, we choose a parsimonious mixture modeling, typically a two or three-component mixture. Next, we use the mixture cumulative distribution function (CDF) to transform data into the unit interval where we apply a beta-kernel smoothing procedure. A bandwidth rule adapted to our methodology is proposed. Finally, the beta-kernel density estimate is back-transformed to recover an estimate of the original claims density. The beta-kernel smoothing provides an automatic fine-tuning of the parsimonious mixture and thus avoids inference in more complex mixture models with many parameters. We investigate the empirical performance of the new method in the estimation of the quantiles with simulated nonnegative data and the quantiles of the individual claims distribution in a non-life insurance application.

Sardet, Laure; Patilea, Valentin

152

The effects of chemical composition and distribution on the preservation of phytolith morphology  

NASA Astrophysics Data System (ADS)

Different types of phytolith even when coming from the same plant react to high temperatures in different ways. To understand the behavior of phytoliths upon heating, we examined composition and distribution of some elements within different phytolith types using SEM-EDS and synchrotron radiation ?-X-ray fluorescence. By analyzing phytoliths from rice husk, rice leaf and Than tree leaf, we find that the compositions and distributions of metal oxides within different phytolith types are quite different. It is well known that metal oxides have been used as fluxing agent to reduce the melting temperature of SiO2 in the production of glass, and different metal oxides can be used to produce a variety of glass with diverse features. Similarly, metal elements including potassium, magnesium and calcium in phytoliths should also act as a fluxing agent under high temperature, and the differential compositions and distributions of these metal elements within the phytoliths resulted in the variable reaction to heating. In sum, there is a negative relationship between the flux elements composition in phytoliths, and the temperatures at which phytoliths deform; furthermore, potassium and calcium in the rice leaf phytolith are almost evenly distributed in all parts, which may cause the phytolith's shape to deform evenly. In comparison, Than tree leaf phytolith is found to have a high percentage of potassium and calcium located exclusively on the outside, which may explain why the deformation of Than tree leaf phytolith occurs firstly at the outside.

Wu, Yan; Yang, Yimin; Wang, Hua; Wang, Changsui

2014-02-01

153

Species composition, abundance, habitat requirements and regional distribution of terrestrial gastropods in Arctic Norway  

Microsoft Academic Search

The species composition, abundance and habitat distributions of the terrestrial gastropods at lat. 70° N in Finnmark county, northern Norway were studied. Within an area with bedrocks of sandstone there were few snail species and abundance was low. Calciumrich bogs and birch woods with a luxuriant undergrowth had a richer gastropod fauna both in number of species and abundance. The

J. Andersen; O. Halvorsen

1984-01-01

154

Composition and On Demand Deployment of Distributed Brain Activity Analysis Application on Global Grids  

E-print Network

1 Composition and On Demand Deployment of Distributed Brain Activity Analysis Application on Global are brain science and high-energy physics. The analysis of brain activity data gathered from the MEG and analyze brain functions and requires access to large-scale computational resources. The potential platform

Abramson, David

155

Composition and distribution of suspended sediments in Lake Michigan during summer stratification  

Microsoft Academic Search

A quantitative description of the composition and distribution of suspended sediments is a necessary prerequisite to the determination of the transport and fate of those particles and of the chemical substances associated with them. This report is the first to make such a description for materials in the Great Lakes. Suspended sediment samples were collected from Lake Michigan during August

Eileen C. Harrsch; David K. Rea

1982-01-01

156

Effect of pH on Protein Distribution in Electrospun PVA/BSA Composite Nanofibers  

E-print Network

Effect of pH on Protein Distribution in Electrospun PVA/BSA Composite Nanofibers Christina Tang, A the nanofiber can be controlled by carefully selecting the pH and the applied polarity of the electric field as the pH affects the net charge on the proteins. Using fluorescently labeled BSA and surface analysis, we

Khan, Saad A.

157

Distribution, composition, and transport of suspended particulate matter in the vicinity of Willapa submarine canyon, Washington  

Microsoft Academic Search

The distribution and composition of suspended particulate matter in the waters over Willapa submarine canyon and the adjacent continental slope off the coast of Wasington describe an apparently continuous botton nepheloid layer ranging in thickness from 160 to 530 m and composed of particles supplied primarily by the nearby Columbia River. Near-bottom particulate concentrations, estimated by continuous vertical profiles of

EDWARD T. BAKER

1976-01-01

158

Probability distributions for the strength of composite materials I: two-level bounds  

Microsoft Academic Search

An upper bound is obtained on the probability distribution for the strength of composite materials. The analysis is based on the chain-of-bundles probability model, and local load sharing is assumed for the nonfailed fiber elements in each bundle. The bound is based on the occurence of two or more adjacent broken fibers in a bundle. This event is necessary but

D. G. Harlow; S. L. Phoenix

1981-01-01

159

COMPOSITION, ABUNDANCE, AND DISTRIBUTION OF ZOOPLANKTON IN THE NEW YORK BIGHT, SEPTEMBER 1974-SEPTEMBER 1975  

E-print Network

COMPOSITION, ABUNDANCE, AND DISTRIBUTION OF ZOOPLANKTON IN THE NEW YORK BIGHT, SEPTEMBER 1974 during autumn 1974 and summer 1975, an offshore (>50 m water depth) zooplankton abundance maximum in March dominated by the pteropodLimacina retroversa, a second offshore maximum in May characterized

160

Species composition and spatial distribution of euphausiids of the yellow sea and relationships with environmental factors  

Microsoft Academic Search

We investigated species composition and spatial distribution of the euphausiid community in the Yellow Sea and identified the relationship with environmental factors (temperature, salinity, chlorophyll a, nitrate, phosphate, and silicate) using bimonthly data from June, 1997 to April, 1998. The environment varied during the sampling period. In warm seasons, thermocline was well developed rendering lower temperature and higher salinity and

Won Duk Yoon; Joon Yong Yang; Donghyun Lim; Sung Hwan Cho; Gyung Soo Park

2006-01-01

161

A creep cavity growth model for creep-fatigue life prediction of a unidirectional W/Cu composite  

NASA Technical Reports Server (NTRS)

A microstructural model was developed to predict creep-fatigue life in a (0)(sub 4), 9 volume percent tungsten fiber-reinforced copper matrix composite at the temperature of 833 K. The mechanism of failure of the composite is assumed to be governed by the growth of quasi-equilibrium cavities in the copper matrix of the composite, based on the microscopically observed failure mechanisms. The methodology uses a cavity growth model developed for prediction of creep fracture. Instantaneous values of strain rate and stress in the copper matrix during fatigue cycles were calculated and incorporated in the model to predict cyclic life. The stress in the copper matrix was determined by use of a simple two-bar model for the fiber and matrix during cyclic loading. The model successfully predicted the composite creep-fatigue life under tension-tension cyclic loading through the use of this instantaneous matrix stress level. Inclusion of additional mechanisms such as cavity nucleation, grain boundary sliding, and the effect of fibers on matrix-stress level would result in more generalized predictions of creep-fatigue life.

Kim, Young-Suk; Verrilli, Michael J.; Halford, Gary R.

1992-01-01

162

Comparative life-cycle cost analysis of underground heat distribution systems  

SciTech Connect

An analytical model was developed to compare the life-cycle costs of two types of underground heat distributions systems: directly buried conduits and concrete trench installations. The costs of initial construction, routine maintenance, operation, repair, and replacement are represented in the model. Comparisons are made to explore the influence of failure rates, heat loss assumptions, the discount rate, and the policy on partial section replacement. Failure rate estimates are obtained from the literature and also from survey results obtained by the US Army. Life-cycle cost computations indicate that, when initial construction costs are the same, concrete trench installations have a cost advantage of $18--$42 per foot over buried steel conduit when other cost components are taken into account over a 25-year lifetime. The cost advantage of concrete trench over fiberglass reinforcement plastic (FRP) buried systems is $32--$133 per foot. The variation in the cost advantage reflects the variation in the estimate of the failure rate for buried steel and FRP systems. Routine maintenance was crucial for the buried systems to avoid dramatic increases in operation and replacement costs that would make the cost advantage of concrete trench installation even greater than stated above. In contrast, the low incidence of failure associated with concrete trench systems made their life-cycle costs relatively insensitive to maintenance policy.

Carnahan, J.V. [Univ. of Illinois, Urbana, IL (United States); Marsh, C. [Army Construction Engineering Research Lab., Champaign, IL (United States)

1998-11-01

163

Controls on the distribution and isotopic composition of helium in deep ground-water flows  

USGS Publications Warehouse

The distribution and isotopic composition of helium in sedimentary basins can be used to interpret the ages of very old ground waters. The piston-flow model commonly used in such interpretation, how ever, does not account for several important factors and as such works well only in very simple flow regimes. In this study of helium transport in a hypothetical sedimentary basin, we develop a numerical model that accounts for the magnitude and distribution of the basal helium flux, hydrodynamic dispersion, and complexities in flow regimes such as subregional flow cells. The modeling shows that these factors exert strong controls on the helium distribution and isotopic composition. The simulations may provide a basis for more accurate interpretations of observed helium concentrations and isotopic ratios in sedimentary basins.

Zhao, X.; Fritzel, T.L.B.; Quinodoz, H.A.M.; Bethke, C.M.; Torgersen, T.

1998-01-01

164

Sleep EEG composition in the first three months of life in monozygotic and dizygotic twins.  

PubMed

We investigated genetic influence on sleep electroencephalogram (EEG) composition by a classical twin study of monozygotic (MZ) and dizygotic (DZ) twins in the first 3 months of life. Polysomnographic (PSG) recordings were obtained in 10 MZ and 20 DZ twin pairs in the 37th, 46th, and 52nd week of postmenstrual age (PMA). The EEG power spectra were generated on the basis of fast Fourier transformation (FFT). Genetic influence on active sleep/rapid eye movement (AS/REM)] and quiet sleep/non rapid eye movement (QS/NREM) sleep composition was estimated by calculating within pair concordance and the intraclass correlation coefficients (ICCs) for delta (0.5-3.5 Hz), theta (4-7.5 Hz), alpha (8-11.5 Hz), sigma (12-14 Hz), and beta (14.5-20 Hz) at central derivation. MZ twins show higher ICCs than DZ twins for alpha, sigma, and beta spectral powers during QS/NREM sleep in the 37th, 46th, and 52nd week PMA. However, there was no significant difference (P > .05) between the 2 types of twins in absolute differences of EEG spectral power of the alpha, beta, and sigma frequency ranges in the 37th, 46th, and 52nd week PMA. The greatest mean absolute difference within MZ and DZ twin pairs and also between MZ and DZ twin groups was identified in the delta frequency range. Our findings gave an indication of genetic influence on alpha, sigma, and beta frequency ranges in the QS/NREM sleep stage. PMID:24323198

Vucinovic, Mirjana; Kardum, Goran; Bonkovic, Mirjana; Resic, Biserka; Ursic, Anita; Vukovics, Jonatan

2014-07-01

165

6-year changes in body composition in women at mid-life: ovarian and chronological aging  

PubMed Central

Context Understanding the menopause association with body weight is important because excess weight increases risk for stroke, incident cardiovascular disease, cardiovascular mortality, and all-cause mortality among the middle-aged. Objective To examine chronological age and ovarian age and consider how these could influence body size and composition in mid-life women. Design and Setting The Study of Women’s Health Across the Nation is a longitudinal, community-based study. This report uses data from the Michigan SWAN site. Participants 543 pre- or early perimenopausal African-American and Caucasian women aged 42–52 years at baseline examination. Main Outcome Measures Waist circumference, fat mass and skeletal muscle mass, from bioelectrical impedance, was assessed in 7 annual serial measures. Annual follicle-stimulating hormone (FSH) values were assayed by ELISA. The final menstrual period (FMP) was defined retrospectively following 12 months of amenorrhea. Results There was an absolute cumulative six-year increase in fat mass of 3.4 kg and a six-year decrease in skeletal muscle mass of ~0.23 kg. There was an absolute cumulative six-year increase of ~5.7 cm in waist circumference. The logFSH change was positively correlated with log(fat mass) change. Waist circumference increased over the time period, but one year following FMP, the rate of increase slowed. Fat mass continued to increase with no change in rate. Conclusions Both time (chronological aging) and ovarian aging contributed to substantial changes in body composition (fat and skeletal muscle mass) and waist circumference. These changes have important ramifications for establishing a metabolic environment that can be healthy or unhealthy. PMID:17192296

Sowers, MaryFran; Zheng, Huiyong; Tomey, Kristin; Karvonen-Gutierrez, Carrie; Jannausch, Mary; Li, Xizhao; Yosef, Matheos; Symons, James

2009-01-01

166

Phospholipid and triacylglycerol fatty acid composition of major life stages of sunn pest, Eurygaster integriceps (Heteroptera: Scutelleridae).  

PubMed

Phospholipid and triacylglycerol fatty acid compositions of whole animals from all life stages of Eurygaster integriceps, including eggs, nymphs, pre-diapausing adults and diapausing adults, were determined. The fatty acid composition of total lipids of their food, wheat, was also determined. The major components of the insects and their food were the expected C16 and C18 saturated and unsaturated fatty acids. Since fatty acid compositions of third-stadium nymphs were not similar to the profiles of their food, most likely, dietary fatty acids are modified by the insect. The fact is that the food does not provide C20 polyunsaturated fatty acids, but the insect tissue lipids include these components. We suggest biosynthesis of the C20 components by elongation/desaturation of C18:2n-6, an abundant component of the diets. We also show differences in fatty acid profiles from each of the life stages. PMID:12031463

Bashan, Mehmet; Akbas, Halit; Yurdakoc, Kadir

2002-06-01

167

The Effect of Cavity Shape and Hybrid Layer on the Stress Distribution of Cervical Composite Restorations  

PubMed Central

Objectives: The aim of this finite elemental stress analysis study was to evaluate the effect of cavity shape and hybrid layer on the stress distribution of the mandibular premolar tooth under occlusal loading. Methods: The mandibular premolar tooth was selected as the model based on the anatomical measurements suggested by Wheeler. Four different mathematical models were evaluated: 1) a saucer-shaped non-carious cervical lesion restored with a composite without a hybrid layer, 2) a saucer-shaped non-carious cervical lesion restored with a composite with a hybrid layer, 3) a wedge-shaped non-carious cervical lesion restored with a composite without a hybrid layer, and 4) a wedge-shaped non-carious cervical lesion restored with a composite with a hybrid layer. A 200 N force was applied from the buccal tubercule and central fossa of the premolar tooth. The findings were drawn by the SAPLOT program. Results: In models 2 and 4, the output showed that a hybrid layer acts as a stress absorber. Additionally, when the cavity shape was changed, the stress distribution was very different. Conclusions: Cavity shape and hybrid layer play an important role in stress distribution in cervical restorations. PMID:21494386

Eliguzeloglu, Evrim; Eraslan, Oguz; Omurlu, Huma; Eskitascioglu, Gurcan; Belli, Sema

2011-01-01

168

Antarctic Marine Biodiversity - What Do We Know About the Distribution of Life in the Southern Ocean?  

PubMed Central

The remote and hostile Southern Ocean is home to a diverse and rich community of life that thrives in an environment dominated by glaciations and strong currents. Marine biological studies in the region date back to the nineteenth century, but despite this long history of research, relatively little is known about the complex interactions between the highly seasonal physical environment and the species that inhabit the Southern Ocean. Oceanographically, the Southern Ocean is a major driver of global ocean circulation and plays a vital role in interacting with the deep water circulation in each of the Pacific, Atlantic, and Indian oceans. The Census of Antarctic Marine Life and the Scientific Committee on Antarctic Research Marine Biodiversity Information Network (SCAR-MarBIN) have strived to coordinate and unify the available scientific expertise and biodiversity data to improve our understanding of Southern Ocean biodiversity. Taxonomic lists for all marine species have been compiled to form the Register of Antarctic Marine Species, which currently includes over 8,200 species. SCAR-MarBIN has brought together over 1 million distribution records for Southern Ocean species, forming a baseline against which future change can be judged. The sample locations and numbers of known species from different regions were mapped and the depth distributions of benthic samples plotted. Our knowledge of the biodiversity of the Southern Ocean is largely determined by the relative inaccessibility of the region. Benthic sampling is largely restricted to the shelf; little is known about the fauna of the deep sea. The location of scientific bases heavily influences the distribution pattern of sample and observation data, and the logistical supply routes are the focus of much of the at-sea and pelagic work. Taxa such as mollusks and echinoderms are well represented within existing datasets with high numbers of georeferenced records. Other taxa, including the species-rich nematodes, are represented by just a handful of digital records. PMID:20689841

Griffiths, Huw J.

2010-01-01

169

Life Limiting Behavior in Interlaminar Shear of Continuous Fiber-Reinforced Ceramic Matrix Composites at Elevated Temperatures  

NASA Technical Reports Server (NTRS)

Interlaminar shear strength of four different fiber-reinforced ceramic matrix composites was determined with doublenotch shear test specimens as a function of test rate at elevated temperatures ranging from 1100 to 1316 C in air. Life limiting behavior, represented as interlaminar shear strength degradation with decreasing test rate, was significant for 2-D crossplied SiC/MAS-5 and 2-D plain-woven C/SiC composites, but insignificant for 2-D plain-woven SiC/SiC and 2-D woven Sylramic (Dow Corning, Midland, Michigan) SiC/SiC composites. A phenomenological, power-law delayed failure model was proposed to account for and to quantify the rate dependency of interlaminar shear strength of the composites. Additional stress rupture testing in interlaminar shear was conducted at elevated temperatures to validate the proposed model. The model was in good agreement with SiC/MAS-5 and C/SiC composites, but in poor to reasonable agreement with Sylramic SiC/SiC. Constant shear stress-rate testing was proposed as a possible means of life prediction testing methodology for ceramic matrix composites subjected to interlaminar shear at elevated temperatures when short lifetimes are expected.

Choi, Sung R.; Calomino, Anthony M.; Bansal, Narottam P.; Verrilli, Michael J.

2006-01-01

170

Loading Analysis of Composite Wind Turbine Blade for Fatigue Life Prediction of Adhesively Bonded Root Joint  

NASA Astrophysics Data System (ADS)

Nowadays wind energy is widely used as a non-polluting cost-effective renewable energy resource. During the lifetime of a composite wind turbine which is about 20 years, the rotor blades are subjected to different cyclic loads such as aerodynamics, centrifugal and gravitational forces. These loading conditions, cause to fatigue failure of the blade at the adhesively bonded root joint, where the highest bending moments will occur and consequently, is the most critical zone of the blade. So it is important to estimate the fatigue life of the root joint. The cohesive zone model is one of the best methods for prediction of initiation and propagation of debonding at the root joint. The advantage of this method is the possibility of modeling the debonding without any requirement to the remeshing. However in order to use this approach, it is necessary to analyze the cyclic loading condition at the root joint. For this purpose after implementing a cohesive interface element in the Ansys finite element software, one blade of a horizontal axis wind turbine with 46 m rotor diameter was modelled in full scale. Then after applying loads on the blade under different condition of the blade in a full rotation, the critical condition of the blade is obtained based on the delamination index and also the load ratio on the root joint in fatigue cycles is calculated. These data are the inputs for fatigue damage growth analysis of the root joint by using CZM approach that will be investigated in future work.

Salimi-Majd, Davood; Azimzadeh, Vahid; Mohammadi, Bijan

2014-07-01

171

Tool life and hole quality in drilling aramid and fibrous composites  

NASA Astrophysics Data System (ADS)

This paper deals with the behavior of the twist drills intended for aramid composites and with the quality of the holes produced with various process parameters. The experimental apparatus consists of a precision drilling machine instrumented with automatic feeding, piezo-electric load transducer and position sensor. It is connected to a personal computer via an analog to digital card for data acquisition and analysis. The hole quality has been assessed by means of both optical microscopy and digital image processing. The results concern the influence of the tool wear on thrust force, cutting torque and hole quality. The thrust force is significantly affected by tool accidental breakages, whilst the cutting torque has an almost constant trend. The study of the damaged zones shows that at the entry side no correlation exists between hole quality and working conditions, while at the exit side a significant correlation can be drawn between the damage and the maximum thrust force. Therefore, the monitoring of this latter could be effective for the best performance of the twist drill during its life.

di Ilio, A.; Tagliaferri, V.; Veniali, F.

172

A Comparison of Various Stress Rupture Life Models for Orbiter Composite Pressure Vessels and Confidence Intervals  

NASA Technical Reports Server (NTRS)

In conjunction with a recent NASA Engineering and Safety Center (NESC) investigation of flight worthiness of Kevlar Ovenvrapped Composite Pressure Vessels (COPVs) on board the Orbiter, two stress rupture life prediction models were proposed independently by Phoenix and by Glaser. In this paper, the use of these models to determine the system reliability of 24 COPVs currently in service on board the Orbiter is discussed. The models are briefly described, compared to each other, and model parameters and parameter error are also reviewed to understand confidence in reliability estimation as well as the sensitivities of these parameters in influencing overall predicted reliability levels. Differences and similarities in the various models will be compared via stress rupture reliability curves (stress ratio vs. lifetime plots). Also outlined will be the differences in the underlying model premises, and predictive outcomes. Sources of error and sensitivities in the models will be examined and discussed based on sensitivity analysis and confidence interval determination. Confidence interval results and their implications will be discussed for the models by Phoenix and Glaser.

Grimes-Ledesma, Lorie; Murthy, Pappu, L. N.; Phoenix, S. Leigh; Glaser, Ronald

2006-01-01

173

The relationship among distributive and procedural justice and correctional life satisfaction, burnout, and turnover intent: An exploratory study  

Microsoft Academic Search

Distributive and procedural justice, two dimensions of organizational justice, have been found to be salient antecedents of many correctional staff attitudes, such as job stress, job satisfaction, and organizational commitment; however, little correctional research has examined their relationships with the life satisfaction, burnout, and turnover intent. Multivariate regression equations were estimated to determine the association of personal characteristics, distributive justice,

Eric G. Lambert; Nancy L. Hogan; Shanhe Jiang; O. Oko Elechi; Barbaranne Benjamin; Angela Morris; John M. Laux; Paula Dupuy

2010-01-01

174

Investigation of the effect of matrix volume fraction on fiber stress distribution in polypropylene fiber composite using a simulation method  

Microsoft Academic Search

The study of the fracture behavior of polypropylene\\/glass fiber (PP\\/GF) composites can be an interesting subject for many investigators. Since glass fiber and polypropylene have different elastic moduli, a complex stress distribution will be developed when the composite body is loaded uniaxially in the direction of fibers. Thus, the prediction of stress distribution by using a simulation method can be

M. Homayonifar; S. M. Zebarjad

2007-01-01

175

Determing Lamprey Species Composition, Larval Distribution, and Adult Abundance in the Deschutes River, Oregon, Subbasin; 2005-2006 Annual Report.  

SciTech Connect

Information about lamprey species composition, distribution, life history, abundance, habitat requirements, and exploitation in the lower Deschutes River Subbasin is extremely limited. During 2002, we began a multi-year study to assess the status of lamprey in the Deschutes River subbasin. The objectives of this project are to determine ammocoete (larval lamprey) distribution and associated habitats; Lampretra species composition; numbers of emigrants; adult escapement and harvest rates at Sherars Falls. This report describes the preliminary results of data collected during 2005. We continued documenting ammocoete (larval) habitat selection by surveying four perennial eastside tributaries to the Deschutes River (Warm Springs River, Badger, Beaver and Shitike creeks) within the known ammocoete distribution. The results of 2003-2005 sampling indicate that positive relationships exist between: presence of wood (P = < 0.001), depositional area (P = < 0.001), flow (P = < 0.001), and fine substrate (P = < 0.001). Out-migrants numbers were not estimated during 2005 due to our inability to recapture marked larvae. In Shitike Creek, ammocoete and microphthalmia out-migration peaked during November 2005. In the Warm Spring River, out-migration peaked for ammocoetes in April 2006 and December 2005 for microphthalmia. Samples of ammocoetes from each stream were retained in a permanent collection of future analysis. An escapement estimate was generated for adult Pacific lamprey in the lower Deschutes River using a two event mark-recapture experiment during run year 2005. A modified Peterson model was used to estimate the adult population of Pacific lamprey at 3,895 with an estimated escapement of 2,881 during 2005 (95% CI= 2,847; M = 143; C = 1,027 R = 37). A tribal creel was also conducted from mid-June through August. We estimated tribal harvest to be approximately 1,015 adult lamprey during 2005 (95% CI= +/- 74).

Graham, Jennifer C.; Brun, Christopher V. (Confederated Tribes of the Warm Springs Reservation of Oregon, Department of Natural Resources, John Day, OR)

2006-05-01

176

Molecular insight into systematics, host associations, life cycles and geographic distribution of the nematode family Rhabdiasidae.  

PubMed

Rhabdiasidae Railliet, 1915 is a globally distributed group of up to 100 known species of nematodes parasitic in amphibians and reptiles. This work presents the results of a molecular phylogenetic analysis of 36 species of Rhabdiasidae from reptiles and amphibians from six continents. New DNA sequences encompassing partial 18S rDNA, ITS1, 5.8S rDNA, ITS2 and partial 28S rDNA regions of nuclear ribosomal DNA were obtained from 27 species and pre-existing sequences for nine species were incorporated. The broad taxonomic, host and geographical coverage of the specimens allowed us to address long-standing questions in rhabdiasid systematics, evolution, geographic distribution, and patterns of host association. Our analysis demonstrated that rhabdiasids parasitic in snakes are an independent genus sister to the rest of the Rhabdiasidae, a status supported by life cycle data. Based on the combined evidence of molecular phylogeny, morphology and life cycle characteristics, a new genus Serpentirhabdias gen. nov. with the type species Serpentirhabdias elaphe (Sharpilo, 1976) comb. nov. is established. The phylogeny supports the monophyly of Entomelas Travassos, 1930, Pneumonema Johnston, 1916 and the largest genus of the family, Rhabdias Stiles and Hassall, 1905. DNA sequence comparisons demonstrate the presence of more than one species in the previously monotypic Pneumonema from Australian scincid lizards. The distribution of some morphological characters in the genus Rhabdias shows little consistency within the phylogenetic tree topology, in particular the apical structures widely used in rhabdiasid systematics. Our data suggest that some of the characters, while valuable for species differentiation, are not appropriate for differentiation among higher taxa and are of limited phylogenetic utility. Rhabdias is the only genus with a cosmopolitan distribution, but some of the lineages within Rhabdias are distributed on a single continent or a group of adjacent zoogeographical regions. Serpentirhabdias, Entomelas and Pneumonema show rather strict specificity to their host groups. The evolution of the Rhabdiasidae clearly included multiple host switching events among different orders and families of amphibians as well as switching between amphibians and squamatan reptiles. Only a few smaller lineages of Rhabdias demonstrate relatively strict associations with a certain group of hosts. PMID:24560917

Tkach, Vasyl V; Kuzmin, Yuriy; Snyder, Scott D

2014-04-01

177

Recycling and reuse of waste from electricity distribution networks as reinforcement agents in polymeric composites.  

PubMed

Of the waste generated from electricity distribution networks, wooden posts treated with chromated copper arsenate (CCA) and ceramic insulators make up the majority of the materials for which no effective recycling scheme has been developed. This study aims to recycle and reuse this waste as reinforcement elements in polymer composites and hybrid composites, promoting an ecologically and economically viable alternative for the disposal of this waste. The CCA wooden posts were cut, crushed and recycled via acid leaching using 0.2 and 0.4N H2SO4 in triplicate at 70°C and then washed and dried. The ceramic insulators were fragmented in a hydraulic press and separated by particle size using a vibrating sieve. The composites were mixed in a twin-screw extruder and injected into the test specimens, which were subjected to physical, mechanical, thermal and morphological characterization. The results indicate that the acid treatment most effective for removing heavy metals in the wood utilizes 0.4NH2SO4. However, the composites made from wood treated with 0.2NH2SO4 exhibited the highest mechanical properties of the composites, whereas the use of a ceramic insulator produces composites with better thermal stability and impact strength. This study is part of the research and development project of ANEEL (Agência Nacional de Energia Elétrica) and funded by CPFL (Companhia Paulista de Força e Luz). PMID:23663959

Zimmermann, Matheus V G; Zattera, Ademir J

2013-07-01

178

Impact of early life ovariectomy on blood pressure and body composition in a female mouse model of systemic lupus erythematosus.  

PubMed

Because of the preponderance of women affected by the chronic autoimmune disease systemic lupus erythematosus (SLE), estrogen is thought to contribute to SLE disease progression. This is supported by evidence from experimental animal models of SLE showing that removal of estrogen in young female mice delays autoantibody production and renal injury and lengthens survival. Blood pressure and changes in body composition are important cardiovascular risk factors that can be regulated by estrogens. Because cardiovascular disease is the leading cause of death in patients with SLE, we used an established female mouse model of SLE (NZBWF1) to test whether early life removal of estrogen impacts the development of hypertension and changes in body composition commonly associated with SLE. Eight-week-old female SLE and control mice (NZW/LacJ) underwent either a sham operation or ovariectomy. Body weight, body composition (fat and lean masses), and renal injury (albuminuria) were monitored until mice reached 34 wk of age, at which time mean arterial pressure was assessed in conscious animals by a carotid catheter. Early life removal of the ovaries delayed the onset of autoantibody production and albuminuria while causing an increase in body weight and fat mass. Blood pressure in the adult was not altered by early life removal of the ovaries. These data suggest that estrogens may have a permissive role for the development of SLE while helping to maintain normal body weight and composition, which is associated with reduced cardiovascular risk. PMID:25324553

Gilbert, Emily L; Ryan, Michael J

2014-10-15

179

Distribution and abundance of the life stages of the blue shark Prionace glauca in the Southwest Atlantic  

Microsoft Academic Search

The composition and magnitude of the catches of the life stages of both sexes of the blue shark Prionace glauca were recorded at sea from 2004 to 2006 during seven commercial longline fishing cruises off Southern Brazil between latitudes of 24°S and 38°S and longitudes 29°W and 52°W. P. glauca occurred in all sets and constituted 63% of the pooled

Santiago Montealegre-Quijano; Carolus M. Vooren

2010-01-01

180

Fine root distribution and persistence under field conditions of three co-occurring Great Basin species of different life form  

Microsoft Academic Search

Summary • Fine roots of an annual grass, a perennial grass and a perennial shrub were examined. Based on life histories and tissue composition, we expected the greatest root persistence for the shrub and shortest for the annual grass. • Roots were observed with minirhizotrons over 2 yr for number, length and diameter changes. A Cox proportional hazard regression correlated

Michael S. Peek; A. Joshua Leffler; Carolyn Y. Ivans; Ronald J. Ryel; Martyn M. Caldwell

2004-01-01

181

Life  

NSDL National Science Digital Library

Run the classic game of life, learning about probabilities, chaos and simulation. This activity allows the user to run a randomly generated world or test out various patterns. This is a very powerful activity with a wide range of options. It runs in a separate window.

182

Distribution, chemistry, isotopic composition and origin of diagenetic carbonates: Magnus Sandstone, North Sea  

SciTech Connect

Diagenetic ferroan carbonates grew in the Upper Jurassic reservoir sandstones of the Magnus oilfield in porewaters which differed in composition across the field. These porewaters remained compositionally different and stratified for at least 35 M.y. Variations in carbonate chemistry across the field are attributable to these porewater variations, which resulted from displacement of marine depositional water from the crest of the field by meteoric water during late Cimmerian subaerial exposure. Original depositional facies and detrital mineralogy strongly influenced diagenetic carbonate distribution. The objective of this paper is twofold: (1) to describe the occurrence of burial diagenetic magnesian siderite and ankerite from the Magnus Sandstone, and (2) to show that variations in the elemental and isotopic geochemistry of siderite and ankerite relate to long-lived variations in the composition of the porewaters in the sandstone during diagenesis.

Macaulay, C.I.; Haszeldine, R.S. (Univ. of Glasgow (United Kingdom)); Fallick, A.E. (Scottish Univ. Research and Reactor Centre, Glasgow (United Kingdom))

1993-01-01

183

Composite  

NASA Astrophysics Data System (ADS)

Particle distribution and hot workability of an in situ Al-TiCp composite were investigated. The composite was fabricated by an in situ casting method using the self-propagating high-temperature synthesis of an Al-Ti-C system. Hot-compression tests were carried out, and power dissipation maps were constructed using a dynamic material model. Small globular TiC particles were not themselves fractured, but the clustering and grain boundary segregation of the particles contributed to the cracking of the matrix by causing the debonding of matrix/particle interfaces and providing a crack propagation path. The efficiency of power dissipation increased with increasing temperature and strain rate, and the maximum efficiency was obtained at a temperature of 723 K (450 °C) and a strain rate of 1/s. The microstructural mechanism occurring in the maximum efficiency domain was dynamic recrystallization. The role of particles in the plastic flow and the microstructure evolution were discussed.

Kim, Su-Hyeon; Cho, Young-Hee; Lee, Jung-Moo

2014-06-01

184

Habitat and distribution of post-recruit life stages of the squid Loligo forbesii  

NASA Astrophysics Data System (ADS)

This study models habitat preferences of the squid Loligo forbesii through its post-recruitment life cycle in waters around Scotland (UK). Trawl survey and market sample data from 1985 to 2004 are used to model seasonal habitats of immature, maturing and mature squid (maturity being inferred from size and season). Squid presence-absence and catch rate in areas of presence were analysed using generalised additive models, relating spatiotemporal patterns of distribution and abundance to ecogeographic variables. For all maturity classes, higher abundance in winter and spring (i.e., quarters 1 and 2) was associated with deeper water while higher abundance in summer and autumn (quarters 3 and 4) was associated with shallower water, consistent with seasonal onshore-offshore migrations but suggesting that most spawning may take place in deeper waters. The preferred SST range was generally 8-8.75 °C while preferred salinity values were below 35‰ in winter and summer and above 35‰ in spring and autumn. Squid were positively associated with gravel substrate and negatively associated with mud. Seasonal changes in habitat use were more clearly evident than changes related to inferred maturity, although the two effects cannot be fully separated due to the annual life cycle. Habitat selection for this species can be satisfactorily modelled on a seasonal basis; predictions based on such models could be useful for fishers to target the species more effectively, and could assist managers wishing to protect spawning grounds. The extent to which this approach may be useful for other cephalopods is discussed.

Smith, Jennifer M.; Macleod, Colin D.; Valavanis, Vasilis; Hastie, Lee; Valinassab, Tooraj; Bailey, Nick; Santos, M. Begoña; Pierce, Graham J.

2013-10-01

185

Determing Lamprey Species Composition, Larval Distribution, and Adult Abundance in the Deschutes River, Oregon, Subbasin; 2001-2002 Annual Report.  

SciTech Connect

Information about lamprey species composition, distribution, life history, abundance, habitat requirements and exploitation in lower Deschutes River tributaries is extremely limited. To assess the status of lampreys in the Deschutes River subbasin, baseline information is needed. We operated to rotary screw traps in the Warm Springs River and Shitike Creek to gain an understanding of species composition, migration time and production. We identified Pacific lampreys in two life stages, ammocoete and macropthalmia. It appears that Pacific lamprey macropthalmia out-migrate during winter in the Warm Springs River. We saw peak movements by ammocoetes in the spring in Shitike Creek and winter in the Warm Springs River. We found no relationship between stream discharge and the number of lamprey collected. Very few macropthalmia were collected in Shitike Creek. Ammocoete size in the Warm Springs River and Shitike Creek were different. The ammocoetes in the Shitike Creek trap were close in size to the macropthalmia collected in the Warm Springs River trap. We also completed planning and preparation for larval and associated habitat data collection. This preparation included purchasing necessary field equipment, selecting and marking sampling areas and attending training with US Fish and Wildlife Service (USFWS) and the Confederated Tribes of Umatilla Indian Reservation (CTUIR). Because lamprey identification is difficult we met with US Geological Survey (USGS) to assist us with larval lamprey identification techniques. We have also been working in coordination with the Oregon Department of Fish and Wildlife (ODFW) to prepare and implement creel surveys and a mark-recapture study at Sherar's Falls to estimate adult lamprey escapement.

Graham, Jennifer C.; Brun, Christopher V. (Confederated Tribes of the Warm Springs Reservation of Oregon, Department of Natural Resources)

2003-05-01

186

Composition and distribution of suspended sediments in Lake Michigan during summer stratification  

Microsoft Academic Search

A quantitative description of the composition and distribution of suspended sediments is a necessary prerequisite to the determination\\u000a of the transport and fate of those particles and of the chemical substances associated with them. This report is the first\\u000a to make such a description for materials in the Great Lakes. Suspended sediment samples were collected from Lake Michigan\\u000a during August

Eileen C. Harrsch; David K. Rea

1982-01-01

187

Maximum natural frequencies of polymer composite micro-beams by optimum distribution of carbon nanotubes  

Microsoft Academic Search

Optimum distribution of multi-walled carbon nanotubes (MWCNTs) within a polymer composite micro-beam is sought to achieve its highest natural frequencies given a weight percent (wt.%) of MWCNTs. To this end, the micro-beam is divided into ten segments which are perfectly bonded to their neighbors. Each segment is made of low-viscosity, thermosetting polyester epoxy\\/amine resin LY-5052 and is reinforced by MWCNTs.

Hossein Rokni; Abbas S. Milani; Rudolf J. Seethaler

2011-01-01

188

Probability distributions for the strength of composite materials II: A convergent sequence of tight bounds  

Microsoft Academic Search

A sequence of convergent upper bounds is developed for the probability distribution of strength of composite materials. The analysis is based on the well-known chain-of-bundles model, and local load sharing is assumed for the nonfailed fiber elements in each bundle. The bounds are based on the occurrence ofk or more adjacent broken fibers in a bundle, an event which is

D. G. Harlow; S. L. Phoenix

1981-01-01

189

Species composition and spatial distribution of euphausiids of the yellow sea and relationships with environmental factors  

Microsoft Academic Search

We investigated species composition and spatial distribution of the euphausiid community in the Yellow Sea and identified\\u000a the relationship with environmental factors (temperature, salinity, chlorophyll a, nitrate, phosphate, and silicate) using\\u000a bimonthly data from June, 1997 to April, 1998. The environment varied during the sampling period. In warm seasons, thermocline\\u000a was well developed rendering lower temperature and higher salinity and

Won Duk Yoon; Joon Yong Yang; Donghyun Lim; Sung Hwan Cho; Gyung Soo Park

2006-01-01

190

Modelling of ceramic matrix composite microstructure using a two-dimensional fractal spatial particle distribution  

NASA Astrophysics Data System (ADS)

Particulate composite reinforcements are good candidates for the fracture toughness of ceramics. In order to predict mechanical response of ceramic matrix composites, an efficient method capable of modelling their complex microstructure is needed. The purpose of this research is the development of such a model using fractal spatial particle distribution. A review of different toughness mechanisms for particulate composites and associated models for deriving their constitutive relationships is presented in chapter 2. These different toughening mechanisms as well constitutive properties depend on particle shape, size and spatial distribution, which lend themselves to a self-similar fractal based modelling approach. A self-similar distribution of particles linked to the fractal geometry is proposed. Fractal geometry provides an ideal tool for describing the randomness and disorder of the system. Its foundations are reviewed in chapter three with emphasis on iterated function systems that are subsequently used to obtain the particle configurations in the proposed model. For the sake of completeness, a review of fractal structure in science is given to illustrate possible applications. Derivation of the volume fraction associated with self similar distributions is provided in chapter 4. This is followed by a description of the numerical model and the boundary conditions. A Finite Element simulation is performed for different volume fractions, generators and number of particles for different displacements (two uniaxial and biaxial cases) and 2-D stress state cases. From these simulations the inverse distribution of the maximum principal stress is computed. Then the self similar models are compared with the model obtained by the Yang Teriari Gokhale (Y.T.G.) method and model obtained by only one iteration. Fractal dimension for real microstructure are computed and microstructure based on the fractal dimension and number of particle is simulated. It can be derived that the fractal dimension can be related to the average radius of circular particle in special cases. General conclusion and recommendation for future work brings this investigation to a close.

Cottet, Arnaud J.

191

Evaluation of flawed composite structural components under static and cyclic loading. [fatigue life of graphite-epoxy composite materials  

NASA Technical Reports Server (NTRS)

The effects of initial defects on the fatigue and fracture response of graphite-epoxy composite laminates are presented. The structural laminates investigated were a typical angle ply laminate, a polar/hoop wound pressure vessel laminate, and a typical engine fan blade laminate. Defects investigated were full and half penetration circular holes, full and half penetration slits, and countersink holes. The effects of the defect size and type on the static fracture strength, fatigue performance, and residual static strength are shown as well as the results of loadings on damage propagation in composite laminates. The data obtained were used to define proof test levels as a qualification procedure in composite structure subjected to cyclic loading.

Porter, T. R.

1979-01-01

192

Life cycle strain mapping of composite airframe structures by using FBG sensors  

NASA Astrophysics Data System (ADS)

The objective of this work is to develop a system for monitoring the structural integrity of composite airframe structures by strain mapping over the entire lifecycle of the structure. Specifically, we use fiber Bragg grating sensors to measure strain in a pressure bulkhead made of carbon fiber reinforced plastics (CFRPs) through a sequence of lifecycle stages (molding, machining, assembly, operation and maintenance) and detect the damage, defects, and deformation that occurs at each stage from the obtained strain distributions. In previous work, we have evaluated strain monitoring at each step in the FRP molding and machining stages of the lifecycle. In the work reported here, we evaluate the monitoring of the changes in strain that occur at the time of bolt fastening during assembly. The results show that the FBG sensors can detect the changes in strain that occur when a load is applied to the structure during correction of thermal deformation or when there is an offset in the hole position when structures are bolted together. We also conducted experiments to evaluate the detection of damage and deformation modes that occur in the pressure bulkhead during operation. Those results show that the FBG sensors detect the characteristic changes in strain for each mode.

Sekine, K.; Takahashi, I.; Kume, M.; Takeya, H.; Iwahori, Y.; Minakuchi, S.; Takeda, N.; Koshioka, Y.

2011-04-01

193

Species composition, richness, and distribution of marine bivalve molluscs in Bah?a de Mazatl?n, M?xico  

PubMed Central

Abstract We describe the composition and distribution of bivalve molluscs from the sandy and rocky intertidal and the shallow subtidal environments of Bahía de Mazatlán, México. The bivalve fauna of the bay is represented by 89 living species in 28 families, including 37 new records and four range extensions: Lithophaga hastasia, Adula soleniformis, Mactrellona subalata, and Strigilla ervilia. The number of species increases from the upper (44) and lower intertidal (53) to the shallow subtidal (76), but only 11 (17%) have a wide distribution in the bay (i.e., found in all sampling sites and environments). The bivalve assemblages are composed of four main life forms: 27 epifaunal species, 26 infaunal, 16 semi-infaunal, and 20 endolithic. A taxonomic distinctness analysis identified the sampling sites and environments that contribute the most to the taxonomic diversity (species to suborder categories) of the bay. The present work increased significantly (31%) to 132 species previous inventories of bivalves of Bahía de Mazatlán. These species represent 34% of the bivalve diversity of the southern Golfo de California and approximately 15% of the Eastern Tropical Pacific region. PMID:24843252

Esqueda-Gonzalez, Maria del Carmen; Rios-Jara, Eduardo; Galvan-Villa, Cristian Moises; Rodriguez-Zaragoza, Fabian Alejandro

2014-01-01

194

Software for analysis of chemical mixtures--composition, occurrence, distribution, and possible toxicity  

USGS Publications Warehouse

The composition, occurrence, distribution, and possible toxicity of chemical mixtures in the environment are research concerns of the U.S. Geological Survey and others. The presence of specific chemical mixtures may serve as indicators of natural phenomena or human-caused events. Chemical mixtures may also have ecological, industrial, geochemical, or toxicological effects. Chemical-mixture occurrences vary by analyte composition and concentration. Four related computer programs have been developed by the National Water-Quality Assessment Program of the U.S. Geological Survey for research of chemical-mixture compositions, occurrences, distributions, and possible toxicities. The compositions and occurrences are identified for the user-supplied data, and therefore the resultant counts are constrained by the user’s choices for the selection of chemicals, reporting limits for the analytical methods, spatial coverage, and time span for the data supplied. The distribution of chemical mixtures may be spatial, temporal, and (or) related to some other variable, such as chemical usage. Possible toxicities optionally are estimated from user-supplied benchmark data. The software for the analysis of chemical mixtures described in this report is designed to work with chemical-analysis data files retrieved from the U.S. Geological Survey National Water Information System but can also be used with appropriately formatted data from other sources. Installation and usage of the mixture software are documented. This mixture software was designed to function with minimal changes on a variety of computer-operating systems. To obtain the software described herein and other U.S. Geological Survey software, visit http://water.usgs.gov/software/.

Scott, Jonathon C.; Skach, Kenneth A.; Toccalino, Patricia L.

2013-01-01

195

Distribution of taxonomic classes and the compositional structure of the asteroid belt  

NASA Technical Reports Server (NTRS)

This paper reviews previous studies on the distribution of the asteroid taxonomic classes and analyzes the techniques, results, and interpretations of these studies, with special attention given to the strong and weak points of these studies and the important caveat for their interpretation. It is concluded that, in spite of the differences in class definition, the rather ordered heliocentric distribution of the composition is real and must be due to either primordial, evolutionary, or dynamical processes, or to a combination of all three. In general, the distribution of asteroid taxonomic classes is characterized by moderate-albedo asteroids dominant in the inner asteroid belt, and low-albedo asteroids prevalent in the outer belt and beyond.

Gradie, Jonathan C.; Chapman, Clark R.; Tedesco, Edward F.

1989-01-01

196

Fatigue life prediction and strength degradation of wind turbine rotor blade composites  

Microsoft Academic Search

Wind turbine rotor blades are subjected to a large number of highly variable loads, but life predictions are typically based on constant amplitude fatigue behaviour. Therefore, it is important to determine how service life under variable amplitude fatigue can be estimated from constant amplitude fatigue behaviour.\\u000a\\u000aA life prediction contains different, partly independent, elements:\\u000a·\\u0009the counting method, used for

R. P. L. Nijssen

2006-01-01

197

Enhancing Composition Window of Bicontinuous Structures by Designed Polydispersity Distribution of ABA Triblock Copolymers  

E-print Network

The phase behavior of polydisperse ABA triblock copolymers is studied using dissipative particle dynamics simulations, focusing on the emergence and property of bicontinuous structures. Bicontinuous structures are characterized by two separate, intermeshed nanoscopic domains extending throughout the material. The connectivity of polymeric bicontinuous structures makes them highly desirable for many applications. For conventional monodisperse diblock and triblock copolymers, regular bicontinuous structures (i.e., gyroid and Fddd) can be formed over a narrow composition window of ~3%. We demonstrate that the composition window for the formation of bicontinuous structures can be regulated by designed polydispersity distributions of ABA triblock copolymers. In particular, introducing polydispersity in both A and B blocks can lead to a significant enhancement of the composition window of bicontinuous structures with both continuous A and B domains. The mechanism of the bicontinuous structure enhancement is elucidated from the distribution of the long and short blocks. Furthermore, it is shown that the polymeric bicontinuous structures from polydisperse ABA triblock copolymers possess good continuity throughout the sample, making them ideal candidates for advanced applications.

Yue Li; Hu-Jun Qian; Zhong-Yuan Lu; An-Chang Shi

2013-10-22

198

Polymer beads in microtubule-filled composites: Effects on length distributions and permittivities  

NASA Astrophysics Data System (ADS)

The effects of adding poly(methylmethacrylate) beads to tubule-filled composites were examined in terms of changes in tubule distribution and dielectric properties of the composites. The beads had an average diameter of 51±29 ?m, whereas the copper-coated tubules, which were shaped like hollow cylinders and derived from a phospholipid template, had an average length of 30±22 ?m and an average diameter of 1 ?m. Incorporating a small amount of beads increased the permittivity value of the composite, but adding more beads resulted in a dramatic decrease in the permittivity value. In fact, a permittivity maximum appeared at around 5 vol % beads for various tubule loadings. The results could be explained in terms of volume exclusion and decreased tubule length effects. At low bead loadings, the volume exclusion effect dominated as the tubules were pushed closer together, resulting in a higher permittivity value. At higher bead loadings, the tubules were broken into shorter pieces and this became the dominant effect. Consequently, the shorter tubules formed fewer conducting pathways and the permittivity declined in value. In addition, the De Loor model for composites containing a dielectric matrix and conductors as fillers correctly predicted a permittivity maximum and provided the best fit to the permittivity data.

Chiou, Bor-Sen; Lankford, Andrew R.; Schoen, Paul E.

2004-01-01

199

A study of the charged ice grains in the Enceladus plume with a composite size distribution  

NASA Astrophysics Data System (ADS)

We study the negatively charged ice grains in the Enceladus plume ranging from nanometer to micrometer in size based on Cassini's multiple instrument observations. We have constructed a composite size distribution by combining the CAPS nanograin size distributions (Hill et al., 2012 JGR) and the CDA dust power-law size distribution (Kempf et al., 2008 Icarus). We also study the charging of the ice grains using RPWS-LP data (Morooka et al., 2011 JGR). E3 and E5 CDA data are not available, but RPWS detected impacts of micron sized dust grains with the same power law size distribution (Ye et al., 2012 AGU meeting). Our size distribution formula is fitted with E3 and E5 CAPS and RPWS data, and constrained with the total dust charge density inferred from the RPWS-LP cold plasma data. The fitting with E17 and E18 CAPS nanograin data (Tokar et al., 2012 AGU meeting) and RPWS dust data (Ye et al., 2013 MAPS workshop) will also be discussed. Based on the charge per grain and the size distribution, the densities, source rate, motion, and currents of the ice grains can be calculated. Our size distribution implies that the grains ~2-20 nm dominate in both charge density and number density. But the mass density is very sensitive to the larger grains. We discuss the mass densities and source rates with different size distribution parameters, and compare with the water vapor plume. We study the trajectories of the charged ice grains in both Enceladus and Saturn frames, and calculate the dust currents from their motion. We find that the total dust pickup current at Enceladus is ?10^5 A. We will also discuss the ion and dust current systems and resulting magnetic perturbations near the moon.

Dong, Y.; Hill, T. W.

2013-12-01

200

Effects of diet macronutrient composition on body composition and fat distribution during weight maintenance and weight loss  

PubMed Central

Qualitative aspects of diet may affect body composition and propensity for weight gain or loss. We tested the hypothesis that consumption of a relatively low glycemic load (GL) diet would reduce total and visceral adipose tissue under both eucaloric and hypocaloric conditions. Participants were 69 healthy overweight men and women. Body composition was assessed by DXA and fat distribution by CT scan at baseline, after 8 weeks of a eucaloric diet intervention, and after 8 weeks of a hypocaloric (1000 kcal/d deficit) diet intervention. Participants were provided all food for both phases, and randomized to either a low GL diet (?45 points per 1000 kcal; n=40) or high GL diet (>75 points per 1000 kcal, n=29). After the eucaloric phase, participants who consumed the low GL diet had 11% less intra-abdominal fat (IAAT) than those who consumed the high GL diet (P<0.05, adjusted for total fat mass and baseline IAAT). Participants lost an average of 5.8 kg during the hypocaloric phase, with no differences in the amount of weight loss with diet assignment (P=0.39). Following weight loss, participants who consumed the low GL diet had 4.4% less total fat mass than those who consumed the high GL diet (P<0.05, adjusted for lean mass and baseline fat mass). Consumption of a relatively low GL diet may affect energy partitioning, both inducing reduction in IAAT independent of weight change, and enhancing loss of fat relative to lean mass during weight loss. PMID:23671029

Goss, Amy M.; Goree, Laura Lee; Ellis, Amy C.; Chandler-Laney, Paula C.; Casazza, Krista; Lockhart, Mark E.; Gower, Barbara A.

2012-01-01

201

Fatigue life prediction and experiment research for composite laminates with circular hole  

Microsoft Academic Search

Based on the fatigue prediction model of exponential function and Whitney-Nuismer(WN) criterion of static strength for the\\u000a composite material laminate with a circular hole, the stress correct factor (?) was put forward and a new fatigue prediction\\u000a model for composite material laminate was set up. T300\\/KH304, which is recently studied and is a high capability composite\\u000a material, was used as

Hong-yu Qi; Wei-dong Wen; Lian-wen Xun

2004-01-01

202

Local-scale distribution of organic matter composition and wettability at surfaces of preferential flow paths  

NASA Astrophysics Data System (ADS)

Surfaces of preferential flow paths in structured soils consist of clay-organic coatings (i.e., cutanes) on soil aggregates or linings on biopores (i.e., worm burrows and decayed root channels). The outermost layer of such surfaces is mostly covered by organic matter (OM). The composition of this OM finally controls wettability and sorption properties that are relevant for transport along the flow path. However, the local distribution of OM-properties along such surfaces is largely unknown because analyzes without disturbing the coating layer surfaces have not been possible to date. The objective of this study is to compare the local 2D distribution of soil OM composition at intact aggregate and biopore surfaces with that of the wettability. The OM composition is determined using Fourier transformed infrared spectroscopy in diffuse reflectance mode (DRIFT) in terms of the ratios of CH/CO functional molecular groups. Intact surfaces of aggregated soil samples were scanned using a DRIFT mapping procedure in a 1 mm grid. Wettability was observed by means of contact angle measurements using a Goniometer with a high-speed camera. The aggregate sample surfaces were distinguished into regions of earthworm burrows, root channels, clay-organic coatings and uncoated regions. In contrast to the uncoated surface areas, organic coatings on worm burrows and root channels show relatively higher CH/CO-ratios that correspond with longer water drop infiltration. Both, the OM composition of coatings along preferential flow path surfaces and the water repellence are spatially variable at this local scale. The results indicate yet unknown implications for preferential flow and transport especially for reactive solutes.

Leue, Martin; Ellerbrock, Ruth H.; Gerke, Horst H.

2010-05-01

203

Free-standing carbon nanotube composite sensing skin for distributed strain sensing in structures  

NASA Astrophysics Data System (ADS)

The technical challenges of managing the health of critical infrastructure systems necessitate greater structural sensing capabilities. Among these needs is the ability for quantitative, spatial damage detection on critical structural components. Advances in material science have now opened the door for novel and cost-effective spatial sensing solutions specially tailored for damage detection in structures. However, challenges remain before spatial damage detection can be realized. Some of the technical challenges include sensor installations and extensive signal processing requirements. This work addresses these challenges by developing a patterned carbon nanotube composite thin film sensor whose pattern has been optimized for measuring the spatial distribution of strain. The carbon nanotube-polymer nanocomposite sensing material is fabricated on a flexible polyimide substrate using a layer-by-layer deposition process. The thin film sensors are then patterned into sensing elements using optical lithography processes common to microelectromechanical systems (MEMS) technologies. The sensor array is designed as a series of sensing elements with varying width to provide insight on the limitations of such patterning and implications of pattern geometry on sensing signals. Once fabrication is complete, the substrate and attached sensor are epoxy bonded to a poly vinyl composite (PVC) bar that is then tested with a uniaxial, cyclic load pattern and mechanical response is characterized. The fabrication processes are then utilized on a larger-scale to develop and instrument a component-specific sensing skin in order to observe the strain distribution on the web of a steel beam. The instrumented beam is part of a larger steel beam-column connection with a concrete slab in composite action. The beam-column subassembly is laterally loaded and strain trends in the web are observed using the carbon nanotube composite sensing skin. The results are discussed in the context of understanding the properties of the thin film sensor and how it may be advanced toward structural sensing applications.

Burton, Andrew R.; Minegishi, Kaede; Kurata, Masahiro; Lynch, Jerome P.

2014-04-01

204

On the Relationship Between Site Geology and the Distribution of Surface Regolith Compositions at the Apollo Sites  

NASA Technical Reports Server (NTRS)

Some considerations are discussed on how information on site geology can be obtained from the distribution of data points on 2-element plots of composition of lunar regolith samples collected along a traverse.

Korotev, Randy L.

2000-01-01

205

Phytoplankton distributions and species composition across the Texas-Louisiana continental shelf during two flow regimes of the Mississippi River  

E-print Network

Phytoplankton abundance and species composition were examined over the Texas-Louisiana continental shelf during May 1992 and May 1993, as part of a phytoplankton diversity study funded by the Office of Naval Research. Phytoplankton distribution data...

Bontempi, Paula Susan

2012-06-07

206

Astrobiology: The Study of the Origin, Evolution, and Distribution of Life in the Universe  

ERIC Educational Resources Information Center

Life as people know it here on Earth exchanges energy and materials with the environment. Life forms grow, develop, produce waste products, and reproduce, storing genetic information in DNA and RNA and passing it from one generation to the next. Life evolves, adapting to changes in the environment and changing the environment in return. The basic…

Scalice, Daniella; Wilmoth, Krisstina

2004-01-01

207

Electrical Resistance of SiC/SiC Ceramic Matrix Composites for Damage Detection and Life-Prediction  

NASA Technical Reports Server (NTRS)

Ceramic matrix composites (CMC) are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems due to their low density high thermal conductivity. The employment of these materials in such applications is limited by the ability to accurately monitor and predict damage evolution. Current nondestructive methods such as ultrasound, x-ray, and thermal imaging are limited in their ability to quantify small scale, transverse, in-plane, matrix cracks developed over long-time creep and fatigue conditions. CMC is a multifunctional material in which the damage is coupled with the material s electrical resistance, providing the possibility of real-time information about the damage state through monitoring of resistance. Here, resistance measurement of SiC/SiC composites under mechanical load at both room temperature monotonic and high temperature creep conditions, coupled with a modal acoustic emission technique, can relate the effects of temperature, strain, matrix cracks, fiber breaks, and oxidation to the change in electrical resistance. A multiscale model can in turn be developed for life prediction of in-service composites, based on electrical resistance methods. Results of tensile mechanical testing of SiC/SiC composites at room and high temperatures will be discussed. Data relating electrical resistivity to composite constituent content, fiber architecture, temperature, matrix crack formation, and oxidation will be explained, along with progress in modeling such properties.

Smith, Craig; Morscher, Gregory; Xia, Zhenhai

2009-01-01

208

Determination of Non-Symmetric 3-D Fiber-Orientation Distribution and Average Fiber Length in Short-Fiber Composites  

Microsoft Academic Search

A mathematical procedure is proposed for recovering from image analysis the three-dimensional (3-D) non-symmetric density distribution of fiber orientation and the average fiber length in short-fiber composites. The determination of fiber-orientation distribution and average fiber length is essential for assessing the mechanical and physical properties of a short-fiber composite. The average fiber length can be obtained from one micrograph, while

Y. T. Zhu; W. R. Blumenthal; T. C. Lowe

1997-01-01

209

Electromechanical response of 1–3 piezoelectric composites: A numerical model to assess the effects of fiber distribution  

Microsoft Academic Search

A finite element-based numerical model is developed to characterize the effects of fiber distribution in 1–3 piezoelectric active fiber\\/active matrix composites under primarily static electric fields and elastic stress conditions. Upon identifying 14 characteristic periodic and randomized fiber configurations, the influence of fiber distribution on the coupled response of model ceramic–matrix and polymer–matrix fiber composites with widely different constituent material

Ronit Kar-Gupta; T. A. Venkatesh

2007-01-01

210

The stress distribution and curvature of a general compositionally graded semiconductor layer  

NASA Astrophysics Data System (ADS)

The physical system considered is a thin, strained-layer structure. It is shown that the stress distribution and curvature for such a structure, with arbitrary compositional gradiation and with general thickness variation of temperature of epitaxial mismatch strain can be determined by means of elementary formulae. As an illustration, the results are applied to compute the stress in a GaAs/In xGa 1- xAs/In 0.12Ga 0.88As ternary epitaxial structure with X varying through the thickness of the 1185 middle layer.

Freud, L. B.

1993-09-01

211

Probabilistic Modeling of the Aeroelastic Life Cycle for Risk Evaluation of Composite Structures  

Microsoft Academic Search

Virtual aeroelastic tests using Monte Carlo simulations can be used to quantify the aeroelastic reliability of damage-tolerant composite aircraft structures, enabling aircraft manufacturers, operators, and flight certification authorities to establish design, maintenance and service guidelines that reduce lifecycle cost. A probabilistic \\/ reliability methodology and computer simulation capability for composite airframes is presented in this paper and used to study

Andrey V. Styuart; Luciano Demasi; Eli Livne; Kuen Y. Lin

212

Local Abundance Patterns of Noctuid Moths in Olive Orchards: Life-History Traits, Distribution Type and Habitat Interactions  

PubMed Central

Local species abundance is related to range size, habitat characteristics, distribution type, body size, and life-history variables. In general, habitat generalists and polyphagous species are more abundant in broad geographical areas. Underlying this, local abundance may be explained from the interactions between life-history traits, chorological pattern, and the local habitat characteristics. The relationship within taxa between life-history traits, distribution area, habitat characteristics, and local abundance of the noctuid moth (Lepidoptera: Noctuidae) assemblage in an olive orchard, one of the most important agro-ecosystems in the Mediterranean basin, was analyzed. A total of 66 species were detected over three years of year-round weekly samplings using the light-trap method. The life-history traits examined and the distribution type were found to be related to the habitat-species association, but none of the biological strategies defined from the association to the different habitats were linked with abundance. In contrast to general patterns, dispersal ability and number of generations per year explained differences in abundance. The relationships were positive, with opportunistic taxa that have high mobility and several generations being locally more abundant. In addition, when the effect of migrant species was removed, the distribution type explained abundance differences, with Mediterranean taxa (whose baricenter is closer to the studied area) being more abundant. PMID:21529251

Perez-Guerrero, Sergio; Redondo, Alberto Jose; Yela, Jose Luis

2011-01-01

213

D-STATCOM Control in Distribution Networks with Composite Loads to Ensure Grid Code Compatible Performance of  

E-print Network

of the uncertain system. The change in system model due to the variation of load compositions in the composite load Performance of Photovoltaic Generators N. K. Roy and H. R. Pota School of Engineering and IT The University of distribution networks with photovoltaic generators. The controller is designed based on the H norm

Pota, Himanshu Roy

214

Design for the Maximum Natural Frequency of Laminated Composite Plates by Optimally Distributed Short Fibers  

NASA Astrophysics Data System (ADS)

A new design method is proposed for vibration of functional fibrous composite plates, which imitate micro structures of natural materials such as bones and shells. The material has local anisotropy induced by optimally distributed short fibers which are defined in each element of the finite element method. To design such locally anisotropic plates, the present optimum design method combines a genetic algorithm method (GA) with a layerwise optimization (LO) concept. The LO concept reduces a multi-layer optimization into iterations of a single-layer optimization, and the GA is used for the single-layer optimization to determine fiber orientation angles in each element. The fundamental frequency of the plates is chosen as the objective function to be maximized. It was revealed that the present plates give higher fundamental frequencies than conventional plates reinforced by parallel straight fibers. Further optimally distributed short fibers indicated specific orientations even though no constraint was imposed on those directions.

Honda, Shinya; Narita, Yoshihiro

215

Life cycle and life strategy features of Puccinia glechomatis (Uredinales) favorable for extending the natural range of distribution  

Microsoft Academic Search

The objective of this study was to find features in microcyclic rust fungi (Uredinales) on wild host plants favorable for\\u000a extension of the natural range of distribution. Puccinia glechomatis, a leptosporic rust fungus and its herbal host Glechoma hederacea (Lamiaceae), both natives to Eurasia and introduced in North America, were used for this study. Although the host has been\\u000a known

Jörg Böllmann; Markus Scholler

2006-01-01

216

Life Prediction Issues in Thermal/Environmental Barrier Coatings in Ceramic Matrix Composites  

NASA Technical Reports Server (NTRS)

Issues and design requirements for the environmental barrier coating (EBC)/thermal barrier coating (TBC) life that are general and those specific to the NASA Ultra-Efficient Engine Technology (UEET) development program have been described. The current state and trend of the research, methods in vogue related to the failure analysis, and long-term behavior and life prediction of EBCITBC systems are reported. Also, the perceived failure mechanisms, variables, and related uncertainties governing the EBCITBC system life are summarized. A combined heat transfer and structural analysis approach based on the oxidation kinetics using the Arrhenius theory is proposed to develop a life prediction model for the EBC/TBC systems. Stochastic process-based reliability approach that includes the physical variables such as gas pressure, temperature, velocity, moisture content, crack density, oxygen content, etc., is suggested. Benefits of the reliability-based approach are also discussed in the report.

Shah, Ashwin R.; Brewer, David N.; Murthy, Pappu L. N.

2001-01-01

217

Transverse tension fatigue life characterization through flexure testing of composite materials  

Microsoft Academic Search

The transverse tension fatigue life of S2\\/8552 glass–epoxy and IM7\\/8552 carbon–epoxy was characterized using flexure tests of 90-degree laminates loaded in 3-point and 4-point bending. The influence of specimen polishing and specimen configuration on transverse tension fatigue life was examined using the glass–epoxy laminates. Results showed that 90-degree flexure specimens with polished machined edges and polished tension-side surfaces had lower

T. Kevin O'Brien; Arun D Chawan; Ronald Krueger; Isabelle L Paris

2002-01-01

218

Composition, diversity and distribution of microbenthos across the intertidal zones of Ryazhkov Island (the White Sea).  

PubMed

The composition and distribution of the main unicellular eukaryotic groups (diatom algae, ciliates, dinoflagellates (DF), other phototrophic (PF) and heterotrophic flagellates (HF)) were investigated in sandy sediments at five stations allocated across the tidal sheltered beach of the White Sea. Overall, 75 diatoms, 98 ciliates, 16 DF, 3 PF and 34 HF species were identified; some are new records for the White Sea. Common species for each group are illustrated. Diatoms and ciliates showed high alpha-diversity (species richness per sample), whereas flagellates were characterized by high beta-diversity (species turnover across the intertidal flat). Each group demonstrated its own spatial pattern that was best matched with its own subset of abiotic variables, reflecting group-specific responses to environmental gradients. Species richness increased from the upper intertidal zone seaward for ciliates but decreased for HF, whereas autotrophs showed a relatively uniform pattern with a slight peak at the mid-intertidal zone. Across the littoral zone, all groups showed distinct compositional changes; however, the position of the boundary between "upper" and "lower" intertidal communities varied among groups. Most of the species found at Ryazhkov Island are known from many other regions worldwide, indicating a wide geographic distribution of microbial eukaryotic species. PMID:23871644

Azovsky, Andrey; Saburova, Maria; Tikhonenkov, Denis; Khazanova, Ksenya; Esaulov, Anton; Mazei, Yuri

2013-11-01

219

The distribution of compositional classes in the asteroid belt: A cosmochemical fingerprint?  

NASA Technical Reports Server (NTRS)

Studies of the physical properties of the asteroids show a nonrandom distribution of types across the belt for asteroid classes E, S, M, F, C, P, and D. The general trend is for asteroids in the inner belt to have higher albedos and stronger mafic silicate absorption features than those asteroids located further out in the belt. One interpretation of this trend is that the asteroids, which occupy the region between the silicate rich terrestrial planets and the volatile rich outer planets, have preserved in their heliocentric compositional distribution a cosmochemical fingerprint of the thermodynamic conditions present in the solar nebula at the time of their formation. This hypothesis predicts that the differences in the spectral properties among the low albedo classes (C, P, F, P, and D) are due to temperature controlled processes which formed carbonaceous opaques. If this is true then the exact composition of the opaque components could, in principle, be used to determine the thermodynamic conditions between the orbits of Mars and Jupiter during the formation of the asteroids.

Gradie, J.

1985-01-01

220

Litter sex composition affects life-history traits in yellow-bellied marmots  

E-print Network

Charles E. Young Drive South, Los Angeles, CA 90095-1606, USA; and 2 Rocky Mountain Biological Laboratory-bellied marmots (Marmota flaviventris) and documented the effects of weaned litter sex composition and anogenital

Blumstein, Daniel T.

221

Molecular Structures of Polymer/Sulfur Composites for Lithium-Sulfur Batteries with Long Cycle Life  

SciTech Connect

Vulcanizedpolyaniline/sulfur (SPANI/S) nanostructures were investigated for Li-S battery applications, but the detailed molecular structures of such composites have not been fully illustrated. In this paper, we synthesize SPANI/S composites with different S content in a nanorod configuration. FTIR, Raman, XPS, XRD, SEM and elemental analysis methods are used to characterize the molecular structure of the materials. We provide clear evidence that a portion of S was grafted on PANI during heating and connected the PANI chains with disulfide bonds to form a crosslinked network and the rest of S was encapsulated within it.. Polysulfides and elementary sulfur nanoparticles are physically trapped inside the polymer network and are not chemically bound to the polymer. The performance of the composites is further improved by reducing the particle size. Even after 500 cycles a capacity retention rate of 68.8% is observed in the SPANI/S composite with 55% S content.

Xiao, Lifen; Cao, Yuliang; Xiao, Jie; Schwenzer, Birgit; Engelhard, Mark H.; Saraf, Laxmikant V.; Nie, Zimin; Exarhos, Gregory J.; Liu, Jun

2013-04-26

222

Structural investigation of composite wind turbine blade considering various load cases and fatigue life  

Microsoft Academic Search

This study proposes a structural design for developing a medium scale composite wind turbine blade made of E-glass\\/epoxy for a 750kW class horizontal axis wind turbine system. The design loads were determined from various load cases specified at the IEC61400-1 international specification and GL regulations for the wind energy conversion system. A specific composite structure configuration, which can effectively endure

C. Kong; J. Bang; Y. Sugiyama

2005-01-01

223

Somatic Maintenance Resources in the Honeybee Worker Fat Body Are Distributed to Withstand the Most Life-Threatening Challenges at Each Life Stage  

PubMed Central

In a global transcriptome analysis of three natural and three manipulated honeybee worker phenotypes at different ages, we have investigated the distribution of investment in somatic maintenance of the fat body. Gene expression is modulated so that the bees are able to resist the most life-threatening challenges at the actual life stage. Different modes of maintenance and repair are regulated, apparently to meet the environmental challenges most detrimental to survival and reproductive potential for the hive. We observed a broad down-regulation of genomic and cellular maintenance in the short-lived foragers and nurse bees compared to the long-lived winter bees. Our results show that survival and reproduction of the entire hive is given priority over the individual bees, hence supporting the idea of the honeybee society as a superorganism. Our results also fit the disposable soma theory of aging. PMID:23940531

Seehuus, Siri-Christine; Taylor, Simon; Petersen, Kjell; Aamodt, Randi M.

2013-01-01

224

A detailed investigation of ambient aerosol composition and size distribution in an urban atmosphere.  

PubMed

This research was executed between March 2009 and March 2010 to monitor particulate matter size distribution and its composition in Istanbul. Particulate matter composition was determined using ion chromatography and inductively coupled plasma optical emission spectrometry. The sampling point is adjacent to a crowded road and the Bosporus Strait. Two prevailing particulate modes are found throughout PM10 by sampling with a nine-stage low-volume cascade impactor. First mode in the fine mode is found to be between 0.43 and 0.65 ?m, whereas the other peak was observed between 3.3 and 4.7 ?m, referring to the coarse mode. The mean PM10 concentration was determined as 41.2 ?g/m(3), with a standard deviation of 16.92 ?g/m(3). PM0.43 had the highest mean concentration value of 10.67 ?g/m(3), making up nearly one fourth of the total PM10 mass. For determining the effect of traffic on particulate matter (PM) composition and distribution, four different sampling cycles were applied: entire day, nighttime, rush hour, and rush hour at weekdays. SO4(-2) and organic carbon/elemental carbon proportions are found to be lower in night samples, representing a decrease in traffic. The long-range transports of dust storms were observed during the sampling periods. Their effects were determined analytically and their route models were run by the HYSPLIT model and validated through satellite photographs taken by the NASA Earth Observatory. PMID:22968673

Kuzu, S Levent; Saral, Arslan; Demir, Selami; Summak, Gülsüm; Demir, Göksel

2013-04-01

225

On the limit theorem for life time distribution connected with some reliability systems and their validation by means of the Monte Carlo method  

NASA Astrophysics Data System (ADS)

We prove the limit theorem for life time distribution connected with reliability systems when their life time is a Pascal Convolution of independent and identically distributed random variables. We show that, in some conditions, such distributions may be approximated by means of Erlang distributions. As a consequnce, survival functions for such systems may be, respectively, approximated by Erlang survival functions. By using Monte Carlo method we experimantally confirm the theoretical results of our theorem.

Gheorghe, Munteanu Bogdan; Alexei, Leahu; Sergiu, Cataranciuc

2013-09-01

226

Analysis of fragmentation in the single filament composite: Roles of fiber strength distributions and exclusion zone models  

Microsoft Academic Search

Exact equations are derived governing the evolution of fragments in a long fiber loaded according to the “single filament composite test.” These equations are derived with no a priori assumptions regarding the distribution for fiber strength except that the distribution of fiber flaws along the length follows a compound Poisson process in terms of flaw strength. Furthermore, the interface model

C.-Y. Hui; S. L. Phoenix; L. Kogan

1996-01-01

227

A new decoupling method for accurate quantification of polyethylene copolymer composition and triad sequence distribution with 13C NMR  

NASA Astrophysics Data System (ADS)

13C NMR is a powerful analytical tool for characterizing polyethylene copolymer composition and sequence distribution. Accurate characterization of the composition and sequence distribution is critical for researchers in industry and academia. Some common composite pulse decoupling (CPD) sequences used in polyethylene copolymer 13C NMR can lead to artifacts such as modulations of the decoupled 13C NMR signals (decoupling sidebands) resulting in systematic errors in quantitative analysis. A new CPD method was developed, which suppresses decoupling sidebands below the limit of detection (less than 1:40,000 compared to the intensity of the decoupled signal). This new CPD sequence consists of an improved Waltz-16 CPD, implemented as a bilevel method. Compared with other conventional CPD programs this new decoupling method produced the cleanest 13C NMR spectra for polyethylene copolymer composition and triad sequence distribution analyses.

Zhou, Zhe; Kümmerle, Rainer; Qiu, Xiaohua; Redwine, David; Cong, Rongjuan; Taha, Angela; Baugh, Dan; Winniford, Bill

2007-08-01

228

Development of a fatigue-life methodology for composite structures subjected to out-of-plane load components  

NASA Technical Reports Server (NTRS)

The efforts to identify and implement a fatigue life methodology applicable to demonstrate delamination failures for use in certifying composite rotor blades are presented. The RSRA/X-Wing vehicle was a proof-of-concept stopped rotor aircraft configuration which used rotor blades primarily constructed of laminated carbon fiber. Delamination of the main spar during ground testing demonstrated that significant interlaminar stresses were produced. Analysis confirmed the presence of out-of-plane load components. The wear out (residual strength) methodology and the requirements for its implementation are discussed.

Sumich, Mark; Kedward, Keith T.

1991-01-01

229

Astrobiology: exploring the origins, evolution, and distribution of life in the Universe.  

PubMed

The search for the origins of life and its presence beyond Earth is strengthened by new technology and by evidence that life tolerates extreme conditions and that planets are widespread. Astrobiologists learn how planets develop and maintain habitable conditions. They combine biological and information sciences to decipher the origins of life. They examine how biota, particularly microorganisms, evolve, at scales from the molecular to the biosphere level, including interactions with long-term planetary changes. Astrobiologists learn how to recognize the morphological, chemical, and spectroscopic signatures of life in order to explore both extraterrestrial samples and electromagnetic spectra reflected from extrasolar planets. PMID:11543275

Des Marais, D J; Walter, M R

1999-01-01

230

Realistic modeling of environmental tracer migration and composite age distributions in a pine beetle impacted watershed  

NASA Astrophysics Data System (ADS)

Descriptions of age in hydrologic systems are often limited to the residence time in the surface water system or the subsurface with little consideration of the interaction between the two, or the different ways geochemical tracers are altered in each domain. Understanding the way tracer concentrations change in each domain is essential to accurate estimation of age, but few models have explicitly modeled the fully coupled system or considered distributions of age. This work presents a numerical laboratory that is specifically designed to investigate composite age distributions (CADs) and their connections to tracer concentrations. The CAD is defined here as the combination of the residence time distributions for surface flows, vadose zone, and groundwater systems, providing an accounting for the total time a discrete fluid parcel has spent within the integrated hydrologic system. CADs are generated by particle tracking through a fully integrated flow model and it is straight forward to realistically simulate the transport of environmental tracers such as 85-Krypton and 39-Argon that can be used for estimating water ages. This framework allows explicit modeling of the different processes in each domain that affect tracer concentrations including the mixing of different source waters, partial equilibrium with the atmosphere through the vadose zone, evaporative enrichment in surface flows, and diffusive fractionation in the subsurface. Transient forcings, such as seasonal or daily variations in precipitation, can also be simulated and the effects of this transience on concentrations and age distributions can easily be investigated. The model domain used to demonstrate these tools is based on a well-defined watershed within Rocky Mountain National Park. The mountain pine beetle has devastated the park's forests and the massive tree-kill has begun to affect the quality and distribution of the water resources. Accurate modeling of the CADs in the park is a crucial step in understanding the long-term environmental impacts of the infestation, and comparisons to measured concentrations are needed to validate those models, making it an ideal test platform. The flow model is a combination of deterministic and geostatistically specified properties that provides a realistic representation of the study site, with age distributions and tracer concentrations subsequently simulated by particle tracking. The simulated concentrations are used to compute inferred mean ages and estimates of the entire age distribution, which are then compared to the known CADs and the domain specific age distributions for several scenarios.

Engdahl, N. B.; Maxwell, R. M.

2013-12-01

231

A study of stiffness, residual strength and fatigue life relationships for composite laminates  

NASA Technical Reports Server (NTRS)

Qualitative and quantitative exploration of the relationship between stiffness, strength, fatigue life, residual strength, and damage of unnotched, graphite/epoxy laminates subjected to tension loading. Clarification of the mechanics of the tension loading is intended to explain previous contradictory observations and hypotheses; to develop a simple procedure to anticipate strength, fatigue life, and stiffness changes; and to provide reasons for the study of more complex cases of compression, notches, and spectrum fatigue loading. Mathematical models are developed based upon analysis of the damage states. Mathematical models were based on laminate analysis, free body type modeling or a strain energy release rate. Enough understanding of the tension loaded case is developed to allow development of a proposed, simple procedure for calculating strain to failure, stiffness, strength, data scatter, and shape of the stress-life curve for unnotched laminates subjected to tension load.

Ryder, J. T.; Crossman, F. W.

1983-01-01

232

Estimation of prokaryotic supergenome size and composition from gene frequency distributions  

PubMed Central

Background Because prokaryotic genomes experience a rapid flux of genes, selection may act at a higher level than an individual genome. We explore a quantitative model of the distributed genome whereby groups of genomes evolve by acquiring genes from a fixed reservoir which we denote as supergenome. Previous attempts to understand the nature of the supergenome treated genomes as random, independent collections of genes and assumed that the supergenome consists of a small number of homogeneous sub-reservoirs. Here we explore the consequences of relaxing both assumptions. Results We surveyed several methods for estimating the size and composition of the supergenome. The methods assumed that genomes were either random, independent samples of the supergenome or that they evolved from a common ancestor along a known tree via stochastic sampling from the reservoir. The reservoir was assumed to be either a collection of homogeneous sub-reservoirs or alternatively composed of genes with Gamma distributed gain probabilities. Empirical gene frequencies were used to either compute the likelihood of the data directly or first to reconstruct the history of gene gains and then compute the likelihood of the reconstructed numbers of gains. Conclusions Supergenome size estimates using the empirical gene frequencies directly are not robust with respect to the choice of the model. By contrast, using the gene frequencies and the phylogenetic tree to reconstruct multiple gene gains produces reliable estimates of the supergenome size and indicates that a homogeneous supergenome is more consistent with the data than a supergenome with Gamma distributed gain probabilities.

2014-01-01

233

[Floristic composition and distribution of the Andean subtropical riparian forests of Lules River, Tucuman, Argentina].  

PubMed

We studied the floristic composition and distribution of the riparian forest of two hydrographical systems in a subtropical Andean region. Using uni and multivariate techniques, we tested the hypotheses that a differentiable riparian forest exists, composed by native vegetation typical of the Yungas phytogeographical province, and that the distribution of vegetation varied significantly with geomorphologic characteristics. Parallel transects along the water courses were used to collect presence-absence data of vegetation in eleven sites. Detrended Correspondence Analysis defined a group of common riparian species for the studied area (Solanum riparium, Phenax laevigatus, Tipuana tipu, Cestrum parqui, Carica quercifolia, Acacia macracantha, Celtis iguanaea, Juglans australis, Pisoniella arborescens, Baccharis salicifolia, Cinnamomum porphyrium and Eugenia uniflora) and identified two reference sites. The distribution of the riparian vegetation varied significantly with the geomorphic characteristics along the studied sites. Riparian habitats were composed by native and exotic species. A distinct riparian flora, different in structure and function from adjacent terrestrial vegetation, could not be identified. Riparian species were similar to the adjacent terrestrial strata. These species would not be limited by the proximity to the river. Anthropogenic impacts were important factors regulating the introduction and increase of exotic vegetation. The lack of regulation of some activities in the zone could cause serious problems in the integrity of this ecosystem. PMID:20411737

Sirombra, Martín G; Mesa, Leticia M

2010-03-01

234

Life Cycle Modeling of Concrete Bridge Design: Comparison of Engineered Cementitious Composite Link Slabs  

E-print Network

in significant envi- ronmental burdens and social costs. There is an ongoing effort to identify material material consumption. Construction related traffic congestion is the greatest contributor to most life: Concrete infrastructure represents an enormous investment of materials, energy, and capital, and results

Lepech, Michael D.

235

Transverse Tension Fatigue Life Characterization Through Flexure Testing of Composite Materials  

NASA Technical Reports Server (NTRS)

The transverse tension fatigue life of S2/8552 glass-epoxy and IM7/8552 carbon-epoxy was characterized using flexure tests of 90-degree laminates loaded in 3-point and 4-point bending. The influence of specimen polishing and specimen configuration on transverse tension fatigue life was examined using the glass-epoxy laminates. Results showed that 90-degree bend specimens with polished machined edges and polished tension-side surfaces, where bending failures where observed, had lower fatigue lives than unpolished specimens when cyclically loaded at equal stress levels. The influence of specimen thickness and the utility of a Weibull scaling law was examined using the carbon-epoxy laminates. The influence of test frequency on fatigue results was also documented for the 4-point bending configuration. A Weibull scaling law was used to predict the 4-point bending fatigue lives from the 3-point bending curve fit and vice-versa. Scaling was performed based on maximum cyclic stress level as well as fatigue life. The scaling laws based on stress level shifted the curve fit S-N characterizations in the desired direction, however, the magnitude of the shift was not adequate to accurately predict the fatigue lives. Furthermore, the scaling law based on fatigue life shifted the curve fit S-N characterizations in the opposite direction from measured values. Therefore, these scaling laws were not adequate for obtaining accurate predictions of the transverse tension fatigue lives.

OBrien, T. Kevin; Chawan, Arun D.; Krueger, Ronald; Paris, Isabelle

2001-01-01

236

Nano-enhanced aerospace composites for increased damage tolerance and service life damage monitoring  

NASA Astrophysics Data System (ADS)

This study deals with new generation composite systems which apart from the primary reinforcement at the typical fiber scale (~10 ?m) are also reinforced at the nanoscale. This is performed via incorporation of nano-scale additives in typical aerospace matrix systems, such as epoxies. Carbon Nanotubes (CNTs) are ideal candidates as their extremely high aspect ratio and mechanical properties render them advantageous to other nanoscale materials. The result is the significant increase in the damage tolerance of the novel composite systems even at very low CNT loadings. By monitoring the resistance change of the CNT network, information both on the real time deformation state of the composite is obtained as a reversible change in the bulk resistance of the material, and the damage state of the material as an irreversible change in the bulk resistance of the material. The irreversible monotonic increase of the electrical resistance can be related to internal damage in the hybrid composite system and may be used as an index of the remaining lifetime of a structural component.

Paipetis, A.; Matikas, T. E.; Barkoula, N. M.; Karapappas, P.; Vavouliotis, A.; Kostopoulos, V.

2009-03-01

237

Base composition and gene distribution: critical patterns in mammalian genome organization.  

PubMed

Recent success in developing transcriptional maps of large genomic regions provide excellent opportunities for the investigation of mammalian genome organization. Detailed definition of organizational features will, in the short term, aid in prioritizing genomic sequencing efforts and in interpreting sequencing results and, in the long term, will surely provide insights into the structural, functional and evolutionary basis for the mammalian chromosome and chromosomal banding patterns. For such efforts, human chromosome 21 provides an excellent model system because the physical and clone maps are detailed, and several transcriptional mapping projects have provided large numbers of novel genes. It is, therefore, valuable at this point to examine these transcriptional mapping data and to compare them with the isochore model of the mammalian genome, which describes patterns in base composition and predicts gene distributions. Not only do compelling organizational patterns appear, but new questions about additional possible patterns in gene size, structure, conservation and transcription can be asked. PMID:9257535

Gardiner, K

1996-12-01

238

The role of composition-dependent catalyst structure on chirality distributions of as-grown SWCNTs  

NASA Astrophysics Data System (ADS)

The exemplary physiochemical properties of single-walled carbon nanotubes (SWCNTs) are largely determined by their diameter and chiral angle, specified as chiral indices (n,m). Despite the significant progress that has been made in purifying mixtures of SWCNTs to obtain monodisperse samples (in terms of chirality), large-scale applications require improvements in the homogeneity of as-grown SWCNTs. Recent reports have shown that a potential route to controlling the chirality distribution of SWCNTs during growth is through catalyst design [1,2]. In this talk, we present our approach which is based on tuning the catalyst composition, independent of size, to perturb the catalyst structure and ultimately influence the SWCNT chirality. 1. Harutyunyan et al., Science 326, 116 (2009). 2. Chiang et al., Nature Mater. 8, 882 (2009).

Mohan Sankaran, R.

2010-03-01

239

Effects of Life History Strategy on Fish Distribution and Use of Estuarine Salt Marsh and Shallow-Water Flat Habitats  

Microsoft Academic Search

To assess the potential for habitat isolation effects on estuarine nekton, we used two species with different dispersal abilities\\u000a and life history strategies, mummichog (Fundulus heteroclitus) and pinfish (Lagodon rhomboides) to examine: (1) distribution trends among estuarine shallow-water flat and various intertidal salt marsh habitats and (2)\\u000a the influence of salt marsh habitat size and isolation. Collections were conducted using

David L. Meyer; Martin H. Posey

2009-01-01

240

The bacteriological composition of biomass recovered by flushing an operational drinking water distribution system.  

PubMed

This study investigates the influence of pipe characteristics on the bacteriological composition of material mobilised from a drinking water distribution system (DWDS) and the impact of biofilm removal on water quality. Hydrants in a single UK Distribution Management Area (DMA) with both polyethylene and cast iron pipe sections were subjected to incremental increases in flow to mobilise material from the pipe walls. Turbidity was monitored during these operations and water samples were collected for physico-chemical and bacteriological analysis. DNA was extracted from the material mobilised into the bulk water before and during flushing. Bacterial tag-encoded 454 pyrosequencing was then used to characterize the bacterial communities present in this material. Turbidity values were high in the samples from cast iron pipes. Iron, aluminium, manganese and phosphate concentrations were found to correlate to observed turbidity. The bacterial community composition of the material mobilised from the pipes was significantly different between plastic and cast iron pipe sections (p < 0.5). High relative abundances of Alphaproteobacteria (23.3%), Clostridia (10.3%) and Actinobacteria (10.3%) were detected in the material removed from plastic pipes. Sequences related to Alphaproteobacteria (22.8%), Bacilli (16.6%), and Gammaproteobacteria (1.4%) were predominant in the samples obtained from cast iron pipes. The highest species richness and diversity were found in the samples from material mobilised from plastic pipes. Spirochaeta spp., Methylobacterium spp. Clostridium spp. and Desulfobacterium spp., were the most represented genera in the material obtained prior to and during the flushing of the plastic pipes. In cast iron pipes a high relative abundance of bacteria able to utilise different iron and manganese compounds were found such as Lysinibacillus spp., Geobacillus spp. and Magnetobacterium spp. PMID:24565801

Douterelo, I; Husband, S; Boxall, J B

2014-05-01

241

Decompression vs. Decomposition: Distribution, Amount, and Gas Composition of Bubbles in Stranded Marine Mammals  

PubMed Central

Gas embolic lesions linked to military sonar have been described in stranded cetaceans including beaked whales. These descriptions suggest that gas bubbles in marine mammal tissues may be more common than previously thought. In this study we have analyzed gas amount (by gas score) and gas composition within different decomposition codes using a standardized methodology. This broad study has allowed us to explore species-specific variability in bubble prevalence, amount, distribution, and composition, as well as masking of bubble content by putrefaction gases. Bubbles detected within the cardiovascular system and other tissues related to both pre- and port-mortem processes are a common finding on necropsy of stranded cetaceans. To minimize masking by putrefaction gases, necropsy, and gas sampling must be performed as soon as possible. Before 24?h post mortem is recommended but preferably within 12?h post mortem. At necropsy, amount of bubbles (gas score) in decomposition code 2 in stranded cetaceans was found to be more important than merely presence vs. absence of bubbles from a pathological point of view. Deep divers presented higher abundance of gas bubbles, mainly composed of 70% nitrogen and 30% CO2, suggesting a higher predisposition of these species to suffer from decompression-related gas embolism. PMID:22675306

de Quiros, Yara Bernaldo; Gonzalez-Diaz, Oscar; Arbelo, Manuel; Sierra, Eva; Sacchini, Simona; Fernandez, Antonio

2012-01-01

242

Two-dimensional distribution of sodium polysulfide composition in sulfur electrodes of sodium-sulfur cells  

SciTech Connect

Distributions of the sodium polysulfide composition in the sulfur electrode of the sodium-sulfur cell and the current density in the cell are investigated using a two-dimensional and two-component (ionic and electronic) conduction model. The following points are clarified from the results of calculations and experiments. The polarization of a vertically supported cell at the end of charge starts partially from the upper surface of the solid electrolyte due to the gravitational drop of the sodium polysulfide melt, but the polarization at the end of discharge is axially almost uniform. A dual mat design of which a porous graphite mat has a high electric resistance adjacent to the electrolyte is preferable for improving the rechargeability. An oriented mat of which the radial resistivity is smaller than the axial resistivity is able to reduce the cell resistance. The larger the current density is, the larger the nonuniformity of the melt composition becomes, and the sulfur utilization is reduced by the high current density operation. Voids of the melt at the electrolyte surface accelerate the degradation of the solid electrolyte and reduce the sulfur utilization. Voids at the metal container side accelerate the corrosion of the metal container.

Kawamoto, H. (Hitachi, Ltd., Advanced Reactor and Nuclear Fuel Cycle Dept., Hitachi Works, Hitachi-shi, Ibaraki-ken 317 (JP))

1989-07-01

243

A requirement for reduced pressure and modified atmosphere composition in lunar and martian biological life support systems  

NASA Astrophysics Data System (ADS)

The Controlled Environment Systems Research Facility at the PlaceTypeUniversity of Place- NameGuelph (country-regionplaceCanada) represents an extensive collection of variable pressure plant growth chambers devoted to the study of biological systems including plants and microbes, in life support roles for space exploration. To simplify engineering requirements for plant growth structures on the Moon or Mars, lower pressures are required in order to reduce mass and decrease atmospheric leakage. Few facilities exist that can provide low pressure plant growth capabilities coupled with complete control over temperature, vapour pressure deficit (humidity), gas composition, nutrient delivery, and pressure. The Controlled Environment Systems Research Facility maintains five canopy-scale hypobaric plant growth chambers with capabilities ideally suited for low pressure advanced life support research. System performance evaluations during low pressure experiments on radish (Raphanus sativa L. cv. Cherry Bomb II) have demonstrated temperature control of +/- 0.5 ° C, vapour pressure deficit control of +/- 0.5 mb, CO2 injection control of +/- 20 ` ?mol mol-1 , and leakage rates of less than 1% per day. Keywords: hypobaric, plant growth chamber, advanced life support, controlled environment, low pressure, atmospheric control

Dixon, Mike; Stasiak, Michael; Wehkamp, Cara Ann; Lawson, Jamie

244

Fatigue, fracture, and life prediction criteria for composite materials in magnets  

SciTech Connect

An explosively-bonded copper/Inconel 718/copper laminate conductor was proposed to withstand the severe face compression stresses in the central core of the Alcator C-MOD tokamak toroidal field (TF) magnet. Due to the severe duty of the TF magnet, it is critical that an accurate estimate of useful life be determined. As part of the effort to formulate an appropriate life prediction, fatigue crack growth experiments were performed on the laminate as well as its components. Metallographic evaluation of the laminate interface revealed many shear bands in the Inconel 718. Shear bands and shear band cracks were produced in the Inconel 718 as a result of the explosion bonding process. These shear bands were shown to have a detrimental effect on the crack growth behavior of the laminate, by significantly reducing the load carrying capability of the reinforcement layer and providing for easy crack propagation paths. Fatigue crack growth rate was found not only to be dependent on temperature but also on orientation. Fatigue cracks grew faster in directions which contained shear bands in the plane of the propagating crack. Fractography showed crack advancement by fatigue cracking in the Inconel 718 and ductile tearing of the copper at the interface. However, further away from the interfaces, the copper exhibited fatigue striations indicating that cracks were now propagating by fatigue. Laminate life prediction results showed a strong dependence on shear band orientation, and exhibited little variation between room temperature and 77{degree}K. Predicted life of this laminate was lower when the crack propagation was along a shear band than when crack propagation was across the shear bands. Shear bands appear to have a dominating effect on crack growth behavior.

Wong, F.M.G.

1990-06-01

245

Chamber-confined silicon-carbon nanofiber composites for prolonged cycling life of Li-ion batteries  

NASA Astrophysics Data System (ADS)

Silicon is a promising high capacity (4200 mA h g-1) anode material for lithium ion batteries but the significant volume change (over 300%) of silicon during lithiation/delithiation remains a challenge in terms of silicon pulverization and solid-electrolyte-interphase (SEI) accumulation in the silicon composite electrode. To alleviate the volumetric change of silicon, we built a flexible and self-supporting carbon-enhanced carbon nanofiber (CNF) structure with vacant chamber to encapsulate Si nanoparticles (vacant Si@CNF@C). This composite was tested directly without any polymer and current collector. The confined vacant chamber allowed the increasing volume of silicon and SEI accumulates to be well retained for a long cycle life. This chamber-confined silicon-carbon nanofiber composite exhibited an improved performance in terms of good cycling performance (620 mA h g-1), high coulombic efficiency (99%), and good capacity retention (80%) after 200 cycles. This self-supported silicon-carbon nanofiber structure showed high flexibility and good electrochemical performance for the potential as flexible electrode for lithium-ion batteries.

Fu, Kun; Lu, Yao; Dirican, Mahmut; Chen, Chen; Yanilmaz, Meltem; Shi, Quan; Bradford, Philip D.; Zhang, Xiangwu

2014-06-01

246

Chamber-confined silicon-carbon nanofiber composites for prolonged cycling life of Li-ion batteries.  

PubMed

Silicon is a promising high capacity (4200 mA h g(-1)) anode material for lithium ion batteries but the significant volume change (over 300%) of silicon during lithiation/delithiation remains a challenge in terms of silicon pulverization and solid-electrolyte-interphase (SEI) accumulation in the silicon composite electrode. To alleviate the volumetric change of silicon, we built a flexible and self-supporting carbon-enhanced carbon nanofiber (CNF) structure with vacant chamber to encapsulate Si nanoparticles (vacant Si@CNF@C). This composite was tested directly without any polymer and current collector. The confined vacant chamber allowed the increasing volume of silicon and SEI accumulates to be well retained for a long cycle life. This chamber-confined silicon-carbon nanofiber composite exhibited an improved performance in terms of good cycling performance (620 mA h g(-1)), high coulombic efficiency (99%), and good capacity retention (80%) after 200 cycles. This self-supported silicon-carbon nanofiber structure showed high flexibility and good electrochemical performance for the potential as flexible electrode for lithium-ion batteries. PMID:24882561

Fu, Kun; Lu, Yao; Dirican, Mahmut; Chen, Chen; Yanilmaz, Meltem; Shi, Quan; Bradford, Philip D; Zhang, Xiangwu

2014-07-01

247

Out-Life Characteristics of IM7/977-3 Composites  

NASA Technical Reports Server (NTRS)

The capability to manufacture large structures leads to weight savings and reduced risk relative to joining smaller components. However, manufacture of increasingly large composite components is pushing the out-time limits of epoxy/ carbon fiber prepreg. IM7/977-3 is an autoclave processable prepreg material, commonly used in aerospace structures. The out-time limit is reported as 30 days by the manufacturer. The purpose of this work was to evaluate the material processability and composite properties of 977-3 resin and IM7/977-3 prepreg that had been aged at room temperature for up to 60 days. The effects of room temperature aging on the thermal and visco-elastic properties of the materials were investigated. Neat resin was evaluated by differential scanning calorimetry to characterize thermal properties and change in activation energy of cure. Neat resin was also evaluated by rheometry to characterize its processability in composite fabrication. IM7/977-3 prepreg was evaluated by dynamic mechanical analysis to characterize the curing behavior. Prepreg tack was also evaluated over 60 days. The overall test results suggested that IM7/977-3 was a robust material that offered quality laminates throughout this aging process when processed by autoclave.

Miller, Sandi G.; Sutter, James K.; Hou, Tan-Hung; Scheiman, Daniel A.; Martin, Richard E.; Maryanski, Michael; Schlea, Michelle; Gardner, John M.; Schiferl, Zack R.

2010-01-01

248

Linewidth reduction of DSM lasers due to effects of composite cavity and distributed reflectors  

SciTech Connect

Spectral properties of dynamic single-mode (DSM) lasers are theoretically analyzed in terms of the effects of composite cavity and distributed reflectors. The authors find unique reduction mechanisms of adiabatic chirp and linewidth in distributed reflector (DR) lasers and complex-coupled (CC) (i.e., gain + index-coupled) DSM lasers. Introducing convenient functions of effective length and detuning coefficient, these reduction mechanisms are explained from the viewpoints of modal phase and modal gain behaviors. For CC-DSM lasers, it is shown that the arrangement of index and gain corrugation, namely, anti-phase or in-phase combination, will suppress or enhance an effective linewidth enhancement factor [alpha][sub eff], respectively. Numerical results show that DR structures are much superior in the spectral and single-mode properties to DFB and DBR structures, both in index-coupled (IC) and CC lasers. By introducing gain coupling into the IC-DFB laser, [alpha][sub eff] can be reduced to half the material [alpha], and it will be further reduced by adopting the CC-DR laser structure proposed here.

Kudo, Koji; Arai, Shigehisa; Shim, Jong In (Tokyo Institute of Tech., Tokyo (Japan). Dept. of Physical Electronics)

1993-06-01

249

Linewidth reduction of DSM lasers due to effects of composite cavity and distributed reflectors  

NASA Astrophysics Data System (ADS)

Spectral properties of dynamic single-mode (DSM) lasers are theoretically analyzed in terms of the effects of composite cavity and distributed reflectors. We find unique reduction mechanisms of adiabatic chirp and linewidth in distributed reflector (DR) lasers and complex-coupled (CC) (i.e., gain + of effective length and detuning coefficient, these reduction mechanisms are explained from the viewpoints of modal phase and modal gain behaviors. For CC-DSM lasers, it is shown that the arrangement of index and gain corrugation, namely, anti-phase or in-phase combination, will suppress or enhance an effective linewidth enhancement factor alpha(sub eff), respectively. Numerical results show that DR structures are much superior in the spectral and single mode properties to DFB and DBR structures, both in index-couples (IC) and CC lasers. By introducing gain coupling into the IC-DFB laser, alpha(sub eff) can be reduced to half the material alpha, and it will be further reduced by adopting the CC-DR laser structure proposed here.

Kudo, Koji; Arai, Shigehisa; Shim, Jong In

1993-06-01

250

Archaeal Assemblages Inhabiting Temperate Mixed Forest Soil Fluctuate in Taxon Composition and Spatial Distribution over Time  

PubMed Central

This study explored the persistence and spatial distribution of a diverse Archaeal assemblage inhabiting a temperate mixed forest ecosystem. Persistence under native conditions was measured from 2001 to 2010, 2011, and 2012 by comparison of 16S rRNA gene clone libraries. The Archaeal assemblages at each of these time points were found to be significantly different (AMOVA, P < 0.01), and the nature of this difference was dependent on taxonomic rank. For example, the cosmopolitan genus g_Ca. Nitrososphaera (I.1b) was detected at all time points, but within this taxon the abundance of s_SCA1145, s_SCA1170, and s_Ca. N. gargensis fluctuated over time. In addition, spatial heterogeneity (patchiness) was measured at these time points using 1D TRFLP-SSCP fingerprinting to screen soil samples covering multiple spatial scales. This included soil collected from small volumes of 3 cubic centimeters to larger scales—over a surface area of 50?m2, plots located 1.3?km apart, and a separate locality 23?km away. The spatial distribution of Archaea in these samples changed over time, and while g_Ca. Nitrososphaera (I.1b) was dominant over larger scales, patches were found at smaller scales that were dominated by other taxa. This study measured the degree of change for Archaeal taxon composition and patchiness over time in temperate mixed forest soil. PMID:23983618

Swanson, Colby A.; Sliwinski, Marek K.

2013-01-01

251

A Comparative Size-Composition-Distribution Analysis Of Xenoliths In Plutons  

NASA Astrophysics Data System (ADS)

Field geologists and petrologists have long recognized the significance of xenoliths both in terms of their presence, as well as their conspicuous absence within plutonic rocks. However, few quantitative studies exist on the size and distribution of xenoliths in plutons. We report an exploratory set of size, composition, and distribution studies of xenoliths from a variety of different plutons of granodiorite to diorite composition that bear on processes of xenolith a) incorporation into magmas, b) deformation and displacement in magma chambers, c) preservation in magmas, and d) dissolution and melting in magmas. Four plutons, assembled at depths ranging from subvolcanic to 25 km, have been studied in detail (Jackass Lakes granodiorite, CA; Andalshatten granodiorite and Vega granodiorite, Norway; and Wooley Creek qtz-diorite, CA); two additional plutons (Krakfjellet, Norway, Main Donegal, Ireland) have been evaluated based on published observations. The following observations are summarized: 1) xenoliths in the studied intrusions range in size from sub-mm2 to > km2 and from << 1 to > 8% of total intrusion area, exclusive of screens that may be attached to the host rocks in 3D; 2) in plutons that intrude metasedimentary host rocks, xenoliths of carbonate/quartzite/bte-schist are common whereas pelite and pelitic migmatite are uncommon; 3) statistical size-frequency analysis of a variety of xenolith lithologies display fractal dimensions with D ~ 1 to 3 in log space over a range of sizes. However, in most cases, the density of small xenolith sizes diminishes; 4) plutons with compositions corresponding to higher solidi (e.g., tonalites, qtz diorites, gabbros, etc.) tend to contain migmatitic xenoliths (where bulk composition is appropriate), some of which underwent partial melting in situ; 5) virtually all xenoliths from mm to km in scale have been displaced relative to a fixed host-rock reference frame; none can be shown to be in situ; 6) in all plutons examined, some xenoliths have undergone post-incorporation rotation; 7) "raft trains" of xenoliths sometimes preserve ghost stratigraphy of the adjacent host rocks. However, in no case can the pre-intrusion host rock stratigraphy be restored by removing intrusive units; 8) host plutonic rocks that envelope larger xenoliths and screens often display variable textural and lithologic changes within a few meters of the xenolith including reaction halos possibly due to melt-rock reaction, and mutually intrusive felsic (sometimes pegmatitic and often hydrous) dikes; 9) metasedimentary and metavolcanic xenoliths may show evidence for ductile deformation after incorporation into the host magma, whereas meta-plutonic xenoliths generally do not; 10) hypersolidus fabric trends and magnitudes in the host plutons generally do not show any systematic variability approaching xenolith contacts. Together, these observations indicate that when preserved, xenoliths in plutons may provide a range of useful metrics to evaluate magma compositional evolution (e.g., in situ assimilation), rheology (e.g., near-solidus magma viscosity and crystallinity), and mechanisms of host rock deformation and xenolith incorporation (e.g., fragmentation processes).

Gates, K.; Marko, W. T.; Yoshinobu, A. S.

2012-12-01

252

Structure-induced high dielectric constant and low loss of CNF/PVDF composites with heterogeneous CNF distribution  

NASA Astrophysics Data System (ADS)

The enhancement of dielectric constant in a polymer while maintaining low loss through composite methods has been challenging. In this paper, we report that through designing multi-layered structures with carbon nanofiber (CNF)/poly(vinylidene fluoride) (PVDF) composites intercalated by a pure PVDF layer, enhanced dielectric constant and low loss were achieved. The dielectric loss was similar to that of pure PVDF at high frequencies and even lower than pure PVDF at low frequencies. The results were achieved by designing special multi-layered structures including CNF/PVDF composite layers. The multi-layered sandwich-like or laminate structure composites with transversely heterogeneous CNF distributions were prepared using a simple two-step processing including solution casting and compression molding methods. The dielectric constant obtained from the sandwich structure containing 5, 7 and 15 wt% CNF/PVDF composite layers is even more independent of the frequency in a wide range from 102 to 106 Hz. Furthermore, the effects of the heterogeneous CNF distribution on the dielectric properties were studied by designing different multi-layered composite structures with varying architecture while maintaining the same CNF concentration level. It is shown that varying this stack-up architecture of different CNF distributions plays an important role in the enhancement level of the dielectric constant while having negligible effect on the dielectric loss of the nanocomposite, which is determined mainly by the CNF loading content.

Sun, L. L.; Li, B.; Zhao, Y.; Mitchell, G.; Zhong, W. H.

2010-07-01

253

MinSORTING: an Excel macro for modelling sediment composition and grain-size distribution  

NASA Astrophysics Data System (ADS)

Detrital mineral analyses are gaining increasing attention in the geosciences as new single-grain analytical techniques are constantly improving their resolution, and consequently widening their range of application, including sedimentary petrology, tectonic geomorphology and archaeology (Mange and Wright, 2007; von Eynatten and Dunkl, 2012). We present here MinSORTING, a new tool to quickly predict the size distribution of various minerals and rock fragments in detrital sediments, based on the physical laws that control sedimentation by tractive wind or water currents (Garzanti et al., 2008). The input values requested by the software are the sediment mean size, sorting, fluid type (seawater, freshwater, air) and standard sediment composition chosen from a given array including nine diverse tectonic settings. MinSORTING calculates the bulk sediment density and the settling velocity. The mean size of each single detrital component, assumed as lognormally-distributed, is calculated from its characteristic size-shift with respect to bulk sediment mean size, dependent in turn on its density and shape. The final output of MinSORTING is the distribution of each single detrital mineral in each size classes (at the chosen 0.25, 0.5 or 1 phi intervals). This allows geochronolgists to select the most suitable grain size of sediment to be sampled in the field, as well as the most representative size-window for analysis. Also, MinSORTING provides an estimate of the volume/weight of the fractions not considered in both sizes finer and coarser than the selected size-window. A beta version of the software is available upon request from: alberto.resentini@unimib.it Mange, M., and Wright, D. (eds), 2007. Heavy minerals in use. Developments in Sedimentology Series, 58. Elsevier, Amsterdam. Garzanti, E., Andò, S., Vezzoli, G., 2008. Settling-equivalence of detrital minerals and grain-size dependence of sediment composition. Earth and Planetary Science Letters 273, 138-151. von Eynatten, H., and Dunkl, I., 2012. Assessing the sediment factory: The role of single grain analysis. Earth Sciences Reviews, 115, 97-120.

Resentini, Alberto; Malusà, Marco G.; Garzanti, Eduardo

2013-04-01

254

Composition and distribution of retinal and 3-hydroxyretinal in the compound eye of the dragonfly.  

PubMed

Retinoids in the compound eyes of nymphs and adult dragonflies in 11 families of the 3 suborders were extracted by the oxime method, and analysed by high performance liquid chromatography. Almost all of the species examined contained both retinal and 3-hydroxyretinal in the compound eye. The ratio of 11-cis 3-hydroxyretinal to 11-cis retinal (3-OH ratio) was calculated as an index of the retinoid composition. The 3-OH ratios of the whole eye of nymphs in all the suborders and of adults of the suborder Zygoptera were very high, 2.2 at the minimum, but in Anisozygoptera and Anisoptera most of the ratios were distributed between 1 and 2.7. In the family Gomphidae, exceptionally low 3-OH ratios, less than 1, were observed in several species. The regional distributions of the retinals in the adult compound eyes were also examined. In the Zygopteran compound eye, both retinals were distributed evenly all over the eye, while in the compound eye of the other two suborders, the 3-OH ratios in the dorsal area of the eye were extremely low. In several species of Gomphidae and Libellulidae the ratios in the dorsal areas were zero. From the correspondence of these results and the compartment of the compound eye, it appeared that the large ommatidia in the dorsal area contained only retinal. This was confirmed when the large facet region in the dorsal part of the compound eye of an Anax was excised and examined, and only retinal was detected. However, the ventral area of the true dragonflies' compound eye which did not include the large ommatidia contained both retinals, and the 3-OH ratio was more than ten. The biological significance of using both retinals as chromophores of visual pigments in the dragonfly eye is discussed in relation to the structure of the ommatidia and to the vision of dragonflies. PMID:2920812

Seki, T; Fujishita, S; Obana, S

1989-01-01

255

Biochemical composition of deep-sea decapod crustaceans with two different benthic life strategies off the Portuguese south coast  

NASA Astrophysics Data System (ADS)

The objectives of the present study were to characterize the benthic life strategies of Aristeus antennatus (Crustacea: Penaeidea), Parapenaeus longirostris (Crustacea: Penaeidea) and Nephrops norvegicus (Crustacea: Astacidea) on the basis of biochemical composition (proximate chemical composition, total lipids, glycogen and cholesterol contents), and its response to biological and environmental factors (sex, maturation, reproduction, food availability and depth) into account. The specimens were collected at depths between 200 and 600 m off the Portuguese south coast (Algarve). The nektobenthic species ( A. antennatus and P. longirostris) showed higher protein, lipid, cholesterol and glycogen contents, and lower moisture content in the muscle than the benthic-endobenthic species ( N. norvegicus). Consequently, the energy content of the nektobenthic species was also higher. Principal component analyses were used to assess the relationship between the different biochemical contents and to relate them to the biotic and abiotic factors. Depth seems to have the most important role in the observed trends of the biochemical composition. The increase of the ovarian lipid levels occurs as a result of the maturation process. The highest values were obtained in mature N. norvegicus females. The differences can be due to maternal investment (lipid metabolism of the female is geared to the provision of egg lipid), since N. norvegicus produce large lecithotrophic eggs. The biochemical differences observed in the three species did not seem to be due to distinct trophic strategies, but instead were a consequence of depth, which may have a significant interspecific effect on food intake. It was also evident that reproductive cycle has profound effects upon the biochemistry of the three species. Gonadal maturation has large associated energy costs due to the increase in biosynthetic work. Moreover, the biochemical composition would be influenced by or synchronized with seasonal feeding activity or food availability.

Rosa, R.; Nunes, M. L.

2003-01-01

256

Evaluation of hole quality and bit life in graphite epoxy composites using video scanning  

E-print Network

(December 1985) THOMAS EDWARD LEDNICKY, B. S. , TEXAS A&M UNIVERSITY; M. S. , TEXAS A6 M UNIVERSITY; CHAIRMAN OF ADVISORY COMMITTEE: DR. C. L. HOUGH In this study two carbide bit designs, the standard twist drill and the dagger drill were tested... determined by using regression analysis. These tool life equations were used as the basis for comparison of the four different methods. For the standard twist drills the predictive equations took a 1&near logarithmic form, and the hole quality methods...

Lednicky, Thomas Edward

2012-06-07

257

A meta-analysis of the genomic and transcriptomic composition of complex life  

PubMed Central

It is now clear that animal genomes are predominantly non-protein-coding, and that these sequences encode a wide array of RNA transcripts and other regulatory elements that are fundamental to the development of complex life. We have previously argued that the proportion of an animal genome that is non-protein-coding DNA (ncDNA) correlates well with its apparent biological complexity. Here we extend on that work and, using data from a total of 1,627 prokaryotic and 153 eukaryotic complete and annotated genomes, show that the proportion of ncDNA per haploid genome is significantly positively correlated with a previously published proxy of biological complexity, the number of distinct cell types. This is in contrast to the amount of the genome that encodes proteins, which we show is essentially unchanged across Metazoa. Furthermore, using a total of 179 RNA-seq data sets from nematode (47), fruit fly (72), zebrafish (20) and human (42), we show, consistent with other recent reports, that the vast majority of ncDNA in animals is transcribed. This includes more than 60 human loci previously considered “gene deserts,” many of which are expressed tissue-specifically and associated with previously reported GWAS SNPs. These results suggest that ncDNA, and the ncRNAs encoded within it, may be intimately involved in the evolution, maintenance and development of complex life. PMID:23759593

Liu, Ganqiang; Mattick, John S.; Taft, Ryan J.

2013-01-01

258

Reliability based optimal design of water distribution networks considering life cycle components  

Microsoft Academic Search

Water distribution systems play an important role in supplying water to consumers in a timely and efficient manner. The importance and complexity of such systems lead to extensive research in the area of optimal design of water distribution networks. Traditionally, only system costs are considered in design with few models incorporating environmental impacts. This paper presents a model for designing

Kalyan R. Piratla; Samuel T. Ariaratnam

2012-01-01

259

Effects of fiber spatial distribution and interphase on transverse damage in fiber-reinforced ceramic matrix composites  

Microsoft Academic Search

The major objectives of this research were to study the effects of fiber spatial distribution and interphase thermo-mechanical properties on transverse damage initiation. The material model studied was a unidirectional, continuous fiber-reinforced composite. Radial matrix cracking and interfacial debonding at the fiber\\/matrix interface were of primary concern. With regards to the fiber spatial distribution, a reconstruction scheme was devised from

Vatsal Narottamdas Bulsara

1998-01-01

260

Application of composite flow laws to grain size distributions derived from polar ice cores  

NASA Astrophysics Data System (ADS)

Apart from evaluating the crystallographic orientation, focus of microstructural analysis of natural ice during the last decades has been to create depth-profiles of mean grain size. Several ice flow models incorporated mean grain size as a variable. Although such a mean value may coincide well with the size of a large proportion of the grains, smaller/larger grains are effectively ignored. These smaller/larger grains, however, may affect the ice flow modeling. Variability in grain size is observed on centimeter, meter and kilometer scale along deep polar ice cores. Composite flow laws allow considering the effect of this variability on rheology, by weighing the contribution of grain-size-sensitive (GSS, diffusion/grain boundary sliding) and grain-size-insensitive (GSI, dislocation) creep mechanisms taking the full grain size distribution into account [1]. Extraction of hundreds of grain size distributions for different depths along an ice core has become relatively easy by automatic image processing techniques [2]. The shallow ice approximation is widely adopted in ice sheet modeling and approaches the full-Stokes solution for small ratios of vertical to horizontal characteristic dimensions. In this approximation shear stress in the vertical plain dominates the strain. This assumption is not applicable at ice divides or dome structures, where most deep ice core drilling sites are located. Within the upper two thirds of the ice column longitudinal stresses are not negligible and ice deformation is dominated by vertical strain. The Dansgaard-Johnsen model [3] predicts a dominating, constant vertical strain rate for the upper two thirds of the ice sheet, whereas in the lower ice column vertical shear becomes the main driver for ice deformation. We derived vertical strain rates from the upper NEEM ice core (North-West Greenland) and compared them to classical estimates of strain rates at the NEEM site. Assuming intervals of constant accumulation rates, we found a variation of vertical strain rates by a factor 2-3 in the upper ice column. We discuss the current applicability of composite flow laws to grain size distributions extracted from ice cores drilled at sites where the flow direction rotates by 90 degrees with depth (i.e. ice divide). An interesting finding is that a transition to a glacial period in future would be associated with a decrease in vertical strain rate (due to a reduced accumulation rate) and an increase of the frequency of small grains (due to an enhanced impurity content). Composite flow laws assign an enhanced contribution of GSS creep to this transition. It is currently unclear which factor would have a greater influence. [1] Herwegh et al., 2005, J. Struct. Geol., 27, 503-521 [2] T. Binder et al., 2013, J. Microsc., 250, 130-141 [3] W. Dansgaard & S.J. Johnsen, 1969, J. Glaciol., 8, 215-223

Binder, Tobias; de Bresser, Hans; Jansen, Daniela; Weikusat, Ilka; Garbe, Christoph; Kipfstuhl, Sepp

2014-05-01

261

Spatial distribution and cellular composition of adult brain proliferative zones in the teleost, Gymnotus omarorum  

PubMed Central

Proliferation of stem/progenitor cells during development provides for the generation of mature cell types in the CNS. While adult brain proliferation is highly restricted in the mammals, it is widespread in teleosts. The extent of adult neural proliferation in the weakly electric fish, Gymnotus omarorum has not yet been described. To address this, we used double thymidine analog pulse-chase labeling of proliferating cells to identify brain proliferation zones, characterize their cellular composition, and analyze the fate of newborn cells in adult G. omarorum. Short thymidine analog chase periods revealed the ubiquitous distribution of adult brain proliferation, similar to other teleosts, particularly Apteronotus leptorhynchus. Proliferating cells were abundant at the ventricular-subventricular lining of the ventricular-cisternal system, adjacent to the telencephalic subpallium, the diencephalic preoptic region and hypothalamus, and the mesencephalic tectum opticum and torus semicircularis. Extraventricular proliferation zones, located distant from the ventricular-cisternal system surface, were found in all divisions of the rombencephalic cerebellum. We also report a new adult proliferation zone at the caudal-lateral border of the electrosensory lateral line lobe. All proliferation zones showed a heterogeneous cellular composition. The use of short (24 h) and long (30 day) chase periods revealed abundant fast cycling cells (potentially intermediate amplifiers), sparse slow cycling (potentially stem) cells, cells that appear to have entered a quiescent state, and cells that might correspond to migrating newborn neural cells. Their abundance and migration distance differed among proliferation zones: greater numbers and longer range and/or pace of migrating cells were associated with subpallial and cerebellar proliferation zones. PMID:25249943

Olivera-Pasilio, Valentina; Peterson, Daniel A.; Castelló, María E.

2014-01-01

262

Assessing Historical Fish Community Composition Using Surveys, Historical Collection Data, and Species Distribution Models  

PubMed Central

Accurate establishment of baseline conditions is critical to successful management and habitat restoration. We demonstrate the ability to robustly estimate historical fish community composition and assess the current status of the urbanized Barton Creek watershed in central Texas, U.S.A. Fish species were surveyed in 2008 and the resulting data compared to three sources of fish occurrence information: (i) historical records from a museum specimen database and literature searches; (ii) a nearly identical survey conducted 15 years earlier; and (iii) a modeled historical community constructed with species distribution models (SDMs). This holistic approach, and especially the application of SDMs, allowed us to discover that the fish community in Barton Creek was more diverse than the historical data and survey methods alone indicated. Sixteen native species with high modeled probability of occurrence within the watershed were not found in the 2008 survey, seven of these were not found in either survey or in any of the historical collection records. Our approach allowed us to more rigorously establish the true baseline for the pre-development fish fauna and then to more accurately assess trends and develop hypotheses regarding factors driving current fish community composition to better inform management decisions and future restoration efforts. Smaller, urbanized freshwater systems, like Barton Creek, typically have a relatively poor historical biodiversity inventory coupled with long histories of alteration, and thus there is a propensity for land managers and researchers to apply inaccurate baseline standards. Our methods provide a way around that limitation by using SDMs derived from larger and richer biodiversity databases of a broader geographic scope. Broadly applied, we propose that this technique has potential to overcome limitations of popular bioassessment metrics (e.g., IBI) to become a versatile and robust management tool for determining status of freshwater biotic communities. PMID:21966438

Labay, Ben; Cohen, Adam E.; Sissel, Blake; Hendrickson, Dean A.; Martin, F. Douglas; Sarkar, Sahotra

2011-01-01

263

Antarctic Marine Biodiversity - What Do We Know About the Distribution of Life in the Southern Ocean?  

Microsoft Academic Search

The remote and hostile Southern Ocean is home to a diverse and rich community of life that thrives in an environment dominated by glaciations and strong currents. Marine biological studies in the region date back to the nineteenth century, but despite this long history of research, relatively little is known about the complex interactions between the highly seasonal physical environment

Huw J. Griffiths; Richard Kazimierz Frank Unsworth

2010-01-01

264

LETTER doi:10.1038/nature12169 Barium distributions in teeth reveal early-life dietary  

E-print Network

for reconstruct- ing diet as they contain precise temporal and chemical records of early life4 . Teeth begin at weaning as Ba (and Ca) content and bioavail- ability is markedly different across plant and animal food sources11,12 . To test this hypothesis, we investigated Ba/Ca patterns in teeth from human children

Gunawardena, Jeremy

265

Life history, distribution, and production of Diporeia near the Keweenaw Peninsula Lake Superior  

Microsoft Academic Search

Benthic amphipods are a keystone species in food webs of marine and freshwater systems. The amphipod in the phylogroup Diporeia found in the Great Lakes has historically been a dominant member of the benthic community and is critical to the fisheries food web. This study investigates water depth, life stage, sex, production, lipid content, and gut fullness as influences and

Nancy A. Auer; Bridget A. Cannon; Martin T. Auer

2009-01-01

266

Distribution of early life history stages of fishes in selected pools of the Upper Mississippi River  

Microsoft Academic Search

Effective management of the fishery resources of the Upper Mississippi River and successful mitigation of the loss of critical habitat depend in part on an understanding of the reproductive and early life history requirements of the affected fishes. However, little is known about the use of nursery areas by fishes in the river. Of the nearly 130 species identified in

Leslie E. Holland

1986-01-01

267

Composition and distribution of pythium communities in wheat fields in eastern washington state.  

PubMed

ABSTRACT Pythium spp. were isolated from a mixture of soil and roots collected from 80 wheat fields in eastern Washington in the summer of 2000 from an area encompassing approximately 27,000 km(2). These sites covered a range of soil textures (coarse to fine, silty loess), average annual precipitation (200 to 600 mm), and average annual temperatures (7 to 11 degrees C). Soil type and annual precipitation run in an east-west gradient, while temperature has a north-south gradient. Species were identified using classical methods and by sequencing the internal transcribed spacer (ITS)-1 region of the rDNA and comparing these sequences to a database from a worldwide collection of Pythium spp. The species with the highest frequency of occurrence among all the sites were P. abappressorium sp. nov. (A) (50%), P. rostratum (R) (40%), P. debaryanum (D) (37.5%), P. heterothallicum (H) (33.7%), P.oligandrum (O) (31.2%), an unidentified P. sp. (aff. echinulatum) (E) (25%), and P. ultimum (U) (18%). P. intermedium, P. irregulare, P. paroecandrum, P. sylvaticum, P. dissimile, and P. dissoticum were isolated at a low frequency. From one to six species were isolated at each site, and there were 46 different species combinations detected. The species presence/absence data from all sites were analyzed with Jaccard's similarity coefficient hierarchical cluster analysis. Six communities were identified (species within each community designation in order of frequency among the sites within the community)-AD, AOU, AR, DEH, HE, and RU. In general, P. abappressorium was evenly distributed over all zones. AOU was more prevalent in zones with lower precipitation and coarser soil, while DEH and HE were associated with zones with higher precipitation and finer-textured soils on the basis of comparison of frequency distributions with the expected distribution over all the sites. The RU community was more prevalent in higher temperature zones. Canonical correspondence analysis was performed to examine the relationship between species and environmental variables. Soil type and precipitation were highly correlated with each other and with axis 1, which separated P. ultimum and P. abappressorium (lower variable values) from P. heterothallicum (higher variable values). Axis 2 and 3 were most correlated with temperature, and these axes separated P. oligandrum (higher value) from P. debaryanum (lower value) and P. ultimum-P. rostratum from the other species. The results suggest that Pythium species composition, distributions, and associations on a given crop may be influenced by environmental factors at a mesoscale level (100 to 1,000,000 ha). PMID:18943168

Paulitz, T C; Adams, K

2003-07-01

268

The plankton community in Norwegian coastal waters—abundance, composition, spatial distribution and diel variation  

NASA Astrophysics Data System (ADS)

The purpose of the present study was to explore the composition and variation of the pico-, nano- and micro-plankton communities in Norwegian coastal waters and Skagerrak, and the co-occurrence of bacteria and viruses. Samples were collected along three cruise transects from Jæren, Lista and Oksøy on the south coast of Norway and into the North Sea and Skagerrak. We also followed a drifting buoy for 55 h in Skagerrak in order to observe diel variations. Satellite ocean color images (SeaWiFS) of the chlorophyll a (chl a) distribution compared favorably to in situ measurements in open waters, while closer to the shore remote sensing chl a data was overestimated compared to the in situ data. Using light microscopy, we identified 49 micro- and 15 nanoplankton sized phototrophic forms as well as 40 micro- and 12 nanoplankton sized heterotrophic forms. The only picoeukaryote (0.2-2.0 ?m) we identified was Resultor micron (Pedinophyceae ). Along the transects a significant variation in the distribution and abundance of different plankton forms were observed, with Synechococcus spp and autotrophic picoeukaryotes as the most notable examples. There was no correlation between viruses and chl a, but between viruses and bacteria, and between viruses and some of the phytoplankton groups, especially the picoeukaryotes. Moreover, there was a negative correlation between nutrients and small viruses (Low Fluorescent Viruses) but a positive correlation between nutrients and large viruses (High Fluorescent Viruses). The abundance of autotrophic picoplankton, bacteria and viruses showed a diel variation in surface waters with higher values around noon and late at night and lower values in the evening. Synechococcus spp were found at 20 m depth 25-45 nautical miles from shore apparently forming a bloom that stretched out for more than 100 nautical miles from Skagerrak and up the south west coast of Norway. The different methods used for assessing abundance, distribution and diversity of microorganisms yielded complementary information about the plankton community. Flow cytometry enabled us to map the distribution of the smaller phytoplankton forms, bacteria and viruses in more detail than has been possible before but detection and quantification of specific forms (genus or species) still requires taxonomic skills, molecular analysis or both.

Bratbak, Gunnar; Jacquet, Stéphan; Larsen, Aud; Pettersson, Lasse H.; Sazhin, Andrey F.; Thyrhaug, Runar

2011-09-01

269

Resonance line shape, strain and electric potential distributions of composite magnetoelectric sensors  

NASA Astrophysics Data System (ADS)

Multiferroic composite magnetoelectric (ME) sensors are based on the elastic coupling of a magnetostrictive phase and a piezoelectric phase. A deformation of the magnetostrictive phase causes strain in the piezoelectric phase and thus an induced voltage. Such sensors may be applied both for static as well as for dynamic magnetic field measurements. Particularly high sensitivities are achieved for operation at a mechanical resonance. Here, the resonance line shape of layered (2-2 composite) cantilever ME sensors at the first bending-mode resonance is investigated theoretically. Finite element method (FEM) simulations using a linear material model reveal an asymmetric resonance profile and a zero-response frequency for the ME coefficient. Frequency-dependent strain and electric potential distributions inside the magnetoelectric composite are studied for the case of a magnetostrictive-piezoelectric bilayer. It is demonstrated that a positive or a negative voltage may be induced across the piezoelectric layer depending on the position of the neutral plane. The frequency-dependent induced electric potential is investigated for structured cantilevers that exhibit magnetostriction only at specific positions. For static operation an induced voltage is obtained locally at positions with magnetostriction. In addition to this direct effect a resonance-assisted effect is observed for dynamic operation. Magnetostriction in a limited area of the cantilever causes a global vibration of the cantilever. Thus, deformation of the piezoelectric layer and an induced electric potential also occur in areas of the cantilever without magnetostriction. The direct and the resonance-assisted pathway may induce voltages of equal or of opposite sign. The net induced voltage results from the superposition of the two effects. As the resonance-assisted induced voltage changes sign upon passing the resonance frequency, while the direct component is constant, an asymmetric line shape and a zero-response frequency result for the ME coefficient. The zero-response oscillator frequency may be below or above the resonance frequency. The calculated FEM resonance line shapes are fitted successfully to a superposition function of a constant component and a resonant component with a Lorentzian line shape. Equivalence of the superposition function line shape to a Fano resonance profile is derived for frequencies around the resonance. Fano resonances are ubiquitous in physics occurring due to the constructive and destructive quantum interference of two different scattering pathways, e.g., for photons or electrons. The superposition fit parameters describing the resonance line shape are calculated as a function of the cantilever substrate thickness. The inclusion of loss by adjustment of the damping parameter is discussed. The results derived here also are applicable to higher order modes or longitudinal resonance modes.

Gerken, Martina

2013-06-01

270

Phytogeographic distribution groups of benthic marine algae in the North Atlantic Ocean. A review of experimental evidence from life history studies  

NASA Astrophysics Data System (ADS)

Experimentally determined lethal temperatures and temperatures limiting growth or reproduction in the life histories of 15 benthic algal species were used to infer possible phytogeographic boundaries in the North Atlantic Ocean. These appeared to correspond closely with phytogeographic boundaries based on distribution data. Many boundaries appeared to be of a composite nature. For instance, the southern boundary of Nemalion helminthoides is interpreted as a “southern reproduction boundary” on the N. Atlantic E. shore and a “southern lethal boundary” on the N. Atlantic W. shore. The northern boundary on both sides of the ocean is a “northern reproduction boundary”. N. helminthoides is a typical representative of the “amphiatlantic temperate distribution group”, to which seven other of the fifteen investigated species belong ( Chondrus crispus, Desmarestia aculeata, D. viridis, Monostroma grevillei, Acrosiphonia “arcta” with a comparable composite southern boundary; Rhodochorton purpureum with a “southern lethal boundary”). Polysiphonia ferulacea and Dictyota dichotoma are treated as representatives of the “amphiatlantic tropical-to-warm-temperate distribution group”, and P. denudata as representative of the “amphiatlantic tropical-to-temperate group”. P. harveyi belongs to the N.E. American temperate group and is bounded by a “northern reproduction boundary” and a “southern reproduction boundary”. This is one of the very few species endemic to N.E. America. This poor endemism is ascribed to the vast adverse sediment shores and their additional acting as barriers to glacial northsouth displacements of the flora; it is not related to the wide annual temperature fluctuations (>20 °C) typical for N.E. America. The temperate algal flora of Japan, however, which is extremely rich in endemic species is subject to equally wide annual temperature fluctuations. Bonnemaisonia hamifera is such a Japanese endemic, which has been accidentally introduced into the North Atlantic Ocean where its life history seems to be disrupted: it is maintained mainly by vegetative propagation of the heteromorphic tetrasporophyte. The species of the “warm temperate Mediterranean-Atlantic group” are probably too stenothermous for life on N.E. American shores; they need annual temperature fluctuations<20 °C. Acrosymphyton purpuriferum seems to belong to this group, but arguments are presented to unite this species with A. caribaeum and to range it under the “amphiatlantic tropical-to-warm-temperate group”. Clathromorphum circumscriptum belongs to the “Arctic distribution group” and has a “southern reproduction boundary” across the ocean along the 3 °C February isotherm. This species is able to survive temperatures of about 20 °C. Five amphiequatorial temperate species discussed in this paper and four in another related paper have similar maximum winter temperatures of 14-17 °C (mean monthly values) allowing reproduction. Their amphiequatorial distribution can be explained by assuming similar low temperatures in the euphotic zone along E. Pacific and E. Atlantic equatorial coasts i.e. in narrow inshore belts of intensified upwelling during the presumably intensified glacial circulation of the ocean gyres.

van den Hoek, C.

1982-06-01

271

Particle number concentration, size distribution and chemical composition during haze and photochemical smog episodes in Shanghai.  

PubMed

The aerosol number concentration and size distribution as well as size-resolved particle chemical composition were measured during haze and photochemical smog episodes in Shanghai in 2009. The number of haze days accounted for 43%, of which 30% was severe (visibility<2km) and moderate (2km?visibility<3km) haze, mainly distributed in winter and spring. The mean particle number concentration was about 17,000/cm(3) in haze, more than 2 times that in clean days. The greatest increase of particle number concentration was in 0.5-1?m and 1-10?m size fractions during haze events, about 17.78 times and 8.78 times those of clean days. The largest increase of particle number concentration was within 50-100nm and 100-200nm fractions during photochemical smog episodes, about 5.89 times and 4.29 times those of clean days. The particle volume concentration and surface concentration in haze, photochemical smog and clean days were 102, 49, 15?m(3)/cm(3) and 949, 649, 206?m(2)/cm(3), respectively. As haze events got more severe, the number concentration of particles smaller than 50nm decreased, but the particles of 50-200nm and 0.5-1?m increased. The diurnal variation of particle number concentration showed a bimodal pattern in haze days. All soluble ions were increased during haze events, of which NH4(+), SO4(2-) and NO3(-) increased greatly, followed by Na(+), K(+), Ca(2+) and Cl(-). These ions were very different in size-resolved particles during haze and photochemical smog episodes. PMID:25193840

Wang, Xuemei; Chen, Jianmin; Cheng, Tiantao; Zhang, Renyi; Wang, Xinming

2014-09-01

272

Analysing Group Creativity: A Distributed Cognitive Study of Joint Music Composition Shahin Nabavian (shahin@dcs.qmul.ac.uk)  

E-print Network

Analysing Group Creativity: A Distributed Cognitive Study of Joint Music Composition Shahin in an instance of group creativity by conducting a pilot study that looked closely at a group of expert musicians identified three key processes (attainment, experimentation and structuring) that help the group achieve

Bryan-Kinns, Nick

273

Measurement Issues Related to Studies of Childhood Obesity: Assessment of Body Composition, Body Fat Distribution, Physical Activity, and Food Intake  

Microsoft Academic Search

This article reviews the current status of various methodologies used in obesity and nutrition re- search in children, with particular emphasis on identify- ing priorities for research needs. The focus of the article is 1) to review methodologic aspects involved with mea- surement of body composition, body-fat distribution, en- ergy expenditure and substrate use, physical activity, and food intake in

Michael I. Goran

274

Effect of sulfate on the transformation of corrosion scale composition and bacterial community in cast iron water distribution pipes  

EPA Science Inventory

The stability of iron corrosion products and the bacterial composition of biofilm in drinking water distribution systems (DWDS) could have great impact on the water safety at the consumer ends. In this work, pipe loops were setup to investigate the transformation characteristics ...

275

Physical and biological control of protistan community composition, distribution and abundance in the seasonal ice zone of the Southern Ocean between 30 and 80°E  

NASA Astrophysics Data System (ADS)

Protists are critical components of the Antarctic marine ecosystem as they comprise most of the living carbon and are the base of the Antarctic food web. They are also key determinants of vertical carbon flux and mediate draw-down of atmospheric CO 2 by the ocean. The community composition, abundance and distribution of marine protists (phytoplankton and protozoa) was studied during the Baseline Research on Oceanography, Krill and the Environment-West (BROKE-West) survey, in the seasonal ice zone during the 2005-2006 austral summer between 30°E and 80°E. Light and electron microscopy were used to determine the protistan composition and abundance in samples obtained at 30 sites from surface waters and at 26 sites from the depth of the maximum in situ chlorophyll fluorescence (Chl max). Cluster analysis was used to identify 5 groups of sample sites at the surface and 5 at the Chl max that were of similar protist composition and abundance. The physical characteristics, taxonomic composition, indicator taxa, and taxonomic diversity were determined for each group. In the southwest, a bloom of colonial Phaeocystis antarctica dominated the protistan community composition and biomass amongst the receding ice, but this was replaced by the flagellate life stage/s of this haptophyte in waters to the north. In the southeast, a diatom bloom had the highest diversity of protist taxa observed during the survey and centric diatoms dominated the biomass. Outside these blooms, grazing by krill probably reduced the composition and abundance of large diatoms and autotrophic dinoflagellates in coastal to mid-inshore waters. Only in offshore waters did large diatoms and dinoflagellates increase in abundance and diversity, despite low concentrations of iron and silicate at many of these sites. This increase was probably due to reduced top-down control by krill and other large zooplankton. Large diatoms dominated in offshore waters, despite other coincident studies showing that the trophic structure and function of the microbial community was frequently typical of nanoflagellate-dominated systems in high-nutrient low-chlorophyll waters. Nanoflagellate abundances were low during the survey and were either poorly resolved by our study or limited by microheterotrophic grazing. We propose that protistan abundance and composition in the sea-ice zone of the Indian Sector were determined by synoptic-scale oceanographic features, meso-scale changes caused by sea-ice retreat and meso- to nano- scale interactions between grazers and the composition and abundance of their protistan prey.

Davidson, Andrew T.; Scott, Fiona J.; Nash, Geraldine V.; Wright, Simon W.; Raymond, Ben

2010-05-01

276

Revisiting citation aging: a model for citation distribution and life-cycle prediction  

Microsoft Academic Search

The study of citation distribution provides retrospective and prospective picture of the evolving impact of a corpus of publications\\u000a on knowledge community. All distribution models agree on the rise of the number of citations in the first years following\\u000a the publication to reach a peak and then tend to be less cited when time passes. However, questions such as how

Hamid Bouabid

2011-01-01

277

Simple Sequence Repeats in Escherichia coli: Abundance, Distribution, Composition, and Polymorphism  

PubMed Central

Computer-based genome-wide screening of the DNA sequence of Escherichia coli strain K12 revealed tens of thousands of tandem simple sequence repeat (SSR) tracts, with motifs ranging from 1 to 6 nucleotides. SSRs were well distributed throughout the genome. Mononucleotide SSRs were over-represented in noncoding regions and under-represented in open reading frames (ORFs). Nucleotide composition of mono- and dinucleotide SSRs, both in ORFs and in noncoding regions, differed from that of the genomic region in which they occurred, with 93% of all mononucleotide SSRs proving to be of A or T. Computer-based analysis of the fine position of every SSR locus in the noncoding portion of the genome relative to downstream ORFs showed SSRs located in areas that could affect gene regulation. DNA sequences at 14 arbitrarily chosen SSR tracts were compared among E. coli strains. Polymorphisms of SSR copy number were observed at four of seven mononucleotide SSR tracts screened, with all polymorphisms occurring in noncoding regions. SSR polymorphism could prove important as a genome-wide source of variation, both for practical applications (including rapid detection, strain identification, and detection of loci affecting key phenotypes) and for evolutionary adaptation of microbes.[The sequence data described in this paper have been submitted to the GenBank data library under accession numbers AF209020–209030 and AF209508–209518.] PMID:10645951

Gur-Arie, Riva; Cohen, Cyril J.; Eitan, Yuval; Shelef, Leora; Hallerman, Eric M.; Kashi, Yechezkel

2000-01-01

278

Cosmopolitan distribution of the large composite microbial mat spirochete, Spirosymplokos deltaeiberi  

NASA Technical Reports Server (NTRS)

Inocula from organic-rich black muds immediately underlying intertidal laminated microbial mats dominated by Microcoleus chthonoplastes yielded large, variable diameter spirochetes. These unusual spirochetes, previously reported only from the Alfacs Peninsula at the delta of the Ebro river in northeast Spain, contain striking arrays of cytoplasmic granules packed into their protoplasmic cylinders. On several occasions, both in summer and winter, the huge spirochetes were recognized in samples from mats growing in the Sippewissett salt marsh at Woods Hole Massachusetts. They were also seen in similar samples from microbial mats at North Pond, Laguna Figueroa, Baja California Norte, Mexico. The identity of these spirochetes was confirmed by electron microscopy: number and disposition of flagella, composite structure, measurements of their distinctive cytoplasmic granules. The granules, larger, more conspicuous and present in addition to ribosomes, are hypothesized to contain ATPases. As culture conditions worsen, these spirochetes retract into membrane-bounded round bodies in which they form refractile inclusions. From morphology and behavior we conclude the North American spirochetes from both Atlantic and Pacific intertidal microbial mats are indistinguishable from those at the delta of the Ebro river. We conclude a cosmopolitan distribution for Spirosymplokos deltaeiberi.

Margulis, L.; Navarrete, A.; Sole, M.

1998-01-01

279

Distribution and size composition of the arctic lamprey Lethenteron camtschaticum in the North Pacific  

NASA Astrophysics Data System (ADS)

Results of the long-term study of the spatial and vertical distribution of the parasitic anadromous Arctic lamprey Lethenteron camtschaticum (Tilesius, 1811) (Petromyzontidae) in the North Pacific and data on its size composition are given. This species is most frequent in the northwestern Sea of Japan and the western Bering Sea. The maximum concentrations are noted in waters of southern Primorye, southwestern Sakhalin, the northwestern part of the Sea of Okhotsk, and the northern part of the Bering Sea, which is probably explained by the increased number of its victims, Pacific salmon. Near the bottom, Pacific lampreys are extremely few and are primarily encountered at depths less that 400 m, and in the Pelagic zone, in the 100-m layer. The catches have contained Arctic lampreys having a total length of 15-79 cm. The lampreys of several size groups in the catches may indicate that L. camtschaticum spends not less than four years in the sea. No relationship has been found between the body length and the capture depth. Analyzed are the relationships between the body length and weight and the body length and the condition factor. The seasonal dynamics of these indices are considered.

Orlov, A. M.; Baitalyuk, A. A.; Pelenev, D. V.

2014-03-01

280

Body surface temperature distribution in relation to body composition in obese women.  

PubMed

Adipose tissue levels and human obesity are known to be associated with increased heat production. At the same time, subcutaneous adipose tissue provides an insulating layer that impedes heat loss. The energy implications of obesity and body thermoregulatory mechanisms remain relatively poorly understood. This study attempted to examine the potential relationship between body composition (subcutaneous and visceral fat) determined by bioimpedance as well as BMI (body mass index), and skin surface temperature distribution recorded at rest. One specific aim of this study was to draw a thermal map of body areas in obese women and compare this with women of normal body mass, and thus to identify body regions within which heat transfer is particularly impeded. As high fat content is a good insulator, it could reduce the body's ability to respond effectively to changes in environmental temperature, which would be problematic for thermal homeostasis. Our results showed that core temperature did not differ between obese and normal body mass participants, while skin temperature of most body surfaces was lower in obese subjects. The results of regression analysis showed that the mean body surface temperature (Tmean) decreased with increasing percentage of body fat (PBF) of the abdominal area. The opposite relationship was observed for the front area of the hand (simultaneous increase in Tmean and PBF). We also found a negative correlation between BMI and Tmean of the thigh areas, both the front and the back. From this it could be concluded that the mean body surface temperature is dependent on body fat. PMID:24956951

Chudecka, Monika; Lubkowska, Anna; Kempi?ska-Podhorodecka, Agnieszka

2014-07-01

281

Species composition and distribution of adult Anopheles (Diptera: Culicidae) in Panama.  

PubMed

Anopheles (Diptera: Culicidae) species composition and distribution were studied using human landing catch data over a 35-yr period in Panama. Mosquitoes were collected from 77 sites during 228 field trips carried out by members of the National Malaria Eradication Service. Fourteen Anopheles species were identified. The highest average human biting rates were recorded from Anopheles (Nyssorhynchus) albimanus (Wiedemann) (9.8 bites/person/night) and Anopheles (Anopheles) punctimacula (Dyar and Knab) (6.2 bites/person/night). These two species were also the most common, present in 99.1 and 74.9%, respectively, of the sites. Anopheles (Nyssorhynchus) aquasalis (Curry) was encountered mostly in the indigenous Kuna Yala Comarca along the eastern Atlantic coast, where malaria case history and average human biting rate (9.3 bites/person/night) suggest a local role in malaria transmission. An. albimanus, An. punctimacula, and Anopheles (Anopheles) vestitipennis (Dyar and Knab) were more abundant during the rainy season (May-December), whereas An. aquasalis was more abundant in the dry season (January-April). Other vector species collected in this study were Anopheles (Kerteszia) neivai (Howard, Dyar, and Knab) and Anopheles (Anopheles) pseudopunctipennis s.l. (Theobald). High diversity of Anopheles species and six confirmed malaria vectors in endemic areas of Panama emphasize the need for more detailed studies to better understand malaria transmission dynamics. PMID:18826025

Loaiza, J R; Bermingham, E; Scott, M E; Rovira, J R; Conn, J E

2008-09-01

282

Species Composition and Distribution of Adult Anopheles (Diptera: Culicidae) in Panama  

PubMed Central

Anopheles (Diptera: Culicidae) species composition and distribution were studied using human landing catch data over a 35-yr period in Panama. Mosquitoes were collected from 77 sites during 228 field trips carried out by members of the National Malaria Eradication Service. Fourteen Anopheles species were identified. The highest average human biting rates were recorded from Anopheles (Nyssorhynchus) albimanus (Wiedemann) (9.8 bites/person/night) and Anopheles (Anopheles) punctimacula (Dyar and Knab) (6.2 bites/person/night). These two species were also the most common, present in 99.1 and 74.9%, respectively, of the sites. Anopheles (Nyssorhynchus) aquasalis (Curry) was encountered mostly in the indigenous Kuna Yala Comarca along the eastern Atlantic coast, where malaria case history and average human biting rate (9.3 bites/person/night) suggest a local role in malaria transmission. An. albimanus, An. punctimacula, and Anopheles (Anopheles) vestitipennis (Dyar and Knab) were more abundant during the rainy season (May–December), whereas An. aquasalis was more abundant in the dry season (January–April). Other vector species collected in this study were Anopheles (Kerteszia) neivai (Howard, Dyar, and Knab) and Anopheles (Anopheles) pseudopunctipennis s.l. (Theobald). High diversity of Anopheles species and six confirmed malaria vectors in endemic areas of Panama emphasize the need for more detailed studies to better understand malaria transmission dynamics. PMID:18826025

LOAIZA, J. R.; BERMINGHAM, E.; SCOTT, M. E.; ROVIRA, J. R.; CONN, J. E.

2010-01-01

283

Grain size distribution and composition of modern dune and beach sediments, Malindi Bay coast, Kenya  

NASA Astrophysics Data System (ADS)

Grain size distribution and heavy mineral content of beach and dune sediments from the Malindi Bay coast, Kenya were determined. Grain sizes were determined by dry sieving sediments; samples represent the upper 5 mm of surficial sediment, collected from the four main geomorphological units (beach, berm zone, foredune and dunefield), during three observation periods, covering the southeast and northeast monsoon seasons. Sediment samples were grouped according to whether they were collected from the northern or southern sector of the Sabaki river. The heavy mineral content of several samples collected from the beach, berm zone and sand dunes was obtained by using separating funnels and tetrabromomethane to gain insight into the mineral distribution, the mineralogy and comment on the economic potential of prospecting for the heavy minerals. The petrographic parameters determined include the heavy mineral weight percentages and the mineral composition of the heavy fractions obtained using a petrographic microscope. The Malindi Bay shore is dominated by terrigenous deposits brought in by the Sabaki river which consist mainly of fine- to medium-grained quartz sand. The sediments also contain heavy minerals averaging about 15%, with highest concentration being 67% by weight for the samples analyzed. The heavy mineral suite here is dominated by opaque iron-titanium minerals as well as some red garnet and zircon. The results demonstrate a good relationship between the heavy mineral concentrations and the corresponding geomorphological elements. There are some differences between the various geomorphological units, with a subtle trend from the beach to the dunes. During all three observation periods grain size decreases slightly from the beach to the foredune. The sediment size fraction 0.625?, present on the beach, was absent in the immediate aeolian environments, except for the steep slopes of sand sheets and interdune valleys. The berm zone rarely has sediments coarser than 1.125?. The grain size parameters at different beach locations do not suggest a general trend of longshore variations, except on the beach close to the river mouth. The differences between the seasons were larger than those between the geomorphological units. During the northeast monsoon the mean size was coarser, sorting was worse and the distribution was more positively skewed.

Abuodha, J. O. Z.

2003-02-01

284

Structural Health Monitoring of Composite Materials Using Distributed Fiber Bragg Sensors  

NASA Technical Reports Server (NTRS)

Health monitoring of polymer matrix composite materials using fiber optic Bragg grating (FBG) sensors is accomplished using a tunable IR (infrared) laser via transmission mode. Results are presented from experiments of composite structures with FBG's embedded at various orientations, and surface measurements of various cryogenic composite vessels.

Grant, Joseph; Kual, Raj; Taylor, Scott; Jackson, Kurt V.; Myers, George; Wang, Y.; Sharma, A.; Burdine, Robert (Technical Monitor)

2002-01-01

285

Deformation and Life Analysis of Composite Flywheel Disk and Multi-disk Systems  

NASA Technical Reports Server (NTRS)

In this study an attempt is made to put into perspective the problem of a rotating disk, be it a single disk or a number of concentric disks forming a unit. An analytical model capable of performing an elastic stress analysis for single/multiple, annular/solid, anisotropic/isotropic disk systems, subjected to both pressure surface tractions, body forces (in the form of temperature-changes and rotation fields) and interfacial misfits is derived and discussed. Results of an extensive parametric study are presented to clearly define the key design variables and their associated influence. In general the important parameters were identified as misfit, mean radius, thickness, material property and/or load gradation, and speed; all of which must be simultaneously optimized to achieve the "best" and most reliable design. Also, the important issue of defining proper performance/merit indices (based on the specific stored energy), in the presence of multiaxiality and material anisotropy is addressed. These merit indices are then utilized to discuss the difference between flywheels made from PMC and TMC materials with either an annular or solid geometry. Finally two major aspects of failure analysis, that is the static and cyclic limit (burst) speeds are addressed. In the case of static limit loads, upper, lower, and out-of-plane bounds for disks with constant thickness are presented for both the case of internal pressure loading (as one would see in a hydroburst test) and pure rotation (as in the case of a free spinning disk). The results (interaction diagrams) are displayed graphically in designer friendly format. For the case of fatigue, a representative fatigue/life master curve is illustrated in which the normalized limit speed versus number of applied cycles is given for a cladded TMC disk application.

Arnold, S. M.; Saleeb, A. F.; AlZoubi, N. R.

2001-01-01

286

Glass Composition Constraint Recommendations for Use in Life-Cycle Mission Modeling  

SciTech Connect

The component concentration limits that most influence the predicted Hanford life-cycle HLW glass volume by HTWOS were re-evaluated. It was assumed that additional research and development work in glass formulation and melter testing would be performed to improve the understanding of component effects on the processability and product quality of these HLW glasses. Recommendations were made to better estimate the potential component concentration limits that could be applied today while technology development is underway to best estimate the volume of HLW glass that will eventually be produced at Hanford. The limits for concentrations of P2O5, Bi2O3, and SO3 were evaluated along with the constraint used to avoid nepheline formation in glass. Recommended concentration limits were made based on the current HLW glass property models being used by HTWOS (Vienna et al. 2009). These revised limits are: 1) The current ND should be augmented by the OB limit of OB ? 0.575 so that either the normalized silica (NSi) is less that the 62% limit or the OB is below the 0.575 limit. 2) The mass fraction of P2O5 limit should be revised to allow for up to 4.5 wt%, depending on CaO concentrations. 3) A Bi2O3 concentration limit of 7 wt% should be used. 4) The salt accumulation limit of 0.5 wt% SO3 may be increased to 0.6 wt%. Again, these revised limits do not obviate the need for further testing, but make it possible to more accurately predict the impact of that testing on ultimate HLW glass volumes.

McCloy, John S.; Vienna, John D.

2010-05-03

287

Europa's Crust and Ocean: Origin, Composition, and the Prospects for Life  

USGS Publications Warehouse

We have considered a wide array of scenarios for Europa's chemical evolution in an attempt to explain the presence of ice and hydrated materials on its surface and to understand the physical and chemical nature of any ocean that may lie below. We postulate that, following formation of the jovian system, the europan evolutionary sequence has as its major links: (a) initial carbonaceous chondrite rock, (b) global primordial aqueous differentiation and formation of an impure primordial hydrous crust, (c) brine evolution and intracrustal differentiation, (d) degassing of Europa's mantle and gas venting, (e) hydrothermal processes, and (f) chemical surface alteration. Our models were developed in the context of constraints provided by Galileo imaging, near infrared reflectance spectroscopy, and gravity and magnetometer data. Low-temperature aqueous differentiation from a carbonaceous CI or CM chondrite precursor, without further chemical processing, would result in a crust/ocean enriched in magnesium sulfate and sodium sulfate, consistent with Galileo spectroscopy. Within the bounds of this simple model, a wide range of possible layered structures may result; the final state depends on the details of intracrustal differentiation. Devolatilization of the rocky mantle and hydrothermal brine reactions could have produced very different ocean/crust compositions, e.g., an ocean/crust of sodium carbonate or sulfuric acid, or a crust containing abundant clathrate hydrates. Realistic chemical-physical evolution scenarios differ greatly in detailed predictions, but they generally call for a highly impure and chemically layered crust. Some of these models could lead also to lateral chemical heterogeneities by diapiric upwellings and/or cryovolcanism. We describe some plausible geological consequences of the physical-chemical structures predicted from these scenarios. These predicted consequences and observed aspects of Europa's geology may serve as a basis for further analys is and discrimination among several alternative scenarios. Most chemical pathways could support viable ecosystems based on analogy with the metabolic and physiological versatility of terrestrial microorganisms. ?? 2000 Academic Press.

Kargel, J.S.; Kaye, J.Z.; Head, J. W., III; Marion, G.M.; Sassen, R.; Crowley, J.K.; Ballesteros, O.P.; Grant, S.A.; Hogenboom, D.L.

2000-01-01

288

Influence of Ply Waviness on Fatigue Life of Tapered Composite Flexbeam Laminates  

NASA Technical Reports Server (NTRS)

Nonlinear tapered flexbeam laminates, with significant ply waviness, were cut from a full-size composite rotor hub flexbeam. The specimens were tested under combined axial tension and cyclic bending loads. All of the specimens had wavy plies through the center and near the surfaces (termed marcelled areas), although for some of the specimens the surface marcels were very obvious, and for others they were much smaller. The specimens failed by first developing cracks through the marcels at the surfaces, and then delaminations grew from those cracks, in both directions. Delamination failure occurred in these specimens at significantly shorter fatigue lives than similar specimens without waviness, tested in ref. 2. A 2D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. In addition, the FE model duplicated the waviness observed in one of the test specimens. The model was analyzed using a geometrically nonlinear FE code. Modifications were made to the original model to reduce the amplitude of the marcels near the surfaces. The analysis was repeated for each modification. Comparisons of the interlaminar normal stresses, sigma(sub n), in the various models showed that under combined axial-tension and cyclic-bending loading, for marcels of the same aspect ratio, sigma(sub n) stresses increased as the distance along the taper, from thick to thin end, increased. For marcels of the same aspect ratio and at the same X-location along the taper, sigma(sub n) stresses decreased as the distance from the surface into the flexbeam interior increased. A technique was presented for determining the smallest acceptable marcel aspect ratio at various locations in the flexbeam.

Murri, Gretchen B.

1999-01-01

289

Crustacea in Arctic and Antarctic sea ice: distribution, diet and life history strategies.  

PubMed

This review concerns crustaceans that associate with sea ice. Particular emphasis is placed on comparing and contrasting the Arctic and Antarctic sea ice habitats, and the subsequent influence of these environments on the life history strategies of the crustacean fauna. Sea ice is the dominant feature of both polar marine ecosystems, playing a central role in physical processes and providing an essential habitat for organisms ranging in size from viruses to whales. Similarities between the Arctic and Antarctic marine ecosystems include variable cover of sea ice over an annual cycle, a light regimen that can extend from months of total darkness to months of continuous light and a pronounced seasonality in primary production. Although there are many similarities, there are also major differences between the two regions: The Antarctic experiences greater seasonal change in its sea ice extent, much of the ice is over very deep water and more than 80% breaks out each year. In contrast, Arctic sea ice often covers comparatively shallow water, doubles in its extent on an annual cycle and the ice may persist for several decades. Crustaceans, particularly copepods and amphipods, are abundant in the sea ice zone at both poles, either living within the brine channel system of the ice-crystal matrix or inhabiting the ice-water interface. Many species associate with ice for only a part of their life cycle, while others appear entirely dependent upon it for reproduction and development. Although similarities exist between the two faunas, many differences are emerging. Most notable are the much higher abundance and biomass of Antarctic copepods, the dominance of the Antarctic sea ice copepod fauna by calanoids, the high euphausiid biomass in Southern Ocean waters and the lack of any species that appear fully dependent on the ice. In the Arctic, the ice-associated fauna is dominated by amphipods. Calanoid copepods are not tightly associated with the ice, while harpacticoids and cyclopoids are abundant. Euphausiids are nearly absent from the high Arctic. Life history strategies are variable, although reproductive cycles and life spans are generally longer than those for temperate congeners. Species at both poles tend to be opportunistic feeders and periods of diapause or other reductions in metabolic expenditure are not uncommon. PMID:16905428

Arndt, Carolin E; Swadling, Kerrie M

2006-01-01

290

Analysis of distribution transformer losses and life expectancy using measured harmonic data  

Microsoft Academic Search

Three-phase distribution transformer in electrical power systems are usually designed for utilizing at the rated frequency and linear load. A different performance compared with that of the designed transformer occur when non-linear loads introduce harmonics to the supply. With the increasing use of nonlinear load the harmonic ay overheat the transformer leading to a poor power quality. The increased losses

D. M. Said; K. M. Nor; M. S. Majid

2010-01-01

291

A method for determining oceanic particle size distributions and particle composition using scanning electron microscopy coupled with energy dispersive spectroscopy  

NASA Astrophysics Data System (ADS)

To understand the behavior of light scattered in seawater, it is necessary to know the size distribution of particles in seawater, as well as their composition (refractive index distribution) and complex shape. A method has been developed to determine marine PSDs and simultaneously characterize their chemical compositions by utilizing a scanning electron microscope (SEM) coupled with an energy dispersive spectrometer (EDS) and applying sophisticated image analysis techniques that minimized user bias including automatic image thresholding. The method was validated by verifying the PSD and chemical composition of Arizona test dust, which has a well-documented size distribution and chemical composition. PSDs of field samples collected from the coastal Long Island Sound and the remote South Pacific Ocean were also determined. Where applicable, PSDs agreed well overall with other PSD determining methods such as electroresistive counting and near-forward diffraction theory inversions. The method performed optimally when the particle mass on the filter was between 0.4mg and 1.0mg. With this in mind, measuring particle beam attenuation coefficient at 650nm (c650) can provide immediate feedback in the field to determine filter volumes for sample preparation.

Groundwater, Heather; Twardowski, Michael S.; Dierssen, Heidi M.; Sciandre, Antoine; Freeman, Scott A.

2010-06-01

292

Chemical composition and size distribution of airborne particulate matters in Beijing during the 2008 Olympics  

NASA Astrophysics Data System (ADS)

Size-segregated aerosol samples were collected daily in Beijing from 1 Jun. to 20 Sep. during the Beijing Olympic Games in 2008 to investigate aerosol concentrations, particle size distributions, and sources as well as the effects of pollution control measures on the chemical compositions (including Water-soluble ions, trace elements, elemental carbon (EC), and organic carbon (OC)) in aerosols of different sizes. Water-soluble ions, EC, OC, and trace elements accounted for 45.0%, 1.6%, 14.7%, and 11.4% of the total particle mass (PM), respectively. Approximately 56%, 56%, 30%, 71% and 55% of the PM, water-soluble ions, trace elements, EC and OC, respectively, were associated with particles smaller than 2.1 ?m. Sulfate, nitrate, and ammonium were the dominant ions, which together accounted for approximately 77% of total water-soluble ions. The crustal elements accounted for the majority of the trace elements present. Different sources showed different mass size distributions. Anthropogenic source compounds, such as sulfate, nitrate, ammonium, OC, EC, and toxic elements, were mainly present in fine mode aerosols, whereas crustal elements, such as Al, Fe, Ca, Mg and Ba, primarily occurred in the coarse mode. SO42- and NH4+ concentrations were strongly correlated (r2 = 0.90, slope = 1.63) in the fine mode, thereby indicating that SO42- was mainly present as (NH4)2SO4; in contrast, a weak correlation between SO42- and NH4+ (r2 = 0.18, slope = 0.54) was observed in the coarse mode, indicating that SO42- was associated with other ions. Similarly, SO42- and NO3- exhibited a stronger correlation in the fine mode than in the coarse mode, indicating that SO42- and NO3- were formed via the same in-cloud processes in fine particles. The OC/EC ratio and the correlations between EC and OC concentrations showed that the sources of carbonaceous species were secondary organic carbon from fine particles and the long-range transport of coarse carbonaceous particles from biomass burning. The concentrations of atmospheric pollutants declined during the 2008 Olympic Games, indicating that the pollution control measures were effective in decreasing particulate air pollution in Beijing.

Li, Xingru; Wang, Lili; Wang, Yuesi; Wen, Tianxue; Yang, Yongjie; Zhao, Yanan; Wang, Yingfeng

2012-04-01

293

Distribution, composition and flux of particulate material over the European margin at 47° 50°N  

NASA Astrophysics Data System (ADS)

In the framework of the Ocean Margin Exchange project, a multi-disciplinary study has been conducted at the shelf edge and slope of the Goban Spur in order to determine the spatial distribution, quantity and quality of particle flux, and delineate the transport mechanisms of the major organic and inorganic components. We present here a synthesis view of the major transport modes of both biogenic and lithogenic material being delivered to the open slope of the Goban Spur. We attempt to differentiate between the direct biogenic flux from the surface mixed layer and the advective component, both biogenic and lithogenic. Long-term moorings, instrumented with sediment traps, current meters and transmissometers have yielded samples and near-continuous recordings of hydrographic variables (current direction and speed, temperature and salinity) and light transmission for a period of 2.5 years. Numerous stations have been occupied for CTD casts with light transmission and collection of water samples. The sedimenting material has been analysed for a variety of marker compounds including phytoplankton pigments, isotopic, biomineral and trace metal composition and microscopical analyses. These samples are augmented by seasonal information on the distribution and composition of fine particles and marine snow in the water column. The slope shows well-developed bottom nepheloid layers always present and intermediate nepheloid layers intermittently present. Concentrations are mainly in the range 50-130 mg m -3 in nepheloid layers and 6-25 mg m -3 in clear water. A seasonal variability in the concentration at the clear water minimum is argued to be related to seasonal variations in vertical flux and aggregate break-up in transit during summer months. It is suggested that the winter sink for this seasonal change in particulate matter involves some re-aggregation and scavenging, and some conversion of particulate to dissolved organic matter. This may provide a slow seasonal pump of dissolved organic carbon to the deep ocean interior. Differences in trapped quantities at different water depths are interpreted as due to lateral flux from the continental margin. There is a major lateral input between 600 and 1050 m at an inner station and between 600 and 1440 m at an outer one. The transport is thought to be related to intermediate nepheloid layers, but those measured are too dilute to be able to supply the flux. Observed bottom nepheloid layers are highly concentrated very close to the bed (up to 5 g m -3), with a population of large aggregates. Some of these are capable of delivering the flux seen offshore during intermittent detachment of nepheloid layers into mid-water. Concentrated bottom nepheloid layers are also able to deliver large particles with unstable phytoplankton pigments to the deep sea floor in a few tens of days. Calculated CaCO 3 fluxes are adjusted for dissolution, which is inferred from Ca/Al ratios to be occurring in the CaCO 3-saturated upper water column where up to 80% of the CaCO 3 resulting from primary production is dissolved.

McCave, I. N.; Hall, I. R.; Antia, A. N.; Chou, L.; Dehairs, F.; Lampitt, R. S.; Thomsen, L.; van Weering, T. C. E.; Wollast, R.

294

Southern scandinavian aerosol composition and elemental size distribution characteristics dependence on air-mass history  

NASA Astrophysics Data System (ADS)

The influence of aerosol long range transport in southern Sweden was investigated from a data base consisting of simultaneous cascade impactor measurements at three sampling stations, two coastal and one inland rural location. The study focused on S and heavy metals determined by particle induced X-ray emission (PIXE) analysis. The influence of local emissions was minimized by eliminating samples which were strongly suspected to be contaminated. These were identified through size distribution alterations in combination with the concentration levels obtained. Based on air mass back trajectories the samples were classified into either a southern, a northern or an eastern sector or into one of the buffer sectors located in between the sectors mentioned above. Sector S elemental concentrations were generally one order of magnitude higher than those of sector N, while intermediate concentrations were found in the E sector. Intercomparisons of simultaneous fine mode elemental concentration measurements classified into sectors S and N, respectively, provides a method for calculating the sector S foreign contribution of the elemental concentrations in southern Sweden. These calculations, not based on emission data, result in a foreign contribution of the order of 50-90 % (lowest for components like V and Ni and highest for Ti, Mn and Zn) to the metal concentrations. The multivariate statistical method SIMCA revealed that the sector S aerosol elemental composition was dependent on particle size in the accumulation mode. Elements such as S and V (or Ni) normally assumed to originate mainly from the same sources (fossil fuel combustion) were clearly separated and instead S clustered with K, Mn and Zn. This indicates that the transformation processes are more important for the covariation of S with other elements than the source origin. Transformation of SO 2 in hygroscopic particles rich in K., Mn and Zn (compared with less hygroscopic particles rich in V and Ni) is a possible mechanism which would explain the results found.

Martinsson, Bengt G.; Hansson, Hans-Christen; Lannefors, Hans O.

295

Global distribution, composition, and abundance of olivine on the surface of Mars from thermal infrared data  

NASA Astrophysics Data System (ADS)

We used spectral indexing and linear deconvolution to compare thermal infrared emission spectra of Fo91, Fo68, Fo53, Fo39, Fo18, and Fo1 olivine samples to Mars Global Surveyor Thermal Emission Spectrometer (TES) data over low-albedo regions of Mars. The Fo91, Fo68, Fo53, and Fo39 spectral end-members were confidently identified on Mars, a range of compositions wider than inferred from Martian meteorites. Small (less than hundreds of square kilometers) occurrences of the Fo91 spectral end-member are present in the rims of the Argyre and Hellas impact basins and may represent Martian mantle materials. The Fo68 spectral end-member is common throughout the highlands, chasmata, outflow channels, and Nili Fossae region. The Fo53 spectral end-member occurs in eastern Syrtis Major, the Nili Fossae region, and smooth-floored craters of the highlands. Although less abundant than Fo68 and Fo53, the distribution of the Fo39 spectral end-member suggests that some olivine on Mars is more Fe-rich than olivine in Martian meteorites. Global maps of olivine show that (1) materials containing 10-20% of olivine are common in the southern highlands of Mars, (2) olivine is most common near the topographic dichotomy boundary, and (3) olivine becomes uncommon near the poles suggesting that it may be influenced by topography and/or latitude (climate). Olivine is found in early Noachian to Amazonian terrains, some of which may be coeval with phyllosilicate and sulfate deposits detected by OMEGA implying that any early Noachian wet period of Mars' climate history may have been globally inhomogeneous or insufficient to weather the olivine that remains today.

Koeppen, William C.; Hamilton, Victoria E.

2008-05-01

296

Distributions  

NSDL National Science Digital Library

This online, interactive lesson on distributions provides examples, exercises, and applets which explore the basic types of probability distributions and the ways distributions can be defined using density functions, distribution functions, and quantile functions.

Siegrist, Kyle

2008-12-24

297

Failure models for textile composites  

NASA Technical Reports Server (NTRS)

The goals of this investigation were to: (1) identify mechanisms of failure and determine how the architecture of reinforcing fibers in 3D woven composites controlled stiffness, strength, strain to failure, work of fracture, notch sensitivity, and fatigue life; and (2) to model composite stiffness, strength, and fatigue life. A total of 11 different angle and orthogonal interlock woven composites were examined. Composite properties depended on the weave architecture, the tow size, and the spatial distributions and strength of geometrical flaws. Simple models were developed for elastic properties, strength, and fatigue life. A more complicated stochastic model, called the 'Binary Model,' was developed for damage tolerance and ultimate failure. These 3D woven composites possessed an extraordinary combination of strength, damage tolerance, and notch insensitivity.

Cox, Brian

1995-01-01

298

Estimation in step-stress partially accelerated life tests for the Burr type XII distribution using type I censoring  

Microsoft Academic Search

In this paper, step-stress partially accelerated life tests are considered when the lifetime of a product follows a Burr type XII distribution. Based on type I censoring, the maximum likelihood estimates (MLEs) are obtained for the distribution parameters and acceleration factor. In addition, asymptotic variance and covariance matrix of the estimators are given. An iterative procedure is used to obtain

A. M. Abd-Elfattah; Amal S. Hassan; S. G. Nassr

2008-01-01

299

Ion angular distribution in plasma of vacuum arc ion source with composite cathode and elevated gas pressure.  

PubMed

The Metal Vapor Vacuum Arc (MEVVA) ion sources are capable of generating ion beams of almost all metals of the periodic table. For this kind of ion source, a combination of gas feeding with magnetic field allows the simultaneous generation of both metal and gaseous ions. That makes the MEVVA ion source an excellent instrument for science and application. This work presents results of investigation for ion angular distributions in vacuum arc plasma of Mevva-V.Ru ion source for composite cathodes and for elevated gas pressure. It was shown that for all the cathode materials, singly charged ions have wider angular distribution than multiply charged ions. Increasing the working gas pressure leads to a significant change in the angular distribution of gaseous ions, while with the distribution of metal ions gas remains practically unchanged. The reasons for such different influences are discussed. PMID:24593598

Nikolaev, A G; Savkin, K P; Yushkov, G Yu; Oks, E M

2014-02-01

300

Strength Prediction and Optimization of Composites with Statistical Fiber Flaw Distributions  

Microsoft Academic Search

For continuous fiber reinforced polymeric composites the process domi nating tensile strength is fiber fracture. This phenomena results in stress concentrations in adjacent fibers over some distance which is directly associated with the ineffective length. This length is the controlling factor in the theory of bundle strength for polymer-based composites. The associated stress concentration factor, C, is normally associated with

Zhanjun Gao; Kenneth L. Reifsnider; Greg Carman

1992-01-01

301

Thermoelectric figure of merit for bulk nanostructured composites with distributed parameters  

SciTech Connect

The effective properties of composites whose structure includes nanocontacts between bulk-phase macrocrystallites are considered. A model for such a nanostructured composite is constructed. Effective values of the thermoelectric power, thermal and electrical conductivities, and thermoelectric figure of merit are calculated in the mean-field approximation.

Snarskii, A. A. [National Technical University 'Kyiv Polytechnic Institute' (Ukraine); Sarychev, A. K. [Russian Academy of Sciences, Institute for Theoretical and Applied Electromagnetics (Russian Federation); Bezsudnov, I. V., E-mail: biv@akuan.ru ['Nauka-Service' Scientific and Production Company (Russian Federation); Lagarkov, A. N. [Russian Academy of Sciences, Institute for Theoretical and Applied Electromagnetics (Russian Federation)

2012-05-15

302

Size distribution and chemical composition of secondary organic aerosol formed from C1-initiated oxidation of toluene.  

PubMed

Secondary organic aerosol (SOA) formed from C1-initiated oxidation of toluene was investigated in a home-made smog chamber. The size distribution and chemical composition of SOA particles were measured using aerodynamic particle sizer spectrometer and the aerosol laser time-of-flight mass spectrometer (ALTOFMS), respectively. According to a large number of single aerosol diameter and mass spectra, the size distribution and chemical composition of SOA were obtained statistically. Experimental results showed that SOA particles created by C1-initiated oxidation of toluene is predominantly in the form of fine particles, which have diameters less than 2.5 microm (i.e., PM2.5), and glyoxal, benzaldehyde, benzyl alcohol, benzoquinone, benzoic acid, benzyl hydroperoxide and benzyl methyl nitrate are the major products components in the SOA. The possible reaction mechanisms leading to these products are also proposed. PMID:22893963

Huang, Mingqiang; Zhang, Weijun; Gu, Xuejun; Hu, Changjin; Zhao, Weixiong; Wang, Zhenya; Fang, Li

2012-01-01

303

The Influence of Body Composition, Fat Distribution, and Sustained Weight Loss on Left Ventricular Mass and Geometry in Obesity  

Microsoft Academic Search

Alterations in left ventricular mass and geometry vary along with the degree of obesity, but mechanisms underlying such covariation are not clear. In a case–control study, we examined how body composition and fat distribution relate to left ventricular structure and examine how sustained weight loss affects left ventricular mass and geometry. At the 10-year follow-up of the Swedish obese subjects

Dimitris Kardassis; Odd Bech-Hanssen; Marie Schönander; Lars Sjöström; Kristjan Karason

2012-01-01

304

Characterization of melting properties in dark chocolates from varying particle size distribution and composition using differential scanning calorimetry  

Microsoft Academic Search

Melting properties in dark chocolates processed from varying particle size distribution (PSD), fat and lecithin content were studied using differential scanning calorimetry (DSC). Compositional parameters were PSD (D90 (90% finer than this size) of 18, 25, 35 and 50?m), fat (25%, 30% and 35%) and lecithin (0.3% and 0.5%) contents. Variations in PSD had no influence on crystallinity of products.

Emmanuel Ohene Afoakwa; Alistair Paterson; Mark Fowler; Joselio Vieira

2008-01-01

305

Composition, Distribution, and Characterization of Suspected Endocrine-Disrupting Pesticides in Beijing GuanTing Reservoir (GTR)  

Microsoft Academic Search

GuanTing Reservoir (GTR) is one of two main water resources for the agriculture, industry, and living uses of Beijing (China).\\u000a As a result of extensive pollution over the last few decades (particularly the 1980s), the reservoir has not supplied potable\\u000a water to Beijing city since 1997. Composition, distribution, and characterization of 31 suspected endocrine-disrupting pesticides\\u000a in surface water, pore water,

Nandong Xue; Xiaobai Xu

2006-01-01

306

Evaluation of the Fiber Stress Distribution in Aramid\\/Epoxy Model Composite Using Micro-Raman Spectroscopy and FEM Analysis  

Microsoft Academic Search

A single-fiber pull-out model composite for an aramid\\/epoxy system was specially designed to measure the stress distribution of the aramid fiber embedded in the matrix using micro-Raman spectroscopy. The stress transfer length of the fiber obtained was about 400-500 mum, which was equal to the result of FEM analysis. Just after the initiation and propagation of the fiber\\/matrix interfacial debonding,

Kazuto Tanaka; Kohji Minoshima; Hideo Yamada

2007-01-01

307

Effect of high temperature and fiber distribution on matrix microcracking and toughness of ceramic-matrix composites  

Microsoft Academic Search

This study investigates effect of fiber distribution and temperature on matrix microcracking and toughness of the material, because ceramic-matrix composites are expected to work under high-temperature circumstances. In chapter 2, 3, and 4, two theoretical models of microcracking (two-fiber model and ring model) are proposed and used for the analyses of microcracking. Stress intensity factors or strain energy release rates

Xu Yongli

1991-01-01

308

Effect of the pulse repetition rate on the composition and ion charge-state distribution of pulsed vacuum arcs  

Microsoft Academic Search

The plasma composition and ion charge-state distributions of pulsed vacuum arcs have been investigated for carbon, aluminum, silver, platinum, and tantalum cathodes using a time-of-flight (TOF) charge-to-mass spectrometer. With the exception of carbon, it was found that all results depend on the arc pulse repetition rate, a fact which, up to now, has not been reported in the literature. It

George Y. Yushkov; A. Anders

1998-01-01

309

Analysis of the distribution of the isotopic composition of evapotranspiration flux in a semi-arid savanna.  

NASA Astrophysics Data System (ADS)

The cycling of water in semi-arid regions is critical for the ecohydrologic processes of savanna systems. Stable isotopes of water serve as important tracers of water movement, and studies of how the isotopic distribution of rainfall is transformed through geomorphic basin characteristics into an isotopic distribution of runoff have yielded insight into watershed dynamics. However, in many drylands, the majority of return flux of water out of ecosystems is in the form of evapotranspiration. Through a combination of field measurements and modeling, we present a study of the factors that influence the transformation of the isotopic distribution of precipitation into an isotopic distribution of evapotranspiration. Field observations were collected at a micrometerological tower located in a mixed-savanna in Laikipa, Kenya. The tower is equipped with an off-axis integrated cavity output spectroscopy system (ICOS), and the isotopic composition of atmospheric water vapor has been sampled at 1 Hz from 2010 through 2012. Evapotranspiration isotopic composition is estimated based on Keeling plots for each 30 minute time period, with seasonal dynamics evident throughout this multi-year study. Isotopic analysis of collected rainfall and cryogenic vacuum distillation of soil and plant samples at the site aid in the interpretation of water cycling. A decrease in the variance of evapotranspiration flux composition relative to precipitation is indicative of soil water mixing as well as runoff and recharge effects. Stochastic modeling of the isotopic inputs and outputs of the semi-arid systems demonstrates the strength of the influence that rainfall climatology, plant rooting depth, and evapotranspiration characteristics have on the ratio of the variances of input and output isotopic composition.

Good, Stephen; O'Connor, Molly; Soderberg, Keir; Wang, Lixin; Caylor, Kelly

2013-04-01

310

Microbial Biomass Distribution and Compositional Changes Associated with a Warmer Climate in Boreal Forest Soils  

NASA Astrophysics Data System (ADS)

Predicting the physiological and structural changes of the microbial community in warming soils is essential for a functional understanding of climate feedback mechanisms. Laboratory and field experiments have often found that warming increases soil organic carbon (SOC) mineralization and decreases microbial biomass, but remain more inconclusive regarding microbial community structure. These experiments, however, have been limited to responses on a time scale of months to years, while soil properties change over decades to centuries. Studies along climate gradients may prove helpful in elucidating how climate history affects soil properties, including microbial community structure. We present the phospholipid fatty acid (PLFA) based community characterization of the organic (L, F, H) and mineral (B; top 10cm) horizons of podzols from two mesic boreal forest sites similar in most aspects (e.g. stand type, class and age) but differing in mean annual temperature (MAT) by almost 6°C. This temperature difference is similar to the warming predicted for this region by 2100. Results are compared to respiration rates in laboratory incubations. We observed consistent PLFA derived biomass per unit SOC throughout the profile, independent of depth or site. The organic horizons contained similar amounts of SOC and PLFA as the top 10 cm of the mineral horizon (2.5-3.4 kg C m-2; 10.3-12.6 mmol PLFA m-2). Within the organic horizon, the greatest proportion of SOC and PLFA were found in the F horizon. The overall distribution of PLFA among the soil horizons was largely unaffected by climate regime, except that biomass was shifted from F to L horizons at the warmer site (from 12% to 29% of total organic horizon PLFA located in L) indicating that biomass was located closer to the surface in warmer sites. A similar shift was found in respiration (26 vs. 42% of organic horizon CO2 from L). As expected, community structure changed with depth. The abundance of fungal and protozoan PLFA decreased and that of Gram+ and Gram- bacteria increased in deeper soil horizons. Within each horizon, community composition was well constrained and did not vary with climate except for higher contributions of long chain (C20+) saturated fatty acids at the colder site. Interestingly, the ratio cy17:0/16:1?7, a physiological indicator of elevated stress or dormancy for the bacterial communities, was elevated within the warmer sites and mineral horizons. This is congruent with SOC normalized respiration rates that were least 5x lower in B relative to the LFH horizons and 50% lower within F and H horizons from the warmer relative colder site. In combination these results suggest that the microbial community in deeper soil horizons and from the warmer climate regime contain a microbial community equally abundant relative to the soil C pool sizes, but not as prolific in CO2 production. Overall, our results suggest that relatively warm climatic regimes in the boreal zone can promote shallower peaks of soil microbial biomass and respiration and shifts in physiology compared to cooler systems, but no discernible differences in community composition.

Kohl, L.; Jérôme, J.; Billings, S. A.; Edwards, K.; Morrill, P. L.; Ziegler, S. E.

2013-12-01

311

Source apportionment of ambient fine particle from combined size distribution and chemical composition data during summertime in Beijing  

NASA Astrophysics Data System (ADS)

Continuous particle number concentration and chemical composition data were collected over one month during summertime in Beijing to investigate the source apportionment of ambient fine particles. Particle size distributions from 15 nm to 2.5 ?m in diameter and composition data, such as organic matter, sulfate, nitrate, ammonium, chlorine, and gaseous pollutants, were analyzed using positive matrix factorisation (PMF) which indentified eight factors: cooking, solid mode exhaust, nucleation mode exhaust, accumulation mode, secondary nitrate, secondary sulfate, coal-fired power plant and road dust. Nearly two-thirds of particle number concentrations were attributed to cooking (22.8%) and motor vehicle (37.5%), whereas road dust, coal-fired power plant and regional sources contributed 69.0% to particle volume concentrations. Local and remote sources were distinguished using size distributions associated with each factor. Local sources were generally characterised by unimodal or bimodal number distributions, consisting mostly of particles less 0.1 ?m in diameter, and regional sources were defined by mostly accumulation mode particles. Nearly one third of secondary nitrate and secondary sulfate was transported from the surrounding areas of Beijing during study period. Overall the introduction of combination of particle number concentration and chemical composition in PMF model is successful at separating the components and quantifying relative contributions to the particle number and volume population in a complex urban atmosphere.

Liu, Z. R.; Wang, Y. S.; Liu, Q.; Hu, B.; Sun, Y.

2013-01-01

312

Mesoscale distribution and community composition of zooplankton in the Mozambique Channel  

NASA Astrophysics Data System (ADS)

Recent studies have shown the Mozambique Channel to exhibit high mesoscale variability, but how mesoscale features influence the zooplankton community in this region is not known. The biovolume, biomass, vertical distribution and community composition of mesozooplankton (>200 µm) associated with mesoscale eddies in the Mozambique Channel was investigated during four cruises in September 2007, December 2008, November 2009 and April/May 2010. Stations were categorized according to their location in cyclonic (cold-core) or anticyclonic (warm-core) eddies, frontal, divergence or shelf regions. Mean mesozooplankton biovolume in the upper 200 m was 0.33 ml m-3, with zooplankton largely concentrated in the upper 100 m during all four cruises (weighted mean depth=66.6 m). Sampling depth was the most important predictor of biovolume, which was greatest for net samples with a mid-depth of 0-40 m, but declined deeper in the water column. Biovolume at the shelf (0.37 ml m-3), divergence and cyclonic eddy stations (0.31 ml m-3) was significantly greater than at frontal and anticyclonic eddy stations (0.20 ml m-3). Mean biovolume was significantly higher during 2008 and 2010 compared to 2007 and 2009, and was also significantly higher for samples collected at night (and twilight) than during the day. The mesozooplankton community in 2007 was strongly dominated by small copepods (~70-80% abundance) followed by appendicularians (10%), ostracods (8%) and chaetognaths (7%). The most abundant copepods were the Paracalanids, Oncaea spp., Oithona spp. and Corycaeus spp. Multivariate analysis showed that the communities in 2007 and 2008 were most strongly structured by depth, but classification (cyclonic/anticyclonic) was also important in 2007 when mesoscale features were more strongly developed. Zooplankton assemblages showed a high degree of homogeneity, with differences between mesoscale features largely due to differing abundances of similar taxa. These observations suggest that mesoscale eddy and shelf interactions play a fundamental role in shaping the Mozambique Channel pelagic ecosystem through the concentration, enhanced growth and redistribution of zooplankton communities. Although frontal areas between eddies were poor in zooplankton biomass, the extensive inter-eddy divergence areas were as rich in biomass as the small cyclonic eddy core regions. These patterns are important for understanding the favorability of observed foraging areas for higher trophic levels.

Huggett, Jenny A.

2014-02-01

313

Analysis of knitted fabric reinforced composites: Part I. Fibre orientation distribution  

Microsoft Academic Search

The fibre orientation distributions in different types of warp knitted fabric are studied. The fibre orientations are represented by orientation tensors. This allows for the production of second- and fourth-order approximations of the orientation distribution function, which contain the relevant part of the orientation distribution for second- and fourth-order tensorial properties, respectively. Also, the symmetry that is present in the

B. Gommers; I. Verpoest; P. Van Houtte

1998-01-01

314

S3QL: A distributed domain specific language for controlled semantic integration of life sciences data  

PubMed Central

Background The value and usefulness of data increases when it is explicitly interlinked with related data. This is the core principle of Linked Data. For life sciences researchers, harnessing the power of Linked Data to improve biological discovery is still challenged by a need to keep pace with rapidly evolving domains and requirements for collaboration and control as well as with the reference semantic web ontologies and standards. Knowledge organization systems (KOSs) can provide an abstraction for publishing biological discoveries as Linked Data without complicating transactions with contextual minutia such as provenance and access control. We have previously described the Simple Sloppy Semantic Database (S3DB) as an efficient model for creating knowledge organization systems using Linked Data best practices with explicit distinction between domain and instantiation and support for a permission control mechanism that automatically migrates between the two. In this report we present a domain specific language, the S3DB query language (S3QL), to operate on its underlying core model and facilitate management of Linked Data. Results Reflecting the data driven nature of our approach, S3QL has been implemented as an application programming interface for S3DB systems hosting biomedical data, and its syntax was subsequently generalized beyond the S3DB core model. This achievement is illustrated with the assembly of an S3QL query to manage entities from the Simple Knowledge Organization System. The illustrative use cases include gastrointestinal clinical trials, genomic characterization of cancer by The Cancer Genome Atlas (TCGA) and molecular epidemiology of infectious diseases. Conclusions S3QL was found to provide a convenient mechanism to represent context for interoperation between public and private datasets hosted at biomedical research institutions and linked data formalisms. PMID:21756325

2011-01-01

315

Derangement of composite filler distribution inside syringe-type delivery systems.  

PubMed

Used and almost emptied syringes of two brands of composites contained material close to the pestle-head that appeared to be more granular and dry, as compared to the composite obtained from unused syringes. The present results suggest that a derangement of filler and matrix phases occurred inside the used syringes when compared to unused controls. Stress imposed on the composite material inside the unused syringes resulted in a comparable derangement of filler and matrix phases. Although this derangement was limited, the effect could contribute to intra- and interlaboratory scattering of data. PMID:8299865

Braem, M J; Lambrechts, G; Davidson, C L; Vansant, E F; Vanhoof, C

1993-01-01

316

Development of Atmospheric Neutral Analyzer for Neutral Mass Composition and Velocity Distribution Measurements in the Upper Atmosphere  

NASA Astrophysics Data System (ADS)

In order to understand the temporal and spatial variability of the ionosphere-thermosphere system, simultaneous measurements of the composition and density of the neutral atmosphere and the velocity distribution of individual species are essential. However, most conventional types of instruments for neutral atmosphere lack the simultaneous capability of measuring neutral atmospheric velocity and resolving neutral mass. We are designing the Atmospheric Neutral Analyzer (ANA) instrument to measure neutral composition and velocity distribution simultaneously in the thermosphere. It is designed to measure the detailed, mass-resolved 2-dimensional velocity distribution of neutral species, and to derive the corresponding density, mass composition, bulk velocity and temperature from the measured distribution. The ANA is comprised of 4 sections; Entrance Aperture (EA), Ion Accelerator (IA), Radio-Frequency Ion Mass Analyzer (MA) and Imaging Particle Detector (PD). The EA consists of a planar aperture slit and deflection electrode, and functions as an incident-particle selector and collimator. A small fraction of the neutral particles is ionized by electron beam. The IA acts as a particle energy selector by accelerating the ionized neutral particles. The MA acts as an ion velocity selector. The radio-frequency voltage is applied to grids and selectively accelerates ions of matching speed. As a result, ions with a particular mass-per-charge are selected. The PD, which is comprised of a retarding grid, micro-channel plate and charge coupled device, detects the mass-selected ions, and a 2-dimensional image of velocity distribution is obtained. We present the detailed design of the ANA in this paper.

Shimoyama, M.; Hayashi, A.; Ishiguro, K.; Hirahara, M.; Yau, A. W.

2012-12-01

317

Life history and vertical distribution of the mesopelagic fish Cyclothone alba (family Gonostomatidae) in Sagami Bay, Central Japan  

NASA Astrophysics Data System (ADS)

Life history and vertical distribution of the mesopelagic fish Cyclothone alba (family Gonostomatidae) are described on the basis of over 4000 specimens taken during a series of 15 cruises from December 1982 to December 1984 at a station near the center of Sagami Bay, Central Japan. C. alba does not undertake diel vertical migrations, being concentrated in the mesopelagic zone between 300 and 500 m, with peak abundance at 350 m both day and night. Spawning occurs mainly during the late spring and summer months in Sagami Bay. C. alba is semelparous, releasing about 200-650 eggs at the end of its life. Duration of the egg and larval stages is estimated to be about 2-3 months. Many males and some females mature at 1 year, and all individuals mature by 2 years of age. Sexual dimorphism in smaller males and larger females results from an earlier decline of growth rate in males: on the average, males reach 17.5 mm SL (standard length) in 1 year and 21 mm SL in 2 years, whereas females reach 19 mm SL in 1 year and 26 mm SL in 2 years. It is suggested that such precocious maturation, together with its small larvalized form, is attained through progenesis.

Miya, Masaki; Nemoto, Takahisa

1986-08-01

318

Life cycle analysis of distributed concentrating solar combined heat and power: economics, global warming potential and water  

NASA Astrophysics Data System (ADS)

We report on life cycle assessment (LCA) of the economics, global warming potential and water (both for desalination and water use in operation) for a distributed concentrating solar combined heat and power (DCS-CHP) system. Detailed simulation of system performance across 1020 sites in the US combined with a sensible cost allocation scheme informs this LCA. We forecast a levelized cost of 0.25 kWh-1 electricity and 0.03 kWh-1 thermal, for a system with a life cycle global warming potential of ˜80 gCO2eq kWh-1 of electricity and ˜10 gCO2eq kWh-1 thermal, sited in Oakland, California. On the basis of the economics shown for air cooling, and the fact that any combined heat and power system reduces the need for cooling while at the same time boosting the overall solar efficiency of the system, DCS-CHP compares favorably to other electric power generation systems in terms of minimization of water use in the maintenance and operation of the plant. The outlook for water desalination coupled with distributed concentrating solar combined heat and power is less favorable. At a projected cost of 1.40 m-3, water desalination with DCS-CHP would be economical and practical only in areas where water is very scarce or moderately expensive, primarily available through the informal sector, and where contaminated or salt water is easily available as feed-water. It is also interesting to note that 0.40-1.90 m-3 is the range of water prices in the developed world, so DCS-CHP desalination systems could also be an economical solution there under some conditions.

Norwood, Zack; Kammen, Daniel

2012-12-01

319

Composites  

NASA Astrophysics Data System (ADS)

The Composites market is arguably the most challenging and profitable market for phenolic resins aside from electronics. The variety of products and processes encountered creates the challenges, and the demand for high performance in critical operations brings value. Phenolic composite materials are rendered into a wide range of components to supply a diverse and fragmented commercial base that includes customers in aerospace (Space Shuttle), aircraft (interiors and brakes), mass transit (interiors), defense (blast protection), marine, mine ducting, off-shore (ducts and grating) and infrastructure (architectural) to name a few. For example, phenolic resin is a critical adhesive in the manufacture of honeycomb sandwich panels. Various solvent and water based resins are described along with resin characteristics and the role of metal ions for enhanced thermal stability of the resin used to coat the honeycomb. Featured new developments include pultrusion of phenolic grating, success in RTM/VARTM fabricated parts, new ballistic developments for military vehicles and high char yield carbon-carbon composites along with many others. Additionally, global regional market resin volumes and sales are presented and compared with other thermosetting resin systems.

Taylor, John G.

320

Lipid composition and partitioning of deepwater chondrichthyans: inferences of feeding ecology and distribution  

Microsoft Academic Search

The composition of lipids and fatty acids was determined for the livers, muscle, pancreas, kidney and stomach fluids of deepwater\\u000a chondrichthyan species (including 11 squaliformes, 3 chimaeriformes, 1 hexanchiforme and 3 carcharhiniformes) caught as bycatch\\u000a from continental waters off south-eastern Australia. The lipid class, fatty acid and fatty alcohol composition differed markedly\\u000a in each tissue and in each species. The

Heidi Pethybridge; Ross Daley; Patti Virtue; Peter Nichols

2010-01-01

321

Seasonal distribution and fatty acid composition of littoral microalgae in the Yenisei River  

Microsoft Academic Search

We studied fatty acid (FA) composition of littoral microalgae in the fast-flowing oligotrophic river, the Yenisei, Siberia,\\u000a monthly for 3 years. Seasonal dynamics of species composition had similar patterns in all the studied years. In springs, a\\u000a pronounced dominance of filamentous green algae occurred, in summer and autumn diatoms were abundant, and in late autumn and\\u000a winter epilithic biofilms consisted primarily

Nadezhda N. Sushchik; Michail I. Gladyshev; Elena A. Ivanova; Elena S. Kravchuk

2010-01-01

322

Adaptive component composition and load balancing for distributed stream processing applications  

Microsoft Academic Search

Providing real-time and QoS support to stream processing applications running on top of large-scale overlays is challenging\\u000a due to the inherent heterogeneity and resource limitations of the nodes and the multiple QoS demands of the applications that\\u000a must concurrently be met. In this paper we propose an integrated adaptive component composition and load balancing mechanism\\u000a that (1) allows the composition

Thomas Repantis; Yannis Drougas; Vana Kalogeraki

2009-01-01

323

Reliability analysis of GFRP pultruded composite rods  

Microsoft Academic Search

The mechanical properties of FRP composites have a remarkable scatter, even when the specimens are prepared and tested under identical conditions. Proposes a new computerized method for estimating accurately the parameters (X0, ?, ?) of Weibull distribution function. Calculates the safe design of fatigue life data of glass fibre (ER 1150 F-183) reinforced polyester (Q 8520 A) pultruded composite rods

M. H. Abdallah; Enayat M. Abdin; A. I. Selmy; U. A. Khashaba

1996-01-01

324

Distribution of stable isotopes in arid storms . I. Relation between the distribution of isotopic composition in rainfall and in the consequent runoff  

NASA Astrophysics Data System (ADS)

Temporal distributions of the isotopic composition in arid rain storms and in the associated runoff were investigated in a small arid rocky basin in Israel. Customized rain and runoff samplers provided sequential water samples hermetically sealed in high-density PVC bags. In several storms where the runoff was isotopically depleted, compared with the rainfall, the difference could not be explained by fractionation effects occurring during overland flow. A water-balance study relating the runoff discharge to rainfall over a rocky watershed showed that the entire discharge is produced by a very small segment (1-2mm) of the rain storm. The major objective, therefore, was to provide quantitative relations between segments of rainfall (rain showers and rain spells) and runoff. The time distribution of the composition of stable isotopes (oxygen and hydrogen) was used to quantify the correlation between the rain spell's amount and the consequent runoff. The aim of this work was to (a) utilize the dynamic variations in the isotopic composition in rainfall and runoff and model the magnitude of surface-storage capacity associated with runoff processes of overland flow, and (b) characterize the isotopic composition of the percolating water with respect to the isotopic distribution in rainfall and runoff events. The conceptual model postulates an isotopic mixing of overland flow with water within the depression storage. A transport model was then formulated in order to estimate the physical watershed parameters that control the development of overland flow from a certain rainfall period. Part I (this paper) presents the results and the assessment of the relative depression storage obtained from oxygen-18 and deuterium analyses that lead to the physical and mathematical formulation of a double-component model of kinematic-wave flow and transport, which is presented in Part II (accompanying paper). Résumé Les variations temporelles, en zone aride, de la composition isotopique des précipitations et du ruissellement associé ont étéétudiées dans un petit bassin rocheux aride en Israël. Des préleveurs spécialement adaptés pour la pluie et le ruissellement ont fourni des échantillons séquentiels dans des sacs en PVC haute densité hermétiquement fermés. Au cours de plusieurs épisodes pluvieux où le ruissellement était isotopiquement appauvri par rapport à la pluie, la différence ne pouvait pas être expliquée par des effets de fractionnement intervenant au cours de l'écoulement en surface. Un bilan hydrologique rapportant l'écoulement de surface à la pluie sur un bassin versant rocheux montre que l'écoulement dans sa totalité est alimenté par une très petite partie (1-2mm) de l'averse. C'est pourquoi l'objectif essentiel a été de rechercher des relations quantitatives entre des parties de la pluie (averses et épisodes pluvieux) et le ruissellement. La répartition temporelle de la composition en isotopes stables (oxygène et hydrogène) a été utilisée pour quantifier la corrélation entre la hauteur tombée pendant l'épisode pluvieux et le ruissellement produit. Le but de ce travail était (a) d'utiliser les variations dynamiques de la composition isotopique dans la pluie et dans le ruissellement pour modéliser l'ordre de grandeur de la capacité de stockage de surface associée aux processus de ruissellement de l'écoulement de surface, et (a) de caractériser la composition isotopique de l'eau d'infiltration par rapport à la variation isotopique observée dans les pluies et dans les écoulements correspondants. Resumen La distribución temporal de la composición isotópica de las tormentas en zonas áridas y la correspondiente escorrentía se analizó en una pequeña cuenca rocosa en Israel. Los medidores de lluvia y escorrentía proporcionaron muestras de agua secuenciales, selladas herméticamente en bolsas de PVC de alta densidad. En muchas tormentas en las que la escorrentía tenía una composición isotópica distinta de la lluvia, la diferencia no podía explicarse por efectos de fraccionamien

Adar, E. M.; Dody, A.; Geyh, M. A.; Yair, A.; Yakirevich, A.; Issar, A. S.

325

Decapod crustacean larval communities in the Balearic Sea (western Mediterranean): Seasonal composition, horizontal and vertical distribution patterns  

NASA Astrophysics Data System (ADS)

Decapod crustaceans are the main target species of deep water bottom trawl fisheries in the Balearic Sea but little is known about their larval stages. This work focuses on the species composition of the decapod larval community, describing the main spatio-temporal assemblages and assessing their vertical distribution. Mesozooplankton sampling was carried out using depth-stratified sampling devices at two stations located over the shelf break and the mid slope, in the north-western and southern Mallorca in late autumn 2009 and summer 2010. Differences among decapod larvae communities, in terms of composition, adult's habitat such as pelagic or benthic, and distribution patterns were observed between seasons, areas and station. Results showed that for both seasons most species and developmental stages aggregated within the upper water column (above 75 m depth) and showed higher biodiversity in summer compared to late autumn. Most abundant species were pelagic prawns (e.g., Sergestidae) occurring in both seasons and areas. The larval assemblages' distributions were different between seasonal hydrographic scenarios and during situations of stratified and non-stratified water column. The vertical distribution patterns of different larval developmental stages in respect to the adult's habitat were analyzed in relation to environmental variables. Fluorescence had the highest explanatory power. Four clearly different vertical patterns were identified: two corresponding to late autumn, which were common for all the main larval groups and other two in summer, one corresponding to larvae of coastal benthic and the second to pelagic species larvae.

Torres, Asvin P.; Dos Santos, Antonina; Balbín, Rosa; Alemany, Francisco; Massutí, Enric; Reglero, Patricia

2014-10-01

326

Analysis of fragmentation in the single filament composite: Roles of fiber strength distributions and exclusion zone models  

NASA Astrophysics Data System (ADS)

Exact equations are derived governing the evolution of fragments in a long fiber loaded according to the "single filament composite test." These equations are derived with no a priori assumptions regarding the distribution for fiber strength except that the distribution of fiber flaws along the length follows a compound Poisson process in terms of flaw strength. Furthermore, the interface model and the fiber stress profile in the exclusion zone around a fiber break can be arbitrary as long as the exclusion zone is well defined. Explicit and exact closed-form solutions of the governing equations are obtained under these general conditions including random initial breaks before load is applied, which have exponentially distributed spacings of a given normalized rate a along the fiber. We demonstrate this method by finding the exact closed-form solution for a bilinear stress interface model proposed earlier.

Hui, C.-Y.; Phoenix, S. L.; Kogan, L.

1996-10-01

327

Composition and distribution of the main active components in selenium-enriched fruit bodies of Cordyceps militaris link.  

PubMed

Selenium-enriched Cordyceps militaris fruit bodies are industrially cultivated as functional food or medicinal food in China and southeast Asia. However, composition of selenium compounds and distribution of the main bioactive components are still unknown. In the selenium-enriched fruit bodies, the main soluble selenium compounds of low molecular weight were identified as SeMet (selenomethionine), and the main selenium compounds bound in proteins were identified as SeMet and SeCys (methylselenocysteine). Trace minerals as Se (selenium), Zn (zinc), Fe (iron) and the main active components as adenosine, cordycepin and carotenoids were mostly distributed in the terminal of fruit bodies, while P (phosphorus) and K (potassium) were evenly distributed in the fruit bodies. The results indicated that terminal of the fruit bodies should be the better materials for production of advanced functional food. So cultivation of relatively short and thick fruit bodies with bigger terminals deserves further research. PMID:23200005

Dong, Jing Z; Ding, J; Yu, Pei Z; Lei, Can; Zheng, Xiao J; Wang, Y

2013-04-15

328

Distribution of common genotypes of Myzus persicae (Hemiptera: Aphididae) in Greece, in relation to life cycle and host plant.  

PubMed

Microsatellite genotyping was used to identify common clones in populations of the Myzus persicae group from various hosts and regions in mainland Greece and southern Italy and to compare their distribution and occurrence on tobacco and other crops. Common clones were defined as genotypes collected at more than one time or in more than one population; and, therefore, unlikely to be participating in the annual sexual phase on peach. Sixteen common genotypes were found, accounting for 49.0% of the 482 clonal lineages examined. Eight of these genotypes were subjected, in the laboratory, to short days and found to continue parthenogenetic reproduction, i.e. they were anholocyclic. Four of the six commonest genotypes were red, and one of these accounted for 29.6% of the samples from tobacco and 29.4% of those from overwintering populations on weeds. All six commonest genotypes were found on weeds and five of them both on tobacco and on other field crops. In mainland Greece, the distribution of common clones corresponded closely with that of anholocyclic lineages reported in a previous study of life cycle variation. Common genotypes were in the minority in the commercial peach-growing areas in the north, except on weeds in winter and in tobacco seedbeds in early spring, but predominated further south, away from peach trees. This contrasts with the situation in southern Italy, reported in a previous paper, where peaches were available for the sexual phase, yet all samples from tobacco were of common genotypes. PMID:17524157

Blackman, R L; Malarky, G; Margaritopoulos, J T; Tsitsipis, J A

2007-06-01

329

Statistical Continuum Theory for the Effective Conductivity of Fiber Filled Polymer Composites: Effect of Orientation Distribution and Aspect Ratio  

SciTech Connect

Effective conductivity of polymer composites, filled with conducting fibers such as carbon nanotubes, is studied using statistical continuum theory. The fiber orientation distribution in the matrix plays a very important role on their effective properties. To take into account their orientation, shape and distribution, two-point and three-point probability distribution functions are used. The effect of fibers orientation is illustrated by comparing the effective conductivity of microstructures with oriented and non-oriented fibers. The randomly oriented fibers result in an isotropic effective conductivity. The increased fiber orientation distribution can lead to higher anisotropy in conductivity. The effect of fiber’s aspect ratio on the effective conductivity is studied by comparing microstructures with varying degrees of fiber orientation distribution. Results show that the increase in anisotropy leads to higher conductivity in the maximum fiber orientation distribution direction and lower conductivity in the transverse direction. These results are in agreement with various models from the literature that show the increase of the aspect ratio of fibers improves the electrical and thermal conductivity.

Mikdam, Amed; Makradi, A.; Ahzi, Said; Garmestani, Hamid; Li, Dongsheng; Remond, Y.

2010-03-01

330

Deep-sea surface-dwelling enteropneusts from the Mid-Atlantic Ridge: Their ecology, distribution and mode of life  

NASA Astrophysics Data System (ADS)

The ecology, distribution and mode of life of three species of surface-dwelling enteropneusts is described, based on ROV observations and samples on the flanks of the Northern Mid-Atlantic Ridge (MAR) at comparative stations north and south of the Sub-Polar Front. Tergivelum cinnabarinum was most abundant in the north (mean=4.56 ind. 1000 m-2±3.50 s.d.) and occurred at low densities in the south (mean=1.19±1.68 s.d.). Yoda purpurata was dominant in the south (mean=17.00 ind. 1000 m-2±12.32 s.d.) but only one individual was found in the north. The within-station distribution of all enteropneust species encountered was generally random. T. cinnabarinum was larger (mean total length 142 mm) than Y. purpurata (mean total length 70 mm). Size distributions suggested smaller individuals of both species on the western side of the MAR. Size and density of enteropneusts were generally higher in areas with higher carbon flux to the seafloor. A single individual of Allapasus isidis was observed drifting and settling to the seafloor at the SW site. Traces on the seafloor made by T. cinnabarinum covered a much higher percentage of the total seabed area surveyed (mean=0.323%±0.155 s.d.) than those of Y. purpurata (mean=0.034%±0.037 s.d.). Stable isotope values for T. cinnabarinum suggested that it was a typical surficial deposit feeder. Enteropneusts appear to be abundant and an important bioturbator on the sedimented seafloor of the MAR at around 2500 m depth.

Jones, Daniel O. B.; Alt, Claudia H. S.; Priede, Imants G.; Reid, William D. K.; Wigham, Benjamin D.; Billett, David S. M.; Gebruk, Andrey V.; Rogacheva, Antonina; Gooday, Andrew J.

2013-12-01

331

Composites  

NASA Astrophysics Data System (ADS)

It is commonly known that the properties of sintered materials are strongly related to technological conditions of the densification process. This paper shows the sintering behavior of a NiAl-Al2O3 composite, and its individual components sintered separately. Each kind of material was processed via the powder metallurgy route (hot pressing). The progress of sintering at different stages of the process was tested. Changes in the microstructure were examined using scanning and transmission electron microscopy. Metal-ceramics interface was clean and no additional phases were detected. Correlation between the microstructure, density, and mechanical properties of the sintered materials was analyzed. The values of elastic constants of NiAl/Al2O3 were close to intermetallic ones due to the volume content of the NiAl phase particularly at low densities, where small alumina particles had no impact on the composite's stiffness. The influence of the external pressure of 30 MPa seemed crucial for obtaining satisfactory stiffness for three kinds of the studied materials which were characterized by a high dense microstructure with a low number of isolated spherical pores.

Chmielewski, M.; Nosewicz, S.; Pietrzak, K.; Rojek, J.; Strojny-N?dza, A.; Mackiewicz, S.; Dutkiewicz, J.

2014-11-01

332

Fine root distribution and persistence under field conditions of three co-occurring Great Basin species of different life form.  

PubMed

Fine roots of an annual grass, a perennial grass and a perennial shrub were examined. Based on life histories and tissue composition, we expected the greatest root persistence for the shrub and shortest for the annual grass. Roots were observed with minirhizotrons over 2 yr for number, length and diameter changes. A Cox proportional hazard regression correlated root persistence with soil water, depth, diameter and date of production. In 2001, grass roots had similar persistence times, but shrub roots had the shortest. In 2002, the annual had the longest median root persistence, the perennial grass intermediate and the perennial shrub had the shortest. All species responded similarly to the magnitude of seasonal precipitation; root numbers increased with favorable soil moisture and disappeared with drying; fewer, thinner roots at greater soil depths were found in the drier year (2001). Root persistence increased with soil moisture, diameter and earlier appearance in the spring. Plasticity in root morphology and placement was influenced by water availability, yet persistence was surprisingly contrary to expectations. PMID:15720631

Peek, Michael S; Leffler, A Joshua; Ivans, Carolyn Y; Ryel, Ronald J; Caldwell, Martyn M

2005-01-01

333

Adaptive workflow-oriented services composition and allocation in distributed environment  

Microsoft Academic Search

With the increasing scale of distributed resources, which couples a wide variety of geographically distributed computational resources, storage systems, data sources and computational kernels, service management and scheduling is a complex undertaking. Since most services on the Internet are mutually independent, users have trouble in accessing several services to achieve a single purpose. Furthermore, the resources are owned by different

Jing-Fan Tang; Bo Zhou; Zhi-Jun He; U. Pompe

2004-01-01

334

Nitrate distribution and isotopic composition in vadose-zone sediments underlying large dairy operations  

NASA Astrophysics Data System (ADS)

Understanding the transport and cycling of nitrate in the vadose zone is essential to 1) linking agronomic models of nitrate flux out of the root zone to groundwater models of nitrate loading at the water table, 2) quantifying the impact of vadose-zone biogeochemical processes on nitrate isotopic composition for the purpose of source attribution, and 3) constraining transport time scales through the vadose zone in order to assess the impact of changes in agricultural nutrient management on underlying groundwater quality. In this study, we have investigated the isotopic composition of water-leachable nitrate extracted from sediment cores underlying three dairy operations in the southern San Joaquin Valley of California. One of the dairy operations is new (less than ten years old) and is sited on former range land; the other two operations are older (with one having been continuously operated for over a century). All use dairy wastewater for irrigation, and have vadose zones of 25-60 meters thickness developed in sedimentary sequences dominated by alluvial fan deposits. Sediment core samples from a UC-Davis monitor well drilling program were extracted with an equal amount of ultrapure water, and analyzed for nitrate isotopic composition using the denitrifying bacteria method at LLNL. The range in nitrate isotopic composition (?15N,air = 4.8 to 26.6 permil, ?18O,VSMOW = -0.3 to 16.2 permil) is large, comparable to isotopic compositions observed in dairy wastewater-impacted groundwaters (Singleton et al., 2007, ES&T 41:759-765), and varies from site to site. The range is the largest on the oldest operation (?15N = 5.2 to 26.6), and most tightly clustered on the youngest operation (?15N = 4.8 to 7.8). Leachable nitrate-?18O correlates with nitrate-?15N along a characteristic denitrification trend for individual cores. Leachable nitrate-?15N is not simply correlated with leachable nitrate concentration (which is generally high in shallow sediments and decreases with depth). In one core, the most enriched isotopic compositions are associated with the highest leachate nitrate concentrations. Observed nitrate isotopic compositions are consistent with nitrification of ammonium and mineralized organic N compounds from manure-rich wastewater, followed at some locations by denitrification. Sediment core patterns indicate that these processes can occur in the deep vadose zone. Profiles of leachable nitrate concentration and isotopic composition also differ significantly with respect to the duration of overlying dairy operations on a decadal timescale.

Esser, B. K.; Singleton, M. J.; Moran, J. E.; Roberts, S. K.; Barton, C. G.; Watanabe, N.; Harter, T.

2009-12-01

335

Depth distribution and composition of seed banks under different tree layers in a managed temperate forest ecosystem  

NASA Astrophysics Data System (ADS)

In the present work we examined the composition and distribution across three soil layers of the buried soil seed bank under three different overstory types ( Fagus sylvatica, Quercus robur, Pinus sylvestris) and in logging areas in a 4383-ha forest in central Belgium. The objectives were: (1) to investigate whether species composition and species richness of soil seed banks are affected by different forest stands; (2) to examine how abundant are habitat-specific forest species in seed banks under different planted tree layers. The study was carried out in stands which are replicated, managed in the same way (even-aged high forest), and growing on the same soil type with the same land-use history. In the investigated area, the seed bank did show significant differences under oak, beech, pine and in logging areas, respectively in terms of size, composition and depth occurrence. All species and layers taken together, the seed bank size ranked as follows: oakwood > beechwood > logging area > pinewood. The same pattern was found for forest species. Seed numbers of Betula pendula, Calluna vulgaris, Dryopteris dilatata and Rubus fruticosus were significantly higher under the beech canopy. Carex remota, Impatiens parviflora and Lotus sp. showed a significantly denser seed bank in logging areas, while Digitalis purpurea seeds were significantly more abundant in soils under the oak canopy. The fact that the seed bank of an originally homogeneous forest varies under different planted stands highlights that a long period of canopy conversion can affect the composition and depth of buried seeds.

Godefroid, Sandrine; Phartyal, Shyam S.; Koedam, Nico

2006-05-01

336

Distribution and Stable Isotopic Composition of Amino Acids from Fungal Peptaibiotics: Assessing the Potential for Meteoritic Contamination  

NASA Astrophysics Data System (ADS)

The presence of nonprotein ?-dialkyl-amino acids such as ?-aminoisobutyric acid (?-AIB) and isovaline (Iva), which are considered to be relatively rare in the terrestrial biosphere, has long been used as an indication of the indigeneity of meteoritic amino acids. However, recent work showing the presence of ?-AIB and Iva in peptides produced by a widespread group of filamentous fungi indicates the possibility of a terrestrial biotic source for the ?-AIB observed in some meteorites. We measured the amino acid distribution and stable carbon and nitrogen isotopic composition of four ?-AIB-containing fungal peptides and compared this data to similar meteoritic measurements. We show that the relatively simple distribution of the C4 and C5 amino acids in fungal peptides is distinct from the complex distribution observed in many carbonaceous chondrites. We also identify potentially diagnostic relationships between the stable isotopic compositions of pairs of amino acids from the fungal peptides that may aid in ruling out fungal contamination as a source of meteoritic amino acids.

Elsila, Jamie E.; Callahan, Michael P.; Glavin, Daniel P.; Dworkin, Jason P.; Brückner, Hans

2011-03-01

337

How Rocky Are They? The Composition Distribution of Kepler's Sub-Neptune Planet Candidates within 0.15 AU  

E-print Network

The Kepler Mission has found thousands of planetary candidates with radii between 1 and 4 R$_\\oplus$. These planets have no analogues in our own Solar System, providing an unprecedented opportunity to understand the range and distribution of planetary compositions allowed by planet formation and evolution. A precise mass measurement is usually required to constrain the possible composition of an individual super-Earth-sized planet, but these measurements are difficult and expensive to make for the majority of Kepler planet candidates. Fortunately, adopting a statistical approach helps us to address this question without them. In particular, we apply hierarchical Bayesian modeling to a subsample of Kepler planet candidates that is complete for $P1.2$ R$_\\oplus$ and draw upon interior structure models which yield radii largely independent of mass by accounting for the thermal evolution of a gaseous envelope around a rocky core. Assuming the envelope is dominated by hydrogen and helium, we present the current-da...

Wolfgang, Angie

2014-01-01

338

Sources, distribution and composition of the suspended sediments, Kuwait Bay, Northern Arabian Gulf  

Microsoft Academic Search

Qualitative and quantitative assessment of suspended sediment levels and transport pathways in Kuwait's northern territorial waters are described, with special reference to Kuwait Bay. Near-surface water samples were collected from 12 stations, covering the whole of the embayment. Suspended sediment concentrations (SSCs) were derived. Heavy metal concentrations, mineralogical composition and grain size constituents were derived for the suspended sediments retained

A. N. Al-Ghadban; A. El-Sammak

2005-01-01

339

Moisture Diffusion in a Fiber-reinforced Composite: Part I – Non-Fickian Transport and the Effect of Fiber Spatial Distribution  

Microsoft Academic Search

The results of an investigation into the effects of non-Fickian sorption and fiber spatial distribution on moisture diffusion in laminated composite materials are presented as part of a study to develop a predictive model for fiber-reinforced composite moisture transport mechanics. Experimental diffusion rate data are obtained from gravimetric analysis of T800\\/924 carbon fiber epoxy composites using Fickian absorption models adapted

David A. Bond

2005-01-01

340

Macro-void distribution analysis in strand-based wood composites using an X-ray computer tomography technique  

Microsoft Academic Search

A database from a series of cross-sectional density distributions in a 0.16 × 0.34 × 1.28m strand-based wood composite specimen\\u000a has been successfully developed using X-ray computer tomography (CT) techniques. Using conventional image processing techniques,\\u000a the CT images of the specimen were analyzed with respect to the size and position of the macro-voids. Finally, CT images and\\u000a the measurement results

Masatoshi Sugimori; Frank Lam

1999-01-01

341

Martian Surface Composition From Multiple Datasets, Part II: Chemical Analysis of Global Mineral Distributions from MGS-TES  

NASA Astrophysics Data System (ADS)

Koeppen and Hamilton [2008, JGR-Planets] produced global mineral maps of Mars from Thermal Emission Spectrometer (TES) data using a library of mineral and amorphous phase spectra and a linear least squares fitting algorithm. Here we will use known or estimated bulk chemistries of the phases in the Koeppen and Hamilton [2008] spectral library, along with each phase's modeled abundance in the TES data from that work, to calculate effective bulk chemistry for Martian dark regions at a spatial resolution of ~3x6 km. By doing this, we are able to analyze global bulk chemical variation as well as enable direct comparisons between TES data and chemical/elemental abundance maps (e.g., wt.% SiO2) produced using data collected by the Gamma Ray Spectrometer. A second chemical analysis also makes use of the Koeppen and Hamilton [2008] global mineral maps and focuses on the spatial variations in solid solution chemistry among feldspars, pyroxenes, high silica phases (e.g., silica, phyllosilicates, zeolites), and sulfates. Koeppen and Hamilton [2008] demonstrated that there is a range of Mg-Fe olivine compositions on Mars and that there are distinct geographic distributions of those phases, pointing to spatial variations in geologic processes. We use the same methodology to search for correlations between geography (e.g., geologic unit, latitude), elevation, and chemical (solid solution) composition. Preliminary analyses of pyroxene chemical variation reveal that globally, low-Ca pyroxenes are dominated by the clinopyroxene pigeonite and that among orthopyroxenes, Mg-rich phases (enstatite) are virtually never identified and phases with greater proportions of Fe (bronzite and hypersthene) are identified in distinct geographic and/or geologic terrains. Only the distribution of hypersthene (the composition of pyroxene in the Martian meteorite ALH 84001) correlates with the OMEGA-mapped distribution of low-Ca pyroxene suggesting that OMEGA-based maps of high-Ca pyroxene may include pigeonite. Many of the chemical-spatial variations observed among solid solution phases in TES data correspond to both relative surface age and the distribution of lithologic units identified by Rogers and Christensen [2007, JGR-Planets], where the lithologic units were identified using a different analytical approach, giving us confidence in the variations observed in our mineral maps. These results point to variations in and/or the evolution of igneous compositions over time. Any observable variations in other phase groups (e.g., sulfates, phyllosilicates) may indicate variations in the timing and extent of aqueous or alteration processes over time.

Hamilton, V. E.; Rogers, D.

2010-12-01

342

Measurement of dijet angular distributions and search for quark compositeness in pp collisions at ?s = 7 TeV.  

PubMed

Dijet angular distributions are measured over a wide range of dijet invariant masses in pp collisions at ?s = 7 TeV, at the CERN LHC. The event sample, recorded with the CMS detector, corresponds to an integrated luminosity of 36 pb?¹. The data are found to be in good agreement with the predictions of perturbative QCD, and yield no evidence of quark compositeness. With a modified frequentist approach, a lower limit on the contact interaction scale for left-handed quarks of ?? = 5.6 TeV (?? = 6.7 TeV) for destructive (constructive) interference is obtained at the 95% confidence level. PMID:21668222

Khachatryan, V; Sirunyan, A M; Tumasyan, A; Adam, W; Bergauer, T; Dragicevic, M; Erö, J; Fabjan, C; Friedl, M; Frühwirth, R; Ghete, V M; Hammer, J; Hänsel, S; Hartl, C; Hoch, M; Hörmann, N; Hrubec, J; Jeitler, M; Kasieczka, G; Kiesenhofer, W; Krammer, M; Liko, D; Mikulec, I; Pernicka, M; Rohringer, H; Schöfbeck, R; Strauss, J; Taurok, A; Teischinger, F; Wagner, P; Waltenberger, W; Walzel, G; Widl, E; Wulz, C-E; Mossolov, V; Shumeiko, N; Suarez Gonzalez, J; Benucci, L; Cerny, K; De Wolf, E A; Janssen, X; Maes, T; Mucibello, L; Ochesanu, S; Roland, B; Rougny, R; Selvaggi, M; Van Haevermaet, H; Van Mechelen, P; Van Remortel, N; Beauceron, S; Blekman, F; Blyweert, S; D'Hondt, J; Devroede, O; Gonzalez Suarez, R; Kalogeropoulos, A; Maes, J; Maes, M; Tavernier, S; Van Doninck, W; Van Mulders, P; Van Onsem, G P; Villella, I; Charaf, O; Clerbaux, B; De Lentdecker, G; Dero, V; Gay, A P R; Hammad, G H; Hreus, T; Marage, P E; Thomas, L; Vander Velde, C; Vanlaer, P; Wickens, J; Adler, V; Costantini, S; Grunewald, M; Klein, B; Marinov, A; McCartin, J; Ryckbosch, D; Thyssen, F; Tytgat, M; Vanelderen, L; Verwilligen, P; Walsh, S; Zaganidis, N; Basegmez, S; Bruno, G; Caudron, J; Ceard, L; De Favereau De Jeneret, J; Delaere, C; Demin, P; Favart, D; Giammanco, A; Grégoire, G; Hollar, J; Lemaitre, V; Liao, J; Militaru, O; Ovyn, S; Pagano, D; Pin, A; Piotrzkowski, K; Schul, N; Beliy, N; Caebergs, T; Daubie, E; Alves, G A; De Jesus Damiao, D; Pol, M E; Souza, M H G; Carvalho, W; Da Costa, E M; De Oliveira Martins, C; Fonseca De Souza, S; Mundim, L; Nogima, H; Oguri, V; Prado Da Silva, W L; Santoro, A; Silva Do Amaral, S M; Sznajder, A; Torres Da Silva De Araujo, F; Dias, F A; Dias, M A F; Fernandez Perez Tomei, T R; Gregores, E M; Marinho, F; Novaes, S F; Padula, Sandra S; Darmenov, N; Dimitrov, L; Genchev, V; Iaydjiev, P; Piperov, S; Rodozov, M; Stoykova, S; Sultanov, G; Tcholakov, V; Trayanov, R; Vankov, I; Dyulendarova, M; Hadjiiska, R; Kozhuharov, V; Litov, L; Marinova, E; Mateev, M; Pavlov, B; Petkov, P; Bian, J G; Chen, G M; Chen, H S; Jiang, C H; Liang, D; Liang, S; Wang, J; Wang, J; Wang, X; Wang, Z; Xu, M; Yang, M; Zang, J; Zhang, Z; Ban, Y; Guo, S; Guo, Y; Li, W; Mao, Y; Qian, S J; Teng, H; Zhang, L; Zhu, B; Zou, W; Cabrera, A; Gomez Moreno, B; Ocampo Rios, A A; Osorio Oliveros, A F; Sanabria, J C; Godinovic, N; Lelas, D; Lelas, K; Plestina, R; Polic, D; Puljak, I; Antunovic, Z; Dzelalija, M; Brigljevic, V; Duric, S; Kadija, K; Morovic, S; Attikis, A; Galanti, M; Mousa, J; Nicolaou, C; Ptochos, F; Razis, P A; Rykaczewski, H; Finger, M; Finger, M; Assran, Y; Mahmoud, M A; Hektor, A; Kadastik, M; Kannike, K; Müntel, M; Raidal, M; Rebane, L; Azzolini, V; Eerola, P; Czellar, S; Härkönen, J; Heikkinen, A; Karimäki, V; Kinnunen, R; Klem, J; Kortelainen, M J; Lampén, T; Lassila-Perini, K; Lehti, S; Lindén, T; Luukka, P; Mäenpää, T; Tuominen, E; Tuominiemi, J; Tuovinen, E; Ungaro, D; Wendland, L; Banzuzi, K; Korpela, A; Tuuva, T; Sillou, D; Besancon, M; Choudhury, S; Dejardin, M; Denegri, D; Fabbro, B; Faure, J L; Ferri, F; Ganjour, S; Gentit, F X; Givernaud, A; Gras, P; Hamel de Monchenault, G; Jarry, P; Locci, E; Malcles, J; Marionneau, M; Millischer, L; Rander, J; Rosowsky, A; Shreyber, I; Titov, M; Verrecchia, P; Baffioni, S; Beaudette, F; Bianchini, L; Bluj, M; Broutin, C; Busson, P; Charlot, C; Dahms, T; Dobrzynski, L; Granier de Cassagnac, R; Haguenauer, M; Miné, P; Mironov, C; Ochando, C; Paganini, P; Sabes, D; Salerno, R; Sirois, Y; Thiebaux, C; Wyslouch, B; Zabi, A; Agram, J-L; Andrea, J; Besson, A; Bloch, D; Bodin, D; Brom, J-M; Cardaci, M; Chabert, E C; Collard, C; Conte, E; Drouhin, F; Ferro, C; Fontaine, J-C; Gelé, D; Goerlach, U; Greder, S; Juillot, P; Karim, M; Le Bihan, A-C; Mikami, Y; Van Hove, P; Fassi, F; Mercier, D; Baty, C; Beaupere, N; Bedjidian, M; Bondu, O; Boudoul, G; Boumediene, D; Brun, H; Chanon, N; Chierici, R; Contardo, D; Depasse, P; El Mamouni, H; Falkiewicz, A; Fay, J; Gascon, S; Ille, B; Kurca, T; Le Grand, T; Lethuillier, M; Mirabito, L; Perries, S; Sordini, V; Tosi, S; Tschudi, Y; Verdier, P; Xiao, H; Megrelidze, L; Roinishvili, V; Lomidze, D; Anagnostou, G; Edelhoff, M; Feld, L; Heracleous, N; Hindrichs, O; Jussen, R; Klein, K; Merz, J; Mohr, N; Ostapchuk, A; Perieanu, A; Raupach, F; Sammet, J; Schael, S; Sprenger, D; Weber, H; Weber, M; Wittmer, B; Ata, M; Bender, W; Erdmann, M; Frangenheim, J; Hebbeker, T; Hinzmann, A; Hoepfner, K; Hof, C; Klimkovich, T; Klingebiel, D; Kreuzer, P; Lanske, D; Magass, C; Masetti, G; Merschmeyer, M; Meyer, A; Papacz, P; Pieta, H; Reithler, H; Schmitz, S A; Sonnenschein, L; Steggemann, J; Teyssier, D; Bontenackels, M; Davids, M; Duda, M; Flügge, G; Geenen, H; Giffels, M; Haj Ahmad, W; Heydhausen, D; Kress, T; Kuessel, Y; Linn, A; Nowack, A; Perchalla, L; Pooth, O; Rennefeld, J; Sauerland, P; Stahl, A; Thomas, M

2011-05-20

343

Micromechanically-based acoustic characterization of the fiber orientation distribution function of morphologically textured short-fiber composites: prediction of thermomechanical and physical properties  

Microsoft Academic Search

We apply our recently-developed acoustic approach to characterize the fiber orientation distribution function (ODF) of short fiber composites to predict relevant anisotropic thermomechanical properties of such composites. The acoustic approach consists of a tight coupling of acoustic velocity measurements and micromechanics modeling. It can not completely characterize the ODF, but delivers information regarding lower-order terms of the ODF when expanded

Martin L Dunn; Hassel Ledbetter

2000-01-01

344

Relations of low contrast visual acuity, quality of life and multiple sclerosis functional composite: a cross-sectional analysis  

PubMed Central

Background Although common and often disabling in multiple sclerosis (MS), visual dysfunction is currently not adequately accounted for in both clinical routine and MS trials. Sloan low contrast letter acuity (SLCLA) is a standardised chart-based measure of visual function particular at low contrast and has been suggested as additional visual component to the Multiple Sclerosis Functional Composite (MSFC). Here, we evaluate the relations between SLCLA, retinal integrity, MSFC, and quality of life (QoL) in MS patients. Methods Cross-sectional analysis of retinal nerve fibre layer (RNFL) thickness, MSFC, SLCLA (2.5% and 1.25% contrast levels), visual evoked potentials, and QoL (Short Form (SF) 36, National Eye Institute Visual Functioning Questionnaire (NEIVFQ)) using baseline data of 92 MS patients from an ongoing prospective longitudinal trial. Relations between RNFL thickness or P100 latency and SLCLA were analysed using generalised estimating equations (GEE) accounting for intra-individual inter-eye dependencies and corrected for age, gender, and history of optic neuritis. Pearson’s correlations were used to assess relations between SLCLA, MSFC, and QoL. Results SLCLA reflected RNFL thickness (p?=?0.021) and P100 latency (p?=?0.004) and predicted vision-related QoL, reflected by the NEIVFQ39 subscores “general vision” and “near activities” (p?

2014-01-01

345

Fatty acid composition and distribution in the blubber of bottlenose dolphins (Tursiops truncatus)  

E-print Network

walrus (Odobenus rosmarus divergens) showed higher amounts of 16:0, 16:1n-7, 18:1n-9, 20:1n-9, 20:5n-3, 22:5n-3, and 22:6n-3. The composition of cetacean blubber was somewhat different compared to pinniped blubber. Ackman et al. (1965) found high... walrus (Odobenus rosmarus divergens) showed higher amounts of 16:0, 16:1n-7, 18:1n-9, 20:1n-9, 20:5n-3, 22:5n-3, and 22:6n-3. The composition of cetacean blubber was somewhat different compared to pinniped blubber. Ackman et al. (1965) found high...

Samuel, Asha Melina

2012-06-07

346

Distribution and enantiomeric composition of amino acids in the Murchison meteorite  

NASA Technical Reports Server (NTRS)

Studies of the amino acid contents and enantiomeric compositions of a single stone from the Murchison meteorite are reported. Water-extracted and 6M HCl-extracted samples from the meteorite interior of meteorite fragments were analyzed by gas chromatography and combined gas chromatography-chemical ionization mass spectrometry. Examination of the D/L ratios of glutamic acid, aspartic acid, proline, leucine and alanine reveals those amino acids extractable by water to be partially racemized, whereas the acid-extracted amino acids were less racemized. The amino acid composition of the stone is similar to those previously reported, including the absence of serine, threonine, tyrosine phenylalanine and methionine and the presence of unusual amino acids including such as isovaline, alpha-aminoisobutyric acid and pseudoleucine. It is concluded that the most likely mechanism accounting for the occurrence of nonracemic amino acid mixtures in the Murchison meteorite is by extraterrestrial stereoselective synthesis or decomposition reactions.

Engel, M. H.; Nagy, B.

1982-01-01

347

Composition and distribution of meiobenthos in amursky bay (peter the great bay, the east sea)  

Microsoft Academic Search

Qualitative and quantitative composition of meiobenthos was studied in Amursky Bay (Peter the Great Bay, the East Sea). Ten\\u000a taxonomic groups were found, where nematodes were dominant. Density of meiobenthos in ground sediments of the Bay were not\\u000a uniform, and the average density was measured at 126.4±62.3 ind. m-2. 56 species of nematodes were detected, and dominant species wereSabatieria palmaris,

Olga N. Pavlyuk; Julia A. Trebukhova

2005-01-01

348

Spectroscopic study of the Moses Lake dune field, Washington: Determination of compositional distributions and source lithologies  

NASA Astrophysics Data System (ADS)

Source lithologies and transport histories of materials within the Ephrata Fan are investigated. Data were collected using a variety of remote-sensing, laboratory spectroscopic, and field observations and techniques. Laboratory thermal emission spectra were collected of bedrock within the Grand Coulee, dune samples, and clast deposits. Factor analysis, target transformation, and end-member recovery techniques were applied to the set of dune samples as well as a set of grain size fractions. The dune sample spectra are composed of three components that represent basalt, granodiorite, and clay compositions. The basalt and granodiorite components are similar to spectra of clast and bedrock samples from the Grand Coulee and the Ephrata Fan. The clay component is similar to weathering surfaces located within the dune field. The same components were recovered from the set of grain size fractions from a single dune sample demonstrating a relatively higher basalt concentration with grain sizes greater than ~250 ?m. Thermal Infrared Multispectral Scanner (TIMS) data display significant intradune compositional variation and no discernable interdune compositional variation, indicating that the basalt and granodiorite components were likely deposited simultaneously and subsequently separated by wind based on grain size. Basalt and granodiorite bedrock units within the Channeled Scablands are source materials for the deposits within the Ephrata Fan and Moses Lake dune field. The Columbia River, located 20 km west of the dune field, is not a likely source of material.

Bandfield, Joshua L.; Edgett, Kenneth S.; Christensen, Philip R.

2002-11-01

349

Composition and lipid spatial distribution of HDL particles in subjects with low and high HDL-cholesterol[S  

PubMed Central

A low level of high density lipoprotein cholesterol (HDL-C) is a powerful risk factor for cardiovascular disease. However, despite the reported key role of apolipo-proteins, specifically, apoA-I, in HDL metabolism, lipid molecular composition of HDL particles in subjects with high and low HDL-C levels is currently unknown. Here lipidomics was used to study HDL derived from well-characterized high and low HDL-C subjects. Low HDL-C subjects had elevated triacylglycerols and diminished lysophosphatidylcholines and sphingomyelins. Using information about the lipid composition of HDL particles in these two groups, we reconstituted HDL particles in silico by performing large-scale molecular dynamics simulations. In addition to confirming the measured change in particle size, we found that the changes in lipid composition also induced specific spatial distributions of lipids within the HDL particles, including a higher amount of triacylglycerols at the surface of HDL particles in low HDL-C subjects. Our findings have important implications for understanding HDL metabolism and function. For the first time we demonstrate the power of combining molecular profiling of lipoproteins with dynamic modeling of lipoprotein structure. PMID:20431113

Yetukuri, Laxman; Soderlund, Sanni; Koivuniemi, Artturi; Seppanen-Laakso, Tuulikki; Niemela, Perttu S.; Hyvonen, Marja; Taskinen, Marja-Riitta; Vattulainen, Ilpo; Jauhiainen, Matti; Oresic, Matej

2010-01-01

350

Simplified Shear Solution for Determination of the Shear Stress Distribution in a Composite Panel from the Applied Shear Resultant  

NASA Technical Reports Server (NTRS)

The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate or panel based on laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from global load resultants (as determined, for instance, by finite element analysis) at a given location in a structure and used to evaluate the margin of safety on a ply by ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. Comparisons to existing theories are made for a variety of laminates, and design examples are provided illustrating the use of the method for determining through-thickness shear stress margins in several types of composite panels and in the context of a finite element structural analysis.

Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.; Collier, Craig S.

2008-01-01

351

The design of a CCA framework with distribution, parallelism, and recursive composition  

Microsoft Academic Search

HPE is a platform of parallel components that complies to the # component model, whose components are intrinsically parallel. This paper describes the design of a new CCA framework based on HPE, aimed to reconcile distribution and parallelism of components. Besides exposing the essential differences between the two platforms, the new framework has a set of features that distinguishes it

Francisco Heron de Carvalho-Junior; R. C. Corre?a

2010-01-01

352

Distribution, composition and flux of particulate material over the European margin at 47°–50°N  

Microsoft Academic Search

In the framework of the Ocean Margin Exchange project, a multi-disciplinary study has been conducted at the shelf edge and slope of the Goban Spur in order to determine the spatial distribution, quantity and quality of particle flux, and delineate the transport mechanisms of the major organic and inorganic components. We present here a synthesis view of the major transport

I. n. Mccave; I. R Hall; A. N Antia; L. Chou; F. Dehairs; R. S. Lampitte; L. Thomsen; T. C. E van Weering; R. Wollast

2001-01-01

353

Polymorphisms in the leptin receptor gene, body composition and fat distribution in overweight and obese women  

Microsoft Academic Search

OBJECTIVE: Leptin is an adipocyte-secreted hormone involved in body weight regulation, acting through the leptin receptor, localised centrally in the hypothalamus as well as peripherally, amongst others on adipose tissue. The aim of this study was to evaluate whether polymorphisms in the leptin receptor (LEPR) gene were related to obesity and body fat distribution phenotypes, such as waist and hip

M Wauters; I Mertens; M Chagnon; T Rankinen; RV Considine; YC Chagnon; LF Van Gaal; C Bouchard

2001-01-01

354

[Spatial distribution and composition of perfluorinated compounds in soils around the Huaihe River].  

PubMed

In order to analyze the occurrence and composition of perfluorinated compounds (PFCs), 18 topsoil samples were collected around the Huaihe River in October, 2008. Total fluoride (TF) and extractable organic fluorine (EOF) were determined using combustion ion chromatography (CIC), and PFCs were quantified by HPLC/MS-MS. Among the sixteen PFCs analyzed, eleven PFCs were detected. Concentrations of PFCs ranged from n. d. to 1.22 ng x g(-1), and perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorooctane sulfonate (PFOS) were the predominant PFCs. Concentrations of PFCs showed no significant difference, but compositions varied from soil to soil. PFCs mainly came from emissions of local small chemical plants and atmospheric dry and wet deposition. The results from mass balance analysis indicated that PFCs only accounted for 0.3% of EOF and EOF comprised 0.02% of TF. There was still a large amount of organic fluorine besides PFCs, and inorganic fluorine and non-extractable organic fluorine comprised the major portion of TF. Furthermore, the current analysis method could not detect all kinds of PFCs and related unknown organic fluorine. PMID:24191567

Meng, Jing; Wang, Tie-Yu; Wang, Pei; Lü, Yong-Long

2013-08-01

355

Exclusive Breastfeeding and Other Foods in the First Six Months of Life: Effects on Nutritional Status and Body Composition of Brazilian Children  

PubMed Central

Objective. To evaluate the effect of exclusive breastfeeding and consumption of other foods in the first six months of life in the nutritional status and body composition of children. Methods. A retrospective cohort study with 185 children aged from 4 to 7 years was monitored during the first months of life in a program of support to breastfeeding. We evaluated weight, height, waist circumference, and body composition by using DEXA. The nutritional status was assessed by the BMI/age index. The parameters of adiposity were classified by using as the cutoff point, the 85th percentile of the sample itself, according to gender and age. Confounding factors considered were variables related to maternal, pregnancy, birth, sociodemographic, health, lifestyle, and diet. Bivariate and multivariate analyses were performed, the latter by means of multiple logistic regression. Results. The median exclusive breastfeeding was 3 months. Of the children, 42.7% received cow's milk and 35.7% received infant formula. Regarding nutritional status, 21.1% of the children showed changes. The variables of infant feeding were not independently associated with nutritional status and body composition of the children and there were no differences between the groups studied. Conclusion. Breastfeeding was not a protective factor to overweight and body fat in children. PMID:23193378

Magalhaes, Tais C. A.; Vieira, Sarah A.; Priore, Silvia E.; Ribeiro, Andreia Q.; Lamounier, Joel A.; Franceschini, Sylvia C. C.; Sant'Ana, Luciana F. R.

2012-01-01

356

Carbon, nitrogen and sulfur in lunar fines 15012 and 15013 - Abundances, distributions and isotopic compositions  

NASA Technical Reports Server (NTRS)

Lunar fines 15012,16 and 15013,3 were analyzed by stepwise pyrolysis and acid hydrolysis as well as complete combustion in oxygen to determine carbon, nitrogen and sulfur. In addition, hydrogen was analysed during pyrolysis as well as during hydrolysis. By comparison of the distribution frequencies of C, N, S, H2 and Fe with He-4, considered to have arisen from solar wind contribution, it is concluded that nitrogen and hydrogen have largely a solar origin. Carbon has a significant solar contribution, and metallic iron may have resulted from solar wind interaction with ferrous minerals on the lunar surface. Sulfur probably has a predominantly lunar origin. There is no direct evidence for meteorotic contribution to these samples. Solar wind interaction also has a marked effect on the stable isotope distribution of C-13/C-12, N-15/N-14, and S-34/S-32. In all cases, the heavy isotope was most enriched in the smallest grain-size fraction.

Chang, S.; Lawless, J.; Romiez, M.; Kaplan, I. R.; Petrowski, C.; Sakai, H.; Smith, J. W.

1974-01-01

357

The ion energy distributions and ion flux composition from a high power impulse magnetron sputtering discharge  

Microsoft Academic Search

The energy distribution of sputtered and ionized metal atoms as well as ions from the sputtering gas is reported for a high power impulse magnetron sputtering (HIPIMS) discharge. High power pulses were applied to a conventional planar circular magnetron Ti target. The peak power on the target surface was 1–2 kW\\/cm2 with a duty factor of about 0.5%. Time resolved, and

J. Bohlmark; M. Lattemann; J. T. Gudmundsson; A. P. Ehiasarian; Y. Aranda Gonzalvo; N. Brenning; U. Helmersson

2006-01-01

358

Uptake and Distribution of Arsenic in Chickpea: Effects on Seed Yield and Seed Composition  

Microsoft Academic Search

Chickpea plants were grown in arsenic (As)–contaminated soils (5 mg kg of dry soil) and investigated for As uptake, distribution, and effects on growth, yield, and quality of seeds. The roots accumulated the greatest As (7 mg kg dry weight), followed by stem (4.8 mg), leaves (4.0 mg), and seeds (0.7 mg). Arsenic inhibited the growth of the roots and

Jahid A. Malik; Shilpa Goel; Rajat Sandhir; Harsh Nayyar

2011-01-01

359

Composition, Distribution, and Characterization of Organochlorine Pesticides in Sandstorm Depositions in Beijing, China  

Microsoft Academic Search

Sandstorms which distribute a great number of particles are a special atmospheric occurrence and are uncommon in northern\\u000a China. This study was conducted to determine, for the first time, the concentration of organochlorine pesticides (OCPs) in\\u000a sandstorm depositions. Samples were collected from urban areas of Beijing and a total of eight OCPs were measured. All samples\\u000a contained OCP residues. The

S. Fu; K. Li; Z. Z. Yang; X. B. Xu

2008-01-01

360

Pressure drop and gas distribution in compost based biofilters: medium mixing and composition effects.  

PubMed

The pressure drop and gas distribution in four different filter media for compost biofilters were studied as a function of three superficial loading rates of moist air and by carrying out the filter medium homogenization by mixing. The filter media used were compost, compost with cane bagasse, lava rock and aerobic sludge previously dried to 60% of water content. The pressure drop increased when lava rock and cane bagasse were used as bulking agents. The same trend was observed when water was added to the filter medium. Pressure drop tended to decrease with time as flow channels were formed inthe filter media. Tracer studies were carried out to quantify the gas distribution and the effect of channel formation. For the biofilters submitted to an airflow of 10, 40 and 70 l min(-1), an average normalized time of 0.96, 0.89 and 0.82, respectively were obtained. The results showed that channel formation was increased as the superficial loading rate was also increased. An operational practice that this work proposes and evaluates to improve gas distribution and medium moisture control is to carry out intermittent medium mixing. The medium moisture and void volume achieved under mixing condition were around 50% and 0.40, respectively with an average constant pressure drop of 11, 45 and 78 cm of water m(-1) for air velocities of 75, 300 and 525 m h(-1). PMID:12916833

Morgan-Sagastume, J M; Revah, S; Noyola, A

2003-07-01

361

Composition and fatty acid distribution of bovine milk phospholipids from processed milk products  

PubMed Central

The aim of this work was to assess the accuracy of different extraction methods of phospholipids and to measure the effect that processing has on phospholipid composition. Four methods of extracting phospholipids from buttermilk powder were compared to optimize recovery of sphingomyelin. Using the optimal method, the phospholipid profile of four dairy products (raw milk, raw cream, homogenized and pasteurized milk, and buttermilk powder) was determined. A total lipid extraction by the Folch method followed by a solid-phase extraction using the Bitman method was the most efficient technique to recover milk sphingomyelin. Milk processing (churning, centrifuging, homogenization, spray-drying) affected the profile of milk phospholipids, leading to a loss of sphingomyelin and phosphatidylcholine after centrifugation for cream separation. We also observed a corresponding decrease in the saturation content of the raw cream phospholipids, and a loss of phosphatidylethanolamine after spray-drying to produce buttermilk powder. PMID:20828196

Gallier, Sophie; Gragson, Derek; Cabral, Charles; Jiménez-Flores, Rafael; Everett, David W.

2014-01-01

362

Composition, distribution, and characterization of polycyclic aromatic hydrocarbons in soil in Linfen, China  

SciTech Connect

A total of 10 surface soil samples representing the entire area of Linfen City were collected and analyzed for the presence of 16 polycyclic aromatic hydrocarbons. The total polycyclic aromatic hydrocarbon concentration ranged from 1.1 to 63.7 {mu} g g{sup -1}. Analysis of the sources of contamination revealed that polycyclic aromatic hydrocarbons in the soil were derived from combustion sources. Specifically, the primary source of polycyclic aromatic hydrocarbons was coal combustion, but the samples were also effected to varying degrees by traffic emissions. Furthermore, increased levels of contamination were observed in northeast Linfen due to the distribution of industrial plants.

Fu, S.; Cheng, H.X.; Liu, Y.H.; Xia, X.J.; Xu, X.B. [Chinese Academy of Sciences, Beijing (China)

2009-02-15

363

Manipulating intensity and phase distribution of composite Laguerre-Gaussian beams.  

PubMed

We propose a method to manipulate the intensity and phase distributions of a beam with non-zero orbital angular momentum (OAM). We investigate the superposition of coherent consecutive OAM modes, with concordant topological charges values, showing that it is possible to predict and control the phase and the radial and angular dimension of the resulting beam by acting on the number of superposed modes (N) and on their minimum value of the OAM (m(min)). A general analysis from the Wigner function formalism is adopted for the geometric characterization of the beam. PMID:25090528

Parisi, G; Mari, E; Spinello, F; Romanato, F; Tamburini, F

2014-07-14

364

The effects of propagation and source distribution on cosmic ray composition and anisotropy.  

NASA Technical Reports Server (NTRS)

We consider the propagation and source distribution of cosmic rays. The principal requirement for the various models we consider is that they should be capable of holding particles in dense regions of the galactic disk for periods of time sufficient to produce the observed fragmentation products of cosmic rays. This can be achieved by both simple and compound diffusion provided that suitable mean free paths and boundary conditions are chosen. The bulk of the anisotropy is caused by the discrete nature of the cosmic ray sources. However, models which reproduce the fragmentation products will in general yield anisotropies consistent with available upper limits.

Ramaty, R.; Lingenfelter, R. E.

1971-01-01

365

Effects of martial arts exercise on body composition, serum biomarkers and quality of life in overweight/obese premenopausal women: a pilot study.  

PubMed

Various exercise interventions have been shown to benefit weight control and general health in different populations. However, very few studies have been conducted on martial arts exercise (MAE). The objective of this pilot study is to evaluate the efficacy of 12 weeks of MAE intervention on body composition, serum biomarkers and quality of life (QOL) in overweight/obese premenopausal women. We found that subjects in the MAE group did not lose body weight, while they significantly decreased fat-free mass and muscle mass as compared to those in the control group, who demonstrated an increase in these parameters. The MAE group demonstrated an increase in serum IGF-I concentration, but no change in others. MAE may be a feasible and effective approach to improve body composition and QOL in overweight/obese premenopausal women. Our study underscores the need for further studies using larger samples to establish possible benefits of MAE in various populations. PMID:24665215

Chyu, Ming-Chien; Zhang, Yan; Brismée, Jean-Michel; Dagda, Raul Y; Chaung, Eugene; Von Bergen, Vera; Doctolero, Susan; Shen, Chwan-Li

2013-01-01

366

Effects of martial arts exercise on body composition, serum biomarkers and quality of life in overweight/obese premenopausal women: a pilot study  

PubMed Central

Various exercise interventions have been shown to benefit weight control and general health in different populations. However, very few studies have been conducted on martial arts exercise (MAE). The objective of this pilot study is to evaluate the efficacy of 12 weeks of MAE intervention on body composition, serum biomarkers and quality of life (QOL) in overweight/obese premenopausal women. We found that subjects in the MAE group did not lose body weight, while they significantly decreased fat-free mass and muscle mass as compared to those in the control group, who demonstrated an increase in these parameters. The MAE group demonstrated an increase in serum IGF-I concentration, but no change in others. MAE may be a feasible and effective approach to improve body composition and QOL in overweight/obese premenopausal women. Our study underscores the need for further studies using larger samples to establish possible benefits of MAE in various populations. PMID:24665215

Chyu, Ming-Chien; Zhang, Yan; Brismee, Jean-Michel; Dagda, Raul Y.; Chaung, Eugene; Von Bergen, Vera; Doctolero, Susan; Shen, Chwan-Li

2013-01-01

367

Body composition at 6 months of life: comparison of air displacement plethysmography and dual-energy X-ray absorptiometry.  

PubMed

Body composition assessment during infancy is important because it is a critical period for obesity risk development, thus valid tools are needed to accurately, precisely, and quickly determine both fat and fat-free mass. The purpose of this study was to compare body composition estimates using dual-energy x-ray absorptiometry (DXA) and air displacement plethysmography (ADP) at 6 months old. We assessed the agreement between whole body composition using DXA and ADP in 84 full-term average-for-gestational-age boys and girls using DXA (Lunar iDXA v11-30.062; Infant whole body analysis enCore 2007 software, GE, Fairfield, CT) and ADP (Infant Body Composition System v3.1.0, COSMED USA, Concord, CA). Although the correlations between DXA and ADP for %fat (r = 0.925), absolute fat mass (r = 0.969), and absolute fat-free mass (r = 0.945) were all significant, body composition estimates by DXA were greater for both %fat (31.1 ± 3.6% vs. 26.7 ± 4.7%; P < 0.001) and absolute fat mass (2,284 ± 449 vs. 1,921 ± 492 g; P < 0.001), and lower for fat-free mass (5,022 ± 532 vs. 5,188 ± 508 g; P < 0.001) vs. ADP. Inter-method differences in %fat decreased with increasing adiposity and differences in fat-free mass decreased with increasing infant age. Estimates of body composition determined by DXA and ADP at 6 months of age were highly correlated, but did differ significantly. Additional work is required to identify the technical basis for these rather large inter-method differences in infant body composition. PMID:22522885

Fields, David A; Demerath, Ellen W; Pietrobelli, Angelo; Chandler-Laney, Paula C

2012-11-01

368

Transparent exopolymeric particles' distribution in the northern Adriatic and their relation to microphytoplankton biomass and composition.  

PubMed

Transparent exopolymer particles (TEP) are generated during transformation processes within the non-living organic matter continuum in the seawater. Seasonal dynamics of TEP along the Po River Delta-Rovinj transect was followed during the 3-year period, using a spectrophotometric method of determination of TEP. Relationships between TEP and phytoplankton biomass (chlorophyll a), abundance and composition, as well as phaeophytin, were analysed. Microphytoplankton spring blooms are confirmed to be an important source of TEP, with some species more related to TEP concentration dynamics, such as Chaetoceros sp. and Skeletonema costatum. Notable spatial west to east gradient of autotrophic biomass and consequently of TEP was observed, as well as gradual decrease with depth. In addition, TEP concentration increments were observed up to 2 months before the mucilage events followed by the decrease of TEP concentration during the event itself. Pattern of TEP dynamics in the years with mucilage events was the most pronounced in 2002, when the event was spatially and temporally the most extended. PMID:16257040

Radi?, Tomislav; Kraus, Romina; Fuks, Dragica; Radi?, Jadranka; Pecar, Osvin

2005-12-15

369

Characterization of elemental and structural composition of corrosion scales and deposits formed in drinking water distribution systems.  

PubMed

Corrosion scales and deposits formed within drinking water distribution systems (DWDSs) have the potential to retain inorganic contaminants. The objective of this study was to characterize the elemental and structural composition of extracted pipe solids and hydraulically-mobile deposits originating from representative DWDSs. Goethite (alpha-FeOOH), magnetite (Fe(3)O(4)) and siderite (FeCO(3)) were the primary crystalline phases identified in most of the selected samples. Among the major constituent elements of the deposits, iron was most prevalent followed, in the order of decreasing prevalence, by sulfur, organic carbon, calcium, inorganic carbon, phosphorus, manganese, magnesium, aluminum and zinc. The cumulative occurrence profiles of iron, sulfur, calcium and phosphorus for pipe specimens and flushed solids were similar. Comparison of relative occurrences of these elements indicates that hydraulic disturbances may have relatively less impact on the release of manganese, aluminum and zinc, but more impact on the release of organic carbon, inorganic carbon, and magnesium. PMID:20576284

Peng, Ching-Yu; Korshin, Gregory V; Valentine, Richard L; Hill, Andrew S; Friedman, Melinda J; Reiber, Steve H

2010-08-01

370

Distribution, abundance and carbon isotopic composition of gaseous hydrocarbons in Big Soda Lake, Nevada - An alkaline, meromictic lake  

NASA Technical Reports Server (NTRS)

The study of the distribution and isotopic composition of low molecular weight hydrocarbon gases at the Big Soda Lake, Nevada, has shown that while neither ethylene nor propylene were found in the lake, ethane, propane, isobutane and n-butane concentrations all increased with water column depth. It is concluded that methane has a biogenic origin in both the sediments and the anoxic water column, and that C2-C4 alkanes have biogenic origins in the monimolimnion water and shallow sediments. The changes observed in delta C-13/CH4/ and CH4/(C2H6 + C3H8) with depth in the water column and sedimeents are probably due to bacterial processes, which may include anaerobic methane oxidation and different rates of methanogenesis, and C2-to-C4 alkane production by microorganisms.

Oremland, R. S.; Des Marais, D. J.

1983-01-01

371

Abundance, distribution, and isotopic composition of particulate black carbon in the northern Gulf of Mexico  

NASA Astrophysics Data System (ADS)

exists increasing evidence supporting the important role of black carbon in global carbon cycles. Particulate black carbon (PBC) is allochthonous and has distinct reactivities compared to the bulk particulate organic carbon (tot-POC) in marine environments. However, the abundance, geochemical behavior of PBC and its importance in oceanic carbon budget remain poorly understood. Here we report the abundance, distribution, and stable isotopic signatures of BC derived from the chemo-thermal oxidation (CTO-375) method (BCCTO) in the Gulf of Mexico. Our results show that BCCTO abundance decreased from shelf to basin, and more than a half of riverine BCCTO could be removed over the shelf. Moreover, BCCTO is much more refractory compared to the tot-POC and has ?13C values lower than those of BC-excluded POC. These results highlight the significance of PBC in marine carbon cycles and potentially suggest the need for a new end-member term in quantifying POC sources in the ocean.

Yang, Weifeng; Guo, Laodong

2014-11-01

372

The Effect of Community on Distributed Bio-inspired Service Composition  

NASA Astrophysics Data System (ADS)

The Future Internet is expected to cater for both a larger number and variety of services, which in turn will make basic tasks such as service lifecycle management increasingly important and difficult. At the same time, the ability for users to efficiently discover and compose these services will become a key factor for service providers to differentiate themselves in a competitive market. In previous work, we examined the effect adding biological mechanisms to services had on service management and discovery. In this paper we examine the effects of community on services, specifically in terms of composing services in a distributed fashion. By introducing aspects of community we aim to demonstrate that services can further improve their sustainability and indeed their efficiency.

Carroll, Raymond; Balasubramaniam, Sasitharan; Botvich, Dmitri; Donnelly, William

373

Distribution and Compositional Constraints on Subsurface Ice in Arcadia Planitia, Mars  

NASA Astrophysics Data System (ADS)

Knowledge of the present-day quantity and distribution of water ice on Mars can help to understand past Martian climates, and also has implications for future human exploration. Within the northern mid-latitudes, there are many geomorphological features such as ice-exposing impacts (Dundas et al., 2014) and expanded secondary craters (Viola et al., 2014) that are indicative of widespread ice.Impact crater morphology can reveal subsurface structure, such as when terraces form in layered target material (Ormö et al., 2013). We create Digital Terrain Models (DTMs) using the Mars Reconnaissance Orbiter’s HiRISE (High Resolution Imaging Science Experiment) stereo image pairs to measure terrace depths within craters (and thus the depths to the boundary of the subsurface layer). Radar sounding from the SHARAD instrument, also on the Mars Reconnaissance Orbiter, provides an independent mechanism for probing the subsurface and shows an extensive subsurface reflector in Arcadia Planitia (180-225E, 38-50N). Assuming the change in material strengths responsible for the terraces is the same dielectric interface that causes the radar reflectors, combining the terrace depths with radar delay times allows us to determine the radar wave velocity (and thus dielectric constant) of the layer of material between the surface and subsurface reflector.We present results from combining these observational datasets to map the distribution and constrain the dielectric constant of this widespread layer. Preliminary results suggest this decameters-thick layer is relatively pure excess (higher water ice abundances than can fit into the pore spaces of the regolith) ice. We compare our dielectric constant calculations with a 3-component dielectric mixing model to put limits on the porosity and purity of the ice. Understanding the conditions that emplaced and preserved this ice layer is important to improving our understanding of the Martian climate system.

Bramson, Ali M.; Byrne, Shane; Putzig, Nathaniel E.; Mattson, Sarah; Plaut, Jeffrey J.; Holt, John W.

2014-11-01

374

Properties of wine polymeric pigments formed from anthocyanin and tannins differing in size distribution and subunit composition.  

PubMed

To explore the effect of tannin composition on pigment formation, model ferments of purified 3-O-monoglucoside anthocyanins (ACN) were conducted either alone or in the presence of two different tannins. Tannins were isolated from grape seeds (Sd) or skins (Sk) following exhaustive extraction in 70% v/v acetone. The Sd and Sk tannin fractions had a mean degree of polymerization of 5.2 and 25.6, respectively. The Sd fraction was highly galloylated, at 22%, but galloylation was <2% in the Sk fraction. The Sk fraction was distinguished by a high proportion of prodelphinidin, at 58%. After a 6 month aging period, polymeric pigments were quantified and their color properties determined following isolation by solid-phase extraction. Wine color and polymeric pigment were highest in the treatment containing ACN+Sd and similar in the ACN+Sk and ACN treatments. The same trend between treatments was observed for total and polymeric nonbleachable pigments. Only minor changes in tannin subunit composition were found following ACN incorporation, but the size distribution of polymeric pigments determined by gel permeation chromatography decreased, in particular for the ACN+Sk treatment. Color incorporation in the higher molecular mass range was lower for ACN+Sk wines than for ACN+Sd wines. Compositional differences between the two tannin fractions may therefore limit the incorporation of ACNs in the colored form. The results suggest that in the ACN+Sk and ACN treatments, the formation of lower molecular mass oligomeric pigments was favored. In polymeric pigments derived from ACNs, the presence of ethyl- and vinyl-linked ACNs to the level of trimers was identified using mass spectrometry. PMID:25356846

Bindon, Keren; Kassara, Stella; Hayasaka, Yoji; Schulkin, Alex; Smith, Paul

2014-11-26

375

Influence of hydraulic regimes on bacterial community structure and composition in an experimental drinking water distribution system.  

PubMed

Microbial biofilms formed on the inner-pipe surfaces of drinking water distribution systems (DWDS) can alter drinking water quality, particularly if they are mechanically detached from the pipe wall to the bulk water, such as due to changes in hydraulic conditions. Results are presented here from applying 454 pyrosequencing of the 16S ribosomal RNA (rRNA) gene to investigate the influence of different hydrological regimes on bacterial community structure and to study the potential mobilisation of material from the pipe walls to the network using a full scale, temperature-controlled experimental pipeline facility accurately representative of live DWDS. Analysis of pyrosequencing and water physico-chemical data showed that habitat type (water vs. biofilm) and hydraulic conditions influenced bacterial community structure and composition in our experimental DWDS. Bacterial community composition clearly differed between biofilms and bulk water samples. Gammaproteobacteria and Betaproteobacteria were the most abundant phyla in biofilms while Alphaproteobacteria was predominant in bulk water samples. This suggests that bacteria inhabiting biofilms, predominantly species belonging to genera Pseudomonas, Zooglea and Janthinobacterium, have an enhanced ability to express extracellular polymeric substances to adhere to surfaces and to favour co-aggregation between cells than those found in the bulk water. Highest species richness and diversity were detected in 28 days old biofilms with this being accentuated at highly varied flow conditions. Flushing altered the pipe-wall bacterial community structure but did not completely remove bacteria from the pipe walls, particularly under highly varied flow conditions, suggesting that under these conditions more compact biofilms were generated. This research brings new knowledge regarding the influence of different hydraulic regimes on the composition and structure of bacterial communities within DWDS and the implication that this might have on drinking water quality. PMID:23182667

Douterelo, I; Sharpe, R L; Boxall, J B

2013-02-01

376

Composition, structure and layer charge distribution in K-bentonite illite/smectite clays: Evidence from HRTEM  

SciTech Connect

Fourteen illite/smectite (I/S) clays separated from lower Paleozoic K-bentonites have been studied by XRD, XRF, HRTEM, and alkylamonium ion exchange. The samples represent the full range of commonly occurring I/S compositions in diagenetic K-bentonites. Chemical analysis and XRD data show that the increases in the amount of tetrahedral Al[sup +3] for Si[sup +4] substitution and the amount of fixed-K, are the principle factors controlling the increases in the proportion of illite layers and the degree of ordering in I/S. Extrapolation of the chemical data indicates: (1) a constant fixed-K content of 0.75 per illite layer (half cell); and (2) a montmorillonitic and a phengitic end-member compositions, respectively, for smectite and illite. The magnitude and distribution of layer charge of expandable component of I/S determined by alkylammonium ion exchange is characteristic of smectite in I/S with 15--100% expandability, confirming the two-component nature of I/S in this range. The layer charge data both from XRD and HRTEM for alkylammonium ion-exchanged I/S with < 15% expandability suggest a vermiculitic, rather than a smectitic charge for the expandable interlayers. The HRTEM data demonstrate that the postulated fundamental particles are the result of disintegration of larger I/S crystals. The data is consistent with a layer-by-layer transformation mechanism in which randomly distributed high-, intermediate-, and low-charged interlayers of a precursor smectite preferentially incorporate K[sup +] ions in response to an increasingly negative tetrahedral charge. A neoformation process involving dissolution of smectite and reprecipitation of illite is unlikely because such a mechanism requires precipitation of illite particles with surface charges significantly higher than that of a smectite.

Cetin, K.; Huff, W.D. (Univ. of Cincinnati, OH (United States). Dept. of Geology)

1992-01-01

377

Amino acid composition, molecular weight distribution and gel electrophoresis of walnut (Juglans regia L.) proteins and protein fractionations.  

PubMed

As a by-product of oil production, walnut proteins are considered as an additional source of plant protein for human food. To make full use of the protein resource, a comprehensive understanding of composition and characteristics of walnut proteins are required. Walnut proteins have been fractionated and characterized in this study. Amino acid composition, molecular weight distribution and gel electrophoresis of walnut proteins and protein fractionations were analyzed. The proteins were sequentially separated into four fractions according to their solubility. Glutelin was the main component of the protein extract. The content of glutelin, albumin, globulin and prolamin was about 72.06%, 7.54%, 15.67% and 4.73% respectively. Glutelin, albumin and globulin have a balanced content of essential amino acids, except for methionine, with respect to the FAO pattern recommended for adults. SDS-PAGE patterns of albumin, globulin and glutelin showed several polypeptides with molecular weights 14.4 to 66.2 kDa. The pattern of walnut proteins in two-dimension electrophoresis (2-DE) showed that the isoelectric point was mainly in the range of 4.8-6.8. The results of size exclusion chromatogram indicated molecular weight of the major components of walnut proteins were between 3.54 and 81.76 kDa. PMID:24473146

Mao, Xiaoying; Hua, Yufei; Chen, Guogang

2014-01-01

378

Influence of Cow Bone Particle Size Distribution on the Mechanical Properties of Cow Bone-Reinforced Polyester Composites  

PubMed Central

This work was carried out to investigate the influence of cow bone particle size distribution on the mechanical properties of polyester matrix composites in order to consider the suitability of the materials as biomaterials. Cow bone was procured from an abattoir, washed with water, and sun-dried for 4 weeks after which it was crushed with a sledge hammer and was further pulverized with laboratory ball mill. Sieve size analysis was carried out on the pulverized bone where it was sieved into three different sizes of 75, 106, and 300??m sieve sizes. Composite materials were developed by casting them into tensile and flexural tests moulds using predetermined proportions of 2, 4, 6, and 8%. The samples after curing were striped from the moulds and were allowed to be further cured at room temperature for 3 weeks before tensile and flexural tests were performed on them. Both tensile and flexural strength were highly enhanced by 8 wt% from 75??m while toughness was highly enhanced by 6 and 8?wt% from 300??m. This shows that fine particles lead to improved strength while coarse particles lead to improved toughness. The results show that these materials are structurally compatible and are being developed from animal fibre based particle; it is expected to also aid the compatibility with the surface conditions as biomaterials. PMID:24324892

Oladele, Isiaka Oluwole; Adewole, Temitope Akinyemi

2013-01-01

379

Influence of cow bone particle size distribution on the mechanical properties of cow bone-reinforced polyester composites.  

PubMed

This work was carried out to investigate the influence of cow bone particle size distribution on the mechanical properties of polyester matrix composites in order to consider the suitability of the materials as biomaterials. Cow bone was procured from an abattoir, washed with water, and sun-dried for 4 weeks after which it was crushed with a sledge hammer and was further pulverized with laboratory ball mill. Sieve size analysis was carried out on the pulverized bone where it was sieved into three different sizes of 75, 106, and 300??m sieve sizes. Composite materials were developed by casting them into tensile and flexural tests moulds using predetermined proportions of 2, 4, 6, and 8%. The samples after curing were striped from the moulds and were allowed to be further cured at room temperature for 3 weeks before tensile and flexural tests were performed on them. Both tensile and flexural strength were highly enhanced by 8 wt% from 75??m while toughness was highly enhanced by 6 and 8?wt% from 300??m. This shows that fine particles lead to improved strength while coarse particles lead to improved toughness. The results show that these materials are structurally compatible and are being developed from animal fibre based particle; it is expected to also aid the compatibility with the surface conditions as biomaterials. PMID:24324892

Oladele, Isiaka Oluwole; Adewole, Temitope Akinyemi

2013-01-01

380

Impact of prebiotic synthesis and diagenesis on the distribution, stereochemistry, and stable isotope composition of amino acids in carbonaceous meteorites  

NASA Astrophysics Data System (ADS)

Simulation experiments for prebiotic synthesis result in racemic mixtures (D/L = 1.0) for protein and non-protein amino acids, irrespective of the composition of the precursor gas mixtures or the energy sources employed. It is therefore not surprising that it was commonly assumed that if amino acids in carbonaceous meteorites were formed by similar reactions they would also be racemic. Engel and Nagy1 and more recently Glavin et al.2 have shown that protein amino acids in carbonaceous meteorites often exhibit a moderate to strong L-amino acid excess (D/L ? 1.0). Engel3 hypothesized that this extraterrestrial L-excess might be the precursor material from which life as we know it originated. Stable isotope analysese.g 4 confirmed that the L-amino acid excess in meteorites was indigenous rather than the result of contamination subsequent to impact on Earth. A key question that arises is that since there are no known mechanisms for the direct prebiotic synthesis of amino acids with an L-enantiomer excess, how did these compounds come to exist in carbonaceous meteorites? It has been proposed5 and references therein that a series of diagenetic reactions subsequent to synthesis are responsible for the L-enantiomer excess. In this paper, this hypothesis is further explored with respect to explaining the range of D/L values for amino acids in the various types of carbonaceous meteorites as well as in different stones of the same meteorite. Possible effects of diagenesis on the stable isotope compositions of these compounds are also addressed.

Engel, Michael H.

2013-09-01

381

Life-cycle costs of non-PCB distribution transformer alternatives. Final report, January-December 1988  

SciTech Connect

The U.S. Navy is investigating transformer alternatives to replace PCB transformers. Currently, NCEL is making a technical evaluation of various non PCB transformer replacement alternatives and determining the Life Cycle Costs (LCC) of these transformers. These include mineral oil, silicon oil, RTemp, amorphous core, vapor-cooled, ventilated dry, sealed dry, and cast coil at kVA ratings of 25, 75, 150, 300, 350, 500, 750, 1000, and 1500. Life cycle savings of amorphous core transformers over conventional silicon steel are also analyzed and show substantial savings. A 1500 kVA amorphous core transformer that is loaded at 90 percent and with a 15 percent price differential over a similar silicon steel transformer can produce life cycle savings of nearly $75,000 with a payback of 2 to 3 years. For the purpose of transformer cost comparison, life cycle costs are composed of the purchase price, load and no-load costs. Life cycle costs are computed for the entire life cycle of 30 years. Energy costs of 0.06/k Wh is used throughout this report with a compound growth rate of 5 percent over the assumed life cycle of 30 years for each transformer.

Pulle, C.

1990-05-01

382

A piezolaminated composite degenerated shell finite element for active control of structures with distributed piezosensors and actuators  

NASA Astrophysics Data System (ADS)

This paper deals with the formulation of a nine-noded piezolaminated degenerated shell finite element for modeling and analysis of multilayer composite general shell structures with bonded/embedded distributed piezoelectric sensors and actuators. The distributed PZT sensors and actuators used in the composite smart structures are relatively thin and could have arbitrary variation of curvatures and thicknesses. They cannot be modeled with shell elements based on curvilinear shell theories which would need the specification of constant shell curvatures and thicknesses. Modeling them with piezo finite elements available in popular commercial codes like ABAQUS, ANSYS, MARC, etc, would need relatively greater computational effort as they are based on solid element formulation. In view of these, the present proposed degenerated piezoelectric shell element would be a better choice giving good computational accuracy and efficiency. The main advantage of a degenerate shell element is that it is not based on any shell theories and is applicable over a wide range of curvatures and thicknesses. This element is developed by using the degenerate solid approach based on Reissner-Mindlin assumptions which allow the shear deformation and rotary inertia effect to be considered and the 3D field is reduced to a 2D field in terms of mid-surface nodal variables. Uniformly reduced integration is carried out to overcome membrane locking and shear locking and the numerical integration is carried out in all three directions to obtain accurate results. The present element has 45 elastic degrees of freedom and 10 electric degrees of freedom per piezoelectric layer in the element. The potential induced due to bending deformation is more accurately represented by assuming quadratic variation of the electric potential through the thickness of each piezoelectric layer. This is achieved by interpolating using nodal mid-plane electric potentials and one electric degree of freedom representing the potential difference between the top and bottom surfaces of the piezoelectric layer. Few case studies of composite general shells with piezoelectric sensors and actuators have been considered by modeling them with the above elements and the active vibration control performance has been studied using linear quadratic Gaussian (LQG) control.

Balamurugan, V.; Narayanan, S.

2008-06-01

383

Site and still life  

E-print Network

This thesis uses the still life as a medium for investigating architecture and the city . An analogy is established between what the thesis defines as still life and an urban composition (a site in East Cambridge). Through ...

Willey, Guy Phillip

1993-01-01

384

Distribution  

Microsoft Academic Search

e're closer than you think: Portland's geographic location and Oregon's transportation infra - structure offer unmatched con - nectivity and time savings to international and domestic markets. Our economic development practices combine project-ready property with efficient, high-capacity infrastructure to create today's logistics advantages. Connecting people, places and products is the core of Portland's distribution and logistics industry sec - tor.

F. Gregory; B. Boyd; R. Bridges; D. Mitchell; J. Halsell; S. Fancher; D. King; R. Fore; E. Mango; D. Berlinrut; M. Leinbach; M. Maier; M. Wetmore; H. Herring; J. Guidi; M. Coolidge; J. Heald; T. Knox; D. Bartine; R. Bailey; H. Delgado; P. Conant; J. Madura; R. Thomas; F. Merceret; G. Allen; E. Bensman; R. Dittemore; N. Feldman; C. Boykin; H. Tileston; F. Brody; L. Hagerman; S. Pearson; L. Uccellini; W. Vaughan; J. Golden; D. Johnson; J. McQueen; B. Roberts; L. Freeman; G. Jasper; B. Hagemeyer; A. McCool; X. W. Proenza; S. Glover

2006-01-01

385

Hydrothermal processing of duckweed: effect of reaction conditions on product distribution and composition.  

PubMed

Influences of operating conditions such as temperature (270-380 °C), time (10-120 min), reactor loading (0.5-5.5 g), and K2CO3 loading (0-50 wt.%) on the product (e.g. crude bio-oil, water soluble, gas and solid residue) distribution from the hydrothermal processing of duckweed were determined. Of the four variables, temperature and K2CO3 loading were always the most influential factors to the relative amount of each component. The presence of K2CO3 is unfavorable for the production of bio-oil and gas. Hydrothermal processing duckweed produces a bio-oil that is enriched in carbon and hydrogen and has reduced levels of O compared with the original duckweed feedstock. The higher heating values of the bio-oil were estimated within the range of 32-36 MJ/kg. Major bio-oil constituents include ketones and their alkylated derivatives, alcohols, heterocyclic nitrogen-containing compounds, saturated fatty acids and hydrocarbons. The gaseous products were mainly CO2 and H2, with lesser amounts of CH4 and CO. PMID:23021946

Duan, Peigao; Chang, Zhoufan; Xu, Yuping; Bai, Xiujun; Wang, Feng; Zhang, Lei

2013-05-01

386

Macrobenthos composition, distribution and abundance within Sungai Pulai estuary, Johor, Malaysia  

NASA Astrophysics Data System (ADS)

Macrobenthos are very useful organisms for monitoring marine environmental and widely use in marine ecology research. They are able to monitor the difference phase in the recovery stage of disturbed sites by appear different species macrobenthos after the cessation of the impact. Univariate and multivariate methods were use to study the macrobenthos community within Sungai Pulai estuary, Johor, Malaysia. Five sub-samples were taken at each sampling sites by using 10 cm diameter corer. Crustaceans were the most abundant at Tanjung Adang (St. 1) and the station of non-seagrass area (St. 2) while polychaetes were the most abundant at Merambong Shoal (St. 3). Higher density of macrobenthos was found at St.3 followed by St. 1 and St. 2. The commonly used population indices such as diversity, richness, evenness and dominance were employed to determine the differences in diversity and abundance of macrobenthos. The diversity, richness and evenness index values showed slight increment from Station 1 to Station 3, while the dominance index decreasing trend from Station 1 to Station 3. A total 21 polychaete families were collected in Sungai Pulai estuary, which was dominated by the Spionidae, Capitellidae and Glyceridae. Cluster (Bray-Curtis similarities) analyses revealed that the Tanjung Adang and Merambong Shoal population were clearly separated from the station non-seagrass. For the time being factors that influence the pattern of distribution of the macrobenthos cannot be determined and subjected to further studies.

Shi, Guan Wan; Min, Lee Di; Ghaffar, Mazlan Abd; Ali, Masni Md; Cob, Zaidi Che

2014-09-01

387

Spatial distribution of summertime particulate matter and its composition in Greece  

NASA Astrophysics Data System (ADS)

A field campaign was conducted in Greece during the summer of 2012 (8 June - 26 July) to investigate ambient particulate matter (PM) levels, chemical composition and contribution of regional and local sources. Simultaneous collection of PM1, PM2.5 and PM10 samples from seven different sampling sites in Greece were collected, two sites in Athens - Ag. Paraskevi Demokritos campus (suburban background), - Penteli (National Observatory of Athens NOA premises, suburban background), one in Thessaloniki (suburban background), two stations in Patras - Centre (urban background), - suburbs/ICE FORTH campus (suburban background), one at Finokalia in the northeast part of Crete (remote background) and the last one at the Navarino Environmental Observatory (NEO) in southwest Peloponnese (rural background). These different background sites were chosen in order to estimate both the local emissions sources and the long range transport. A suite of continuous/online instruments were deployed in selected sites including an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF AMS), an Aerosol Chemical Speciation Monitor (ACSM), a Proton Transfer Reaction-Mass Spectrometer (PTR-MS), a Tapered Element Oscillating Microbalance (TEOM), Nephelometers and Aethalometers, gas-phase monitors, etc. The collected filter samples from all sites were analyzed for major ions, OC/EC, metals, etc. The fine PM mass concentration and chemical measurements were quite similar in all sites suggesting significant contributions of transported regional pollution and smaller contributions of local sources. The campaign average PM2.5 ranged from 17.5 to 20 ?g m-3 for the different sites. The Athens suburban site in Demokritos had the highest concentration PM2.5 levels. Sulphates and organics were the major PM2.5 components while nitrates, mineral dust and sea-salt for the coastal areas were also important for the PM10 fraction. The sulphate levels were similar in all sites, while the concentration of the organics and mineral dust were more variable. Most of the organic aerosol was highly oxygenated.

Tsiflikiotou, Maria; Papanastasiou, Dimitris; Zarmpas, Paulos; Paraskevopoulou, Despoina; Diapouli, Evangelia; Kostenidou, Evangelia; Kaltsonoudis, Christos; Bougiatioti, Aikaterini; Theodosi, Christina; Kouvarakis, George; Liakakou, Eleni; Vassilatou, Vassiliki; Siakavaras, Dimitris; Biskos, George; Eleftheriadis, Konstantinos; Gerasopoulos, Evangelos; Mihalopoulos, Nikos; Pandis, Spyros

2014-05-01

388

Barely visible impact damage detection for composite sandwich structures by optical-fiber-based distributed strain measurement  

NASA Astrophysics Data System (ADS)

The authors developed an impact damage-detection system for large-scale composite sandwich structures using an optical fiber network running throughout the structure. A Brillouin-based sensing system with high spatial resolution (pre-pump pulse Brillouin optical time-domain analysis (PPP-BOTDA)) was utilized for distributed strain measurement. The PPP-BOTDA sensing system can measure axial strain along the optical fiber by employing stimulated Brillouin scattering. The system realizes a spatial resolution of 10 cm, a sampling interval of 5 cm, and a sensing range of more than 1 km. Our previous study revealed that a non-uniform axial strain within centimeter spatial resolution broadens the width of the Brillouin gain spectrum, which is the output of the PPP-BOTDA. The specific response of the PPP-BOTDA was employed to detect non-uniform strain distribution along a residual facesheet dent in a damaged area. First, the response of the optical fiber sensor network, formed in the adhesive layer, was simulated to clarify the effectiveness and limitations of the proposed damage-detection technique. The system was then validated by an experiment. As the damage became larger, the width of the Brillouin gain spectra became broader. Consequently, the location and size of barely visible damage could be estimated. The system developed is quite useful for a first inspection of large-scale sandwich structures in aerospace and marine applications.

Minakuchi, S.; Okabe, Y.; Mizutani, T.; Takeda, N.

2009-08-01

389

Extending the shelf-life and proximate composition stability of ready to eat foods in vacuum or modified atmosphere packaging  

Microsoft Academic Search

The stability of the proximate composition (moisture, proteins, lipids and ash) and the microbiological state of cooked ‘ready to eat’ foods in vacuum or modified atmosphere packaging were examined and compared with conventionally packaged (in air) foods. The study was carried out for 7 and 29 days, during which time the food products were stored at 3°C. Vacuum or modified

M. Antonia Murcia; Magdalena Mart??nez-Tomé; M. Carmen Nicolás; Ana M Vera

2003-01-01

390

The elemental composition of purple sea urchin (Strongylocentrotus purpuratus) calcite and potential effects of pCO2 during early life stages  

NASA Astrophysics Data System (ADS)

Ocean acidification will likely have negative impacts on invertebrates producing skeletons composed of calcium carbonate. Skeletal solubility is partly controlled by the incorporation of "foreign" ions (e.g. magnesium) into the crystal lattice of these skeletal structures, a process that is sensitive to a variety of biological and environmental factors. Here we explore effects of life stage, oceanographic region of origin, and changes in the partial pressure of carbon dioxide in seawater (pCO2) on trace elemental composition in the purple sea urchin (Strongylocentrotus purpuratus). We show that, similar to other urchin taxa, adult purple sea urchins have the ability to precipitate skeleton composed of a range of biominerals spanning low- to high-Mg calcites. Mg / Ca and Sr / Ca ratios were substantially lower in adult spines compared to adult tests. On the other hand, trace elemental composition was invariant among adults collected from four oceanographically distinct regions spanning a range of carbonate chemistry conditions (Oregon, Northern California, Central California, and Southern California). Skeletons of newly settled juvenile urchins that originated from adults from the four regions exhibited intermediate Mg / Ca and Sr / Ca between adult spine and test endmembers, indicating that skeleton precipitated during early life stages is more soluble than adult spines and less soluble than adult tests. Mean skeletal Mg / Ca or Sr / Ca of juvenile skeleton did not vary with source region when larvae were reared under present-day, global-average seawater carbonate conditions (400 ?atm; pHT = 8.02 ± 0.03 1 SD; ?calcite = 3.3 ± 0.2 1 SD). However, when reared under elevated pCO2 (900 ?atm; pHT = 7.73 ± 0.03; ?calcite = 1.8 ± 0.1), skeletal Sr / Ca in juveniles exhibited increased variance across the four regions. Although larvae from the northern populations (Oregon, Northern California, Central California) did not exhibit differences in Mg or Sr incorporation under elevated pCO2 (Sr / Ca = 2.10 ± 0.06 mmol mol-1; Mg / Ca = 67.4 ± 3.9 mmol mol-1), juveniles of Southern California origin partitioned ~8% more Sr into their skeletons when exposed to higher pCO2 (Sr / Ca = 2.26 ± 0.08 vs. 2.09 ± 0.005 mmol mol-1 1 SD). Together these results suggest that the diversity of carbonate minerologies present across different skeletal structures and life stages in purple sea urchins does not translate into an equivalent geochemical plasticity of response associated with geographic variation or temporal shifts in seawater properties. Rather, composition of S. purpuratus skeleton precipitated during both early and adult life history stages appears relatively robust to spatial gradients and predicted future changes in carbonate chemistry. An exception to this trend may arise during early life stages, where certain populations of purple sea urchins may alter skeletal mineral precipitation rates and composition beyond a given pCO2 threshold. This potential for geochemical plasticity during early development in contrast to adult stage geochemical resilience adds to the growing body of evidence that ocean acidification can have differing effects across organismal life stages.

LaVigne, M.; Hill, T. M.; Sanford, E.; Gaylord, B.; Russell, A. D.; Lenz, E. A.; Hosfelt, J. D.; Young, M. K.

2013-06-01

391

Cell surface distribution of fibronectin and vitronectin receptors depends on substrate composition and extracellular matrix accumulation  

PubMed Central

We used antibodies against the alpha subunits of the human fibronectin receptor (FNR) and vitronectin receptor (VNR) to localize simultaneously FNR and VNR at major substrate adhesion sites of fibroblasts and melanoma cells with double-label immunofluorescence microscopy. In early (2-6-h) serum-containing cultures, both FNR and VNR coaccumulated in focal contacts detected by interference reflection microscopy. Under higher resolution immunoscanning electron microscopy, FNR and VNR were also observed to be distributed randomly on the dorsal cell surface. As fibronectin-containing extracellular matrix fibers accumulated beneath the cells at 24 h, FNR became concentrated at contacts with these fibers and was no longer detected at focal contacts. VNR was not observed at matrix contacts but remained strikingly localized in focal contacts of the 24-h cells. Since focal contacts represent the sites of strongest cell-to-substrate adhesion, these results suggest that FNR and VNR together play critical roles in the maintenance of stable contacts between the cell and its substrate. In addition, the accumulation of FNR at extracellular matrix contacts implies that this receptor might also function in the process of cellular migration along fibronectin-containing matrix cables. To define the factors governing accumulation of FNR and VNR at focal contacts, fibroblasts in serum-free media were plated on substrates coated with purified ligands. Fibronectin-coated surfaces fostered accumulation of FNR but not VNR at focal contacts. On vitronectin- coated surfaces, or substrata derivatized with a tridecapeptide containing the cell attachment sequence Arg-Gly-Asp, both FNR and VNR became concentrated at focal contacts. These observations suggest that the availability of ligand is critical to the accumulation of FNR and VNR at focal contacts, and that FNR might also recognize substrate- bound vitronectin. PMID:2454933

1988-01-01

392

Spatial Distribution of Total, Ammonia-Oxidizing, and Denitrifying Bacteria in Biological Wastewater Treatment Reactors for Bioregenerative Life Support  

Microsoft Academic Search

Bioregenerative life support systems may be necessary for long-term space missions due to the high cost of lifting supplies and equipment into orbit. In this study, we investigated two biological wastewater treatment reactors designed to recover potable water for a spacefaring crew being tested at Johnson Space Center. The experiment (Lunar-Mars Life Support Test Project—Phase III) consisted of four crew

Yuko Sakano; Karen D. Pickering; Peter F. Strom; Lee J. Kerkhof

2002-01-01

393

Inuence of Gold-Copper Alloy Catalyst Composition on Crystal Growth and Dopant Distribution in Silicon and Germanium Nanowires  

NASA Astrophysics Data System (ADS)

A combination of local electrode atom probe tomography (LEAP) and transmission electron microscopy characterization were used to investigate growth of and dopant incorporation in silicon and germanium nanowires (Si and GeNWs) via the vapor-liquid- solid (VLS) mechanism. A sample structure was developed that enabled isolation of the catalyst-mediated contribution to doping in individual nanowires during LEAP analysis. As a result, the distribution coefficient - a thermodynamic quantity describing axial junction abruptness - was measured in nanowires for the first time, providing a fundamental framework for comparison of junction abruptness in nanowires. These investigations also enabled the identification of a previously unknown radial anisotropy in dopant incorporation through the catalyst, with variations in dopant concentration across the VLS-defined diameter of the nanowire as large as two orders of magnitude. Finite element modeling of the doping process, coupled with in situ TEM observations reported in the literature, suggests that this radially inhomogeneous dopant distribution is a direct consequence of growth from a faceted liquid-solid interface, rather than the commonly assumed planar interface. Au-Cu alloy catalysts were explored as alternatives to Au-catalyzed VLS nanowire growth as a means to alleviate or eliminate axial and radial doping gradients in nanowires. Both an aqueous solution and electron beam lithographic method for creating Au-Cu alloy catalysts of controlled composition were developed, and GeNW growth was demonstrated from both types of catalyst. LEAP characterization of Au-Cu alloy catalyzed P-doped GeNWs revealed that alloying with Cu results in more abrupt axial doping junctions, as well as a more homogeneous radial distribution of dopants within the VLS-defined diameter of the nanowire.

Connell, Justin G.

394

A study on the sensitivities of simulated aerosol optical properties to composition and size distribution using airborne measurements  

NASA Astrophysics Data System (ADS)

We present a flexible framework to calculate the optical properties of atmospheric aerosols at a given relative humidity based on their composition and size distribution. The similarity of this framework to climate model parameterisations allows rapid and extensive sensitivity tests of the impact of uncertainties in data or of new measurements on climate relevant aerosol properties. The data collected by the FAAM BAe-146 aircraft during the EUCAARI-LONGREX and VOCALS-REx campaigns have been used in a closure study to analyse the agreement between calculated and measured aerosol optical properties for two very different aerosol types. The agreement achieved for the EUCAARI-LONGREX flights is within the measurement uncertainties for both scattering and absorption. However, there is poor agreement between the calculated and the measured scattering for the VOCALS-REx flights. The high concentration of sulphate, which is a scattering aerosol with no absorption in the visible spectrum, made the absorption measurements during VOCALS-REx unreliable, and thus no closure study was possible for the absorption. The calculated hygroscopic scattering growth factor overestimates the measured values during EUCAARI-LONGREX and VOCALS-REx by ?30% and ?20%, respectively. We have also tested the sensitivity of the calculated aerosol optical properties to the uncertainties in the refractive indices, the hygroscopic growth factors and the aerosol size distribution. The largest source of uncertainty in the calculated scattering is the aerosol size distribution (?35%), followed by the assumed hygroscopic growth factor for organic aerosol (?15%), while the predominant source of uncertainty in the calculated absorption is the refractive index of organic aerosol (28-60%), although we would expect the refractive index of black carbon to be important for aerosol with a higher black carbon fraction.

Esteve, A. R.; Highwood, E. J.; Morgan, W. T.; Allen, G.; Coe, H.; Grainger, R. G.; Brown, P.; Szpek, K.

2014-06-01

395

Distribution, movements, and life-history characteristics of Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri in the upper Yellowstone River drainage.  

E-print Network

??Distribution and abundance of Yellowstone cutthroat trout, Oncorhynchus clarkii bouvieri, has declined across the historic range because of anthropogenic influences. Habitat has been fragmented and… (more)

Ertel, Brian Daniel.

2011-01-01

396

Distribution and Carbon-Isotope Composition of Lipid Biomarkers in Lake Sediments on the Tibetan Plateau, China  

NASA Astrophysics Data System (ADS)

The goal of this study was to determine the carbon source and microbial community structure in different lake environments on the Tibetan Plateau using carbon isotopes and lipid biomarkers. Microbial mats and sediments were collected from Erhai-, Qinghai-, Gahai-, and Chaka-lakes, which have different pHs (7.4-9.5) and salinities (0.1-21%). Phospholipid fatty acids (PLFA) have different distribution patterns in algal mats, sandy mud, and salt deposits, which may reflect changes in microbial community structure in different environments. For example, terminally branched fatty acids reflect heterotrophic bacteria and varied from less than 1% in a brown algal mat in Lake Gahai to 23% in a salt deposit in Lake Chaka. The cyclopropyl fatty acids may reflect stress conditions under different salinities. These compounds varied from 0% in algal mats living on the bank of the lake, which received freshwater run off, to 12% in grey mud in the saline lake water. On the other hand, long-chain n-alkanes in these samples reflect contributions of a mixture of epicuticular waxes of higher plants and submerged or floating aquatic macrophytes. Carbon isotopes of lipid biomarkers indicate different sources of organic carbon in different lake sediments. For example, carbon isotopes of total organic carbon and lipid biomarkers averaged -23.9 ± 1.5‰ (n = 2) and -26.0 ± 3.1‰ (n = 18), respectively, in Lake Erhai, and averaged -30.0 ± 1.5‰ (n = 4) and -33.5 ± 3.3‰ (n = 92), respectively, in Lake Gahai. These results suggest that a relatively heavy carbon source is going into Lake Erhai compared to carbon sources going into Lake Gahai. This study indicates that the distribution patterns of the lipid biomarkers and theirs carbon-isotope compositions can be used to evaluate the community structure and the source of carbon that supports microbial growth in lake sediments on the Tibetan Plateau.

Tuo, J.; Li, Q.; Li, Y.; Jiang, H.; Dong, H.; Zhang, C. L.

2005-12-01

397

I Am Crrarn Soc, 1 5 [2] 316-2r (1992) Distribution of Matrix Cracks in a Uniaxial Ceramic Composite  

E-print Network

obtained for a unidirectional ceramic-matrix composite (Sic fibers in a calcium aluminosilicate matrixI Am Crrarn Soc, 1 5 [2] 316-2r (1992) journal Distribution of Matrix Cracks in a Uniaxial Ceramic, debonding betwecn the fiber and the matrix near the matrix As the load is increased, more matrix cracks

Barber, James R.

398

Glycemic index and glycemic load in relation to changes in body weight, body fat distribution, and body composition in adult Danes13  

Microsoft Academic Search

Background: A diet with a high glycemic index (GI) and glycemic load (GL) may promote overconsumption of energy and increase the risk of weight gain. Objective: The objective of the study was to investigate the relation between GI and GL of habitual diets and subsequent 6-y changes in body weight, body fat distribution, and body composition in a ran- dom

Helle Hare-Bruun; Anne Flint; Berit L Heitmann

399

Distribution Patterns and Size–Age Composition in Aggregations of the Gastropod Mollusk Nucella heyseana in Peter the Great Bay, Sea of Japan  

Microsoft Academic Search

Gastropods Nucella heyseana were collected from 1999 to 2001 from different habitats in Vostok Bay (Sea of Japan). The spatial distribution, the seasonal and interannual dynamics, and the composition of aggregations of this mollusk were analyzed. In Vostok Bay, N. heyseana inhabits biotopes that are typical of this species and other members of the genus and sometimes forms aggregations with

N. I. Selin; A. S. Dolganova

2003-01-01

400

Linking catalyst composition to chirality distributions of as-grown single-walled carbon nanotubes by tuning NixFe1-x nanoparticles  

NASA Astrophysics Data System (ADS)

Chirally pure single-walled carbon nanotubes (SWCNTs) are required for various applications ranging from nanoelectronics to nanomedicine. Although significant efforts have been directed towards separation of SWCNT mixtures, including density-gradient ultracentrifugation , chromatography and electrophoresis, the initial chirality distribution is determined during growth and must be controlled for non-destructive, scalable and economical production. Here, we show that the chirality distribution of as-grown SWCNTs can be altered by varying the composition of NixFe1-x nanocatalysts. Precise tuning of the nanocatalyst composition at constant size is achieved by a new gas-phase synthesis route based on an atmospheric-pressure microplasma. The link between the composition-dependent crystal structure of the nanocatalysts and the resulting nanotube chirality supports epitaxial models and is a step towards chiral-selective growth of SWCNTs.

Chiang, Wei-Hung; Mohan Sankaran, R.

2009-11-01

401

Effect of aggregation pheromone trap of Riptortus pedestris (Hemiptera: Alydidae) on the distribution and composition of its egg parasitoids.  

PubMed

The aggregation pheromone of Riptortus pedestris (F.) (Hemiptera: Alydidae) is known to attract its egg parasitoids Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) and Gryon japonicum (Ashmead) (Hymenoptera: Scelionidae). Distribution and composition of these egg parasitoids were compared in a soybean field in the presence and absence of aggregation pheromone-baited traps for two consecutive years. Three traps were installed on the edge of a soybean field, first without and then with aggregation pheromone in a before-after design, and changes in parasitism were assessed on nonviable host eggs released at distances of 9, 18, 27, and 36 m from the trap. A significant interactive effect of pheromone installation and distance was found in egg parasitism by both parasitoids. Parasitism on eggs recovered from 9 m away was up to 2.2 and 3.2 times higher in presence of pheromone than without pheromone for O. nezarae and G. japonicum, respectively. Parasitism by O. nezarae was always higher than that by G. japonicum, but their relative abundance, clutch size, and sex ratio were not affected by pheromone installation, irrespective of distance from the trap. In conclusion, aggregation pheromone increases abundance of parasitoids up to 18 m from trap installation points and does not affect the relative abundance of parasitoid species. PMID:24224237

Lim, Un Taek; Mainali, Bishwo Prasad

2013-10-01

402

Ion acceleration in Ar-Xe and Ar-He plasmas. I. Electron energy distribution functions and ion composition  

SciTech Connect

Electron energy distribution functions (eedf), ion production, and ion composition are studied in Ar-Xe and Ar-He expanding helicon plasmas. It was found that under the conditions of constant total flow rate, Xe, in addition to Ar, changes the eedf from Maxwellian-like to Druyvesteyn-like with a shortening of the high energy tail at {approx}15 eV. The electron temperature exponentially decreases from {approx}7 eV in pure Ar plasma to {approx}4 eV in pure Xe plasma. Xenon ions dominate the ion population for Xe filling fractions greater than 10%. The plasma density increases by {approx}15% with increasing Xe fraction. For an Ar-He plasma, increasing the helium fraction increases the electron temperature from {approx}7 eV in pure Ar plasma to {approx}14 eV for a He filling fraction of 80%. The plasma density drops by more than three orders of magnitude from 1.14x10{sup 11} cm{sup -3} to 6.5x10{sup 7} cm{sup -3}. However, the inferred ion densities indicate that even at a helium fraction of 80%, argon ions significantly outnumber helium ions.

Biloiu, Ioana A.; Scime, Earl E. [Department of Physics, West Virginia University, Morganton, West Virginia 26506 (United States)

2010-11-15

403

Source apportionment of ambient particles: Comparison of positive matrix factorization analysis applied to particle size distribution and chemical composition data  

NASA Astrophysics Data System (ADS)

Positive matrix factorization (PMF) method was used to identify the sources of ambient particles (PM 10) in Augsburg in winter 2006/07. The analyses were carried out separately with particulate chemical composition (PCC) data at an urban traffic site and with particle size distribution (PSD) data at an urban background site on daily and hourly base, respectively. For PCC data, six factors are identified and associated with NaCl (6.7% of PM 10), secondary sulfate (13.0%), biomass burning (13.3%), secondary nitrate (30.5%), traffic emission (16.5%) and re-suspended dust (20.0%). For PSD data, seven factors are identified and are associated with fresh and aged traffic sources, secondary aerosols, stationary combustion, nucleation particles, re-suspended dust and long range transported dust. The two traffic factors were dominated by ultrafine particles (diameter < 100 nm), and accounted for 25% and 40% of total particle number concentration (NC). Stationary combustion factor, consisting of particles around 100 nm, accounted for 26% of total NC. Re-suspended dust was mainly composed of particles with diameters > 2.5 ?m. The two different approaches (PCC and PSD data) led to comparable results with strong correlations for secondary nitrate and sulfate/secondary aerosols ( r = 0.92), which are considered to origin mainly from long range transport. Traffic emissions ( r = 0.52) and re-suspended dust ( r = 0.62) showed weaker correlation due to influences of local sources at the different sites.

Gu, Jianwei; Pitz, Mike; Schnelle-Kreis, Jürgen; Diemer, Jürgen; Reller, Armin; Zimmermann, Ralf; Soentgen, Jens; Stoelzel, Matthias; Wichmann, H.-Erich; Peters, Annette; Cyrys, Josef

2011-04-01

404

Species composition and distribution of the Antarctic plunderfishes (Pisces, Artedidraconidae) from the Ross Sea off Victoria Land  

NASA Astrophysics Data System (ADS)

Among the notothenioid fish, the Antarctic plunderfishes (family Artedidraconidae) are a poorly known component of the bottom fauna of the continental shelf despite their relative importance. The family is composed of 25 small- to medium-sized endemic species and four genera, Artedidraco, Dolloidraco, Histiodraco and Pogonophryne, which are the most benthic and sedentary of the notothenioid fish. In the framework of "Victoria Land Transect Project", several samples of plunderfishes were collected by means of an Agassiz trawl. Sampling activities were carried out between 100 and 500 m depth in five sites over nearly 4° latitude off Victoria Land. Overall, trawling yielded 80 specimens of plunderfish, including all species of Artedidraco reported from the Ross Sea, i.e. Artedidraco glareobarbatus, A. loennbergi, A. orianae, A. shackletoni and A. skottsbergi, and the monotypic genus Histiodraco. The use of multivariate statistical analyses on catch data indicated sampling site as the main factor affecting species composition. Histiodraco velifer and A. skottsbergi were caught almost exclusively in the southernmost sites, characterizing the artedidraconid fauna of Cape Russell. A. orianae was sampled only in the northernmost sites, such as Cape Adare and Hallett Peninsula. A. loennbergi appeared to be a ubiquitous species, whereas A. glareobarbatus was caught only at the Hallett Peninsula. Plunderfishes showed a particular distribution pattern in relation to depth as well. A. glareobarbatus was the shallowest species, being sampled within 100 m. A. orianae and A. shackletoni showed a similar distribution, being caught mostly at 100-200 m, whereas A. skottsbergi was mainly sampled at 200-300 m. H. velifer was caught in a wide depth range, but mostly in deeper waters (400 m). A. loennbergi was eurybathic, showing a wider depth distribution than other species. Univariate measures of diversity indicated Cape Adare as the poorer site in terms of species richness and diversity. Number of species, diversity and equitability were quite similar off Hallett Peninsula and Cape Russell, indicating the absence of a latitudinal trend. Generally, all univariate indices decreased from shallow (100 m) to deep waters (500 m).

La Mesa, Mario; Cattaneo-Vietti, Riccardo; Vacchi, Marino

2006-04-01

405

Assessing Community-Level and Single-Species Models Predictions of Species Distributions and Assemblage Composition after 25 Years of Land Cover Change  

PubMed Central

To predict the impact of environmental change on species distributions, it has been hypothesized that community-level models could give some benefits compared to species-level models. In this study we have assessed the performance of these two approaches. We surveyed 256 bird communities in an agricultural landscape in southwest France at the same locations in 1982 and 2007. We compared the ability of CQO (canonical quadratic ordination; a method of community-level GLM) and GLMs (generalized linear models) to i) explain species distributions in 1982 and ii) predict species distributions, community composition and species richness in 2007, after land cover change. Our results show that models accounting for shared patterns between species (CQO) slightly better explain the distribution of rare species than models that ignore them (GLMs). Conversely, the predictive performances were better for GLMs than for CQO. At the assemblage level, both CQO and GLMs overestimated species richness, compared with that actually observed in 2007, and projected community composition was only moderately similar to that observed in 2007. Species richness projections tended to be more accurate in sites where land cover change was more marked. In contrast, the composition projections tended to be less accurate in those sites. Both modelling approaches showed a similar but limited ability to predict species distribution and assemblage composition under conditions of land cover change. Our study supports the idea that our community-level model can improve understanding of rare species patterns but that species-level models can provide slightly more accurate predictions of species distributions. At the community level, the similar performance of both approaches for predicting patterns of assemblage variation suggests that species tend to respond individualistically or, alternatively, that our community model was unable to effectively account for the emergent community patterns. PMID:23349818

Bonthoux, Sebastien; Baselga, Andres; Balent, Gerard

2013-01-01

406

Life cycle monitoring of large-scale CFRP VARTM structure by fiber-optic-based distributed sensing  

Microsoft Academic Search

This study demonstrated fiber-optic-based life cycle monitoring of a representative carbon fiber reinforced plastic (CFRP) stiffened panel manufactured by vacuum assisted resin transfer molding (VARTM). A single optical fiber was embedded between the stiffeners and the skin during the laminate lay-up process and the formed fiber-optic network was then utilized to monitor the manufacturing process and subsequent impact tests. A

Shu Minakuchi; Nobuo Takeda; Shin-ichi Takeda; Yosuke Nagao; Alessandro Franceschetti; Xiaolin Liu

2011-01-01

407

Effect of Seawater on the Fatigue Life and Failure Distribution of Flood-Lubricated Angular Contact Ball Bearings  

Microsoft Academic Search

Reductions in rolling contact fatigue life as high as 80 percent were observed during flood-lubricated angular-contact ball bearing studies when 1 percent by volume of seawater was added to various lubricants as a contaminant. The lubricants investigated were of different chemical and physical classes and included mineral oils, triaryl phosphate, and two recently developed mineral-oil-base sea-water-emulsifying hydraulic fluids of different

I. M. Felsen; R. W. McQuaid; J. A. Marzani

1972-01-01

408

Impacts of leaves, roots, and earthworms on soil organic matter composition and distribution in sycamore maple stands  

NASA Astrophysics Data System (ADS)

The relative contributions of leaf and root material to soil organic matter (SOM) are poorly understood despite the importance of constraining SOM sources to conceptual and numeric models of SOM dynamics. Selective ingestion and bioturbation of litter and soil by earthworms can alter the fate and spatial distribution of OM in soils, including stabilization pathways of leaf and root litter. However, studies on the contributions of leaves, roots, and earthworms to SOM dynamics are rare. In 3 stands of sycamore maple (Acer pseudoplatanus) with minimal O horizon development and high earthworm activity, we sampled surface litter (> 2 mm) from the Oi horizon, fine roots (< 2 mm), bulk mineral soils (0-20 cm depth), and earthworm casts from Lumbricus terrestris middens. The chemical composition of these samples was estimated by wet-chemical degradation followed by GC-MS analysis. In addition, elemental analyses (C and N) were performed on bulk soils and earthworm casts, before and after physical fractionation by means of particle size and density. Relative to bulk soils, earthworm casts were highly enriched in organic matter, dominated by large particulate OM, and had lower acid to aldehyde ratios among lignin monomers (a proxy for extent of decomposition), confirming that L. terrestris casts stabilize recent plant litter inputs. Maple fine roots and surface litter were distinguished by different profiles of carboxylic acids estimated by GC-MS, facilitating interpretation of OM sources in bulk soil and earthworm casts. Earthworm casts were characterized by a distribution of carboxylic acids similar to that of surface litter while bulk soils had a carboxylic acid profile much closer to that of roots. These results confirm that L. terrestris is primarily a surface, leaf feeder and suggest that OM in the bulk soil may be dominated by root inputs. In bulk soils, the ratio of lignin to hydroxy- and diacids derived from suberin and cutin was low relative to plant litter, confirming the often-observed selective preservation of aliphatic over aromatic biomolecules. The ratio of lignin to cutin/suberin acids in earthworm casts was also low; based on the minimal extent of decomposition in casts evident by lignin acid to aldehyde ratios, we attribute this to selective ingestion by L. terrestris of leaf litter rich in aliphatic biomolecules at the expense of woody debris and petioles rich in lignin, rather than selective preservation.

Rivera, N.; Mueller, K. E.; Mueller, C. W.; Oleksyn, J.; Hale, C.; Freeman, K. H.; Eissenstat, D.

2009-12-01

409

Integration of Cu-coated single-mode optical fiber into carbon/PEEK composite for distributed structural health monitoring based on Rayleigh backscatter reflectometry  

NASA Astrophysics Data System (ADS)

In this paper a technique for integrating copper coated silica optical fibers into AS-4/PEEK composite for Structural Health Monitoring (SHM) is presented. The integration steps are described in detail. X-ray and microscopic images indicate a successfully integrated optical fiber which does not seem to affect the fiber/matrix distribution around it. Optical backscatter reflectometry shows losses of approximately 2dBm-1 along the integrated parts of the optical fiber due to temperature induced shrinkage of the composite