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1

The Relative Abundance, Distribution, Composition, and Life History Characteristics of Fishes in Gloucester Harbor  

Microsoft Academic Search

This study described the fish community structure in Gloucester Harbor and detailed seasonal and spatial characteristics of relative abundance, community composition, and life history traits. Four otter trawl sta- tions and four seine stations were sampled monthly from June 1998 to May 1999. This study was the first effort to assess the Gloucester Harbor fish community in more than 30

Anthony R. Wilbur

2

Fatigue life prediction in composites  

Microsoft Academic Search

Because of the relatively large number of possible failure mechanisms in fibre reinforced composite materials, the prediction of fatigue life in a component is not a simple process. Several mathematical and statistical models have been proposed, but the experimental evidence to support them is limited so far. In this paper, an attempt has been made to fit experimental results to

R. J. Huston

1994-01-01

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.

Dangol, D. R.

2012-01-01

4

Fatigue life prediction in titanium matrix composites  

SciTech Connect

Methods used for life prediction of titanium matrix composites under isothermal and thermomechanical (TMF) fatigue are reviewed. Models containing a single parameter are shown to have applicability only under limited conditions. Two models, a dominant damage and a life fraction model, demonstrate predictive capabilities over a broad range of loads, frequencies, temperatures, and TMF parameters. Relationships between the underlying fatigue mechanisms and the individual terms in the models are illustrated.

Nicholas, T. [Wright Lab., Wright-Patterson AFB, OH (United States). Materials Directorate

1995-10-01

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

Fatigue life characterization for piezoelectric macrofiber composites  

NASA Astrophysics Data System (ADS)

In an effort to aid the investigation into lightweight and reliable materials for actuator design, a study was developed to characterize the temperature-dependent lifetime performance of a piezoelectric macrofiber composite (MFC). MFCs are thin rectangular patches of polyimide film, epoxy and a single layer of rectangular lead zirconium titanate (PZT) fibers. In this study, the useful life of the MFC is characterized to determine the effect of temperature on the performance of the composite as it is fatigued by cyclic piezoelectric excitation. The test specimen consists of the MFC laminated to a cantilevered stainless steel beam. Beam strain and tip displacement measurements are used as a basis for determining the performance of the MFC as it is cyclically actuated under various operating temperatures. The temperature of the beam laminate is held constant and then cycled to failure, or 250 million cycles, in order to determine the useful life of the MFC over a temperature range from - 15 to 145?°C. The results of the experiments show a strong temperature dependence of the operational life for the MFC. Damage inside the composite was identified through in situ visual inspection and during post-test microstructural observation; however, no degradation in operational performance was identified as it was cyclically actuated up to the point of failure, regardless of temperature or actuation cycle number.

Henslee, Isaac A.; Miller, David A.; Tempero, Tyler

2012-10-01

7

Estimating Linear Models for Compositional Distributional Semantics  

Microsoft Academic Search

In distributional semantics studies, there is a growing attention in compositionally determining the distributional meaning of word sequences. Yet, compositional dis- tributional models depend on a large set of parameters that have not been explored. In this paper we propose a novel approach to estimate parameters for a class of com- positional distributional models: the addi- tive models. Our approach

Fabio Massimo Zanzotto; Ioannis Korkontzelos; Francesca Fallucchi; Suresh Manandhar

2010-01-01

8

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

9

Life cycle energy analysis of fiber-reinforced composites  

Microsoft Academic Search

Life cycle assessment is a technique to assess environmental aspects associated with a product or process by identifying energy, materials, and emissions over its life cycle. The energy analysis includes four stages of a life cycle: material production phase, manufacturing phase, use phase, and end-of-life phase. In this study, the life cycle energy of fiber-reinforced composites manufactured by using the

Young S. Song; Jae R. Youn; Timothy G. Gutowski

2009-01-01

10

Proposed Framework for Thermomechanical Life Modeling of Metal Matrix Composites.  

National Technical Information Service (NTIS)

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...

G. R. Halford B. A. Lerch J. F. Saltsman

1993-01-01

11

A New Method for Estimating Life Distributions from Incomplete Data.  

National Technical Information Service (NTIS)

We construct a new estimator for a continuous life distribution from incomplete data, the Piecewise Exponential Estimator (PEXE). We show that the PEXE is strongly consistent under a mild restriction on the distribution of the censoring random variables (...

J. Kitchin N. A. Langberg F. Proschan

1980-01-01

12

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

13

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

14

Considerations concerning fatigue life of metal matrix composites  

NASA Technical Reports Server (NTRS)

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 was quantified using the mechanical properties of its constituents. The fatigue life regions controlled by fiber fracture and matrix were also quantitatively defined.

Radhakrishnan, V. M.; Bartolotta, Paul A.

1993-01-01

15

Composition and distributional patterns in arctic rotifers  

Microsoft Academic Search

Based on collections of rotifers from 212 localities in arctic North America, the patterns of distribution and composition are evaluated. An attempt is made to discern the dominant components of the rotifer community in arctic habitats. One hundred and sixty five species of rotifers are reported, three of which represent new records for North America. With increasing latitude and decreasing

R. Chengalath; W. Koste

1989-01-01

16

Mean residual life of lifetime distributions  

Microsoft Academic Search

This paper characterizes the general behaviors of the MRL (mean residual lives) for both continuous and discrete lifetime distributions, with respect to their failure rates. For the continuous lifetime distribution with failure rates with only one or two change-points, the characteristic of the MRL depends only on its mean and failure rate at time zero. For failure rates with “roller

L. C. Tang; Y. Lu; E. P. Chew

1999-01-01

17

Distributed avatar management for Second Life  

Microsoft Academic Search

Second Life (SL) is currently the most popular social virtual world, i.e., a digitalization of the real world where avatars can meet, socialize and trade. SL is managed through a Client\\/Server (C\\/S) architecture with a very high cost and limited scalability. A scalable and cheap alternative to C\\/S is to use a Peer-to-Peer (P2P) approach, where SL users rely only

Matteo Varvello; Stefano Ferrari; Ernst Biersack; Christophe Diot

2009-01-01

18

Predictive Distributions in Life Tests under Competing Causes of Failure.  

National Technical Information Service (NTIS)

In competing risk life testing models, the units under test can fail due to one of several competing risks. The estimation of parameters in such compound models was investigated; predictive distributions and probabilities are derived for such situations, ...

G. A. Bancroft I. R. Dunsmore

1975-01-01

19

Gamma Distribution in Acceptance Sampling Based on Life Tests  

Microsoft Academic Search

The gamma distribution is assumed as a model for lifetime. The problem of acceptance sampling when the life test is truncated at a pre- assigned time is discussed. For various acceptance numbers, various confidence levels, and various values of the ratio of the fixed experiment time to the specified mean life, the tables of this paper give the minimum sample

Shanti S. Gupta

1961-01-01

20

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

21

Generation of finite life distributional Goodman diagrams for reliability prediction  

NASA Technical Reports Server (NTRS)

The methodology of developing finite life distributional Goodman diagrams and surfaces is described for presenting allowable combinations of alternating stress and mean stress to the design engineer. The combined stress condition is that of an alternating bending stress and a constant shear stress. The finite life Goodman diagrams and surfaces are created from strength distributions developed at various ratios of alternating to mean stress at particular cycle life values. The conclusions indicate that the Von Mises-Hencky ellipse, for cycle life values above 1000 cycles, is an adequate model of the finite life Goodman diagram. In addition, suggestions are made which reduce the number of experimental data points required in a fatigue data acquisition program.

Kececioglu, D.; Guerrieri, W. N.

1971-01-01

22

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 infuence 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 an 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.

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

1981-01-01

23

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

24

Some Theorems Relevant to Life Testing from an Exponential Distribution  

Microsoft Academic Search

A life test on $N$ items is considered in which the common underlying distribution of the length of life of a single item is given by the density \\\\begin{equation*}\\\\tag{1} p(x; \\\\theta, A) = \\\\begin{cases}\\\\frac{1}{\\\\theta} e^{-(x-A)\\/\\\\theta},\\\\quad\\\\text{for} x \\\\geqq A \\\\\\\\ 0,\\\\quad\\\\text{otherwise}\\\\end{cases}\\\\end{equation*} where $\\\\theta > 0$ is unknown but is the same for all items and $A \\\\geqq 0.$ Several lemmas are

B. Epstein; M. Sobel

1954-01-01

25

A life prediction model for laminated composite structural components  

NASA Technical Reports Server (NTRS)

A life prediction methodology for laminated continuous fiber composites subjected to fatigue loading conditions was developed. A summary is presented of research completed. A phenomenological damage evolution law was formulated for matrix cracking which is independent of stacking sequence. Mechanistic and physical support was developed for the phenomenological evolution law proposed above. The damage evolution law proposed above was implemented to a finite element computer program. And preliminary predictions were obtained for a structural component undergoing fatigue loading induced damage.

Allen, David H.

1990-01-01

26

Life cycle assessment of carbon fiber-reinforced polymer composites  

Microsoft Academic Search

Purpose  The use of carbon fiber-reinforced polymer matrix composites is gaining momentum with the pressure to lightweight vehicles;\\u000a however energy intensity and cost remain major barriers to the wide-scale adoption of this material for automotive applications.\\u000a This study determines the relative life cycle benefits of two precursor types (conventional textile-type acrylic fibers and\\u000a renewable-based lignin), part manufacturing technologies (conventional SMC and

Sujit Das

2011-01-01

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

Study of metal distributions in ? composites  

NASA Astrophysics Data System (ADS)

The micro proton-induced x-ray emission technique has been used to study the elemental distribution profiles of 0953-2048/11/6/003/img9 high-0953-2048/11/6/003/img10 composites on varying the 0953-2048/11/6/003/img11 content. Measurements revealed that Ag agglomeration starts to appear in samples with 0953-2048/11/6/003/img12, becoming prominent at 50 wt%. These results are further supported by x-ray diffraction (XRD) measurements performed on the same samples. The XRD results identified a crystalline Ag phase to be present in all of the samples (7-50 wt% 0953-2048/11/6/003/img11), a crystalline 0953-2048/11/6/003/img11 phase in the 25 and 50 wt% 0953-2048/11/6/003/img11 samples and no evidence for Ag replacing Cu or orthogonal-to-tetragonal transformation.

Faiz, M.; Ahmed, M.; Hamdan, N. M.; Ziq, Kh A.; Shirokoff, J.

1998-06-01

29

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

30

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

31

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

32

NPU-Based Image Compositing in a Distributed Visualization System  

Microsoft Academic Search

This paper describes the first use of a network processing unit (NPU) to perform hardware-based image composition in a distributed rendering system. The image composition step is a notorious bottleneck in a clustered rendering system. Furthermore, image compositing algorithms do not necessarily scale as data size and number of nodes increase. Previous researchers have addressed the composition problem via software

David Pugmire; Laura Monroe; Carolyn Connor Davenport; Andrew Dubois; David Dubois; Stephen Poole

2007-01-01

33

Bayesian estimation of life parameters in the Weibull distribution.  

NASA Technical Reports Server (NTRS)

Development of a Bayesian analysis of the scale and shape parameters in the Weibull distribution and the corresponding reliability function with respect to the usual life-testing procedures. For the scale parameter theta, Bayesian estimates of theta and reliability are obtained for the uniform, exponential, and inverted gamma prior probability densities. Bhattacharya's results (1967) for the one-parameter exponential life-testing distribution are reduced to a special case of these results. A fully Bayesian analysis of both the scale and shape parameters is developed by assuming independent prior distributions; since in the latter case, analytical tractability is not possible, Bayesian estimates are obtained through a conjunction of Monte Carlo simulation and numerical-integration techniques. In both cases, a computer simulation is carried out, and a comparison is made between the Bayesian and the corresponding minimum-variance unbiased, or maximum likelihood, estimates. As expected, the Bayesian estimates are superior.

Canavos, G. C.; Tsokos, C. P.

1973-01-01

34

Isothermal life prediction of composite lamina using a damage mechanics approach  

NASA Technical Reports Server (NTRS)

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. The effect of the fiber orientation on loading direction is accounted for while predicting composite life. The application is currently limited to isothermal cases where the internal thermal stresses that might arise from thermal strain mismatch between fibers and matrix are negligible. The theory is formulated to predict the fatigue life of a composite lamina under either load or strain control. It is applied currently to predict the life of tungsten-copper composite lamina at 260 C under tension-tension load control. The calculated life of the lamina is in good agreement with available composite low cycle fatigue data.

Abuelfoutouh, Nader M.; Verrilli, Michael J.; Halford, Gary R.

1989-01-01

35

Composite Overwrap Pressure Vessels: Mechanics and Stress Rupture Lifing Philosophy  

NASA Technical Reports Server (NTRS)

The NASA Engineering and Safety Center (NESC) has been conducting an independent technical assessment to address safety concerns related to the known stress rupture failure mode of filament wound pressure vessels in use on Shuttle and the International Space Station. The Shuttle's Kevlar-49 fiber overwrapped tanks are of particular concern due to their long usage and the poorly understood stress rupture process in Kevlar-49 filaments. Existing long term data show that the rupture process is a function of stress, temperature and time. However due to the presence of load sharing liners and the complex manufacturing procedures, the state of actual fiber stress in flight hardware and test articles is not clearly known. Indeed non-conservative life predictions have been made where stress rupture data and lifing procedures have ignored the contribution of the liner in favor of applied pressure as the controlling load parameter. With the aid of analytical and finite element results, this paper examines the fundamental mechanical response of composite overwrapped pressure vessels including the influence of elastic-plastic liners and degraded/creeping overwrap properties. Graphical methods are presented describing the non-linear relationship of applied pressure to Kevlar-49 fiber stress/strain during manufacturing, operations and burst loadings. These are applied to experimental measurements made on a variety of vessel systems to demonstrate the correct calibration of fiber stress as a function of pressure. Applying this analysis to the actual qualification burst data for Shuttle flight hardware revealed that the nominal fiber stress at burst was in some cases 23% lower than what had previously been used to predict stress rupture life. These results motivate a detailed discussion of the appropriate stress rupture lifing philosophy for COPVs including the correct transference of stress rupture life data between dissimilar vessels and test articles.

Thesken, John C.; Murthy, Pappu L. N.; Phoenix, Leigh

2007-01-01

36

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

37

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

38

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

39

Life cycle assessment of overhead and underground primary power distribution.  

PubMed

Electrical power can be distributed in overhead or underground systems, both of which generate a variety of environmental impacts at all stages of their life cycles. While there is considerable literature discussing the trade-offs between both systems in terms of aesthetics, safety, cost, and reliability, environmental assessments are relatively rare and limited to power cable production and end-of-life management. This paper assesses environmental impacts from overhead and underground medium voltage power distribution systems as they are currently built and managed by Southern California Edison (SCE). It uses process-based life cycle assessment (LCA) according to ISO 14044 (2006) and SCE-specific primary data to the extent possible. Potential environmental impacts have been calculated using a wide range of midpoint indicators, and robustness of the results has been investigated through sensitivity analysis of the most uncertain and potentially significant parameters. The studied underground system has higher environmental impacts in all indicators and for all parameter values, mostly due to its higher material intensity. For both systems and all indicators the majority of impact occurs during cable production. Promising strategies for impact reduction are thus cable failure rate reduction for overhead and cable lifetime extension for underground systems. PMID:20553042

Bumby, Sarah; Druzhinina, Ekaterina; Feraldi, Rebe; Werthmann, Danae; Geyer, Roland; Sahl, Jack

2010-07-15

40

Distributed middleware services composition and synthesis technology  

Microsoft Academic Search

The highly distributed and resource constrained nature of computing in Networked Embedded Systems ne- cessitates an application specific middleware-a kind of dis- tributed operating system that provides global services for the application. We propose to automatically synthesize the middleware from abstract, platform-independent algorithm models. The modeling language captures the temporal and computational aspects of the distributed algorithms in a pro-

M. Maroti; P. Volgyesi; G. Simon; G. Karsai; A. Ledeczi

2003-01-01

41

Classes of Discrete Decreasing and Increasing Mean-Residual-Life Distributions  

Microsoft Academic Search

Discrete failure-time distributions can be appropriate to model lifetimes. This paper represents two well-known non-parametric families of discrete distributions: decreasing and increasing mean-residual-life. It provides two parametric families of discrete distributions which are suitable for fitting decreasing and increasing mean-residual-life models to discrete life-test data.

Nader Ebrahimi

1986-01-01

42

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.

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

43

Gestational and early life influences on infant body composition at one year.  

PubMed

Excess weight gain during both pre- and postnatal life increases risk for obesity in later life. Although a number of gestational and early life contributors to this effect have been identified, there is a dearth of research to examine whether gestational factors and weight gain velocity in infancy exert independent effects on subsequent body composition and fat distribution. The purpose of this study was to test the hypothesis that birth weight, as a proxy of prenatal weight gain, and rate of weight gain prior to 6 months would be associated with total and truncal adiposity at 12 months of age. Healthy, term infants (N=47) were enrolled in the study and rate of weight gain (g/day) was assessed at 0-3 months, 3-6 months, and 6-12 months. Total and regional body composition were measured by dual-energy X-ray absorptiometry at 12 months. Stepwise linear regression modeling indicated that lean mass at 12 months, after adjusting for child length, was predicted by rate of weight gain during each discrete period of infancy (P<0.05), and by maternal pre-pregnancy BMI (P<0.05). Total fat mass at 12 months was predicted by rate of weight gain during each discrete period (P<0.01), and by older maternal age at delivery (P<0.05). Trunk fat mass at 12 months, after adjusting for leg fat mass, was predicted by rate of weight gain from 0-3 months and 3-6 months (P<0.05). Results suggest that growth during early infancy may be a critical predictor of subsequent body composition and truncal fat distribution. PMID:22628019

Chandler-Laney, P C; Gower, B A; Fields, D A

2012-05-25

44

Distribution and composition of interstellar matter  

NASA Technical Reports Server (NTRS)

Some of the problems associated with the observation of interstellar matter are described. The characteristics of the high resolution spectrograph are summarized and observations of matter distribution are given.

Salpeter, E. E.

1979-01-01

45

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

46

Reconfirmation of the Three-Domain Classification of Life by Cluster Analysis of Protein Length Distributions  

NASA Astrophysics Data System (ADS)

The classification of life should be based on the intrinsic mechanism in the evolution of life. We found new methods to classify life into Archaea, Bacteria and Eucarya based on the correlation analysis and spectral analysis of protein length distributions. We show that there is rich evolutionary information stored in the fluctuations of protein length distributions. The intrinsic mechanism of diversification of life is revealed by the properties of protein length distributions.

Li, Dirson Jian; Zhang, Shengli

47

Composite fault location for Distribution Management Systems  

Microsoft Academic Search

The problem of fault location is an integral part of Distribution Management System (DMS) solutions. This paper presents a method of locating fault in unsymmetrical networks, including both radial and meshed parts of the network. The real-time information regarding the topological condition of the network and the status updates of the Fault Indicators are used as input to the fault

I. Dzafic; P. Mohapatra; H. T. Neisius

2010-01-01

48

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

49

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

50

Fatigue Life Analysis of Tapered Hybrid Composite Flexbeams  

NASA Technical Reports Server (NTRS)

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 two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) obtained from the above codes using the virtual crack closure technique (VCCT) at a resin crack location in the flexbeams are presented for both hybrid material types. These results compare well with each other and suggest that the initial delamination growth from the resin crack 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 and compared with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared reasonably well with the test results.

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

2002-01-01

51

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

52

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

53

Stress Rupture Life Reliability Measures for Composite Overwrapped Pressure Vessels  

NASA Technical Reports Server (NTRS)

Composite Overwrapped Pressure Vessels (COPVs) are often used for storing pressurant gases onboard spacecraft. Kevlar (DuPont), glass, carbon and other more recent fibers have all been used as overwraps. Due to the fact that overwraps are subjected to sustained loads for an extended period during a mission, stress rupture failure is a major concern. It is therefore important to ascertain the reliability of these vessels by analysis, since the testing of each flight design cannot be completed on a practical time scale. The present paper examines specifically a Weibull statistics based stress rupture model and considers the various uncertainties associated with the model parameters. The paper also examines several reliability estimate measures that would be of use for the purpose of recertification and for qualifying flight worthiness of these vessels. Specifically, deterministic values for a point estimate, mean estimate and 90/95 percent confidence estimates of the reliability are all examined for a typical flight quality vessel under constant stress. The mean and the 90/95 percent confidence estimates are computed using Monte-Carlo simulation techniques by assuming distribution statistics of model parameters based also on simulation and on the available data, especially the sample sizes represented in the data. The data for the stress rupture model are obtained from the Lawrence Livermore National Laboratories (LLNL) stress rupture testing program, carried out for the past 35 years. Deterministic as well as probabilistic sensitivities are examined.

Murthy, Pappu L. N.; Thesken, John C.; Phoenix, S. Leigh; Grimes-Ledesma, Lorie

2007-01-01

54

Fast adaptive composite grid methods on distributed parallel architectures  

NASA Technical Reports Server (NTRS)

The fast adaptive composite (FAC) grid method is compared with the adaptive composite method (AFAC) under variety of conditions including vectorization and parallelization. Results are given for distributed memory multiprocessor architectures (SUPRENUM, Intel iPSC/2 and iPSC/860). It is shown that the good performance of AFAC and its superiority over FAC in a parallel environment is a property of the algorithm and not dependent on peculiarities of any machine.

Lemke, Max; Quinlan, Daniel

1992-01-01

55

Extension of Pot Life of HTPB-Based Composite Propellants.  

National Technical Information Service (NTIS)

The pot life of propellants with the binder HTPB and containing 85% ammonium perchlorate was determined with a plastograph at 58 C. The isocyanate curing agents DDI and IPDI were tested; IPDI gives longer pot life. The influence of some additives was stud...

R. Sanden

1982-01-01

56

Wear and Life Characteristics of Microwave-Sintered Copper-Graphite Composite  

NASA Astrophysics Data System (ADS)

Copper-graphite composite is an important tribological material used in electrical sliding contact applications like electrical brushes in motors and generators. The electrical sliding contact experiences multiple stresses such as mechanical pressure and temperature. Traditional life tests under normal operating condition would be a time-consuming process due to the longer expected life of the composite. Accelerated wear testing was carried out to evaluate the life characteristics of the composite. This work focuses on evaluation of tribological performance of microwave-sintered copper-graphite composite using accelerated wear testing methodology using high temperature pin-on-disc tribometer. Microstructural studies of worn out surfaces were carried out using SEM with EDAX. Reliability and analysis on life characteristics were performed on the time-to-failure data using temperature-nonthermal-accelerated life-stress model. The obtained times-to-failure data from the accelerated wear testing was extrapolated to normal usage condition. Temperature and pressure are significantly affecting the wear performance. Self-lubricating action of graphite and improvement in wear resistance is helpful in extending the life of copper graphite composite. The life of the composite obtained through testing at mean and 99% reliability are 18,725 and 16,950 h, respectively.

Rajkumar, K.; Aravindan, S.; Kulkarni, M. S.

2012-11-01

57

Particle distribution in cast metal matrix composites—Part I  

Microsoft Academic Search

The widespread adoption of particulate metal matrix composites (MMCs) for engineering applications has been hindered by the high cost of producing components of even minimally complex shape. Casting technology may be the key to overcoming this problem, although several technical challenges currently exist with this method. Achieving a uniform distribution of reinforcement within the matrix is one such challenge which

J. Hashim; L. Looney; M. S. J. Hashmi

2002-01-01

58

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

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

A Reliability Analysis Approach to Fatigue Life Dispersion of Laminated Glass Fiber Composite Materials.  

National Technical Information Service (NTIS)

The statistical nature of the fatigue life of laminated glass fiber composite materials (FRP) is studied. Four different FRP laminates (satin woven FRP, plain woven FRP, roving woven FRP, and SMC laminated FRP) were used in the experiments. Unidirectional...

T. Tanimoto S. Amijima H. Ishikawa K. J. Miller R. F. Smith

1979-01-01

61

Composition and Analysis of a Model Waste for a Celss (Controlled Ecological Life Support System).  

National Technical Information Service (NTIS)

A model waste based on a modest vegetarian diet is given, including composition and elemental analysis. Its use is recommended for evaluation of candidate waste treatment processes for a Controlled Ecological Life Support System (CELSS).

T. Wydeven

1983-01-01

62

Composition and analysis of a model waste for a CELSS (Controlled Ecological Life Support System)  

NASA Technical Reports Server (NTRS)

A model waste based on a modest vegetarian diet is given, including composition and elemental analysis. Its use is recommended for evaluation of candidate waste treatment processes for a Controlled Ecological Life Support System (CELSS).

Wydeven, T. J.

1983-01-01

63

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

64

Fatigue Life of Composite Structures in Extreme Environments.  

National Technical Information Service (NTIS)

Prediction of the dynamic response and the fatigue life of structures, i.e. panels, subjected to both high temperatures/ thermal gradients and high level acoustic excitations. The determination of reliable approximations of the statistics of the panel res...

P. C. Chen M. P. Mignolet

2005-01-01

65

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

66

Age distribution curve in psychiatric admissions inversely correlates with Life Satisfaction.  

PubMed

A strong inverse correlation was found between the age-distribution curve of psychiatric admissions and the U-bend Life Satisfaction curve. It may indicate that the peak of mental disorders at midlife reflects a less satisfactory period of life or, conversely, that the mental health load burdens of Life Satisfaction. PMID:24908542

Le Bon, Olivier; Le Bon, Serge-Daniel

2014-09-30

67

Evaluation of Mean Life of Power Equipment based on 3-parameter Weibull Distribution  

NASA Astrophysics Data System (ADS)

Evaluation of the mean life of equipments is a basic issue for effective equipment maintenance. This paper presents a method to estimate the mean life and its standard deviation of power system equipments with limited end-of-life failure data. We propose a model using 3-parameter Weibull distribution based on the results Li (2004) produced. It is assumed that the mean life of power equipments consists of “non end-of-life failure period” and “period of aging end-of-life failure”, which is represented by a location parameter of Weibull distribution. Three parameters of Weibull distribution are estimated by applying Levenberg-Marquardt method, which is one of the optimization algorithms. The computational procedures of non-linear regression, which take account both of good convergence and practical use, are proposed. Numerical examples show that our model better fits to actual data than 2-parameter Weibull distribution model.

Zhou, Yicheng; Kato, Moritoshi; Saitou, Naoki; Yokoyama, Ryuichi

68

Aging behavior and life prediction of graphite composites  

NASA Technical Reports Server (NTRS)

This paper presents experimental data from two independent tests, designed to determine the long-term reliability of composite materials. The technique of accelerated aging at elevated temperatures is employed. In the first set, graphite fiber, epoxy composites in five ply layups are manufactured and tested in the standard short-beam shear mode. In the second set, Nomex honeycomb, graphite fiber/epoxy composite face and rear sheet sandwich coupons are tested. After satisfying simple consistency checks, data interpretation is attempted within the framework of an Arrhenius degradation model. The elevated temperature is assumed to influence the degradation according to this temperature-dependent rate law. From these tests on five-ply composites and honeycomb sandwiches, it is concluded that aging is not a serious problem.

Ramohalli, Kumar; Raasch, David

1989-01-01

69

On changing points of mean residual life and failure rate function for some generalized Weibull distributions  

Microsoft Academic Search

The failure rate function and mean residual life function are two important characteristics in reliability analysis. Although many papers have studied distributions with bathtub-shaped failure rate and their properties, few have focused on the underlying associations between the mean residual life and failure rate function of these distributions, especially with respect to their changing points. It is known that the

M Xie; T. N Goh; Y Tang

2004-01-01

70

Carbon nanofiber polymer composites: evaluation of life cycle energy use.  

PubMed

Holistic evaluation of emerging nanotechnologies using systems analysis is pivotal for guiding their safe and sustainable development. While toxicity studies of engineered nanomaterials are essential, understanding of the potential large scale impacts of nanotechnology is also critical for developing sustainable nanoproducts. This work evaluates the life cycle energetic impact associated with the production and use of carbon nanofiber (CNF) reinforced polymer nanocomposites (PNC). Specifically, both simple CNF and carbon nanofiber-glass fiber (CNF-GF) hybrid PNCs are evaluated and compared with steel for equal stiffness design. Life cycle inventory is developed based on published literature and best available engineering information. A cradle-to-gate comparison suggests that for equal stiffness design, CNF reinforced PNCs are 1.6-12 times more energy intensive than steel. It is anticipated that the product use phase may strongly influence whether any net savings in life cycle energy consumption can be realized. A case study involving the use of CNF and CNF-GF reinforced PNCs in the body panels of automobiles highlights that the use of PNCs with lower CNF loading ratios has the potential for net life cycle energy savings relative to steel owing to improved fuel economy benefits. Other factors such as cost, toxicity impact of CNF, and end-of-life issues specific to CNFs need to be considered to evaluate the final economic and environmental performance of CNF reinforced PNC materials. PMID:19368217

Khanna, Vikas; Bakshi, Bhavik R

2009-03-15

71

Spatial distribution of volatile compounds in graphite composites  

NASA Technical Reports Server (NTRS)

The distribution of water and other volatile compounds such as acetone and phenol was measured as a function of depth in four graphite resin matrix composites. Precision abrasion mass spectrometry was used to qualitatively and quantitatively characterize the indigenous volatile compounds in the as received condition and after drying in an environmentally controlled oven. The total amount of water in the composites varied from 0.12 wt% to 1.1 wt% and the times required to dry the samples ranged from less than 96 h to much greater than 555 h.

Grayson, M. A.; Wolf, C. J.; Kourtides, D. A.

1980-01-01

72

Viscoelastically prestressed polymeric matrix composites – Potential for useful life and impact protection  

Microsoft Academic Search

A viscoelastically prestressed polymeric matrix composite (VPPMC) is produced by applying tension to polymeric fibres, the tensile load being released prior to moulding the fibres into a matrix. Following matrix solidification, compressive stresses imparted by the viscoelastically strained fibres improve composite tensile, flexural and impact properties. This study focuses on the potential for useful life and impact protection capability by

Kevin S. Fancey

2010-01-01

73

Effects of cyclic stress distribution models on fatigue life predictions.  

National Technical Information Service (NTIS)

The fatigue analysis of a wind turbine component typically uses representative samples of cyclic loads to determine lifetime loads. In this paper, several techniques currently in use are compared to one another based on fatigue life analyses. The generali...

H. J. Sutherland P. S. Veers

1994-01-01

74

Continuous self-healing life cycle in vascularized structural composites.  

PubMed

By incorporating 3D microvascular networks containing a two-part reactive chemistry within a fiber-reinforced composite, continuous cycles of self-healing after interlaminar delamination are achieved. An interpenetrating vasculature shows improved in situ fluid mixing over segregated microchannels, resulting in full recovery (>100%) of mode-I fracture resistance. PMID:24729175

Patrick, Jason F; Hart, Kevin R; Krull, Brett P; Diesendruck, Charles E; Moore, Jeffrey S; White, Scott R; Sottos, Nancy R

2014-07-01

75

An experimental study on fatigue life of interference-fit composite joint  

NASA Astrophysics Data System (ADS)

An experimental study on fatigue life of an interference-fit composite joint is presented. The experimental results show that suitable interference can increase fatigue life in comparison with the push-fit case. For the material and the laying studied, when the interference is 2 percent, the fatigue life is increased 2-3 times. An explanation for the result is given. In order to obtain the current result, some methods of processing and assembling are emphasized in the experiment. An explanation is given for the definition of fatigue life limitation and the choice of the best interference.

Liu, Ping; Zhang, Kaida

1991-12-01

76

Observation of Lightning Phenomena on Distribution Lines using Composite Techniques  

NASA Astrophysics Data System (ADS)

For the rationalization of lightning protection design of distribution lines, it is important to clarify the behavior of distribution line when direct or nearby lightning occurs. Because of the lower insulation level than is for transmission line, in study on lightning protection design of distribution line, not only direct lightning strokes but also induced voltages caused by nearby strokes must be taken into account. So it is necessary to grasp the frequency of occurrence on lightning phenomena around distribution lines. For this aim, lightning phenomena on TEPCO’s distribution lines in use had been continuously observed for 6 years (1996-2001). The observation was carried out in composite way, using still-cameras and sensors for acquisition of lightning surge waveform data. Through the observation, new interesting phenomena about lightning performance on distribution lines in fields became apparent. In some case, in spite of direct striking to the line, flashover did not occur. This fact means that distribution line has a certain level of lightning resistance. Moreover, it was confirmed that AC following current generated between both ends of insulator disappeared naturally. These results are the interesting discoveries that can be useful to estimate the fault ratio precisely.

Hirai, Takao; Okabe, Shigemitsu; Takinami, Tsutomu; Chindo, Takuji

77

Three-Axis Distributed Fiber Optic Strain Measurement in 3D Woven Composite Structures  

NASA Technical Reports Server (NTRS)

Recent advancements in composite materials technologies have broken further from traditional designs and require advanced instrumentation and analysis capabilities. Success or failure is highly dependent on design analysis and manufacturing processes. By monitoring smart structures throughout manufacturing and service life, residual and operational stresses can be assessed and structural integrity maintained. Composite smart structures can be manufactured by integrating fiber optic sensors into existing composite materials processes such as ply layup, filament winding and three-dimensional weaving. In this work optical fiber was integrated into 3D woven composite parts at a commercial woven products manufacturing facility. The fiber was then used to monitor the structures during a VARTM manufacturing process, and subsequent static and dynamic testing. Low cost telecommunications-grade optical fiber acts as the sensor using a high resolution commercial Optical Frequency Domain Reflectometer (OFDR) system providing distributed strain measurement at spatial resolutions as low as 2mm. Strain measurements using the optical fiber sensors are correlated to resistive strain gage measurements during static structural loading. Keywords: fiber optic, distributed strain sensing, Rayleigh scatter, optical frequency domain reflectometry

Castellucci, Matt; Klute, Sandra; Lally, Evan M.; Froggatt, Mark E.; Lowry, David

2013-01-01

78

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

Microsoft Academic Search

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 ofNemalion helminthoides is

C. van den Hoek

1982-01-01

79

The Schiff angular bremsstrahlung distribution from composite media  

NASA Astrophysics Data System (ADS)

The Schiff differential for the angular distribution of bremsstrahlung is widely employed, but calculations involving composite materials (i.e. compounds and mixtures) are often undertaken in a somewhat ad hoc fashion. In this work, we suggest an alternative approach to power-law estimates of the effective atomic number utilising Seltzer and Berger's combined approach in order to generate single-valued effective atomic numbers applicable over a large energy range (in the worst case deviation from constancy of about 2% between 10 keV and 1 GeV). Differences with power-law estimates of Z for composites are potentially significant, particularly for low-Z media such as biological or surrogate materials as relevant within the context of medical physics. As an example, soft tissue differs by >70% and cortical bone differs by >85%, while for high-Z composites such as a tungsten-rhenium alloy the difference is of the order of 1%. Use of the normalised Schiff formula for shape only does not exhibit strong Z dependence. Consequently, in such contexts the differences are negligible - the power-law approach overestimates the magnitude by 1.05% in the case of water and underestimates it by <0.1% for the high-Z alloys. The differences in the distribution are most pronounced for small angles and where the bremsstrahlung quanta are low energy.

Taylor, M. L.; Dalton, B.; Franich, R. D.

2012-12-01

80

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

81

Effect of Internal Clearance on Load Distribution and Life of Radially Loaded Ball and Roller Bearings.  

National Technical Information Service (NTIS)

The effect of internal clearance on radially loaded deepgroove ball and cylindrical roller bearing load distribution and fatigue life was determined for four clearance groups defined in the bearing standards. The analysis was extended to negative clearanc...

E. V. Zaretsky F. B. Oswald J. V. Poplawski

2012-01-01

82

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

83

Performance-based optimal design and rehabilitation of water distribution networks using life cycle costing  

Microsoft Academic Search

A new multiobjective formulation is proposed for the optimal design and rehabilitation of a water distribution network, with minimization of life cycle cost and maximization of performance as objectives. The life cycle cost is considered to comprise the initial cost of pipes, the cost of replacing old pipes with new ones, the cost of cleaning and lining existing pipes, the

Nirmal Jayaram; K. Srinivasan

2008-01-01

84

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

85

Physical Activity, Body Composition, and Perceived Quality of Life of Adults with Visual Impairments  

ERIC Educational Resources Information Center

Relatively little is known about the health and fitness of adults with visual impairments. This article documents the physical activity levels and body-composition profiles of young and middle-aged adults with visual impairments and addresses the concomitant effects of these factors on perceived quality of life. (Contains 2 tables.)

Holbrook, Elizabeth A.; Caputo, Jennifer L.; Perry, Tara L.; Fuller, Dana K.; Morgan, Don W.

2009-01-01

86

Prediction of creep-rupture life of unidirectional titanium matrix composites subjected to transverse loading  

NASA Astrophysics Data System (ADS)

Titanium matrix composites (TMCs) incorporating unidirectional fiber reinforcement are considered as enabling materials technology for advanced engines which require high specific strength and elevated temperature capability. The resistance of unidirectional TMCs to deformation under longitudinally applied sustained loading at elevated temperatures has been well documented. Many investigators have shown that the primary weakness of the unidirectional TMC is its susceptibility to failure under very low transverse loads, especially under sustained loading. Hence, a reliable model is required to predict the creep-rupture life of TMCs subjected to different transverse stress levels over a wide range of temperatures. In this article, we propose a model to predict the creep-rupture life of unidirectional TMC subjected to transverse loading based on the creep-rupture life of unidirectional TMC subjected to transverse loading based on the creep-rupture behavior of the corresponding fiberless matrix. The model assumes that during transverse loading, the effective load-carrying matrix ligament along a row of fibers controls the creep-rupture strength and the fibers do not contribute to the creep resistance of the composite. The proposed model was verified using data obtained from different TMC fabricated using three matrix compositions, which exhibited distinctly different types of creep behavior. The results show that the creep-rupture life of the transverse TMC decreases linearly with increasing ratio of the fiber diameter to the ply thickness. The creeprupture life is also predicted to be independent of fiber spacing along the length of the specimen.

John, Reji; Khobaib, M.; Smith, Paul R.

1996-10-01

87

Bayesian life test sampling plans for the two parameter exponential distribution  

Microsoft Academic Search

In this paper we consider the determination of Bayesian life test acceptance sampling plans for finite lots when the underlying lifetime distribution is the two parameter exponential. It is assumed that the prior distribution is the natural conjugate prior, that the costs associated with the actions accept and reject are known functions of the lifetimes of the items, and that

A. M. Nigm; M. A. Ismail

1985-01-01

88

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

89

Effect of Internal Clearance on Load Distribution and Life of Radially Loaded Ball and Roller Bearings  

NASA Technical Reports Server (NTRS)

The effect of internal clearance on radially loaded deepgroove ball and cylindrical roller bearing load distribution and fatigue life was determined for four clearance groups defined in the bearing standards. The analysis was extended to negative clearance (interference) conditions to produce a curve of life factor versus internal clearance. Rolling-element loads can be optimized and bearing life maximized for a small negative operating clearance. Life declines gradually with positive clearance and rapidly with increasing negative clearance. Relationships were found between bearing life and internal clearance as a function of ball or roller diameter, adjusted for load. Results are presented as life factors for radially loaded bearings independent of bearing size or applied load. In addition, a modified Stribeck Equation is presented that relates the maximum rolling-element load to internal bearing clearance.

Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.

2012-01-01

90

Distributed framework for composite event recognition in a calibrated pan-tilt camera network  

Microsoft Academic Search

In this paper, we propose a real-time distributed framework for composite event recognition in a calibrated pan-tilt camera network. A composite event comprises of events that occur simultaneously or sequentially at different locations across time. Distributed composite event recognition requires distributed multi-camera multi-object tracking and distributed multi-camera event recognition. We apply belief propagation to reach a consensus on the global

Ayesha Choudhary; Santanu Chaudhury; Subhashis Banerjee

2010-01-01

91

Energy, ecology and the distribution of microbial life.  

PubMed

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

2013-07-19

92

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

93

Morphology, size distribution and elemental composition of several dental debris  

NASA Astrophysics Data System (ADS)

We investigated morphologies, size distributions and elemental compositions of dental debris formed by cutting/grinding teeth or dental alloys. The average size of debris formed by cutting/grinding dental alloy was around 100 ?m and that of teeth was 20 ?m. The debris formed by grinding with diamond or carborundum point had isotropic irregular shape, while the debris formed by cutting with carbide bar had characteristic lathe-cut shape. The elemental analysis indicated that the debris formed by grinding dental alloy with carborundum point consisted of not only the particles of the alloy but also the particles of Si compounds with the size of around 10 ?m. The particles of Si compounds would be formed by abrasion of the grinding instrument (carborundum, SiC). Similarly, the debris formed by grinding with diamond point also contained submicro-sized particles consisting of C compounds. The results indicate that the morphology and composition of dental debris are varied depending on the combination between the workpiece and the cutting/grinding materials and that the dental debris consist of both the workpiece and the cutting/grinding materials in some combination. In addition, some of the debris of tooth had the size less than 2 ?m, which has a potential to induce inflammation. Though the inflammation can be expected at low level, it is required to investigate the details in future.

Abe, Shigeaki; Iwadera, Nobuki; Esaki, Mitsue; Aoyama, Ken-Ichi; Akasaka, Tsukasa; Uo, Motohiro; Morita, Manabu; Yawaka, Yasutaka; Watari, Fumio

2012-12-01

94

Probabilistic Residual Strength Model Developed for Life Prediction of Ceramic Matrix Composites  

NASA Technical Reports Server (NTRS)

For the next generation of reusable launch vehicles, NASA is investigating introducing ceramic matrix composites (CMCs) in place of current superalloys for structural propulsion applications (e.g., nozzles, vanes, combustors, and heat exchangers). The higher use temperatures of CMCs will reduce vehicle weight by eliminating and/or reducing cooling system requirements. The increased strength-to-weight ratio of CMCs relative to superalloys further enhances their weight savings potential. However, in order to provide safe designs for components made of these new materials, a comprehensive life prediction methodology for CMC structures needs to be developed. A robust methodology for lifing composite structures has yet to be adopted by the engineering community. Current industry design practice continues to utilize deterministic empirically based models borrowed from metals design for predicting material life capabilities. The deterministic nature of these models inadequately addresses the stochastic character of brittle composites, and their empirical reliance makes predictions beyond the experimental test conditions a risky extrapolation. A team of engineers at the NASA Glenn Research Center has been developing a new life prediction engineering model. The Probabilistic Residual Strength (PRS) model uses the residual strength of the composite as its damage metric. Expected life and material strength are both considered probabilistically to account for the observed stochastic material response. Extensive experimental testing has been carried out on C/SiC (a candidate aerospace CMC material system) in a controlled 1000 ppm O2/argon environment at elevated temperatures of 800 and 1200 C. The test matrix was established to allow observation of the material behavior, characterization of the model, and validation of the model's predictive capabilities. Sample results of the validation study are illustrated in the graphs.

Thomas, David J.; Verrilli, Michael J.; Calomino, Anthony M.

2004-01-01

95

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

96

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

NASA Technical Reports Server (NTRS)

The electric resistance of woven SiC fiber reinforced SiC matrix composites were measured under tensile loading conditions. The results show that the electrical resistance is closely related to damage and that real-time information about the damage state can be obtained through monitoring of the resistance. Such self-sensing capability provides the possibility of on-board/in-situ damage detection or inspection of a component during "down time". The correlation of damage with appropriate failure mechanism can then be applied to accurate life prediction for high-temperature ceramic matrix composites.

Smith, Craig; Morscher, Gregory N.; Xia, Zhenhai

2008-01-01

97

Thermal Residual Stress Distribution in Carbon Fiber\\/Novel Thermal Plastic Composite  

Microsoft Academic Search

Thermal residual stress is one of the major factors affecting composite mechanical performance. In this paper, a 3-D FEA technique\\u000a was utilized to analyze the thermal residual stress distribution in Carbon fiber\\/PPESK composite. Parabolic failure criterion\\u000a was used to predict composite potential failure zone. Results indicate that, thermal residual stress distributions in different\\u000a parts of the composite are different. At

Chun Lu; Ping Chen; Qi Yu; Julong Gao; Baijie Yu

2008-01-01

98

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 (Vf), 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, P. A.

1991-01-01

99

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

100

Body composition changes in the first 6 months of life according to method of feeding.  

PubMed

Background: Early feeding choices may affect long-term health outcomes. Therefore, understanding body composition changes in healthy breastfed infants has become an important research focus. Objectives: The aims of this review were to investigate the body composition changes that occur during weight loss in breastfed term newborns and to examine body composition differences between exclusively/predominantly breastfed and exclusively formula-fed infants in the first 6 months of life. Methods: We performed a review of the existing literature using PubMed. We searched for studies published in English since January 1, 2000, that involved human infants ranging in age from birth to 6 months. We used the following MEDLINE Medical Subject Headings: ((breastfeeding) OR (infant formula)) AND ((body composition) OR (bioelectrical impedance) OR (absorptiometry, photon) OR (total body potassium) OR (isotope dilution) OR (air-displacement plethysmography)). Our search yielded 6 studies. Results: Two studies reported that newborn weight loss was due to a reduction in the quantity of both fat mass and fat-free mass. Three out of 4 articles that evaluated body composition changes according to method of feeding reported no differences in body composition between exclusively/predominantly breastfed and exclusively formula-fed infants in the first 4.5 months of life. One study reported that exclusively breastfed infants at 3 months of age and exclusively breastfed boys at 6 months of age had higher fat mass contents compared to exclusively formula-fed infants. Conclusion: Because of the limited number of studies available, larger studies are needed to clarify the differences in body composition between exclusively/predominantly breastfed and exclusively formula-fed infants. PMID:24352651

Giannì, Maria Lorella; Roggero, Paola; Orsi, Anna; Piemontese, Pasqua; Garbarino, Francesca; Bracco, Beatrice; Garavaglia, Elisa; Agosti, Massimo; Mosca, Fabio

2014-05-01

101

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

102

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

103

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

104

Thermodynamic models of the distribution of life-related organic molecules in the interstellar medium  

NASA Astrophysics Data System (ADS)

New equilibrium thermodynamic distribution models of organic substances important to life in giant molecular clouds are suggested. These models use the normal distribution law of the standard enthalpy and the free energy (Helmholtz energy) for various organic molecules, amino acids, and nucleic acid components. These models were used to forecast organic molecule resources in the interstellar medium of the observable universe. The resources of the main biological molecules were estimated from radio-astronomical data.

Dolomatov, Michel Y.; Zhuravleva, Nadezhda A.

2014-05-01

105

The galactic habitable zone and the age distribution of complex life in the Milky Way.  

PubMed

We modeled the evolution of the Milky Way Galaxy to trace the distribution in space and time of four prerequisites for complex life: the presence of a host star, enough heavy elements to form terrestrial planets, sufficient time for biological evolution, and an environment free of life-extinguishing supernovae. We identified the Galactic habitable zone (GHZ) as an annular region between 7 and 9 kiloparsecs from the Galactic center that widens with time and is composed of stars that formed between 8 and 4 billion years ago. This GHZ yields an age distribution for the complex life that may inhabit our Galaxy. We found that 75% of the stars in the GHZ are older than the Sun. PMID:14704421

Lineweaver, Charles H; Fenner, Yeshe; Gibson, Brad K

2004-01-01

106

Required characteristics of statistical distribution models for life cycle cost estimation  

Microsoft Academic Search

Life cycle cost (LCC) is used as the decision objective in many engineering problems such as project selection and bidding. An important nature of LCC estimation is uncertainty. Therefore, cost elements and system cost are usually represented by statistical distributions. A number of statistical models have been used for modeling LCC in the literature. It appears to be lack of

R. Jiang; W. J. Zhang; P. Ji

2003-01-01

107

Distribution, ecology, life history, genetic variation, and risk of extinction of nonhuman primates from Costa Rica  

Microsoft Academic Search

We examined the association between geographic distribution, ecological traits, life history, genetic diversity , and risk of extinction in nonhuman primate species from Costa Rica. All of the current nonhuman pri- mate species from Costa Rica are included in the study; spider monkeys (Ateles geoffroyi), howling monkeys (Alouatta palliata), capuchins (Cebus capucinus), and squirrel monkeys (Saimiri oerstedii). Geographic distri- bution

María E. Zaldívar; Oscar Rocha; Kenneth E. Glander; Gabriel Aguilar; Ana S. Huertas; Ronald Sánchez; Grace Wong

2004-01-01

108

Collecting and Querying Distributed Traces of Composite Service Executions  

Microsoft Academic Search

The development of new Web services by composition of existing ones is becoming a widespread approach to realise business-to-business collabo- rations. The composite services obtained in this way are then eventually used in other compositions. Given the dynamic nature of the Web, this recursive compo- sition of services rapidly leads to intricate dependencies between them. On the other hand, businesses

Marie-christine Fauvet; Marlon Dumas; Boualem Benatallah

2002-01-01

109

Temperature Effects on Gametophyte Life-History Traits and Geographic Distribution of Two Cryptic Kelp Species  

PubMed Central

A major determinant of the geographic distribution of a species is expected to be its physiological response to changing abiotic variables over its range. The range of a species often corresponds to the geographic extent of temperature regimes the organism can physiologically tolerate. Many species have very distinct life history stages that may exhibit different responses to environmental factors. In this study we emphasized the critical role of the haploid microscopic stage (gametophyte) of the life cycle to explain the difference of edge distribution of two related kelp species. Lessonia nigrescens was recently identified as two cryptic species occurring in parapatry along the Chilean coast: one located north and the other south of a biogeographic boundary at latitude 29–30°S. Six life history traits from microscopic stages were identified and estimated under five treatments of temperature in eight locations distributed along the Chilean coast in order to (1) estimate the role of temperature in the present distribution of the two cryptic L. nigrescens species, (2) compare marginal populations to central populations of the two cryptic species. In addition, we created a periodic matrix model to estimate the population growth rate (?) at the five temperature treatments. Differential tolerance to temperature was demonstrated between the two species, with the gametophytes of the Northern species being more tolerant to higher temperatures than gametophytes from the south. Second, the two species exhibited different life history strategies with a shorter haploid phase in the Northern species contrasted with considerable vegetative growth in the Southern species haploid stage. These results provide strong ecological evidence for the differentiation process of the two cryptic species and show local adaptation of the life cycle at the range limits of the distribution. Ecological and evolutionary implications of these findings are discussed.

Oppliger, L. Valeria; Correa, Juan A.; Engelen, Aschwin H.; Tellier, Florence; Vieira, Vasco; Faugeron, Sylvain; Valero, Myriam; Gomez, Gonzalo; Destombe, Christophe

2012-01-01

110

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

111

Flexural strength distribution of 3D SiC/SiC composite  

NASA Astrophysics Data System (ADS)

Flexural strength of a four-step, three-dimensional (3D) braiding SiC/SiC composite was tested at room temperature. The strength distribution was studied based on Weibull distribution and Normal distribution as well as examined by the Kolmogorov test. The results indicated that the flexural failure behavior of the composite was rather brittle with a small displacement. And the statistical strength distribution of the 3D SiC/SiC composite was in agreement with two-parameter Weibull distribution of the Weibull modulus, m=8.1545 and normal distribution. And the predicated mean flexural strength of the 3D SiC/SiC composite by the two-parameter Weibull distribution was consistent with the tested value.

Wu, Shoujun; Cheng, Laifei; Dong, Ning; Zhang, Litong; Xu, Yongdong

2006-12-01

112

Factors Influencing the Fatigue Life of an HY-80 Composition Steel Fully Quenched and Tempered to Various Strength Levels.  

National Technical Information Service (NTIS)

The report evaluates the effects of strength level, Charpy V-notch energy, prestraining, prestraining and stress relieving, and austenitizing temperature on the fatigue life of a fully quenched HY-80 steel composition. The fatigue data developed indicate ...

A. R. Willner M. L. Salive

1964-01-01

113

Life.  

National Technical Information Service (NTIS)

Discusses the general characteristics of life as we know it. Uses a number of examples to show how life has adapted to earth conditions and certain life forms can withstand environmental shocks. Describes the conditions on Mars with the question raised as...

1994-01-01

114

Distribution and variation of plagioclase compositions on Mars  

NASA Astrophysics Data System (ADS)

This study presents the first global compositional maps of plagioclase, the most abundant mineral in the Martian crust. Linear deconvolutions of spectra from the Thermal Emission Spectrometer (TES) allowed calculation of average plagioclase compositions for dust-free areas on Mars ±60° of the equator (approximately 40% of the surface for this range of latitudes). As a whole, surface type 1 and 2 terrains are virtually identical with respect to their average plagioclase compositions, ˜An60. The majority of TES observations were modeled as labradorite and bytownite (between An50 and An90), while fewer observations were modeled with other plagioclase compositions that did not correlate with specific geologic terrains. The lack of diversity in average plagioclase compositions across multiple geologic units may represent an upper Martian crust with minimal variation in plagioclase compositions. Alternatively, aeolian, fluvial, and/or impact activity may have redistributed heterogeneous crustal material forming a relatively homogeneous, global surface layer.

Milam, Keith A.; McSween, Harry Y.; Moersch, Jeffrey; Christensen, Philip R.

2010-09-01

115

Chemical composition and size distributions for fly ashes  

Microsoft Academic Search

Inter-particle variations in particle diameter and chemical composition in coal fly ashes are significant, and can be quantitatively studied using currently available microanalytical techniques. One such technique, computer controlled scanning electron microscopy (CCSEM), is now routinely used to determine chemical compositions and diameters of individual fly ash particles, using statistically significant sample sizes. This paper proposes simple mathematical formulae for

Sarbajit Ghosal; Jon L. Ebert; Sidney A. Self

1995-01-01

116

Life support systems and optimal isotope composition in cosmonaut habitats for long-term missions  

NASA Astrophysics Data System (ADS)

Differences in the isotope content of the biogenous chemicals of cosmonaut habitats are given a theoretical consideration. Rationale is given to the hypothesis according to which the biochemical and biophysical processes in plants, animals, and humans must be impacted by the isotopes of all the biogenous chemicals in cosmonaut habitats. Organisms were found to persistently make preference of lighter fractions of stable isotopes from the biogenous chemicals. In most of the compounds the light fraction of stable isotopes constitutes the greater portion by mass. However, the optimal isotope composition of biogenous chemicals is still unknown and necessitates biochemical, toxicological, biological and other kinds of research. The functions of a life support system should also include production and maintenance of an optimal isotope composition for habitats, i.e. water, oxygen, food stuffs in order to improve metabolism in and performance of cosmonauts.

Siniak, I. E.; Grigoriev, A. I.

117

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

Microsoft Academic Search

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.

Mehmet Bashan; Halit Akbas; Kadir Yurdakoc

2002-01-01

118

Observation of Lightning Phenomena on Distribution Lines using Composite Techniques  

Microsoft Academic Search

For the rationalization of lightning protection design of distribution lines, it is important to clarify the behavior of distribution line when direct or nearby lightning occurs. Because of the lower insulation level than is for transmission line, in study on lightning protection design of distribution line, not only direct lightning strokes but also induced voltages caused by nearby strokes must

Takao Hirai; Shigemitsu Okabe; Tsutomu Takinami; Takuji Chindo

2004-01-01

119

Space Station environmental control and life support system distribution and loop closure studies  

NASA Technical Reports Server (NTRS)

The NASA Space Station's environmental control and life support system (ECLSS) encompasses functional elements concerned with temperature and humidity control, atmosphere control and supply, atmosphere revitalization, fire detection and suppression, water recovery and management, waste management, and EVA support. Attention is presently given to functional and physical module distributions of the ECLSS among these elements, with a view to resource requirements and safety implications. A strategy of physical distribution coupled with functional centralization is for the air revitalization and water reclamation systems. Also discussed is the degree of loop closure desirable in the initial operational capability status Space Station's oxygen and water reclamation loops.

Humphries, William R.; Reuter, James L.; Schunk, Richard G.

1986-01-01

120

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

121

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

122

Analysis of Energy Distribution in a Ceramic/GRP Composite.  

National Technical Information Service (NTIS)

Ceramic/GRP composite targets were impacted by hemispherically nosed tungsten alloy projectiles (L = 55 mm, D = 17 mm, m = 214 g) at velocities of about 1000 m/s. The impact velocities were chosen close to the ballistic limit of this projectile-target com...

E. StraBburger, H. Senf

1995-01-01

123

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

124

Effective permittivity of planar composites with randomly or periodically distributed conducting fibers  

NASA Astrophysics Data System (ADS)

Theoretical and experimental studies have been conducted on the effective electromagnetic properties of planar composites at microwave frequencies, with embedded conductive fibers of various volume concentrations. Two types of distribution are considered: random and periodic. Experimental results for the transmission coefficient and effective permittivity are obtained via the free space method. Simulation results are obtained using the finite element method (FEM). Good agreement is found between the measured and computed results, indicating the suitability of the FEM as a theoretical modeling tool for such composites, as compared to other numerical methods, such as the method of moments. It is also found that the type of distribution affects the effective permittivity of the composites: lower microwave permittivity with broader peak response is observed for composites with randomly distributed fibers, in comparison to that with periodically distributed fibers.

Liu, L.; Matitsine, S. M.; Gan, Y. B.; Rozanov, K. N.

2005-09-01

125

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

126

Research on electric potential distributions of composite insulators and glass insulators by numerical simulation  

Microsoft Academic Search

At present, glass insulators and composite insulators are widely used in high voltage line owing to their outstanding features. In this paper, finite element method (FEM) is introduced and simulation modeling is outlined, and FEM software-ANSYS is employed to calculate the electric potential distribution of composite insulators and glass insulators under different conditions. The aim of the computation is to

Fan Yadong; Wen Xishan; Deng Wei; Li Xiaoping

2006-01-01

127

Numerical modelling of particle distribution effects on fatigue in Al–SiC p composites  

Microsoft Academic Search

Various reports in the literature have highlighted the effects of particle distribution on the fatigue behaviour of particulate reinforced metal matrix composites (PMMCs), although few attempts have been made at modelling such effects. A micromechanical understanding of the effects of clustering on short crack growth behaviour in Al–SiCp composites has been achieved via finite element modelling. Comparison of preliminary models

J Boselli; P. D Pitcher; P. J Gregson; I Sinclair

2001-01-01

128

Chemical composition and size distributions of coastal aerosols observed on the US East Coast  

Microsoft Academic Search

Characterization of coastal aerosols is important to the study of the atmospheric input of nutrients to the adjacent marine and the ocean ecosystems. Over a land–ocean transition zone, however, aerosol composition could be strongly modified by anthropogenic emissions and transport processes. This work focuses on examining aerosol properties, in particular chemical composition, particle-size distributions and iron (Fe) solubility, over the

Lili Xia; Yuan Gao

2010-01-01

129

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.

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

2013-01-01

130

Monomer abundance distribution patterns as a universal biosignature: examples from terrestrial and digital life.  

PubMed

Organisms leave a distinctive chemical signature in their environment because they synthesize those molecules that maximize their fitness. As a result, the relative concentrations of related chemical monomers in life-bearing environmental samples reflect, in part, those compounds' adaptive utility. In contrast, rates of molecular synthesis in a lifeless environment are dictated by reaction kinetics and thermodynamics, so concentrations of related monomers in abiotic samples tend to exhibit specific patterns dominated by small, easily formed, low-formation-energy molecules. We contend that this distinction can serve as a universal biosignature: the measurement of chemical concentration ratios that belie formation kinetics or equilibrium thermodynamics indicates the likely presence of life. We explore the features of this biosignature as observed in amino acids and carboxylic acids, using published data from numerous studies of terrestrial sediments, abiotic (spark, UV, and high-energy proton) synthesis experiments, and meteorite bodies. We then compare these data to the results of experimental studies of an evolving digital life system. We observe the robust and repeatable evolution of an analogous biosignature in a digital lifeform, suggesting that evolutionary selection necessarily constrains organism composition and that the monomer abundance biosignature phenomenon is universal to evolved biosystems. PMID:21253717

Dorn, Evan D; Nealson, Kenneth H; Adami, Christoph

2011-03-01

131

Gorillas are a host for Dientamoeba fragilis: an update on the life cycle and host distribution.  

PubMed

Dientamoeba fragilis is a gastrointestinal protozoan that has a worldwide distribution and is emergeing as a common cause of diarrhea. As D. fragilis has a propensity to cause chronic illness with symptoms similar to irritable bowel syndrome (IBS) it is not surprising that some patients with D. fragilis are misdiagnosed as having IBS. In contrast to most other pathogenic protozoa very little is known about its life cycle, epidemiology and mode of transmission. What role animal reservoirs play in the transmission of this parasite is unknown. Consequently we undertook a prospective study to determine the host distribution of D. fragilis. Over a 2-year-period, 608 faecal samples from a wide range of animal and bird species, including pigs and other food species, were screened using permanent stained smears for the presence of D. fragilis. Trophozoites of D. fragilis were only detected in Western lowland gorillas (3/10) (Gorilla g. gorilla) and confirmed by PCR targeting the SSU rRNA gene. The limited host range detected suggests human infection may not involve transmission from other animal species. In addition, we provide an update on the limited knowledge about the life cycle of this parasite and its host distribution. PMID:18022187

Stark, Damien; Phillips, Owen; Peckett, Donna; Munro, Ursula; Marriott, Deborah; Harkness, John; Ellis, John

2008-01-25

132

Thermal history, chemical composition and relationship of comets to the origin of life  

NASA Technical Reports Server (NTRS)

The role of thermal processes in determining the chemical composition of comets is considered, and implications of possible cometary constituents for the origin and evolution of life on earth are discussed. It is shown that the inclusion of short-lived Al-26 from a nearby supernova explosion into cometary nuclei could lead to comets with surfaces cool enough to retain H2O and interiors warm enough for thermal processing to occur, with the production of complex organic molecules such as amino acids and nucleic acid bases. It is thus suggested that comets may have played a part in seeding the primitive earth with biological polymers capable of self-replication or of evolving towards that capability, and may even be responsible for the subsequent introduction of organic material capable of infecting already existing cells.

Irvine, W. M.; Leschine, S. B.; Schloerb, F. P.

1980-01-01

133

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

134

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.

2010-01-01

135

Study on Composition Distribution and Ferromagnetism of Monodisperse FePt Nanoparticles  

NASA Astrophysics Data System (ADS)

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.

Wang, H. B.; Wang, H.; Zhang, J.; Yang, F. J.; Xu, Y. M.; Li, Q.

2010-03-01

136

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

137

Fatigue-life behavior and matrix fatigue crack spacing in unnotched SCS-6/Timetal 21S metal matrix composites  

NASA Technical Reports Server (NTRS)

Fatigue tests of the SCS-6/Timetal 21S composite system were performed to characterize the fatigue behavior for unnotched conditions. The stress-life behavior of the unnotched (9/90)2s laminates was investigated for stress ratios of R = 0.1 and R = 0.3. The occurrence of matrix cracking was also examined in these specimens. This revealed multiple matrix crack initiation sites throughout the composite, as well as evenly spaced surface cracks along the length of the specimens. No difference in fatigue lives were observed for stress ratios of R = 0.1 and R = 0.3 when compared on a stress range basis. The unnotched SCS-6/Timetal 21S composites had shorter fatigue lives than the SCS-6/Ti-15-3 composites, however the neat Timetal 21S matrix material had a longer fatigue life than the neat Ti-15-3.

Ward, G. T.; Herrmann, D. J.; Hillberry, B. M.

1993-01-01

138

Changes in chemical composition and antioxidative properties of rye ginger cakes during their shelf-life.  

PubMed

Changes in chemical composition and antioxidative properties of rye ginger cakes during their shelf-life were investigated in this study. In particular, the changes in antioxidants content, antioxidative and reducing capacity, and Maillard reaction development in rye ginger cakes after long-term storage were addressed. Ginger cakes produced according to the traditional and current recipe were stored for 5 years at room temperature in a dark place. The total phenolic compounds (TPC), inositol hexaphosphate (IP6), reduced (GSH) and oxidised glutathione (GSSG) contents, antioxidant and reducing capacity and Maillard reaction products (MRPs) were determined in ginger cakes after storage and then compared to those measured after baking. After long-term storage a decrease in TPC and IP6 contents in cakes was noted. In contrast, an increase in antioxidative and reducing capacity of stored cakes was observed. Long-term storage induced formation of furosine, advanced and final Maillard reaction products and caused changes in both reduced and oxidised forms of glutathione. After long-term storage the modest changes in furosine, FAST index and browning in ginger cake formulated with dark rye flour may suggest that this product is the healthiest among others. Therefore, traditional rye ginger cakes can be considered as an example of a healthy food that is also relatively stable during long term storage as noted by the small chemical changes observed in its composition. PMID:22980898

Zieli?ski, Henryk; del Castillo, Maria Dolores; Przygodzka, Ma?gorzata; Ciesarova, Zuzana; Kukurova, Kristina; Zieli?ska, Danuta

2012-12-15

139

Thermal analysis of soft magnetic composite motors using a hybrid model with distributed heat sources  

Microsoft Academic Search

This paper presents a hybrid thermal model with distributed heat sources for thermal analysis of soft magnetic composite (SMC) motors. The model uses a combination of lumped and distributed thermal parameters, which can be obtained from motor dimensions and thermal constants. The model can be used to calculate the core loss in each part, in combination with three-dimensional magnetic field

Youguang Guo; Jian Guo Zhu; Wei Wu

2005-01-01

140

Influence of particle size distribution on insertion processes in composite electrodes. Potential step and EIS theory  

Microsoft Academic Search

Diffusion of guest species in particles of host material in composite electrodes is investigated for potential step and EIS methods taking particle size distribution into consideration. Theoretical expressions are derived for the output response to a potential step and the diffusion impedance considering linear diffusion in particles. Numerical calculations are used to demonstrate the effects of particle size distribution. Generalisation

J.-P. Diard; B. Le Gorrec; C. Montella

2001-01-01

141

Space Station Environmental Control and Life Support System architecture - Centralized versus distributed  

NASA Technical Reports Server (NTRS)

Both Centralized and Distributed approaches are being evaluated for the installation of Environmental Control and Life Support (ECLS) equipment in the Space Station. In the Centralized facility concept, integrated processing equipment is located in two modules with plumbing used to circulate ECLS services throughout the Station. The Distributed approach locates the ECLS subsystems in every module of the Space Station with each subsystem designed to meet its own module needs. This paper defines the two approaches and how the advantages and disadvantages of each are tied to the choice of Space Station architecture. Other considerations and evaluations include: crew movement, Station evolution and the ducting impact needed to circulate ECLS services from centrally located processing equipment.

Boehm, A. M.; Behrend, A. F.

1984-01-01

142

The Bias-corrected Mass Distribution Of Compositional Classes In The Main Asteroid Belt  

NASA Astrophysics Data System (ADS)

Each compositional class of asteroid is a relic of the temperature and composition conditions in which it formed. The current distribution reveals the history of the Solar System, and each body acts as a marker of any mixing that occurred since formation. The remnant of a primordial temperature gradient, seen as transition from the S class to C class dominating in different regions of the asteroid belt has been a paradigm for three decades (Gradie & Tedesco 1982, Science, 216, 1405). In this work, we reexamine the architecture of the asteroid belt by determining the bias-corrected distribution of 99.99% of its mass based on compositional information provided by ground-based and space-based measurements. We report an updated view of the distribution of asteroid compositions. This material is based upon work supported by the National Science Foundation under Grant No. 0907766.

DeMeo, Francesca E.; Carry, B.

2012-10-01

143

Scaling effects on damage development, strength, and stress-rupture life laminated composites in tension  

NASA Astrophysics Data System (ADS)

The damage development and strength of ply-level scaled carbon/epoxy composite laminates having stacking sequence of ({+}thetasb{n}/{-}thetasb{n}/90sb{2n} rbracksb{s} where constraint ply angle, theta, was 0sp°, 15sp°, 30sp°,\\ 45sp°,\\ 60sp°, and 75sp°, and size was scaled as n = 1, 2, 3, and 4, is reported in Part I. X-radiography was used to monitor damage developments. First-ply failure stress, and tensile strength were recorded. First-ply failure of the midplane 90sp° plies depended on the stiffness of constraint plies, and size. All 24 cases were predicted using Zhang's shear-lag model and data generated from lbrack0sb2/90sb2rbracksb{s} cross-ply tests. Laminate strength was controlled by the initiation of a triangular-shaped local delamination of the surface angle plies. This delamination was predicted using O'Brien's strain energy release rate model for delamination of surface angle plies. For each ply angle, the smallest laminate was used to predict delamination (and strength) of the other sizes. The in-situ tensile strength of the 0sp° plies within different cross-ply, and quasi-isotropic laminates of varying size and stacking sequence is reported in Part II. No size effect was observed in the strength of 0sp° plies for those lay-ups having failure confined to the gauge section. Laminates exhibiting a size-strength relationship, had grip region failures for the larger sizes. A statistically significant set of 3-point bend tests of unidirectional beams were used to provide parameters for a Weibull model, to re-examine relationship between ultimate strength of 0sp° plies and specimen volume. The maximum stress in the 0sp° plies in bending, and the tensile strength of the 0sp° plies (from valid tests only) was the same. Weibull theory predicted loss of strength which was not observed in the experiments. An effort to model the durability and life of quasi-isotropic E-glass/913 epoxy composite laminates under steady load and in an acidic environment is reported in Part III. Stress-rupture tests of unidirectional coupons immersed in a weak hydrochloric acid solution was conducted to determine their stress-life response. Creep tests were conducted on unidirectional coupons parallel and transverse to the fibers, and on {±}45sp° layups to characterize the lamina stress- and time-dependent compliances. These data were used in a composite stress-rupture life model, based on the critical element modeling philosophy of Reifsnider, to predict the life of two ply-level thickness-scaled quasi-isotropic laminates.

Lavoie, J. Andre

144

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

145

Pair-Distribution Functions of Composite Fermion Liquids  

Microsoft Academic Search

Pair-distribution functions g(r) of Laughlin quasielectrons (QE’s) are calculated for the fractional quantum Hall liquids at electron filling factors ? = 4\\/11 and 3\\/8. They all have a shoulder at a medium range. The intra- and inter-cluster contributions to g(r) are identified, supporting the idea of cluster formation (QE pairs at ? = 4\\/11 and QE triplets at ? =

Arkadiusz Wo´js; Daniel Wodzin´ski; John J. Quinn

2006-01-01

146

Structure, composition, and distribution of plastid nucleoids in Narcissus pseudonarcissus  

Microsoft Academic Search

The size, frequency and distribution of the nucleoids of chloroplasts (cl-nucleoids) and chromoplasts (cr-nucleoids) of the daffodil have been investigated in situ using the DNA-specific fluorochrome 4'6-diamidino-2-phenylindole. Chromoplasts contain fewer nucleoids (approx. 4) than chloroplasts (> 10), and larger chromoplasts (cultivated form, approx. 4) contain more than smaller ones (wild type, approx. 2). During chromoplast development the nucleoid number decreases

P. Hansmann; H. Falk; K. Ronai; P. Sitte

1985-01-01

147

A scaling distribution for grain composition of debris flow  

NASA Astrophysics Data System (ADS)

Debris flow is composed of a wide range of grains. This study proposes a general form of grain size distribution, P (D) = CD-?exp (-D / Dc), which is satisfied well by various debris flows and by soils and sediments related to debris flows. The parameters ? and Dc are found to be related to debris-flow density in power laws. In particular, ? represents some characteristic porosity of soil in a natural condition and controls the variation of soils in developing debris flows; and Dc defines a characteristic size governing the sediment concentration. Field observations indicate that debris flows fall into a certain range of parameters (?, Dc). Almost all debris flows have ? < 0.10, and most debris flows of high density have ? < 0.05. Moreover, experiments show that the exponent ? increases during soil failures under rainfall, providing an index varying in the course of debris flow initiation. Finally, grain size distribution is used to evaluate the properties of debris flows in different regions. The distribution provides a simple but quantitative method of predicting a potential flow through the source soils.

Yong, Li; Xiaojun, Zhou; Pengcheng, Su; Yingde, Kong; Jingjing, Liu

2013-06-01

148

Battery cycle life balancing in a microgrid through flexible distribution of energy and storage resources  

NASA Astrophysics Data System (ADS)

In this paper, a microgrid consisting of four fuel cell-battery hybrid Distributed Energy Resources (DERs) is devised for an industrial crusher-conveyor load. Each fuel cell was accompanied by a Li-ion battery to provide energy storage support under islanded condition of the microgrid since the fuel cells typically have poor transient response characteristics. After carrying out extensive modeling and analysis in MATLAB®, the battery utilization was found to vary significantly based on the DER's ‘electrical’ placement within the microgrid. This paper presents, under such conditions, a variety of battery life balancing solutions through the use of the new framework of Flexible Distribution of EneRgy and Storage Resources (FDERS). It is based on an in-situ reconfiguration approach through ‘virtual’ reactances that help in changing the ‘electrical’ position of each DER without physically displacing any component in the system. Several possible approaches toward balancing the battery utilization are compared in this paper taking advantage of the flexibility that FDERS offers. It was observed that the estimated battery life is dependent on factors such as cycling sequence, pattern, and occurrence.

Khasawneh, Hussam J.; Illindala, Mahesh S.

2014-09-01

149

Viral distribution and life strategies in the Bach Dang Estuary, Vietnam.  

PubMed

Although the structure and dynamics of planktonic viruses in freshwater and seawater environments are relatively well documented, little is known about the occurrence and activity of these viruses in estuaries, especially in the tropics. Viral abundance, life strategies, and morphotype distribution were examined in the Bach Dang Estuary (Vietnam) during the dry season in 2009. The abundance of both viruses and their prokaryotic hosts decreased significantly from upstream to downstream, probably as the result of nutrient dilution and osmotic stress faced by the freshwater communities. The antibiotic mitomycin-C revealed that the fraction of lysogenic cells was substantially higher in the lower seawater part of the estuary (max 27.1%) than in the upper freshwater area where no inducible lysogens were observed. The question of whether there is a massive, continuous induction of marine lysogens caused by the mixing with freshwater is considered. Conversely, the production of lytic viruses declined as salinity increased, indicating a spatial succession of viral life strategies in this tropical estuary. Icosahedral tailless viruses with capsids smaller than 60 nm dominated the viral assemblage throughout the estuary (63.0% to 72.1% of the total viral counts), and their distribution was positively correlated with that of viral lytic production. Interestingly, the gamma-proteobacteria explained a significant portion of the variance in the <60 nm and 60 to 90 nm tailless viruses (92% and 80%, respectively), and in the Myoviridae (73%). Also, 60% of the variance of the tailless larger viruses (>90 nm) was explained by the beta-proteobacteria. Overall, these results support the view that the environment, through selection mechanisms, probably shapes the structure of the prokaryotic community. This might be in turn a source of selection for the virioplankton community via specific affiliation favoring particular morphotypes and life strategies. PMID:21390531

Bettarel, Yvan; Bouvier, Thierry; Agis, Martin; Bouvier, Corinne; Chu, Thuoc Van; Combe, Marine; Mari, Xavier; Nghiem, Minh Ngoc; Nguyen, Thuy Thanh; Pham, Thu The; Pringault, Olivier; Rochelle-Newall, Emma; Torréton, Jean-Pascal; Tran, Huy Quang

2011-07-01

150

Quantifying distributed damage in composites via the thermoelastic effect  

SciTech Connect

A new approach toward quantifying transverse matrix cracking in composite laminates using the thermoelastic effect is developed. The thermoelastic effect refers to the small temperature changes that are generated in components under dynamic loading. Two models are derived, and the theoretical predictions are experimentally verified for three types of laminates. Both models include damage-induced changes in the lamina stress state and lamina coefficients of thermal expansion conduction effects, and epoxy thickness. The first model relates changes in the laminate TSA signal to changes in longitudinal laminate stiffness and Poisson's ratio. This model is based on gross simplifying assumptions and can be used on any composite laminate layup undergoing transverse matrix cracking. The second model relates TSA signal changes to longitudinal laminate stiffness, Poisson's ratio, and microcrack density for (0[sub p]90[sub q])[sub s] and (90[sub q]/0[sub p])[sub s] cross-ply laminates. Both models yield virtually identical results for the cross-ply laminates considered. A sensitivity analysis is performed on both models to quantify the effects of reasonable property variations on the normalized stiffness vs. normalized TSA signal results for the three laminates under consideration. The results for the cross-ply laminates are very insensitive, while the (+/- 45)[sub 5s] are particularly sensitive to epoxy thickness and longitudinal lamina coefficient of thermal expansion. Experiments are conducted on (0[sub 3]/90[sub 3])[sub s] and (90[sub 3]/0[sub 3])[sub s] Gl/Ep laminates and (+/- 45)[sub 5s] Gr/Ep laminates to confirm the theoretical developments of the thesis. There is a very good correlation between the theoretical predictions and experimental results for the Gl/Ep laminates.

Mahoney, B.J.

1992-01-01

151

Composition of peptidoglycans in Bacteroidaceae: determination and distribution of lanthionine.  

PubMed Central

Peptidoglycans of organisms belonging to the strictly anaerobic family Bacteroidaceae were investigated for the presence of lanthionine. Different procedures for the quantitation of lanthionine were compared. Performic acid and peroxide oxidation procedures on 35S-labeled peptidoglycan from Fusobacterium nucleatum Fev1 resulted in low yields of cysteic acid (42 and 60%, respectively) and many other additional unidentified oxidation products. Lanthionine was, however, recovered in high yield (89% or more) from acid hydrolysates of unoxidized peptidoglycans. Lanthionine was found exclusively in some species of Fusobacterium, in particular F. nucleatum, F. necrophorum, F. russi, and F. gonidiaformans, for which lanthionine may be ascribed a function as a taxonomic marker. Peptidoglycans of these bacteria are thus proposed to belong to a new chemotype, assigned A1 delta. One strain of Fusobacterium, F. mortiferum VPI 0473 contained both lanthionine and diaminopimelic acid in about equal proportions. Species of F.plauti had a composition atypic of gram-negative cells. Chemotypic differences were also indicated among the species of Bacteroides investigated. Thus, some species contained lysine and not diaminopimelic acid as the major dibasic amino acid (e.g., F. asaccharolyticus). It is concluded that peptidoglycans of gram-negative organisms constitute a somewhat more heterogeneous group than hitherto assumed. Images

Vasstrand, E N; Jensen, H B; Miron, T; Hofstad, T

1982-01-01

152

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

153

Perchlorate in The Great Lakes: Distribution, Isotopic Composition and Origin  

NASA Astrophysics Data System (ADS)

Concentrations, stable chlorine and oxygen isotopic compositions, and 36Cl abundances of perchlorate were investigated in the five Laurentian Great Lakes. Samples were collected during monitoring cruises in 2007 and 2008 of the U.S. EPA's RV Lake Guardian and in 2010 at the water supply intake of Marquette, MI on the southern shore of Lake Superior. Concentrations of perchlorate were measured by IC/MS/MS at 24 locations, including one or two depth profiles in each lake. Mean concentrations (?g/L) are: Superior, 0.06 × 0.01; Michigan, 0.10 × 0.01; Huron, 0.11 × 0.01; Erie, 0.08 × 0.01, and Ontario, 0.09 × 0.01. Concentration vs. depth is nearly constant in each lake, indicating well-mixed conditions. Perchlorate was extracted from near-surface water by passing 15,000 to 80,000 L of water through 1-L cartridges containing Purolite A530E bifunctional anion-exchange resin. In the laboratory, perchlorate was eluted from the resin, purified, and precipitated as a >99% pure crystalline phase. Milligram amounts were recovered from each lake. Chlorine and oxygen isotopic analyses were performed at Caltech using the Cameca 7f-GEO SIMS instrument, following validation of the SIMS method with analyses of USGS-37 and USGS-38 isotopic reference materials. Results indicate a relatively narrow range in ?37Cl values (+2.9 to +3.9 ‰) and a wider range in ?18O values (-4.0 to +4.1 ‰), with a general geographic trend of increasing ?18O from west to east. Oxygen-17 was measured at UIC using dual-inlet IRMS of O2 produced by decomposition of KClO4. Great Lakes perchlorate has mass-independent oxygen isotopic variations with positive ?17O values (+1.6 ‰ to +2.7 ‰) divided into two distinct groups: Lake Superior (+2.7 ‰) and the other four lakes (~ +1.7 ‰). The isotopic data indicate that perchlorate is dominantly of natural origin, having stable isotopic compositions resembling those of perchlorate from pre-industrial groundwaters in the western USA. The 36Cl/Cl ratios decrease from Lake Superior (66,500×10-15) to Lake Ontario (7,400×10-15). The high 36Cl/Cl ratios in the lakes having longer water residence times may be explained by retention of perchlorate formed during the time of the 36Cl bomb pulse (1952-1964). Mass balance of perchlorate indicates that substantial biodegradation or uptake of perchlorate may occur in Lake Erie. 36Cl/Cl results confirm that perchlorate in the Great Lakes has dominantly natural origin. These data provide better constraints on possible perchlorate source(s), mixing proportions, and isotopic exchange or fractionation processes within the lakes, as well as better estimates of the regional atmospheric deposition flux of perchlorate and the 36Cl abundance of bomb-pulse perchlorate.

Poghosyan, A.; Sturchio, N. C.; Jackson, W. A.; Guan, Y.; Eiler, J. M.; Hatzinger, P. B.

2013-12-01

154

Characterization of Cyanobacterial Hydrocarbon Composition and Distribution of Biosynthetic Pathways  

PubMed Central

Cyanobacteria possess the unique capacity to naturally produce hydrocarbons from fatty acids. Hydrocarbon compositions of thirty-two strains of cyanobacteria were characterized to reveal novel structural features and insights into hydrocarbon biosynthesis in cyanobacteria. This investigation revealed new double bond (2- and 3-heptadecene) and methyl group positions (3-, 4- and 5-methylheptadecane) for a variety of strains. Additionally, results from this study and literature reports indicate that hydrocarbon production is a universal phenomenon in cyanobacteria. All cyanobacteria possess the capacity to produce hydrocarbons from fatty acids yet not all accomplish this through the same metabolic pathway. One pathway comprises a two-step conversion of fatty acids first to fatty aldehydes and then alkanes that involves a fatty acyl ACP reductase (FAAR) and aldehyde deformylating oxygenase (ADO). The second involves a polyketide synthase (PKS) pathway that first elongates the acyl chain followed by decarboxylation to produce a terminal alkene (olefin synthase, OLS). Sixty-one strains possessing the FAAR/ADO pathway and twelve strains possessing the OLS pathway were newly identified through bioinformatic analyses. Strains possessing the OLS pathway formed a cohesive phylogenetic clade with the exception of three Moorea strains and Leptolyngbya sp. PCC 6406 which may have acquired the OLS pathway via horizontal gene transfer. Hydrocarbon pathways were identified in one-hundred-forty-two strains of cyanobacteria over a broad phylogenetic range and there were no instances where both the FAAR/ADO and the OLS pathways were found together in the same genome, suggesting an unknown selective pressure maintains one or the other pathway, but not both.

Coates, R. Cameron; Podell, Sheila; Korobeynikov, Anton; Lapidus, Alla; Pevzner, Pavel; Sherman, David H.; Allen, Eric E.; Gerwick, Lena; Gerwick, William H.

2014-01-01

155

Characterization of cyanobacterial hydrocarbon composition and distribution of biosynthetic pathways.  

PubMed

Cyanobacteria possess the unique capacity to naturally produce hydrocarbons from fatty acids. Hydrocarbon compositions of thirty-two strains of cyanobacteria were characterized to reveal novel structural features and insights into hydrocarbon biosynthesis in cyanobacteria. This investigation revealed new double bond (2- and 3-heptadecene) and methyl group positions (3-, 4- and 5-methylheptadecane) for a variety of strains. Additionally, results from this study and literature reports indicate that hydrocarbon production is a universal phenomenon in cyanobacteria. All cyanobacteria possess the capacity to produce hydrocarbons from fatty acids yet not all accomplish this through the same metabolic pathway. One pathway comprises a two-step conversion of fatty acids first to fatty aldehydes and then alkanes that involves a fatty acyl ACP reductase (FAAR) and aldehyde deformylating oxygenase (ADO). The second involves a polyketide synthase (PKS) pathway that first elongates the acyl chain followed by decarboxylation to produce a terminal alkene (olefin synthase, OLS). Sixty-one strains possessing the FAAR/ADO pathway and twelve strains possessing the OLS pathway were newly identified through bioinformatic analyses. Strains possessing the OLS pathway formed a cohesive phylogenetic clade with the exception of three Moorea strains and Leptolyngbya sp. PCC 6406 which may have acquired the OLS pathway via horizontal gene transfer. Hydrocarbon pathways were identified in one-hundred-forty-two strains of cyanobacteria over a broad phylogenetic range and there were no instances where both the FAAR/ADO and the OLS pathways were found together in the same genome, suggesting an unknown selective pressure maintains one or the other pathway, but not both. PMID:24475038

Coates, R Cameron; Podell, Sheila; Korobeynikov, Anton; Lapidus, Alla; Pevzner, Pavel; Sherman, David H; Allen, Eric E; Gerwick, Lena; Gerwick, William H

2014-01-01

156

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.

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

2009-01-01

157

Composite compatible printed circuit technology for the distribution of electrical signals  

NASA Astrophysics Data System (ADS)

The combination of sensing and actuating technologies within composite structures without affecting their structural performance is a major problem in the development, and acceptance, of smart materials technologies. A technique has been developed which uses a woven polyester cloth material, patterned with thin, integral, conductors to create a flexible, composite compatible, method of distributing electrical power throughout a structural panel. The cloths can be considered as printed circuit boards for inclusion within composite structures. It is capable of distributing power throughout a structure in a predetermined, controlled manner. This allows embedded components to be accurately positioned and many external connections to be made to the structure, via a PCB like connector, at a convenient position. The technique therefore considerably simplifies the construction of complex systems. The technology is demonstrated with reference to a piezoelectric actuated composite structure.

Treen, Andrew; Morris, G.; Fixter, G.; Farmer, S.

1996-02-01

158

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

159

The Effects of Blockiness on the Chemical Composition Distribution of Partially Functionalized Polystyrene  

NASA Astrophysics Data System (ADS)

Monodisperse polystyrene has been functionalized chemically to make random copolymers with controlled sequence distribution of the unmodified and modified styrene segments. The sequence blockiness of the resulting random copolymers can be controlled via the temperature of reaction, with a high temperature reaction resulting in a ``truly random'' copolymer, and a low temperature resulting in a ``random blocky'' copolymer. Interaction chromatography has been employed to estimate the chemical composition distribution of these partially functionalized polystyrenes. Two different chemical systems will be discussed; i.e., the brominated and borylated polystyrene systems. The results of our analysis reveal that the chemical composition distribution of ``random blocky'' copolymers is narrower than that of the corresponding ``truly random'' copolymers. The chemical composition of the two systems will be compared directly, and the influence of ``chain conformation inversion'' will be discussed.

Powers, Wayne; Genzer, Jan; Ryu, Chang Y.

2012-02-01

160

Composition and molecular weight distribution of carob germ protein fractions.  

PubMed

Biochemical properties of carob germ proteins were analyzed using a combination of selective extraction, reversed-phase high-performance liquid chromatography (RP-HPLC), size exclusion chromatography (SEC) coupled with multiangle laser light scattering (SEC-MALS), and electrophoretic analysis. Using a modified Osborne extraction procedure, carob germ flour proteins were found to contain approximately 32% albumin and globulin and approximately 68% glutelin with no prolamins detected. The albumin and globulin fraction was found to contain low amounts of disulfide-bonded polymers with relatively low M(w) ranging up to 5 x 10(6) Da. The glutelin fraction, however, was found to contain large amounts of high molecular weight disulfide-bonded polymers with M(w) up to 8 x 10(7) Da. When extracted under nonreducing conditions and divided into soluble and insoluble proteins as typically done for wheat gluten, carob germ proteins were found to be almost entirely ( approximately 95%) in the soluble fraction with only ( approximately 5%) in the insoluble fraction. As in wheat, SEC-MALS analysis showed that the insoluble proteins had a greater M(w) than the soluble proteins and ranged up to 8 x 10(7) Da. The lower M(w) distribution of the polymeric proteins of carob germ flour may account for differences in functionality between wheat and carob germ flour. PMID:20557053

Smith, Brennan M; Bean, Scott R; Schober, Tilman J; Tilley, Michael; Herald, Thomas J; Aramouni, Fadi

2010-07-14

161

Preferential distribution and oxidation inhibiting\\/catalytic effects of boron in carbon fiber reinforced carbon (CFRC) composites  

Microsoft Academic Search

Two different batches of CFRC composites were prepared in the absence\\/presence of B with the expectation of increasing oxidation stability and improving the processing compatibility of CFRC composites in commercial applications. The composites were examined to reveal the nature of substitutional B in oxidation, crystallinity and distribution preference in the composites. Substitutional B acts both a catalyst and an inhibitor

Young-Jae Lee; Hyeok-Jong Joo; Ljubisa R Radovic

2003-01-01

162

Separation and composition distribution determination of triblock copolymers by thermal field-flow fractionation.  

PubMed

Thermal field-flow fractionation (ThFFF) is used to separate a linear triblock copolymer of polystyrene, poly(tert-butyl acrylate), and poly(methyl methacrylate) by composition. Fractions were collected and subjected to off-line NMR analysis. The resultant mole fraction versus retention time plots for each of the three polymer components confirmed the success of the separation and yielded the composition distribution of the copolymer. The composition distribution was also obtained using a second approach that involved solving a series of equations comprised of polymer thermal diffusion coefficients and quasi-elastic light scattering, differential refractometry, and UV detector responses. Both sets of data showed similar trends of composition variations in each polymer component as a function of retention time. However, discrepancies were observed in the mole fraction values. The ability to compositionally separate and to determine composition distribution of copolymers is important as demonstrated by the presence of diblock impurities in the ThFFF with off-line NMR results. PMID:23975085

Ponyik, Charles A; Wu, David T; Williams, S Kim Ratanathanawongs

2013-11-01

163

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

164

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 Overwrapped 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 uncertainties 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

2007-01-01

165

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

166

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.

167

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

168

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

169

Visceral Adipocyte Hypertrophy is Associated With Dyslipidemia Independent of Body Composition and Fat Distribution in Women  

PubMed Central

OBJECTIVE We assessed whether subcutaneous and omental adipocyte hypertrophy are related to metabolic alterations independent of body composition and fat distribution in women. RESEARCH DESIGN AND METHODS Mean adipocyte diameter of paired subcutaneous and omental adipose tissue samples was obtained in lean to obese women. Linear regression models predicting adipocyte size in both adipose tissue depots were computed using body composition and fat distribution measures (n = 150). In a given depot, women with larger adipocytes than predicted by the regression were considered as having adipocyte hypertrophy, whereas women with smaller adipocytes than predicted were considered as having adipocyte hyperplasia. RESULTS Women characterized by omental adipocyte hypertrophy had higher plasma and VLDL triglyceride levels as well as a higher total-to-HDL cholesterol ratio compared with women characterized by omental adipocyte hyperplasia (P < 0.05). Conversely, women characterized by subcutaneous adipocyte hypertrophy or hyperplasia showed a similar lipid profile. In logistic regression analyses, a 10% enlargement of omental adipocytes increased the risk of hypertriglyceridemia (adjusted odds ratio [OR] 4.06, P < 0.001) independent of body composition and fat distribution measures. A 10% increase in visceral adipocyte number also raised the risk of hypertriglyceridemia (adjusted OR 1.55, P < 0.02). Associations between adipocyte size and homeostasis model assessment of insulin resistance were not significant once adjusted for adiposity and body fat distribution. CONCLUSIONS These results suggest that omental, but not subcutaneous, adipocyte hypertrophy is associated with an altered lipid profile independent of body composition and fat distribution in women.

Veilleux, Alain; Caron-Jobin, Maude; Noel, Suzanne; Laberge, Philippe Y.; Tchernof, Andre

2011-01-01

170

Perinatal bisphenol A exposure promotes hyperactivity, lean body composition, and hormonal responses across the murine life course  

PubMed Central

The development of adult-onset diseases is influenced by perinatal exposure to altered environmental conditions. One such exposure, bisphenol A (BPA), has been associated with obesity and diabetes, and consequently labeled an obesogen. Using an isogenic murine model, we examined the effects of perinatal exposure through maternal diet to 50 ng (n=20), 50 ?g (n=21), or 50 mg (n=18) BPA/kg diet, as well as controls (n=20) on offspring energy expenditure, spontaneous activity, and body composition at 3, 6, and 9 mo of age, and hormone levels at 9 and 10 mo of age. Overall, exposed females and males exhibited increased energy expenditure (P<0.001 and 0.001, respectively) throughout the life course. In females, horizontal and vertical activity increased (P=0.07 and 0.06, respectively) throughout the life course. Generally, body composition measures were not different throughout the life course in exposed females or males (all P>0.44), although body fat and weight decreased in exposed females at particular ages (all P<0.08). Milligram-exposed females had improved glucose, insulin, adiponectin, and leptin profiles (all P<0.10). Thus, life-course analysis illustrates that BPA is associated with hyperactive and lean phenotypes. Variability across studies may be attributable to differential exposure duration and timing, dietary fat and phytoestrogen content, or lack of sophisticated phenotyping across the life course.—Anderson, O.S., Peterson, K.E., Sanchez, B.N., Zhang, Z., Mancuso, P., Dolinoy, D.C. Perinatal bisphenol A exposure promotes hyperactivity, lean body composition, and hormonal responses across the murine life course.

Anderson, Olivia S.; Peterson, Karen E.; Sanchez, Brisa N.; Zhang, Zhenzhen; Mancuso, Peter; Dolinoy, Dana C.

2013-01-01

171

Chemical composition distribution analysis of photoresist copolymers and influence on ArF lithographic performance  

NASA Astrophysics Data System (ADS)

For getting information about the distribution of chemical composition, several model polymers were prepared under different polymerization conditions and were measured by critical adsorption point-liquid chromatography (CAP-LC). In the copolymer system of 8- and 9- (4-oxatricyclo[5.2.1.02,6]decane-3-one) acrylate (OTDA) and 2-ethyl-2-adamantyl methacrylate (EAdMA), the peak shapes of the CAP-LC chromatogram varied according to the polymerization condition although they indicated same molecular weight and averaged chemical composition. The difference of the CAP-LC elution curves was related to the chemical composition distribution of copolymers for CAP-LC measurement combined with proton nuclear magnetic resonance (1H-NMR). The terpolymers consisted of ?-hydroxy-?-butyrolactone methacrylate (GBLMA), 2-methyl-2-adamantyl methacrylate (MAdMA) and 1-hydroxy-3-adamantyl methacrylate (HAdMA) were prepared under various polymerization conditions. In the terpolymer system that had same molecular weight and average chemical composition, the solubility parameter (?) and the dissolution rate were measured. The ? value and the dissolution rate curve were different among these terpolymers. It was suggested that the ? value and the chemical composition distribution of these terpolymers have a significant influence on the lithographic performance.

Momose, Hikaru; Yasuda, Atsushi; Ueda, Akifumi; Iseki, Takayuki; Ute, Koichi; Nishimura, Takashi; Nakagawa, Ryo; Kitayama, Tatsuki

2007-03-01

172

Color preference, seasonality, spatial distribution and species composition of thrips (Thysanoptera: Thripidae) in northern highbush blueberries  

Microsoft Academic Search

We investigated color preference, seasonal abundance, spatial distribution and species composition of thrips in northern highbush blueberries, Vaccinium corymbosum L., in New Jersey (USA). White sticky traps were more attractive to thrips compared with yellow or blue traps. Thrips captures using white sticky traps showed that their flight activity begins 20–30 d after the onset of flowering, with 10, 50 and

C. R. Rodriguez-Saona; S. Polavarapu; J. D. Barry; D. Polk; R. Jörnsten; P. V. Oudemans; O. E. Liburd

2010-01-01

173

Dominant Mechanisms that Shape the Airborne Particle Size and Composition Distribution in Central California  

Microsoft Academic Search

The size and composition of ambient airborne particulate matter is reported for winter conditions at five locations in (or near) the San Joaquin Valley in central California. Two distinct types of airborne particles were identified based on diurnal patterns and size distribution similarity: hygroscopic sulfate\\/ammonium\\/nitrate particles and less hygroscopic particles composed of mostly organic carbon with smaller amounts of elemental

Jorn D. Herner; Qi Ying; Jeremy Aw; Oliver Gao; Daniel P. Y. Chang; Michael J. Kleeman

2006-01-01

174

Composition-resolved size distributions of volcanic aerosols in the Mt. Etna plumes  

Microsoft Academic Search

Particle size distributions for soluble and insoluble species in Mt. Etna's summit plumes were measured across an extended size range (10 nm < d < 100 ?m) using a combination of techniques. Automated scanning electron microscopy (QEMSCAN) was used to chemically analyze many thousands of insoluble particles (collected on pumped filters) allowing the relationships between particle size, shape, and composition

R. S. Martin; T. A. Mather; D. M. Pyle; M. Power; A. G. Allen; A. Aiuppa; C. J. Horwell; E. P. W. Ward

2008-01-01

175

Localized elastic modulus distribution of nanoclay\\/epoxy composites by using nanoindentation  

Microsoft Academic Search

The enhancement of mechanical properties by the use of nanoclay platelets in epoxy resin has been extensively investigated through numerous experimental techniques recently. Elastic modulus was obtained mainly from the tensile test of bone-like nanoclay\\/epoxy specimens. The results from the tensile test have only showed the globalized mechanical properties of composites and their localized elastic modulus distribution has been neglected.

Chun Ki Lam; Kin Tak Lau

2006-01-01

176

Cluster effect in frequency selective composites with randomly distributed long conductive fibres  

NASA Astrophysics Data System (ADS)

The transmission coefficient and effective permittivity of frequency selective composites with embedded long conductive fibres have been investigated experimentally and numerically at microwave frequencies. A cluster effect due to the overlapping of fibres is proposed to explain the dispersive microwave properties of composites with randomly distributed fibres. It is observed that the fibre clusters have multiple resonance frequencies that are related to the lengths of the cluster or those of the individual fibres. Interaction between overlapping fibres in a cluster cannot be eliminated by electrical isolation. Cluster effect can explain the appearance of broad resonance peak found in randomly distributed fibres, though the resonance frequency remains close to that of single fibre. This behaviour can be used in the design of composites with broadband frequency selective properties.

Liu, L.; Matitsine, S.; Gan, Y. B.; Rozanov, K. N.

2007-12-01

177

What is the difference? Evidence on the distribution of wealth, health, life expectancy, and health insurance coverage.  

PubMed

There is a literature of long standing that considers the relationship between income and differentials in mortality and morbidity, but information on differentials over the distribution of accumulated wealth have been far more scarce and subject to measurement problems. This paper provides evidence from the Survey of Consumer Finances, which is designed as a survey of wealth, on the distribution of wealth and income and how those distributions have shifted in recent years. Particular attention is paid to the distribution of wealth across minority groups and across age groups. The paper also examines the relationship between wealth and health status, life expectancy, and health insurance coverage. PMID:18680166

Kennickell, Arthur B

2008-09-10

178

Size distribution and composition of magnetic precipitates in amorphous Ni P alloy  

NASA Astrophysics Data System (ADS)

Primary crystallization of Ni(P) particles in hypoeutectic Ni-P amorphous alloy is investigated. Small-angle scattering with polarized neutrons is used to find simultaneously the particle size distribution and the size dependence of the particle composition. The size distribution consists of a peak at particle radius of ?1 nm and a tail spanning from ?2 to 15 nm.The composition of the particles forming the peak decreases from ?9 to ?2 at% P while their radii increase from 0.8 to 2 nm. The particles in the tail of the size distribution (2-15 nm) have nearly constant P content in the range of 0-2 at%.

Tatchev, Dragomir; Hoell, Armin; Kranold, Rainer; Armyanov, Stephan

2005-12-01

179

The effect of composite damage on fatigue life of the high pressure vessel for natural gas vehicles  

Microsoft Academic Search

In order to examine how the damages such as scratches, cuts and gouges on the composite materials have effects on the fatigue life of NGV vessels, several experiments on real vessels were conducted and finite element analyses were applied. The flaw depths of COPV used in the experiments were 1.5mm, 2.0mm, 3.0mm, and 4.0mm, while the flaw lengths were 50mm,

Young-Seob Kim; Lae-Hyun Kim; Ji-Sang Park

180

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

181

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

182

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

183

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.

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

2011-01-01

184

Reliability and life prediction of ceramic composite structures at elevated temperatures  

NASA Technical Reports Server (NTRS)

Methods are highlighted that ascertain the structural reliability of components fabricated of composites with ceramic matrices reinforced with ceramic fibers or whiskers and subject to quasi-static load conditions at elevated temperatures. Each method focuses on a particular composite microstructure: whisker-toughened ceramics, laminated ceramic matrix composites, and fabric reinforced ceramic matrix composites. In addition, since elevated service temperatures usually involve time-dependent effects, a section dealing with reliability degradation as a function of load history has been included. A recurring theme throughout this chapter is that even though component failure is controlled by a sequence of many microfailure events, failure of ceramic composites will be modeled using macrovariables.

Duffy, Stephen F.; Gyekenyesi, John P.

1994-01-01

185

Study of changes in life zone distribution in north-east China by climate–vegetation classification  

Microsoft Academic Search

Life zones and their changes in distribution in north-east China were studied based on climate–vegetation relationships. The warmth index (WI) and aridity index (the ratio of evaporation [evaporation rate, ER] to precipitation) were used to represent the site condition. The typical site condition of each vegetation type was determined as the classification criterion. The boundaries of the four potential vegetation

Qi-Jing Liu; Akihiko Kondoh; Nobuo Takeuchi

1998-01-01

186

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.

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

2011-01-01

187

Study on Composition Distribution and Ferromagnetism of Monodisperse FePt Nanoparticles  

Microsoft Academic Search

Monodisperse FePt nanoparticles with size of 4.5 and 6.0 nm were prepared by simultaneous reduction of platinum acetylacetonate\\u000a and thermal decomposition of iron pentacarbonyl in benzylether. The crystallography structure, size, and composition of the\\u000a FePt nanoparticles were examined by X-ray diffraction and transmission electron microscopy. Energy dispersive X-ray spectrometry\\u000a measurements of individual particles indicate a broad compositional distribution in both the

H. B. Wang; H. Wang; J. Zhang; F. J. Yang; Y. M. Xu; Q. Li

2010-01-01

188

Carbon black (CB)-filled conductive polymer composites: CB distribution and electrical properties  

NASA Astrophysics Data System (ADS)

Carbon black (CB) distribution and electrical properties of CB-filled conductive polymer composites were studied theoretically and experimentally in detail. Several important fundamental issues have been addressed. The CB distribution in a neat semicrystalline polymer was elucidated using RuO4 vapor staining technique and transmission electron microscopy (TEM). It has been found that CB particles were presented between the lamellae of the semicrystalline polymer. Based on the TEM results, schematic models for the CB distribution in neat semicrystalline polymers were developed. The CB distribution in binary immiscible polymer blends was investigated theoretically and experimentally. A thermodynamic model was derived to predict CB distribution in immiscible polymer blends. The predictions obtained by simulation agreed very well with the experimental observations. An in-complete wetting model was also developed for the case when one of the two polymer components has a very high viscosity. The positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effects of CB-filled a semicrystalline polyurethane-based shape memory polymer (SMP) composites were studied. It has been observed that apart from the CB content and the CB type, thermal aging could impose a pronounced influence on their PTC and NTC effects. The PTC and NTC effects of CB-filled immiscible polymer blends were investigated. Some novel physical effects, such as double-PTC effect, have been observed and explained in terms of their morphological features. Schematic models were also given to predict the PTC and NTC effects of the composites with different morphologies. The effects of mechanical strain on the electrical resistance of CB-filled neat polymers and immiscible polymer blends were elucidated. Positive strain coefficient (PSC) and negative strain coefficient (NSC) effects were observed and explained using tunneling junction and two-process models. A CB-filled neat polymer composite that is very sensitive to mechanical strain was also successfully prepared, which has potential applications in making strain sensors.

Feng, Jiyun

189

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

190

Model life table fitting by maximum likelihood estimation: a procedure to reconstruct paleodemographic characteristics from skeletal age distributions.  

PubMed

A procedure is presented that uses the regression coefficients for the Coale and Demeny west model life tables to model selected demographic characteristics from skeletal age-at-death distributions. Model death distributions were constructed and compared to a given skeletal distribution, using methods of maximum likelihood estimation to determine the best fit. Two chi-square tests are employed to evaluate the degree of fit. The resulting model includes estimates of demographic characteristics including gross reproductive rate, crude birth rate and life expectancy. The procedure is applied to three archaeological skeletal samples as test cases: two from eastern North America and one from Mexico. These display a range of correspondence (between the best fitting model and the data) from good to poor. The proposed procedure is a potentially powerful tool for both reconstructing paleodemographic rates and illuminating differences between typical human patterns and those found in archaeological populations. PMID:2750878

Paine, R R

1989-05-01

191

Hierarchical Process Composition: Dynamic maintenance of structure in a distributed environment. Doctoral thesis  

SciTech Connect

This dissertation is an in-depth study of a method, called Hierarchial Process Composition (HPC), for organizing, developing, and maintaining large distributed programs. HPC extends the process abstraction to nested collections of processes, allowing a multiprocess program in place of any single process, and provides a rich set of structuring mechanisms for building distributed applications. The emphasis in HPC is on structural and architectural issues in distributed software systems, especially interactions involving dynamic reconfiguration, protection, and distribution. The major contributions of this work come from the detailed consideration, based on case studies, formal analysis, and a prototype implementation, of how abstraction and composition interact in unexpected ways with each other and with a distributed environment. HPC ties processes together with heterogeneous interprocess communication mechanisms, such as TCP/IP and remote-procedure call. Explicit structure determines the logical connectivity between processes, masking differences in communication mechanisms. HPC supports one-to-one, parallel channel, and many-to-many (multicasting) connectivity. Efficient computation of end-to-end connectivity from the communication structure is a challenging problem, and a third-party connection facility is needed to implement dynamic reconfiguration when the logical connectivity changes.

Friedberg, S.A.

1988-01-01

192

Inference of stratospheric aerosol composition and size distribution from SAGE II satellite measurements  

NASA Technical Reports Server (NTRS)

A method for inferring stratospheric aerosol composition and size distribution from the water vapor concentration and aerosol extinction measurements obtained in the Stratospheric Aerosol and Gas Experiment (SAGE) II and the associated temperature from the NMC. The aerosols are assumed to be sulfuric acid-water droplets. A modified Levenberg-Marquardt algorithm is used to determine model size distribution parameters based on the SAGE II multiwavelength aerosol extinctions. It is found that the best aerosol size information is contained in the aerosol radius range between about 0.25 and 0.80 micron.

Wang, Pi-Huan; Mccormick, M. P.; Fuller, W. H.; Yue, G. K.; Swissler, T. J.; Osborn, M. T.

1989-01-01

193

Spatial Distribution of Yarns and Mechanical Properties in 3D Braided Tubular Composites  

NASA Astrophysics Data System (ADS)

This paper outlines a method which links the following analytically simulated events in sequence: (1) braiding of a 3D preform of tubular cross-section characterized by a set of braiding parameters defining the braiding setup and braiding steps; (2) geometric description of the yarn topology in the braided preform in explicit terms of a set of topological parameters defined by the preform shape and the braiding parameters; (3) description of the exact yarn distribution after preform consolidation with a binding matrix the values of the topological parameters are related to the exterior dimensions and surface features of the consolidated preform; and (4) forecasting the mechanical properties in the final composite via a suitable micromechanics model that takes into account the spatial yarn distribution in the composite and properties of the constituents.

Wang, Y. Q.; Wang, A. S. D.

1997-03-01

194

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

195

Effects of organic chlorine on the chemical composition and carbon number distribution of pyrolysis tars  

Microsoft Academic Search

This paper reports that in order to quantify the effects of chlorine on the composition and distribution of tar products, droplets containing varying amounts of toluene and chlorinated hydrocarbon additives were pyrolyzed in nitrogen. Three chlorinated organics were studied: o-dichlorobenzene, 1,2-dichloroethane, and trichloroethylene. It was found that the pyrolysis of chloro-organics results in the sequestration of hydrogen, leading to a

J. A. Mulholland; A. F. Sarofim; P. Sosothikul; A. L. Lafleur

1993-01-01

196

Automated shape composition based on cell biology and distributed genetic programming  

Microsoft Academic Search

Motivated by the ability of living cells to form specic shapes and structures, we present a computational approach using distributed genetic programming to discover cell-cell inter- action rules for automated shape composition. The key con- cept is to evolve local rules that direct virtual cells to pro- duce a self-organizing behavior that leads to the formation of a macroscopic, user-dened

Linge Bai; Manolya Eyiyurekli; David E. Breen

2008-01-01

197

Research on space charge distribution in composite of Low Density Polyethylene and Nano Silver  

Microsoft Academic Search

Double-solution mixture method was employed in the preparation of the composite of low density polyethylene\\/Nano-silver. Space charge distributions in samples with different nano-silver concentrations were measured using the pulsed electro-acoustic (PEA) method. In the experiment, samples were tested under three different levels of electrical stress, respectively: 10kV\\/mm, 30kV\\/mm and 50kV\\/mm. Discharge characteristics of the samples were examined as well. Test

Chuan Cai; Xuguang Li; Yi Yin; Zhe Li; Pingkai Jiang

2008-01-01

198

Source contributions to the size and composition distribution of urban particulate air pollution  

Microsoft Academic Search

A mechanistic air quality model has been constructed which is capable of predicting the contribution of individual emissions source types to the size- and chemical-composition distribution of airborne particles. This model incorporates all of the major aerosol processes relevant to regional air pollution studies including emissions, transport, deposition, gas-to-particle conversion and fog chemistry. In addition, the aerosol is represented as

Michael J Kleeman; Glen R Cass

1998-01-01

199

Effect of emissions control strategies on the size and composition distribution of urban particulate air pollution  

Microsoft Academic Search

The predicted behavior of the size- and chemical-composition distribution of airborne particles in the Los Angeles area is examined as it changes in response to specific emissions control strategies. Model calculations indicate that strategies currently envisioned to control the emissions of primary particles in the Los Angeles area effectively reduce the atmospheric concentrations of particles between 0.1--0.3 μm particle diameter

Michael J. Kleeman; Glen R. Cass

1999-01-01

200

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

NASA Technical Reports Server (NTRS)

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.

Des Marais, D. J.; Walter, M. R.

1999-01-01

201

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.

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

2014-01-01

202

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

203

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

204

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

National Technical Information Service (NTIS)

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 sta...

A. R. Shah D. N. Brewer P. L. N. Murthy

2001-01-01

205

Investigation of fatigue life for a medium scale composite wind turbine blade  

Microsoft Academic Search

In order to satisfy fatigue requirements in designing a cost effective wind turbine, the wind turbine blade, which is an expensive key component of the wind turbine system, must achieve very long operating life of 20–30 years. In this study, the fatigue life of a medium scale (750kW) horizontal axis wind turbine system (HAWIS), which has been developed by the

Changduk Kong; Taekhyun Kim; Dongju Han; Yoshihiko Sugiyama

2006-01-01

206

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

Microsoft Academic Search

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,

1990-01-01

207

Materials design for sustainability through life cycle modeling of engineered cementitious composites  

Microsoft Academic Search

Evaluating and enhancing construction material sustainability requires a life cycle perspective of the structures in which\\u000a they are used, since material properties and durability can have a profound effect on overall infrastructure performance.\\u000a A framework is proposed to evaluate and enhance the design of “greener” materials that integrates material design, structural\\u000a design, and life cycle modeling of the built system.

Alissa Kendall; Gregory A. Keoleian; Michael D. Lepech

2008-01-01

208

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.

209

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

210

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

211

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

212

Probabilistic model of the strength, crack resistance, and fatigue life of a unidirectionally reinforced fibrous composite  

Microsoft Academic Search

In this study, the authors investigated a class of kinetic equations of the statistical type, which are intended for evaluation of the reliability of unidirectionality reinforced fibrous composites and which are based on a Markovian type of discrete random processes.

Yu. V. Sokolkin; A. M. Postnykh; A. A. Chekalkin

1992-01-01

213

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

SciTech Connect

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, M.; Kedward, K.T.

1991-02-01

214

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

215

Effect of Calorie Restriction with or without Exercise on Body Composition and Fat Distribution  

PubMed Central

Context There is debate over the independent and combined effects of dieting and increased physical activity on improving metabolic risk factors (body composition and fat distribution). Objective The objective of the study was to conduct a randomized, controlled trial (CALERIE) to test the effect of a 25% energy deficit by diet alone or diet plus exercise for 6 months on body composition and fat distribution. Design This was a randomized, controlled trial. Setting The study was conducted at an institutional research center. Participants Thirty-five of 36 overweight but otherwise healthy participants (16 males, 19 females) completed the study. Intervention Participants were randomized to either control (healthy weight maintenance diet, n = 11), caloric restriction (CR; 25% reduction in energy intake, n = 12), or caloric restriction plus exercise (CR+EX; 12.5% reduction in energy intake + 12.5% increase in exercise energy expenditure, n = 12) for 6 months. Main Outcome Measures Changes in body composition by dual-energy x-ray absorptiometry and changes in abdominal fat distribution by multislice computed tomography were measured. Results The calculated energy deficit across the intervention was not different between CR and CR+EX. Participants lost approximately 10% of body weight (CR: - 8.3 ± 0.8, CR+EX: - 8.1 ± 0.8 kg, P = 1.00), approximately 24% of fat mass (CR: - 5.8 ± 0.6, CR+EX: - 6.4 ± 0.6 kg, P = 0.99), and 27% of abdominal visceral fat (CR: 0.9 ± 0.2, CR+EX: 0.8 ± 0.2 kg, P = 1.00). Both whole-body and abdominal fat distribution were not altered by the intervention. Conclusion Exercise plays an equivalent role to CR in terms of energy balance; however, it can also improve aerobic fitness, which has other important cardiovascular and metabolic implications.

Redman, Leanne M.; Heilbronn, Leonie K.; Martin, Corby K.; Alfonso, Anthony; Smith, Steven R.; Ravussin, Eric

2009-01-01

216

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

217

SPATIAL AND TEMPORAL DISTRIBUTIONS OF PACIFIC HAKE MERLUCCIUS PRODUCTUS LARVAE AND ESTIMATES OF SURVIVAL DURING EARLY LIFE STAGES  

Microsoft Academic Search

ABSTRACT Information on the distribution and abundance,of Pacific hake,larvae was,examined,for evidence,of strong or weak,year classes and larval drift. Esti- mates of larval mortality rates were derived and ap- plied to a life-table simulation,to examine,hy- potheses about factors that produce,strong or weak year classes. Indices of late-stage larval abundance indicated that strong year classes were established during the egg or larval

Anne Babcock Hollowed

218

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

219

Effects of hole machining defects on strength and fatigue life of composite laminates  

Microsoft Academic Search

The effects of hole machining defects on strength and fatigue life of carbon\\/epoxy laminates subjected to static and fatigue loading are presented. Dry specimens were subjected to pin loading and uniaxial compressive loading at room temperature. The KTH method, a new method which gives defect-free holes, was used to machine holes in the specimens. For comparison, holes were also machined

Erik Persson; Ingvar Eriksson; Leif Zackrisson

1997-01-01

220

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

221

Particle Distribution and Hot Workability of In Situ Synthesized Al-TiCp 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

2014-02-01

222

The Chemical Composition and Nitrogen Distribution of Chinese Yak (Maiwa) Milk  

PubMed Central

The paper surveyed the chemical composition and nitrogen distribution of Maiwa yak milk, and compared the results with reference composition of cow milk. Compared to cow milk, yak milk was richer in protein (especially whey protein), essential amino acids, fat, lactose and minerals (except phosphorus). The contents of some nutrients (total protein, lactose, essential amino acids and casein) were higher in the warm season than in the cold season. Higher ratios of total essential amino acids/total amino acids (TEAA/TAA) and total essential amino acids/total non essential amino acids (TEAA/TNEAA) were found in the yak milk from the warm season. However its annual average ratio of EAA/TAA and that of EAA/NEAA were similar to those of cow milk. Yak milk was rich in calcium and iron (p < 0.05), and thus may serve as a nutritional ingredient with a potential application in industrial processing.

Li, Haimei; Ma, Ying; Li, Qiming; Wang, Jiaqi; Cheng, Jinju; Xue, Jun; Shi, John

2011-01-01

223

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.

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

2012-01-01

224

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

225

Investigation of the relationship between chemical composition and size distribution of airborne particles by partial least squares and positive matrix factorization  

Microsoft Academic Search

(1) Two multivariate data analysis methods, partial least square (PLS) and positive matrix factorization (PMF), were used to analyze aerosol size distribution data and composition data. The relationships between the size distribution data and composition data were investigated by PLS. Three latent variables summarized chemical composition data and most variations in size distribution data especially for large particles and proved

Liming Zhou; Philip K. Hopke; Charles O. Stanier; Spyros N. Pandis; John M. Ondov; J. Patrick Pancras

2005-01-01

226

Thermal conductivity of diamond\\/copper composites with a bimodal distribution of diamond particle sizes prepared by pressure infiltration method  

Microsoft Academic Search

The thermal conductivity of diamond\\/copper composites with bimodal particle sizes was studied. The composites were prepared\\u000a through pressure infiltration of liquid copper into diamond preforms with a mixture of 40 and 100 ?m-size diamonds. The permeability\\u000a of the preforms with different coarse-to-fine volume ratios of diamonds was investigated. The thermal conductivity of the\\u000a diamond\\/copper composites with bimodal size distribution was

Chao Chen; Hong Guo; Ke Chu; Fazhang Yin; Ximing Zhang; Yuanyuan Han; Yeming Fan

2011-01-01

227

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

228

Experimental Investigation of the Shuttle Transportation System Composite Overwrapped Pressure Vessels for Stress Rupture Life  

NASA Technical Reports Server (NTRS)

A viewgraph presentation describing stress rupture testing on Composite Overwrapped Pressure Vessels (COPV) is shown. The topics include: 1) Purpose for Testing; 2) NASA WSTF COPV Test Program; 3) NASA WSTF Test Facilities; 4) COPV Impact Study; 5) Fluids Compatibility Testing; 6) Stress Rupture Testing; and 7) COPV Lifting.

Greene, Nathanael; Saulsberry, Regor; Yoder, Tommy; Forsyth, Brad; Carillo, Marlene; Thesken, John

2006-01-01

229

Computation Method on Fatigue Life of a Full Composite Wind Turbine Blade  

Microsoft Academic Search

The generation of load spectrum for epoxy resin blade of large-scale wind turbine is researched in this paper, so are an engineering estimating method of the fatigue failure and accumulated fatigue damage. Meanwhile, Load cases are considered, calculated and evaluated. First, a 3 dimensional finite element modal for calculation of fatigue failure is proposed based on the composite laminated technology

Jing Wang; Zhihua Huang; Yinghui Li

2010-01-01

230

Composite-flywheel durability and life. Part II. Long-term materials data  

SciTech Connect

Large-scale use of modern high-modulus composite materials for engineering structures has occurred only fairly recently, over a period of approximately fifteen years. This situation presents a major obstacle to designers who wish to determine the absolute or comparative properties of various composite materials. While compilations of elastic stiffness characteristics and quasi-static strength properties are available in compiled form for a number of common composite materials, it is much more difficult to obtain collected information concerning the long-term behavior, especially the fatigue behavior of composite materials and laminates. This data manual, which will be periodically updated, is an attempt to establish a beginning for such a compilation. While this attempt is modest, limited only to polymer matrix composite systems which are of interest or potential interest to energy storage systems, it does represent an effort to collect information which is otherwise widely scattered and to present the information in a manner which greatly facilitates comparison of properties between the various materials reported. The information is categorized in five sections which deal with graphite epoxy, glass epoxy, boron epoxy, Kevlar epoxy, and miscellaneous materials. Fatigue data were obtained from various sources and fit with a single relationship having the form S/S/sub ult/ = a+b/(log /sub 10/N)/sup x/. The curve that was found to be the best fit of the data in each case was plotted as a graph of normalized stress amplitude versus logarithm of the number of cycles to failure using the same scale (and plot size) for the ordinate and abscissa in each case in order to maximize the utility of these plots for comparison purposes. Other information that was available pertaining to the data and how it was obtained is listed.

Reifsnider, K.L.; Jen, M.H.R.

1982-09-01

231

Using and Distributing Spaceflight Data: The Johnson Space Center Life Sciences Data Archive  

NASA Technical Reports Server (NTRS)

Life sciences data collected before, during and after spaceflight are valuable and often irreplaceable. The Johnson Space Center Life is hard to find, and much of the data (e.g. Sciences Data Archive has been designed to provide researchers, engineers, managers and educators interactive access to information about and data from human spaceflight experiments. The archive system consists of a Data Acquisition System, Database Management System, CD-ROM Mastering System and Catalog Information System (CIS). The catalog information system is the heart of the archive. The CIS provides detailed experiment descriptions (both written and as QuickTime movies), hardware descriptions, hardware images, documents, and data. An initial evaluation of the archive at a scientific meeting showed that 88% of those who evaluated the catalog want to use the system when completed. The majority of the evaluators found the archive flexible, satisfying and easy to use. We conclude that the data archive effectively provides key life sciences data to interested users.

Cardenas, J. A.; Buckey, J. C.; Turner, J. N.; White, T. S.; Havelka,J. A.

1995-01-01

232

High-cycle fatigue life extension of glass fiber\\/polymer composites with carbon nanotubes  

Microsoft Academic Search

The present work shows that the addition of small volume fractions of multi-walled carbon nanotubes (CNTs) to the matrix results\\u000a in a significant increase in the high-cycle fatigue life. It is proposed that carbon nanotubes tend to inhibit the formation\\u000a of large cracks by nucleating nano-scale damage zones. In addition, the contribution to energy absorption from the fracture\\u000a of nanotubes

Christopher S. Grimmer; C. K. H. Dharan

2009-01-01

233

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

234

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

2014-06-12

235

On the Determination of a Safe Life for Classes of Distributions Classified by Failure Rate.  

National Technical Information Service (NTIS)

Using a lower tolerance bound as the derated life provides a guaranteed service period with the confidence level as a measure of safety in situations where mass production is contemplated. However, when only a limited number of items are to be produced, t...

S. C. Saunders

1966-01-01

236

Supporting the Life-Cycle of Multimedia and Visualization Using Distributed Performance Support Systems  

Microsoft Academic Search

UK Higher Education Institutions have invested significantly in the implementation of multimedia and visualization material in teaching, learning and assessment of civil and building engineering-with mixed results. The paper focuses on the use and life cycle of digital imagery and visualization material, which is embedded within multimedia teaching aids to improve student understanding. It describes ways in which these materials

N. M. Bouchlaghem; N. Beacham; Willy Sher

1999-01-01

237

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

238

Does diet breadth control herbivorous insect distribution size? Life history and resource outlets for specialist butterflies  

Microsoft Academic Search

Although butterfly distributions are known to be positively correlated with the number of larval hostplants used it is not known to what extent larval hostplant number uniquely influences butterfly distributions and to what extent effects are indirect through other variables. This issue is central to understanding the part generalism and specialism in host use play in organism persistence and conservation.

Roger L. H. Dennis; Tim G. Shreeve; Henry R. Arnold; David B. Roy

2005-01-01

239

Source apportionment of Baltimore aerosol from combined size distribution and chemical composition data  

NASA Astrophysics Data System (ADS)

Several multivariate data analysis methods have been applied to a combination of particle size and composition measurements made at the Baltimore Supersite. Partial least squares (PLS) was used to investigate the relationship (linearity) between number concentrations and the measured PM2.5 mass concentrations of chemical species. The data were obtained at the Ponca Street site and consisted of six days' measurements: 6, 7, 8, 18, 19 July, and 21 August 2002. The PLS analysis showed that the covariance between the data could be explained by 10 latent variables (LVs), but only the first four of these were sufficient to establish the linear relationship between the two data sets. More LVs could not make the model better. The four LVs were found to better explain the covariance between the large sized particles and the chemical species. A bilinear receptor model, PMF2, was then used to simultaneously analyze the size distribution and chemical composition data sets. The resolved sources were identified using information from number and mass contributions from each source (source profiles) as well as meteorological data. Twelve sources were identified: oil-fired power plant emissions, secondary nitrate I, local gasoline traffic, coal-fired power plant, secondary nitrate II, secondary sulfate, diesel emissions/bus maintenance, Quebec wildfire episode, nucleation, incinerator, airborne soil/road-way dust, and steel plant emissions. Local sources were mostly characterized by bi-modal number distributions. Regional sources were characterized by transport mode particles (0.2- 0.5?m).

Ogulei, David; Hopke, Philip K.; Zhou, Liming; Patrick Pancras, J.; Nair, Narayanan; Ondov, John M.

240

Chemically modified graphene/polyimide composite films based on utilization of covalent bonding and oriented distribution.  

PubMed

Herein, we have developed a rather simple composite fabrication approach to achieving molecular-level dispersion and planar orientation of chemically modified graphene (CMG) in the thermosetting polyimide (PI) matrix as well as realizing strong adhesion at the interfacial regions between reinforcing filler and matrix. The covalent adhesion of CMG to PI matrix and oriented distribution of CMG were carefully confirmed and analyzed by detailed investigations. Combination of covalent bonding and oriented distribution could enlarge the effectiveness of CMG in the matrix. Efficient stress transfer was found at the CMG/PI interfaces. Significant improvements in the mechanical performances, thermal stability, electrical conductivity, and hydrophobic behavior were achieved by addition of only a small amount of CMG. Furthermore, it is noteworthy that the hydrophilic-to-hydrophobic transition and the electrical percolation were observed at only 0.2 wt % CMG in this composite system. This facile methodology is believed to afford broad application potential in graphene-based polymer nanocomposites, especially other types of high-performance thermosetting systems. PMID:22496499

Huang, Ting; Lu, Renguo; Su, Chao; Wang, Hongna; Guo, Zheng; Liu, Pei; Huang, Zhongyuan; Chen, Haiming; Li, Tongsheng

2012-05-01

241

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

242

Progressive failure methodologies for predicting residual strength and life of laminated composites  

NASA Technical Reports Server (NTRS)

Two progressive failure methodologies currently under development by the Mechanics of Materials Branch at NASA Langley Research Center are discussed. The damage tolerance/fail safety methodology developed by O'Brien is an engineering approach to ensuring adequate durability and damage tolerance by treating only delamination onset and the subsequent delamination accumulation through the laminate thickness. The continuum damage model developed by Allen and Harris employs continuum damage laws to predict laminate strength and life. The philosophy, mechanics framework, and current implementation status of each methodology are presented.

Harris, Charles E.; Allen, David H.; Obrien, T. Kevin

1991-01-01

243

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

244

Temporal variations in the abundance and composition of biofilm communities colonizing drinking water distribution pipes.  

PubMed

Pipes that transport drinking water through municipal drinking water distribution systems (DWDS) are challenging habitats for microorganisms. Distribution networks are dark, oligotrophic and contain disinfectants; yet microbes frequently form biofilms attached to interior surfaces of DWDS pipes. Relatively little is known about the species composition and ecology of these biofilms due to challenges associated with sample acquisition from actual DWDS. We report the analysis of biofilms from five pipe samples collected from the same region of a DWDS in Florida, USA, over an 18 month period between February 2011 and August 2012. The bacterial abundance and composition of biofilm communities within the pipes were analyzed by heterotrophic plate counts and tag pyrosequencing of 16S rRNA genes, respectively. Bacterial numbers varied significantly based on sampling date and were positively correlated with water temperature and the concentration of nitrate. However, there was no significant relationship between the concentration of disinfectant in the drinking water (monochloramine) and the abundance of bacteria within the biofilms. Pyrosequencing analysis identified a total of 677 operational taxonomic units (OTUs) (3% distance) within the biofilms but indicated that community diversity was low and varied between sampling dates. Biofilms were dominated by a few taxa, specifically Methylomonas, Acinetobacter, Mycobacterium, and Xanthomonadaceae, and the dominant taxa within the biofilms varied dramatically between sampling times. The drinking water characteristics most strongly correlated with bacterial community composition were concentrations of nitrate, ammonium, total chlorine and monochloramine, as well as alkalinity and hardness. Biofilms from the sampling date with the highest nitrate concentration were the most abundant and diverse and were dominated by Acinetobacter. PMID:24858562

Kelly, John J; Minalt, Nicole; Culotti, Alessandro; Pryor, Marsha; Packman, Aaron

2014-01-01

245

Temporal Variations in the Abundance and Composition of Biofilm Communities Colonizing Drinking Water Distribution Pipes  

PubMed Central

Pipes that transport drinking water through municipal drinking water distribution systems (DWDS) are challenging habitats for microorganisms. Distribution networks are dark, oligotrophic and contain disinfectants; yet microbes frequently form biofilms attached to interior surfaces of DWDS pipes. Relatively little is known about the species composition and ecology of these biofilms due to challenges associated with sample acquisition from actual DWDS. We report the analysis of biofilms from five pipe samples collected from the same region of a DWDS in Florida, USA, over an 18 month period between February 2011 and August 2012. The bacterial abundance and composition of biofilm communities within the pipes were analyzed by heterotrophic plate counts and tag pyrosequencing of 16S rRNA genes, respectively. Bacterial numbers varied significantly based on sampling date and were positively correlated with water temperature and the concentration of nitrate. However, there was no significant relationship between the concentration of disinfectant in the drinking water (monochloramine) and the abundance of bacteria within the biofilms. Pyrosequencing analysis identified a total of 677 operational taxonomic units (OTUs) (3% distance) within the biofilms but indicated that community diversity was low and varied between sampling dates. Biofilms were dominated by a few taxa, specifically Methylomonas, Acinetobacter, Mycobacterium, and Xanthomonadaceae, and the dominant taxa within the biofilms varied dramatically between sampling times. The drinking water characteristics most strongly correlated with bacterial community composition were concentrations of nitrate, ammonium, total chlorine and monochloramine, as well as alkalinity and hardness. Biofilms from the sampling date with the highest nitrate concentration were the most abundant and diverse and were dominated by Acinetobacter.

Kelly, John J.; Minalt, Nicole; Culotti, Alessandro; Pryor, Marsha; Packman, Aaron

2014-01-01

246

Shape reconstruction of composite structures with monitoring of modeling changes using Brillouin scattering based distributed optical fiber strain sensor network  

Microsoft Academic Search

This research proposes a novel approach for the shape reconstruction of composite structures using one of Brillouinscattering based distributed optical fiber strain sensors, PPP-BOTDA system. We have constructed a displacement reconstruction algorithm using the finite element model of the target structure. The remarkable point is that, not only using raw distributed strain data, but using an index of the non-uniformity

Mayuko Nishio; Nobuo Takeda

2009-01-01

247

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

PubMed

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

2013-07-01

248

Life history, distribution and abundance of the giant earthworm Rhinodrilus alatus RIGHI 1971: conservation and management implications.  

PubMed

Rhinodrilus alatus is an endemic giant earthworm of the Brazilian Cerrado hotspot used as live bait for about 80 years. The goal of this study was to gather ecological data about this species, which will support the establishment of management strategies. The life history, distribution and abundance of R. alatus were investigated in Cerrado, pastures and Eucalyptus plantation areas following the harvesting activities of the local extractors of this species. We found that this earthworm is abundant in all of the sampled areas, showing its resilience to land-use conversion. The Capture Per Unit Effort was 4.4 ± 5 individuals per 100 metres of transect and 5.6 ± 3 individuals per hour. The earthworm's annual cycle is markedly seasonal, with an aestivation period throughout the driest and coldest season of the year. Significant differences in the length and diameter of the body and in the diameter and depth of the aestivation chambers were found between the juveniles and adults. The distribution range of the species was expanded from two to 17 counties. The life history, abundance, distribution and resilience of R. alatus to certain perturbations are key elements to be considered in conservation and management strategies for this species. PMID:24789384

Drumond, M A; Guimarães, A Q; El Bizri, H R; Giovanetti, L C; Sepúlveda, D G; Martins, R P

2013-11-01

249

Impact of filler size and distribution on roughness and wear of composite resin after simulated toothbrushing  

PubMed Central

Objectives Nanofilled composite resins are claimed to provide superior mechanical properties compared with microhybrid resins. Thus, the aim of this study was to compare nanofilled with microhybrid composite resins. The null hypothesis was that the size and the distribution of fillers do not influence the mechanical properties of surface roughness and wear after simulated toothbrushing test. Material and methods Ten rectangular specimens (15 mm x 5 mm x 4 mm) of Filtek Z250 (FZ2), Admira (A), TPH3 (T),Esthet-X (EX), Estelite Sigma (ES), Concept Advanced (C), Grandio (G) and Filtek Z350 (F) were prepared according to manufacturer's instructions. Half of each top surface was protected with nail polish as control surface (not brushed) while the other half was assessed with five random readings using a roughness tester (Ra). Following, the specimens were abraded by simulated toothbrushing with soft toothbrushes and slurry comprised of 2:1 water and dentifrice (w/w). 100,000 strokes were performed and the brushed surfaces were re-analyzed. Nail polish layers were removed from the specimens so that the roughness (Ra) and the wear could be assessed with three random readings (µm). Data were analyzed by ANOVA and Tukey's multiple-comparison test (?=0.05). Results Overall outcomes indicated that composite resins showed a significant increase in roughness after simulated toothbrushing, except for Grandio, which presented a smoother surface. Generally, wear of nanofilled resins was significantly lower compared with microhybrid resins. Conclusions As restorative materials suffer alterations under mechanical challenges, such as toothbrushing, the use of nanofilled materials seem to be more resistant than microhybrid composite resins, being less prone to be rougher and worn.

de OLIVEIRA, Gabriela Ulian; MONDELLI, Rafael Francisco Lia; CHARANTOLA RODRIGUES, Marcela; FRANCO, Eduardo Batista; ISHIKIRIAMA, Sergio Kiyoshi; WANG, Linda

2012-01-01

250

Monomer Abundance Distribution Patterns as a Universal Biosignature: Examples from Terrestrial and Digital Life  

Microsoft Academic Search

Organisms leave a distinctive chemical signature in their environment because they synthesize those molecules that maximize\\u000a their fitness. As a result, the relative concentrations of related chemical monomers in life-bearing environmental samples\\u000a reflect, in part, those compounds’ adaptive utility. In contrast, rates of molecular synthesis in a lifeless environment are dictated by reaction kinetics and thermodynamics,\\u000a so concentrations of related

Evan D. Dorn; Kenneth H. Nealson; Christoph Adami

2011-01-01

251

Prolongation of ifosfamide elimination half-life in obese patients due to altered drug distribution  

Microsoft Academic Search

The pharmacokinetics of intravenous ifosfamide were determined in 16 patients with carcinoma of the bronchus. In all 25% (4) of these patients were obese (i.e. >20% over their ideal body weight). The terminal elimination half-life (t1\\/2 ß) was found to be higher in the obese group than in the control group (6.36 h, range 5.77–7.45 h) vs 4.95 h, range

M. J. Lind; J. M. Margison; T. Cerny; N. Thatcher; P. M. Wilkinson

1989-01-01

252

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

253

Personality and Reduced Incidence of Walking Limitation in Late Life: Findings From the Health, Aging, and Body Composition Study  

PubMed Central

Objectives. To examine the association between openness to experience and conscientiousness and incident reported walking limitation. Method. The study population consisted of 786 men and women aged 71–81 years (M = 75 years, SD = 2.7) participating in the Health, Aging, and Body Composition—Cognitive Vitality Substudy. Results. Nearly 20% of participants (155/786) developed walking limitation during 6 years of follow-up. High openness was associated with a reduced risk of walking limitation (hazard ratio [HR] = 0.83, 95% confidence interval [CI] = 0.69–0.98), independent of sociodemographic factors, health conditions, and conscientiousness. This association was not mediated by lifestyle factors and was not substantially modified by other risk factors for functional disability. Conscientiousness was not associated with risk of walking limitation (HR = 0.91, 95% CI = 0.77–1.07). Discussion. Findings suggest that personality dimensions, specifically higher openness to experience, may contribute to functional resilience in late life.

Ferrucci, Luigi; Costa, Paul T.; Faulkner, Kimberly; Rosano, Caterina; Satterfield, Suzanne; Ayonayon, Hilsa N.; Simonsick, Eleanor M.

2012-01-01

254

[The antipyrine test in occupational medicine research--evaluation of individual reproducibility and frequency distribution of half-life].  

PubMed

The antipyrine half-life is a reliable index of biotransformation capacity of the liver. The half-lives were estimated in 137 subjects; the result was a logarithmic normal distribution of these parameters. Therefore our patients were subdivided into groups of so-called fast, intermediate and slow metabolisers (fast: t50 less than 7.6 h and slow: t50 greater than 14.9 h). Under conditions given here the intraindividual coefficient of variation was about 11.5%. The antipyrine elimination curves were calculated by a computer programme and the values were analysed statistically. PMID:2741499

Uhlig, H; Damrau, J; Skölziger, R

1989-02-01

255

[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

256

Distribution of gaseous and particulate organic composition during dark ozonolysis of monoterpenes  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) affects atmospheric composition, air quality and radiative transfer. However, major difficulties are encountered in the development of reliable models for SOA formation. Constraints on processes involved in SOA formation can be obtained by interpreting the speciation and evolution of organics in the gaseous and condensed phases simultaneously. In this study we investigate SOA formation from dark ozonolysis of ?-pinene with particular emphasis upon the mass distribution of gaseous and particulate organic species. Experiments were performed in the EUropean PHOtoREactor (EUPHORE) simulation chamber, including on-line gas-phase composition obtained from Chemical-Ionization-Reaction Time-Of-Flight Mass-Spectrometry (CIR-TOF-MS) measurements, and off-line analysis of SOA samples performed by Electrospray Ionisation Ion Trap Mass Spectrometry (ESI-MS). A detailed chamber box model designed to simulate SOA formation was developed for comparison with the experimental results, coupling an equilibrium gas/particle partitioning module to the ?-pinene oxidation scheme extracted from the Master Chemical Mechanism (MCMv3.1). The simulated temporal profile of SOA mass is in reasonable agreement with the observations, both in terms of the shape and magnitude. Sensitivity analysis highlights the importance of the choice of vapour pressure estimation method. Comparisons of the simulated mass spectrum with the CIR-TOF-MS mass spectrum show a similar mass distribution for gaseous organics. The ESI-MS measurements show the presence in the condensed phase of monomer and oligomer type organics. Comparisons of the simulated condensed phase mass spectrum with the ESI-MS mass spectrum show that most of the peaks in the monomer region are in reasonable agreement, i.e. explained in the simulation by the gas/particle partitioning of semi-volatile organic compounds (SVOC) formed during the ?-pinene gas-phase oxidation. The simulated composition is used to (i) propose chemical structures for the principal gaseous SVOC and condensed monomer organic species and (ii) explore the possible contribution of a range of accretion reactions occurring in the condensed phase. We find that oligomer formation through esterification reactions gives the best agreement between the observed and simulated mass spectra. Extending this approach to characterise the gaseous and particulate organic composition from other organic precursors, under various experimental conditions, will help greatly our understanding SOA formation, and therefore assist in the development of reliable SOA schemes for incorporation into 3D chemical transport models.

Camredon, Marie; Hamilton, Jacqui F.; Alam, Mohammed S.; Wyche, Kevin P.; Carr, Timo; White, Iain R.; Monks, Paul S.; Rickard, Andrew R.; Bloss, William J.

2010-05-01

257

Small Sample Acceptance Sampling Tables Using B10 Reliable Life and B10 Hazard Rate Criteria Based on the Weibull Distribution.  

National Technical Information Service (NTIS)

Acceptance criteria are established for B sub 10 reliable life and B sub 10 hazard (instantaneous failure) rate, assuming that a Weibull failure time distribution with shape parameter 0.6 = or < beta = or < 2.0 applies. B sub 10 reliable life is the time ...

D. J. Fisk

1968-01-01

258

Development of a Composite Lifestyle Index and Its Relationship to Quality of Life Improvement: The CLI Pilot Study  

PubMed Central

An important component to optimal health is quality of life (QOL). Several healthy lifestyle behaviors have independently shown to improve QOL. The simultaneous implementation of multiple lifestyle behaviors is thought to be difficult, and the current literature lacks the assessment of multiple lifestyle behaviors simultaneously with respect to the effect on QOL. This current pilot study sought to develop a method to quantify multiple lifestyle behaviors into a single index value. This value was then measured with QOL for a possible correlation. The results showed that it is possible to convert multiple raw healthy lifestyle data points into a composite value and that an improvement in this value correlates to an improved QOL. After 12 months of participation in a cardiovascular risk reduction program, study participants (N = 35) demonstrated a 37.4% (P < 0.001) improvement in the composite lifestyle index (CLI). The improved CLI demonstrated a correlation with a statistically significant improvement in how participants rated their overall health in 12 months (r = 0.701, P < 0.001) as well as the number of self-reported unhealthy days per month in 12 months (r = ?0.480, P = 0.004).

Lenz, Thomas L.; Gillespie, Nicole D.; Skradski, Jessica J.; Viereck, Laura K.; Packard, Kathleen A.; Monaghan, Michael S.

2013-01-01

259

Structure, Bonding, and Composition of Precambrian Carbonaceous Materials: Evidence of Early Life or Abiotic Processes?  

NASA Astrophysics Data System (ADS)

Robust detection of carbonaceous biosignatures is essential in the search for life elsewhere in the universe. However, the biogenicity of ancient kerogen-like residues on our own planet is suspect in some cases, such as microbe-like features within 3.5 Ga Apex cherts, potentially the oldest evidence of life on Earth, and stromatolite-like features within the slightly younger Strelley Pool Chert. We analyzed carbonaceous material in situ within these cherts using TEM, EELS, XANES, and SIMS. Samples were compared with Gunflint kerogen, graphite, amorphous carbon, and two abiotic Fischer-Tropsch-type (FTT) carbons. The two Archean samples are similar to Gunflint kerogen. Carbonaceous material is localized along quartz grain boundaries and at triple junctions, and when mechanically separated from chert particles it appears as long strings or crisscrossing networks. EELS spectra indicate a complex, kerogen-like substance distinct from both amorphous carbon and graphite, containing significant domains of polyaromatic carbon. The higher energy resolution of corresponding XANES spectra allows the resolution of a spectral peak consistent with carbonyl functional groups and a minor peak attributable to phenol groups. Minor concentrations of N, S, and P are detected with SIMS. These results strongly suggest that the ancient carbonaceous materials preserved within the Apex and Strelley Pool Cherts are indeed kerogen, and that the respective microbe-like and stromatolite- like features are also biogenic. FTT carbon is visually and spectrally distinct from ancient kerogen-like matter, but contains some similar characteristics. For example, EELS and XANES spectra of FTT material are similar except for much larger concentrations of carbonyl. We present one possible model for geologic processing of FTT products within an ancient hydrothermal vent. Hydrophobic FTT molecules may aggregate and precipitate on vent walls, protected by precipitated chert. During diagenesis, FTT material would lose volatile groups and condense to form polyaromatic domains, significantly reducing the intensity of the original carbonyl peak. Afterwards, the structure and bonding of this mature FTT material may be virtually identical to kerogen. This model depends on several assumptions: (1) the original FTT products are complex enough to withstand typical abiotic degradation processes during diagenesis; (2) N, S, and P can be easily incorporated into FTT products; (3) carbonyl groups on hydrocarbon chains can be efficiently transformed into hydroxyl groups on polyaromatic domains during condensation.

de Gregorio, B. T.; Sharp, T. G.; Flynn, G. J.

2006-12-01

260

Composites  

NSDL National Science Digital Library

In this activity, learners explore how composites work by creating and testing their own composite for an imaginary company. This activity shows learners that composites are simply materials that are made up of two or more visibly distinct substances. Use this activity to talk about how composites are everywhere in our lives.

Research, Cornell C.

2003-01-01

261

Chemical composition and size distribution of secondary organic aerosol formed from the photooxidation of isoprene.  

PubMed

Photooxidation of isoprene leads to the formation of secondary organic aerosol (SOA). In this study, the chemical composition of SOA formed from OH-initiated photooxidation of isoprene has been investigated with gas chromatography/mass spectrometry (GC/MS) and a home-made aerosol time-of-flight mass spectrometer. Sampling particles generated in a home-made smog chamber. The size distribution of SOA particles was detected by a TSI 3321 aerodynamic particle size spectrometer in real time. Results showed that SOA created by isoprene photooxidation was predominantly in the form of fine particles, which have diameters less than 2.5 microm. The obtained mass spectra of individual particles show that products of the OH-initiated oxidation of isoprene contain methyl vinyl ketone, methacrolein, formaldehyde, and some other hydroxycarbonyls. The possible reaction mechanisms leading to these products were also discussed. PMID:20108685

Liu, Xianyun; Zhang, Weijun; Wang, Zhenya; Zhao, Weixiong; Tao, Ling; Yang, Xibin

2009-01-01

262

Investigation on stress distribution of multilayered composite structure (MCS) using infrared thermographic technique  

NASA Astrophysics Data System (ADS)

In this paper, the thermoelastic stress analysis (TSA) on a multilayered composite structure (MCS) was investigated by means of lock-in thermographic image technique (LITI). The application of thermoelastic stress analysis on MCS becomes particularly complicated due to consisting of different material components, which determines the different thermoelastic coupling response depended on material thermal-physical property. The thermoelastic coupling constants (TCC) of GFRP, medium-carbon steel and foam were obtained through thermomechanical calibration experiments, respectively. An artificial neural network was proposed to determine the component of MCS. Comparisons between finite element analysis (FEA) and LITI measurement are reported. It is found that the stress distribution of MCS can be evaluated with good accuracies using LITI measurement.

Liu, Junyan; Gong, Jinlong; Liu, Liqiang; Qin, Lei; Wang, Yang

2013-11-01

263

[Spatial distribution and species composition of prosthecate bacteria in Lake Ba?kal].  

PubMed

From the water column of Lake Baikal, several strains of prosthecate bacteria belonging to the genera Caulobacter and Brevundimonas were isolated. In this article, the methods applied for their isolation and cell number determination are described; the occurrence frequency and spatial distribution of these microorganisms in the lake are demonstrated. Characterization of the species composition of cultivable and uncultivable prosthecate bacteria was carried out using the methods of traditional and molecular microbiology, respectively. A comparative phylogenetic analysis of the DNA sequences of uncultivable bacteria, which showed homology to the members of the alpha subclass of proteobacteria, was carried out. It was demonstrated that the lake water column is inhabited by uncultivable alpha-proteobacteria of uncertain phylogenetic affinity, in addition to representatives of the species Caulobacter vibrioides and C. leidyi, which were detected by traditional microbiological methods. PMID:17974212

Lapteva, N A; Bel'kova, N L; Parfenova, V V

2007-01-01

264

Distribution of composite CYP1A1 genotypes in Africans, African-Americans and Caucasians.  

PubMed

We present the genotype distribution of the CYP1A1 gene in a sample of over 300 subjects of various ethnic origins. Genotypes are presented as composites of eight possible alleles, taking into account the three major polymorphisms, including a recently described African-American-specific MspI RFLP. A new nomenclature system is presented for clarifying the various haplotypes. Interesting interracial differences in allelic frequencies and admixture rates were observed for the three polymorphisms. Because of the importance of the CYP1A1 gene (which encodes the aromatic hydrocarbon hydroxylase) as a biomarker of genetic susceptibility to environmental carcinogens such as polycyclic aromatic hydrocarbons, these data may provide a useful reference for future studies of relationships between CYP1A1 genotype and disease susceptibility. PMID:8860004

Garte, S J; Trachman, J; Crofts, F; Toniolo, P; Buxbaum, J; Bayo, S; Taioli, E

1996-01-01

265

LIFE-CYCLE CONSIDERATIONS FOR WIDE-AREA DISTRIBUTION OF MULTIMEDIA DATA  

Microsoft Academic Search

Various applications for world-wide multimedia object distribution arise currently as more and more companies integrate streamed continuous media elements in their web pages and as TV broadcasters add computer programs and data to their video streams.Currently, the streams that can be found on the web have only very small data volume, but as network capacities increase, the data volume that

Carsten Griwodz; Ralf Steinmetz

266

Characterization of distributions by relationships between failure rate and mean residual life  

Microsoft Academic Search

The characterizations described use relations between the failure rate function and conditional expectation. The theorems proved here extend the results of some authors and can be used in the context of the renewal process. The utility of these results is demonstrated by using them to characterize some common distributions

J. M. Ruiz; Jorge Navarro

1994-01-01

267

Distribution of gaseous and particulate organic composition during dark ?-pinene ozonolysis  

NASA Astrophysics Data System (ADS)

Secondary Organic Aerosol (SOA) affects atmospheric composition, air quality and radiative transfer, however major difficulties are encountered in the development of reliable models for SOA formation. Constraints on processes involved in SOA formation can be obtained by interpreting the speciation and evolution of organics in the gaseous and condensed phase simultaneously. In this study we investigate SOA formation from dark ?-pinene ozonolysis with particular emphasis upon the mass distribution of gaseous and particulate organic species. A detailed model for SOA formation is compared with the results from experiments performed in the EUropean PHOtoREactor (EUPHORE) simulation chamber, including on-line gas-phase composition obtained from Chemical-Ionization-Reaction Time-Of-Flight Mass-Spectrometry measurements, and off-line analysis of SOA samples performed by Ion Trap Mass Spectrometry and Liquid Chromatography. The temporal profile of SOA mass concentration is relatively well reproduced by the model. Sensitivity analysis highlights the importance of the choice of vapour pressure estimation method, and the potential influence of condensed phase chemistry. Comparisons of the simulated gaseous- and condensed-phase mass distributions with those observed show a generally good agreement. The simulated speciation has been used to (i) propose a chemical structure for the principal gaseous semi-volatile organic compounds and condensed monomer organic species, (ii) provide evidence for the occurrence of recently suggested radical isomerisation channels not included in the basic model, and (iii) explore the possible contribution of a range of accretion reactions occurring in the condensed phase. We find that oligomer formation through esterification reactions gives the best agreement between the observed and simulated mass spectra.

Camredon, M.; Hamilton, J. F.; Alam, M. S.; Wyche, K. P.; Carr, T.; White, I. R.; Monks, P. S.; Rickard, A. R.; Bloss, W. J.

2010-03-01

268

Fe-Stimulated Changes in Phytoplankton Biomarker Distributions and Carbon Isotopic Compositions During SOFeX  

NASA Astrophysics Data System (ADS)

We participated in the Southern Ocean Iron Experiment (SOFeX) to investigate phytoplankton community responses to four sequential iron enrichments (0.7 nM each) at 66°S, 172°W (Southern Patch). Pigment biomarker distributions and stable carbon isotopic compositions were monitored in the patch and at outside stations to infer changes in phytoplankton biomass, composition and growth physiology, with the ultimate goal of developing a set of proxies that can be used to test the iron hypothesis in the sedimentary record. Prior to iron addition, the phytoplankton community was dominated by (in order of decreasing biomass) diatoms, haptophytes, pelagophytes and dinoflagellates, as evidenced by measured distributions of fucoxanthin, 19'-hex-fucoxanthin, 19'-but-fucoxanthin and peridinin, respectively. A 10-fold increase in Chl concentration (0.2 to 2 mg m-3 was observed during the three-week period following the initial iron enrichment. Ratios of xanthophyll cycle carotenoids (diadinoxanthin and diatoxanthin) to photosynthetic carotenoids (w:w) decreased by a factor of 2 to 3 during bloom development, suggesting a reduction in the relative rates of non-photochemical quenching. The latter may also reflect a transition from iron- to light-limited growth inside the patch. Apparent net phytoplankton community growth rate (net photoautotrophic growth minus losses due to grazing, export and dilution) ranged from 0.06 to 0.10 d-1 based on temporal changes in phytoplankton C and Chl concentrations, respectively. Apparent net growth rates were also computed on the basis of observed increases in taxon-specific carotenoids and varied three-fold (diatoms: 0.11 d-1, pelagophytes: 0.08 d-1, dinoflagellates: 0.06 d-1, and haptophytes: 0.04 d-1). These class-specific differences in biomass accumulation may be a consequence of variable degrees of iron limitation and/or grazing selectivity. Preliminary carbon isotope data will be presented and discussed in the context of patch dynamics.

Bidigare, R. R.; Christensen, S.; Brown, S. L.; Selph, K. E.; Sheridan, C.; Cassar, N.; Landry, M. R.

2002-12-01

269

Where did the Trojan asteroids form? Constraints from composition and size distributions  

NASA Astrophysics Data System (ADS)

We propose to make near-infrared (0.8 - 2.5 ?m) spectral observations of 15 small to medium sized (<100 km) Jovian Trojan asteroids. These objects are part of a substantial population of primitive bodies trapped in Jupiter's stable Lagrange regions. Because they may have become trapped in these orbits at the end of the initial phase of planetary formation and subsequent migration, the physical properties of Trojans provide unique perspectives on chemical and dynamical processes that shaped the Solar System. Indeed, in recognition of their importance, the Trojans are one of only five allowable target destinations for NASA's next New Frontiers mission. Previous observations have identified two spectral classes, suggesting that the Trojans are comprised of two distinct compositional groups, perhaps representing distinct outer Solar System reservoirs for their formation. These new proposed observations will: (a) Enable a search for minor absorptions due to ices, organics, and/or silicates in the smallest Trojans yet observed, near and below the size regime thought to represent the largest collisional fragments from impacts within the Trojan clouds; and (b) Test whether the two spectral groups previously identified have different cumulative size distributions, which would suggest different internal strengths and support the hypothesis of distinct compositions and origins.

Emery, Joshua; Bell, Jim; Trilling, David; Patience, Jennifer; Brown, Mike

2014-08-01

270

Temperature Distribution in a Composite of Opaque and Semitransparent Spectral Layers  

NASA Technical Reports Server (NTRS)

The analysis of radiative transfer becomes computationally complex for a composite when there are multiple layers and multiple spectral bands. A convenient analytical method is developed for combined radiation and conduction in a composite of alternating semitransparent and opaque layers. The semi- transparent layers absorb, scatter, and emit radiation, and spectral properties with large scattering are included. The two-flux method is used, and its applicability is verified by comparison with a basic solution in the literature. The differential equation in the two-flux method Is solved by deriving a Green's function. The solution technique is applied to analyze radiation effects in a multilayer zirconia thermal barrier coating with internal radiation shields for conditions in an aircraft engine combustor. The zirconia radiative properties are modeled by two spectral bands. Thin opaque layers within the coating are used to decrease radiant transmission that can degrade the zirconia insulating ability. With radiation shields, the temperature distributions more closely approach the opaque limit that provides the lowest metal wall temperatures.

Siegel, Robert

1997-01-01

271

Spatial variation in life-history trade-offs results in an ideal free distribution in Black Brant Geese.  

PubMed

Ideal free distribution theory predicts that individuals distribute themselves so fitness is equal among patches. In this paper we evaluate all components of adult fitness to assess the hypothesis that individuals distribute themselves among seven brood-rearing areas so that trade-offs among different life history traits result in equal mean fitness among individuals using different areas. We used estimates of vital rates (clutch size, nest survival, pre-fledging survival, post-fledging survival, juvenile survival, and breeding probability) to estimate brood-rearing-area-specific per capita recruitment rates and survival for adult females. We summed brood-rearing-area-specific per capita recruitment and adult survival to calculate brood-rearing-area-specific estimates of lambda. We found little variation in lambda among brood-rearing areas and lifetime fitness implications of changing brood-rearing area were negligible (< 1% brood-rearing area mean fitness). We conclude that adult female Black Brant distribute themselves in an ideal free manner, resulting in equal fitness among females using these areas. PMID:25000763

Nicolai, Christopher A; Sedinger, James S; Ward, David H; Boyd, W Sean

2014-05-01

272

Tracing subsoil organic matter compositional changes by radiocarbon and plant leaf wax distributional changes  

NASA Astrophysics Data System (ADS)

The carbon pool in subsoils is thought to be considerably larger than in the upper 30 cm. However, factors like turnover, stabilization and distribution of organic matter (OM) are less well understood than in topsoils. The investigation of changes in OM composition with depth enables a better understanding of the peculiarity of subsoil OM in contrast to the already extensively studied topsoil OM. Analysis of long chained n-alkanes and n-fatty acids in soil profiles sampled in high resolution, combined with radiocarbon data of bulk soil, is a tool to demonstrate spatial distribution and the degradation of plant leaf wax-derived material as a defined source of soil organic. We analysed the OM in 3.15 m long soil transects under an even aged European beech (Fagus sylvatica L.) forest in Northern Germany (Grinderwald, Lower Saxony) for lipid and radiocarbon analysis. Samples were taken from a grid raster with eight sampling points increasing in distance to the main tree (45cm grid dimension) and from five depths (10, 35, 60, 85, 110 cm) resulting 40 samples per transect. Organic carbon contents in the podzolic Cambisol decrease from 1.69 % in the A-horizon to 0.02 % in the C-horizon at 110 cm depth. The distribution of organic carbon contents shows no significant trend with increasing distance to the beeches in all transects. We compare the distribution of long-chain n-alkanes (C27, C29 and C31) and n-fatty acids (>C20), known as components mainly derived from leaf waxes of higher plants, in the different transect/depth intervals. Distributional and quantitative changes in the transects, combined with bulk soil 14C-analyses, reflecting apparent mean residence time of OM, are used to identify how fast OM is degraded from surface to subsoil horizons. Furthermore, spatial OM heterogeneity in the transects is investigated. We expect a more significant heterogeneity in the lipid distribution and nearly similar decreasing contents for n-alkanes as well as n-fatty acids. Furthermore, the comparison between these two compound classes with increasing depth gives information on the accumulation of more resistant (aliphatic) and more easily degradable (carboxylic acids) OM components.

John, Stephan; Angst, Gerrit; Mueller, Carsten W.; Heinze, Stefanie; Marschner, Bernd; Rethemeyer, Janet

2014-05-01

273

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

274

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

275

Biology, Systematics, Life Cycle, and Distribution of Angiostrongylus cantonensis, the Cause of Rat Lungworm Disease  

PubMed Central

Angiostrongylus cantonensis is a metastrongyloid nematode in the family Angiostrongylidae. It is the cause of angiostrongyliasis (rat lungworm disease), which manifests as eosinophilic meningitis. First described in 1935 from rats in China, A. cantonensis was placed in the genus Parastrongylus in 1986, but most workers have not adopted this treatment. The taxonomy of A. cantonensis and related worms is largely based on adult morphology, notably of the male bursa. However, identification of infective third stage larvae is more difficult. The natural life cycle involves rats as the definitive host and snails or slugs as the intermediate host. Human infection, as accidental hosts, results in worms maturing in the brain, but dying there instead of moving back into the bloodstream, as in rats, thereby leading to eosinophilic meningitis. The disease is an emerging infectious disease; Angiostrongylus cantonensis continues to be reported in new regions beyond its native range.

2013-01-01

276

Effects of particle shape and size distributions on the electrical and magnetic properties of nickel\\/polyethylene composites  

Microsoft Academic Search

Electrical and magnetic properties of composite materials prepared by incorporating various nickel-based fillers of different shapes into polyethylene were investigated. The fillers used were nickel powders, nickel filamentary powders, nickel flakes, and nickel-coated graphite fibers. The particle-size distributions of the fillers were determined both before and after the processing of the composite samples. A wide range of filler volume fractions

H. S. Goektuerk; Thomas J. Fiske; Dilhan M. Kalyon

1993-01-01

277

Three-dimensional Finite Element Analysis of Stress Distribution in Composite Resin Cores with Fiber Posts of Varying Diameters  

Microsoft Academic Search

Using three-dimensional finite element analysis (3D-FEA), stress distributions in the remaining radicular tooth structure were investigated under the condition of varying diameters of fiber post for fiber post-reinforced composite resin cores (fiber post and core) in maxillary central incisors. Four 3D-FEA models were constructed: (1) fiber post (?1.2, ?1.4, and ?1.6 mm) and composite resin core; and (2) gold-cast post

Kazuhiko OKAMOTO; Teruo INO; Naoki IWASE; Eitaroh SHIMIZU; Megumi SUZUKI; Goh SATOH; Shuji OHKAWA; Masanori FUJISAWA

2008-01-01

278

Composition distribution and magnetic characteristics of sputtered Permalloy films with substrate angle  

SciTech Connect

Permalloy sputtered films for a thin magnetic head are deposited under precisely controlled conditions. The head pattern on a substrate shows not only a flat portion but also an inclined portion. The film characteristics on the inclined portions are important for a good thin-film head. Using a rf magnetron sputtering device with an 8-in. target, the angular distributions of sputtered Permalloy atoms (Ni and Fe), composition profile, and the magnetic characteristics were investigated. The results showed that the angular distributions of the Ni--Fe atoms depended on the rf power and were different from those of the cosine rule. A comparison of the film characteristics between the flat and inclined portions was carried out using a special substrate holder, in which nine glass substrates were fixed. The film thickness of the inclined portion differed, depending on the positions where the substrates were fixed. The coercive forces decreased with decreasing sputtering gas pressures, and those of thin films deposited on the inclined substrates were 20--50 A/m.

Nakagawa, Y.; Ohshita, Y.; Narishige, S.; Setoyama, E.

1989-05-01

279

Archaeal assemblages inhabiting temperate mixed forest soil fluctuate in taxon composition and spatial distribution over time.  

PubMed

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?m(2), 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

280

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.

Swanson, Colby A.; Sliwinski, Marek K.

2013-01-01

281

Atmospheric Neutral Analyzer (ANA) for In-situ Neutral Mass Composition and Velocity Distribution Measurements  

NASA Astrophysics Data System (ADS)

We present the design and the development of an atmospheric neutral analyzer, a new imaging instrument for in-situ measurements of both the mass composition of neutrals and their 2-dimensional velocities in the upper atmosphere. This instrument combines radio-frequency mass analysis and CCD particle imaging to provide images of detailed 2D velocity distribution functions of individual mass species. It comprises an entrance aperture, electron source, ion accelerator, a radio-frequency (RF) ion mass analyzer, and an imaging particle detector. The electron source ionizes a collimated fraction of the incident neutral particles while preserving their velocities. The ion accelerator accelerates all ionized neutrals to a fixed energy in the perpendicular direction to the entrance aperture plane. The mass analyzer further accelerates those of a specific velocity (and hence mass) for further detection, using a RF electric field of specific amplitude and frequency. In the imaging particle detector, the detected ions produce charges on the surface of a micro-channel plate (MCP) detector, and a phosphor screen converts these charges to a visual image of the incident velocity distribution and registers the image on a CCD detector.

Yau, A. W.; King, P.; Amerl, P. V.

2006-12-01

282

Spatial distributions of ultrafine particles and their behavior and chemical composition in relation to roadside sources  

NASA Astrophysics Data System (ADS)

Vertical and horizontal distributions of the chemical components of ultrafine particles (UFP; <0.1 ?m) in relation to roadside sources were investigated by using a newly developed PM 0.1 collection system with a UFP impactor filter (50% cut-off, 0.1 ?m; air flow rate, 40.0 L min -1). UFP were measured at a suburban roadside, at two background sites in Saitama (summer 2007 and winter 2008), and at two levels on a high-rise building in Tokyo (summer and winter 2005). The results from the high-rise building showed that ultrafine elemental carbon from vehicle exhaust can reach the upper atmosphere regardless of season because of the high diffusivity of UFP. The total concentrations of the carbonaceous and ionic components at all sites except the roadside site in summer were mostly within the same range. Therefore, UFP diffuse both vertically and horizontally, and its chemical components are distributed uniformly. The UFP composition in summer reflected not only the vehicle exhaust contribution but also photochemical formation, especially at the low-elevation sites, where the samplers were installed several meters above ground level. The results also showed that ionic components contributed to increases in the UFP levels.

Kudo, Shinji; Sekiguchi, Kazuhiko; Kim, Kyung Hwan; Sakamoto, Kazuhiko

2011-11-01

283

Sulfide isotopic compositions in shergottites and ALH84001, and possible implications for life on Mars  

SciTech Connect

The shergottite and ALH84001 meteorites hold keys for understanding geologic and possibly biologic processes on Mars. Recently, it has been proposed that carbonates in ALH84001, and the Fe-sulfides they contain, are products of extraterrestrial biogenic activity. Here we report ion microprobe analyses of sulfides in shergottites and ALH84001. The sulfur isotope ratios of igneous pyrrhotites in shergottites (mean {delta}{sup 34}S{sub CDT}: Shergotty = -0.4{per_thousand}, Zagami = +2.7{per_thousand}, EETA79001A = 1.9{per_thousand}, EETA79001B = -1.7{per_thousand}, LEW88516 = -1.9{per_thousand}, QUE94201 = +0.8{per_thousand}) are similar to those of terrestrial ocean-floor basalts, suggesting that the sulfur isotopic composition of the Martian mantle may be similar to that of the mantle of the Earth. The sulfur isotopic systematics of ALH84001 sulfides are distinct from the shergottites. Measured sulfur isotope ratios of eight pyrite grains ({delta}{sup 34}S{sub CDT} = +2.0 to +7.3{per_thousand}) in crushed zones confirm previously reported analyses of isotopically heavy sulfides and are indistinguishable from an Fe-sulfide zone within a carbonate globule ({delta}{sup 34}S{sub CDT} = +6.0{per_thousand}). Analyses of synthesized, fine-grained mixtures of sulfide, carbonate, and magnetite indicate than the measured sulfur isotope ratio is independent of the presence of carbonate and magnetite in the sputtered volume, confirming the accuracy of the analysis of the fine-grained sulfide in the carbonate globule. Terrestrial biogenic sulfate reduction typically results in light isotopic enrichments. The similarity of {delta}{sup 34}S values of the sulfides in ALH84001 imply that the Fe-sulfide zones within ALH84001 carbonates are probably not the result of bacterial reduction of sulfate. 38 refs., 3 figs., 1 tab.

Greenwood, J.P.; McSween, H.Y. Jr. [Univ. of Tennessee, Knoxville, TN (United States)] [Univ. of Tennessee, Knoxville, TN (United States); Riciputi, L.R. [Oak Ridge National Lab., TN (United States)] [Oak Ridge National Lab., TN (United States)

1997-10-01

284

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

2000-01-01

285

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

286

Anchovy shelf life as affected by different chilling methods during distribution.  

PubMed

Anchovies are a very labile fish and deteriorate fast under chilling conditions. In the South of Spain, fishing boats land their catches in wooden boxes with ice (12 to 14 kg). For some years now, fish processors have prepared this species for market distribution by placing about 7 kg fish in expanded polystyrene (EPS) boxes containing water and ice. Then, in the distribution market, boxes are dewatered and re-iced. Transportation of the fish in EPS boxes containing water and ice was recently forbidden on the grounds that boxes for transportation of fish in ice must have holes to let melted ice drain away. In this paper, the effect of preserving the anchovy in water and ice from landing to the distribution market was studied and compared with the more traditional methods of storing the fish in ice in either wooden or EPS boxes. Physical, chemical, microbiological, and sensory analyses were carried out over three different storage trials to account for the effect of seasonality. Little differences were found among lots, but some of the parameters showed that fish transported in water and ice did present less spoilage than fish stored in ice, especially when compared to the wooden boxes. According to these results, chilling of this fish in water and ice can be used as an alternative preserving method during transport. PMID:11848567

Careche, Mercedes; García, Raul; Borderías, Javier

2002-02-01

287

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

288

Composition and spatial distribution of volatile deposits in Loki Patera, Io  

NASA Astrophysics Data System (ADS)

Loki Patera is an active volcanic feature on Jupiter's moon Io which, at approximately 200 km in diameter, is perhaps the largest active lava lake in the solar system. Several images taken by the narrow angle camera of Voyager 1 during its 1979 flyby of Io reveal the patera surface is populated with many bright features roughly 2 to 4 km in diameter, colloquially referred to as "bergs." The bergs may be gas vents, similar to terrestrial fumaroles, which allow the sulfur-rich volatiles in the lava beneath the solid patera crust to escape and deposit on the surface. This thesis examines the spatial distribution of the bergs and their spectral signature in comparison with other features in the Loki region. The spectral analysis specifically focuses on the brightness in the blue and violet filters in an attempt to determine their composition and better understand how the bergs are related to the volcanic activity observed at Loki. The spatial distribution analysis reveals that the bergs are not randomly distributed across the patera surface and they avoid the inner and outer margins of the patera. There are no bergs within 4.96 km of the outer margin and only one berg occurs closer than 4.02 km to the inner margin. The bergs also avoid each other; bergs are on average 5.34 km from each other, and there is little deviation from this mean aside from the bergs in the southwest corner, which are spaced further apart. This corner has fewer bergs than elsewhere in the patera and is the site of the most volcanic activity. Data from the Voyager and Galileo missions were included in the spectral analyses. Assuming a macroscopic mixture, the spectral signature of the bergs indicate compositions ranging from bare basalt in the southwestern portion of the patera to approximately 43% sulfur and 57% basalt for the bergs. Other features around Loki, such as the large island in the middle of the patera, have slightly different brightnesses in the blue and violet filters which may indicate the presence of some SO 2 in addition to sulfur. There is evidence that a few of the largest bergs were not resurfaced between the Voyager and Galileo observations, suggesting some bergs may be fixed features. The bergs may be sulfur volatiles deposited on top of large mounds in the patera which could form during resurfacing events. One type of terrestrial lava mound, tumuli, typically have a linear crack running along the axis of the mound. If the bergs are a much larger version of tumuli seen on Earth, the axial fissure could provide a route for volatiles beneath the crust to escape onto the surface and deposit around the opening.

Landis, Claire E.

289

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

290

Longitudinal variation of thermospheric neutral winds and composition and their effects on the F region electron density distribution  

NASA Astrophysics Data System (ADS)

Longitudinal variations of thermospheric neutral winds and composition at mid-latitudes and their effects on the F region ionosphere electron density distribution are investigated using the Utah State University Global Assimilation of Ionospheric Measurements (USU-GAIM) model. For this study, seasonally averaged radio occultation data from the six FORMOSAT-3/COSMIC satellites were assimilated by the model. The data assimilation model is based on an Ensemble Kalman filter technique and a physics-based model of the ionosphere/plasmasphere (IPM). The model calculates 3-dimensional plasma density distribution in the ionosphere and estimates the physical drivers, including the magnetic meridional wind and neutral composition. The geographic zonal and meridional winds are then inferred from the magnetic meridional wind based on a decoupling procedure that considers the longitudinal variation of magnetic declination and a wind decomposition into zonal harmonics. In order to study the relative role of zonal variations of neutral wind, neutral composition and the magnetic field direction in the F region electron density distribution, additional simulations with the IPM model were performed considering different harmonic components of the estimated neutral wind and neutral composition. Model calculations were also performed using HWM93 and HWM07 empirical winds and the resulting densities and corresponding winds were compared with the USU-GAIM results. The results indicate that longitudinal changes in the geomagnetic field geometry play a major role in the F region electron density distribution but zonal changes in the neutral wind and composition can also be important.

Lomidze, L.; Scherliess, L.

2012-12-01

291

Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season  

Microsoft Academic Search

Aerosol particle number size distribution and chemical composition were measured at two low altitude sites, one urban and one relatively pristine valley, in Central Nepal during the 2009 pre-monsoon season (May-June). This is the first time that aerosol size distribution and chemical composition were measured simultaneously at lower elevations in the middle Himalayan region in Nepal. The aerosol size distribution

P. Shrestha; A. P. Barros; A. Khlystov

2010-01-01

292

Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season  

Microsoft Academic Search

Aerosol particle number size distribution and chemical composition were measured at two low altitude sites, one urban and one relatively pristine valley, in Central Nepal during the 2009 pre-monsoon season (May-June). This is the first time that aerosol size distribution and chemical composition were measured simultaneously at lower elevation in the Middle Himalayan region in Nepal. The aerosol size distribution

P. Shrestha; A. P. Barros; A. Khlystov

2010-01-01

293

Vertical distribution and composition of phytoplankton under the influence of an upper mixed layer.  

PubMed

The vertical distribution of phytoplankton is of fundamental importance for the dynamics and structure of aquatic communities. Here, using an advection-reaction-diffusion model, we investigate the distribution and competition of phytoplankton species in a water column, in which inverse resource gradients of light and a nutrient can limit growth of the biomass. This problem poses a challenge for ecologists, as the location of a production layer is not fixed, but rather depends on many internal parameters and environmental factors. In particular, we study the influence of an upper mixed layer (UML) in this system and show that it leads to a variety of dynamic effects: (i) Our model predicts alternative density profiles with a maximum of biomass either within or below the UML, thereby the system may be bistable or the relaxation from an unstable state may require a long-lasting transition. (ii) Reduced mixing in the deep layer can induce oscillations of the biomass; we show that a UML can sustain these oscillations even if the diffusivity is less than the critical mixing for a sinking phytoplankton population. (iii) A UML can strongly modify the outcome of competition between different phytoplankton species, yielding bistability both in the spatial distribution and in the species composition. (iv) A light limited species can obtain a competitive advantage if the diffusivity in the deep layers is reduced below a critical value. This yields a subtle competitive exclusion effect, where the oscillatory states in the deep layers are displaced by steady solutions in the UML. Finally, we present a novel graphical approach for deducing the competition outcome and for the analysis of the role of a UML in aquatic systems. PMID:19896955

Ryabov, Alexei B; Rudolf, Lars; Blasius, Bernd

2010-03-01

294

Undernutrition during early life alters neuropeptide Y distribution along the arcuate/paraventricular pathway.  

PubMed

Perinatal nutrient restriction exerts profound influences on brain development. Animals that suffer undernutrition during lactation also display impaired weight gain. Feeding behavior is mainly modulated by neural and hormonal inputs to the hypothalamus. The arcuate-paraventricular neuropeptidergic Y pathway has a prominent role in appetite regulation. The aim of this work was to study the effects of protein undernutrition during lactation on this hypothalamic pathway. We used rats from 5 to 60 postnatal (P) days whose dams were fed a 0% protein diet (PFG) or a normoprotein diet (CG) from P1 to P10. To reproduce the same amount of calorie ingested by the PFG we used an underfed group (UFG). Immunohistochemistry was performed to assess neuropeptide Y (NPY) distribution in the arcuate, periventricular and paraventricular nuclei. Our results showed a NPY immunostaining peak at P10 in all nuclei in CG animals. In UFG animals this peak was observed by P15, while, in the PFG animals only by P20. Our results suggest that the neuropeptidergic arcuate-paraventricular pathway suffered a delay in NPY distribution in undernourished animals, particularly those fed a 0% protein diet, reflecting an effect on this pathway maturation that could explain previously reported alterations on feeding behavior in these animals. PMID:24183962

Rocha, M L M; Fernandes, P P; Lotufo, B M; Manhães, A C; Barradas, P C; Tenorio, F

2014-01-01

295

A note on Brock: prioritarianism, egalitarianism and the distribution of life years.  

PubMed

The moral philosopher Dan Brock has argued that equality of health outcomes "even if achievable" is problematic as a goal in its own right-because it is open to the levelling down objection. The levelling down objection to egalitarianism has received surprisingly little attention in the bioethics literature on distribution of health and healthcare and deserves more attention. This paper discusses and accepts an example given by Brock showing that prioritarianism and egalitarianism may judge distributions of health outcomes differently. We should accept that levelling down is never a good thing, all things considered, but that equality often is. By discussing variants of Brock's example, it is demonstrated that if equality, prioritarianism and aggregation are combined, as in a population-wide summary measure of health, such as the health achievement index, this combined set of principles is not open to levelling down. The paper suggests-although a more thorough investigation of the properties of the achievement index is needed-that this measure (a) is always sensitive to inequality in health, (b) is always sensitive to average health, (c) can assign priority to those with lowest health outcomes and (d) is not sensitive to levelling down. Levelling down is not an embarrassment for egalitarians if they adopt a pluralist theory that integrates fairness with goodness. Equality is not the only value egalitarians promote. But equality is so important that we should not reject it. PMID:19717696

Norheim, O F

2009-09-01

296

In situ formation by laser cladding of a TiC composite coating with a gradient distribution  

Microsoft Academic Search

An in situ method was developed to produce an Ni alloy composite coating reinforced by in situ reacted TiC particles with a gradient distribution, using one-step laser cladding with a pre-placed powder mixture on a 5CrMnMo steel substrate. Dispersed and ultra-fine TiC particles were formed in situ in the coating. Most of the TiC particles, with a marked gradient distribution,

Xiaolei Wu

1999-01-01

297

Estimating primary mass composition at energies 1017-1018 eV from EAS radio emission lateral distribution  

NASA Astrophysics Data System (ADS)

Distribution of maximum depths of extensive air showers (EAS) with energies of 1017-1018 eV is restored from the lateral distribution of EAS radio emission measured by the LOPES experiment (40-80 MHz). Dependence of the EAS maximum depth on its energy is constructed and mass composition of cosmic rays is estimated. It follows from the obtained dependencies that the fraction of light cosmic ray's nuclei increases in the energy range under consideration.

Kalmykov, N. N.; Konstantinov, A. A.; Vedeneev, O. V.

2013-02-01

298

Atmospheric Neutral Analyzer for In-Situ Neutral Mass Composition and Velocity Distribution Measurements in Ionosphere-Thermosphere Coupling Studies  

Microsoft Academic Search

The atmospheric neutral analyzer (ANA) is a new instrument for measuring in-situ the mass composition and velocity distributions of neutrals in the upper atmosphere. It combines radio frequency (RF) mass analysis and charge-coupled device (CCD) particle imaging to provide images of detailed two-dimensional velocity distribution functions of individual mass species. It comprises an entrance aperture (EA), electron source (ES), ion

P. V. Amerl; E. P. King; A. W. Yau

2006-01-01

299

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

300

Assessing historical fish community composition using surveys, historical collection data, and species distribution models.  

PubMed

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

301

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.

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

2011-01-01

302

Composition and distribution of sublittoral zoobenthos in Kemskaya Bay of the White Sea  

NASA Astrophysics Data System (ADS)

Data on the distribution of the zoobenthos in Kemskaya Bay (the Kem’ River estuary and the White Sea), which is subject to the strong influence of the river discharge, are presented. The number of species at the sampling stations varied from 4 to 65. The density of the communities and the zoobenthos biomass ranged from 342 ± 68 to 4293 ± 96 ind./m2 and from 0.418 ± 0.081 to 1975.22 ± 494.36 g/m2, respectively. The Shannon index values varied between 1.19 to 4.7 bit/ind. At the upper part of the estuary, detritivores dominated, while, in the central part and at outlets, sestonophages prevailed. The changes in the quantitative indices of the zoobenthos along the gradient of the water salinity were traced, and the relations of these indices with seven more environmental factors were revealed. It was found that the species composition, the biodiversity, and the trophic structure of the zoobenthos significantly correlate with some of the above mentioned parameters. Multiple regression analysis was used to assess the combined effect of the factors, and it revealed which of them play a determining role in Kemskaya Bay: for the species composition, these are the depth, the water color, and the content of total suspended matter; for the number, these are the contents of pelite and Corg in the bottom sediments. The biomass depends on the water salinity, the water chromaticity, and the Corg contents in the sediments and suspended matter. The Shannon index value is determined by the water color, the Corg contents in the sediments, and the pelite content. The calculations of the ecological stress values revealed two zones with an unstable state of the zoobenthos.

Denisenko, N. V.

2009-12-01

303

Life span and tissue distribution of 111indium-labeled blood platelets in hypomagnesemic lambs  

SciTech Connect

Circulating platelets may be activated by exposed triple-helical collagen in atherosclerotic lesions in Mg-deficient ruminants. Autologous platelets, labeled in vitro with 111In and determined to be active, were injected into 5 hypomagnesemic and 3 control lambs fed semipurified diets with 100 or 2,000 mg of Mg/kg of feed for 3 months. During the first 68 hours, 111In concentrations were 11 times higher in packed cells than in plasma. Packed-cell 111In increased 60% during the first 2 hours, probably due to initial tissue sequestration and later release of labeled platelets. Thereafter, platelet half-life span averaged 60 and 63 hours for hypomagnesemic and control lambs. After 68 hours, lambs were injected with native vascular collagen fibrils at 500 micrograms/kg of body weight to initiate reversible platelet aggregation. Within 1 minute, 83% of packed-cell 111In disappeared from circulation. Thirty minutes later, the lambs were euthanatized and necropsied and in the lungs, liver, and spleen, 111In averaged 24%, 19%, and 9%, respectively, of 111In injected 68 hours earlier. Organ deposits were not affected by Mg intake, but 111In in the lungs was somewhat lower in 2 lambs injected with inactivated collagen. Pathologic changes induced by reversible platelet aggregation were compatible with right ventricular failure complicated by pulmonary edema, similar to changes in hypomagnesemic lambs that died spontaneously. Platelets in blood exposed to vascular lesions in hypomagnesemic ruminants could be a major mortality risk factor in grass tetany disease.

Schneider, M.D.; Miller, J.K.; White, P.K.; Ramsey, N.

1983-05-01

304

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

305

Groundwater age, life expectancy and transit time distributions in advective dispersive systems; 2. Reservoir theory for sub-drainage basins  

NASA Astrophysics Data System (ADS)

Groundwater age and life expectancy probability density functions (pdf) have been defined, and solved in a general three-dimensional context by means of forward and backward advection-dispersion equations [Cornaton F, Perrochet P. Groundwater age, life expectancy and transit time distributions in advective-dispersive systems; 1. Generalized reservoir theory. Adv Water Res (xxxx)]. The discharge and recharge zones transit time pdfs were then derived by applying the reservoir theory (RT) to the global system, thus considering as ensemble the union of all inlet boundaries on one hand, and the union of all outlet boundaries on the other hand. The main advantages in using the RT to calculate the transit time pdf is that the outlet boundary geometry does not represent a computational limiting factor (e.g. outlets of small sizes), since the methodology is based on the integration over the entire domain of each age, or life expectancy, occurrence. In the present paper, we extend the applicability of the RT to sub-drainage basins of groundwater reservoirs by treating the reservoir flow systems as compartments which transfer the water fluxes to a particular discharge zone, and inside which mixing and dispersion processes can take place. Drainage basins are defined by the field of probability of exit at outlet. In this way, we make the RT applicable to each sub-drainage system of an aquifer of arbitrary complexity and configuration. The case of the well-head protection problem is taken as illustrative example, and sensitivity analysis of the effect of pore velocity variations on the simulated ages is carried out.

Cornaton, F.; Perrochet, P.

2006-09-01

306

The role of microstructure and phase distribution in the failure mechanisms and life prediction model for PSZ coatings  

NASA Technical Reports Server (NTRS)

Partially Stabilized Zirconia (PSZ) may become widely used for Thermal Barrier Coatings (TBC). Failure of these coatings can occur due to thermal fatigue in oxidizing atmospheres. The failure is due to the strains that develop due to thermal gradients, differences in thermal expansion coefficients, and oxidation of the bond coating. The role of microstructure and the cubic, tetragonal, and monoclinic phase distribution in the strain development and subsequent failure will be discussed. An X-ray diffraction technique for accurate determination of the fraction of each phase in PSZ will be applied to understanding the phase transformations and strain development. These results will be discussed in terms of developing a model for life prediction in PSZ coatings during thermal cycling.

Sisson, R. D., Jr.; Sone, Ichiro; Biederman, R. R.

1985-01-01

307

Free vibrations of laminated composite shells with uniformly distributed attached mass using higher order shell theory including stiffness effect  

NASA Astrophysics Data System (ADS)

In this paper, free vibrations of a cross-ply composite shell with or without a uniformly distributed attached mass are analyzed using higher order shell theory. The results of free vibrations without distributed attached mass are validated by previous literatures. The stiffness effect of this distributed attached mass are also considered and compared with those well-known published results in which this effect is ignored. Various results for composite shells under a variety of conditions such as variations in the thickness of the shell, variation in the thickness of the distributed attached mass, variation in the radii of curvatures and various elasticity moduli are presented in this paper. In some cases, to verify the novel results, first-order shear deformation theory (FSDT) is also used. In this paper, parameters which influence the natural frequencies of the shells with attached mass including the stiffness of the mass are investigated. Parameters which are investigated in this paper are thickness of the shell, thickness of the distributed attached mass, elasticity moduli of the distributed attached mass and radius of curvatures of shells. Increasing the thickness or elasticity moduli of the distributed attached mass will increase the fundamental natural frequency of the shell. The effect of the stiffness of the distributed attached mass is decreased by decreasing the radii of curvatures or increasing the thickness of the shells.

Khalili, S. M. R.; Tafazoli, S.; Malekzadeh Fard, K.

2011-12-01

308

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

309

DNA search efficiency is modulated by charge composition and distribution in the intrinsically disordered tail  

PubMed Central

Intrinsically disordered tails are common in DNA-binding proteins and can affect their search efficiency on nonspecific DNA by promoting the brachiation dynamics of intersegment transfer. During brachiation, the protein jumps between distant DNA regions via an intermediate state in which the tail and globular moieties are bound to different DNA segments. While the disordered tail must be long and positively charged to facilitate DNA search, the effect of its residue sequence on brachiation is unknown. We explored this issue using the NK-2 and Antp homeodomain transcription factors. We designed 566 NK-2 tail-variants and 55 Antp tail-variants having different net charges and positive charge distributions and studied their dynamics and DNA search efficiencies using coarse-grained molecular dynamics simulations. More intersegment transfers occur when the tail is moderately positively charged and the positive charges are clustered together in the middle of the tail or towards its N terminus. The presence of a negatively charged residue does not significantly affect protein brachiation, although it is likely that the presence of many negatively charged residues will complicate the DNA search mechanism. A bioinformatic analysis of 1,384 wild-type homeodomains illustrates that the charge composition and distribution in their N-tail sequences are consistent with an optimal charge pattern to promote intersegment transfer. Our study thus indicates that the residue sequence of the disordered tails of DNA-binding proteins has unique characteristics that were evolutionarily selected to achieve optimized function and suggests that the sequence-structure-function paradigm known for structured proteins is valid for intrinsically disordered proteins as well.

Vuzman, Dana; Levy, Yaakov

2010-01-01

310

The microscopic state of the solar wind: Links between composition, velocity distributions, waves and turbulence  

NASA Technical Reports Server (NTRS)

An overview is given of the microscopic state of the solar wind with emphasis on recent Ulysses high-latitude observations and previous Helios in-ecliptic observations. The possible links between composition, ionization state. velocity distribution functions of electrons, protons and heavy ions. kinetic plasma waves and MHD-scale turbulence are elaborated. Emphasis is placed on a connection of interplanetary kinetic-scale phenomena with their generating microscopic processes in the corona. The fast streams seem to consist of mesoscale pressure-balanced plasma filaments and magnetic flux tubes, reminiscent of the supergranular-size structures building the open corona, from which copious Alfven waves emanate. The wind from the magnetically structured and active corona shows developed compressive turbulence and considerable abundance and ionization state variations. Some modelling attempts to explain the observed element fractionation are briefly reviewed. The causes of the nonthermal particle features. such as proton-ion differential streaming, ion beams. temperature anisotropies, and skewed distributions associated with collisionless heat conduction, are ultimately to be searched in the fact, that the corona is never quiescent but fundamentally variable in space and time. Consequently, the radial evolution of the internal state of the wind resembles at all latitudes a complicated relaxation process, in the course of which the free (in comparison with LTE conditions) particle kinetic energy is converted into plasma waves and MHD turbulence on a wide range of scales. This leads to intermittent wave-particle interactions and unsteady anomalous transport, mixed with the weak effects of the rare Coulomb collisions. Spherical expansion and large-scale inhomogeneity forces the wind to attain microscopically a complex internal state of dynamic statistical equilibrium.

Marsch, E.

1995-01-01

311

Pyrolysis as a way to close a CFRC life cycle: Carbon fibers recovery and their use as feedstock for a new composite production  

NASA Astrophysics Data System (ADS)

Pyrolysis is shown to be an efficient method for recycling carbon fiber composites in the form of both uncured prepregs scraps or as cured end-of-life objects. The pyrolytic process leads to different products in three physical states of matter. The gaseous fraction, called syngas, can be used as energy feedstock in the process itself. The oil fraction can be used as fuel or chemical feedstock. The solid residue contains substantially unharmed carbon fibers that can be isolated and recovered for the production of new composite materials, thus closing the life cycle of the composite in a "cradle to cradle" approach. All the pyrolysis outputs were thoroughly analyzed and characterized in terms of composition for oil and gas fraction and surface characteristics of the fibers. In particular, it is of paramount importance to correlate the aspect and properties of the fibers obtained with different composite feedstock and operational conditions, that can be significantly different, with the reinforcing performance in the newly produced Recycled Carbon Fibers Reinforced Polymers. Present results have been obtained on a pyrolysis pilot plant that offers the possibility of treating up to 70kg of materials, thus leading to a significant amount of products to be tested in the further composites production, focused mainly on chopped carbon fiber reinforcement.

Giorgini, Loris; Benelli, Tiziana; Mazzocchetti, Laura; Leonardi, Chiara; Zattini, Giorgio; Minak, Giangiacomo; Dolcini, Enrico; Tosi, Cristian; Montanari, Ivan

2014-05-01

312

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 ...

313

Composition and Organic Carbon Distribution of Organomineral Complex in Black Soil under Different Land Uses and Management Systems  

Microsoft Academic Search

Organomineral complexes form the basis of soil fertility and have significant effects on the soil environment. In this research, we aimed to study the composition and organic carbon (C) distribution of organomineral complexes in a black soil under different land uses and management by means of ultrasonic dispersion and particle assortment. The results showed that the fine sand–size complex (20–200

Xueying Hou; Xiaozeng Han; Haibo Li; Baoshan Xing

2010-01-01

314

Composition and distribution of nitrogen and population of bacteroids in nodules of Chinese milk vetch, red clover, and soybean  

Microsoft Academic Search

Generally, in Chinese milk vetch (CV) and red clover (RC) the symbiotic N2 fixation activity is higher than in soybean (SB) per unit of nodule mass. To analyze the cause of this phenomenon, the composition and distribution of the nodule nitrogen and population as well as some biochemical properties of the nodule bacteroids of the above plants cultured in vermiculite

Jianzhong Wu; Yasuhiro Arima

1993-01-01

315

On the chemical state and distribution of Zr- and V-based additives in reactive hydride composites  

NASA Astrophysics Data System (ADS)

Reactive hydride composites (RHCs) are very promising hydrogen storage materials for future applications due to their reduced reaction enthalpies and high gravimetric capacities. At present, the materials' functionality is limited by the reaction kinetics. A significant positive influence can be observed with addition of transition-metal-based additives. To understand the effect of these additives, the chemical state and changes during the reaction as well as the microstructural distribution were investigated using x-ray absorption near-edge structure (XANES) spectroscopy and anomalous small-angle x-ray scattering (ASAXS). In this work, zirconium- and vanadium-based additives were added to 2LiBH4-MgH2 composites and 2LiH-MgB2 composites and measured in the vicinity of the corresponding absorption edge. The measurements reveal the formation of finely distributed zirconium diboride and vanadium-based nanoparticles. The potential mechanisms for the observed influence on the reaction kinetics are discussed.

Bösenberg, U.; Vainio, U.; Pranzas, P. K.; Bellosta von Colbe, J. M.; Goerigk, G.; Welter, E.; Dornheim, M.; Schreyer, A.; Bormann, R.

2009-05-01

316

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

317

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.

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

2010-01-01

318

New Method for Determining the Elemental Composition and Distribution in Semiconductor Core-Shell Quantum Dots  

PubMed Central

In the biological sciences the use of core-shell quantum dots (QDs) has gained wide usage, but analytical challenges still exist for characterizing the QD structure. The application of energy-dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy (XPS) to bulk materials is relatively straightforward, however, for meaningful applications of surface science techniques to multilayer nanoparticles requires novel modifications and analysis methods. To experimentally characterize the elemental composition and distribution in CdSe/CdS/ZnS QDs, we first develop a XPS signal subtraction technique capable of separating the overlapped selenium 3s (core) and sulfur 2s (shell) peaks (both peaks have binding energies near 230eV) with higher precision than is typically reported in the nanoparticle literature. This method is valid for any nanoparticle containing selenium and sulfur. Then we apply a correction formula to the XPS data and determine that the 2 nm stoichiometric CdSe core is surrounded by 2 CdS layers and a stoichimetric ZnS monolayer. These findings and the multi-approach methodology represent a significant advancement in the detailed surface science study of multi-layer nanoparticles. In agreement with recent surprising findings, the time-of-flight secondary mass spectrometry measurements suggest that the surface sites of the QDs used in this study are primarily covered with a mixture of octadecylphosphonic acid and trioctylphophine oxide.

Zorn, Gilad; Dave, Shivang R.; Gao, Xiaohu; Castner, David G.

2011-01-01

319

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

320

Composition, physiochemical properties, nitrogen fraction distribution, and amino acid profile of donkey milk.  

PubMed

This study investigated the changes in chemical composition, nitrogen fraction distribution, and AA profile of milk samples obtained during lactation from the Jiangyue breed of donkey in Northwest China. Results showed that donkey milk contained 9.53% total solids, 1.57% protein, 1.16% fat, 6.33% lactose, and 0.4% ash on average, which is more similar to mare and human milk than to the milk of other mammals. Throughout the lactation investigated, pH and density were constant, protein and ash content showed an apparent negative trend (an increase in lactose content during 120 d postpartum, followed by a decrease), fat content exhibited wide variability, and variations in the content and percentage of whey protein, casein, and AA were small. The casein to whey protein ratio of 52:37 was between the lower value of human milk and the higher value of cow milk. Sodium dodecyl sulfate-PAGE results demonstrated that donkey milk is rich in beta-lactoglobulin and lysozyme. The percentages of 8 essential AA in protein of donkey milk were 38.2%, higher than those of mare and cow milk; donkey milk also had higher levels of serine (6.2%), glutamic acid (22.8%), arginine (4.6%), and valine (6.5%) and a lower level of cystine (0.4%). PMID:17369203

Guo, H Y; Pang, K; Zhang, X Y; Zhao, L; Chen, S W; Dong, M L; Ren, F Z

2007-04-01

321

Composition and distribution of bacteria in an operating rainwater harvesting tank.  

PubMed

In this study, we investigated the phylogenetic distribution of the bacteria present in an operating rainwater tank by denaturing gradient gel electrophoresis (DGGE), and compared the bacterial composition in rainwater and biofilm from the inlet and outlet of the tank. Seventeen species were identified, the DGGE profiles of which showed a clear difference between the planktonic bacterial community and the community in the biofilm. Most of the bacteria were closely related to fresh water, soil, and biofilm bacteria found in natural environments. The high proportion of Proteobacteria indicates the generally clean oligotrophic nature of the tank water. Biofilm formation is an advantage for bacteria that exist in oligotrophic environments. The groups identified in the biofilm, such as Sphingomonas, Bacillus, and Sphingophyxis, have been demonstrated to degrade certain contaminants and to act as bio-control agents. Thus, biofilm formation in rainwater tanks not only represents a survival strategy for bacteria, but also serves as a natural filter by removing contaminants and bacteria from rainwater. PMID:21508560

Kim, Mikyeong; Han, Mooyoung

2011-01-01

322

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

323

Composition and Distribution of Streambed Sediments in the Penobscot River, Maine, May 1999  

USGS Publications Warehouse

Sediment samples were collected and geophysical surveys were run along 50 miles of the Penobscot River, Maine, in the spring of 1999 to produce maps that describe the composition and distribution of streambed sediments for selected areas in the river channel. The objective of the sediment survey was to locate areas along the river where fine-grained, easily transportable sediment types were deposited between Old Town and Medway, Maine. These data can be used to design future sediment-sampling programs to assess the quality of streambed sediments and evaluate the health of the Penobscot River. This report describes the results of the sediment survey and the methods used to collect, analyze, and interpret the data used to create maps of streambed-sediment types in the study area. Deposits of fine-grained sediments (mud and sand) are scattered along the shorelines of the mainland and the islands and at the downstream ends of islands and at the mouths of brooks and streams. The most extensive depositional areas were found in the Mattaseunk Dam impoundment near Medway. The main areas of the river channel consist primarily of gravel, sand, and rock.

Dudley, Robert W.; Giffen, Sarah E.

2001-01-01

324

Community composition, distribution, and contribution of microbenthos in offshore sediments from the Yellow Sea  

NASA Astrophysics Data System (ADS)

We investigated the spatial distribution and composition of microbenthos in the seafloor sediments from 48 stations in the Yellow Sea using epifluorescence microscopy and quantitative protargol staining techniques. The bacterial abundance ranged from 2.4×10 8 to 1.9×10 9 cells cm -3 in the wet sediment, about three orders of magnitude higher than that of phototrophic (PNFs, from 6.4×10 5 to 8.8×10 6 cells cm -3) and heterotrophic nanoflagellates (HNFs, from 5.8×10 4 to 5.9×10 6 cells cm -3) and four orders of magnitude higher than that of cyanobacteria (from 2.3×10 4 to 2.3×10 6 cells cm -3) in the upper 5 cm of sediments. The abundance of diatoms varied greatly, from 3-1.1×10 5 cells cm -3 in the upper 8 cm of sediments, whereas those of heterotrophic microflagellates (HMFs, 1-182 cells cm -3) and ciliates (1-221 cells cm -3) were less varied and lower. The biomass partitioning indicates the primary importance of benthic bacteria (50.3 ?g C cm -3 on average), followed by PNFs (40.7 ?g C cm -3), HNFs (19.3 ?g C cm -3), and finally by cyanobacteria (8.8 ?g C cm -3). Benthic diatoms (0.8 ?g C cm -3), ciliates (0.15 ?g C cm -3), and HMFs (0.03 ?g C cm -3) contribute relatively small fractions to the total biomass of the microbenthos. About 95% of diatoms, 77% of ciliates, and 56% of HMFs were distributed in the upper 2 cm of sediments, whereas no distinct vertical distributions were observed for bacteria, cyanobacteria, PNFs, and HNFs. The microbenthos are quantitatively important in the shallow seafloor, wherein their main components have an average abundance three orders of magnitude higher than the corresponding planktonic organisms in the same sea area. Our estimates indicate that pico-sized phytobenthos might contribute a large proportion to the primary production. Benthic ciliates and heterotrophic flagellates contribute about 90% to the estimated combined metabolic rate of micro- and meiobenthic consumers in the whole sea area, with nanoheterotrophs accounting for the majority. The data suggest the potential for the rapid primary and secondary production of microbenthos and detrital utilization in the shallow seafloor sediments of the Yellow Sea.

Meng, Zhaocui; Xu, Kuidong; Lei, Yanli

2011-09-01

325

Strength distribution of reinforcing fibers in a Nicalon fiber/chemically vapor infiltrated silicon carbide matrix composite  

NASA Technical Reports Server (NTRS)

The strength distribution of fibers within a two-dimensional laminate ceramic/ceramic composite consisting of an eight harness satin weave of Nicalon continuous fiber within a chemically vapor infiltrated SiC matrix was determined from analysis of the fracture mirrors of the fibers. Comparison of the fiber strengths and the Weibull moduli with those for Nicalon fibers prior to incorporation into composites suggests that possible fiber damage may occur either during the weaving or during another stage of the composite manufacture. Observations also indicate that it is the higher-strength fibers which experience the greatest extent of fiber pullout and thus make a larger contribution to the overall composite toughness than do the weaker fibers.

Eckel, Andrew J.; Bradt, Richard C.

1989-01-01

326

Carbon nanotube sensor thread for distributed strain and damage monitoring on IM7/977-3 composites  

NASA Astrophysics Data System (ADS)

Laminated composite materials are used in applications where light weight is a key requirement. However, minor delamination damage in composites can propagate and lead to the failure of components. Failure occurs because delamination reduces the local bending stiffness and increases bending stress, which leads to the propagation of damage and eventual failure. These failures may be avoided if the damage could be detected early and repaired. Although many damage detection methods have been investigated, none are in widespread use today to prevent the failure of composites. This paper describes the use of carbon nanotube sensor thread to monitor strain and damage in composite materials. Sensor thread was bonded onto an IM7-laminated composite coupon to measure surface strain in a quasi-static uniaxial tensile test. The sensor thread was calibrated against a strain gage, which was also mounted to the coupon. The sensor thread measured the average strain over the length of the sample and indicated when the strain exceeded a nominal safe level. Sensor thread was also bonded to the surface of laminated composite panels in different patterns and detected, located and partially characterized the damage caused by multiple impacts to the panel. The new findings in this paper can be summarized as; (1) carbon nanotube sensor thread was tested as a distributed sensor for the first time on IM7/977-3 composites; (2) the sensor thread was found to monitor strain and detect damage in the composites with a potential sensitivity down to the micro-crack level; (3) the sensor thread was barely visible on the composite and did not add significant mass or affect the integrity of the composite; (4) the data acquisition system developed was simple and reliable.

Song, Yi; Hehr, Adam; Shanov, Vesselin; Alvarez, Noe; Kienzle, Nicholas; Cummins, Joshua; Koester, Dave; Schulz, Mark

2014-07-01

327

Effects of particle shape and size distributions on the electrical and magnetic properties of nickel/polyethylene composites  

SciTech Connect

Electrical and magnetic properties of composite materials prepared by incorporating various nickel-based fillers of different shapes into polyethylene were investigated. The fillers used were nickel powders, nickel filamentary powders, nickel flakes, and nickel-coated graphite fibers. The particle-size distributions of the fillers were determined both before and after the processing of the composite samples. A wide range of filler volume fractions were used. In some cases, the volume fraction approached the maximum packing fraction of the solid phase to significantly exceed the percolation threshold. The composite samples were characterized in terms of their volume resistivity, dielectric constant, and magnetic permeability values. Filler particles of asymmetric shapes were very effective in terms of altering the electrical properties of the composite samples. At the highest loading levels of the nickel fillers, the volume resistivity values of the composites decreased by more than 17 orders of magnitude. AT such high filler concentrations, the dielectric constant values of the composite samples increased considerably, to values that were greater than 1,000. The permeability values of the samples increased linearly with the volume fraction of the nickel filler and were insensitive to the shape of the fillers. The highest relative permeability value measured was 5.8 for composites with 67% by volume of nickel powder.

Goektuerk, H.S.; Fiske, T.J.; Kalyon, D.M. (Highly Filled Materials Inst., Hoboken, NJ (United States))

1993-12-15

328

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

329

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

330

Surface and subsurface composition of the Life in the Atacama field sites from rover data and orbital image analysis  

Microsoft Academic Search

The Life in the Atacama project examined six different sites in the Atacama Desert (Chile) over 3 years in an attempt to remotely detect the presence of life with a rover. The remote science team, using only orbital and rover data sets, identified areas with a high potential for life as targets for further inspection by the rover. Orbital data

Jennifer L. Piatek; Craig Hardgrove; Jeffrey E. Moersch; Darrell M. Drake; Michael B. Wyatt; Michael Rampey; Orion Carlisle; Kim Warren-Rhodes; James M. Dohm; Andrew N. Hock; Nathalie A. Cabrol; David S. Wettergreen; Edmond A. Grin; Guillermo Chong Diaz; Peter Coppin; Shmuel Weinstein; Charles S. Cockell; Lucia Marinangeli; Gian Gabriele Ori; Trey Smith; Dominic Jonak; Michael Wagner; Kristen Stubbs; Geb Thomas; Erin Pudenz; Justin Glasgow

2007-01-01

331

The Ichthyoplankton of Selected Estuaries in Sarawak and Sabah: Composition, Distribution and Habitat Affinities  

NASA Astrophysics Data System (ADS)

The ichthyoplankton assemblages of 23 estuaries in Sarawak and Sabah were surveyed with particular reference to the culturally and commercially important clupeid Tenualosa toli. The species composition, distribution and density of all fish larvae were recorded, together with the physical characteristics of each estuary. A more detailed study was made of the Lupar and Lassa estuaries, which are the ' core area ' for T. toli. The estuaries fall into two groups. The first consists of the estuaries of the ' core area ' from the Sebako in the west to the Lassa in the east, and the Labuk and Kinabatangan estuaries of eastern Sabah. They are large and deep, have middle-range salinities with no halocline, are highly turbid and have tidal ranges of >3·5 m and strong currents. There is little seasonal change in freshwater input and their waters are not peat-stained. Their total zooplankton biomasses (approximately 0·05 g m -3dry weight, excluding fish larvae) are an order of magnitude greater than biomasses in the second group of estuaries. The second group consists of all estuaries east of the Lassa as far as the Papar in Sabah. They are mostly smaller, shallower and have more variable salinities than the ' core area ' estuaries, with marked haloclines and seasonal changes in freshwater inflow, lower turbidities, weaker currents, tidal ranges of <2 m and low overall zooplankton biomasses. The composition of the ichthyoplankton is different in these two groups of estuaries. The assemblage in the first group (' core area ') of estuaries consists primarily of taxa associated with estuarine and/or turbid water conditions, whereas those in the smaller estuaries of the second group have mainly marine and clearer water affinities. Only the Gobiidae are ubiquitous. Very few larvae of freshwater species were recorded in any of the estuaries. The number of fish larvae was highly variable, but the mean densities (0·01-9·23 m -3) were similar, and similarly variable, to the densities reported for other tropical estuaries. The diversity of the ichthyoplankton assemblage in Sarawak and Sabah estuaries (56 taxa, 26 families) is lower than in most other tropical estuaries of the Indo-west Pacific. This is possibly because of their rigorous physical nature, particularly the very high turbidities and current speeds, or in smaller, less physically rigorous estuaries, the low biomass of zooplankton available as food for the larvae.

Blaber, S. J. M.; Farmer, M. J.; Milton, D. A.; Pang, J.; Boon-Teck, O.; Wong, P.

1997-08-01

332

Stress distribution and strength prediction of composite laminates with multiple holes  

NASA Astrophysics Data System (ADS)

The major purpose of this study was to investigate failure of composite laminates with multiple unloaded holes in close proximity. The least square boundary collocation method for anisotropic materials was utilized to determine the state of stress. The approach utilized collocation on both the internal and external boundaries, making it relatively easy to implement. The method compared favorably to both published and finite element solutions. A failure prediction approach for an infinite, symmetric and balanced laminate, with two holes in close proximity was presented. The baseline material for consideration was IM7/977-3, a carbon fiber/epoxy lamina. The failure prediction method was an extension of the Whitney-Nuismer point stress failure criterion and was flexible enough to account for an arbitrary characteristic dimension value. Conditions for holes oriented transverse to the load and in-line with the load were considered. Both the "hole interaction effect" and "hole size effect" were simultaneously included in the failure prediction. Multiple hole spacings, hole size ratios, and layups were considered for stress distribution and strength prediction. For two equal holes oriented transverse to the load, the predicted strength was at least 95.0% of the single hole strength when the center to center distance divided by diameter, or l/D, was ? 3.5. For this same condition, the strength prediction response was nearly layup independent for l/D ? 3.0. The presented failure prediction approach was compared to published experimental data and was shown to have good correlation. A series of design curves were presented that allow for the quick determination of a structure's strength with two holes by only requiring the characteristic dimension for a single hole. Two approaches to approximately determine the orthotropic stress concentration factor by using only two parameters were presented. Ten composite materials were investigated to determine the accuracy of the approximation for a variety of material systems. The results showed that a good approximation to the orthotropic stress concentration factor can be obtained by using only the parameters Ex/Ey and Ex/Gxy, regardless of the material system.

Esp, Brian

333

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

334

Bayesian statistical approaches to compositional analyses of transgenic crops 2. Application and validation of informative prior distributions.  

PubMed

Bayesian approaches to evaluation of crop composition data allow simpler interpretations than traditional statistical significance tests. An important advantage of Bayesian approaches is that they allow formal incorporation of previously generated data through prior distributions in the analysis steps. This manuscript describes key steps to ensure meaningful and transparent selection and application of informative prior distributions. These include (i) review of previous data in the scientific literature to form the prior distributions, (ii) proper statistical model specification and documentation, (iii) graphical analyses to evaluate the fit of the statistical model to new study data, and (iv) sensitivity analyses to evaluate the robustness of results to the choice of prior distribution. The validity of the prior distribution for any crop component is critical to acceptance of Bayesian approaches to compositional analyses and would be essential for studies conducted in a regulatory setting. Selection and validation of prior distributions for three soybean isoflavones (daidzein, genistein, and glycitein) and two oligosaccharides (raffinose and stachyose) are illustrated in a comparative assessment of data obtained on GM and non-GM soybean seed harvested from replicated field sites at multiple locations in the US during the 2009 growing season. PMID:23261475

Harrison, Jay M; Breeze, Matthew L; Berman, Kristina H; Harrigan, George G

2013-03-01

335

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

336

Lithium Isotopic Composition of Mantle Plumes and the Distribution of Lithium Isotopes Among Earth's Reservoirs  

NASA Astrophysics Data System (ADS)

We have determined lithium isotopic compositions of seventy nearly unaltered basaltic lavas from the Samoan and Cook-Austral volcanic chains, and Pitcairn Island. In addition, the Li isotope record of Mauna Kea has been extended from 3.1 km to 3.3 km using the newly recovered deep drill core of Hawaii Scientific Drilling Project (HSDP-2). From the results of the Hawaii and South Pacific hotspots, we examine the source components of mantle plumes and consider the distribution of Li isotopes among Earth's major reservoirs. The total ?^{7}Li range observed in South Pacific and Hawaiian islands is 2.5 to 7.5‰, suggesting considerable heterogeneity in the deep mantle. The Hawaiian plume occupies the lower range, 2.5 to 5.7‰. Cook-Austral samples depict mixing between HIMU and depleted mantle (DM) components. The DM endmember has ?^{7}Li values of 3.2 to 4.2‰, identical to MORB. HIMU type lavas are isotopically heavier than MORB, reflecting the influence of recycled oceanic crust. The most extreme HIMU signature was observed at Mangaia (7.4‰; Nishio et al., 2005). The EM1 composition shown by Pitcairn is relatively light (3.3 to 4.1‰) and resembles the global average of subducting sediments (~3‰). Malumalu seamount of the Samoan chain defines the most extreme composition of the EM2 mantle; ?^{7}Li range from 4.5 to 5.6‰. High 3He/4He samples of Ofu Island (R/Ra = 24 to 33.7) suggest that the least degassed mantle has ?^{7}Li of about 3‰. In addition to these classic mantle endmembers, we observe an additional component that elevates Samoan lavas above the typical mantle baseline (~3‰) up to 7.5‰. The source of this enrichment is likely mantle wedge material that has been metasomatized by 7Li-rich slab fluids (Elliott et al., 2004). On the other hand, recent studies suggest that a large portion of subducted Li can be retained in high-pressure metamorphosed slab (Marschall et al., in press). This implies that deeply subducted slab need not be isotopically light but can be the origin of elevated ?^{7}Li of HIMU lavas. The global ocean island basalts yield an average ?^{7}Li value of 4.7 ± 0.9‰ (1?). Thus the deep mantle is isotopically heavier than the upper mantle (3 to 4‰), volcanic arcs (3.5 ± 1.5‰), and the upper continental crust (0 ± 2‰). The implication is that heavy Li that enters the subduction zone is not significantly recycled to the crust but largely returned to the deep mantle via the slab-modified mantle wedge and possibly the residual slab. Unusually light Li does not appear to to be common in the deep mantle although it has been implicated by orogenic eclogites and subcontinental mantle xenoliths. References: Elliott T., A. Jeffcoate, and C. Bouman (2004) Earth Planet. Sci. Lett. 220, 231-245. Marschall H.R., R. Altherr, T. Ludwig et al. (in press) Geochim. Cosmochim. Acta. Nishio N., S. Nakai, T. Kogiso, and H.G. Barsczus (2005)Geochem. J. 39, 91-103.

Chan, L.; Hart, S. R.; Blusztajn, J. S.; Lassiter, J. C.; Frey, F. A.; Hauri, E. H.

2006-12-01

337

Monitoring of Pb Contamination in Loire Estuary: Trends, Distribution and Isotopic composition  

NASA Astrophysics Data System (ADS)

The Loire River is one of the largest river systems in Western Europe and constitutes a major continental input to marine environment in the Bay of Biscay. Its catchment area flows through agricultural, industrial areas and through a more and more urbanized estuary. Even if Loire River is not considered as a highly polluted system, some studies identified a Pb contamination of its estuary due to industrial inputs and combustion of leaded gasoline up to the mid 90's. A retrospective study, based on the analysis (Pb contents and isotopic composition) of Mytilus edulis samples collected by the French mussel watch program (RNO/ROCCH) has highlighted this contamination and its trend between 1985-2005 (Couture et al., 2010). This poster will first complete the work initiated by Couture et al. Pb contents and isotopic signatures in mussel samples collected by RNO/ROCCH over the last 10 years will be presented and discussed. Results will be compared to measurements performed on various environmental samples (sediment, biota…) collected in the frame of the environmental monitoring project RS2E started in 2012 by the "Observatoire des Sciences de l'Univers Nantes-Atlantique" (OSUNA). This new data will contribute to a better characterisation of Pb contents and distribution along the Loire Estuary. Moreover, some key samples will be submitted to HR-ICP-MS for Pb isotopic analysis. Discrimination of anthropic Pb sources requires both precise and accurate isotope ratio determination and also high versatility due to the complex matrix, which is typical for marine and estuarine samples. These measurements will contribute to a more accurate definition and characterisation of main actual anthropic Pb sources (urban, agricultural, industrial or atmospheric deposition). Couture R.- M., Chiffoleau J.-F., Auger D., Claisse D., Gobeil C. and Cossa D. (2010) Seasonal and decadal variation in lead sources to eastern north Atlantic mussels. Environ. Sci. Technol. 44, 1211-1216.

Brach-Papa, Christophe; Chiffoleau, Jean-François; Knoery, Joel; Chouvelon, Tiphaine; Auger, Dominique; Bretaudeau, Jane; Crochet, Sylvette; Rozuel, Emmanuelle; Thomas, Batien; Vasileva, Emilia; Oriani, Anna Maria

2014-05-01

338

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.

339

Fibrosis in Human Adipose Tissue: Composition, Distribution, and Link With Lipid Metabolism and Fat Mass Loss  

PubMed Central

OBJECTIVE Fibrosis is a newly appreciated hallmark of the pathological alteration of human white adipose tissue (WAT). We investigated the composition of subcutaneous (scWAT) and omental WAT (oWAT) fibrosis in obesity and its relationship with metabolic alterations and surgery-induced weight loss. RESEARCH DESIGN AND METHODS Surgical biopsies for scWAT and oWAT were obtained in 65 obese (BMI 48.2 ± 0.8 kg/m2) and 9 lean subjects (BMI 22.8 ± 0.7 kg/m2). Obese subjects who were candidates for bariatric surgery were clinically characterized before, 3, 6, and 12 months after surgery, including fat mass evaluation by dual energy X-ray absorptiometry. WAT fibrosis was quantified and characterized using quantitative PCR, microscopic observation, and immunohistochemistry. RESULTS Fibrosis amount, distribution and collagen types (I, III, and VI) present distinct characteristics in lean and obese subjects and with WAT depots localization (subcutaneous or omental). Obese subjects had more total fibrosis in oWAT and had more pericellular fibrosis around adipocytes than lean subjects in both depots. Macrophages and mastocytes were highly represented in fibrotic bundles in oWAT, whereas scWAT was more frequently characterized by hypocellular fibrosis. The oWAT fibrosis negatively correlated with omental adipocyte diameters (R = ?0.30, P = 0.02), and with triglyceride levels (R = ?0.42, P < 0.01), and positively with apoA1 (R = 0.25, P = 0.05). Importantly, scWAT fibrosis correlated negatively with fat mass loss measured at the three time points after surgery. CONCLUSIONS Our data suggest differential clinical consequences of fibrosis in human WAT. In oWAT, fibrosis could contribute to limit adipocyte hypertrophy and is associated with a better lipid profile, whereas scWAT fibrosis may hamper fat mass loss induced by surgery.

Divoux, Adeline; Tordjman, Joan; Lacasa, Daniele; Veyrie, Nicolas; Hugol, Danielle; Aissat, Abdelhalim; Basdevant, Arnaud; Guerre-Millo, Michele; Poitou, Christine; Zucker, Jean-Daniel; Bedossa, Pierre; Clement, Karine

2010-01-01

340

Catalyst composition for polymerizing alpha-olefin polymers of relatively narrow molecular weight distribution  

SciTech Connect

A process is described for preparing a supported catalyst composition for use in alpha-olefin polymerization reactions comprising the steps of: contacting a solid, porous carrier having reactive OH groups with a liquid containing at least one organomagnesium composition. Removing the liquid, whereby a supported magnesium (Mg) composition in the form of a solid powder is formed; and drying the solid powder, without washing, rinsing or decantantation thereof, until it comprises not more than about 6% by weight of the liquid.

Lo, F.Y.; Nowlin, T.E.; Wu, M.M.

1987-05-26

341

Effects of composition and compositional distribution on the electronic structure of ZnSe1-xTex ternary quantum dots  

NASA Astrophysics Data System (ADS)

We report results of first-principles density functional theory (DFT) calculations for the electronic structure of ZnSe1-xTex ternary quantum dots (TQDs) and the effects of composition and compositional distribution on the electron density distribution, electronic density of states, and band gap. We analyze the electronic structure of five types of nanocrystal configurations, namely, pristine ZnSe and ZnTe quantum dots, as well as ZnSe/ZnTe core/shell, ZnTe/ZnSe reverse core/shell, and randomly alloyed ZnSe1-xTex TQDs. We find that the band gaps for ZnSe/ZnTe core/shell TQDs are nonlinearly dependent on the number of Te atoms in the shell, whereas presence of Te in the core of alloyed ZnSe1-xTex TQDs modifies the electronic energy levels abruptly and significantly in the limits of x --> 0 and x --> 1. Our results imply that distribution of Te atoms in the TQD in the form of a ZnSe/ZnTe core/shell configuration allows for optimum tunability of the band gap and wave function confinement in TQDs.

Pandey, Sumeet C.; Maroudas, Dimitrios

2011-12-01

342

Fatigue behavior and life prediction of a SiC/Ti-24Al-11Nb composite under isothermal conditions. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

Metal Matrix Composites (MMC) and Intermetallic Matrix Composites (IMC) were identified as potential material candidates for advanced aerospace applications. They are especially attractive for high temperature applications which require a low density material that maintains its structural integrity at elevated temperatures. High temperature fatigue resistance plays an important role in determining the structural integrity of the material. This study attempts to examine the relevance of test techniques, failure criterion, and life prediction as they pertain to an IMC material, specifically, unidirectional SiC fiber reinforced titanium aluminide. A series of strain and load controlled fatigue tests were conducted on unidirectional SiC/Ti-24Al-11Nb composite at 425 and 815 C. Several damage mechanism regimes were identified by using a strain-based representation of the data, Talreja's fatigue life diagram concept. Results of these tests were then used to address issues of test control modes, definition of failure, and testing techniques. Finally, a strain-based life prediction method was proposed for an IMC under tensile cyclic loadings at elevated temperatures.

Bartolotta, Paul A.

1991-01-01

343

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

344

The effectiveness of an indoor intermittent training program for improving lung function, physical capacity, body composition and quality of life in children with asthma.  

PubMed

Abstract Objective: The objective of this study is to analyze the effects of a 12-week indoor intermittent training program on lung function, physical capacity, body composition and quality of life in children with asthma. Methods: Participants were randomized in an experimental group (EG, 58 children, age?=?11.55?±?1.01 years) and in a control group (CG, 47 children, age?=?11.51?±?1.42 years). The training program was conducted indoors and consisted of alternating high- and low-intensity stimuli, for three sessions of 60?min/week, for 12 weeks. Physical exercise and sports activities were organized to follow the criteria of the American College of Sports Medicine (1999) and previous interventions' studies. Results: In EG, there was a significant improvement (p?life were all shown. The dyspnea index decreased significantly and there were no episodes of EIA. There is a significant positive correlation (p?composition and quality of life in children with asthma. These training adaptations are particularly relevant for those patients suffering from asthma as a regular physical exercise routine will greatly improve their quality of life. PMID:24471516

Latorre-Román, Pedro Ángel; Navarro-Martínez, Ana Vanesa; García-Pinillos, Felipe

2014-06-01

345

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

346

Can distributed generation offer substantial benefits in a Northeastern American context? A case study of small-scale renewable technologies using a life cycle methodology  

Microsoft Academic Search

Renewable distributed electricity generation can play a significant role in meeting today's energy policy goals, such as reducing greenhouse gas emissions, improving energy security, while adding supply to meet increasing energy demand. However, the exact potential benefits are still a matter of debate. The objective of this study is to evaluate the life cycle implications (environmental, economic and energy) of

Mourad Ben Amor; Pascal Lesage; Pierre-Olivier Pineau; Réjean Samson

2010-01-01

347

Checklist of the avian species of Plasmodium Marchiafava & Celli, 1885 (Apicomplexa) and their distribution by avian family and Wallacean life zones  

Microsoft Academic Search

The 34 valid species of avian Plasmodium are listed with their authorities and type-hosts. Plasmodium species are also listed by the avian family in which they occur and by the number of avian families and species which they parasitise. A key to the subgenera of Plasmodium occurring in birds is presented. The distribution of the parasites by the Wallacean life

Gordon F. Bennett; Madonna A. Bishop; Michael A. Peirce

1993-01-01

348

Size distributions and elemental compositions of particulate matter on clear, hazy and foggy days in Beijing, China  

Microsoft Academic Search

Total suspended particulates (TSP) samples were collected using low pressure impactors (Andersen Series 20–800, USA) on typical\\u000a clear, hazy and foggy days in Beijing in order to investigate the characteristics of size distributions and elemental compositions\\u000a of particulate matter (PM) in different weather conditions. The concentrations of sixteen elements, including Na, Mg, Al,\\u000a K, Ca, Mn, Fe, Ni, Cu, Zn,

Yongjie Yang; Yuesi Wang; Weiwei Huang; Bo Hu; Tianxue Wen; Ya’nan Zhao

2010-01-01

349

Measurement of Dijet Angular Distributions and Search for Quark Compositeness in pp Collisions at s=7TeV  

Microsoft Academic Search

Dijet angular distributions are measured over a wide range of dijet invariant masses in pp collisions at s=7TeV, at the CERN LHC. The event sample, recorded with the CMS detector, corresponds to an integrated luminosity of 36pb-1. The data are found to be in good agreement with the predictions of perturbative QCD, and yield no evidence of quark compositeness. With

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

2011-01-01

350

EFFECTS OF TRANSPORTED ASIAN DUST STORM ON AEROSOL COMPOSITION AND SIZE DISTRIBUTION IN CENTRAL TAIWAN IN 2002  

Microsoft Academic Search

The effects of the long-range transported Asian dust (AD) on the aerosol compositions and size distributions in Central Taiwan during spring 2002 were studied by using measurements with dichotomous sampler and micro-orifice uniform deposited impactor. The air quality in central Taiwan was found significantly different due to the passage of the AD. An 80% increase in PM2.5-10 and 60 to

Man-Ting Cheng; Yu-Chi Lin; Wei-Te Lee; Shaw Chen Liu

351

Evaluation of two fiber optic-based solar collection and distribution systems for advanced space life support.  

PubMed

Growing plants in an enclosed controlled environment is crucial in developing bioregenerative life-support systems (BLSS) for space applications. The major challenge currently facing a BLSS is the extensive use of highly energy-intensive electric light sources, which leads to substantial energy wastes through heat dissipations by these lamps. An alternative lighting strategy is the use of a solar irradiance collection, transmission, and distribution system (SICTDS). Two types of fiber optic-based SICTDS, a Fresnel-lens Himawari and a parabolic-mirror optical waveguide (OW) lighting system, were evaluated. The overall efficiency for the OW SICTDS of 40.5% exceeded by 75% that for the Himawari of 23.2%. The spectral distributions of the light delivered by the Himawari and the OW SICTDS were almost identical and had practically no difference from that of terrestrial solar radiation. The ratios of photosynthetically active radiation (PAR) to total emitted radiation (k) of 0.39 +/- 0.02 for the Himawari and 0.41 +/- 0.04 for the OW SICTDS were statistically indistinguishable, were not significantly different from that of 0.042 +/- 0.01 for terrestrial solar radiation, and were comparable to that of 0.35 for a high-pressure sodium (HPS) lamp. The coefficients of variation (CV) of 0.34 and 0.39 for PPF distributions, both at 50 mm X 50 mm square grid arrays, corresponding to the Himawari and the OW SICTDS, respectively, were comparable with each other but were both significantly greater than the CV of 0.08 corresponding to the HPS lamp. The average fresh weight or dry weight of lettuce grown in the solar chamber with either the Himawari or the OW SICTDS showed no statistical difference from the average fresh weight or dry weight of lettuce grown in the reference chamber with the HPS lamp. The results of this study suggest that an SICTDS could help reduce the electric power demand in a BLSS. PMID:12807140

Jack, D A; Nakamura, T; Sadler, P; Cuello, J L

2002-01-01

352

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

353

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

354

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

355

The Chemical Composition of the Primary Cosmic Rays around the Knee Region by Measuring Lateral Distributions of Air Cherenkov Photons  

NASA Astrophysics Data System (ADS)

For a study of the chemical composition at the Knee region, we have measured lateral distributions both of air Cherenkov photons and of charged particles simultaneously at Mt. Chacaltaya in Bolivia since August 2001. The measured lateral distributions of air Cherenkov photons were fitted with an empirical function which includes a parameter reflecting mass numbers of primary cosmic rays. The observed distributions of this parameter were compared with those simulated using the CORSIKA code with the QGSJET hadronic interaction model for three species of primary cosmic rays: proton, C, Fe. As a result, the mean logarithmic mass number of primary cosmic rays ln A in the energy range from 1014 to 1016 eV was determined. The result shows that ln A decreases in the range from 1014.1 to 1014.7 eV and increases from 1014.7 to 1015.8 eV.

Tokuno, H.; Kakimoto, F.; Ogio, S.; Harada, D.; Kurashina, Y.; Tsunesada, Y.; Tajima, N.; Miranda, P.; Morizawa, A.; Matsubara, Y.; Yoshii, H.; Velarde, A.; BASJE Collaboration

2003-07-01

356

Quantitative assessment on the orientation and distribution of carbon fibers in a conductive polymer composite using high-frequency ultrasound.  

PubMed

Conductive polymer composites, typically fabricated from a mix of conductive fillers and a polymer substrate, are commonly applied as bipolar plates in a fuel cell stack. Electrical conductivity is a crucial property that greatly depends on the distribution and orientation of the fillers. In this study, a 50-MHz ultrasound imaging system and analysis techniques capable of nondestructively assessing the properties of carbon fibers (CFs) in conductive polymer composites were developed. Composite materials containing a mix of polycarbonate substrates and 0 to 0.3 wt% of CFs were prepared using an injection molding technique. Ultrasonic A-line signals and C-scan images were acquired from each composite sample in regions at a depth of 0.15 mm beneath the sample surface (region A) and those at a depth of 0.3 mm (region B). The integrated backscatter (IB) and the Nakagami statistical parameter were calculated to quantitatively assess the samples. The area ratio, defined as the percentage of areas composed of CF images normalized by that of the whole C-scan image, was applied to further quantify the orientation of CFs perpendicular to the sample surface. Corresponding to the increase in CF concentrations from 0.1 to 0.3 wt%, the average IB and Nakagami parameter (m) of the composite samples increased from -78.10 ± 2.20 (mean ± standard deviation) to -72.66 ± 1.40 dB and from 0.024 ± 0.012 to 0.048 ± 0.011, respectively. The corresponding area ratios were respectively estimated to be 0.78 ± 0.35%, 2.33 ± 0.66%, and 2.20 ± 0.60% in region A of the samples; those of CFs with a perpendicular orientation were 0.04 ± 0.03%, 0.08 ± 0.02%, and 0.12 ± 0.05%. The area ratios in region B of the samples were calculated to be 1.19 ± 0.54%, 2.81 ± 0.42%, and 2.64 ± 0.76%, and those of CFs with a perpendicular orientation were 0.07 ± 0.04%, 0.12 ± 0.04%, and 0.14 ± 0.03%. According to the results of the orientations and ultrasonic images, CFs tended to distribute more uniformly in the deeper regions of the samples. This study validates that the distribution and orientation of CFs in conductive polymer composites could be sensitively and quantitatively assessed by high-frequency ultrasound in conjunction with current analysis methods. PMID:22622982

Lin, Yi-Hsun; Huang, Chih-Chung; Wang, Shyh-Hau

2012-05-01

357

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.

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

358

Identity, Meaning, and Engagement with School: A Native American Student's Composition of a Life Map in a Senior English Class  

ERIC Educational Resources Information Center

This case study of a Native American high school senior focuses on one of the final assignments he completed before dropping out of school early in the school year. The task was to draw a life map--a nonverbal text that identified 10 key life events on his journey to that point--as part of a larger unit on identity for his senior English class.…

Smagorinsky, Peter; Anglin, Joanna L.; O'Donnell-Allen, Cindy

2012-01-01

359

Composites  

NASA Astrophysics Data System (ADS)

Ca3Co4O9 is one of the most promising p-type thermoelectric materials because of its high dimensionless figure of merit ZT. However, polycrystalline Ca3Co4O9 ceramics shows lower ZT value than that for single crystal Ca3 Co4O9 due to its higher electrical resistivity ?. Mikami et al. have reported that the addition of Ag to Ca3Co4O9 ceramics could successfully reduce ? and enhance the power factor. On the other hand, Ohtaki et al. reported that a composite structure could be highly effective to reduce ? for ZnO dually doped with Al and Ga. In this work, we tried to enhance the power factor and reduce ? by forming Ca3Co4O9/[Ca2(Co0.65Cu0.35)2O4]0.624CoO2 composite structure. As a result, the ZT value for Ca3Co4O9/[Ca2(Co0.65Cu0.35)2O4]0.624CoO2 composites reached 0.164 at 700 °C, which was 40 % higher than the value for Ca3Co4O9.

Obata, Kohei; Chonan, Yasunori; Komiyama, Takao; Abe, Kazunori; Aoyama, Takashi; Yamaguchi, Hiroyuki; Sugiyama, Shigeaki

2014-06-01

360

Airborne Brake Wear Debris: Size Distributions, Composition, and a Comparison of Dynamometer and Vehicle Tests  

Microsoft Academic Search

Particle size distributions of light-duty vehicle brake wear debris are reported with careful attention paid to avoid sampling biases. Electrical low-pressure impactor and micro- orifice uniform deposit impactor measurements yield consistent size distributions, and the net particulate matter mass from each method is in good agreement with gravimetric filter measurements. The mass mean diameter of wear debris from braking events

PAUL G. S ANDERS; TOM M. D ALKA; M. M ATTI M ARICQ

361

Creating Composite Age Groups to Smooth Percentile Rank Distributions of Small Samples  

ERIC Educational Resources Information Center

Individually administered tests are often normed on small samples, a process that may result in irregularities within and across various age or grade distributions. Test users often smooth distributions guided by Thurstone assumptions (normality and linearity) to result in norms that adhere to assumptions made about how the data should look. Test…

Lopez, Francesca; Olson, Amy; Bansal, Naveen

2011-01-01

362

Fuzzy load flow in balanced and unbalanced radial distribution systems incorporating composite load model  

Microsoft Academic Search

This paper presents a fuzzy approach load flow for balanced and unbalanced radial distribution systems with incorporating load model. Fuzzy set theory proposes an appropriate way to model inexactly expressed information and data which have uncertainty. In this paper the combination of fuzzy models and techniques for electrical distribution systems is presented. The theories relating to the fuzzy numbers are

Belal Mohammadi Kalesar; Ali Reza Seifi

2010-01-01

363

Aerosol size distribution and elemental composition in urban areas of Northern China  

Microsoft Academic Search

Based on monitoring data collected in the northern cities of China since 1980, the particle size spectra, distribution modes and the elements distribution features are discussed in this article. It is found that the major aerial contaminant in urban aerosol of northern China is fine dust. It makes up about 70% of the total suspended particulate matter by mass concentration.

Liang-Xi Zhong; Yong-Seung Chung

1996-01-01

364

Influence of gas pressure and cathode composition on ion energy distributions in filtered cathodic vacuum arcs  

NASA Astrophysics Data System (ADS)

We report measurements of ion energy distributions of ionized species in titanium and aluminium filtered cathodic vacuum arcs operating in oxygen and nitrogen gas atmospheres. The ion energy distributions were recorded using a Hiden mass selected ion energy analyzer. The results show that a significant reduction in ion energies and a change in the shape of ion energy distributions occurs as the gas pressure is increased. The degree of the energy reduction depends on both the type of gas and the metal ions making up the arc plasma. This has important implications for the deposition of thin films, such as titanium nitride, commonly produced using vacuum arcs in reactive gas atmospheres. The ion energy distributions of the cathode ion species in the absence of background gas and at low gas pressures are well fitted by shifted Maxwellian distributions. As the gas pressure rises the distributions consist of a progressively increasing thermalized Maxwellian component and a decreasing shifted Maxwellian. An investigation of energy distributions of species in arcs triggered on alloyed cathodes showed that the relative abundance of ions of different charge states and their energy distributions varied as alloy metals were introduced. This indicates that the electron temperature in the cathode spot and hence the cathode spot dynamics is affected by the presence of the alloy metal.

Bilek, M. M. M.; Martin, P. J.; McKenzie, D. R.

1998-03-01

365

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

366

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

367

Aerosol Size Distribution, Composition, and Hygroscopicity Measurements During CSTRIPE Using an Aerosol Mass Spectrometer and a Dual Differential Mobility Analyzer  

NASA Astrophysics Data System (ADS)

During July 2003, the CIRPAS Twin Otter aircraft was deployed in the CSTRIPE (Coastal STRatocumulus Imposed Perturbation Experiment) field experiment in order to quantify the effects of aerosols on the microphysics and dynamics of marine stratocumulus clouds. In order to characterize the effects of different aerosol types on stratocumulus clouds, various air masses were sampled, including local fire plumes, pollution over the San Joaquin valley, unperturbed marine stratocumulus clouds, and stratocumulus clouds perturbed by seeding flares. Some research flights were also dedicated to characterize the seeding flares in the clear sky. Measurements of aerosol mass distribution and composition, using an Aerodyne Aerosol Mass Spectrometer (AMS), and size distribution and hygroscopic behavior, using a Dual Differential Mobility Analyzer (Dual DMA) with one column at dry conditions and another at a relative humidity of approximately 70 percent, will be presented here. During a number of in-cloud sampling periods, the Counter-flow Virtual Impactor (CVI) was used to select and dry cloud droplets, which were then analyzed by the AMS and the Dual DMA. The AMS composition measurements showed that sulfate and organics comprised most of the mass of the non-refractory components of the aerosol. The DMA showed a mixture of unimodal and bimodal size distributions in most types of air masses. The air mass over the San Joaquin valley, however, showed strong evidence of freshly nucleated particles, with aerosol number concentrations often above 80,000 cm-3.

Bahreini, R.; Varutbangkul, V.; Conant, W. C.; Flagan, R. C.; Seinfeld, J. H.; Buzorius, G.; Jonsson, H. H.

2003-12-01

368

Distribution and stable isotopic composition of amino acids from fungal peptaibiotics: assessing the potential for meteoritic contamination.  

PubMed

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 C(4) and C(5) 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. PMID:21417942

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

2011-03-01

369

Abundance, composition, and distribution of crustacean zooplankton in relation to hypolimnetic oxygen depletion in west-central Lake Erie  

USGS Publications Warehouse

Samples of crustacean zooplankton were collected monthly in west-central Lake Erie in April and June to October 1968, and in July and August 1970, before and during periods of hypolimnetic dissolved oxygen (DO) depletion. The water column at offshore stations was thermally stratified from June through September 1968, and the hypolimnion contained no DO in mid-August of 1968 or 1970. Composition, abundance, and vertical distribution of crustacean zooplankton changed coincidentally with oxygen depletion. From July to early August, zooplankton abundance dropped 79% in 1968 and 50% in 1970. The declines were attributed largely to a sharp decrease in abundance of planktonic Cyclops bicuspidatus thomasi. Zooplankton composition shifted from mainly cyclopoid copepods in July to mainly cladocerans and copepod nauplii in middle to late August. We believe that mortality of adults and dormancy of copepodites in response to anoxia was the probable reason for the late summer decline in planktonic C. b. thomasi.

Heberger, Roy F.; Reynolds, James B.

1977-01-01

370

Source apportionment of Baltimore aerosol from combined size distribution and chemical composition data  

Microsoft Academic Search

Several multivariate data analysis methods have been applied to a combination of particle size and composition measurements made at the Baltimore Supersite. Partial least squares (PLS) was used to investigate the relationship (linearity) between number concentrations and the measured PM2.5 mass concentrations of chemical species. The data were obtained at the Ponca Street site and consisted of six days’ measurements:

David Ogulei; Philip K. Hopke; Liming Zhou; J. Patrick Pancras; Narayanan Nair; John M. Ondov

2006-01-01

371

Monte Carlo Simulation of Thermal Conductivity in Randomly Distributed Nanowire Composites  

NASA Astrophysics Data System (ADS)

In this paper, we investigated the thermal conductivity of composites made of two types of randomly stacked nanowires with high contrast ratio of bulk thermal conductivity. Thermal conductivity predictions based on solving the phonon Boltzmann transport equation by using the Monte Carlo method are presented for different contrast ratios of thermal conductivity, sizes of nanowires and the volumetric fractions in the composites. For composites made of nanowires with high contrast ratio thermal conductivity, the thermal conductivity of the nanocomposites increase dramatically when the volumetric fraction of high thermal conductivity nanowire is higher than the geometry percolation threshold, although existing correlations in percolation theory do not fit the results due to the phonon interface scattering. On the other hand, when the the size of nanowires is small and the volumetric fraction of high thermal conductivity nanowire is less than percolation threshold, the thermal conductivity of the nanocomposites decreases with increasing the volumetric fraction of the high thermal conductivity nanowires. The results of this study may help the development of nanoscale thermoelectric materials in which the figure of merit is optimized by choosing appropriate nanowire size, property contrast and composition. RY acknowledges the funding support for this work by DoD/AFOSR MURI grant FA9550-06-1-0326. The simulation was conducted on a 24-node cluster supported by Intel Corporation and managed by Prof. Gang Chen and Mr. Lu Hu at MIT.

Tian, W.; Yang, R.

2007-03-01

372

On the density profile within random and oriented wood-based composite panels: horizontal distribution  

Microsoft Academic Search

Wood composites are produced from the processing of discontinuous wood elements such as flakes and strands, with resin and other additives. Consolidation of the loose mat structure into a panel is achieved under heat and pressure, and the final product structure and properties are therefore governed not only by the properties of the wood elements but also by the forming

Azzeddine Oudjehane; Frank Lam

1998-01-01

373

Effects of hormone replacement modalities on low density lipoprotein composition and distribution in ovariectomized cynomolgus monkeys  

Microsoft Academic Search

This study was designed to determine the effect of several hormone replacement therapies on LDL size, density, heterogeneity, and composition in surgically postmenopausal cynomolgus monkeys fed an atherogenic diet. Groups (n = 5 each) of ovariectomized cynomolgus monkeys were untreated (control), or treated with conjugated equine estrogens, medroxyprogesterone acetate (progesterone), combined estrogen-progesterone, or tamoxifen for 9 weeks. There were no

James M. Manning; Gilberto Campos; Iris J. Edwards; William D. Wagner; Janice D. Wagner; Michael R. Adams; John S. Parks

1996-01-01

374

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

375

Body composition and fat distribution among older Jat females: A rural–urban comparison  

Microsoft Academic Search

The aim of the present cross-sectional study is to describe and compare age related changes in body composition and fat patterning among rural and urban Jat females of Haryana State, India. A total of 600 females (rural=300, urban=300), ranging in age from 40 to 70 years were selected by the purposive sampling method. Body weight, height, two circumferences (waist and

Maninder Kaur; Indu Talwar

2011-01-01

376

The Relationship Between Filler Loading and Particle Size Distribution in Composite Resin Technology  

Microsoft Academic Search

Distinct composite structures are characterized by the ratio of liquid resin volume to non-filler volume of the material constituting the filler. If the ratio is less than one, there is high particle-to-particle interaction. If the ratio is greater than one, particles are pushed apart, and the burden of energy dissipation falls upon the resin.

M. Cross; W. H. Douglas; R. P. Fields

1983-01-01

377

Origins, composition and distribution of the bees of Cuba (Hymenoptera: Apoidea: Anthophila)  

Microsoft Academic Search

The origins of the Cuban bee fauna are reviewed. This fauna began to form 40 million years ago during the Proto Antilles period, through ancestors that arrived in successive invasions from adjacent continental areas. The composition of the Antillean fauna has evolved continuously over millions of years until the present time. The native bee fauna of Cuba is represented by

Julio A. Genaro

2008-01-01

378

[Species composition and main populations spatial distribution pattern in Korean pine broadleaved forest in Xiaoxing' An Mountains of Northeast China].  

PubMed

Taking the Korean pine broadleaved forest in Liangshui Nature Reserve of Heilongjiang Province, Northeast China as test object, this paper studied the species composition and diameter class structure, and by using point pattern analysis, analyzed the spatial distribution pattern and spatial association of the main populations. In the Reserve, there were a total of 16 species with diameter greater than 1 cm in tree layer, and great differences were observed in the densities of main populations. Coniferous trees such as Pinus koraiensis and Abies nephrolepis were dominant. The diameter class structure of the populations presented as an inverse "J" curve, indicating a good regeneration across the community. The main populations were mostly in aggregated distribution pattern, except that the P. koraiensis populations at the scales of 19-21 m and 44 m as well as the Acer tegmentosum populations close to the largest research scale were in random distribution. The P. koraiensis populations at all research scales were approximately in random distribution, and had the minimum aggregation. A. nephrolepis, Tilia amurensis, and A. tegmentosum populations all presented a random distribution trend. Except that the P. koraiensis and A. nephrolepis at 2-3 m scale and the A. nephrolepis and A. tegmentosum populations at 37-81 m scale had significant positive association, no significant associations were observed between other populations. All the tree species presented an overall non-significant positive association. PMID:24564130

Hou, Hong-Ya; Wang, Li-Hai

2013-11-01

379

Comonomer compositional distribution, physical properties, and enzymatic degradability of bacterial poly(3-hydroxybutyrate-co-3-hydroxy-4-methylvalerate) copolyesters.  

PubMed

Poly(3-hydroxybutyrate-co-3-hydroxy-4-methylvalerate) (P(3HB-co-3H4MV)) was synthesized by using Ralstonia eutropha strain PHB(-)4 (PHA-negative mutant) harboring with the N149S/D171G double mutation of PHA synthase gene from Aeromonas caviae (PhaC(Ac) NSDG mutant) with 4-methylvaleric acid and fructose as the carbon sources. Because the microbially synthesized P(3HB-co-3H4MV) samples were found to have broad comonomer compositional distribution, P(3HB-co-3H4MV) samples with 3H4MV content of 7, 11, and 35 mol % were fractionated into several fractions with different comonomer composition ranging from 2 to 47 mol % by using a chloroform/n-hexane mixture. It was confirmed that a series of well-fractionated P(3HB-co-3H4MV) samples had a statistically random distribution. Physical properties and structure of the fractionated P(3HB-co-3H4MV) random copolymers were investigated. Both the melting temperature and glass-transition temperature of P(3HB-co-3H4MV) copolymers decreased with an increase in the 3H4MV composition. The degree of X-ray crystallinity of fractionated P(3HB-co-3H4MV) films decreased from 60 to 13% as the 3H4MV fraction increased from 0 to 39 mol %. Enzymatic degradation test for fractionated P(3HB-co-3H4MV) films was carried out at 37 degrees C in the presence of PHB depolymerase from Ralstonia pickettii T1. The rates of enzymatic erosion markedly increased with an increase in the 3H4MV composition to reach the highest one at 7 mol % of 3H4MV, followed by a decrease in erosion rate. PMID:20441146

Tanadchangsaeng, Nuttapol; Tsuge, Takeharu; Abe, Hideki

2010-06-14

380

The thermal conductivity of pressure infiltrated SiC p\\/Al composites with various size distributions: Experimental study and modeling  

Microsoft Academic Search

High volume fractions (56–65vol.%) of SiCp\\/Al composites with various size distributions were prepared by powder injection molding (PIM) and pressure infiltration. An equivalent diameter approach for the thermal conductivity of the composites with a multimodal size distribution is proposed in the framework of Hasselman–Johnson model. Results of the present model are compared to an existing model of differential effective medium

Ke Chu; Chengchang Jia; Xuebing Liang; Hui Chen; Hong Guo

2009-01-01

381

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

382

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

383

[Composition, distribution and abundance of gastropod larvae in the South of Quintana Roo,Mexico and north of Belice].  

PubMed

To know the composition, abundance and distribution of gastropod larvae, monthly samplings were carried out in the south of Quintana Roo, Mexico and north of Belize, from April to December, 1996. Collections were made in six sites at Chinchorro Bank, four in the South Coast and six at Hol-Chan, Belize, between the 10 and 20 hrs. At each station 2.5 m3 of seawater were pumped through a 202 microns mesh; 27 species were identified. The most abundant species were: South Coast, Rissoina sp. 1., Limacina sp. 1 and Natica sp. 1, Chinchorro Bank, Limacina sp. 1, Creseis acicula, Cerithiopsis hero and Rissoina sp. 1 and Hol-Chan, Limacina sp. 2, Alaba incerta and Rissoina sp. 1. The highest abundance was in rainy season. Apparently the presence of winds, coastal currents and food availability, control the distribution and abundance of larvae. PMID:11487926

Oliva Rivera, J; de Jesús Navarrete, A

2000-12-01

384

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

385

Phase composition and distribution of corrosion products grown on galvanised steel in contact with hot water  

NASA Astrophysics Data System (ADS)

The composition of localised corrosion products formed on galvanised steel in contact with hot water was determined using X-ray diffraction, electron probe microanalysis, Raman and Mössbauer spectroscopies. Iron carbonate, a Zn Fe mixed carbonate, goethite, lepidocrocite and akaganeite were identified together with some Fe-free components. The necessity of using different, complementary techniques of analysis is emphasised and some features of the corrosion mechanism are discussed.

Palombarini, G.; Carbucicchio, M.

2006-01-01

386

Phase composition and distribution of corrosion products grown on galvanised steel in contact with hot water  

NASA Astrophysics Data System (ADS)

The composition of localised corrosion products formed on galvanised steel in contact with hot water was determined using X-ray diffraction, electron probe microanalysis, Raman and Mössbauer spectroscopies. Iron carbonate, a Zn-Fe mixed carbonate, goethite, lepidocrocite and akaganeite were identified together with some Fe-free components. The necessity of using different, complementary techniques of analysis is emphasised and some features of the corrosion mechanism are discussed.

Palombarini, G.; Carbucicchio, M.

387

Phase composition and distribution of corrosion products grown on galvanised steel in contact with hot water  

Microsoft Academic Search

The composition of localised corrosion products formed on galvanised steel in contact with hot water was determined using\\u000a X-ray diffraction, electron probe microanalysis, Raman and Mssbauer spectroscopies. Iron carbonate, a Zn–Fe mixed carbonate,\\u000a goethite, lepidocrocite and akaganeite were identified together with some Fe-free components. The necessity of using different,\\u000a complementary techniques of analysis is emphasised and some features of the

G. Palombarini; M. Carbucicchio

2006-01-01

388

The In Situ Ply Shear Strength Distributions in Graphite\\/Epoxy Laminated Composites  

Microsoft Academic Search

An experimental and analytical investigation was performed to study the in situ ply shear strength in fiber-reinforced laminated composites. The effects of ply orientation and laminate thickness on the ply shear strength in laminates were the major concerns of the study. T300\\/1034-C Graphite\\/Epoxy cross-ply laminates were selected for the tests, and a rail shear fixture was used for measuring ply

Fu-Kuo Chang; Ming-Huei Chen

1987-01-01

389

Distribution and Composition of Microbial Populations in a Landfill Leachate Contaminated Aquifer (Grindsted, Denmark)  

Microsoft Academic Search

To investigate whether landfill leachates affected the microbial biomass and\\/or community composition of the extant microbiota,\\u000a 37 samples were collected along a 305-m transect of a shallow landfill-leachate polluted aquifer. The samples were analyzed\\u000a for total numbers of bacteria by use of the acridine orange direct count method (AODC). Numbers of dominant, specific groups\\u000a of bacteria and total numbers of

L. Ludvigsen; H.-J. Albrechtsen; D. B. Ringelberg; F. Ekelund; T. H. Christensen

1999-01-01

390

Composition, distribution and supposed origin of mineral inclusions in sessile oak wood — consequences for microdensitometrical analysis  

Microsoft Academic Search

SEM and light-microscopical observations, supported by chemical microanalysis with an EDXA system, revealed that light-saturated\\u000a pixels observed in X-ray negatives of sessile oak (Quercus petraea Liebl.) wood were caused by inorganic deposits present inside multiseriate ray and axial parenchyma cells. Calcium oxalate\\u000a crystals, silica grains and amorphous granules with varied mineral compositions have been identified. The wood strips of three

Dries Vansteenkiste; Joris Van Acker; Marc Stevens; Didier Le Thiec; Gérard Nepveu

2007-01-01

391

[Distribution and changes in species composition and abundance of ichthyoplankton in the Yangtze estuary].  

PubMed

Based on four surveys of eggs and larvae in the Yangtze estuary in 2005 (April and November) and 2006 (April and September), combined with the historical data of the wetland in 1990 (September) and 1991 (March), we analyzed seasonal changes in fish species composition and quantity of ichthyoplankton. Thirty-six species of egg and larvae were collected and marine fish species were the highest represented ecological guild. Average fish species and average abundance in spring were lower than in autumn for every survey. The total number of eggs in brackish water was higher than in fresh water, but the total number of larvae and juveniles in brackish water was lower. The abundance of eggs and larvae during from 2005 to 2006 in both spring and autumn was higher compared to those from 1990 to 1991. Obvious differences in species composition in September between 1990 and 2006 were found, especially for Erythroculter ilishaeformis and Neosalanx taihuensis. Fish species composition and quantity within the ichthyoplankton community has obviously changed in the Yangtze estuary over the last 20 years. PMID:22653852

Zhang, Heng; Yang, Sheng-Long; Meng, Hai-Xing

2012-06-01

392

The distribution and composition of deep-sea microbenthos in a bathyal region of the western Coral Sea  

NASA Astrophysics Data System (ADS)

The distribution and composition of bathyal (298-1610 m) microbenthos were examined on the Queensland continental slope, the Coral Sea Plateau and the adjacent Queensland and Townsville troughs in the western Coral Sea. Two conspicuous changes in community composition were recorded: (1) ciliates were undetected below 700 m and (2) yeasts and yeast-like cells were undetected above 1150 m. Densities of flagellates decreased, whereas amoebae densities increased significantly with water depth. Densities of living Foraminifera ( overlinex = 56 cm-2) increased significantly from the continental slope to the adjacent troughs. Bacterial numbers ranged from 0.1 to 71.0 × 10 8 cells g -1 dry wt of sediment and decreased significantly with water depth. Chlorophyll a (0.0-19.0 ?g g -1 dry wt) and phaeopigment (0.0-4.9 ?g g -1 dry wt) concentrations suggest that phytodetritus is a major source of organic matter in this tropical region. Concentrations of organic carbon (0.22-0.52%) and nitrogen (<0.01-0.02%) were low compared to most other deep-sea sediments, with a shallow sediment depth distribution indicating little burial of organic matter. These findings, coupled with the presence of abundant protozoan populations (˜10 6 m -2), suggest the potential for rapid microbial activity and dentrital utilization in bathyal surface sediments of the western Coral Sea.

Alongi, Daniel M.

1987-07-01

393

The Impact of Oil Consumption Mechanisms on Diesel Exhaust Particle Size Distributions and Detailed Exhaust Chemical Composition  

SciTech Connect

Detailed exhaust emission data have been taken from a Cummins N-14 single cylinder research engine in which the oil consumption was varied by different engine modifications. Low sulfur fuel was used, and oil consumption was varied by modifying the intake valve stem seals, the exhaust valve stem seals, the oil control ring and combinations of these modifications. Detailed measurements of exhaust gas particle size distributions and chemical composition were made for the various oil consumption configurations for a range of engine loads and speeds. The particulate mass was measured with TEOM and traditional gravimetric filter methods. Filter data for EC/OC, sulfates and trace metals have been taken and analyzed. The trace metals in the particulate mass serve as the basis for assessing oil consumption at the different operating conditions. The data indicate that the oil consumption for the steady state testing done here was approximately an order of magnitude below oil consumption values cited in the literature. We did measure changes in the details of the chemical composition of the particulate for the different engine operating conditions, but it did not correlate with changes in the oil consumption. Furthermore, the data indicate that the particle size distribution is not strongly impacted by low level oil consumption variations observed in this work.

Stetter, J; Forster, N; Ghandhi, J; Foster, D

2003-08-24

394

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.

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

395

ALUMINUM-CONTAINING SCALES IN WATER DISTRIBUTION SYSTEMS: PREVALENCE AND COMPOSITION  

EPA Science Inventory

Aluminum (Al) deposits in distribution systems can have important detrimental effects on tap water quality because they can increase turbidity and interfere with disinfection, and they can increase energy loss during water transport. There is also the possibility that they have ...

396

A review of the floral composition and distribution of mangroves in Sri Lanka  

Microsoft Academic Search

Recently published reports list numbers and distributions of Sri Lankan mangrove species that outnumber the actual species present in the field. The present study serves to review this literature and highlight the causes of such apparently large species numbers, while providing an objective and realistic review of the mangrove species actually present in Sri Lanka today. This study is based

L. P. JAYATISSA; F. DAHDOUH-GUEBAS; N. KOEDAM

2002-01-01

397

Vertical distribution and isotopic composition of living planktonic foraminifera in the western North Atlantic  

Microsoft Academic Search

Thirteen species of planktonic foraminifera collected with vertically stratified zooplankton tows in the slope water, Gulf Stream cold core ring, and northern Sargasso Sea show significant differences in their vertical distributions in the upper 200 meters of these different hydrographic regimes. Gulf Stream cold core rings may be responsible for a southern displacement of the faunal boundary associated with the

R. G. Fairbanks; P. H. Wiebe; A. W. H. Be

1980-01-01

398

Bacterial Composition of Biofilms Collected From Two Service Areas in a Metropolitan Drinking Water Distribution System  

EPA Science Inventory

The development and succession of bacteria were examined by 16S rRNA gene clone libraries generated from various biofilms within a metropolitan water distribution system. Biofilms were obtained from off-line devices using polycarbonate coupons from annular reactors incubated for ...

399

Distribution of Friction Heat during Cold-Rolling of Metals by Using Composite Rolls  

Microsoft Academic Search

The problem of transient frictional heating in cold rolling of metals is considered. The roll is assumed to be composed of periodic concentric stratified cylinders with different thermal properties. First, the temperature distributions in the considered bodies are obtained by solving the corresponding boundary value problems of heat conduction. Next, the influence of the geometric and thermal properties of the

S. Matysiak; S. Konieczny; A. Yevtushenko

1998-01-01

400

Salp distribution and size composition in the Atlantic sector of the Southern Ocean  

NASA Astrophysics Data System (ADS)

Salp abundance and length frequency were measured during the large-scale CCAMLR 2000 Survey conducted in the Atlantic Sector of the Southern Ocean in the 1999/2000 season. Results from regional surveys around Elephant Island in 1994/95 and 1996/97 seasons also were examined. During the CCAMLR 2000 Survey, salp abundance was higher in the Antarctic Peninsula and South Sandwich Island areas than in the central Scotia Sea. The probable reason for this pattern is a negative relationship with phytoplankton abundance; the central Scotia Sea having greater phytoplankton concentrations than required for optimal salp filter-feeding performance. Cluster analysis of salp size composition resulted in three cluster groups for each of the three surveys. Clusters comprising large salps occurred in warmer waters in all three surveys. The size composition of the salp populations suggests that the timing of intense asexual reproductive budding was earlier in warmer waters. As surface water temperatures generally decrease from north to south, and increase from spring to summer, the general spatio-temporal pattern of asexual reproduction by budding is likely to proceed from north to south as the summer season progresses.

Kawaguchi, S.; Siegel, V.; Litvinov, F.; Loeb, V.; Watkins, J.

2004-06-01

401

Development of Reliability Based Life Prediction Methods for Thermal and Environmental Barrier Coatings in Ceramic Matrix Composites  

NASA Technical Reports Server (NTRS)

Literature survey related to the EBC/TBC (environmental barrier coating/thermal barrier coating) fife models, failure mechanisms in EBC/TBC and the initial work plan for the proposed EBC/TBC life prediction methods development was developed as well as the finite element model for the thermal/stress analysis of the GRC-developed EBC system was prepared. Technical report for these activities is given in the subsequent sections.

Shah, Ashwin

2001-01-01

402

Vertical distribution and isotopic composition of living planktonic foraminifera in the Western north atlantic.  

PubMed

Thirteen species of planktonic foraminifera collected with vertically stratified zooplankton tows in the slope water, Gulf Stream cold core ring, and northern Sargasso Sea show significant differences in their vertical distributions in the upper 200 meters of these different hydrographic regimes. Gulf Stream cold core rings may be responsible for a southern displacement of the faunal boundary associated with the Gulf Stream when reconstructed from the deep-sea sediment record. Oxygen isotope analyses of seven species reveal that nonspinose species (algal symbiont-barren) apparently calcify in oxygen isotope equilibrium, whereas spinose species usually calcify out of oxygen isotope equilibrium by approximately -0.3 to -0.4 per mil in delta(18)O values. The isotope data indicate that foraminifera shells calcify in depth zones that are significantly narrower than the overall vertical distribution of a species would imply. PMID:17730814

Fairbanks, R G; Wiebe, P H; Bé, A W

1980-01-01

403

Vertical distribution and isotopic composition of living planktonic foraminifera in the western North Atlantic  

SciTech Connect

Thirteen species of planktonic foraminifera collected with vertically stratified zooplankton tows in the slope water, Gulf Stream cold core ring, and northern Sargasso Sea show significant differences in their vertical distributions in the upper 200 meters of these different hydrographic regimes. Gulf Stream cold core rings may be responsible for a southern displacement of the faunal boundary associated with the Gulf Stream when reconstructed from the deep-sea sediment record. Oxygen isotope analyses of seven species reveal that nonspinose species (algal symbiont-barren) apparently calcify in oxygen isotope equilibrium, whereas spinose species usually calcify out of oxygen isotope equilibrium by approximately -0.3 to -0.4 per mil in delta/sup 18/O values. The isotope data indicate that foraminifera shells calcify in depth zones that are significantly narrower than the overall vertical distribution of a species would imply.

Fairbanks, R.G. (Columbia Univ., Palisades, NY); Wiebe, P.H.; Be, A.W.H.

1980-01-04

404

Composition, enantiomeric distribution, and antimicrobial activity of Tanacetum argenteum subsp. flabellifolium essential oil  

Microsoft Academic Search

Tanacetum argenteum (Lam.) Willd. subsp. flabellifolium (Boiss. & Heldr.) Grierson of Asteraceae is an endemic species in Turkey. Hydrodistillation of aerial parts using a Clevenger apparatus yielded an essential oil, which was subsequently analyzed by gas chromatography–mass spectroscopy (GC–MS). ?-Pinene (29%), (E)-sesquilavandulol (16%), and camphor (14%) were found as main constituents. Enantiomeric distribution of the monoterpenes ?-pinene and camphor was

Nurhayat Tabanca; Fatih Demirci; Betül Demirci; David E. Wedge; K. Hüsnü Can Baser

2007-01-01

405

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

406

Spatial distribution characteristics of stable carbon isotope compositions in desert plant Reaumuria soongorica (Pall.) Maxim  

Microsoft Academic Search

In order to investigate the distribution characteristics of stable carbon isotope ratios (?\\u000a 13C) in the desert plant Reaumuria soongorica, the ?\\u000a 13C values of leaves were measured in 407 individuals of 21 populations. Soil physicochemical properties including soil water\\u000a content, soil total dissolved solids, soil total nitrogen, soil total phosphorus and soil organic content were also analyzed\\u000a in order

Jianying Ma; Fahu Chen; Huiwen Zhang; Dunsheng Xia

2007-01-01

407

Species Composition, Distribution and Management of Trees in Rice Paddy Fields in Central Lao, PDR  

Microsoft Academic Search

Presence of different types of trees dispersed singly or in small groups throughout the fields is a very common feature in\\u000a the extensive rice paddies of Laos and Thailand. Factors such as land-settlement history, proximity to forest, and role of\\u000a species in the local culture are known to influence the nature and distribution of tree species so retained. The extent

Y. Kosaka; S. Takeda; S. Prixar; S. Sithirajvongsa; K. Xaydala

2006-01-01

408

Soil organic carbon stocks, distribution, and composition affected by historic land use changes on adjacent sites  

Microsoft Academic Search

Historic alterations in land use from forest to grassland and cropland to forest were used to determine impacts on carbon\\u000a (C) stocks and distribution and soil organic matter (SOM) characteristics on adjacent Cambisols in Eastern Germany. We investigated\\u000a a continuous Norway spruce forest (F-F), a former cropland afforested in 1930 (C-F), and a grassland deforested in 1953 (F-G).\\u000a For C