bluuebunny/crossref_metadata_2025 huggingface dataset:
Indentation-induced two-way shape memory surfaces
Authors: Fei Xueling , Zhang Yijun , Grummon David S. , Cheng Yang-Tse
Published: February 2009

A method is described for the creation of surfaces with cyclically reversible topographical form. Using spherical and cylindrical indenters applied to NiTi shape-memory alloys, an indentation-planarization technique is shown to result in a two-way shape memory effect that can drive flat-to-wavy surface transitions on changing temperature. First, it is shown that deep spherical indents, made in martensitic NiTi, exhibit pronounced two-way cyclic depth changes. After planarization, these two-way cyclic depth changes are converted to reversible surface protrusions, or “exdents.” Both indent depth changes and cyclic exdent amplitudes can be related to the existence of a subsurface deformation zone in which indentation has resulted in plastic strains beyond that which can be accomplished by martensite detwinning reactions. Cylindrical indentation leads to two-way displacements that are about twice as large as that for the spherical case. This is shown to be due to the larger deformation zone under cylindrical indents, as measured by incremental grinding experiments.
Slip distance model for the indentation size effect at the initiation of plasticity in ceramics and metals
Authors: Bushby A.J. , Zhu T.T. , Dunstan D.J.
Published: February 2009

The indentation size effect, in which the contact pressure increases as the size of contact decreases, has been observed for many years for both spherical and pointed indenters. The concept of strain gradient plasticity has been used to describe this phenomenon, but it is often necessary to introduce a material length scale l* to fit experimental data. Here we present a theory based on the concept of dislocation slip distance, which naturally generates the scaling and incorporates the material parameters that influence the size effect. We compare this model with experimental data for a range of ceramics and tungsten metal and show that the yield strain and Burgers vector are the important material parameters in the indentation size effect.
Numerical investigation of indentation fatigue on polycrystalline copper
Authors: Xu B.X. , Yue Z.F. , Chen X.
Published: February 2009

The dynamic indentation response of polycrystalline copper under cyclic fatigue loading is studied with a flat cylindrical indenter. First, a simple analytical model shows that in a purely elastic solid, the indentation depth responds with the same wavelength and frequency as the applied sinusoidal fatigue load. Next, a numerical simulation of an indentation fatigue test on an elastic-plastic solid (polycrystalline copper) is performed. Finite element analyses reveal that the mean indentation depth is controlled by both the mean of the indentation fatigue load and the load amplitude, while the amplitude of the indentation depth is independent of the mean load. Further investigations indicate that with an increased number of cycles, the increment of indentation depth reaches a constant rate. The steady state indentation depth rate is dependent not only on the amplitude of indentation fatigue load but also on the fatigue mean load, which is similar to strain accumulation during a conventional fatigue test. A parallel indentation experiment on annealed polycrystalline copper also confirms the effect of the fatigue mean load, indicating consistency with numerical results.
Predicting macroscopic plastic flow of high-performance, dual-phase steel through spherical nanoindentation on each microphase
Authors: Choi Byoung-Wook , Seo Dong-Han , Yoo Jang-Yong , Jang Jae-il
Published: February 2009

An attempt was made to predict the macroscopic plastic flow of a high-performance pipeline steel, consisting of dual constituent phases (soft ferrite and hard bainite), by performing nanoindentation experiments on each microphase with two spherical indenters that have different radii (550 nm and 3.3 μm). The procedure is based on the well known concepts of indentation stress-strain and constraint factor, which make it possible to relate indentation hardness to the plastic flow of the phases. Additional consideration of the indentation size effect for sphere and application of a simple “rule-of-mixture” led us to a reasonably successful estimation of the macroscopic plastic flow of the steel from the microphases properties, which was verified by comparing the predicted stress-strain curve with that directly measured from the conventional tensile test of a bulky sample.
Influence of the indenter tip geometry and environment on the indentation modulus of enamel
Authors: Guidoni G.M. , He L.H. , Schöberl T. , Jäger I. , Dehm G. , Swain M.V.
Published: February 2009

The aim of the investigation was to study the influence of indenter tip geometry on the conventionally obtained indentation modulus of enamel by nanoindentation. Indentation tests on bovine enamel using three different diamond pyramidal indenters with half face angles 65.27°, 45°, and 35.26° were conducted to evaluate the indentation modulus using the Oliver–Pharr method [W.C. Oliver and G.M. Pharr,J. Mater. Res.7,1564 (1992)]. In addition, three different dehydration conditions were studied: wet under Hank's balanced salt solution, laboratory dried, and vacuum dehydrated. For the Berkovich indenter (65.27°) and 45° pyramidal indenters, there was only a small difference between indentation modulus values, whereas for the cube-corner indenter (35.26°) a ratio of 2.4 between laboratory dry and wet samples was found. A detailed evaluation, including indentation creep and recovery as well as pileup, resulted in a reduction of this latter ratio to 1.7. This still large difference was rationalized on the basis of the different deformation mechanisms generated by indenters of different face angles.
Storage and loss stiffnesses and moduli as determined by dynamic nanoindentation
Authors: Wright Wendelin J. , Nix W.D.
Published: February 2009

The storage and loss stiffnesses for the composite response of the sample, indenter, and load frame during dynamic nanoindentation are derived. In the first part of the analysis, no physical model is assigned to the composite system. It is shown that this case is equivalent to the conventional nanoindentation analysis. In the second part of the analysis, the sample is modeled as a standard linear solid in series with the indenter and load frame. The results for the storage and loss stiffnesses as computed by the two methods differ by at most ∼3% for the elastomeric system under consideration. Results for the storage and loss moduli are also similar. The relative merits and weaknesses of each analysis are discussed.
Pressure sensitive flow and constraint factor in amorphous materials below glass transition
Authors: Prasad K. Eswar , Keryvin V. , Ramamurty U.
Published: February 2009

The constraint factor, C (given by the hardness-yield strength ratio H/Y in the fully plastic regime of indentation), in metallic glasses, is greater than three, a reflection of the sensitivity of their plastic flow to pressure. Furthermore, C increases with increasing temperature. In this work, we examine if this is true in amorphous polymers as well, through experiments on amorphous poly(methyl methacrylate) (PMMA). Uniaxial compression as well as spherical indentation tests were conducted in the 248–348 K range to construct H/Y versus indentation strain plots at each temperature and obtain the C-values. Results show that C increases with temperature in PMMA as well. Good correlation between the loss factors, measured using a dynamic mechanical analyzer, and C, suggest that the enhanced sensitivity to pressure is possibly due to β-relaxation. We offer possible mechanistic reasons for the observed trends in amorphous materials in terms of relaxation processes.
Influence of the loading rate on the indentation response of Ti-based metallic glass
Authors: Sort J. , Fornell J. , Li W. , Suriñach S. , Baró M.D.
Published: February 2009

The mechanical behavior of Ti-based metallic glass has been investigated by means of indentation experiments at different loading rates. Contrary to many crystalline materials, an increase of the loading rate causes a reduction of hardness, i.e., a mechanical softening. This effect is ascribed to deformation-induced creation of excess free volume, which is more pronounced for higher strain rates. The decrease of hardness is accompanied with an increase of the contact stiffness and a reduction of the reduced elastic modulus. Finite element simulations reveal that the mechanical response of this material can be described using the Mohr-Coulomb yield criterion. The changes in the nanoindentation curves with the increase of loading rate are well reproduced by decreasing the value of the Mohr-Coulomb cohesive stress. This result is consistent with the presumed enhancement of free volume.
Microindentation and nanoindentation of human fingernails at varying relative humidity
Authors: Farran Laura , Ennos A. Roland , Eichhorn Stephen J.
Published: February 2009

The indentation properties of human fingernails at varying humidity are reported. The samples were indented using both microindentation, to obtain their Vickers hardness and also nanoindented using a Berkovich indenter tip. The relative humidity (RH) of the samples was controlled by using salt solutions with a sealed and enclosed environment surrounding the testing equipment. It was shown that the Vickers hardness of the samples is sensitive to RH, with recovery of the nail material more readily occurring for nails tested at >55% RH. This recovery mechanism is discussed in terms of the structure of the nails, and this approach is also suggested as a technique for following recovery mechanisms in natural materials under varying humidity. The hardness obtained by nanoindentation is similar to previously published data, but does not change with humidity. The modulus of the nails is also insensitive to relative humidity, but in the same range as the value derived from the microindentation tests.
Validity of the reduced modulus concept to describe indentation loading response for elastoplastic materials with sharp indenters
Authors: Choi In-suk , and Ruth Schwaiger Oliver Kraft
Published: February 2009

Recent computational parametric studies have developed reverse algorithms to extract material properties of elastoplastic materials using experimental sharp nanoindentation. These methods used reduced modulus in their parameters to include the effect of indenter compliance. To investigate the validity of using reduced modulus, we conducted experimental indentation of a couple of representative cases for elastoplastic metals with a diamond and a sapphire Berkovich tip. Then, we performed a finite element study for sharp indentation of the same material systems. Both computational and experimental results indicate that the use of reduced modulus is invalid to describe indentation loading response for elastoplastic materials in a certain material regime. Our results show that indenter compliance is overestimated by the previous predictions using reduced modulus. This overestimation leads to underestimation of indenter curvature and causes error in extracting material properties by reverse algorithms.
Effect of crystallographic orientation on phase transformations during indentation of silicon
Authors: Gerbig Y.B , Stranick S.J. , Morris D.J. , Vaudin M.D. , Cook R.F.
Published: February 2009

In a statistical nanoindentation study using a spherical probe, the effect of crystallographic orientation on the phase transformation of silicon (Si) was investigated. The occurrence and the contact pressures at which events associated with phase transformation occur, for an indentation force range from 20 to 200 mN, were analyzed and compared for the orientations Si(001), Si(110), and Si(111). It was found that plastic deformation combined with phase transformation during loading was initiated at lower forces (contact pressures) for Si(110) and Si(111) than for Si(001). Also, the contact pressure at which the phase transformation occurred during unloading was strongly influenced by the crystallographic orientation, with up to 38% greater values for Si(110) and Si(111) compared to Si(001). Mapping the residual stress field around indentations by confocal Raman microscopy revealed significant differences in the stress pattern for the three orientations.
A new insight on reversible deformation and incipient plasticity during nanoindentation test in MgO
Authors: Montagne Alex , Tromas Christophe , Audurier Valérie , Woirgard Jacques
Published: February 2009

In this study, nucleation of dislocations in magnesium oxide (MgO) during nanoindentation with a spherical indenter is investigated. For flat and defect-free surfaces prepared by chemo/mechanical polishing, reversible load–displacement curves have been obtained for load as high as 300 mN, whereas on a cleaved MgO surface, pop-in and plastic deformation occur at 10 mN with the same indenter. Furthermore, these reversible curves deviate from the Hertz contact theory. Indented areas have then been characterized by atomic force microscopy and nanoetching. In some cases, few slip lines are observed for reversible indentation tests. However, the slip lines position indicate that the nucleation process of the corresponding dislocations is different from that involved during a pop-in phenomenon.
Viscoelastic and poroelastic mechanical characterization of hydrated gels
Authors: Galli Matteo , Comley Kerstyn S.C. , Shean Tamaryn A.V. , Oyen Michelle L.
Published: February 2009

Measurement of the mechanical behavior of hydrated gels is challenging due to a relatively small elastic modulus and dominant time-dependence compared with traditional engineering materials. Here polyacrylamide gel materials are examined using different techniques (indentation, unconfined compression, dynamic mechanical analysis) at different length-scales and considering both viscoelastic and poroelastic mechanical frameworks. Elastic modulus values were similar for nanoindentation and microindentation, but both indentation techniques overestimated elastic modulus values compared to homogeneous loading techniques. Hydraulic and intrinsic permeability values from microindentation tests, deconvoluted using a poroelastic finite element model, were consistent with literature values for gels of the same composition. Although elastic modulus values were comparable for viscoelastic and poroelastic analyses, time-dependent behavior was length-scale dependent, supporting the use of a poroelastic, instead of a viscoelastic, framework for future studies of gel mechanical behavior under indentation.
Nanoindentation of histological specimens: Mapping the elastic properties of soft tissues
Authors: Akhtar R. , Schwarzer N. , Sherratt M.J. , Watson R.E.B. , Graham H.K. , Trafford A.W. , Mummery P.M. , Derby B.
Published: February 2009

Although alterations in the gross mechanical properties of dynamic and compliant tissues have a major impact on human health and morbidity, there are no well-established techniques to characterize the micromechanical properties of tissues such as blood vessels and lungs. We have used nanoindentation to spatially map the micromechanical properties of 5-μm-thick sections of ferret aorta and vena cava and to relate these mechanical properties to the histological distribution of fluorescent elastic fibers. To decouple the effect of the glass substrate on our analysis of the nanoindentation data, we have used the extended Oliver and Pharr method. The elastic modulus of the aorta decreased progressively from 35 MPa in the adventitial (outermost) layer to 8 MPa at the intimal (innermost) layer. In contrast, the vena cava was relatively stiff, with an elastic modulus >30 MPa in both the extracellular matrix-rich adventitial and intimal regions of the vessel. The central, highly cellularized, medial layer of the vena cava, however, had an invariant elastic modulus of ∼20 MPa. In extracellular matrix-rich regions of the tissue, the elastic modulus, as determined by nanoindentation, was inversely correlated with elastic fiber density. Thus, we show it is possible to distinguish and spatially resolve differences in the micromechanical properties of large arteries and veins, which are related to the tissue microstructure.
In situ scanning electron microscopy indentation studies on multilayer nitride films: Methodology and deformation mechanisms
Authors: Rzepiejewska-Malyska K.A. , Mook W.M. , Parlinska-Wojtan M. , Hejduk J. , Michler J.
Published: February 2009

Systematic studies of the deformation mechanisms of multilayer transition metal nitride coatings TiN/CrN, TiN/NbN, and NbN/CrN, and corresponding reference coatings of TiN, NbN, and CrN deposited by a direct current (dc) magnetron sputtering process onto silicon 〈100〉 have been performed. Mechanical characterization was conducted using a combination of microindentation and nanoindentation in the load range 30 to 150 mN and 0.5 to 3.5 mN, respectively. For both load ranges, scanning electron microscopy (SEM) in situ indentation was used to observe the indentation process including any pileup, sink-in, and fracture mechanisms specific to each coating. The coatings’ microstructure, both before and after indentation, was analyzed using transmission electron microscopy (TEM). It was possible to both correlate the indentation load–displacement response to surface roughness effects and fracture modes (substrate and film cracking) and observe deformation mechanisms within the coatings.
Scale effects for strength, ductility, and toughness in “brittle” materials
Authors: Gerberich W.W. , Michler J. , Mook W.M. , Ghisleni R. , Östlund F. , Stauffer D.D. , Ballarini R.
Published: February 2009

Decreasing scales effectively increase nearly all important mechanical properties of at least some “brittle” materials below 100 nm. With an emphasis on silicon nanopillars, nanowires, and nanospheres, it is shown that strength, ductility, and toughness all increase roughly with the inverse radius of the appropriate dimension. This is shown experimentally as well as on a mechanistic basis using a proposed dislocation shielding model. Theoretically, this collects a reasonable array of semiconductors and ceramics onto the same field using fundamental physical parameters. This gives proportionality between fracture toughness and the other mechanical properties. Additionally, this leads to a fundamental concept of work per unit fracture area, which predicts the critical event for brittle fracture. In semibrittle materials such as silicon, this can occur at room temperature when the scale is sufficiently small. When the local stress associated with dislocation nucleation increases to that sufficient to break bonds, an instability occurs resulting in fracture.
Nanoindentation analysis as a two-dimensional tool for mapping the mechanical properties of complex surfaces
Authors: Randall Nicholas X. , Vandamme Matthieu , Ulm Franz-Josef
Published: February 2009

Instrumented indentation (referred to as nanoindentation at low loads and low depths) has now become established for the single point characterization of hardness and elastic modulus of both bulk and coated materials. This makes it a good technique for measuring mechanical properties of homogeneous materials. However, many composite materials are composed of material phases that cannot be examined in bulk form ex situ (e.g., carbides in a ferrous matrix, calcium silicate hydrates in cements, etc.). The requirement for in situ analysis and characterization of chemically complex phases obviates conventional mechanical testing of large specimens representative of these material components. This paper will focus on new developments in the way that nanoindentation can be used as a two-dimensional mapping tool for examining the properties of constituent phases independently of each other. This approach relies on large arrays of nanoindentations (known as grid indentation) and statistical analysis of the resulting data.
Maternal Origin and Migratory History of Steelhead and Rainbow Trout Captured in Rivers of the Central Valley, California
Authors: Zimmerman Christian E. , Edwards George W. , Perry Kathleen
Published: February 2009

Steelhead Oncorhynchus mykiss (anadromous rainbow trout) in the Central Valley of California were listed as threatened under the Endangered Species Act in 1998. Unfortunately, little is known about the distribution of steelhead in the tributaries of the Sacramento‐San Joaquin River system in the Central Valley or the relationship between sympatric anadromous and nonanadromous life history types. We used analysis of otolith strontium: Calcium (Sr:Ca) ratios to determine maternal origin (anadromous versus nonanadromous) and migratory history (anadromous versus nonanadromous) of rainbow trout collected in Central Valley rivers between 2001 and 2007. Of the 964 otoliths examined, 224 were determined to be from the progeny of steelhead females and 740 from the progeny of nonanadromous rainbow trout females. Progeny of steelhead maternal origin were present at all of the sites sampled, but the proportion varied among sites (0.04‐0.74). Based on transects of otolith Sr:Ca ratios, only five fish were confirmed to be adult steelhead. This is a conservative estimate of the distribution of adult steelhead since, due to conservation concerns, our sampling only collected a limited number of adults. The remaining 214 fish older than age 4 were not anadromous, and 16 of them were determined to be the progeny of steelhead females. Overall, these results refine our understanding of the distribution of steelhead in Central Valley rivers and confirm reports of steelhead occurrence in those rivers.
Using Trace Elements in Pectoral Fin Rays to Assess Life History Movements in Sturgeon: Estimating Age at Initial Seawater Entry in Klamath River Green Sturgeon
Authors: Allen Peter J. , Hobbs James A. , Cech Joseph J. , Van Eenennaam Joel P. , Doroshov Serge I.
Published: February 2009

To investigate the timing of the initial entry of green sturgeonAcipenser medirostrisinto seawater, we examined the ratios of strontium and barium to calcium in pectoral fin rays via laser ablation‐inductively coupled plasma‐mass spectrometry. In a reference group of six hatchery fish that was reared 1‐2 years in freshwater and 1‐3 years in seawater, we found a significant increase in the Sr:Ca ratio, a decrease in the Ba:Ca ratio, and an increase in the Sr:Ba ratio in calcified growth zones during the transition from freshwater to seawater. In 10 wild adults captured in the Klamath River, California, combined evaluation of the Sr:Ca and Ba:Ca ratios provided a clearer understanding of fish movements than the Sr:Ba ratio, probably because wild fish have a more complex life history. The Ba:Ca ratio dropped significantly between growth zones 1 and 2 (ages 0.5‐1.5), indicating a transition into saline waters, such as the Klamath River estuary. The Sr:Ca ratio increased slightly in the same location but attained the values found in reference fish held in seawater between growth zones 3 and 4 (ages 2.5‐3.5). The Sr:Ca, Ba:Ca, and Sr:Ba ratios in growth zones 4‐6 (ages 4.5‐6.5) of wild fish were similar to those found in reference fish held in seawater and corroborated the results of previous physiological studies as well as the limited field data. These results demonstrate the usefulness of trace element analyses of green sturgeon pectoral fin rays and confirm an early age of entry into seawater for this species.
Effects of American Water Willow Establishment on Density, Growth, Diet, and Condition of Age‐0 Largemouth Bass in Kansas Reservoirs
Authors: Strakosh Timothy R. , Gido Keith B. , Guy Christopher S.
Published: February 2009

Many Kansas reservoirs are currently experiencing decreased sport fish production as a result of the typical aging processes that occur in impounded systems. American water willow Justicia americana was planted in three Kansas reservoirs (>1,800 ha) for littoral zone habitat enhancement to mitigate sport fish losses and increase the recruitment of age‐0 largemouth bass Micropterus salmoides. We investigated whether the density, growth, condition, and diet of age‐0 largemouth bass in coves with water willow differed from coves without water willow in these reservoirs. Samples of largemouth bass were collected from 2001 to 2004 in June, July, and August. We found a consistent pattern among reservoirs and sample years; coves with water willow had significantly greater densities of age‐0 largemouth bass than control coves, but no significant differences were found in growth, condition, or diet. Water willow beds appeared to buffer wave action, trapping fine sediments and floating debris, which significantly increased the overall habitat complexity. The additional organic material may have augmented littoral productivity, supporting the higher densities without physiologically hindering the age‐0 largemouth bass. Overall, our study suggests that water willow establishment is an effective means of enhancing littoral nursery habitat for age‐0 largemouth bass.
Silurian lichid trilobites from northwestern Canada: Ontogeny and phylogeny of lichids
Authors: Campbell Margaret J. , Chatterton Brian D. E.
Published: February 2009

Previously unknown ontogenies of five lichid genera,Dicranopeltis, Platylichas, Borealarges, DicranogmusandRadiolichas, are described and placed in the context provided by a review of known lichid ontogenies. Lichid phylogenies have been based on holaspid morphology alone without reference to ontogeny. To broaden knowledge of lichid phylogeny, an analysis, based on the last protaspid instar of lichids and possible sister group taxa, is conducted. The results of this analysis show that, within the lichids, the traditional subfamily groupings are not supported, and the sister group of lichids is more likely to be found within the Proetida than the Odontopleurida. Tubercles, a prominent feature of lichid morphology, have not been considered taxonomically significant. An examination suggests that tubercle arrangement and the pattern of change of tubercle arrangement through ontogeny could be important in defining taxa. It is recommended that future work on lichid phylogeny include ontogenetic information and patterns of change in development.
Eocene ostracodes from Hahajima Island of the Ogasawara (Bonin) Islands, northwestern Pacific, and their paleobiogeographic significance in the West Pacific
Authors: Yamaguchi Tatsuhiko , Kamiya Takahiro
Published: February 2009

During the Eocene, Hahajima Island of the Ogasawara (Bonin) Islands of the Izu-Mariana Arc in the North Pacific was located near the present-day position of western Pacific Micronesia. We identified 17 Eocene ostracode species from the island, of which are new species and likely endemic to this island or to the West Pacific. These new species are systematically described herein and include:Costa matsumaruin. sp.,Cytherelloidea ogasawaraensisn. sp.,Havanardia ujiiein. sp.,Jugosocythereis nishiin. sp.,Neonesidea boninensisn. sp.,Schizocythere antiquimicronesianan. sp., andUroleberis hahajimaensisn. sp. The Eocene ostracode fauna has a higher rate of endemism than does the modern Micronesian fauna and contains Tethyan genera. These findings contradict a hypothesis that the Pacific fauna had a higher endemism rate after the Paleogene. The findings support another hypothesis that some genera invaded the Pacific from Tethys during the Paleogene. They suggest that West Pacific species did not disperse to the periphery of the Indo-West Pacific region during the Middle–Late Eocene. The “center of origin” hypothesis cannot be applied to Middle–Late Eocene marine ostracode biogeography.
Cranial morphology and systematics of an extraordinary sample of the Late Neogene dwarf tapir,Tapirus polkensis(Olsen)
Authors: Hulbert Richard C. , Wallace Steven C. , Klippel Walter E. , Parmalee Paul W.
Published: February 2009

The previously poorly known“Tapiravus” polkensisOlsen, 1960 (Mammalia, Perissodactyla, Tapiridae) is now known from abundant, well preserved specimens from both the type area in central Florida and from the Gray Fossil Site (GFS) in eastern Tennessee. The latter has produced over 75 individuals, the greatest number of tapirids from a single fossil site, including many articulated skeletons. Almost all linear measurements taken on skulls, mandibles, and cheek teeth from GFS have coefficients of variation less than 10 (most between 3 and 7), indicating the presence of a single species. However, the sample reveals considerable intraspecific variation for a few key morphologic features, including development of the sagittal crest, outline shape of the nasals, and number and relative strength of lingual cusps on the P1. The Florida sample ofT. polkensisis more limited, but has the same state as the GFS sample for all preserved characters of systematic significance, and while the Florida teeth are on average smaller (especially narrower lower cheek teeth), they fall either within or just below the observed range of the Gray Fossil Site population. The new material supports a reassignment of“Tapiravus” polkensisto the genusTapirus, and demonstrates that the geologic age of the species is significantly younger than previously thought, Hemphillian rather than Barstovian.Tapirus polkensisis the smallest known North AmericanTapirus, and smaller than any of the extant species in the genus, with an estimated average mass of 125 kg.
Cardiocystella, a new cornute stylophoran from the Upper Cambrian Whipple Cave Formation, Eastern Nevada, USA
Authors: Sumrall Colin D. , Sprinkle James , Pruss Sara , Finnegan Seth
Published: February 2009

Two new well-preserved cornute stylophorans from the Upper Cambrian Whipple Cave Formation represent a new genus and species assigned here to Cardiocystella prolixora. These nearly complete specimens contain morphological information not available from other cornute specimens previously collected from this formation. Both specimens are preserved with superior faces exposed. One specimen contains a nearly complete theca but a somewhat disrupted aulacophore, whereas the other theca has been partially damaged by burrows but has a nearly complete but moderately eroded aulacophore. Cardiocystella prolixora exhibits wide marginals, abundant supracentral platelets, and an aulacophore with cover plates. Supracentral platelets cover much of the interior regions of the theca, which lacks a visible zygal bar in both specimens. In holotype 1791TX13, a bulge in the superior face of the theca likely shows the zygal bar position. The wide marginals of these new specimens resemble those of a specimen previously described from a partial theca and aulacophore assigned to Archaeocothurnus species indeterminate (Sumrall et al., 1997); however, the specimens described here are heart-shaped rather than boot-shaped. The placement of this specimen in a new genus and species is based on its unique marginal shape and arrangement.
The first remopleuridioidean trilobite and the earliestParabolinellaspecies recorded in the Furongian of Scandinavia
Authors: Terfelt Fredrik , Ahlgren John
Published: February 2009

The furongian of Mount Kinnekulle, Västergötland, Sweden (Fig. 1) is exposed in a number of road cuts, stream cuts, and abandoned alum shale quarries scattered around the mountain (e.g., Westergård, 1922, fig. 18; Müller and Hinz, 1991, fig. 2). Stratigraphically, the exposed successions span theOlenus gibbosusZone through thePeltura paradoxaZone (Fig. 2), and they have a maximum thickness of ca 12 m (Westergård, 1943). The strata consist of interfingering layers of alum shale and bituminous limestone (colloquially referred to as “orsten”). Trilobites, predominantly olenids, occur frequently throughout the succession, although they are generally restricted to the limestones. During an investigation of trilobites in theLotagnostus americanusZone (Fig. 2) at two localities on Kinnekulle, the second author (JA) recovered two unusual trilobites. After a closer examination they could be assigned toElkanaspisLudvigsen, 1982 andParabolinellaBr⊘gger, 1882, both of which are extremely rare in the Furongian of Scandinavia.
A replacement name for †Psammorhynchus Grande & Hilton, 2006 (Actinopterygii, Acipenseriformes, Acipenseridae)
Authors: Grande Lance , Hilton Eric J.
Published: February 2009

In 2006, we (Grande & Hilton, 2006) described a well-preserved fossil sturgeon (Acipenseridae) from the Late Cretaceous of Montana and proposed the name †Psammorhynchus longipinnis Grande & Hilton for the new species. Through accidental discovery of an on-line taxonomic database of flatworms (Tyler et al., 2006) and subsequent investigation, we recently discovered that the genus-group name is preoccupied by Psammorhynchus Meixner, 1938 in Platyhelminthes (“Turbellaria”). Therefore, under Article 60 of the International Code of Zoological Nomenclature (ICZN, 1999), a replacement name is required for the junior homonym †Psammorhynchus Grande and Hilton.
Sulfate attack on hardened Portland cement pastes with different porosities in presence of water-repelling admixtures
Authors: Hashem F.S.
Published: February 2009

Different cement pastes were prepared using ordinary Portland cement with various water/cement (w/c) ratios in both the presence and absence of calcium stearate as a water-repelling admixture. The various w/c ratios used were (0·32–0·20). Superplasticiser (sodium salt of naphthalene formaldehyde sulfonic acid polycondensate) was used for mixtures with w/c = 0·20 to facilitate the mixing process. The different cement pastes were cured in a humid atmosphere (approximately 95% relative humidity) for the first 24 h, then under water for the remaining time up to 28 days. After 28 days of hydration, the different specimens were immersed in 7% sodium sulfate solution for up to 16 months. The degree of sulfate attack on different specimens was investigated using: X-ray diffraction analysis and scanning electron microscopy. The results of the compressive strength, percentage of expansion, bulk density and mass change at various curing ages showed an increase in the sulfate resistance of the hardened cement pastes prepared with w/c ratios of 0·24 and 0·20. The presence of 0·5% calcium stearate as an admixture in the cement pastes improved the sulfate resistance in the pastes with different w/c ratios used in this study and that related to its waterproofing effects. This conclusion was confirmed by both X-ray analysis and scanning electron microscopy.
An Iterative Ensemble Kalman Filter for Multiphase Fluid Flow Data Assimilation
Authors: Gu Yaqing , Oliver Dean S.
Published: February 2009

The dynamical equations for multiphase flow in porous media are highly non-linear and the number of variables required to characterize the medium is usually large, often two or more variables per simulator gridblock. Neither the extended Kalman filter nor the ensemble Kalman filter is suitable for assimilating data or for characterizing uncertainty for this type of problem. Although the ensemble Kalman filter handles the nonlinear dynamics correctly during the forecast step, it sometimes fails badly in the analysis (or updating) of saturations.

This paper focuses on the use of an iterative ensemble Kalman filter for data assimilation in nonlinear problems, especially of the type related to multiphase flow in porous media. Two issues are key: (1) iteration to enforce constraints and (2) ensuring that the resulting ensemble is representative of the conditional pdf (i.e. that the uncertainty quantification is correct). The new algorithm is compared to the ensemble Kalman filter on several highly nonlinear example problems, and shown to be superior in the prediction of uncertainty.
The Physics of Fine-Particle Movement Through Permeable Aquifers
Authors: Champlin Jerry B.F.
Published: February 2009

The movement of fine particles through porous, permeable materials is closely interwoven with the migration of soluble ions. Since either the particles orthe ions can represent an economic mineral accumulation as a consequence ofgeochemical concentration, it is of great importance to mineral explorationefforts to be able to establish the parameters that influence particulatemigration through aquifers. Not only are economically interesting depositsformed by such migration, but they also may be ruined, as in the case of manyoil fields where standard secondary recovery methods have caused plugging ofthe productive formations.

Recent experimental work has shown close alliance between the relative movement of both trace ions and particles and the over-all concentration of common salts dissolved in ground water. Most importantly, the spacial stability of fineparticles such as the sesquioxides and the clays in formations is dependent onthe nature of the anionic portion of the dominant salt in solution.

These results have great potential, applied in exploration or exploitation programs for minerals. Not only do they provide answers for particulate migration problems in the oil fields and ore concentration mechanisms in the uranium deposits, but also they explain the untoward migration of certain radioisotopes from waste storage ponds or cribs at the national reactor-fuel reprocessing plants. By careful development and engineering practice, fine particles tagged with almost any radioactive or activatable ions may become one of the most useful tools in tracing subsurface movement of fluids.

Introduction

Considerable concern has been expressed by several industries during the past several decades about the effects of fine-particulate matter suspended in water passing through permeable rock. An early concern of the petroleum industry included the problem of subsurface reservoir plugging by fine particles during secondary production operations. More recently, the atomic energy industry has been concerned with particulate migration because of the movement of radioactive ions. Even the interest in applications of nuclear explosions underground has included concern over the effects of the fine-particulate matter that makes up large portions of the rubble produced by the explosion.
Some Applications of Transient Flow Simulation To Promote Understanding the Performance of Gas Pipeline Systems
Authors: Rachford H.H. , Dupont Todd
Published: February 2009

A recently developed model of gas transmission in the transient state wasapplied to provide insight into the process. A simple two-pipe transmissionsystem with a compressor station was modeled to reveal the consequences ofcompressor upset. The resulting disturbances produce oscillatory response akinto that in an organ pipe. Such disturbances propagate over long distances intransmission lines, and the propagated wave form depends upon accuratelyspecifying as data the time scale upon which the disturbance is generated.

Introduction

Steady flow in piping systems is a simple process with few surprises forthose who deal with it quantitatively. Since, moreover, optimization of boththe design and operation of steady-flow pipeline systems is a tractableproblem, usually with well defined solutions, steady state has tended to becomethe goal of the industry, and certainly to be the framework for any intuitiveconsideration of pipeline response.

By contrast, although considerable effort has been devoted to itssimulation, the transient state often tends to be largely ignored inquantitative design considerations, and if discussed at all is often discussedin the framework of a "succession of steady states." But real pipelinesrarely attain the goal of steady state, being repeatedly upset by changes indemand, loss or addition of equipment, addition of supply, and the like. Thetransient situation in pipe line systems is often rich in surprises and, thus, often somewhat misunderstood. It is the purpose of this paper to apply thetransient model presented in a companion paper to a few situations in whichtransient states are important, and by so doing to study the consequences oftransients and thereby promote understanding of the underlying process.
The Permeability of Coal to Gas and Water
Authors: Dabbous M.K. , Reznik A.A. , Taber J.J. , Fulton P.F.
Published: February 2009

Air and water permeabilities of a large number of samples from the Pittsburghand Pocahontas coals were measured at various overburden and mean flowpressures. A wide variation (< 0.0 1 to > 100 md) in the air and waterpermeabilities was obtained for each type of coal, and flow was primarilythrough microfractures. Overburden pressure has the most significant effect onthe single-phase permeability. Considerable hysteresis was observed for bothair and water permeabilities. Gas permeabilities are affected to a lesserdegree by mean flow pressure above atmospheric. However, at subatmospheric meanpressures, appreciable increase in permeability occurs for low-permeabilitysamples.

This was attributed to gaseous molecules desorbed at pore necks. At highoverburden pressure (~> 400 psig) water permeabilities are smaller than orequal to air permeabilities measured at the same pressures.

Introduction

The permeability of coal to gas and water is of interest to engineers in boththe mining and the petroleum industries. Much of the interest of the miningengineer stems from concern for the health and safety of the coal miner becausethe flow of methane into coal mines is one of the major causes of mine disasters in thiscountry. Some deep mines produce 10 to 15 MMscf/D of methane and require thecirculation of as much as 10 to 15 tons of air per ton of coal mined in orderto clear the gas from the mine. If this little-known source of natural gascould be produced from the coal before the coal is mined, it would help relievethe gas shortage as we11 as protect the safety of the coal miner.

In recent years a number of petroleum companies have shown an interest in coalas a primary energy material that can be converted into electrical energy orinto gaseous and liquid products. Both above- and below-ground processes arebeing studied intensively. Knowledge of the basic permeability and relativepermeability of coal to gas and water should be very useful to petroleumengineers contemplating these new processes for the conversion of coal intoenergy forms suitable for the consumer.

Although some studies of the permeability of coal to gas and to water have beenconducted, no gas/water relative permeability studies have been reported eventhough the presence of significant quantities of water is known to have amarked effect on the flow of methane from the coal seam. In this and a relatedpaper, we present the results of gas/water relative permeability studies onPittsburgh and Pocahontas coal samples.
Air-Water Relative Permeability Studies of Pittsburgh and Pocahontas Coals
Authors: Reznik A.A. , Dabbous M.K. , Fulton P.F. , Taber J.J.
Published: February 2009

Air and water relative permeabilities have been measured for numerous samplesof Pittsburgh and Pocahontas coals. Tests were performed under steady<stateconditions for both drainage and imbibition cycles. Results indicate that theflow of gas is greatly reduced during the latter process, whereas duringdrainage it is largely undiminished over a wide water-saturation range. It isalso shown that imbibition saturation distributions obtained from liquid-waterimbibition as opposed to water-vapor adsorption produce gas permeability curvesof radically different character. The effective permeabilities to both gas andwater were significantly reduced with the application of overburden pressuresin the range of 0 to 1,000 psig, but the general shapes of the relativepermeability curves remained the same.

Introduction

Past studies of the spatial and dynamic properties of coal have been limited tosingle-phase flow. The present energy shortage has created renewed interest inthe in-situ combustion of coal to low-Btu gas. The infusion of water into coalseams appears to be effective in abating methane emissions from coal mines.Both these processes require a detailed understanding of two-phase (liquid andgas) flow behavior in coal beds.

The purpose of this paper is to extend the work of Dabbous et al. to includethe two-phase flow data on Pittsburgh and Pocahontas coals for air-watersystems. The present data consist of air and water permeabilities measured asfunctions of saturation, saturation history, and overburden pressure.

The experimental apparatus and cutting and mounting techniques employed in thisstudy are identical with those described in the first paper. We note, however, that the structural integrity of the samples was maintained during tests thatin some cases extended intermittently over a 6-month period.

Measurement of Relative Permeabilities

Almost all the effective and relative permeabilities to air and water weremeasured under approximately steady-state conditions by the stationary-phasemethod in which one of the fluids is immobilized within the sample by capillaryforces. However, in a series of runs conducted on a sample of Pittsburgh coal, gas and water relative permeabilities were determined by the Penn State method- that is, the fluids were flowed simultaneously until steady-state equilibriumwas established.
Non-Darcy-Flow Studies in Anisotropie Porous Media
Authors: Cooper J. W. , Wang Xiuli , Mohanty K. K.
Published: February 2009

The velocity-pressure drop relationship in the near-wellbore region of high capacity gas and condensate reservoirs often deviates from Darcy's law. Furthermore, many naturally occurring porous media are anisotropic and often layered. This study is directed at combining these facts in developing a mechanistic understanding of non-Darcy gas flow in anisotropic porous media. Non-Darcy flow coefficients, permeabilities, and electrical tortuosities are measured in cores with layers both in the parallel and perpendicular directions to flow and in nonlayered, anisotropic cores. The presence of a connate water saturation decreases permeability in all cores but increases the non-Darcy coefficient significantly only in the perpendicular core. Both a macroscopic and a pore-scale network (microscopic) model of anisotropy are proposed. The product of permeability and non-Darcy coefficient is shown to be less anisotropic than either the permeability or the non-Darcy coefficient tensors in both experiments and simulations. In the microscopic model, the non-Darcy term has been found to be tensorial and proportional to the square of the superficial velocity at the macroscopic scale. As the pore-scale anisotropic parameter increases, the non-Darcy coefficient and tortuosity increase, but permeability decreases. Models show order of magnitude agreement with experimental data.
An Autophagic Vacuolar Myopathy-Like Disorder Presenting as Nonimmune Hydrops in a Female Fetus
Authors: Kepron Charis , Blumenthal Andrea , Chitayat David , Cutz Ernest , Superti-Furga Andrea , Keating Sarah
Published: February 2009

A 37-year-old woman presented for routine obstetrical care at 15 weeks' gestational age and the fetus was found to have hydrops fetalis. Following elective termination of the pregnancy at 18 weeks' gestational age, pathologic examination of the female conceptus revealed findings suggestive of a lysosomal storage disease within the liver and cardiac muscle. Enzyme assays for β-galactosidase, neuraminidase, α-l-iduronidase, β-glucuronidase, β-glucosidase, Morquio disease type A enzyme, β-fucosidase, α-mannosidase, and β-mannosidase were all normal, ruling out many of the common storage diseases. Electron microscopy identified vacuoles within hepatocytes, Kupffer cells, and cardiac myocytes resembling the autophagic vacuoles characteristic of a group of diseases known as the autophagic vacuolar myopathies (AVMs). Because these diseases are exceptionally rare in females, and because such autophagic vacuoles have never before been described in liver, we propose a novel entity of “AVM-like lysosomal storage disease” presenting as nonimmune hydrops in a female fetus.