bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and some biological properties of analogue of angiotensin with modified proline structure
Authors: Procházka Zdenko , Ancans Yuris E. , Myshlyakova Nataliya V. , Ratkevich Marita P. , Strazda Gunta M.
Published: February 2010

The [1-asparagine]angiotensin analogue was synthesized by fragment condensation employing the azide method. Proline in the position 7 in this analogue and phenylalanine in the position 8 were substituted with 2-[1-(2-oxo-3-aminopyrrolidinyl)]-3-phenylpropanoic acid. The analogue does not exhibit any agonistic nor antagonistic activity in myotropic, histamin releasing and pressoric tests.
Arenig biostratigraphy of the Pointe-de-Lévy slice, Quebec Appalachians, Canada
Authors: Maletz Jörg
Published: February 2010

The Pointe-de-Lévy slice includes a nearly complete Arenig graptolite succession. A conspicuous gap exists in the Yapeenian (Ya) to lower Darriwilian (Da) part (Ya 1 – Da 1). The lithological column is compiled from several sections at Lévis, Quebec, that yield only parts of the complete succession. The graptolite zonation can be compared closely with that from the Cow Head Group of western Newfoundland and the Deep Kill Formation of eastern New York. The Shumardia "Limestone" is differentiated into four graptolite zones and subzones, of which the youngest zone clearly belongs to the Llanvirn. The Araneograptus murrayi and Holmograptus lentus zones are documented for the first time from the Lévis area. The Undulograptus dentatus Zone of the latest Arenig is introduced.
Graptolites of the genus Mediograptus Bouček and Přibyl from the uppermost Llandovery of Cornwallis Island, Arctic Canada
Authors: Loydell David K. , Mckenniff John , Lenz Alfred C.
Published: February 2010

Isolated specimens of three species of Mediograptus are described from latest Llandovery (Telychian) strata of the Cape Phillips Formation, Cornwallis Island. One species is new, Mediograptus? bicercis n.sp., whereas the other two, Mediograptus flittoni and Mediograptus morleyae, have previously been recorded only from the Telychian of Wales. A possible paleolatitudinal control on mediograptid distribution is suggested, with one suite of taxa characterizing higher paleolatitudes (Bohemia), the other, including the species described herein, lower paleolatitudes (Wales, Arctic Canada). The diagnosis for the genus Mediograptus is emended.
40Ar/39Ar age of shear zones in the southwest Meguma Zone between Yarmouth and Meteghan, Nova Scotia
Authors: Culshaw Nicholas , Reynolds Peter
Published: February 2010

The Cape St. Marys, Cranberry Point, and Chebogue Point shear zones lie within a zone of D2 deformation that overprinted D1 fabrics and reactivated F1 folds between the shear zones. D2 was accompanied by greenschist-facies metamorphism that variably overprinted earlier metamorphism of varying grade. A collection of single muscovite grains from pressure shadows defining L2 in a sample from the Cape St. Marys shear zone yields an average apparent age of 316 ± 5 Ma. The age obtained for these grains from an isotope correlation diagram is 320 ± 5 Ma. Ages for muscovite separates for two samples from the Cranberry Point shear zone are 325 ± 4 and 319 ± 4 Ma. An amphibolite from this zone yields a discordant spectrum interpreted to reflect the combined effects of Acadian metamorphism and excess argon. The muscovite ages approximate the time of syntectonic deformation because muscovite closure temperatures approximate the temperature of metamorphism during D2. Thus, together with published data from the Chebogue Point shear zone, our data indicate a Mid-Carboniferous age, ca. 320 Ma, for D2 within this system of three shear zones and reactivated folds.
Fractures in the northern plains, stream patterns, and the midcontinent stress field
Authors: Stauffer Mel R. , Gendzwill Don J.
Published: February 2010

Fractures in Late Cretaceous to Late Pleistocene sediments in Saskatchewan, eastern Montana, and western North Dakota form two vertical, orthogonal sets trending northeast–southwest and northwest–southeast. The pattern is consistent, regardless of rock type or age (except for concretionary sandstone). Both sets appear to be extensional in origin and are similar in character to joints in Alberta. Modem stream valleys also trend in the same two dominant directions and may be controlled by the underlying fractures.Elevation variations on the sub-Mannville (Early Cretaceous) unconformity form a rectilinear pattern also parallel to the fracture sets, suggesting that fracturing was initiated at least as early as Late Jurassic. It may have begun earlier, but there are insufficient data at present to extend the time of initiation.We interpret the fractures as the result of vertical uplift together with plate motion: the westward drift of North America. The northeast–southwest-directed maximum principal horizontal stress of the midcontinent stress field is generated by viscous drag effects between the North American plate and the mantle. Vertical uplift, erosion, or both together produce a horizontal tensile state in near-surface materials, and with the addition of a directed horizontal stress through plate motion, vertical tension cracks are generated parallel to that horizontal stress (northeast–southwest). Nearly instantaneous elastic rebound results in the production of second-order joints (northwest–southeast) perpendicular to the first. In this manner, the body of rock is being subjected with time to complex alternation of northeast–southwest and northwest–southeast horizontal stresses, resulting in the continuous and contemporaneous production of two perpendicular extensional joint sets.
Collision along an irregular margin: a regional plate tectonic interpretation of the Canadian Appalachians
Authors: Stockmal G. S. , Colman-Sadd S. P. , Keen C. E. , O'Brien S. J. , Quinlan G.
Published: February 2010

An idealized plate tectonic model for the pre-Carboniferous development of the Canadian Appalachians explains the 400 km dextral offset of tectonostratigraphic zones from Quebec and northern New Brunswick to Newfoundland and the up to 600 km offset of oppositely verging belts of Acadian deformation from the Gaspé Peninsula to eastern Newfoundland. It is proposed that these offsets, which occur at the St. Lawrence promontory, result from the collision of an irregular North American passive continental margin with island arc and continental crust to the east, along an east-dipping subduction zone. The line of subduction is assumed to have been linear and the subducting slab to have maintained its mechanical integrity during collision. A "jigsaw fit" of the opposite sides of the Iapetus Ocean is made unnecessary by invoking lithospheric delamination and tectonic wedging during the Acadian orogeny in Newfoundland. The model is consistent with surface geology and recent deep seismic reflection observations from north of Newfoundland.
Geology of the Springdale Group: a newly recognized Silurian epicontinental-type caldera in Newfoundland
Authors: Coyle Marylou , Strong D. F.
Published: February 2010

Volcanic–sedimentary facies and structural relationships of the Silurian Springdale Group in west-central Newfoundland are indicative of a large collapse caldera with an area of more than 2000 km2. Basaltic flows, andesite flows and pyroclastic rocks, silicic ash-flow tuffs, high-silica rhyolite domes, and volcanically derived debris flows and breccias, fluviatile red sandstones, and conglomerates make up the group. It is bounded on the east and west by up-faulted basement rocks, which include gneisses, amphibolites, and pillow lavas, and in the northwest it unconformably overlies Lower Orodovician submarine volcanics. These margins are intruded by cogenetic and younger granitoid rocks. The volcanic rocks form a calc-alkaline series, although gaps in silica content at 52–56, 67–68, and 73–74% separate them into four groups: basalts, andesites–dacites, rhyolites, and high-silica rhyolites.The high-silica rhyolites are chemically comparable to melts thought to form the upper parts of large, layered silicic magma chambers of epicontinental regions. Such an environment is also suggested by the large area of the Springdale caldera and the fact that it is one of a number of calderas that make up a large Silurian volcanic field in western Newfoundland. An epicontinental tectonothermal environment for central Newfoundland in Silurian–Devonian times is readily explained by the fact that this magmatic activity followed a period of destruction and closure of the early Paleozoic Iapetus Ocean, with trapped heat and basaltic magma causing large-scale melting of thickened and subducted continental crust in an overall transpressional tectonic regime.
The petrology of North Mountain basalts from the wildcat oil well Mobil Gulf Chinampas N-37, Bay of Fundy, Canada
Authors: Greenough John D. , Papezik V. S.
Published: February 2010

Basalts totalling 236 m in thickness were intersected in the wildcat oil well Mobil Gulf Chinampas N-37 in the Bay of Fundy. A 5.5 m section of conventional core retrieved from the middle of the basalt section sampled two fine-grained, phenocryst-poor, amygdaloidal basalt flows. The basalts, though somewhat altered, show concentrations of ferromagnesian elements (e.g., Fe, Mg, Cr, Ni) and immobile elements (e.g., Zr, Nb, Ta, Hf) as well as chondrite-normalized REE patterns typical of high-Ti quartz-normative tholeiites and are identical to more evolved samples of the North Mountain basalts at Digby. These petrographic and geochemical characteristics allow correlation with middle unit flows of the North Mountain basalts. The lower unit of North Mountain basalt may be as thick in the well as in the Digby area (~200 m), but the upper unit is either missing or very thin (< 68 m). A 25 m thick sedimentary section just above the conventional core but within the basalt sequence has not been reported on land and hints at the existence of a basalt unit not present on North Mountain. The conclusion that North Mountain basalts occur in the Chinampas well suggests that the flows underlie most of the Bay of Fundy, originally covered 9400 km2, and had a total volume of 2350 km3.
The phyllocarid crustacean Montecaris from the Devonian of northwestern Canada
Authors: Pratt Brian R.
Published: February 2010

The presence of Montecaris in North America is confirmed by a fragment of this phyllocarid crustacean from the Headless Formation (Middle Devonian) of the Mackenzie Mountains.
Glaciofluvial erosional morphology and sediments of the Coronation–Spondin Scabland, east-central Alberta
Authors: Sjogren D. B. , Rains R. B.
Published: February 2010

Spatially discontinuous meltwater channel networks on the Canadian Prairies are usually interpreted as having formed subaerially in front of the retreating Laurentide ice sheet. Evidence in the Coronation–Spondin scabland, east-central Alberta, supports an alternative formation by progressive channelization of a subglacial sheetflow of water. The scabland is an integrated channel network with varying degrees of anabranching, the channels having highly variable sizes, shapes, and orientations. Enhanced scour at some channel confluences reflects contemporaneous channel utilization. Channels also display convex-up, concave-up, and undulatory along-channel profiles, with some junctions at the same elevations. Longitudinal grooves in large-scale channels are associated with numerous boulder deposits. Residual hills, demarcated by channels, display composite and streamlined forms. Superimposed on residuals are erosional transverse bedforms, longitudinal grooves, and undulating surfaces that indicate submergence for all but the last phase of channelization. Glaciofluvial deposits are found as pendant bars on the distal end of some large, flat-topped residuals, or as mantles superimposed on some residuals. The scabland is interpreted to have formed as a waning, subglacial sheetflood diverted around hummocky terrain to the southwest. A rapidly subsiding ice roof, and instability in the flow, eventually concentrated meltwater into discrete channels. Abrupt cessation of flow left discontinuous gravel–boulder deposits, and ice sheet loading formed small-scale glaciotectonic features as the ice recoupled to its bed. Subsequent deglaciation barely modified the scabland, leaving it straddling part of the modern topographic divide between the Battle and Red Deer river basins.
Geology and geochemistry of an Archean mafic dike complex in the Chan Formation: basis for a revised plate-tectonic model of the Yellowknife greenstone belt
Authors: Maclachlan Kate , Helmstaedt Herb
Published: February 2010

An Archean mafic dike complex in the Chan Formation at the base of the mafic volcanic section of the Yellowknife greenstone belt consists of multiple metagabbro dikes and sills separated by screens of pillowed mafic volcanic rocks, which are cut by a younger postvolcanic metadiabase dike swarm. Field relationships and geochemical characteristics are compatible with a comagmatic origin for the metagabbro and metavolcanic rocks that were fed through and deposited on an older, rift-related, supracrustal sequence of the Dwyer Group. The synvolcanic metagabbro dikes have extended the strike length of the volcanic section by at least 100%. The mafic rocks of the Chan Formation are geochemically similar to mid-ocean ridge basalt, possibly with a minor subduction-zone component. Preliminary εNd values for metagabbroic rocks are consistent with the derivation of magmas predominantly from a normal, depleted-mantle source. The Chan Formation is interpreted to have formed in a marginal basin-like setting, adjacent to a previously rifted and attenuated protocontinental margin.
Late Paleozoic collision, delamination, short-lived magmatism, and rapid denudation in the Meguma Terrane (Nova Scotia, Canada): constraints from 40Ar/39Ar isotopic data
Authors: Keppie J. D. , Dallmeyer R. D.
Published: February 2010

The Meguma Terrane consists of 8–15 km of early Paleozoic stratified rocks, deposited on a continental basement, that were deformed and metamorphosed during the late Paleozoic as a result of lithospheric plate collision. The oldest cleavage (previously published, whole-rock, 40Ar/39Ar plateau ages of 415–395 Ma) dates the onset of crustal thickening, which was followed by voluminous, but short-lived, Late Devonian granitic and minor mafic magmatism (380–370 Ma). This magmatism may have been the product of delamination of the lower lithosphere and upwelling of asthenosphere, which effected melting above the new Moho and resulted in intrusion at depths of 5–12 km. 40Ar/39Ar plateau ages of hornblende, muscovite, and biotite indicate that, at the present erosion level, most of the Meguma Terrane cooled through ~300 °C by 368–360 Ma, slightly earlier than for the southwestern Meguma Terrane (ca. 345 Ma). The present erosion level was exhumed by the latest Devonian–Early Carboniferous (Visean): the age of the oldest unconformably overlying rocks. Subsequent burial beneath ~6 km of Carboniferous sediments would not have been sufficient to completely rejuvenate older intracrystalline mica systems and result in the observed 40Ar/39Ar mica plateau ages between ca. 350 and 260 Ma. Such rejuvenation may have resulted from migration of hot fluids along shear zones derived from the lower crust and mantle, and from granitoid magma intruded at ca. 316 Ma. The recurrence of deformation, magmatism and denudation in the middle Carboniferous suggests that further delamination may have occurred. The temperature of these fluids decreased from 400–500 °C during the Carboniferous to 300–400 °C during the Early Permian.
The Antimonio Formation in Sonora, Mexico, and the Triassic – Jurassic boundary
Authors: González-León Carlos M. , Taylor David G. , Stanley Jr George D.
Published: February 2010

The Antimonio Formation furnishes a record of sedimentation across the Triassic–Jurassic system boundary and is one of a few stratigraphic sections globally that preserves latest Triassic to Hettangian ammonoids in stratigraphic succession. The boundary falls near the middle of the formation, within a 155 m thick stratigraphic section, which is divided into five distinct sedimentary packages. The laminated shales and siltstones in the middle of package 4 represent deposition in an anoxic or disaerobic setting. Although shales of package 4 themselves are poorly fossiliferous, they are bounded below and above by Triassic and Jurassic biotas, respectively. The Triassic–Jurassic system boundary should fall within or stratigraphically close to the laminated beds. The transgressive–regressive signature from the Antimonio Formation corresponds closely to that of the Gabbs and Sunrise formations in Nevada and jointly shows eustatic regressive events at or near the beginning of the latest Triassic Crickmayi Zone and another near the top of the Hettangian. The beds from package 4 indicate a transgression closely associated with the Triassic–Jurassic system boundary.
New Nassellaria (Radiolaria) from the Lower Jurassic of the Canadian Cordillera
Authors: Cordey Fabrice , Carter Elizabeth S.
Published: February 2010

New nassellarian radiolarians are described from the Insular and Intermontane belts of the Canadian Cordillera in British Columbia. Two new genera (Atalanta n.gen. and Nitrader n.gen.) and three new species (Atalanta emmela n.gen., n.sp., Atalanta epaphrodita n.gen., n.sp., and Nitrader montegufonensis n.gen., n.sp.) were found in Lower Jurassic carbonate concretions of the Sandilands Formation of the Queen Charlotte Islands and in a chert pebble extracted from a Cretaceous conglomerate of the Intermontane Belt possibly correlative with the Spences Bridge Group. The discovery of new taxa within two distinct belts of the Canadian Cordillera stresses their biostratigraphic significance.
Centrifuge testing and numerical analysis of box culverts installed in induced trenches
Authors: McGuigan Benjamin L. , Valsangkar Arun J.
Published: February 2010

Induced trench construction is routinely used for circular conduits, but its application for box culverts is less common. To understand the complex soil–structure interaction issues related to the design of induced trench box culverts, centrifuge tests were performed to measure earth pressures on a model box culvert installed in several induced trench configurations. These tests were modelled with FLAC and good agreement was achieved. A parametric study performed with FLAC identified a preferred compressible zone geometry having a width of 1.2 times the culvert width and a thickness of 0.5 times the culvert height. For this geometry, the earth pressure on the top was 0.28 times the overburden, the lateral earth pressure on the sides was 0.47 times the mid-height overburden, and the contact pressure at the base was 0.73 times the overburden plus the pressure from the dead load of the culvert. The average base contact pressures for the induced trench geometry were 35% lower than those for the corresponding positive projecting case. The induced trench method, therefore, appears to be a viable option for box culverts installed under high embankments.
Consolidation theory for a composite foundation considering radial and vertical flows within the column and the variation of soil permeability within the disturbed soil zone
Authors: Lu Meng-Meng , Xie Kang-He , Guo Biao
Published: February 2010

To remedy the contradiction between the equal strain assumption and the flow continuity assumption at a soil–column interface, the traditional flow continuity assumption was abandoned and the radial and vertical flows within a stone column were incorporated to consider the column consolidation and deformation in a coupled fashion. Moreover, two possible variation patterns of the horizontal permeability coefficient of soil within the disturbed soil zone were included, to reflect the detrimental influence on the surrounding soil due to column construction. In addition, a linearly changed total vertical stress along the column depth was assumed, to achieve a more realistic stress distribution in practice. By considering the above mentioned characteristics, the governing equations for this type of consolidation problem were developed. The solutions for the governing equations were subsequently derived by using a new initial condition obtained from the equilibrium condition and equal strain assumption. On the basis of this, the average degree of consolidation of the composite foundation was obtained and discussed. Finally, a parametric study was performed and an application example was introduced to help engineers better utilize the present solution when applied to an actual design.
Measurement of electrical conductivity of pore water in saturated sandy soils using time domain reflectometry (TDR) measurements
Authors: Chen R. P. , Chen Y. M. , Xu W. , Yu X.
Published: February 2010

Studying solute transport in soils is hampered by a lack of technology for continuously monitoring ionic concentration of contaminants. The electrical conductivity of pore water is a strong indicator of ionic concentration of contamination in soil. Using the bulk electrical conductivity of a soil measured by time domain reflectrometry (TDR) to predict the soil pore-water electrical conductivity appears to be a promising technique. This study presents a new method for estimating the pore-water electrical conductivity of saturated sandy soils using a single TDR test. The effects of pore-water electrical conductivity, temperature, porosity, and ionic types on the electrical conductivity of soil were studied. An average value of the exponent in the Archie’s Law was found to be 1.457 for the saturated sandy soils used in this study. A laboratory model infiltration test was also conducted with continuous monitoring of the electrical conductivity of the pore water by TDR. The results showed that TDR is able to provide a reasonably accurate estimation of the electrical conductivity of pore water. Consequently, it may be possible to monitor the in situ ionic contamination in saturated sandy soils using TDR technology.
Interpretation of T-bar penetrometer tests at shallow embedment and in very soft soils
Authors: White D. J. , Gaudin C. , Boylan N. , Zhou H.
Published: February 2010

The cylindrical T-bar penetrometer was developed for profiling the undrained strength of soft soils in the centrifuge and is now a widely-used offshore site investigation tool. The conventional interpretation of the T-bar test is to convert the measured penetration resistance to soil strength using a single bearing factor associated with steady flow of soil around the bar. This paper describes a new analysis for the interpretation of T-bar penetrometer tests at shallow embedment and in soft soils, which is an increasingly significant consideration in the design of seabed infrastructure, including pipelines. The analysis captures two mechanisms that are usually neglected: (i) soil buoyancy and (ii) the reduced bearing factor arising from the shallow failure mechanism mobilized prior to the full flow of soil around the bar. The framework derives from theoretical considerations and is calibrated using large deformation finite element analyses. The depth at which the steady deep penetration condition is reached is shown to depend on the normalized soil strength, su/γ′D, and may be up to several diameters deep. The effect of this new procedure on the inferred soil strength compared with the conventional approach is illustrated through T-bar tests in three different centrifuge samples, spanning a range of strength ratios.
A LAGRANGIAN FOR THE CHIRAL (½, 0) ⊕ (0, ½) QUARTET NUCLEON RESONANCES
Authors: DMITRAŠINOVIĆ V. , HOSAKA ATUSHI , NAGATA KEITARO
Published: February 2010

We study the nucleon and three N* resonances' properties in an effective linear realization chiral SUL(2)×SUR(2) and UA(1) symmetric Lagrangian. We place the nucleon fields into the so-called "naive" (½, 0) ⊕ (0, ½) and "mirror" (0, ½) ⊕ (½, 0) (fundamental) representations of SUL(2)×SUR(2), two of each — distinguished by their UA(1) chiral properties, as defined by an explicit construction of the nucleon interpolating fields in terms of three quark (Dirac) fields. We construct the most general one-meson–baryon chiral interaction Lagrangian assuming various parities of these four nucleon fields. We show that the observed masses of the four lowest-lying nucleon states can be well reproduced with the effective Lagrangian, after spontaneous symmetry breakdown, without explicit breaking of UA(1) symmetry. This does not mean that explicit UA(1) symmetry breaking does not occur in baryons, but rather that it does not have a unique mass prediction signature that exists, e.g. in the case of spinless mesons. We also consider briefly the axial couplings with chiral representation mixing.
DISCRETE DAMAGE MODELLING OF HIGHLY-FILLED COMPOSITES VIA A DIRECT MULTISCALE "MORPHOLOGICAL APPROACH"
Authors: DARTOIS SOPHIE , NADOT-MARTIN CAROLE , HALM DAMIEN , DRAGON ANDRÉ , FANGET ALAIN
Published: February 2010

A nonclassical multiscale "morphological approach" devoted to highly-filled particulate composites was proposed by Nadot et al.1 It is extended by developing complementary ingredients in order to describe the evolution of damage by decohesion of grain/matrix interfaces. A defect nucleation criterion allows the evolution of the number of defects to be followed, and a closure criterion monitors the respective proportions of open and closed defects. The nucleation criterion is associated with a critical value of the current distance between two points located on both sides of the interface considered, whereas the closure criterion is based on the normal component of the displacement jump across the interface. The "morphological approach" is tested at macroscopic and local scales for a random particulate microstructure under loading paths involving tension and compression. The corresponding results are a specific contribution of this work. At global scale, the numerical results presented show the effects of damage induced anisotropy and recovery of mechanical properties by defects closure. Thanks to explicit schematization of the microstructure, the discrete model provides, at microscale, the characteristics of damage (chronology of events, position and morphology of defects) as well as its effects on local strains.
A STRESS STATE DEPENDENT DAMAGE MODEL FOR THE HIGH TEMPERATURE FAILURE OF FREE-CUTTING STEELS
Authors: FOSTER A. D. , LIN J. , FARRUGIA D. C. J. , DEAN T. A.
Published: February 2010

Free-Cutting Steels (FCS), also referred to as Free Machining Steels, are characterised by their excellent chip formation and low cutting force during machining. However, the microstructure features which provide the advantageous machining properties have been linked to poor formability during secondary processing such as those occurring during hot rolling of bar products (Y. Liu et al., On micro-damage in hot metal working Part 1: Experimental investigation, Eng. Trans.54 (2006) 271–287). In this paper physically-based modelling equations are formulated from microstructure and flow stress observations, specifically for the high temperature deformation of FCS. The isotropic, viscoplastic-damage and stress state dependent material model is determined for a typical low-carbon FCS. The model is integrated with the commercial FE code ABAQUS Explicit through user routine VUMAT. Results are validated with the recently introduced conical splay test.
EXPERIMENTAL INVESTIGATION OF THE EFFECT OF MECHANICAL LOADING ON THERMAL TRANSPORT IN CERAMIC MATRIX COMPOSITES
Authors: SHEIKH MOHAMMED A. , HAYHURST DAVID R. , TAYLOR SARAH C. , TAYLOR ROY
Published: February 2010

This paper presents the results of experimental measurements of transverse thermal diffusivity for six different industrial Ceramic Matrix Composite materials under the action of in-plane uni-axial mechanical loading. Measurements have also been taken using a one-dimensional Laser Flash technique on 8 mm diameter disc specimens without mechanical load. These results have been used to benchmark data obtained using a three-dimensional Laser Flash rig developed to operate on large mechanical test specimens whilst being loaded in a test machine. The latter facility has been used to measure the degradation of transverse thermal diffusivity with uni-axial strain. For five of the composites tested the degradation of transverse thermal diffusivity was small; and the degradation of transverse thermal diffusivity was linear with strain. One composite showed evidence of fibre pullout, and a decrease of transverse thermal diffusivity to a low value. The different behaviours observed were believed to be associated with the weave type/composite lay-up, and the selection of composite constituent materials, although insufficient data is available to make general conclusions.
CURRENT CAPABILITIES OF THE THERMO-MECHANICAL MODELLING OF WELDING PROCESSES
Authors: HYDE T. H. , YAGHI A. H. , TANNER D. W. J. , BENNETT C. J. , BECKER A. A. , WILLIAMS E. J. , SUN W.
Published: February 2010

Some fundamental principles and advanced applications of thermo-mechanical modelling techniques used for industrial welding processes are described. The paper covers a range of modelling procedures comprising welding simulation and residual stress analysis of multi-pass, thick-walled ferritic steel pipes; welding simulation and distortion analysis of nickel-based superalloy thin plates; and inertia friction welding of dual alloy drive shafts. A number of pertinent mechanical and metallurgical concepts are discussed, including material behaviour models and material properties, microstructural evolution, solid state phase transformation and post-weld heat treatment. The paper emphasises the general methodologies of thermal modelling procedures and their role in the holistic process of the life assessment and design improvement of power plant piping systems and aeroengine casings and shaft components, operating under high temperature creep and fatigue service conditions.
The Biogenesis of Chylomicrons
Authors: Mansbach Charles M. , Siddiqi Shadab A.
Published: February 2010

The absorption of dietary fat is of increasing concern given the rise of obesity not only in the United States but throughout the developed world. This review explores what happens to dietary fat within the enterocyte. Absorbed fatty acids and monoacylglycerols are required to be bound to intracellular proteins and/or to be rapidly converted to triacylglycerols to prevent cellular membrane disruption. The triacylglycerol produced at the level of the endoplasmic reticulum (ER) is either incorporated into prechylomicrons within the ER lumen or shunted to triacylglycerol storage pools. The prechylomicrons exit the ER in a specialized transport vesicle in the rate-limiting step in the intracellular transit of triacylglycerol across the enterocyte. The prechylomicrons are further processed in the Golgi and are transported to the basolateral membrane via a separate vesicular system for exocytosis into the intestinal lamina propria. Fatty acids and monoacylglycerols entering the enterocyte via the basolateral membrane are also incorporated into triacylglycerol, but the basolaterally entering lipid is much more likely to enter the triacylglycerol storage pool than the lipid entering via the apical membrane.
Locomotion in Response to Shifting Climate Zones: Not So Fast
Authors: Feder Martin E. , Garland Theodore , Marden James H. , Zera Anthony J.
Published: February 2010

Although a species' locomotor capacity is suggestive of its ability to escape global climate change, such a suggestion is not necessarily straightforward. Species vary substantially in locomotor capacity, both ontogenetically and within/among populations, and much of this variation has a genetic basis. Accordingly, locomotor capacity can and does evolve rapidly, as selection experiments demonstrate. Importantly, even though this evolution of locomotor capacity may be rapid enough to escape changing climate, genetic correlations among traits (often due to pleiotropy) are such that successful or rapid dispersers are often limited in colonization or reproductive ability, which may be viewed as a trade-off. The nuanced assessment of this variation and evolution is reviewed for well-studied models: salmon, flying versus flightless insects, rodents undergoing experimental evolution, and metapopulations of butterflies. This work reveals how integration of physiology with population biology and functional genomics can be especially informative.
Circadian Organization of Behavior and Physiology in Drosophila
Authors: Allada Ravi , Chung Brian Y.
Published: February 2010

Circadian clocks organize behavior and physiology to adapt to daily environmental cycles. Genetic approaches in the fruit fly, Drosophila melanogaster, have revealed widely conserved molecular gears of these 24-h timers. Yet much less is known about how these cell-autonomous clocks confer temporal information to modulate cellular functions. Here we discuss our current knowledge of circadian clock function in Drosophila, providing an overview of the molecular underpinnings of circadian clocks. We then describe the neural network important for circadian rhythms of locomotor activity, including how these molecular clocks might influence neuronal function. Finally, we address a range of behaviors and physiological systems regulated by circadian clocks, including discussion of specific peripheral oscillators and key molecular effectors where they have been described. These studies reveal a remarkable complexity to circadian pathways in this “simple” model organism.
Role of Colonic Short-Chain Fatty Acid Transport in Diarrhea
Authors: Binder Henry J.
Published: February 2010

Short-chain fatty acids (SCFA) are the major anion in stool and are synthesized from nonabsorbed carbohydrate by the colonic microbiota. Nonabsorbed carbohydrate are not absorbed in the colon and induce an osmotically mediated diarrhea; in contrast, SCFA are absorbed by colonic epithelial cells and stimulate Na-dependent fluid absorption via a cyclic AMP–independent process involving apical membrane Na-H, SCFA-HCO3, and Cl-SCFA exchanges. SCFA production represents an adaptive process to conserve calories, fluid, and electrolytes. Inhibition of SCFA synthesis by antibiotics and administration of PEG, a substance that is not metabolized by colonic microbiota, both result in diarrhea. In contrast, increased production of SCFA as a result of providing starch that is relatively resistant to amylase digestion [so-called resistant starch (RS)] to oral rehydration solution (RS-ORS) improves the efficacy of ORS and represents an important approach to improve the effectiveness of ORS in the treatment of acute diarrhea in children under five years of age.
The Mammalian Circadian Timing System: Organization and Coordination of Central and Peripheral Clocks
Authors: Dibner Charna , Schibler Ueli , Albrecht Urs
Published: February 2010

Most physiology and behavior of mammalian organisms follow daily oscillations. These rhythmic processes are governed by environmental cues (e.g., fluctuations in light intensity and temperature), an internal circadian timing system, and the interaction between this timekeeping system and environmental signals. In mammals, the circadian timekeeping system has a complex architecture, composed of a central pacemaker in the brain's suprachiasmatic nuclei (SCN) and subsidiary clocks in nearly every body cell. The central clock is synchronized to geophysical time mainly via photic cues perceived by the retina and transmitted by electrical signals to SCN neurons. In turn, the SCN influences circadian physiology and behavior via neuronal and humoral cues and via the synchronization of local oscillators that are operative in the cells of most organs and tissues. Thus, some of the SCN output pathways serve as input pathways for peripheral tissues. Here we discuss knowledge acquired during the past few years on the complex structure and function of the mammalian circadian timing system.
Light, Time, and the Physiology of Biotic Response to Rapid Climate Change in Animals
Authors: Bradshaw William E. , Holzapfel Christina M.
Published: February 2010

Examination of temperate and polar regions of Earth shows that the nonbiological world is exquisitely sensitive to the direct effects of temperature, whereas the biological world is largely organized by light. Herein, we discuss the use of day length by animals at physiological and genetic levels, beginning with a comparative experimental study that shows the preeminent role of light in determining fitness in seasonal environments. Typically, at seasonally appropriate times, light initiates a cascade of physiological events mediating the input and interpretation of day length to the output of specific hormones that ultimately determine whether animals prepare to develop, reproduce, hibernate, enter dormancy, or migrate. The mechanisms that form the basis of seasonal time keeping and their adjustment during climate change are reviewed at the physiological and genetic levels. Future avenues for research are proposed that span basic questions from how animals transition from dependency on tropical cues to temperate cues during range expansions, to more applied questions of species survival and conservation biology during periods of climatic stress.
Integrated Brain Circuits: Astrocytic Networks Modulate Neuronal Activity and Behavior
Authors: Halassa Michael M. , Haydon Philip G.
Published: February 2010

The past decade has seen an explosion of research on roles of neuron-astrocyte interactions in the control of brain function. We highlight recent studies performed on the tripartite synapse, the structure consisting of pre- and postsynaptic elements of the synapse and an associated astrocytic process. Astrocytes respond to neuronal activity and neurotransmitters, through the activation of metabotropic receptors, and can release the gliotransmitters ATP, d-serine, and glutamate, which act on neurons. Astrocyte-derived ATP modulates synaptic transmission, either directly or through its metabolic product adenosine. d-serine modulates NMDA receptor function, whereas glia-derived glutamate can play important roles in relapse following withdrawal from drugs of abuse. Cell type–specific molecular genetics has allowed a new level of examination of the function of astrocytes in brain function and has revealed an important role of these glial cells that is mediated by adenosine accumulation in the control of sleep and in cognitive impairments that follow sleep deprivation.
TH17 Cells in Asthma and COPD
Authors: Alcorn John F. , Crowe Christopher R. , Kolls Jay K.
Published: February 2010

Asthma and chronic obstructive pulmonary disease (COPD) represent two classes of chronic obstructive lung disorders that may share some similar immunologic mechanisms of disease. Asthma is a complex human disease characterized by airway hyperresponsiveness (AHR) and inflammation, whereas COPD is marked by progressive emphysematic changes in the lung. Recently it has been shown that advanced COPD is characterized by lymphoid follicles, drawing attention to immunological mechanisms in COPD. Despite numerous studies in mice to elucidate the immunologic mechanisms of asthma, sufficient current treatment options are limited. Clinically, many asthma patients fail to satisfactorily respond to standard steroid therapy, and this type of steroid-resistant, severe asthma has been linked to the presence of neutrophilic inflammation in the lung. The role of neutrophils, macrophages, and their secreted proteases in COPD needs to be better defined. Recently, the T lymphocyte subset TH17 was shown to play a role in regulating neutrophilic and macrophage inflammation in the lung, suggesting a potential role for TH17 cells in severe, steroid-insensitive asthma and COPD.
The Cardiac Mitochondrion: Nexus of Stress
Authors: Baines Christopher P.
Published: February 2010

The emergence of mitochondria as critical regulators of cardiac myocyte survival and death has revolutionized the field of cardiac biology. Indeed, it is now well recognized that mitochondrial dysfunction plays a crucial role in the pathogenesis of multiple cardiac diseases. A panoply of mitochondrial proteins/complexes ranging from canonical apoptosis proteins such as Bcl2 and Bax, through the mitochondrial permeability transition pore, to ion channels such as mitochondrial KATP channels and connexin-43 have now been implicated as critical regulators of cardiac cell death. The purpose of this review, therefore, is to focus on these mitochondrial mediators/inhibitors of cell death and to address the specific mechanisms that underlie their ability to influence cardiac pathology.
Nitric oxide produced by endothelial nitric oxide synthase promotes diuresis
Authors: Perez-Rojas Jazmin M. , Kassem Kamal M. , Beierwaltes William H. , Garvin Jeffrey L. , Herrera Marcela
Published: February 2010

Extracellular fluid volume is highly regulated, at least in part, by peripheral resistance and renal function. Nitric oxide (NO) produced by NO synthase type 3 (NOS 3) in the nonrenal vasculature may promote fluid retention by reducing systemic vascular resistance and arterial pressure. In contrast, NO produced by renal NOS 3 promotes water excretion by reducing renal vascular resistance, increasing glomerular filtration, and inhibiting reabsorption along the nephron. Thus, the net effect of NO from NOS 3 on urinary volume (UV) is unclear. We hypothesized that NO produced by NOS 3 promotes water excretion primarily due to renal tubular effects. We gave conscious wild-type and NOS 3 −/− mice an acute volume load and measured UV, blood pressure, plasma renin concentration (PRC), Na+, vasopressin, and urinary Na+and creatinine concentrations. To give the acute volume load, we trained mice to drink a large volume of water while in metabolic cages. On the day of the experiment, water was replaced with 1% sucrose, and mice had access to it for 1 h. Volume intake was similar in both groups. Over 3 h, wild-type mice excreted 62 ± 10% of the volume load, but NOS 3 −/− excreted only 42 ± 5% ( P < 0.05). Blood pressure in NOS 3 −/− was 118 ± 3 compared with 110 ± 2 mmHg in wild-type mice ( P < 0.05), but it did not change following volume load in either strain. PRC, vasopressin, and glomerular filtration rate were similar between groups. Urinary Na+excretion was 49.3 ± 7.0 in wild-type vs. 37.8 ± 6.4 μmol/3 h in NOS 3 −/− mice ( P < 0.05). Bumetanide administration eliminated the difference in volume excretion between wild-type and NOS 3 −/− mice. We conclude that 1) NO produced by NOS 3 promotes water and Na+excretion and 2) the renal epithelial actions of NO produced by NOS 3 supersede the systemic and renal vascular actions.
T lymphocytes mediate hypertension and kidney damage in Dahl salt-sensitive rats
Authors: De Miguel Carmen , Das Satarupa , Lund Hayley , Mattson David L.
Published: February 2010

This study examined mechanisms by which immune cells participate in the development of hypertension and renal disease in Dahl salt-sensitive (SS) rats. Increasing dietary salt from 0.4% to 4.0% NaCl significantly increased renal infiltration of T lymphocytes from 8.8 ± 1.2 × 105to 14.4 ± 2.0 × 105cells/2 kidneys, increased arterial blood pressure from 131 ± 2 to 165 ± 6 mmHg, increased albumin excretion rate from 17 ± 3 to 129 ± 20 mg/day, and resulted in renal glomerular and tubular damage. Furthermore, renal tissue ANG II was not suppressed in the kidneys of SS rats fed 4.0% NaCl. Administration of the immunosuppressive agent mycophenolate mofetil (MMF; 20 mg·kg−1·day−1) prevented the infiltration of T lymphocytes and attenuated Dahl SS hypertension and renal disease. In contrast to vehicle-treated rats, Dahl SS rats administered MMF demonstrated a suppression of renal tissue ANG II from 163 ± 26 to 88 ± 9 pg/g of tissue when fed high salt. Finally, it was demonstrated that the T lymphocytes isolated from the kidney possess renin and angiotensin-converting enzyme activity. These data indicate that infiltrating T cells are capable of participating in the production of ANG II and are associated with increased intrarenal ANG II, hypertension, and renal disease. The suppression of T-cell infiltration decreased intrarenal ANG II and prevented Dahl SS hypertension and kidney damage. As such, infiltrating cells are capable of participating in the established phase of Dahl SS hypertension.
Urinary tract obstruction induces transient accumulation of COX-2-derived prostanoids in kidney tissue
Authors: Nørregaard Rikke , Jensen Boye L , Topcu Sukru Oguzkan , Wang Guixian , Schweer Horst , Nielsen Søren , Frøkiær Jørgen
Published: February 2010

Inhibitors of cyclooxygenase (COX)-2 prevent suppression of aquaporin-2 and reduce polyuria in the acute phase after release of bilateral ureteral obstruction (BUO). We hypothesized that BUO leads to COX-2-mediated local accumulation of prostanoids in inner medulla (IM) tissue. To test this, rats were subjected to BUO and treated with selective COX-1 or COX-2 inhibitors. Tissue was examined at 2, 6, 12, and 24 h after BUO. COX-2 protein abundance increased in IM 12 and 24 h after onset of BUO but did not change in cortex. COX-1 did not change at any time points in any region. A full profile of all five primary prostanoids was obtained by mass spectrometric determination of PGE2, PGF2α, 6-keto-PGF1α, PGD2, and thromboxane (Tx) B2 concentrations in kidney cortex/outer medulla and IM fractions. IM concentration of PGE2, 6-keto-PGF1α, and PGF2α was increased at 6 h BUO, and PGE2 and PGF2α increased further at 12 h BUO. TxB2 increased after 12 h BUO. 6-keto-PGF1α remained significantly increased after 24 h BUO. The COX-2 inhibitor parecoxib lowered IM PGE2, TxB2, 6-keto-PGF1α, and PGF2α below vehicle-treated BUO and sham rats at 6, 12 and, 24 h BUO. The COX-1 inhibitor SC-560 lowered PGE2, PGF2α, and PGD2 in IM compared with untreated 12 h BUO, but levels remained significantly above sham. In cortex tissue, PGE2 and 6-keto-PGF1α concentrations were elevated at 6 h only. In conclusion, COX-2 activity contributes to the transient increase in prostacyclin metabolite 6-keto-PGF1α and TxB2 concentration in the kidney IM, and COX-2 is the predominant isoform that is responsible for accumulation of PGE2 and PGF2α with minor, but significant, contributions from COX-1. PGD2 synthesis is mediated exclusively by COX-1. In BUO, therapeutic interventions aimed at the COX-prostanoid pathway should target primarily COX-2.
Response of cardiac sympathetic nerve activity to intravenous irbesartan in heart failure
Authors: Ramchandra Rohit , Watson Anna M. D. , Hood Sally G. , May Clive N.
Published: February 2010

To determine the effect of irbesartan treatment on resting levels and arterial baroreflex control of cardiac sympathetic nerve activity (CSNA) in heart failure (HF), we studied conscious normal sheep and sheep with HF induced by rapid ventricular pacing for 8–10 wk ( n = 7 per group). In HF, there is a large increase in CSNA that is detrimental to outcome. The causes of this increase in CSNA and the effect of angiotensin receptor blockers on CSNA in HF are unclear. CSNA, arterial blood pressure, heart rate (HR), and arterial baroreflex curves were recorded during a resting period and after 90 min of irbesartan infusion (12 mg·kg−1·h−1 iv). This dose of irbesartan abolished the pressor response to intravenous ANG II infusion but caused only a slight decrease in the pressor response to centrally administered ANG II. In HF, there was a large increase in CSNA (from 44 ± 3 to 87 ± 3 bursts/100 heartbeats). Irbesartan reduced arterial pressure in the normal and HF groups, but the usual baroreflex-mediated increases in CSNA and HR were prevented. This resulted from a significant leftward shift in the CSNA and HR baroreflex curves in both groups. Irbesartan also decreased the sensitivity of the arterial baroreflex control of CSNA. Short-term treatment with an angiotensin receptor blocker, at a dose that abolished the response to circulating, but not central, ANG II, prevented the reflex increase in CSNA in response to the drug-induced fall in arterial pressure.