bluuebunny/crossref_metadata_2025 huggingface dataset:
Twenty-fifth anniversary special paper: Marine geotechnical engineering in Canada
Authors: Clark J. I. , Guigné J. Y.
Published: May 2008

Marine geotechnical engineering in Canada is over one hundred years old, having started with overwater drilling and testing for bridges and nearshore structures. Its growth has been sporadic, with not much attention being directed to the geotechnical properties of marine soils until the late 1970's when design of artificial islands made up of large caissons started to develop. For about the last 15 years, marine geotechnical engineering has been driven by the oil and gas industry. Most of the action has been in the Beaufort Sea, where complex site conditions have necessitated detailed geotechnical field drilling, sampling programs, and in situ testing. Very little geotechnical engineering research work or site investigation has been carried out off the east coast except for the Hibernia site on the Grand Banks. In the coming years we can expect to see dramatic changes in site investigation methods. The use of robotics and expert systems coupled with innovative geophysical techniques could dramatically change our methods of site characterization and measurement of geotechnical properties. Key words: marine geotechnical engineering, Beaufort Sea, Grand Banks, Scotian Shelf, in situ testing, geophysical – geotechnical relationship, future trends.
Drilled pile behaviour in granular deposits
Authors: Sharma Hari D. , Joshi R. C.
Published: May 2008

The results of full-scale pile load tests, field monitoring, and laboratory tests on undisturbed soil samples have been used to compare soil parameters determined from in situ tests and in the laboratory for pile design in granular deposits. These results indicate a close agreement between the field- and laboratory-determined rebound or recompression index of oil sand. Also, a good agreement is indicated between field-measured and calculated pile head settlements. However, the measured average skin friction along the pile shaft in sandy till is about 20% more than the calculated values obtained from empirical and finite element analytical work using laboratory- and field-determined soil parameters. Theoretical t–z curves provided a good approximation of the field behaviour for the pile shaft resistance. Key words: drilled piles, belled piles, oil sand, skin friction, rebound, settlement, load test.
The mechanism of deformation and fracture in potash rock
Authors: Lajtai Emery Z. , Duncan E. J. Scott
Published: May 2008

Specimens of potash rock from the Rocanville mine of the Potash Corporation of Saskatchewan were subjected to uniaxial compression tests and to time-dependent creep tests under static, uniaxial loading.During the first cycle of loading, the main sources of the measured strain are compaction and dilation at grain boundaries and consolidation of the clay phase. The crystals of halite and sylvite deform elastically at low stress and in a brittle manner at high stress. There is little, if any, evidence for constant-volume plastic deformation at any level of uniaxial stress.The stress–strain curve can be divided into three parts, each representing a different dominant deformational process: a low-stress quasi-elastic, an intermediate-stress ductile, and a high-stress brittle mechanism. The three parts are separated by the yield point (1–8 MPa) and the crack initiation point (10–13 MPa). The strength of the Rocanville potash specimens ranged between 15 and 18 MPa.The deformation of potash rock is strongly time dependent. There is evidence for the existence of all three stages of creep: transient, steady-state, and tertiary. There is very little interrelationship between the axial and lateral creep strains; the volumetric strain is negative at low stress and positive (dilatant) at high stress, but rarely, if ever, constant. Key words: creep, dilatant, ductile, elastic, fracture, microfracture, plastic, potash, salt.
Modelling of flow through potash tailings piles
Authors: Wong D. K. H. , Barbour S. L. , Fredlund D. G.
Published: May 2008

Modelling the flow of brine through potash tailings requires that the saturated and unsaturated hydraulic properties of the tailings be established; in particular, the relationships of fluid content and permeability to matric suction are required. The in situ and laboratory testing techniques used for determining these properties are described and the results are presented.Numerical modelling techniques for the flow of brine through potash tailings are demonstrated by performing a computer simulation of an open-trench infiltration test conducted at the Lanigan Division Potash Mine in Saskatchewan. The responses of the field instrumentation during the infiltration test were compared with the results of the simulation. The simulation utilizes the measured fluid content versus suction curves and the calculated permeability versus suction curves as input parameters. Good agreement was observed between the measured and simulated field responses. The effects of varying the hydraulic properties of the tailings are examined to arrive at a better understanding of the flow mechanism involved. Key words: saturated–unsaturated, seepage, finite element modelling, brine, potash, tailings, infiltration.
Dynamic moduli and damping ratios for cemented sands at low strains
Authors: Saxena Surendra K. , Avramidis Anestis S. , Reddy Krishna R.
Published: May 2008

This paper advances the present understanding of the beneficial effects of cementation of sands on their dynamic behavior at low strain amplitudes. The influence of important parameters such as cement content, effective confining pressure, density, and curing period is discussed in detail on the basis of extensive resonant column test results. A newly proposed relationship for maximum dynamic shear modulus is compared with reported relationships. Empirical relations for maximum dynamic Young's modulus, dynamic shear damping, and dynamic longitudinal damping are developed for the first time. All the relations developed are nondimensional and adaptable to any system of units. Correlations between dynamic moduli and static strength from triaxial (drained) tests are developed for an effective confining pressure equal to 49 kPa. Key words: resonant column test, cemented sand, dynamic moduli, dynamic damping.
Physicochemical and geotechnical characteristics of recent Saguenay Fjord sediments
Authors: Locat Jacques , Leroueil Serge
Published: May 2008

In the spring of 1985 the first goetechnical reconnaissance of recent Saguenay Fjord sediments took place, in which were recorded the two Saint-Jean-Vianney slides of 1663 and 1971. Cores from the upper part of the fjord were tested onboard the ship and in the laboratory. The mineralogy of the recent sediments is like that of the raised marine deposits of the area, except for the organic content, which is higher. The microstructure of the sediment is quite typical of flocculated marine soils. The freshly sedimented soil, in its sedimentary environment, has gained strength and sensitivity (up to 12) in excess of what is usually expected for such material. It has been concluded that the physicochemical characteristics of the sediment, such as depicted by its initial plasticity (before leaching), are first-order parameters in the source of apparent overconsolidation and structuration. Key words: recent sediments, shear strength, sensitivity, consolidation, structuration, microstructure, landslide, physicochemistry, mineralogy.
Failure state of a sand in simple shear
Authors: Budhu Muniram
Published: May 2008

The stress state in many practical geotechnical problems is analogous to simple shear strain. However, the devices available to test soil samples in simple shear strain impose nonuniform stress and strain fields. Consequently, the interpretation of results from simple shear tests is often questioned. In this article, results of tests on loose and dense Leighton Buzzard sand from two specially instrumented simple shear devices–Cambridge University's device and a Norwegian Geotechnical Institute type–are used to interpret the failure mode and the failure stress state. The data were obtained from the centre of the samples, a region removed from stress concentrations. Failure was observed to be initiated on vertical planes and occurred very soon after shear displacement was applied. However, neither these vertical planes nor the horizontal planes were the planes of maximum stress obliquity mobilized during the tests. Key words: deformation, failure, loads, sand, shear tests, simple shear, stresses.
Cyclic shear strength of a loose glacial till
Authors: Lefebvre Guy , Malenfant Serge
Published: May 2008

The liquefaction potential of a loose glacial till is assessed by laboratory cyclic tests and by comparison with test results obtained on a clean sand, using the same testing procedures. The laboratory testing program of both soils included cyclic triaxial tests on saturated specimens and constant volume cyclic simple shear tests on dry specimens. The till and the sand exhibited very similar behaviour during cycling and mobilized nearly identical cyclic shear strengths in the triaxial as well as in the simple shear tests. The 28% fines content in the till did not make it more resistant to liquefaction than a clean sand. Key words: liquefaction, sand, silty sand, cyclic simple shear test, cyclic triaxial test.
MODELING THE PERFORMANCE OF COMMUNICATION SCHEMES ON NETWORK TOPOLOGIES
Authors: LEMEIRE JAN , DIRKX ERIK , COLITTI WALTER
Published: May 2008

This paper investigates the influence of the interconnection network topology of a parallel system on the delivery time of an ensemble of messages, called the communication scheme. More specifically, we focus on the impact on the performance of structure in network topology and communication scheme. We introduce causal structure learning algorithms for the modeling of the communication time. The experimental data, from which the models are learned automatically, is retrieved from simulations. The qualitative models provide insight about which and how variables influence the communication performance. Next, a generic property is defined which characterizes the performance of individual communication schemes and network topologies. The property allows the accurate quantitative prediction of the runtime of random communication on random topologies. However, when either communication scheme or network topology exhibit regularities the prediction can become very inaccurate. The causal models can also differ qualitatively and quantitatively. Each combination of communication scheme regularity type, e.g. a one-to-all broadcast, and network topology regularity type, e.g. torus, possibly results in a different model which is based on different characteristics.
CHARGES AND MASS SPECTRUM IN THE PISANO–PLEITEZ–FRAMPTON 3-3-1 GAUGE MODEL
Authors: COTĂESCU ION I. , PALCU ADRIAN
Published: May 2008

The Pisano–Pleitez–Frampton 3-3-1 model is revisited here within the framework of the general method for solving gauge models with high symmetries. This exact algebraical approach — proposed several years ago by one of us — was designed to include a minimal Higgs mechanism that spontaneously breaks the gauge symmetry up to the universal U(1)em electromagnetic one and, consequently, to supply the mass spectrum and the couplings of the currents for all the particles in the model. We prove in this paper that this powerful tool, when is applied to the PPF 3-3-1 model, naturally recovers the whole Standard Model phenomenology and, in addition, predicts — since a proper parametrization is employed — viable results such as: (i) the exact expressions for the boson and fermion masses, (ii) the couplings of the charged and neutral currents and (iii) a plausible neutrino mass pattern. A generalized Weinberg transformation is implemented, while the mixing between the neutral bosons Z and Z′ is performed as a necessary step by the method itself. Some phenomenological consequences are also sketched, including the strange possibility that simultaneously m(Z) = m(Z′) and m(W) = m(V) hold.
PROJECTIVE ℚ-FACTORIAL TORIC VARIETIES COVERED BY LINES
Authors: CASAGRANDE CINZIA , DI ROCCO SANDRA
Published: May 2008

We give a structural theorem for ℚ-factorial toric varieties covered by lines in ℙN, and compute their dual defect. This yields a characterization of defective ℚ-factorial toric varieties in ℙN. The combinatorial description of such varieties is used to characterize some finite sets of monomials with discriminant equal to one.
SYNTHESIS OF SINGLE-WALLED CARBON NANOTUBES FROM LIQUEFIED PETROLEUM GAS
Authors: ZHANG QIANG , LIU YI , HUANG JIAQI , QIAN WEIZHONG , WANG YAO , WEI FEI
Published: May 2008

Hydrocarbons such as methane, ethylene, and CO with high purity (> 99.9%) have been widely used to synthesize single-walled carbon nanotubes (SWCNTs). Here, liquefied petroleum gas (LPG) was used to synthesize SWCNTs by catalytic chemical vapor deposition. The LPG converted into CNTs and other stable hydrocarbons. The BET specific surface area of SWCNT was about 583 m2/g. The as-grown SWCNT showed good graphitization. The graphitization can be further modulated by the growth temperature. Certain amount of sulfur in LPG was a promoter for SWCNT growth. Compared SWCNTs obtained from methane, more semiconductive SWCNTs were synthesized from LPG as carbon source. The LPG is in low price, thus, a methodology to lower the production cost of SWCNTs with hydrocarbon mixtures is realized.
Mélanges and ophiolites during the Pan-African orogeny: the case of the Bou-Azzer ophiolite suite (Morocco)
Authors: Bousquet Romain , El Mamoun Rachid , Saddiqi Omar , Goffé Bruno , Möller Andreas , Madi Atman
Published: May 2008

Since the discovery of ophiolite sequences, the Bou-Azzer inlier has been considered a key area for understanding the evolution of the northern margin of the West African craton during the Pan-African orogeny. For about 20 years, it had been commonly accepted that the Bou-Azzer inlier represents an accretionary mélange accreted onto the West African craton under blueschist metamorphic conditions, similar to the Franciscan Complex and the Sanbagawa facies series. This would imply that a low geothermal gradient was prevalent during the subduction of the Pan-African oceanic plate, and that the ocean was subducted with a high convergence rate. A reinvestigation of the metamorphic conditions by a thermodynamic approach shows that the ophiolite sequence of Bou-Azzer underwent HT greenschist metamorphic conditions instead of blueschist metamorphic conditions. We propose that the ophiolites of Bou-Azzer are not similar to the Sanbagawa facies series or to the Franciscan Complex, but bear similarities to the Albanian or Cyprus ophiolites, which represent dismembered ophiolite sequences overprinted by greenschist conditions.
Late Neoproterozoic carbonate productivity in a rifting context: the Adoudou Formation and its associated bimodal volcanism onlapping the western Saghro inlier, Morocco
Authors: Álvaro J. Javier , Macouin Mélina , Ezzouhairi Hassan , Charif A. , Ayad N. Ait , Ribeiro M. Luisa , Ader Magali
Published: May 2008

An interval of episodic carbonate productivity, lithostratigraphically recognized as the ‘Calcaires inférieurs’ (upper member of the Adoudou Formation), took place across the Neoproterozoic–Cambrian transition onlapping the western Saghro inlier, Morocco. Sedimentation of the ‘Calcaires inférieurs’ was highly variable: in relatively stable substrates, a peritidal-dominated mixed platform is recorded where deposition was primarily controlled by autocyclic processes and accommodation space availability, whereas, in unstable substrates, the tectonic activity associated with the inherited block-faulting basement led to deposition of complex slide sheets composed of penecontemporaneous isoclinal folds and disrupted strata. The uppermost part of the ‘Calcaires inférieurs’ displays a negative δ
13
C shift reaching values of −6.5‰. This shift may represent the δ
13
C excursion to −6‰ that marks the Neoproterozoic–Cambrian boundary in the western Anti-Atlas. Two volcanic episodes bracketed the carbonate productivity. They consist of lower basaltic flows and an upper rhyolitic ignimbrite, with a SiO
2
gap between 52 and 74 wt%. The basic rocks resemble those of tholeiitic magmas in continental rifts. The felsic rocks show high light to heavy rare earth element abundances and negative Nb, Ta, P and Ti anomalies, and were probably generated as a result of either fractional crystallization coupled with relative crustal contamination, or from a different magmatic source. The lower basic flows of tholeiitic affinity predated and geochemically differ from the alkaline magmatism of the Alougoum volcanic complex (Boho jbel) that surrounds the neighbouring Bou-Azzer inlier.
REE patterns, Nd-Sm and U-Pb ages of the metamorphic rocks of the Diagorou-Darbani greenstone belt (Liptako, SW Niger): implication for Birimian (Palaeoproterozoic) crustal genesis
Authors: Soumaila A. , Henry P. , Garba Z. , Rossi M.
Published: May 2008

The Palaeoproterozoic Diagorou–Darbani greenstone belt in Liptako (Niger) is made up of micaschists, various amphibolites, metaconglomerates, and metabasalts intruded by granodioritic plutons. One of these plutons, the Dargol granodiorite, is dated at 2174±4 Ma, this age is comparable with those previously reported by many researchers. The micaschists (Type 1 sediments) and intercalated amphibolites have REE patterns variously enriched in light REE (LREE), suggesting oceanic arc-related rocks. The protolith of these micaschists have calc-alkaline affinities, with crystallization ages around 2273–2278 Ma, and T
DM
close to 2.3 Ga. This age is suggestive of an early Palaeoproterozoic magmatic event in crustal growth. The metaconglomerates (Type 2 sediments) exhibit REE patterns depleted in heavy REE (HREE) typical of tonalite–trondhjemite–granodiorite (TTG), the protolith of which may have been crystallized at 2187±55 Ma. These results, together with the earlier ones, led to a Palaeoproterozoic geodynamic model in which the crustal genesis was completely related to subduction zones, with an early Palaeoproterozoic magmatic event. Partial melting of a mantle slab generated the granitoid rocks of calc-alkaline affinities, whereas those with TTG characters could have been produced by direct partial melting of subducted oceanic crust. The crustal growth may have been the result of a continuous input of crustal materials in the interval time of 2.3–2.15 Ga, corresponding to ages recorded by various detrital zircon grains of micaschists and conglomerates.
The Anti-Atlas chain (Morocco): the southern margin of the Variscan belt along the edge of the West African craton
Authors: Soulaimani Abderrahmane , Burkhard Martin
Published: May 2008

Broadly synchronous circum-Atlantic Variscan–Alleghanian orogenic belts developed during the Late Palaeozoic Gondwana–Laurentia collision. In the northern part of the West African craton (WAC), the Variscan orogeny produced basement-controlled structures in the Anti-Atlas, which represents the pericratonic foreland, now located south of the Variscan domains of Morocco and north of the Mauritanides belt. New structural field observations document the strong involvement of the basement and the inversion and folding of the Palaeozoic sedimentary basins at the edge the WAC. Two contrasting domains differently responding to regional NW–SE shortening are recognized: (1) a narrow belt along the Atlantic coast characterized by thin-skinned folding and ESE-vergent thrusting (para-autochthonous Anti-Atlas); (2) a large area between the WAC
sensu stricto
and the South Atlas front showing huge basement uplifts amidst a folded Palaeozoic cover with upright polyharmonic folds (autochthonous Anti-Atlas). The structural trend of the basement inliers is inherited at least in some case from previous Proterozoic fractures. Compressional reactivations led to basement uplift and concomitant folding of the Palaeozoic cover. Cover series are horizontally shortened by mostly upright symmetrical buckle folds of various wavelengths in response to thickness variations between abundant incompetent silt and shale horizons and rare competent carbonate and quartzite beds. Deformation is greatest near the borders of and between closely spaced basement uplifts. Regionally, deformation intensity decreases, either abruptly or progressively, towards the SE and it vanishes within the undeformed Tindouf basin.
Devonian extension of the Pan-African crust north of the West African craton, and its bearing on the Variscan foreland deformation: evidence from eastern Anti-Atlas (Morocco)
Authors: Baidder Lahssen , Raddi Youssef , Tahiri Mohamed , Michard André
Published: May 2008

The Anti-Atlas belt belongs to the northern fringe of the West African craton, moderately deformed during the Variscan orogeny south of the Meseta Block. Field-based investigations into the stratigraphy and structure of the Palaeozoic cover have been performed in the eastern part of Anti-Atlas, with emphasis on the Devonian terranes. The Pan-African basement, which crops out in the Ougnat massif, was fragmented into a mosaic of tilted blocks during a sequence of extensional faulting events that occurred from Cambrian to (mostly) Late Devonian times. The Devonian normal fault pattern indicates a multi-directional extension, with a dominant northward direction. The Variscan compression resulted in the inversion of the palaeofaults as strike-slip–reverse faults, the kinematics of which points to a NE-trending regional direction of shortening, probably Permian in age. The occurrence of the Late Devonian palaeofault array accounts for the thick-skinned style of the (eastern) Anti-Atlas belt. The Devonian paleogeography of the Anti-Atlas can be correlated with that of the Meseta, but the lack of any Late Devonian compressional event in the Anti-Atlas shows that the two domains were not mechanically coupled at that time.
A complex multi-chamber magmatic system beneath a late Cenozoic volcanic field: evidence from CSDs and thermobarometry of clinopyroxene from a single nephelinite flow (Djbel Saghro, Morocco)
Authors: Berger Julien , Ennih Nasser , Liégeois Jean-Paul , Nkono Collin , Mercier Jean-Claude C. , Demaiffe Daniel
Published: May 2008

We used quantitative textural measurement, electron microprobe microanalysis and thermobarometry on clinopyroxene from a Cenozoic pyroxene-nephelinite flow located along the northern boundary of the West African craton to decipher magma differentiation processes in underlying magma chambers. The crystal size distributions of clinopyroxene phenocrysts show straight but also curved and kinked patterns and the clinopyroxene show large compositional variations in a single flow (Mg-number 48–88). These observations are strong evidence for magma mixing between a nephelinite magma and a more differentiated phonolitic melt at depth. Detailed thermobarometry on these clinopyroxene shows that at least three magma chambers are present below Saghro and that they are emplaced at the main physical interface within the lithosphere: (1) at the crust–mantle boundary, where the mantle-derived nephelinite has been mixed with a pre-existing phonolitic magma chamber; (2) at the lower–upper crust boundary; (3) close to the surface in a sub-volcanic magma chamber. Some high-pressure phenocrysts (up to 14 kbar) have also probably crystallized within the upper lithospheric mantle. The high clinopyroxene proportion in samples from the base of the flow is thought to reflect crystal settling during cooling of the nephelinite flow at the surface.
Possible primary sources of diamond in the North African diamondiferous province
Authors: Kahoui M. , Mahdjoub Y. , Kaminsky F. V.
Published: May 2008

The Eglab shield is the easternmost part of the Reguibat rise, which belongs to the West African craton (WAC). It corresponds to the amalgamation of the Yetti and Eglab Palaeoproterozoic domains. These domains are separated by a mega-shear zone called the ‘Yetti–Eglab Junction’ where fieldwork has led to the discovery of kimberlite indicator minerals but no diamond. In the southwestern part of this zone, an outcrop of Archaean basement and a komatiitic–picritic dyke had been recognized. Within the Eglab shield, deep-seated lithospheric faults control emplacement of alkaline complexes, and of small circular structures made up of mafic, ultramafic and silica-undersaturated rocks. These structural zones are characterized by widespread development of dyke swarms and repeated reactivations of earlier Eburnean trends from the Neoproterozoic to Mesozoic. Accordingly, they are sites of high magmatic permeability and crustal weakness. In this study, we summarize all known earlier and newly obtained structural, geophysical, geological and geochemical data on this area. They indicate that the ‘Yetti–Eglab Junction’ has good possibilities for the finding of kimberlite or/and other diamondiferous rocks. The features of the Eglab shield provide a possible explanation for the enigmatic sources of the diamond-bearing Reggane placer deposit located at the boundary of the WAC.
First report of ultrahigh-temperature sapphirine + spinel + quartz and orthopyroxene + spinel + quartz parageneses discovered in Al–Mg granulites from the Khanfous area (In Ouzzal metacraton, Hoggar, Algeria)
Authors: Adjerid Z. , Ouzegane K. , Godard G. , Kienast J. R.
Published: May 2008

The Archaean to Palaeoproterozoic Khanfous area from the Archaean In Ouzzal granulite terrane (Western Hoggar, Algeria) preserves exceptional thermal-peak (1150<
T
< 1300 °C) mineral parageneses, consisting of orthopyroxene+spinel+quartz, sapphirine+spinel+quartz and sapphirine+orthopyroxene+quartz, in quartz-rich Al–Mg granulites. Reaction textures coupled with
P
–
T
FMASH pseudosections indicate that rocks experienced complex multi-stage evolution. Our results suggest that the Khanfous area, as well as the entire northern In Ouzzal metacraton, experienced ultrahigh-temperature crustal metamorphism attributed to a 2 Ga Palaeoproterozoic event, followed by exhumation along a clockwise
P
–
T
path. The extreme temperatures attained suggest delamination of the lithosphere and ascent of the asthenosphere after crustal thickening.
Activation of hepatocytes by extracellular heat shock protein 72
Authors: Galloway Elizabeth , Shin Thomas , Huber Nadine , Eismann Thorsten , Kuboki Satoshi , Schuster Rebecca , Blanchard John , Wong Hector R. , Lentsch Alex B.
Published: May 2008

Heat shock protein (HSP) 72 is released by cells during stress and injury. HSP-72 also stimulates the release of cytokines in macrophages by binding to Toll-like receptors (TLR) 2 and 4. Circulating levels of HSP-72 increase during hepatic ischemia-reperfusion injury. The role of extracellular HSP-72 (eHSP-72) in the injury response to ischemia-reperfusion is unknown. Therefore, the objective of the present study was to determine whether eHSP-72 has any direct effects on hepatocytes. Primary mouse hepatocytes were treated with purified human recombinant HSP-72. Conditioned media were evaluated by ELISA for the cytokines, TNF-α, IL-6, and macrophage inflammatory protein 2 (MIP-2). Stimulation of hepatocytes with eHSP-72 did not induce production of TNFα or IL-6 but resulted in dose-dependent increases in MIP-2 production. To evaluate the pathway responsible for this response, expression of TLR2 and TLR4 was confirmed on hepatocytes by immunohistochemistry. Hepatocyte production of MIP-2 was significantly decreased in hepatocytes obtained from TLR2 or TLR4 knockout mice. MIP-2 production was found to be partially dependent on NF-κB because inhibition of NF-κB with Bay 11-7085 significantly decreased eHSP-72-induced MIP-2 production. Inhibitors of p38 mitogen-activated protein kinase or c-Jun NH2-terminal kinase had no effect on production of MIP-2 induced by eHSP-72. The data suggest that eHSP-72 binds to TLR2 and TLR4 on hepatocytes and signals through NF-κB to increase MIP-2 production. The fact that eHSP-72 did not increase TNF-α or IL-6 production may be indicative of a highly regulated signaling pathway downstream from TLR.
Deficiency of glucose-dependent insulinotropic polypeptide receptor prevents ovariectomy-induced obesity in mice
Authors: Isken Frank , Pfeiffer Andreas F. H. , Nogueiras Rubén , Osterhoff Martin A. , Ristow Michael , Thorens Bernard , Tschöp Matthias H. , Weickert Martin O.
Published: May 2008

Menopause and premature gonadal steroid deficiency are associated with increases in fat mass and body weight. Ovariectomized (OVX) mice also show reduced locomotor activity. Glucose-dependent-insulinotropic-polypeptide (GIP) is known to play an important role both in fat metabolism and locomotor activity. Therefore, we hypothesized that the effects of estrogen on the regulation of body weight, fat mass, and spontaneous physical activity could be mediated in part by GIP signaling. To test this hypothesis, C57BL/6 mice and GIP-receptor knockout mice (Gipr−/−) were exposed to OVX or sham operation ( n = 10 per group). The effects on body composition, markers of insulin resistance, energy expenditure, locomotor activity, and expression of hypothalamic anorexigenic and orexigenic factors were investigated over 26 wk in all four groups of mice. OVX wild-type mice developed obesity, increased fat mass, and elevated markers of insulin resistance as expected. This was completely prevented in OVX Gipr−/− animals, even though their energy expenditure and spontaneous locomotor activity levels did not significantly differ from those of OVX wild-type mice. Cumulative food intake in OVX Gipr−/− animals was significantly reduced and associated with significantly lower hypothalamic mRNA expression of the orexigenic neuropeptide Y (NPY) but not of cocaine-amphetamine-related transcript (CART), melanocortin receptors (MCR-3 and MCR-4), or thyrotropin-releasing hormone (TRH). GIP receptors thus interact with estrogens in the hypothalamic regulation of food intake in mice, and their blockade may carry promising potential for the prevention of obesity in gonadal steroid deficiency.
Candidate genes and sensory functions in health and irritable bowel syndrome
Authors: Camilleri Michael , Busciglio Irene , Carlson Paula , McKinzie Sanna , Burton Duane , Baxter Kari , Ryks Michael , Zinsmeister Alan R.
Published: May 2008

Adrenergic and serotonergic (ADR-SER) mechanisms alter gut (GI) function; these effects are mediated through G protein transduction. Candidate genetic variations in ADR-SER were significantly associated with somatic scores in irritable bowel syndrome (IBS) and gastric emptying but not small bowel or colonic transit. Our aim was to assess whether candidate ADR-SER genes are associated with motor and sensory GI functions in IBS and subgroups on the basis of bowel dysfunction. In 122 patients with IBS and 39 healthy controls, we assessed gastrointestinal somatic symptoms and affect by validated questionnaires. We measured: gastric volume (GV), maximum tolerated volume, rectal compliance, sensation thresholds and ratings, and genetic variations including α 2A (C-1291G), α 2C (Del 332–325), GNβ 3 (C825T), and 5-HTTLPR. Demographics and genotype distributions were similar in the patients with IBS subgrouped on bowel function. There were significant associations between 5-HTTLPR SS genotype and absence of IBS symptoms and between 5-HTTLPR LS/SS genotype and increased rectal compliance and increased pain ratings, particularly at 12 and 24 mmHg distensions. GNβ 3 was associated only with fasting GV; we did not detect associations between α 2A genotype and the gastrointestinal sensory or motor functions tested. We concluded that 5-HTTLPR LS/SS genotype is associated with both increased pain sensation and increased rectal compliance though the latter effect is unlikely to contribute to increased pain sensation ratings with LS/SS genotype. The data suggest the hypotheses that the endophenotype of visceral hypersensitivity in IBS may be partly related to genetic factors, and the association of GNβ 3 with fasting GV may explain, in part, the reported association of GNβ 3 with dyspepsia.
Regulation of the epithelial sodium channel by membrane trafficking
Authors: Butterworth Michael B. , Edinger Robert S. , Frizzell Raymond A. , Johnson John P.
Published: May 2008

The epithelial Na+channel (ENaC) is a major regulator of salt and water reabsorption in a number of epithelial tissues. Abnormalities in ENaC function have been directly linked to several human disease states including Liddle's syndrome, psuedohypoaldosteronism, and cystic fibrosis and may be implicated in states as diverse as salt-sensitive hypertension, nephrosis, and pulmonary edema. ENaC activity in epithelial cells is highly regulated both by open probability and number of channels. Open probability is regulated by a number of factors, including proteolytic processing, while ENaC number is regulated by cellular trafficking. This review discusses current understanding of apical membrane delivery, cell surface stability, endocytosis, retrieval, and recycling of ENaC and the molecular partners that have so far been shown to participate in these processes. We review known sites and mechanisms of hormonal regulation of trafficking by aldosterone, vasopressin, and insulin. While many details of the regulation of ENaC trafficking remain to be elucidated, knowledge of these mechanisms may provide further insights into ENaC activity in normal and disease states.
Kidney-specific expression of human organic cation transporter 2 (OCT2/SLC22A2) is regulated by DNA methylation
Authors: Aoki Masayo , Terada Tomohiro , Kajiwara Moto , Ogasawara Ken , Ikai Iwao , Ogawa Osamu , Katsura Toshiya , Inui Ken-ichi
Published: May 2008

Human organic cation transporter 2 (OCT2/SLC22A2), which is specifically expressed in the kidney, plays critical roles in the renal secretion of cationic compounds. Tissue expression and membrane localization of OCT2 are closely related to the tissue distribution, pharmacological effects, and/or adverse effects of its substrate drugs. However, the molecular mechanisms underlying the kidney-specific expression of OCT2 have not been elucidated. In the present study, therefore, we examined the contribution of DNA methylation of the promoter region for the OCT2 gene to its tissue-specific expression using human tissue samples. In vivo methylation status of the proximal promoter region of OCT2 and that of OCT1, a liver-specific organic cation transporter, were investigated by bisulfite sequencing using human genomic DNA extracted from the kidney and liver. All CpG sites in the OCT2 proximal promoter were hypermethylated in the liver, while hypomethylated in the kidney. On the other hand, the promoter region of OCT1 was hypermethylated in both the kidney and liver. The level of methylation of the OCT2 promoter was especially low at the CpG site in the E-box, the binding site of the basal transcription factor upstream stimulating factor (USF) 1. In vitro methylation of the OCT2 proximal promoter dramatically reduced the transcriptional activity, and an electrophoretic mobility shift assay showed that methylation at the E-box inhibited the binding of USF1. These results indicate that kidney-specific expression of human OCT2 is regulated by methylation of the proximal promoter region, interfering with the transactivation by USF1.
PPARγAgonists: Potential as Therapeutics for Neovascular Retinopathies
Authors: Pershadsingh Harrihar A. , Moore David M.
Published: May 2008

The angiogenic, neovascular proliferative retinopathies, proliferative diabetic retinopathy (PDR), and age‐dependent macular degeneration (AMD) complicated by choroidal neovascularization (CNV), also termed exudative or “wet” AMD, are common causes of blindness. The antidiabetic thiazolidinediones (TZDs), rosiglitazone, and troglitazone are PPARγagonists with demonstrable antiproliferative, and anti‐inflammatory effects, in vivo, were shown to ameliorate PDR and CNV in rodent models, implying the potential efficacy of TZDs for treating proliferative retinopathies in humans. Activation of the angiotensin II type 1 receptor (AT1‐R) propagates proinflammatory and proliferative pathogenic determinants underlying PDR and CNV. The antihypertensive dual AT1‐R blocker (ARB), telmisartan, recently was shown to activate PPARγand improve glucose and lipid metabolism and to clinically improve PDR and CNV in rodent models. Therefore, the TZDs and telmisartan, clinically approved antidiabetic and antihypertensive drugs, respectively, may be efficacious for treating and attenuating PDR and CNV humans. Clinical trials are needed to test these possibilities.
Several Existence Theorems of Nonlinear m‐Point BVP for an Increasing Homeomorphism and Homomorphism on Time Scales
Authors: Sang Yanbin , Su Hua , Xiao Yafeng
Published: May 2008

Several existence theorems of positive solutions are established for nonlinear
m‐point boundary value problem for the following dynamic equations on time scales , t ∈ (0, T), , , where ϕ : R → R is an increasing homeomorphism and homomorphism and ϕ(0) = 0. As an application, an example to demonstrate our results is given.
A Critical Review of the Recent Improvements in Minimizing Nuclear Waste by Innovative Gas-Cooled Reactors
Authors: Bomboni E. , Cerullo N. , Lomonaco G. , Romanello V.
Published: May 2008

This paper presents a critical review of the recent improvements in minimizing nuclear waste in terms of quantities, long-term activities, and radiotoxicities by innovative GCRs, with particular emphasis to the results obtained at the University of Pisa. Regarding these last items, in the frame of some EU projects (GCFR, PUMA, and RAPHAEL), we analyzed symbiotic fuel cycles coupling current LWRs with HTRs, finally closing the cycle by GCFRs. Particularly, we analyzed fertile-free and Pu-Th-based fuel in HTR: we improved plutonium exploitation also by optimizing Pu/Th ratios in the fuel loaded in an HTR. Then, we chose GCFRs to burn residual MA. We have started the calculations on simplified models, but we ended them using more “realistic” models of the reactors. In addition, we have added the GCFR multiple recycling option usingkeffcalculations for all the reactors. As a conclusion, we can state that, coupling HTR with GCFR, the geological disposal issues concerning high-level radiotoxicity of MA can be considerably reduced.
C‐Peptide Effects on Renal Physiology and Diabetes
Authors: Rebsomen L. , Khammar A. , Raccah D. , Tsimaratos M.
Published: May 2008

The C‐peptide of proinsulin is important for the biosynthesis of insulin and has for a long time been considered to be biologically inert. Animal studies have shown that some of the renal effects of the C‐peptide may in part be explained by its ability to stimulate the Na,K‐ATPase activity. Precisely, the C‐peptide reduces diabetes‐induced glomerular hyperfiltration both in animals and humans, therefore, resulting in regression of fibrosis. The tubular function is also concerned as diabetic animals supplemented with C‐peptide exhibit better renal function resulting in reduced urinary sodium waste and protein excretion together with the reduction of the diabetes‐induced glomerular hyperfiltration. The tubular effectors of C‐peptide were considered to be tubule transporters, but recent studies have shown that biochemical pathways involving cellular kinases and inflammatory pathways may also be important. The matter theory concerning the C‐peptide effects is a metabolic one involving the effects of the C‐peptide on lipidic metabolic status.This review concentrates on the most convincing data which indicate that the C‐peptide is a biologically active hormone for renal physiology.
MEMS Switches and SiGe Logic for Multi‐GHz Loopback Testing
Authors: Keezer D. C. , Minier D. , Ducharme P. , Viens D. , Flynn G. , McKillop J.
Published: May 2008

We describe the use of microelectromechanical system (MEMS) switches and SiGe logic devices for both passive and active loopback testing of wide data buses at rates up to 6.4 Gbps per signal. Target applications include HyperTransport, fully buffered DIMM, and PCI Express, among others. Recently introduced MEMS devices provide >7 GHz bandwidth in a very small package (needed to handle wide buses). SiGe logic supports >7 Gbps signals when active shaping of the waveform is required. Each loopback module typically supports between 9 and 16 differential channels. Multiple cards are used to handle applications with very wide buses or multiple ports. Passive cards utilize MEMS for switching between the loopback (self‐test) mode and traditional automated test equipment (ATE) source/receiver channels. Future active card designs may provide additional waveform‐shaping functions, such as buffering, amplitude attenuation/modulation, deskew, delay adjustment, jitter injection, and so forth. The modular approach permits precalibration of the loopback electronics and easy reconfiguration between debug or characterization testing and high‐volume production screening.
High Definition X‐Ray Fluorescence: Principles and Techniques
Authors: Chen Z. W. , Gibson Walter M. , Huang Huapeng
Published: May 2008

Energy dispersive X‐ray fluorescence (EDXRF) is a well‐established and powerful tool for nondestructive elemental analysis of virtually any material. It is widely used for environmental, industrial, pharmaceutical, forensic, and scientific research applications to measure the concentration of elemental constituents or contaminants. The fluorescing atoms can be excited by energetic electrons, ions, or photons. A particular EDXRF method, monochromatic microfocus X‐ray fluorescence (MμEDXRF), has proven to be remarkably powerful in measurement of trace element concentrations and distributions in a large variety of important medical, environmental, and industrial applications. When used with state‐of‐the‐art doubly curved crystal (DCC) X‐ray optics, this technique enables high‐sensitivity, compact, low‐power, safe, reliable, and rugged analyzers for insitu, online measurements in industrial process, clinical, and field settings. This new optic‐enabled MμEDXRF technique, called high definition X‐ray fluorescence (HD XRF), is described in this paper.
Meshing Force of Misaligned Spline Coupling and the Influence on Rotor System
Authors: Zhao Guang , Liu Zhansheng , Chen Feng
Published: May 2008

Meshing force of misaligned spline coupling is derived, dynamic equation of rotor‐spline coupling system is established based on finite element analysis, the influence of meshing force on rotor‐spline coupling system is simulated by numerical integral method. According to the theoretical analysis, meshing force of spline coupling is related to coupling parameters, misalignment, transmitting torque, static misalignment, dynamic vibration displacement, and so on. The meshing force increases nonlinearly with increasing the spline thickness and static misalignment or decreasing alignment meshing distance (AMD). Stiffness of coupling relates to dynamic vibration displacement, and static misalignment is not a constant. Dynamic behaviors of rotor‐spline coupling system reveal the following: 1X‐rotating speed is the main response frequency of system when there is no misalignment; while 2X‐rotating speed appears when misalignment is present. Moreover, when misalignment increases, vibration of the system gets intricate; shaft orbit departs from origin, and magnitudes of all frequencies increase. Research results can provide important criterions on both optimization design of spline coupling and trouble shooting of rotor systems.
Note on Product Summability of an Infinite Series
Authors: Sulaiman W. T.
Published: May 2008

New results concerning product summability of an infinite series are given. Some special cases are also deduced.
Continuously Increasing Price in an Inventory Cycle: An Optimal
Strategy for E-Tailers
Authors: Joglekar Prafulla , Lee Patrick , Farahani Alireza M.
Published: May 2008

Operations researchers have always assumed that when a product's unit cost
is constant and its demand curve is known and stationary, a retailer of the product would find it optimal to replenish the inventory with a fixed quantity and to sell the product always at a fixed price. We present, with proof, a model that shows that, in such a case, an e-tailer is better off using a continuously increasing price strategy than using a fixed price strategy within each inventory cycle. Sensitivity analysis shows that this strategy is particularly profitable when demand is highly price sensitive and the inventory ordering and carrying costs are high.
Printed Antenna Arrays with High Side Lobe Suppression
Authors: Nešić Aleksandar , Radnović Ivana , Mićić Zoran
Published: May 2008

The problem of side lobe suppression (SLS) in printed antenna arrays has been investigated in the paper. Influence of several factors that make difficult design and realization of antenna arrays with relatively high SLS has been analyzed. We introduced a new type of printed antenna array with symmetrical pentagonal dipoles and symmetrical tapered feed network with Chebyshev distribution enabling SLS better than 34 dB in E-plane. Agreement between simulated and measured results is very good. The antenna is suitable for integration with other microwave circuits. Presented antenna is low cost and very simple for realization.
Numerical Simulations and Design Optimization of the PHT Loop of Natural Circulation BWR
Authors: Durga Prasad G. V. , Gopa Kishor G. , Pandey Manmohan , Dixit Uday S.
Published: May 2008

Mathematical modeling and numerical simulation of natural circulation boiling water reactor (NCBWR) are very important in order to study its performance for different designs and various off-design conditions and for design optimization. In the present work, parametric studies of the primary heat transport loop of NCBWR have been performed using lumped parameter models and RELAP5/MOD3.4 code. The lumped parameter models are based on the drift flux model and homogeneous equilibrium mixture (HEM) model of two-phase flow. Numerical simulations are performed with both models. Compared to the results obtained from the HEM model, those obtained from the drift flux model are closer to RELAP5. The variations of critical heat flux with various geometric parameters and operating conditions are thoroughly investigated. The material required to construct the primary heat transport (PHT) loop of NCBWR has been minimized using sequential quadratic programming. The stability of NCBWR has also been verified at the optimum point.
Constraint‐Preserving Boundary Conditions for the Linearized Baumgarte‐Shapiro‐Shibata‐Nakamura Formulation
Authors: Alekseenko Alexander M.
Published: May 2008

We derive two sets of explicit homogeneous algebraic
constraint‐preserving boundary conditions for the
second‐order in time reduction of the linearized Baumgarte‐Shapiro‐Shibata‐Nakamura (BSSN) system. Our second‐order
reduction involves components of the linearized extrinsic
curvature only. An initial‐boundary value problem
for the original linearized BSSN system is formulated and
the existence of the solution is proved using the properties
of the reduced system. A treatment is proposed for
the full nonlinear BSSN system to construct constraint‐preserving boundary conditions without invoking the second order in time reduction. Energy estimates on the principal
part of the BSSN system (which is first order in temporal
and second order in spatial derivatives) are obtained. Generalizations
to the case of nonhomogeneous boundary data
are proposed.