bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective stress analysis of the stability of embankments on soft soils
Authors: Pilot G. , Trak B. , Rochelle P. La
Published: April 2011

This paper presents the results of a study of stability by effective stress analysis of four embankments that were built to failure; three of these embankments are located in Narbonne, Lanester, and Cubzac in France, and the fourth one in Saint-Alban, Québec. After an outline of the procedures followed to obtain the required data and parameters, a brief discussion is presented on the defects inherent in the methods of analysis in terms of effective stresses. The factors of safety obtained by the effective stress analyses are compared with the results of total stress analyses. It is concluded that, in spite of the limitations of the method of effective stress analysis, this approach, as used in the present paper, remains a useful tool for the engineer.
Full-displacement pressuremeter testing in sand
Authors: Hughes J. M. O. , Robertson P. K.
Published: April 2011

An alternative approach to pressuremeter testing in sand, where the pressuremeter is pushed closed-ended, is discussed. Observations from cone penetration testing in sands are used to provide a theoretical background to the expected stress conditions around a full-displacement pressuremeter probe pushed into sand. The anticipated stress paths followed during the pressure expansion phase of the test are discussed. Data from both self-boring and full-displacement pressuremeter tests in sand are presented to support some of the suggested theoretical background. Key words: pressuremeter testing, in situ testing, sand.
Effective stress paths and yielding in soft clays below embankments
Authors: Folkes D. J. , Crooks J. H. A.
Published: April 2011

Current methods of predicting the response of soft clays to surface loading are often unsuccessful because the assumed constitutive relationships, including effective stress path behaviour, are incorrect. In particular, the transition from small-strain to large-strain behaviour (i.e. yielding) is frequently not taken into account. Recent laboratory testing has demonstrated that the behaviour of soft clays is largely controlled by yielding. The locus of effective stress states causing yield is known as the yield envelope (YE).The effective stress paths (ESP's) in soft clay foundations below the centre of six fills were determined from computed total stresses and measured pore-water pressures. Yield behaviour is clearly indicated by ESP shapes. The yield envelopes inferred from analyses of field data are similar to those obtained from laboratory testing. Effective stress path shapes vary widely, depending on a variety of factors, including imposed stress level, rate of construction, and boundary drainage conditions. This finding contradicts an earlier conclusion that soft clay behaviour can be characterized by a single ESP. Because of the wide range of possible ESP shapes, the parameters [Formula: see text] does not provide an adequate basis for determining the effective stress state in a soft clay.The ESP/YE analyses indicate that yield can occur either during loading or during excess pore-water pressure dissipation following completion of loading. Yield of sensitive soils during loading is usually followed by strain softening. However, in some soils, dilatant behaviour appears to occur. Yield during dissipation of excess pore-water pressure is characterized by a dramatic change in cv and increased compressibility. Key words: soft clay, yield, effective stress paths, field behaviour, strain softening, rate of consolidation.
Performance assessment of a railway turnout geotextile
Authors: Raymond Gerald P.
Published: April 2011

Many railways have been making increasing use of the heavier mass per unit area geotextiles, bringing into question the financial viability of their use. In order to assess the viability of turnout geotextiles, two closely spaced turnouts, positioned on an embankment constructed of compacted clay at Rosser, near Winnipeg, were rehabilitated in September 1981. Under one turnout, a Turn Out Pack System (TOPS) geotextile of variable mass per unit area (550–1100 g/m2 (16–32 oz/yd2)) was used; with the other, no geotextile was used. The ballast was a metamorphic granodioritic gneiss known locally as Kenora granite. This article summarizes the findings of excavations made to assess the performance of the geotextile. The assessment excavations were made in August 1984 after an average of 13.6 × 106 gross tonnes (15 × 106 gross tons) per year per track of traffic. The results clearly show the damage penalty to the ballast from fouling caused at the nongeotextile locations. Key words: railways, ballast, subballast, geotextile, fouling, pumping, fines, equivalent opening size (EOS).
In situ testing and its application to foundation engineering
Authors: Robertson P. K.
Published: April 2011

The status of in situ testing and its application to foundation engineering are presented and discussed. The in situ test methods are discussed within the framework of three groups: logging, specific, and combined test methods. The major logging test methods discussed are standard penetration test (SPT), cone penetration test (CPT), and the flat plate dilatometer test (DMT). The major specific test methods discussed are the prebored pressuremeter test (PMT), the self-bored pressuremeter test (SBPMT), and the screw plate load test (SPLT). Discussion is also presented on recent tests that combine features of logging tests (using the CPT) and specific tests (e.g. the seismic, the electrical resistivity/dielectric, and the lateral stress sensing cone penetration tests). A brief discussion is also presented on the applicability, as perceived by the author, of existing in situ test methods and the future of in situ testing applied to foundation engineering. Key words: in situ testing, foundation engineering, penetration testing, pressuremeter.
Practical guidelines for microwave drying of soils
Authors: Carter Michael , Bentley Stephen P.
Published: April 2011

This note provides practical guidelines for the use of microwave drying in the determination of soil water contents. The results are based on over 250 individual tests performed on sand, sandy clay, estuarine clay, marl, lateritic clay, kaolin, and bentonite (sodium). All soils tested fell into one of three distinct categories and drying times for each are presented as a function of initial sample mass. The recommended drying times give results within 0.5 wt% of those obtained by standard oven drying. No limitations were observed in the performance of a 600-W domestic microwave oven. Key words: water contents, microwave, drying, sand, silt, clay, procedures.
Debris flows: some physical characteristics and behaviour
Authors: Fannin R. J. , Rollerson T. P.
Published: April 2011

Field observations on 449 debris flows in the Queen Charlotte Islands, British Columbia, are summarized. Movement of debris is classified according to seven characteristic types designated for the purposes of the study. Data on the physical characteristics of the events are presented. An analysis of the data is made with reference to event initiation, yield, and deposition using both mechanistic and morphological criteria. For those events which initiate on an open slope, the infinite slope model is used to establish a relationship between field drainage class and slope angle, for assumed frictional and cohesive soil strength parameters. The field drainage classes are directly related to the postulated location of the groundwater surface within the depth of the rupture plane. Deposition of channelized events is found to be influenced by the ratio of channel width to channel gradient, with the onset of deposition expected when the ratio exceeds unity. Five classes of depositional area are proposed. The magnitude of debris material deposited by an event is described by a channel debris yield rate which shows considerable variation with each event type. The conclusions of this study are based on postevent field measurements of deposited and eroded debris material. A limitation of the study arises from the difficulty of accurately describing an event some years after it has taken place. Key words : slope stability, debris flow, infinite slope analysis, debris yield.
Construction and performance of a full-scale geotextile reinforced test embankment, Sackville, New Brunswick
Authors: Rowe R. Kerry , Gnanendran C.T. , Landva A.O. , Valsangkar A.J.
Published: April 2011

The instrumentation, construction, and field performance of a full-scale geotextile reinforced test embankment constructed on a soft compressible soil is presented. A relatively high-strength polyester woven geotextile was used as reinforcement. The construction sequence, the observed pore pressure response, and the vertical and horizontal displacements are reported. The development and propagation of cracks in relation to the construction sequence and the manner in which the embankment failed are described. The field data suggest that the shear strength of the foundation soil was mobilized at a fill thickness between 5 and 5.7 m. However, due to the stabilizing effect of the geotextile reinforcement, the embankment did not fail until the geotextile reached its ultimate tensile strength and tore when the fill thickness reached 8.2 m. The failure of the embankment was of a viscoplastic nature and although additional fill could be placed after failure of the geotextile and embankment at 8.2 m, no additional gain in the net height (i.e., relative to the surrounding area) could be maintained above the maximum of 6.6 m recorded when the fill thickness reached 8.2 m. Key words : embankment, geotextile reinforcement, field behaviour, stability, deformations, pore pressures.
Vehicle bearing capacity of frozen ground over a soft substrate
Authors: Shoop Sally A.
Published: April 2011

Freezing temperatures may allow the use of vehicles and heavy equipment on otherwise inaccessible or sensitive areas such as swamps, bogs, tundra, and peatlands. Predicting operable conditions on frozen ground is useful for forestry, mining, oil exploration, construction, and military operations. Guidelines for estimating the frost depth necessary to support a given vehicle load have been generated based on experience in forestry operations on peatlands and similarities in the strength behavior of frozen peat and frozen soils. Correlation with information in the literature leads to a simple equation relating safe trafficability of frozen ground over soft ground: P = Cz2, where P is the maximum load and C is a constant depending on the strength of the frozen layer, which has a thickness z. Values for the constant C and a chart showing required frozen thickness for a variety of vehicles are given. Key words : bearing capacity, frozen ground, peat, frost, vehicle mobility, strength.
Evidence for recent groundwater flow through Late Wisconsinan till near Toronto, Ontario
Authors: Gerber R E , Howard K WF
Published: April 2011

The Northern till is a thick (~50 m) Late Winsconsinan diamict unit that occurs throughout south-central Ontario. The till has generally been regarded as massive and uniform, with a very low vertical hydraulic conductivity. It is similar to many other till units of mid-continental North American glaciated terrain in that it is believed to inhibit recharge to underlying aquifers and afford a high degree of protection to these aquifers from surface and near-surface sources of contamination. Standard methods of estimating hydraulic conductivity (K) for the Northern till, such as laboratory testing of core samples (other studies) and risingfalling head field piezometer tests (this study and other studies), characteristically yield values on the order of 1011 to 109 m/s. Typically, these values indicate advective traveltimes through the till on the order of hundreds to thousands of years. In contrast, isotopic evidence (2H, 18O, and 3H) from till pore waters indicates the presence of modern (post-1952) waters at depths of up to 50 m, suggesting either that certain facies of the till are considerably more permeable or that minor sand lenses or hydrogeologically active secondary permeability structures are locally important. In some areas, vertical flow velocities may approach 1 m/year. By comparing pore-water isotopic data from cores acquired using mud (sodium bentonite) and dry rotary methods, this study further demonstrates that representative pore-water samples can be obtained using a drilling fluid providing care is taken in preparing core samples for analysis.

Key words: till, aquitard, permeability, recharge, contaminant transport, isotopes.
Shear strength characteristics of two saprolitic soils
Authors: Gan Julian K-M , Fredlund D G
Published: April 2011

The saturated and unsaturated shear strength behavior of an undisturbed, completely decomposed fine ash tuff and an undisturbed, completely decomposed granite from Hong Kong were studied using direct shear and triaxial tests. The completely decomposed fine ash tuff is a fine- to medium-grained saprolite. The completely decomposed granite is a coarse-grained saprolite. Results show that matric suction increases the shear strength of both soils. The extent of the increase is the shear strength with matric suction is related to the soil-water characteristic curve for the soil and to the amount of dilation during shear. The effect of matric suction on the shear strength was more pronounced for the fine- to medium-grained completely decomposed fine ash tuff than for the coarse-grained completely decomposed granite. These studies on the saprolitic soils provide insight into the understanding of the shear strength of unsaturated, coarse-grained soils.

Key words: saprolites, shear strength, matric suction, triaxial, direct shear, coarse-grained soils.
Geothermal modeling of soil or mine tailings with concurrent freezing and deposition
Authors: Nixon JF (Derick) , Holl Nick
Published: April 2011

A geothermal model is described that simulates simultaneous deposition, freezing, and thawing of mine tailings or sequentially placed layers of embankment soil. When layers of soil or mine tailings are placed during winter subfreezing conditions, frozen layers are formed in the soil profile that may persist with time. The following summer, warmer soil placement may not be sufficient to thaw out layers from the preceding winter. Remnant frozen soil layers may persist for many years or decades. The analysis is unique, as it involves a moving upper boundary and different surface snow cover functions applied in winter time. The model is calibrated based on two uranium mines in northern Saskatchewan. The Rabbit Lake scenario involves tailings growth to a height of 120 m over a period of 24 years. At Key Lake, tailings increase in height at a rate of 1.3 m/year. Good agreement between the observed position of frozen layers and those predicted by the model is obtained. Long-term predictions indicate that from 80 to 200 years would be required to thaw out the frozen layers formed during placement, assuming 1992 placement conditions continue. Deposition rates of 1.5-3 m/year give the largest amounts of frozen ground. The amount of frozen ground is sensitive to the assumed snow cover function during winter.Key words: geothermal, model, tailings, freezing, deposition.
Split Set friction stabilizers: an experimental study of strength distribution and the effect of corrosion
Authors: Stimpson Brian
Published: April 2011

The pull-out strength of the widely used Split Set stabilizer for rock support, as measured in full-scale field tests in various rock types, has been shown to increase with time after installation. Several physical mechanisms for this increase have been postulated. In a series of laboratory tests in which one of these mechanisms, namely corrosion, was isolated so that its effect could be studied, anchorage capacity as measured by a special push test was found to increase up to 192% after Split Set samples installed in concrete were allowed to corrode for 90 days in a high-humidity environment. It is concluded that one major contributor to the significant increase of pull-out strength with time of Split Sets is corrosion. However, although substantial improvements in strength from this mechanism may be counted on over the short term, it is anticipated that over longer periods of time the strength capacity will decline as the amount of corrosion increases. The study also examined the distribution of strength along the length of the Split Set.Key words: rock reinforcement, friction stabilizers, load capacity, corrosion.
Overdamped slug test in monitoring wells: review of interpretation methods with mathematical, physical, and numerical analysis of storativity influence
Authors: Chapuis Robert P
Published: April 2011

Several methods are available to interpret slug tests; however, when applied to the same test data, they usually yield very different results. The methods are classified into three categories depending on their assumptions about the solid matrix deformability during the test. This paper deals with overdamped tests for elastic solids that deform instantaneously. It provides a unified interpretation of transmissivity T and storativity S based on the velocity graph for variable-head tests in monitoring wells or cased boreholes. If S has little influence, the velocity graph is a straight line. If S has some influence, the graph should give a smooth curve. However, smooth curves are exceptions in practice, thereby leading to a reexamination of the influence of S during a slug test. Three independent approaches are used. (1) A mathematical review shows that the overdamped solution, as adapted from a heat conduction problem, did not correctly treat storativity terms and the type of problem: it corresponds to a special pulse test, not a slug test. (2) A physical investigation of deformability shows that the influence of S does not exceed 1% of the initial slug for most compressible materials. Thus, it is almost impossible to detect its influence in test results. (3) Numerical analyses confirm that S has a negligible influence: test results provide straight lines, not curves. The numerical analysis of the special pulse test provides exactly the classical solution, and the correct values of T and S after eliminating the confusion about storativity terms. It is concluded that (1) S has a negligible influence in slug tests, (2) the existing classical solution giving T and S must be abandoned, and (3) the velocity-graph equation and its integral equation (Hvorslev or Bouwer and Rice) which correctly describe the process must be used.Key words: slug test, hydraulic conductivity, storativity, numerical modeling.
Ground movements due to pile driving in an excavation in soft soil
Authors: Wong I H , Chua T S
Published: April 2011

An excavation in soft clay for the construction of a deep basement frequently is accompanied by large ground movements that may damage piles preinstalled at the base of the excavation. In a recent project involving the construction of a 10 m wide, 3.7 m deep drain, the construction method adopted entailed excavating the site soils and then driving precast concrete piles. The excavation was supported by steel sheet piles braced by one level of struts. Large settlements and horizontal movements of the ground were observed during pile driving. These movements exceeded those occurring during the excavation phase. Concrete aprons outside a one-story building adjacent to the excavation were badly damaged during excavation and pile driving. However, the building supported on steel piles was undamaged.Key words: deep excavation, sheet piles, pile driving, ground movement, basement construction.
Comparative evaluation of building responses to an adjacent braced excavation
Authors: Boone S J , Westland J , Nusink R
Published: April 2011

Construction data from a large braced excavation are evaluated in comparison to several methods of predicting the response of buildings to excavation-induced ground movements. The project included an excavation of up to about 20 m depth, over 650 m long, and 20 m wide made through generally competent glacial overburden. Excavation support was achieved using a braced soldier-pile and lagging wall system. A detailed instrumentation program was undertaken by the owner to monitor contractor compliance with ground and structure movement criteria. Data from 46 structures, with damage ranging from negligible to moderate categories, are presented, with four cases presented in detail. A modified approach to estimating potential damage categorization is provided and compared to case histories. Good agreement is demonstrated between actual and estimated damage categories.Key words: building damage, excavations, cracking, angular distortion, settlement.
Microstructure of Omani expansive soils
Authors: Al-Rawas Amer Ali , McGown A
Published: April 2011

The fundamental factors controlling the expansive nature of Omani soils are their characteristics with respect to geology, mineralogy, engineering, and microstructure. The first three factors have been extensively studied, however, the fourth has not yet been fully investigated and no work has been published on this aspect. Therefore, this paper deals with the microstructure characteristics of these soils. The scanning electron microscope was employed in this investigation. Three samples selected from different sites where expansive soils problems were known (Al-Khod, Al-Murtafa'a, and Duqm) were investigated. Two specimens from each sample, representing the vertical and horizontal planes, were tested. In addition, two samples that were subjected to swelling were tested to investigate the microfabric changes caused by swelling. The fabric of the Omani expansive soils studied generally consists of dense clay matrices, although clay-granular matrices are occasionally observed. In addition, no connectors have been observed and only few aggregations have been seen. Pore spaces are mainly of the intra-assemblage and intra-elemental types. Significant microfabric changes were induced by swelling.Key words: microstructure, microfabric, SEM, expansive soils, Oman, clay minerals.
Mobilized strength components of Athabasca oil sand in triaxial compression
Authors: Wong Ron CK
Published: April 2011

Dense uncemented Athabasca oil sand specimens exhibit unusually high peak strength, dilation with severe softening, and residual strength in drained triaxial compression tests. Computer tomography scanning, X-ray imaging, and scanning electron microscopy techniques are used to examine the microstructural features of the sheared specimens, such as interlocked structure, shear-banding pattern, and porosity distributions inside and outside shear bands. The characteristics of these microstructural features are used to explain the macrodeformation responses observed in the triaxial compression tests. Mobilization of strength components derived from interlocked structure, dilation, rolling, and critical state are analyzed for pre-peak, post-peak softening, and residual states.Key words: oil sand, interlocked structure, shear dilation, shear band, critical state.
Tire-reinforced earthfill. Part 3: Environmental assessment
Authors: O'Shaughnessy Vince , Garga Vinod K
Published: April 2011

A reinforced earthfill was constructed using approximately 10 000 scrap tires. Water samples were collected from a drainage system installed below the tire-reinforced earthfill and analyzed for chemical quality. Additional tests on water quality were performed in laboratory test columns in which tire chips were embedded in sand or clay to provide a conservative estimate of the potential release of toxic compounds. Field monitoring of the effluent indicated that no significant adverse effects on groundwater quality had occurred over a period of 2 years. Laboratory batch tests performed on tire chips embedded in sand provided evidence of an increase in solution of certain metal elements which in some cases exceeds their respective drinking-water standards. This increase was attributed to the exposed steel reinforcement found in the tire chips. The amount of organic compounds leached from the tire chips decreased with the number of exposure periods or pore volumes flushed through the soil.Key words: whole scrap tires, water quality, tire chips, field investigation, laboratory lysimeter tests.
Testing of a new generation horizontal soil sampler
Authors: Ariaratnam Samuel T , Allouche Erez N , Biggar Kevin W
Published: April 2011

Sampling using horizontal directional drilling allows the collection of soil samples from suspected zones located beneath structures and other surface-subsurface obstacles. However, current horizontal sampling techniques are time consuming and thus expensive. This paper describes the design and testing of a new multiple-port sampler for collection of soil samples from directionally drilled boreholes. The device uses a new methodology for horizontal sampling to improve cost-effectiveness and sample quality.Key words: horizontal directional drilling, horizontal wells, design, remediation, site characterization, sampling.
Éléments de couplage thermomécanique dans la consolidation de sols non saturés
Authors: Saix C , Devillers P , El Youssoufi M S
Published: April 2011

Thermomechanical couplings in the consolidation of an unsaturated clayey silty sand are investigated. The couplings are analysed through the influence of the temperature (relative to the total vertical stress) on the mechanical characteristics (relative to thermal) of the consolidation. They are evidenced by means of two types of tests (thermal consolidation and mechanical consolidation). The two types of tests lead to quantitative results comparable with regards to characteristic parameters of both types of consolidation. Some elements of interpretation are proposed to integrate all of the experimental results within a framework of thinking resorting to the thermoelastoplastic behaviour of the soil under study and to the thermal and mechanical hardening phenomena.Key words: unsaturated soils, consolidation, thermal, mechanical, coupling, hardening.
Seepage forces and confining pressure effects on piping erosion
Authors: Tomlinson S S , Vaid Y P
Published: April 2011

An experimental study of piping erosion is presented. Various artificial granular filter and base soil combinations are tested in a permeameter under variable confining pressures to determine the critical gradient where soil erodes through the filter. Previous research has concentrated on establishing a filter to soil grain size ratio criteria, typically D15f /D85s < 4, which separates safe from potentially unsafe filters. These works often ignored self-filtration zone formation phenomena and rarely documented the influence of variables such as confining pressure, filter thickness, and hydraulic gradient. To adequately control all variables that may influence piping erosion, a new permeameter was designed and careful attention was paid to sample preparation. Artificial glass beads were water pluviated to permit consistent repeatable uniform samples. By monitoring head, settlement, confining pressure, amount of eroded soil, and water outflow rate, the onset of piping can be determined. It is shown that the grain-size ratio is the most important parameter affecting piping erosion. A soil-filter system with D15f /D85s < 8 will not fail, whereas a D15f /D85s > 12 will not be able to retain base soil. For 8 < D15f /D85s < 12, piping will only occur if the hydraulic gradient exceeds a critical threshold. The critical gradient is lower if the head is rapidly increased, as a filtration zone is inhibited from forming. A very thin filter has a similar effect. Stability is somewhat inversely related to the confining pressure level for small grain-size ratios.Key words: filters, seepage forces, confining stress, piping erosion.
The prediction of groundborne vibration from percussive piling
Authors: Hope V S , Hiller D M
Published: April 2011

Environmental assessments of proposed infrastructure projects include an appraisal of the vibration that would be generated by potential construction methods. This paper considers one part of that process: prediction of groundborne vibration from percussive piling. Various methods for predicting the magnitude of the groundborne vibration generated by percussive piling have been described in the literature. In general, the accuracy of the predictors is limited. The paper investigates the reasons for this, through the development of theoretical models and analysis of field data from an extensive programme of on-site vibration monitoring. It is found that some widespread assumptions about the relationship between the energy rating of a percussive piling hammer and the vibrational energy developed in the ground are invalid. Ground conditions are shown to have a dominant influence on the magnitude of the groundborne vibration generated by percussive piling, and piling vibration predictors which take no account of soil type yield considerably less accurate estimates than site-specific predictions.Key words: piling, vibration, monitoring, prediction, environmental assessment.
A GENETIC APPROACH FOR LONG TERM VIRTUAL ORGANIZATION DISTRIBUTION
Authors: SÁNCHEZ-ANGUIX VÍCTOR , VALERO SOLEDAD , GARCÍA-FORNES ANA
Published: April 2011

An agent-based Virtual Organization is a complex entity where dynamic collections of agents agree to share resources in order to accomplish a global goal or offer a complex service. An important problem for the performance of the Virtual Organization is the distribution of the agents across the computational resources. The final distribution should provide a good load balancing for the organization. In this article, a genetic algorithm is applied to calculate a proper distribution across hosts in an agent-based Virtual Organization. Additionally, an abstract multi-agent system architecture which provides infrastructure for Virtual Organization distribution is introduced. The developed genetic solution employs an elitist crossover operator where one of the children inherits the most promising genetic material from the parents with higher probability. In order to validate the genetic proposal, the designed genetic algorithm has been successfully compared to several heuristics in different scenarios.
Effect of the Ionic Conductivity of the Electrolyte in Composite SOFC Cathodes
Authors: Küngas Rainer , Vohs John M. , Gorte Raymond J.
Published: April 2011

Solid oxide fuel cell (SOFC) cathodes were prepared by infiltration of 35 wt % La0.8Sr0.2FeO3(LSF) into porous scaffolds of three, zirconia-based electrolytes in order to determine the effect of the ionic conductivity of the electrolyte material on cathode impedances. The electrolyte scaffolds were 10 mol % Sc2O3-stabilized zirconia (ScSZ), 8 mol % Y2O3-stabilized zirconia (YSZ), and 3 mol % Y2O3- 20 mol % Al2O3-doped zirconia (YAZ), prepared by tape casting with graphite pore formers. Each electrolyte scaffold was 65% porous, with identical pore structures as determined by scanning electron microscopy (SEM). Both symmetric cells and fuel cells were prepared and tested between 873 and 1073 K, using LSF composites that had been calcined to 1123 or 1373 K. Literature values for the electrolyte conductivities were confirmed using the ohmic losses from the impedance spectra. The electrode impedances decreased with increasing electrolyte conductivity, with the dependence being between to the power of 0.5 and 1.0, depending on the operating temperature and LSF calcination temperature.
mTORC1 inhibition increases neurotensin secretion and gene expression through activation of the MEK/ERK/c-Jun pathway in the human endocrine cell line BON
Authors: Li Jing , Liu Jianyu , Song Jun , Wang Xiaofu , Weiss Heidi L. , Townsend Courtney M. , Gao Tianyan , Evers B. Mark
Published: April 2011

The mammalian target of rapamycin (mTOR) signaling exists in two complexes: mTORC1 and mTORC2. Neurotensin (NT), an intestinal hormone secreted by enteroendocrine (N) cells in the small bowel, has important physiological effects in the gastrointestinal tract. The human endocrine cell line BON abundantly expresses the NT gene and synthesizes and secretes NT in a manner analogous to that of N cells. Here, we demonstrate that the inhibition of mTORC1 by rapamycin (mTORC1 inhibitor), torin1 (both mTORC1 and mTORC2 inhibitor) or short hairpin RNA-mediated knockdown of mTOR, regulatory associated protein of mTOR (RAPTOR), and p70 S6 kinase (p70S6K) increased basal NT release via upregulating NT gene expression in BON cells. c-Jun activity was increased by rapamycin or torin1 or p70S6K knockdown. c-Jun overexpression dramatically increased NT promoter activity, which was blocked by PD98059, an mitogen-activated protein kinase kinase (MEK) inhibitor. Furthermore, overexpression of MEK1 or extracellular signal-regulated kinase 1 (ERK1) increased c-Jun expression and NT promoter activity. More importantly, PD98059 blocked rapamycin- or torin1-enhanced NT secretion. Consistently, rapamycin and torin1 also increased NT gene expression in Hep3B cells, a human hepatoma cell line that, similar to BON, expresses high levels of NT. Phosphorylation of c-Jun and ERK1/2 was also increased by rapamycin and torin1 in Hep3B cells. Finally, we showed activation of mTOR in BON cells treated with amino acids, high glucose, or serum and, concurrently, the attenuation of ERK1/2 and c-Jun phosphorylation and NT secretion. Together, mTORC1, as a nutrient sensor, negatively regulates NT secretion via the MEK/ERK/c-Jun signaling pathway. Our results identify a physiological link between mTORC1 and MEK/ERK signaling in controlling intestinal hormone gene expression and secretion.
Role of cysteine residues in cell surface expression of the human riboflavin transporter-2 (hRFT2) in intestinal epithelial cells
Authors: Subramanian Veedamali S. , Rapp Laramie , Marchant Jonathan S. , Said Hamid M.
Published: April 2011

The water-soluble vitamin B2 (riboflavin, RF) is an essential micronutrient for normal cell function and survival. Recent studies have identified a role for the human riboflavin transporter-2 (hRFT2) in normal intestinal RF absorption. However, little is known about the cell biology of this transporter and specifically about the molecular determinant(s) that dictate its cell surface expression in human intestinal epithelial cells. Here we show that the full-length hRFT2 protein fused to green fluorescent protein (GFP) (GFP-hRFT2) is expressed exclusively at the apical membrane domain of Caco-2 cells. COOH-terminal sequence was essential in dictating cell surface expression with a specific role for conserved cysteine residues (C463 and C467). Mutation of C463 and C467 ablated RF uptake, explained by retention of the constructs within the endoplasmic reticulum. Modeling analysis suggested a potential disulfide bridge between C463 and C386. Consistent with this prediction, mutating the C386 site in the context of the full-length transporter resulted in intracellular retention, whereas mutation of another conserved cysteine (C326A) was without effect on hRFT2 targeting. Intracellular trafficking of hRFT2 was also examined and appeared to involve distinct vesicular structures, the motility of vesicles critically dependent on an intact microtubule network. These results demonstrate a potential role for specific cysteine residues in the cell surface expression of the hRFT2 in human intestinal epithelial cells.
The extracellular matrix: an active or passive player in fibrosis?
Authors: Wight Thomas N. , Potter-Perigo Susan
Published: April 2011

Fibrosis is characterized by excessive accumulation of collagen and other extracellular matrix (ECM) components, and this process has been likened to aberrant wound healing. The early phases of wound healing involve the formation of a provisional ECM containing fibrin, fibrinogen, and fibronectin. Fibroblasts occupy this matrix and proliferate in response to activators elaborated by leukocytes that have migrated into the wound and are retained by the ECM. This coincides with the appearance of the myofibroblast, a specialized form of fibroblast whose differentiation is primarily driven by cytokines, such as transforming growth factor-β (TGF-β), and by mechanical tension. When these signals are reduced, as when TGF-β secretion is reduced, or as in scar shrinkage, myofibroblasts undergo apoptosis, resulting in a collagen-rich, cell-poor scar. Retention of myofibroblasts in fibrosis has been described as the result of imbalanced cytokine signaling, especially with respect to levels of activated TGF-β. ECM components can regulate myofibroblast persistence directly, since this phenotype is dependent on extracellular hyaluronan, tenascin-C, and the fibronectin splice variant containing the “extra domain A,” and also, indirectly, through retention of TGF-β-secreting cells such as eosinophils. Thus the ECM is actively involved in both cellular and extracellular events that lead to fibrosis. Targeting components of the ECM as cells respond to injury and inflammatory stimuli holds promise as a means to avoid development of fibrosis and direct the wound-healing process toward reestablishment of a healthy equilibrium.
Colitis decreases mechanosensitive K2P channel expression and function in mouse colon sensory neurons
Authors: La Jun-Ho , Gebhart G. F.
Published: April 2011

TREK-1, TREK-2 and TRAAK are mechanosensitive two-pore domain K+ (K2P) channels thought to be involved in the attenuation of mechanotransduction. Because colon inflammation is associated with colon mechanohypersensitivity, we hypothesized that the role of these channels in colon sensory (dorsal root ganglion, DRG) neurons would be reduced by colon inflammation. Accordingly, we studied the functional expression of mechanosensitive K2P channels in colon sensory neurons in both thoracolumbar (TL) and lumbosacral (LS) DRG that represent the splanchnic and pelvic nerve innervations of the colon, respectively. In colon DRG neurons identified by retrograde tracer previously injected into the colon wall, 62% of TL neurons and 83% of LS neurons expressed at least one of three K2P channel mRNAs; the proportion of neurons expressing the TREK-1 gene was greater in LS than in TL DRG. In electrophysiological studies, single-channel activities of TREK-1a, TREK-1b, TREK-2, and TRAAK-like channels were detected in cultured colon DRG neuronal membranes. After trinitrobenzene sulfonic acid-induced colon inflammation, we observed significant decreases in the amount of TREK-1 mRNA, in the response of TREK-2-like channels to membrane stretch, and in the whole cell outward current during osmotic stretch in LS colon DRG neurons. These findings document that the majority of DRG neurons innervating the mouse colon express mechanosensitive K2P channels and suggest that a decrease in their expression and activities contributes to the increased colon mechanosensitivity that develops in inflammatory bowel conditions.
Sources of alveolar soluble TNF receptors during acute lung injury of different etiologies
Authors: Dorr Anthony D. , Wilson Michael R. , Wakabayashi Kenji , Waite Alicia C. , Patel Brijesh V. , van Rooijen Nico , O'Dea Kieran P. , Takata Masao
Published: April 2011

Elevated soluble tumor necrosis factor-α receptor (sTNFR) levels in bronchoalveolar lavage fluid (BALF) are associated with poor patient outcome in acute lung injury (ALI). The mechanisms underlying these increases are unknown, but it is possible that pulmonary inflammation and increased alveolar epithelial permeability may individually contribute. We investigated mechanisms of elevated BALF sTNFRs in two in vivo mouse models of ALI. Anesthetized mice were challenged with intratracheal lipopolysaccharide or subjected to injurious mechanical ventilation. Lipopolysaccharide instillation produced acute intra-alveolar inflammation, but minimal alveolar epithelial permeability changes, with increased BALF sTNFR p75, but not p55. Increased p75 levels were markedly attenuated by alveolar macrophage depletion. In contrast, injurious ventilation induced substantial alveolar epithelial permeability, with increased BALF p75 and p55, which strongly correlated with total protein. BALF sTNFRs were not increased in isolated buffer-perfused lungs (devoid of circulating sTNFRs) subjected to injurious ventilation. These results suggest that lipopolysaccharide-induced intra-alveolar inflammation upregulates alveolar macrophage-mediated production of sTNFR p75, whereas enhanced alveolar epithelial permeability following mechanical ventilation leads to increased BALF p75 and p55 via plasma leakage. These data provide new insights into differential regulation of intra-alveolar sTNFR levels during ALI and may suggest sTNFRs as potential markers for evaluating the pathophysiology of ALI.
Skeletal muscle metabolism in individuals with spinal cord injury
Authors: McCully Kevin K. , Mulcahy Tara K. , Ryan Terence E. , Zhao Qun
Published: April 2011

With increasing survival rates in people with spinal cord injuries (SCI), detection and prevention of metabolic and cardiovascular disease have become increasingly important. Few studies have evaluated in vivo mitochondrial function in paralyzed skeletal muscle. The purpose of this study was to compare oxidative muscle metabolism using the rate of phosphocreatine (PCr) resynthesis measured by magnetic resonance spectroscopy (MRS) in people with SCI and able-bodied (AB) controls. Eight subjects with complete SCI (American Spinal Injury Association Impairment Scale A, levels T3–T12, injury duration 2–13 years) were compared with 12 AB controls. T1-weighted1H MR images of the thigh were taken to identify skeletal muscle. Phosphorous MRS was performed with a 13 × 13-cm2surface coil placed on the right vastus lateralis in a 3 Tesla clinical MRI scanner. PCr resynthesis was measured after electrical stimulation for 60 s at 4 Hz in SCI and AB and in AB subjects after 39 s of voluntary isometric contractions. Resting metabolites were not different between SCI and AB, except for an elevated phosphodiester peak. PCr recovery was slower in AB subjects using electrical stimulation compared with voluntary exercise (28.4 ± 6.1 vs. 41.5 ± 4.3 s; P < 0.05). PCr recovery rates and calculated muscle maximum oxidative capacity in SCI were both 52% of electrically stimulated AB ( P < 0.001). In vivo oxidative metabolism was reduced in paralyzed muscle to a similar extent as seen in people with mitochondrial myopathies and heart failure.
Relationship between upper and lower limb conduit artery vasodilator function in humans
Authors: Thijssen Dick H. J. , Rowley Nicola , Padilla Jaume , Simmons Grant H. , Laughlin M. Harold , Whyte Greg , Cable N. Timothy , Green Daniel J.
Published: April 2011

Brachial artery flow-mediated dilation (FMD) is a strong predictor of future cardiovascular disease and is believed to represent a “barometer” of systemic endothelial health. Although a recent study [Padilla et al. Exp Biol Med (Maywood) 235: 1287–1291, 2010] in pigs confirmed a strong correlation between brachial and femoral artery endothelial function, it is unclear to what extent brachial artery FMD represents a systemic index of endothelial function in humans. We conducted a retrospective analysis of data from our laboratory to evaluate relationships between the upper (i.e., brachial artery) vs. lower limb (superficial femoral n = 75; popliteal artery n = 32) endothelium-dependent FMD and endothelium-independent glyceryl trinitrate (GTN)-mediated dilation in young, healthy individuals. We also examined the relationship between FMD assessed in both brachial arteries ( n = 42). There was no correlation between brachial and superficial femoral artery FMD ( r2= 0.008; P = 0.46) or between brachial and popliteal artery FMD ( r2= 0.003; P = 0.78). However, a correlation was observed in FMD between both brachial arteries ( r2= 0.34; P < 0.001). Brachial and superficial femoral artery GTN were modestly correlated ( r2= 0.13; P = 0.007), but brachial and popliteal artery GTN responses were not ( r2= 0.08; P = 0.11). Collectively, these data indicate that conduit artery vasodilator function in the upper limbs (of healthy humans) is not predictive of that in the lower limbs, whereas measurement of FMD in one arm appears to be predictive of FMD in the other. These data do not support the hypothesis that brachial artery FMD in healthy humans represents a systemic index of endothelial function.
Serial Magnetic Resonance Spectroscopy Reveals a Direct Metabolic Effect of Cediranib in Glioblastoma
Authors: Kim Heisoog , Catana Ciprian , Ratai Eva-Maria , Andronesi Ovidiu C. , Jennings Dominique L. , Batchelor Tracy T. , Jain Rakesh K. , Sorensen A. Gregory
Published: April 2011

Proton magnetic resonance spectroscopy is increasingly used in clinical studies of brain tumor to provide information about tissue metabolic profiles. In this study, we evaluated changes in the levels of metabolites predominant in recurrent glioblastoma multiforme (rGBM) to characterize the response of rGBM to antiangiogenic therapy. We examined 31 rGBM patients treated with daily doses of cediranib, acquiring serial chemical shift imaging data at specific time points during the treatment regimen. We defined spectra from three regions of interest (ROI)—enhancing tumor (ET), peritumoral tissue, and normal tissue on the contralateral side (cNT)—in post-contrast T1-weighted images, and normalized the concentrations of N-acetylaspartate (NAA) and choline (Cho) in each ROI to the concentration of creatine in cNT (norCre). We analyzed the ratios of these normalized metabolites (i.e., NAA/Cho, NAA/norCre, and Cho/norCre) by averaging all patients and categorizing two different survival groups. Relative to pretreatment values, NAA/Cho in ET was unchanged through day 28. However, after day 28, NAA/Cho significantly increased in relation to a significant increase in NAA/norCre and a decrease in Cho/norCre; interestingly, the observed trend was reversed after day 56, consistent with the clinical course of GBM recurrence. Notably, receiver operating characteristic analysis indicated that NAA/Cho in tumor shows a high prediction to 6-month overall survival. These metabolic changes in these rGBM patients strongly suggest a direct metabolic effect of cediranib and might also reflect an antitumor response to antiangiogenic treatment during the first 2 months of treatment. Further study is needed to confirm these findings. Cancer Res; 71(11); 3745–52. ©2011 AACR.
IFN-γ Inhibits Gastric Carcinogenesis by Inducing Epithelial Cell Autophagy and T-Cell Apoptosis
Authors: Tu Shui Ping , Quante Michael , Bhagat Govind , Takaishi Shigeo , Cui Guanglin , Yang Xiang Dong , Muthuplani Sureshkumar , Shibata Wataru , Fox James G. , Pritchard D. Mark , Wang Timothy C.
Published: April 2011

IFN-γ mediates responses to bacterial infection and autoimmune disease, but it is also an important tumor suppressor. It is upregulated in the gastric mucosa by chronic Helicobacter infection; however, whether it plays a positive or negative role in inflammation-associated gastric carcinogenesis is unexplored. To study this question, we generated an H+/K+-ATPase-IFN-γ transgenic mouse that overexpresses murine IFN-γ in the stomach mucosa. In contrast to the expected proinflammatory role during infection, we found that IFN-γ overexpression failed to induce gastritis and instead inhibited gastric carcinogenesis induced by interleukin-1beta (IL-1β) and/or Helicobacter infection. Helper T cell (Th) 1 and Th17 immune responses were inhibited by IFN-γ through Fas induction and apoptosis in CD4 T cells. IFN-γ also induced autophagy in gastric epithelial cells through increased expression of Beclin-1. Finally, in the gastric epithelium, IFN-γ also inhibited IL-1β- and Helicobacter-induced epithelial apoptosis, proliferation, and Dckl1+ cell expansion. Taken together, our results suggest that IFN-γ coordinately inhibits bacterial infection and carcinogenesis in the gastric mucosa by suppressing putative gastric progenitor cell expansion and reducing epithelial cell apoptosis via induction of an autophagic program. Cancer Res; 71(12); 4247–59. ©2011 AACR.