bluuebunny/crossref_metadata_2025 huggingface dataset:
A field method for the determination of rock-mass modulus
Authors: Lo K. Y. , Yung T. C. B. , Lukajic B.
Published: June 2008

A field test for measuring rock modulus was developed and performed at the site of Darlington Generating Station in shaly limestone. The new method yields a value consistent with the rock-mass modulus evaluated from extensometer measurements in the tunnels.A complementary laboratory program to study the effect of specimen size on the elastic parameter was also performed by using compressional and shear wave velocity measurements. It was shown that beyond a threshold value of size, the Poisson's ratio increases, whereas both dynamic shear modulus and Young's modulus decrease with increasing volume of specimen towards the field value of static modulus. Key words: rock-mass modulus, field tests, shear wave velocity, size effect.
Analysis of progressive deformation of the Edmonton Convention Centre excavation
Authors: Chan D. H. , Morgenstern N. R.
Published: June 2008

A finite element analysis was performed of the deformations observed during the excavation of the Edmonton Convention Centre. Local geology in the Edmonton area consists of layers of shale with weak bentonite seams overlain by glacial deposits. The presence of the bentonite seams, which possess strain-softening characteristics, controls the stability of the excavation, which is located in a valley wall. To simulate the influence of the bentonite seams a strain-softening finite element model is used to estimate the amount of deformation in the foundation of the excavation. Field measurements indicated that localized progressive straining had occurred during the excavation process, and substantial heave of the foundation floor was observed. The finite element results show progressive deformation of the excavation and propagation of shear zones. Good agreement between the finite element results and the field observations is obtained. Key words: progressive failure, strain softening, finite element analysis, shear band, excavation stability.
Full-displacement pressuremeter method for rigid piles under lateral loads and moments
Authors: Meyerhof G. G. , Sastry V. V. R. N.
Published: June 2008

The results of full-displacement pressuremeter tests in beds of sand, clay, and layered soil have been used to estimate the lateral soil pressures, ultimate capacity, and displacements of instrumented rigid model piles under eccentric and inclined loads. Comparisons of these estimates with observations on the piles under horizontal load and pure moment have been made and reasonable agreement is found. The analyses are also compared with some field case records. Key words: bearing capacity, clay, displacements, horizontal load, lateral pressure, layered soil, model test, moment, pile, pressuremeter, sand.
Determination of friction values for the design of side slopes lined or protected with geosynthetics
Authors: Eigenbrod K. D. , Locker J. G.
Published: June 2008

For an economic design of side slopes lined with geomembranes or protected with geotextiles, the frictional resistance at the soil–geosynthetic interface has to be known. Direct shear testing appears to be an appropriate method by which to determine these frictional resistances. As low normal stresses apply for most typical conditions along side slopes, two simple direct shear box devices were designed for tests at low normal stresses. Soil–geosynthetic interaction was tested for 4 soil types (2 clay and 2 sand types), 19 geotextiles, and 2 geomembranes. It was found that the friction between soils and geosynthetics is less than the angle of shearing resistance for the soil. The nonwoven geotextiles mobilized more than 90% of the sand friction, whereas woven geotextiles had efficiencies between 86 and 76%. For the clays, the efficiencies recorded were approximately 60% for woven geotextiles and 70% for nonwoven geotextiles. It was further observed that for granular materials the shear strength reached after repeated loading and unloading is independent of the degree of compaction. Based on the results obtained in this study and data reported in the literature, design recommendations are suggested for side slopes protected by geotextiles or lined by geomembranes. Key words: geosynthetics, frictional resistance, relative efficiency, soil–geosynthetic interface, low stress levels, direct shear test, side slopes.
Geotechnical properties of two deep-sea marine soils from the Labrador Sea
Authors: Morin Pierre , Dawe C. Roy
Published: June 2008

Cores from two deep-sea sites from the Labrador Sea have been extensively studied using various analyses. X-ray techniques provided a continuous profile of bulk densities and an accurate description of the bedding. The soil structure was analyzed by scanning electron microscopy. Detailed identification, laboratory shear strength, and compressibility tests have been used to determine the geotechnical properties of the soils, both in their intact and remolded states. Geological data and fabric observations are compared with geotechnical properties in order to explain the observed overconsolidation of the surficial sediments. Characterization of the seabed materials is further improved by using existing empirical correlations with soils of onshore and offshore origin. Key words: marine sediments, deep-sea investigation, overconsolidation, laboratory testing, offshore.
Transient seepage model for saturated–unsaturated soil systems: a geotechnical engineering approach
Authors: Lam L. , Fredlund D. G. , Barbour S. L.
Published: June 2008

A two-dimensional finite element model is proposed to simulate transient seepage for complex groundwater flow systems. The complete soil system is treated as a continuum encompassing flow in both saturated and unsaturated zones. In the unsaturated zone, the air phase is assumed to be continuous and open to atmospheric pressure. The coefficient of permeability of the unsaturated soil is assumed to be a function of pore-water pressure.The governing differential equation is derived within a framework familiar to geotechnical engineers. The stress state variables and the constitutive relationships for an unsaturated soil are used in the derivation. The finite element solution to the governing differential equation is based on the Galerkin weighted-residual method. The nonlinearity of the equation is solved by iterative procedures.The finite element formulation is implemented into a computer model named TRASEE. The model can be applied to a wide variety of problems involving complex boundary conditions and geometries with arbitrary degrees of heterogeneity and anisotropy. Example problems are presented to demonstrate the capabilities of the model. The results indicate that the quantity of water flow in the unsaturated zone may be substantial, and that the phreatic line is not a flow line. It has been found that the traditional "saturated-only" flow-net technique can be approximated as a special case to the proposed saturated–unsaturated model. Key words: unsaturated flow, finite element model, phreatic line, permeability function, transient seepage.
A capped plasticity model applied to Boston blue clay
Authors: McCarron W O , Chen W. F.
Published: June 2008

The performance of a capped plasticity model is evaluated with respect to Boston blue clay. Computed and measured responses are compared for laboratory stress paths and boundary value problems involving construction of highway embankments. It is shown that simplifying assumptions in the model development may lead to difficulties in calibrating the model for general stress paths. The chief model limitations are the use of a circular deviatoric plane and the assumption of symmetry about the hydrostatic axis. However, given the simplicity of the model, it performs well if the limitations are recognized. Key words: cap model, soil plasticity, finite element, embankment analysis.
Settlement instrumentation to observe open-pit mine backfill and a prototype foundation in western Canada
Authors: Thomson S. , Sonnenberg R.
Published: June 2008

Reclaimed land from open-pit mining operations must have essentially completed settling under self-weight and must be capable of supporting light structures before it can be returned to the public domain. The settlement of the spoil from one open-pit mining operation west of Edmonton, Alberta, was monitored by a series of magnetic extensometers installed in boreholes. Time–settlement plots indicated that self-weight settlement occurs within a 3–5 year period.Tests of individual small footings pointed out the necessity of placing shallow foundations on beneficiated soil. The results of a second series of small footings led to the founding of an 8 × 10 m prototype instrumented, reinforced foundation on a 1 m thick soil–flyash mat. Observations to date indicate an entirely acceptable settlement pattern. Key words: settlement, spoil, reclaimed land, prototype foundation, instrumentation.
Drained creep of undisturbed cohesive marine sediments
Authors: Tian W.-M. , Silva A.J. , Veyera G.E. , Sadd M.H.
Published: June 2008

Long-term, drained triaxial creep and direct simple shear creep tests were conducted on undisturbed marine specimens from the Gulf of Mexico and the north-central Pacific. Results indicated that time-dependent deformations can be represented by a power law equation, and the creep strain rate can be represented by an equation similar to that suggested earlier by other researchers. However, it was found that the m parameter suggested by these scientists was not a constant but dependent on stress level and sediment plasticity. Ageing effects were evidenced in triaxial specimens by the increase of shear strength with both test duration and stress level. The results provided a guide for the development of mathematical stress–strain–time relationships that will be developed in a separate paper. Key words : drained triaxial creep, simple shear creep, stress–strain–time behavior.
Analysis of foundation deformations beneath the Syncrude tailings dyke
Authors: Alencar J. , Morgenstern N.R. , Chan D.H.
Published: June 2008

The paper presents the results obtained in the finite element simulation of 8 years of construction of a section of Syncrude's tailings dyke, which is located in northern Alberta and has been used to store oil sand mining waste. The site investigation for the construction of this dyke indicated that a region of the foundation contained a presheared, overconsolidated clay shale lying practically horizontal at about 20 m depth. Significant horizontal displacements have occurred along this layer. The section analyzed in this work is the one which showed the largest horizontal movements in the foundation. High pore pressures have been measured along this section, and the lateral displacements measured in the foundation have reached values over 25 cm. The major purposes of the finite element analyses were to identify the factors that have significantly influenced the deformation mechanisms and to determine a combination of parameters, within the acceptable range of values for each material, that would reproduce satisfactorily the field observations. Linear, nonlinear, and effective stresses analyses were carried out. The total stress analyses underestimated the displacements measured in the field very significantly. The displacements calculated by the effective stress analyses are in very good agreement with the measured values, and the combination of parameters necessary to reach those results are within the acceptable range of variability for each material involved, based on laboratory test results. The interpolation of the pore pressures based on the piezometer measurements and their incorporation into the analyses as known quantities at each stage of the loading process was found to be relatively simple and efficient, causing a substantial improvement of the results compared with the total stress analyses. Key words : tailing dyke, deformation analysis, shear zone, effective stress modelling, history matching.
Evaluation of liquefaction potential of foundation soils at Duncan Dam
Authors: Pillai V.S. , Stewart R.A.
Published: June 2008

A comprehensive program of field, laboratory, and analytical investigations was carried out to evaluate the potential of liquefaction for the foundation soils at Duncan Dam. Duncan Dam was completed in 1967 under the Columbia River Treaty in southeastern British Columbia. The 39 m high zoned embankment dam is founded on a sequence of sands, silts, and gravels. Some of the foundation soils may liquefy during earthquake loading and this would affect the stability and performance of the dam. The liquefaction studies were carried out in two phases to characterize the engineering properties of the foundation soils and to assess its potential for triggering liquefaction using the total stress approach. This paper describes methods of assessment of liquefaction potential using soil parameters based on field penetration data (Seed's method) and laboratory testing of undisturbed soil samples obtained in situ after freezing the ground (Lab method) and presents the results of triggering analysis. Influence of confining stress (Kσ) and initial static shear stress (Kα) on liquefaction were investigated and site-specific Kσ and Kα curves were developed.For the design earthquake (M 6.5, PGA = 0.12g) both the Lab method and Seed's method predict a significant extent of liquefaction of the foundation soils under the downstream slope in the right half of the dam. Key words : sand, liquefaction, confining stress, density, cyclic resistance ratio.
Post-liquefaction stability and deformation analysis of Duncan Dam
Authors: Pillai V.S. , Salgado F.M.
Published: June 2008

Duncan Dam is a 39 m high zoned embankment and is founded on a deep deposit of unconsolidated sediments consisting of sands, silts, and gravels that are susceptible to liquefaction during earthquake loading. A comprehensive program of field, laboratory, and analytical investigations was conducted to evaluate the liquefaction potential of the foundation soils and performance of the dam during an earthquake. This paper describes the evaluation procedures and analyses and presents results of the post-liquefaction stability and deformation analysis of the dam. Analyses were carried out based on the total stress approach using two methods, namely the Lab method and Seed's method. The Lab method is a site–specific (direct), laboratory-based approach utilizing soil parameters from laboratory tests on undisturbed soil samples obtained in situ after freezing the ground. Seed's method is indirect and is based on field penetration data and past experience from earthquakes. The Lab method indicates that the residual strength of the liquefied sand is dependent on the effective confining stress, whereas Seed's method does not. Post-liquefaction deformations of the dam were computed using a pseudodynamic finite element procedure applying pre- and post-liquefaction stress–strain relationships and gravity and inertia forces satisfying the work–energy theorem. The Lab method predicts factors of safety of greater than 1.3 for the post-liquefaction limit equilibrium stability and acceptable deformations. On the contrary, Seed's method predicts factors of safety equal to or less than 1.0 and large deformations indicative of a flow slide. The merits of the two methods are discussed. Key words : sand, liquefaction, residual strength, performance, deformation.
Fractal analysis of the slake durability test
Authors: Vallejo Luis E.
Published: June 2008

Fragments of siltstone were subjected to the slake durability test. The profiles of the rock fragments experienced changes during the test as a result of saturation and abrasion-induced stresses. The profiles of the fragments were evaluated before and after the test using fractal analysis. Fractal analysis uses the concept of fractal dimension to calculate the roughness of profiles. Before the test, the profiles of the siltstone particles had an average fractal dimension equal to 1.1364. After the test, the average fractal dimension of the profiles became equal to 1.1187. The change in fractal dimension was a reflection of the smoothing action on the particle profiles by the combined effects of abrasion and wetting and drying action that take place during the slake durability test. Key words : durability, shape of rock fragments, fractal dimension.
Collapse of dry sand
Authors: Skopek Peter , Morgenstern N.R. , Robertson P.K. , Sego D.C.
Published: June 2008

Loose cohesionless saturated materials have proved responsible for a number of serious or catastrophic flow slides. Liquefaction failures with no obvious triggering mechanism have also been recorded. This phenomenon of sudden liquefaction without a presence of cyclic shear stresses is often referred to as spontaneous or static liquefaction. Results from previously published studies suggest that liquefaction is triggered not by the undrained loading and generation of pore pressures but by the collapse of the metastàble sand structure, which in turn generates the driving pore pressures in a saturated material. Hence, the collapse is a characteristic response of a material to certain stress states rather than a result of some enforced undrained loading. This theory is evaluated on very loose dry Ottawa sand. It is shown that the very loose dry sand when subjected to a constant deviatoric stress path significantly changes its behavior at a certain discreet stress state, increases compressibility, and becomes increasingly unstable. This results in collapse – vigorous contraction of the specimen. This structural collapse appears to be equivalent to the pore-pressure generation in collapsing, very loose saturated sand. Key words : dry sand, collapse, liquefaction, stress path, triaxial cell.
Effect of aging on the penetration resistance of sands
Authors: Joshi R.C. , Achari Gopal , Kaniraj Shenbaga R. , Wijeweera H.
Published: June 2008

The main objective of this study was to understand the effect of aging on the penetration resistance of freshly deposited sands. Two types of sand, locally available river sand used as masonry sand and Beaufort Sea sand, were selected for the study. The sands were allowed to age under a constant stress of 100 kPa in a specially designed apparatus in a dry state, as well as submerged in distilled water and in simulated sea water. Penetration resistance of the sand beds was measured periodically by pushing 4 probes into the sand bed. Mineralogical and fabric studies on freshly deposited and aged sand samples were conducted to detect the effect of aging, if any, on sand grains. The results indicate that aging significantly increases the penetration resistance of sands. The rate of increase in penetration resistance was higher for the submerged sand as compared with the dry sand. The increase in penetration resistance of the sand in a dry state was attributed to rearrangement of sand grains. In the submerged state, besides the rearrangement of sand particles, partial cementation caused by precipitation of salts and probably also silica on the sand grains and in the pores resulted in the larger increase in the penetration resistance. Key words : sand, aging, penetration resistance, freezing and thawing, sea water, distilled water.
Undrained shear strength for liquefaction flow failure analysis
Authors: Konrad J.-M. , Watts B.D.
Published: June 2008

An important factor in evaluating the stability of hydraulic fills against flow sliding is the undrained steady-state strength mobilized in the field. This paper proposes an empirical relationship between three factors: the undrained strength back-calculated from fills that failed by flow sliding, equivalent clean sand normalized blow-count values, and soil-specific parameters from steady-state laboratory testing. It is shown that Suo, which is a reference value of steady-state strength at maximum void ratio, is an important soil parameter. The proposed method offers an explanation for the performance of many artificial sand islands in the Beaufort Sea, indicates the extreme sensitivity of Suoto soil type and the usefulness of Suofor assessing the potential strength loss of soils for use in safety assessments of existing hydraulic fills. Key words : undrained strength, liquefaction, sand, field, case-histories, analysis.
Ground-penetrating radar used to assess aggregate in catastrophic flood deposits, northeast Alberta, Canada
Authors: Fisher Timothy G. , Jol Harry M. , Smith Derald G.
Published: June 2008

Coarse-grained aggregate deposited by a catastrophic flood located north of Fort McMurray, Alberta, was examined using ground-penetrating radar (GPR) and lithostratigraphic logging techniques. GPR transects were acquired from an upper scoured zone of flood deposits. Sedimentary structures (cross-beds and plane-beds) within the coarse sand and gravel and determinations of depth to bedrock (sediment thickness of the aggregate) were recognized in the GPR profiles by their varying dielectric properties. Fine-grained, conductive underlying oil-sand, till, or glaciolacustrine sediment (silt and clay) attenuated the radar signal. The sedimentary structures mapped from the GPR transects were confirmed in adjacent trench exposures. We suggest that GPR is an efficient methodology for determining volumes of aggregate reserves, thicknesses of aggregate deposits, and mapping sedimentary structures of high-energy fluvial sediments. Key words : aggregate, ground-penetrating radar, Alberta, spillway.
Techniques for sealing cone penetrometer holes
Authors: Lutenegger Alan J. , DeGroot Don J.
Published: June 2008

Direct penetration exploration tools such as the electric cone penetrometer (CPT) and piezocone (CPTU) are being increasingly used for site investigation studies to evaluate stratigraphy and obtain groundwater samples. Most of these techniques are considered full-displacement direct-push or direct-drive penetration methods which can leave open pathways that may allow the movement of surface or subsurface contaminants into uncontaminated layers. Sealing techniques are needed to protect groundwater conditions following the use of these types of exploration tools. A survey of industry techniques for sealing CPT holes indicates that a number of methods can be used to place grout mixtures and other seal materials into a hole either (1) after pulling the tool, (2) as the tool is pulled, or (3) simultaneously with advance of the tool. Selection of a particular method depends primarily on the soil and groundwater conditions at a given site but may also depend on other variables such as equipment availability, time, and cost. In some cases, the method of sealing may be dictated by a regulatory agency. Seal materials used for this practice typically consist of grout mixtures composed of bentonite slurries, neat cement, a combination of the two, or dry granular bentonite, which are placed to provide permanent low hydraulic conductivity barriers. A number of techniques that have been used to seal CPT holes are described, and the advantages and disadvantages of the various techniques are presented. Key words : groundwater, cone penetrometer, hydraulic barriers, contaminants.
A conceptual model for clay soils subjected to negative pore-water pressures
Authors: Murray E.J. , Geddes J.D.
Published: June 2008

Understanding and predicting the volume change behaviour of soils subjected to negative pore-water pressures presents a complex problem that requires a sound theoretical model matched to experimental evidence. A complete model must cover both saturated and unsaturated behaviour and relate stress levels to pore-water pressures and volume changes. A conceptual model for clay soils is presented which employs the principles of critical state soil mechanics. In developing the model, consideration is given to negative pore-water pressures arising as a result of the independent response to reductions in water content and reductions in confining stresses. In this way the limits of the conceptual model are defined. Key words : suction, negative pore-water pressure, volume change, unsaturated soil, critical state.
STRATEGIC AGENT BASED WEB SYSTEM DEVELOPMENT METHODOLOGY
Authors: LEE JONGWON , LEE HEESEOK
Published: June 2008

The web system linked by Internet becomes important not only as a functional application system within a company but as a critical backbone for conducting business in a highly competitive market. It is driving companies to come up with a whole new set of business strategies. This paper proposes a methodology to link these strategies to effective system artifacts. Strategic agents are extracted from the three interacting perspectives of customers, competitors, and company itself. The methodology consists of strategic requirement analysis, agent modeling, system design, and system implementation. A real-life case is illustrated to demonstrate the feasibility of our methodology. The resulting Internet system is more likely to be competitive in this dynamic business world.
Immix
Authors: Blackburn Stephen M. , McKinley Kathryn S.
Published: June 2008

Programmers are increasingly choosing managed languages for modern applications, which tend to allocate many short-to-medium lived small objects. The garbage collector therefore directly determines program performance by making a classic space-time tradeoff that seeks to provide space efficiency, fast reclamation, and mutator performance. The three canonical tracing garbage collectors: semi-space, mark-sweep, and mark-compact each sacrifice one objective. This paper describes a collector family, called
mark-region
, and introduces
opportunistic
defragmentation, which mixes copying and marking in a single pass. Combining both, we implement
immix
, a novel high performance garbage collector that achieves all three performance objectives. The key insight is to allocate and reclaim memory in contiguous regions, at a coarse
block
grain when possible and otherwise in groups of finer grain
lines
. We show that immix outperforms existing canonical algorithms, improving total application performance by 7 to 25% on average across 20 benchmarks. As the mature space in a generational collector, immix matches or beats a highly tuned generational collector, e.g. it improves jbb2000 by 5%. These innovations and the identification of a new family of collectors open new opportunities for garbage collector design.
Sound, complete and scalable path-sensitive analysis
Authors: Dillig Isil , Dillig Thomas , Aiken Alex
Published: June 2008

We present a new, precise technique for fully path- and context-sensitive program analysis. Our technique exploits two observations: First, using quantified, recursive formulas, path- and context-sensitive conditions for many program properties can be expressed exactly. To compute a closed form solution to such recursive constraints, we differentiate between
observable
and
unobservable
variables, the latter of which are existentially quantified in our approach. Using the insight that unobservable variables can be eliminated outside a certain scope, our technique computes satisfiability- and validity-preserving closed-form solutions to the original recursive constraints. We prove the solution is as precise as the original system for answering may and must queries as well as being small in practice, allowing our technique to scale to the entire Linux kernel, a program with over 6 million lines of code.
Fair stateless model checking
Authors: Musuvathi Madanlal , Qadeer Shaz
Published: June 2008

Stateless model checking is a useful state-space exploration technique for systematically testing complex real-world software. Existing stateless model checkers are limited to the verification of safety properties on terminating programs. However, realistic concurrent programs are nonterminating, a property that significantly reduces the efficacy of stateless model checking in testing them. Moreover, existing stateless model checkers are unable to verify that a nonterminating program satisfies the important liveness property of livelock-freedom, a property that requires the program to make continuous progress for any input.

To address these shortcomings, this paper argues for incorporating a fair scheduler in stateless exploration. The key contribution of this paper is an explicit scheduler that is (strongly) fair and at the same time sufficiently nondeterministic to guarantee full coverage of safety properties.We have implemented the fair scheduler in the CHESS model checker. We show through theoretical arguments and empirical evaluation that our algorithm satisfies two important properties: 1) it visits all states of a finite-state program achieving state coverage at a faster rate than existing techniques, and 2) it finds all livelocks in a finite-state program. Before this work, nonterminating programs had to be manually modified in order to apply CHESS to them. The addition of fairness has allowed CHESS to be effectively applied to real-world nonterminating programs without any modification. For example, we have successfully booted the Singularity operating system under the control of CHESS.
Exploring ocean data
Authors: Bellingham James G. , Godin Mike
Published: June 2008

In fall of 2004, we met Jim Gray and began to converse about the data needs of ocean scientists. The conversations ultimately led to the development of a unique portal for exploring multidisciplinary data sets, which we call the Metadata Oriented Query Assistant (MOQuA). At the time, we were working with an extremely rich data set which included measurements from ships, satellites, aircraft, moorings, and a variety of underwater robots. The data set also included output from both atmospheric and ocean models. We initially made the data available via a state-of-the-art data server. However, serious users did not use the server, instead approaching us for copies of the relevant portions. Our experience convinced us that we needed a far more capable portal, but framing the seemingly divergent needs of ocean scientists in a way which could be satisfied via an intuitive interface was challenging. In the course of many conversations and interactions with Jim, we realized that we needed to structure the interaction around questions rather than visualizations, and this simple insight lead to the development of MOQuA system.
Unsteady Solutions in a Third‐Grade Fluid Filling the Porous Space
Authors: Hayat T. , Mambili-Mamboundou H. , Mahomed F. M.
Published: June 2008

An analysis is made of the unsteady flow of a third‐grade fluid in a porous medium. A modified Darcy′s law is considered in the flow modelling. Reduction and solutions are obtained by employing similarity and numerical methods. The effects of pertinent parameters on the flow velocity are studied through graphs.
Scaling Analysis on Pulsating Flame Spread over Liquids
Authors: Takahashi Kozue , Ito Akihiko , Kudo Yuji , Konishi Tadashi , Saito Kozo
Published: June 2008

Scaling analyses based on subsurface layer instability were performed to explore the role of three independent (surface tension, gravity, and viscosity) influences on the mechanism of pulsating flame spread under normal and microgravity conditions. These three influences form two independent pi-numbers: the Marangoni (Ma) number and Grashof (Gr) number, which include the characteristic length scale ratio (depth of subsurface circulation)/(horizontal length of preheated liquid surface). The Prandtl (Pr) number was introduced to compensate for the different thermal diffusivity and kinematic viscosity of different liquids. Also a nondimensional flame spread rate,V/VD(=Vδ/D, whereδis the quenching distance andDis the diffusivity of fuel vapor) was introduced. Using these nondimensional parameters, the flame spread mechanism was divided into two separate regimes: for the shallow liquid pool the nondimensional flame spread rate was correlated with{Gr0.2/(Ma·Pr)}1.0, while for the deep liquid pool it was correlated with{Gr0.2/(Ma·Pr)}1.5.
High‐Speed Near Infrared Optical Receivers Based on Ge Waveguide Photodetectors Integrated in a CMOS Process
Authors: Masini Gianlorenzo , Sahni Subal , Capellini Giovanni , Witzens Jeremy , Gunn Cary
Published: June 2008

We discuss our approach to monolithic intergration of Ge photodectors with CMOS electronics for high‐speed optical transceivers. Receivers based on Ge waveguide photodetectors achieve a sensitivity of −14.2 dBm (10−12 bit error rate (BER)) at 10 Gbps and 1550 nm.
TiO2 Nanoparticles‐Photocatalytic Oxidation of Selected Cycloalkanols
Authors: Mohamed Omima S. , Ahmed Saleh A. , Mostafa Mostafa F. , Abdel-Wahab Aboel-Magd A.
Published: June 2008

Photocatalytic oxidation of cyclohexanol (1), cyclopentanol (2), and cycloheptanol (3) was investigated by using titanium dioxide (Degussa P25) as a semiconductor photocatalyst .The effect of different operational parameters such as the catalyst, the solvent, time, and oxidant was also studied. Results showed a high percentage of conversion for 1–3 (71.6%, 94.2%, and 100%, resp.) and that the primary photocatalytic oxidation products are the corresponding cycloalkanones (4–6). They were formed with high selectivity (>85%). Several other products were also identified using GC, GC/MS techniques and authentic samples. The photocatalytic activity is explained by a photoinduced electron transfer mechanism through the formation of electron‐hole pair at the surface of the semiconductor particles. A first‐order kinetic model was observed for the photocatalytic oxidation of the investigated cycloalkanols.
One Dimensional Polymeric Organic Photonic Crystals for DFB Lasers
Authors: Scotognella F. , Monguzzi A. , Cucini M. , Meinardi F. , Comoretto D. , Tubino R.
Published: June 2008

We present a very simple method to realize a one‐dimensional photonic crystal (1D PC), consisting of a dye‐doped polymeric multilayer. Due to the high photonic density of states at the edges of the photonic band‐gap (PBG), a surface emitting distributed feedback (DFB) laser is obtained with this structure. Furthermore, the incidence angle dependence of the PBG of the polymeric multilayer is reported.
Synthesis of Visible‐Light‐Activated Yellow Amorphous TiO2 Photocatalyst
Authors: Randorn Chamnan , Irvine John T. S. , Robertson Peter
Published: June 2008

Visible‐light‐activated yellow amorphous TiO2 (yam‐TiO2) was synthesised by a simple and organic‐free precipitation method. TiN, an alternative precursor for TiO2 preparation, was dissolved in hydrogen peroxide under acidic condition (pH ~ 1) adjusted by nitric acid. The yellow precipitate was obtained after adjusting pH of the resultant red brown solution to 2 with NH4OH. The BET surface area of this sample was 261 m2/g. The visible light photoactivity was evaluated on the basis of the photobleaching of methylene blue (MB) in an aqueous solution by using a 250 W metal halide bulb equipped with UV cutoff filter (λ > 420 nm) under aerobic conditions. Yam‐TiO2 exhibits an interesting property of being both surface adsorbent and photoactive under visible light. It was assigned to the η2‐peroxide, an active intermediate form of the addition of H2O2 into crystallined TiO2 photocatalyst. It can be concluded that an active intermediate form of titanium peroxo species in photocatalytic process can be synthesised and used as a visible‐light‐driven photocatalyst.
Extensive Atrophic Gastritis Increases Intraduodenal Hydrogen Gas
Authors: Urita Yoshihisa , Watanabe Toshiyasu , Maeda Tadashi , Arita Tomohiro , Sasaki Yosuke , Ishii Takamasa , Yamamoto Tatsuhiro , Kugahara Akiro , Nakayama Asuka , Nanami Makie , Domon Kaoru , Ishihara Susumu , Kato Hirohito , Hike Kazuo , Hara Norikok , Watanabe Shuji , Nakanishi Kazushige , Sugimoto Motonobu , Miki Kazumasa
Published: June 2008

Objective. Gastric acid plays an important part in the prevention of bacterial colonization of the gastrointestinal tract. If these bacteria have an ability of hydrogen (H2) fermentation, intraluminal H2 gas might be detected. We attempted to measure the intraluminal H2 concentrations to determine the bacterial overgrowth in the gastrointestinal tract.Patients and methods. Studies were performed in 647 consecutive patients undergoing upper endoscopy. At the time of endoscopic examination, we intubated the stomach and the descending part of the duodenum without inflation by air, and 20 mL of intraluminal gas samples of both sites was collected through the biopsy channel. Intraluminal H2 concentrations were measured by gas chromatography.Results. Intragastric and intraduodenal H2 gas was detected in 566 (87.5%) and 524 (81.0%) patients, respectively. The mean values of intragastric and intraduodenal H2 gas were8.5±15.9and13.2±58.0 ppm, respectively. The intraduodenal H2 level was increased with the progression of atrophic gastritis, whereas the intragastric H2 level was the highest in patients without atrophic gastritis.Conclusions. The intraduodenal hydrogen levels were increased with the progression of atrophic gastritis. It is likely that the influence of hypochlorhydria on bacterial overgrowth in the proximal small intestine is more pronounced, compared to that in the stomach.
Quantum Electrodynamic Modeling of Silicon‐Based Active Devices
Authors: Shi Shouyuan , Redding Brandon , Creazzo Tim , Marchena Elton , Prather Dennis W.
Published: June 2008

We propose a time‐domain analysis of an active medium based on a coupled quantum mechanical and electromagnetic model to accurately simulate the dynamics of silicon‐based photonic devices. To fully account for the nonlinearity of an active medium, the rate equations of a four‐level atomic system are introduced into the electromagnetic polarization vector. With these auxiliary differential equations, we solve the time evolution of the electromagnetic waves and atomic population densities using the FDTD method. The developed simulation approach has been used to model light amplification and amplified spontaneous emission in silicon nanocrystals, as well as the lasing dynamics in a novel photonic crystal‐based silicon microcavity.
Developments in Gigascale Silicon Optical Modulators Using Free Carrier Dispersion Mechanisms
Authors: Basak Juthika , Liao Ling , Liu Ansheng , Rubin Doron , Chetrit Yoel , Nguyen Hat , Samara-Rubio Dean , Cohen Rami , Izhaky Nahum , Paniccia Mario
Published: June 2008

This paper describes the recent advances made in silicon optical modulators employing the free carrier dispersion effect, specifically those governed by majority carrier dynamics. The design, fabrication, and measurements for two different devices are discussed in detail. We present an MOS capacitor‐based modulator delivering 10 Gbps data with an extinction ratio of ∼4 dB and a pn‐diode‐based device with high‐speed transmission of 40 Gbps and bandwidth greater than 30 GHz. Device improvements for achieving higher extinction ratios, as required for certain applications, are also discussed. These devices are key components of integrated silicon photonic chips which could enable optical interconnects in future terascale processors.
Variational Homotopy Perturbation Method for Solving Higher Dimensional Initial Boundary Value Problems
Authors: Noor Muhammad Aslam , Mohyud-Din Syed Tauseef
Published: June 2008

We suggest and analyze a technique by combining the variational iteration method
and the homotopy perturbation method. This method is called the variational homotopy
perturbation method (VHPM). We use this method for solving higher dimensional initial boundary
value problems with variable coefficients. The developed algorithm is quite efficient and is
practically well suited for use in these problems. The proposed scheme finds the solution without any
discritization, transformation, or restrictive assumptions and avoids the round‐off errors. Several
examples are given to check the reliability and efficiency of the proposed technique.
Morphable 3D‐Mosaics: A Hybrid Framework for Photorealistic Walkthroughs of Large Natural Environments
Authors: Komodakis Nikos , Tziritas Georgios
Published: June 2008

This paper presents a hybrid (geometry‐ & image‐based) framework suitable for providing photorealistic
walkthroughs of large, complex outdoor scenes at interactive frame rates. To this end, based just on a sparse
set of real stereoscopic views from the scene, a set of morphable 3D-mosaics is automatically constructed
first, and then, during rendering, a continuous morphing between those 3D‐mosaics that are nearby to the
current viewpoint is taking place. The morphing is both photometric, as well as geometric, while we also
ensure that it proceeds in a physically valid manner, thus remaining transparent to the user. The effectiveness
of our framework has been demonstrated in the 3D visual reconstruction of the Samaria Gorge in Crete,
which is one of the largest and most beautiful gorges in Europe.
Kaposi's Sarcoma–Associated Herpesvirus Confers a Survival Advantage to Endothelial Cells
Authors: Wang Ling , Damania Blossom
Published: June 2008

Kaposi's sarcoma–associated herpesvirus (KSHV) is associated with three different human malignancies, including Kaposi's sarcoma (KS), primary effusion lymphoma, and multicentric Castleman's disease. The KS lesion is of endothelial cell in origin and is highly dependent on autocrine and paracrine factors for survival and growth. In this study, we show that KSHV infection of endothelial cells induces the activation of the prosurvival phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin pathway. KSHV infection of endothelial cells augmented cell survival in the presence of apoptotic inducers, including etoposide and staurosporine, and under conditions of serum deprivation. We found that KSHV infection of endothelial cells also increased the ability of these cells to form an in vitro tubular network under conditions of stress and growth factor deprivation. Finally, we show that the nuclear factor-κB and PI3K pathways are also required for endothelial tubular network formation. Collectively, these results suggest that KSHV infection of endothelial cells modulates cell signaling pathways and induces cell survival and angiogenesis, thereby contributing to the pathogenesis induced by KSHV. [Cancer Res 2008;68(12):4640–8]
Stopping Treatment Can Reverse Acquired Resistance to Letrozole
Authors: Sabnis Gauri J. , Macedo Luciana F. , Goloubeva Olga , Schayowitz Adam , Brodie Angela M.H.
Published: June 2008

Using the intratumoral aromatase xenograft model, we have observed that despite long-lasting growth inhibition, tumors eventually begin to grow during continued letrozole treatment. In cells isolated from these long-term letrozole-treated tumors (LTLT-Ca), estrogen receptor-α (ERα) levels were decreased, whereas signaling proteins in the mitogen-activated protein kinase cascade were up-regulated along with human epidermal growth factor receptor 2 (Her-2). In the current study, we evaluated the effect of discontinuing letrozole treatment on the growth of letrozole-resistant cells and tumors. The cells formed tumors equally well in the absence or presence of letrozole and had similar growth rates. After treatment was discontinued for 6 weeks, letrozole was administered again. Marked tumor regression was observed with this second course of letrozole treatment. Similarly, in MCF-7Ca xenografts, a 6-week break in letrozole treatment prolonged the responsiveness of the tumors to letrozole. To understand the mechanisms of this effect, LTLT-Ca cells were cultured in the absence of letrozole for 16 weeks. The resulting cell line (RLT-Ca) exhibited properties similar to MCF-7Ca cells. The cell growth was inhibited by letrozole and stimulated by estradiol. The expression of phosphorylated mitogen-activated protein kinase (MAPK) was reduced and ERα and aromatase levels increased compared with LTLT-Ca cells and were similar to levels in MCF-7Ca cells. These results indicate that discontinuing treatment can reverse letrozole resistance. This could be a beneficial strategy to prolong responsiveness to aromatase inhibitors for patients with breast cancer. [Cancer Res 2008;68(12):4518–24]
Suppression of Colorectal Oncogenesis by Selenium-Enriched Milk Proteins: Apoptosis and K-ras Mutations
Authors: Hu Ying , McIntosh Graeme H. , Le Leu Richard K. , Woodman Richard , Young Graeme P.
Published: June 2008

The chemical form and bioavailability of dietary selenium may influence its protectiveness against colorectal cancer. Selenium is readily incorporated into milk proteins by feeding cows with selenized-yeast. This study examined whether a dairy source of organic selenium (as milk proteins) is more effective than a yeast source at inhibiting oncogenesis in carcinogen-treated mice and whether it regulates the homeostatic response to carcinogen-induced DNA damage. Dietary interventions are as follows: selenium-enriched milk protein isolate (Tatura-Bio Se; 0.5 or 1 ppm selenium) or milk protein control and selenized-yeast (Sel-Plex; 1 or 4 ppm selenium) with casein or casein alone as control. After 4 weeks on diet, mice received a single azoxymethane (10 mg/kg) injection to induce mutations and were killed 6 hours later. Measures were as follows: plasma selenium, cell proliferation, and acute apoptotic response to azoxymethane (AARGC). Separate groups of mice on the same diets were given 4 weekly azoxymethane (15 mg/kg) injections to induce oncogenesis. Mice were killed 6 or 30 weeks after the last azoxymethane injection. Measures were as follows: aberrant crypt foci (ACF), cancers, and K-ras mutations. Dairy-selenium at 1 ppm significantly suppressed ACF and cancers, whereas yeast-selenium at an equivalent selenium intake had no effect. Dairy-selenium significantly increased plasma selenium levels and AARGC, and reduced cell proliferation and frequency of K-ras mutations in ACF relative to an equivalent dose of selenium from yeast. Selenium-enriched milk protein isolate is superior to selenized-yeast in terms of its bioavailability and capacity to suppress oncogenesis. Suppression may be a consequence of enhanced apoptotic deletion of azoxymethane-induced DNA lesions and the subsequent reduction in frequency of K-ras mutations. [Cancer Res 2008;68(12):4936–44]
Protein Phosphatase 2A and Rapamycin Regulate the Nuclear Localization and Activity of the Transcription Factor GLI3
Authors: Krauß Sybille , Foerster John , Schneider Rainer , Schweiger Susann
Published: June 2008

Gain-of-function alterations to the sonic hedgehog (SHH) signaling cascade have been found in a wide range of tumors. Three SHH effectors, GLI1, GLI2, and GLI3, regulate transcription of diverse genes involved in cell growth and cell proliferation. Here, we show that protein phosphatase 2A (PP2A), its regulatory subunit, α4, and rapamycin, an inhibitor of the mammalian target of rapamycin kinase complex 1 (mTORC1), regulate the nuclear localization and transcriptional activity of GLI3. An increase in PP2A activity or treatment with rapamycin leads to cytosolic retention of GLI3 and, consequently, reduced transcription of the GLI3 target gene and cell cycle regulator, cyclin D1. Conversely, inhibition of PP2A results in increased expression of cyclin D1. In summary, our findings reveal the existence of a hitherto unrecognized molecular cross-talk between the oncogenic SHH pathway and the tumor suppressor PP2A and suggest a novel mechanism underlying the anticancerogenic effects of rapamycin. [Cancer Res 2008;68(12):4658–65]