bluuebunny/crossref_metadata_2025 huggingface dataset:
The challenge of changing deeply held student beliefs about the relativity of simultaneity
Authors: Scherr Rachel E. , Shaffer Peter S. , Vokos Stamatis
Published: November 2002

Previous research indicates that after standard instruction, students at all levels often construct a conceptual framework in which the ideas of absolute simultaneity and the relativity of simultaneity co-exist. We describe the development and assessment of instructional materials intended to improve student understanding of the concept of time in special relativity, the relativity of simultaneity, and the role of observers in inertial reference frames. Results from pretests and post-tests are presented to demonstrate the effect of the curriculum in helping students deepen their understanding of these topics. Excerpts from taped interviews and classroom interactions help illustrate the intense cognitive conflict that students encounter as they are led to confront the incompatibility of their deeply held beliefs about simultaneity with the results of special relativity.
A simple method for measuring atmospheric pressure
Authors: Velasco S. , González A. , Román F. L. , White J. A.
Published: November 2002

A simple and low-cost experimental method for measuring atmospheric pressure is proposed. A 100 ml glass syringe is used. The only theoretical requirement is Boyle’s law for ideal gases.
The vanishing of magnetic flux over a closed surface
Authors: Karaoglu Bekir
Published: November 2002

A simple proof of the vanishing of magnetic flux over a closed surface, based on elementary vector algebra and symmetry considerations, is presented.
The 2001 Paul Klopsteg Memorial Lecture: Cosmology: Man’s place in the universe (a deconstruction)
Authors: Trimble Virginia
Published: November 2002

The history of the universe makes a reasonably coherent story, beginning with a hot, dense phase (the Big Bang), continuing with the formation and evolution of galaxies, stars, and planets, and reaching by now the appearance of life and intelligence (suitably defined). Some parts of the story, for instance, the evolution of stars, are well understood. Others are only fuzzy outlines (the formation of galaxies and the beginnings of life). All are heavily dependent upon the universe having key characteristics very close to the actual ones. These include the four forces of physics and about four cosmological parameters. CMPitU is a talk that tries to tell this story. The deconstruction addressed how much confidence we can place in the various chapters and variants in narrative technique.
The relationship between mathematics preparation and conceptual learning gains in physics: A possible “hidden variable” in diagnostic pretest scores
Authors: Meltzer David E.
Published: November 2002

There have been many investigations into the factors that underlie variations in individual student performance in college physics courses. Numerous studies report a positive correlation between students’ mathematical skills and their exam grades in college physics. However, few studies have examined students’ learning gain resulting from physics instruction, particularly with regard to qualitative, conceptual understanding. We report on the results of our investigation into some of the factors, including mathematical skill, that might be associated with variations in students’ ability to achieve conceptual learning gains in a physics course that employs interactive-engagement methods. It was found that students’ normalized learning gains are not significantly correlated with their pretest scores on a physics concept test. In contrast, in three of the four sample populations studied it was found that there is a significant correlation between normalized learning gain and students’ preinstruction mathematics skill. In two of the samples, both males and females independently exhibited the correlation between learning gain and mathematics skill. These results suggest that students’ initial level of physics concept knowledge might be largely unrelated to their ability to make learning gains in an interactive-engagement course; students’ preinstruction algebra skills might be associated with their facility at acquiring physics conceptual knowledge in such a course; and between-class differences in normalized learning gain may reflect not only differences in instructional method, but student population differences (“hidden variables”) as well.
A noncalculus proof that Fermat’s principle of least time implies the law of refraction
Authors: Helfgott Harald , Helfgott Michel
Published: November 2002

We provide an algebraic proof of the fact that Fermat’s principle of least time implies Snell’s law. This proof is closer to Fermat’s original approach than the usual calculus-based developments of the subject.
AGTR2
Mutations in X-Linked Mental Retardation
Authors: Vervoort Virginie S. , Beachem Michael A. , Edwards Penny S. , Ladd Sydney , Miller Karin E. , de Mollerat Xavier , Clarkson Katie , DuPont Barbara , Schwartz Charles E. , Stevenson Roger E. , Boyd Ellen , Srivastava Anand K.
Published: November 2002

Two angiotensin II (Ang II)–specific receptors, AGTR1 and AGTR2, are expressed in the mammalian brain. Ang II actions on blood pressure regulation, water electrolyte balance, and hormone secretion are primarily mediated by AGTR1. The function of AGTR2 remains unclear. Here, we show that expression of the
AGTR2
gene was absent in a female patient with mental retardation (MR) who had a balanced X;7 chromosomal translocation. Additionally, 8 of 590 unrelated male patients with MR were found to have sequence changes in the
AGTR2
gene, including one frameshift and three missense mutations. These findings indicate a role for AGTR2 in brain development and cognitive function.
The Domestication of Social Cognition in Dogs
Authors: Hare Brian , Brown Michelle , Williamson Christina , Tomasello Michael
Published: November 2002

Dogs are more skillful than great apes at a number of tasks in which they must read human communicative signals indicating the location of hidden food. In this study, we found that wolves who were raised by humans do not show these same skills, whereas domestic dog puppies only a few weeks old, even those that have had little human contact, do show these skills. These findings suggest that during the process of domestication, dogs have been selected for a set of social-cognitive abilities that enable them to communicate with humans in unique ways.
Genetic Evidence for an East Asian Origin of Domestic Dogs
Authors: Savolainen Peter , Zhang Ya-ping , Luo Jing , Lundeberg Joakim , Leitner Thomas
Published: November 2002

The origin of the domestic dog from wolves has been established, but the number of founding events, as well as where and when these occurred, is not known. To address these questions, we examined the mitochondrial DNA (mtDNA) sequence variation among 654 domestic dogs representing all major dog populations worldwide. Although our data indicate several maternal origins from wolf, >95% of all sequences belonged to three phylogenetic groups universally represented at similar frequencies, suggesting a common origin from a single gene pool for all dog populations. A larger genetic variation in East Asia than in other regions and the pattern of phylogeographic variation suggest an East Asian origin for the domestic dog, ∼15,000 years ago.
Combining Sensory Information: Mandatory Fusion Within, but Not Between, Senses
Authors: Hillis J. M. , Ernst M. O. , Banks M. S. , Landy M. S.
Published: November 2002

Humans use multiple sources of sensory information to estimate environmental properties. For example, the eyes and hands both provide relevant information about an object's shape. The eyes estimate shape using binocular disparity, perspective projection, etc. The hands supply haptic shape information by means of tactile and proprioceptive cues. Combining information across cues can improve estimation of object properties but may come at a cost: loss of single-cue information. We report that single-cue information is indeed lost when cues from within the same sensory modality (disparity and texture gradients in vision) are combined, but not when different modalities (vision and haptics) are combined.
Whole-Genome Analysis of Photosynthetic Prokaryotes
Authors: Raymond Jason , Zhaxybayeva Olga , Gogarten J. Peter , Gerdes Sveta Y. , Blankenship Robert E.
Published: November 2002

The process of photosynthesis has had profound global-scale effects on Earth; however, its origin and evolution remain enigmatic. Here we report a whole-genome comparison of representatives from all five groups of photosynthetic prokaryotes and show that horizontal gene transfer has been pivotal in their evolution. Excluding a small number of orthologs that show congruent phylogenies, the genomes of these organisms represent mosaics of genes with very different evolutionary histories. We have also analyzed a subset of “photosynthesis-specific” genes that were elucidated through a differential genome comparison. Our results explain incoherencies in previous data-limited phylogenetic analyses of phototrophic bacteria and indicate that the core components of photosynthesis have been subject to lateral transfer.
A Kinetic Framework for a Mammalian RNA Polymerase in Vivo
Authors: Dundr Miroslav , Hoffmann-Rohrer Urs , Hu Qiyue , Grummt Ingrid , Rothblum Lawrence I. , Phair Robert D. , Misteli Tom
Published: November 2002

We have analyzed the kinetics of assembly and elongation of the mammalian RNA polymerase I complex on endogenous ribosomal genes in the nuclei of living cells with the use of in vivo microscopy. We show that components of the RNA polymerase I machinery are brought to ribosomal genes as distinct subunits and that assembly occurs via metastable intermediates. With the use of computational modeling of imaging data, we have determined the in vivo elongation time of the polymerase, and measurements of recruitment and incorporation frequencies show that incorporation of components into the assembling polymerase is inefficient. Our data provide a kinetic and mechanistic framework for the function of a mammalian RNA polymerase in living cells.
Mechanisms of AIF-Mediated Apoptotic DNA Degradation in
Caenorhabditis elegans
Authors: Wang Xiaochen , Yang Chonglin , Chai Jijie , Shi Yigong , Xue Ding
Published: November 2002

Apoptosis-inducing factor (AIF), a mitochondrial oxidoreductase, is released into the cytoplasm to induce cell death in response to apoptotic signals. However, the mechanisms underlying this process have not been resolved. We report that inactivation of the
Caenorhabditis elegans
AIF homolog
wah-1
by RNA interference delayed the normal progression of apoptosis and caused a defect in apoptotic DNA degradation. WAH-1 localized in
C. elegans
mitochondria and was released into the cytosol and nucleus by the BH3-domain protein EGL-1 in a caspase (CED-3)–dependent manner. In addition, WAH-1 associated and cooperated with the mitochondrial endonuclease CPS-6/endonuclease G (EndoG) to promote DNA degradation and apoptosis. Thus, AIF and EndoG define a single, mitochondria-initiated apoptotic DNA degradation pathway that is conserved between
C. elegans
and mammals.
Extent of Chromatin Spreading Determined by
roX
RNA Recruitment of MSL Proteins
Authors: Park Yongkyu , Kelley Richard L. , Oh Hyangyee , Kuroda Mitzi I. , Meller Victoria H.
Published: November 2002

The untranslated
roX1
and
roX2
RNAs are components of the
Drosophila
male-specific lethal (MSL) complex, which modifies histones to up-regulate transcription of the male X chromosome.
roX
genes are normally located on the X chromosome, and
roX
transgenes can misdirect the dosage compensation machinery to spread locally on other chromosomes. Here we define MSL protein abundance as a determinant of whether the MSL complex will spread in cis from an autosomal
roX
transgene. The number of expressed
roX
genes in a nucleus was inversely correlated with spreading from
roX
transgenes. We suggest a model in which MSL proteins assemble into active complexes by binding nascent
roX
transcripts. When MSL protein/
roX
RNA ratios are high, assembly will be efficient, and complexes may be completed while still tethered to the DNA template. We propose that this local production of MSL complexes determines the extent of spreading into flanking chromatin.
Electron Acceleration by a Wake Field Forced by an Intense Ultrashort Laser Pulse
Authors: Malka V. , Fritzler S. , Lefebvre E. , Aleonard M.-M. , Burgy F. , Chambaret J.-P. , Chemin J.-F. , Krushelnick K. , Malka G. , Mangles S. P. D. , Najmudin Z. , Pittman M. , Rousseau J.-P. , Scheurer J.-N. , Walton B. , Dangor A. E.
Published: November 2002

Plasmas are an attractive medium for the next generation of particle accelerators because they can support electric fields greater than several hundred gigavolts per meter. These accelerating fields are generated by relativistic plasma waves—space-charge oscillations—that can be excited when a high-intensity laser propagates through a plasma. Large currents of background electrons can then be trapped and subsequently accelerated by these relativistic waves. In the forced laser wake field regime, where the laser pulse length is of the order of the plasma wavelength, we show that a gain in maximum electron energy of up to 200 megaelectronvolts can be achieved, along with an improvement in the quality of the ultrashort electron beam.
Arsenic Mobility and Groundwater Extraction in Bangladesh
Authors: Harvey Charles F. , Swartz Christopher H. , Badruzzaman A. B. M. , Keon-Blute Nicole , Yu Winston , Ali M. Ashraf , Jay Jenny , Beckie Roger , Niedan Volker , Brabander Daniel , Oates Peter M. , Ashfaque Khandaker N. , Islam Shafiqul , Hemond Harold F. , Ahmed M. Feroze
Published: November 2002

High levels of arsenic in well water are causing widespread poisoning in Bangladesh. In a typical aquifer in southern Bangladesh, chemical data imply that arsenic mobilization is associated with recent inflow of carbon. High concentrations of radiocarbon-young methane indicate that young carbon has driven recent biogeochemical processes, and irrigation pumping is sufficient to have drawn water to the depth where dissolved arsenic is at a maximum. The results of field injection of molasses, nitrate, and low-arsenic water show that organic carbon or its degradation products may quickly mobilize arsenic, oxidants may lower arsenic concentrations, and sorption of arsenic is limited by saturation of aquifer materials.
Ancient DNA Evidence for Old World Origin of New World Dogs
Authors: Leonard Jennifer A. , Wayne Robert K. , Wheeler Jane , Valadez Raúl , Guillén Sonia , Vilà Carles
Published: November 2002

Mitochondrial DNA sequences isolated from ancient dog remains from Latin America and Alaska showed that native American dogs originated from multiple Old World lineages of dogs that accompanied late Pleistocene humans across the Bering Strait. One clade of dog sequences was unique to the New World, which is consistent with a period of geographic isolation. This unique clade was absent from a large sample of modern dogs, which implies that European colonists systematically discouraged the breeding of native American dogs.
A Critical Role for IL-21 in Regulating Immunoglobulin Production
Authors: Ozaki Katsutoshi , Spolski Rosanne , Feng Carl G. , Qi Chen-Feng , Cheng Jun , Sher Alan , Morse Herbert C. , Liu Chengyu , Schwartzberg Pamela L. , Leonard Warren J.
Published: November 2002

The cytokine interleukin-21 (IL-21) is closely related to IL-2 and IL-15, and their receptors all share the common cytokine receptor γ chain, γ
c
, which is mutated in humans with X-linked severe combined immunodeficiency disease (XSCID). We demonstrate that, although mice deficient in the receptor for IL-21 (IL-21R) have normal lymphoid development, after immunization, these animals have higher production of the immunoglobulin IgE, but lower IgG1, than wild-type animals. Mice lacking both IL-4 and IL-21R exhibited a significantly more pronounced phenotype, with dysgammaglobulinemia, characterized primarily by a severely impaired IgG response. Thus, IL-21 has a significant influence on the regulation of B cell function in vivo and cooperates with IL-4. This suggests that these γ
c
-dependent cytokines may be those whose inactivation is primarily responsible for the B cell defect in humans with XSCID.
Fluorometric Detection of Enzyme Activity with Synthetic Supramolecular Pores
Authors: Das Gopal , Talukdar Pinaki , Matile Stefan
Published: November 2002

The reversible blockage of synthetic pores formed by rigid-rod β barrels, either by substrates or products, was used to sense a variety of enzymatic reactions in high-throughput format with “naked-eye” fluorescent detection. Improvement of sensor sensitivity beyond three orders of magnitude by straightforward internal mutations underscores the functional plasticity of rigid-rod β barrels. Such detectors of enzyme activity with the aforementioned characteristics are needed in areas as diverse as proteomics and environmentally benign organic synthesis.
Crystal Structure of
Escherichia coli
MscS, a Voltage-Modulated and Mechanosensitive Channel
Authors: Bass Randal B. , Strop Pavel , Barclay Margaret , Rees Douglas C.
Published: November 2002

The mechanosensitive channel of small conductance (MscS) responds both to stretching of the cell membrane and to membrane depolarization. The crystal structure at 3.9 angstroms resolution demonstrates that
Escherichia coli
MscS folds as a membrane-spanning heptamer with a large cytoplasmic region. Each subunit contains three transmembrane helices (TM1, -2, and -3), with the TM3 helices lining the pore, while TM1 and TM2, with membrane-embedded arginines, are likely candidates for the tension and voltage sensors. The transmembrane pore, apparently captured in an open state, connects to a large chamber, formed within the cytoplasmic region, that connects to the cytoplasm through openings that may function as molecular filters. Although MscS is likely to be structurally distinct from other ion channels, similarities in gating mechanisms suggest common structural elements.
Determination of the Equation of State of Dense Matter
Authors: Danielewicz Paweł , Lacey Roy , Lynch William G.
Published: November 2002

Nuclear collisions can compress nuclear matter to densities achieved within neutron stars and within core-collapse supernovae. These dense states of matter exist momentarily before expanding. We analyzed the flow of matter to extract pressures in excess of 10
34
pascals, the highest recorded under laboratory-controlled conditions. Using these analyses, we rule out strongly repulsive nuclear equations of state from relativistic mean field theory and weakly repulsive equations of state with phase transitions at densities less than three times that of stable nuclei, but not equations of state softened at higher densities because of a transformation to quark matter.
Grasping Primate Origins
Authors: Bloch Jonathan I. , Boyer Doug M.
Published: November 2002

The evolutionary history that led to Eocene-and-later primates of modern aspect (Euprimates) has been uncertain. We describe a skeleton of Paleocene plesiadapiform
Carpolestes simpsoni
that includes most of the skull and many postcranial bones. Phylogenetic analyses indicate that Carpolestidae are closely related to Euprimates.
C. simpsoni
had long fingers and an opposable hallux with a nail. It lacked orbital convergence and an ankle specialized for leaping. We infer that the ancestor of Euprimates was primitively an arboreal grasper adapted for terminal branch feeding rather than a specialized leaper or visually directed predator.
It's a Dog's Life
Authors: Caro Tim
Published: November 2002

The African Wild Dog
Behavior, Ecology, and Conservation. Scott Creel and Nancy Marusha Creel. Princeton University Press, Princeton, NJ, 2002. 355 pp. $90, £62.00. ISBN 0-691-01655-0. Paper, $45, £29.95. ISBN 0-691-01654-2.

The authors incorporate findings from their own six-year study of one of the world's most interesting and endangered large carnivores.
Nevertheless, It Does Move Us
Authors: Pasachoff Jay M.
Published: November 2002

Galileo Galilei
. Philip Glass, composer. Libretto by Mary Zimmerman with Philip Glass and Arnold Weinstein. Brooklyn Academy of Music, New York, 1 to 5 October, 2002.

This opera explores the life and science of the Renaissance astronomer in reverse, working from a frail, blind old man back to a fidgety young boy.
The Faculty of Language: What Is It, Who Has It, and How Did It Evolve?
Authors: Hauser Marc D. , Chomsky Noam , Fitch W. Tecumseh
Published: November 2002

We argue that an understanding of the faculty of language requires substantial interdisciplinary cooperation. We suggest how current developments in linguistics can be profitably wedded to work in evolutionary biology, anthropology, psychology, and neuroscience. We submit that a distinction should be made between the faculty of language in the broad sense (FLB) and in the narrow sense (FLN). FLB includes a sensory-motor system, a conceptual-intentional system, and the computational mechanisms for recursion, providing the capacity to generate an infinite range of expressions from a finite set of elements. We hypothesize that FLN only includes recursion and is the only uniquely human component of the faculty of language. We further argue that FLN may have evolved for reasons other than language, hence comparative studies might look for evidence of such computations outside of the domain of communication (for example, number, navigation, and social relations).
Prediction of grout penetration in fractured rocks by numerical simulation
Authors: Yang M J , Yue Z Q , Lee P KK , Su B , Tham L G
Published: November 2002

As fractures in rock significantly reduce the strength as well as the stiffness of the rock mass, grouting may be required to improve the performance of the rock mass in engineering or mining projects. During grouting, mortar of cement or other materials is injected into the rock mass so that the fractures can be filled up and the rock mass can act as an integral unit. Unlike water, grouts are usually viscous and behave as non-Newtonian fluids. Therefore, the equations describing the flow of grout are more complicated and the solutions are quite difficult to obtain. The problem is further aggravated by the fact that the fractures are mostly randomly distributed, and it is rarely possible to accurately define the fractures and the distribution patterns. In this paper, a numerical model is proposed for analyzing the grouting process. The model is based on the stochastic approach, and it can provide the depth of penetration and the fluid pressure due to the flow of grout, which is modeled as a Bingham fluid, in the fractured rock mass. Parametric studies have been carried out to investigate the effects of various factors on the depth of penetration, and a regression formula is developed for calculating the penetration depth. Experiments have been carried out and their results are used to validate the present method.Key words: stochastic fractures, fractured rock mass, grout flow, grout penetration.
Quality of samples retrieved from great depth and its influence on consolidation properties
Authors: Tanaka Hiroyuki , Ritoh Fusao , Omukai Naoki
Published: November 2002

Pleistocene sediments deposited in Osaka Bay have been extensively investigated to depths of up to 400 m. Consolidation properties, especially preconsolidation pressure, are somewhat scattered with depth. The quality of samples retrieved from great depths has been evaluated based on the indices calculated from the volumetric strain or the void ratio changes in the recompression process. The study reveals that these indices do not simply increase with an increase in sampling depth. The potential for sample disturbance during sample setting in the constant rate of strain (CRS) oedometer was also investigated. These tests have revealed that the preconsolidation pressure, as measured in the laboratory, is not influenced significantly by swelling. In addition, preconsolidation pressures indicate that the sediments are slightly overconsolidated, with a departure from normally consolidated behaviour that could be explained by cementation.Key words: sampling, preconsolidation pressure, sample disturbance, oedometer test, Pleistocene clay, great depth.
Pavement displacement sensitivity to layer moduli
Authors: Stolle Dieter
Published: November 2002

The backcalculation of layer moduli using falling weight deflectometer data has proven to be challenging owing to the insensitivity of displacement measurements to the stiffness characteristics of some layers. This note describes a rigorous, yet simple, finite element technique for identifying the relationship between surface displacement and the elastic modulus of each layer. An example is given to demonstrate the application of the procedure.Key words: pavements, subgrade, backcalculation, contribution ratio.
A model for static liquefaction in triaxial compression and extension
Authors: Boukpeti N , Mróz Z , Drescher A
Published: November 2002

The response of the elastoplastic refined Superior sand constitutive model in undrained triaxial compression and extension tests is presented. The model is aimed at realistic simulation of liquefaction occurring in loose, saturated, granular materials under monotonic static loading. The yield surface introduced previously in the original Superior sand model is modified, and a non-associated flow rule is used. The isotropic hardeningsoftening is related to plastic deformation and distance to a reference yield curve. The refined model accounts for the different response of materials with different deposition densities. The model prediction of undrained triaxial compression and extension tests is compared with experimental results. The higher tendency for liquefaction response in extension is well described. Instability and phase-transformation states also are discussed, and the energy of liquefaction is quantified.Key words: static liquefaction, constitutive model, triaxial tests, liquefaction energy.
A dual fracture model to simulate large-scale flow through fractured rocks
Authors: Wang E Z , Yue Z Q , Tham L G , Tsui Y , Wang H T
Published: November 2002

Discrete fracture network models can be used to study groundwater flow in fractured rock masses. However, one may find that it is not easy to apply such models to practical projects as it is difficult to investigate every fracture and measure its hydraulic parameters. To overcome such difficulties, a dual fracture model is proposed. Taking into account the hydraulic characteristics of the various elements of the fracture system, a hydrogeological medium is assumed to consist of two components: the dominant fracture network and the fractured rock matrix. As the dominant fracture network consists of large fractures and faults, it controls the groundwater flow in rock masses. Depending on the permeabilities of the in-fill materials, these fractures and faults may serve as channels or barriers of the flow. The fractured rock matrix, which includes rock blocks and numerous small fractures, plays a secondary role in groundwater flow in such medium. Although the small fractures and rock blocks possess low permeability, their numbers and their total porosity are relatively large. Therefore, they provide large volume for groundwater storage. In this paper, the application of the proposed model to simulate the groundwater flow for a hydropower station before and after reservoir storage is reported. The implications of the results on the design of the station are also highlighted.Key words: seepage flow, dual fracture model, dominant fracture, fractured rock matrix, case studies, rock-filled dam.
A structured Cam Clay model
Authors: Liu M D , Carter J P
Published: November 2002

A theoretical study of the behaviour of structured soil is presented. A new model, referred to as the Structured Cam Clay model, is formulated by introducing the influence of soil structure into the Modified Cam Clay model. The proposed model is hierarchical, i.e., it is identical to the Modified Cam Clay soil model if a soil has no structure or if its structure is removed by loading. Three new parameters describing the effects of soil structure are introduced, and the results of a parametric study are also presented. The proposed model has been used to predict the behaviour of structured soils in both compression and shearing tests. By making comparisons of predictions with experimental data and by conducting the parametric study it is demonstrated that the new model provides satisfactory qualitative and quantitative modelling of many important features of the behaviour of structured soils.Key words: calcareous soils, clays, fabric, structure, constitutive relations, plasticity.
Instrumented load tests in mudstone: pile capacity and settlement prediction
Authors: Omer J R , Delpak R , Robinson R B
Published: November 2002

The present work stems from the design of a viaduct in South Wales, U.K., where full-scale pile testing was carried out to assess whether the proposed design methods would meet the required load capacity and settlement criteria for the working piles. Five fully instrumented large diameter bored cast in situ piles, up to 30 m deep, were installed in weathered mudstone and tested under vertical loading. A sixth pile, which had no shaft instrumentation, was formed with a voided toe. In conjunction with vast soil data from 218 site investigation boreholes, the extensive data produced from the load tests were analyzed to quantify the key parameters considered to influence load transfer and settlement behaviour. Each pile was first calibrated using four methods to establish the as-built stiffness, taking into account the nonlinearity of concrete and the effect of partial steel encasement. It is demonstrated that the current national norms for bored pile design in cohesive soil  soft rock are overconservative for South Wales ground conditions. To ameliorate this, alternative methods are proposed, which lead to improved reliability and accuracy in shaft and base capacity assessment. In addition, a numerical model is developed that can be used to predict the complete load-settlement variation up to the ultimate state. The model is sufficiently expounded to allow its immediate application in pile design by geotechnical engineers.Key words: piled foundations, load tests, bearing capacity and settlement, Mercia mudstone.
Prediction and analysis of subsidence induced by shield tunnelling in the Madrid Metro extension
Authors: Melis Manuel , Medina Luis , Rodríguez José M
Published: November 2002

The development of tunnelling projects under heavily populated cities has been rapidly increasing around the world during the last decades. Since tunnel construction can have disastrous effects on buildings, structures, and utilities near the excavation, construction methods have necessarily to provide maximum safety inside and outside the tunnel. To predict and correct dangerous ground movements due to the tunnelling works, the authors developed a numerical model to simulate the earth pressure balance (EPB) excavation procedure and injection to complement some deficiencies found in previous analytical or empirical subsidence estimating procedures. This model takes into account the full excavation sequence and has been validated by a large amount of monitoring data from the previous Madrid Metro extension. In the present paper, several predictive methods are used to predict the ground movements generated during a new Madrid Metro extension project consisting of 48 km of tunnel (19992003). At the end of the works the results will be compared with data from monitored sections placed in all five cities linked by the extension. Conclusions about the applicability and accuracy of the methods will be established with the aim of helping researchers and engineers in their future projects.Key words: ground movements, monitoring, numerical modelling and analysis, settlement, tunnels.
Modeling deformation behaviour of clay liners in a small centrifuge
Authors: Viswanadham B VS , Mahesh K V
Published: November 2002

In modern solid waste landfills, liner systems are essential structural elements that ensure that waste materials are safely separated from the environment. Many liner systems have been developed and used over the past decade. Among impermeable layers, clay liners are regarded as one of the very significant components of liner system and are being used worldwide as a waste containment system in landfills. One of the failures associated with clay liners is the occurrence of nonuniform settlements, resulting from the sudden collapse of waste, or the decomposition of waste materials, and (or) the subgrade over which the liner is laid. This paper deals with the use of a small centrifuge to model the deformation behaviour of clay liners. Model tests were performed in a small geotechnical centrifuge to investigate the behaviour of clay liners in landfills subjected to nonuniform settlements at sharp curvatures. A parametric study was conducted to analyze the influence of parameters like thickness, consistency, and overburden on the behaviour of clay liners. The clay liner without any overburden is observed to experience severe cracking in the form of deep and wide cracks at the maximum curvature zone. The depth and width of the cracks are found to decrease with an increase in clay liner thickness. The cracking failure pattern is suppressed by shearing for a clay liner with an increase in overburden pressure. Based on model test results, the clay liner with an adequate overburden is found to be free from cracking failure even when subjected to sharp curvatures. The effective usage of a small geotechnical centrifuge to model the deformation behaviour of clay liners is demonstrated adequately.Key words: landfills, municipal solid waste, clay liners, centrifuge modeling, nonuniform settlements, model tests.
Effect of undrained creep on instability behaviour of loose sand
Authors: Leong W K , Chu J
Published: November 2002

Prefailure instability in the form of a runway deformation can occur for loose sand under undrained conditions. The effect of creep on the instability behaviour of loose sand is studied experimentally in this note. Previous studies have established that instability can only occur when the stress state is above the instability line. However, if creep is allowed to develop under undrained conditions, instability can still possibly occur even when the stress state at which creep develops is below the instability line. A boundary that specifies the condition in which instability may be induced by undrained creep is determined based on the experimental data.Key words: laboratory test, liquefaction, sands, shear strength.
Prediction of freezing-induced movements for an underground construction project in Japan
Authors: Konrad J-M
Published: November 2002

This paper presents the results of a thermomechanical simulation of freezing around an existing tunnel in Kobe (Japan) to predict the deformations associated with ice lens formation and those resulting from thaw after construction is completed. The frost heave characteristics used in the numerical model were obtained from laboratory freezing tests conducted on undisturbed samples provided by the Osaka Soil Test Laboratory. With the planned construction schedule, the predictions suggest a maximum frost heave at the ground surface of about 4.8 cm while the expected thaw settlement in the tunnel's centerline was about 13 cm. Observed frost penetration and surface frost heave movements agree well with the predictions. Grout injected during thaw was successful in preventing excessive thaw settlement.Key words: frost, soils, heave, model, monitoring, field.
Adsorption of single-ring model naphthenic acids on soils
Authors: Peng Jimin , Headley J V , Barbour S L
Published: November 2002

The adsorption of single-ring model naphthenic acids on soils was investigated using a batch partitioning method. The influence of the molecular structure of the sorbate, the organic carbon content of the sorbent, the temperature, the solution salt (calcium chloride) concentration, and the pH on the adsorption isotherms was determined. The adsorption coefficients (Kd) for two structurally related model naphthenic acids, 4-methycyclohexaneacetic acid (4MACH) and 4-methylcyclohexanecarboxylic acid (4MCCH), were 0.18 and 0.11 mL/g, respectively. The Kd values determined for the individual cis and trans isomers were equal for a given model naphthenic acid within the experimental precision of the data. In contrast to reported differences observed for the biodegradation of geometric isomers of model naphthenic acids, the structure of the cis and trans isomers investigated had negligible effects on the measured adsorption isotherms. The adsorption coefficients of 4MACH for two soils with organic carbon contents of 1.6 and 2.7% were 0.18 and 0.22 mL/g, respectively. For the two temperatures studied, similar Kd values were obtained for 4MACH (0.18 mL/g at 23°C and 0.21 mL/g at 4°C), indicating a predominantly physical adsorption process. Inorganic salt solutions of calcium chloride (CaCl2) had significant effects on adsorption as the Kd increased from 0.10 to 0.22 mL/g within the range of pore fluid chemistry investigated (0-30 mM CaCl2). Likewise, the adsorption of 4MACH was significantly influenced by pH with the Kd being 0.20, 0.18, and 0.11 mL/g in acidic (pH 2.9), neutral (pH 6.8), and alkaline solutions (pH 10), respectively. The low values of Kd indicated that there would be little adsorption of the single-ring model naphthenic acids by soils. This will result in high partitioning to the water column in aquatic environments.Key words: model naphthenic acids, adsorption coefficients, soils, batch partitioning method.
Parameters deduced from the pressuremeter test
Authors: Fawaz A , Boulon M , Flavigny E
Published: November 2002

This paper presents a study of the pressuremeter test and the results that can be obtained from this test. Hostun's fine sand was chosen as the material upon which to perform the experimental study of the pressuremeter. Numerical simulations of the pressuremeter tests have been made with the commercially available PLAXIS software. The numerical results have been compared with the experimental ones. The variation of the parameters resulting from an applied surcharge was studied experimentally and numerically. Finally, the relationship between the magnitude of the deformation and the pressuremeter modulus was analyzed.Key words: sand, pressuremeter, triaxial, pressure, modulus, deformation, numerical simulation.
Mini suction probe for matric suction measurements
Authors: Meilani Inge , Rahardjo Harianto , Leong Eng-Choon , Fredlund Delwyn G
Published: November 2002

A modified triaxial apparatus with mini suction probes was fabricated to study the matric suction along the specimen height during unsaturated triaxial testing. Three mini suction probes were placed at 3/4, 1/2, and 1/4 height of the specimen, each at 120° apart in the lateral direction. This paper presents the development of the mini probe for matric suction measurements. Evaluation of the performance shows that the fabricated mini probe provides a rapid response and accurate reading under negative and positive pore-water pressure changes. Matric suctions as high as 400 kPa were successfully measured on soil specimens over a time span of 15 h. On the other hand, the mini suction probes were also found to be able to measure a matric suction of 200 kPa for a longer period of 155 h.Key words: matric suction, mini suction probe, triaxial, unsaturated soils, mid-height pore-water pressure measurement.
Dynamic analysis of laterally loaded pile groups in sand and clay
Authors: Mostafa Yasser E , Naggar M Hesham El
Published: November 2002

Pile foundations supporting bridge piers, offshore platforms, and marine structures are required to resist not only static loading but also lateral dynamic loading. The static py curves are widely used to relate pile deflections to nonlinear soil reactions. The p-multiplier concept is used to account for the group effect by relating the load transfer curves of a pile in a group to the load transfer curves of a single pile. Some studies have examined the validity of the p-multiplier concept for the static and cyclic loading cases. However, the concept of the p-multiplier has not yet been considered for the dynamic loading case, and hence it is undertaken in the current study. An analysis of the dynamic lateral response of pile groups is described. The proposed analysis incorporates the static py curve approach and the plane strain assumptions to represent the soil reactions within the framework of a Winkler model. The model accounts for the nonlinear behaviour of the soil, the energy dissipation through the soil, and the pile group effect. The model was validated by analyzing the response of pile groups subjected to lateral Statnamic loading and comparing the results with field measured values. An intensive parametric study was performed employing the proposed analysis, and the results were used to establish dynamic soil reactions for single piles and pile groups for different types of sand and clay under harmonic loading with varying frequencies applied at the pile head. "Dynamic" p-multipliers were established to relate the dynamic load transfer curves of a pile in a group to the dynamic load transfer curves for a single pile. The dynamic p-multipliers were found to vary with the spacing between piles, soil type, peak amplitude of loading, and the angle between the line connecting any two piles and the direction of loading. The study indicated the effect of pile material and geometry, pile installation method, and pile head conditions on the p-multipliers. The calculated p-multipliers compared well with p-multipliers back-calculated from full scale field tests.Key words: lateral, transient loading, nonlinear, pilesoilpile interaction, py curves, Statnamic.
COMPUTING BY COMMUNICATION IN NETWORKS OF MEMBRANES
Authors: PĂUN ANDREI , PĂUN GHEORGHE , ROZENBERG GRZEGORZ
Published: November 2002

In this paper we consider networks of membranes which compute by communication only, using symport/antiport rules. Such rules are used both for communication with the environment and for direct communication among membranes. It turns out that, rather surprisingly, networks with a small number of membranes are computationally universal. This is proved both for the case of three membranes where each membrane communicates with each other membrane, and for the case of four membranes consisting of two pairs such that only the membranes within each pair communicate directly. A single pair of communicating membranes can compute the Parikh images of matrix languages. Several open problems are also formulated.
SHUFFLE DECOMPOSITIONS OF REGULAR LANGUAGES
Authors: CÂMPEANU C. , SALOMAA K. , VÁGVÖLGYI S.
Published: November 2002

We study the shuffle quotient operation and introduce equivalence relations it defines with respect to a (regular) language. Corresponding to an arbitrary shuffle decomposition we construct a normalized decomposition that is defined in terms of maximal languages. Using closure properties of the normalized decompositions we show that for certain subclasses of regular languages we can effectively decide whether or not the language has a non-trivial shuffle decomposition. We show that shuffle decomposition is undecidable for context-free languages.
A PTAS FOR MINIMIZING TOTAL COMPLETION TIME OF BOUNDED BATCH SCHEDULING
Authors: DENG XIAOTIE , FENG HAODI , LI GUOJUN , LIU GUIZHEN
Published: November 2002

We consider a batch processing system {pi : i = 1, 2,…,n} where pi is the processing time of job i, and up to B jobs can be processed together such that the handling time of a batch is the longest processing time among jobs in the batch. The number of job types m is not fixed and all the jobs are released at the same time. Jobs are executed non-preemptively. Our objective is to assign jobs to batches and sequence the batches so as to minimize the total completion time. The best previously known result is a 2–approximation algorithm. In this paper, we establish the first polynomial time approximation scheme (PTAS) for the problem.
ON UNIVERSALLY POLYNOMIAL CONTEXT-FREE LANGUAGES
Authors: TRAN NICHOLAS
Published: November 2002

A language is universally polynomial if its intersection with every NP-complete language is in P. Such a language would provide an automatic method for generating easy instances of intractable problems. In this note, we give a complete characterization of universally polynomial languages that are context-free, answering an open question in [4].
A NOTE ON THE DETERMINATION OF THE IMMEDIATE PREDECESSORS IN A DISTRIBUTED COMPUTATION
Authors: ANCEAUME EMMANUELLE , HELARY JEAN-MICHEL , RAYNAL MICHEL
Published: November 2002

A distributed computation can be modeled as a partially ordered set (poset) of relevant events (the relevant events are the subset of the primitive events that are meaningful for an observer). This short note presents a general protocol that, when superimposed on a distributed computation, provides each relevant event with a timestamp that identifies exactly its immediate predecessors in the poset. This determination is done on the fly and without using additional control messages. So, the proposed protocol provides an on the fly computation of the Hasse diagram (transitive reduction) of the event graph produced by a distributed computation. The protocol is particularly simple and efficient. It is based on a general condition that allows application messages to piggyback control information whose size can be smaller than n (the number of processes). Interestingly, when one is not interested in tracking the immediate predecessors, the proposed protocol can be simplified to get an efficient vector clock protocol that does not require particular channel assumptions.
PATTERN MATCHING CODE MINIMIZATION IN REWRITING-BASED PROGRAMMING LANGUAGES
Authors: NEDJAH NADIA , MOURELLE LUIZA DE MACEDO
Published: November 2002

We compile pattern matching for overlapping patterns in term rewriting systems into a minimal, tree matching automata. The use of directed acyclic graphs that shares all the isomorphic subautomata allows us to reduce space requirements. These are duplicated in the tree automaton. We design an efficient method to identify such subautomata and avoid duplicating their construction while generating the dag automaton. We compute some bounds on the size of the automata, thereby improving on previously known equivalent bounds for the tree automaton.
THE EFFECT OF ASYMMETRY ON THE ON-LINE MULTICAST ROUTING PROBLEM
Authors: FALOUTSOS MICHALIS , PANKAJ RAJESH , SEVCIK KENNESTH C.
Published: November 2002

In this paper, we study the problem of multicast routing on directed graphs. We define the asymmetry of a graph to be the maximum ratio of weights on opposite directed edges between a pair of nodes for all node-pairs. We examine three types of problems according the membership behavior: (i) the static, (ii) the join-only, (iii) the join-leave problems. We study the effect of the asymmetry on the worst case performance of two algorithms: the Greedy and Shortest Paths algorithms. The worst case performance of Shortest Paths is poor, but it is affected by neither the asymmetry nor the membership behavior. In contrast, the worst case performance of Greedy is a proportional to the asymmetry in a some cases. We prove an interesting result for the join-only problem: the Greedy algorithm has near-optimal on-line performance.
THE EXISTENCE OF ω-CHAINS FOR TRANSITIVE MIXED LINEAR RELATIONS AND ITS APPLICATIONS
Authors: DANG ZHE , IBARRA OSCAR H.
Published: November 2002

We show that it is decidable whether a transitive mixed linear relation has an ω-chain. Using this result, we study a number of liveness verification problems for generalized timed automata within a unified framework. More precisely, we prove that (1) the mixed linear liveness problem for a timed automaton with dense clocks, reversal-bounded counters, and a free counter is decidable, and (2) the Presburger liveness problem for a timed automaton with discrete clocks, reversal-bounded counters, and a pushdown stack is decidable.