bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization and Reconstruction of Crack Forces for a Cracked de Laval Rotor Based on State Space Theory
Authors: Alugongo Alfayo A. , Jin Chen
Published: June 2008

A non-linear cracked rotor model accounting for shaft weakening parallel and perpendicular to the crack is investigated. The system equation bears discontinuity, and numerical treatment has been applied leading to bifurcation and chaos. Based on State Space Theory, the dynamics of the crack is reconstructed as a ‘crack force’ manifesting the action of the crack on the rotor. Further non-linear characteristics are reconstructed and could be adopted in condition monitoring of rotors. It is demonstrated that, the largest Lyapunov exponent of the simulated time series sufficiently indicates the system’s chaotic state. An interesting discussion and characterization of the cracked rotor is presented to emphasize the modeling.
Vibration Isolation and Chaotic Vibration
Authors: Jiang Rong-Jun , Zhu Shi-Jian
Published: June 2008

Taking single degree of freedom vibration isolation system under simple harmonic excitation as an example, and considering the energy, the vibration isolation performance in different conditions was studied theoretically and numerically. The results shows that when the simple harmonic excitation import energy is definite, the vibration isolation performance at the primary harmonic frequency of the nonlinear vibration isolation system is better than that of the linear system, and the vibration isolation performance of the nonlinear vibration isolation system in chaotic vibration state is much better than that in non-chaotic vibration state. For the same isolated object, if can let the vibration isolation system vibrate chaotically, the system will possess the best isolation performance at the primary frequency.
Matching Solutions Based on Small and Large δ Approaches
Authors: Andrianov Igor V. , Awrejcewicz Jan
Published: June 2008

Two-point Pade´ and quasifractional approximations are matched in order to achieve uniform and suitable analytical solution. The introduced approach is applied to Thomas-Fermi and Schro¨dinger equations.
Dynamics of Two Van Der Pol Oscillators Coupled via a Bath
Authors: Camacho Erika , Rand Richard , Howland Howard
Published: June 2008

In this work we study a system of two van der Pol oscillators, x and y, coupled via a “bath” z: x¨−ε(1−x2)x˙+x=k(z−x)y¨−ε(1−y2)y˙+y=k(z−y)z˙=k(x−z)+k(y−z) We investigate the existence and stability of the in-phase and out-of-phase modes for parameters ε > 0 and k > 0. To this end we use Floquet theory and numerical integration. Surprisingly, our results show that the out-of-phase mode exists and is stable for a wider range of parameters than is the in-phase mode. This behavior is compared to that of two directly coupled van der Pol oscillators, and it is shown that the effect of the bath is to reduce the stability of the in-phase mode. We also investigate the occurrence of other periodic motions by using bifurcation theory and the AUTO bifurcation and continuation software package. Our motivation for studying this system comes from the presence of circadian rhythms in the chemistry of the eyes. We present a simplified model of a circadian oscillator which shows that it can be modeled as a van der Pol oscillator. Although there is no direct connection between the two eyes, they can influence each other by affecting the concentration of melatonin in the bloodstream, which is represented by the bath in our model.
Nonlinear Oscillations of a Particle in the Plane Under Longitudinal End Excitation
Authors: Jha Rajesh K. , Parker Robert G.
Published: June 2008

We study the forced vibrations of a two degree of freedom lumped parameter model of a belt span under longitudinal excitation. The belt inertia is modelled as a particle and the belt elasticity is modelled by two identical linear springs. Numerical integration is used to calculate free responses and perform frequency and amplitude sweeps. Frequency sweep results indicate parametric resonances, jump phenomena, sub- and super-harmonic responses, quasiperiodicity and chaos. Amplitude sweep at a low frequency shows bifurcations of limit cycles and the period doubling route to chaos. Poincare sections are computed to show the chaotic nature of the responses.
Metric Damping of MDOF Systems in High Transient Motion
Authors: Al Majid A. , Allezy A. , Dufour R.
Published: June 2008

This article deals with damping due to transient motion in the case of a Multi-Degree-Of-Freedom (MDOF) system. The main aim of this research is to make the method presented in a previous article by the authors available for MDOF systems. An original method based on relativity concepts is developed in order to identify, prove and evaluate a metric damping due to time-varying forcing frequencies. An additional dimension for each Degree-Of-Freedom (DOF) is introduced. The variational problem of the metric of a Riemannian space gives the geodesic equations, i.e. equations of motion which, after time integration is carried out with several types of numerical schemes, permits predicting the forced transient response of a 3-DOF system. The proposed metric approach is validated experimentally.
Nonlinear Vibrations of an Inclined Cable
Authors: Berlioz A. , Lamarque C.-H.
Published: June 2008

An experimental and theoretical study is carried out with the aim of using existing breadboard type construction in order to validate dynamic models. This experimental study highlights the nonlinear dynamic behavior of a cable consisting of a steel wire surrounded by copper wire. New measurements around the first frequency of vibration of the cable in and out of the plane and around the second harmonic of this frequency were also carried out. These results are in good agreement with the results obtained analytically via new finite (1,2,4) degree-of-freedom models.
Finding Unstable Fixed Points From Time Series Data
Authors: Maehara Takaaki , Nakai Mikio
Published: June 2008

This study employs topological methods to extract unstable fixed points in phase space from both numerical and experimental time series data. Conley index of an isolated invariant subset and the R-B method can determine unstable fixed points contained in strange attractor from numerical time series data. For experimental time series data, the theorem for the relationship between index pairs and Conley index enables one to predict them with acceptable accuracy. As a corollary, some results for Duffing oscillator and piecewise linear system are shown.
A Plethora of Nonlinear Dynamics Phenomena Observed in a Simple Cantilever Plate
Authors: Malatkar Pramod , Nayfeh Ali H.
Published: June 2008

An experimental study of the response of a rectangular, aluminum cantilever plate under transverse harmonic excitation is presented. Three test sequences, each involving a frequency sweep around a particular natural frequency of the plate and a different amplitude of base excitation, were performed. A couple of interesting nonlinear dynamics phenomena presented themselves in every test sequence. These phenomena include two-to-one and three-to-one internal resonances, external combination resonance, energy transfer between widely spaced modes, period-doubled motions, and chaos. In addition, the influence of the excitation amplitude on the energy transfer between widely spaced modes via modulation was also analyzed. It was found experimentally that the amount of energy transfer between the high- and low-frequency modes is strongly dependent on the closeness of the modulation frequency to the natural frequency of the low-frequency mode. If the modulation frequency is close to the low-mode frequency, then the amplitude of the low-mode response is large, otherwise it is small.
Colacogloea: a new genus in the auricularioid Heterobasidiomycetes
Authors: Oberwinkler Franz , Bauer Robert , Bandoni Robert J.
Published: June 2008

A new genus, Colacogloea, is described in the auricularioid Heterobasidiomycetes having simple septal pores. The genus is based on Platygloea peniophorae, a mycoparasite of some Aphyllophorales species. It is a segregate from the heterogeneous Platygloea s.l. The most important distinguishing features of Colacogloea are (i) the frequently simultaneous presence of basidial and conidial stages, (ii) a dimorphic life cycle including a yeast phase, (iii) mycoparasitism by colacosomes, (iv) simple septal pores with rounded margins, but without associated electron-opaque bandings and globules, and (v) aseptate basidiospores. Key words: Heterobasidiomycetes, Platygloea, Colacogloea peniophorae, mycoparasitism, colacosomes.
In vitro mycorrhization of Casuarina and Allocasuarina species by Pisolithus isolates
Authors: Thoen Daniel , Sougoufara Bassirou , Dommergues Yvon
Published: June 2008

Five Casuarina species and five Allocasuarina species were inoculated in vitro with three isolates of Pisolithus sp. (Ors.X004 and Ors.7870 from Senegal, PR86 from Australia) to test their ability to form ectomycorrhizas. The mycorrhiza-forming ability varied between fungal isolates. The greatest differences occurred between Casuarina and Allocasuarina species. On Casuarina species, Pisolithus isolates formed only a fungal sheath. However, Ors.X004 induced well-developed ectomycorrhizas on Casuarina equisetifolia, whereas PR86 failed to form any fungal sheath on Casuarina cunninghamiana. On Allocasuarina species, Pisolithus isolates formed generally well-developed ectomycorrhizas. In addition, isolates Ors.7870 and PR86 invaded the cortical cells of Allocasuarina luehmannii and Allocasuarina decaisneana, respectively, thus forming ectendomycorrhizas. Epidermal cells of both Casuarina and Allocasuarina mycorrhizas showed tannin deposits. In fully developed ectomycorrhizas, the epidermal cells were radially elongated and the Hartig net never developed beyond the epidermal cells. In general, the ability to form ectomycorrhizas was more common with the genus Allocasuarina than the genus Casuarina.Key words: Casuarina, Allocasuarina, Pisolithus, ectomycorrhizas.
Aseptic germination of oospores of Phytophthora palmivora
Authors: Sharma Navin
Published: June 2008

Oospores of Phytophthora palmivora were harvested from pairings of isolates of A1 and A2 mating types. The oospores were subjected to sonication and treatment with hemicellulase and cellulase before plating onto agar medium. After incubation at 20 °C, germination of the oospores was observed as the emergence of germ tubes which terminated in germ sporangia. The number of oospores that germinated from any pairing was raised by exposing the oospores to a temperature of 40 °C during the enzyme treatment and allowing a maturation period of the oospores of at least 4 weeks. Oospore germination was depressed by chilling to −12 °C during the enzyme treatment. The addition of an extract from papaya foliage did not significantly affect the frequency of oospore germination. Following the techniques described in this study, sexual progeny, freed from contamination by alien organisms or vegetative hyphae of the parent isolates, can be reliably obtained. Key words: Phytophthora palmivora, oospore, germination.
The development of the central cell of Brassica campestris prior to fertilization
Authors: Sumner M. J. , Caeseele L. van
Published: June 2008

The development of the central cell of Brassica campestris cv. Candle (canola-rapeseed) was examined using techniques of light and electron microscopy and cytochemistry. The mature central cell is devoid of the large central vacuole characteristic of the early cellular stage of megagametophyte development. Prior to anthesis, cell wall projections, of the transfer cell type, develop on the lateral wall of the central cell. These central cell wall projections extend from the midregion of the megagametophyte to the egg apparatus and are immediately adjacent to the starch-containing region of the inner and outer integuments. The cell wall projections are periodic acid – thiocarbohydrazide – silver proteinate positive as are the contents of dictyosome vesicles that appear to contribute to their formation. Mitochondria are associated with the wall projections as is a network of central cell endoplasmic reticulum that extends from the wall projections to the egg apparatus. Microtubules are associated with the migrating chalazal polar nucleus. The two polar nuclei partially fuse prior to double fertilization, united by nuclear bridges and endoplasmic reticulum interconnections. Proplastids are a characteristic feature of the immature cellular megagametophyte. By anthesis, the proplastids of the mature central cell develop into chloroplasts with stacked thylakoids and starch deposits. Microbodies are frequently found associated with lipid bodies, and polysomes with the endoplasmic reticulum of the mature central cell. Key words: Brassica, central cell, megagametophyte, ovule, transfer cell.
Stimulation of DNA synthesis and DNA polymerase activity by benzyladenine during early germination of maize axes
Authors: Vázquez-Ramos Jorge M. , Jiménez Jorge Reyes
Published: June 2008

Benzyladenine, a synthetic cytokinin, stimulates DNA synthesis during early germination of maize. A peak of stimulation is observed at 6 h in the period of 0–9 h of imbibition of embryo axes. Stimulation of DNA synthesis by the phytoregulator is dependent on RNA and (or) protein synthesis, since α-amanitin and cycloheximide inhibit such stimulation. Although DNA polymerase activity is stimulated by incubation of axes in the presence of benzyladenine, enzyme amount is apparently not increased. An enzyme located in the nuclei seems to be preferentially stimulated, and studies with specific inhibitors for polymerases and use of different templates suggest this enzyme could be of type γ. The nature of the mechanism of stimulation of DNA synthesis is discussed. Key words: benzyladenine, DNA synthesis, DNA polymerase, maize, germination.
Enzyme electromorph variation in the lichen family Umbilicariaceae: within-stand polymorphism in umbilicate lichens of eastern Canada
Authors: Hageman C. , Fahselt D.
Published: June 2008

This is the first intensive study in which many populations of several lichen species were examined using isoelectric focusing and specific staining to investigate levels of enzyme variability. Enzyme profiles were produced for 48 stands representing the following eastern Canadian species of umbilicate lichens, three of which were mainly apotheciate and three of which were sterile: Lasallia papulosa, Umbilicaria deusta, U. hirsuta, U. mammulata, U. muhlenbergii, and U. vellea. Interthalline variation in electromorph patterns was evident within all 48 stands examined, both sexual and sterile, and levels of variability were generally no higher when apothecia were present. In attempting to characterize any taxon electrophoretically it is thus critical to understand the nature of this variability. Phenomena such as somatic mutations or fusions may contribute to the maintenance of genetic variation in those lichens that have lost the ability to produce meiospores. Key words: lichen, population, variation, enzyme, electromorph, Umbilicaria.
Nitrogen source effects on Al toxicity in nonmycorrhizal and mycorrhizal pitch pine (Pinus rigida) seedlings. I. Growth and nutrition
Authors: Cumming Jonathan R. , Weinstein Leonard H.
Published: June 2008

Previous studies indicated that the association of Pisolithus tinctorius with pitch pine (Pinus rigida) seedling roots prevented Al toxicity from developing when seedlings were exposed to 200 μM Al in sand culture. The ectomycorrhizal fungus reduced seedling Al uptake and maintained P nutrition when seedlings were cultured on one-quarter strength Johnson's solution containing 3.5 and 0.5 mM [Formula: see text] and [Formula: see text], respectively. To broaden the scope of these findings, nonmycorrhizal and mycorrhizal seedlings were grown on one-quarter strength Johnson's solution modified to contain [Formula: see text], NH4NO3, or [Formula: see text]. Seedlings were exposed to 0 or 200 μM Al for 6 weeks. Reductions in seedling height growth rate and final shoot weight in response to Al occurred in nonmycorrhizal seedlings grown with [Formula: see text]. Root weights were consistently reduced by Al under all N-source combinations. Increasing proportions of [Formula: see text], in the nutrient solution increased cation accumulation in roots and shoots and depressed tissue anion concentrations. The coprecipitation of Al and Pi in roots of Al-treated seedlings further limited P availability in this treatment. Mycorrhizal infection maintained growth and foliar P levels under Al exposure, suggesting that Al-induced P limitation was a critical factor in nonmycorrhizal seedlings grown on primarily [Formula: see text]-based nutrient solutions. Key words: Pinus rigida, ectomycorrhizal, aluminium toxicity, nitrogen source.
Nitrogen source effects on Al toxicity in nonmycorrhizal and mycorrhizal pitch pine (Pinus rigida) seedlings. II. Nitrate reduction and NO3− uptake
Authors: Cumming Jonathan R.
Published: June 2008

Nitrogen source utilization, mediated by the ectomycorrhizal symbiont Pisolithus tinctorius, may modulate Al toxicity in pitch pine (Pinus rigida) seedlings. Nitrate reduction, occurring primarily in the roots of pitch pine seedlings, represents a critical metabolic pathway that may be directly sensitive to Al or indirectly affected by changes in NO3− availability associated with Al exposure or mycorrhizal infection. To investigate these possibilities, pitch pine seedlings were grown in sand culture with NO3−, NH4NO3, or NH4+ and exposed to 0 or 200 μM Al for 6 weeks. Foliar N concentrations, root nitrate reductase (NR) activity, and Al inhibition of NR activity were highly dependent on the proportion of NO3− of the nutrient solution. The association of Pisolithus tinctorius with seedling roots reduced both root and foliar NR activity compared with non-inoculated controls, suggesting that NO3− uptake and translocation to foliage was reduced by the symbiont. This was confirmed by using 36ClO3− to measure unidirectional plasma membrane NO3− fluxes. Mycorrhizal root tips absorbed 50% less NO3− than nonmycorrhizal root tips. Preferential use of NH4+ by ectomycorrhizal roots may thus result in reduced movement of Al into root tissue and amelioration of Al toxicity. Key words: Pinus rigida, ectomycorrhizae, aluminum toxicity, nitrogen source.
Hackberry (Celtis occidentalis) at the northeastern limit of its distribution in North America: population structure and radial growth patterns
Authors: Houle Gilles , Bouchard France
Published: June 2008

Populations established on the limits of the geographical distribution of a species often differ in their demographic characteristics and in the growth pattern of their individuals from more centrally located populations. We studied the age structure and the radial growth patterns of hackberry populations (Celtis occidentalis L.) at the northeastern limit of the species distribution in North America, at Lake St. Paul, Quebec, Canada. There are two populations of hackberry in the area: the first one occupies an isthmus separating two small lakes (Geese Lake population), and the second one can be found on the upper section of a floodplain along a shallow river (Godefroy River population). The oldest hackberry trees on the Geese Lake site were 54 years old, but those on the Godefroy River site were much older, i.e., 114 years old. The annual ring width patterns revealed two episodes of accelerated growth corresponding to two periods of release from suppression as a result of disturbance. These periods of release occurred concurrently on both study sites, but release was more evident on the Geese Lake site. A progressive decrease in growth from 1960 to 1974 might have resulted from canopy closure following disturbance events. Radial growth rates on the study sites (1.90 and 1.13 mm/year for the Geese Lake and the Godefroy River populations, respectively) were similar to those reported for populations located further south (e.g., 1.70 mm/year in Illinois). We propose that the Geese Lake population recently (≈ 1930) got established as an outpost of the Godefroy River population. The establishment would have occurred at the time when Dutch elm disease was first introduced in North America. It seems likely that hackberry extended its populations during that period into areas where previously closed forest canopy became opened. Key words: dendrochronology, Dutch elm disease, hackberry, Lake St. Paul, rare plants, release.
Temperature dependence of dielectric properties of moist soils
Authors: Jaganathan Arun P. , Allouche Erez N.
Published: June 2008

Heating of soil using microwaves has several applications in geosciences, including soil remediation, neutralization of land mines, and microwave-enhanced thermography. Numerical simulation of microwave-induced soil heating processes requires knowledge of the electrical properties of the soil as a function of temperature, moisture content, and frequency of the electromagnetic wave. This paper describes a semi-empirical model for calculating the dielectric properties of moist soils at various moisture contents, temperatures, and frequencies (within the band of 1–10 GHz). The proposed model is an extension of the generalized refractive mixing dielectric model (GRMDM) for moist soils. Predictions of the proposed model were found to be in good agreement with experimental data reported in the literature. Results of a parametric study suggest that the temperature dependency of the dielectric properties of moist sand is more pronounced for higher volumetric moisture contents.
Estimating compaction behavior of fine-grained soils based on compaction energy
Authors: Sivrikaya Osman , Togrol Ergun , Kayadelen Cafer
Published: June 2008

For successful designs of geotechnical structures, rational determination of the engineering properties of soils is an important process. In this context, compaction parameters, maximum dry unit weight (γdmax), and optimum water content (wopt) are required to be determined at various compaction energies. This paper proposes correlation equations that relate γdmax and wopt obtained from standard Proctor (SP) and modified Proctor (MP) tests to the index properties. To develop accurate relations, the data collected from the literature and the authors’ own database have been used. It has been found that while wopt has the best correlation with plastic limit (wp), γdmax can be estimated more accurately from wopt than it can from wp. In addition, the empirical methods including compaction energy (E) are described for estimating wopt and γdmax of fine-grained soils. The variables of the developed models for wopt and γdmax are wp, E, and wopt. It has been shown that the proposed correlations including the compaction energy will be useful for a preliminary design of a project where there is a financial constraint and limited time.
The hydrologic response of aquifers at surface-mine sites in western North Dakota
Authors: Moran Stephen R. , Cherry John A.
Published: June 2008

The excavation of mine pits in western North Dakota causes groundwater to flow laterally through the moderately to highly permeable fractured coal beds into the pits. Because of the low fracture-controlled storativity of the coal, the lateral flow results in rapid spread of a dewatered zone in the coal. The coal is generally overlain by saturated silty or clayey aquitards or fine sand that provide downward leakage to the coal. Existing analytical solutions for analysis of the problem of water-level decline and seepage flux are based on such extensive simplifying assumptions that they are a poor approximation of the field conditions. Numerical models for layered systems with transient saturated and unsaturated zones require efforts in analysis that are generally unwarranted relative to the nature of the field information. As an alternative to these approaches we applied a method based on existing analytical solutions with empirical adjustments to account for the effect of leakage. Results obtained using a programable pocket calculator indicating that, for areas for which mining is proposed, steady-state water levels in the coal will be rapidly attained as downward leakage through the overlying beds supplies all of the water maintaining the lateral flow regime in the coal.Predictions from analyses using representative values of hydraulic parameters for two mine sites indicate that significant declines in water levels adjacent to the mines will likely be restricted to within about 3 km of the highwall.
Effectiveness of seepage control elements for embankments on semipervious foundations
Authors: Lefebvre Guy , Lupien Claude , Pare J. Jacques , Tournier Jean-Pierre
Published: June 2008

Results of seepage analyses for two dams on semipervious foundations obtained with finite element techniques are presented in order to assess the relative effectiveness of seepage control elements in reducing the downstream exit gradient. After presenting results to illustrate the effect of permeability anisotropy, the effectivenesses of a downstream relief trench, an upstream impervious blanket, a partial cut-off, and a more pervious drain material are compared in terms of the factor of safety against piping at the downstream toe.
Heaving behaviour of soils in the step freezing mode
Authors: Penner Edward
Published: June 2008

Results are presented over a wide range of soil textures supporting the linear relation between the logarithm of frost heave rate and the cold-side temperature – overburden pressure ratio proposed by Penner and Ueda. The relation is simple to determine experimentally, permits heave predictions at various other temperature and pressure conditions for engineering purposes, and allows soil frost susceptibility comparisons to be made with the results determined by other laboratories.
On the consolidation of sedimenting clays
Authors: Koppula S. D. , Morgenstern N. R.
Published: June 2008

A comprehensive formulation for the estimation of excess pore pressures during consolidation, when sedimentation takes place, is presented. The development is based on the general nonlinear behaviour of the soil whose properties are assumed to vary with depth and time. Because finite strains entail large changes in soil properties, of which compressibility and permeability are the main factors, these properties are related to effective stress by power laws. By combining these with other assumptions made in the classical Terzaghi theory, together with the vertical equilibrium of the soil–water system including the self-weight of the soil, the equation governing the process of consolidation in a sedimenting clay was derived.The consolidation equation thus obtained is nonlinear. Previously published equations governing linear and nonlinear consolidation behaviour of clay soils may be derived from the general nonlinear equation. The data from the deltaic deposits of the continental shelf off Louisiana are studied and the results of applying the developed nonlinear equation to the history of these deposits agree well with the observations.
Landslides and surficial deposits in urban areas of British Columbia: A review
Authors: Evans S. G.
Published: June 2008

Landslides in surficial deposits occur commonly in the urban environment of British Columbia. Three groups of surficial materials are especially prone to slope failure. These are glaciomarine sediments, glaciolacustrine deposits, and glacial till that mantles steep mountain slopes. The geological and geotechnical characteristics of these three materials are examined and discussed.The sensitivity, metastable fabric, and geological heterogeneity of glaciomarine sediments control their landslide behaviour. A regional variation in glaciolacustrine deposits is suggested. The Southern Interior and Columbia deposits are dominated by silt varves and those of the Northern Interior by clay varves. The silts are sensitive and collapsible under certain moisture and loading conditions. The effect of urbanisation on these silts in the semiarid Southern Interior is considerable. The retrogressive behaviour of slides in silts and clays in urban areas is also examined.Open-slope and channelled debris flows in till mantles are discussed. They occur mainly on steep slopes in the Coast Ranges as a response to heavy, relief-induced rainfall. The effect of urbanization on slope stability is also discussed.
A landslide in glacial lake clays in central British Columbia
Authors: Thomson S. , Mekechuk John
Published: June 2008

The CNR line in central British Columbia was built across an old landslide along the valley of the Fraser River near the city of McBride. Failure occurred shortly after the completion of construction in 1914 and the railway was relocated just off the slide area by construction of a timber pile trestle. In 1927 the railway was moved back to its original alignment by rebuilding the old embankment on the old slide area.During the waning phases of glaciation, sedimentation in glacial lakes in the Rocky Mountain trench resulted in thick, laminated deposits of silts and silty clays that cover the outer edges of the alluvial fans along the mountain front.Starting in late 1974 and continuing through 1976 track subsidence took place that required a series of track raises. In 1977 a track offset of 15 m was completed and a site investigation was carried out that provided data for the design of a stabilizing berm.It is interesting to note that, for a period of 47 years, a sidehill fill in the scarp area of a slide performed satisfactorily. Re-initiation of the landslide is considered to be due to an increase in pore pressure within the slide mass. The ingress of water to the slide area is vertical infiltration into the alluvial fans and thence laterally into the slide mass. There has been an increase in the average annual precipitation in east central British Columbia and the cumulative effects of this precipitation resulted in the slope failure of 1974.
Study of beam–soil interaction using finite element and centrifugal models
Authors: Leshchinsky D. , Frydman S. , Baker R.
Published: June 2008

A comparison is presented between the results of centrifugal model tests and finite element analyses for the problem of load transfer to a rigid tie beam buried in sand. The finite element program utilized a nonlinear elastic (hyperbolic) soil constitutive relation, obtained from tests in simple shear. It was found that, for this particular type of problem, the finite element solution may reasonably represent the interaction between the beam and the surrounding soil. It is pointed out that this agreement does not ensure that the use of such finite element analyses would be justified in problems involving rotation of principal directions, and local unloading.The effect of compaction of the fill was investigated, and it was found that compaction leads to an increase in load transferred to the beam above that which is due to density effects alone.Key words: finite elements, centrifuge, models, soil–structure interaction, buried structures.
A case for the extension of the unified soil classification system
Authors: Mirza Cameran
Published: June 2008

Growing inefficiences in the communication of geotechnical data relevant to site subsoil conditions may be one cause of the growth in litigation involving the geotechnical profession. In order to improve intra and interdisciplinary communication, a case is presented for the extension of the unified soil classification system to include the geological origin of the materials being classified. The proposed extension is simple, comprising lower and upper case letters as suffixes to the symbols already in use. It is thought that the adoption of this extension will put the emphasis back on geology in geotechnical practice.
The influence of lateral spreading on settlements beneath a fill
Authors: Crawford C.B. , Jitno H. , Byrne P.M.
Published: June 2008

The discrepancy between calculated consolidation settlements and measured settlements under a 3.8 m high section of an earth embankment is investigated in this paper. A conventional one-dimensional analysis underestimated the observed settlement by 40%. A two-dimensional finite-element analysis was carried out to assess the effects of lateral spreading on vertical movements, and the results were in close agreement with the measured values. Key words : case history, consolidation, finite element analysis, settlement.
Electrical strengthening of clays by dielectrophoresis
Authors: Lo K.Y. , Shang J.Q. , Inculet I.I.
Published: June 2008

The theory of dielectrophoresis in clay–water–electrolyte systems is developed in this paper. Dielectrophoresis is the motion of particles generated by a nonuniform electric field. The dielectrophoretic forces on clay particles are determined by the effective polarizability and configuration of the nonuniform electric field. In most clay–water–electrolyte systems, including natural clays, the dielectrophoretic forces are directed towards the lower field intensity, determined by the negative polarizability. In the experimental program, an ac voltage of 60 Hz and 15 kV was applied through insulated electrodes on block samples of Leda clay for 28 days. The relationship between the soil undrained shear strength after treatment and the distribution of electric field provides direct experimental support for the theory developed. Under three electrical-field configurations, the overall shear strengths increased up to 44.0%, concurrent with significant reduction of sensitivity. The improvement of soil properties was also reflected as increases of preconsolidation pressure and shearing resistance in terms of effective stresses. The electrochemical reactions associated with electric current were minimized by insulation to the electrodes. Key words : dielectrophoresis, electrokinetics, soil improvement, sensitive clay, shear strength.
Finite-element analysis of deep excavation in layered sandy and clayey soil deposits
Authors: Ou Chang-Yu , Lai Ching-Her
Published: June 2008

This paper presents an application of finite-element analysis to deep excavation in layered sandy and clayey soil deposits using a combination of the hyperbolic and the Modified Cam-clay models. In the analysis, the drained behavior of cohesionless soil and the undrained behavior of cohesive soil were simulated using the hyperbolic and Modified Cam-clay models, respectively. A rational procedure for determining soil parameters for each of the models was established. A simulation of the dewatering process during excavation was proposed. The analytical procedure was confirmed through an analysis of three actual excavation cases. Finally, analyses considering pore-water pressure dissipation during the actual elapsed time for each construction phase were carried out. The results indicate that the calculated displacement of a retaining wall during excavation is smaller than that given by undrained analysis. It was thought that some degree of pore-water pressure dissipation actually occurs during the intermediate excavation stages. This results in a decrease in the final deformation of the wall and ground.-surface settlement than would be predicted by undrained analysis. Key words : finite-element analysis, deep excavation, hyperbolic model, Cam-clay model.
On the imaging of stress changes in particulate media: an experimental study
Authors: Santamarina J.C. , Potts B.
Published: June 2008

The stiffness of soils depends on the state of stress. Therefore, the velocity of wave propagation can be used to assess the state of stress and its changes. Indeed, given sufficient data, measurements can be inverted to produce a tomographic image of the stress field. A preliminary study of this approach was conducted with simulated data and is summarized briefly. Results of an experimental study are then presented. Three common geotechnical systems were tested: a footing, a moving surface load, and a retaining wall. Calculated velocity changes are compared with predicted velocity changes, with stress changes being estimated by classical analytical solutions. Good agreement is found in the three cases. The need for accuracy in travel-time measurements, difficulties in tomographic imaging, and the propagation of uncertainty from inverted velocities to stresses are discussed. Key words : geophysical methods, tomography, wave propagation, stress, retaining wall, footings.
A re-examination of the strain field around a simple pile
Authors: Silvestri V. , Tabib C.
Published: June 2008

This technical note describes the analysis of the strain field around a simple pile. The analytical solution is obtained by using a spherical coordinate system of reference. It is shown that the expressions for the various strains are very simple. Streaming motions and octahedral shear strain contours are presented in graphical forms. Key words : simple pile, streaming motion, strain field.
Titania encapsulation of flat gold nanoparticles — A simple route to Au@TiO2 core-shell nanosheets
Authors: McDowell Jeffrey J , McKelvey J Ian , Richard Laura A , Banks Jeffrey T
Published: June 2008

We report the attachment of a uniform coating of a thin layer of amorphous TiO2 to flat gold nanoparticles via a simple sol–gel process. Coatings of variable thickness ranging from 5 to 100 nm have been produced. Activation of the Au particles was unnecessary. However, the ability to coat the flat gold nanoparticles was dependent on the method used for their synthesis. In addition, the amorphous TiO2 shell was hydrothermally treated to induce crystallization to the anatase polymorph. The desired nanocrystalline anatase morphology was obtained by heating in water at 70 °C for 1 week. A similar result was also obtained when the material was heated to 130 °C for 5 min in a microwave reactor. These new Au@TiO2 nanosheets were characterized by TEM, EDX, and SAED.Key words: core-shell, titanium dioxide, anisotropic nanoparticles, semiconductor thin films, nanocomposite material.
QUINTESSENTIAL INFLATION FROM 5D WARPED PRODUCT SPACES ON A DYNAMICAL FOLIATION
Authors: DA SILVA LUCIO FABIO P. , AGUILAR JOSÉ EDGAR MADRIZ
Published: June 2008

Assuming the existence of a 5D purely kinetic scalar field on the class of warped product spaces we investigate the possibility of mimic both an inflationary and a quintessential scenarios on 4D hypersurfaces, by implementing a dynamical foliation on the fifth coordinate instead of a constant one. We obtain that an induced chaotic inflationary scenario with a geometrically induced scalar potential and an induced quasi-vacuum equation of state on 4D dynamical hypersurfaces is possible. While on a constant foliation, the universe can be considered as matter-dominated today, in a family of 4D dynamical hypersurfaces, the universe can be passing period of accelerated expansion with a deceleration parameter nearly -1. This effect of the dynamical foliation results negligible at the inflationary epoch allowing for a chaotic inflationary scenario and becomes considerable at the present epoch allowing a quintessential scenario.
OPEN INFLATIONARY UNIVERSES IN GAUSS–BONNET BRANE COSMOLOGY
Authors: DEL CAMPO SERGIO , HERRERA RAMÓN , SAAVEDRA JOEL
Published: June 2008

In this paper, we study a type of one-field approach for open inflationary universe scenario in the context of braneworld models with a Gauss–Bonnet correction term. For a one-bubble universe model, we determine and characterize the existence of the Coleman–De Lucia instanton together with the period of inflation after tunneling has occurred. Our results are compared with those analogous obtained when the usual Einstein Theory of Gravitation is used.
U-SPIN TESTS OF THE STANDARD MODEL AND NEW PHYSICS
Authors: NAGASHIMA MAKIKO , SZYNKMAN ALEJANDRO , LONDON DAVID
Published: June 2008

Within the standard model, a relation involving branching ratios and direct CP asymmetries holds for the B-decay pairs that are related by U-spin. The violation of this relation indicates new physics (NP). In this paper, we assume that the NP affects only the ΔS = 1 decays, and show that the NP operators are generally the same as those appearing in B → πK decays. The fit to the latest B → πK data shows that only one NP operator is sizeable. As a consequence, the relation is expected to be violated for only one decay pair: [Formula: see text] and [Formula: see text].
A NOTE ON THE QUANTUM OF TIME
Authors: ISIDRO JOSÉ M. , GONZÁLEZ-SANTANDER J. L. , FERNÁNDEZ DE CÓRDOBA P.
Published: June 2008

Quantum mechanics rests on the assumption that time is a classical variable. As such, classical time is assumed to be measurable with infinite accuracy. However, all real clocks are subject to quantum fluctuations, which leads to the existence of a nonzero uncertainty in the time variable. The existence of a quantum of time modifies the Heisenberg evolution equation for observables. Here we propose and analyse a generalisation of Heisenberg's equation for observables evolving in real time (the time variable measured by real clocks), that takes the existence of a quantum of time into account. This generalisation of Heisenberg's equation turns out to be a delay-differential equation.
Bone Marrow Subsets Differentiate into Endothelial Cells and Pericytes Contributing to Ewing's Tumor Vessels
Authors: Reddy Krishna , Zhou Zhichao , Schadler Keri , Jia Shu-Fang , Kleinerman Eugenie S.
Published: June 2008

Hematopoietic progenitor cells arising from bone marrow (BM) are known to contribute to the formation and expansion of tumor vasculature. However, whether different subsets of these cells have different roles in this process is unclear. To investigate the roles of BM-derived progenitor cell subpopulations in the formation of tumor vasculature in a Ewing's sarcoma model, we used a functional assay based on endothelial cell and pericyte differentiation in vivo. Fluorescence-activated cell sorting of human cord blood/BM or mouse BM from green fluorescent protein transgenic mice was used to isolate human CD34+/CD38−, CD34+/CD45+, and CD34−/CD45+ cells and mouse Sca1+/Gr1+, Sca1−/Gr1+, VEGFR1+, and VEGFR2+ cells. Each of these progenitor subpopulations was separately injected intravenously into nude mice bearing Ewing's sarcoma tumors. Tumors were resected 1 week later and analyzed using immunohistochemistry and confocal microscopy for the presence of migrated progenitor cells expressing endothelial, pericyte, or inflammatory cell surface markers. We showed two distinct patterns of stem cell infiltration. Human CD34+/CD45+ and CD34+/CD38− and murine VEGFR2+ and Sca1+/Gr1+ cells migrated to Ewing's tumors, colocalized with the tumor vascular network, and differentiated into cells expressing either endothelial markers (mouse CD31 or human vascular endothelial cadherin) or the pericyte markers desmin and α-smooth muscle actin. By contrast, human CD34−/CD45+ and mouse Sca1−/Gr1+ cells migrated predominantly to sites outside of the tumor vasculature and differentiated into monocytes/macrophages expressing F4/80 or CD14. Our data indicate that only specific BM stem/progenitor subpopulations participate in Ewing's sarcoma tumor vasculogenesis. (Mol Cancer Res 2008;6(6):929–36)
Zinc α2-Glycoprotein: A Multidisciplinary Protein
Authors: Hassan Md. Imtaiyaz , Waheed Abdul , Yadav Savita , Singh Tej P. , Ahmad Faizan
Published: June 2008

Zinc α2-glycoprotein (ZAG) is a protein of interest because of its ability to play many important functions in the human body, including fertilization and lipid mobilization. After the discovery of this molecule, during the last 5 decades, various studies have been documented on its structure and functions, but still, it is considered as a protein with an unknown function. Its expression is regulated by glucocorticoids. Due to its high sequence homology with lipid-mobilizing factor and high expression in cancer cachexia, it is considered as a novel adipokine. On the other hand, structural organization and fold is similar to MHC class I antigen-presenting molecule; hence, ZAG may have a role in the expression of the immune response. The function of ZAG under physiologic and cancerous conditions remains mysterious but is considered as a tumor biomarker for various carcinomas. There are several unrelated functions that are attributed to ZAG, such as RNase activity, regulation of melanin production, hindering tumor proliferation, and transport of nephritic by-products. This article deals with the discussion of the major aspects of ZAG from its gene structure to function and metabolism. (Mol Cancer Res 2008;6(6):892–906)
Usefulness of Pancreatic Duct Stenting prior to Surgery as a Guide to Decide the Feasibility of Limited Pancreatic Resection
Authors: Okamoto Tomoyoshi , Gocho Takeshi , Futagawa Yasuro , Fujioka Shuichi , Yanaga Katsuhiko , Ikeda Keiichi , Kakutani Hiroshi , Tajiri Hisao
Published: June 2008

Background/Aims: The purpose of this study was to introduce our procedure of limited pancreatic resection with preoperative pancreatic duct stenting to prevent complications. Patients and Methods: Subjects comprised 6 patients with neoplasm who underwent preoperative pancreatic stenting. Pancreatic stents were placed within 7 days before elective surgery. After intraoperative ultrasonography, the relationship between the main pancreatic duct (MPD) and the lesion was confirmed by measuring the distance. Partial resection was surrendered if a sufficient margin of excised tumor was not obtained or injury to the MPD was likely to occur. Branches of pancreatic duct recognized were ligated as much as possible. Results: Mild pancreatitis was present after stenting in 2 patients. Three patients actually underwent partial resection. In patients with partial resection, enhanced visualization of the MPD was useful for deciding the operative procedure and prevented iatrogenic injury to the MPD during dissection. Conclusions: Pancreatic duct stenting prior to pancreatic surgery seems useful as a guide for determining the feasibility of limited pancreatic resection and to prevent missing injury to the MPD.
Pre-Operative Staging with Positron Emission Tomography in Patients with Pelvic Recurrence of Rectal Cancer
Authors: Faneyte Ian F. , Dresen Raphaëla C. , Edelbroek Michela A.L. , Nieuwenhuijzen Grard A.P. , Rutten Harm J.T.
Published: June 2008

Background/Aim:The treatment of pelvic recurrences of rectal cancer is primarily surgical. The substantial morbidity and mortality of such resections warrant stringent patient selection. Recent literature reports PET to be of additional value to CT for the detection of metastases in colorectal cancer patients. We studied the clinical impact of PET in pelvic rectal cancer recurrence. Methods:PET findings in 37 pelvic recurrences of rectal cancer were evaluated retrospectively. Comparison was made to CT and MRI findings. It was analyzed whether PET had been decisive in clinical decision making or could have been so. Results:Thirty-two patients had 37 rectal cancer recurrences. PET differed from conventional imaging in 13 cases (35%): seven PET scans showed lesions that were not seen with CT or MRI. PET scans were negative in six lesions detected by CT or MRI. PET alone changed management in five recurrences (14%). Four PET scans were false-positive; this had clinical implications in 2 patients. Conclusion:In a selected population with pelvic rectal cancer recurrences, PET had additional value to conventional imaging, mainly in detecting lymph node metastases. PET findings thus had a significant impact on selection of patients for curative surgery.