bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of Cytomegalovirus (CMV) DNA in EDTA Whole-Blood Samples: Evaluation of the Quantitative
artus
CMV LightCycler PCR Kit in Conjunction with Automated Sample Preparation
Authors: Michelin Birgit D. A. , Hadžisejdić Ita , Bozic Michael , Grahovac Maja , Hess Markus , Grahovac Blaženka , Marth Egon , Kessler Harald H.
Published: February 2008

Whole blood has been found to be a reliable matrix for the detection and quantitation of cytomegalovirus (CMV) DNA. In this study, the performance of the
artus
CMV LightCycler (LC) PCR kit in conjunction with automated sample preparation on a BioRobot EZ1 workstation was evaluated. The accuracy, linearity, analytical sensitivity, and inter- and intra-assay variations were determined. A total of 102 clinical EDTA whole-blood samples were investigated, and results were compared with those obtained with the in vitro diagnostics (IVD)/Conformité Européene (CE)-labeled CMV HHV6,7,8 R-gene quantification kit. When the accuracy of the new kit was tested, seven of eight results were found to be within ±0.5 log
10
unit of the expected panel results. Determination of linearity resulted in a quasilinear curve over more than 5 log units. The lower limit of detection of the assay was determined to be 139 copies/ml in EDTA whole blood. The interassay variation ranged from 15 to 58%, and the intra-assay variation ranged from 7 to 35%. When clinical samples were tested and the results were compared with those of the routinely used IVD/CE-labeled assay, 53 samples tested positive and 13 samples tested negative by both of the assays. One sample was found to be positive with the
artus
CMV LC PCR kit only, and 35 samples tested positive with the routinely used assay only. The majority of discrepant results were found with low-titer samples. In conclusion, use of the
artus
CMV LC PCR kit in conjunction with automated sample preparation on the BioRobot EZ1 workstation may be suitable for the detection and quantitation of CMV DNA in EDTA whole blood in the routine low-throughput laboratory; however, low-positive results may be missed by this assay.
Clinical Evaluation of NucliSENS Magnetic Extraction and NucliSENS Analyte-Specific Reagents for Real-Time Detection of Human Metapneumovirus in Pediatric Respiratory Specimens
Authors: Ginocchio Christine C. , Manji Ryhana , Lotlikar Madhavi , Zhang Fan
Published: February 2008

In this study, we evaluated the NucliSENS miniMAG (MM) and easyMAG (EM) nucleic acid extraction platforms (bioMérieux, Durham, NC) in combination with the NucliSENS EasyQ basic kit and analyte-specific reagents (ASRs) (bioMérieux) for the detection of human metapneumovirus (hMPV) in respiratory samples. Total nucleic acids from pediatric clinical samples (
n
= 653) and an hMPV-specific inhibition control (h-IC) were coextracted using the MM and/or the EM. Nucleic acid sequence-based amplification and real-time molecular beacon detection of hMPV were performed using a NucliSENS EasyQ analyzer (bioMérieux). Positive results were confirmed using an in-house-validated reverse transcriptase PCR ASR-based assay. The inclusion of the h-IC monitored the entire process, including the efficiency of nucleic acid extraction, amplification, and detection. The percentages of samples with inhibited amplification of the h-IC after initial NA extraction by EM and MM were 1.88% and 3.17%, respectively. After reprocessing of a new aliquot, the final h-IC inhibition rates were 0% (EM) and 1.06% (MM). The limit of detection of the assay was between 2 (EM extraction) and 10 (MM extraction) RNA copies/reaction, and specificity was 100% when testing viral respiratory isolates and clinical samples. hMPV was detected in 5.6% of pediatric samples tested and was also detected in three coinfections with respiratory syncytial virus (RSV). hMPV was the second most frequently detected respiratory virus in children of 0 to 2 years of age, after RSV. In summary, NucliSENS extraction and ASRs provided a sensitive and specific method for the detection of hMPV in respiratory samples.
Validation of the BrockTB Stat-Pak Assay for Detection of Tuberculosis in Eurasian Badgers (
Meles meles
) and Influence of Disease Severity on Diagnostic Accuracy
Authors: Chambers Mark A. , Crawshaw Tim , Waterhouse Sue , Delahay Richard , Hewinson R. Glyn , Lyashchenko Konstantin P.
Published: February 2008

A lateral-flow immunoassay (BrockTB Stat-Pak) for detecting tuberculosis in Eurasian badgers was 49% sensitive and 93% specific against culture for
M. bovis
(
n
= 1,464) at necropsy. However, the sensitivity was significantly higher (66 to 78%) in animals with more severe tuberculosis, indicating that the BrockTB Stat-Pak may be useful for the detection of badgers with the greatest risk of transmitting disease.
High-Resolution Genotyping of
Campylobacter
Species by Use of PCR and High-Throughput Mass Spectrometry
Authors: Hannis James C. , Manalili Sheri M. , Hall Thomas A. , Ranken Raymond , White Neill , Sampath Rangarajan , Blyn Lawrence B. , Ecker David J. , Mandrell Robert E. , Fagerquist Clifton K. , Bates Anna H. , Miller William G. , Hofstadler Steven A.
Published: February 2008

In this work we report on a high-throughput mass spectrometry-based technique for the rapid high-resolution identification of
Campylobacter jejuni
strain types. This method readily distinguishes
C. jejuni
from
C. coli
, has a resolving power comparable to that of multilocus sequence typing (MLST), is applicable to mixtures, and is highly automated. The strain typing approach is based on high-performance mass spectrometry, which “weighs” PCR amplicons with enough mass accuracy to unambiguously determine the base composition of each amplicon (i.e., the numbers of A's, G's, C's, and T's). Amplicons are derived from PCR primers which amplify short (<140-bp) regions of the housekeeping genes used by conventional MLST strategies. The results obtained with a challenge panel that comprised 25 strain types of
C. jejuni
and 25 strain types of
C. coli
are presented. These samples were parsed and resolved with demonstrated sensitivity down to 10 genomes/PCR from pure isolates.
New Immuno-PCR Assay for Detection of Low Concentrations of Shiga Toxin 2 and Its Variants
Authors: Zhang Wenlan , Bielaszewska Martina , Pulz Matthias , Becker Karsten , Friedrich Alexander W. , Karch Helge , Kuczius Thorsten
Published: February 2008

Shiga toxin (Stx)-producing
Escherichia coli
(STEC) strains secrete toxins that are major virulence factors and diagnostic targets, but some STEC strains secrete Stx in amounts that cannot be detected using conventional cell cytotoxicity or immunological assays. Therefore, there is an urgent need for more-sensitive Stx detection methods. We describe the development of an assay that can detect low concentrations of Stx2 and its variants. An immuno-PCR Stx2 assay was developed based on an enzyme immunoassay (EIA) combining antibody capture and DNA amplification to increase the signal. The immuno-PCR assay detected 10 pg/ml of purified Stx2, compared to 1 ng/ml Stx2 detected by commercial EIA. Consequently, immuno-PCR detected Stx2 and its variants in STEC strains that produce the toxins at levels that are nondetectable by using the EIA, as well as the Stx2 in EIA-negative enriched stool cultures from patients. Our data demonstrate that the immuno-PCR developed here is a highly sensitive and specific method for the detection of trace amounts of Stx2 and Stx2 variants. It is therefore suitable for use by clinical microbiological laboratories to improve the toxin detection in clinical samples.
Emergence of G12 Rotavirus Strains in Delhi, India, in 2000 to 2007
Authors: Sharma S. , Ray P. , Gentsch J. R. , Glass R. I. , Kalra V. , Bhan M. K.
Published: February 2008

The prospect that rotavirus diarrhea in children may soon be prevented by vaccines has placed a new priority on understanding the diversity of rotavirus strains and the mechanism by which these strains evolve over time. We have characterized a total of 465 rotavirus strains collected in North India from 2000 to 2007 for G and P types by reverse transcription-PCR and sequencing. The novel G12 rotavirus strains recently detected in other countries were first detected in India in 2001 and have emerged as the predominant strains in Delhi, India, during 2005 to 2007. While the VP7 sequence was highly homologous among G12 strains isolated in Delhi, suggesting recent emergence from a common ancestor, the strains had a diverse constellation of other gene segments, demonstrating substantial reassortment. For the entire period, the common rotavirus G types G1 (26%), G2 (25%), and G9 (14%) comprised 65% of the strains, and common P types, P[4] (19%), P[6] (22%), and P[8] (35%), comprised 76% of the total P types. Of note, we detected a high percentage of unusual (17%) strains and fecal specimens with mixed (12% G and 15% P) rotavirus infections having a variety of genomic constellations. For the first time, we identified two novel rotavirus strains with unusual G/P combinations, G2P[11] and G3P[11], in patients with diarrhea. The study highlights the great diversity among rotaviruses isolated from Indian children, the opportunity for genetic reassortment between strains, and the emergence of a novel G12 strain in our country. Due to the demonstrated effect of antigenic diversity on rotavirus vaccines, it will be important to continue careful monitoring of these strains as rotavirus vaccine programs are implemented in India.
Vaccine Protection by Live, Attenuated Simian Immunodeficiency Virus in the Absence of High-Titer Antibody Responses and High-Frequency Cellular Immune Responses Measurable in the Periphery
Authors: Mansfield Keith , Lang Sabine M. , Gauduin Marie-Claire , Sanford Hannah B. , Lifson Jeffrey D. , Johnson R. Paul , Desrosiers Ronald C.
Published: February 2008

An attenuated derivative of simian immunodeficiency virus strain 239 deleted of V1-V2 sequences in the envelope gene (SIV239ΔV1-V2) was used for vaccine/challenge experiments in rhesus monkeys. Peak levels of viral RNA in plasma of 10
4
to 10
6.5
copies/ml in the weeks immediately following inoculation of SIV239ΔV1-V2 were 10- to 1,000-fold lower than those observed with parental SIV239 (∼10
7.3
copies/ml). Viral loads consistently remained below 200 copies/ml after 8 weeks of infection by the attenuated SIV239ΔV1-V2 strain. Viral localization experiments revealed large numbers of infected cells within organized lymphoid nodules of the colonic gut-associated lymphoid tissue at 14 days; double-labeling experiments indicated that 93.5% of the virally infected cells at this site were positive for the macrophage marker CD68. Cellular and humoral immune responses measured principally by gamma interferon enzyme-linked immunospot and neutralization assays were variable in the five vaccinated monkeys. One monkey had responses in these assays comparable to or only slightly less than those observed in monkeys infected with parental, wild-type SIV239. Four of the vaccinated monkeys, however, had low, marginal, or undetectable responses in these same assays. These five vaccinated monkeys and three naïve control monkeys were subsequently challenged intravenously with wild-type SIV239. Three of the five vaccinated monkeys, including the one with strong anti-SIV immune responses, were strongly protected against the challenge on the basis of viral load measurements. Surprisingly, two of the vaccinated monkeys were strongly protected against SIV239 challenge despite the presence of cellular anti-SIV responses of low-frequency and low-titer anti-SIV antibody responses. These results indicate that high-titer anti-SIV antibody responses and high-frequency anti-SIV cellular immune responses measurable by standard assays from the peripheral blood are not needed to achieve strong vaccine protection, even against a difficult, neutralization-resistant strain such as SIV239.
Standardized and Highly Efficient Expansion of Epstein-Barr Virus-Specific CD4
+
T Cells by Using Virus-Like Particles
Authors: Adhikary Dinesh , Behrends Uta , Feederle Regina , Delecluse Henri-Jacques , Mautner Josef
Published: February 2008

Epstein-Barr virus (EBV)-specific T-cell lines generated by repeated stimulation with EBV-immortalized lymphoblastoid B-cell lines (LCL) have been successfully used to treat EBV-associated posttransplant lymphoproliferative disease (PTLD) in hematopoietic stem cell transplant recipients. However, PTLD in solid-organ transplant recipients and other EBV-associated malignancies respond less efficiently to this adoptive T-cell therapy. LCL-stimulated T-cell preparations are polyclonal and contain CD4
+
and CD8
+
T cells, but the composition varies greatly between lines. Because T-cell lines with higher CD4
+
T-cell proportions show improved clinical efficacy, we assessed which factors might compromise the expansion of this T-cell population. Here we show that spontaneous virus production by LCL and, hence, the presentation of viral antigens varies intra- and interindividually and is further impaired by acyclovir treatment of LCL. Moreover, the stimulation of T cells with LCL grown in medium supplemented with fetal calf serum (FCS) caused the expansion of FCS-reactive CD4
+
T cells, whereas human serum from EBV-seropositive donors diminished viral antigen presentation. To overcome these limitations, we used peripheral blood mononuclear cells pulsed with nontransforming virus-like particles as antigen-presenting cells. This strategy facilitated the specific and rapid expansion of EBV-specific CD4
+
T cells and, thus, might contribute to the development of standardized protocols for the generation of T-cell lines with improved clinical efficacy.
Human APOBEC3G Can Restrict Retroviral Infection in Avian Cells and Acts Independently of both UNG and SMUG1
Authors: Langlois Marc-André , Neuberger Michael S.
Published: February 2008

APOBEC3 proteins are mammal-specific cytidine deaminases that can restrict retroviral infection. The exact mechanism of the restriction remains unresolved, but one model envisions that uracilated retroviral cDNA, generated by cytidine deamination, is the target of cellular glycosylases. While restriction is unaffected by UNG deficiency, it has been suggested that the SMUG1 glycosylase might provide a backup. We found that retroviral restriction can be achieved by introducing human APOBEC3G into chicken cells (consistent with the components necessary for APOBEC3-mediated restriction predating mammalian evolution) and used this assay to show that APOBEC3G-mediated restriction can occur in cells deficient in both UNG and SMUG1.
Role of Dendritic Cells in Antibody-Dependent Enhancement of Dengue Virus Infection
Authors: Boonnak Kobporn , Slike Bonnie M. , Burgess Timothy H. , Mason Randall M. , Wu Shuenn-Jue , Sun Peifang , Porter Kevin , Rudiman Irani Fianza , Yuwono Djoko , Puthavathana Pilaipan , Marovich Mary A.
Published: February 2008

Dengue viruses (DV), composed of four distinct serotypes (DV1 to DV4), cause 50 to 100 million infections annually. Durable homotypic immunity follows infection but may predispose to severe subsequent heterotypic infections, a risk conferred in part by the immune response itself. Antibody-dependent enhancement (ADE), a process best described in vitro, is epidemiologically linked to complicated DV infections, especially in Southeast Asia. Here we report for the first time the ADE phenomenon in primary human dendritic cells (DC), early targets of DV infection, and human cell lines bearing Fc receptors. We show that ADE is inversely correlated with surface expression of DC-SIGN (DC-specificintercellular adhesion molecule-3-grabbingnonintegrin) and requires Fc gamma receptor IIa (FcγRIIa). Mature DC exhibited ADE, whereas immature DC, expressing higher levels of DC-SIGN and similar FcγRIIa levels, did not undergo ADE. ADE results in increased intracellular de novo DV protein synthesis, increased viral RNA production and release, and increased infectivity of the supernatants in mature DC. Interestingly, tumor necrosis factor alpha and interleukin-6 (IL-6), but not IL-10 and gamma interferon, were released in the presence of dengue patient sera but generally only at enhancement titers, suggesting a signaling component of ADE. FcγRIIa inhibition with monoclonal antibodies abrogated ADE and associated downstream consequences. DV versatility in entry routes (FcγRIIa or DC-SIGN) in mature DC broadens target options and suggests additional ways for DC to contribute to the pathogenesis of severe DV infection. Studying the cellular targets of DV infection and their susceptibility to ADE will aid our understanding of complex disease and contribute to the field of vaccine development.
A Bispecific Antibody Composed of a Nonneutralizing Antibody to the gp41 Immunodominant Region and an Anti-CD89 Antibody Directs Broad Human Immunodeficiency Virus Destruction by Neutrophils
Authors: Duval Mark , Posner Marshall R. , Cavacini Lisa A.
Published: February 2008

In addition to the direct neutralization of virus, there is a broader potential for antibody-mediated inhibition of human immunodeficiency virus (HIV) by targeting HIV to effector cells. We demonstrate here that a bispecific antibody incorporating a broadly reactive anti-gp41 antibody, F240, and an anti-IgA receptor (CD89) antibody is effective at directing neutrophils to destroy HIV. Not only are neutrophils the predominant type of white blood cells and very efficient at mediating cell cytotoxicity, they are relatively resistant to infection with HIV. Therefore, they represent a significant weapon against infection if they can be directed and armed to destroy HIV and infected cells.
Phosphorylation of IRF-3 on Ser 339 Generates a Hyperactive Form of IRF-3 through Regulation of Dimerization and CBP Association
Authors: Clément Jean-François , Bibeau-Poirier Annie , Gravel Simon-Pierre , Grandvaux Nathalie , Bonneil Éric , Thibault Pierre , Meloche Sylvain , Servant Marc J.
Published: February 2008

The IκB kinase-related kinases, TBK1 and IKKi, were recently shown to be responsible for the C-terminal phosphorylation of IRF-3. However, the identity of the phosphoacceptor site(s) targeted by these two kinases remains unclear. Using a biological assay based on the IRF-3-mediated production of antiviral cytokines, we demonstrate here that all Ser/Thr clusters of IRF-3 are required for its optimal transactivation capacity. In vitro kinase assays using full-length His-IRF-3 as a substrate combined with mass spectrometry analysis revealed that serine 402 and serine 396 are directly targeted by TBK1. Analysis of Ser/Thr-to-Ala mutants revealed that the S396A mutation, located in cluster II, abolished IRF-3 homodimerization, CBP association, and nuclear accumulation. However, production of antiviral cytokines was still present in IRF-3 S396A-expressing cells. Interestingly, mutation of serine 339, which is involved in IRF-3 stability, also abrogated CBP association and dimerization without affecting gene transactivation as long as serine 396 remained available for phosphorylation. Complementation of IRF-3-knockout mouse embryonic fibroblasts also revealed a compensatory mechanism of serine 339 and serine 396 in the ability of IRF-3 to induce expression of the interferon-stimulated genes ISG56 and ISG54. These data lead us to reconsider the current model of IRF-3 activation. We propose that conventional biochemical assays used to measure IRF-3 activation are not sensitive enough to detect the small fraction of IRF-3 needed to elicit a biological response. Importantly, our study establishes a molecular link between the role of serine 339 in IRF-3 homodimerization, CBP association, and its destabilization.
An active school model to promote physical activity in elementary schools: Action schools! BC
Authors: Naylor P-J , Macdonald H M , Warburton D E R , Reed K E , McKay H A
Published: February 2008

Objective:

To assess the impact of an active school model on children’s physical activity (PA).

Design:

16-month cluster randomised controlled trial.

Setting:

10 elementary schools in Greater Vancouver, BC.

Participants:

515 children aged 9–11 years.

Intervention:

Action Schools! BC (AS! BC) is an active school model that provided schools with training and resources to increase children’s PA. Schools implemented AS! BC with support from either external liaisons (liaison schools, LS; four schools) or internal champions (champion schools, CS; three schools). Outcomes were compared with usual practice (UP) schools (three schools).

Main outcome measurements:

PA was measured four times during the study using pedometers (step count, steps/day).

Results:

Boys in the LS group took 1175 more steps per day, on average, than boys in the UP group (95% CI: 97 to 2253). Boys in the CS group also tended to have a higher step count than boys in the UP group (+804 steps/day; 95% CI: −341 to 1949). There was no difference in girls’ step counts across groups.

Conclusions:

The positive effect of the AS! BC model on boys’ PA is important in light of the current global trend of decreased PA.
Oral administration of the probioticLactobacillus fermentumVRI-003 and mucosal immunity in endurance athletes
Authors: Cox A J , Pyne D B , Saunders P U , Fricker P A
Published: February 2008

Objective

To evaluate the ability of a probioticLactobacillus fermentumVRI-003 (PCC) to enhance the mucosal immune system of elite athletes.

Design and setting

A double-blind, placebo-controlled, crossover trial was conducted over a 4-month period of winter training.

Participants

20 healthy elite male distance runners.

Interventions

PCC was given at a daily dose of 1.26×1010as a freeze-dried powder in gelatin capsules. Placebo capsules contained an inert excipient.

Main outcome measures

Treadmill performance (monthly), mucosal and systemic immunity (monthly), training (daily) and illness (daily) were assessed. Serum cytokine levels, salivary IgA levels and incidence, duration and severity of respiratory tract infections were measured.

Results

Subjects reported less than half the number of days of respiratory symptoms during PCC treatment (30 days) compared with placebo (72 days, p<0.001). Illness severity was also lower for episodes occurring during the PCC treatment (p = 0.06). There were no significant differences in the mean change in salivary IgA and IgA1 levels, or in interleukin (IL)4 and IL12 levels, between treatments. However, PCC treatment elicited a twofold (p = 0.07) greater change in whole-blood culture interferon gamma (IFNγ) compared with placebo. No substantial changes in running performance measures were seen over the study period.

Conclusions

Prophylactic administration of PCC was associated with a substantial reduction in the number of days and severity of respiratory illness in a cohort of highly trained distance runners. Maintenance of IFNγ levels may be one mechanism underpinning the positive clinical outcomes.
An examination of the smoking identities and taxonomies of smoking behaviour of youth
Authors: Okoli C T C , Richardson C G , Ratner P A , Johnson J L
Published: February 2008

Objective:

To address observations that the smoking identities of youth are valid descriptors of their smoking behaviour, we examined the relationships between self-reported smoking identities, perceived levels of addiction, and established taxonomies of smoking behaviour of youth.

Method:

Cross-sectional data were collected on demographics, perceived extent of addiction to tobacco, smoking history, and self-reported smoking identity from questionnaires administered to 8225 students in British Columbia, Canada. A total of 7246 participants were categorised according to four smoking taxonomies established in the literature. Differences in perceived physical and mental addiction between smoking identity groups were calculated. The strength of the associations between the taxonomies of smoking and the smoking identity groups was also assessed.

Results:

There were significant differences in perceived levels of physical (Kruskal–Wallis χ2  3985.02, p<0.001) and mental (Kruskal–Wallis χ2  4046.09, p<0.001) addiction to tobacco by the participants’ self-reported smoking identity. Youth smoking identities were modestly associated with the established smoking taxonomies (Pearson C contingency coefficient  0.64–0.72).

Conclusion:

Self-reported smoking identities appear to provide valid characterisations of the smoking behaviour of youths that complement and elaborate existing taxonomies of smoking behaviour. Questions about self-reported smoking identity should be used in conjunction with smoking behaviour taxonomies when investigating youth smoking behaviours.
Les argiles de l'est du Canada et leur contribution à la compréhension du comportement de l'argile
Authors: Rochelle Pierre La , Tavenas François , Leroueil Serge
Published: February 2008

This paper offers a brief and incomplete retrospective of the last 25 years of research on clays in Canada, and especially on the sensitive clays. The implication of this research on the improvement of our knowledge of the behaviour of clays in general is emphasized. The development of special techniques for the study of sensitive clays, such as sampling, and the application of limit and critical states concepts to natural clays have contributed greatly to the important leap forward in our understanding of the soil masses and in the solution of practical problems: the problems of stability, of compressibility, and of consolidation are discussed. Finally, the prominent role of the Canadian Geotechnical Journal in the diffusion and even in the orientation of research in Canada is emphasized. Key words: research, clays, sensitive clays, limit state, critical state, brittleness, sampling, strength, stability, consolidation.
A method for evaluating the representative elementary volume based on joint survey of rock masses
Authors: Oda Masanobu
Published: February 2008

The representative elementary volume of a statistically homogeneous rock mass is defined as the minimum volume beyond which any submass behaves essentially like the whole rock mass. A simple, but still general, method for the determination of the minimum volume is given on the basis of the crack tensor concept; it is concluded that the size must be at least three times larger than a typical length of joint traces. Key words: computer simulation, rock hydraulics, site investigation.
Geotechnical aspects of seabed pits in the Grand Banks area
Authors: Clark J. I. , Landva J.
Published: February 2008

Ice-created seabed pits found on the Grand Banks of Newfoundland can be analysed in terms of probable range of soil strength properties and failure mechanisms to determine the ice loads transmitted to the seabed. Almost all pits are less than 3 m deep; their existence can be explained by indentation failures caused by rolling icebergs. About 3.5% of the pits are more than 5 m deep and cannot be explained by iceberg impact. This paper presents a possible mechanism for their formation consisting of two actions: (1) the hard grounding of an iceberg, such that the keel becomes embedded in the seabed, and (2) the passive failure of the soil after the grounding event, predominantly caused by the loads associated with wave forces on the iceberg at the time of grounding or shortly thereafter. A 10 m deep pit located in the Hibernia area is analysed with respect to its configuration and soil parameters. Calculations have shown that, though waves in the Grand Banks area cause forces on the iceberg of a sufficient magnitude to create pits of the order of 10 m deep or more in the stiff Grand Banks soils, the controlling factor of pit depth is the ability of the iceberg keel to deliver these loads to the soil. Key words: iceberg pits, iceberg scour, pit formation, ice–seabed interaction.
A hydrochemical study of urban landslides caused by heavy rain: Scarborough Bluffs, Ontario, Canada
Authors: Eyles N. , Howard K. W. F.
Published: February 2008

Scarborough Bluffs is a 15 km long stretch of the Lake Ontario shoreline east of downtown Toronto. This heavily urbanized area currently represents Canada's most serious erosion problem. The worst affected zone is 1.5 km long and lies along South Marine Drive where 50 m high bluffs are failing by shallow retrogressive failures of jointed glacial clays over underlying deltaic sands and clays. The erosion rate is about four times that for the coastline as a whole.Heavy rains in the Toronto area in August and September 1986 produced a spate of slope failures and mud flows. Particularly heavy storms on September 10 and 29 triggered extensive retrogressive slope failures at South Marine Drive. Hydrochemical investigations of discharge waters suggest that slope failure was caused by surface runoff on the bluff top recharging lower slope areas by infiltration through joints in the upper clay capping. Discharge of water from the lower slope is impeded by less permeable barriers in the deltaic stratigraphy at the site and by a cover of clayey slope debris. Data suggest that provision for adequate drainage of the bluff top, by interceptor drains, is a prerequisite for controlling slope behaviour in the area. Key words: slopes, erosion, groundwater, hydrochemical, recharge, drainage.
Viscous-type sliding laws for landslides
Authors: Vulliet Laurent , Hutter Kolumban
Published: February 2008

Sliding of a moving soil mass along a basal surface is analyzed and viscous-type sliding laws are presented. They relate the relative sliding velocity at the base—or at an interface—to the state of stress at this surface. Examples of practical parameter determination illustrate the suitability of this approach; two landslides (in Switzerland and in France) provide the data for this purpose. A third site (La Frasse, Switzerland) serves as an example of three-dimensional analysis of creeping slopes using the proposed formulation. Comparison of computed and measured velocity distributions shows the method to be promising. Key words: landslides, creep, sliding law, time dependence, interface.
Lateral resistance and deflection of flexible piles
Authors: Meyerhof G. G. , Sastry V. V. R. N. , Yalcin A. S.
Published: February 2008

The ultimate lateral resistance and the groundline lateral deflections under working loads of freestanding single model piles and small pile groups, of various materials and different embedded lengths, subjected to horizontal load have been investigated. The test results of piles of various stiffnesses in sand and clay are compared with theoretical analyses based on the concept of an effective embedment depth in terms of the behaviour of equivalent rigid piles. Key words: clay, piles, displacements, lateral load, lateral resistance, pile stiffness, sand, ultimate load.
Dynamic behaviour of single piles under strong harmonic excitation
Authors: Han Yingcai , Novak Milos
Published: February 2008

Dynamic experiments were conducted on large-scale model piles in sand subjected to strong horizontal and vertical excitation. The theoretical response curves are calculated using DYNA2 and PILAY2 computer codes, and using also for the vertical direction, the theory of nonlinear vibration. The theoretical curves are compared with the experimental results. The dynamic behaviour of the pile is presented as frequency response curves for displacement, stiffness, dashpot constants, and damping ratios. The influence of excitation intensity, repeated loading, and cap contact with soil on the dynamic behaviour of single piles is investigated. Key words: dynamics, vibration, piles, foundations, nonlinear vibration, testing, deep foundations.
Two case histories of major frost heaving in refrigerated buildings: thermal analyses, repairs, and prevention
Authors: Chapuis Robert P.
Published: February 2008

Two cases of major slab uplifts (15 and 41 cm) of the floors of two refrigerated buildings are analyzed. These uplifts were caused by vertical heaving of the natural soils, at depths between 2 and 4 m, during frost penetration. In one case, conditions are met that justify, with no risk of large error, the use of the equation of frost penetration into a multilayered system with latent heat. The thickness of the frozen natural soil, as measured in boreholes, corresponds closely to the value that could have been anticipated from the operating conditions and from the thermal properties of the insulation and of the backfilled and natural soil layers. The two repairs effected are described and recommendations to prevent the occurrence of these problems are given. Key words: frozen soils, heaving, building, case history.
Clayey barrier assessment for impoundment of domestic waste leachate (southern Ontario) including clay–leachate compatibility by hydraulic conductivity testing
Authors: Quigley Robert. M. , Fernandez Federico , Rowe R. Kerry
Published: February 2008

The current use of engineered clayey barriers to control the chemical flux entering the groundwater adjacent to landfill sites is discussed. New analytical methods to predict flux–time relationships controlled by advection and diffusion are presented briefly, followed by an assessment of macropore flow problems inherent in laboratory and especially field-compacted clays.The clay–leachate compatability of southern Ontario (Sarnia) clays is then assessed with respect to domestic waste leachate using hydraulic conductivity as the assessment tool. The dominant role of channel flow through macropores, even in very carefully controlled laboratory samples, is emphasized, as is the critical role of soil smectite and vermiculite in retardation of species such as K+ from domestic leachate.The Sarnia brown and grey clays seem compatible with domestic waste leachate at least with respect to hydraulic conductivity, k. In spite of extensive K+ retardation, leachate effected a slight decrease in k of the water-compacted brown and grey samples, a feature also observed recently for the contaminated grey clay zone at a field site. Key words: clay barriers, hydraulic conductivity, compatibility, domestic leachate, channel flow, potassium retardation, migration modelling.
Viscosity and dielectric constant controls on the hydraulic conductivity of clayey soils permeated with water-soluble organics
Authors: Fernandez F. , Quigley R. M.
Published: February 2008

Water-soluble organic liquids may, under some circumstances, dramatically increase the hydraulic conductivity, k, of water-saturated clayey soils, thus destroying their effectiveness as barriers for contaminants. Double-layer contraction at constant void ratio with resultant increases in the pore space available for flow has been identified as a primary mechanism for such increases in k. This paper shows, however, that the increased viscosity of solutions of some organics in water results in significant decreases in k.Pure alcohols (ethanol and methanol) and other water solubles (dioxane) when permeated through water-compacted clay samples produce an initial decrease in k, followed by a gradual increase to equilibrium values. The "hydrocarbon" front raises the viscosity of the pore fluid and causes an initial drop in k. Tests using aqueous solutions of ethanol and dioxane show decreases in k at concentrations up to ~70%. Only at high concentrations does the dielectric constant, double-layer effect overcome the viscosity effect and produce net increases in k.Effective stresses σ′vof 160 kPa during permeation with ethanol and dioxane prevent the increases in k. Physicochemically induced consolidation and increased K0-shearing effects that close shrinkage cracks are operative. Key words: hydraulic conductivity, liquid hydrocarbons, clay, viscosity, dielectric constant.
Correlation between standard penetration test values and overburden pressure for desert sands
Authors: Ismael Nabil F. , Jeragh A. M. , Khalidi O. A. , Mollah M. A.
Published: February 2008

The influence of the effective overburden pressure on the standard penetration test (SPT) values in calcareous desert sands is examined by field tests. A simple field testing procedure is proposed and employed in Kuwait at five sites having different relative densities for the surface soils. The correction factors for the SPT are determined from test results and compared with the most reliable correlations for clean silica sand. Key words: field tests, plate bearing tests, overburden pressure, standard penetration test, correction factors, relative density, calcareous soils, shear strength, compressibility.
A method to estimate active-layer thickness on the basis of correlations between terrain and climatic parameters as measured in northern Quebec
Authors: Gray James T. , Pilon Jean , Poitevin Jean
Published: February 2008

Field studies recently conducted on the west coast of Ungava Bay, in the southern part of the continuous permafrost zone, have permitted the establishment of the pattern of active-layer development for six different geomorphological and vegetational terrain types. All study sites were situated on horizontal surfaces free from local topographic influences, to permit the explanation of thaw progression, in terms of the earth materials, moisture content, and vegetation cover characterizing each terrain type. Thermal properties for organic and mineral soil, and for bedrock, were calculated from field data on texture, bulk density, and moisture content of the earth materials at the sites, and were used to explain thaw-layer development for each terrain type. A linear regression was established for each group of sites between the logarithmic transformation of thaw penetration and an atmospheric thawing index obtained through interpolations of air temperature data from the two closest meteorological stations—Kuujjuaq (Fort Chimo) and Koartaq (Cape Hope's Advance). This regression was then used to estimate the total thickness of the active layer at the end of the thaw season for each terrain type, and to assess probable variations in active-layer depths in the region over a 20 year time period. Probable spatial variations of active layers for extreme climatic variations in the Ungava Peninsula are also briefly presented. Key words: active layer, permafrost, thermal, thaw penetration, terrain analyses, Ungava.
MASTER-SLAVE SYNCHRONIZATION OF LUR'E SYSTEMS BASED ON TIME-VARYING DELAY FEEDBACK CONTROL
Authors: HUANG HE , CAO JINDE
Published: February 2008

This paper deals with the master-slave synchronization problem of Lur'e systems based on time-varying delay feedback control. The time-varying delay is only assumed to be bounded. Delay-dependent conditions are derived such that the controlled slave system can track the master system. The synchronization criteria are expressed in terms of linear matrix inequality, which can be checked readily by using some standard numerical packages. A simulation example is provided to demonstrate the effectiveness of the proposed approach.
EXPONENTIAL SYNCHRONIZATION IN DRIVE-RESPONSE SYSTEMS OF HOPFIELD-TYPE NEURAL NETWORKS WITH TIME DELAYS
Authors: LI CHUN-HSIEN , YANG SUH-YUH
Published: February 2008

In this paper we investigate the drive-response type synchronization of Hopfield-type neural networks with connection time delays for both discrete and distributed cases. By employing the Lyapunov functional method, we propose a sufficient condition to ensure the occurrence of synchronization with exponential rates. This criterion is independent of time delays as well as the types of delay. We prove that the exponential synchronization occurs provided a certain weighted sum of the connection and coupling strengths is negative enough, no matter that the connection time delay is of discrete or distributed case. Numerical examples are provided to illustrate the results.
PARTIAL SYNCHRONIZATION IN OSCILLATOR ARRAYS WITH ASYMMETRIC COUPLING
Authors: HILLIER DÁNIEL , GÜNEL SERKAN , SUYKENS JOHAN A. K. , VANDEWALLE JOOS
Published: February 2008

A new form of cluster synchronization is explored in cellular arrays of chaotic oscillators. Previously, it was shown in the literature that symmetries of the coupling topology with uniform interaction weights lead to several coexisting clusters of synchronized cells. In this study a new phenomenon is presented where highly asymmetric interaction weights can give rise to cluster synchronization regimes with partial synchronization. In addition, cluster or partial synchronization regimes corresponding to asymmetric interaction patterns can break the underlying symmetries of the network topology and boundary conditions at the expense of some residual synchronization error.
CONTROLLED PARAMETER MODULATIONS IN SECURE DIGITAL SIGNAL TRANSMISSIONS
Authors: PALANIYANDI P. , LAKSHMANAN M.
Published: February 2008

We propose a simple method for secure digital signal transmission by making some modifications in the single-step parameter modulation technique propo sed earlier to overcome certain inherent deficiencies. In the modified method, the parameter modulation is effectively regulated or controlled by the chaotic signal obtained from the transmitting chaotic system so that it has the maximum security. Then, the same idea is also extended to the multistep parameter modulation technique. It is found that both the methods are secure against ciphertext (return map) and plaintex attacks. We have illustrated these methods by means of the Lorenz system.
UNIFORM APPROACH FOR STABILITY ANALYSIS OF FAST SUBSYSTEM OF TWO-TIME SCALE NONLINEAR SYSTEMS
Authors: ALBERTO LUÍS F. C. , CHIANG HSIAO-DONG
Published: February 2008

A new uniform methodology to study the fast subsystem stability of general two-time scale nonlinear systems is developed. It consists of a direct method that provides estimates of the stability region of the fast subsystem that are uniform with respect to the slow variables, which are treated as uncertainties. The methodology is illustrated on small power systems leading to much improved results in estimating the stability region, critical clearing times as compared to traditional methods. As a by-product, it gives the required theoretical support to justify and to correct the heuristic approaches used in power system stability analysis literature.
HORSESHOE IN THE HYPERCHAOTIC MCK CIRCUIT
Authors: YANG FANGYAN , LI QINGDU , ZHOU PING
Published: February 2008

The well-known Matsumoto–Chua–Kobayashi (MCK) circuit is of significance for studying hyperchaos, since it was the first experimental observation of hyperchaos from a real physical system. In this paper, we discuss the existence of hyperchaos in this circuit by virtue of topological horseshoe theory. The two disjoint compact subsets producing a horseshoe found in a specific 3D cross-section, both expand in two directions under the fourth Poincaré return map, this fact means that there exists hyperchaos in the circuit.
THE CONNECTEDNESS LOCUS OF A FAMILY OF REAL BIQUADRATIC POLYNOMIALS
Authors: SUN YESHUN , YIN YONGCHENG
Published: February 2008

In this paper we present a precise description of the connectedness locus of the family of polynomials (z2 + x)2 + y, where x, y are real numbers.
UNCERTAINTIES FACILITATE AGGRESSIVE BEHAVIOR IN A SPATIAL HAWK–DOVE GAME
Authors: PERC MATJAŽ
Published: February 2008

We study effects of additive spatiotemporal random variations, introduced to the payoffs of a spatial hawk–dove game, on the evolution of the reconciliatory and the aggressive strategy. We show that uncertainties facilitate aggressive behavior for a broad range of resource values. In particular, aggressors thrive best if stochastic influences are of the order of magnitude of deterministic payoff values. We argue that random payoff variations are potent and plausible promoters of aggressive behavior in human as well as animal societies if only the hawk–dove game payoff ranking applies.
OLD AND NEW RESULTS ON STRANGE NONCHAOTIC ATTRACTORS
Authors: JORBA ÀNGEL , TATJER JOAN CARLES , NÚÑEZ CARMEN , OBAYA RAFAEL
Published: February 2008

Classical and new results concerning the topological structure of skew-products semiflows, coming from nonautonomous maps and differential equations, are combined in order to establish rigorous conditions giving rise to the occurrence of strange nonchaotic attractors on 𝕋d × ℝ. A special attention is paid to the relation of these sets with the almost automorphic extensions of the base flow. The scope of the results is clarified by applying them to the Harper map, although they are valid in a much wider context.
CHAOTIC ATTRACTORS OF THE CONJUGATE LORENZ-TYPE SYSTEM
Authors: YANG QIGUI , CHEN GUANRONG , HUANG KUIFEI
Published: February 2008

A new conjugate Lorenz-type system is introduced in this paper. The system contains as special cases the conjugate Lorenz system, conjugate Chen system and conjugate Lü system. Chaotic dynamics of the system in the parametric space is numerically and thoroughly investigated. Meanwhile, a set of conditions for possible existence of chaos are derived, which provide some useful guidelines for searching chaos in numerical simulations. Furthermore, some basic dynamical properties such as Lyapunov exponents, bifurcations, routes to chaos, periodic windows, possible chaotic and periodic-window parameter regions and the compound structure of the system are demonstrated with various numerical examples.
GENERATING 3-D SCROLL GRID ATTRACTORS OF FRACTIONAL DIFFERENTIAL SYSTEMS VIA STAIR FUNCTION
Authors: DENG WEIHUA
Published: February 2008

This paper discusses the stair function approach for the generation of scroll grid attractors of fractional differential systems. The one-directional (1-D) n-grid scroll, two-directional (2-D) (n × m)-grid scroll and three-directional (3-D) (n × m × l)-grid scroll attractors are created from a fractional linear autonomous system with a simple stair function controller. Being similar to the scroll grid attractors of classical differential systems, the scrolls of 1-D n-grid scroll, 2-D (n × m)-grid scroll and 3-D (n × m × l)-grid scroll attractors are located around the equilibria of fractional differential system on a line, on a plane or in 3D, respectively and the number of scrolls is equal to the corresponding number of equilibria.
PERIODIC OSCILLATIONS ARISING AND DEATH IN DELAY-COUPLED NEURAL LOOPS
Authors: HSU CHENG-HSIUNG , YANG TZI-SHENG
Published: February 2008

We consider the system consisting of two identical n-neural loops which are coupled via a single neuron of each loop with discrete time delay. A framework describing the linearized stability region in the parameter space for the trivial steady state solution is constructed. In the boundary of the stability region, a periodic oscillation may arise from the Hopf bifurcation while these periodic oscillations could be dead owing to the change of coupling strength, delay or meeting a pitchfork bifurcation. The examples of n = 4 and n = 5 show the phenomena of oscillation arising or death, and the effects of the coupling strengths and delay on the stability and oscillation. The criticalities of pitchfork and Hopf bifurcations are investigated by using the normal form method for retarded functional differential equations.
BIFURCATIONS, STABILITY AND SYNCHRONIZATION IN DELAYED OSCILLATORY NETWORKS
Authors: BONNIN MICHELE , CORINTO FERNANDO , GILLI MARCO
Published: February 2008

Current studies in neurophysiology award a key role to collective behaviors in both neural information and image processing. This fact suggests to exploit phase locking and frequency entrainment in oscillatory neural networks for computational purposes. In the practical implementation of artificial neural networks delays are always present due to the non-null processing time and the finite signal propagation speed. This manuscript deals with networks composed by delayed oscillators, we show that either long delays or constant external inputs can elicit oscillatory behavior in the single neural oscillator. Using center manifold reduction and normal form theory, the equations governing the whole network dynamics are reduced to an amplitude-phase model (i.e. equations describing the evolution of both the amplitudes and the phases of the oscillators). The analysis of a network with a simple architecture reveals that different kind of phase locked oscillations are admissible, and the possible coexistence of in-phase and anti-phase locked solutions.