Innovative Solutions for Slope Stability Reinforcement and Characterization: Vol. III, TR-489, 2005

Soil slope instability concerning highway infrastructure is an ongoing problem in Iowa, as slope failures endanger public safety and continue to result in costly repair work. Volume I of this current study summarizes research methods and findings, while Volume II provides procedural details for incorporating into practice an infrequently-used testing technique–borehole shear tests. Volume III of this study of field investigation of fifteen slopes in Iowa demonstrates through further experimental testing how lateral forces develop along stabilizing piles to resist slope movements. Results establish the feasibility of an alternative stabilization approach utilizing small-diameter pile elements. Also, a step-by-step procedure that can be used by both state and county transportation agencies to design slope reinforcement using slender piles is documented. Initial evidence of the efficiency and cost-effectiveness of stabilizing nuisance slope failures with grouted micropiles is presented. Employment of the remediation alternative is deemed more appropriate for stabilizing shallow slope failures. Overall, work accomplished in this research study included completing a comprehensive literature review on the state of the knowledge of slope stability and slope stabilization, the preparation and performance of fourteen full-scale pile load tests, the analysis of load test results, and the documentation of a design methodology for implementing the technology into current practices of slope stabilization. Recommendations for further research include monitoring pilot studies of slope reinforcement with grouted micropiles, supplementary experimental studies, and advanced numerical studies.

Phenotypic stability and genetic gains in six-year girth growth of Hevea clones

Rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Müell. Arg.] budgrafts of seven clones were evaluated on five contrasting sites in the plateau region of the São Paulo State, Brazil. The objective of this work was to study the phenotypic stability for girth growth. The experimental design was a randomized block design with three replications and seven treatments. Analysis of variance of girth at six-year plant growth indicated a highly significant clone x site interaction. Only linear sites and clone x site components of clone x year interaction were significant, indicating that the performance of clones over sites for this trait could be predicted. The clones GT 1 and PB 235 showed the greatest stability in relation to girth growth, with foreseen responses to change, introduced in the sites. The clones PB 235 and IAN 873 showed significative difference in relation to regression coefficient, representing clones with specific adaptability on favorable and unfavorable sites respectively. The clone GT 1 became the most promissory one in the study of stability and adaptability even showing low girth growth. Expected genetic gains from planting sites, along with estimates of clonal variance and repeatability of clonal means are generally greatest or close to the greatest when selection is done at the same site.

Preliminary description and slope stability analyses of the 2008 Little Salmon lake and 2007 Mt. Steele landslides, Yukon

In August 2008, reactivation of the Little Salmon Lake landslide occurred. During this event, hundreds of conical mounds of variable size and composition formed in the deposition zone. The characteristics of these landforms are described and a potential mechanism for their formation is proposed. A preliminary slope stability analysis of the 2007 Mount Steele rock and ice avalanche was also undertaken. The orientation of very high persistence (>20 m long) structural planes (e.g., faults, joints and bedding) within bedrock in the source zone was obtained using an airborne-LiDAR digital elevation model and the software COLTOP-3D. Using these discontinuity orientation measurements, kinematic, surface wedge and simple three-dimensional distinct element slope stability analyses were performed.

Stability-dependent behavioural and electro-cortical reorganizations during intentional switching between bimanual tapping modes

This study investigated behavioural and electro-cortical reorganizations accompanying intentional switching between two distinct bimanual coordination tapping modes (In-phase and Anti-phase) that differ in stability when produced at the same movement rate. We expected that switching to a less stable tapping mode (In-to-Anti switching) would lead to larger behavioural perturbations and require supplementary neural resources than switching to a more stable tapping mode (Anti-to-In switching). Behavioural results confirmed that the In-to-Anti switching lasted longer than the Anti-to-In switching. A general increase in attention-related neural activity was found at the moment of switching for both conditions. Additionally, two condition-dependent EEG reorganizations were observed. First, a specific increase in cortico-cortical coherence appeared exclusively during the In-to-Anti switching. This result may reflect a strengthening in inter-regional communication in order to engage in the subsequent, less stable, tapping mode. Second, a decrease in motor-related neural activity (increased beta spectral power) was found for the Anti-to-In switching only. The latter effect may reflect the interruption of the previous, less stable, tapping mode. Given that previous results on spontaneous Anti-to-In switching revealing an inverse pattern of EEG reorganization (decreased beta spectral power), present findings give new insight on the stability-dependent neural correlates of intentional motor switching. © 2010 Elsevier Ireland Ltd. All rights reserved

Stability of soybean yield through different sowing periods

Soybean yield is highly affected by sowing period and there are significant productivity losses when sowings are done outward a relatively restricted period in many regions of Brazil. Breeding cultivars less sensitive to photoperiod and to temperature variations is desirable for adaptation to wider sowing period and wider latitude range and also make irrigated soybean cultivation possible during the fall-winter seasons in frost free regions. The possibility of selecting high yielding and stable lines for yield during various sowing periods was studied by analyzing the behavior of 100 non-selected advanced lines (F9 and F10), from each one of all possible biparental crosses involving the genotypes BR85-29009, OCEPAR 8, FT-2, and BR-13. Experiments were set up in a completely randomized design with single-plant hill plots and received supplementary irrigation. Sowing was on Sept 27, Oct 20, Nov 17, and Dec 17 in 1993/94 and Sept 20, Oct 20, Nov 17, and Dec 14 in 1994/95 at Londrina, PR, Brazil. Procedures of regression analysis and minimum variance among planting date means were efficient for selecting stable lines during the four sowing seasons. It was possible to select stable and high yielding genotypes through the four sowing periods in all the crosses. No specific cross was clearly better to produce a greater number of stable genotypes.

Factors Influencing Stability of Granular Base Course Mixes, Progress Report, HR-99, 1965

The problems of laboratory compaction procedures, the effect of gradation and mineralogy on shearing strength, and effect of stabilizing agents on shearing strength of granular base course mixes are discussed. For the materials tested, a suitable laboratory compaction procedure was developed which involves the use of a vibratory table to prepare triaxial test specimens. A computer program has been developed to facilitate the analysis of the test data of the effect of gradation and mineralogy on shearing strength of soils. The effects of the following materials have been selected for evaluation as stabilizing agents’ portland cement, sodium and calcium chloride, lime organic cationic waterproofer, and asphaltic materials.

Factors Influencing Stability of Granular Base Course Mixes, Progress Report, HR-99, 1964 (April)

The problems of laboratory compaction procedures, the effect of gradation and mineralogy on shearing strength, and effect of stabilizing agents on shearing strength of granular base course mixes are discussed. For the materials tested, a suitable laboratory compaction procedure was developed which involves the use of a vibratory table to prepare triaxial test specimens. A computer program has been developed to facilitate the analysis of the test data of the effect of gradation and mineralogy on shearing strength of soils. The effects of the following materials have been selected for evaluation as stabilizing agents’ portland cement, sodium and calcium chloride, lime organic cationic waterproofer, and asphaltic materials.

Factors Influencing Stability of Granular Base Course Mixes, Progress Report, HR-99, 1964 (November)

The problems of laboratory compaction procedures, the effect of gradation and mineralogy on shearing strength, and effect of stabilizing agents on shearing strength of granular base course mixes are discussed. For the materials tested, a suitable laboratory compaction procedure was developed which involves the use of a vibratory table to prepare triaxial test specimens. A computer program has been developed to facilitate the analysis of the test data of the effect of gradation and mineralogy on shearing strength of soils. The effects of the following materials have been selected for evaluation as stabilizing agents’ portland cement, sodium and calcium chloride, lime organic cationic waterproofer, and asphaltic materials.

Impairment of the Bacterial Biofilm Stability by Triclosan

The accumulation of the widely-used antibacterial and antifungal compound triclosan (TCS) in freshwaters raises concerns about the impact of this harmful chemical on the biofilms that are the dominant life style of microorganisms in aquatic systems. However, investigations to-date rarely go beyond effects at the cellular, physiological or morphological level. The present paper focuses on bacterial biofilms addressing the possible chemical impairment of their functionality, while also examining their substratum stabilization potential as one example of an important ecosystem service. The development of a bacterial assemblage of natural composition – isolated from sediments of the Eden Estuary (Scotland, UK) – on non-cohesive glass beads (,63 mm) and exposed to a range of triclosan concentrations (control, 2 – 100 mg L21) was monitored over time by Magnetic Particle Induction (MagPI). In parallel, bacterial cell numbers, division rate, community composition (DGGE) and EPS (extracellular polymeric substances: carbohydrates and proteins) secretion were determined. While the triclosan exposure did not prevent bacterial settlement, biofilm development was increasingly inhibited by increasing TCS levels. The surface binding capacity (MagPI) of the assemblages was positively correlated to the microbial secreted EPS matrix. The EPS concentrations and composition (quantity and quality) were closely linked to bacterial growth, which was affected by enhanced TCS exposure. Furthermore, TCS induced significant changes in bacterial community composition as well as a significant decrease in bacterial diversity. The impairment of the stabilization potential of bacterial biofilm under even low, environmentally relevant TCS levels is of concern since the resistance of sediments to erosive forces has large implications for the dynamics of sediments and associated pollutant dispersal. In addition, the surface adhesive capacity of the biofilm acts as a sensitive measure of ecosystem effects

Conformational changes modulate the activity of human RAD51 protein.

Homologous recombination provides a major pathway for the repair of DNA double-strand breaks in mammalian cells. Defects in homologous recombination can lead to high levels of chromosomal translocations or deletions, which may promote cell transformation and cancer development. A key component of this process is RAD51. In comparison to RecA, the bacterial homologue, human RAD51 protein exhibits low-level strand-exchange activity in vitro. This activity can, however, be stimulated by the presence of high salt. Here, we have investigated the mechanistic basis for this stimulation. We show that high ionic strength favours the co-aggregation of RAD51-single-stranded DNA (ssDNA) nucleoprotein filaments with naked duplex DNA, to form a complex in which the search for homologous sequences takes place. High ionic strength allows differential binding of RAD51 to ssDNA and double-stranded DNA (dsDNA), such that ssDNA-RAD51 interactions are unaffected, whereas those between RAD51 and dsDNA are destabilized. Most importantly, high salt induces a conformational change in RAD51, leading to the formation of extended nucleoprotein filaments on ssDNA. These extended filaments mimic the active form of the Escherichia coli RecA-ssDNA filament that exhibits efficient strand-exchange activity.

Stability of the Helical TomoTherapy Hi·Art II detector for treatment beam irradiations.

The Hi·Art II Helical TomoTherapy (HT) unit is equipped with a built-in onboard MVCT detector used for patient imaging and beam monitoring. Our aim was to study the detector stability for treatment beam measurements. We studied the MVCT detector response with the 6 MV photon beam over time, throughout short-term (during an irradiation) and long-term (two times 50 days) periods. Our results show a coefficient of variation ≤ 1% for detector chambers inside the beam (excluding beam gradients) for short- and long-term response of the MVCT detector. Larger variations were observed in beam gradients and an influence of the X-ray target where degradation was found. The results assume that an 'air scan' procedure is performed daily to recalibrate the detector with the imaging beam. On short term, the detector response stability is comparable to other devices. Long-term measure- ments during two 50-day periods show a good reproducibility. 

Full activation of the T cell receptor requires both clustering and conformational changes at CD3.

T cell receptor (TCR-CD3) triggering involves both receptor clustering and conformational changes at the cytoplasmic tails of the CD3 subunits. The mechanism by which TCRalphabeta ligand binding confers conformational changes to CD3 is unknown. By using well-defined ligands, we showed that induction of the conformational change requires both multivalent engagement and the mobility restriction of the TCR-CD3 imposed by the plasma membrane. The conformational change is elicited by cooperative rearrangements of two TCR-CD3 complexes and does not require accompanying changes in the structure of the TCRalphabeta ectodomains. This conformational change at CD3 reverts upon ligand dissociation and is required for T cell activation. Thus, our permissive geometry model provides a molecular mechanism that rationalizes how the information of ligand binding to TCRalphabeta is transmitted to the CD3 subunits and to the intracellular signaling machinery.

Concrete Pavement Mixture Design and Analysis (MDA): Evaluation of Foam Drainage Test to Measure Air Void Stability in Concrete

The stability of air bubbles in fresh concrete can have a profound influence of the potential durability of the system, because excessive losses during placement and consolidation can compromise the ability of the mixture to resist freezing and thawing. The stability of air void systems developed by some air entraining admixtures (AEAs) could be affected by the presence of some polycarboxylate-based water reducing admixtures (WRAs). The foam drainage test provides a means of measuring the potential stability of air bubbles in a paste. A barrier to acceptance of the test was that there was little investigation of the correlation with field performance. The work reported here was a limited exercise seeking to observe the stability of a range of currently available AEA/WRA combinations in the foam drainage test; then, to take the best and the worst and observe their stabilities on concrete mixtures in the lab. Based on the data collected, the foam drainage test appears to identify stable combinations of AEA and WRA.