(Table 1) Experimental shear strength values for IODP Exp315 and Exp316 holes

We investigate the mechanics of slope failures on the Nankai accretionary complex offshore Japan in the vicinity of a major out-of-sequence thrust fault (termed the "megasplay"). Incorporating laboratory-measured shear strength of slope sediments sampled during Integrated Ocean Drilling Project (IODP) Expeditions 315 and 316 with local seafloor slope angles from bathymetric data and constraints on in-situ effective stress conditions from drilling, we find that slopes in the study area are stable and submarine landslides are not expected to occur under static conditions. In order to assess the possibility of slope failure triggered by coseismic rupture of the megasplay fault, we use empirical relations for strong ground motion attenuation from earthquakes with Mw 6-9. We find that the slope sediments should be stable based on computations from one model, developed from a catalog of worldwide subduction zone earthquakes (Youngs et al., 1997, doi:10.1785/gssrl.68.1.58). However, using a different model developed primarily from a catalog of crustal earthquakes in Japan (Kanno et al., 2006, doi:10.1785/0120050138), we find that slopes should be unstable for earthquakes 8 <= Mw <= 9, and possibly unstable for events with 6 <= Mw < 8, depending on the proximity of rupture to the seafloor. Considering limitations of the models and geologic observations of slope failure recurrence, the true slope stability is likely to be in between the predictions of the two models, and we suggest that it may be modulated by long-term pore pressure fluctuations.

AMS 14C and calibrated ages of sediment core GeoB10426-1

Newly acquired bathymetric and seismic reflection data have revealed mass-transport deposits (MTDs) on the northeastern Cretan margin in the active Hellenic subduction zone. These include a stack of two submarine landslides within the Malia Basin with a total volume of approximately 4.6 km**3 covering an area of about 135 km**2. These two MTDs have different geometry, internal deformations and transport structures. The older and stratigraphic lower MTD is interpreted as a debrite that fills a large part of the Malia Basin, while the second, younger MTD, with an age of at least 12.6 cal. ka B.P., indicate a thick, lens-shaped, partially translational landslide. This MTD comprises multiple slide masses with internal structure varying from highly deformed to nearly undeformed. The reconstructed source area of the older MTD is located in the westernmost Malia Basin. The source area of the younger MTD is identified in multiple headwalls at the slope-basin-transition in 450 m water depth. Numerous faults with an orientation almost parallel to the southwest-northeast-trending basin axis occur along the northern and southern boundaries of the Malia Basin and have caused a partial steepening of the slope-basin-transition. The possible triggers for slope failure and mass-wasting include (i) seismicity and (ii) movement of the uplifting island of Crete from neotectonics of the Hellenic subduction zone, and (iii) slip of clay-mineral-rich or ash-bearing layers during fluid involvement.

The Mineralogy and Strength Characteristics of Selected Glaciolacustrine Clays in the Puget Sound Region

The combination of rainy climate, glaciolacustrine clays, and steep topography of the Puget Lowland creates slope stability issues for the regional population. Several glaciolacustrine deposits of laminated silt and clay of different ages contribute to the likelihood of slope failure. The glaciolacustrine deposits are generally wet, range in thickness from absent to >30m, and consist of laminated silt and clay with sand interbeds at the tops and bottoms, sandy laminae throughout the deposits, occasional dropstones and shear zones. The glaciolacustrine deposits destabilize slopes by 1) impeding groundwater flow percolating through overlying glacial outwash sediments, 2) having sandy laminae that lower strength by increasing pore pressure during wet seasons, and 3) increasing the potential for block-style failure because of secondary groundwater pathways such as laminae and vertical fractures. Eight clay samples from six known landslide deposits were analyzed in this study for their mineralogy, clay fraction and strength characteristics. The mineralogy was determined using X-ray Diffractometry (XRD) which revealed an identical mineralogic suite among all eight samples consisting of chlorite, illite and smectite. Nonclay minerals appearing in the X-ray diffractogram include amphibole and plagioclase after removal of abundant quartz grains. Hydrometer tests yielded clay-size fraction percentages of the samples ranging from 10% to 90%, and ring shear tests showed that the angle of residual shear resistance (phi_r) ranged from 11° to 31°. Atterberg limits of the samples were found to have liquid limits ranging from 33 to 83, with plastic limits ranging from 25 to 35 and plasticity indices ranging from 6 to 48. The results of the hydrometer and residual shear strength tests suggest that phi_r varies inversely with the clay-size fraction, but that this relationship was not consistent among all eight samples. The nature of the XRD analysis only revealed the identity of the clay minerals present in the samples, and provided no quantitative information. Thus, the extent to which the mineralogy influenced the strength variability among the samples cannot be determined given that the mineral assemblages are identical. Additional samples from different locations within each deposit along with quantitative compositional analyses would be necessary to properly account for the observed strength variability.

Physical properties and age determination of sediment cores from the Hinlopen/Yermak Megaslide north of Spitsbergen, Arctic Ocean

Integrated interpretation of multi-beam bathymetric, sediment-penetrating acoustic (PARASOUND) and seismic data show a multiple slope failure on the northern European continental margin, north of Spitsbergen. The first slide event occurred during MIS 3 around 30 cal. ka BP and was characterised by highly dynamic and rapid evacuation of ca. 1250 km**3 of sediment from the lower to the upper part of the continental slope. During this event, headwalls up to 1600 m high were created and ca. 1150 km**3 material from hemi-pelagic sediments and from the lower pre-existing trough mouth fan has been entrained and transported into the semi-enclosed Sophia Basin. This megaslide event was followed by a secondary evacuation of material to the Nansen Basin by funnelling of the debris through the channel between Polarstern Seamount and the adjacent continental slope. The main slide debris is overlain by a set of fining-upward sequences as evidence for the associated suspension cloud and following minor failure events. Subsequent adjustment of the eastern headwalls led to failure of rather soft sediments and creation of smaller debris flows that followed the main slide surficial topography. Discharge of the Hinlopen ice stream during the Last Glacial Maximum and the following deglaciation draped the central headwalls and created a fan deposit of glacigenic debris flows.

(Table 1) Experimental details and results

Factor-of-safety analyses of submarine slope failure depend critically on the shear strength of the slope material, which is often evaluated with residual strength values and for normally consolidated sediments. Here, we report on direct measurements of both shear strength and cohesion for a quartz-clay mixture over a wide range of overconsolidation ratios (OCRs). For normally consolidated sediment at low stresses, cohesion is the dominant source of shear strength compared to friction. Significant increases in peak shear strength occur for OCR > 4, and the primary source of this strength increase is due to increased cohesion, rather than friction. The proportion of added shear strength due to cohesion depends log-linearly on the OCR. We show that at shallow depths where OCR values can be high, overconsolidated clays can be stronger than pure or nearly pure quartz sediments, which are cohesionless under near-surface conditions. Our data also suggest that areas which have experienced significant unroofing due to previous mass movements are less likely to experience subsequent failure at shallow depths due to increased peak strength, and if failure occurs it is expected to be deeper where the OCR is lower. In seismically active areas, this is one potential explanation for the general observation of lower slope failure recurrence compared to rates expected from triggering due to local earthquakes.

Origin of an enigmatic regional Mio-Pliocene unconformity on the Demerara plateau

The Demerara plateau, located offshore French Guiana and Suriname, is part of a passive transform continental margin particularly prone to develop slope instabilities, probably in relation to the presence of a free distal border along its steep continental slope. Slope failure occurred at different periods (Cretaceous to Neogene) and shows an overall retrogressive evolution through time. Upslope these failure headscarp, an enigmatic regional MioPliocene unconformity has been discovered through the interpretation of new academic and industrial datasets. The aim of this work is to describe and understand the origin of this surface. Our analysis shows that this unconformity is made of a series of valleys that cross-cut sedimentary strata. Each one of these valleys has a short lateral extent and is closed along two perpendicular directions, which suggests that it could correspond to a highly meandering system, or to some sub-circular depressions. The infill of these features is equivalent to the regional stratigraphic strata found outside the structures, but in a subdued position. This seems to imply that the structures have originated by a local loss of sediments at their base or by sliding processes. Furthermore, these depressions intersect each other through time, while migrating progressively downslope. We discuss a series of hypotheses that try to explain the onset and evolution of these depressions forming the Mio-Pliocene unconformity (Canyons? Slope failures? Contourite moats? Hydrate pockmarks?). Having established that these structures are depressions formed by collapse, and have many similarities with structures recently described in the literature as pockmarks associated with gas hydrate dissolution, we favor this hypothesis. We propose that these hydrate pockmarks form with a mass failure that was triggered by fluid-overpressure development at the base of the hydrate stability zone.

Prognostic Value of a New Cardiopulmonary Exercise Testing Parameter in Chronic Heart Failure: Oxygen Uptake Efficiency at Peak Exercise - Comparison with Oxygen Uptake Efficiency Slope

INTRODUCTION: A growing body of evidence shows the prognostic value of oxygen uptake efficiency slope (OUES), a cardiopulmonary exercise test (CPET) parameter derived from the logarithmic relationship between O(2) consumption (VO(2)) and minute ventilation (VE) in patients with chronic heart failure (CHF). OBJECTIVE: To evaluate the prognostic value of a new CPET parameter - peak oxygen uptake efficiency (POUE) - and to compare it with OUES in patients with CHF. METHODS: We prospectively studied 206 consecutive patients with stable CHF due to dilated cardiomyopathy - 153 male, aged 53.3±13.0 years, 35.4% of ischemic etiology, left ventricular ejection fraction 27.7±8.0%, 81.1% in sinus rhythm, 97.1% receiving ACE-Is or ARBs, 78.2% beta-blockers and 60.2% spironolactone - who performed a first maximal symptom-limited treadmill CPET, using the modified Bruce protocol. In 33% of patients an cardioverter-defibrillator (ICD) or cardiac resynchronization therapy device (CRT-D) was implanted during follow-up. Peak VO(2), percentage of predicted peak VO(2), VE/VCO(2) slope, OUES and POUE were analyzed. OUES was calculated using the formula VO(2) (l/min) = OUES (log(10)VE) + b. POUE was calculated as pVO(2) (l/min) / log(10)peakVE (l/min). Correlation coefficients between the studied parameters were obtained. The prognosis of each variable adjusted for age was evaluated through Cox proportional hazard models and R2 percent (R2%) and V index (V6) were used as measures of the predictive accuracy of events of each of these variables. Receiver operating characteristic (ROC) curves from logistic regression models were used to determine the cut-offs for OUES and POUE. RESULTS: pVO(2): 20.5±5.9; percentage of predicted peak VO(2): 68.6±18.2; VE/VCO(2) slope: 30.6±8.3; OUES: 1.85±0.61; POUE: 0.88±0.27. During a mean follow-up of 33.1±14.8 months, 45 (21.8%) patients died, 10 (4.9%) underwent urgent heart transplantation and in three patients (1.5%) a left ventricular assist device was implanted. All variables proved to be independent predictors of this combined event; however, VE/VCO2 slope was most strongly associated with events (HR 11.14). In this population, POUE was associated with a higher risk of events than OUES (HR 9.61 vs. 7.01), and was also a better predictor of events (R2: 28.91 vs. 22.37). CONCLUSION: POUE was more strongly associated with death, urgent heart transplantation and implantation of a left ventricular assist device and proved to be a better predictor of events than OUES. These results suggest that this new parameter can increase the prognostic value of CPET in patients with CHF.

Monitoring and failure mechanism interpretation of an unstable slope in Southern Switzerland based on terrestrial laser scanner

We present the application of terrestrial laser scanning (TLS) for the monitoring and characterization of an active landslide area in Val Canaria (Ticino, Southern Swiss Alps). At catchment scale, the study area is affected by a large Deep Seated Gravitational Slope Deformation (DSGSD) area presenting, in the lower boundary, several retrogressive landslides active since the 1990s. Due to its frequent landslide events this area was periodically monitored by TLS since 2006. Periodic acquisitions provided new information on 3D displacements at the bottom of slope and the detection of centimetre to decimetre level scale changes (e.g. rockfall and pre-failure deformations). In October 2009, a major slope collapse occured at the bottom of the most unstable area. Based on the comparison between TLS data before and after the collapse, we carried out a detailed failure mechanism analysis and volume calculation.

Geosynthetic-Reinforced Soil Structure Built to Restore Original Geometry of a 12 m High Slope After Failure Using Local Soil

This paper presents a study case in which a geosynthetic-reinforced soil (GRS) structure was used to rebuild a 12 m high slope after its failure. The failed slope is located between the parking lot of a private company and a public school. Due to surrounding structures restrictions, this project required a solution with rapidity in execution. In addition, as a requirement established by its owner, this structure should recover the original geometry of the slope. Besides the importance regarding surrounding constructions, an interesting aspect of this study case relies on the versatility of geosynthetic materials. A woven geotextile was used as reinforcement. Five other geosynthetic materials were used in this study case. Facing comprised a geocell filled with local soil cover and grass mats, resulting in a green facing. A geonet was used to hold the grass mats in place before grass roots development. Regarding the drainage system, geocomposite drains and geopipes were installed to drain subsurface water. A nonwoven geotextile was used as filter in drainage trenches, which were placed near the structure toe. Additionally to the GRS structure, the lower portion of the slope was reinforced with soil nailing technique. The face of the nailed soil portion was covered with sandbags and shotcrete. It emphasizes the flexibility of GRS structures regarding their application with other technical options in Geotechnical Engineering. The economic aspect of this study case also deserves attention. It did not require soil transportation and other design and construction steps, e.g. concrete structures design and construction.

Unsaturated Infinite Slope Stability Considering Surface Flux Conditions

A slope stability model is derived for an infinite slope subjected to unsaturated infiltration flow above a phreatic surface. Closed form steady state solutions are derived for the matric suction and degree of saturation profiles. Soil unit weight, consistent with the degree of saturation profile, is also directly calculated and introduced into the analyzes, resulting in closed-form solutions for typical soil parameters and an infinite series solution for arbitrary soil parameters. The solutions are coupled with the infinite slope stability equations to establish a fully realized safety factor function. In general, consideration of soil suction results in higher factor of safety. The increase in shear strength due to the inclusion of soil suction is analogous to making an addition to the cohesion, which, of course, increases the factor of safety against sliding. However, for cohesive soils, the results show lower safety factors for slip surfaces approaching the phreatic surface compared to those produced by common safety factor calculations. The lower factor of safety is due to the increased soil unit weight considered in the matric suction model but not usually accounted for in practice wherein the soil is treated as dry above the phreatic surface. The developed model is verified with a published case study, correctly predicting stability under dry conditions and correctly predicting failure for a particular storm.

Impact of gender on benefits of exercise training on sympathetic nerve activity and muscle blood flow in heart failure

We compared the effects of exercise training on neurovascular control and functional capacity in men and women with chronic heart failure (HF). Forty consecutive HF outpatients from the Heart Institute, University of Sao Paulo, Brazil were divided into the following four groups matched by age: men exercise-trained (n = 12), men untrained (n = 10), women exercise-trained (n = 9), women untrained (n = 9). Maximal exercise capacity was determined from a maximal progressive exercise test on a cycle ergometer. Forearm blood flow was measured by venous occlusion plethysmography. Muscle sympathetic nerve activity (MSNA) was recorded directly using the technique of microneurography. There were no differences between groups in any baseline parameters. Exercise training produced a similar reduction in resting MSNA (P = 0.000002) and forearm vascular resistance (P = 0.0003), in men and women with HF. Peak VO(2) was similarly increased in men and women with HF (P = 0.0003) and VE/VCO(2) slope was significantly decreased in men and women with HF (P = 0.0007). There were no significant changes in left-ventricular ejection fraction in men and women with HF. The benefits of exercise training on neurovascular control and functional capacity in patients with HF are independent of gender.

Reliability and Failure Modes of Implant-Supported Y-TZP and MCR Three-Unit Bridges

Purpose: Chipping within veneering porcelain has resulted in high clinical failure rates for implant-supported zirconia (yttria-tetragonal zirconia polycrystals [Y-TZP]) bridges. This study evaluated the reliability and failure modes of mouth-motion step-stress fatigued implant-supported Y-TZP versus palladium-silver alloy (PdAg) three-unit bridges. Materials and Methods: Implant-abutment replicas were embedded in polymethylmethacrylate resin. Y-TZP and PdAg frameworks, of similar design (n = 21 each), were fabricated, veneered, cemented (n = 3 each), and Hertzian contact-tested to obtain ultimate failure load. In each framework group, 18 specimens were distributed across three step-stress profiles and mouth-motion cyclically loaded according to the profile on the lingual slope of the buccal cusp of the pontic. Results: PdAg failures included competing flexural cracking at abutment and/or connector area and chipping, whereas Y-TZP presented predominantly cohesive failure within veneering porcelain. Including all failure modes, the reliability (two-sided at 90% confidence intervals) for a ""mission"" of 50,000 and 100,000 cycles at 300 N load was determined (Alta Pro, Reliasoft, Tucson, AZ, USA). No difference in reliability was observed between groups for a mission of 50,000. Reliability remained unchanged for a mission of 100,000 for PdAg, but significantly decreased for Y-TZP. Conclusions: Higher reliability was found for PdAg for a mission of 100,000 cycles at 300 N. Failure modes differed between materials.

Ergospirometry and Echocardiography in Early Stage of Heart Failure with Preserved Ejection Fraction and in Healthy Individuals

AbstractBackground:Heart failure with preserved ejection fraction is a syndrome characterized by changes in diastolic function; it is more prevalent among the elderly, women, and individuals with systemic hypertension (SH) and diabetes mellitus. However, in its early stages, there are no signs of congestion and it is identified in tests by adverse remodeling, decreased exercise capacity and diastolic dysfunction.Objective:To compare doppler, echocardiographic (Echo), and cardiopulmonary exercise test (CPET) variables - ergospirometry variables - between two population samples: one of individuals in the early stage of this syndrome, and the other of healthy individuals.Methods:Twenty eight outpatients diagnosed with heart failure according to Framingham’s criteria, ejection fraction > 50% and diastolic dysfunction according to the european society of cardiology (ESC), and 24 healthy individuals underwent Echo and CPET.Results:The group of patients showed indexed atrial volume and left ventricular mass as well as E/E’ and ILAV/A´ ratios significantly higher, in addition to a significant reduction in peak oxygen consumption and increased VE/VCO2 slope, even having similar left ventricular sizes in comparison to those of the sample of healthy individuals.Conclusion:There are significant differences between the structural and functional variables analyzed by Echo and CPET when comparing two population samples: one of patients in the early stage of heart failure with ejection fraction greater than or equal to 50% and another of healthy individuals.