Effect of Liquefaction on Pile Shaft Friction Capacity

Piled foundations are commonly used worldwide, and observed failures of these foundations during earthquakes has led to active research in this area. However, the way in which piles support axial loads during earthquakes is still not fully understood. In this paper, the results from centrifuge tests are presented which consider how axial loads are carried by piles during earthquake loading. It will be shown that the piles in dry soils mobilise additional shaft friction to carry the seismically induced axial loading. However, in the case of a pile group passing through a liquefiable soil layer and founded in a dense sand layer, the pile group suffered large settlements as it loses the shaft friction in the liquefied layer and attempted to mobilise additional end bearing capacity. Further, with the post-seismic dissipation of pore pressures and the consequent settlement of the soil, the piles register significant down drag forces. This resulted in a reduction of the loads being supported as shaft friction and required further end bearing capacity to be mobilised

Endothelial Progenitor Cells Enter the Aging Arena

Age is a significant risk factor for the development of vascular diseases, such as atherosclerosis. Although pharmacological treatments, including statins and anti-hypertensive drugs, have improved the prognosis for patients with cardiovascular disease, it remains a leading cause of mortality in those aged 65 years and over. Furthermore, given the increased life expectancy of the population in developed countries, there is a clear need for alternative treatment strategies. Consequently, the relationship between aging and progenitor cell-mediated repair is of great interest. Endothelial progenitor cells (EPCs) play an integral role in the cellular repair mechanisms for endothelial regeneration and maintenance. However, EPCs are subject to age-associated changes that diminish their number in circulation and function, thereby enhancing vascular disease risk. A great deal of research is aimed at developing strategies to harness the regenerative capacity of these cells. In this review, we discuss the current understanding of the cells termed “EPCs,” examine the impact of age on EPC-mediated repair and identify therapeutic targets with potential for attenuating the age-related decline in vascular health via beneficial actions on EPCs

Point-of-Care Virologic Testing to Improve Outcomes of HIV-Infected Children in Zambia: A Clinical Trial Protocol

In the absence of early infant diagnosis (EID) and immediate antiretroviral therapy (ART), some 50% of untreated HIV-infected infants die before age 2. Conventional EID requires sophisticated instruments that are typically placed in centralized or reference laboratories. In low-resource settings, centralized systems often lead to result turnaround times of several months, long delays in diagnosis, and adverse outcomes for HIV-infected children. Our clinical trial tests the effectiveness of a new point-of-care (POC) diagnostic technology to identify HIV-infected infants and start providing them life-saving ART as soon as possible

Mock observations with the Millennium Simulation: cosmological downsizing and intermediate-redshift observations

Only by incorporating various forms of feedback can theories of galaxy formation reproduce the present-day luminosity function of galaxies. It has also been argued that such feedback processes might explain the counterintuitive behaviour of 'downsizing' witnessed since redshifts z ≃ 1–2. To examine this question, observations spanning 0.4 < z < 1.4 from the Deep Extragalactic Evolutionary Probe (DEEP)2/Palomar survey are compared with a suite of equivalent mock observations derived from the Millennium Simulation, populated with galaxies using the galform code. Although the model successfully reproduces the observed total mass function and the general trend of 'downsizing', it fails to accurately reproduce the colour distribution and type-dependent mass functions at all redshifts probed. This failure is shared by other semi-analytical models which collectively appear to 'over-quench' star formation in intermediate-mass systems. These mock lightcones are also a valuable tool for investigating the reliability of the observational results in terms of cosmic variance. Using variance estimates derived from the lightcones, we confirm the significance of the decline since z ∼ 1 in the observed number density of massive blue galaxies which, we argue, provides the bulk of the associated growth in the red sequence. We also assess the limitations arising from cosmic variance in terms of our ability to observe mass-dependent growth since z ∼ 1

The Challenge of Machine Learning in Space Weather Nowcasting and Forecasting

The numerous recent breakthroughs in machine learning (ML) make imperative to carefully ponder how the scientific community can benefit from a technology that, although not necessarily new, is today living its golden age. This Grand Challenge review paper is focused on the present and future role of machine learning in space weather. The purpose is twofold. On one hand, we will discuss previous works that use ML for space weather forecasting, focusing in particular on the few areas that have seen most activity: the forecasting of geomagnetic indices, of relativistic electrons at geosynchronous orbits, of solar flares occurrence, of coronal mass ejection propagation time, and of solar wind speed. On the other hand, this paper serves as a gentle introduction to the field of machine learning tailored to the space weather community and as a pointer to a number of open challenges that we believe the community should undertake in the next decade. The recurring themes throughout the review are the need to shift our forecasting paradigm to a probabilistic approach focused on the reliable assessment of uncertainties, and the combination of physics-based and machine learning approaches, known as gray-box.Comment: under revie

Weighted cue integration in the rodent head direction system.

How the brain combines information from different sensory modalities and of differing reliability is an important and still-unanswered question. Using the head direction (HD) system as a model, we explored the resolution of conflicts between landmarks and background cues. Sensory cue integration models predict averaging of the two cues, whereas attractor models predict capture of the signal by the dominant cue. We found that a visual landmark mostly captured the HD signal at low conflicts: however, there was an increasing propensity for the cells to integrate the cues thereafter. A large conflict presented to naive rats resulted in greater visual cue capture (less integration) than in experienced rats, revealing an effect of experience. We propose that weighted cue integration in HD cells arises from dynamic plasticity of the feed-forward inputs to the network, causing within-trial spatial redistribution of the visual inputs onto the ring. This suggests that an attractor network can implement decision processes about cue reliability using simple architecture and learning rules, thus providing a potential neural substrate for weighted cue integration

Weighted cue integration in the rodent head direction system

How the brain combines information from different sensory modalities and of differing reliability is an important and still-unanswered question. Using the head direction (HD) system as a model, we explored the resolution of conflicts between landmarks and background cues. Sensory cue integration models predict averaging of the two cues, whereas attractor models predict capture of the signal by the dominant cue. We found that a visual landmark mostly captured the HD signal at low conflicts: however, there was an increasing propensity for the cells to integrate the cues thereafter. A large conflict presented to naive rats resulted in greater visual cue capture (less integration) than in experienced rats, revealing an effect of experience. We propose that weighted cue integration in HD cells arises from dynamic plasticity of the feed-forward inputs to the network, causing within-trial spatial redistribution of the visual inputs onto the ring. This suggests that an attractor network can implement decision processes about cue reliability using simple architecture and learning rules, thus providing a potential neural substrate for weighted cue integration

The impact of assisted reproductive technology treatments on maternal and offspring outcomes in singleton pregnancies: A review of systematic reviews

Objectives: Assisted reproductive technology (ART) treatments are commonly used to aid conception in subfertile couples. We aimed to evaluate the risks of adverse maternal and offspring outcomes in singleton pregnancy conceived with different ART treatments and techniques. / Evidence review: We searched MEDLINE, EMBASE, CENTRAL and HTA until December 2020 for all systematic reviews evaluating adverse outcomes in pregnancies conceived with various ART techniques, autologous or donor gametes, and embryo development stages. We assessed review quality using the AMSTAR2 tool risk (RR) or odds ratio (OR) with 95% confidence intervals (CI) from the top quality reviews for each of the outcomes of interest across the identified ART treatments and population subgroups. / Results: We included 24 systematic reviews, most reported on observational studies. Compared to spontaneous conception, ART pregnancies had a higher risk of placenta previa (PP) (RR 3.71, 95%CI 2.67-5.16), antepartum haemorrhage (APH) (RR 2.11, 95%CI 1.86-2.38), preterm birth (PTB) (RR 1.71, 95%CI 1.59-1.83), very preterm birth (VPTB) (RR 2.12, 95%CI 1.73-2.59), small for gestational age (SGA) (RR 1.35, 95%CI 1.20-1.52), low birthweight (LBW) (RR 1.61, 95%CI 1.49-1.75) and very low birthweight (VLBW) (RR 2.12, 95%CI 1.84-2.43). Frozen vs fresh embryo transfer was associated with a lower risk for PTB (RR 0.90, 95%CI 0.84-0.97), SGA (RR 0.61, 95%CI 0.56-0.67), LBW (RR 0.72, 95%CI 0.67-0.77) and VLBW (RR 0.76, 95%CI 0.69–0.82). Embryo transfer at blastocyst vs cleavage showed higher risk for PTB (RR 1.10, 95%CI 1.01-1.20) and large for gestational age (LGA) (RR 1.12, 95%CI 1.03-1.21) with lower risk for SGA (RR 0.84, 95%CI 0.76-0.92). Using donor vs autologous oocytes increased the odds of PTB (OR 1.57, 95%CI 1.33-1.86), LBW (OR 1.94, 95%CI 1.10-3.41) and VLBW (OR 1.37, 95%CI 1.22–1.54) as well as maternal complications (postpartum haemorrhage OR 1.96, 95% CI 1.20-3.20, gestational diabetes OR 1.27 95%CI 1.03-1.56, hypertensive disorders of pregnancy OR 2.63, 95%CI 2.17-3.18, and caesarean section OR 2.28, 95%CI 2.14-2.42). / Conclusions: ART treatments are associated with increased risks of adverse maternal and offspring outcomes, especially with donor oocytes. The characteristics of ART treatment should be incorporated into prenatal care planning to mitigate those risks