Numerical characterization of cohesive and non-cohesive 'sediments' under different consolidation states using 3D DEM triaxial experiments

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Elyashiv, H., Bookman, R., Siemann, L., ten Brink, U., & Huhn, K. Numerical characterization of cohesive and non-cohesive 'sediments' under different consolidation states using 3D DEM triaxial experiments. Processes, 8(10), (2020): 1252, doi:10.3390/pr8101252.The Discrete Element Method has been widely used to simulate geo-materials due to time and scale limitations met in the field and laboratories. While cohesionless geo-materials were the focus of many previous studies, the deformation of cohesive geo-materials in 3D remained poorly characterized. Here, we aimed to generate a range of numerical ‘sediments’, assess their mechanical response to stress and compare their response with laboratory tests, focusing on differences between the micro- and macro-material properties. We simulated two endmembers—clay (cohesive) and sand (cohesionless). The materials were tested in a 3D triaxial numerical setup, under different simulated burial stresses and consolidation states. Variations in particle contact or individual bond strengths generate first order influence on the stress–strain response, i.e., a different deformation style of the numerical sand or clay. Increased burial depth generates a second order influence, elevating peak shear strength. Loose and dense consolidation states generate a third order influence of the endmember level. The results replicate a range of sediment compositions, empirical behaviors and conditions. We propose a procedure to characterize sediments numerically. The numerical ‘sediments’ can be applied to simulate processes in sediments exhibiting variations in strength due to post-seismic consolidation, bioturbation or variations in sedimentation rates.This research received no external funding

Mechanisms of Chinese tallow (Triadica sebifera) invasion and their management implications – A review

Ecosystems are under increasing stress from environmental change, including invasion by non-native species that can disrupt ecological processes and functions. Chinese tallow [Triadica sebifera (L.) Small] is a highly invasive tree species in southeastern US forests, prairies, and wetlands, and effectively managing this invasive species is a significant challenge for scientists and land managers. In this review, we synthesize the literature on invasion ecology and management of Chinese tallow. Our review suggests that the invaded range of Chinese tallow is currently limited by dispersal in many areas and by low temperatures and low soil moisture, and by high soil salinity and frequent flooding in others, but these barriers may be overcome by increased dispersal, phenotypic plasticity, and/or rapid evolution. Invasions by Chinese tallow are facilitated by both the invasiveness of the species and the invasibility of the recipient communities. Invasiveness of Chinese tallow has been attributed to fast growth, high fecundity, a persistent seed bank, aggressive resprouting, abiotic stress tolerance, and the ability to transform fire maintained ecosystems. Some of these traits may be enhanced in invasive populations. Anthropogenic and natural disturbances, lack of herbivore pressure, and facilitation by soil microbes enhance the intensity of Chinese tallow invasions. Biological control of Chinese tallow is being developed. Treatments such as herbicides, prescribed fire, and mechanical control can effectively control Chinese tallow at the local scale. A combination of these treatments improves results. However, a proactive management approach would simultaneously achieve invasion control and promote subsequent ecological restoration, especially in the context of legacy effects, secondary invasions, and/or variable ecosystem responses to different control treatments. Future research should clarify the roles of species invasiveness and community invasibility, increase our understanding of the effects of Chinese tallow in invaded communities, and develop viable management regimes that are effective in both controlling or reducing the probability of Chinese tallow invasion and restoring desired native communities

Sequence dependent antitumour efficacy of the vascular disrupting agent ZD6126 in combination with paclitaxel

The clinical success of small-molecule vascular disrupting agents (VDAs) depends on their combination with conventional therapies. Scheduling and sequencing remain key issues in the design of VDA–chemotherapy combination treatments. This study examined the antitumour activity of ZD6126, a microtubule destabilising VDA, in combination with paclitaxel (PTX), a microtubule-stabilising cytotoxic drug, and the influence of schedule and sequence on the efficacy of the combination. Nude mice bearing MDA-MB-435 xenografts received weekly cycles of ZD6126 (200 mg kg−1 i.p.) administered at different times before or after PTX (10, 20, and 40 mg kg−1 i.v.). ZD6126 given 2 or 24 h after PTX showed no significant benefit, a result that was attributed to a protective effect of PTX against ZD6126-induced vascular damage and tumour necrosis, a hallmark of VDA activity. Paclitaxel counteracting activity was reduced by distancing drug administrations, and ZD6126 given 72 h after PTX potentiated the VDA's antitumour activity. Schedules with ZD6126 given before PTX improved therapeutic activity, which was paralleled by a VDA-induced increase in cell proliferation in the viable tumour tissue. Paclitaxel given 72 h after ZD6126 yielded the best response (50% tumours regressing). A single treatment with ZD6126 followed by weekly administration of PTX was sufficient to achieve a similar response (57% remissions). These findings show that schedule, sequence and timing are crucial in determining the antitumour efficacy of PTX in combination with ZD6126. Induction of tumour necrosis and increased proliferation in the remaining viable tumour tissue could be exploited as readouts to optimise schedules and maximise therapeutic efficacy

Timing of Favorable Conditions, Competition and Fertility Interact to Govern Recruitment of Invasive Chinese Tallow Tree in Stressful Environments

The rate of new exotic recruitment following removal of adult invaders (reinvasion pressure) influences restoration outcomes and costs but is highly variable and poorly understood. We hypothesize that broad variation in average reinvasion pressure of Triadica sebifera (Chinese tallow tree, a major invader) arises from differences among habitats in spatiotemporal availability of realized recruitment windows. These windows are periods of variable duration long enough to permit establishment given local environmental conditions. We tested this hypothesis via a greenhouse mesocosm experiment that quantified how the duration of favorable moisture conditions prior to flood or drought stress (window duration), competition and nutrient availability influenced Triadica success in high stress environments. Window duration influenced pre-stress seedling abundance and size, growth during stress and final abundance; it interacted with other factors to affect final biomass and germination during stress. Stress type and competition impacted final size and biomass, plus germination, mortality and changes in size during stress. Final abundance also depended on competition and the interaction of window duration, stress type and competition. Fertilization interacted with competition and stress to influence biomass and changes in height, respectively, but did not affect Triadica abundance. Overall, longer window durations promoted Triadica establishment, competition and drought (relative to flood) suppressed establishment, and fertilization had weak effects. Interactions among factors frequently produced different effects in specific contexts. Results support our ‘outgrow the stress’ hypothesis and show that temporal availability of abiotic windows and factors that influence growth rates govern Triadica recruitment in stressful environments. These findings suggest that native seed addition can effectively suppress superior competitors in stressful environments. We also describe environmental scenarios where specific management methods may be more or less effective. Our results enable better niche-based estimates of local reinvasion pressure, which can improve restoration efficacy and efficiency by informing site selection and optimal Management

Vascular disrupting agent for neovascular age related macular degeneration: a pilot study of the safety and efficacy of intravenous combretastatin A-4 phosphate

BACKGROUND: This study was designed to assess the safety, tolerability, and efficacy of intravenous infusion of CA4P in patients with neovascular age-related macular degeneration (AMD). METHODS: Prospective, interventional, dose-escalation clinical trial. Eight patients with neovascular AMD refractory to at least 2 sessions of photodynamic therapy received CA4P at a dose of 27 or 36 mg/m2 as weekly intravenous infusion for 4 consecutive weeks. Safety was monitored by vital signs, ocular and physical examinations, electrocardiogram, routine laboratory tests, and collection of adverse events. Efficacy was assessed using retinal fluorescein angiography, optical coherence tomography, and best corrected visual acuity (BCVA). RESULTS: The most common adverse events were elevated blood pressure (46.7%), QTc prolongation (23.3%), elevated temperature (13.3%), and headache (10%), followed by nausea and eye injection (6.7%). There were no adverse events that were considered severe in intensity and none resulted in discontinuation of treatment. There was reduction of the excess foveal thickness by 24.15% at end of treatment period and by 43.75% at end of the two-month follow-up (p = 0.674 and 0.161, respectively). BCVA remained stable throughout the treatment and follow-up periods. CONCLUSIONS: The safety profile of intravenous CA4P was consistent with that reported in oncology trials of CA4P and with the class effects of vascular disruptive agents; however, the frequency of adverse events was different. There are evidences to suggest potential efficacy of CA4P in neovascular AMD. However, the level of systemic safety and efficacy indicates that systemic CA4P may not be suitable as an alternative monotherapy to current standard-of-care therapy

Hybrid photonic-bandgap accelerating cavities

In a recent investigation, we studied two-dimensional point-defected photonic bandgap cavities composed of dielectric rods arranged according to various representative periodic and aperiodic lattices, with special emphasis on possible applications to particle acceleration (along the longitudinal axis). In this paper, we present a new study aimed at highlighting the possible advantages of using hybrid structures based on the above dielectric configurations, but featuring metallic rods in the outermost regions, for the design of extremely-high quality factor, bandgap-based, accelerating resonators. In this framework, we consider diverse configurations, with different (periodic and aperiodic) lattice geometries, sizes, and dielectric/metal fractions. Moreover, we also explore possible improvements attainable via the use of superconducting plates to confine the electromagnetic field in the longitudinal direction. Results from our comparative studies, based on numerical full-wave simulations backed by experimental validations (at room and cryogenic temperatures) in the microwave region, identify the candidate parametric configurations capable of yielding the highest quality factor.Comment: 13 pages, 5 figures, 3 tables. One figure and one reference added; minor changes in the tex