Halogen-free flame-retardant compounds. Thermal decomposition and flammability behavior for alternative polyethylene grades

The effect of six halogen-free flame retardant (FR) formulations was investigated on the thermal stability of two low-density polyethylenes (LDPE) and one linear low-density polyethylene (LLDPE), by means of thermogravimetric analysis (TGA) under nitrogen and air atmosphere. The relative data were combined with flammability properties and the overall performance of the FRs was correlated with the type of branching in the polyethylene grades and to their processing behavior. The thermal degradation kinetics was further determined based on the Kissinger and Coats-Redfern methods. In terms of flammability, the addition of a triazine derivative and ammonium polyphosphate at a loading of 35 wt. %. was found to be the most efficient, leading to UL 94 V0 ranking in the case of the LDPE grade produced in an autoclave reactor. - 2019 by the authors.Funding: This publication was made possible by the NPRP award [NPRP 9-161-1-030] from the Qatar National Research Fund (a member of The Qatar Foundation). The statements made herein are solely the responsibility of the author(s)

Cultivars to face climate change effects on crops and weeds: a review

International audienceAbstractClimate change is caused by the release of greenhouse gases in the atmosphere. Climate change will impact many activities, but its effects on agricultural production could be acute. Estimates of annual damages in agriculture due to temperature increase or extended periods of drought will be more costly than damages in other activities. Yield losses are caused both by direct effects of climate change on crops and by indirect effects such as increased inputs in crop production for weed control. One possible solution to counteract the effects of climate change is to seek crop cultivars that are adapted to highly variable, extreme climatic conditions and pest changes. Here we review the effects of climate change on crop cultivars and weeds. Biomass increase will augment marketable yield by 8–70 % for C3 cereals, by 20–144 % for cash and vegetable crops, and by 6–35 % for flowers. Such positive effects could however be reduced by decreasing water and nutrient availability. Rising temperature will decrease yields of temperature-sensitive crops such as maize, soybean, wheat, and cotton or specialty crops such as almonds, grapes, berries, citrus, or stone fruits. Rice, which is expected to yield better under increased CO2, will suffer serious yield losses under high temperatures. Drought stress should decrease the production of tomato, soybean, maize, and cotton. Nevertheless, reviews on C4 photosynthesis response to water stress in interaction with CO2 concentration reveal that elevated CO2 concentration lessens the deleterious effect of drought on plant productivity. C3 weeds respond more strongly than C4 types to CO2 increases through biomass and leaf area increases. The positive response of C3 crops to elevated CO2 may make C4 weeds less competitive for C3 crops, whereas C3 weeds in C4 or C3 crops could become a problem, particularly in tropical regions. Temperature increases will mainly affect the distribution of weeds, particularly C4 type, by expanding their geographical range. This will enhance further yield losses and will affect weed management systems negatively. In addition, the expansion of invasive weed species such as itchgrass, cogongrass, and witchweed facilitated by temperature increases will increase the cost for their control. Under water or nutrient shortage scenarios, an r-strategist with characteristics in the order S-C-R, such as Palmer amaranth, large crabgrass, johnsongrass, and spurges, will most probably prevail. Selection of cultivars that secure high yields under climate change but also by competing weeds is of major importance. Traits related with (a) increased root/shoot ratio, (b) vernalization periods, (c) maturity, (d) regulation of node formation and/or internode distance, (e) harvest index variations, and (f) allelopathy merit further investigation. The cumulative effects of selecting a suitable stress tolerator-competitor cultivar will be reflected in reductions of environmental pollution, lower production costs, and sustainable food production

Two-loop Sudakov form factor in ABJM

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited

Symptomatic intracranial abscess after treating lower cervical spine fracture with halo vest: a case report and review of literature

We present the case of a nineteen year old male, who sustained a fracture of anterior-superior surface of C7, combined with anterior subluxation at the level of C6–C7 vertebrae. After x-ray and CT examination, he was treated conservatively by a Halo-vest. After mobilization, the patient was discharged from the hospital with instructions to visit the outpatient's clinic at regular bases

Seed-shattering phenology at soybean harvest of economically important weeds in multiple regions of the United States. Part 1: Broadleaf species

Potential effectiveness of harvest weed seed control (HWSC) systems depends upon seed shatter of the target weed species at crop maturity, enabling its collection and processing at crop harvest. However, seed retention likely is influenced by agroecological and environmental factors. In 2016 and 2017, we assessed seed-shatter phenology in 13 economically important broadleaf weed species in soybean [Glycine max (L.) Merr.] from crop physiological maturity to 4 wk after physiological maturity at multiple sites spread across 14 states in the southern, northern, and mid-Atlantic United States. Greater proportions of seeds were retained by weeds in southern latitudes and shatter rate increased at northern latitudes. Amaranthus spp. seed shatter was low (0% to 2%), whereas shatter varied widely in common ragweed (Ambrosia artemisiifolia L.) (2% to 90%) over the weeks following soybean physiological maturity. Overall, the broadleaf species studied shattered less than 10% of their seeds by soybean harvest. Our results suggest that some of the broadleaf species with greater seed retention rates in the weeks following soybean physiological maturity may be good candidates for HWSC

Seed-shattering phenology at soybean harvest of economically important weeds in multiple regions of the United States. Part 3: Drivers of seed shatter

Seed retention, and ultimately seed shatter, are extremely important for the efficacy of harvest weed seed control (HWSC) and are likely influenced by various agroecological and environmental factors. Field studies investigated seed-shattering phenology of 22 weed species across three soybean [Glycine max (L.) Merr.]-producing regions in the United States. We further evaluated the potential drivers of seed shatter in terms of weather conditions, growing degree days, and plant biomass. Based on the results, weather conditions had no consistent impact on weed seed shatter. However, there was a positive correlation between individual weed plant biomass and delayed weed seed-shattering rates during harvest. This work demonstrates that HWSC can potentially reduce weed seedbank inputs of plants that have escaped early-season management practices and retained seed through harvest. However, smaller individuals of plants within the same population that shatter seed before harvest pose a risk of escaping early-season management and HWSC

Seed-shattering phenology at soybean harvest of economically important weeds in multiple regions of the United States. Part 2: Grass species

Seed shatter is an important weediness trait on which the efficacy of harvest weed seed control (HWSC) depends. The level of seed shatter in a species is likely influenced by agroecological and environmental factors. In 2016 and 2017, we assessed seed shatter of eight economically important grass weed species in soybean [Glycine max (L.) Merr.] from crop physiological maturity to 4 wk after maturity at multiple sites spread across 11 states in the southern, northern, and mid-Atlantic United States. From soybean maturity to 4 wk after maturity, cumulative percent seed shatter was lowest in the southern U.S. regions and increased moving north through the states. At soybean maturity, the percent of seed shatter ranged from 1% to 70%. That range had shifted to 5% to 100% (mean: 42%) by 25 d after soybean maturity. There were considerable differences in seed-shatter onset and rate of progression between sites and years in some species that could impact their susceptibility to HWSC. Our results suggest that many summer annual grass species are likely not ideal candidates for HWSC, although HWSC could substantially reduce their seed output during certain years

Surface softening in metal-ceramic sliding contacts: An experimental and numerical investigation

This study investigates the tribolayer properties at the interface of ceramic/metal (i.e., WC/W) sliding contacts using various experimental approaches and classical atomistic simulations. Experimentally, nanoindentation and micropillar compression tests, as well as adhesion mapping by means of atomic force microscopy, are used to evaluate the strength of tungsten?carbon tribolayers. To capture the influence of environmental conditions, a detailed chemical and structural analysis is performed on the worn surfaces by means of XPS mapping and depth profiling along with transmission electron microscopy of the debris particles. Experimentally, the results indicate a decrease in hardness and modulus of the worn surface compared to the unworn one. Atomistic simulations of nanoindentation on deformed and undeformed specimens are used to probe the strength of the WC tribolayer and despite the fact that the simulations do not include oxygen, the simulations correlate well with the experiments on deformed and undeformed surfaces, where the difference in behavior is attributed to the bonding and structural differences of amorphous and crystalline W-C. Adhesion mapping indicates a decrease in surface adhesion, which based on chemical analysis is attributed to surface passivation