Resin-modified glass ionomers (RMGI) set by at least 2 mechanisms dependent upon reactant diffusion prior to gelation. Each reaction’s kinetics and setting mechanism may rely on and/or compete with ...the other. In this study, we investigated RMGI setting reaction interactions using differential scanning calorimetry (DSC) by varying light-cure initiation times. A RMGI was analyzed with isothermal and dynamic temperature scan DSC with light-curing occurring immediately, or at 5 or 10 minutes after mixing as well as without light-activation. Results show that as time allowed for the acid-base reaction increased, the light-activation polymerization exotherm decreased. Conversely, analysis of DSC data suggests that earlier light-activation may limit the acid-base reaction and result in a different structured material. During early RMGI development, acid-base and light-polymerization reactions compete with and inhibit one another.
Polystyrene−clay nanocomposites have been prepared using a bulk polymerization technique. Three new “onium” salts have been used to prepare the nanocomposites, two are functionalized ammonium salts ...while the third is a phosphonium salt. By TGA/FTIR, both ammonium and phosphonium treatments have been shown to degrade by a Hofmann elimination mechanism at elevated temperatures. TGA/FTIR showed that the phosphonium treatment is the most thermally stable treatment when compared to the two ammonium salts. The nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, strength and elongation at break, as a measure of the mechanical properties, thermogravimetric analysis, and cone calorimetry. The onset temperature of the degradation is increased by about 50 °C and the peak heat release rate is reduced by 27−58%, depending upon the amount of clay that is present. The mass loss rates are also significantly reduced in the presence of the clay.
Polystyrene−clay and polystyrene−graphite nanocomposites have been prepared and used to explore the process by which the presence of clay or graphite in a nanocomposite enhances the thermal stability ...of polymers. This study has been designed to determine if the presence of paramagnetic iron in the matrix can result in radical trapping and thus enhance thermal stability. Nanocomposites were prepared by bulk polymerization using both iron-containing and iron-depleted clays and graphites, and they were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, and cone calorimetry. The presence of structural iron, rather than that present as an impurity, significantly increases the onset temperature of thermal degradation in polymer−clay nanocomposites. Intercalated nanocomposites show an iron effect, but this is less important for exfoliated systems. Polymer−graphite nanocomposites show no difference between iron-free and iron-containing nanocomposites, presumably because the iron is not nanodispersed in the graphite.
Harnessing solar energy to grow algal biomass on wastewater nutrients could provide a holistic solution to nutrient management problems on dairy farms. The production of algae from a portion of ...manure nutrients to replace high-protein feed supplements which are often imported (along with considerable nutrients) onto the farm could potentially link consumption and supply of on-farm nutrients. The objective of this research was to assess the ability of benthic freshwater algae to recover nutrients from dairy manure and to evaluate nutrient uptake rates and dry matter/crude protein yields in comparison to a conventional cropping system. Benthic algae growth chambers were operated in semi-batch mode by continuously recycling wastewater and adding manure inputs daily. Using total nitrogen (TN) loading rates of
0.64–1.03
g
m
−2
d
−1
, the dried algal yields were
5.3–5.5
g
m
−2
d
−1
. The dried algae contained 1.5–2.1% P and 4.9–7.1% N. At a TN loading rate of
1.03
g
m
−2
d
−1
, algal biomass contained 7.1% N compared to only 4.9% N at a TN loading rate of
0.64
g
m
−2
d
−1
. In the best case, algal biomass had a crude protein content of 44%, compared to a typical corn silage protein content of 7%. At a dry matter yield of
5.5
g
m
−2
d
−1
, this is equivalent to an annual N uptake rate of
1430
kg
ha
−1
yr
−1
. Compared to a conventional corn/rye rotation, such benthic algae production rates would require 26% of the land area requirements for equivalent N uptake rates and 23% of the land area requirements on a P uptake basis. Combining conventional cropping systems with an algal treatment system could facilitate more efficient crop production and farm nutrient management, allowing dairy operations to be environmentally sustainable on fewer acres.
Livestock wastes are potential sources of endocrine disrupting compounds to the environment. Steroidal estrogen hormones such as estradiol, estrone, and estriol are a particular concern because there ...is evidence that low nanogram per liter concentrations of estrogens in water can adversely affect the reproductive biology of fish and other aquatic vertebrate species. We performed a literature review to assess the current state of science regarding estrogen physicochemical properties, livestock excretion, and the fate of manure-borne estrogens in the environment. Unconjugated steroidal estrogens have low solubility in water (0.8−13.3 mg L-1) and are moderately hydrophobic (log K ow 2.6−4.0). Cattle excrete mostly 17α-estradiol, 17β-estradiol, estrone, and respective sulfated and glucuronidated counterparts, whereas swine and poultry excrete mostly 17β-estradiol, estrone, estriol, and respective sulfated and glucuronidated counterparts. The environmental fate of estrogens is not clearly known. Laboratory-based studies have found that the biological activity of these compounds is greatly reduced or eliminated within several hours to days due to degradation and sorption. On the other hand, field studies have demonstrated that estrogens are sufficiently mobile and persistent to impact surface and groundwater quality. Future research should use standardized methods for the analysis of manure, soil, and water. More information is needed about the types and amounts of estrogens that exist in livestock wastes and the fate of manure-borne estrogens applied to agricultural lands. Field and laboratory studies should work toward revealing the mechanisms of estrogen degradation, sorption, and transport so that the risk of estrogen contamination of waterways can be minimized.
Craniosynostosis, the premature fusion of one or more cranial sutures, occurs in ∼1 in 2250 births, either in isolation or as part of a syndrome. Mutations in at least 57 genes have been associated ...with craniosynostosis, but only a minority of these are included in routine laboratory genetic testing.
We used exome or whole genome sequencing to seek a genetic cause in a cohort of 40 subjects with craniosynostosis, selected by clinical or molecular geneticists as being high-priority cases, and in whom prior clinically driven genetic testing had been negative.
We identified likely associated mutations in 15 patients (37.5%), involving 14 different genes. All genes were mutated in single families, except for
(two families). We classified the other positive diagnoses as follows: commonly mutated craniosynostosis genes with atypical presentation (
,
); other core craniosynostosis genes (
,
); genes for which mutations are only rarely associated with craniosynostosis (
,
,
,
); and known disease genes for which a causal relationship with craniosynostosis is currently unknown (
,
). In two further families, likely novel disease genes are currently undergoing functional validation. In 5 of the 15 positive cases, the (previously unanticipated) molecular diagnosis had immediate, actionable consequences for either genetic or medical management (mutations in
,
,
,
).
This substantial genetic heterogeneity, and the multiple actionable mutations identified, emphasises the benefits of exome/whole genome sequencing to identify causal mutations in craniosynostosis cases for which routine clinical testing has yielded negative results.
The potential of three floating aquatic macrophytes to improve the water quality of anaerobically digested flushed dairy manure wastewater (ADFDMW) was evaluated. In undiluted ADFDMW (total chemical ...oxygen demand 2010
mg/l), growth of water hyacinth (
Eichhornia crassipes) was inhibited and both pennywort (
Hydrocotyle umbellata) and water lettuce (
Pistia stratiotes) failed to grow. In a 1:1 dilution of ADFDMW, all three plants grew successfully. However, growth of pennywort and water lettuce was limited while water hyacinth growth was robust. High salinity appears to be the principal reason for inhibition, as well as possibly uncharacterized soluble compounds.
In terms of reductions in nutrients, chemical oxygen demand (COD), solids and salinity, water hyacinth performed better than water lettuce and pennywort in diluted ADFDMW. Reduction in nutrients and COD followed first-order kinetics, with water hyacinth exhibiting the highest rates. For water hyacinth, total Kjeldahl nitrogen was reduced by 91.7%, ammonium by 99.6%, total phosphorus by 98.5%, and soluble reactive phosphorus by 96.5% in 31-day batch growth. A polyculture of the three plant species in 1:1 diluted ADFDMW exhibited the next best performance. The high biomass yield of the diluted water hyacinth culture corresponded with high EC and Na
+ reductions, suggesting that EC measurement might be a simple tool to monitor performance of water hyacinth growth and nutrient reduction under high plant growth rate conditions.
Nanocomposite formation brings about an enhancement of many properties for a polymer, including enhanced fire retardancy. This study was carried out to determine if the presence of clay causes ...changes in the degradation pathway of polystyrene. In the case of virgin PS, the degradation pathway is chain scission followed by β-scission (depolymerization), producing styrene monomer, dimer and trimer, through an intra-chain reaction. As the clay loading is increased, the evolved products produced through inter-chain reactions become significant. Due to the barrier effect of the clay layers, the radicals have more opportunity to undergo radical transfer, producing tertiary radicals, and then radical recombination reactions, producing head-to-head structures, and hydrogen abstraction from the condensed phase also occurs. In the presence of clay, the color of solid residues darkens as the clay content increases. It is thought that this color change is caused by the formation of conjugated double bonds in the presence of clay.
The degradation pathway of ethylene–vinyl acetate copolymers and their nanocomposites is investigated using TGA/FT-IR, TGA, GC–MS, cone calorimetry and UV techniques to determine if the presence of ...the clay has an effect on the degradation pathway. The first step of the degradation, the loss of acetic acid by chain stripping, has been shown to be accelerated by the presence of clay. In this work we show that clay does affect the degradation pathway and that the presence of hydroxyl groups on the edges of the clay could be the cause of the accelerated initial step. The products of the second step of the degradation are changed in quantity and some new products are produced, showing that the clay also has an effect on this step of the degradation pathway. A scheme is suggested to account for the role of the clay in the degradation.
The change in the degradation pathway of a polymer by incorporation of clay has a significant effect on the fire retardancy of polymer/clay nanocomposites. Since the clay layers act as a barrier to ...mass transport and lead to superheated conditions in the condensed phase, extensive random scission of the products formed by radical recombination is an additional degradation pathway of polymers in the presence of clay. The polymers that show good fire retardancy upon nanocomposite formation exhibit significant intermolecular reactions, such as inter-chain aminolysis/acidolysis, radical recombination and hydrogen abstraction. In the case of the polymers that degrade through a radical pathway, the relative stability of the radical is the most important factor for the prediction of the effect that nanocomposite formation has on the reduction in the peak heat release rate. The more stable is the radical produced by the polymer, the better is the fire retardancy, as measured by the reduction in the peak heat release rate, of the polymer/clay nanocomposite.
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