Cellulose hydrogels physically crosslinked by glycine: Synthesis,characterization, thermal and mechanical properties

Biopolymers are very efficient for significant applications ranging from tissue engineering, biological devices to water purification. There is a tremendous potential value of cellulose because of its being the most abundant biopolymer on earth, swellability, and functional groups to be modified. A novel, highly efficient route for the fabrication of mechanically stable and natural hydrogels is described in which cellulose and glycine are dissolved in an alkaline solution of NaOH and neutralized in an acidic solution. The dissolving temperature and the glycine amount are essential parameters for the self-assembly of cellulose chains and for tuning the morphology and the aggregate structures of the resulting hydrogels. Glycine plays the role of a physical crosslinker based on the information obtained from FTIR and Raman spectra. Among the prepared set of hydrogels, CL5Gly30 hydrogels have the highest capacity to absorb water. The prepared CL5Gly30 gels can absorb up to seven times their dry weight due to its porous 3-D network structure. CL5Gly10 hydrogel exhibits 80% deformation under 21 N force executed. The method developed in this article can contribute to the application of heavy metal adsorption in aqueous solutions for water purification and waste management. © 2019 The Authors. 137 published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48380.     

Iron cycling in a littoral freshwater beach: Implications for floc trace metal dynamics

This field-based study demonstrates that highly dynamic trace metal (Ag, Co, Cu and Pb) behavior in suspended floc and the sediment surface fine-grained lamina (SFGL) is linked specifically to Fe mineral cycling between these two compartments driven by rapidly fluctuating energy regimes in a shallow, littoral beach of Lake Ontario. Results reveal distinct, Fe mineral controls on trace metal sequestration patterns under quiescent conditions. Higher metal sequestration occurred in floc associated with amorphous Fe oxyhydroxides (FeOOH), while less reactive crystalline Fe oxides (FeOx) dominated bed metal sequestration. Spatial shifts in energy regime governing floc settling and sediment erosion controlled the mixing of FeOOH and FeOx, resulting in discernible, hydrodynamic-dependent floc and SFGL trace metal associations. Low turbulence offshore limited compartment mixing, resulting in enrichment of FeOOH and metals in floc and SFGL over bulk bed sediments. In contrast, higher turbulence nearshore increased bed erosion resulting in less distinct floc and SFGL-FeOOH/metal abundances and partitioning. Diurnal shifts in energy regime impacting floc and SFGL geochemistry were observed nearshore. Accumulation of FeOOH and trace metals occurred in the SFGL under calm morning conditions, while diurnal wind-induced waves rapidly re-cycled the SFGL back into the overlying water-column. Post mixing, re-suspended FeOOH and smaller floc particulates entrained within a higher photosynthetically-induced pH water-column increased overall floc trace metal uptake. Taken together, these findings demonstrate highly dynamic linkages between energy regime and physico-chemistry impacted Fe mineral cycling resulting in observable compartment-specific trace metal partitioning patterns for littoral floc and surficial sediments in beach environments.     

Comparative analysis of bacterial community composition in bulk tank raw milk by culture-dependent and culture-independent methods using the viability dye propidium monoazide

Microbial diversity of 3 raw milk samples after 72 h of storage at 4°C in a bulk tank was analyzed by culture-dependent and -independent methods. The culture-dependent approach was based on the isolation of bacteria on complex and selective media, chemotaxonomic differentiation of isolates, and subsequent identification by 16S rRNA gene sequencing. The culture-independent approach included the treatment of raw milk with the dye propidium monoazide before direct DNA extraction by mechanic and enzymatic cell lysis approaches, and cloning and sequencing of the 16S rRNA genes. The selective detection of viable bacteria improved the comparability between bacterial compositions of raw milk based on culture-dependent and -independent methods, which was the major objective of this study. Several bacterial species of the phyla Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria were detected by the culture-dependent method, whereas mainly bacteria of the phylum Proteobacteria as well as low proportions of the phyla Bacteroidetes and Actinobacteria were detected by the culture-independent method. This led to the conclusion that the phylum Firmicutes was strongly discriminated by the culture-independent approach. Generally, species richness detected by the culture-dependent method was higher than that detected by the culture-independent method for all samples. However, few taxa could be detected solely by the direct DNA-based method. In conclusion, the combination of culture-dependent and -independent methods led to the detection of the highest bacterial diversity for the raw milk samples analyzed. It was shown that DNA extraction from raw milk as the essential step in culture-independent methods causes the discrimination of taxa by incomplete cell lysis. Treatment of raw milk with the viability dye propidium monoazide was optimized for the application in raw milk without former removal of milk ingredients and proved to be a suitable tool to ensure comparability of bacterial diversity depicted by both methods.     

Properties of cast urethane elastomers prepared from poly(ϵ-caprolactone)s

General information on the methods of lactone polymerization has been given. The method applied in this study for obtaining poly(?-caprolactone) with the use of sodium derivatives of ethanediol, diethylene glycol, 1,5-pentanediol, and 1,10-decanediol has been discussed, and the results of the experiments have been given. The properties of cast urethane elastomers prepared from the obtained poly(?-caprolactone) have also been presented.     

Propellanes VIII. Electrocyclic Reactions of Tetraenic Propellanes

The electrocyclic reaction sequence of tetraenic propellanes is analogous to that of their parent, cis-9,10-dihydronaphthalene as a member of the (CH)¹⁰ family. Irradiation of Ia-e afforded IIa-e of which IIb and IIc have been isolated. These are the first stable derivatives of tetracyclo [4.4.0.0^2,10.0^5,7]deca-3,8-diene. Thermal bond-realignment of IIa-e led, due to fluxional isomerism in prebullvalene and its derivatives, to prebullvalenes of the III series. Only in the case of the prebullvalene lactone was it possible to observe IVd alongside of IIId in its room terperature NMR spectrum. Irradiation of the prebullvalene ether IIIe afforded a bullvalene ether which at low temperature shows the presence of XIII (R=R=?CH₂-O-CH₂-) and XV.     

Preparation of pure fatty acid methyl esters by countercurrent distribution

Summary Acetonitrile-pentane-hexane makes a desirable solvent system for preparation of pure methyl esters because of its immiscibility, selectivity toward unsaturation, low boiling point, stability, and ease of recovery. Since separated esters are removed from the apparatus dissolved in the pentane-hexane layer, successive batches may be fractionated without removing the acetonitrile layer from the instrument. Applications have been illustrated for the preparation of methyl linolenate from an 85% linolenate concentrate, methyl linoleate from safflower esters, and methyl arachidonate from pig liver lipids. This procedure provides a source of “natural” fatty acids with the double bond configuration unchanged, in contrast to those from the conventional bromination-debromination process. Automation of the process is completed by use of a recording refractometer which monitors concentration of solutions issuing from the extractor. Resolutions to be anticipated with lesser numbers of extraction tubes than 200 are calculated for an equal mixture of linoleate and linolenate. Presented at the 50th meeting, American Oil Chemists' Society, New Orleans, La., April 20–22, 1959. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U.S. Department of Agriculture.     

Nutrient fluxes and sulfur cycling in the organic-rich sediment of Makirina Bay (Central Dalmatia, Croatia)

Fluxes of dissolved nutrients in the organic-rich sediment of Makirina Bay (Croatia) were estimated in in-situ incubation experiments and compared to those calculated from a diagenetic model based on the concentration vs. depth profiles in the pore water extracted from a sediment core at the same sampling site. Benthic fluxes observed in the in-situ experiment were strongly influenced by the decomposition of sedimentary organic matter by bacterial sulfate reduction and precipitation of authigenic pyrite and calcite. Assimilation of dissolved nitrate and ammonia within the sediment resulted in peculiar nitrate and ammonia concentration profiles. Differences between the benthic and diffusive fluxes indicated that the effects of bioturbation and irrigation, which were not taken into account in the model calculation of diffusive fluxes, should not be considered as negligible. They are, however, extremely difficult to estimate because of the heterogeneity of the sediment. Sulfate reduction in the pore water could not be detected, although it was obvious from pyrite precipitation and the isotopic compositions of different sedimentary sulfur species. It is suggested that reoxidation of sulfide and upward diffusion of sulfate from the sediment layer accumulated during past salt production can account for the scattered sulfate vs. depth profile. The distribution and stable isotope compositions of sedimentary sulfur species were studied in more detail. The influx of sulfate was explained by rapid sulfate reduction in the sediment. The sulfate reduction rate was highest in the upper part of the sediment column, as concluded from delta(34)S values. In lower horizons, the concentration of organic sulfur increased, while concentrations of sulfide decreased. The mirror-imaged concentration vs. depth profiles of sulfide and organic sulfur, as well as their stable isotopic compositions, show that they were formed simultaneously, most probably in competitive processes.     

Crash dieting: the effects of eating and drinking on driving performance

Previous research suggests that compared to mobile phone use, eating and drinking while driving is more common and is seen as lower risk by drivers. Nevertheless, snacking at the wheel can affect vehicle control to a similar extent as using a hands-free phone, and is actually a causal factor in more crashes. So far, though, there has not been a controlled empirical study of this problem. In an effort to fill this gap in the literature, we used the Brunel University Driving Simulator to test participants on a typical urban scenario. At designated points on the drive, which coincided with instructions to eat or drink, a critical incident was simulated by programming a pedestrian to walk in front of the car. Whilst the driving performance variables measured were relatively unaffected by eating and drinking, perceived driver workload was significantly higher and there were more crashes in the critical incident when compared to driving normally. Despite some methodological limitations of the study, when taken together with previous research, the evidence suggests that the physical demands of eating and drinking while driving can increase the risk of a crash.     

Synthesis and structure characterization of Ru nanoparticles stabilized by PVP or γ-Al2O3

Uniform and stable Ru nanoparticles were synthesized by reduction of RuCl₃ in ethylene glycol (EG) in the presence of poly(N-vinyl-2-pyrrolidone) by using microwave-assisted solvothermal method. The obtained materials were characterized by UV-vis, FT-IR, XPS, XRD and TEM techniques, and used as precursors of heterogeneous metal colloid catalysts. Characterization by TEM showed that as-prepared PVP-stabilized Ru nanoparticles have small average diameters (below 2 nm) and narrow size distributions (1-3 nm). Diffraction data confirmed that a crystallite size is around 2.0 nm. A colloidal Ru/γ-Al₂O₃ catalyst was obtained by two different methods: immobilization of the PVP-stabilized Ru colloid on the support or by in situ deposition of Ru colloid, e.g., reduction of RuCl₃ with EG in the presence of the γ-alumina. It was found that both synthesis methods produced the Ru/γ-Al₂O₃ catalysts with narrow size distributions of metallic nanoparticles, that are distributed uniformly over the support. However, only in situ preparation of the colloidal Ru/γ-Al₂O₃ catalyst results in chlorine free system with high activity for hydrogen chemisorption. The H₂ uptake on the Ru(PVP)/γ-Al₂O₃ catalyst was very low because the ruthenium surface was strongly occluded with a thin layer of polymer molecules.