The elastic behaviour of hydrogels

The mechanical properties and the swelling behaviour of aqueous poly(acryl amide) and poly(acryl amide-co-Na acrylate) gels were investigated. The ionic networks were prepared by hydrolysis of the nonionic ones, in this way preserving the network topology. By measurement of the modulus it was detected that networks prepared in solution contain a rather large portion of elastically ineffective rings. Hydrolysing a part of the amide groups resulted in a considerably increased swelling ratio. The modulus of such ionic gels did not show the predicted decrease with rising swelling ratio, but on the contrary increased up to a fivefold value. The reason for this behaviour is seen in the limited extensibility (non-Gaussian behaviour) of the network chains. At constant swelling ratio, the modulus of gels having identical topology decreased with rising degree of hydrolysis. This reflects the influence of the ionic groups on the mean-square end-to-end distance of the free polymer chains.     

Parameters of rye,wheat, barley,and oat sourdoughs fermented with Lactobacillus plantarum LUHS135 that influence the quality of mixed rye–wheat bread,including acrylamide formation

A Lactobacillus plantarum strain was used for the production of rye, wheat, barley, and oat sourdoughs, and the influence of different sourdoughs on mixed rye–wheat bread quality parameters and acrylamide formation was evaluated. L. plantarum LUHS135 demonstrated versatile carbohydrate metabolism, good growth and acidification rates, and the ability to excrete amylolytic and proteolytic enzymes in various cereal sourdoughs. The same starter and different cereal substrates allow to produce sourdoughs showing different characteristics. The type of sourdough and its quantity had significant influence on acrylamide content in bread (P ≤ 0.0001), and using 5% or 10% of wheat sourdough, 5%, 15%, or 20% of barley sourdough, and 5% or 15% of oat sourdough, it is possible to reduce acrylamide content in bread. Thus, manufacturers need to take into account application of apparent technological approaches for acrylamide in bread reducing.     

Modeling Ozone Reaction Rate Constants of Micropollutants Using Quantitative Structure-Property Relationships

A quantitative structure-property relationship model was developed using piecewise linear regression (with two submodels) to predict second-order rate constants with ozone for a wide range of structurally diverse micropollutants. The model was developed using a set of pre-selected structurally diverse micropollutants for which rate constants had been determined experimentally, and then validated with an external data set. A classification function was developed using linear discriminant analysis to classify micropollutants into high-reactive or low-reactive compounds before using the appropriate submodel. The applicability domain of the model was determined using the Williams plot.     

Sugar-Fat Seesaw: A Systematic Review of the Evidence

Further to reports of a reciprocal relationship between sugar and fat intakes, this review aimed to provide an in-depth analysis and to determine the likely influence of this relationship on the achievement of population dietary guidelines. Using systematic methods, relevant literature was selected according to preset criteria.

A strong and consistent inverse association was found between total sugars and total fat intakes expressed as percentage energy. Fewer studies considered absolute intakes and these reported a positive relationship, which may be influenced by confounding with energy intakes. Evidence for an inverse relationship between percentage energy from fat and extrinsic sugars was weaker and less consistent than for fat and total sugars. Reciprocal relationships were also observed for sugar-saturated fat, sugar?protein, sugar?alcohol, and sugar?starch expressed as percentage energy. Under-reporting of dietary intakes had no major influence on the findings.

This review confirms the existence of the sugar?fat seesaw on a percentage energy basis and concludes that it is most likely explained by a combination of mathematical and food compositional effects. This finding is relevant because dietary guidelines are expressed as percentage energy and implies that at the population level multiple guidelines may be difficult to achieve in practice.     

Structural and Chemical Effects of Plasma Treatment on Close‐Packed Colloidal Nanoparticle Layers

The interaction of nitrogen, oxygen, and hydrogen plasmas with spin‐coated arrays of colloidal cobalt–platinum particles was investigated with a large variety of microscopic and spectroscopic techniques. It could be demonstrated that the organic ligands of the nanoparticles can be completely removed. Yet, due to the short (～1.6 nm) interparticle distances within the layers, strong degradation and sintering effects are observed after hydrogen and nitrogen plasma treatments. In the case of oxygen plasma, the shape and size of the individual particles are unaffected and can be preserved, even if a short hydrogen plasma is subsequently applied to reduce the particles back to their metallic state. Nevertheless, the mesoscopic order of the particle arrays is slightly decreased as observed by the breakup of larger ordered areas into smaller domains forming island–trench structures. Probing the surface chemistry of the particles with temperature programmed desorption, a rather complex surface chemistry is found to result from the plasma treatments. The first TPD spectrum after the cleaning process with oxygen and subsequent hydrogen plasmas reveals that the particles are loaded with adsorbed and implanted hydrogen. After removal of this hydrogen, subsequent TPD spectra using CO as a probe molecule, show broad signals between 190 and 360 K pointing to nonmetallic surface properties. While the platinum was found to be completely reduced, XPS measurements reveal a remaining fraction of oxidic cobalt species which are enriched at the surface. Thus, although the structure of the close‐packed Co–Pt nanoparticle arrays can be qualitatively preserved during plasma‐based ligand removal, the treatment leads to a complex materials system the chemical properties of which are influenced by the particle components, the substrate, and the plasma media.