Selective Complexation and Membrane Transport of Guanidinium Salts by Calix[6]arene Amides

The p-tert-butylcalix[6]arene hexamide 2 and syn-1,3,5–trimethoxy-2,4,6-triamide 4 were synthesized by reaction of α-chloro-N,N-diethylacetamide and the corresponding calix[6]arenes 1 and 3 , respectively. ¹H NMR spectroscopy shows that 2 is a mixture of different conformations whereas 4 is fixed in a cone conformation. Extraction experiments, (S-L) and (H₂O–CDCl₃) with picrate salts, indicate that 2 complexes both alkali metal (1:2 complex) and guanidinium salts (1:1 complex) but 4 complexes only guanidinium (1:1 complex). Incorporated in supported liquid membranes (Accurel^® / o-nitrophenyl n-octyl ether) the calixarenes 2 and 4 transport guanidinium salts. The hexamide 2 is a more efficient carrier of guanidinium but the syn-1,3,5-trimethoxy-2,4,6-triamide 4 is much more selective. Both 2 and 4 are sufficiently lipophilic to give membranes that are stable over longer periods (weeks).     

Drawing non‐layered tidy trees in linear time

The well‐known Reingold–Tilford algorithm produces tidy‐layered drawings of trees: drawings where all nodes at the same depth are vertically aligned. However, when nodes have varying heights, layered drawing may use more vertical space than necessary. A non‐layered drawing of a tree places children at a fixed distance from the parent, thereby giving a more vertically compact drawing. Moreover, non‐layered drawings can also be used to draw trees where the vertical position of each node is given, by adding dummy nodes. In this paper, we present the first linear‐time algorithm for producing non‐layered drawings. Our algorithm is a modification of the Reingold–Tilford algorithm, but the original complexity proof of the Reingold–Tilford algorithm uses an invariant that does not hold for the non‐layered case. We give an alternative proof of the algorithm and its extension to non‐layered drawings. To improve drawings of trees of unbounded degree, extensions to the Reingold–Tilford algorithm have been proposed. These extensions also work in the non‐layered case, but we show that they then cause a O(n²) run‐time. We then propose a modification to these extensions that restores the O(n) run‐time. Copyright © 2013 John Wiley & Sons, Ltd.     

Turbidity study of the process of film formation of thin films of aqueous acrylic dispersions

This study was directed towards determining the factors that define the process of film formation of binder particles in drying aqueous dispersion coatings, based on acrylic polymers. The work described focuses on the infrastructure of drying and ageing thin films of acrylic latices.

In concentrated latices the binder particles are arranged in closely packed structures which cause colored light patterns, the so-called Bragg diffractions. The light waves move within the latex film, where the waves are scattered by the internal structure composed of the spheres and water voids. The pattern of light transmission reveals the internal structure of the latex film. From the change in interference during the drying process of a thin latex film, it is possible to follow the internal movement and deformation of polymer spheres (coalescence process). Further coalescence results in a transparent film. When this film is immersed in water, the remaining internal interfaces between the adhered binder particles swell, thus regenerating the interference pattern. It is expected that during ageing of the film, the proportion of internal interfaces will decrease with time, so that when the aged film is immersed in water the remaining internal interfaces will swell. The resulting interference pattern reveals the decrease in the interfaces between the deformed polymer particles in the dried latex film (auto-adhesion process).     

Influence of the Interphase on Impact Properties of Zirconium Silicate Filled High-Density Polyethylene

Yellow zirconium silicate is a promising substitute for cadmium pigments used in plastics. However, the incorporation of zircon pigment in HDPE without loss of impact strength is required. By introducing the untreated pigment in the polymer, the impact strength reduces to 60% of the value for the unfilled polymer. Different types of silane coupling agents were used to regain the impact strength of the composite. Octadecylsilane acted as a wetting agent rather than as a coupling agent. The impact strength hardly improved. A vinyl functional and a methacryloxy functional silane improved the impact strength to 70% relative to the unfilled polymer. The physically bonded, interdiffused network formed by silane and polymer improves the impact strength by the flexible nature of the interphase. An azidosilane improved the impact strength only to 73%: the interphase bonded covalently to the polymer as well as to the filler, in that way improving the impact strength, but behaving as a brittle system. A relatively thick, flexible interphase bonded covalently to filler and polymer was created. This interphase improved the impact strength to the value of the unfilled polymer.     

A study on composites of Nylon-6 with hollow glass microspheres

Summary The preparation of nylon-6/hollow glass microspheres composites by the RIM procedure, leading to a new material with reduced density and increased stiffness, is described. The shear moduli of these composites show a linear dependency on the filler concentration. By means of a modified Kerner equation the shear moduli of the various glass spheres were calculated. A linear dependency between the shear modulus of a glass sphere and its wall thickness is demonstrated. A direct method for the determination of the shear moduli of those glass spheres having a density lower than the matrix material is presented.     

Making minor rural road networks safer: The effects of 60 km/h-zones

For safety reasons a maximum speed limit of 60 km/h has been applied to minor rural roads in the Netherlands since 1998. To support this structurally, a part of these roads have also received additional physical measures in a so-called “low cost design” that is expected to reduce the number of traffic casualties by 10–20%. This measure has been implemented as much as possible in an area oriented way. To measure the design's effectivity, road safety in 20 specific rural areas was studied for 5 years before changes were implemented and, on average, 3.5 years thereafter. The study examined 851 km of roads, and a control study was done on 2105 km of comparable roads with a speed limit of 80 km/h. Both the study and the control roads are managed by water boards. Results show that the measures implemented on the roads in the 60 km/h-zones had statistically significant effects (p < 0.05) on casualty accidents (−24% overall), especially at intersections (−44%). This high reduction is probably caused by the concentration of technical interventions at intersections. Both outcomes are somewhat higher than previously expected and are comparable with the outcome of a meta-analysis of safety effects on area-wide urban traffic calming schemes. However, the cost-effectiveness ratio of the 60 km/h zones measures (€33,000 per prevented KSI-casualty) is much more favourable than the ratio in urban 30 km/h-zones (€86,000 per prevented KSI-casualty).     

"Experience-sharing" as an antidote to dependence-making behavior of general practitioners

This article explores how group-dynamic interventions can be used to teach health professionals to counter impulses to make clients dependent on them. The basic assumption, derived from Kohut's work on narcissism, is that dependence-making behavior is connected with deep-rooted feelings of insufficiency resulting from a defective autonomy. A part of the standard Dutch General Practice (GP) training program, experience-sharing in groups of 12 GP trainees, offers opportunities to explore these feelings. The format of this experience-sharing (well-defined boundaries, minimal structure, facilitating leaders) often evokes behavior in which the peculiarities of the dependence-making behavior of the GP's vis-à-vis patients are mirrored: that is, dependent behavior. In order to analyze and influence this behavior, use can be made of Levine's model of group psychotherapy, which focuses on enhancing autonomy. In this paper we show, by means of four group cases, how Levine's framework can be used to enhance autonomy, lessen dependence, and thus diminish the tendency of GP's toward dependence-making behavior.     

The use of whey protein particles in gluten-free bread production,the effect of particle stability

Wheat dough has unique properties for bread making due to its elastic and strain hardening behaviour. A mesoscopically structured whey protein particle system possesses those elastic and strain hardening properties when mixed with starch to a certain extent. However, the extensibility is lower and the particles are more stable than gluten particles upon kneading, probably due to a too high degree of internal crosslinking. This study describes the relation between the number of disulphide bonds of a mesoscopic whey protein particle suspension blocked by NEM treatment and the resulting properties of a dough and bread prepared with that suspension. This study shows that the properties of the particle network are influenced by the ability to form disulphide bonds. Our study shows that a certain amount of disulphide bonds is essential, but too many disulphide bonds can lead to too stiff dough and poorer bread properties.     

Modulation of rheological properties by heat-induced aggregation of whey protein solution

Heat-induced protein aggregation at low protein concentrations generally leads to higher viscosities. We here report that aggregated protein can yield weaker gels than those from native protein at the same concentration. Aggregated protein was produced by heating a solution of whey protein isolate (WPI) at 3% and 9% w/w. The higher protein concentration resulted in a larger aggregate size and a higher intrinsic viscosity. The protein fraction in native WPI had the smallest size and the lowest intrinsic viscosity. The same trend was observed for the shear viscosity after concentrating the suspensions containing aggregates to around 15% w/w. Suspensions containing aggregates that were produced from a higher concentration possessed a higher viscosity. After reheating the concentrated suspensions, the suspension from the 9% w/w aggregate system produced the weakest gel, followed by the one from 3% w/w, while the native WPI yielded the strongest gel. Reactivity of the aggregates was also an important factor that influenced the resulting gel properties. We conclude that aggregation of whey protein solution is a feasible route to manipulate the gel strength of concentrated protein systems, without having to alter the concentration of the protein.