Nanohybrid scratch resistant coatings for teeth and bone viscoelasticity manifested in tribology

We cover teeth surfaces with nanohybrid coatings containing an inorganic ceramic and an organic copolymer constituents. We report the first ever values of scratch penetration depth and scratch recovery for bare and coated teeth. We find that uncoated teeth undergo viscoelastic recovery (healing) after microscratching – the first manifestation of bone viscoelasticity in tribology. The coatings fill "valleys" in teeth surfaces. In each case a large improvement in the scratch resistance as compared to uncoated teeth is seen. The extent of the improvement depends on the inorganic/organic component ratios in the nanohybrids. Electronic Publication     

Colloidal aggregation induced by the reduction in pH and the synthesis of new molecular structures during the milk fermentation process

The use of different inocula in the milk‐to‐yoghurt transformation influences the kinetics of the fermentation process. The aim of this work was to study the kinetics induced by Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (Lb–St). The milk‐to‐yoghurt transformation showed no delay in the production of lactic acid for yoghurt produced using Lactobacillus johnsonii with S. thermophilus (La1–St) or Lactobacillus casei with S. thermophilus (Lc1–St); the delays were 20–70 min and 40–80 min, respectively. The absence of delay was 1.0/min (Lb–St) as compared with 0.015/min (La1–St) and 0.7/min (Lc1–St). The kinetics was fitted using second‐order reaction.     

Pressurised feeding systems

Pressurised feeding is by no means new. Whitworth patented a method for pressurising steel in refractory lined ingot moulds in the mid 1800s, while accounts of pressurising aluminium castings during solidification appeared in the 1930s, and the pressurisation of risers in steel and iron castings surfaced in the 1950s. It is appropriate to distinguish between cases where the whole casting and rigging has been pressurised and those where the feeder heads alone were pressurised. Generally speaking, pressurising the whole casting has not proved especially effective. Early experiments with aluminium involved top pouring of moulds contained in an autoclave. The considerable height through which the metal fell undoubtedly mitigated results. Furthermore, since the alloys were of a non-skin forming variety (i.e. long freezing range) the puncture of the partially solidified surface led to further property degradation.

Work of Watmough and Berry in the US in 1961, repeated by Irani and Kondic at Birmingham published eight years later, employed aluminium sand cast bars with pressurised feeder heads surrounded by stout insulating sleeves. The results of both sets of experiments with long-freezing range alloys, showed excellent promise in terms of reducing dispersed porosity. During the nineties Fischer-Disa picked up this concept and successfully implemented it on a production basis for both aluminium and ductile iron. Most recently MSU in collaboration with US metal casters has applied the technique to tilt-poured permanent moulding (gravity-die casting). The results of this recent work will be described in detail.     

Adaptive control for a radio‐controlled helicopter in a vertical flying stand

In this paper, we focus on the design and implementation of a controller for a two degree‐of‐freedom system. This system is composed of a small‐scale helicopter which is mounted on a vertical platform. The model is based on Lagrangian formulation and the controller is obtained by classical pole‐placement techniques for the yaw dynamics and adaptive pole‐placement for the altitude dynamics. Experimental results show the performance of such a controller. Copyright © 2004 John Wiley & Sons, Ltd.     

Improved retention of imidacloprid (Confidor) in soils by adding vermicompost from spent grape marc

Batch sorption experiments of the insecticide imidacloprid by ten widely different Spanish soils were carried out. The sorption was studied for the active ingredient and its registered formulation Confidor. The temperature effect was studied at 15 degrees C and 25 degrees C. The addition of a vermicompost from spent grape marc (natural and ground), containing 344 g kg(-1) organic carbon, on the sorption of imidacloprid by two selected soils, a sandy loam and a silty clay loam, having organic carbon content of 3.6 g kg(-1) and 9.3 g kg(-1), respectively, was evaluated. Prior to the addition of this vermicompost, desorption isotherms with both selected soils, were also performed. The apparent hysteresis index (AHI) parameter was used to quantify sorption-desorption hysteresis. Sorption coefficients, K(d) and K(f), for the active ingredient and Confidor(R) in the different soils were similar. Sorption decreased with increasing temperature, this fact has special interest in greenhouse systems. A significant correlation (R(2)=0.965; P<0.01) between K(f) values and the organic carbon (OC) content was found, but some soils showed higher sorption coefficients than that expected from their OC values. The normalized sorption coefficients with the soil organic carbon content (K(oc)) were dispersed and low, implying that other characteristics of soils could contribute to the retention capacity as well. The spent grape marc vermicompost was an effective sorbent of this insecticide (K(f)=149). The sorption of imidacloprid increased significantly in soils amended with this vermicompost. The most pronounced effect was found in the sandy loam soil with low OC content, where the addition of 5% and 10% of vermicompost increased K(f) values by 8- and 15-fold, respectively. Soil desorption of imidacloprid was slower for the soil with the higher OC and clay content.     

Model reference adaptive control with unknown relative degree

This work presents an indirect, model reference adaptive control for minimum phase linear systems of arbitrary relative degree. Global stability of the closed-loop system is proved in spite of bounded disturbances and asympotic tracking is achieved in the ideal case.     

Characterization of linear copolymers by methods sensitive to the refractive index increment

For linear copolymer molecules, the refractive index increment depends on the chemical composition of the molecules. However, the polydispersity in chemical composition of the sample introduces a great complexity in the data analysis in order to obtain a true molecular weight distribution. Even when the mean chemical composition does not depend on the molecular weight, a correction has to be applied when the output of an instrument depends quadratically on the refractive index Increment of the sample, such as in a light-scattering measurement. For that purpose, the light-scattering expressions are written in terms of polydispersity in chemical composition, which in turn is modeled using linear copolymerization equations. The microstructure effects, which are related to the order in which two different kinds of monomers appear along the chain, are not as yet taken into account in this approach.