Agglomeration and breakage of nanoparticles in stirred media mills—a comparison of different methods and models

The increasing industrial demand for nanoparticles challenges the application of stirred media mills to grind in the sub-micron size range. It was shown recently [Mende et al., 2003. Mechanical production and stabilization of submicron particles in stirred media mills. Powder Technology 132, 64-73] that the grinding behavior of particles in the sub-micron size range in stirred media mills and the minimum achievable particle size is strongly influenced by the suspension stability and thus the agglomeration behavior of the suspension. Therefore, an appropriate modeling of the process must include a superposition of the two opposing processes in the mill i.e., breakage and agglomeration which can be done by means of population balance models. Modeling must now include the influence of colloidal surface forces and hydrodynamic forces on particle aggregation and breakup. The superposition of the population balance models for agglomeration and grinding with the appropriate kernels leads to a system of partial differential equations, which can be solved in various ways numerically. Here a modified h-p Galerkin algorithm which is implemented in the commercially available software package PARSIVAL developed by CiT (CiT GmbH, Rastede, Germany) and the moment methodology according to [Diemer and Olsen, 2002a. A moment methodology for coagulation and breakage problems: Part I—analytical solution of the steady-state population balance. Chemical Engineering Science 57 (12), 2193-2209; Diemer and Olsen, 2002b. A moment methodology for coagulation and breakage problems: Part II—moment models and distribution reconstruction. Chemical Engineering Science 57 (12), 2211-2288] are used and compared to explicit data on alumina. This includes a comparison of the derived particle size distributions, moments and its accuracy depending on the starting particle size distribution and the used agglomeration and breakage kernels. Finally, the computational effort of both methods in comparison to the prior mentioned parameters is evaluated in terms of practical application.     

Tractor stability indicator

Tractor overturns are a major cause of death in farm operations. The overturns are the result of interactions between the tractor operator, the tractor and the environment. Numerous variables involved in tractor overturn have been identified. Previous stability analyses have resulted in attempts to design devices to warn or prevent tractor rollover but to date nothing has proved successful. A newer approach to the rollover problem is to develop instrumentation that will give the operator instantaneous cues concerning the tractor's stability as it is operated. The device is perceived as a learning instrument which will increase both cognitive and motor skills.     

Diacetyl reduction by commercial Saccharomyces cerevisiae strains during vinification

Microbially derived diacetyl accumulation during vinification imparts a buttery wine aroma, which has stylistic implications. However, at higher concentrations diacetyl induces an aromatic off‐flavour. Saccharomyces cerevisiae is able to reduce diacetyl to below the sensory threshold. Therefore, characterization of the diacetyl reduction in commercial wine yeasts creates new opportunities to manage the risk of wine associated off‐flavours. Diacetyl reduction by two commercial S. cerevisiae strains was characterized in Pinot blanc grape must of the vintage 2012 with different initial diacetyl concentrations (0–50 mg/L). Highest diacetyl reduction was found in the first two days after wine yeasts were inoculated. No further decrease in diacetyl content was observed after the fourth day. All assays in which diacetyl was added showed the same final diacetyl concentration of approximately 2 mg/L. However, a significantly lower amount of diacetyl was found in grape must without adding diacetyl. The present results indicate that commercial wine yeasts are able to reduce much higher amounts of diacetyl than normally expected during the vinification procedure. However, the constant final diacetyl concentration indicates that diacetyl accumulation may be the result of wine matrix binding effects, which prevent a complete reduction by active wine yeasts. Copyright © 2013 The Institute of Brewing & Distilling.     

Sparse Multi-Scale Diffeomorphic Registration: The Kernel Bundle Framework

In order to detect small-scale deformations during disease propagation while allowing large-scale deformation needed for inter-subject registration, we wish to model deformation at multiple scales and represent the deformation compactly at the relevant scales only. This paper presents the kernel bundle extension of the LDDMM framework that allows multiple kernels at multiple scales to be incorporated in the registration. We combine sparsity priors with the kernel bundle resulting in compact representations across scales, and we present the mathematical foundation of the framework with derivation of the KB-EPDiff evolution equations. Through examples, we illustrate the influence of the kernel scale and show that the method achieves the important property of sparsity across scales. In addition, we demonstrate on a dataset of annotated lung CT images how the kernel bundle framework with a compact representation reaches the same accuracy as the standard method optimally tuned with respect to scale.     

Sliding Wear Behavior of ZTA with Different Yttria Stabilizer Content

In this study, tribological investigations were carried out on ZTA ceramics with 17 vol% Y‐TZP and different stabilizer contents (1, 1.5, and 2 mol% yttria) to analyze the influence of zirconia transformation on wear properties. Samples were tested in a linearly reciprocating ball on flat setup with different applied loads. Raising the fracture toughness by transformation toughening, microcracking, and residual stresses improves the wear resistance only at transition load but increases the wear at high loads. Higher yttria content of 2 mol% and lower zirconia grain size and thus low transformability, decreases fracture toughness but increases the wear resistance at high loads. Therefore the adjustment of stabilizer content on zirconia volume fraction in ZTA plays a decisive role in tribological applications.     

The effect of slaughter operations on the contamination of chicken carcasses with thermotolerant Campylobacter

To evaluate the effect of specific slaughter operations on the contamination of broiler carcasses with naturally occurring thermotolerant Campylobacter, experiments were carried out in two Danish commercial slaughter plants (Plant I and Plant II). Six broiler flocks determined Campylobacter positive prior to slaughter were investigated at four sampling locations within each slaughter plant. Quantification of thermotolerant Campylobacter in 30 neck skin samples per flock per sampling location showed that the evisceration operation in Plant I led to a significant increase in the Campylobacter concentration of 0.5 log(10) cfu/g in average, whereas no significant changes were observed during this operation in Plant II. Air chilling (Plant I) and water chilling (Plant II), both including a carcass wash prior to the chilling operation, caused similar, but significant reductions of 0.83 and 0.97 log(10) cfu/g, respectively. In packed frozen chickens (Plant II) an additional reduction of 1.38 log(10) cfu/g in average was obtained due to the freezing operation. In packed chilled chickens (Plant I), however, the number of thermotolerant Campylobacter per gram remained at the same level as after air chilling. Enumeration of thermotolerant Campylobacter in 30 intestinal samples per flock showed that in two of the six flocks examined the within flock colonization was very low (<3% and 27% positive samples). The remaining four flocks were colonized at percentages of 100 (three flocks) and 97 (one flock) and had intestinal mean counts ranging from 6.65 to 8.20 log(10) cfu/g. A correlation between Campylobacter concentrations in intestinal content and on chicken carcasses after the defeathering operation was documented. This finding indicates that a reduction in the Campylobacter concentration on chicken carcasses may also be obtained by interventions aimed at reducing the concentration of Campylobacter in the intestines of the living birds.