Solubility and absorption rate of carbon dioxide into non-respiring foods. Part 3: Cooked meat products

The solubility and diffusion of carbon dioxide into cooked meat products (cooked ham and meat sausage with different pH-levels) was determined at different starting pressures and gas to product volume ratios by monitoring pressure changes over time in a closed chamber at constant temperatures (0, 4, and 8 °C). Good correlation of the CO₂ solubility between the packaging parameters (gas to product volume ratio and initial partial pressure) and the meat products water content was found. The solubility of CO₂ followed Henry’s law and the initial partial pressure of CO₂ influenced the solubility mostly. Only small variations in the diffusion constants and absorption rates were found within the experimental design. A pH difference of 0.5 in the two meat sausage types did not influence either solubility or diffusion significantly.     

Facets of visual aesthetics

Visual aesthetics has been shown to critically affect a variety of constructs such as perceived usability, satisfaction, and pleasure. Given the importance of visual aesthetics in human–computer interaction, it is vital that it is adequately assessed. The present research aimed at providing a precise operational definition and to develop a new measure of perceived visual aesthetics of websites. Construction of the Visual Aesthetics of Website Inventory (VisAWI) was based on a comprehensive and broad definition of visual aesthetics so that the resulting instrument would completely describe the domain of interest. Four interrelated facets of perceived visual aesthetics of websites were identified and validated in a series of seven studies. Simplicity and Diversity have repeatedly been treated as formal parameters of aesthetic objects throughout the history of empirical aesthetics, Colors are a critical property of aesthetic objects, and Craftsmanship addresses the skillful and coherent integration of the relevant design dimensions. These four facets jointly represent perceived visual aesthetics, but are still distinguishable from each other and carry unique meaning. The subscales contained in the VisAWI demonstrate good internal consistencies. Evidence for the convergent, divergent, discriminative, and concurrent validity of the VisAWI is provided. Overall, the present research suggests that the VisAWI appears to be a sound measure of visual aesthetics of websites comprising facets of both practical and theoretical interest.     

A critical approach to viscosity index

The viscosity index (VI) is a useful tool for lubricant users and refiners, since it is a measure of the effect of temperature changes on the viscosity of the oil. However, it was found that the viscosity index does not correlate with the flow activation energy E_a, which is the theoretically defined dependence of the viscosity on temperature. In this way, two oils may have the same flow activation energy but a viscosity index varying by up to 120. We therefore believe that the VI does not always give a proper representation of the effect of temperature on the kinematic viscosity.¹³C NMR spectroscopy was used to identify the molecules with a high VI. Twenty different oil samples produced from eight different vacuum gas oils with viscosity indices ranging from −104 to 146 were analyzed and key parameters identified for high VI molecules: long alkyl chains, methyl branching in the centre of the molecule, low content of aromatic compounds, no ethyl branching and no tertiary carbons.A correlation based on four selected peaks was developed, giving a very good prediction of the viscosity index.     

On the usefulness of non-gradient approaches in topology optimization

Topology optimization is a highly developed tool for structural design and is by now being extensively used in mechanical, automotive and aerospace industries throughout the world. Gradient-based topology optimization algorithms may efficiently solve fine-resolution problems with thousands and up to millions of design variables using a few hundred (finite element) function evaluations (and even less than 50 in some commercial codes). Nevertheless, non-gradient topology optimization approaches that require orders of magnitude more function evaluations for extremely low resolution examples keep appearing in the literature. This forum article discusses the practical and scientific relevance of publishing papers that use immense computational resources for solving simple problems for which there already exist efficient solution techniques.     

Development and validation of an extensive growth and growth boundary model for psychrotolerant Lactobacillus spp. in seafood and meat products

A new and extensive growth and growth boundary model for psychrotolerant Lactobacillus spp. was developed and validated for processed and unprocessed products of seafood and meat. The new model was developed by refitting and expanding an existing cardinal parameter model for growth and the growth boundary of lactic acid bacteria (LAB) in processed seafood (O. Mejlholm and P. Dalgaard, J. Food Prot. 70. 2485–2497, 2007). Initially, to estimate values for the maximum specific growth rate at the reference temperature of 25 °C (μ_ref) and the theoretical minimum temperature that prevents growth of psychrotolerant LAB (T_min), the existing LAB model was refitted to data from experiments with seafood and meat products reported not to include nitrite or any of the four organic acids evaluated in the present study. Next, dimensionless terms modelling the antimicrobial effect of nitrite, and acetic, benzoic, citric and sorbic acids on growth of Lactobacillus sakei were added to the refitted model, together with minimum inhibitory concentrations determined for the five environmental parameters. The new model including the effect of 12 environmental parameters, as well as their interactive effects, was successfully validated using 229 growth rates (μ_max values) for psychrotolerant Lactobacillus spp. in seafood and meat products. Average bias and accuracy factor values of 1.08 and 1.27, respectively, were obtained when observed and predicted μ_max values of psychrotolerant Lactobacillus spp. were compared. Thus, on average μ_max values were only overestimated by 8%. The performance of the new model was equally good for seafood and meat products, and the importance of including the effect of acetic, benzoic, citric and sorbic acids and to a lesser extent nitrite in order to accurately predict growth of psychrotolerant Lactobacillus spp. was clearly demonstrated. The new model can be used to predict growth of psychrotolerant Lactobacillus spp. in seafood and meat products e.g. prediction of the time to a critical cell concentration of bacteria is considered useful for establishing the shelf life. In addition, the high number of environmental parameters included in the new model makes it flexible and suitable for product development as the effect of substituting one combination of preservatives with another can be predicted. In general, the performance of the new model was unacceptable for other types of LAB including Carnobacterium spp., Leuconostoc spp. and Weissella spp.     

Magnetic properties of Ni-Co thick-film magnetoresistors

Magnetic susceptibility from 300 to 900 K, room temperature hysteresis cycles and saturation magnetization were investigated in screen printed and fired NiCo-based layers prepared at various peak temperatures. A bulk NiCo metal sheet of comparable composition was also studied. Values of the magnetic polarization J of 0.28 and 0.435 T were obtained (at 200 kA/m) for films prepared at 750 and 950°C, respectively, in contrast with J=0.98 T for the bulk alloy. In addition, the magnetoresistive responses of the layers and the sheet were plotted. These data suggest that strains, pores and lack of composition homogeneity in the films concur in affecting their magnetic properties, and are responsible for their reduced magnetoresistance anisotropy (e.g. ca. 4% for films as compared to ca. 8% for the bulk alloy at H=80 kA/m).     

Deployment of Mobile Switching Centers in a Telecommunications Network: A Stochastic Programming Approach

We consider a network design problem arising in mobile communications. At the core of the network is a number of mobile switching centers (MSCs), each serving a number of base station controllers (BSCs). The network design problem involves three major groups of decisions – deployment of a number of new MSCs, allocation of BSCs to new and existing MSCs, and capacity expansion of transmission links interconnecting the MSCs. These decisions must be made so as to minimize the incurred costs while meeting customer demand and observing the capacity restrictions. We formulate the problem as a two-stage stochastic program with mixed-integer recourse. To solve the problem we apply a dual decomposition procedure, solving scenario subproblems by means of branch and cut. The solution procedure has been tested on a real life problem instance provided by SONOFON, a Danish mobile communication network operator, and we report results of our computational experiments.