Optimal experimental design for estimating the kinetic parameters of processes described by the Weibull probability distribution function

The optimum experimental design for determining the kinetic parameters of the model resulting from the Weibull probability density junction was studied, by defining the sampling conditions that lead to a minimum confidence region of the estimates, for a number of observations equal to the number of parameters. It was found that for one single isothermal experiment the optimum sampling times corresponded always to fractional concentrations that are irrational numbers (approximately 0.70 and 0.19) whose product is exactly l/e’. The experimental determination of the equilibtium conversion (for growth kinetics) is vety important, but in some situations this is not possible, e.g. due to product degradation over the length of time required. Sampling times leading to a maximum precision were determined as a function of the maximum conversion (or yield) attainable. For studies of kinetic parameters over a range of temperatures, performed with a minimum of three isothermal experiments, it was proved that the optimum design consists of two experiments at one limit temperature with two sampling times (those corresponding to fractional concentrations of approximate[v 0.70 and 0.19) and another at the other limit temperature for a sampling time such that the fractional concentration is lie. Case studies are included for clarijication of the concepts and procedures

Optimal experimental design for estimating the kinetic parameters of processes described by the first-order Arrhenius model under linearly increasing temperature profiles

The optimum experimental design for systems following the ®rst-order Arrhenius model under linearly increasing temperature pro®les was studied by determining the sampling conditions that lead to a minimum con®dence region of the model parameters. It was found that experiments should be started at the lowest possible temperature and, for each initial temperature, there is an optimal heating rate. This heating rate is often too high to be feasible, implying that experiments have to be conducted at a lower practicable heating rate. In this situation the experiments should be replicated in order to improve the precision of the estimates. If both the initial temperature and the heating rate are ®xed at their optimal values, the optimal sampling times correspond to fractional concentrations that are irrational numbers (approximately 0.70 and 0.19) whose product is exactly 1=e2, as earlier found for the Bigelow model. A case study based on the estimation of the kinetic parameters of the acid hydrolysis of sucrose is also presente

Development of a non-isothermal method for determination of diffusional parameters

A non-isothermal method for determination of diffusional parameters was developed. The dependence of diffusivity on temperature was described by an Arrhenius type equation, 'with the pre-exponential factor and the,activation energy as parameters. These parameters were obtained by optimization of the fit between experimental and theoretical values, using the Simplex method of minimization. Equilibrium conditions were described with a constant unit partition coefficient. This model was applied to the diffusion of acetic acid into turnips. Results compared well with values obtained with the conventional method, using a set of experiments at isothermal conditions. The non-isothermal method has significant advantages, nameiy the need for much less experimental data and better insight into the statistical significance of the results

A critical survey of predictive mathematical models for migration from packaging

The migration of chemicals from food contact materials into foods is an important issue in food safety.The assessment of materials compliance with regulations includes migration monitoring for many monomers and additives. However,it is recognized that predictive mathematical modelling can be used in many cases, to avoid or to reduce the effort on migration experiments. This article reviews the approaches followed to apply mathematical models to migration, particularly the models used, the approaches to estimate model parameters, and the systems used to experimentally validate the models. Conclusions on the issues requiring further research are drawn

Improvement in planning and resource management for an automotive company’s parts feeding system

The increasing sophistication of the automotive market and the constant change in customer requirements increases companies’ concern to ensure efficient internal logistic flows in line with Just-In-Time philosophy and Lean principles, to deal with wastes and variability. Variability arises from the growing differentiation of products, from the adoption of multi and mixed model assembly lines, and from the uncertainty in customer demand resulting from the worldwide outbreak of COVID-19. Considering the automotive supplier company as research subject, several problems were found to be compromising the efficiency of one of its in-plant parts’ feeding systems, the most critical problem being the lack of planning and management of resources (human and material) needed to perform the logistic service. Through Action-Research methodology stages, the actions taken culminated in the development of a simulation and decision-support tool for the component supply system resource management and efficiency improvement. The simulations made revealed reliable and adjusted results of workload and workforce to face the variations in customer demand and the existing product mix. After the tool creation, resource planning and balancing was no longer based on managers experience and empirical knowledge only but based on scientific knowledge: concise and reliable data from information systems, measurements, study of times, and literature review on in-plant milk run systems, lean, just-in-time and continuous improvement techniques.info:eu-repo/semantics/publishedVersio

Future Food: Sustainable Diets for Healthy People and a Healthy Planet

The current food system is associated with poor health outcomes, food insecurity, and significant environmental damage. While, globally, more than enough food calories are produced than theoretically needed, this does not guaranty a good quality diet for all. At the same time, the environmental pressures of the current food system threaten several planetary boundaries, which define the environmental limits within which humans can safely operate. This narrative review gives a brief overview of the shortcomings of the current food system regarding its impact on nutrition, health, and the environment. It outlines recent advancements in the development of guidelines for a healthy and sustainable diet and discusses options on how to realize such a dietary transformation, involving all stakeholders in the food value chain

Do Urban Hedgehogs (Erinaceus europaeus) Represent a Relevant Source of Zoonotic Diseases?

[EN] Urban fauna is defined as animal species that can live in urban environments. Several species, including the western-European hedgehog (Erinaceus europaeus), have now been identified as part of this urban fauna, becoming permanent residents of parks and gardens in different cities across Europe. Due to the importance that this phenomenon represents for zoonotic disease surveillance, several authors have been conducting zoonotic agents’ surveys on hedgehog. The aim of this study is to compare zoonotic diseases’ prevalence in hedgehogs in urban environments with those from more rural areas. A systematic review with meta-analysis of twelve studied of zoonotic diseases’ (in urban and rural areas of Europe) was therefore conducted for this purpose. Fifteen different zoonoses have been assessed in urban environments and six in rural areas. Anaplasma phagocytophilum was the most prevalent zoonotic agent found in urban habitats (96%). Dermatophytosis shows statistically significant differences between locations (p-value < 0.001), with a higher prevalence in urban Poland (55%; n = 182). Our results suggest further research and a standardized monitoring of different hedgehog populations are essential to understanding the epidemiology of several zoonotic pathogens in different habitat types (urban, rural, natural, industrial, etc.) and preventing possible disease outbreaksSIThis work was supported by National Funds from FCT—Portuguese Foundation for Science and Technology (FCT) under grant number 2021.04520.BD. The authors of the research unit CITAB (CJB and PAO) received funding from FCT; reference for the project UIDB/04033/2020. The author of the research unit CECAV (FS) received funding from FCT; reference for the project UIDB/CVT/00772/202

Electroanalytical determination of codeine in pharmaceutical preparations

A square wave voltammetric (SWV) method and a flow injection analysis systemwi th electrochemical detection (FIA-EC) using a glassy carbon electrode were evaluated for the determination of codeine in pharmaceutical preparations. The interference of several compounds, such as acetaminophen,guaiacol, parabens, ephedrine, acetylsalicylic acid and caffeine, that usually appear associated with codeine pharmaceutical preparations was studied. It was verified that these electroanalytical methods could not be used with acetaminophen present in the formulations and that with guaiacol, parabens or ephedrine present the use of the FIA-EC system was impracticable. A detection limit of 5 µmol L- 1 and a linear calibration range from 40 to 140 µmol L- 1 was obtained with the SWV method. For the flow injection analysis procedure a linear calibration range was obtained from 7 to 50 µmol L- 1 with a detection limit of 3 µmol L- 1 and the FIA-EC systemallowed a sampling rate of 115 samples per hour. The results obtained by the two methods, SWV and FIA-EC, were compared with those obtained using reference methods and demonstrated good agreement, with relative deviations lower than 4%

Influence of low oxygen and high carbon dioxide on shredded Galega kale quality for development of modified atmosphere packages

Respiration rate, sensory attributes, colour alterations, and water, chlorophyll and ascorbic acid contents were monitored during storage of shredded Galega kale (Brassica oleracea var. acephala DC.) at 20 ◦C to define an adequate range of O2 and CO2 partial pressures for product preservation. Different low O2 and high CO2 atmospheres were tested. First, tolerance to low O2 partial pressures (1, 2, 3 or 21 kPa O2 with balance N2) was tested. Quality retention was improved as O2 partial pressure was reduced and there was no induction of anaerobic respiration. Then, tolerance to high CO2 partial pressures (0, 10, 15 or 20 kPa CO2 plus 21 kPa O2 and balance N2) was tested. The high CO2 partial pressures extended the shelf life of the shredded kale and no symptoms of CO2 injury were detected. Finally, combinations of low O2 and high CO2 (1 or 2 kPa O2 plus 15 or 20 kPa CO2, with balance N2, and an air control) were analysed. No differences were observed among the different gas combinations. An atmosphere of 1–2 kPa O2 plus 15–20 kPa CO2 and balance N2 extends the shelf life of shredded Galega kale to 4–5 days at 20◦C, compared with 2–3 days in air storage. Predictive models of chlorophyll a and b degradation as a function of time and gas composition were developed