scholarly journals Impact of Partitioning in Short-Term Food Contact Applications Focused on Polymers in Support of Migration Modelling and Exposure Risk Assessment

Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 121
Author(s):  
Rainer Brandsch ◽  
Mark Pemberton ◽  
Dieter Schuster ◽  
Frank Welle
Keyword(s):  
Steady State ◽  
Real Life ◽  
Minor Role ◽  
Contact Period ◽  
Worst Case ◽  
Food Contact ◽  
Consumer Safety ◽  
Prolonged Contact ◽  
Repeated Use ◽  
Migration Testing

Food contact materials (FCMs) can transfer chemicals arising from their manufacture to food before consumption. Regulatory frameworks ensure consumer safety by prescribing methods for the assessment of FCMs that rely on migration testing either into real-life foods or food simulants. Standard migration testing conditions for single-use FCMs are justifiably conservative, employing recognized worst-case contact times and temperatures. For repeated-use FCMs, the third of three consecutive tests using worst-case conditions is taken as a surrogate of the much shorter contact period that often occurs over the service life of these items. Food contact regulations allow for the use of migration modelling for the chemicals in the FCM and for the partitioning that occurs between the FCM and food/simulant during prolonged contact, under which steady-state conditions are favored. This study demonstrates that the steady-state is rarely reached under repeated-use conditions and that partitioning plays a minor role that results in migration essentially being diffusion controlled. Domains of use have been identified within which partitioning does not play a significant role, allowing modelling based upon diffusion parameters to be used. These findings have the potential to advance the modelling of migration from repeated-use articles for the benefit of regulatory guidance and compliance practices.

Risk-Based Robust Bidding Strategies for EVs’ Aggregators in Day-ahead Markets with Uncertainty

2020 ◽  
Author(s):  
Ahmed Abdelmoaty ◽  
Wessam Mesbah ◽  
Mohammad A. M. Abdel-Aal ◽  
Ali T. Alawami
Keyword(s):  
Robust Optimization ◽  
Electricity Market ◽  
Real Life ◽  
Optimization Approach ◽  
Case Scenario ◽  
Worst Case ◽  
Bidding Strategies ◽  
Wind Generators ◽  
Proposed Model ◽  
Optimal Bidding

In the recent electricity market framework, the profit of the generation companies depends on the decision of the operator on the schedule of its units, the energy price, and the optimal bidding strategies. Due to the expanded integration of uncertain renewable generators which is highly intermittent such as wind plants, the coordination with other facilities to mitigate the risks of imbalances is mandatory. Accordingly, coordination of wind generators with the evolutionary Electric Vehicles (EVs) is expected to boost the performance of the grid. In this paper, we propose a robust optimization approach for the coordination between the wind-thermal generators and the EVs in a virtual<br>power plant (VPP) environment. The objective of maximizing the profit of the VPP Operator (VPPO) is studied. The optimal bidding strategy of the VPPO in the day-ahead market under uncertainties of wind power, energy<br>prices, imbalance prices, and demand is obtained for the worst case scenario. A case study is conducted to assess the e?effectiveness of the proposed model in terms of the VPPO's profit. A comparison between the proposed model and the scenario-based optimization was introduced. Our results confirmed that, although the conservative behavior of the worst-case robust optimization model, it helps the decision maker from the fluctuations of the uncertain parameters involved in the production and bidding processes. In addition, robust optimization is a more tractable problem and does not suffer from<br>the high computation burden associated with scenario-based stochastic programming. This makes it more practical for real-life scenarios.<br>

scholarly journals Development and Validation of a UHPLC-qTOF MS Method for the Determination of Sorbitol-Based Nuclear Clarifying Agents in Food Simulants after Migration from Food Contact Materials

2021 ◽  
Vol 11 (9) ◽  
pp. 3789
Author(s):  
Emmanouil D. Tsochatzis ◽  
Georgios Theodoridis ◽  
Helen G. Gika
Keyword(s):  
A Posteriori ◽  
Contact Materials ◽  
Food Contact ◽  
Food Simulants ◽  
Target Analytes ◽  
Commission Regulation ◽  
Development And Validation ◽  
Migration Testing ◽  
Analytical Standards

Nuclear clarifying agents (NCAs) are a class of substances frequently used as additives in the production of polymers to improve their physical properties. Some are EU regulated under Commission Regulation (EU) no. 10/2011 can be used as additives in the production of food contact plastics. However, limited analytical methods for their analysis are currently available, in part due to poor solubility in most common organic solvents and lack of analytical standards of known purity. In this work, a simple and sensitive method was developed to analyze 4 EU-regulated sorbitol-based nucleating agents in food simulants, following solubility studies to establish effective solvents. The method was shown to be accurate and precise and can be used with official food simulant D1 (50% v/v ethanol/H2O). Application to other ethanolic simulants is also possible, but due to solubility issues, a posteriori conversion of those simulants into simulant D1 is required. Finally, the method was applied to quantify the target analytes in simulants after migration testing with polypropylene (PP) beverage cups.

scholarly journals Decision making under interval uncertainty: toward (somewhat) more convincing justifications for Hurwicz optimism-pessimism approach

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Warattaya Chinnakum ◽  
Laura Berrout Ramos ◽  
Olugbenga Iyiola ◽  
Vladik Kreinovich
Keyword(s):  
Decision Making ◽  
Real Life ◽  
Interval Uncertainty ◽  
Lower And Upper Bounds ◽  
Worst Case ◽  
Content Type ◽  
Expected Gain ◽  
Utility Approach ◽  
Interval Valued ◽  
Weighted Combination

Purpose In real life, we only know the consequences of each possible action with some uncertainty. A typical example is interval uncertainty, when we only know the lower and upper bounds on the expected gain. A usual way to compare such interval-valued alternatives is to use the optimism–pessimism criterion developed by Nobelist Leo Hurwicz. In this approach, a weighted combination of the worst-case and the best-case gains is maximized. There exist several justifications for this criterion; however, some of the assumptions behind these justifications are not 100% convincing. The purpose of this paper is to find a more convincing explanation. Design/methodology/approach The authors used utility approach to decision-making. Findings The authors proposed new, hopefully more convincing, justifications for Hurwicz’s approach. Originality/value This is a new, more intuitive explanation of Hurwicz’s approach to decision-making under interval uncertainty.

scholarly journals Modeling and Control of Double-Sided LCC Compensation Topology with Semi-Bridgeless Active Rectifier for Inductive Power Transfer System

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3921
Author(s):  
Cha ◽  
Kim ◽  
Park ◽  
Choi
Keyword(s):  
Steady State ◽  
Equivalent Circuit ◽  
Small Signal ◽  
Power Transfer ◽  
Large Signal ◽  
Signal Model ◽  
Worst Case ◽  
Inductive Power Transfer ◽  
Active Rectifier ◽  
Inductive Power

This paper proposes the modeling and design of a controller for an inductive power transfer (IPT) system with a semi-bridgeless active rectifier (S-BAR). This system consists of a double-sided Inductor-Capacitor-Capacitor (LCC) compensation network and an S-BAR, and maintains a constant output voltage under load variation through the operation of the rectifier switches. Accurate modeling is essential to design a controller with good performance. However, most of the researches on S-BAR have focused on the control scheme for the rectifier switches and steady-state analysis. Therefore, modeling based on the extended describing function is proposed for an accurate dynamic analysis of an IPT system with an S-BAR. Detailed mathematical analyses of the large-signal model, steady-state operating solution, and small-signal model are provided. Nonlinear large-signal equivalent circuit and linearized small-signal equivalent circuit are presented for intuitive understanding. In addition, worst case condition is selected under various load conditions and a controller design process is provided. To demonstrate the effectiveness of the proposed modeling, experimental results using a 100 W prototype are presented.

scholarly journals Characterization of steady-state fluorescence properties of polystyrene latex spheres using off- and online spectroscopic methods

2018 ◽  
Vol 11 (7) ◽  
pp. 3987-4003 ◽  
Author(s):  
Tobias Könemann ◽  
Nicole J. Savage ◽  
J. Alex Huffman ◽  
Christopher Pöhlker
Keyword(s):  
Steady State ◽  
Polystyrene Latex ◽  
Fluorescence Properties ◽  
Minor Role ◽  
Spectroscopic Techniques ◽  
Fluorescent Properties ◽  
Qualitative Comparison ◽  
Steady State Fluorescence ◽  
Research Communities ◽  
Latex Spheres

Abstract. Fluorescent dyed polystyrene latex spheres (PSLs) are commonly used for characterization and calibration of instruments detecting fluorescence signals from particles suspended in the air and other fluids. Instruments like the Ultraviolet Aerodynamic Particle Sizer (UV-APS) and the Waveband Integrated Bioaerosol Sensor (WIBS) are widely used for bioaerosol research, but these instruments present significant technical and physical challenges requiring careful characterization with standard particles. Many other research communities use flow cytometry and other instruments that interrogate fluorescence from individual particles, and these also frequently rely on fluorescent PSLs as standards. Nevertheless, information about physical properties of commercially available PSLs provided by each manufacturer is generally proprietary and rarely available, making their use in fluorescence validation and calibration very difficult. This technical note presents an overview of steady-state fluorescence properties of fluorescent and non-fluorescent PSLs, as well as of polystyrene-divinylbenzene (PS-DVB) particles, by using on- and offline spectroscopic techniques. We show that the “fluorescence landscape” of PSLs is more complex than the information typically provided by manufacturers may imply, especially revealing multimodal emission patterns. Furthermore, non-fluorescent PSLs also exhibit defined patterns of fluorescent emission originating from a mixture of polystyrene and detergents, which becomes a crucial point for fluorescence threshold calibrations and qualitative comparison between instruments. By comparing PSLs of different sizes, but doped with the same dye, changes in emission spectra from bulk solutions are not immediately obvious. On a single-particle scale, however, fluorescence intensity values increase with increasing particle size. No significant effect in the fluorescence signatures was detectable by comparing PSLs in dry vs. wet states, indicating that solvent water may only play a minor role as a fluorescence quencher. Because information provided by manufacturers of commercially available PSLs is generally very limited, we provide the steady-state excitation–emission matrices (EEMs) of PSLs as open-access data within the Supplement. Detergent and solvent effects are also discussed in order to provide information not available elsewhere to researchers in the bioaerosol and other research communities. These data are not meant to serve as a fundamental library of PSL properties because of the variability of fluorescent properties between batches and as a function of particle aging and agglomeration. The data presented, however, provide a summary of spectral features which are consistent across these widely used fluorescent standards. Using these concepts, further checks will likely be required by individual researchers using specific lots of standards.

scholarly journals Finite element modelling of creep process - steady state stresses and strains

2014 ◽  
Vol 18 (suppl.1) ◽  
pp. 179-188 ◽  
Author(s):  
Aleksandar Sedmak ◽  
Ljubica Milovic ◽  
Mirko Pavisic ◽  
Pejo Konjatic
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Finite Element Modelling ◽  
Residual Life ◽  
Longitudinal Crack ◽  
Real Life ◽  
Creep Process ◽  
The Finite Element Method ◽  
Cylindrical Pipe ◽  
Element Modelling

Finite element modelling of steady state creep process has been described. Using an analogy of visco-plastic problem with a described procedure, the finite element method has been used to calculate steady state stresses and strains in 2D problems. An example of application of such a procedure have been presented, using real life problem - cylindrical pipe with longitudinal crack at high temperature, under internal pressure, and estimating its residual life, based on the C*integral evaluation.

Concentration and Detection of Caliciviruses from Food Contact Surfaces

2002 ◽  
Vol 65 (6) ◽  
pp. 999-1004 ◽  
Author(s):  
ANIL TAKU ◽  
BALDEV R. GULATI ◽  
PAUL B. ALLWOOD ◽  
KERRIN PALAZZI ◽  
CRAIG W. HEDBERG ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Food Service ◽  
Contact Period ◽  
Norwalk Virus ◽  
Buffer Solution ◽  
Simple Method ◽  
Food Contact ◽  
Food Contact Surfaces ◽  
Contact Surfaces ◽  
Elution Method

Outbreaks of human Norwalk virus (NV) and Norwalk-like viruses often originate in food service establishments. No reliable method is available for the detection of these human caliciviruses on food contact surfaces. We describe a simple method for the detection of NV from stainless steel work surfaces using cultivable feline calicivirus (FCV) as a model. Stainless steel surfaces were artificially contaminated with known amounts of FCV, followed by its elution in a buffer solution. Three methods of virus elution were compared. In the first method, moistened cotton swabs or pieces of nylon filter (1MDS) were used to elute the contaminating virus. The second method consisted of flooding the contaminated surface with eluting buffer, allowing it to stay in contact for 15 min, followed by aspiration of the buffer (aspiration method) after a contact period of 15 min. The third method, the scraping-aspiration method, was similar to the aspiration method, except that the surfaces were scraped with a cell scraper before buffer aspiration. Maximum virus recovery (32 to 71%) was obtained with the scraping-aspiration method using 0.05 M glycine buffer at pH 6.5. Two methods (organic flocculation and filter adsorption elution) were compared to reduce the volume of the eluate recovered from larger surfaces. The organic flocculation method gave an average overall recovery of 55% compared to the filter-adsorption-elution method, which yielded an average recovery of only 8%. The newly developed method was validated for the detection of NV by artificial contamination of 929-cm2 stainless steel sheets with NV-positive stool samples and for the detection of the recovered virus by reverse transcription–polymerase chain reaction.

scholarly journals Contamination Levels in Recollected PET Bottles from Non-Food Applications and their Impact on the Safety of Recycled PET for Food Contact

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 4998
Author(s):  
Roland Franz ◽  
Frank Welle
Keyword(s):  
Safety Concern ◽  
Food Product ◽  
Feed Stream ◽  
Recycled Pet ◽  
Worst Case ◽  
Pet Bottles ◽  
Food Contact ◽  
Contamination Levels ◽  
Carry Over ◽  
The Impact

PET beverage bottles have been recycled and safely reprocessed into new food contact packaging applications for over two decades. During recollection of post-consumer PET beverage bottles, PET containers from non-food products are inevitably co-collected and thereby enter the PET recycling feed stream. To explore the impact of this mixing on the safety-in-use of recycled PET (rPET) bottles, we determined the concentrations of post-consumer substances in PET containers used for a range of non-food product applications taken from the market. Based on the chemical nature and amounts of these post-consumer substances, we evaluated their potential carry-over into beverages filled in rPET bottles starting from different fractions of non-food PET in the recollection systems and taking worst-case cleaning efficiencies of super-clean recycling processes into account. On the basis of the Threshold of Toxicological Concern (TTC) concept and Cramer classification tools, we present a risk assessment for potential exposure of the consumer to the identified contaminants as well as unidentified, potentially genotoxic substances in beverages. As a result, a fraction of 5% non-food PET in the recycling feed stream, which is very likely to occur in the usual recollection systems, does not pose any risk to the consumer. Our data show that fractions of up to 20%, which may sporadically be contained in certain, local recollection systems, would also not raise a safety concern.

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