scholarly journals Bisphenol A Release from Dental Composites and Resin-Modified Glass Ionomers under Two Polymerization Conditions

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 46
Author(s):  
Antonin Tichy ◽  
Marketa Simkova ◽  
Radka Vrbova ◽  
Adela Roubickova ◽  
Michaela Duskova ◽  
...  
Keyword(s):  
Bisphenol A ◽  
Artificial Saliva ◽  
Daily Intake ◽  
Dental Resin ◽  
Case Scenario ◽  
Worst Case ◽  
Initial Release ◽  
Liquid Chromatography Tandem Mass ◽  
Polymerization Conditions

Bisphenol A (BPA)-based monomers are commonly contained in dental resin-based materials. As BPA is an endocrine disruptor, its long-term release from restorative composites and resin-modified glass ionomers (RM-GICs) under two polymerization conditions was measured in this study. Specimens of two conventional composites containing BPA-based monomers, two “BPA-free” composites, and two RM-GICs were polymerized from one side for 20 s at 1300 mW/cm2 or for 5 s at 3000 mW/cm2. The amounts of BPA released in artificial saliva and methanol after 1, 4, 9, 16, 35, 65, 130, and 260 days were measured using liquid chromatography–tandem mass spectrometry. The highest amounts of BPA were released from conventional composites, followed by RM-GICs, while the least was released from “BPA-free” composites. Amounts of released BPA were significantly higher in methanol and decreased gradually after the first day. Fast polymerization (5 s at 3000 mW/cm2) resulted in a significantly higher release of BPA after 1 day, but the effect of polymerization conditions was not significant overall. In conclusion, fast polymerization increased the initial release of BPA, but the released amounts were significantly lower than the current tolerable daily intake (4 μg/kg body weight/day) even in methanol, representing the worst-case scenario of BPA release.

scholarly journals Release of Bisphenol A from Milled and 3D-Printed Dental Polycarbonate Materials

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5868
Author(s):  
Antonin Tichy ◽  
Marketa Simkova ◽  
Josef Schweiger ◽  
Pavel Bradna ◽  
Jan-Frederik Güth
Keyword(s):  
Bisphenol A ◽  
Endocrine Disruptor ◽  
Artificial Saliva ◽  
Daily Intake ◽  
Tandem Mass ◽  
Case Scenario ◽  
Worst Case ◽  
Chromatography Tandem Mass Spectrometry ◽  
Liquid Chromatography Tandem Mass ◽  
3D Printed

Polycarbonates are polymers of bisphenol A (BPA), a well-known endocrine disruptor. This study evaluated the release of BPA from polycarbonate crowns that were (1) milled from Temp Premium Flexible (ZPF, Zirkonzahn, Italy) or Tizian Blank Polycarbonate (TBP, Schütz Dental, Germany), or (2) 3D-printed (Makrolon 2805, Covestro, Germany). Commercial prefabricated polycarbonate crowns (3M, USA) and milled poly(methyl methacrylate) (PMMA) crowns (Temp Basic, Zirkonzahn, Italy) were included for comparison. The crowns were stored at 37 °C in artificial saliva (AS) or methanol, which represented the worst-case scenario of BPA release. Extracts were collected after 1 day, 1 week, 1 month and 3 months. BPA concentrations were measured using liquid chromatography-tandem mass spectrometry. The amounts of released BPA were expressed in micrograms per gram of material (μg/g). After 1 day, the highest amounts of BPA were measured from milled polycarbonates, TBP (methanol: 32.2 ± 3.8 mg/g, AS: 7.1 ± 0.9 mg/g) and ZPF (methanol 22.8 ± 7.7 mg/g, AS: 0.3 ± 0.03 mg/g), followed by 3D-printed crowns (methanol: 11.1 ± 2.3 mg/g, AS: 0.1 ± 0.1 mg/g) and prefabricated crowns (methanol: 8.0 ± 1.6 mg/g, AS: 0.07 ± 0.02 mg/g). Between 1 week and 3 months, the average daily release of BPA in methanol and AS decreased below 2 mg/g and 0.6 mg/g, respectively. No BPA was released from PMMA in AS, and the cumulative amount released in methanol was 0.2 ± 0.06 mg/g. In conclusion, polycarbonates could be a relevant source of BPA, but the current tolerable daily intake of BPA (4 mg/kg body weight) should not be exceeded.

scholarly journals Modelling of Health Risk Associated with the Intake of Pesticides from Romanian Fruits and Vegetables

2020 ◽  
Vol 12 (23) ◽  
pp. 10035
Author(s):  
Mariana Minuț ◽  
Mihaela Roșca ◽  
Raluca-Maria Hlihor ◽  
Petronela Cozma ◽  
Maria Gavrilescu
Keyword(s):  
Exposure Assessment ◽  
Pesticide Residues ◽  
Fruits And Vegetables ◽  
Daily Intake ◽  
Case Scenario ◽  
Worst Case ◽  
Short Term Exposure ◽  
Fruit Samples ◽  
German Children

This study is focused on the assessment of risks caused by pesticide residues to Romanian and other European populations, by modelling the acute and chronic risks considering short- and long-term exposures to pesticide residues in specific fruits and vegetables from different Romanian regions. Data were obtained from the Romanian 2016 official monitoring programme. For assessing the dietary risk, we used the Pesticide Residue Intake model—PRIMo. According to the official data, it was found that 50.44% of fruit samples and 28.25% of vegetable samples were contaminated with pesticides. Our study focused on acute risks and chronic risks (in a maximalist worst-case scenario) posed by pesticide residues in strawberries, apples, lettuce and potatoes, given both their high degree of consumption and contamination with pesticides. The short-term exposure assessment of children’s health due to consumption of apples, lettuce and potatoes contaminated with dimethoate, chlorothalonil and carbendazim, revealed exposure levels higher than the acute reference dose (ARfD, as 100%), raising acute risks. On the other hand, the long-term exposure assessment showed that the highest percentage from the acceptable daily intake (ADI, as 100%) was obtained for German children (DE child) (273.9%), followed by Netherlands children (NL child) (143.7%) diets, based on consumption of apples with dimethoate residues. Therefore, serious measures are needed for banning pesticides such as dimethoate, chlorothalonil and carbendazim from all countries in the EU. This would reduce the health risks generated by the consumption of contaminated fruits and vegetables.

A Case Study - Life Extension of Offshore Bridge Bearings

2021 ◽  
Author(s):  
Ahmed Abdelkhalek ◽  
Govindavilas Sudhesh ◽  
Anjan Sarkar ◽  
Mohammed Eissa
Keyword(s):  
Cost Savings ◽  
Holistic Approach ◽  
Life Extension ◽  
Case Scenario ◽  
Worst Case ◽  
Maintenance And Repair ◽  
Seasonal Monitoring ◽  
The Impact ◽  
Bridge Bearings

Abstract Structural bearings of 47 offshore platform-link bridges with average age of 40 years were inspected and recommended for replacements due to their poor condition. Replacement of bridge bearings involves major risk and production interruptions given the structural modifications, and critical piping and E&I disconnections required for safe jacking-lifting activities required during the process. This paper presents the approach adopted to assure the integrity of the bridges and extend their lives without the need to replace the bearings. The approach employed failure mode and effect analysis to identifying and narrowing down areas that need focused efforts while tackling the problem. Scenario based structural assessments were carried out to examine the impact of the level of movement-allowing bearings functionality on the integrity of the bridge and its supporting structures; identify critical locations to be targeted during focused inspections; and establish envelopes for monitoring thermal expansion and contraction of the bridges. Guidelines were developed and implemented for integrated inspection-maintenance and repair campaign, which aimed to tackle corrosion issues and to install movement-monitoring indicators. Indicator seasonal monitoring is employed to establish the functionality of bearings on the long-term. The what-if structural assessments revealed that even in the worst-case scenario (in which the bearing are completely jammed) the option of local strengthening of the bridge and its supporting elements is more attractive than bearing replacement. The integrated inspection-maintenance and repair campaigns revealed that excessive corrosion levels observed from historic visual inspections on external non-critical bearing components (e.g: guide plates, angles, etc.) is not indicative of the condition of the internal load-bearing components (pedestals) which experienced much lower corrosion levels. The seasonal monitoring of bridge movements revealed that the 40+ years old Teflon pads are still functional and allow the bridges expansion and contraction. The developed holistic approach enabled demonstration of the fitness for service of the bearings, and provided means for assuring their long-term performance through monitoring. The results assured safety, integrity and delivered significant cost savings through aversion brownfield modifications, and production loss associated with bridge jacking and bearing replacement operations.

scholarly journals Paradoxes of Poweshiek Skipperling (Oarisma poweshiek) (Lepidoptera: Hesperiidae): Abundance Patterns and Management of a Highly Imperiled Prairie Species

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Ann B. Swengel ◽  
Scott R. Swengel
Keyword(s):  
Tallgrass Prairie ◽  
Fire Management ◽  
First Year ◽  
Case Scenario ◽  
Worst Case ◽  
Abundance Patterns ◽  
In Fire ◽  
Percent Unit ◽  
Oarisma Poweshiek

Although Oarisma poweshiek sometimes occurred in localized abundance, its known range is centered on the highly decimated northern tallgrass prairie of North America. To aid its conservation, we analyze surveys from 1988 to 1997 of populations no longer being found. While we recorded 2403 individuals at 20 sites, five sites had 87% of individuals, while 12 sites had only 2% of individuals. Most surveys during O. poweshiek flight had zero individuals recorded. In peak vegetative characteristics for O. poweshiek, fire management had the highest mean abundance but the lowest median abundance and lowest percent occurrence compared to idling and haying. Mean abundance was by far the lowest in the first year postfire compared to longer since fire. Median abundance and percent unit surveys where O. poweshiek was found indicated higher abundances the longer since fire. Although this skipper occasionally exhibited super-recoveries after fire, the median result in fire-managed occupied sites was zero. In a few years, abundance appeared synchronized across many sites, either low (1993, 1997) or high (1994-1995). It is only through a constant focus on avoiding the worst-case scenario that the rare best-case scenario of long-term population persistence appears possible for O. poweshiek.

scholarly journals Background levels of polycyclic aromatic hydrocarbons and legacy organochlorine pesticides in wheat sampled in 2017 and 2018 in Poland

2020 ◽  
Vol 192 (2) ◽  
Author(s):  
Marek Łukasz Roszko ◽  
Karolina Juszczyk ◽  
Magdalena Szczepańska ◽  
Olga Świder ◽  
Krystyna Szymczyk
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Health Risks ◽  
Aromatic Hydrocarbons ◽  
Fossil Fuels ◽  
Daily Intake ◽  
Value Assessment ◽  
Case Scenario ◽  
Worst Case ◽  
Background Levels ◽  
Polycyclic Aromatic

AbstractBoth polycyclic aromatic hydrocarbons (PAHs) and legacy organochlorine insecticides (OCPs), including DDT, are dangerous chemical contaminants. The aims of this study were to (i) determine background levels of PAHs and legacy OCPs for wheat samples collected in 2017 and 2018 in Poland, (ii) identify differences between levels in wheat harvested in various regions of Poland, (iii) evaluate differences in contamination sources manifested by the profiles of the identified chemicals, (iv) identify possible correlations between different classes of chemicals present in wheat, and (v) assess the health risks associated with the presence of PAHs and OCPs in Polish wheat. Average concentrations found in the samples were 0.09 ± 0.03 μg kg−1 for benzo[a]pyrene (BaP) (formerly used as a single PAH marker), 0.43 ± 0.16 for the more recently introduced collective PAH 4 marker (benzo[a]anthracene + benzo[a]pyrene + chrysene + benzo[b]fluoranthene), and 1.07 ± 0.68 μg kg−1 for DDT and its metabolites. The PAH profiles indicated contamination from combustion-related emission sources (liquid fossil fuels, coal, biomass). Health risks associated with the presence of PAHs and OCPs in cereals were assessed using the margin of exposure (MOE) approach. The MOE values calculated based on the highest concentrations found in this study exceeded 50,000 for both BaP and PAH 4. The calculated worst-case scenario value for DDT and metabolites was as low as 0.3% of the respective tolerable daily intake (TDI) value. Assessment of dietary risk has shown that the presence of the two contaminant classes in Polish wheat grains is of low concern.

scholarly journals Dental Composites – a Low-Dose Source of Bisphenol A?

2020 ◽  
pp. S295-S304 ◽  
Author(s):  
M. ŠIMKOVÁ ◽  
A. TICHÝ ◽  
M. DUŠKOVÁ ◽  
P. BRADNA
Keyword(s):  
Bisphenol A ◽  
Low Dose ◽  
Daily Intake ◽  
Dental Composite ◽  
Dental Composites ◽  
Mass Spectrometry Detection ◽  
Endocrine Disrupting ◽  
Liquid Chromatography Tandem Mass ◽  
Dental Restorative ◽  
Kinetics Of

Dental composite materials often contain monomers with bisphenol A (BPA) structure in their molecules, e.g. bisphenol-A glycidyl dimethacrylate (Bis-GMA). In this study, it was examined whether dental restorative composites could be a low-dose source of BPA or alternative bisphenols, which are known to have endocrine-disrupting effects. Bis-GMA-containing composites Charisma Classic (CC) and Filtek Ultimate Universal Restorative (FU) and “BPA-free” Charisma Diamond (CD) and Admira Fusion (AF) were examined. Specimens (diameter 6 mm, height 2 mm, n=5) were light-cured from one side for 20 s and stored at 37 °C in methanol which was periodically changed over 130 days to determine the kinetics of BPA release. BPA concentrations were measured using a dansyl chloride derivatization method with liquid chromatography – tandem mass spectrometry detection. The amounts of BPA were expressed in nanograms per gram of composite (ng/g). BPA release from Bis-GMA-containing CC and FU was significantly higher compared to “BPA-free” CD and AF. The highest 1-day release was detected with FU (15.4±0.8 ng/g), followed by CC (9.1±1.1 ng/g), AF (2.1±1.3 ng/g), and CD (1.6±0.8 ng/g), and the release gradually decreased over the examined period. Detected values were several orders of magnitude below the tolerable daily intake (4 µg/kg body weight/day). Alternative bisphenols were not detected. BPA was released even from “BPA-free” composites, although in significantly lower amounts than from Bis-GMA-containing composites. Despite incubation in methanol, detected amounts of BPA were substantially lower than current limits suggesting that dental composites should not pose a health risk if adequately polymerized.

scholarly journals Vivax malaria in children: clinical features and response to chloroquine.

1969 ◽  
Vol 39 (4) ◽  
pp. 364-377
Author(s):  
Jaime Carmona Fonseca ◽  
Rosa M. Uscátegui ◽  
Adriana María Correa
Keyword(s):  
Vivax Malaria ◽  
Standard Dose ◽  
Therapeutic Option ◽  
Normal Liver ◽  
Acute Attack ◽  
Case Scenario ◽  
Worst Case ◽  
Intention To Treat ◽  
Late Failure

Introduction: In Colombia is not very common to find updated information about vivax malaria in children. Aims: Describe the clinical and paraclinical disease picture and evaluate the standard dose of chloroquine effectiveness as a cure for the acute attack of vivax malaria in children between 4 and 10 years old. Methods: Experimental design, balanced, not blind, 82 patients and habitants in El Bagre and Turbo, Colombia. Follow-up: 30 days. Results: Symptoms-signs agreed with the known. There were found 62% long-term malnutrition, 53% anemia, low retinol (19 μg/dl), normal leukocyte count, normal liver tests and normal creatinine coefficient. After 25-28 day of treatment, all alterations had disappeared on children except malnutrition. According with the analysis techniques, the chloroquine late failure proportion was: by the intention to treat 2.4% (0 to 24%), by the protocol 2.6% (0 to 25%), and in the worst-case scenario 7.3% (0 to 29%). Conclusion: The clinical and paraclinical depict was similar than adults. Malaria, was the main responsible for clinics and paraclinical alterations. Chloroquine, without primaquine, proved highly effective for the acute attack of vivax malaria in children and should be retained as the first therapeutic option.

scholarly journals Robust hedging in incomplete markets

2018 ◽  
Vol 18 (3) ◽  
pp. 473-493 ◽  
Author(s):  
SALLY SHEN ◽  
ANTOON PELSSER ◽  
PETER SCHOTMAN
Keyword(s):  
Incomplete Markets ◽  
Pension Fund ◽  
Model Misspecification ◽  
Risk Exposure ◽  
Investment Horizon ◽  
Case Scenario ◽  
Worst Case ◽  
Risky Assets ◽  
Substantial Risk

AbstractWe considered a pension fund that needs to hedge uncertain long-term liabilities. We modeled the pension fund as a robust investor facing an incomplete market and fearing model uncertainty for the evolution of its liabilities. The robust agent is assumed to minimize the shortfall between the assets and liabilities under an endogenous worst-case scenario by means of solving a min–max robust optimization problem. When the funding ratio is low, robustness reduces the demand for risky assets. However, cherishing the hope of covering the liabilities, a substantial risk exposure is still optimal. A longer investment horizon or a higher funding ratio weakens the investor's fear of model misspecification. If the expected equity return is overestimated, the initial capital requirement for hedging can be decreased by following the robust strategy.

scholarly journals Ambiguity, Nominal Bond Yields, and Real Bond Yields

2020 ◽  
Vol 2 (2) ◽  
pp. 177-192 ◽  
Author(s):  
Guihai Zhao
Keyword(s):  
Risk Premium ◽  
Bond Yields ◽  
Case Scenario ◽  
Worst Case ◽  
Inflation Risk ◽  
Expectations Hypothesis ◽  
Long Run ◽  
Short Run ◽  
The Difference

This paper presents an equilibrium bond-pricing model that jointly explains the upward-sloping nominal and real yield curves and the violation of the expectations hypothesis. Instead of relying on the inflation risk premium, the ambiguity-averse agent faces different amounts of Knightian uncertainty in the long run versus the short run; hence, the model-implied nominal and real short rate expectations are upward sloping under the agent’s worst-case equilibrium beliefs. The expectations hypothesis roughly holds under investors’ worst-case beliefs. The difference between the worst-case scenario and the true distribution makes realized excess returns on long-term bonds predictable. (JEL D81, D84, E23, E31, E43, E44, G12)

scholarly journals Occurrence and Exposure Assessment of Mycotoxins in Ready-to-Eat Tree Nut Products through Ultra-High Performance Liquid Chromatography Coupled with High Resolution Q-Orbitrap Mass Spectrometry

Metabolites ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 344
Author(s):  
Alfonso Narváez ◽  
Yelko Rodríguez-Carrasco ◽  
Luigi Castaldo ◽  
Luana Izzo ◽  
Giulia Graziani ◽  
...  
Keyword(s):  
High Performance ◽  
Daily Intake ◽  
Monomethyl Ether ◽  
Health State ◽  
Fungal Contamination ◽  
Alternariol Monomethyl Ether ◽  
Case Scenario ◽  
Worst Case ◽  
Tree Nut ◽  
Orbitrap Mass Spectrometry

Tree nuts have become popular snacks due to their attributed benefits in the health state. Nevertheless, their susceptibility to fungal contamination lead to the occurrence of potentially dangerous mycotoxins. Hence, the aim of this work was to evaluate the presence of mycotoxins in ready-to-eat almonds, walnuts, and pistachios from Italian markets. The most relevant mycotoxin found in almonds was α-zearalanol in 18% of samples (n = 17) ranging from 3.70 to 4.54 µg/kg. Walnut samples showed frequent contamination with alternariol, present in 53% of samples (n = 22) at levels from 0.29 to 1.65 µg/kg. Pistachios (n = 15) were the most contaminated commodity, with β-zearalenol as the most prevalent toxin present in 59% of samples ranging from 0.96 to 8.60 µg/kg. In the worst-case scenario, the exposure to zearalenone-derived forms accounted for 15.6% of the tolerable daily intake, whereas it meant 12.4% and 21.2% of the threshold of toxicological concern for alternariol and alternariol monomethyl-ether, respectively. The results highlighted the extensive presence of Alternaria toxins and zearalenone-derived forms, scarcely studied in ready-to-eat tree nut products, highlighting the necessity to include these mycotoxins in analytical methods to perform more realistic risk assessments.

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