66 research outputs found
Replacing the Monte Carlo Simulation with the COS Method for PFE (Potential Future Exposure) Calculations
No full textTo fulfil the need in the industry for fast and accurate PFE calculations in practice, a new, semi-analytical method of calculating the PFE metric for CCR has been developed, tested and analyzed in this thesis. Herewith we focus on the calculation of PFEs for liquid IR and FX portfolios involving up to three correlated risk-factors: a domestic and foreign short rate and the exchange rate of this currency pair. Both netting-set level and counterparty level PFEs are covered in our research. The short rates are modelled under the one-factor Hull-White (HW1F) model and for the exchange rate we assume they follow geometric Brownian motion. The key insight is that the cumulative distribution function (CDF) can be recovered semi-analytically using Fourier-cosine expansion, whereby the series coefficients are readily available from the characteristic function of the total exposure. The characteristic function in turn can be solved numerically via quadrature rules. Risk metrics, such as the potential future exposure (PFE), can be attained once the CDF is reconstructed using the Fourier series.Our theoretical error analysis predicts stable convergence of the COS method and observed exponential convergence of the COS method for both netting-set and counterparty level PFE calculations. For three artificial portfolios of different sizes, it was observed that the COS method is at least five times more accurate than the Monte Carlo (MC) simulation method but takes only one-tenth of the CPU time of the MC method. The advantage of the COS method becomes even more prominent when the number of derivatives in a portfolio increases. We conclude that the COS method is a much more efficient alternative for MC method for PFE calculations, at least for portfolios involving three risk factors.Our theoretical error analysis predicts stable convergence of the COS method and observed exponential convergence of the COS method for both netting-set and counterparty level PFE calculations. For three artificial portfolios of different sizes, it was observed that the COS method is at least five times more accurate than the Monte Carlo (MC) simulation method but takes only one-tenth of the CPU time of the MC method. The advantage of the COS method becomes even more prominent when the number of derivatives in a portfolio increases. We conclude that the COS method is a much more efficient alternative for MC method for PFE calculations, at least for portfolios involving three risk factors.We conducted theoretical analysis on the error convergence and observed exponential convergence of the COS method for both netting-set and counterparty level PFE calculations. For three artificial portfolios of different sizes, it was observed that the COS method is at least five times more accurate than the Monte Carlo (MC) simulation method but takes only one-tenth of the CPU time of the MC method. The advantage of the COS method becomes even more prominent when the number of derivatives in a portfolio increases. We conclude that the COS method is a much more efficient alternative for MC method for PFE calculations, at least for portfolios involving three risk factors.Applied Mathematic
Can sterilization of disposable face masks be an alternative for imported face masks?: A nationwide field study including 19 sterilization departments and 471 imported brand types during COVID-19 shortages
No full textBackgroundFace masks, also referred to as half masks, are essential to protect healthcare professionals working in close contact with patients with COVID-19-related symptoms. Because of the Corona material shortages, healthcare institutions sought an approach to reuse face masks or to purchase new, imported masks. The filter quality of these masks remained unclear. Therefore, the aim of this study was to assess the quality of sterilized and imported FFP2/KN95 face masks.MethodsA 48-minute steam sterilization process of single-use FFP2/KN95 face masks with a 15 minute holding time at 121°C was developed, validated and implemented in the Central Sterilization Departments (CSSD) of 19 different hospitals. Masks sterilized by steam and H2O2 plasma as well as new, imported masks were tested for particle filtration efficiency (PFE) and pressure drop in a custom-made test setup.ResultsThe results of 84 masks tested on the PFE dry particle test setup showed differences of 2.3±2% (mean±SD). Test data showed that the mean PFE values of 444 sterilized FFP2 face masks from the 19 CSSDs were 90±11% (mean±SD), and those of 474 new, imported KN95/FFP2 face masks were 83±16% (mean±SD). Differences in PFE of masks received from different sterilization departments were found.ConclusionFace masks can be reprocessed with 121 °C steam or H2O2 plasma sterilization with a minimal reduction in PFE. PFE comparison between filter material of sterilized masks and new, imported masks indicates that the filter material of most reprocessed masks of high quality brands can outperform new, imported face masks of unknown brands. Although the PFE of tested face masks from different sterilization departments remained efficient, using different types of sterilization equipment, can result in different PFE outcomes.Medical Instruments & Bio-Inspired TechnologyChemE/Advanced Soft Matte
Setting conservation management thresholds using a novel participatory modeling approach
No full textWe devised a participatory modeling approach for setting management thresholds that show when management intervention is required to address undesirable ecosystem changes. This approach was designed to be used when management thresholds: must be set for environmental indicators in the face of multiple competing objectives; need to incorporate scientific understanding and value judgments; and will be set by participants with limited modeling experience. We applied our approach to a case study where management thresholds were set for a mat-forming brown alga, Hormosira banksii, in a protected area management context. Participants, including management staff and scientists, were involved in a workshop to test the approach, and set management thresholds to address the threat of trampling by visitors to an intertidal rocky reef. The approach involved trading off the environmental objective, to maintain the condition of intertidal reef communities, with social and economic objectives to ensure management intervention was cost-effective. Ecological scenarios, developed using scenario planning, were a key feature that provided the foundation for where to set management thresholds. The scenarios developed represented declines in percent cover of H. banksii that may occur under increased threatening processes. Participants defined 4 discrete management alternatives to address the threat of trampling and estimated the effect of these alternatives on the objectives under each ecological scenario. A weighted additive model was used to aggregate participants' consequence estimates. Model outputs (decision scores) clearly expressed uncertainty, which can be considered by decision makers and used to inform where to set management thresholds. This approach encourages a proactive form of conservation, where management thresholds and associated actions are defined a priori for ecological indicators, rather than reacting to unexpected ecosystem changes in the future
The evolution of corporate no net loss and net positive impact biodiversity commitments: Understanding appetite and addressing challenges
No full textThe World Economic Forum has identified biodiversity loss as an increasingly significant and impactful risk facing business. However, businesses themselves can negatively impact on biodiversity. Recognizing this, a number of companies have developed their own biodiversity commitments, including those to achieve a no net loss (NNL) or net positive impact (NPI) on biodiversity by balancing or outweighing any negative impacts through mitigation activities. We reviewed corporate‐level NNL and NPI commitments over the last two decades to establish the extent of their adoption, retraction, and scientific foundation. Between 2001 and 2016, 66 companies had made NNL/NPI environmental commitments. Thirty three of these 66 companies made specific biodiversity commitments. The numbers of companies making commitments increased in that period. However, some commitments were retracted, or their status became unclear, leaving only 18 companies with active NNL/NPI biodiversity commitments in 2016. Added to this, many of the commitments are lacking science‐based criteria that would allow more transparent and systematic assessment of corporate activities. Thus, although commitments are being made, they may not be delivering as intended. To secure real biodiversity gains, we recommend advancing methods to assess biodiversity risks to businesses, and using science‐based criteria to deepen corporate commitments and actions. Concerted effort from all sectors is needed to halt and reverse biodiversity loss, and the “biodiversity policy super‐year” of 2020 is the perfect moment for business to deliver through well‐framed and implemented commitments to biodiversity NPI
Interest rate models for estimating counterparty credit risk: Dynamic Nelson-Siegel and Displaced Diffusion
No full textIn this study, two interest rate models are analysed in context of counterparty credit risk. The goal of the study is to find a model that performs well on historical simulation for the PFE and EPE. The two models analysed are the Dynamic Nelson-Siegel model and the Displaced Diffusion model.In the Dynamic Nelson-Siegel model, a Nelson-Siegel curve is fitted against the historical yield curves. The fit gives an historical series of the parameter values of the Nelson-Siegel curve, which are modelled via a stochastic process to obtain future yield curve predictions. In historical backtesting, the classic model using AR(1) processes for the parameters performs inadequate. Analysis on the underlying assumptions of the model show that the mean-reverting behaviour that is modeled is the cause. In addition the data is likely to feature heteroskedastic behaviour, which is not incorporated by the model. An adjusted model in which one parameter is modeled with a random walk with drift performs well on longer maturity rates, however shorter maturity rates are not modeled satisfactory. The Displaced Diffusion model uses a lognormal diffusion process that is shifted to model Libor rates. As it is a Libor market model, all libor rates are modelled seperately using correlated Brownian motions. The shift parameter allows negative rates to be modeled, and is initially assumed constant. The backtesting results are mixed; some observed libor rates are modeled inadequately and some cannot be rejected to come from the Displaced Diffusion model and thus are modelled correctly. When backtesting the PFE, the results are good at the short term. At the 2-year window, PFE estimates are not always conservative but the number of excesses are of medium severity when compared to the probabilities used in the green-orange-red system dictated by the Basel committee for VaR backtesting.Applied Mathematic
The Investigation and Characterization of Redox Enzymes Using Protein Film Electrochemistry
No full textabstract: Redox reactions are crucial to energy transduction in biology. Protein film electrochemistry (PFE) is a technique for studying redox proteins in which the protein is immobilized at an electrode surface so as to allow direct exchange of electrons. Establishing a direct electronic connection eliminates the need for redoxactive mediators, thus allowing for interrogation of the redox protein of interest. PFE has proven a versatile tool that has been used to elucidate the properties of many technologically relevant redox proteins including hydrogenases, laccases, and glucose oxidase.
This dissertation is comprised of two parts: extension of PFE to a novel electrode material and application of PFE to the investigation of a new type of hydrogenase. In the first part, mesoporous antimony-doped tin oxide (ATO) is employed for the first time as an electrode material for protein film electrochemistry. Taking advantage of the excellent optical transparency of ATO, spectroelectrochemistry of cytochrome c is demonstrated. The electrochemical and spectroscopic properties of the protein are analogous to those measured for the native protein in solution, and the immobilized protein is stable for weeks at high loadings. In the second part, PFE is used to characterize the catalytic properties of the soluble hydrogenase I from Pyrococcus furiosus (PfSHI). Since this protein is highly thermostable, the temperature dependence of catalytic properties was investigated. I show that the preference of the enzyme for reduction of protons (as opposed to oxidation of hydrogen) and the reactions with oxygen are highly dependent on temperature, and the enzyme is tolerant to oxygen during both oxidative and reductive catalysis.Dissertation/ThesisDoctoral Dissertation Biochemistry 201
Integrating decision triggers into conservation management practice
No full text1. Decision triggers show great potential for facilitating timely management action, promoting evidence-based management and preventing undesirable changes to the status of species, ecosystems and threats. Integration of decision triggers into day-to-day management practice has been slow, constrained by insufficient resources and limited in-house expertise. Arguably, the greatest impediment is the lack of an overarching process with robust and accessible methods for developing and implementing decision triggers in a manner that fits within an organisation’s current processes and skill sets.
2. We identify the steps necessary for setting decision triggers and highlight how these steps align with commonly used conservation planning and management frameworks, for ease of adoption.
3. We emphasise that decision triggers do not require a known ecological threshold, and can be applied to data rich and data poor contexts, with single or multiple management objectives.
4. Synthesis and applications. This work highlights the necessary steps involved, and importantly, the suite of methods that can be used to set decision triggers with the aim to support practitioners in the development of robust and defensible decision triggers. </p
PHOTOFIELD EMISSION STUDY OF METAL SURFACES (ELECTRON YIELD IN PFE, LASER-INDUCED THERMAL EFFECTS)
No full textIn this thesis the efforts made to better understand the mech- anisms and to refine the apparatus of photofield emission are described. Photofield electron yield and photofield emission from surface electronic have been measured. Both demonstrate the surface sensitivity of this new technique. Analyses of laser-induced thermal effects are also reported which allows the simultaneous determination of both the temperature and workfunction of a laser illuminated surface as small as 50(ANGSTROM) in spatial extent. Theoretical calculations of photofield emission based on the relativistic elec- tronic band structure of tungsten are also carried out and the results are compared to experiment. Data from W(110) and W(111) for a number of different photon energies between 2.41eV and 3.54eV are reported. The measured yield is compared to the theoretical models of the photoexcitation process. Based on this comparison, it is concluded that the spatial variation of the vector potential (\u27)A near the metal-vacuum interface is the dominant excitation mechanism in producing the photocurrent from a laser illuminated field emission tip. Photofield emission from surface electronic states is a unique probe to examine the radiation field near the vicinity of a metal sur- face since the surface states are localized within the first atomic layer of the surface. Studies of photofield emission from surface states on W(100), Mo(100) and Ir(111) are presented in the text. Data analysis shows that photofield emission from localized sur- face states depends predominantly on the normal component of the vector potential (\u27)A. Laser-induced thermal effects on various surfaces of tungsten and molybdenum have been studied using field emitted electrons. Energy distributions measured by a dispersive electron energy ana- lyzer allow the temperature increase of a laser-illuminated surface to be determined to within (+OR-)10 K. In addition to estimating the tem- perature rise, small temperature-induced variations in the work func- tion (PHI) can also be determined. Fits to experimental data indicate that changes in (PHI) of a laser-illuminated surface can be estimated to within (+OR-)2 meV. Photofield emission energy distributions from W(110) and W(111) were measured from 2.41eV to 3.54cV. Results are compared with theoretical expectations based on a relativistic electronic band structure and on a free electron model. Data analysis shows that surface emission is strong in PFE and that effects of bulk direct tran- sitions, although small, are still observable. It can be concluded that photofield emission provides means for inspecting the electronic band structure of transition metals between the Fermi energy and the vacuum level. (Abstract shortened with permission of author.
A high sensitivity iron-dependent bioreporter used to measure iron bioavailability in freshwaters
No full textA Nostoc sp. PCC 7120 iron bioreporter containing iron-regulated schizokinen transporter gene alr0397 promoter fused to the luxAB genes was examined to optimize its response to bioavailable iron. Doseresponse relationships between luciferase activity and free ferric ion (Fe3+) concentrations pFe (-lg [Fe3+]) were generated by measuring luciferase activities of the bioreporter in trace metalbuffered Fraquil medium with various incubation times. The results were best demonstrated by sigmoidal curves (pFe 18.821.7, Fe3+ = 10-18.810-21.7 M) with the linear range extending from pFe 19.621.5 (Fe3+ = 10-19.610-21.5 M) after a 12-h incubation time. Optimal conditions for the use of this bioreporter to sense the iron bioavailability were determined to be: a 12-h exposure time, initial cell density of OD730 nm = 0.06, high nitrate (100 mu M), high phosphate (10 mu M), moderate Co2+ (0.122.5 nM), Zn2+ (0.1612 nM), Cu2+ (0.0450 nM), and wide range of Mn2+ concentration (0.922300 nM). The applicability of using this iron bioreporter to assess iron availability in the natural environment has been tested using water samples from eutrophic Taihu, Donghu, and Chaohu lakes. It is indicated that the bioreporter is a useful tool to assess bioavailable iron in various water quality samples, especially in eutrophic lakes with high bioavailable iron.A Nostoc sp. PCC 7120 iron bioreporter containing iron-regulated schizokinen transporter gene alr0397 promoter fused to the luxAB genes was examined to optimize its response to bioavailable iron. Doseresponse relationships between luciferase activity and free ferric ion (Fe3+) concentrations pFe (-lg [Fe3+]) were generated by measuring luciferase activities of the bioreporter in trace metalbuffered Fraquil medium with various incubation times. The results were best demonstrated by sigmoidal curves (pFe 18.821.7, Fe3+ = 10-18.810-21.7 M) with the linear range extending from pFe 19.621.5 (Fe3+ = 10-19.610-21.5 M) after a 12-h incubation time. Optimal conditions for the use of this bioreporter to sense the iron bioavailability were determined to be: a 12-h exposure time, initial cell density of OD730 nm = 0.06, high nitrate (100 mu M), high phosphate (10 mu M), moderate Co2+ (0.122.5 nM), Zn2+ (0.1612 nM), Cu2+ (0.0450 nM), and wide range of Mn2+ concentration (0.922300 nM). The applicability of using this iron bioreporter to assess iron availability in the natural environment has been tested using water samples from eutrophic Taihu, Donghu, and Chaohu lakes. It is indicated that the bioreporter is a useful tool to assess bioavailable iron in various water quality samples, especially in eutrophic lakes with high bioavailable iron
Primary Failure of Eruption: Clinical and Genetic Findings in the Mixed Dentition
No full textCONTROL ID: 2639647
TITLE: Primary Failure of Eruption: Clinical and Genetic Findings in the Mixed Dentition
AUTHORS (FIRST NAME INITIAL LAST NAME): C. Grippaudo1, I. D'Apolito1, C. Cafiero1, B. Ricci1, S. A. Frazier-
Bowers2
AUTHORS/INSTITUTIONS: C. Grippaudo, I. D'Apolito, C. Cafiero, B. Ricci, Dental Institute, Università Cattolica,
Rome, ITALY|S.A. Frazier-Bowers, Department of Orthodontics, University of North Carolina, Chapel Hill, North
Carolina, UNITED STATES|
PREFERRED PRESENTATION TYPE: Oral
CURRENT SCIENTIFIC GROUPS & NETWORKS: Craniofacial Biology
ABSTRACT BODY:
Objectives: Eruption disorders represent an enigmatic aspect of dental and orthodontic diagnosis. Since the discovery
that Primary Failure of Eruption (PFE, MIM #125350) is due to a genetic defect, several mutations of the PTH1R gene
have been identified as causative. This study aimed to refine our understanding of the phenotype:genotype correlation
of PFE and PTH1R mutations in the mixed dentition. This characterization may lead to improved diagnostic
approaches and provide the foundation for downstream mechanistic studies to understand the pathogenesis of
PTH1R mutations.
Methods: DNA was extracted from saliva samples of 29 patients (3 families and 23 unrelated individuals) who
presented with clinical evidence of infraoccluded teeth. Mutational analysis was completed for the coding regions of
PTH1R gene following PCR amplification and direct sequencing.
Results: Eight of 29 cases revealed a heterozygous pathogenic variant in the PTH1R gene; 5 of 8 variants represent
distinct mutations within the cohort. One mutation (c.1765 T>C p.Trp89Arg) was found to segregate within a family
(n=3) represented by two generations. Mutational analysis using the dbSNP, HGMD and the ESP databases identified
the mutations were previously unreported. In silico analyses of all variants further predicted a putative pathogenic
effect. Extended clinical analysis of the cohrot verified that all the novel mutations co-segregated with the PFE
phenotype that included affection of the mixed dentition. Six of the 8 patients carrying a functional PTH1R mutation
were children in mixed dentition with one or more primary teeth affected.
Conclusions: We report that PFE in the mixed and permanent dentition positively correlates with pathogenic mutations
in the PTH1R gene. Further studies to identify additional genes and correlate the pathogenesis of PFE from mixed to
permanent dentition are ongoing and forthcoming.
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KEYWORDS: Primary failure of eruption (PFE), orthodontics, Dental eruption, genetics, mixed dention.
Support Funding Agency/Grant Number - Abstracts:
Financial Interest Disclosure: NONE
AWARDS:
Group Author Abstracts - Abstract:
Session Chair Volunteers - Abstracts: Not Interested
Special Scheduling Needs - Abstracts:
Student Status - Abstracts: No
Student Other Designation - Abstracts:
Abstract Submission - Track Selection: Clinician Trac
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