| 14531. |
- Lacayo, Martha, et al.
(författare)
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Degradation of toxaphene by Bjerkandera sp. strain BOL13 using waste biomass as a cosubstrate
- 2006
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 71:4, s. 549-554
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Tidskriftsartikel (refereegranskat)abstract
- The white-rot fungus Bjerkandera sp. strain BOL13 was capable of degrading toxaphene when supplied with wood chips, wheat husk or cane molasses as cosubstrates in batch culture experiments. Approximately 85% of toxaphene was removed when wheat husk was the main substrate. The production of lignin peroxidase was only stimulated when wheat husk was present in the liquid medium. Although xylanase was always detected, wheat husk supported the highest xylanase production. A negligible amount of beta-glucosidase and cellulase were found in the batch culture medium. To the best of our knowledge, this is the first reported case of toxaphene degradation by white-rot fungi.
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| 14532. |
- Lacayo-Romero, Martha, et al.
(författare)
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Degradation of toxaphene in aged and freshly contaminated soil
- 2006
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 63:4, s. 609-615
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Tidskriftsartikel (refereegranskat)abstract
- Degradation of toxaphene in soil from both newly contaminated (from Sweden) and aged spills (from Nicaragua) were studied. The newly contaminated soil contained approximately 11 mg kg(-1) toxaphene while the aged Nicaraguan soil contained approximately 100 mg kg(-1). Degradation was studied in anaerobic bioreactors, some of which were supplied with lactic acid and others with Triton X-114. In this study we found that the lower isomers Parlar 11, 12 were degraded while the concentration of isomer Parlar 15 increased. This supported an earlier evaluation which indicated that less chlorinated isomers are formed from more heavily isomers. Lactic acid when added to the soil, interfere with the degradation of toxaphene. Lactic acid was added; several isomers appeared to degrade rather slowly in newly contaminated Swedish soil. The Swedish soil, without any external carbon source, showed the slowest degradation rate of all the compounds studied. When Triton X-114 at 0.4 mM was added, the degradation rate of the compounds increased. This study illustrates that biodegradation of toxaphene is a complex process and several parameters have to be taken into consideration. Degradation of persistent pollutants in the environment using biotechnology is dependent on bioavailability, carbon sources and formation of metabolites.
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| 14533. |
- Landberg, Hanna, et al.
(författare)
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Comparison and Evaluation of Multiple Users' Usage of the Exposure and Risk Tool : Stoffenmanager 5.1
- 2015
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 0003-4878 .- 1475-3162. ; 59:7, s. 821-835
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Tidskriftsartikel (refereegranskat)abstract
- Stoffenmanager is an exposure and risk assessment tool that has a control banding part, with risk bands as outcome and a quantitative exposure assessment part, with the 90th percentile of the predicted exposure as a default outcome. The main aim of the study was to investigate whether multiple users of Stoffenmanager came to the same result when modelling the same scenarios. Other aims were to investigate the differences between outcomes of the control banding part with the measured risk quota and to evaluate the conservatism of the tool by testing whether the 90th percentiles are above the measured median exposures. We investigated airborne exposures at companies in four different types of industry: wood, printing, metal foundry, and spray painting. Three scenarios were modelled and measured, when possible, at each company. When modelled, 13 users visited each company on the same occasion creating individual assessments. Consensus assessments were also modelled for each scenario by six occupational hygienists. The multiple users' outcomes were often spread over two risk bands in the control banding part, and the differences in the quantitative exposure outcomes for the highest and lowest assessments per scenario varied between a factor 2 and 100. Four parameters were difficult for the users to assess and had a large impact on the outcome: type of task, breathing zone, personal protection, and control measures. Only two scenarios had a higher measured risk quota than predicted by the control banding part, also two scenarios had slightly higher measured median exposure value than modelled consensus in the quantitative exposure assessment part. Hence, the variability between users was large but the model performed well.
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| 14534. |
- Landberg, Hanna E, et al.
(författare)
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A Study of the Validity of Two Exposure Assessment Tools : Stoffenmanager and the Advanced REACH Tool
- 2017
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Ingår i: Annals of Work Exposures and Health. - : Oxford University Press. - 2398-7308 .- 2398-7316. ; 61:5, s. 575-588
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Tidskriftsartikel (refereegranskat)abstract
- The use of exposure modelling tools for estimating chemical airborne exposure has increased since the European Union's REACH legislation for safe use of industrial chemicals came into force. Two tools that European Chemicals Agency recommends are Stoffenmanager® and the Advanced REACH Tool (ART). The aim of this study was to investigate the validity of these two exposure modelling tools by comparing the lack of agreement between estimated and measured exposure. We examined the airborne chemical exposure at companies in seven different types of industries: wood, printing, foundry, spray painting, flour milling, chemical industry, and plastic moulding industry. The inhalable exposure of liquids or powders at two to three situations at each company was modelled with both tools and measured. To study the validity of the tools, the mean differences and precisions (lack of agreement) of exposures from both situations handling liquids and powders were calculated by using the 50th percentile outcome of the tools and the geometric mean of the measured exposure (all data were ln transformed). For Stoffenmanager, the mean difference and precision of the situations concerning liquids were 0.22 ± 1.0 and for powders -0.024 ± 0.66. It was also shown that Stoffenmanager overestimated low exposures and underestimated high exposures. Stoffenmanager showed higher agreement with the measured exposure in the wood and flour mill industries than in foundry and the plastic moulding industry. For ART, the mean difference and precision of liquids were -0.55 ± 0.88 and for powders -1.4 ± 1.6. ART showed lower agreement with the measured exposure in the wood industry.
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| 14535. |
- Landberg, Hanna E., et al.
(författare)
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Evaluation of risk assessment approaches of occupational chemical exposures based on models in comparison with measurements
- 2018
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Ingår i: Safety Science. - : Elsevier. - 0925-7535 .- 1879-1042. ; 109, s. 412-420
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Tidskriftsartikel (refereegranskat)abstract
- Risk assessments of chemicals in work places are needed to protect workers' health and safety. Several different strategies can be used for conducting risk assessments. The aim of this study was to investigate approaches to risk assessment of chemicals based on exposure assessment models relative to occupational exposure limits values (OELs) and derived no-effect levels (DNELs) and in comparison with measurements relative to OELs. A second aim was to evaluate the modelled recommended outcome and compare it with measurements of exposure. In this study, 29 situations were assessed with ECETOC TRA, Stoffenmanager (R) 5.1 and ART. Personal exposure measurements were also performed. The percentage of measured exposure exceeding the recommended output was calculated to investigate the level of conservatism. All the modelled exposures were compared with OELs and DNELs where possible, and the GM of the measured exposure was compared with OELs (risk quotas). For ECETOC TRA, 31% of measured exposure exceeded modelled exposure. For Stoffenmanager (R) it was 17% and for ART and ART B it was 3% and 0% respectively. Hence, according to our data, ECETOC TRA is the least conservative. An investigation of the risk quotas showed that ECETOC TRA had 4 false safe situations, meaning the risk was low when the model was used but was high when measurements were used. This may lead to underestimating risks. All models had an elevated proportion, ECETOC TRA and ART the highest, of false unsafe situations meaning the risk was low when measurements were used but high when models were used.
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| 14536. |
- Landgren, Marcus, et al.
(författare)
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Similar 1-year subjective outcome after a distal radius fracture during the 10-year-period 2003-2012 : A longitudinal register-based study involving 3,666 patients
- 2017
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Ingår i: Acta Orthopaedica. - : Taylor & Francis Group. - 1745-3674 .- 1745-3682. ; 88:4, s. 451-456
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: During the last decades, treatment of distal radius fractures (DRFs) has changed, with surgical intervention being more common and with new techniques. We investigated whether this change has influenced the subjective outcome. Here we report, year by year, the 1-year score after a DRF over a 10-year-period, using a patient-reported outcome measure.Patients and methods: Patients aged 18 years or more with a DRF between 2003 and 2012 were prospectively and consecutively registered in a longitudinal outcome database. 1 year after the fracture, all the patients were sent a validated subjective outcome questionnaire, the Disabilities of the Arm, Shoulder, and Hand (DASH). The lower the score (0-100), the better the outcome.Results: Between 2003 and 2012, 3,666 patients (2,833 of them women; mean age 62 (18-98) years) were included. 22% were operated and the rate remained constant over the years. The surgical methods shifted from external fixators (42%) and fragment-specific plates (45%) in 2003, to mainly volar locking plates (65%) in 2012. 70% of the patients responded to the 1-year DASH questionnaire. The median DASH score was 9 (IQR: 2-25) for the cohort, both in surgically treated patients (9 (IQR: 3-25)) and in non-surgically treated patients (9 (IQR 2-27)). Subgroup analysis showed a higher median DASH score for women than for men; for patients with AO type C fractures rather than type B or type A fractures; for patients with external fixation or fragment-specific fixation than for those who underwent surgery using volar locking plates; and for patients who were operated by a general orthopedic surgeon rather than a hand surgeon.Interpretation: The shift in surgical treatment had no influence on the subjective outcome for the cohort.
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| 14537. |
- Larsson, Karl, 1974-
(författare)
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General approximation schemes for option prices in stochastic volatility models
- 2012
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Ingår i: Quantitative finance (Print). - : Taylor & Francis. - 1469-7688 .- 1469-7696. ; 12:6, s. 873-891
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we develop a general method for deriving closed-form approximations of European option prices and equivalent implied volatilities in stochastic volatility models. Our method relies on perturbations of the model dynamics and we show how the expansion terms can be calculated using purely probabilistic methods. A flexible way of approximating the equivalent implied volatility from the basic price expansion is also introduced. As an application of our method we derive closed-form approximations for call prices and implied volatilities in the Heston [Rev. Financial Stud., 1993, 6, 327–343] model. The accuracy of these approximations is studied and compared with numerically obtained values.
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| 14538. |
- Larsson, Karl, 1974-, et al.
(författare)
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Jumps and stochastic volatility in oil prices : Time series evidence
- 2011
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Ingår i: Energy Economics. - : Elsevier. - 0140-9883 .- 1873-6181. ; 33:3, s. 504-514
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we examine the empirical performance of affine jump diffusion models with stochastic volatility in a time series study of crude oil prices. We compare four different models and estimate them using the Markov Chain Monte Carlo method. The support for a stochastic volatility model including jumps in both prices and volatility is strong and the model clearly outperforms the others in terms of a superior fit to data. Our estimation method allows us to obtain a detailed study of oil prices during two periods of extreme market stress included in our sample; the Gulf war and the recent financial crisis. We also address the economic significance of model choice in two option pricing applications. The implied volatilities generated by the different estimated models are compared and we price a real option to develop an oil field. Our findings indicate that model choice can have a material effect on the option values.
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| 14539. |
- Larsson, Karl, 1974-
(författare)
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Pricing Commodity Swaptions in Multifactor Models
- 2011
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Ingår i: Journal of Derivatives. - : Institutional Investor. - 1074-1240 .- 2168-8524. ; 19:2, s. 32-44
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Tidskriftsartikel (refereegranskat)abstract
- The menu of swaps available in the market today ranges far beyond the basic fixed-for-floating interest rateswap. Commodity swaps specifying a series of future cash flows, whereby one counterparty pays a fixed dollar amount and the other pays the price appreciation on some underlying commodity, are a prime example. And if commodity swaps become popular, commodity swaptions will naturally be introduced. But valuing commodity swaptions involves modeling the behavior of both future interest rates and future commodity prices for all of the payment dates. The standard approach is Monte Carlo simulation, which is complicated and time consuming. Here, Larsson introduces an approximation that is quite mild in terms of the error it introduces and for which the execution time for a given level of accuracy is improved by several orders of magnitude.
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| 14540. |
- Larsson, Matz, 1955-, et al.
(författare)
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Is the Capacity for Vocal Learning in Vertebrates Rooted in Fish Schooling Behavior?
- 2018
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Ingår i: Evolutionary biology. - : Springer. - 0071-3260 .- 1934-2845. ; 45:4, s. 359-373
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Forskningsöversikt (refereegranskat)abstract
- The capacity to learn and reproduce vocal sounds has evolved in phylogenetically distant tetrapod lineages. Vocal learners in all these lineages express similar neural circuitry and genetic factors when perceiving, processing, and reproducing vocalization, suggesting that brain pathways for vocal learning evolved within strong constraints from a common ancestor, potentially fish. We hypothesize that the auditory-motor circuits and genes involved in entrainment have their origins in fish schooling behavior and respiratory-motor coupling. In this acoustic advantages hypothesis, aural costs and benefits played a key role in shaping a wide variety of traits, which could readily be exapted for entrainment and vocal learning, including social grouping, group movement, and respiratory-motor coupling. Specifically, incidental sounds of locomotion and respiration (ISLR) may have reinforced synchronization by communicating important spatial and temporal information between school-members and extending windows of silence to improve situational awareness. This process would be mutually reinforcing. Neurons in the telencephalon, which were initially involved in linking ISLR with forelimbs, could have switched functions to serve vocal machinery (e.g. mouth, beak, tongue, larynx, syrinx). While previous vocal learning hypotheses invoke transmission of neurons from visual tasks (gestures) to the auditory channel, this hypothesis involves the auditory channel from the onset. Acoustic benefits of locomotor-respiratory coordination in fish may have selected for genetic factors and brain circuitry capable of synchronizing respiratory and limb movements, predisposing tetrapod lines to synchronized movement, vocalization, and vocal learning. We discuss how the capacity to entrain is manifest in fish, amphibians, birds, and mammals, and propose predictions to test our acoustic advantages hypothesis.
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