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294 results on '"Wold S"'

14. Nanoparticles of WC-Co, WC, Co and Cu of relevance for traffic wear particles – Particle stability and reactivity in synthetic surface water and influence of humic matter

Author

Hedberg, Yolanda, Hedberg, Jonas, Isaksson, Sara, Mei, Nanxuan, Blomberg, Eva, Wold, S., Odnevall Wallinder, Inger, Hedberg, Yolanda, Hedberg, Jonas, Isaksson, Sara, Mei, Nanxuan, Blomberg, Eva, Wold, S., and Odnevall Wallinder, Inger

Abstract

Studded tyres made of tungsten carbide cobalt (WC-Co) are in the Northern countries commonly used during the winter time. Tungsten (W)-containing nano- and micron-sized particles have been detected close to busy roads in several European countries. Other typical traffic wear particles consist of copper (Cu). The aims of this study were to investigate particle stability and transformation/dissolution properties of nanoparticles (NPs) of WC-Co compared with NPs of tungsten carbide (WC), cobalt (Co), and Cu. Their physicochemical characteristics (primarily surface oxide and charge) are compared with their extent of sedimentation and metal release in synthetic surface water (SW) with and without two different model organic molecules, 2,3- and 3,4-dihydroxybenzoic acid (DHBA) mimicking certain sorption sites of humic substances, for time periods up to 22 days. The WC-Co NPs possessed a higher electrochemical and chemical reactivity in SW with and without DHBA molecules as compared with NPs of WC, Co, and Cu. Co was completely released from the WC-Co NPs within a few hours of exposure, although it remained adsorbed/bonded to the particle surface and enabled the adsorption of negatively charged DHBA molecules, in contrast with the WC NPs (no adsorption of DHBA). The DHBA molecules were found to rapidly adsorb on the Co and Cu NPs. The sedimentation of the WC and WC-Co NPs was not influenced by the presence of the 2,3- or 3,4-DHBA molecules. A slight influence (slower sedimentation) was observed for the Co NPs, and a strong influence (slower sedimentation) was observed for the Cu NPs in SW with 2,3-DHBA compared with SW alone. The extent of metal release increased in the order: WC < Cu < Co < WC-Co NPs. All NPs released more than 1 wt-% of their metal total mass. The release from the Cu NPs was most influenced by the presence of DHBA molecules., QC 20170607

Published
2017
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17. Cluster-based design in environmental QSAR

Author

Eriksson, L., Lennart, E., Johansson, E., Wold, S., Müller, M., and Publica

Subjects
multivariate design, multivariate QSAR, PLS, soil sorption
Abstract

In QSAR analysis in environmental sciences adverse effects of chemicals released to the environment are modelled and predicted as a function of the chemical properties of the pollutants. Usually, the set of compounds under study contains several classes of substances, i.e., a more or less strongly clustered set. It is then needed to ensure that the selected training set comprises compounds representing all those chemical classes. Multivariate design in the principal properties of the compound classes is usually appropriate for selecting a meaningful training set. However, with clustered data, often seen in environmental chemistry and toxicology, a single multivariate design may be suboptimal. This because of the risk of ignoring small classes with few members and only selecting training set compounds from the largest classes. In this paper, a procedure for training set selection recognizing clustering is proposed. Here, when non-selective biological or environmental responses are model led, local multivariate designs are constructed within each cluster (class). The chosen compounds arising from the local designs are finally united in the overall training set, which thus will contain members from all clusters. Our illustration deals with a set of 66 compounds, categorized into five classes, for which the soil sorption coefficient is available. The training set selection is discussed, followed by multivariate QSAR modelling, model validation and interpretation, and predictions for the test set.

Published
1997

38. OC13.01: Multiple gestation and cervical shortening: serial transvaginal cervical length must begin at 16 weeks.

Author

Jackson, D.N., Iriye, B., Sheldon, P., Giacobbe, L., Kamyar, M., Wold, S., Gorski, L., and Huang, W.

Abstract

The percentage of patients requiring cerclage was 37.5%, 58.8%, 43.3%, and 10% of patients with short cervix first seen at 16-18, 18 1/7-20, 20 1/7-22, and 22 1/7-24 weeks, respectively. OC13.01: Multiple gestation and cervical shortening: serial transvaginal cervical length must begin at 16 weeks Despite progesterone use, progressive shortening triggered cerclage in 30/109 (27.5% of short cervix and 2.3% of all multiples). [Extracted from the article]

Published
2022
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46. Book reviews

Author

Mason, S., primary, Lyklema, J., additional, Harriman, A., additional, Roberts, D. R., additional, Brown, R. G., additional, Wold, S., additional, and Blum, L., additional

Published
1992
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48. THREE-BLOCK BIFOCAL PLS (3BIF-PLS) AND ITS APPLICATION IN QSAR.

Author

Eriksson, L., Damborsky, J., Earll, M., Johansson, E., Trygg, J., and Wold, S.

Subjects
LEAST squares, HALOCARBONS, HYDROCARBONS, SOILS, SOIL remediation
Abstract

When X and Y are multivariate, the two-block partial least squares (PLS) method is often used. In this paper, we outline an extension addressing a special case of the three-block (X/Y/Z) problem, where Z sits "under" Y. We have called this approach three-block bi-focal PLS (3B1F-PLS). It views the X/Y relationship as the dominant problem, and seeks to use the additional information in Z in order to improve the interpretation of the Y-part of the X/Y association. Two data sets are used to illustrate 3BIF-PLS. Example 1 relates to single point mutants of haloalkane dehalogenase from Sphingomonas paucimobilis UT26 and their ability to transform halogenated hydrocarbons, some of which are found as organic pollutants in soil. Example II deals with soil remediation capability of bacteria. Whole bacterial communities are monitored over lime using "DNA-fingerprinting" technology to see how pollution affects population composition. Since the data sets are large, hierarchical multivariate modelling is invoked to compress data prior to 3BIF-PLS analysis. It is concluded that the 3BIF-PLS approach works well. The paper contains a discussion of pros and cons of the method, and hints at further developmental opportunities. [ABSTRACT FROM AUTHOR]

Published
2004
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