| 1. |
- Schijven, Dick, et al.
(författare)
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Large-scale analysis of structural brain asymmetries in schizophrenia via the ENIGMA consortium
- 2023
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences (PNAS). - 0027-8424 .- 1091-6490. ; 120:14
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Tidskriftsartikel (refereegranskat)abstract
- Left-right asymmetry is an important organizing feature of the healthy brain that may be altered in schizophrenia, but most studies have used relatively small samples and heterogeneous approaches, resulting in equivocal findings. We carried out the largest case-control study of structural brain asymmetries in schizophrenia, with MRI data from 5,080 affected individuals and 6,015 controls across 46 datasets, using a single image analysis protocol. Asymmetry indexes were calculated for global and regional cortical thickness, surface area, and subcortical volume measures. Differences of asymmetry were calculated between affected individuals and controls per dataset, and effect sizes were meta-analyzed across datasets. Small average case-control differences were observed for thickness asymmetries of the rostral anterior cingulate and the middle temporal gyrus, both driven by thinner left-hemispheric cortices in schizophrenia. Analyses of these asymmetries with respect to the use of antipsychotic medication and other clinical variables did not show any significant associations. Assessment of age- and sex-specific effects revealed a stronger average leftward asymmetry of pallidum volume between older cases and controls. Case-control differences in a multivariate context were assessed in a subset of the data (N = 2,029), which revealed that 7% of the variance across all structural asymmetries was explained by case-control status. Subtle case-control differences of brain macrostructural asymmetry may reflect differences at the molecular, cytoarchitectonic, or circuit levels that have functional relevance for the disorder. Reduced left middle temporal cortical thickness is consistent with altered left-hemisphere language network organization in schizophrenia.
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| 2. |
- Sumaila, U. Rashid, et al.
(författare)
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WTO must ban harmful fisheries subsidies
- 2021
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 374:6567, s. 544-544
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Menkveld, Albert J., et al.
(författare)
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Nonstandard Errors
- 2024
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Ingår i: JOURNAL OF FINANCE. - : Wiley-Blackwell. - 0022-1082 .- 1540-6261. ; 79:3, s. 2339-2390
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Tidskriftsartikel (refereegranskat)abstract
- In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence-generating process (EGP). We claim that EGP variation across researchers adds uncertainty-nonstandard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for more reproducible or higher rated research. Adding peer-review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants.
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| 4. |
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| 5. |
- Hagelin, Niclas, 1969-
(författare)
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Empirical essays on financial markets, firms, and derivatives
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of five self-contained studies. The first three investigate the impact of derivatives on the markets for the underlying assets, while the other two examine how and why firms use derivatives. A summary of each of the five studies follows.The first study investigates the relationship between option market activity and cash market volatility on the OMX index. The main concern is whether index option market activity affects the volatility of the underlying market. Option market activity is defined as trading volume divided by open interest, and both total option market activity as well as option market activity broken down by calls and puts is examined. The study contributes by investigating empirical evidence relating to two time periods, each with different market conditions. The results suggest that put option market activity, in contrast to call option market activity, influenced the cash market volatility and that the influence was different for the two periods investigated. However, the findings also indicated that a documented effect of option market activity on cash market volatility can be difficult to interpret.The second study examines expiration day effects of index futures and options on the Swedish market. The expiration day effect arises from the cash settlement procedure that is used to avoid the problems associated with physical delivery. Instead, the cash settlement procedure has reportedly been associated with arbitrageurs scrambling to unwind their arbitrage positions. While the results for the period 1988-1998 indicate that trading volumes on the cash market were significantly higher on expiration days than on other days, no evidence is found suggesting that price distortions occurred. This could be due to the longer settlement period on the Swedish market, compared with that on the Canadian, German, and the US markets, where price distortions have been documented. However, some price distortion may have been experienced for the first half of the sample period, and the cause of this finding is discussed.The third study investigates the impact of warrant and stock option introductions on the Swedish market. The results suggest that warrant introductions have no real effect on the underlying stock. The evidence indicates, on average, that no significant impact occurs on the price, volatility, bid-ask spread, trading volume, or number of actual trading days of the underlying stocks in the year following the warrant introduction. In contrast, the introduction of stock options is found to have a positive effect on the underlying stocks (i.e., volatility and bid-ask spreads are found to decrease). The finding that the introduction of warrants did not result in any changes in the investigated variables for the underlying stocks can be a result of infrequent trading in the warrants.The fourth study provides survey evidence on the use of derivatives among Swedish nonfinancial firms. The evidence for the Swedish firms is also compared with earlier findings for the US and New Zealand. The results show that (1) firms in Sweden used derivatives to the same extent as firms in New Zealand did, but to a larger extent than US firms did; (2) the usage of derivatives was more common among larger than among smaller firms; (3) the principal use of derivatives was for hedging purposes and those firms that engaged in speculative activity tended to be larger rather than smaller firms; and (4) lack of knowledge about derivatives within the firm was the issue of most concern for financial directors.The fifth and last study examines why widely held firms engage in hedging activities. The study contributes to the previous research by not only examining firm characteristics associated with use of currency derivatives in general, but also by analyzing the type of foreign exchange exposure that is hedged. More specifically, the association between firm characteristics and hedging of translation exposure and transaction exposure is investigated. This is of interest since translation exposure and transaction exposure tend to affect firms differently. The results show that transaction exposure hedging with currency derivatives was related to variables that represent indirect costs of financial distress and the underinvestment problem associated with costly external financing. Notably, translation exposure hedging with currency derivatives was unrelated to these proxy variables. The results suggest that firms hedge transaction exposure with currency derivatives to increase firm value, while there was no evidence that translation exposure hedges are used for that reason.
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| 6. |
- Lukasczyk, J., et al.
(författare)
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Report of the TopoInVis TTK Hackathon : Experiences, Lessons Learned, and Perspectives
- 2021
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Ingår i: Mathematics and Visualization. - Cham : Springer Nature. ; , s. 359-373, s. 359-373
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Konferensbidrag (refereegranskat)abstract
- This paper documents the organization, the execution, and the results of the Topology ToolKit (TTK) hackathon that took place at the TopoInVis 2019 conference. The primary goal of the hackathon was to promote TTK in our research community as a unified software development platform for topology-based data analysis algorithms. To this end, participants were first introduced to the structure and capabilities of TTK, and then worked on their own TTK-related projects while being mentored by senior TTK developers. Notable outcomes of the hackathon were first steps towards Python and Docker packages, further integration of TTK in Inviwo, the extension of TTK with new algorithms, and the discovery of current limitations of TTK as well as future development directions.
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| 7. |
- Veide Vilg, Jenny, 1973, et al.
(författare)
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Seasonal and spatial variation in biochemical composition of Saccharina latissima during a potential harvesting season for Western Sweden
- 2015
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Ingår i: Botanica Marina. - : Walter de Gruyter GmbH. - 0006-8055 .- 1437-4323. ; 58:6, s. 435-447
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Tidskriftsartikel (refereegranskat)abstract
- This study monitored the biomass composition of Saccharina latissima during a potential harvesting season on the West coast of Sweden, in order to find suitable harvest times for biorefinery purposes. Specimens of S. latissima were sampled at three locations in June, August and October and the biomass was analysed for its macromolecular composition, as well as for the content of several specific compounds, e.g. sugars and fatty acids. PERMANOVA analyses showed that there was a significant difference in the biomass composition among time points. The total carbohydrate concentration was lowest in June and peaked at 360 mg g-1 dry weight in August, while the mannitol content was highest, 90 mg g-1, in June and decreased throughout the sampling period. Total protein and fatty acid concentrations were found to be approximately 80 and 3 mg g-1, respectively, with relatively little variation over time. Overall, there was little spatial variation in the macromolecular composition, although the concentration of some specific monosaccharides and fatty acids, as well as the total phenolic content, differed among localities. We discuss the implications of the observed variation in biomass composition of S. latissima for future biorefinery purposes.
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