| 1. |
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| 2. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 3. |
- Kanoni, Stavroula, et al.
(författare)
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Implicating genes, pleiotropy, and sexual dimorphism at blood lipid loci through multi-ancestry meta-analysis.
- 2022
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Ingår i: Genome biology. - : Springer Science and Business Media LLC. - 1474-760X .- 1465-6906 .- 1474-7596. ; 23:1
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Tidskriftsartikel (refereegranskat)abstract
- Genetic variants within nearly 1000 loci are known to contribute to modulation of blood lipid levels. However, the biological pathways underlying these associations are frequently unknown, limiting understanding of these findings and hindering downstream translational efforts such as drug target discovery.To expand our understanding of the underlying biological pathways and mechanisms controlling blood lipid levels, we leverage a large multi-ancestry meta-analysis (N=1,654,960) of blood lipids to prioritize putative causal genes for 2286 lipid associations using six gene prediction approaches. Using phenome-wide association (PheWAS) scans, we identify relationships of genetically predicted lipid levels to other diseases and conditions. We confirm known pleiotropic associations with cardiovascular phenotypes and determine novel associations, notably with cholelithiasis risk. We perform sex-stratified GWAS meta-analysis of lipid levels and show that 3-5% of autosomal lipid-associated loci demonstrate sex-biased effects. Finally, we report 21 novel lipid loci identified on the X chromosome. Many of the sex-biased autosomal and X chromosome lipid loci show pleiotropic associations with sex hormones, emphasizing the role of hormone regulation in lipid metabolism.Taken together, our findings provide insights into the biological mechanisms through which associated variants lead to altered lipid levels and potentially cardiovascular disease risk.
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| 4. |
- Speliotes, Elizabeth K., et al.
(författare)
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Association analyses of 249,796 individuals reveal 18 new loci associated with body mass index
- 2010
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 42:11, s. 937-948
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Tidskriftsartikel (refereegranskat)abstract
- Obesity is globally prevalent and highly heritable, but its underlying genetic factors remain largely elusive. To identify genetic loci for obesity susceptibility, we examined associations between body mass index and ~2.8 million SNPs in up to 123,865 individuals with targeted follow up of 42 SNPs in up to 125,931 additional individuals. We confirmed 14 known obesity susceptibility loci and identified 18 new loci associated with body mass index (P < 5 × 10−8), one of which includes a copy number variant near GPRC5B. Some loci (at MC4R, POMC, SH2B1 and BDNF) map near key hypothalamic regulators of energy balance, and one of these loci is near GIPR, an incretin receptor. Furthermore, genes in other newly associated loci may provide new insights into human body weight regulation.
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| 5. |
- Gaulton, Kyle J, et al.
(författare)
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Genetic fine mapping and genomic annotation defines causal mechanisms at type 2 diabetes susceptibility loci.
- 2015
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 47:12, s. 1415-1415
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Tidskriftsartikel (refereegranskat)abstract
- We performed fine mapping of 39 established type 2 diabetes (T2D) loci in 27,206 cases and 57,574 controls of European ancestry. We identified 49 distinct association signals at these loci, including five mapping in or near KCNQ1. 'Credible sets' of the variants most likely to drive each distinct signal mapped predominantly to noncoding sequence, implying that association with T2D is mediated through gene regulation. Credible set variants were enriched for overlap with FOXA2 chromatin immunoprecipitation binding sites in human islet and liver cells, including at MTNR1B, where fine mapping implicated rs10830963 as driving T2D association. We confirmed that the T2D risk allele for this SNP increases FOXA2-bound enhancer activity in islet- and liver-derived cells. We observed allele-specific differences in NEUROD1 binding in islet-derived cells, consistent with evidence that the T2D risk allele increases islet MTNR1B expression. Our study demonstrates how integration of genetic and genomic information can define molecular mechanisms through which variants underlying association signals exert their effects on disease.
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| 6. |
- Locke, Adam E, et al.
(författare)
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Genetic studies of body mass index yield new insights for obesity biology.
- 2015
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 518:7538, s. 197-401
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Tidskriftsartikel (refereegranskat)abstract
- Obesity is heritable and predisposes to many diseases. To understand the genetic basis of obesity better, here we conduct a genome-wide association study and Metabochip meta-analysis of body mass index (BMI), a measure commonly used to define obesity and assess adiposity, in up to 339,224 individuals. This analysis identifies 97 BMI-associated loci (P < 5 × 10(-8)), 56 of which are novel. Five loci demonstrate clear evidence of several independent association signals, and many loci have significant effects on other metabolic phenotypes. The 97 loci account for ∼2.7% of BMI variation, and genome-wide estimates suggest that common variation accounts for >20% of BMI variation. Pathway analyses provide strong support for a role of the central nervous system in obesity susceptibility and implicate new genes and pathways, including those related to synaptic function, glutamate signalling, insulin secretion/action, energy metabolism, lipid biology and adipogenesis.
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| 7. |
- Shungin, Dmitry, et al.
(författare)
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New genetic loci link adipose and insulin biology to body fat distribution.
- 2015
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 518:7538, s. 187-378
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Tidskriftsartikel (refereegranskat)abstract
- Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms.
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| 8. |
- Scott, Robert A., et al.
(författare)
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An Expanded Genome-Wide Association Study of Type 2 Diabetes in Europeans
- 2017
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 66:11, s. 2888-2902
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Tidskriftsartikel (refereegranskat)abstract
- To characterize type 2 diabetes (T2D)-associated variation across the allele frequency spectrum, we conducted a meta-analysis of genome-wide association data from 26,676 T2D case and 132,532 control subjects of European ancestry after imputation using the 1000 Genomes multiethnic reference panel. Promising association signals were followed up in additional data sets (of 14,545 or 7,397 T2D case and 38,994 or 71,604 control subjects). We identified 13 novel T2D-associated loci (P < 5 x 10(-8)), including variants near the GLP2R, GIP, and HLA-DQA1 genes. Our analysis brought the total number of independent T2D associations to 128 distinct signals at 113 loci. Despite substantially increased sample size and more complete coverage of low-frequency variation, all novel associations were driven by common single nucleotide variants. Credible sets of potentially causal variants were generally larger than those based on imputation with earlier reference panels, consistent with resolution of causal signals to common risk haplotypes. Stratification of T2D-associated loci based on T2D-related quantitative trait associations revealed tissue-specific enrichment of regulatory annotations in pancreatic islet enhancers for loci influencing insulin secretion and in adipocytes, monocytes, and hepatocytes for insulin action-associated loci. These findings highlight the predominant role played by common variants of modest effect and the diversity of biological mechanisms influencing T2D pathophysiology.
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| 9. |
- Scott, Robert A., et al.
(författare)
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Large-scale association analyses identify new loci influencing glycemic traits and provide insight into the underlying biological pathways
- 2012
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 44:9, s. 991-1005
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Tidskriftsartikel (refereegranskat)abstract
- Through genome-wide association meta-analyses of up to 133,010 individuals of European ancestry without diabetes, including individuals newly genotyped using the Metabochip, we have increased the number of confirmed loci influencing glycemic traits to 53, of which 33 also increase type 2 diabetes risk (q < 0.05). Loci influencing fasting insulin concentration showed association with lipid levels and fat distribution, suggesting impact on insulin resistance. Gene-based analyses identified further biologically plausible loci, suggesting that additional loci beyond those reaching genome-wide significance are likely to represent real associations. This conclusion is supported by an excess of directionally consistent and nominally significant signals between discovery and follow-up studies. Functional analysis of these newly discovered loci will further improve our understanding of glycemic control.
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| 10. |
- Scott, Robert A, et al.
(författare)
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No interactions between previously associated 2-hour glucose gene variants and physical activity or BMI on 2-hour glucose levels
- 2012
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Ingår i: Diabetes. - Alexandria, VA : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 61:5, s. 1291-1296
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Tidskriftsartikel (refereegranskat)abstract
- Gene-lifestyle interactions have been suggested to contribute to the development of type 2 diabetes. Glucose levels 2 h after a standard 75-g glucose challenge are used to diagnose diabetes and are associated with both genetic and lifestyle factors. However, whether these factors interact to determine 2-h glucose levels is unknown. We meta-analyzed single nucleotide polymorphism (SNP) × BMI and SNP × physical activity (PA) interaction regression models for five SNPs previously associated with 2-h glucose levels from up to 22 studies comprising 54,884 individuals without diabetes. PA levels were dichotomized, with individuals below the first quintile classified as inactive (20%) and the remainder as active (80%). BMI was considered a continuous trait. Inactive individuals had higher 2-h glucose levels than active individuals (β = 0.22 mmol/L [95% CI 0.13-0.31], P = 1.63 × 10(-6)). All SNPs were associated with 2-h glucose (β = 0.06-0.12 mmol/allele, P ≤ 1.53 × 10(-7)), but no significant interactions were found with PA (P > 0.18) or BMI (P ≥ 0.04). In this large study of gene-lifestyle interaction, we observed no interactions between genetic and lifestyle factors, both of which were associated with 2-h glucose. It is perhaps unlikely that top loci from genome-wide association studies will exhibit strong subgroup-specific effects, and may not, therefore, make the best candidates for the study of interactions.
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| 11. |
- Berndt, Sonja I., et al.
(författare)
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Genome-wide meta-analysis identifies 11 new loci for anthropometric traits and provides insights into genetic architecture
- 2013
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 45:5, s. 501-U69
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Tidskriftsartikel (refereegranskat)abstract
- Approaches exploiting trait distribution extremes may be used to identify loci associated with common traits, but it is unknown whether these loci are generalizable to the broader population. In a genome-wide search for loci associated with the upper versus the lower 5th percentiles of body mass index, height and waist-to-hip ratio, as well as clinical classes of obesity, including up to 263,407 individuals of European ancestry, we identified 4 new loci (IGFBP4, H6PD, RSRC1 and PPP2R2A) influencing height detected in the distribution tails and 7 new loci (HNF4G, RPTOR, GNAT2, MRPS33P4, ADCY9, HS6ST3 and ZZZ3) for clinical classes of obesity. Further, we find a large overlap in genetic structure and the distribution of variants between traits based on extremes and the general population and little etiological heterogeneity between obesity subgroups.
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| 12. |
- Do, Ron, et al.
(författare)
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Common variants associated with plasma triglycerides and risk for coronary artery disease
- 2013
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 45:11, s. 1345-
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Tidskriftsartikel (refereegranskat)abstract
- Triglycerides are transported in plasma by specific triglyceride-rich lipoproteins; in epidemiological studies, increased triglyceride levels correlate with higher risk for coronary artery disease (CAD). However, it is unclear whether this association reflects causal processes. We used 185 common variants recently mapped for plasma lipids (P < 5 x 10(-8) for each) to examine the role of triglycerides in risk for CAD. First, we highlight loci associated with both low-density lipoprotein cholesterol (LDL-C) and triglyceride levels, and we show that the direction and magnitude of the associations with both traits are factors in determining CAD risk. Second, we consider loci with only a strong association with triglycerides and show that these loci are also associated with CAD. Finally, in a model accounting for effects on LDL-C and/or high-density lipoprotein cholesterol (HDL-C) levels, the strength of a polymorphism's effect on triglyceride levels is correlated with the magnitude of its effect on CAD risk. These results suggest that triglyceride-rich lipoproteins causally influence risk for CAD.
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| 13. |
- Kilpeläinen, Tuomas O, et al.
(författare)
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Genome-wide meta-analysis uncovers novel loci influencing circulating leptin levels
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Leptin is an adipocyte-secreted hormone, the circulating levels of which correlate closely with overall adiposity. Although rare mutations in the leptin (LEP) gene are well known to cause leptin deficiency and severe obesity, no common loci regulating circulating leptin levels have been uncovered. Therefore, we performed a genome-wide association study (GWAS) of circulating leptin levels from 32,161 individuals and followed up loci reaching P<10(-6) in 19,979 additional individuals. We identify five loci robustly associated (P<5 × 10(-8)) with leptin levels in/near LEP, SLC32A1, GCKR, CCNL1 and FTO. Although the association of the FTO obesity locus with leptin levels is abolished by adjustment for BMI, associations of the four other loci are independent of adiposity. The GCKR locus was found associated with multiple metabolic traits in previous GWAS and the CCNL1 locus with birth weight. Knockdown experiments in mouse adipose tissue explants show convincing evidence for adipogenin, a regulator of adipocyte differentiation, as the novel causal gene in the SLC32A1 locus influencing leptin levels. Our findings provide novel insights into the regulation of leptin production by adipose tissue and open new avenues for examining the influence of variation in leptin levels on adiposity and metabolic health.
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| 14. |
- Lu, Yingchang, et al.
(författare)
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New loci for body fat percentage reveal link between adiposity and cardiometabolic disease risk
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- To increase our understanding of the genetic basis of adiposity and its links to cardiometabolic disease risk, we conducted a genome-wide association meta-analysis of body fat percentage (BF%) in up to 100,716 individuals. Twelve loci reached genome-wide significance (P<5 × 10(-8)), of which eight were previously associated with increased overall adiposity (BMI, BF%) and four (in or near COBLL1/GRB14, IGF2BP1, PLA2G6, CRTC1) were novel associations with BF%. Seven loci showed a larger effect on BF% than on BMI, suggestive of a primary association with adiposity, while five loci showed larger effects on BMI than on BF%, suggesting association with both fat and lean mass. In particular, the loci more strongly associated with BF% showed distinct cross-phenotype association signatures with a range of cardiometabolic traits revealing new insights in the link between adiposity and disease risk.
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| 15. |
- Roselli, Carolina, et al.
(författare)
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Multi-ethnic genome-wide association study for atrial fibrillation
- 2018
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 50:9, s. 1225-1233
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Tidskriftsartikel (refereegranskat)abstract
- Atrial fibrillation (AF) affects more than 33 million individuals worldwide(1) and has a complex heritability(2). We conducted the largest meta-analysis of genome-wide association studies (GWAS) for AF to date, consisting of more than half a million individuals, including 65,446 with AF. In total, we identified 97 loci significantly associated with AF, including 67 that were novel in a combined-ancestry analysis, and 3 that were novel in a European-specific analysis. We sought to identify AF-associated genes at the GWAS loci by performing RNA-sequencing and expression quantitative trait locus analyses in 101 left atrial samples, the most relevant tissue for AF. We also performed transcriptome-wide analyses that identified 57 AF-associated genes, 42 of which overlap with GWAS loci. The identified loci implicate genes enriched within cardiac developmental, electrophysiological, contractile and structural pathways. These results extend our understanding of the biological pathways underlying AF and may facilitate the development of therapeutics for AF.
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| 16. |
- Willer, Cristen J., et al.
(författare)
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Discovery and refinement of loci associated with lipid levels
- 2013
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 45:11, s. 1274-1283
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Tidskriftsartikel (refereegranskat)abstract
- Levels of low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides and total cholesterol are heritable, modifiable risk factors for coronary artery disease. To identify new loci and refine known loci influencing these lipids, we examined 188,577 individuals using genome-wide and custom genotyping arrays. We identify and annotate 157 loci associated with lipid levels at P < 5 x 10(-8), including 62 loci not previously associated with lipid levels in humans. Using dense genotyping in individuals of European, East Asian, South Asian and African ancestry, we narrow association signals in 12 loci. We find that loci associated with blood lipid levels are often associated with cardiovascular and metabolic traits, including coronary artery disease, type 2 diabetes, blood pressure, waist-hip ratio and body mass index. Our results demonstrate the value of using genetic data from individuals of diverse ancestry and provide insights into the biological mechanisms regulating blood lipids to guide future genetic, biological and therapeutic research.
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| 17. |
- Bremer, Kåre, et al.
(författare)
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An ordinal classification for the families of flowering plants
- 1998
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Ingår i: ANNALS OF THE MISSOURI BOTANICAL GARDEN. - : MISSOURI BOTANICAL GARDEN. - 0026-6493. ; 85:4, s. 531-553
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Recent cladistic analyses are revealing the phylogeny of flowering plants in increasing detail, and there is support for the monophyly of many major groups above the family level. With many elements of the major branching sequence of phylogeny established
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| 18. |
- Jandrić, Petar, et al.
(författare)
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Teaching in the Age of Covid-19
- 2020
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Ingår i: Postdigital Science and Education. - : Springer Science and Business Media LLC. - 2524-4868 .- 2524-485X. ; 2:3, s. 1069-1230
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A collection of 84 author's testimonies and workspace photographs between 18 March and 5 May 2020.
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| 19. |
- Jandrić, Petar, et al.
(författare)
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Teaching in the Age of Covid-19—1 Year Later
- 2021
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Ingår i: Postdigital Science and Education. - : Springer. - 2524-485X .- 2524-4868. ; 3:3, s. 1073-1223
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Tidskriftsartikel (refereegranskat)
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| 20. |
- Mahajan, Anubha, et al.
(författare)
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Refining the accuracy of validated target identification through coding variant fine-mapping in type 2 diabetes
- 2018
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Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 50:4, s. 559-571
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Tidskriftsartikel (refereegranskat)abstract
- We aggregated coding variant data for 81,412 type 2 diabetes cases and 370,832 controls of diverse ancestry, identifying 40 coding variant association signals (P < 2.2 × 10−7); of these, 16 map outside known risk-associated loci. We make two important observations. First, only five of these signals are driven by low-frequency variants: even for these, effect sizes are modest (odds ratio ≤1.29). Second, when we used large-scale genome-wide association data to fine-map the associated variants in their regional context, accounting for the global enrichment of complex trait associations in coding sequence, compelling evidence for coding variant causality was obtained for only 16 signals. At 13 others, the associated coding variants clearly represent ‘false leads’ with potential to generate erroneous mechanistic inference. Coding variant associations offer a direct route to biological insight for complex diseases and identification of validated therapeutic targets; however, appropriate mechanistic inference requires careful specification of their causal contribution to disease predisposition.
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| 21. |
- Simonsson, Christian, et al.
(författare)
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A unified framework for prediction of liver steatosis dynamics in response to different diet and drug interventions
- 2024
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Ingår i: Clinical Nutrition. - : CHURCHILL LIVINGSTONE. - 0261-5614 .- 1532-1983. ; 43:6, s. 1532-1543
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Tidskriftsartikel (refereegranskat)abstract
- Background & aims: Non-alcoholic fatty liver disease (NAFLD) is a common metabolic disorder, characterized by the accumulation of excess fat in the liver, and is a driving factor for various severe liver diseases. These multi -factorial and multi-timescale changes are observed in different clinical studies, but these studies have not been integrated into a uni fied framework. In this study, we aim to present such a uni fied framework in the form of a dynamic mathematical model. Methods: For model training and validation, we collected data for dietary or drug -induced interventions aimed at reducing or increasing liver fat. The model was formulated using ordinary differential equations (ODEs) and the mathematical analysis, model simulation, model formulation and the model parameter estimation were all performed in MATLAB. Results: Our mathematical model describes accumulation of fat in the liver and predicts changes in lipid fluxes induced by both dietary and drug interventions. The model is validated using data from a wide range of drug and dietary intervention studies and can predict both short-term (days) and long-term (weeks) changes in liver fat. Importantly, the model computes the contribution of each individual lipid flux to the total liver fat dynamics. Furthermore, the model can be combined with an established bodyweight model, to simulate even longer scenarios (years), also including the effects of insulin resistance and body weight. To help prepare for corresponding eHealth applications, we also present a way to visualize the simulated changes, using dynamically changing lipid droplets, seen in images of liver biopsies. Conclusion: In conclusion, we believe that the minimal model presented herein might be a useful tool for future applications, and to further integrate and understand data regarding changes in dietary and drug induced changes in ectopic TAG in the liver. With further development and validation, the minimal model could be used as a disease progression model for steatosis. (c) 2024 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 22. |
- Williamson, Alice, et al.
(författare)
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Genome-wide association study and functional characterization identifies candidate genes for insulin-stimulated glucose uptake
- 2023
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Ingår i: Nature Genetics. - : Springer Nature. - 1061-4036 .- 1546-1718. ; 55:6, s. 973-983
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Tidskriftsartikel (refereegranskat)abstract
- Distinct tissue-specific mechanisms mediate insulin action in fasting and postprandial states. Previous genetic studies have largely focused on insulin resistance in the fasting state, where hepatic insulin action dominates. Here we studied genetic variants influencing insulin levels measured 2 h after a glucose challenge in >55,000 participants from three ancestry groups. We identified ten new loci (P < 5 × 10-8) not previously associated with postchallenge insulin resistance, eight of which were shown to share their genetic architecture with type 2 diabetes in colocalization analyses. We investigated candidate genes at a subset of associated loci in cultured cells and identified nine candidate genes newly implicated in the expression or trafficking of GLUT4, the key glucose transporter in postprandial glucose uptake in muscle and fat. By focusing on postprandial insulin resistance, we highlighted the mechanisms of action at type 2 diabetes loci that are not adequately captured by studies of fasting glycemic traits.
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| 23. |
- Abdollahi Sani, Negar, et al.
(författare)
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Flexible lamination-fabricated ultra-high frequency diodes based on self-supporting semiconducting composite film of silicon micro-particles and nano-fibrillated cellulose
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Low cost and flexible devices such as wearable electronics, e-labels and distributed sensors will make the future "internet of things" viable. To power and communicate with such systems, high frequency rectifiers are crucial components. We present a simple method to manufacture flexible diodes, operating at GHz frequencies, based on self-adhesive composite films of silicon micro-particles (Si-ΌPs) and glycerol dispersed in nanofibrillated cellulose (NFC). NFC, Si-ΌPs and glycerol are mixed in a water suspension, forming a self-supporting nanocellulose-silicon composite film after drying. This film is cut and laminated between a flexible pre-patterned Al bottom electrode and a conductive Ni-coated carbon tape top contact. A Schottky junction is established between the Al electrode and the Si-ΌPs. The resulting flexible diodes show current levels on the order of mA for an area of 2 mm2, a current rectification ratio up to 4 × 103 between 1 and 2 V bias and a cut-off frequency of 1.8 GHz. Energy harvesting experiments have been demonstrated using resistors as the load at 900 MHz and 1.8 GHz. The diode stack can be delaminated away from the Al electrode and then later on be transferred and reconfigured to another substrate. This provides us with reconfigurable GHz-operating diode circuits.
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| 24. |
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| 25. |
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| 26. |
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| 27. |
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| 28. |
- Baskaran, Karthikeyan, et al.
(författare)
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Effects of Optical Defocus on Resolution Acuity in Preferred Retinal Locus
- 2011
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Ingår i: <em>Invest Ophthalmol Vis Sci</em> 2011;52: E-Abstract 1900..
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Konferensbidrag (refereegranskat)abstract
- PurposeResolution acuity in the peripheral visual field is primarily limited by retinal sampling. In healthy eyes, the correction of peripheral refractive errors does not produce significant visual benefits other than improved detection and low contrast acuity. However, studies (Lundstrom L et al, Optom Vis Sci, 2007;84:1046-52) have shown that peripheral refractive corrections improve resolution acuity in subjects with central visual field loss (CFL) who have an established preferred retinal locus (PRL). The aim of this study was to evaluate the effect of optical defocus on high contrast resolution acuity in the PRL. MethodsResolution acuity was evaluated under spherical defocus in the PRL of three low vision subjects (mean age 75 years) with long standing CFL (due to age-related macular degeneration). Off-axis refractive error at the PRL was measured by an open-field COAS-HD VR aberrometer and was corrected accordingly. The PRL for subject 1 was located at 10{degrees} in the temporal visual field (left eye), subject 2 at 20{degrees} in the nasal visual field (right eye) and subject 3 at 15{degrees} in the inferior visual field (left eye). Stimuli consisting of high-contrast Gabor patches with a visible diameter of 3{o} were presented on a CRT monitor situated 1.0 meter from the subject. Resolution thresholds for static visual acuity (SVA) and dynamic visual acuity (DVA) were obtained using an adaptive Bayesian algorithm. Fixation was aided using illuminated concentric rings covering {+/-}25{degrees} in the visual field. Defocus was altered in 1D steps up to {+/-}4D. When measuring DVA, the sine-wave gratings drifted within the Gaussian envelope at an angular velocity of 1{degrees}/sec. ResultsResolution thresholds for both SVA and DVA in the PRL varied significantly with the amount of optical defocus. The results show a 2 - 3 line decrease (logMAR) in SVA and DVA with 4 D positive and negative defocus. There was no significant difference between SVA and DVA with increasing defocus. In the absence of defocus, SVA was significantly better than DVA in the PRL. ConclusionsDefocus as low as one dioptre has an impact on both static and dynamic high contrast resolution acuity for CFL subjects using a PRL. The results of this study suggest that, for CFL subjects using a PRL, resolution acuity is not only sampling limited but also influenced by the optics of the eye.
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| 29. |
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| 30. |
- Berggren, Magnus, et al.
(författare)
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Browsing the Real World using Organic Electronics, Si-Chips, and a Human Touch
- 2016
-
Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 28:10, s. 1911-1916
-
Tidskriftsartikel (refereegranskat)abstract
- Two different e-labels were developed to explore the feasibility and to identify scientifi c and engineering challenges of the Real-World-Web platform. First was a printed biosensor e-label, comprising Si-chips with an array of different printegrated devices, and second, an e-label to explore the feasibility of transferring data, through the human body, between a mobile device and different distributed e-labels, adhered onto the body or onto dedicated devices and surfaces of one's ambience. The silicon chips utilized in e-labels, include analogue and digital circuitry to receive and handle sensory input, to perform signal processing, and to transmit information to antennas and displays. When used, the e-label is turned on, and a sample is then added onto the sensor area. The display provides simple instructions and updated information to the user. All data handling, electrical probing, and analysis of the sensor is performed by the Si-chips, and the sensing data is finally shown in the printed display. The second e-label exemplifies an ID-tag for body area networks (BAN) communication applications, which, in part, is manufactured and integrated in the same way as the first e-label, but with another choice of Si-chips and capacitive antennas.
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| 31. |
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| 32. |
- de Peppo, Giuseppe Maria, et al.
(författare)
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Osteogenic response of human mesenchymal stem cells to well-defined nanoscale topography in vitro
- 2014
-
Ingår i: International Journal of Nanomedicine. - 1176-9114 .- 1178-2013. ; 9:1, s. 2499-2515
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Tidskriftsartikel (refereegranskat)abstract
- Background: Patterning medical devices at the nanoscale level enables the manipulation of cell behavior and tissue regeneration, with topographic features recognized as playing a significant role inthe osseointegration of implantable devices. Methods: In this study, we assessed the ability of titanium-coated hemisphere-like topographic nanostructures of different sizes (approximately 50, 100, and 200 nm) to influence the morphology, proliferation, and osteogenic differentiation of human mesenchymal stem cells (hMSCs). Results: We found that the proliferation and osteogenicdifferentiation of hMSCs was influenced by the size of the underlying structures, suggesting that size variations in topographic features at the nanoscale level, independently of chemistry, can be exploited to control hMSC behavior in a size-dependent fashion. Conclusion: Our studies demonstrate that colloidal lithography, in combination with coating technologies, can be exploited to investigate the cell response to well defined nanoscale topography and to develop next-generation surfaces that guide tissue regeneration and promote implant integration.
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| 33. |
- de Peppo, Giuseppe Maria, 1981, et al.
(författare)
-
Osteogenic response of human mesenchymal stem cells to well-defined nanoscale topography in vitro
- 2014
-
Ingår i: International journal of nanomedicine. - : Informa UK Limited. - 1176-9114 .- 1178-2013. ; 9:1, s. 2499-2515
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Patterning medical devices at the nanoscale level enables the manipulation of cell behavior and tissue regeneration, with topographic features recognized as playing a significant role in the osseointegration of implantable devices. Methods: In this study, we assessed the ability of titanium-coated hemisphere-like topographic nanostructures of different sizes (approximately 50, 100, and 200 nm) to influence the morphology, proliferation, and osteogenic differentiation of human mesenchymal stem cells (hMSCs). Results: We found that the proliferation and osteogenic differentiation of hMSCs was influenced by the size of the underlying structures, suggesting that size variations in topographic features at the nanoscale level, independently of chemistry, can be exploited to control hMSC behavior in a size-dependent fashion. Conclusion: Our studies demonstrate that colloidal lithography, in combination with coating technologies, can be exploited to investigate the cell response to well defined nanoscale topography and to develop next-generation surfaces that guide tissue regeneration and promote implant integration.
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| 34. |
- Folkersen, Lasse, et al.
(författare)
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Genomic and drug target evaluation of 90 cardiovascular proteins in 30,931 individuals.
- 2020
-
Ingår i: Nature metabolism. - : Springer Science and Business Media LLC. - 2522-5812. ; 2:10, s. 1135-1148
-
Tidskriftsartikel (refereegranskat)abstract
- Circulating proteins are vital in human health and disease and are frequently used as biomarkers for clinical decision-making or as targets for pharmacological intervention. Here, we map and replicate protein quantitative trait loci (pQTL) for 90 cardiovascular proteins in over 30,000 individuals, resulting in 451 pQTLs for 85 proteins. For each protein, we further perform pathway mapping to obtain trans-pQTL gene and regulatory designations. We substantiate these regulatory findings with orthogonal evidence for trans-pQTLs using mouse knockdown experiments (ABCA1 and TRIB1) and clinical trial results (chemokine receptors CCR2 and CCR5), with consistent regulation. Finally, we evaluate known drug targets, and suggest new target candidates or repositioning opportunities using Mendelian randomization. This identifies 11 proteins with causal evidence of involvement in human disease that have not previously been targeted, including EGF, IL-16, PAPPA, SPON1, F3, ADM, CASP-8, CHI3L1, CXCL16, GDF15 and MMP-12. Taken together, these findings demonstrate the utility of large-scale mapping of the genetics of the proteome and provide a resource for future precision studies of circulating proteins in human health.
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| 35. |
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| 36. |
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| 37. |
- Gustafsson, Lennart, et al.
(författare)
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Studying disk movements by novel image-analysis method
- 1995
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Ingår i: Journal of engineering mechanics. - 0733-9399 .- 1943-7889. ; 121:8, s. 931-934
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Tidskriftsartikel (refereegranskat)abstract
- An image-analysis method developed to study granular flow, the accumulating particle trajectories (APT) method, is shown to be a versatile tool to study the movements of disks. The moving disks, which are provided with suitable dot patterns, are video-recorded and the recorded sequences are analyzed to provide trajectories of the disks and the dots, thus making it possible to study both translational and rotational movements. It is also possible to introduce time markers in the trajectories. Up to eight images per second can be analyzed. The filtering necessary to attenuate electronic noise in the video equipment is performed as time filtering between consecutive images and is very efficient. The method's demands for processing power are very moderate and, therefore, particle movements during time spans corresponding with thousands of video frames can be easily presented as analysis results. The method can be implemented at relatively low cost.
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| 38. |
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| 39. |
- Gustafsson, Lennart, et al.
(författare)
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Studying mixed granular flows by image analysis
- 1996
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Ingår i: Engineering mechanics. - : American Society of Civil Engineers (ASCE). - 0784401721 ; , s. 100-103
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Konferensbidrag (refereegranskat)abstract
- Studying mixed granular flows where particles differ in size, density, surface friction, etc. is of importance for such applications as separation and mixing of granular materials. Using the APT (Accumulating Particle Trajectories) method the flow of particles of any one kind can be extracted from the total flow of all particles. It is required only that the different kinds of particles be given different gray values. The flow in a model experiment is shown
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| 40. |
- Jandrić, Petar, et al.
(författare)
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Teaching in the Age of Covid-19 : The New Normal
- 2022
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Ingår i: Postdigital Science and Education. - : Springer Science and Business Media LLC. - 2524-485X .- 2524-4868. ; 4:3, s. 877-1015
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Tidskriftsartikel (refereegranskat)abstract
- On 17 March 2020, Postdigital Science and Education launched a call for testimonies about teaching and learning during very frst Covid-19 lockdowns. The resulting article, ‘Teaching in the Age of Covid-19’ (attached), presents 81 written testimonies and 80 workspace photographs submitted by 84 authors from 19 countries. On 17 March 2021, Postdigital Science and Education launched a call for a sequel article of testimonies about teaching and learning during very first Covid-19 lockdowns. The resulting article, ‘Teaching in the Age of Covid-19—1 Year Later’(attached), consists of 74 textual testimonies and 76 workspace photographs submitted by 77 authors from 20 countries.These two articles have been downloaded almost 100,000 times and have been cited more than 100 times. This shows their value as historical documents. Recent analyses, such as ‘Teaching in the Age of Covid-19—A Longitudinal Study ’(attached), also indicate their strong potential for educational research. As the Covid-19 pandemic seems to wind down, pandemic experiences have entered the mainstream. They shape all educational research of today and arguably do not require special treatment. Yet, our unique series of pandemic testimonies provides a unique opportunity to longitudinally trace what happens to the same people over the years—and this opportunity should not be missed.Today, we launch a call for fnal sequel: Teaching in the Age of Covid-19—The New Normal. In this sequel, we would like to hear about ways in which you—contributors to the previous articles—have established your own new normal. We hope that this will be the last iteration in this series of testimony articles. Unless the world faces another strong pandemic outburst, we would like to end the series with this last article.
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| 41. |
- Jones, Owen R., et al.
(författare)
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Senescence rates are determined by ranking on the fast-slow life-history continuum
- 2008
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 11:7, s. 664-673
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Tidskriftsartikel (refereegranskat)abstract
- Comparative analyses of survival senescence by using life tables have identified generalizations including the observation that mammals senesce faster than similar-sized birds. These generalizations have been challenged because of limitations of life-table approaches and the growing appreciation that senescence is more than an increasing probability of death. Without using life tables, we examine senescence rates in annual individual fitness using 20 individual-based data sets of terrestrial vertebrates with contrasting life histories and body size. We find that senescence is widespread in the wild and equally likely to occur in survival and reproduction. Additionally, mammals senesce faster than birds because they have a faster life history for a given body size. By allowing us to disentangle the effects of two major fitness components our methods allow an assessment of the robustness of the prevalent life-table approach. Focusing on one aspect of life history - survival or recruitment - can provide reliable information on overall senescence.
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| 42. |
- Kristiansson, Håkan, et al.
(författare)
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Effect of Optical Defocus on Peripheral Resolution Acuity in Old Healthy Emmetropes
- 2011
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Konferensbidrag (refereegranskat)abstract
- Background: A recent study by Rosén et al found peripheral low contrast resolution acuity, but not high contrast acuity, to be affected by defocus in young healthy eyes. Since aging causes considerable degradation in peripheral optics even in healthy subjects we wanted to see if, older subjects were also sensitive to defocus in low contrast acuity. Purpose: The aim of this study was to evaluate the effect of optical defocus on high and low contrast resolution acuity in the peripheral visual field of healthy older emmetropes. Subjects: High- and low-contrast resolution acuity was evaluated under spherical defocus in the 20° nasal visual field of four healthy older emmetropic subjects. The off-axis refractive error at the 20° nasal visual field was measured by a COAS-HD VR aberrometer and was corrected accordingly for each subject. Methods: Resolution thresholds for visual acuity (VA) were obtained using stimuli consisting of high- (100%) and low- (10%) contrast gratings that were presented on a CRT monitor situated 1.0 meter from the subject. Stimuli, 3° in diameter were presented for 300 ms using a 2AFC paradigm. Two repeated measurements, for both high and low contrast, were obtained for each point of defocus in 1.0 D steps up to ±4 D at 45mm vertex distance. The results are corrected to effective defocus at the corneal plane. Results: Defocus had no visible effect on high contrast VA, although there was a slight decrease in VA with higher amounts of positive defocus. However, defocus was found to have a significant effect on low contrast VA. Moreover, low contrast resolution was more sensitive to positive defocus than the negative defocus. Conclusions: Defocus has an impact on low contrast resolution whereas no such effect was found for high contrast resolution. These results are similar to those obtained by Rosén et al1 in young eyes. These results suggest that low contrast optotypes could possibly be used for determining subjective refraction in low vision subjects.
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| 43. |
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| 44. |
- Lewis, Peter, 1971-, et al.
(författare)
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Dynamic Visual Acuity in the Peripheral Visual Field Using Gabor Patches
- 2010
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Konferensbidrag (refereegranskat)abstract
- Purpose:To evaluate dynamic visual acuity (DVA) in the peripheral visual field. This ability is important within the areas of sports, traffic safety, as well as for people with low vision; specifically those with central visual field loss. In this study we investigated both static- and dynamic visual acuity in the periphery of normally sighted observers using Gabor patches. Methods:DVA and static visual acuity (SVA) was measured on the right eye of normally sighted emmetropes. Stimuli consisted of high-contrast Gabor patches; sine wave gratings multiplied by a Gaussian hull with a diameter of 2º, with the sine gratings drifting at 1, 2, and 4 degrees per second. Stimuli were presented, using MATLAB and Psychophysics Toolbox, on one of seven CRT monitors at the following retinal eccentricities: 10, 20 and 30 degrees, nasally and temporally as well as in the fovea. Subjects were informed to maintain fixation on a central fixation object during measurements at eccentric locations. An Adaptive Bayesian algorithm was employed to determine resolution thresholds at each eccentricity. Results:The results show a trend towards both better static- and dynamic visual acuities for the temporal visual field at retinal eccentricities 20° and 30° compared to nasally. There appears to be a more rapid decrease in both static- and dynamic visual acuity with increasing eccentricity for the nasal visual field. In addition, we did not find any difference in DVA and SVA in the peripheral visual field for the velocities used in this study. Conclusions:Results of these first preliminary measurements suggest that dynamic visual acuity measured with drifting Gabor patches is greater in the temporal visual field for eccentricities 20 degrees or larger. To confirm these results more measurements need to be performed on a lager sample of subjects.
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| 45. |
- Lewis, Peter, 1971-
(författare)
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Improving Peripheral Vision Through Optical Correction and Stimulus Motion
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The loss of central vision subsequent to macular disease is often extremely debilitating. People with central field loss (CFL) must use other peripheral areas of the retina in order to see; areas with inferior resolution capacity, which are also affected by off-axis optical errors. The overall aim of the work encompassed by this thesis was to identify and evaluate methods of improving vision for people with CFL; with focus on the effects of off-axis optical correction and stimulus motion on resolution acuity and contrast sensitivity.Off-axis optical errors were measured using a commercially-available COAS-HD VR open-view aberrometer. We used adaptive psychophysical methods to evaluate grating resolution acuity and contrast sensitivity in the peripheral visual field; drifting gratings were employed to measure the effect of motion on these two measures of visual performance. The effect of sphero-cylindrical correction and stimulus motion on visual performance in healthy eyes and in subjects with CFL was also studied; in addition, the effect of adaptive optics aberration correction was examined in one subject with CFL.The COAS-HD aberrometer provided rapid and reliable measurements of off-axis refractive errors. Correction of these errors gave improvements in low-contrast resolution acuity in subjects with higher amounts of oblique astigmatism. Optical correction also improved high-contrast resolution acuity in most subjects with CFL, but not for healthy subjects. Adaptive optics correction improved both high and low contrast resolution acuity in the preferred retinal locus of a subject with CFL. The effect of stimulus motion depended on spatial frequency; motion of 7.5 Hz improved contrast sensitivity for stimuli of low spatial frequency in healthy and CFL subjects. Motion of 15 Hz had little effect on contrast sensitivity for low spatial frequency but resulted in reduced contrast sensitivity for higher spatial frequencies in healthy subjects. Finally, high-contrast resolution acuity was relatively insensitive to stimulus motion in the periphery.This thesis has served to broaden the knowledge regarding peripheral optical errors, stimulus motion and their effects on visual function, both in healthy subjects and in people with CFL. Overall it has shown that correction of off-axis refractive errors is important for optimizing peripheral vision in subjects with CFL; the use of an open-view aberrometer simplifies the determination of these errors. In addition, moderate stimulus motion can have a beneficial effect on contrast sensitivity for objects of predominantly low spatial frequency.
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| 46. |
- Lewis, Peter, 1971-, et al.
(författare)
-
Naso-temporal Asymmetry of Peripheral Static and Dynamic Visual Acuity
- 2011
-
Konferensbidrag (refereegranskat)abstract
- SummaryStatic and dynamic visual acuity was evaluated in the peripheral visual field on normally sighted emmetropes. The results show a significant asymmetry for both static and dynamic visual acuity between the nasal and temporal visual fields. IntroductionIt is well known that visual performance thresholds decrease rapidly with increasing retinal eccentricity1. This reduction in performance can be attributed to both optical factors and reduced neural sampling2-3; the latter being the predominant limiting factor in the peripheral retina3. Previous studies have shown that slowly moving stimuli are more easily resolved than stationary stimuli in the peripheral retina4. There is little evidence published regarding resolution thresholds for moving stimuli in more than a few limited directions in the visual field. In this study, static visual acuity (SVA) and dynamic visual acuity (DVA) thresholds were measured at 10° intervals both nasally and temporally on healthy, young emmetropes. DVA was measured at angular velocities of 1 °/s and 2 °/s using drifting Gabor patches. DiscussionStatic and dynamic visual acuity was measured on the right eye of emmetropic subjects. Results for SVA showed significantly better resolution in the temporal visual field compared with the nasal visual field at eccentricities 20° and beyond. The mean difference in acuity at 20° was approximately 0.2 LogMAR and at 30°, 0.3 LogMAR. The difference between the thresholds for DVA showed a similar naso-temporal asymmetry; the reduction in DVA paralleling the decrease in SVA for eccentricities 10° and beyond. No significant differences were observed between averaged results of SVA and DVA for the eccentricities tested in this study. ConclusionsThe results of this study confirm previous research conducted by Frisén (1987) showing better resolution for static stimuli presented in the temporal visual field compared to the nasal visual field. We have found that this is also true for DVA.
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| 47. |
- Lewis, Peter, et al.
(författare)
-
Objectively Determined Refraction Improves Peripheral Vision
- 2014
-
Ingår i: Optometry and Vision Science. - 1040-5488 .- 1538-9235. ; 91:7, s. 740-746
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose. The purpose of this study was twofold: to verify a fast, clinically applicable method for determining off-axis refraction and to assess the impact of objectively obtained off-axis refractive correction on peripheral low-contrast visual acuity. Methods. We measured peripheral low-contrast resolution acuity with Gabor patches both with and without off-axis correction at 20 degrees in the nasal visual field of 10 emmetropic subjects; the correction was obtained using a commercial open-field Hartmann-Shack wavefront sensor, the COAS-HD VR aberrometer. Off-axis refractive errors were calculated for a 5-mm circular pupil inscribed within the elliptical wavefront by COAS using the instruments' inbuilt "Seidel sphere" method. Results. Most of the subjects had simple myopic astigmatism, at 20 degrees in the nasal visual field ranging from -1.00 to -2.00 DC, with axis orientations generally near 90 degrees. The mean uncorrected and corrected low-contrast resolution acuities for all subjects were 0.92 and 0.86 logMAR, respectively (an improvement of 0.06 logMAR). For subjects with a scalar power refractive error of 1.00 diopters or more, the average improvement was 0.1 logMAR. The observed changes in low-contrast resolution acuity were strongly correlated with off-axis astigmatism (Pearson r = 0.95; p < 0.0001), the J(180) cross-cylinder component (Pearson r = 0.82; p = 0.0034), and power scalar (Pearson r = -0.75; p = 0.0126). Conclusions. The results suggest that there are definite benefits in correcting even moderate amounts of off-axis refractive errors; in this study, as little as -1.50 DC of off-axis astigmatism gave improvements of up to a line in visual acuity. It may be even more pertinent for people who rely on optimal peripheral visual function, specifically those with central visual field loss; the use of open-field aberrometers could be clinically useful in rapidly determining off-axis refractive errors specifically for this patient group who are generally more challenging to refract.
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| 48. |
- Lewis, Peter, 1971-, et al.
(författare)
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Resolution of static and dynamic stimuli in the peripheral visual field
- 2011
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Ingår i: Vision Research. - : Elsevier BV. - 0042-6989 .- 1878-5646. ; 51:16, s. 1829-1834
-
Tidskriftsartikel (refereegranskat)abstract
- In a clinical setting, emphasis is given to foveal visual function, and tests generally only utilize static stimuli. In this study, we measured static (SVA) and dynamic visual acuity (DVA) in the central and peripheral visual field on healthy, young emmetropic subjects using stationary and drifting Gabor patches. There were no differences between SVA and DVA in the peripheral visual field; however, SVA was superior to DVA in the fovea for both velocities tested. In addition, there was a clear naso-temporal asymmetry for both SVA and DVA for isoeccentric locations in the visual field beyond 10 degrees eccentricity. The lack of difference in visual acuity between static and dynamic stimuli found in this study may reflect the use of drift-motion as opposed to displacement motion used in previous studies.
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| 49. |
- Lewis, Peter, 1971-, et al.
(författare)
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The Effect of Refractive-Correction on Peripheral Low-Contrast Resolution Acuity
- 2012
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Purpose: High-contrast resolution acuity in the peripheral retina has been shown to be sampling-limited, however, a recent study indicates that peripheral low-contrast resolution acuity (PLCRA) is degraded by imposition of optical defocus. On the other hand, it has not been investigated whether refractive errors present in the peripheral field of normal, emmetropic eyes are sufficient to degrade PLCRA. The aim of this study was to evaluate the effect of peripheral refractive-correction on PLCRA in young emmetropes.Methods: Low-contrast (10 %) resolution acuity was measured off-axis (20° nasal visual field) on the right eyes of 10 emmetropic subjects (age 22 ± 2 years), both with and without peripheral refractive correction. Central and peripheral refractive errors were acquired using an open-field COAS-HD VR aberrometer. Stimuli, consisting of low-contrast Gabor patches with a visible diameter of 2°, were presented on a CRT monitor situated 3.0 meters from the subjects. Resolution thresholds were determined using a 2-alternative forced-choice Bayesian algorithm.Results: All the subjects had off-axis astigmatism (against-the-rule) at 20° in the nasal visual field ranging from -1.00 DC to -2.00 DC; of which four had -1.00 DC, three had -1.25 DC, one had -1.50 DC and the remaining two had -2.00 DC. Two of the subjects with -1.25 DC had -0.50 DS to -0.75 DS spherical errors; the rest had purely cylindrical errors. The mean uncorrected and corrected low-contrast resolution acuities for all subjects were 0.92 logMAR and 0.86 logMAR respectively. This shows an improvement in resolution acuity of 0.06 logMAR (p = 0.028) after correction of off-axis refractive errors. However when grouped according to the amount of astigmatism, the -1.00 DC group showed no difference in acuity with correction, the -1.25 DC, -1.50 DC and -2.00 DC groups improved on average by 0.05, 0.14 and 0.16 logMAR respectively.Conclusions: Correction of off-axis refractive errors had a positive effect on low-contrast resolution thresholds in the peripheral visual field on the emmetropic subjects in this study. Moreover, the effects become appreciable only for those subjects having larger degrees of astigmatism. This suggests that optical factors influence peripheral visual tasks involving low-contrast. There may be benefits in correcting even moderate amounts of off-axis refractive errors, especially for people who rely on optimal peripheral visual function.
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| 50. |
- Maranon, Antonio, et al.
(författare)
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Option framing and Markov chain: A descriptive approach in a state-space modeling of customer behavior
- 2015
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In the field of marketing, option framing is a product or service configuration where the consumers customize the package they wish to procure either by adding options to a base model, an initial configuration with a minimum number of essential features, or by subtracting options from a fully-loaded model, a product or service configuration with both essential and all of the optional features. Additive framing is selecting features to augment the base model, while subtractive framing is deselecting features from the fully-loaded model. A focal issue for companies that could possibly offer such products or services with option framing is finding out which process, additive or subtractive framing, is bound to give a final configuration with more features. The scenarios of option framing can be described by a finite Markov chain process. The Markov chain attempts to capture the decision process of the two types of framing through the estimated probabilities of movement from one phase to the other. In each of the decision phases, the key measure is the number of features in the configuration and the transition probabilities. The option framing is used on an actual study, where the empirical results verify the theories favoring subtractive framing, such as differential loss aversion and anchoring-adjustment theories. Separate Markov chains are evaluated for additive and subtractive framing, with the final configurations of the product or service package, along with the corresponding number of options, as main results.
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