| 1. |
- Johansson, Anna Maria, et al.
(författare)
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Variation in the VWF Gene in Swedish Patients with Type 1 von Willebrand Disease.
- 2011
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Ingår i: Annals of Human Genetics. - : Wiley. - 1469-1809 .- 0003-4800. ; 75, s. 447-455
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Tidskriftsartikel (refereegranskat)abstract
- The spectrum of mutations in the von Willebrand factor (VWF) gene in a Swedish type 1 von Willebrand disease (VWD) population was investigated. To gain more knowledge about the dynamics of VWD mutations, the data were analyzed from a population genetics perspective. The VWF gene was resequenced in 54 Swedish patients diagnosed with type 1 VWD. Fifty-five variable sites were located in exons, 10 in the promoter and 38 in introns. The spectrum of mutations was similar to a European study, but included 10 new candidate mutations. The synonymous sites were evenly distributed along the coding sequence, whereas nonsynonymous sites were located into three clusters. Overall, 44% of patients had no mutations or candidate mutations and no promoter haplotype was significantly associated with disease. In 11 patients (20%), more than one mutation or candidate mutation was detected. The allelic identity for the putative disease-causing mutations was approximately 0.1, compatible with an overall disease frequency of 1%. VWF sequences for exon 28 from eight monkey species were compared with the variable positions found in our patients. Positions classified as mutations were overrepresented among sites that were fixed in all eight monkey species. No general increase of the mutation rate was found for the pseudogene region.
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| 2. |
- Kurbasic, Azra, et al.
(författare)
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Relative risks and effective number of meioses: A unified approach for general genetic models and phenotypes
- 2006
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Ingår i: Annals of Human Genetics. - : Wiley. - 1469-1809 .- 0003-4800. ; 70:6, s. 907-922
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Tidskriftsartikel (refereegranskat)abstract
- Many common diseases are known to have genetic components, but since they are non-Mendelian, i.e. a large number of genetic factors affect the phenotype, these components are difficult to localize. These traits are often called complex and analysis of siblings is a valuable tool for mapping them. It has been shown that the power of the affected relative pairs method to detect linkage of a disease susceptibility locus depends on the locus contribution to increased risk of relatives compared with population prevalence Risch, 1990a,b). In this paper we generalize calculation of relative risk to arbitrary phenotypes and genetic models, but also show that the relative risk can be split into the relative risk at the main locus and the relative risk due to interaction between the main locus and loci at other chromosomes. We demonstrate how the main locus contribution to the relative risk is related to probabilities of allele sharing identical by descent at the main locus, as well as power to detect linkage. To this end we use the effective number of meioses, introduced by Hossjer (2005a) as a convenient tool. Relative risks and effective number of meioses are computed for several genetic models with binary or quantitative phenotypes, with or without polygenic effects.
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| 3. |
- Lace, B., et al.
(författare)
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Age of SERPINA1 gene PI Z mutation: Swedish and Latvian population analysis
- 2008
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Ingår i: Annals of Human Genetics. - : Wiley. - 1469-1809 .- 0003-4800. ; 72:3, s. 300-304
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Tidskriftsartikel (refereegranskat)abstract
- Alpha 1-antitrypsin (A1AT) deficiency, one of the most common inborn errors of metabolism in Caucasians, is characterized by a low serum concentration of A1AT and a high risk of pulmonary emphysema and liver disease. The allelic frequency for the most common protease inhibitor (PI) Z mutation in the SERPINA1 gene is 2-5% in Caucasians of European descent. The objective of our study was to estimate the PI Z mutation age using molecular analysis in Latvian and Swedish populations, which have the highest frequency of PI Z mutation. DNA samples of heterozygous and homozygous PI Z allele carriers from Latvia (n = 21) and Sweden (n = 65) were analysed; 113 unrelated healthy donors from Latvia were used as a control group. MALDI-TOF analysis was performed on all samples. Pairwise Fst was computed to compare the PI Z mutation ages between the two populations and controls. A p value less than 0.05 was considered significant. Analysis of non-recombinant SNPs revealed that the PI Z mutation age was 2902 years in Latvia (SD 1983) and 2362 years in Sweden (SD 1614) which correlates with previous studies based on microsatellite analysis.
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| 4. |
- Popat, S, et al.
(författare)
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Variation in the CTLA4/CD28 gene region confers an increased risk of coeliac disease
- 2002
-
Ingår i: Annals of Human Genetics. - : Wiley. - 1469-1809 .- 0003-4800. ; 66:2, s. 125-137
-
Tidskriftsartikel (refereegranskat)abstract
- Susceptibility to coeliae disease involves HLA and non-HLA-linked genes. The CTLA4/CD28 gene region encodes immune regulatory T-cell surface molecules and is a strong candidate as a susceptibility locus. We evaluated CTLA4/CD28 in coeliac disease by genetic linkage and association and combined Our findings with published studies through a meta-analysis. 116 multiplex families were genotyped across CTLA4/CD28 using eight markers. The contribution of CTLA4/CD28 to coeliac disease was assessed by non-parametric linkage and association analyses. Seven studies were identified that had evaluated the relationship between CTLA4/CD28 and coeliac disease and a pooled analysis of data undertaken. In our study there was evidence for a relationship between variation in the CTLA4/CD28 region and coeliae disease by linkage and association analyses. However. the findings did not attain formal statistical significance (p=0.004 and 0.039. respectively). Pooling findings with published results showed significant evidence for linkage (504 families) and association (910 families) : p values. 0.0001 and 0.0014 at D2S2214. respectively. and 0.0008 and 0.0006 at D2S116, respectively. These findings suggest that variation in the CD28/CTLA4 gene region is a determinant of coeliac disease susceptibility. Dissecting the sequence variation underlying this relationship will depend on further analyses utilising denser sets of markers.
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| 5. |
- Sjakste, T., et al.
(författare)
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Association of microsatellite polymorphisms of the human 14q13.2 region with type 2 diabetes mellitus in latvian and finnish populations
- 2007
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Ingår i: Annals of Human Genetics. - : Wiley. - 1469-1809 .- 0003-4800. ; 71, s. 772-776
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Tidskriftsartikel (refereegranskat)abstract
- A polymorphic microsatellite in intron 6 of the human proteasome core particle PSMA6 gene (HSMS006), and four other microsatellites localized upstream on human chromosome 14q13.2 (HSMS801, HSMS702, HSMS701, HSMS602), were genotyped in 104 type 2 diabetic patients and 129 age-matched control subjects from Latvia and replicated in 91 type 2 diabetic patients and 88 age-matched healthy control subjects from the Botnia Study in Finland. In type 2 diabetic patients from both populations the HSMS006 (TG)22 allele was two times more frequent compared to the control group. In the Latvian population the (CAA)8 allele of the HSMS602 marker was less frequent in the diabetic group, as was the (AC)24 allele of microsatellite HSMS801. Allele frequencies of the HSMS701 and 702 repeats were similar in healthy controls and type 2 diabetic patients. In conclusion, our data suggest that variants in the PSMA6 gene on chromosome 14q13.2 are associated with type 2 diabetes.
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| 6. |
- Sjölander, Arvid, et al.
(författare)
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Fine Mapping of Disease Genes Using Tagging SNPs
- 2007
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Ingår i: Annals of Human Genetics. - : Wiley. - 1469-1809 .- 0003-4800. ; 71:6, s. 815-827
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Tidskriftsartikel (refereegranskat)abstract
- We describe a haplotype clustering approach for localising a disease mutation within a fixed genomic region, which supplements tagging SNP (tSNP) information with (external) information on linkage disequilibrium. By applying our method to simulated data based on the coalescent, and on real haplotype data, we demonstrate that there are situations where significant gains can be made by incorporating tagged SNPs into the analysis. The issues we explore are important not only to these types of studies, but also to studies that select tSNPs based on (external) HapMap phase II data, and those that use genome-wide markers.
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| 7. |
- Horsfall, Laura J., et al.
(författare)
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Prevalence of Clinically Relevant UGT1A Alleles and Haplotypes in African Populations
- 2011
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Ingår i: Annals of Human Genetics. - : Wiley. - 0003-4800 .- 1469-1809. ; 75:2, s. 236-246
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Tidskriftsartikel (refereegranskat)abstract
- Variation of a short (TA)(n) repeat sequence (rs8175347) covering the TATA box of UGT1A1 (UDP-glucuronosyltransferase1A1) is associated with hyperbilirubinaemia (Gilbert's syndrome) and adverse drug reactions, and is used for dosage advice for irinotecan. Several reports indicate that the low-activity (risk) alleles ((TA)(7) and (TA)(8))) are very frequent in Africans but the patterns of association with other variants in the UGT1A gene complex that may modulate these responses are not well known. rs8175347 and two other clinically relevant UGT1A variants (rs11692021 and rs10929302) were assayed in 2616 people from Europe and Africa. Low-activity (TA)(n) alleles frequencies were highest in equatorial Africa, (TA)(7,) being the most common in Cameroon, Ghana, southern Sudan, and in Ethiopian Anuak. Haplotypic diversity was also greatest in equatorial Africa, but in Ethiopia was very variable across ethnic groups. Resequencing of the promoter of a sample subset revealed no novel variations, but rs34547608 and rs887829 were typed and shown to be tightly associated with (TA)(n). Our results illustrate the need for investigation of the effect of UGT1A variants other than (TA)(n) on the risk of irinotecan toxicity, as well as hyperbilirubinaemia due to hemolytic anaemia or human immunodeficiency virus protease inhibitors, so that appropriate pharmacogenetic advice can be given.
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| 8. |
- Itan, Yuval, et al.
(författare)
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Detecting Gene Duplications in the Human Lineage
- 2010
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Ingår i: Annals of Human Genetics. - : Wiley. - 0003-4800 .- 1469-1809. ; 74:6, s. 555-565
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Tidskriftsartikel (refereegranskat)abstract
- Gene duplications represent an important class of evolutionary events that is likely to have contributed to the unique human phenotype in the short evolutionary time since the human-chimpanzee divergence. With the availability of both human and chimpanzee genome drafts in high coverage re-sequencing assemblies and the high annotation quality of most human genes, it should now be possible to identify all human lineage-specific gene duplication events (human inparalogues) and a few pioneering studies have attempted to do that. However, the different levels of coverage in the human and chimpanzee's genomes assemblies, and the differing levels of gene annotation, have led to problematic assumptions and oversimplifications in the algorithms and the datasets used to detect human lineage-specific gene duplications. In this study, we have developed a set of bioinformatic tools to overcome a number of the conceptual problems that are prevalent in previous studies and have collected a reliable and representative set of human inparalogues.
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| 9. |
- Konings, A., et al.
(författare)
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Candidate gene association study for noise-induced hearing loss in two independent noise-exposed populations
- 2009
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Ingår i: Annals of Human Genetics. - : Wiley. - 0003-4800 .- 1469-1809. ; 73:2, s. 215-224
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Tidskriftsartikel (refereegranskat)abstract
- Millions of people are daily exposed to high levels of noise. Consequently, noise-induced hearing loss (NIHL) is one of the most important occupational health hazards worldwide. In this study, we performed an association study for NIHL based on a candidate gene approach. 644 Single Nucleotide Polymorphisms (SNPs) in 53 candidate genes were analyzed in two independent NIHL sample sets, a Swedish set and part of a Polish set. Eight SNPs with promising results were selected and analysed in the remaining part of the Polish samples. One SNP in PCDH15 (rs7095441), resulted in significant associations in both sample sets while two SNPs in MYH14 (rs667907 and rs588035), resulted in significant associations in the Polish sample set and significant interactions with noise exposure level in the Swedish sample set. Calculation of odds ratios revealed a significant association of rs588035 with NIHL in the Swedish high noise exposure level group. Our studies suggest that PCDH15 and MYH14 may be NIHL susceptibility genes, but further replication in independent sample sets is mandatory.
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| 10. |
- Lappalainen, T, et al.
(författare)
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Migration waves to the Baltic Sea region
- 2008
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Ingår i: Annals of Human Genetics. - Oxford : Blackwell Publishing. - 0003-4800 .- 1469-1809. ; 72, s. 337-348
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the population history of the Baltic Sea region, known to be affected by a variety of migrations and genetic barriers, was analyzed using both mitochondrial DNA and Y-chromosomal data. Over 1200 samples from Finland, Sweden, Karelia, Estonia, Setoland, Latvia and Lithuania were genotyped for 18 Y-chromosomal biallelic polymorphisms and 9 STRs, in addition to analyzing 17 coding region polymorphisms and the HVS1 region from the mtDNA. It was shown that the populations surrounding the Baltic Sea are genetically similar, which suggests that it has been an important route not only for cultural transmission but also for population migration. However, many of the migrations affecting the area from Central Europe, the Volga-Ural region and from Slavic populations have had a quantitatively different impact on the populations, and, furthermore, the effects of genetic drift have increased the differences between populations especially in the north. The possible explanations for the high frequencies of several haplogroups with an origin in the Iberian refugia (H1, U5b, I1a) are also discussed.
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| 11. |
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| 12. |
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| 13. |
- Pemberton, T.J., et al.
(författare)
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Using population mixture to optimize the utility of genomic databases: linkage disequilibrium and association study design in India
- 2008
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Ingår i: Annals of Human Genetics. - : Wiley. - 0003-4800 .- 1469-1809. ; 72:4, s. 535-546
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Tidskriftsartikel (refereegranskat)abstract
- When performing association studies in populations that have not been the focus of large-scale investigations of haplotype variation, it is often helpful to rely on genomic databases in other populations for study design and analysis – such as in the selection of tag SNPs and in the imputation of missing genotypes. One way of improving the use of these databases is to rely on a mixture of database samples that is similar to the population of interest, rather than using the single most similar database sample. We demonstrate the effectiveness of the mixture approach in the application of African, European, and East Asian HapMap samples for tag SNP selection in populations from India, a genetically intermediate region underrepresented in genomic studies of haplotype variation.
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| 14. |
- Wirapati, Pratyaksha, et al.
(författare)
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Detecting Epistasis with Restricted Response Patterns in Pairs of Biallelic Loci
- 2011
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Ingår i: Annals of Human Genetics. - : Wiley. - 0003-4800 .- 1469-1809. ; 75:1, s. 133-145
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Tidskriftsartikel (refereegranskat)abstract
- P>Well-established examples of genetic epistasis between a pair of loci typically show characteristic patterns of phenotypic distributions in joint genotype tables. However, inferring epistasis given such data is difficult due to the lack of power in commonly used approaches, which decompose the epistatic patterns into main plus interaction effects followed by testing the interaction term. Testing additive-only or all terms may have more power, but they are sensitive to nonepistatic patterns. Alternatively, the epistatic patterns of interest can be enumerated and the best matching one is found by searching through the possibilities. Although this approach requires multiple testing correction over possible patterns, each pattern can be fitted with a regression model with just one degree of freedom and thus the overall power can still be high, if the number of possible patterns is limited. Here we compare the power of the linear decomposition and pattern search methods, by applying them to simulated data generated under several patterns of joint genotype effects with simple biological interpretations. Interaction-only tests are the least powerful; while pattern search approach is the most powerful if the range of possibilities is restricted, but still includes the true pattern.
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| 15. |
- Zaros, C, et al.
(författare)
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On the origin of the transthyretin Val30Met familial amyloid polyneuropathy.
- 2008
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Ingår i: Annals of Human Genetics. - : Wiley. - 0003-4800 .- 1469-1809. ; 72:Pt 4, s. 478-84
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Tidskriftsartikel (refereegranskat)abstract
- Transthyretin (TTR) familial amyloid polyneuropathy is a severe autosomal dominant neuropathy of adulthood, frequently linked to the pathogenic Val30Met variant of the TTR gene. The condition was initially described in northern Portugal, which is the first focus of the disease. Other important clusters of families are found in Sweden, Japan and South America. The origin of the Val30Met mutation and its distribution through the populations remains unclear. In the present work, we aimed at refining the history of the Val30Met mutation in patients affected with TTR amyloid neuropathy from Portugal, Sweden and Brazil. The decay of haplotype sharing was studied in 60 patients to estimate the age of the Most Recent Common Ancestor (MRCA) of mutation carriers in these populations. Our results showed a common haplotype in Portuguese and Brazilian patients and an age estimate of the MRCA of 750 and 650 years, respectively. In contrast, a different haplotype was found in the Swedish Val30Met patients with a corresponding age estimate for the MRCA, of 375 years. This work strengthens the hypothesis of different founders in Portuguese and Swedish Val30Met carriers and suggested a Portuguese origin of the Brazilian mutation. The age estimates of the MRCA are in line with the current historical knowledge of these populations.
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| 16. |
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| 17. |
- Chotai, Jayanti
(författare)
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On the lod score method in linkage analysis.
- 1984
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Ingår i: Annals of Human Genetics. - 0003-4800 .- 1469-1809. ; 48:Pt 4, s. 359-78
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Tidskriftsartikel (refereegranskat)abstract
- Genetic epidemiology deals with the interaction of environmental and genetic determinants in common diseases. Linkage analysis is an important branch of this field. The current practice of claiming linkage between two genetic loci when the maximum lod score z(theta) exceeds 3 has not received theoretical justification, whether considered as a sequential or as a fixed sample size test. Within the framework of significance testing, Wald's (1947) formulae are not applicable to allow this procedure a sequential interpretation. Considered as a fixed sample size test, we find that a chi 2 approximation would instead be very adequate. Since repeated significance testing is performed on linkage data, the nominal significance level should be more stringent for each test than the overall level. Some recent developments in group sequential trials by Pocock (1977) and in repeated significance testing by Woodroofe (1979) seem to indicate that the critical value of the maximum lod score should lie roughly between 0.9 and 3.3, depending on the maximum number of repetitions anticipated, on whether the significance level is desired to be 0.05, 0.01 or 0.001, and on whether the test is derived from a one-sided or a two-sided consideration. In terms of the group sequential approach, if a maximum of twenty repetitions is allowed, if z(theta) greater than log10 A is considered as a one-sided test and assumed to be symmetric when linkage is absent, then the type I error is approximately given by 1/A. We also treat the confidence interval approach for exclusion of unlikely recombination values.
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| 18. |
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| 19. |
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| 20. |
- Khabou, Boudour, et al.
(författare)
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Potential dysfunctional effects of synonymous variants: Insights from an exhaustive in silico analysis of the ABCB4 gene
- 2018
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Ingår i: Annals of Human Genetics. - : WILEY. - 0003-4800 .- 1469-1809. ; 82:6, s. 457-468
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Tidskriftsartikel (refereegranskat)abstract
- The multiple drug resistance 3 (MDR3) protein is a canalicular phospholipid translocator involved in the bile secretion and encoded by the ABCB4 gene. Its deficiency is related to a large spectrum of liver diseases. Taking into account the increased evidence about the involvement of synonymous variants in inherited diseases, this study aims to explore the putative effects of silent genetic variants on the ABCB4 expression. We performed an exhaustive computational approach using ESE finder, RegRNA 2.0, MFOLD, SNPfold, and %MinMax software added to the measurement of the Relative Synonymous Codon Usage. This analysis included 216 synonymous variants distributed throughout the ABCB4 gene. Results have shown that 11 synonymous coding SNPs decrease the ESE activity, while 8 of them change the codon frequency. Besides, the c.24Camp;gt;T variation, located 21 nucleotides downstream the start A (Adenine) U (Uracil) G (Glutamine) AUG causes an increase in the local stability. Moreover, the computational analysis of the 3UTR region showed that six of the eight variants located in this region affected the Wild Type (WT) pattern of the miRNA targets sites and/or their proper display. The 26 sSNPs retained as putatively functional possessed a very low allele frequency, supporting their pathogenicity. In conclusion, the obtained results suggest that some synonymous SNPs in the ABCB4 gene, considered up to now as neutral, may be involved in the MDR3 deficiency.
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| 21. |
- Lathrop, G M, et al.
(författare)
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Tests of gene order from three-locus linkage data.
- 1987
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Ingår i: Annals of Human Genetics. - 0003-4800 .- 1469-1809. ; 51:Pt 3, s. 235-49
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Tidskriftsartikel (refereegranskat)abstract
- Exact tests for gene order are derived and compared for three loci using linkage data from phase-known, completely informative marker loci (i.e. parents are heterozygotes with at most one allele identical at each locus), or from triple back-cross matings. A simulation method, based on resampling genotypes of children, is introduced to obtain approximations to the distribution of the test statistics for general mating types in families consisting of children and parents, with or without grandparents, as are used in many studies in human gene mapping. The method is illustrated by an application to linkage data on chromosome 13.
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| 22. |
- Popat, S, et al.
(författare)
-
Variation in the CTLA4/CD28 gene region confers an increased risk of coeliac disease.
- 2002
-
Ingår i: Annals of human genetics. - 0003-4800 .- 1469-1809. ; 66:Pt 2, s. 125-37
-
Tidskriftsartikel (refereegranskat)abstract
- Susceptibility to coeliac disease involves HLA and non-HLA-linked genes. The CTLA4/CD28 gene region encodes immune regulatory T-cell surface molecules and is a strong candidate as a susceptibility locus. We evaluated CTLA4/CD28 in coeliac disease by genetic linkage and association and combined our findings with published studies through a meta-analysis. 116 multiplex families were genotyped across CTLA4/CD28 using eight markers. The contribution of CTLA4/CD28 to coeliac disease was assessed by non-parametric linkage and association analyses. Seven studies were identified that had evaluated the relationship between CTLA4/CD28 and coeliac disease and a pooled analysis of data undertaken. In our study there was evidence for a relationship between variation in the CTLA4/CD28 region and coeliac disease by linkage and association analyses. However, the findings did not attain formal statistical significance (p = 0.004 and 0.039, respectively). Pooling findings with published results showed significant evidence for linkage (504 families) and association (940 families): p values, 0.0001 and 0.0014 at D2S2214, respectively, and 0.0008 and 0.0006 at D2S116, respectively. These findings suggest that variation in the CD28/CTLA4 gene region is a determinant of coeliac disease susceptibility. Dissecting the sequence variation underlying this relationship will depend on further analyses utilising denser sets of markers.
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Dokter, Adriaan M., et al.
(författare)
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Twilight ascents by common swifts, Apus apus, at dawn and dusk: acquisition of orientation cues?
- 2013
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Ingår i: Animal Behaviour. - : Elsevier BV. - 1095-8282 .- 0003-3472. ; 85:3, s. 545-552
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Tidskriftsartikel (refereegranskat)abstract
- Common swifts are specialist flyers spending most of their life aloft, including night-time periods when this species roosts on the wing. Nocturnal roosting is preceded by a vertical ascent in twilight conditions towards altitudes of up to 2.5 km, behaviour previously explained as flight altitude selection for sleeping. We examined the nocturnal flight behaviour of swifts, as uniquely identified by a Doppler weather radar in central Netherlands using continuous measurements during two consecutive breeding seasons. Common swifts performed twilight ascents not only at dusk but also at dawn, which casts new light on the purpose of these ascents. Dusk and dawn ascents were mirror images of each other when time-referenced to the moment of sunset and sunrise, suggesting that the acquisition of twilight-specific light-based cues plays an important role in the progression of the ascents. Ascent height was well explained by the altitude of the 280 K isotherm, and was not significantly related to wind, cloud base height, humidity or the presence of nocturnal insects. We hypothesize that swifts profile the state of the atmospheric boundary layer during twilight ascents and/or attempt to maximize their perceptual range for visual access to distant horizontal landmarks, including surrounding weather. We compare twilight profiling by swifts with vertical twilight movements observed in other taxa, proposed to be related to orientation and navigation. (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
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| 27. |
- Niazi Ardekani, Mehdi, 1990-, et al.
(författare)
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Turbulence modulation in channel flow of finite-size spheroidal particles
- 2018
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Ingår i: Journal of Fluid Mechanics. - : Cambridge University Press (CUP). - 0022-1120 .- 1469-7645. ; 859, s. 887-901
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Tidskriftsartikel (refereegranskat)abstract
- Finite-size particles modulate wall-bounded turbulence, leading, for the case of spherical particles, to increased drag also owing to the formation of a particle wall layer. Here, we study the effect of particle shape on the turbulence in suspensions of spheroidal particles at volume fraction phi = 10 % and show how the near-wall particle dynamics deeply changes with the particle aspect ratio and how this affects the global suspension behaviour. Direct numerical simulations are performed using a direct-forcing immersed boundary method to account for the dispersed phase, combined with a soft-sphere collision model and lubrication corrections for short-range particle-particle and particle-wall interactions. The turbulence reduces with the aspect ratio of oblate particles, leading to drag reduction with respect to the single-phase flow for particles with aspect ratio AR <= 1/3, when the significant reduction in Reynolds shear stress is more than the compensation by the additional stresses, induced by the solid phase. Oblate particles are found to avoid the region close to the wall, travelling parallel to it with small angular velocities, while preferentially sampling high-speed fluid in the wall region. Prolate particles also tend to orient parallel to the wall and avoid its vicinity. Their reluctance to rotate around the spanwise axis reduces the wall-normal velocity fluctuation of the flow and therefore the turbulence Reynolds stress, similar to oblates; however, they undergo rotations in wall-parallel planes which increase the additional solid stresses due to their relatively larger angular velocities compared to the oblates. These larger additional stresses compensate for the reduction in turbulence activity and lead to a wall drag similar to that of single-phase flows. Spheres on the other hand, form a layer close to the wall with large angular velocities in the spanwise direction, which increases the turbulence activity in addition to exerting the largest solid stresses on the suspension, in comparison to the other studied shapes. Spherical particles therefore increase the wall drag with respect to the single-phase flow.
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| 28. |
- Zade, Sagar, et al.
(författare)
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Experimental investigation of turbulent suspensions of spherical particles in a squareduct
- 2018
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Ingår i: Journal of Fluid Mechanics. - : CAMBRIDGE UNIV PRESS. - 0022-1120 .- 1469-7645. ; 857, s. 748-783
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Tidskriftsartikel (refereegranskat)abstract
- We report experimental observations of turbulent flow with spherical particles in a square duct. Three particle sizes, namely 2H/d(p) = 40, 16 and 9 (2H being the duct full height and d(p) being the particle diameter), are investigated. The particles are nearly neutrally buoyant with a density ratio of 1.0035 and 1.01 with respect to the suspending fluid. Refractive index matched-particle image velocimetry (RIM-PIV) is used for fluid velocity measurement even at the highest particle volume fraction (20 %) and particle tracking velocimetry (PTV) for the particle velocity statistics for the flows seeded with particles of the two largest sizes, whereas only pressure measurements are reported for the smallest particles. Settling effects are seen at the lowest bulk Reynolds number R-e2H approximate to 10 000, whereas, at the highest R-e2H approximate to 27 000, particles are in almost full suspension. The friction factor of the suspensions is found to be significantly larger than that of single-phase duct flow at the lower R-e2H investigated; however, the difference decreases when increasing the flow rate and the total drag approaches the values of the single-phase flow at the higher Reynolds number considered, R-e2H = 27 000. The pressure drop is found to decrease with the particle diameter for volume fractions lower than (sic) = 10% for nearly all R-e2H investigated. However, at the highest volume fraction (sic) = 20 %, we report a peculiar non-monotonic behaviour: the pressure drop first decreases and then increases with increasing particle size. The decrease of the turbulent drag with particle size at the lowest volume fractions is related to an attenuation of the turbulence. The drag increase for the two largest particle sizes at (sic) = 20 %, however, occurs despite this large reduction of the turbulent stresses, and it is therefore due to significant particle-induced stresses. At the lowest Reynolds number, the particles reside mostly in the bottom half of the duct, where the mean velocity significantly decreases; the flow is similar to that in a moving porous bed near the bottom wall and to turbulent duct flow with low particle concentration near the top wall.
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| 29. |
- Zbinden, Jan, 1994, et al.
(författare)
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A multi-dimensional framework for prosthetic embodiment: a perspective for translational research
- 2022
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Ingår i: Journal of NeuroEngineering and Rehabilitation. - : Springer Science and Business Media LLC. - 1743-0003. ; 19:1
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Forskningsöversikt (refereegranskat)abstract
- The concept of embodiment has gained widespread popularity within prosthetics research. Embodiment has been claimed to be an indicator of the efficacy of sensory feedback and control strategies. Moreover, it has even been claimed to be necessary for prosthesis acceptance, albeit unfoundedly. Despite the popularity of the term, an actual consensus on how prosthetic embodiment should be used in an experimental framework has yet to be reached. The lack of consensus is in part due to terminological ambiguity and the lack of an exact definition of prosthetic embodiment itself. In a review published parallel to this article, we summarized the definitions of embodiment used in prosthetics literature and concluded that treating prosthetic embodiment as a combination of ownership and agency allows for embodiment to be quantified, and thus useful in translational research. Here, we review the potential mechanisms that give rise to ownership and agency considering temporal, spatial, and anatomical constraints. We then use this to propose a multi-dimensional framework where prosthetic embodiment arises within a spectrum dependent on the integration of volition and multi-sensory information as demanded by the degree of interaction with the environment. This framework allows for the different experimental paradigms on sensory feedback and prosthetic control to be placed in a common perspective. By considering that embodiment lays along a spectrum tied to the interactions with the environment, one can conclude that the embodiment of prosthetic devices should be assessed while operating in environments as close to daily life as possible for it to become relevant.
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| 30. |
- Sundbom, Magnus, et al.
(författare)
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Substantial Decrease in Comorbidity 5 Years After Gastric Bypass: A Population-based Study From the Scandinavian Obesity Surgery Registry.
- 2017
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Ingår i: Annals of Surgery. - Philadelphia PA, USA : Lippincott Williams & Wilkins. - 0003-4932 .- 1528-1140. ; 265:6, s. 1166-1171
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To evaluate effect on comorbid disease and weight loss 5 years after Roux-en-Y gastric bypass (RYGB) surgery for morbid obesity in a large nationwide cohort. Background: The number patients having surgical procedures to treat obesity and obesity-related disease are increasing. Yet, population-based, long-term outcome studies are few. Methods: Data on 26,119 individuals [75.8% women, 41.0 years, and body mass index (BMI) 42.8 kg/m2] undergoing primary RYGB between May 1, 2007 and June 30, 2012, were collected from 2 Swedish quality registries: Scandinavian Obesity Surgery Registry and the Prescribed Drug Registry. Weight, remission of type 2 diabetes mellitus, hypertension, dyslipidemia, depression, and sleep apnea, and changes in corresponding laboratory data were studied. Five-year follow-up was 100% (9774 eligible individuals) for comorbid diseases. Results: BMI decreased from 42.8 ± 5.5 to 31.2 ± 5.5 kg/m2 at 5 years, corresponding to 27.7% reduction in total body weight. Prevalence of type 2 diabetes mellitus (15.5%–5.9%), hypertension (29.7%–19.5%), dyslipidemia (14.0%–6.8%), and sleep apnea (9.6%–2.6%) was reduced. Greater weight loss was a positive prognostic factor, whereas increasing age or BMI at baseline was a negative prognostic factor for remission. The use of antidepressants increased (24.1%–27.5%). Laboratory status was improved, for example, fasting glucose and glycated hemoglobin decreased from 6.1 to 5.4 mmol/mol and 41.8% to 37.7%, respectively. Conclusions: In this nationwide study, gastric bypass resulted in large improvements in obesity-related comorbid disease and sustained weight loss over a 5-year period. The increased use of antidepressants warrants further investigation. Studies with long-term results after bariatric surgery are surprisingly rare, 1–5 especially in the light of the large number of procedures performed worldwide. In most studies there is a 1 to 2-year follow-up, 6 and at such an early point in time, it is impossible to evaluate the true effect of gastric bypass, because patients have just reached their nadir in weight. Moreover, for this group of patients, the longstanding remission of obesity-related comorbidities, for example, diabetes mellitus, hypertension, dyslipidemia, and sleep apnea, are of utmost importance. The Scandinavian Obesity Surgery Registry (SOReg) was launched in 2007 as a quality registry for the expanding number of bariatric surgeries in Sweden. 7 In 2015, SOReg contained more than 50,000 bariatric procedures (>98% national coverage), with all 43 operating centers reporting to the registry. There has been an expansion of bariatric surgery, with 3300 bariatric procedures performed in 2008, 4800 in 2009, 7800 in 2010, and 8600 in 2011. There has been a slight decrease in procedures, and currently approximately 7000 performed annually, and approximately 95% of the reported procedures have been primary laparoscopic gastric bypass. 8 Perioperative complication rates (eg, 1.2% leaks) and mortality are low (0.04%), the latter validated with the Swedish Population Register. Regular audits are performed by randomly comparing data in SOReg with patient charts at the surgical centers, demonstrating a high validity with less than 2% incorrect values. 7 Furthermore, by cross-linkage with the national Prescribed Drug Registry (PDR), a 100% follow-up of the occurrence of comorbid disease (defined as medical treatment) can be achieved. The present study reports outcome in weight and obesity-related comorbid disease in a nationwide cohort of 26,119 individuals over 5 years after primary Roux-en-Y gastric bypass (RYGB) in Sweden, using the prospective SOReg database with cross-linkage with the PDR.
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