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| 2. |
- Huang, Lucy, et al.
(författare)
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Haplotype variation and genotype imputation in African populations
- 2011
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Ingår i: Genetic Epidemiology. - : Wiley. - 0741-0395 .- 1098-2272. ; 35:8, s. 766-780
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Tidskriftsartikel (refereegranskat)abstract
- Sub-Saharan Africa has been identified as the part of the world with the greatest human genetic diversity. This high level of diversity causes difficulties for genome-wide association (GWA) studies in African populationsfor example, by reducing the accuracy of genotype imputation in African populations compared to non-African populations. Here, we investigate haplotype variation and imputation in Africa, using 253 unrelated individuals from 15 Sub-Saharan African populations. We identify the populations that provide the greatest potential for serving as reference panels for imputing genotypes in the remaining groups. Considering reference panels comprising samples of recent African descent in Phase 3 of the HapMap Project, we identify mixtures of reference groups that produce the maximal imputation accuracy in each of the sampled populations. We find that optimal HapMap mixtures and maximal imputation accuracies identified in detailed tests of imputation procedures can instead be predicted by using simple summary statistics that measure relationships between the pattern of genetic variation in a target population and the patterns in potential reference panels. Our results provide an empirical basis for facilitating the selection of reference panels in GWA studies of diverse human populations, especially those of African ancestry.
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| 3. |
- Razouki, Sabah, et al.
(författare)
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Improving Fine Grained Gypsiferous Soil by Increased Compaction
- 2012
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Ingår i: The international journal of pavement engineering. - : Informa UK Limited. - 1029-8436 .- 1477-268X. ; 3:1, s. 32-38
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Tidskriftsartikel (refereegranskat)abstract
- Presented in this paper is a study of the effect of compactive effort (CE) and long-term soaking on the strength characteristics of a clayey gypsiferous subgrade soil. The tested soil is A-6 (6) soil according to American Association of State Highway and Transportation Officials (AASHTO) soil classification system. To study the effect of CE and long term soaking on the properties of the tested soil, various California bearing ratio soil samples were prepared and compacted at optimum moisture content of the modified AASHTO compaction, but using four different chosen CEs of 12, 25, 56 and 70 blows/layer and then soaked for 0, 4, 7, 15, 30 and 120 days. The California bearing ratio (CBR) tests indicate that the CBR increases significantly in a nonlinear manner with increasing CE for all soaking periods, indicating improvement in soil strength with increased compaction. The rate of increase dies out with increasing CE. The CBR tests reveal also that there is a serious drop in the CBR due to soaking for all CEs.
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| 5. |
- Razouki, Sabah, et al.
(författare)
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Strong Correlation between the Bearing Capacity and CBR of a Gypsiferous Subgrade Soil Subjected to Long-Term Soaking
- 2005
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Konferensbidrag (refereegranskat)abstract
- Presented in this paper is a correlation between the bearing capacity of a gypsiferous subgrade soil with the corresponding CBR value. The geotechnical tests carried out on this soil indicate that the soil is sandy lean clay of CL group according to the USCS and A-6 (6) group according to AASHTO Soil Classification System. The soil contains about 33% gypsum content. For this purpose, thirty six CBR samples were prepared at optimum moisture content (of the modified AASHTO compaction test) namely 11.5% at compactive efforts of 1, 2 and 4.56 times that of the Proctor compaction (standard AASHTO). These samples were soaked for 0, 4, 7, 15, 30, and 120 days under the effect of 40 lbs (178 N) surcharge load. For each soaking period, three pairs of CBR soil samples were prepared, one for each compactive effort. The first CBR sample from each pair was used to determine the CBR value while the second CBR sample was used to obtain triaxial soil samples for unconsolidated undrained tests to arrive at the corresponding shear strength parameters. The present paper reveals that for each soaking period, there is a linear increase of the ultimate bearing capacity with increasing compactive effort, while a significant drop in the ultimate bearing capacity of the tested soil took place with increasing soaking period. The paper reveals also that there is a strong linear correlation between the estimated ultimate bearing capacity and the corresponding CBR value indicating that the Rosenak's equation correlating the bearing capacity with CBR value is very conservative.
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| 6. |
- Razouki, Sabah, et al.
(författare)
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Using Gypsiferous Soil for Embankments in Hot Desert Areas
- 2008
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Ingår i: Proceedings of the Institution of Civil Engineers. - : Institution of Civil Engineers (ICE). - 1747-650X .- 1747-6518. ; 161:2, s. 63-71
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Tidskriftsartikel (refereegranskat)abstract
- A study of the strength characteristics of a fine-grained gypsiferous soil intended for use as a construction material for forming highway and airport embankments in desert areas is reported herein. The tested soil was a sandy lean clay (CL) according to the Unified Soil Classification System and an A-6 (6) soil according to American Association of State Highway and Transportation Officials (AASHTO) soil classification system, containing about 35% total soluble salts (TSS) of which 33% was gypsum. To study the properties of the tested soil, various California bearing ratio (CBR) soil samples were prepared at the dry optimum moisture content of 2% and soaked for 0, 4, 7, 15 and 30 days. The CBR tests revealed that there was a serious drop in the CBR due to soaking, which is in full agreement with the drop in c and f with soaking period, indicating that if gypsiferous soils are used as fill material they should be protected from ingress of water. To study the deformation properties of the tested soil, vertical swelling/settlement measurements were carried out on each CBR sample during soaking using a 0$002 mm dial gauge. The effect of soaking period on the distribution of moisture, TSS and gypsum content was also studied. It was observed that there was an increase in moisture content and a decrease in TSS and hence gypsum with increasing soaking for CBR samples compacted at the dry optimum moisture content.
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