https://repository.seku.ac.ke/handle/123456789/19 2026-04-08T19:08:05Z 2026-04-08T19:08:05Z Hong, Wei Mo, Liantong Pan, Changluan Riara, Martin M. Wei, Mi Zhang, Jizhe https://repository.seku.ac.ke/handle/123456789/8335 2026-04-08T08:53:59Z 2020-01-20T00:00:00Z

Investigation of rejuvenation and modification of aged asphalt binders by using aromatic oil-SBS polymer blend Hong, Wei; Mo, Liantong; Pan, Changluan; Riara, Martin M.; Wei, Mi; Zhang, Jizhe In this paper, long-term aged base asphalt and SBS modified asphalt binders were rejuvenated and modified simultaneously using a compound rejuvenator containing 77% aromatic oil and 23% SBS polymer. Aromatic oil was used for rejuvenation purpose due to its softening effect while SBS polymer was used for modification purpose because of its potential to form a polymer network. Conventional bitumen tests, dynamic shear rheological (DSR) test and bending beam rheological (BBR) test were conducted to evaluate the rejuvenation and modification effects. Test results indicated that use of the compound rejuvenator enhanced the softening point and ductility for both aged base asphalt and SBS modified asphalt binders. The polymer modification effect of compound rejuvenator was well distinguished by the plateau region of phase angle master curves. Aromatic oil had a strong softening effect on aged asphalt binder which improved the performance at low temperatures, but weakened the performance at high temperatures. The incorporation of SBS polymer was a good supplement to balance the overall performance of rejuvenated asphalt binders. The compound rejuvenator can be greatly effective for hot recycling of reclaimed asphalt mixture by means of the simultaneous rejuvenation and modification. https://doi.org/10.1016/j.conbuildmat.2019.117154

2020-01-20T00:00:00Z Sila, Faith Mbaluka, Benjamin Riara, Martin M. Katumo, Ngei https://repository.seku.ac.ke/handle/123456789/8328 2026-04-02T06:59:02Z 2026-03-23T00:00:00Z

Localized surface plasmon resonance and damping mechanisms in transition metals Sila, Faith; Mbaluka, Benjamin; Riara, Martin M.; Katumo, Ngei This work reports the calculated dependence of the localized surface plasmon resonance (LSPR) parameters and damping mechanism on nanoparticle size of unconventional transition metals, including zinc, silver, rhodium, rhenium, molybdenum, tantalum, titanium, and scandium, within the size range of 10 to 400 nm. The study applies Mie theory to determine the peak energies, amplitude, and full width at half maximum (FWHM) of LSPR as a function of size, shape, and material type. We have found that the parameters of LSPR depend on electron structure and damping mechanisms. LSPR amplitude decreased systematically for individual nanoparticles (NPs) for sizes 10…200 nm, after which, a similar trend was exhibited due to radiative damping. Au, Sc and Ag are the only metal NPs that exhibited a significant FWHM of LSPR at sizes approximately below 40 nm. For all investigated transition metal NPs, smaller NPs exhibited higher absorption and lower scattering, while larger NPs showed narrower FWHM and red-shifted LSPR peaks due to retardation effects and multipolar plasmon excitations. The analysis highlights that some transition metal NPs exhibit optical characteristics similar to those of gold, silver, and copper, making them a good alternative for the mentioned ones at specific NP sizes. DOI: https://doi.org/10.15407/spqeo29.01.051

2026-03-23T00:00:00Z Wambulwa, Moses C. Fan, Peng-Zhen Milne, Richard Wu, Zeng-Yuan Luo, Ya-Huang Wang, Yue-Hua Gao, Lian-Ming Xiahou, Zuo-Ying Jin, Ye-Chuan Ye, Lin-Jiang Xu, Zu-Chang Yang, Zhi-Chun Li, De-Zhu Liu, Jie https://repository.seku.ac.ke/handle/123456789/8326 2026-04-01T07:52:16Z 2022-11-01T00:00:00Z

Genetic analysis of walnut cultivars from southwest China: Implications for germplasm improvement Wambulwa, Moses C.; Fan, Peng-Zhen; Milne, Richard; Wu, Zeng-Yuan; Luo, Ya-Huang; Wang, Yue-Hua; Gao, Lian-Ming; Xiahou, Zuo-Ying; Jin, Ye-Chuan; Ye, Lin-Jiang; Xu, Zu-Chang; Yang, Zhi-Chun; Li, De-Zhu; Liu, Jie Walnuts are highly valued for their rich nutritional profile and wide medicinal applications. This demand has led to the intensification of breeding activities in major walnut production areas such as southwest China, in order to develop more superior cultivars. With the increasing number of cultivars, accurate identification becomes fundamental to selecting the right cultivar for grafting, industrial processing or development of new cultivars. To ensure proper identification of cultivars and understand the genetic structure of wild and cultivated material, we genotyped 362 cultivated and wild individuals of walnut trees from southwest China (with two additional populations from Xinjiang, plus three cultivars from Canada, France and Belgium) using 36 polymorphic microsatellite loci. We found relatively low indices of genetic diversity (HO = 0.570, HE = 0.404, NA = 2.345) as well as a high level of clonality (>85% of cultivars), indicating reliance on genetically narrow sources of parental material for breeding. Our STRUCTURE and PCoA analyses generally delineated the two species, though considerable levels of introgression were also evident. More significantly, we detected a distinct genetic group of cultivated Juglans sigillata, which mainly comprised individuals of the popular ‘Yangbidapao’ landrace. Finally, a core set of 18 SSR loci was selected, which was capable of identifying 32 cultivars. In a nutshell, our results call for more utilization of genetically disparate material, including wild walnut trees, as parental sources to breed for more cultivars. The data reported herein will significantly contribute towards the genetic improvement and conservation of the walnut germplasm in southwest China. https://doi.org/10.1016/j.pld.2021.08.005

2022-11-01T00:00:00Z Liu, Jie Milne, Richard I. Zhu, Guang-Fu Spicer, Robert A. Wambulwa, Moses C. Wu, Zeng-Yuan Boufford, David E. Luo, Ya-Huang Provan, Jim Yi, Ting-Shuang Cai, Jie Wang, Hong Gao, Lian-Ming Li, De-Zhu https://repository.seku.ac.ke/handle/123456789/8324 2026-03-31T09:39:59Z 2022-08-01T00:00:00Z

Name and scale matter: Clarifying the geography of Tibetan Plateau and adjacent mountain regions Liu, Jie; Milne, Richard I.; Zhu, Guang-Fu; Spicer, Robert A.; Wambulwa, Moses C.; Wu, Zeng-Yuan; Boufford, David E.; Luo, Ya-Huang; Provan, Jim; Yi, Ting-Shuang; Cai, Jie; Wang, Hong; Gao, Lian-Ming; Li, De-Zhu Geographical names and the entities they represent act as a fundamental cornerstone across numerous disciplines. However, inconsistent geographical names and arbitrarily defined regional geographical scales are common, hindering cross-disciplinary communication and synthesis. The Pan-Tibetan Highlands, comprising the Tibetan Plateau, Himalaya, Hengduan Mountains and Mountains of Central Asia, is a case in point. To rectify these inconsistencies of terminology, we employed a multi-disciplinary approach to standardize the nomenclature of the Tibetan Plateau and the three adjacent mountain regions, defining their spatial extent using historical and contemporary perspectives. A literature meta-analysis indicated that ‘Tibetan Plateau’, ‘Himalaya’ and ‘Hengduan Mountains’ are the most suitable names for these regions in terms of both priority (earliest use) and popularity, whereas ‘Mountains of Central Asia’ emerges as appropriate for the mountain chains to the west of the Tibetan Plateau. The new term ‘Pan-Tibetan Highlands’ is proposed to replace the less precise and arguably misleading ‘High Mountain Asia’ for these regions collectively. Additionally, new geographical boundaries, applicable back through time, are proposed for each region, based on geological and geomorphological features. Using these new boundaries, the Pan-Tibetan Highlands area is 3.95 × 106 km2 with a mean elevation of 3824 m, while the Tibetan Plateau is smaller (1.82 × 106 km2) and higher (4465 m) than commonly assumed. Across the Pan-Tibetan Highlands, the proportion of protected areas is far below the proposed 30% anticipated in the post-2020 Global Biodiversity Framework target with only a few exceptions. Additionally, the Hengduan Mountains showed the highest vascular plant species richness and endemism, followed by Himalaya, Mountains of Central Asia and the Tibetan Plateau. The obvious conservation gap in the Pan-Tibetan Highlands calls for urgent researchbased optimization of conservation networks. Our approach benefits quantitative spatial analysis by providing well-defined geographical scales for various fields, aiding cross-disciplinary comparisons and synthesis.; Geographical names and the entities they represent act as a fundamental cornerstone across numerous disciplines. However, inconsistent geographical names and arbitrarily defined regional geographical scales are common, hindering cross-disciplinary communication and synthesis. The Pan-Tibetan Highlands, comprising the Tibetan Plateau, Himalaya, Hengduan Mountains and Mountains of Central Asia, is a case in point. To rectify these inconsistencies of terminology, we employed a multi-disciplinary approach to standardize the nomenclature of the Tibetan Plateau and the three adjacent mountain regions, defining their spatial extent using historical and contemporary perspectives. A literature meta-analysis indicated that ‘Tibetan Plateau’, ‘Himalaya’ and ‘Hengduan Mountains’ are the most suitable names for these regions in terms of both priority (earliest use) and popularity, whereas ‘Mountains of Central Asia’ emerges as appropriate for the mountain chains to the west of the Tibetan Plateau. The new term ‘Pan-Tibetan Highlands’ is proposed to replace the less precise and arguably misleading ‘High Mountain Asia’ for these regions collectively. Additionally, new geographical boundaries, applicable back through time, are proposed for each region, based on geological and geomorphological features. Using these new boundaries, the Pan-Tibetan Highlands area is 3.95 × 106 km2 with a mean elevation of 3824 m, while the Tibetan Plateau is smaller (1.82 × 106 km2) and higher (4465 m) than commonly assumed. Across the Pan-Tibetan Highlands, the proportion of protected areas is far below the proposed 30% anticipated in the post-2020 Global Biodiversity Framework target with only a few exceptions. Additionally, the Hengduan Mountains showed the highest vascular plant species richness and endemism, followed by Himalaya, Mountains of Central Asia and the Tibetan Plateau. The obvious conservation gap in the Pan-Tibetan Highlands calls for urgent researchbased optimization of conservation networks. Our approach benefits quantitative spatial analysis by providing well-defined geographical scales for various fields, aiding cross-disciplinary comparisons and synthesis. https://doi.org/10.1016/j.gloplacha.2022.103893; https://doi.org/10.1016/j.gloplacha.2022.103893

2022-08-01T00:00:00Z