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Determ.nants and rates of land degradation： Application of stationary tim.-series m.del to data from.a sem.-arid environm.nt in Kenya

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Journal of Arid Land 2018年第1期10卷 1-11页

作者： kevin z m.anga dickson m.nyariki nashon k r m.sim.a dorothy a am.ata departm.nt of range and wildlife sciences south eastern kenya university170-90200 KituiKenya departm.nt of agricultural econom.cs and agribusiness south eastern kenya university170-90200 KituiKenya school of business and econom.cs murangáuniversity of technology75-10200 MurangaKenya

The causes of land degradation in the African drylands have been shown to vary. Som. researchers consider clim.te to be the m.jor contributor to degradation, with anthropogenic factors playing a m.nor role. Others reverse the significance of these two factors. A third group attributes land degradation to clim.te and anthropogenic factors equally. This study was undertaken to establish the factors influencing land degradation in a sem.-arid environm.nt in southeastern Kenya and the rate of change in vegetation types for a period of 35 years （1973-2007）. The reduction in grassland cover was used as an indicator of land degradation. Causes of land degradation were determ.ned by a m.ltiple regression analysis. A log-linear regression analysis was used to establish the rate of vegetation change. The m.ltiple and log-linear regression analyses showed：（1） woody vegetation, livestock population and cultivated area to be the m.in contributors of reduction in grassland cover in the area, and （2） an increase in undesirable woody species, livestock population and cultivated area had a significant （P〈0.05） negative effect on grassland vegetation. Increased hum.n population, low am.unts of rainfall and drought showed no significant negative effect on grassland vegetation cover. In conclusion, hum.n and livestock population growth and increased agricultural land have contributed to intensive crop cultivation and overgrazing in the sem.-arid lands. This overuse of the sem.-arid rangelands has worsened the deterioration of the natural grassland vegetation.

关键词： regression analysis land degradation grassland cover sem.-arid Kenya Sub-Saharan Africa

The Influence of Advanced Paternal Age on Sperm.Chrom.tin Integrity and Early Em.ryo m.rphological Developm.nt during ICSI

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Advances in Reproductive Sciences 2018年第2期6卷 35-49页

作者： m.wusi dickson David m. Adedia Daniel A. Abaye School of Basic and Biom.dical Sciences University of Health and Allied Sciences Ho Ghana

The study determ.ned the im.act of advanced m.le ageing (≥50 years) on sperm.chrom.tin integrity and early em.ryo m.rphological developm.nt in intra-cytoplasm.c sperm.injection (ICSI) technique cycles. Six hundred subfertile m.n were age-grouped;X1 (50 to 59 years), X2 (60 to 69), and X3 (≥70), were com.ared with 600 fertile m.les of known fertility (Y, age 25 - 35 years). Oocytes from.254 wom.n, aged ≤ 30 years, were included. Sperm.were analyzed using acridine orange fluorescence test (AOT) and categorized: “low”, “inter-m.diate” and “high” dam.ge. After ICSI, em.ryos were evaluated and categorized as “good”, “fair” or “poor” quality. Em.ryonic m.rphological developm.nt was assessed at three stages: fertilization, early and late paternal effect. The AOT results were: X1: low = 29, interm.diate = 53 and high = 118;X2: low = 11, interm.diate = 42 and high = 147;X3: low = 8, interm.diate = 24 and high = 168;Y: Low = 486, interm.diate = 71 and high = 43. The fertilization rate was: X1, 329/350 (93.7%);X2, 298/350 (85.1%);X3, 225/350 (64.1%) and, Y, 350/350 (100%). Associations between increasing age and sperm.chrom.tin dam.ge (χ2 (723.249, 6) p m.rphologically poor quality em.ryos over the five days after fertilization. m.le age ≥ 50 years, is highly associated with abnorm.l sperm.chrom.tin organization, an inability to adequately fertilize with ICSI m.thodology, an increase in the num.er of poor quality em.ryos and, a corresponding decrease in the num.er of good quality em.ryos five days after fertilization.

关键词： ICSI Sperm Chrom.tin Integrity m.le Age ≥ 50 AOT Early Em.ryo Developm.nt

Assessing Water Availability and Unm.t Water Dem.nd Using the WEAP m.del in the Sem.-Arid Bweengwa, Kasaka and m.goye Sub-Catchm.nts of Southern Zam.ia

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Journal of Environm.ntal Protection 2021年第4期12卷 280-295页

作者： Tewodros m. Tena Alick Nguvulu dickson m.elwa Phenny m.aanga Departm.nt of Environm.ntal Engineering Copperbelt University Kitwe Zambia Departm.nt of Geom.tics Engineering Copperbelt University Kitwe Zambia Business and Inform.tion Technology Departm.nt Cavendish University Lusaka Zambia

Located in the sem.-arid zone of Zam.ia, the m.tam.-Bweengwa, Kasaka and m.goye sub-catchm.nts have witnessed a high dem.nd for water due to increase in population and socio-econom.c activities putting m.re pressure on water resources. This study assesses the hydrological com.onents and ascertains the available water resources and unm.t dem.nd in the sub-catchm.nts using the Water Evaluation And Planning (WEAP) m.del and hydrom.teorological data collected between 1951 and 2018. The m.del was calibrated and validated on 1971-1981 and 2008-2018 data respectively. The results reveal that the sub-catchm.nts have transitioned from.positive to negative water balance with -164.295 m.3/year for m.tam.-Bweengwa, -19.021 m.3/year for Kasaka and -86.368 m.3/year for m.goye. Evaporation was 1815.259 m.3/year for m.tam.-Bweengwa, 1162.655 m.3/year for Kasaka and 1505.664 m.3/year for m.goye. The dem.nd for water has been increasing over tim. for various purposes such as irrigation, dom.stic, urban/rural water supply and livestock. The overall water storage in the sub-catchm.nts showed a negative water balance for the year 2018. The observed and sim.lated peak stream.low were 8.16 m.sup>3/s and 7.7 m.sup>3/s occurring during the m.nth of January and February respectively. The WEAP m.del perform.nce achieved R2 of 0.98 during calibration and 0.95 for validation, and an NSE of 0.83 for calibration and 0.85 during validation. The values of objective functions show that the hydrology of the m.tam.-Bweengwa, Kasaka and m.goye sub-catchm.nts as predicted by the WEAP m.del provides satisfactory confidence for prediction of future stream.low and hence projection based on future scenarios.

关键词： Water Availability Water Use WEAP m.del River Catchm.nt Stream.low Sem.-Arid Catchm.nt Hydrology

Tum.ur induced osteom.lacia due to a sinonasal hem.ngiopericytom.:A case report

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World Journal of Clinical Cases 2013年第1期1卷 59-63页

作者： Sophie A Jam.l Brendan C dickson Ina Radziunas Division of Endocrinology Department of Medicine University of Toronto Toronto ON M5G 1N8 Canada Departm.nt of Pathology Mount Sinai Hospital Toronto ON M5G 1X5 Canada m.ltidisciplinary Osteoporosis Program Women’s College Hospital Toronto ON M5S 1B1 Canada

Tum.ur induced osteom.lacia(TIO) is a rare and often unrecognized cause of hypophosphatem.a. We report on a case of TIO due to a hem.ngiopericytom. originating from.the left nasal sinus. The patient was a 55-year-old m.le with a 3-year history of left hip pain and an undisplaced left hip fracture. Biochem.cal testing dem.nstrated low levels of serum.phosphate and serum.1,25-dihydroxyvitam.n D, and an elevated level of fibroblast growth factor 23. Octreotide scanning dem.nstrated uptake in the left nasal sinus area and a com.uted tom.graphy scan revealed a left nasal sinus m.ss. The patient underwent surgical resection of the m.ss and histology was consistent with a sinonasal hem.ngiopericytom.. His serum.phosphate levels norm.lized alm.st im.ediately after surgery and he had com.lete resolution of hip pain. Our case highlights the im.ortance of considering TIO when assessing patients with low serum.phosphate.

关键词： Phosphate Osteom.lacia Tum.ur Fibroblast growth factor 23

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Open Journal of Applied Sciences 2013年第8期3卷 441-448页

作者： Violet m. Ndeda dickson O. Owiti Ben O. Aketch David m. Onyango Departm.nt of Zoology Maseno University

Diplostom.m.species m.tacercariae are trem.tode parasites that pose serious econom.c threats to aquaculture practice globally. Identification of Diplostom.m.at m.tacercariae stage has rem.ined equivocal, hence lack of elucidation of the actual role of these species in fish population. 21 Diplostom.id m.tacercariae obtained from.eyes of Nile tilapia were characterized using 18S and ITS rDNA (ITS1-5.8S-ITS2) genes. Phylogenetic analyses of ITS rDNA gene dataset in the m.tacercariae revealed close relationship to Diplostom.m.m.shonense and D. baeri. m.lecular identification using 18S rDNA sequences revealed close relationship to D. com.actum. D. phoxini and D. spathaceum. Overall, genetic analyses in this study depicted a significant unrecognized genetic diversity am.ng Diplostom.m.species. Successful differentiation of Diplostom.m.genera in this study using ribosom.l m.rkers suggested that 18S and ITS rDNA genes are effective genetic m.rkers for inter-species phylogenetic analysis and should be em.loyed in future for identification of diplostom.idea.

关键词： Diplostom.m 18S rDNA Internal Transcribed Spacer Region

Seed Borne Fungal Organism. Associated with Germ.nation Success of Term.nalia brownii (Fresen) in Kenya

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Open Journal of Forestry 2021年第4期11卷 341-351页

作者： Jackline Atieno Gilbert O. Obwoyere dickson L. m.kanji m.chael m. Okeyo Egerton University Njoro Kenya Dryland Eco-Region Research Program.e Kibwezi Kenya

Term.nalia brownii is an indigenous tree species highly valued in the Kenyan drylands for its products such as tim.er for wood curving, m.dicine, and charcoal production, am.ng others. Due to this high value followed ... 详细信息

Term.nalia brownii is an indigenous tree species highly valued in the Kenyan drylands for its products such as timber for wood curving, medicine, and charcoal production, among others. Due to this high value followed by overutilization, its population in the drylands is dwindling. Concern about the species’ low regeneration as shown by low germination has been raised. This research was conducted on the seed borne fungal organisms that are associating with the germination of this species. T. brownii seeds were collected from cluster patches of the species in Kendu Bay, Kimose and Ndumoni in Homabay, Baringo and Kitui counties of Kenya respectively. The seeds were harvested for fruit probing for maturity confirmation. Random sampling was used in selecting thirty trees, 50 meters apart, from which fresh fruits were uniformly collected from the crowns. The research adopted a complete block experimental design where one hundred seeds each from the three sites, were subjected to a germination test, seed borne fungal organisms’ presence, identified organisms cultured and DNA and DNA sequencing carried out for identification. Fungal organisms associated with germination success of T. brownii were Fusariumm.ly:Verdana

关键词： Seed Borne Fungal Organism. Germ.nation Success Term.nalia brownii

Parallelized volum.tric fluorescence m.croscopy with a reconfigurable coded incoherent light-sheet array

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Light(Science & Applications) 2020年第1期9卷 1914-1924页

作者： Yu-Xuan Ren Jianglai Wu Queenie T.K.Lai Hei m.ng Lai dickson m.D.Siu Wutian Wu Kenneth K.Y.Wong Kevin K.Tsia Departm.nt of Electrical and Electronic Engineering The University of Hong KongPokfulam RoadHong KongSAR 999077China Departm.nt of Physics University of CaliforniaBerkeleyCA 94720USA School of Biom.dical Sciences Li Ka Shing Faculty of MedicineThe University of Hong KongHong KongSAR 999077China Departm.nt of Psychiatry Faculty of MedicineThe Chinese University of Hong KongHong KongSAR 999077China GHm.Institute of CNS Regeneration Jinan University601 Huangpu Avenue WestGuangzhou 510632China Re-Stem.Biotechnology Suzhou 215007China

Parallelized fluorescence im.ging has been a long-standing pursuit that can address the unm.t need for a com.rehensive three-dim.nsional(3D)visualization of dynam.cal biological processes with m.nim.l ***,the available approaches are lim.ted to incom.lete parallelization in only two dim.nsions or sparse sam.ling in three *** hereby develop a novel fluorescence im.ging approach,called coded light-sheet array m.croscopy(CLAm.,which allows com.lete parallelized 3D im.ging without m.chanical *** the concept of an“infinity m.rror”,CLAm.generates a light-sheet array with controllable sheet density and degree of ***,CLAm.circum.ents the com.on com.lications of m.ltiple coherent light-sheet generation in term. of dedicated wavefront engineering and m.chanical dithering/***,the encoding of m.ltiplexed optical sections in CLAm.allows the synchronous capture of all sectioned im.ges within the im.ged *** dem.nstrate the utility of CLAm.in different im.ging scenarios,including a light-scattering m.dium.an optically cleared tissue,and m.croparticles in fluidic *** can m.xim.ze the signal-to-noise ratio and the spatial duty cycle,and also provides a further reduction in photobleaching com.ared to the m.jor scanning-based 3D im.ging *** flexible im.lem.ntation of CLAm.regarding both hardware and software ensures com.atibility with any light-sheet im.ging m.dality and could thus be instrum.ntal in a m.ltitude of areas in biological research.

关键词： scattering light m.rror

Reduction of Internal Standard Signals in Quantitative m.LDI-TOF m.ss Spectrom.try

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Journal of Analytical Sciences, m.thods and Instrum.ntation 2012年第3期2卷 120-125页

作者： Walter B. Wilson dickson m. wam.ua Norm.n H. L. Chiu Departm.nt of Chem.stry and Biochem.stry University of North Carolina at Greensboro Greensboro USA Departm.nt of Chem.stry and Biochem.stry University of North Carolina at Greensboro Greensboro USA 2Departm.nt of Nanoscience Joint School of Nanoscience and Nanoengineering Greensboro USA. Departm.nt of Nanoscience Joint School of Nanoscience and Nanoengineering Greensboro USA.

The advantages of com.ining qualitative and quantitative analysis on a single analytical technique have further extended the applications of m.trix-assisted laser desorption/ionization tim.-of-flight m.ss spectrom.try (m.LDI-TOF m.) to the quantitation of various biom.lecules. To achieve absolute quantitation, it is necessary to perform.a calibration with standard dilutions. For the purpose of m.asuring DNA sam.les, a pure DNA oligonucleotide at different concentrations was chosen as a standard to perform.the calibration of m.LDI-TOF m.. In order to overcom. the variation of signal intensity from.repeated m.asurem.nts of each DNA standard dilution, fixed am.unt of an internal standard was added into each DNA standard dilution. Instead of m.intaining at a constant level, the signals of fixed am.unt of internal standard were decreased 73% from.its initial level while the signals of DNA standard continued to increase within a linear dynam.c range for quantitation from.0.20 μm.to 12.5 μm.of DNA. Attem.ts to identify the cause of signal reduction were system.tically carried out. This is the first report on the extent of signal reduction in quantitative m.LDI-TOF m.. These results represent a lim.tation on using m.LDI-TOF m. to m.nitor the changes in concentration of two different com.ounds within a chem.cal or biological system.

关键词： m.LDI m.ss Spectrom.try Quantitation

Preparation and Alkylation of Carbon Nanofibers from.Polym.thyl m.thacrylate

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Journal of m.terials Science and Chem.cal Engineering 2024年第9期12卷 55-68页

作者： Stephen m.khebi Situm. Geoffrey Otieno Austin O. Aluoch dickson m. Andala Jam.s Owour School of Chem.stry and m.terial Science Technical University of Kenya Haile Selassie Avenue Nairobi Kenya Chem.stry Departm.nt Multi-Media University Nairobi Kenya

Carbon nanofibers have revolutionized nanotechnology due to their potential applications in em.rging frontiers of research and industrial sectors. This can be attributed to their superior properties such as higher m.chanical strength, unique surface characteristics, and im.roved adherence that is transm.tted into the polym.r m.trix to form.a nanocom.osite with im.roved properties. Polym.thyl m.thacrylate is a com.on carbon source for the synthesis of carbon nanofibres of its high m.chanical strength, therm.l stability, and low m.isture and water absorbing capacity that allows its products to have several applications. In this work, we report the successful electrospinning of carbon nanofibres from.Poly m.thyl m.thacrylate and functionalizing the resulting carbon nanofibres. The functionalized carbon nanofibres were analyzed to determ.ne their solubility/dispersion in selected organic solvents, then characterized using Fourier transform.infra-red spectroscopy, Ram.n spectroscopy, scanning electron m.croscopy com.ined with Energy dispersive spectroscopy and Therm.lgravim.tric analysis.

关键词： Polym.thyl m.thacrylate Electrospinning Carbon Nanofibres Alkylation