Theoretical Exposition of A Single Electron Quantum Dot

This paper will review atomic-like phenomena in a semiconductor quantum dot which their size, shape and interactions can be precisely controlled through the use of nanofabrication technology. It has been shown that by confining electrons in three dimensions inside semiconductors, quantum dots can show many of the phenomena observed in atoms and nuclei and so called artificial atom. Because of its controlable system, it is possible to explore the correlation effects in regimes that cannot otherwise be accessed in other physical systems. For simplicity, this work will focus on a circular-shape single electron quantum dot trapped by polar two-dimensional harmonic potential in the presence of an external magnetic field. Both Zeeman splitting and spin orbit interaction are neglected in our calculation. The calculation show that Fock-Darwin spectrum will enter Landau regime, where when cyclotron frequency is much larger than potential confinement

Magnetic Nanostructures : Fabrication And Applications From Memory Devices To Biosensor

MAGNETIC NANOSTRUCTURES : FABRICATION AND APPLICATIONS FROM MEMORY DEVICES TO BIOSENSOR. For magnetic storage application, we successfully fabricated nanodots and nanopattern using electron-beam lithography (EBL) technique followed by ion irradiation. Perpendicularly magnetized squared-bits with the sizes of 100 to 500 nmwere clearly observed using magnetic forcemicroscopy (MFM) images. MFM images showed that the most of the patterned squared-bits with size of 100 nm have either uniformly bright or dark magnetic contrasts. Magnetization curves of patterned films were strongly influenced by the bit size and spacing between bits and indicated the existence of exchange coupling between the bits via irradiated spacing. On the other hand, for biosensor application, we recently develop Surface Plasmon Resonance (SPR)-based biosensor for biomolecules detection device.Magnetic nanoparticles such as magnetite (Fe3O4) and CoFe2O4 were purposed as candidate for active materials to increase accumulation of target biomolecules on sensing surface of SPR-based biosensor. Fe3O4 and CoFe2O4 nanoparticles with different sizes of 8 to 17 nm have been successfully synthesized chemically by co-precipitation method. The surface of nanoparticles had been modified using polyethylene glycol (PEG)-4000 to increase the crystallinity, decrease agglomeration and control the shape to more spherical. However, modification using PEG-4000 decreased the saturation magnetization which is due to the existence of α-FeO(OH) and γ-FeO(OH) phases from bonds at interface of CoFe2O4

Application of Pade Approximants to Determination of alpha_s(M_Z^2) from Hadronic Event Shape Observables in e+e- Annihilation

We have applied Pade approximants to perturbative QCD calculations of event shape observables in e+e- --> hadrons. We used the exact O(alpha_s^2) prediction and the [0/1] Pade approximant to estimate the O(alpha_s^3) term for 15 observables, and in each case determined alpha_s(M_Z^2) from comparison with hadronic Z^0 decay data from the SLD experiment. We found the scatter among the alpha_s(M_Z^2) values to be significantly reduced compared with the standard O(alpha_s^2) determination, implying that the Pade method provides at least a partial approximation of higher-order perturbative contributions to event shape observables.Comment: 15 pages, 1 EPS figure, Submitted to Physics Letters

Combine selection for earliness and yield in pedigree developed sorghum (sorghum bicolor l. Moench) progenies in eritrea

Thirteen progenies of sorghum (Sorghum bicolor L. Moench) crosses (Amal and ICSV 91078) that selected using pedigree breeding method, were evaluated along with their parental checks to obtain information on yield potential, earliness, genetic and morphological diversity. The genotypes were evaluated in randomized block design with three replications for three years (2007-2009) at Halhale research center. Significant mean squares were obtained for almost all characters in the individual analysis of variance as well as the combined analysis across seasons, suggesting that, these sorghum genotypes were highly variable for almost all the characters studied, therefore, would respond to selection. Mean values for the combined analysis of the progenies showed that Hal-1-1, Hal-4-9, Hal-13-33, Hal-11-30 and Hal-9-24 were promising cultivars in terms of grain yield and earliness. Combined analyses also showed most characters had relatively higher genotypic and phenotypic variance components and little difference between phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) indicating their variation has a genetic origin that can be exploited for further breeding programs. The genotypes also exhibited varying degrees of heritability estimates. Characters such as plant height, days to 50 % flowering and grain yield responded positively to selection because of high broad sense heritability estimates. High heritability and genetic advance was noted for plant height and days to 50% flowering indicating that these parameters were under additive gene effect and responded well for genetic improvement. However, grain weight showed high heritability with low genetic advance indicating that the trait has non additive gene action and might respond well due to its heterosis

Marker-assisted introgression improves Striga resistance in an Eritrean Farmer-Preferred Sorghum Variety

The parasitic weed Striga hermonthica hampers the production of sorghum, the most important cereal crop in Eritrea. This weed has a complex mode of infestation that adapts to many hosts and environments, complicating conventional breeding for resistance, which is the only form of crop improvement available to Eritrean breeders, but has failed. This study aimed at improving resistance against this parasite by transferring 5 Striga resistant Quantitative Trait Loci (QTLs) from resistance donor N13 to Striga susceptible Farmer-Preferred Sorghum Variety (FPSV) Hugurtay from Eritrea. The method involved backcrossing using marker-assisted selection (MAS) and evaluation of the best introgressed lines for Striga resistance in artificially infested fields. Foreground selection was performed with up to 11 polymorphic simple sequence repeat (SSR) markers linked to Striga resistance QTLs, while background selection was conducted in the BC3F2 generation with 27 polymorphic unlinked SSR markers to identify the best recovery of the recurrent parent (RP) genetic background. Out of 84 BC3F3 lines, L2P3-B, L1P5-A and L2P5P35 performed best with respect to both grain yield and reduced Striga infestation. These lines were more resistant to Striga than Hugurtay, but less resistant than N13. The three lines yielded twice as much as N13, with Area Under Striga Number Progression Curve (AUSNPC) values on average 18% higher than that of N13 and 38% lower than that of Hugurtay. This suggests that the introgressed QTLs conferred significant Striga resistance and yield advantage to these BC3F3 backcross progenies under Striga pressure. These lines have good potential for future release and demonstrate that when MAS is available to conventional breeders, even in countries with no genotyping facilities, it is a useful tool for enhancement, expediency and precision in crop improvement

Sorghum diseases in Eritrea - a survey report

Sorghum (Sorghum bicolor) is one of the main food crops of Eritrea. A total of 35 fields at 15 lowland locations and 13 fields at 8 highland locations planted with a variety of cultivars were surveyed in 2001 for sorghum diseases, based on the percentage of diseased plants in 5 subplots. In highland areas, covered kernel smut (Sporisorium sorghi [Sphacelotheca sorghi]) was predominant followed by head smut (Sporisorium reilianum [Sphacelotheca reiliana]) and about 10% incidence of Striga hermonthica. In lowland areas, leaf blight (Exserohilum turcicum [Setosphaeria turcica]), anthracnose (Colletotrichum graminicola [Glomerella graminicola]), zonate leaf spot (Gloeocercospora sorghi), loose kernel smut (Sporisorium cruentum) and covered kernel smut were important. Striga had between 2-100% incidence and was more prevalent in the drier lowlands. For all diseases, different cultivars exhibited different susceptibilities, and full results are tabulated

MAGNETIC NANOSTRUCTURES : FABRICATION AND APPLICATIONS FROM MEMORY DEVICES TO BIOSENSOR

MAGNETIC NANOSTRUCTURES : FABRICATION AND APPLICATIONS FROM MEMORY DEVICES TO BIOSENSOR. For magnetic storage application, we successfully fabricated nanodots and nanopattern using electron-beam lithography (EBL) technique followed by ion irradiation. Perpendicularly magnetized squared-bits with the sizes of 100 to 500 nmwere clearly observed using magnetic forcemicroscopy (MFM) images. MFM images showed that the most of the patterned squared-bits with size of 100 nm have either uniformly bright or dark magnetic contrasts. Magnetization curves of patterned films were strongly influenced by the bit size and spacing between bits and indicated the existence of exchange coupling between the bits via irradiated spacing. On the other hand, for biosensor application, we recently develop Surface Plasmon Resonance (SPR)-based biosensor for biomolecules detection device.Magnetic nanoparticles such as magnetite (Fe3O4) and CoFe2O4 were purposed as candidate for active materials to increase accumulation of target biomolecules on sensing surface of SPR-based biosensor. Fe3O4 and CoFe2O4 nanoparticles with different sizes of 8 to 17 nm have been successfully synthesized chemically by co-precipitation method. The surface of nanoparticles had been modified using polyethylene glycol (PEG)-4000 to increase the crystallinity, decrease agglomeration and control the shape to more spherical. However, modification using PEG-4000 decreased the saturation magnetization which is due to the existence of α-FeO(OH) and γ-FeO(OH) phases from bonds at interface of CoFe2O4

Water productivity improvement of cereals and foods legumes in the Atbara Basin of Eritrea

The project ‘Water Productivity Improvement of Cereals and Food Legumes in the Atbara Basin of Eritrea’ is an example of organization and implementation of farmers’ participatory research, conducted utilizing the available indigenous knowledge while empowering farming communities. Farmers have been partners in technology development with extension and research, with full decision-making power in planning, implementation, monitoring, and evaluation. The project produced, in partnership with farmers, new varieties of cereals and food legumes which have proven farmer acceptability; established seed systems which supply farmers with quality seed in a sustainable manner; enhanced farmers’ skills in participatory research and in community based seed production; strengthened the capacity of National Institutions to carry out participatory research and technology transfer, and strengthened linkages between research, seed, and extension departments by working together in cooperation with farmers and farmers’ communities. Working conditions, during the course of the project were not always easy and became challenging towards the end of the project, but to work with farmers and learn from them has been an extremely rewarding experience