by Lo-shing Wun. / Bibliography: leaves 69-71 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1986

by Wing-Lit Wong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1989. / Bibliography: leaves 82-84.

Drought and low soil nitrogen are major factors limiting maize production in Sub-Saharan Africa. Genotypic and phenotypic characterization of maize testcross hybrids developed from four biparental populations: CML441 x CML444, CML440 x COMPE, CML444 x K64R and CML312 x NAW was conducted. The objectives were (a) to evaluate the performance of F2:3 line testcrosses across stressed and non-stress conditions, (b) to estimate heritabilities for grain yield and secondary traits, (c) to assess the relationship between testing environments, (d) to estimate genetic correlations among relevant traits, (e) to estimate direct and indirect genetic gain from selection, and (e) to have a preliminary assessment of the efficiency of marker-assisted selection. Studies were conducted under no nitrogen fertilization, low nitrogen, drought, well- watered and high nitrogen in Malawi and Zimbabwe. About 100 entries from each population were tested using an alpha lattice design with two replications at all locations. Traits measured were grain yield, plant height, anthesis date, anthesis-silking interval, ears per plant, grain moisture at harvest and leaf senescence. Highest grain yield across environments was obtained from population CML444 x K64R (3.82 Mg ha-1) and the lowest from CML440 x COMPE (3.64 Mg ha-1). Testcrosses from CML441 x CML444 and CML444 x K64R had higher heritability estimates compared to CML440 x COMPE and CML312 x NAW. Drought and high nitrogen environments had higher heritability estimates than low nitrogen and well-watered conditions. Drought and well-watered environments discriminated testcrosses in a similar manner as well as high and low nitrogen environments. All populations had negative correlations between grain yield and anthesis silking interval, while positive correlations were observed between grain yield and ears per plant. No consistent differences were observed between overall means of best and worst marker based selected line testcrosses across populations and environments. Highest direct expected genetic gains were observed from high nitrogen environments. Direct selection under specific environments (e.g. drought ) was estimated to be more beneficial than indirect selection in other environments.

Correlated many-particle dynamics in Coulombic systems is one of today‟s grand challenges in physics. In order to address this task, the electronic structure and electron correlations of multiply ionised systems are studied in this thesis, aiming to obtain information on the dynamics of electron emission processes at unprecedented ease and high resolution. State-of-the-art multi-electron correlation spectrometers are used, which were originally developed at Oxford University, UK, and which are now frequently in use at the Ångström laboratory in Uppsala, Sweden.The research is so far based mainly on single-photon excitations using laboratory light sources and synchrotron radiation facilities, and expands now gradually into non-linear and time-resolved studies of atoms, molecules and clusters using high intensive Free Electron Lasers (FEL) in the Vacuum Ultra-Violet (VUV) and X-ray spectral region. This development is highly relevant for even more deep-going applications regarding the ion and excited-state balance in the Earth‟s outer atmosphere and in astrophysical contexts, for photochemistry and biochemistry, for materials science, and to test current atomic and molecular structure theories to their limits.We will focus on the multiple ionization of the buckminsterfullerene (C60) which is of scientific interest as an exceptionally stable and symmetric cluster. Its applications are quite large in nanotechnologies.

Drought and low soil nitrogen are major factors limiting maize production in Sub-Saharan Africa. Genotypic and phenotypic characterization of maize testcross hybrids developed from four biparental populations: CML441 x CML444, CML440 x COMPE, CML444 x K64R and CML312 x NAW was conducted. The objectives were (a) to evaluate the performance of F2:3 line testcrosses across stressed and non-stress conditions, (b) to estimate heritabilities for grain yield and secondary traits, (c) to assess the relationship between testing environments, (d) to estimate genetic correlations among relevant traits, (e) to estimate direct and indirect genetic gain from selection, and (e) to have a preliminary assessment of the efficiency of marker-assisted selection. Studies were conducted under no nitrogen fertilization, low nitrogen, drought, well- watered and high nitrogen in Malawi and Zimbabwe. About 100 entries from each population were tested using an alpha lattice design with two replications at all locations. Traits measured were grain yield, plant height, anthesis date, anthesis-silking interval, ears per plant, grain moisture at harvest and leaf senescence. Highest grain yield across environments was obtained from population CML444 x K64R (3.82 Mg ha-1) and the lowest from CML440 x COMPE (3.64 Mg ha-1). Testcrosses from CML441 x CML444 and CML444 x K64R had higher heritability estimates compared to CML440 x COMPE and CML312 x NAW. Drought and high nitrogen environments had higher heritability estimates than low nitrogen and well-watered conditions. Drought and well-watered environments discriminated testcrosses in a similar manner as well as high and low nitrogen environments. All populations had negative correlations between grain yield and anthesis silking interval, while positive correlations were observed between grain yield and ears per plant. No consistent differences were observed between overall means of best and worst marker based selected line testcrosses across populations and environments. Highest direct expected genetic gains were observed from high nitrogen environments. Direct selection under specific environments (e.g. drought ) was estimated to be more beneficial than indirect selection in other environments.

No description available.

WiFi networks have become ubiquitous. However, due to the nature of the radio-wave medium, the performance of 802.11 is unpredictable and highly dependent on the environment. This problem is fundamental to 802.11's decentralized, signal-based airspace arbitration mechanism. When devices have incomplete and inconsistent channel conditions for an overlapping interference domain, their signals alone cannot ensure a fair competition for airspace. As a result, competing flows may suffer from unfair bandwidth distribution if the shared airspace is congested. A useful tool to visualize and diagnose problematic wireless networks is the set of devices interfering with each other at a given time. We say two devices a and b interfere when one of two possible situations occur. First, a is able to sense b's radio signals, though not necessarily decode them, resulting in a unable to send data. Second, a and b aren't in radio range, but their destination devices are, resulting in packet collisions. We call such a set of mutually interfering devices the interference neighbourhood. We present wypy, an online system which merges trace-files and produces a map of interfering devices contained within the trace. wypy is able to identify pairs of devices exhibiting either hidden or exposed terminal interference using a pipeline that consists of trace merging and reconstruction, filtering of simultaneously sending devices, throughput and delay signal calculations, and a test for interference correlation. We evaluate wypy using an in-lab testbed set up in known interference scenarios.

No description available.

No description available.

WiFi networks have become ubiquitous. However, due to the nature of the radio-wave medium, the performance of 802.11 is unpredictable and highly dependent on the environment. This problem is fundamental to 802.11's decentralized, signal-based airspace arbitration mechanism. When devices have incomplete and inconsistent channel conditions for an overlapping interference domain, their signals alone cannot ensure a fair competition for airspace. As a result, competing flows may suffer from unfair bandwidth distribution if the shared airspace is congested. A useful tool to visualize and diagnose problematic wireless networks is the set of devices interfering with each other at a given time. We say two devices a and b interfere when one of two possible situations occur. First, a is able to sense b's radio signals, though not necessarily decode them, resulting in a unable to send data. Second, a and b aren't in radio range, but their destination devices are, resulting in packet collisions. We call such a set of mutually interfering devices the interference neighbourhood. We present wypy, an online system which merges trace-files and produces a map of interfering devices contained within the trace. wypy is able to identify pairs of devices exhibiting either hidden or exposed terminal interference using a pipeline that consists of trace merging and reconstruction, filtering of simultaneously sending devices, throughput and delay signal calculations, and a test for interference correlation. We evaluate wypy using an in-lab testbed set up in known interference scenarios.