Clonal propagation of Betula pendula and Pinus sylvestris using stem cuttings and tissue culture was studied. Cuttings of both species rooted with a high level of success and rooted cuttings showed high levels of survival. Single-internode cuttings, with one axillary bud and leaf, were most successful with Betula pendula. particularly if such cuttings were collected from elongating shoots. Pinus sylvestris cuttings were also successful if collected from elongating shoots. Although exogenous auxin increased speed of rooting and number of roots formed by cuttings it had little effect on the number of cuttings which formed roots and the subsequent survival of these rooted cuttings. Growth and biomass distribution of rooted cuttings of Betula pendula and Pinus sylvestris was similar to that of seedlings. Successful propagation of both species depended on ortets being in a "juvenile" phase of growth. An attempt to produce "juvenile" cutting material from "adult" genotypes of Betula pendula was made by inducing the formation of epicormic shoots. Although these shoots had "juvenile" morphology, and cuttings derived from these shoots had similar rooting characteristics to cuttings taken from young seedlings, cuttings collected from epicormic shoots demonstrated plagiotropic growth of shoots in comparison with the orthotropic habit of cuttings taken from young seedlings. These results suggest that only partial rejuvenation occurred. Methods of enhancing the yield of cuttings from young seedling ortets of Betula pendula and Pinus sylvestris are discussed. A method to propagate Betula pendula by callus culture was developed. Callus nodules, initiated from stem internodes, were induced to undergo morphogenesis with the development of shoots. Although only half of the cultured nodules regenerated shoots, "morphogenic" nodules formed an average of 100 shoots of 4mm in length or greater when subcultured on a medium with BAP (benzylaminopurine) and NAA (napthaleneacetic acid). Other growth substances tested were less successful or unsuccessful at regenerating shoots. These shoots readily rooted outwith aseptic culture in an intermittent spray unit. Level of rooting and survival of rooted shoots was very high. Successfulb morphogenesis depended on the culture of "juvenile" tissues. Rate of growth of tissue-culture plants was the same as genetically similar seedlings, however tissue-culture plants were found to have slightly thinner stems after one season of growth. A cytological investigation of tissue-culture plants revealed the presence of polyploids which were identified through chromosome counts as allotetraploids with 4n=56 chromosomes in comparison with the normal diploid 2n=28 karyotype. These allotetraploids were readily identified by their unusual leaf morphology and very slow growth. No other ploidy levels were found. The frequency of occurrence of these allotetraploids varied with the type of auxin incorporated in the culture medium. NAA was associated with a level of tetraploidy of 11.0 percent whereas IBA (indolebutyric acid) was associated with a level of 3.8 percent. BAP was used in combination with both these auxins. The higher level of tetraploidy, associated with NAA, was more than compensated by a greatly enhanced level of shoot regeneration on callus nodules cultured on a medium with this auxin in comparison with nodules cultured on a medium with IBA. Presence of allotetraploids was of little concern because of their ease of identification and low level of occurrence. Vegetative material taken from genotypes of Betula pendula greater than one year old developed callus tissues but this callus showed little capacity to undergo morphogenesis. A few shoots did develop from callus initiated from shoot internodes collected from a four-year-old genotype. Only one of these shoots formed roots. Study of this plantlet suggested that it was not "juvenile" although its origins were adventitious.

Dissertation submitted in compliance with the requirements for the Master's Degree in Technology: Biotechnology, Technikon Natal, 2001. / Biotechnology techniques such as micropropagation VIa somatic embryogenesis offer potential significant advances in the improvement of forest species, which could sustain forest production in South Africa, as well as globally, without increased use of land. In order to apply such techniques to commercial breeding and clonal programmes of E. grandis species, it is necessary to develop reliable and efficient protocols applicable to explants of proven superior genotypes. Most of the research on E. grandis somatic embryogenesis has used the genetically variable embryos or seedlings as explant sources, which results in the propagation of material of unproven genetic value. In order to exploit somatic embryogenesis maximally for cloning of superior trees, somatic embryos have to be induced from highly selected and, hence, mature trees. The aim of this investigation was to develop such a protocol for E. grandis and to test its applicability to various E. grandis hybrids. Somatic embryos were induced from buds, stems, leaves and petioles, with petioles and buds giving the best results. Thus, these were selected for further studies which involved testing the effect of medium composition on embryogenic callus induction. Media used for this purpose contained MS or B5 nutrients, 1 mg.l' 2,4-D, 0.5 g.r! glutamine, 0.5 g.r! casein hydrolysate, 4 g.r! Gelrite and 30 or 50 g.rl sucrose. All the media tested were able to support induction of embryogenic callus, although the number of explants producing embryogenic calli was affected significantly by the media composition (10-91 %). Callus induction media with B5 nutrients seemed to have a significant effect onn the developmental stage of embryos in the callus induction medium. Presence of 50 g.r! sucrose in the callus induction medium reduced the embryo yield, but the progress of embryo development was enhanced. The callus induction medium containing B5, 1 mg.l' 2,4-D, 0.5 g.rl glutamine, 0.5 g.r! casein hydrolysate, 4 g.r! Gelrite and 30 g.l' sucrose was chosen for subsequent studies. Of all the media tested for embryo development, the medium with B5, 2.5 mg.l' 2iP, 0.5 g.r! glutamine, 0.5 g.r! casein hydrolysate, 4 g.r! Gelrite and 50 g.r! sucrose was found to be the most suitable for embryo development to the cotyledonary stage. Experiments involving incorporation of both ABA and 2iP aiming at maturation of E. grandis somatic embryos led to an increase in size of the cotyledonary embryos formed but not to germination. / M

This thesis explores what patterns, if any, exist to differentiate non-malware from malware, given only a sequence of raw bytes composing either a received file or a fixed-length initial segment of a received file. If any such patterns are found, their effectiveness as filtering criteria is investigated.

by Poon Lai Shun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 59-[64]). / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background of Measurement in Indoor Environment --- p.7 / Chapter 2.1 --- Propagation loss --- p.8 / Chapter 2.1.1 --- Basic concepts --- p.8 / Chapter 2.1.2 --- Indoor propagation --- p.13 / Chapter 2.2 --- Multipath characteristics --- p.15 / Chapter 3 --- Propagation Model --- p.17 / Chapter 4 --- Measurement Sites and Equipment Setup --- p.21 / Chapter 4.1 --- Measurement sites --- p.21 / Chapter 4.2 --- Equipment setup --- p.22 / Chapter 5 --- Measurement Results --- p.27 / Chapter 5.1 --- Propagation loss in the same building --- p.27 / Chapter 5.1.1 --- Measurement in Engineering Building --- p.27 / Chapter 5.1.2 --- Measurement in Hostel --- p.30 / Chapter 5.2 --- Penetration across the atrium and neighboring building --- p.31 / Chapter 5.3 --- Multipath characteristics --- p.33 / Chapter 6 --- Frequency Reuse Planning and Limitations on Measurement --- p.50 / Chapter 6.1 --- Frequency reuse planning --- p.50 / Chapter 6.2 --- Limitations on the propagation loss measurement --- p.53 / Chapter 6.3 --- Limitations on multipath measurement --- p.54 / Chapter 7 --- Conclusions --- p.55 / Appendix --- p.56 / Chapter A --- Method of Calculating Path Loss Slope --- p.56 / Bibliography --- p.59

The average time necessary to add numbers by local parallel computation is directly related to the length of the longest carry propagation chain in the sum. The mean length of longest carry propagation chain when adding two independent uniform random n bit numbers is a well studied topic, and useful approximations as well as an exact expression for this value have been found. My thesis searches for similar formulas for mean length of the longest carry propagation chain in sums that arise when a random n-digit number is multiplied by a number of the form 1 + 2d. Letting Cn, d represent the desired mean, my thesis details how to find formulas for Cn,d using probability, generating functions and linear algebra arguments. I also find bounds on Cn,d to prove that Cn,d = log2 n + O(1), and show work towards finding an even more exact approximation for Cn,d.

An investigation of brake application delays in Australian train brake systems began with a literature review of pneumatic train braking systems. Data located in the review gave examples of brake application delays of pre 1990 designs from the U.K., India and North America. Information on application delays on later Australian designs was scarce. Reading of literature has shown a difference between the Australian and North American control valves in the way the propagation of the pressure reduction rate in the brake pipe is maintained. Control valves of the North American style allow the brake pipe air to be connected for a short time to a small cavity or quick service volume of each valve. The quick service volume is then released to atmosphere. The action of exhausting a small amount of air from the brake pipe helps to ensure a propagation of an adequate pressure reduction rate as it travels to the next valve. Australian control valves rely on the ratio of the volume of brake pipe between control valves and the size of the quick service volume or ‘bulb’ to ensure the propagation of an adequate pressure reduction as it travels to the next valve. The air in a bulb of an Australian valve is not expelled to atmosphere until a brake release is made. The research explored possible reductions in application delays by utilizing an experimental pipe test rack that included 4 control valves and 120 meters of brake pipe. Experiments with different configurations of exhaust orifices or chokes, valves and branch pipe lengths that supplied the valves gave a record acquired by data acquisition of the timing of each valve and the local pressure drop from a valve or each valve for comparison. Experiments with exhaust chokes that gave a reduction drop rate in the brake pipe that approached the minimum required to operate a control valve resulted in instability of the application operation of the control valve. The quick service volume of different sizes was included in the experiments to give comparisons in the propagation of the pressure reduction toward the end of a long train. Further increases into the size of the bulb of a control valve to enhance the propagation features toward the end of a long train are discussed. The branch pipe with different diameters from 12 mm to 20 mm and lengths from 160 mm to 800 mm when fitted to an adaptor pipe bracket were investigated and results show that larger diameters gave larger gulps in the brake pipe. Other components that were studied included the pipe bracket that is fitted on some control valves. The pipe bracket and isolation cock was found to add 282 mm of additional length to the air path and while not changing the operation of the valve, the results showed a smaller drop in local pressure in the brake pipe to assist the pressure reduction rate than shown in valves without pipe brackets.

Dans le contexte actuel où le spectre électromagnétique est saturé, une transmission efficace par les systèmes sans fils exige une connaissance approfondie du comportement du canal de propagation. La modélisation stochastique du canal permet d'évaluer les performances d'un système de communication dans un environnement donné. Ces dernières années, nous assistons à l'apparition de techniques mettant à profit les diversités du canal (diversité temporelle, diversité spatiale et diversité de polarisation). Pour évaluer leurs performances, les sondeurs de canal et les modèles proposés se sont complexifiés. Cette thèse est une contribution au sondage multiparamétrique d'un canal radiofréquence à l'intérieur des bâtiments. Elle aborde l'amélioration du sondeur de canal développé préalablement à TELECOM ParisTech. La caractéristique originale de ce sondeur est l'utilisation de récepteurs cinq-port. Le cinq-port est un circuit interférométrique qui permet de calculer le rapport complexe entre deux signaux hyperfréquences. Son faible coût permet d'exploiter seize chaînes parallèles en réception. Le signal utilisé pour le sondage est un signal chirp couvrant la bande de fréquences entre 2.2 et 2.7 GHz. Des estimations haute-résolution de direction de départ, direction d'arrivée, polarisation, fréquence Doppler et retard sont effectuées pour valider le sondeur. Cette thèse est aussi une contribution à la modélisation statistique des canaux UWB. Un modèle spatio-temporel est élaboré à partir de mesures SIMO (Single Input Multiple Output) couvrant la bande de fréquences entre 2 GHz et 8 GHz. Les valeurs des paramètres du modèle sont comparées pour différents environnements, de type bureau et de type résidentiel, en condition de visibilité et de non visibilité.

No description available.

Little numerical analysis has been done on fluorescence lifetime imaging \emph{in-vivo}. Here, a 3D fluorescence Monte Carlo model is used to evaluate a microvasculature geometry obtained via two-photon microscopy. I found that a bulk-vascularization assumption does not provide an accurate picture of penetration depth of the collected fluorescence signal. Instead the degree of absorption difference between extravascular and intravascular space, as well as the absorption difference between excitation and emission wavelengths must be taken into account to determine the depth distribution. Additionally, I found that using targeted illumination can provide for superior surface vessel sensitivity over wide-field illumination, with small area detection offering an even greater amount of sensitivity to surface vasculature. Depth sensitivity can be enhanced by either increasing the detector area or increasing the illumination area. Finally, it is shown that the excitation wavelength and vessel size can affect intra-vessel sampling distribution, as well as the amount of signal that originates from inside the vessel under targeted illumination conditions. / text

a b s t r a c t A study concerning the propagation of free non-axisymmetric waves in a homogeneous piezoelectric cylinder of transversely isotropic material with axial polarization is carried out on the basis of the linear theory of elasticity and linear electro-mechanical coupling. The solution of the three dimensional equations of motion and quasi-electrostatic equation is given in terms of seven mechanical and three electric potentials. The characteristic equations are obtained by the application of the mechanical and two types of electric boundary conditions at the surface of the piezoelectric cylinder. A novel method of displaying dispersion curves is described in the paper and the resulting dispersion curves are presented for propagating and evanescent waves for PZT-4 and PZT-7A piezoelectric ceramics for circumferential wave numbers m = 1, 2, and 3. It is observed that the dispersion curves are sensitive to the type of the imposed boundary conditions as well as to the measure of the electro-mechanical coupling of the material.