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Skin secretions of amphibians, which contain a large amount of bioactive compounds, play an essential role in their survival. For instance, some toxic or irritant secretions can protect them against predators. Due to the pharmacological and bioactive characteristics of the components in amphibian skin secretion, these secretions have been considered as one of the world’s richest source of such agents. In this study, the skin secretions of the frogs Odorrana livida, Hylarana latouchii and Phyllomedusa sauvagii were collected from the dorsal surface and immediately frozen in liquid nitrogen. Afterwards, a series of molecular techniques, including mRNA isolation, cDNA library construction, PCR, agarose gel analysis and DNA sequencing were applied. The novel peptide sequences were deduced from cloned cDNAs and then confirmed by using MALDI-TOF mass spectrometry and MS/MS fragmentation sequencing. Finally, three novel peptides were chemically-synthesised. The determination of the therapeutic bioactivities of the three novel peptides was carried out by a series of assays. QUB-1384, exhibited BK-receptor agonist-like functions which induced the contraction of rat bladder and uterus tissues. QUB-1906 is a Bowman-Birk inhibitor which could efficiently inhibit the activity of trypsin. The novel dermaseptin peptide, QUB-2949, had broad-spectrum anticancer activities against human cancer cell lines including PC-3 (ATCC-CRL-1435), U251MG (ecacc-09063001), H157 (ATCC-CRL-5802), MCF-7 (ATCC-HTB-22) and MDA-MB-435S (ATCC-HTB-129). Meanwhile, like other dermaseptin peptides, QUB-2949 showed effective growth inhibitory activity against the standard Gram-negative bacterium Escherichia coli (NCTC 10418), the standard Gram-positive bacterium Staphylococcus aureus (NCTC 10788), the pathogenic yeast Candida albicans (NCPF 1467), the drug-resistant bacterium Enterococcus faecalis (ATCC 29212), Methicillin-resistant Staphylococcus aureus (MRSA) (ATCC BAA-2094) and Pseudomonas aeruginosa (NCTC 13437). In addition, according to the results of haemolysis assay and HMEC-1 MTT assay, all the peptides exhibited low cytotoxicity. In conclusion, three novel peptides were found and assessed in this project. The multifunction and low cytotoxicity of these bioactive peptides make them promising candidates for natural drug discovery and provide new prospect for clinical treatments.

This thesis presents several aspects of the control and operation of a DC micro grid with variable generation and energy storage. These aspects mainly concern the dynamic performance improvement of energy storage interface converters, a standardized autonomous control strategy for a DC microgrid, and its stability and dynamics assessment method. Several predictive average current control schemes are proposed for a bi-directional DC- DC converter which is used to interface the energy storage device to the DC microgrid. By properly arranging the sampling and duty cycle updating points, optimal control laws are derived for enhanced dynamic performance. Robustness and static error correction are also analyzed. An autonomous 3-level hierarchical control strategy is proposed for DC microgrids with selective slack terminal(s) assigned to each operation level. The system operational status is acknowledged via the common DC voltage and the transitions between different operational levels are triggered by its variation. A 4-terminal DC micro grid system is established and specific control scheme is outlined to demonstrate the proposed strategy during various operating conditions. During grid-connected condition, a voltage droop based power sharing and coordination strategy among the slack terminals is proposed for power smoothing. A simulation study is carried out to preliminarily verify the effectiveness of the proposed control strategy. A stability and dynamic assessment method is proposed for converter interfaced DC networks. Based on the virtual impedance modelling method, a case study concerning DC voltage variation suppression in a multi-terminal DC network is performed using root locus and open-loop margin analysis. The accuracy of the modeling method and its effectiveness for assessing system stability and dynamic performance is validated using circuit simulation in time domain. A prototype DC micro grid is also established to validate the effectiveness of the control proposals and analytical method.

Elongation of a tissue along one body axis is a conserved morphogenetic process that happens repeatedly during embryo and organ morphogenesis. While the mechanisms of tissue elongation in 2D sheet-like tissues are increasingly well understood, the molecular and cellular mechanisms that elongate topologically distinct tubular and acinar organs may be distinct. In this dissertation, I utilize Drosophila egg chamber (follicle) morphogenesis in the adult female ovary as a model system to understand tissue elongation in the unbounded tube-like organs. The follicle grows spherically during early oogenesis and then elongates during mid-oogenesis along the anterior-posterior axis to become an ellipsoidal organ. Whole-tissue rotation of the follicle during the elongation phase is thought to provide Planar Cell Polarity (PCP) information that orients basal actin bundles and basement membrane Collagen IV fibrils around the circumference, through a process requiring the atypical cadherin Fat2. Despite its essential role in the process, how Fat2 regulates PCP symmetry-breaking to specify rotation in one chirality was unresolved. With long-term live imaging, I showed that the follicle initiates rotation immediately after it buds off from the germarium. To trace the earliest sign of chiral symmetry-breaking, I developed an in toto 3D image analysis platform to comprehensively chart the cytoskeletal PCP in curved structures. In collaboration with my labmate Katherine Lipari, we found that microtubule growth polarity exhibits a bias within the germarium, prior to follicle budding and rotation. This germarial microtubule bias is dependent on Fat2, and provides chiral information that breaks the PCP symmetry prior to rotation. We propose a PCP relay mechanism that initiates from germarial microtubule chirality, to rotational polarity and actin bundle alignment, to finally a polarized basement membrane organization that elongates the organ.The limitations of current ex vivo cultures for long-term morphogenetic analyses compelled me to develop a tool that can track cell motility over extended periods. I developed M-TRAIL, which utilizes cell-ECM interactions to retrospectively trace cell movements in fixed tissues. By making clones overexpressing GFP-tagged ECM proteins, cell motility trajectories are revealed based on the long-lasting traces of fluorescently-tagged ECM proteins deposited onto basement membrane. I applied M-TRAIL to compare ex vivo versus in vivo rotation and between WT and fat2 to validate M-TRAIL’s validity. Strikingly, a previously reported protein-truncating fat2 mutant allele, which does not rotate ex vivo yet produces elongated follicles, actually rotates in vivo at half the speed than WT. These results revalidate the model that tissue rotation is required to build a proper basement membrane that elongate the follicle. The M-TRAIL approach also demonstrates how reliance solely on ex vivo imaging can mislead. By combining our previous work that chart the BM stiffness profile and by measuring BM stiffness in the slow rotating Fat2-truncated follicle, we show that rather than the absolute BM stiffness, an anterior-posteriorly patterned BM stiffness gradient elongate the follicle. By further refining the 3D image analysis platform I developed and use it to chart tissue and cellular scale morphometrics, I found three major cell behaviors that can contribute to follicle elongation, which are oriented cell division, polarized cell shape changes, and cell rearrangement. With analyses of either mutants that fail to elongate or by genetic manipulations that disrupt one particular cell behavior, I found cell shape changes and cell rearrangement play a major role in elongating the follicle. The tools I developed and my findings provide a platform and new insights in understanding the molecular, cellular, and mechanical mechanisms in organ morphogenesis.

Osmotin, a pathogenesis-related (PR) protein, possesses antimicrobial activity. The objectives of this study were: 1) to determine the stability of the recombinant tobacco osmotin (rOSM), 2) to define the antimicrobial profiles of rOSM, and 3) to control Aspergillus niger on strawberries by rOSM. The rOSM was expressed in Escherichia coli and stored at -20, 4, and 25 °C for stability study. The antimicrobial activities of rOSM were tested against A. niger, Penicillium aurantiogriseum, Cryptococcus neoformans and 26 foodborne pathogenic bacteria. Strawberries were inoculated with A. niger spores and treated with rOSM. The infection rates of strawberries were recorded daily at 25 °C for 8 days. The rOSM was stable for 6 months at -20, 4, and 25 °C. The antimicrobial activity of rOSM was dose and microorganism related. The rOSM treated strawberries showed longer shelf-life. These results indicated that rOSM has a potential use in foods for food safety.

The dramatic increase in China’s house prices creates house prices bubble spurring the Chinese economy (Derger & Zhang, 2010). From the U.S. sub-prime loan crisis, however, it is evidenced how severely the fluctuation of house prices can potentially endanger the stability of the real economy, especially for a large housing market such as the US, the European Zone and China. Following the burst of the US house price bubble, the global financial market has been extremely volatile in terms of the debt issues in both the US and countries in the Europe Zone such as Greece, Italy, Portugal and Ireland. Similarly, it is impossible for China to dodge the impact of the global financial and economic crisis because China is over-dependent on exports to stimulate its economic growth. Beijing, the capital city of China, is the biggest city of China in terms of both population and land area; it has the largest commercial housing market. This study investigates whether a house price bubble exists in Beijing housing market in the period from 1999 to 2009. This study examines the efficiency of Beijing housing market and provides appropriate risk management techniques to manage housing bubble crisis in Beijing. In this study, income, inflation, interest rate and construction cost have been using to model the Beijing house price dynamics; the result suggests a house price bubble exists in Beijing housing market.

Background and Aims: Cementless joint prosthesis has been a major module in joint replacement since 1980s. However, bone-implant aseptic loosening is still an important complication. This study was performed to assess the effects of implant surface fabrications and coatings on new bone growth on and in implant surface and on mechanical stability. The study also examines the effects of gap on bone healing in bone-implant interface and exogenous mechanical stimuli on bone growth and mechanical stability. And, lastly, the development of a sheep model for implant research was also undertaken. Materials & Methods: Four types of implants were tested: plasma sprayed porous surface titanium implant with electrochemically deposited 20 μm dicalcium phosphate dihydrate (DCPD) and without coating (TiPL); and grit blasted titanium implants with hydroxyapatite (HA) and without coating (TiGB). Implants were inserted into cancellous and cortical bones with gaps and fits in sheep hind limbs. One group of sheep was treated by dynamic motion therapy (DMT) postoperatively. Specimens were retrieved at five timepoints. Bone-implant mechanical stability was assessed by push-out testing. Bone ongrowth, ingrowth and remodelling were investigated by histology, SEM and BSEM images. Results: Thin electrochemical deposited DCPD coating can improve bone ingrowth in porous surface but cannot improve bone-implant interface mechanical strength. Cortical bone has better ingrowth ability than cancellous bone. Plasma sprayed porous surface has higher bone ongrowth rate and mechanical stability than grit blasted surface. Failure mode in TiPL based implants (including TiPL and DCPD) is through newly formed surrounding bone, while that in TiGB based implants (including TiGB and HA) is through bone-implant interface, HA coating or coating-implant interface. HA coating improves bone-implant gap healing better than grit blasted surface. Tighter bone-implant interface leads to earlier healing and remodelling, while a bigger gap results in less bone growth on implant. The current DMT does not enhance bone-implant interface shear strength, but improves toughness and reduces stiffness. Conclusions: The thin DCPD coating can promote osteogenesis in a porous titanium substrate, but did not improve mechanical stability. Plasma sprayed porous surface also demonstrated its superior in mechanical stability, while HA surface had higher osteoconductivity.

This study systematically investigated the mechanism and efficiency of the ultrasonic control of gamma-alumina ceramic membrane fouling caused by silica particles and dissolved organic matter (DOM). Ultrasound at 20 kHz was applied to a cross-flow filtration system. First, ultrasonic cleaning was explored with filtration of silica particles to investigate influence of both particle characteristics and ultrasonic factors on cleaning. Experimental results indicated that more effective control of fouling occurring at low particle concentrations, hydrophilic particles, and large particle sizes based on measurements of sound wave intensity, images of the cavitation region, and force balance analysis of a particle deposited on the membrane. In addition to the effect of particle characteristics, ultrasonic factors affecting membrane cleaning were explored. Optimal cleaning occurred when the membrane was outside but close to the cavitation region. However, damage in the form of pits and cracks were found when the membrane was within the cavitation region. An increase in the filtration pressure resulted in less improvement in permeate flux of ultrasound. Furthermore, pulsed ultrasound with short pulse intervals resulted in a relative permeate flux improvement close to that of continuous sonication. Second, besides sonophysical cleaning of particle fouled membranes, membrane cleaning was also explored by studying sonochemical reactions of DOM. Property changes of Aldrich and Pahokee peat DOM at different ultrasonic frequencies and energy densities were systematically investigated. Exposure of DOM to ultrasound resulted in decreases in hydrophobicity, aromaticity, and molecular weight, while DOM acidity increased. However, at low ultrasonic frequency (20 kHz) and low energy density, sonochemical transformation of DOM was insignificant. Finally, the effect of solution chemistry on ultrasonic control of membrane fouling caused by DOM and silica particles was examined. Experimental results indicated that more effective control of membrane fouling occurred at high pH, low ionic strength, and in the absence of divalent cations, due to stronger electrostatic repulsion among DOM macromolecules, silica particles, and the membrane. The decrease of the DOM rejection rate by ultrasound may be explained by the decreased steric exclusion effect, because ultrasound partially released membrane pore blocking and/or partially removed the foulant layer from the membrane surface.

Combined free convection and radiation in a nonparticipating or participating medium contained in a square enclosure with isothermal side walls and adiabatic black top and bottom walls is numerically investigated. For radiatively participating media the S6 discrete-ordinate approximation is used to obtain the solution to the radiation transport equation. The SIMPLER algorithm is used to solve the Navier-Stokes equations. The effects of optical thickness, radiation number and emissivity of side walls on heat transfer rates are discussed. The performance of superposing the pure free convection and pure surface radiation mode results of local and total heat transfer rates is evaluated. Such superposed results are compared with combined interacting free convection-radiation models and significant deviations between two models are encountered.