Correlations Between a Cyanobacteria Bloom's Decline and Environmental Dynamics.

Lake Kainui is an ombrogenous peat lake that is eutrophic and has frequent cyanobacterial blooms. This research aimed to elucidate the factors that correlated with cyanobacterial bloom decline in Lake Kainui. Abiotic and biotic variables in Lake Kainui were monitored weekly across the bloom decline phase. Physicochemical parameters measured included nutrients, micronutrients, water temperature, dissolved oxygen (DO), pH and meteorological variables. Planktonic and particle-associated bacterial community composition (BCC) was assessed through time using molecular fingerprinting (ARISA). Total algal, cyanobacterial, planktonic bacteria, planktonic viruses and planktonic crustacean abundances were determined using microscopy. The bloom decline coincided with multiple factors including; an increasing ratio of TN:TP, changes in the ratio of mixing depth (z¬mix) to euphotic depth (zeu) and pH. The lake was stratified for several weeks before the decline and the resulting lake stability potentially created an adverse environment for cyanobacterial dominance. Changes in planktonic biota were various. Virus dynamics were positively correlated with phytoplankton dynamics. If virus abundance was negatively correlated to phytoplankton diversity, it would potentially mean that viruses were controlling the phytoplankton assemblage, however virus abundance was positively correlated to phytoplankton diversity, which suggests that viruses had a positive impact on the bloom. The positive effect was most likely due to to viruses upregulating the amount of dissolved organic matter through lysis. Bacterial abundance showed no clear correlation with other variables, but bacterial community composition (BCC) shifted as the bloom declined. Planktonic Cladocera spiked just after the bloom decline. Bosmina was the dominant species of Cladocera, but was probably too small to ingest colonial Microcystis, which suggests that the Bosmina may be consuming degradation products produced by Microcystis. These observations indicate that if planktonic biota played a role in bloom dynamics it was most likely due to shifts in the biota causing shifts in trophic cycling that alternately favour or disfavour blooming

Phyllosomata associated with large gelatinous zooplankton: hitching rides and stealing bites

During a zooplankton survey 350 km off the coast of Western Australia, we captured a large and robust zooid of a salp (Thetys vagina), to which six late stage larvae (phyllosomata) of the western rock lobster (Panulirus cygnus) were attached. High-throughput sequencing analyses of DNA extracts from midgut glands of the larvae confirmed that each phyllosoma had consumed mainly salp tissue ( x 1⁄4 64.5% + 15.9 of DNA reads). These results resolve long-standing conjecture whether spiny lobster phyllosomata attach to large gelatinous hosts to feed on them

The spatial control of particles in microfluidic systems using surface acoustic waves

Control over particle positioning is of particular importance in microfluidic systems. Acoustic techniques offer a low- power, minimally invasive method of achieving such control. This thesis discusses such control using surface acoustic waves. Mathematical models are first developed to describe the control over particles in liquids using acoustic radiation forces , which highlight the influence of acoustic power and particle size. The formation of both one and two dimensional particle arrays in fluidic channels are t hen demonstrated experimentally in a range of fluidic channels. Particle acceleration during array formation is shown by experiment to be directly proportional to the acoustic power level, indicating both fast and slow regimes of operation for this technique. Additionally, the time taken for particle arrays to form is shown to follow an inverse square relationship with particle size, allowing the possibility of sorting particles according to their size. A method of transporting particle arrays is reported, by sequential increments in the acoustic frequency. This is a cyclic process and the controlled transport of arrays of micron-sized particles by distances greater than 100 11m is demonstrated. A biocompatible microfluidic device is presented, which enables the use of the techniques presented here with biologically relevant samples. A significant biological application is demonstrated by the formation and transportation of arrays of microbubbles. This could allow the characterisation of individual micro bubbles in targeted drug delivery studies, for example.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The spatial control of particles in microfluidic systems using surface acoustic waves

Control over particle positioning is of particular importance in microfluidic systems. Acoustic techniques offer a low- power, minimally invasive method of achieving such control. This thesis discusses such control using surface acoustic waves. Mathematical models are first developed to describe the control over particles in liquids using acoustic radiation forces , which highlight the influence of acoustic power and particle size. The formation of both one and two dimensional particle arrays in fluidic channels are t hen demonstrated experimentally in a range of fluidic channels. Particle acceleration during array formation is shown by experiment to be directly proportional to the acoustic power level, indicating both fast and slow regimes of operation for this technique. Additionally, the time taken for particle arrays to form is shown to follow an inverse square relationship with particle size, allowing the possibility of sorting particles according to their size. A method of transporting particle arrays is reported, by sequential increments in the acoustic frequency. This is a cyclic process and the controlled transport of arrays of micron-sized particles by distances greater than 100 11m is demonstrated. A biocompatible microfluidic device is presented, which enables the use of the techniques presented here with biologically relevant samples. A significant biological application is demonstrated by the formation and transportation of arrays of microbubbles. This could allow the characterisation of individual micro bubbles in targeted drug delivery studies, for example.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Voltaglue bioadhesives energized with interdigitated 3D‐graphene electrodes

Soft tissue fixation of implant and bioelectrodes relies on mechanical means (e.g., sutures, staples, and screws), with associated complications of tissue perforation, scarring, and interfacial stress concentrations. Adhesive bioelectrodes address these shortcomings with voltage cured carbene-based bioadhesives, locally energized through graphene interdigitated electrodes. Electrorheometry and adhesion structure activity relationships are explored with respect to voltage and electrolyte on bioelectrodes synthesized from graphene 3D-printed onto resorbable polyester substrates. Adhesive leachates effects on in vitro metabolism and human-derived platelet-rich plasma response serves to qualitatively assess biological response. The voltage activated bioadhesives are found to have gelation times of 60 s or less with maximum shear storage modulus (G') of 3 kPa. Shear modulus mimics reported values for human soft tissues (0.1-10 kPa). The maximum adhesion strength achieved for the ≈50 mg bioelectrode films is 170 g cm-2 (17 kPa), which exceeds the force required for tethering of electrodes on dynamic soft tissues. The method provides the groundwork for implantable bio/electrodes that may be permanently incorporated into soft tissues, vis-à-vis graphene backscattering wireless electronics since all components are bioresorbable.MOE (Min. of Education, S’pore)Accepted versio

Self-assembled photoadditives in polyester films allow stop and go chemical release

Near-infrared (NIR) triggered chemical delivery allows on-demand release with the advantage of external tissue stimulation. Bioresorbable polyester poly-L-lactic acid (PLLA) was compounded with photoadditives of neat zinc oxide (ZnO) nanoparticles and 980  365 nm LiYF4:Tm3+, Yb3+ upconverting nanoparticles (UCNP). Subsequently, neat ZnO and UCNP blended PLLA films of sub-50 m thickness were knife casted with a hydrophobic small molecule drug mimic, fluorescein diacetate. The PLLA films displayed a 500 times increase in fluorescein diacetate release from the 50 mW NIR irradiated PLLA/photoadditive film compared to non-irradiated PLLA control films. Larger ratios of UCNP/neat ZnO increased photocatalysis efficiency at low NIR duty cycles. The synergistic increase results from the self-assembled photoadditives of neat zinc oxide and upconverting nanoparticles (UCNPs), as seen in transmission electron microscopy. Colloidal ZnO, which does not self-assemble with UCNPs, had less than half the release kinetics of the self-assembled PLLA films under similar conditions, advocating Förster resonance energy transfer as the mechanism responsible for the synergistic increase. Alternative to intensity modulation, pulse width modulation (duty cycles from 0.1 to 1) of the low intensity 50 mW NIR laser diode allowed tailorable release rates from 0.01 to 1.4 % per day. With the low intensity NIR activation, tailorable release rates, and favourable biocompatibility of the constituents, implanted PLLA photoadditive thin films could allow feedback mediated chemical delivery.MOE (Min. of Education, S’pore)Accepted versio