Graduation date: 2003

ABSTRACT The effects of ultrasonic irradiation at different frequencies, i.e. 0.25, 0.5, 1, and 5 MHz, on the biological reaction of the single cell creature have been investigated. When multi-cell creature is exposed to ultrasound, this reaction will lead the biological effect becomes complex. Therefore, in this dissertation, a single cell creature is chosen to study the biological effects induced by ultrasound exposure. The paramecium, which possesses many features typical of higher-order animal cells, was considered as an appropriate choice for this study. The ability shown by ultrasound in promoting and/or accelerating many reactions has been shown to be a useful field. The resonant frequency of paramecium by using the ultrasound irradiation is an important parameter in this research. All other parameters being kept constant, it has been ascertained that an appropriate frequency value of ultrasound can be selected, capable of driving a biological reaction to its suitable yield. The oscillation of the cells in response to the ultrasound radiation is simulated using Rayleigh-Plesset¡¦s bubble activation theory. The resonant frequency of the unicellular creature is then calculated. In the experiment, the resonant (0.5 and 1 MHz) and non-resonant (0.25 and 5 MHz) frequencies were employed. The theoretical resonant frequency of the paramecium vacuole is among 0.5013~1.2703 MHz. In this thesis, the experiment included two different series. The exposure intensity is the major subject of the first experimental series to study the bioeffect of ultrasound. The waveform was set to the tone pulse mode, pulsing 1:1. The exposure duration was continued and maintained 5 minutes. For a given frequency, exposures of the paramecium were made over a range of intensities spanning 0 to 1.7 mW/cm2. The second experimental series was focused on the exposure duration of the ultrasound. The transducers were operating in a pulsed mode with two duty cycles of 1:1 and 1:9. All insonated samples were exposed to ultrasound with a spatial peak temporal peak intensity (SPTP) of 0.127 mW/cm2. The total ¡§with signal¡¨ time was about 6 minutes in each trial. In addition, the control samples and the treated samples would be re-incubated up to the 96 hr. When the 1 MHz frequency of ultrasound was irradiated in the samples, there was about 24% inhibition rate and 30% enhancement rate in the first experimental series. The 0.5 MHz frequency of ultrasound, which approaches to the resonant frequency range, also appeared the inhibitive and beneficial effect. In the second experimental series, the relative growth number was about 32.4% higher than that of unexposed sample. The inhibition or enhancement growth conditions did not appear apparently during irradiation the non-resonant frequency of ultrasound. Moreover, experimental evidence suggests that the sustaining growth effect can be expected, when the irradiation time is divided into parts.

Thèse doctorat : Images et Systèmes : Villeurbanne, INSA : 2005. / Titre provenant de l'écran-titre. Bibliogr. p. 124-135.

The ability to maintain hydraulic continuity in the xylem is essential to supply leaves with the water that must be exchanged for carbon dioxide. The metastable nature of xylem sap causes this system to be inherently vulnerable to failure by rapid vaporization within the conduits. Much of the recent work on hydraulic architecture and cavitation has pursued the elusive mechanism behind apparent hydraulic recovery concurrent with tension in the bulk of the xylem, referred to as "novel refilling". An investigation into the dynamics of this behavior (Chapter 3) revealed two key artifacts that can produce the appearance of novel refilling when in fact no embolism (and therefore, no recovery) has occurred. A further implication of these artifacts is that plant xylem may be more robust against embolism than previously expected. In the absence of novel refilling, it becomes much harder to reconcile the extreme vulnerability reported for ring porous species. Studies of Robinia pseudoacacia (Chapter 4) address whether the artifacts illuminated in chapter 3 provide insight into the ongoing debate about the cavitation resistance of long-vesseled species and whether it is possible to accurately assess cavitation resistance in these species using the centrifuge method. Root pressure, as an alternative to novel refilling, provides plants with a means of reversing cavitation. Studies of Betula papyrifera (Chapter 5), however, show that recovery from embolism by root pressure is limited to early spring and point to an important role for water storage in fibers that minimizes xylem tensions and thus the risk of cavitation.

We present experimentally determined photodisruption enhancement of 50 nm gold spheres irradiated with 780 nm 180 fs pulses using a pump-probe scattering system. Our results indicate a 300 nm cavitation bubble threshold reduction of 31 times when compared to an ultra-pure water base control solution. We utilize a method of matching time between bubble initiation in a continually circulated nanoparticle solution with theoretical focal volume size dependent time between particle-focal volume collision events based on simple particle kinetics. We propose the observed photodisruption is due to electrostatic particle ablation kinetics due to electron photoemission. We apply the Fowler-Dubridge theory for photoemission to nanospheres experiencing strong near-field enhancement to describe particle electric fields induced by non-zero particle charge densities resulting from emitted electrons. An apparent ultra-energy efficient photodisruption mechanism results from multiphoton emission processes in the sub 100 femtosecond pulse regime exceeding typical methods utilizing explosive boiling. In the process of explaining experimental results, we develop a near complete picture of nanoparticle mediated photodisruption as a function of identified relevant system non-dimensional groups and particle enhancement. These results may be used to guide the selection of laser and particle parameters for imaging and different photodisruption regimes. / text

Megasonic cleaning is routinely used in the semiconductor industry to remove particulate contaminants from wafer and mask surfaces. Cleaning is achieved through proper choice of chemical solutions, power density and frequency of acoustic field. Considerable work has been done to increase understanding of particle removal mechanisms in megasonic cleaning using different solution chemistries with varying ionic strengths. However, to date, the focus of all these studies of particle removal has been either cavitation or acoustic streaming.The propagation of sound waves through a colloidal dispersion containing ions is known to result in the generation of two types of oscillating electric potentials, namely, Ionic Vibration Potential (IVP) and Colloid Vibration Potential (CVP). These potentials and their associated electric fields can exert forces on charged particles adhered to a surface, resulting in their removal. In addition, the pressure amplitude of the sound wave is also altered in solutions of higher ionic strengths, which can affect the cavitation process and further aid in the removal of particles from surfaces. To test the two hypotheses, investigations have been conducted on the feasibility of removal of charged particles from silicon wafers in electrolyte solutions of different ionic strengths irradiated with a megasonic field of different power densities. Cleaning experiments have been performed using potassium chloride (KCl) as a model electrolyte and silica particles as model contaminant particles. The cleaning performance in KCl solution has been compared to that in other electrolytes solutions such as sodium chloride, cesium chloride and lithium chloride. In order to characterize the cavitation events in KCl solutions, acoustic pressure and sonoluminescence measurements have been performed using hydrophone and cavitation probe respectively. The results indicate that particle removal efficiency (PRE) increases with KCl concentration and transducer power density and much lower power densities are required at higher KCl concentration for a comparable level of cleaning. Further, cleaning performances in NaCl and CsCl were found to be superior to those in KCl and LiCl solutions. Theoretical computations show that the removal forces due to CVP are much larger in magnitude than those due to IVP and are comparable to van der Waals forces.

Šiame darbe buvo palygintas skirtingo dydžio fluoresceino izo- tio- cianin- (FITC) dekstranų molekulių pernašos efektyvumas naudojant elektroporaciją (vienas 800 V/cm arba 1500 V/cm amplitudės stačiakampis impulsas, impulso trukmė 100 μs ir 0.5 ms) ir sonoporaciją (3 MHz, 100% veikimo ciklas, 500 kPa neigiamu akustiniu slėgis, poveikio trukmė 1-10s. Darbo tikslas – nustatyti optimalias mažų molekulių pernašos į ląsteles elektroporacijos ir sonoporacijos sąlygas, siekiant tolimesniuose tyrimuose apjungti šias dvi pagal metodiką kardinaliai besiskiriančias permeabilizacijos kryptis taip, kad būtų pasiektas sinerginis arba suminis permeabilizacijos efektas. Eksperimentai atlikti naudojant Kiniško žiurkėno kiaušidžių (CHO) ląstelės. Naudojant fluorescencinės mikroskopijos metodiką, pernašos efektyvumas įvertintas pagal fluoresceinu nudažytų ląstelių skaičiaus procentinę išraišką. Į ląsteles įvestos 4, 10, ir 70 kDa (atitinkamai 1.4, 2.3 ir 6 nm hidrodinaminio spindulio) FITC dekstranų molekulės, pagal kurių patekimą į ląstelių vidų buvo interpretuojamas susidariusių porų dydis. Sonoporuotų ląstelių skaičius mažėjo didėjant įvedamų fluorescuojančių molekulių matmenims. Didžiausias sonoporuotų ląstelių pralaidumas nustatytas iki 2.3 nm hidrodinaminio spindulio (4 ir 10 kDa FITC dekstranų) molekulėms, jos į ląsteles galėjo difunduoti praėjus 5 min po sonoporacijos. Naudojant elektroporaciją, ar sonoporaciją magnetiniame lauke, visų dydžių FITC dekstranų pernaša į ląsteles buvo... [toliau žr. visą tekstą] / The aim of the study was to evaluate efficiency of intracellular transfer of FITC dextrans using sonoporation and electroporation in dependence of FITC dextran hydrodynamic radius. The results have shown that in comparison to electroporation (one square-wave pulse, of 1500 V/cm pulse strength, 100 - 500 µs pulse duration), sonoporation (3 MHz, 100% DC, at 500 kPa peak negative pressure) was more efficient for transfer of all sizes FITC dextrans. The results also demonstrated that after cell sonoporation large pores, allowing to pass 70 kDa FITC dextran, completely resealed short after sonoporation (< 1 s). The pores allowing to pass 10 and 4 kDa FITC dextrans completely resealed during 5 and 10 min. respectively. In addition, we applied static magnetic field to examine the US iduced delivery of FITC dextrans into cells, however observed no significant effect.

No description available.

The work reported in this thesis falls into three distinct, though intimately related parts. Part I is concerned with the production of a variable temperature two-phase flow test facility for studying single and two-phase flows around arbitrary two-dimensional bodies. It includes the initial design study required to define an operational envelope for the facility, and the design and constructional features of its main components and ancilliary systems. The design of a two-phase flow vapour ventilation experiment is described, together with the operating procedure for the facility. Part II reports single and two-phase experiments with a two-dimensional circular cylinder, the two-phase flows being generated by inducing natural cavitation. The cavitation inception flow regime was found to be strongly influenced by viscous effects. Three forms of incipient cavitation were observed, two attached or very close to the cylinder surface, and one of a detached nature, occurring well downstream in the wake of the cylindrical test body. These inception modes have been related to the fully wetted viscous flow around the cylinder in the Reynolds number range 10⁵ <R_d<10⁶. The development of cavitation from these three aforementioned incipient states was investigated. Viscous effects were found to influence both the limited and developed cavitation flow regimes. For development of cavitation at Reynolds numbers corresponding broadly to the supercritical range for fully wetted flow, a critical cavitation number was found at which the apparent free stream lines of the flow changed from a concave to a convex disposition. For the experimental configuration used, this critical cavitation number was independent of Reynolds number, for Reynolds numbers above the critical value. With development of cavitation at Reynolds numbers corresponding broadly to the subcritical range for fully wetted flow, no such gross changes in flow pattern were observed, the displacement of the apparent free streamlines of the flow between the limited and fully developed cavitating states being minimal. Part III contains recommendations for modifications to the experimental facility and suggestions for further studies arising from the results reported herein.

Aquaporins (AQP) are membrane bound proteins that facilitate the movement of water and other small neutral solutes across cellular membranes. Plant aquaporins belong to a large family of highly conserved proteins called the Membrane Intrinsic Protein (MIP) superfamily. In many plant species the expression of aquaporin genes and their regulation has been linked to water stress. Grapevines respond to water stress with a variety of physiological mechanisms, including the susceptibility to xylem embolism. The formation of embolised vessels can lead to a reduction in hydraulic conductivity of the xylem. Recently, it has been hypothesised that aquaporins may contribute to the water movement required for embolism recovery of xylem vessels thus restoring the hydraulic pathway. Molecular and physiological techniques have been combined to study the putative role of plasma membrane and tonoplast membrane aquaporins in response to water stress induced xylem embolism in two cultivars of grapevine (Vitis vinifera cv. Chardonnay and Grenache). Water-stress induced cavitation was measured in the stems and petioles of pot grown grapevines of a drought tolerant (Grenache) and a drought sensitive variety (Chardonnay) by the detection of ultrasonic acoustic emissions (UAEs) over both a drying and diurnal cycle. Vulnerability curves were generated by correlating the UAEs with the leaf water potential (ψL). Varietal differences in cavitation vulnerability and hydraulic properties were observed. Grenache was more susceptible to water-stress induced xylem embolism than Chardonnay, and displayed a higher hydraulic capacity (measured by maximum hydraulic conductivity). This is most likely due to anatomical differences of the xylem vessels. Chardonnay displayed vulnerability segmentation, with cavitation occurring first in the petiole and later in the stem, before developing into “runaway” cavitation under severe water stress. Vulnerability segmentation was not observed in Grenache, with both petioles and stems equally vulnerable to the formation of xylem embolism. Under severe water stress, Grenache did not develop runaway cavitation indicating that they must have some mechanism to prevent the onset of runaway cavitation. To determine the role of aquaporins, candidate genes were identified, by screening a Vitis vinifera cv. Cabernet Sauvignon cDNA library, for aquaporin cDNAs encoding members of the Plasma membrane Intrinsic Protein (PIP) and Tonoplast Intrinsic Protein (TIP) subfamilies. The screen resulted in the identification of 11 full-length and two partial aquaporin cDNAs. Sequence analyses of these cDNAs reveal five are homologous to PIP2 aquaporins, six to PIP1 and two to the TIP aquaporins. Functional expression of the fulllength AQP cDNAs in Xenopus oocytes showed PIP2 members have significantly higher water permeability compared to PIP1 aquaporins. VvPIP2;1 showed very high water permeability which was reduced by acidic cytosolic pH, as has been reported for other members of the PIP2 family. Transcript analysis of some of these aquaporin genes provides preliminary evidence that aquaporins may contribute to differences in the hydraulic response of these two grapevine varieties to conditions of water stress. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1313316 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008