Engineering Lipid-stabilized Microbubbles for Magnetic Resonance Imaging guided Focused Ultrasound Surgery

Lipid-stabilized microbubbles are gas-filled microspheres encapsulated with a phospholipid monolayer shell. Because of the high echogenicity provided by its highly compressible gas core, these microbubbles have been adapted as ultrasound contrast agents for a variety of applications such as contrast-enhanced ultrasonography (CEUS), targeted drug delivery and metabolic gas transport. Recently, these lipid-stabilized microbubbles have demonstrated increased potential as theranostic (therapy + diagnostics) agents for non-invasive surgery with focused ultrasound (FUS). For instance, their implementation has reduced the acoustic intensity threshold needed to open the blood-brain-barrier (BBB) with FUS, which potentially allows for the localized delivery of drugs to treat neurodegenerative diseases such as Alzheimer's, Parkinson's and Huntington's diseases. However, the effectiveness of microbubbles for this application is dependent on successful microbubble engineering. One necessary improvement is the development and utilization of monodisperse microbubbles of varying size classes. Another design improvement is the development of a microbubble construct whose fragmentation state during or after FUS surgery can be tracked by magnetic resonance imaging (MRI). Thus, in this thesis, we describe a method to generate and select lipid-coated gas-filled microbubbles of specific size fractions based on their migration in a centrifugal field. We also detail the design and characterization of size-selected lipid-coated microbubbles with shells containing the magnetic resonance (MR) contrast media Gadolinium (Gd(III)), for utility in both MR and ultrasound imaging. Initial characterization of the lipid headgroup labeled Gd(III)-microbubbles by MRI revealed that the Gd(III) relaxivity increased after microbubble fragmentation into non-gas-containing lipid vesicles. This behavior was explained to stem from an increase in interaction between water protons and the Gd(III)-bound lipid fragments due to an increase in lipid headgroup area after microbubble fragmentation. To explore this hypothesis, an alternative construct consisting of Gd(III) preferentially bound to the protective poly(ethylene glycol) (PEG) brush of the lipid shell architecture was also designed and compared to the lipid headgroup-labeled Gd(III)-microbubbles. Nuclear magnetic resonance (NMR) analysis revealed that, in contrast to the headgroup labeled Gd(III)-microbubbles, the relaxivity of the PEG-labeled Gd(III)-microbubbles decreased after microbubble fragmentation. NMR analysis also revealed an independent concentration-dependent enhancement of the transverse MR signal by virtue of the microbubble gas core. The results of this study illustrated the roles that Gd(III) placement on the lipid shell and the presence of the gas core may play on the MR signal when monitoring Gd(III)-microbubble cavitation during non-invasive surgery with FUS

Waste cooking oil transesterification: Influence of impeller type, temperature, speed and bottom clearance on FAME yield

Waste cooking oil (WCO) provides an alternative source of raw material for biodiesel production. The reaction is both kinetics and mass transfer limited. Industrial use of current laboratory result suffer from dimensional non-compatibility because of the difference in the production environment especially as different impeller result in different flow characteristic during chemical reaction. In this work the effect of impeller type on fatty acid methyl ester (FAME) production from WCO was studied. At an alcohol oil mole ratio of 6:1 and 1% catalyst (oil weight), the Taguchi method was used for the experimental design of the transesterification in a 2 L stirred reactor using Rushton and elephant ear impellers. An optimum yield FAME at 70°C, 650 rpm impeller speed and 30 mm impeller bottom clearance (IBC) for Rushton impeller and 70°C, 700 rpm impeller speed and 25 mm IBC for an elephant ear impeller was obtained between 89 to 94%. IBC and speed were observed to have the most significant effect on yield using the signal to noise (S/N) ratio for Rushton and elephant ear impeller. Peak yield time between 5 to 30 min was observed. Correlation between FAME yield, peak time and temperature was high (0.968). The optimum reactor setting was at temperature 70°C, impeller speed of 650 rpm and IBC of 30 mm for Rushton (unbaffled reactor) and temperature 70°C, impeller speed of 700 rpm and IBC of 25 mm for elephant ear (baffled reactor). Physical configuration affected FAME yield/time in this work.Key words: Waste cooking oil, transesterification, impeller, Taguchi, biodiesel

In vitro Culture of Several Rice Cultivars

Tissue culture methods have been established to regenerate certain rice (Oryza sativa L) cultivars, but regeneration of the rice cultivars widely grown in Arkansas has not been reported. This study has established an in vitroculture for the rice cultivars \u27Nortai\u27, \u27Starbonnet\u27, \u27Mars\u27, Tebonnet\u27, \u27Newbonnet\u27, and \u27Lemont\u27. Callus was induced in the dark at either 20 or 28 C from dehusked seeds cultured on Murashige and Skoog (MS) medium (Murashige and Skoog, 1962) containing 40 g L^-1 sucrose, 10 g L^1 agar, 0.5, 1.0, or 2.0 mg L^-1 1 2,4-dichlorophenoxyacetic acid (2,4-D) and adjusted to pH 5.7. After four weeks the calli were weighed, transferred onto MS medium containing no 2,4-D, and maintained in a 1 2-h photoperiod (65 uE m^-2 s^-1) at 25 ± 2 C to induce plant regeneration. Callus production was best when cultured on a medium containing 1.0 mg L^-1 2,4-D and incubated at 28 C. Plant regeneration was observed two to four weeks later. The percentage of calli regenerating platlets varied with the cultivar and the callus induction treatment. Callus induction at 20 C on a medium with a 2,4-D level less than 2.0 mg L^-1 enhanced the regenerability of most cultivars. Regenerates were transplanted to soil and grow normally to maturity. This system can be helpful in improving rice cultivars with tissue culture techniques such as somaclonal variant selection and somatic hybridization

A Practical Study of E-mail Communication through SMTP

Simple Mail Transfer Protocol (SMTP) is an application layer protocol for e-mail communication. It has been adopted as a standard by Internet Engineering Task Force (IETF). SMTP has set conversational and grammatical rules for exchanging messages between connected computers. It has evolved through several revisions and extensions since its formation by Jon Postel in 1981. In SMTP, the sender establishes a full-duplex transmission channel with a receiver. The receiver may be either the ultimate destination or an intermediate forwarding agent. SMTP commands are issued by the sender and are sent to the receiver, which responds to these commands through codes. Each SMTP session between the sender and the receiver consists of three phases namely: connection establishment, mail transactions and connection termination. This paper describes and illustrates the process of e-mail communication through SMTP by issuing the individual SMTP commands directly to transmit e-mail messages. It also describes individual SMTP commands and extensions with practical implementation using a Telnet client