Magnetic resonance characterization of gadolinium-based contrast agents

Several magnetic resonance methods have been used for characterizing gadolinium-based contrast agents in NMR Imaging in this thesis. Many Gd-based contrast agents were studied including Gd DTPA(dimethylenetriaminepentaacetic acid). The zero field splitting energies and g values of Gd complexes were obtained in frozen solutions by the EPR technique. Solvent structures of Gd-based contrast agents were studied by the ESE(Electron Spin Echo) method. Analysis of \sp2H-ESEEM of Gd TTHA(trimethylenetetraaminehexaacetic acid) demonstrated the existence of the second sphere water. The distance between \sp2H-Gd, a\sb{\rm iso}, and quadrupolar coupling constants were obtained by computer simulations of \sp2H-ESEEM of Gd complexes in frozen solutions. Water exchange times between the Gd complexes and bulk water were studied by O-17 NMR. However, it was found that the direct application of the Merbach method to the Gd-based contrast agent system showed some limitations. NMRD(Nuclear Magnetic Resonance Dispersion) studies provided useful information when combined with many other techniques. Data from NMRD simulations were well correlated with ones from EPR, ESEEM, and O-17 NMR. As a result, the combination of several techniques made NMRD analysis more reliable.In the last chapter, the results of low osmolar Gd-based contrast agents studies are described. NMRD measurements were done in water and human plasma. Some of the Gd complexes showed binding behavior with plasma proteins, especially albumin. This binding affinity seems to be varied depending on the balance between the hydrophilic and lipophilic groups in one compound

Brain-Switches for Asynchronous Brain−Computer Interfaces: A Systematic Review

A brain–computer interface (BCI) has been extensively studied to develop a novel communication system for disabled people using their brain activities. An asynchronous BCI system is more realistic and practical than a synchronous BCI system, in that, BCI commands can be generated whenever the user wants. However, the relatively low performance of an asynchronous BCI system is problematic because redundant BCI commands are required to correct false-positive operations. To significantly reduce the number of false-positive operations of an asynchronous BCI system, a two-step approach has been proposed using a brain-switch that first determines whether the user wants to use an asynchronous BCI system before the operation of the asynchronous BCI system. This study presents a systematic review of the state-of-the-art brain-switch techniques and future research directions. To this end, we reviewed brain-switch research articles published from 2000 to 2019 in terms of their (a) neuroimaging modality, (b) paradigm, (c) operation algorithm, and (d) performance

Doctor of Philosophy

dissertationPolymeric gene delivery is introducing specific genes to enhance or silence gene expression using synthesized polymers which have low immunogenicity and good biocompatibility. This dissertations specifically focused on the synthesis and characterization of stimuli-responsive polymers for gene delivery. The polymers are designed to respond to specific biological stimuli such as redox potential and pH changes. In the first stimuli-responsive polymer, a reducible poly(L-lysine) (RPLL) was constructed and mediated gene delivery. Polyplex, polymer/gene complex, biocompatibility can be improved by using amino acids as nontoxic building blocks. To synthesize an amino-acid-based reducible polymer, a decapeptide composed of lysine and cysteine (Cys-Lys8-Cys) has been selected due to primary amines and sulfhydryl functional groups, respectively. A reducible polymer introduced with disulfide bonds enables control of the rate of biodegradation and decomplexation of polyplex which will impact plasmid DNA (pDNA) release. In the second stimuli-responsive polymer, a pH-dependent polymeric-mediated gene delivery was conducted via PLL grafted with either mono-L-histidine (PLL-g-mHis) or poly(L-histidine) (PLL-g-PHis). The pH-sensitive ionizable groups in histidine were used as an endosomolytic agent to construct a pH-sensitive polymeric gene carrier. Two types of histidine grafted PLL, PLL-g-mHis and PLL-g-PHis, were synthesized with the same number of imidazole groups to compare the effective arrangement of histidine in terms of iv endosomolytic activity and transfection efficiency. A wide range of observations have been made to conclude that a stimuli-sensitive property in polymer imparts a rapid response to specific stimulus compared to a nonsensitive polymer and the improved gene transfer activity shows much promise for gene delivery. Since gene carriers have been applied in cancer gene therapy to safely and efficiently deliver a therapeutic gene into the target site, these stimuli-sensitive polymers will bring efficient translation levels of the therapeutic protein to treat cancer. Therefore, it is essential to further investigate the gene expression in vivo applications in an engaging and accessible way

Deceiving Google's Cloud Video Intelligence API Built for Summarizing Videos

Despite the rapid progress of the techniques for image classification, video annotation has remained a challenging task. Automated video annotation would be a breakthrough technology, enabling users to search within the videos. Recently, Google introduced the Cloud Video Intelligence API for video analysis. As per the website, the system can be used to "separate signal from noise, by retrieving relevant information at the video, shot or per frame" level. A demonstration website has been also launched, which allows anyone to select a video for annotation. The API then detects the video labels (objects within the video) as well as shot labels (description of the video events over time). In this paper, we examine the usability of the Google's Cloud Video Intelligence API in adversarial environments. In particular, we investigate whether an adversary can subtly manipulate a video in such a way that the API will return only the adversary-desired labels. For this, we select an image, which is different from the video content, and insert it, periodically and at a very low rate, into the video. We found that if we insert one image every two seconds, the API is deceived into annotating the video as if it only contained the inserted image. Note that the modification to the video is hardly noticeable as, for instance, for a typical frame rate of 25, we insert only one image per 50 video frames. We also found that, by inserting one image per second, all the shot labels returned by the API are related to the inserted image. We perform the experiments on the sample videos provided by the API demonstration website and show that our attack is successful with different videos and images

Ratios of BB and DD Meson Decay Constants in Improved Mock Meson Model

We calculate the ratio $f_{B_s}/f_{B_d}$ by following the Oakes' method which is based on chiral symmetry breaking, but we improve his calculation by performing the calculation of the factor $$/$$ in the mock meson model. In this calculation we improved the mock meson model by using the value of the parameter $\beta$ which is obtained by the variational method in the relativistic quark model. We also calculate $f_{D_s}/f_{D_d}$, and then $(f_{B_s}/f_{B_d})\, /\, (f_{D_s}/f_{D_d})$. In this method we also obtain the ratio $f_{B_s}/f_{D_s}$ and $f_{B_d}/f_{D_d}$ which are important for the knowledge of CP violation and $B$-$\bar{B}$ mixing.Comment: 9 pages, 1 Postscript figur

A Dicationic Calix 4 Pyrrole Derivative and Its Use for the Selective Recognition and Displacement-Based Sensing of Pyrophosphate

A new bis-pyridinium calix[4] pyrrole derivative is reported. This system forms a non-fluorescent complex upon exposure to the chromenolate anion. The resulting supramolecular ensemble binds the pyrophosphate anion with high affinity (K-a (2.55 +/- 0.12) x 10(7) M-1) in acetonitrile. It exhibits sensitive "turn-on" fluorescence when exposed to tetrabutylammonium pyrophosphate, and does so in preference to other anions, including the fluoride and phosphate anions.NRF 2009-0087013BK21 programNational Science Foundation NSF CHE-1057904Chemistr