Jung-Hyu Shin

Facial identification in very low-resolution images simulating prosthetic vision

Familiar facial identification is important to blind or visually impaired patients and can be achieved using a retinal prosthesis. Nevertheless, there are limitations in delivering the facial images with a resolution sufficient to distinguish facial features, such as eyes and nose, through multichannel electrode arrays used in current visual prostheses. This study verifies the feasibility of familiar facial identification under low-resolution prosthetic vision and proposes an edge-enhancement method to deliver more visual information that is of higher quality. We first generated a contrast-enhanced image and an edge image by applying the Sobel edge detector and blocked each of them by averaging. Then, we subtracted the blocked edge image from the blocked contrast-enhanced image and produced a pixelized image imitating an array of phosphenes. Before subtraction, every gray value of the edge images was weighted as 50% (mode 2), 75% (mode 3) and 100% (mode 4). In mode 1, the facial image was blocked and pixelized with no further processing. The most successful identification was achieved with mode 3 at every resolution in terms of identification index, which covers both accuracy and correct response time. We also found that the subjects recognized a distinctive face especially more accurately and faster than the other given facial images even under low-resolution prosthetic vision. Every subject could identify familiar faces even in very low-resolution images. And the proposed edge-enhancement method seemed to contribute to intermediate-stage visual prostheses.

Synthesis of tetrakis(multifluoro-4-pyridyl)porphin derivatives as acetylcholinesterase inhibitors.

New tetrakis(multifluoro-4-pyridyl)porphin derivatives (2-4) and water soluble porphyrin (5) were synthesized to investigate their interactions with acetylcholinesterase from electric eel. These compounds have been found to be the potent reversible inhibitors of the enzyme with Ki values of microM range. In addition, porphyrin (5) showed broad spectrum of anticancer activities.

Solution structure of p21Waf1/Cip1/Sdi1 C-terminal domain bound to Cdk4

Abstract Cyclin-dependent kinase (Cdk) inhibitor p21Waf1/Cip1/Sdi1 a multifunctional protein, has a major role as tumor suppressor, mediating G1/S arrest through inhibition of Cdks. Recent biological studies of Cyclin D1/Cdk4 have proposed that p21 C-terminal domain (p21CT) plays a key role as a potent Cdk4 inhibitor. We report here solution structures of p21CT for both the free and Cdk4-bound forms using 2D transferred NOE spectroscopy and dynamical simulated annealing calculations. Even though p21CT peptide is very flexible in the free state, when it bound to Cdk4, the structure becomes well structured in the binding domain. Therefore we propose that p21CT experiences an extensive conformational change upon Cdk4 binding. This structural change of p21CT may suggest the molecular mechanism of p21 for specificity and inhibition mode to assemble different cyclin-Cdk complexes. Especially, our data suggests that the D149FYHSKRR156 region of p21 is critical for Cdk4 binding, indicating that the major driving force for complex originates from hydrophobic interaction between p21 and Cdk4.

Facile synthesis of 2-O-iodoacetyl protected glycosyl iodides: useful precursors of 1-->2-linked 1,2-trans-glycosides.

The preparation and utilization of novel iodide glycosyl donors, 2-O-iodoacetyl-glycopyranosyl iodides, is described. The mechanism for the reaction of iodine with carbohydrate cyclic ketene acetal was investigated through low-temperature NMR experiments. 2-O-Iodoacetyl-glycopyranosyl iodides can serve as effective glycosyl donors giving 2-O-iodoacetyl 1,2-trans-glycosides in high yields and excellent stereoselectivities. The 2-O-iodoacetyl group was removed selectively with thiourea to afford 2-hydroxy 1,2-trans-glycosides in high yield without affecting other protecting groups and anomeric configurations.

THERMAL REARRANGEMENT OF N-BENZYLANILINIUM HEXAFLUOROANTIMONATES

Abstract We prepared p-substituted N-benzylanilinium hexafluoroantimonates, known cationic initiators, and examined their thermal reaction. The thermal reaction produced 2- or 4-benzylanilinium salts as the major products, which resulted from the rearrangement of the benzyl group. The reaction proceeded at lower temperature with higher yield when the substituent in the benzyl group was electron donating.

Spatiotemporal pixelization Method Based on Vertical Sub-sampling to Improve Reading Ability for Visual Prosthesis

We proposed the spatiotemporal pixelization method based on vertical sub-sampling to improve reading ability for visual prosthesis. To evaluate proposed method, we simulated a test of reading performance of visual prosthesis with five different frame rates at 8×8 pixel arrays. The proposed method showed better reading performance than static pixelization method. The maximum reading speed was found at 50Hz of spatiotemporal pixelization method.

Direct observation of 9-benzonorbornenyl cations

The 9-methyl-, 9-p-fluorophenyl and 9-hydroxy-benzonorbornenyl cations are prepared in superacid media and characterized by NMR spectroscopy and quenching experiments.

19 F NMR study on pentacyclo[4.3.0.02,3.03,8.05,7]nonanyl and tetracyclo[3.3.1.02,8.04,6]nonanyl cation

By comparison of the 19F chemical shift of p-fluorophenyl substituted Coates cation 1 with that of triasteryl cation 2, πσ-participation by the remote cyclopropyl group in ion 1 is shown to be more effective than σ-participation by the adjacent cyclopropyl group in ion 2 in the delocalization of positive charge.