Wan-ho Lee

Two-photon absorption (TPA) cross sections of four representative series of octupolar molecules are theoretically investigated. The general structure--TPA-property relationship is described by using the effective four-state valence-bond three-charge-transfer model. As the charge-transfer character of the ground electronic state increases due to the strong donors or acceptors, (i) the transition dipole matrix elements between the ground and 2-fold degenerate excited states increase, (ii) the ener

We report the fabrication of a flexible graphene-based nonvolatile memory device using Pb(Zr0.35,Ti0.65)O3 (PZT) as the ferroelectric material. The graphene and PZT ferroelectric layers were deposited using chemical vapor deposition and sol–gel methods, respectively. Such PZT films show a high remnant polarization (Pr) of 30 μC cm−2 and a coercive voltage (Vc) of 3.5 V under a voltage loop over ±11 V. The graphene–PZT ferroelectric nonvolatile memory on a plastic substrate displayed an on/off cu

In this research, using direct measurements and Monte Carlo calculations, the potential dose reduction achieved by bismuth shielding in computed tomography was evaluated. The patient dose was measured using an ionisation chamber in a polymethylmethacrylate (PMMA) phantom that had five measurement points at the centre and periphery. Simulations were performed using the MCNPX code. For both the bare and the bismuth-shielded phantom, the differences of dose values between experiment and simulation

In this study, we evaluated the performance of a commercial pixelated cadmium zinc telluride (CZT) detector for spectroscopy and identified its feasibility as a Compton camera for radiation monitoring in a nuclear power plant. The detection system consisted of a 20 mm × 20 mm × 5 mm CZT crystal with 8 × 8 pixelated anodes and a common cathode, in addition to an application specific integrated circuit. The performance of the various radioisotopes 57Co, 133Ba, 22Na, and 137Cs was evaluated. In gen

Nuclear pre-mRNA editing by selective adenosine deamination (A-to-I editing) occurs in all organisms from C. elegans to humans. The nucleotide inosine (I) has been observed in viral transcripts and in eukaryotic mRNAs. Inosine derives the deamination of adenosine (A), a process termed RNA editing. Inosine is not only present in mRNA, but also in tRNA, and was first identified in tRNA from yeast.1 In the eukaryotes, seven to eight tRNAs contain I at position 34, whereas in prokaryotes and plant c

Strain engineering has been utilized to overcome the limitation of geometric scaling in Si-based thin-film transistor (TFT) technology by significantly improving carrier mobility. However, current strain engineering methods have several drawbacks: they generate atomic defects in the interface between Si and strain inducers, they involve high-cost epitaxial depositions and they are difficult to apply to flexible electronics with plastic substrates. Here, we report the formation of a strained Si m

We constructed a mini Compton camera based on an array of CdZnTe detectors and assessed its spectral and imaging properties. The entire array consisted of 6 ×6 Frisch-grid CdZnTe detectors, each with a size of 6 ×6 ×15 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Since it is easier and more practical to grow small CdZnTe crystals rather than large monolithic ones, constructing a mosaic array of parallelepiped crystals can be an effec

Since computed tomography (CT) was introduced about 40 y ago, its use has continuously grown, resulting in the increase of the CT dose. Therefore, an awareness of the CT dose and its potential complications has led to the development of several dose-reduction strategies. One of the strategies is automatic exposure control (AEC), which modulates radiation intensity depending on the patient size, z-axis thickness (Z-DOM) or angular thickness (D-DOM). Another dose-reduction method is the in-plane b

The patient dose incurred from diagnostic procedures during advanced radiotherapy has become an important issue. Many researchers in medical physics are using computational simulations to calculate complex parameters in experiments. However, extended computation times make it difficult for personal computers to run the conventional Monte Carlo method to simulate radiological images with high-flux photons such as images produced by computed tomography (CT). To minimize the computation time withou