Seokjun Hong

Sex differences in amygdala subregions: evidence from subregional shape analysis.

Each subregion of the amygdala is characterized by a distinct cytoarchitecture and function. However, most previous studies on sexual dimorphism and aging have assessed differences in the structure of the amygdala at the level of the amygdala in its entirety rather than at the subregional level. Using an amygdala subregional shape analysis, we investigated the effects of sex, age, and the sex × age interaction on the subregion after controlling for intracranial volume. We found the main effect of age in the subregions and the effect of sex in the superficial nucleus, which showed that men had a larger mean radius than women. We also found a sex × age interaction in the centromedial nucleus, in that the radius of the centromedial nucleus showed a steeper decline with age in women compared with men. Regarding the amygdala volume as a whole, we found only an age effect and did not find any other significant difference between genders. The sex difference in the amygdala subregion and its relevance to the circulating gonadal hormone were discussed.

Mechanical and electrical evaluation for the long-term stability of implanted 3D retinal microelectrode

In this paper, the mechanical and electrical characteristics of 3D microelectrode are presented to provide the long-term stability of the implanted microelectrode. As the dimensions of the microelectrode become smaller, the microelectrode can be easily damaged by mechanical pressure and over-injected electric charge. In order to avoid these destructions, allowable mechanical and electrical stress should be determined. Experiments for durability evaluation are set up and performed to measure the mechanical force and safe charge injection limit. The result of the experiments shows that the allowable mechanical force in vertical and horizontal direction is 0.8165 N and 0.2068 N, respectively. In the charge injection test, it is observed that the density of injected charge is a prior factor in microelectrode dissolution rather than the total amount of injected charge.

Biodegradable polymer droplet for efficient drug delivery using flagellated bacteria

This paper presents a biodegradable polymer droplet for efficient drug delivery using flagellated bacteria. The biodegradability and the localized delivery are the most important features for determining the efficiency of drug delivery. The proposed droplet is made of poly (DL-lactic-co-glycolic acid) for the biodegradability. It is fabricated using a microfluidic device which has a Y-junction microchannel. The fabricated biodegradable droplet has diameter in the range between 20 µm and 30 µm. Then flagellated bacteria, Serratia marcescens, are attached to these droplets for a localized drug delivery. The Serratia marcescens has a chemotaxis to tumor cells, and thus can be used as an actuation source of self-seeking to the tumor site. This paper presents the proposed concept, droplet fabrication, bacteria attachment, and observed rotational motion of the drug delivery methodology. The experimentally achieved maximum angular velocity is 0.11 rad/sec.

Laminated cubic biodegradable polymer structures for bacteria-based, robotic drug delivery

Recently, a bacteria-based drug delivery system has been proposed to achieve effective and localized drug delivery. Researchers have shown that flagellated bacteria have a chemotactic property to tumor cells, and they can be used as an energy source for active drug delivery. Our previous results have reported that a circular droplet made by a biodegradable polymer can be used in this bacteria-based, robotic drug delivery. In this paper, using laminated cubic structures made of several layers of biodegradable polymers for bacteria-based microrobot is proposed. The structures are made by laminating polymer layers and then, micromachining them using a deep X-ray synchrotron radiation into 40 μm x 40 μm x 40 μm cubes. The cubic structure is more beneficial in attaching bacteria in only selective surface directions than a circular structure, and in controlling the volume of drugs to be encapsulated with the outer polymer layer.

Experimental Methods for Trapping Ions Using Microfabricated Surface Ion Traps

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due to their long coherence time and their capability to manipulate and detect individual quantum bits (qubits). In more recent years, microfabricated surface ion traps have received more attention for large-scale integrated qubit platforms. This paper presents a microfabrication methodology for ion traps using micro-electro-mechanical system (MEMS) technology, including the fabrication method for a 14 µm-thick dielectric layer and metal overhang structures atop the dielectric layer. In addition, an experimental procedure for trapping ytterbium (Yb) ions of isotope 174 (174Yb+) using 369.5 nm, 399 nm, and 935 nm diode lasers is described. These methodologies and procedures involve many scientific and engineering disciplines, and this paper first presents the detailed experimental procedures. The methods discussed in this paper can easily be extended to the trapping of Yb ions of isotope 171 (171Yb+) and to the manipulation of qubits.

Guidelines for Designing Surface Ion Traps Using the Boundary Element Method.

Ion traps can provide both physical implementation of quantum information processing and direct observation of quantum systems. Recently, surface ion traps have been developed using microfabrication technologies and are considered to be a promising platform for scalable quantum devices. This paper presents detailed guidelines for designing the electrodes of surface ion traps. First, we define and explain the key specifications including trap depth, q-parameter, secular frequency, and ion height. Then, we present a numerical-simulation-based design procedure, which involves determining the basic assumptions, determining the shape and size of the chip, designing the dimensions of the radio frequency (RF) electrode, and analyzing the direct current (DC) control voltages. As an example of this design procedure, we present a case study with tutorial-like explanations. The proposed design procedure can provide a practical guideline for designing the electrodes of surface ion traps.