IntraBrain Injector (IBI): A Stereotactic-Guided Device for Repeated Delivery of Therapeutic Agents Into the Brain Parenchyma

Jeongmin Lee,Sangwook Lee,Wooram Jung,Guk Bae Kim,Taehun Kim,Jiwon Seong,장혜민,Young Noh,Na Kyung Lee,Boo Rak Lee,Jung-Il Lee,Soo Jin Choi,Wonil Oh,Namkug Kim,Seunghoon Lee,Duk L. Na 대한의학회 2022 Journal of Korean medical science Vol.37 No.31

Background: To deliver therapeutics into the brain, it is imperative to overcome the issue of the blood-brain-barrier (BBB). One of the ways to circumvent the BBB is to administer therapeutics directly into the brain parenchyma. To enhance the treatment efficacy for chronic neurodegenerative disorders, repeated administration to the target location is required. However, this increases the number of operations that must be performed. In this study, we developed the IntraBrain Injector (IBI), a new implantable device to repeatedly deliver therapeutics into the brain parenchyma. Methods: We designed and fabricated IBI with medical grade materials, and evaluated the efficacy and safety of IBI in 9 beagles. The trajectory of IBI to the hippocampus was simulated prior to surgery and the device was implanted using 3D-printed adaptor and surgical guides. Ferumoxytol-labeled mesenchymal stem cells (MSCs) were injected into the hippocampus via IBI, and magnetic resonance images were taken before and after the administration to analyze the accuracy of repeated injection. Results: We compared the planned vs. insertion trajectory of IBI to the hippocampus. With a similarity of 0.990 ± 0.001 (mean ± standard deviation), precise targeting of IBI was confirmed by comparing planned vs. insertion trajectories of IBI. Multiple administrations of ferumoxytol-labeled MSCs into the hippocampus using IBI were both feasible and successful (success rate of 76.7%). Safety of initial IBI implantation, repeated administration of therapeutics, and long-term implantation have all been evaluated in this study. Conclusion: Precise and repeated delivery of therapeutics into the brain parenchyma can be done without performing additional surgeries via IBI implantation.

Polymorphic expressions of ultrathin oxidic layers of Mo on Au(111)

Lee, Taehun,Lee, Yun-Jae,Palotá,s, Krisztiá,n,Lee, Giyeok,Stampfl, Catherine,Soon, Aloysius The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.13

<P>Ultrathin oxidic layers of Mo (<I>i.e.</I> O/Mo) on the Au(111) substrate are investigated using first-principles density-functional theory calculations. Various polymorphic structural models of these O/Mo layers are proposed and compared with previous experimental results - covering both spectroscopic and microscopic approaches of characterization. We find that, through the control of metal-oxygen coordination in these ultrathin oxidic O/Mo films on Au(111), the oxidation state of Mo atoms in the O/Mo layers can be modulated and reduced without intentional creation of oxygen vacancies. This is also assisted by a charge transfer mechanism from the Au substrate to these oxidic films, providing a direct means to tune the surface electronic properties of ultrathinoxide films on metal substrates.</P>

Development of Integrated Chassis Control Algorithms to Improve Vehicle Dynamics

Taehun Hwang(황태훈),Kihong Park(박기홍),Seung-Jin Heo(허승진),Ji Yoel Joeng(정지열),Sangho Lee(이상호),Unkoo Lee(이언구),Kyu Hoon Lee(이규훈),Seung Guan Kee(기승관),Kangwon Lee(이강원) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Most electronic chassis control systems so far have been designed for optimization of its own performance. This, sometimes, has resulted in performance degradation when two or more control modules were operating together. Recently. great R&D effort is being given to judicious integration of individual chassis control systems in an effort to further enhance the overall vehicle performance. In this paper, two integrated control logics - one that integrates the brake and suspension control systems and the other that integrates the brake and steering control systems - have been developed. The main control target of both logics is vehicle dynamics control under critical situations. The two logics were tested under various driving conditions in a reliable simulation environment and their synergetic effects were investigated. The results indicate that the proposed logics can yield better vehicle performance than the cases when the individual chassis control modules work without any integration scheme.

A 103.125-Gb/s Reverse Gearbox IC in 40-nm CMOS for Supporting Legacy 10- and 40-GbE Links

Yoon, Taehun,Lee, Joon-Yeong,Lee, Jinhee,Han, Kwangseok,Lee, Jeong-Sup,Lee, Sangeun,Kim, Taeho,Han, Jinho,Won, Hyosup,Park, Jinho,Bae, Hyeon-Min IEEE 2017 IEEE journal of solid-state circuits Vol.52 No.3

<P>This paper presents the first 103.125-Gb/s multilink gearbox (MLG) IC, which facilitates the transport of independent 10-and 40-GbE signals to 4 x 25.78 Gb/s physical layers, such as 100GBASE-xR4. The IC consumes only 1.37 W while implementing complicated reverse gearbox functionality. The measured TX jitter from 10- and 25-G lanes is 0.407 and 0.448 psrms, respectively. The measured input sensitivities for a BER of 10(-1)2 of the 10- and 25-G RXs are 20 and 42 mVppd, respectively. The proposed gearbox IC, fabricated in a 40-nm CMOS process, occupies 3.7x3.4 mm(2). The power consumption of RX and TX in a 25-G interface is 50.9 and 52 mW, respectively, and those of a 10-G interface are 29 and 24.4 mW, respectively. MLG functionality is verified using embedded self-test logics.</P>

A Power-and-Area Efficient <tex> $10\times 10$</tex> Gb/s Bootstrap Transceiver in 40 nm CMOS for Referenceless and Lane-Independent Operation

Lee, Joon-Yeong,Han, Kwangseok,Yoon, Taehun,Kim, Taeho,Lee, Sang-Eun,Lee, Jeong-Sup,Park, Jinho,Bae, Hyeon-Min IEEE 2016 IEEE journal of solid-state circuits Vol.51 No.10

<P>A phase interpolator (PI)-based 10 x10 Gb/s bootstrap transceiver for referenceless and lane-independent operation is presented. PI output clock signals phase locked to the input data are used as reference clock signals for frequency locking the voltage-controlled oscillator (VCO). The VCO clock signal is then redistributed to the PIs, triggering the bootstrapping between the VCO and the PIs. All lanes operate independently as in VCO-based parallel referenceless designs while saving power and area. The measured recovered-data jitter in each lane is 0.93 ps(rms) and the transceiver passes the OC-192 jitter-tolerance specification. A flip-chip packaged test chip is fabricated in a 40 nm CMOS technology. The test chip achieves figure-of-merits (mW/Gbps) of 2.03 and 2.13 for the receiver and the transmitter, respectively.</P>

Multilevel Model for Ramp Crash Frequency that Reflects Heterogeneity Among Ramp Types

Taehun Lee,Yoon-Young Choi,Seung-Young Kho,Dong-Kyu Kim 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.1

Freeway ramps on a trumpet interchange are classified into six types by their configuration (loop-, direct-, and semi-direct-) and function (on-/off-). Since the effects of crash factors vary for different ramp types, each ramp type has different characteristics for crash occurrence, and this yields heterogeneity among ramp types. Therefore, this study compares the effects of crash factors that vary for different ramp types by developing a multilevel model that reflects the heterogeneity of crashes among ramp types. Based on 1,155 ramp crashes data over a four-year period, three multilevel models with two hierarchies were estimated; an unconditional model, a random coefficients regression model, and a full random coefficients model. The fixed effects of models indicated that offramps are more vulnerable to crash than on-ramps, and crash frequency increases as AADT increases and/or ramp length shortens. The results also implied that the ramp length has different effects on crashes according to ramp types. The random effects showed that the intra-class correlation was 0.185, indicating that 18.5% of the total variance is contributed to the heterogeneity among different ramp types. The findings from the estimated models provide an enhanced understanding about ramp crashes and contribute to the safe design and maintenance of freeway ramps.

Polymer Quantum Dot-Sensitized Solar Cell Incorporating Single-Walled Carbon Nanotubes

Lee, Junyoung,Lee, Jongtaek,Yang, Jonghee,Park, Taehun,Ahn, Sang Jung,Yi, Whikun American Scientific Publishers 2017 Journal of nanoscience and nanotechnology Vol.17 No.8

<P>Regioregular poly(3-hexylthiophene) (P3HT) of conjugated polymer is known to be p-type hole transports material. P3HT is used as a material to substitute for the liquid electrolyte in the quantum dot-sensitized solar cells (QDSSCs). In order to gain high performance of the cell, three different cells using P3HT, pristine P3HT, single-walled carbon nanotube (SWNT)-mixed P3HT (mixing), and SWNT-blended P3HT (blended) are made and their photovoltaic cells measure J-V curve, incident photon to current efficiency, and electrochemical impedance spectroscopy. Those values obtained from experiments are compared with each other.</P>

Over-Stoichiometry in Heavy Metal Oxides: The Case of Iono-Covalent Tantalum Trioxides

Lee, Yun-Jae,Lee, Taehun,Soon, Aloysius American Chemical Society 2018 Inorganic chemistry Vol.57 No.10

<P>Oxides of tantalum (common examples including TaO, TaO<SUB>2</SUB>, and Ta<SUB>2</SUB>O<SUB>5</SUB>) are key oxide materials for modern electronic devices, such as dynamic random-access memory and field effect transistors. Of late, new forms of stable tantalum oxides have been proposed as two-dimensional nanosheet structures with a nonconventional stoichiometry of TaO<SUB>3</SUB> via soft-chemical delamination of RbTaO<SUB>3</SUB>. However, not much is known about the elusive nanosheet-structured TaO<SUB>3</SUB>, unlike other closely related common trioxides of W and Mo. In this work, using first-principles density functional theory calculations, we have studied various TaO<SUB>3</SUB> structures as inspired from previous theoretical and experimental studies and discuss their properties with respect to the more conventional oxide of tantalum, Ta<SUB>2</SUB>O<SUB>5</SUB>. We have calculated their thermodynamics and lattice properties and have found a new stable-layered β-TaO<SUB>3</SUB> and its exfoliated monolayer phase (β′). By further analyzing their electronic structures, we discuss the mixed iono-covalent bonding characteristics in the TaO<SUB>3</SUB> phases, challenging the conventional formal oxidation state model for metal oxides. Finally, we propose how these new TaO<SUB>3</SUB> oxide materials may be potentially useful in photodevice applications.</P><P>In this work, using first-principles density functional theory calculations, we have studied the lattice properties and thermodynamics of various over-stoichiometric TaO<SUB>3</SUB> structures. Here, we report a new stable-layered phase (β-TaO<SUB>3</SUB>) and its exfoliated monolayer phase (β′-TaO<SUB>3</SUB>). By further analyzing their electronic structures, we discuss the mixed iono-covalent bonding characteristics in the TaO<SUB>3</SUB> phases, challenging the conventional formal oxidation state model for metal oxides. Finally, we propose how these new TaO<SUB>3</SUB> oxide materials may be potentially useful in photodevice applications.</P> [FIG OMISSION]</BR>

Polytypism in Hexagonal Tungsten Trioxide: Insights from Ab Initio Molecular Dynamics Simulations

Lee, Yonghyuk,Lee, Taehun,Soon, Aloysius American Chemical Society 2018 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.122 No.37

<P>Temperature-dependent microstructural evolution of hexagonal WO<SUB>3</SUB> (<I>h</I>-WO<SUB>3</SUB>) polytypes is explored via ab initio molecular dynamics calculations within the density-functional theory framework. We present simulated finite temperature radial distribution function and X-ray diffraction patterns to reinterpret recent experimental pair distribution function analysis. This work clearly demonstrates that after a more careful analysis of the finite temperature structural properties of <I>h</I>-WO<SUB>3</SUB>, an intermediate H1-like structure is predicted at higher temperatures, while the more stable H4 polytype (and not the experimentally suggested H2 polytype) is obtained nearer ambient temperatures. This is further corroborated by our electronic structure analysis which shows that the electronic band gap energy of the ambient temperature H4-like structure agrees much better with the experimentally reported band gap energies.</P> [FIG OMISSION]</BR>

Unraveling the Intercalation Chemistry of Hexagonal Tungsten Bronze and Its Optical Responses

Lee, Yonghyuk,Lee, Taehun,Jang, Woosun,Soon, Aloysius American Chemical Society 2016 Chemistry of materials Vol.28 No.13

<P>In an attempt to promote energy saving through the clever control of varying amounts of visible light and solar energy in modern buildings, there has been a surge of interest in the novel design of multifunctional glass windows otherwise known as smart windows. The use of chromogenic materials (e.g., tungsten oxides and their alloys) is widespread in this cooling energy technology, and for the case of hexagonal tungsten oxide (h-WO3)-based systems, the overall efficiency is often hindered by the lack of a systematic and fundamental understanding of the interplay of intrinsic charge transfer between the alkali-metal ions and the host h-WO3. In this work, we present a first-principles hybrid density-functional theory investigation of bulk hexagonal tungsten bronzes (i.e., alkali-metal-intercalated h-WO3) and examine the influence of the intercalation chemistry on their thermodynamic stability as well as optoelectronic properties. We find that the introduction of the alkali-metal ion induces a persistent n-type electronic conductivity, and dramatically reduces the optical transmittance (down to similar to 28%) for infrared wavelengths while maintaining fair optical transparency for next-generation electrochromic devices in very energy efficient chromogenic device technology.</P>