Feasibility and safety of neck level IB-sparing radiotherapy in nasopharyngeal cancer: a long-term single institution analysis

Dowook Kim(Dowook Kim),Bhumsuk Keam(Bhumsuk Keam),Soon-Hyun Ahn(Soon-Hyun Ahn),Chang Heon Choi(Chang Heon Choi),Hong-Gyun Wu(Hong-Gyun Wu) 대한방사선종양학회 2022 Radiation Oncology Journal Vol.40 No.4

Purpose: Nasopharyngeal cancer (NPC) has a higher prevalence of regional nodal metastasis than other head and neck cancers; however, level IB lymph node involvement is rare. We evaluated the safety and feasibility of level IB-sparing radiotherapy (RT) for NPC patients. Materials and Methods: We retrospectively reviewed 236 patients with NPC who underwent definitive intensity-modulated RT with or without chemotherapy between 2004 and 2018. Of them, 212 received IB-sparing RT, and 24 received non-IB-sparing RT. We conducted a propensity score matching analysis to compare treatment outcomes according to IB-sparing status. In addition, dosimetric analysis of the salivary glands was performed to identify the relationship between xerostomia and the IB-sparing RT. Results: The median follow-up duration was 78 months (range, 7 to 194 months). Local, regional, and distant recurrences were observed in 11.9%, 6.8%, and 16.1% of patients, respectively. Of the 16 patients with regional recurrence, 14 underwent IB-sparing RT. The most common site categorization of regional recurrence was level II (75%), followed by retropharyngeal lymph nodes (43.8%); however, there was no recurrence at level IB. In the matched cohorts, IB-sparing RT was not significantly related to treatment outcomes. However, IB-sparing RT patients received a significantly lower mean ipsilateral and contralateral submandibular glands doses (all, p < 0.001) and had a lower incidence of chronic xerostomia compared with non-IB-sparing RT patients (p = 0.006). Conclusion: Our results demonstrated that IB-sparing RT is sufficiently safe and feasible for treating NPC. To reduce the occurrence of xerostomia, IB-sparing RT should be considered without compromising target coverage.

In-situ scanning tunneling microscopy observation of thickness-dependent air-sensitive layered materials and heterodevices

Kim Hyoung Kug,Kim Dowook,Lee Dong Guk,Ahn Eun-Su,Jeong Hyeon-Woo,Lee Gil-Ho,Kim Jun Sung,Kim Tae-Hwan 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.2

Quasi-two-dimensional (Quasi-2D) van der Waals (vdW) materials can be mechanically or chemically exfoliated down to monolayer because of their strong intralayer bonding and the weak interlayer vdW interaction. Thanks to this unique property, one can often fnd exotic thickness-dependent electronic properties from these quasi-2D vdW materials, which can lead to bandgap opening, emerging superconductivity, or enhanced charge density waves with decreasing thickness. Surface-sensitive scanning tunneling microscopy (STM) can provide direct observation of structural and electronic characteristics of such layered materials with atomic precision in real space. However, it is very challenging to preserve the intrinsic surfaces of air-sensitive quasi-2D materials between preparation and measurement. In addition, vdW 2D crystals after exfoliation are extremely hard to explore with a typical STM setup due to their small size (≤ 10 μm). Here, we present a straightforward method compatible with any STM setup having optical access: (1) exfoliating and/or stacking layered materials in a glove box, (2) transferring them to an ultra-high vacuum STM chamber using a suitcase without exposure to air, and (3) navigating surface to locate exfoliated vdW 2D fakes with diferent thicknesses. We successfully demonstrated that the clean surfaces of the air-sensitive Fe3GeTe2 can be efectively protected from unwanted oxidation during transfer. Furthermore, our method provides a simple but useful way to access a specifc tiny stack of layered materials without any ex-situ fabrication processes for STM navigation. Our experimental improvement will open up a new way to investigate air-sensitive layered vdW materials with various thicknesses via surface-sensitive techniques including STM.

Long-term outcomes of low-dose radiotherapy in Kasabach-Merritt syndrome

Dowook Kim,Jung Yoon Choi,Kyung Taek Hong,Hyoung Jin Kang,Il Han Kim,Joo Ho Lee 대한방사선종양학회 2022 Radiation Oncology Journal Vol.40 No.1

Purpose: Reports on results of radiation therapy (RT) for Kasabach-Merritt syndrome (KMS) are limited. We performed a retrospective study to evaluate the response rates and late complications and to determine the adequate RT dose for patients with KMS patients. Materials and Methods: We studied 11 patients who received RT between October 1988 and September 2008 for KMS refractory to pharmacologic therapy. All patients had external hemangiomas and received the diagnosis of KMS within 12 months of birth. All 11 patients received steroids as the first-line therapy; eight patients additionally received interferon-α therapy, and one patient underwent surgery. Nine patients underwent single-course RT with a total dose of 4.5-8 Gy (1.5-2 Gy/ fraction). Two patients received multiple courses of RT, with a cumulative total dose of 12 Gy (2 Gy/fraction) and 18 Gy (1.5 Gy/fraction), respectively. Results: The median follow-up period was 156 months (interquartile range [IQR], 75 to 226 months). The median total dose of RT was 6 Gy, and all patients maintained complete remission until the last follow-up. An additional course of RT was performed for refractory cases or cases of local relapse after initial RT. Rapid platelet count increase after RT was seen in most patients, which returned to normalcy in a median of 20 days (IQR, 5 to 178 days). However, seven patients experienced radiation-related long-term complications. Conclusion: Low-dose RT is effective and yields rapid response in patients with KMS. However, given growth-related late complications, RT should be carefully considered.

Scanning tunneling microscopy study of hidden phases in atomically thin 1T‑TaS2

Yang Wooin,Kim Dowook,Kim Hyoung Kug,Kim Tae-Hwan 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.3

Lower thermal stability due to thinning often leads to unprecedented hidden phases in low-dimensional materials. Such hidden phases can coexist or compete with preexisting electronic phases. We investigate hidden phases observed in atomically thin (6–8 layers) 1T-TaS2 with scanning tunneling microscopy. First, we can electrically induce a hidden stripe phase at room temperature. Such a uniaxial stripe phase has three equivalent orientations by breaking threefold symmetry of 1TTaS 2 . We also reveal that the hidden stripe phase coexists with nearly commensurate charge-density-wave phase. Next, we observe that the emergent stripe phase spontaneously appears without any electric excitation on a tiny flake ( 160 × 80 nm2 ). Our findings may provide a plausible explanation for the previously observed phase transition and twofold optical response in thin 1T-TaS2 devices at room temperature. Furthermore, the hidden stripe phase would be crucial to understand exotic CDW-related phenomena in 1T-TaS2 for potential applications.

Thickness dependent charge density wave networks on thin 1T‑TaS2

Yang Wooin,Kim Dowook,Kim Hyoung Kug,Kim Tae-Hwan 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.3

We investigate mechanically exfoliated thin 1T-TaS2 with scanning tunneling microscopy at room temperature. Sample preparation without air exposure enables access to intrinsic charge-density-wave (CDW) phases of thin 1T-TaS2. At room temperature, we can observe the expected nearly commensurate CDW (NCCDW) phase on thin fakes similar to bulk 1TTaS2. Further analysis reveals that CDW domains in the NCCDW phase become smaller and have a more anisotropic shape with decreasing thickness in the range of 8–28 layers. Our fndings demonstrate that the anisotropic CDW nature of thin 1T-TaS2 would be crucial to understand its exotic CDW-related phenomena and demand a systematic study on its correlation between the thickness-driven CDW domain anisotropy and the intermediate CDW states in thin 1T-TaS2.

무선 센서 네트워크에서 최소파워구성 방법을 이용한 선택적 웨이트 컨트롤 알고리즘

박도욱(Dowook park),김종권(Chongkwon Kim) 한국정보과학회 2006 한국정보과학회 학술발표논문집 Vol.33 No.2D

이 논문은 무선 센서 네트워크에서 최소 파워 구성 방법을 이용하여 에너지를 효율적으로 사용하면서 네트워크의 수명을 늘리고 지연(delay)을 줄이는 방안을 제시한다. 지금까지 에너지를 효율적으로 사용하기 위해 topology control, power-aware routing, sleep management 방법을 각각 독립적으로 연구되었는데 최소파워 구성은 위의 3가지 방법을 통합 최적화하여 에너지 효율적 사용 문제에 접근한다. 이러한 최소파워 구성 방법을 이용하여 선택적 웨이트 컨트롤(Selective weight control) 알고리즘을 제안하여 네트워크 전체 수명을 연장시키고 지연을 줄일 수 있다. 이 알고리즘은 각 노드가 주기적으로 잔류에너지를 인접노드들과 공유하여 에너지 랭크(rank)값을 유지한 상태에서 최소 에너지 경로를 사용하면서 에너지가 주위 노드들보다 작아질 때는 에너지가 많은 노드가 경로에 포함이 되도록 하여 특정 노드가 에너지 고갈되지 않고 네트워크내의 각 노드가 고르게 에너지를 소모하게 한다.

히스토그램과 확률을 이용한 차량 번호 검출 방법

김효연(Kim HyoYeon),정도욱(Jung DoWook),최형일(Choi HyungIl) 한국콘텐츠학회 2015 한국콘텐츠학회 종합학술대회 논문집 Vol.2015 No.5

Cyclometalated Platinum(II) Complexes Derived from a Chiral Pyridine Ligand: Synthesis, Structure, and Catalytic Activity

Myeong Sik Yoon,Dowook Ryu,Jeongryul Kim,Rengan Ramesh,안교한 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.11

A direct cyclometalation of a chiral pyridine derivative, (5R,7R)-5,6,7,8-tetrahydro-6,6-dimethyl-2-phenyl-5,7-methanoquinoline (L), with K2PtCl4 in acetic acid is described. A chiral mononuclear cyclometalated platinum(II) complex (6) was obtained, in which second L was simply coordinated by nitrogen. This new platinum(II) complex was characterized by 1H and 13C NMR spectroscopy, and further by X-ray crystallography. Both the solution and solid structures show C-H遜Cl hydrogen bonding, which explains a distorted square-planar geometry in the solid state. A reactive cationic platinum(II) species (8) was generated from the chloro complex by treatment with silver triflate, whose catalytic efficiency was evaluated in asymmetric aldol and silylcyanation reactions of aldehydes.

Crystal structure of recombinant human stromal cell-derived factor-1α

Ryu, Eui Kyung,Kim, Tae Gyun,Kwon, Taek Hun,Jung, In Duk,Ryu, Dowook,Park, Yeong-Min,Kim, Junhong,Ahn, Kyo Han,Ban, Changill Wiley Subscription Services, Inc., A Wiley Company 2007 Proteins Vol.67 No.4

<P>No. Abstract</P>

Combined thermal characteristics analysis of steam reforming and combustion for 5 kW domestic PEMFC system

Jo, Taehyun,Koo, Bonchan,Lee, Yonghan,Kim, Dowook,Lee, Dohyung Elsevier 2018 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.43 No.31

<P><B>Abstract</B></P> <P>A natural gas-based steam reformer for a domestic polymer electrolyte membrane fuel cell (PEMFC) system is thermodynamically analyzed with a special focus on the heat supply mechanism, which is critical to the endothermic steam reforming process. The interdependence of the reforming and combustion processes is evaluated through a characteristic study of heat transfer from the heat source to the reforming zone. Premixed combustion patterns may be affected by the inclusion of controlling means such as a metal fiber screen or burner placement. In this study, we attempted to enhance reforming performances of a reformer embedded in a 5 kW in-house PEMFC through modification of the combustion pattern by varying the type and placement of the burner and other operating conditions. Reforming input conditions such as steam-carbon ratio (SCR) and fuel distribution ratio (FDR) are also analyzed to quantify the overall performance such as thermal efficiency and fuel conversion rate. In our experiments involving three types of combustors—cylindrical metal fiber burner, flat type metal fiber burner and nozzle-mixing burner—the operating conditions are set so that the SCR and FDR are in the range 3.0–4.0 and 0.4–0.7, respectively. It is found that the cylindrical metal fiber burner at an appropriate location could improve thermal efficiency up to 79% by 10%, compared to other devices. This maximum thermal efficiency output is obtained with 0.63 FDR, which eventually yields 99% hydrogen conversion rate when using a cylindrical metal fiber burner, while the other burners produce 95% conversion. These outputs substantiate that the overall efficiency is strongly affected by an appropriate control for uniform temperature distribution on the catalyst layer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The steam reformer is experimentally studied in terms of operation conditions and the heat exchange between three type combustors and reactor. </LI> <LI> The CMFB could enhance the thermal efficiency by 10%, up to 79%, higher than the FMFB and Nozzle burner. </LI> <LI> Various correlations are discovered between SCR, FDR, internal temperature and performances throughout the experiments. </LI> <LI> The optimal fuel distribution ratio is considered as 0.63 that allows appropriate catalyst layer temperature and also best thermal efficiency. </LI> </UL> </P>