D. J. Park

Predictors of operative morbidity and mortality in gastric cancer surgery

The aim of this study was to identify factors that predict morbidity and mortality in gastric cancer surgery.

Changes in clinicopathological features and survival after gastrectomy for gastric cancer over a 20-year period.

The pattern of gastric cancer in the Western world is changing, with an increased proportion of tumours in the upper stomach. The aim of this study was to investigate changes in clinicopathological features and survival of patients with resected gastric cancer at a single institution, in an area of high incidence in the Far East.

Shape resonance omni-directional terahertz filters with near-unity transmittance

Terahertz transmission filters have been manufactured by perforating metal films with various geometric shapes using femtosecond laser machining. Two dimensional arrays of square, circular, rectangular, c-shaped, and epsilon-shaped holes all support over 99% transmission at specific frequencies determined by geometric shape, symmetry, polarization, and lattice constant. Our results show that plasmonic structures with different geometric shaped holes are extremely versatile, dependable, easy to control and easy to make terahertz filters.

Safety of extended endoscopic mucosal resection and endoscopic submucosal dissection following the Japanese Gastric Cancer Association treatment guidelines.

Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) are widely performed. Indications for these procedures have been extended in Korea and Japan. The aim was to evaluate whether these extended indications are safe.

Terahertz transparency at Fabry-Perot resonances of periodic slit arrays in a metal plate: experiment and theory

We report on a terahertz transparency in periodic arrays of metallic slits using terahertz time- domain spectroscopy. Experimental results and theoretical calculations reveal that Fabry-Perot resonance appearing in spectral region below first Rayleigh minimum strongly enhances terahertz transmission and a symmetric eigenmode inside the slits is excited under the condition of terahertz transparency.

Intraoperative gastroscopy for gastric surgery.

Background:Few reports are available on the use of intraoperative gastroscopy for gastric surgery.Methods:The details of 33 patients (25 early gastric cancers and eight gastric submucosal tumors) who underwent intraoperative gastroscopy from June 2003 to June 2004 were analyzed. The type of operation or resection margin was determined by evaluating both sides of the stomach simultaneously by combined operative and gastroscopic methods.Results:Preoperative endoscopic clipping was done preferentially for early gastric cancer. However, when precise localization was needed, intraoperative gastroscopy was used. Curative gastric resection was possible in 25 early gastric cancer patients after accurate lesion localization. Laparoscopic wedge resections of submucosal tumors were performed in seven patients without stenosis by combined laparoscopic and gastroscopic methods.Conclusions:Intraoperative gastroscopy can be used effectively during gastric surgery for early gastric cancer or submucosal tumors and can be regarded as a modern stethoscope to gastric surgeons.

Terahertz near-field enhancement in narrow rectangular apertures on metal film

We report huge field accumulations in rectangular aperture arrays on thin metal film by using shape resonance in THz frequency region. A huge far-field transmission enhancement is observed in samples of various widths ranging from 10 mum to 1.8 mum which correspond to only an order of lambda/100. Theoretical calculations based on vector diffraction theory indicates 230 times near-field enhancement in case of the 1.8 mum wide rectangular aperture. Transmission measurement through the single rectangular aperture shows that the shape resonance, not the periodicity, is mainly responsible for the transmission enhancement and the corresponding field enhancement.

Femtosecond phase control of spatial localization of the optical near-field in a metal nanoslit array

We demonstrate spatial control of optical near-fields by femtosecond phase shaping in one-dimensional plasmonic structures. The near-field images display striking temporal-phase dependence, switching between double- and single-peak images within one lattice constant. The change of the near-field distribution is studied in the time and spectral domain. The spectral composition change observed by varying the time delay between two phase-locked femtosecond pulses explains the spatial control of the near-field images. Modal expansion calculations of linear light transmission using the surface impedance boundary condition are in excellent agreement with experiments.

Near-to-far-field spectral evolution in a plasmonic crystal: Experimental verification of the equipartition of diffraction orders

We report on drastic changes in the near-field spectrum as it evolves into the far field in periodically corrugated metallic nanoslit arrays. The far-field spectral minimum is located exactly at the near-field spectral maximum, where a quasimonochromatic standing wave pattern is observed in the near field. These results are in excellent agreement with the equipartition of diffraction orders recently proposed [K. G. Lee and Q-Han Park, Phys. Rev. Lett. 95, 103902 (2005)].

Characterization of chemical doping of graphene by in-situ Raman spectroscopy

We explored single-layer graphene and graphene field-effect transistors immersed in nitric acid using in-situ Raman spectroscopy. Two distinct stages were observed in the chemical doping process. The first stage involved blue shifts of the G and 2D peaks, whose saturation occurred rapidly with a time constant in the range of 10–25 s depending on the molar concentration of the acid. In the second stage, the intensity of the D peak, which was associated with structural defect formation, increased for a relatively long period of time. Since the major doping effects appeared during the first stage, the optimal doping conditions under which no noticeable structural defect formation occurred can be determined by monitoring the frequency shift. Transient doping concentrations along with structural defect densities were obtained from the Raman peak positions and intensities. We found that the doping-induced shift in the Dirac point in graphene field-effect transistors exhibited a fast response with respect to fre...