Youngsub Kim

Copeptin in Hemodialysis Patients with Left Ventricular Dysfunction.

Purpose Copeptin has been considered as a useful marker for diagnosis and prediction of prognosis in heart diseases. However, copeptin has not been investigated sufficiently in hemodialysis patients. This study aimed to investigate the general features of copeptin in hemodialysis and to examine the usefulness of copeptin in hemodialysis patients with left ventricular dysfunction (LV dysfunction). Materials and Methods This study included 41 patients on regular hemodialysis. Routine laboratory data and peptides such as the N-terminal of the prohormone brain natriuretic peptide and copeptin were measured on the day of hemodialysis. Body fluid volume was estimated by bioimpedance spectroscopy, and the E/Ea ratio was estimated by echocardiography. Results Copeptin increased to 171.4 pg/mL before hemodialysis. The copeptin had a positive correlation with pre-dialysis body fluid volume (r=0.314; p=0.04). The copeptin level decreased along with body fluid volume and plasma osmolality during hemodialysis. The copeptin increased in the patients with LV dysfunction more than in those with normal LV function (218.7 pg/mL vs. 77.6 pg/mL; p=0.01). Receiver operating characteristic curve analysis showed that copeptin had a diagnostic value in the hemodialysis patients with LV dysfunction (area under curve 0.737; p=0.02) and that the cut-off value was 125.48 pg/mL (sensitivity 0.7, specificity 0.8, positive predictive value 0.9, negative predictive value 0.6). Conclusion Copeptin increases in hemodialysis patients and is higher in patients with LV dysfunction. We believe that copeptin can be a useful marker for the diagnosis of LV dysfunction in hemodialysis patients.

Analysis of Joint movements and muscle length during sit-to-stand at various sitting heights in the Korean elderly daily life

In this study, we analyzed the elderly joint movements and changes in muscle length during STS at various sitting heights through the motion analysis and the musculoskeletal modeling. Five elderly and five young were participated in this experiment. Three heights of sitting posture which could represent typical sitting in Korean daily life were chosen as table seat (42cm), bath seat (21cm) and bottom (0cm). As the results, the elderly showed both smaller knee/hip flexion and larger trunk flexion relatively in comparison to the young during table seat STS. The elderly also showed larger dorsi flexion and smaller ROM of knee, hip, trunk compared to the young during bath seat STS. Additionally, the elderly showed larger plantarflexion, hip flexion, smaller knee flexion and trunk flexion during the first half of bottom STS and larger knee flexion, hip flexion and trunk flexion during the second half of bottom STS. In addition, we could know contraction and relaxation characters of major muscles in lower limb during various STS through the analysis of changes in muscle length by musculoskeltal modeling.

Co-planar waveguide filter with ground perforation for ultra-wideband system

In this paper, a compact co-planar waveguide band-pass filter is proposed for ultra-wideband (UWB) communication systems by utilizing perforation in the ground layer. An aperture compensation technique is developed to control the coupling strength, since UWB filters require a strong coupling strength due to its wide bandwidth (> 50%). The coupling strength appears frequency-distributed and its maximum value rapidly rises as the aperture widens. Then, a pair of capacitively loaded line sections is inserted between two identical parallel coupled lines to formulate a new planar band-pass filter with multi-pole band-pass behavior. The predicted and measured results show attractive properties of the proposed filter with a pass-band of 3.1 to 5.0 GHz (50%), |S/sub 11/| < -18 dB, group delay 800 psec, insertion loss < 1 dB, and the size of 9 /spl times/ 9 mm/sup 2/.

A Virtual Impactor for Hydrodynamic Particle Classification

We demonstrate a passive hydrodynamic particle sorter, a micromachined virtual impactor, for classifying biological substances according to their size. The virtual impactor can classify particles from a fully chaotic mixture composed of various sized particle. The virtual impactor is fabricated through simple silicon bulk micromachining. For preliminary performance test, monodispersed V653 cells with diameter of 10 mum were classified. Percent deviation of the experimental result was 13% compared to the theoretical value. For verifying collection efficiency of the particle sorter, polystyrene beads with diameters of 3 mum and 15 mum were sorted. Collection efficiency of 3 mum polystyrene beads was 68%.

Manual vs. pressure-controlled facemask ventilation for anaesthetic induction in paralysed children: a randomised controlled trial.

During anaesthetic induction with a facemask, the inconsistent inspiratory flow with manual ventilation (MV) raises the peak airway pressure (PAP), which can be significantly higher than PAP during pressure‐controlled ventilation (PCV). In this study, PAP was compared between MV and PCV at the same tidal volume of 8–10 ml/kg during facemask ventilation for anaesthetic induction in children. The occurrence of gastric insufflation (GI) was evaluated with ultrasonography and stethoscopic auscultation.

Rectifier Design Using Distributed Greinacher Voltage Multiplier for High Frequency Wireless Power Transmission

This paper discusses the design of a high frequency Greinacher voltage multiplier as rectifier; it has a greater conversion efficiency and higher output direct current (DC) voltage at high power compared to a simple halfwave rectifier. Multiple diodes in the Greinacher voltage multiplier with distributed circuits consume excited power to the rectifier equally, thereby increasing the overall power capacity of the rectifier system. The proposed rectifiers are a Greinacher voltage doubler and a Greinacher voltage quadrupler, which consist of only diodes and distributed circuits for high frequency applications. For each rectifier, the RF-to-DC conversion efficiency and output DC voltage for each input power and load resistance are analyzed for the maximum conversion efficiency. The input power with maximum conversion efficiency of the designed Greinacher voltage doubler and quadrupler is 3 and 7 dB higher, respectively, than that of the halfwave rectifier.

RCS Characteristic of Electromagnetic Gradient Surface Due to Incident Angle and Polarization

In this paper, reflection and RCS characteristic of the EGS(Electromagnetic Gradient Surface) due to incident angle and polarization is analyzed. Incident angle, , is rotated from to with steps and perpendicular and parallel polarization of incident wave are also considered each incident angle. Reflection and RCS characteristic is not much affected by variation of polarization for normal incidence(

Development and Assessment of an EMG-Based Exoskeleton System

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Net Center of Pressure Analysis during Gait Initiation in Patient with Hemiplegia

An EMG-based exoskeleton system has been developed to assist the upper extremity function in patient with paralysis. A DC motor in the system controlled the elbow joint motion according to the predefined threshold levels of EMG signals from elbow flexor and extensors. The present EMG-based control method could provide active assistive exercises, resulting better rehabilitation program for hemiplegic patients.

Slot-Coupled Circularly Polarized Array Antenna With Substrate-Integrated Waveguide Cavity for Parallel-Plate-Mode Suppression

Gait initiation is a transitional process from the balanced upright standing to the beginning of steady-state walking. Steady-state walking represents the start of repeated gait pattern with steady-state walking speed within one gait cycle. Hemiplegic patients’ gait initiation was analyzed using the 3D motion analysis system synchronized with 2 force plates. The first vertex(V1) in the CoP trajectory was placed on the lateral-posterior point from the leading limb side, and the third vertex(V3) was placed on the lateral-anterior point from the trailing limb side in the CoP of the normal gait initiation. However, V1 was not nearly shown and V3 was placed on the posterior from the trailing limb side in the CoP of the hemiplegic gait initiation. The time and distance from the onset to the toe-off(P1) and from the toe-off to the initial contact( P2) were analyzed that the mean time was larger and the mean distance was shorter when the affected limb was leading limb. The net CoP data obtained on gait initiation with hemiplegic patients suggest that they compensated with different strategies with respect to the limb whether it was leading limb or trailing limb for their impairment.