Jun Seok Kim

ODTPC: On-demand Transmission Power Control for Wireless Sensor Networks

Development of efficient transmission power control algorithms providing both high energy efficiency and good link quality is the current major focus in wireless sensor networks research. In the paper, we propose an efficient transmission power control algorithm for wireless sensor networks, namely, the on-demand transmission power control (ODTPC) algorithm. This new algorithm attempts to reduce the initialization overhead in determining the optimal transmission power level while providing good link qualities. Our testbed experiment results show that ODTPC consumes much less energy than previous transmission power control algorithms (PCBL ( D. Son,et al.) and ATPC (S. Lin, et al.)) and is easily implemented with routing protocols like AODV (C. Perkin, and E. Royer) and Directed Diffusion (C. Intanagonwiwat, et al.).

Interference-aware topology control for low rate wireless personal area networks

The topology control technique can prolong the network lifetime, but it can suffer the significant performance degradation due to the interferences of WLAN or Bluetooth devices. This paper proposes a novel topology control algorithm to reduce the interference effects. The basic idea of the proposed algorithm is to estimate the interference effects exactly and re-construct the robust network topology to the interference variations. From the experimental results, we can see that the proposed algorithm shows the good performance results in terms of the delivery ratio and the energy consumptions.

Efficacy and Safety of Dexmedetomidine for Postoperative Delirium in Adult Cardiac Surgery on Cardiopulmonary Bypass

Background Delirium after cardiac surgery is associated with serious long-term negative outcomes and high costs. The aim of this study is to evaluate neurobehavioral, hemodynamic, and sedative characteristics of dexmedetomidine, compared with the current postoperative sedative protocol (remifentanil) in patients undergoing open heart surgery with cardiopulmonary bypass (CPB). Methods One hundred and forty two eligible patients who underwent cardiac surgery on CPB between April 2012 and March 2013 were randomly divided into two groups. Patients received either dexmedetomidine (range, 0.2 to 0.8 μg/kg/hr; n=67) or remifentanil (range, 1,000 to 2,500 μg/hr, n=75). The primary end point was the prevalence of delirium estimated daily via the confusion assessment method for intensive care. Results When the delirium incidence was compared with the dexmedetomidine group (6 of 67 patients, 8.96%) and the remifentanil group (17 of 75 patients, 22.67%) it was found to be significantly less in the dexmedetomidine group (p<0.05). There were no statistically significant differences between two groups in the extubation time, ICU stay, total hospital stay, and other postoperative complications including hemodynamic side effects. Conclusion This preliminary study suggests that dexmedetomidine as a postoperative sedative agent is as sociated with significantly lower rates of delirium after cardiac surgery.

Outcomes of Alpha 1,3-GT-knockout Porcine Heart Transplants Into a Preclinical Nonhuman Primate Model

BACKGROUND Solid organ xenotransplantation is a potential solution to current organ shortages in allotransplantation. We performed four heart transplantations from alpha1, 3-galactosyltransferase gene-knockout (GT-KO) pigs to cynomolgus monkeys and monitored immunological parameters before and after transplantation. METHODS After blood typing of the cynomolgus monkeys, we assessed the binding activity of immunoglobulin G (IgG) and IgM of monkey serum and serum toxicity toward porcine peripheral blood mononuclear cells (PBMCs) using flow cytometry. Immunosuppressive protocols consisted of anti-thymocyte globulin (25 mg/kg), rituximab (20 mg/kg), anti-CD154mAb (20 mg/kg), cobra venom factor (0.05 mg/kg), tacrolimus, and steroid. Cynomolgus monkeys with A or AB blood type with the lowest antibody binding and serum toxicity activity on porcine PBMCs were selected as recipients. RESULTS Absolute numbers of CD3(+) T cells, CD20(+) B cells, and CD3(+)CD95(+) memory T cells in the peripheral blood were suppressed upto 24 days after transplantation. Interferon gamma production of T cells in response to porcine antigens were also significantly suppressed. Heart xenografts from GT-KO pigs survived for upto 24 days without pathologic evidence of rejection. CONCLUSION We successfully performed 4 heart xenotransplantations using GT-KO pigs. We overcame hyperacute rejection by using GT-KO pigs, and all of the heart xenografts from the GT-KO pigs survived between 11 and 24 days without pathologic evidence of rejection, disseminated intravascular coagulation, or consumptive coagulopathy; however, we need to optimize protocols for immune modulation and postoperative care to attain long-term survival of solid organ xenografts.

The Primary Patency and Fracture Rates of Self-Expandable Nitinol Stents Placed in the Popliteal Arteries, Especially in the P2 and P3 Segments, in Korean Patients

Objective We wanted to evaluate the status of self-expandable nitinol stents implanted in the P2 and P3 segments of the popliteal artery in Korean patients. Materials and Methods We retrospectively analyzed 189 consecutive patients who underwent endovascular treatment for stenoocclusive lesions in the femoropopliteal artery from July 2003 to March 2009, and 18 patients who underwent stent placement in popliteal arterial P2 and P3 segments were finally enrolled. Lesion patency was evaluated by ultrasound or CT angiography, and stent fracture was assessed by plain X-rays at 1, 3, 6 and 12 months and annually thereafter. Results At the 1-month follow-up, stent fracture (Type 2) was seen in one limb (up to P3, 1 of 18, 6%) and it was identified in seven limbs at the 3-month follow-up (Type 2, Type 3, Type 4) (n = 1: up to P2; n = 6: P3). At the 6-month follow-up, one more fracture (Type 1) (up to P3) was noted. At the 1-year follow-up, there were no additional stent fractures. Just four limbs (up to P2) at the 2-year follow-up did not have stent fracture. The primary patency was 94%, 61% and 44% at 1, 3 and 6 months, respectively, and the group with stent implantation up to P3 had a higher fracture rate than that of the group that underwent stenting up to P2 (p < 0.05). Conclusion We suggest that stent placement up to the popliteal arterial P3 segment and over P2 in an Asian population can worsen the stent patency owing to stent fracture. It may be necessary to develop a stent design and structure for the Asian population that can resist the bending force in the knee joint.

Interference-Aware Transmission Power Control for Wireless Sensor Networks

Maintaining the lowest possible transmission power in the wireless sensor networks (WSNs) is vulnerable to the interference fluctuations because of the bad signal-to-interference-plus-noise-ratio (SINR). The previous transmission power control (TPC) algorithms do not consider much for the interferences from other 2.4GHz devices, which can cause significant performance degradations in real world deployments. This paper proposes the interference-aware transmission power control (I-TPC) algorithm for WSNs. In the proposed algorithm, each node dynamically adjusts the transmission power and the received signal strength (RSS) target, hence the appropriate SINR is provided even when the wireless LAN (WLAN) interferences become strong. The experimental results show that the proposed algorithm outperforms the previous algorithms in terms of the energy and the packet reception ratio (PRR) performance in WLAN interference environments.

Clinical outcomes of endovascular treatments for critical limb ischemia with chronic total occlusive lesions limited to below-the-knee arteries

Background Diabetes mellitus tends to have the greatest impact on the smaller vessels and contributes significantly to occlusive disease from the popliteal artery distally. Purpose To evaluate the clinical outcomes after a balloon angioplasty with or without stent placement in diabetic patients with critical limb ischemia (CLI) by chronic total occlusion (CTO) limited to below-the-knee (BTK) arteries. Material and Methods From August 2005, patients who presented CLI and CTO limited to the BTK arteries, and who underwent endovascular treatment, were included in this study. The primary endpoints evaluated were technical success, limb salvage, and primary patency. The secondary endpoints evaluated were 30-day access site, intervention site, and systemic complications. Patency and limb salvage were evaluated using the Kaplan-Meier method and compared using Fishers exact test. Results The BTK endovascular treatment (EVT) was performed on 64 limbs. Technical success rate was 93.8% and limb salvage rate was 90.6%. Three of four limbs with technical failure and three of 60 limbs with technical success underwent BTK amputation and the comparison of these rates were significantly different (75% vs. 5%, P = 0.002). Primary patency rates for the limbs were 75% and 59.1% at 6-month and 12-month follow-up, respectively. Minor complications disappeared through the follow-up periods and there was no 30-day complication or systemic adverse events for the treated vessel. Conclusion Even though EVT for CLI in patients with diabetes and CTO in isolated BTK arteries does not have comparable primary patency, it can lead to a very high rate of limb salvage. This result can accentuate the importance of more blood flow to the foot by means of successful revascularization using EVT rather than long-term patency in CTO of isolated BTK arteries.

The 1,470-nm Bare-Fiber Diode Laser Ablation of the Great Saphenous Vein and Small Saphenous Vein at 1-Year Follow-up Using 8-12 W and a Mean Linear Endovenous Energy Density of 72 J/cm

PURPOSE To demonstrate 1-year outcomes after low-energy endovenous laser ablation (EVLA) of incompetent saphenous veins with linear endovenous energy density (LEED) of 80 J/cm or lower with the use of a 1,470-nm diode laser. MATERIALS AND METHODS Incompetent saphenous veins in 236 patients (355 limbs; Clinical/Etiology/Anatomy/Pathophysiology classifications of C2-C4) were treated by EVLA with a bare-tipped 1,470-nm laser with LEED no greater than 80 J/cm (mean, 72.4 J/cm) and laser power of 8-12 W. Patients were evaluated clinically and with duplex ultrasonography at 1 week and 1, 3, 6, and 12 months after EVLA to assess the technical and clinical success and complication rates. RESULTS In the 355 limbs, the technical success rate was 100%. The great saphenous vein (GSV) remained occluded in all 229 limbs (100%) after 1 week, 202 of 203 limbs (99.5%) after 1 month, 157 of 158 limbs after 3 months (99.3%), all 99 limbs after 6 months (100%), and all 41 limbs after 1 year (100%). The small saphenous vein (SSV) remained occluded in all 103 limbs (100%) after 1 week, all 94 limbs (100%) after 1 month, 68 of 69 limbs (98.5%) after 3 months, 40 of 41 limbs (97.5%) after 6 months, and all 14 limbs after 1 year (100%). Two GSVs and two SSVs were recanalized and underwent repeated EVLA. No major complications occurred, although bruising (21% of cases), pain (15%), and paresthesia (4%) were observed. CONCLUSIONS Low-energy EVLA with the use of a 1,470-nm laser with LEED of 80 J/cm or lower is an effective, safe, and technically successful option for the treatment of incompetent saphenous veins.

Spectrum-Aware Beaconless Geographical Routing Protocol for Mobile Cognitive Radio Networks

A key challenge in cognitive radio networks (CRNs) is how to adaptively and efficiently select a route and assign resources along that route according to the surrounding environment. In this work, we propose a distributed routing protocol for mobile CRNs, in which path selection and resource allocation (e.g., spectrum, transmission power, and transmission rate) are determined by receivers. Because this process is done on perpacket and per- hop basis, the proposed protocol can efficiently adapt to spectrum dynamics and node mobility. In addition, spectrum efficiency is increased through dynamic spectrum allocation and transmission power control. Simulation results show that delivery ratio and throughput are dramatically improved with our routing protocol.

Fluoroscopy-guided endovenous foam sclerotherapy using a microcatheter in varicose tributaries followed by endovenous laser treatment of incompetent saphenous veins: technical feasibility and early results.

OBJECTIVES To evaluate the technical feasibility and preliminary results of endovenous foam sclerotherapy using a microcatheter in varicose tributaries followed by endovenous laser treatment (EVLT) of incompetent saphenous veins. MATERIALS AND METHODS From July 2005 to August 2006, 312 patients (M:F=139:173, mean age 45.8) who presented with varicose veins with reflux in the saphenofemoral, saphenopopliteal junction or tributaries were enrolled. Under ultrasound or fluoroscopy guidance, selective microcatheterization and endovenous foam slcerotherapy were first performed in varicose tributaries, followed by EVLT (980 nm) of incompetent saphenous veins. Follow‐up at 1‐week and 1‐, 3‐, and 6‐month intervals was done. RESULTS Technical success was seen in 410 of 411 limbs (99%). Continued closure of the saphenous veins and the complete sclerosis of varicose tributaries were noted in 332 of 373 limbs (89%) at the 1‐month follow‐up, all 307 limbs (100%) at the 3‐month follow‐up, and all 274 limbs (100%) at the 6‐month follow‐up. No serious complication was noted. CONCLUSION Endovenous foam sclerotherapy using a microcatheter in varicose tributaries followed by EVLT in incompetent saphenous veins is a safe, effective, and technically feasible treatment for varicose veins. It not only reduces additional sclerotherapy and technical failure, but also makes multiple therapeutic sessions unnecessary. The authors have indicated no significant interest with commercial supporters.