Radio-Frequency/Microwave Gas Sensors Using Conducting Polymer.

In this review, the advances in radio-frequency (RF) /microwave chemical gas sensors using conducting polymers are discussed. First, the introduction of various conducting polymers is described. Only polyaniline (PANi), polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), which are mainly used for gas sensors in RF/microwave region, are focused in this review. Sensing mechanism of the three conducting polymers are presented. And the RF/microwave characteristics and RF/microwave applications of the three conducting polymers are discussed. Moreover, the gas sensors using conducting polymers in RF/microwave frequencies are described. Finally, the the challenges and the prospects of the next generation of the RF/microwave based chemical sensors for wireless applications are proposed.

Microwave Properties of Coplanar Waveguide-Based PEDOT:PSS Conducting Polymer Line in Ethanol Gas Atmosphere.

This study aims to investigate the microwave properties of coplanar waveguide (CPW)-based poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conducting polymer line in an ethanol gas atmosphere, with the frequency range of 0.5-2 GHz. For an ethanol-exposed PEDOT:PSS line (test sample), the transmission coefficient (S21) decreased immediately; moreover, the microwave effective conductivity (σm/w) decreased simultaneously, compared with the ethanol-free PEDOT:PSS line (reference sample). The immediate variations in ΔS21 ( = S21,ethanol - S21,free) and Δσm/w ( = σm/w,ethanol - σm/w,free) were approximately 10.2 dB and 2.7 × 104 S/m, respectively. Furthermore, in the analysis of the circuit model of the PEDOT:PSS line, the characteristic impedance and distributed elements, i.e., resistance (R) and inductance (L) per length, of the test sample increased, compared with the reference sample. However, upon stopping the exposure to ethanol gas, the microwave properties of the test sample instantaneously recovered to those of the reference sample. According to these critical observations, we could confirm that the coplanar waveguide with a PEDOT:PSS line shows a significant difference in the diverse microwave properties, through rapid response to the ethanol gas at room temperature.

Real-time Humidity Sensor Based on Microwave Resonator Coupled with PEDOT:PSS Conducting Polymer Film.

A real-time humidity sensor based on a microwave resonator coupled with a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conducting polymer (CP) film is proposed in this paper. The resonator is patterned on a printed circuit board and is excited by electromagnetic field coupling. To enhance the sensitivity of the sensor, the CP film is located in the area with the strongest electric field in the resonator. To investigate the performance, the proposed sensor is placed alongside a reference sensor in a humidity chamber, and humidity is injected at room temperature. The experimental results indicate that the electrical properties of the resonator with the CP film, such as the transmission coefficient (S 21) and resonance frequency, change with the relative humidity (RH). Specifically, as the RH changes from 5% to 80%, S 21 and the resonance frequency change simultaneously. Moreover, the proposed sensor exhibits great repeatability in the middle of the sensing range, which is from 40% to 60% RH. Consequently, our resonator coupled with the CP film can be used as a real-time humidity-sensing device in the microwave range, where various radio-frequency devices are in use.

Clinical value of visually identifiable 18F-fluorodeoxyglucose uptake in primary papillary thyroid microcarcinoma.

OBJECTIVE: This study evaluates the relationship between visually identifiable (18)F-fluorodeoxyglucose (FDG) uptake in primary papillary thyroid microcarcinoma (PTMC) and tumor aggressiveness. STUDY DESIGN: Historical cohort study. SETTING: Tertiary care center. METHODS: Clinicopathological factors and PET/CT findings of 219 PTMC surgical patients who underwent preoperative (18)F-FDG positron emission tomography/computed tomography (PET/CT) were retrospectively reviewed. RESULTS: (18)F-FDG uptake was observed in the tumors of 124 (56.6%) patients. Tumor size (odds ratio [OR] = 1.774; 95% confidence interval [CI], 1.416-2.223; P < .0001) and Hashimoto thyroiditis (OR = 2.815; CI, 1.237-6.404; P = .014) independently predicted (18)F-FDG uptake. Tumor size (OR = 1.495; CI, 1.217-1.835; P < .0001) and BRAF(V600E) mutation (OR = 3.320; CI, 1.056-10.432; P = .040) independently predicted extrathyroidal invasion. Multiplicity (OR = 2.375; CI, 1.278-4.415; P = .006) independently predicted central lymph node metastasis. CONCLUSION: (18)F-FDG uptake in PTMC depends on tumor size and Hashimoto thyroiditis. Therefore, preoperative PET/CT for PTMC may not help in evaluating tumor aggressiveness.

Comparison of laser ablation using multidirectional and forward-firing fiber in human thyroid gland: experimental study.

The aim of this study is to evaluate the differences between forward-firing and multidirectional lasers and to evaluate the effects of exposure times and power on laser ablation of thyroid tissue. This is an experimental, ex vivo study. The experiments were conducted on 3 thyroid glands using 2 power levels (3 and 5 W) and exposure times (3 and 5 minutes) with forward-firing and multidirectional lasers. The length and width of the demarcated zone were measured to assess the size of thermal effect. NADPH staining was performed to determine tissue viability. Thermal transformation caused by the forward-firing laser produced oval necrotic zones, whereas thermal transformation caused by the multidirectional-firing laser produced clear round necrotic zones, which clearly demarcated in both hematoxylin and eosin staining and NADH staining.

Detection of a CO and NH3 gas mixture using carboxylic acid-functionalized single-walled carbon nanotubes.

Carbon nanotubes (CNT) are extremely sensitive to environmental gases. However, detection of mixture gas is still a challenge. Here, we report that 10 ppm of carbon monoxide (CO) and ammonia (NH3) can be electrically detected using a carboxylic acid-functionalized single-walled carbon nanotubes (C-SWCNT). CO and NH3 gases were mixed carefully with the same concentrations of 10 ppm. Our sensor showed faster response to the CO gas than the NH3 gas. The sensing properties and effect of carboxylic acid group were demonstrated, and C-SWCNT sensors with good repeatability and fast responses over a range of concentrations may be used as a simple and effective detection method of CO and NH3 mixture gas.

Effect of plasma treatment on the gas sensor with single-walled carbon nanotube paste.

The effect of plasma treatment on the gas sensing properties of screen-printed single-walled carbon nanotube (SWCNT) pastes is reported. The gas sensors, using SWCNT pastes as a sensing material, were fabricated by photolithography and screen printing. The SWCNT pastes were deposited between interdigitated electrodes on heater membrane by screen printing. In order to functionalize the pastes, they were plasma treated using several gases which produce defects caused by reactive ion etching. The Ar and O(2) plasma-treated SWCNT pastes exhibited a large response to NO(2) exposure and the fluorinated gas, such as CF(4) and SF(6), plasma-treated SWCNT pastes exhibited a large response to NH(3) exposure.

Noxious gas detection using carbon nanotubes with Pd nanoparticles.

Noxious gas sensors were fabricated using carbon nanotubes [CNTs] with palladium nanoparticles [Pd NPs]. An increase in the resistance was observed under ammonia for both CNTs and CNT-Pd sensors. Under carbon monoxide [CO], the two sensors exhibited different behaviors: for CNT sensors, their resistance decreased slightly with CO exposure, whereas CNT-Pd sensors showed an increase in resistance. The sensing properties and effect of Pd NPs were demonstrated, and CNT-Pd sensors with good repeatability and fast responses over a range of concentrations may be used as a simple and effective noxious gas sensor at room temperature.

Detection of a nerve agent simulant using single-walled carbon nanotube networks: dimethyl-methyl-phosphonate.

Single-walled carbon nanotube (SWNT) networks were used to detect hazardous dimethyl-methyl-phosphonate (DMMP) gas in real time, employing two different metals as electrodes. Random networks of SWNTs were simply obtained by drop-casting a SWNT-containing solution onto a surface-oxidized Si substrate. Although the electrical responses to DMMP at room temperature were reversible for both metals, the Pd-contacting SWNT network sensors exhibited a higher response and a shorter response time than those of the Au-contacting SWNT network sensors at the same DMMP concentration, due to the stronger interactions between the SWNTs and Pd surface atoms. In Pd-contacting SWNT network sensors, the response increased linearly with increasing DMMP concentration and reproducible response curves were obtained for DMMP levels as low as 1 ppm. These results indicate that SWNT networks in contact with Pd electrodes can function as good DMMP sensors at room temperature with scalable and fast response and excellent recovery.

Ruptured iliac artery stump aneurysm combined with aortic pseudoaneurysm in a patient with Behçet's disease.

Operative treatment of aneurysm in patients with Behçet's disease frequently results in recurrent aneurysm at the anastomosis site or in the remaining artery. Herein, in a Behçet's patient with aortic and iliac pseudoaneurysms, a ruptured iliac artery stump aneurysm after ligation of the right external iliac artery 1 year prior to this admission is reported. This case suggests that the ligation or interposition of aneurysms associated with Behçet's disease should be done at the intact artery, remote to the diseased segment. In addition, a small pseudoaneurysm of the aorta could be monitored with close follow-up with immunosuppressive medication and surveillance at regular intervals if the aneurysm is not symptomatic and is not rapidly growing to a certain critical size.

Acute renal vein thrombosis, oral contraceptives, and protein S deficiency: a successful catheter-directed thrombolysis.

Acute renal vein thrombosis (RVT) is a rare but noteworthy form of venous thromboembolism. Traditional management has been systemic anticoagulation with heparin, followed by warfarin. We report a case of acute RVT with multiple pulmonary emboli that occurred in a 40-year-old woman who was taking oral contraceptives and was subsequently found to have protein S deficiency. The patient was treated with catheter-directed thrombolysis, and complete resolution of the RVT was achieved. This case suggests that oral contraceptive use in a patient with protein S deficiency may interact in a synergistic manner in the pathogenesis of thrombosis. Also, we believe that catheter-directed thrombolysis is warranted in selective cases in the absence of overriding contraindications.

Abdominal aortic aneurysm repair in patient with a renal allograft: a case report.

Renal transplant recipients requiring aortic reconstruction due to abdominal aortic aneurysm (AAA) pose a unique clinical problem. The concern during surgery is causing ischemic injury to the renal allograft. A variety of strategies for protection of the renal allograft during AAA intervention have been described including a temporary shunt, cold renal perfusion, extracorporeal bypass, general hypothermia, and endovascular stent-grafting. In addition, some investigators have reported no remarkable complications of the renal allograft without any specific measures. We treated a case of AAA in a patient with a renal allograft using a temporary aortofemoral shunt with good result. Since this technique is safe and effective, it should be considered in similar patients with AAA and previously placed renal allografts.