A Study on TiO2 Surface Texturing Effect for the Enhancement of Photocatalytic Reaction in a Total Phosphorous Concentration Measurement System.

Powerful sunlight, a high water temperature, and stagnation in the water flow induce eutrophication in rivers and lakes, which destroys the aquatic ecosystem and threatens the downstream water supply systems. Accordingly, it is very important to perform real-time measurements of nutrients that induce algal growth, especially total phosphorus, to preserve and manage the aquatic ecosystem. To conduct quantitative analysis of the total phosphorus in the aquatic ecosystem, it is essential to perform a pretreatment process and quickly separate the phosphorus, combined with organic and inorganic materials, into a phosphate. In this study, the sandblasting process was used for the physical etching of the wafer, and photocatalytic materials were deposited on the surface with various roughness in order to improve the photocatalytic reaction surface and efficiency. The photocatalytic reaction was applied to combine the pretreated sample with the coloring agent for color development, and the absorbance of the colored sample was analyzed quantitatively to compare and evaluate the characteristics, followed by the surface increase in the photocatalytic materials. In addition, the pretreatment and measurement parts were materialized in a single chip to produce a small and light total phosphorus analysis sensor.

Pd-Decorated Multi-Walled Carbon Nanotube Sensor for Hydrogen Detection.

As hydrogen (H2) gas is highly reactive and explosive in ambient atmosphere, its prompt detection in industrial areas is imperative to prevent serious accidents. In particular, high-performance H2 sensors that can promptly detect even low-concentrations of H2 gas are necessary for safety. Carbon nanotubes (CNTs) have a large surface area and a high surface-to-volume ratio, and therefore, they are suitable for use as sensing materials in gas sensors. Moreover, gold, platinum, and palladium are known to be excellent catalyst metals that increase reactivity with H2 gas through the catalytic effect referred to as spill-over mechanism. In this study, a CNT felt sensor with a palladium (Pd) layer was fabricated, and its reactivity with H2 was evaluated. The sensitivity of a CNT felt sensor to H2 gas at room temperature was found to improve when coated with Pd layer.

Easy-to-Fabricate K2Pd(SO3)2-Dyed Polyester Fabric with Highly Selective and Fast Response to Carbon Monoxide.

Carbon monoxide (CO) is an odorless, colorless, tasteless, extremely flammable, and highly toxic gas. It is produced when there is insufficient oxygen supply during the combustion of carbon to produce carbon dioxide (CO2). CO is produced from operating engines, stoves, or furnaces. CO poisoning occurs when CO accumulates in the bloodstream and can result in severe tissue damage or even death. Many types of CO sensors have been reported, including electrochemical, semiconductor metal-oxide, catalytic combustion, thermal conductivity, and infrared absorption-type for the detection of CO. However, despite their excellent selectivity and sensitivity, issues such as complexity, power consumption, and calibration limit their applications. In this study, a fabricbased colorimetric CO sensor is proposed to address these issues. Potassium disulfitopalladate (II) (K2Pd(SO3)2) is dyed on a polyester fabric as a sensing material for selective CO detection. The sensing characteristics and performance are investigated using optical instruments such as RGB sensor and spectrometer. The sensor shows immediate color change when exposed to CO at a concentration that is even lower than 20 ppm before 2 min. The fast response time of the sensor is attributed to its high porosity to react with CO. This easy-to-fabricate and cost-effective sensor can detect and prevent the leakage of CO simultaneously with high sensitivity and selectivity toward CO.

Chromogenic detection of hydrogen sulfide using squarylium-based chemosensors.

Squarylium-based colorimetric hydrogen sulfide (H2S) chemosensors (SQ1, SQ2, and SQ3) were developed, and their detection properties were systematically characterized. SQ1 exhibited rapid and high resolution H2S sensing properties through significant color changes detectable by naked-eye with limit of detection as low as 7.2 ppb. SQ1 also showed excellent selectivity for H2S detection over other relevant anions and nucleophiles. Sensing mechanisms of SQ1 were investigated based on spectroscopic and 1H NMR analyses with quantum calculations. Furthermore, SQ1 showed an efficient response to H2S under versatile conditions in the solution, solid, and dyed fabric states, which suggests applicability of SQ1 to simple, low-cost, and practical H2S sensors.

Room-Temperature Hydrogen-Gas Sensor Based on Carbon Nanotube Yarn.

The proposed study describes the development of a carbon nanotube (CNT)-based gas sensor capable of detecting the presence of hydrogen (H2) gas at room temperature. CNT yarn used in the proposed sensor was fabricated from synthesized CNT arrays. Subsequently, the yarn was treated by means of a simple one-step procedure, called acid treatment, to facilitate removal of impurities from the yarn surface and forming functional species. To verify the proposed sensor's effectiveness with regard to detection of H2 gas at room temperature, acid-treated CNT and pure yarns were fabricated and tested under identical conditions. Corresponding results demonstrate that compared to the untreated CNT yarn, the acid-treated CNT yarn exhibits higher sensitivity to the presence of H2 gas at room temperature. Additionally, the acid-treated CNT yarn was observed to demonstrate excellent selectivity pertaining to H2 gas.

H2 Gas Sensor Based on Pd-Loaded Carbon Nanotube Film.

Palladium-coated multi-walled carbon nanotube (Pd-MWCNT) nanocomposites have been experimentally proven to show highly improved hydrogen (H2) gas detection characteristics at room temperature when compared with single MWCNTs. In this context, we develop an efficient and convenient method for forming nanocomposites by coating Pd nanoparticles on an MWCNT film. Furthermore, we test the applicability of the nanocomposites as sensing materials in detecting H2 gas at room temperature in a reliable and sensitive manner in contrast with ordinary metal-oxidebased gas sensors that operate at high temperatures. We first study the detection efficacy of the Pd-MWCNT film relative to pure MWCNT film. Subsequently, we investigate the Pd-MWCNT sensor's sensitivity over time for different gas concentrations, the sensor response time, and sensor reproducibility and reliability under various conditions including bending tests. Our sensor exhibits stable reliable detection characteristics and excellent structural flexibility.

Multi-axis Response of a Thermal Convection-based Accelerometer.

A thermal convection-based accelerometer was fabricated, and its characteristics were analyzed in this study. To understand the thermal convection of the accelerometer, the Grashof and Prandtl number equations were analyzed. This study conducted experiments to improve not only the sensitivity, but also the frequency band. An accelerometer with a more voluminous cavity showed better sensitivity. In addition, when the accelerometer used a gas medium with a large density and small viscosity, its sensitivity also improved. On the other hand, the accelerometer with a narrow volume cavity that used a gas medium with a small density and large thermal diffusivity displayed a larger frequency band. In particular, this paper focused on a Z-axis response to extend the performance of the accelerometer.

Tunable Fabry-Perot Interferometer Designed for Far-Infrared Wavelength by Utilizing Electromagnetic Force.

A tunable Fabry-Perot interferometer (TFPI)-type wavelength filter designed for the long-wavelength infrared (LWIR) region is fabricated using micro electro mechanical systems (MEMS) technology and the novel polydimethylsiloxane (PDMS) micro patterning technique. The structure of the proposed infrared sensor consists of a Fabry-Perot interferometer (FPI)-based optical filter and infrared (IR) detector. An amorphous Si-based thermal IR detector is located under the FPI-based optical filter to detect the IR-rays filtered by the FPI. The filtered IR wavelength is selected according to the air etalon gap between reflectors, which is defined by the thickness of the patterned PDMS. The 8 µm-thick PDMS pattern is fabricated on a 3 nm-thick Al layer used as a reflector. The air etalon gap is changed using the electromagnetic force between the permanent magnet and solenoid. The measured PDMS gap height is about 2 µm, ranging from 8 µm to 6 µm, with driving current varying from 0 mA to 600 mA, resulting in a tunable wavelength range of 4 µm. The 3-dB bandwidth (full width at half maximum, FWHM) of the proposed filter is 1.5 nm, while the Free Spectral Range (FSR) is 8 µm. Experimental results show that the proposed TFPI can detect a specific wavelength at the long LWIR region.

Sensitivity and Frequency-Response Improvement of a Thermal Convection-Based Accelerometer.

This paper presents a thermal convection-based sensor fabricated using simple microelectromechanical systems (MEMS)-based processes. This sensor can be applied to both acceleration and inclination measurements without modifying the structure. Because the operating mechanism of the accelerometer is the thermal convection of a gas medium, a simple model is proposed and developed in which the performance of the thermal convection-based accelerometer is closely associated with the Grashof number, Gr and the Prandtl number, Pr. This paper discusses the experiments that were performed by varying several parameters such as the heating power, cavity size, gas media, and air pressure. The experimental results demonstrate that an increase in the heating power, pressure, and cavity size leads to an increase in the accelerometer sensitivity. However, an increase in the pressure and/or cavity size results in a decrease in the frequency bandwidth. This paper also discusses the fact that a working-gas medium with a large thermal diffusivity and small kinematic viscosity can widen the frequency bandwidth and increase the sensitivity, respectively.

A comparison of angled sagittal MRI and conventional MRI in the diagnosis of herniated disc and stenosis in the cervical foramen.

The object of this study is to demonstrate that angled sagittal magnetic resonance imaging (MRI) enables the precise diagnosis of herniated disc and stenosis in the cervical foramen, which is not available with conventional MRI. Due to both the anatomic features of the cervical foramen and the limitations of conventional MR techniques, it has been difficult to identify disease in the lateral aspects of the spinal canal and foramen using only conventional MRI. Angled sagittal MRI oriented perpendicular to the true course of the foramina facilitates the identification of the lateral disease. A review of 43 patients, who underwent anterior cervical discectomy and interbody fusion, is presented with a herniated disc and/or stenosis in the cervical foramen. They all had undergone conventional MRI and angled sagittal MRI. Fifty levels were surgically explored for evidence of foraminal herniated disc and stenosis. The results of each test were correlated with what was found at each explored surgical level. The sensitivity, specificity, and accuracy of both examinations for making the diagnosis of foraminal herniated disc and stenosis were compared. During the diagnosis of foraminal herniated disc, the sensitivity, specificity, and accuracy of angled sagittal MRI were 96.7, 95.0, and 96.0%, respectively, compared with 56.7, 85.0, and 68.0% for conventional MRI. In making the diagnosis of foraminal stenosis, the sensitivity, specificity, and accuracy of angled sagittal MRI were 96.3, 95.7, and 96.0%, respectively, compared with 40.7, 91.3, and 66.0% for conventional MRI. In the above groups, the difference between the tests for making the diagnosis of both foraminal herniated disc and stenosis was found to be statistically significant in sensitivity and accuracy. Angled sagittal MRI was a more accurate test compared to conventional MRI for making the diagnosis of herniated disc and stenosis in the cervical foramen. It can be utilized for the precise diagnosis of foraminal herniated disc and stenosis difficult or ambiguous in conventional MRI.

Takayasu's arteritis presented with subarachnoid hemorrhage: report of two cases.

Takayasu's arteritis is a chronic inflammatory disease that produces a narrowing of the aorta and its major branches. Fibrosis and thickening of the arterial wall often occur in later stages, resulting in a cerebrovascular accident. The authors report two young women patients who presented with subarachnoid hemorrhage (SAH) and occlusive cerebrovasular disease associated with Takayasu's arteritis. Both patients had sudden headache and hemiparesis. Physical examination showed weak radial pulse, carotid bruit, and asymmetrical blood pressure. Erythrocyte sedimentation rate (ESR) was elevated in both patients. SAH was confirmed by brain computerized tomography (CT) or lumbar puncture. Occlusive cerebrovascular disease was diagnosed by brain magnetic resonance imaging (MRI), brain magnetic resonance angiography (MRA), and cerebral angiography. The findings of aortography and cerebral angiography were compatible with Takayasu's arteritis, but intracranial aneurysm was not found in either patient.