Enhancing the Responsiveness of Thermoelectric Gas Sensors with Boron-Doped and Thermally Annealed SiGe Thin Films via Low-Pressure Chemical Vapor Deposition.

Thermoelectric gas sensor (THGS) devices with catalysts and Si0.8Ge0.2 thin films of different boron doping levels of 1018, 1019, and 1020 cm-3 were fabricated, and their transport properties are investigated. SiGe films were deposited on Si3N4/SiO2 multilayers on Si substrates using low-pressure chemical vapor deposition (LPCVD) and thermally annealed at 1050 °C. The Seebeck coefficients of the SiGe films were increased after thermal annealing, ranging from 191 to 275 µV/K at temperatures of 74 to 468 °C in air, and reaching the highest power factor of 6.78 × 10-4 W/mK2 at 468 °C. The thermal conductivity of the SiGe films varied from 2.4 to 3.0 W/mK at 25 °C. The THGS detection performance was tested for the H2 gas in air from 0.01 to 1.0%, and compared to the thermoelectric properties of the SiGe films. The high-temperature annealing treatment process was successful in enhancing the thermoelectric performance of both the SiGe films and sensor devices, achieving the best THGS performance with the sensor device fabricated from the annealed SiGe film with 1018 cm-3 boron-doped Si0.8Ge0.2.

A pilot study to establish human T-cell leukemia virus type 1 (HTLV-1) carrier model using common marmoset (Callithrix jacchus).

BACKGROUND: For the diagnosis and treatment of adult T-cell leukemia/lymphoma (ATLL) caused by human T-lymphotropic virus type 1 (HTLV-1) are required therapeutic modalities urgently. Non-human primate models for ATLL would provide a valuable information for clinical studies. We did a pilot study to establish an ATLL non-human primate model using common marmosets (Callithrix jacchus). METHODS: We inoculated HTLV-1-producing MT-2 cells into 9-month-old marmosets, either intraperitoneally or intravenously. We next administrated MT-2 cells into 13-month-old marmosets under cyclosporine A (CsA) treatment to promote infection. HTLV-1 infection was determined by measuring HTLV-1 antibody titer in the common marmosets. RESULTS: The HTLV-1 antibody titer increased in the intraperitoneally inoculated marmoset with or without CsA treatment, and it kept over five 5 years though proviral copy number (proviral load, PVL) remained low throughout the study. CONCLUSION: We obtained HTLV-1 asymptomatic carriers of common marmosets by inoculating MT-2 cells.

Selective Detection of Target Volatile Organic Compounds in Contaminated Air Using Sensor Array with Machine Learning: Aging Notes and Mold Smells in Simulated Automobile Interior Contaminant Gases.

We investigated the selective detection of target volatile organic compounds (VOCs) which are age-related body odors (namely, 2-nonenal, pelargonic acid, and diacetyl) and a fungal odor (namely, acetic acid) in the presence of interference VOCs from car interiors (namely, n-decane, and butyl acetate). We used eight semiconductive gas sensors as a sensor array; analyzing their signals using machine learning; principal-component analysis (PCA), and linear-discriminant analysis (LDA) as dimensionality-reduction methods; k-nearest-neighbor (kNN) classification to evaluate the accuracy of target-gas determination; and random forest and ReliefF feature selections to choose appropriate sensors from our sensor array. PCA and LDA scores from the sensor responses to each target gas with contaminant gases were generally within the area of each target gas; hence; discrimination between each target gas was nearly achieved. Random forest and ReliefF efficiently reduced the required number of sensors, and kNN verified the quality of target-gas discrimination by each sensor set.

Thermoelectric Array Sensors with Selective Combustion Catalysts for Breath Gas Monitoring.

Inflammable breath gases such as H2 and CH4 are used as bio markers for monitoring the condition of the colon. However, their typical concentrations of below 100 ppm pose sensitivity and selectivity challenges to current gas sensing systems without the use of chromatography. We fabricated a compact, gas-selective thermoelectric array sensor (TAS) that uses micro-machined sensor devices with three different combustion catalysts to detect gases such as H2, CO, and CH4 in breath. Using Pt/Pt-W thin-film micro-heater meanders, Pd/Al2O3, Pt,Pd,Au/Co3O4, and Pt/Al2O3 catalysts were heated to 320, 200, and 125 °C, respectively, and the gas sensing performances of the TAS for each gas and for a model breath gas mixture of 100 ppm H2, 25 ppm CO, 50 ppm CH4, and 199 ppm CO2 in air were investigated. Owing to its high catalyst temperature, the Pd/Al2O3 catalyst burned all three gases, while the Pt,Pd,Au/Co3O4 burned CO and H2 and the Pt/Al2O3 burned H2 selectively. To calibrate the gas concentration of the mixture gas without the use of a gas separation tool, linear discriminant analysis was applied to measure the sensing performance of TAS. To enhance the gas selectivity against H2, a double catalyst structure was integrated into the TAS sensor.

Mixed-Potential Gas Sensors Using an Electrolyte Consisting of Zinc Phosphate Glass and Benzimidazole.

Mixed-potential gas sensors with a proton conductor consisting of zinc metaphosphate glass and benzimidazole were fabricated for the detection of hydrogen produced by intestinal bacteria in dry and humid air. The gas sensor consisting of an alumina substrate with platinum and gold electrodes showed good response to different hydrogen concentrations from 250 parts per million (ppm) to 25,000 ppm in dry and humid air at 100-130 °C. The sensor response varied linearly with the hydrogen and carbon monoxide concentrations due to mass transport limitations. The sensor responses to hydrogen gas (e.g., -0.613 mV to 1000 ppm H2) was higher than those to carbon monoxide gas (e.g., -0.128 mV to 1000 ppm CO) at 120 °C under atmosphere with the same level of humidity as expired air.

Diagnosis by Volatile Organic Compounds in Exhaled Breath from Lung Cancer Patients Using Support Vector Machine Algorithm.

Monitoring exhaled breath is a very attractive, noninvasive screening technique for early diagnosis of diseases, especially lung cancer. However, the technique provides insufficient accuracy because the exhaled air has many crucial volatile organic compounds (VOCs) at very low concentrations (ppb level). We analyzed the breath exhaled by lung cancer patients and healthy subjects (controls) using gas chromatography/mass spectrometry (GC/MS), and performed a subsequent statistical analysis to diagnose lung cancer based on the combination of multiple lung cancer-related VOCs. We detected 68 VOCs as marker species using GC/MS analysis. We reduced the number of VOCs and used support vector machine (SVM) algorithm to classify the samples. We observed that a combination of five VOCs (CHN, methanol, CH3CN, isoprene, 1-propanol) is sufficient for 89.0% screening accuracy, and hence, it can be used for the design and development of a desktop GC-sensor analysis system for lung cancer.

Common marmoset CD117+ hematopoietic cells possess multipotency.

Analysis of the hematopoiesis of non-human primates is important to clarify the evolution of primate-specific hematopoiesis and immune regulation. However, the engraftment and development of the primate hematopoietic system are well-documented only in humans and are not clear in non-human primates. Callithrix jacchus (common marmoset, CM) is a New World monkey with a high rate of pregnancy and small size that lives in closed colonies. As stem cell factor (SCF) is an essential molecule for hematopoietic stem cell development in mice and humans, we focused on CD117, the SCF receptor, and examined whether CD117-expressing cells possess the hematopoietic stem/progenitor cell characteristics of newborn marmoset-derived hematopoietic cells that can develop into T cells and B cells. When CD117(+) cell fractions of the bone marrow were transplanted into immunodeficient NOD (non-obese diabetic)/Shi-scid, common γc-null (NOG) mice, these cells engrafted efficiently in the bone marrow and spleens of the NOG mice. The CD117(+) cells developed into myeloid lineage cells, CD20(+) B cells and CD3(+) T cells, which could express CM cytokines in vivo. The development of B cells did not precede that of T cells. The development of CD8(+) T cells was dominant in NOG mice. The engraftment was comparable for both CD117(+)CD34(+) cells and CD117(+)CD34(-) cells. These results suggest that the CD117(+) cell fraction can differentiate into all three cell lineages, and the development of marmoset immunity in the xenogeneic environment follows diverse developmental pathways compared with human immunity.

Development of an Exhaled Breath Monitoring System with Semiconductive Gas Sensors, a Gas Condenser Unit, and Gas Chromatograph Columns.

Various volatile organic compounds (VOCs) in breath exhaled by patients with lung cancer, healthy controls, and patients with lung cancer who underwent surgery for resection of cancer were analyzed by gas condenser-equipped gas chromatography-mass spectrometry (GC/MS) for development of an exhaled breath monitoring prototype system involving metal oxide gas sensors, a gas condenser, and gas chromatography columns. The gas condenser-GC/MS analysis identified concentrations of 56 VOCs in the breath exhaled by the test population of 136 volunteers (107 patients with lung cancer and 29 controls), and selected four target VOCs, nonanal, acetoin, acetic acid, and propanoic acid, for use with the condenser, GC, and sensor-type prototype system. The prototype system analyzed exhaled breath samples from 101 volunteers (74 patients with lung cancer and 27 controls). The prototype system exhibited a level of performance similar to that of the gas condenser-GC/MS system for breath analysis.

Multiple myeloma developing in a patient with immune thrombocytopenia.

A female diagnosed as having immune thrombocytopenic purpura (ITP) was found to be simultaneously suffering from monoclonal gammopathy of undetermined significance (IgGλ). Urine Bence-Jones protein was negative. During the course, plasma cells accounted for 21.6% of the bone marrow. Based on these clinical features in our case, the second disease was diagnosed as multiple myeloma (MM). Both ITP and MM were successfully treated with corticosteroids, bortezomib, lenalidomide with dexamethasone and eltrombopag olamine. MM with ITP may show the following features: 1) the great majority are IgG types, 2) λ chain types show marked light chain predominance when these two diseases appear simultaneously, 3) κ chain types are predominant in the cases with MM followed by ITP, and 4) MM cases with ITP are more often seen in Japan.

Parkinson Disease: Diffusion MR Imaging to Detect Nigrostriatal Pathway Loss in a Marmoset Model Treated with 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine.

PURPOSE: To investigate the use of diffusion-tensor imaging (DTI) to detect denervation of the nigrostriatal pathway in a nonhuman primate model of Parkinson disease (PD) after treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MATERIALS AND METHODS: This study was approved by the institutional committee for animal experiments. DTI was performed in marmosets (n = 6) by using a 7-T magnetic resonance (MR) imager before and 10 weeks after administration of MPTP. Fixed brains of a normal marmoset and a marmoset model of PD (n = 1) were analyzed by using microscopic tractography. Tyrosine-hydroxylase staining of dopaminergic neurons and three-dimensional histologic analysis also were performed in normal marmosets (n = 2) and a PD marmoset model (n = 2) to validate the course of the nigrostriatal pathway revealed at tractography. Statistical analysis of voxel-based and post hoc region-of-interest analyses of DTI maps was performed by using a paired t test. RESULTS: At voxel-based analysis of DTI before and after treatment, MPTP-treated marmoset brains showed significantly increased axial and radial diffusivity in the bilateral nigrostriatal pathway (P < .05, false discovery rate corrected). The largest area of significantly increased diffusivity was an area of axial diffusivity in the right hemispere (177 mm(3)) that corresponded to the location of dopaminergic neurodegeneration at histologic evaluation. Region-of-interest analysis revealed a 27% increase in axial diffusivity in the right hemisphere (1.198 mm(2)/sec ± 0.111 to 1.522 mm(2)/sec ± 0.118; P = .002). Three-dimensional histologic analysis with tyrosine-hydroxylase staining showed the course of the nigrostriatal pathway and degeneration in the PD marmoset model as the absence of a tyrosine-hydroxylase stained region. Microscopic tractography showed that the connection of the substantia nigra to the striatum followed the same course as the nigrostriatal pathway and fewer fiber tracts in the PD marmoset model. CONCLUSION: DTI and microscopic tractography showed the loss of fiber structures of the nigrostriatal pathway in the marmoset model of PD. The results of this study provide a potential basis for the use of DTI in the clinical diagnosis of PD.

CO Sensing Performance of a Micro Thermoelectric Gas Sensor with AuPtPd/SnO2 Catalyst and Effects of a Double Catalyst Structure with Pt/α-Al2O3.

The CO sensing properties of a micro thermoelectric gas sensor (micro-TGS) with a double AuPtPd/SnO2 and Pt/α-Al2O3 catalyst were investigated. While several nanometer sized Pt and Pd particles were uniformly dispersed on SnO2, the Au particles were aggregated as particles measuring >10 nm in diameter. In situ diffuse reflectance Fourier transform Infrared spectroscopy (DRIFT) analysis of the catalyst showed a CO adsorption peak on Pt and Pd, but no clear peak corresponding to the interaction between CO and Au was detected. Up to 200 °C, CO combustion was more temperature dependent than that of H2, while H2 combustion was activated by repeated exposure to H2 gas during the periodic gas test. Selective CO sensing of the micro-TGS against H2 was attempted using a double catalyst structure with 0.3-30 wt% Pt/α-Al2O3 as a counterpart combustion catalyst. The sensor output of the micro-TGS decreased with increasing Pt content in the Pt/α-Al2O3 catalyst, by cancelling out the combustion heat from the AuPtPd/SnO2 catalyst. In addition, the AuPtPd/SnO2 and 0.3 wt% Pt/α-Al2O3 double catalyst sensor showed good and selective CO detection. We therefore demonstrated that our micro-TGS with double catalyst structure is useful for controlling the gas selectivity of CO against H2.

Sensing properties of Pd-loaded Co3O4 film for a ppb-level NO gas sensor.

We prepared 0.1 wt%-30 wt% Pd-loaded Co3O4 by a colloidal mixing method and investigated the sensing properties of a Pd-loaded Co3O4 sensor element, such as the sensor response, 90% response time, 90% recovery time, and signal-to-noise (S/N) ratio, toward low nitric oxide (NO) gas levels in the range from 50 to 200 parts per billion. The structural properties of the Pd-loaded Co3O4 powder were investigated using X-ray diffraction analysis and transmission electron microscopy. Pd in the powder existed as PdO. The sensor elements with 0.1 wt%-10 wt% Pd content have higher sensor properties than those without any Pd content. The response of the sensor element with a 30 wt% Pd content decreased markedly because of the aggregation and poor dispersibility of the PdO particles. High sensor response and S/N ratio toward the NO gas were achieved when a sensor element with 10 wt% Pd content was used.

Elimination of flammable gas effects in cerium oxide semiconductor-type resistive oxygen sensors for monitoring low oxygen concentrations.

We have investigated the catalytic layer in zirconium-doped cerium oxide, Ce0.9Zr0.1O2 (CeZr10) resistive oxygen sensors for reducing the effects of flammable gases, namely hydrogen and carbon monoxide. When the concentration of flammable gases is comparable to that of oxygen, the resistance of CeZr10 is affected by the presence of these gases. We have developed layered thick films, which consist of an oxygen sensor layer (CeZr10), an insulation layer (Al2O3), and a catalytic layer consisting of CeZr10 with 3 wt% added platinum, which was prepared via the screen printing method. The Pt-CeZr10 catalytic layer was found to prevent the detrimental effects of the flammable gases on the resistance of the sensor layer. This effect is due to the catalytic layer promoting the oxidation of hydrogen and carbon monoxide through the consumption of ambient O2 and/or the lattice oxygen atoms of the Pt-CeZr10 catalytic layer.

Calorimetric thermoelectric gas sensor for the detection of hydrogen, methane and mixed gases.

A novel miniaturized calorimeter-type sensor device with a dual-catalyst structure was fabricated by integrating different catalysts on the hot (Pd/θ-Al2O3) and cold (Pt/α-Al2O3) ends of the device. The device comprises a calorimeter with a thermoelectric gas sensor (calorimetric-TGS), combining catalytic combustion and thermoelectric technologies. Its response for a model fuel gas of hydrogen and methane was investigated with various combustor catalyst compositions. The calorimetric-TGS devices detected H2, CH4, and a mixture of the two with concentrations ranging between 200 and 2000 ppm at temperatures of 100-400 °C, in terms of the calorie content of the gases. It was necessary to reduce the much higher response voltage of the TGS to H2 compared to CH4. We enhanced the H2 combustion on the cold side so that the temperature differences and response voltages to H2 were reduced. The device response to H2 combustion was reduced by 50% by controlling the Pt concentration in the Pt/α-Al2O3 catalyst on the cold side to 3 wt%.

Thermal balance analysis of a micro-thermoelectric gas sensor using catalytic combustion of hydrogen.

A thermoelectric gas sensor (TGS) with a combustion catalyst is a calorimetric sensor that changes the small heat of catalytic combustion into a signal voltage. We analyzed the thermal balance of a TGS to quantitatively estimate the sensor parameters. The voltage signal of a TGS was simulated, and the heat balance was calculated at two sections across the thermoelectric film of a TGS. The thermal resistances in the two sections were estimated from the thermal time constants of the experimental signal curves of the TGS. The catalytic combustion heat Q(catalyst) required for 1 mV of ∆V(gas) was calculated to be 46.1 µW. Using these parameters, we find from simulations for the device performance that the expected Q(catalyst) for 200 and 1,000 ppm H2 was 3.69 µW and 11.7 µW, respectively.

Ultracompact, 160-Gbit/s transmitter optical subassembly based on 40-Gbit/s × 4 monolithically integrated light source.

The first ultracompact transmitter optical subassembly for long-distance, beyond-100-Gbit/s data communication systems based on a monolithically integrated light source is developed. The light source consists of four InGaAlAs-based electroabsorption modulator integrated DFB lasers (EADFB lasers) and their optical multiplexer and these components are monolithically integrated on one chip, resulting in very small chip size of 2.4 × 3.3 mm2. This small chip makes it possible to reduce the size of the transmitter module. Very small transmitter optical subassemblies (TOSAs), using the chip and employing three-dimensional interconnection board, is fabricated, whose volume is only 1.82 cc. By using the TOSA, 40-Gbit/s × 4 operation with the clear eye openings up to 10-km single mode fibre transmission is demonstrated. Electrical crosstalk under the multi-lane operation is also evaluated, and the error-free transmission is achieved with the power penalty to the discrete operation of 1 dB.

Double expression of CD34 and CD117 on bone marrow progenitors is a hallmark of the development of functional mast cell of Callithrix jacchus (common marmoset).

Mast cells (MCs) are developed from hematopoietic progenitor cells and play an important role in inflammation. Study of the kinetics of development and accumulation of primate MC in vivo is crucial for the control of human inflammatory diseases, as evolution of the immune system is quite rapid and inflammation including MC response is considered to be different between mouse and human. In the present study, we examined the development of MC from hematopoietic progenitors of Callithrix jacchus (common marmoset), an experimental animal of nonhuman primates. Bone marrow cells were fractionated for the expression of CD34 and CD117 by cell sorting. MCs were developed in vitro or by transplanting the cells to NOD/SCID/IL-2γc knockout (NOG) mice. In vitro culture of CD34(+)CD117(+) (double positive, DP) cells with stem cell factor could generate high-affinity Fc epsilon receptor (FcεR)-expressing CD117(+) cells with typical granules. The developed MC released ß-hexosaminidase and produced leukotriene C(4) after the stimulation of FcεRI. Transplantation of DP cells gave rise to a marked expansion of CD34(-)CD45(+)CD117(+)FcεR(+) cells in NOG mice. They expressed transcripts encoding chymase 1 and tryptase ß. Differentiation of CD34(-)CD117(+) cells to MCs was relatively limited compared with the DP cells, similarly to human MCs. These results suggest that this marmoset system provides a good model for human MC development.

NO and NO2 sensing properties of WO3 and Co3O4 based gas sensors.

Semiconductor-based gas sensors that use n-type WO3 or p-type Co3O4 powder were fabricated and their gas sensing properties toward NO2 or NO (0.5-5 ppm in air) were investigated at 100 °C or 200 °C. The resistance of the WO3-based sensor increased on exposure to NO2 and NO. On the other hand, the resistance of the Co3O4-based sensor varied depending on the operating temperature and the gas species. The chemical states of the surface of WO3 or those of the Co3O4 powder on exposure to 1 ppm NO2 and NO were investigated by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. No clear differences between the chemical states of the metal oxide surface exposed to NO2 or NO could be detected from the DRIFT spectra.

CO responses of sensors based on cerium oxide thick films prepared from clustered spherical nanoparticles.

Various types of CO sensors based on cerium oxide (ceria) have been reported recently. It has also been reported that the response speed of CO sensors fabricated from porous ceria thick films comprising nanoparticles is extremely high. However, the response value of such sensors is not suitably high. In this study, we investigated methods of improving the response values of CO sensors based on ceria and prepared gas sensors from core-shell ceria polymer hybrid nanoparticles. These hybrid nanoparticles have been reported to have a unique structure: The core consists of a cluster of ceria crystallites several nanometers in size. We compared the characteristics of the sensors based on thick films prepared from core-shell nanoparticles with those of sensors based on thick films prepared from conventionally used precipitated nanoparticles. The sensors prepared from the core-shell nanoparticles exhibited a resistance that was ten times greater than that of the sensors prepared from the precipitated nanoparticles. The response values of the gas sensors based on the core-shell nanoparticles also was higher than that of the sensors based on the precipitated nanoparticles. Finally, improvements in sensor response were also noticed after the addition of Au nanoparticles to the thick films used to fabricate the two types of sensors.

Self-Adaptive Gas Sensor System Based on Operating Conditions Using Data Prediction.

Through the improvement of nanomaterial technologies, a gas sensor was developed for detecting ppm or ppb levels of gas. Our SnO2 nanosheet gas sensor can detect 50 ppb of acetone without the requirement of a novel metal catalyst by exposing the (101) facet containing the Sn2+ state. Despite the high performance, the fluctuation of the gas response value based on operating conditions, even at the same concentration, is a critical problem in gas sensors. Thus, the alarm criteria of the sensor are typically determined by a safety factor. However, this method is not suitable for application in ultrasensitive sensors that require distinguishing minute differences in extremely low concentrations for medical examination or odor analysis. Therefore, we suggest a self-adaptive system that is based on operating conditions in collaboration with the data prediction model. The sensor system is based on a predictive model obtained by the response surface methodology. When the system detects a change in conditions, the alarm criteria are changed appropriately through the calculated values from the predictive model. To prepare a database for an effective predictive model, the gas responses of the SnO2 nanosheet sensor were measured with 20 treatments with 3 independent variables, namely, the temperature, flow rate, and concentration. Our prediction model achieved its best performance on training data with R2 = 0.9299 and less than 5% error in the prediction of unseen data.