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1.
Chemosphere ; 314: 137707, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36592829

RESUMO

In this study, some clays and dead microorganisms were compared in terms of their adsorption ability against special toxic gases. To this end, an experimental investigation was conducted to explore the adsorption kinetics of kaolinite, metakaolinite, radiolarite, and diatomite to ammonia (NH3), ethylene (C2H4), and carbon dioxide (CO2). Numerous analyses, such as x-ray fluorescence (XRF), x-ray diffraction (XRD), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), and particle size distribution, have been performed for mineralogical and structural characterization of studied materials. Also, adsorption characteristics were investigated with the help of an ultra-precision scale and computer-controlled multi-gas control system. Since ammonia has the highest dipole moment among all studied gases, its removal efficiency was found as the highest in all materials. Regarding clay substances, metakaolinite indicated a lower response than kaolinite due to phase transformation. But, considering the microorganisms, diatomite toxic gas uptake is at least five times better than examined clays while the gas uptake behavior of radiolarite is analog to metakaolinite. Moreover, the adsorption behaviors of proposed materials are clarified with Langmuir isotherms, The results could facilitate improvements in applying microorganisms to the toxic gas environment as a natural adsorbent material.


Assuntos
Amônia , Caulim , Caulim/química , Argila/química , Gases , Adsorção
2.
Chemosphere ; 314: 137720, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36596327

RESUMO

Cubic Cu2O micro/nanocrystals were successfully synthesized by liquid-phase reduction using copper salt of CuSO4 or CuCl2·2H2O, and glucose or ascorbic acid as reducing agent, respectively. The activity of the catalysts was evaluated by light-off curves of CO self-sustained catalytic combustion via temperature-programmed oxidation of CO (CO-TPO), with the results showing the activity of catalysts following the order of Cu2O-Cl-GLU > Cu2O-S-GLU > Cu2O-S-AA > Cu2O-Cl-AA, (Cl denotes CuCl2·2H2O, GLU denotes glucose, S denotes CuSO4 and AA denotes ascorbic acid, respectively), corresponding to the ignition temperature of 109 °C, 122 °C, 137 °C and 186 °C, respectively. The crystal structure, elemental valence, morphology and redox property of the prepared catalysts were analyzed by using various characterization techniques. Combined with in situ infrared spectrum, the CO self-sustained catalytic combustion over Cu2O catalysts mainly follows the Mars-van-Krevelen (M-v-K) mechanism: the adsorbed and activated CO reacts with lattice oxygen to yield CO2 and oxygen vacancy, and then the oxygen vacancy can be replenished by gaseous oxygen. Combined with catalytic performance of high-concentration CO, it is found that the catalysts prepared using glucose as reducing agent are more angular compared with ascorbic acid. The Cu2O-Cl-GLU synthesized with glucose and CuCl2·2H2O exhibits the best catalytic activity among all the catalysts tested, attributing to its more obvious edge and rough crystal surface. The unique structure of Cu2O-Cl-GLU leads to the high exposure rate and coordination unsaturation of atoms on the cubic Cu2O micro/nanocrystals that can improve the ability of activating gaseous O2 and low temperature reducibility, and consequently facilitating the catalytic activity.


Assuntos
Nanopartículas , Substâncias Redutoras , Glucose , Nanopartículas/química , Oxirredução , Gases , Oxigênio
3.
Appl Nurs Res ; 69: 151653, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36635009

RESUMO

This study compared the effects of a four-phase and a three-phase early mobilization protocol on respiratory parameters and complications in patients following coronary artery bypass graft surgery. This is a three-arm, parallel-group, randomized controlled clinical trial with 120 candidates for coronary artery bypass graft surgery. Participants were randomly allocated to three groups: four-phase early mobilization protocol, three-phase early mobilization protocol, and control. Arterial blood gases, oxygen saturation, and incidence of pulmonary complications were compared among the groups. Mean arterial blood gases and oxygen saturation improved significantly over time in both four-phase early mobilization protocol and three-phase early mobilization protocol groups compared to control (p < 0.05). There were observed trends for greater improvements in the study outcomes with three-phase early mobilization protocol than four-phase early mobilization protocol; however, did not reach statistically significant levels. The incidence of pulmonary complications was significantly in both intervention groups compared to control (odds ratio: 0.48, 95 % CI 0.007-0.537; p < 0.001). Both four-phase early mobilization and the three-phase early mobilization protocols improved respiratory parameters and reduced pulmonary complications. Statistically insignificant trends were found trends in the three-phase early mobilization protocol, focusing on chest physiotherapy and breathing exercises.


Assuntos
Ponte de Artéria Coronária , Deambulação Precoce , Humanos , Ponte de Artéria Coronária/efeitos adversos , Gases
4.
Environ Monit Assess ; 195(2): 297, 2023 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-36635561

RESUMO

The generation of municipal solid waste is increasing globally and poses a negative impact on society, the economy, and the environment. Applying an integrated system for managing MSW and recovering the material for the production of new products can reduce the negative impacts on the environment. The aim of this paper is to apply the DPSIRO framework to develop a system that reduces the negative impacts of MSW in Bahir Dar city in a sustainable way. The study started by identifying the main driving forces that led to the generation of MSW. Then, pressures and states of the environment resulting from driving forces were investigated. Next, the consequent impacts through driving forces, pressure, and state are identified. Finally, the appropriate responses and outcomes obtained from the responses were studied. Numerical models were used to quantify GHG emissions, leachate, and eutrophication potential. According to the findings, the waste disposal site emits about 46 Gg of greenhouse gases per year in 2020. The eutrophication capacity of organic waste generated in the city was 0.0594 kg N-equivalent or 59.4 g N-equivalent. The waste also contains an average of 1112 mm of leachate per day on an annual basis. The state of the environment has an impact on human health and the ecosystem. Implementing a circular economic system, knowledge transfer, and waste management fees are the main responses suggested to decision and policymakers. The outcomes were quantified in terms of organic fertilizer, income, and renewable energy (briquette) when the actions were taken.


Assuntos
Eliminação de Resíduos , Gerenciamento de Resíduos , Humanos , Resíduos Sólidos/análise , Efeito Estufa , Ecossistema , Etiópia , Gases/análise , Monitoramento Ambiental/métodos , Meio Ambiente , Gerenciamento de Resíduos/métodos , Eliminação de Resíduos/métodos
5.
Int J Mol Sci ; 24(1)2023 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-36614285

RESUMO

Copper-based catalysts have different catalytic properties depending on the oxidation states of Cu. We report operando observations of the Cu(111) oxidation processes using near-ambient pressure scanning tunneling microscopy (NAP-STM) and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). The Cu(111) surface was chemically inactive to water vapor, but only physisorption of water molecules was observed by NAP-STM. Under O2 environments, dry oxidation started at the step edges and proceeded to the terraces as a Cu2O phase. Humid oxidation of the H2O/O2 gas mixture was also promoted at the step edges to the terraces. After the Cu2O covered the surface under humid conditions, hydroxides and adsorbed water layers formed. NAP-STM observations showed that Cu2O was generated at lower steps in dry oxidation with independent terrace oxidations, whereas Cu2O was generated at upper steps in humid oxidation. The difference in the oxidation mechanisms was caused by water molecules. When the surface was entirely oxidized, the diffusion of Cu and O atoms with a reconstruction of the Cu2O structures induced additional subsurface oxidation. NAP-XPS measurements showed that the Cu2O thickness in dry oxidation was greater than that in humid oxidation under all pressure conditions.


Assuntos
Cobre , Vapor , Oxirredução , Cobre/química , Gases
6.
ACS Sens ; 8(1): 94-102, 2023 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-36596238

RESUMO

Hydrogen (H2) gas has recently become a crucial energy source and an imperative energy vector, emerging as a powerful next-generation solution for fuel cells and biomedical, transportation, and household applications. With increasing interest in H2, safety concerns regarding personal injuries from its flammability and explosion at high concentrations (>4%) have inspired the development of wearable pre-emptive gas monitoring platforms that can operate on curved and jointed parts of the human body. In this study, a yarn-type hydrogen gas sensing platform (HGSP) was developed by biscrolling of palladium oxide nanoparticles (PdO NPs) and spinnable carbon nanotube (CNT) buckypapers. Because of the high loading of H2-active PdO NPs (up to 97.7 wt %), when exposed to a flammable H2 concentration (4 vol %), the biscrolled HGSP yarn exhibits a short response time of 2 s, with a high sensitivity of 1198% (defined as ΔG/G0 × 100%). Interestingly, during the reduction of PdO to Pd by H2 gas, the HGSP yarn experienced a decrease in diameter and corresponding volume contraction. These excellent sensing performances suggest that the fabricated HGSP yarn could be applied to a wearable gas monitoring platform for real-time detection of H2 gas leakage even over the bends of joints.


Assuntos
Nanopartículas , Nanotubos de Carbono , Dispositivos Eletrônicos Vestíveis , Humanos , Hidrogênio , Gases
7.
ACS Sens ; 8(1): 243-253, 2023 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-36647806

RESUMO

High performance with lower power consumption is one among the essential features of a sensing device. Minute traces of hazardous gases such as NO2 are difficult to detect. Tin disulfide (SnS2) nanosheets have emerged as a promising NO2 sensor. However, their poor room-temperature conductivity gives rise to inferior sensitivity and sluggish recovery rates, thereby hindering their applications. To mitigate this problem, we present a low-cost ultrasensitive NO2 gas sensor with tin disulfide/multiwalled carbon nanotube (SnS2/MWCNT) nanocomposites, prepared using a single-step hydrothermal method, as sensing elements. Relative to pure SnS2, the conductivity of nanocomposites improved significantly. The sensor displayed a decrease in resistance when exposed to NO2, an oxidizing gas, and exhibited p-type conduction, also confirmed in separate Mott-Schottky measurements. At a temperature of 20 °C, the sensor device has a relative response of about ≈5% (3%) for 25 ppb (1 ppb) of NO2 with complete recovery in air (10 min) and excellent recovery rates with UV activation (0.3 min). A theoretical lower limit of detection (LOD) of 7 ppt implies greater sensitivity than all previously reported SnS2-based gas sensors, to the best of our knowledge. The improved sensing characteristics were attributed to the formation of nano p-n heterojunctions, which enhances the charge transport and gives rise to faster response. The composite sensor also demonstrated good NO2 selectivity against a variety of oxidizing and reducing gases, as well as excellent stability and long-term durability. This work will provide a fresh perspective on SnS2-based composite materials for practical gas sensors.


Assuntos
Dióxido de Nitrogênio , Estanho , Temperatura , Dissulfetos , Gases
9.
Dalton Trans ; 52(4): 977-989, 2023 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-36601863

RESUMO

Single crystals of the new metal-organic framework (MOF) In-adc (HHUD-4) were obtained through the reaction of linear acetylenedicarboxylic acid (H2adc) with In(NO3)3·xH2O as a racemic conglomerate in the chiral tetragonal space groups P4322 and P4122. Fundamentally different from other MOFs with linear linkers and trans-µ-OH-connected infinite {MO6} secondary building units as in the MIL-53-type, the linear adc2- linker leads to the formation of cis-µ-OH connected {InO6} polyhedra, which have otherwise only been found before for V-shaped ligands, as in CAU-10-H. A far-reaching implication of this finding is the possibility that trans-µ-OH/straight MIL-53-type MOFs will have polymorphs of CAU-10-H cis-µ-OH/helical topology and vice versa. HHUD-4 is a microporous MOF with a BET surface area of up to 940 m2 g-1 and a micropore volume of up to 0.39 cm3 g-1. Additionally, HHUD-4 features good adsorption uptakes of 3.77 mmol g-1 for CO2 and 1.25 mmol g-1 for CH4 at 273 K and 1 bar, respectively, and a high isosteric heat of adsorption of 11.4 kJ mol-1 for H2 with a maximum uptake of 6.36 mmol g-1 at 77 K and 1 bar. Vapor sorption experiments for water and volatile organic compounds (VOCs) such as benzene, cyclohexane and n-hexane yielded uptake values of 135, 269, 116 and 205 mg g-1, respectively, at 293 K. While HHUD-4 showed unremarkable results for water uptake and low stability for water, it exhibited good stability with steep VOC uptake steps at low relative pressures and a high selectivity of 17 for benzene/cyclohexane mixtures.


Assuntos
Estruturas Metalorgânicas , Índio , Benzeno/química , Gases , Água
10.
Molecules ; 28(2)2023 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-36677926

RESUMO

Carbon microcoils (CMCs) were formed on stainless steel substrates using C2H2 + SF6 gas flows in a thermal chemical vapor deposition (CVD) system. The manipulation of the SF6 gas flow rate and the SF6 gas flow injection time was carried out to obtain controllable CMC geometries. The change in CMC geometry, especially CMC diameter as a function of SF6 gas flow injection time, was remarkable. In addition, the incorporation of H2 gas into the C2H2 + SF6 gas flow system with cyclic SF6 gas flow caused the formation of the hybrid of carbon nanofibers-carbon microcoils (CNFs-CMCs). The hybrid of CNFs-CMCs was composed of numerous small-sized CNFs, which formed on the CMCs surfaces. The electromagnetic wave shielding effectiveness (SE) of the heating film, made by the hybrids of CNFs-CMCs incorporated carbon paste film, was investigated across operating frequencies in the 1.5-40 GHz range. It was compared to heating films made from commercial carbon paste or the controllable CMCs incorporated carbon paste. Although the electrical conductivity of the native commercial carbon paste was lowered by both the incorporation of the CMCs and the hybrids of CNFs-CMCs, the total SE values of the manufactured heating film increased following the incorporation of these materials. Considering the thickness of the heating film, the presently measured values rank highly among the previously reported total SE values. This dramatic improvement in the total SE values was mainly ascribed to the intrinsic characteristics of CMC and/or the hybrid of CNFs-CMCs contributing to the absorption shielding route of electromagnetic waves.


Assuntos
Calefação , Nanofibras , Carbono , Condutividade Elétrica , Gases
11.
Sensors (Basel) ; 23(2)2023 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-36679476

RESUMO

In recent years, there has been a growing desire to monitor and control harmful substances arising from industrial processes that impact upon our health and quality of life. This has led to a large market demand for gas sensors, which are commonly based on sensors that rely upon a chemical reaction with the target analyte. In contrast, thermal conductivity detectors are physical sensors that detect gases through a change in their thermal conductivity. Thermal conductivity gas sensors offer several advantages over their chemical (reactive) counterparts that include higher reproducibility, better stability, lower cost, lower power consumption, simpler construction, faster response time, longer lifetime, wide dynamic range, and smaller footprint. It is for these reasons, despite a poor selectivity, that they are gaining renewed interest after recent developments in MEMS-based silicon sensors allowing CMOS integration and smart application within the emerging Internet of Things (IoT). This timely review focuses on the state-of-the-art in thermal conductivity sensors; it contains a general introduction, theory of operation, interface electronics, use in commercial applications, and recent research developments. In addition, both steady-state and transient methods of operation are discussed with their relative advantages and disadvantages presented. Finally, some of recent innovations in thermal conductivity gas sensors are explored.


Assuntos
Eletrônica , Qualidade de Vida , Reprodutibilidade dos Testes , Gases , Indústrias
12.
Sensors (Basel) ; 23(2)2023 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-36679682

RESUMO

Sensor arrays are currently attracting the interest of researchers due to their potential of overcoming the limitations of single sensors regarding selectivity, required by specific applications. Among the materials used to develop sensor arrays, graphene has not been so far extensively exploited, despite its remarkable sensing capability. Here we present the development of a graphene-based sensor array prepared by dropcasting nanostructure and nanocomposite graphene solution on interdigitated substrates, with the aim to investigate the capability of the array to discriminate several gases related to specific applications, including environmental monitoring, food quality tracking, and breathomics. This goal is achieved in two steps: at first the sensing properties of the array have been assessed through ammonia exposures, drawing the calibration curves, estimating the limit of detection, which has been found in the ppb range for all sensors, and investigating stability and sensitivity; then, after performing exposures to acetone, ethanol, 2-propanol, sodium hypochlorite, and water vapour, chemometric tools have been exploited to investigate the discrimination capability of the array, including principal component analysis (PCA), linear discriminant analysis (LDA), and Mahalanobis distance. PCA shows that the array was able to discriminate all the tested gases with an explained variance around 95%, while with an LDA approach the array can be trained to accurately recognize unknown gas contribution, with an accuracy higher than 94%.


Assuntos
Grafite , Nanocompostos , Amônia , Grafite/química , Quimiometria , Gases/análise
13.
Sensors (Basel) ; 23(2)2023 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-36679777

RESUMO

A fully transportable laser heterodyne radiometer (LHR), involving a flexible polycrystalline mid-infrared (PIR) fiber-coupling system and operating around 8 µm, was characterized and optimized with the help of a calibrated high temperature blackbody source to simulate solar radiation. Compared to a mid-IR free-space sunlight coupling system, usually used in a current LHR, such a fiber-coupling system configuration makes the mid-infrared (MIR) LHR fully transportable. The noise sources, heterodyne signal, and SNR of the MIR LHR were analyzed, and the optimum operating local oscillator (LO) photocurrent was experimentally obtained. The spectroscopic performance of the MIR LHR was finally evaluated. This work demonstrated that the developed fully transportable MIR LHR could be used for ground-based atmospheric sounding measurements of multiple trace gases in the atmospheric column. In addition, it also has high potential for applications on spacecraft or on an airborne platform.


Assuntos
Lasers , Radiometria , Análise Espectral/métodos , Gases , Luz
14.
Sensors (Basel) ; 23(2)2023 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-36679816

RESUMO

The gas sweetening process removes hydrogen sulfide (H2S) in an acid gas removal unit (AGRU) to meet the gas sales' specification, known as sweet gas. Monitoring the concentration of H2S in sweet gas is crucial to avoid operational and environmental issues. This study shows the capability of artificial neural networks (ANN) to predict the concentration of H2S in sweet gas. The concentration of N-methyldiethanolamine (MDEA) and Piperazine (PZ), temperature and pressure as inputs, and the concentration of H2S in sweet gas as outputs have been used to create the ANN network. Two distinct backpropagation techniques with various transfer functions and numbers of neurons were used to train the ANN models. Multiple linear regression (MLR) was used to compare the outcomes of the ANN models. The models' performance was assessed using the mean absolute error (MAE), root mean square error (RMSE), and coefficient of determination (R2). The findings demonstrate that ANN trained by the Levenberg-Marquardt technique, equipped with a logistic sigmoid (logsig) transfer function with three neurons achieved the highest R2 (0.966) and the lowest MAE (0.066) and RMSE (0.122) values. The findings suggested that ANN can be a reliable and accurate prediction method in predicting the concentration of H2S in sweet gas.


Assuntos
Sulfeto de Hidrogênio , Redes Neurais de Computação , Solventes , Modelos Lineares , Gases
15.
J Chem Phys ; 158(3): 034508, 2023 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-36681639

RESUMO

Simulations of water near extended hydrophobic spherical solutes have revealed the presence of a region of depleted density and accompanying enhanced density fluctuations. The physical origin of both phenomena has remained somewhat obscure. We investigate these effects employing a mesoscopic binding potential analysis, classical density functional theory (DFT) calculations for a simple Lennard-Jones solvent, and Grand Canonical Monte Carlo (GCMC) simulations of a monatomic water (mw) model. We argue that the density depletion and enhanced fluctuations are near-critical phenomena. Specifically, we show that they can be viewed as remnants of the critical drying surface phase transition that occurs at bulk liquid-vapor coexistence in the macroscopic planar limit, i.e., as the solute radius Rs → ∞. Focusing on the radial density profile ρ(r) and a sensitive spatial measure of fluctuations, the local compressibility profile χ(r), our binding potential analysis provides explicit predictions for the manner in which the key features of ρ(r) and χ(r) scale with Rs, the strength of solute-water attraction ɛsf, and the deviation from liquid-vapor coexistence of the chemical potential, δµ. These scaling predictions are confirmed by our DFT calculations and GCMC simulations. As such, our theory provides a firm basis for understanding the physics of hydrophobic solvation.


Assuntos
Física , Água , Solventes/química , Água/química , Soluções , Transição de Fase , Gases
16.
Lett Appl Microbiol ; 76(1)2023 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-36688788

RESUMO

An evaluation of the efficacy of 35% hydrogen peroxide vapor (HPV) against a novel Simian Immunodeficiency retrovirus (SIV) was conducted in a 624m3 GMP grade C manufacturing facility. SIV biological indicators, with an average titre of 7.11×108 TU/mL [equivalent to 1.3×108 Reverse transcriptase (RT) nanounits when analysed by F-PERT], were produced on-site using virus presented within an anticipated worst-case support matrix based on the manufacturers commercially confidential virus support media. SIV biological indicators were distributed around the manufacturing facility, including locations identified as key contamination control points by the manufacturer, and exposed to a HPV cycle. Commercially available biological indicators of 6 log10Geobacillus stearothermophilus were co-located with the SIV Biological Indicator (BIs). HPV was found to be efficacious in eliminating the SIV and commercial G. stearothermophilus BIs and offers a simple and robust method for biodecontamination of gene therapy facilities.


Assuntos
Peróxido de Hidrogênio , Infecções por Papillomavirus , Humanos , Vetores Genéticos , Gases , Terapia Genética , Instalações Industriais e de Manufatura
17.
Anal Methods ; 15(3): 368-376, 2023 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-36597774

RESUMO

Photoionization mass spectrometry (PI-MS) has become a versatile tool in the real-time analysis of volatile organic compounds (VOCs) from the atmosphere or exhaled breath. However, some key species, e.g., acetonitrile, are hard to measure due to their higher ionization energies than photon energy. In this study, the direct and sensitive detection of gaseous acetonitrile based on a photoinduced associative ionization (PAI) reaction was investigated with a laboratory-built PAI time-of-flight mass spectrometer (PAI-TOFMS). By doping CH2Cl2 in the photoionization ion source, the mass signal of acetonitrile that cannot be effectively obtained by photoionization appeared with an extremely high intensity through the PAI reaction between acetonitrile, CH2Cl2, and residual H2O in the system. Though the moisture in the sample gas has an evident impact on the detection efficiency of acetonitrile, with a relative signal intensity decreasing from 100% under dry conditions to 60% at saturated relative humidity, excellent detection sensitivity was still obtained for gaseous acetonitrile in different matrixes. The sensitivity calibration experiment showed that the detection sensitivities of acetonitrile in N2 buffer gas, exhaled gas, and outdoor air were 682.4 ± 5.2, 17.0 ± 0.7, and 23.9 ± 0.2 counts pptv-1, respectively, with an analysis time of 10 s. The corresponding 3σ LODs reached 0.22, 8.82, and 6.28 pptv, which are equivalent to 0.40, 16.0, and 11.4 ng m-3. The performance of the PAI-TOFMS was first demonstrated by analyzing exhaled acetonitrile from healthy non-smokers and smokers and continuous monitoring of acetonitrile in outdoor air. In summary, this study provides a new and highly sensitive method for the real-time detection of acetonitrile through mass spectrometry.


Assuntos
Expiração , Compostos Orgânicos Voláteis , Espectrometria de Massas/métodos , Compostos Orgânicos Voláteis/análise , Fenômenos Químicos , Gases
18.
Biosensors (Basel) ; 13(1)2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-36671911

RESUMO

Quantifying the viscosity of a gas is of great importance in determining its properties and can even be used to identify what the gas is. While many techniques exist for measuring the viscosities of gases, it is still challenging to probe gases with a simple, robust setup that will be useful for practical applications. We introduce a facile approach to estimating gas viscosity using a strain gauge inserted in a straight microchannel with a height smaller than that of the gauge. Using a constrained geometry for the strain gauge, in which part of the gauge deforms the channel to generate initial gauge strain that can be transduced into pressure, the pressure change induced via fluid flow was measured. The change was found to linearly correlate with fluid viscosity, allowing estimation of the viscosities of gases with a simple device.


Assuntos
Gases , Viscosidade , Pressão
19.
Int J Mol Sci ; 24(2)2023 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-36675093

RESUMO

The paper considers the relationship between the structure and properties of nanostructured conductometric sensors based on binary mixtures of semiconductor oxides designed to detect reducing gases in the environment. The sensor effect in such systems is determined by the chemisorption of molecules on the surface of catalytically active particles and the transfer of chemisorbed products to electron-rich nanoparticles, where these products react with the analyzed gas. In this regard, the role is evaluated of the method of synthesizing the composites, the catalytic activity of metal oxides (CeO2, SnO2, ZnO), and the type of conductivity of metal oxides (Co3O4, ZrO2) in the sensor process. The effect of oxygen vacancies present in the composites on the performance characteristics is also considered. Particular attention is paid to the influence of the synthesis procedure for preparing sensitive layers based on CeO2-In2O3 on the structure of the resulting composites, as well as their conductive and sensor properties.


Assuntos
Nanopartículas , Óxidos , Óxidos/química , Gases/química
20.
Molecules ; 28(2)2023 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-36677843

RESUMO

Five types of odor-emitting exhaust gases from medical waste were selected, and their adsorption capacity and desorption efficiency were investigated using activated carbon. The selected gases included polar gases (hydrogen sulfide (H2S) and ammonia (NH3)) and non-polar gases (acetaldehyde (AA), methyl mercaptan (MM), and trimethylamine (TMA))). Commercial activated carbon with a specific surface area of 2276 m2/g was used as the adsorbent. For the removal of odor from medical waste, we investigated: (1) the effective adsorption capacity of a single gas (<1 ppm), (2) the effect of the adsorbed NH3 gas concentration and flow rate, and (3) the desorption rate using NH3 gas. The values of the effective adsorption capacity of the single gas were in the following order: H2S < NH3 < AA < MM < TMA, at 0.2, 4.2, 6.3, 6.6, and 35.7 mg/g, respectively. The results indicate that polar gases have a lower effective adsorption capacity than that of non-polar gases, and that the size of the gas molecules and effective adsorption capacity exhibit a proportional relationship. The effective adsorption performance of NH3 gas showed an increasing trend with NH3 concentration. Therefore, securing optimal conditions for adsorption/desorption is imperative for the highly efficient removal of odor from medical waste.


Assuntos
Sulfeto de Hidrogênio , Resíduos de Serviços de Saúde , Carvão Vegetal , Odorantes , Adsorção , Gases , Amônia
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