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Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Tetragonal graphene nano-capsule (TGC), a novel stable carbon allotrope of sp2 hybridization is designed and doped with phosphorus (P) to study the O3 and SO2 gas sensitivity via density functional theory calculation. Real frequencies verified the natural existence of both TGC and P-doped TGC (PTGC). Both TGC and PTGC suffer structural deformations due to interaction with O3 and SO2 gases. The amount of charge transfer from the adsorbent to the gas molecule is significantly greater for O3 adsorption than SO2 adsorption. The adsorption energies for TGC + O3 and PTGC + O3 complexes are − 3.46 and − 4.34 eV respectively, whereas for TGC + SO2 and PTGC + SO2 complexes the value decreased to − 0.29 and − 0.30 eV respectively. The dissociation of O3 is observed via interaction with PTGC. A significant variation in electronic energy gap and conductivity results from gas adsorption which can provide efficient electrical responses via gas adsorption. The blue/red shift in the optical response proved to be a way of detecting the types of adsorbed gases. The adsorption of O3 is exothermic and spontaneous whereas the adsorption of SO2 is endothermic and non-spontaneous. The negative change in entropy verifies the thermodynamic stability of all the complexes. QTAIM analysis reveals strong covalent or partial covalent interactions between absorbent and adsorbate. The significant variation in electrical and optical response with optimal adsorbent-gas interaction strength makes both TGC and PTGC promising candidates for O3 and SO2 sensing.

Tetragonal graphene nano-capsule (TGC), a novel stable carbon allotrope of sp2 hybridization is designed and doped with phosphorus (P) to study the O3 and SO2 gas sensitivity via density functional theory calculation. Real frequencies verified the natural existence of both TGC and P-doped TGC (PTGC). Both TGC and PTGC suffer structural deformations due to interaction with O3 and SO2 gases. The amount of charge transfer from the adsorbent to the gas molecule is significantly greater for O3 adsorption than SO2 adsorption. The adsorption energies for TGC + O3 and PTGC + O3 complexes are − 3.46 and − 4.34 eV respectively, whereas for TGC + SO2 and PTGC + SO2 complexes the value decreased to − 0.29 and − 0.30 eV respectively. The dissociation of O3 is observed via interaction with PTGC. A significant variation in electronic energy gap and conductivity results from gas adsorption which can provide efficient electrical responses via gas adsorption. The blue/red shift in the optical response proved to be a way of detecting the types of adsorbed gases. The adsorption of O3 is exothermic and spontaneous whereas the adsorption of SO2 is endothermic and non-spontaneous. The negative change in entropy verifies the thermodynamic stability of all the complexes. QTAIM analysis reveals strong covalent or partial covalent interactions between absorbent and adsorbate. The significant variation in electrical and optical response with optimal adsorbent-gas interaction strength makes both TGC and PTGC promising candidates for O3 and SO2 sensing. [ABSTRACT FROM AUTHOR]

As living standards improve worldwide, the demand for energy increases. However, climate changes and decreasing fossil fuel deposits have increased interest in renewable energy sources, including pellets produced from forest residues. This study aimed to compare changes in concentration of gases (CO, CO2, O2, volatile organic compounds—VOCs) in enclosed headspaces above pellets produced from deciduous (oak OA, birch BI) and coniferous (pine PI, spruce SP) dendromass and selected types of commercial pellets during their storage. The experiment measured the concentration of gas released from the pellets in storage daily for 14 days. The highest mean CO concentration was found for PI pellets (1194 ppm), and the lowest was for OA (63.3 ppm). Likewise, the highest CO2 concentration was noted for PI pellets (4650 ppm), and the lowest was for BI (1279 ppm). The largest VOC amount was released in the headspace above PI (88.8 ppm), and the smallest was above BI (4.6 ppm). The oxygen concentration was the lowest as measured for PI (minimum 16.1% v/v) and for SP (19.3% v/v). The threshold limit value (8 h) for CO was exceeded for all the pellets under analysis and, in the case of CO2, only for PI after day 10 of incubation. The study findings are extremely important from a scientific (but mainly from a practical) perspective because of the safety of storing and transporting wood pellets. The knowledge of autooxidation processes in those biofuels can help organize their logistics and storage and result in proper warehouse ventilation and monitoring of noxious gases. [ABSTRACT FROM AUTHOR]

Clostridium perfringens is a versatile pathogen, inducing diseases in the skin, intestine (such as chicken necrotic enteritis (NE)), and other organs. The classical sign of NE is the foul smell gas in the ballooned small intestine. We hypothesized that deoxycholic acid (DCA) reduced NE by inhibiting C. perfringens virulence signaling pathways. To evaluate the hypothesis, C. perfringens strains CP1 and wild-type (WT) HN13 and its mutants were cultured with different bile acids, including DCA and isoallolithocholic acid (isoalloLCA). Growth, hydrogen sulfide (H2S) production, and virulence gene expression were measured. Notably, isoalloLCA was more potent in reducing growth, H2S production, and virulence gene expression in CP1 and WT HN13 compared to DCA, while other bile acids were less potent compared to DCA. Interestingly, there was a slightly different impact between DCA and isoalloLCA on the growth, H2S production, and virulence gene expression in the three HN13 mutants, suggesting possibly different signaling pathways modulated by the two bile acids. In conclusion, DCA and isoalloLCA reduced C. perfringens virulence by transcriptionally modulating the pathogen signaling pathways. The findings could be used to design new strategies to prevent and treat C. perfringens-induced diseases. [ABSTRACT FROM AUTHOR]

ABSTRACT The aim of the present study was to analyze the histomorphology and histopathology of broiler chicken tracheas submitted to different levels of ammonia gas. The experiment was conducted during different seasons in 2019 in the city of Garanhuns, Brazil. Three sheds with rice hull bedding were used: Shed 1, new bedding; Shed 2, reused bedding; Shed 3, reused bedding with an increase in moisture. Twenty-eight birds were housed per shed for a 42-day production cycle. On days D0 (control group), D7, D21, D35 and D42, seven birds per shed were euthanized. Fragments of the trachea were collected and placed into plastic containers with 10% buffered formalin solution (pH 7) for 24 h, subsequently undergoing routine histological processing. The thickness of the tracheal mucosa was measured using digital images, considering ten equidistant points as being separated by 100 µm. Histopathological lesions were analyzed considering distribution and intensity. The birds in Shed 2 (reused bedding) had greater quantity and severity of histopathological lesions, but the differences did not reach statistical significance. Regarding histomorphometry, birds reared in the higher temperature period had thicker tracheal mucosa at the end of the production cycle (D35 and D42) compared to those raised in the cooler temperature period. In conclusion, the difference in bedding did not significantly alter the tracheal mucosa of the birds, whereas temperature exerted an influence on the thickness of the trachea at the end of the production cycle.

This study proposes an assessment method to quantify the risks of the smoke environment for road tunnel fire safety based on previous studies. The assessment method integrates visibility and toxic gases to address the hazards of smoke distribution more comprehensively. Considering that the hazards of visibility reduction and toxic gases for tunnel users vary with exposure time and location in a fire event, the smoke environment (SE) levels are defined as a function of longitudinal location and time. The SE levels simplify smoke distribution as calculated from 3D computational fluid dynamics (CFDs). For easily identifying SE risks, SE levels are illustrated on a 2D map to analyze the potential hazard by quantifying specific areas and times of smoke exposure. To demonstrate the applicability of the assessment method of this study, cases are carried out using CFD simulation to investigate the risks associated with tunnel fires with various tunnel cross-section types, longitudinal velocities, and gradients. In the analysis of the SE level in different cross-section types and longitudinal velocities under the condition of no vehicle, a velocity of 0.9–1.1 m/s can maintain a less serious SE level both upstream and downstream in a horizontal rectangular tunnel, and 0.3–0.5 m/s in a horizontal horseshoe-shaped tunnel. Both rectangular and horseshoe-shaped tunnels reveal an obvious rise within 10–15 min. In the case of inclined tunnels, for both rectangular and horseshoe-shaped tunnels, the SE level near the fire source obviously deteriorates. Thus, the longitudinal velocity range for the purpose of maintaining a relatively less serious SE level should be slightly reduced for inclined tunnels compared with horizontal tunnels. [ABSTRACT FROM AUTHOR]

Environmental risk can result from the interaction between human activity and the environment. Human activities can generate certain changes in the environmental components, thus inducing a potential danger for the health of people, flora, vegetation and fauna through the negative effects they have on water resources, air and soil quality, climate, microclimate, and so on. This paper presents the potable water treatment plant from Zănoaga, located in Petroșani Municipality, and highlights the potential risks related to the activity within this plant. Particular emphasis is placed on the risk to the environment and human health that may arise from improper storage and handling of liquid chlorine tanks, chlorine being a toxic gas if found in high concentrations in air, water or soil. [ABSTRACT FROM AUTHOR]

On August 15, 1984 at Lake Monoun and on August 21, 1986 at Lake Nyos, 37 and 1,746 people, respectively, died from gas fumes. Lakes Monoun and Nyos are peculiar aquatic ecosystems located on the Cameroon Volcanic Line, a strategic site, which continue to draw the attention of scientists, stakeholders, policy makers, public authorities as well as local communities and indigenous. It has been clearly demonstrated that these two lakes store large quantities of toxic gasses in dissolved form in their bottom. Indeed, the extremely diverse microbial communities that colonizes these lakes are capable of producing, storing and releasing gasses. These particularities have earned these lakes the name “killer lakes”. Although relevant results have been obtained after the installation of degassing devices on these lakes, these results are less popularized and Cameroonian society, in particular natives of the disaster-stricken areas have remained skeptic and divided on the origin of gasses: 9.4% of survivors and residents interviewed said it was a nuclear test. Also, 78.13% supported the thesis of a mystical-religious phenomenon. Only 12.47% of the interviewees understood that it was a scientifically explainable phenomenon. Clearly, the gap between science, scientists and societies is quite perceptible. Based on the deadly catastrophes of these two lakes, we present here the fracture that exists between science and African societies still anchored in indigenous beliefs.

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • Adsorption of COCl 2 , O 3 , and HCN gas on C 3 N and Ti-doped C 3 N nanosheet. • Ti-doping on C 3 N results in low band gap semiconductor. • Both sheets show strong adsorbent-gas interaction. • Significant variation in optical and electronic properties was observed due to adsorption. In the present study, we designed the pristine C 3 N and Ti-doped C 3 N nanosheets to investigate the geometrical, electrical, and optical properties using density functional theory calculation. The negative value of the cohesive energy of both nanosheets indicates the structures are energetically stable. Ti-doping in C 3 N results in a conductor-to-semiconductor transition with a band gap of 0.15 eV. We studied the adsorption of COCl 2 , O 3 , and HCN gas molecules on the designed structures. The adsorption energy for COCl 2 , O 3 , and HCN gases significantly increased to −8.63, −9.80, and −5.98 eV respectively after Ti-doping. A significant variation in the band gap of Ti-doped C 3 N is observed due to gas adsorption. The complex structures show a high absorption coefficient of over 104 cm−1 in the visible range with a significant red/blue shifting of absorption peaks. The study proves the Ti-doped C 3 N to be a potential candidate for sensing COCl 2 , O 3 , and HCN gases. [ABSTRACT FROM AUTHOR]

Clostridium perfringens is a versatile pathogen, inducing diseases in the skin, intestine (such as chicken necrotic enteritis (NE)), and other organs. The classical sign of NE is the foul smell gas in the ballooned small intestine. We hypothesized that deoxycholic acid (DCA) reduced NE by inhibiting C. perfringens virulence signaling pathways. To evaluate the hypothesis, C. perfringens strains CP1 and wild-type (WT) HN13 and its mutants were cultured with different bile acids, including DCA and isoallolithocholic acid (isoalloLCA). Growth, hydrogen sulfide (H2S) production, and virulence gene expression were measured. Notably, isoalloLCA was more potent in reducing growth, H2S production, and virulence gene expression in CP1 and WT HN13 compared to DCA, while other bile acids were less potent compared to DCA. Interestingly, there was a slightly different impact between DCA and isoalloLCA on the growth, H2S production, and virulence gene expression in the three HN13 mutants, suggesting possibly different signaling pathways modulated by the two bile acids. In conclusion, DCA and isoalloLCA reduced C. perfringens virulence by transcriptionally modulating the pathogen signaling pathways. The findings could be used to design new strategies to prevent and treat C. perfringens-induced diseases.

Real-time monitoring and accurate prediction of toxic gas concentration in the future are of great significance for emergency capability assessment and rescue work. At present, the method of gas concentration prediction based on artificial intelligence still has problems of low accuracy, slow convergence speed and equal feature importance. This paper proposes a feature-aware LSTM model to predict pollutant gas concentration. First of all, we design a set of multi-component toxic gas monitoring equipment that applies in pollution environment, which can at the same time monitor CO, NO2, NH3, HCN, H2S and SO2, six common pollutants; To accurate estimate the toxic gas concentration, we combine the collected the gas data and the environmental parameters and regard them as the input features, and then we obtain toxic gas data based on the sampling policy and the environmental data as our data-set. Finally, we train a FA-LSTM gas concentration prediction model on these data-set. We test the proposed model and compared with ARIMA, ETS and BP network on the same test set. Experimental results show that the proposed model outperforms traditional concentration prediction model. Also, it is better than other state-of-the-art models in predicting accuracy.

This study presents the investigation of the use of blue phase liquid crystals (BPLCs) for the sensing of toxic gas vapours of toluene, phenol and 1,2 dichloropropane. The vapours of these three toxic solvents were obtained by evaporating at different temperatures within the different times, and BPLC was separately exposed to these gas vapours. The diffusion and adsorption of these vapours on the BPLCs were investigated depending on the dimensions and polarity of the molecules. The optical response of BPLC exposed to gas vapours of toluene, phenol and 1,2 dichloropropane was determined with Bragg reflection wavelength as a function of temperature and time. We found that BPLC produced a remarkable change to the red side of the spectrum due to diffusion of toluene gas vapour by the BPLC sample and itsBragg reflection wavelength change within the time showed a good linearity correlation. Moreover, the diffusion coefficient of the toluene gas vapour in BPLC sample was calculated, and it was determined as 8.224 × 10−12 (cm2/s) by using a least-squares method. [ABSTRACT FROM AUTHOR]

A cost-effective, simple, flexible, and disposable colorimetric film sensor was constructed for the rapid detection of gaseous ammonia. The sensor was designed to consist of three layers, namely top, middle, and bottom layers of a polymeric elastomer. The bromocresol (BCG) indicator embedded in the middle layer of the film facilitated a change in color of the sensor from yellow-orange to blue upon exposure to gaseous ammonia. The color change was visually observed by the naked eye. The sensitivity of the sensor was verified by a successful detection of gaseous ammonia at concentrations from 4 to 235 ppm within 3 min, and the corresponding visual detection of ammonia gas was at a concentration as low as 11 ppm. The sensor also achieved a selective detection of gaseous ammonia over a variety of alkaline chemicals. The color of the sensor exposed to ammonia reverted from blue to the original yellow-orange upon subsequent exposure to the fume of acetic acid or aeration for 48 h, and it showed reliable performance for the detection of gaseous ammonia even after five repeated uses. The applicability of the sensor was validated by attaching it onto a safety helmet for a simulation of an industrial ammonia gas leak. The results indicated that our colorimetric film sensor is affordable, disposable, and reproducible, and can serve as an effective alternative for simple and rapid recognition of gaseous ammonia in environmental and air quality monitoring as well as in industrial applications. [ABSTRACT FROM AUTHOR]

Introduction: Phosgene is a highly toxic gas causing irritation of the airways and eyes though at high dose exposure. The effect on airways can be assessed by peak expiratory flow rate (PEFR) which is a cheaper, simple, and easy to perform test under field conditions and routine monitoring. Thus, this study is undertaken to understand the effect of chronic low-dose phosgene exposure on PEFR and the associated factors. Methods: This study included 287 workers of phosgene production and captive units. After recording the demographic, occupational, and clinical history on a questionnaire, every participant was subjected to clinical examination, chest radiography, and measurement of PEFR using Spirovit SP-10. Results: The mean age and mean duration of the job of participants was 42.8 ± 10.4 years and 18.9 ± 9.6 years, respectively. The PEFR was significantly reduced with increasing age, increasing duration in the job, and those having direct exposure. Conclusion: PEFR is affected by chronic low-dose exposure to phosgene. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are used progressively in sensing areas because of their special electrical properties due to their extremely small size. This paper discusses the gas sensing features of QD-based resistive sensors. Different types of pristine, doped, composite, and noble metal decorated QDs are discussed. In particular, the review focus primarily on the sensing mechanisms suggested for these gas sensors. QDs show a high sensing performance at generally low temperatures owing to their extremely small sizes, making them promising materials for the realization of reliable and high-output gas-sensing devices. [ABSTRACT FROM AUTHOR]

Carbonate-based electrolytes are often employed as the preferred electrolyte for both Li-ion and Na-ion cells. To investigate the fire risk during abuse conditions in real-life scenarios covering the full value chain, not only cell-level studies but also component-level investigation is crucial. Hence, Na-ion advanced electrolyte combustion tests are performed employing the fire propagation apparatus also called Tewarson calorimeter. Heat and combustion products releases are measured, making use of fire calorimetry laws and analytical techniques such as FTIR, NDIR, FID, or paramagnetic analyzers, and optical measurement. Thermal and chemical impacts of Na-ion electrolytes combustion and fires are assessed under well-ventilated and under-ventilated environments. Data are then compared against a carbonate-based electrolyte used in Li-ion batteries to create a comparative study between these technologies. Overall, the heat released rate majorly depends upon the solvents used and is less impacted by inorganic Li or Na salts while the emitted gases depend on both solvent and salt chemistry. Another key observation lies in the different fate of the fluorine element chemically bound to the concerned salts: in similar burning conditions, F from NaPF 6 decomposition is preferably converted in F-containing solid species in the residues whilst LiPF 6 gives off more gaseous species such as HF. • Fire behavior of Na-ion electrolytes with and without additives were studied. • A comparison was established with classical Li-ion electrolyte. • Heat release rate revealed mainly governed by the solvent components. • Chemical threat influenced by salts and additives, and ventilation degree. • Fluorine fate of Na-ion and Li-ion electrolytes reveals a quite different trend. [ABSTRACT FROM AUTHOR]

The timely detection and monitoring of toxic gases are crucial for preserving the ecological environment and preventing their adverse effects on human health. In this study, we investigate the adsorption characteristics and sensitivity performance of Pd- and Pt-decorated InSe monolayers, referred to as Pd-InSe and Pt-InSe, towards five toxic gases (CO, NO, NH 3 , H 2 S, and SO 2) using first-principle calculations. The results show that the doping of Pd and Pt atoms significantly improves the conductivity, adsorption capabilities, and sensing properties of InSe monolayer to these toxic gases. Both Pd-InSe and Pt-InSe monolayers exhibit chemical adsorption of CO, NO, NH 3 , and H 2 S, with adsorption energies ranging from –0.56 eV to –1.04 eV, leading to noticeable changes in the bandgap (8.84 % ∼ 31.03 %). Furthermore, the CO/Pd-InSe and H 2 S/Pt-InSe systems demonstrate excellent sensitivity, with high sensing response values of 1.54×104 and 66.20, respectively, and their sensitivity remains unaffected under humid environments. Importantly, Pt-InSe exhibits a fast recovery time of 0.05 s at 298 K, making it highly promising for the recyclable detection of H 2 S at room temperature. In contrast, Pd-InSe can be utilized as a reusable gas sensor for CO at 448 K with a good recovery time of 0.5 s. This work can provides theoretical guidance for the design and fabrication of InSe-based gas sensors for the detection of toxic gases. [Display omitted] • The influence of Pd and Pt doping on five toxic gases adsorption on InSe was studied. • Both Pd-InSe and Pt-InSe monolayers exhibit chemisorption for the CO, NO, NH3 and H2S. • Adsorption of those hazardous gases on Pd-InSe and Pt-InSe remain unaffected under humid conditions. • Sensing mechanism of Pd-InSe and Pt-InSe towards toxic gases were revealed. • Pt-InSe holds significant promise for the recyclable detection of H2S at room temperature. [ABSTRACT FROM AUTHOR]

The gas sensing and removal prospective was investigated in the current work to analyze a beryllium oxide (BeO) fullerene for the adsorptions of ammonia (NH 3), phosphine (PH 3), and arsine (AsH 3) toxic gases along with applications density functional theory (DFT) calculations. The optimization of models yielded the formations of interacting BeO-NH 3 , BeO-PH 3 , and BeO-AsH 3 complexes with the adsorption strengths of −25.96, −8.75, −29.09 kcal/mol, respectively. The models were analyzed further based on the nature of interactions, in which the beryllium atom showed a significant role of the existence of interactions through the formation of direct Be...N, Be...P, and Be...As interactions. Analyses of structural features indicated a priority of formation for the BeO-AsH 3 complex in comparison with the BeO-NH 3 and BeO-PH 3 complexes. The evaluated electronic features based on the frontier molecular orbitals and transferred charges also indicated a differential diagnosis of models along with a meaningful sensing activity of BeO for the gas substances. As a consequence, the successful formation of BeO-NH 3 , BeO-PH 3 , and BeO-AsH 3 complexes and their featured properties were found useful for approaching the sensing and removal prospective applications. [Display omitted] • Adsorptions of NH 3 , PH 3 , and AsH 3 toxic gases by a BeO fullerene were investigated. • Formations of BeO-NH 3 , BeO-PH 3 , and BeO-AsH 3 complexes were confirmed. • The strength order of complexes was found as BeO-AsH 3 > BeO-NH 3 > BeO-PH 3. • QTAIM analyses indicated the strength order of interactions as Be...As > Be...N > Be...P. • Electronic molecular orbitals variations indicated a sensing function. [ABSTRACT FROM AUTHOR]

• Pure and Ti doped graphene is explored as a detection of COX 2 gas. • Au doped graphene has significant therapeutic potential as a gas sensor. • The physical nature of the gas interactions with Au doped graphene is supported by the DFT calculation. The need for highly sensitive toxic gas sensors is significant, and achieving this sensitivity is possible. Researchers have utilized density functional theory (DFT) computations to examine adsorption of different gas molecules (COX 2 , where X is F, Cl, or Br) over Au-doped and pristine graphene. This investigation aims to determine possibility of employing Au-doped graphene as a basis for gas sensors. Multiple adsorption positions and orientations were examined for each gas molecule. The configuration that exhibited the highest stability was identified, and adsorption energy (E ads) values, considering van der Waals (vdW) interactions, have been computed using NCI analyses. In addition, the electronic properties, including LUMO HOMO orbital density and charge transfer, were analyzed to acquire a deeper understanding of process by which adsorption occurs. Findings indicated that gas molecules under investigation exhibited weak adsorption on pristine graphene, with low E ads values. In contrast, E ads values of every gas molecule on Au-doped graphene displayed varying degrees of increase. Notably, COX 2 exhibited a high sensitivity to Au-doped graphene. Furthermore, in the effect of doping Au into graphene, the E ads absorption of COCl 2 gas has increased from 0.155 to 1.028 eV. This indicates the strong tendency of Au-doped graphene to interact with gas COCl 2 compared to two other COX 2 gas species. This strong adsorption can be ascribed to significant substantial charge transfer (CT) between COCl 2 and Au-doped graphene and orbital hybridization. The charge transfer amount of the doped states has increased by more than double compared to the pure state. The band gap of Au-doped graphene has decreased from 2.14 to 1.83 eV due to the absorption of gas COCl 2 , indicating the highest amount of reduction compared to other gases. Moreover, the enhanced electrical conductivity of Au-doped graphene renders it more valuable and sensitive in the context of sensing COX 2 gases. [Display omitted] [ABSTRACT FROM AUTHOR]

Adsorption mechanism studies of toxic gases (CH 2 O, SO 2 , NH 3 , CO, NO, and NO 2) on pristine, one B-atom and Mo-atom (1B/Mo) and two B-atom and Mo-atom (2B/Mo) co-doped g-C3N4 were investigated based on the density functional theory. It is shown that gases adsorbed on the 1B(2B)/Mo-g-C 3 N 4 surface exhibit a variety of bandgap types such as magnetic half-metal, magnetic metal, and magnetic semiconductor, and the magnetic properties change considerably. The partial density of states suggests strong hybridization between gas molecules with Mo-4d (B1-2p and B2-2p) and C-2p (N-2p). NH 3 gas adsorbed on the 1B(2B)/Mo-g-C 3 N 4 surface acts as a donor and the remaining five gas molecules act as acceptors. CH 2 O gas adsorbed on 1B/Mo-g-C 3 N 4 has suitable adsorption energy, large charge transfer, short recovery time, and large conductivity change. Therefore 1B/Mo-g-C 3 N 4 can be used as a good sensor to detect CH 2 O. Lower sensitivity, long recovery times, or insignificant conductivity changes make 1B/Mo-g-C 3 N 4 unsuitable for the detection of CO, NO, NH 3 , and SO 2 gases. However, 1B/Mo-g-C 3 N 4 can be used as a one-time detection for NO 2 gas. The recovery time of gases adsorbed on the surface of 2B/Mo-g-C 3 N 4 ranges from 1.93 × 1020 h to 6.43 × 1068 h. However, the large adsorption energies (−2.12 eV to −4.99 eV), the high sensitivity, and the high electrical conductivity allow the use of 2B/Mo-g-C 3 N 4 as a disposable assay for gas molecules. [Display omitted] • Gas adsorption exhibits a variety of band gap types. • Strong hybridization between gases and Mo-4d (B1-2p and B2-2p) and C-2p (N-2p) • 1B/Mo-g-C 3 N 4 can be a good sensor for CH 2 O detection. • 2B/Mo-g-C 3 N 4 can be used as a one-time detection of gas molecules. [ABSTRACT FROM AUTHOR]

This study proposes an assessment method to quantify the risks of the smoke environment for road tunnel fire safety based on previous studies. The assessment method integrates visibility and toxic gases to address the hazards of smoke distribution more comprehensively. Considering that the hazards of visibility reduction and toxic gases for tunnel users vary with exposure time and location in a fire event, the smoke environment (SE) levels are defined as a function of longitudinal location and time. The SE levels simplify smoke distribution as calculated from 3D computational fluid dynamics (CFDs). For easily identifying SE risks, SE levels are illustrated on a 2D map to analyze the potential hazard by quantifying specific areas and times of smoke exposure. To demonstrate the applicability of the assessment method of this study, cases are carried out using CFD simulation to investigate the risks associated with tunnel fires with various tunnel cross-section types, longitudinal velocities, and gradients. In the analysis of the SE level in different cross-section types and longitudinal velocities under the condition of no vehicle, a velocity of 0.9–1.1 m/s can maintain a less serious SE level both upstream and downstream in a horizontal rectangular tunnel, and 0.3–0.5 m/s in a horizontal horseshoe-shaped tunnel. Both rectangular and horseshoe-shaped tunnels reveal an obvious rise within 10–15 min. In the case of inclined tunnels, for both rectangular and horseshoe-shaped tunnels, the SE level near the fire source obviously deteriorates. Thus, the longitudinal velocity range for the purpose of maintaining a relatively less serious SE level should be slightly reduced for inclined tunnels compared with horizontal tunnels.

The advantages and disadvantages of gas sensors for measuring the content of toxic substances in work zone air are reviewed. The main standards and normative documents outlining the requirements for the instrumentation for measuring the content of harmful substances in work zone air are considered. Experimental setup for investigating the characteristics of amperometric sensors, measurement procedure and experimental results are described. Comparative analysis of the characteristics of sensors produced by various manufacturers are presented. Recommendations are given on the practical use of the obtained data for developing measuring instruments satisfying the requirements of the domestic regulations. [ABSTRACT FROM AUTHOR]

[Display omitted] A sandwich-like melamine/phytic acid/silicon nitride hybrid (SW-Si 3 N 4) sheets were prepared by supramolecular wrapping as the hybrid flame retardants for thermoplastic polyurethane (TPU). The introduction of Si 3 N 4 sheets as a template could not only induce the generation of two-dimensional phytic/melamine (PAMA) capping layers, but also produce the synergistic flame-retardant effect on TPU composites. Cone test showed that heat release rate (HRR), smoke production rate (SPR) and total smoke production (TSP) values of TPU were decreased obviously by adding SW-Si 3 N 4. TG-IR test indicated the dramatic inhibition of aromatic compound, hydrocarbons, CO and HCN release. Besides, the thermal conductivity of composites was obviously improved by adding SW-Si 3 N 4. This work may provide better reference for developing multi-functional TPU composites for diverse application. [ABSTRACT FROM AUTHOR]

Objectives: A paper filter was prepared by pitch based activated carbon fibers to investigate the removal efficiency of toxic gas. Also, changes in pore characteristics and mechanical properties according to the ratio of the adsorbent and the binder were observed to optimize the decrease in specific surface area and micropore, which are the unique characteristics of activated carbon fibers. In addition, it is intended to establish optimized paper filter derived activated carbon fiber manufacturing conditions through evaluation of toxic gas removal characteristics. Method: The pore characteristics of the activated carbon fiber and prepared paper were analyzed by measuring the BET specific surface area, and SEM analysis was performed on the fine surface shape. Tensile strength and air permeability were performed according to ISO 1924-2 and ASTM D737: 04, respectively. The adsorption performance of the prepared filter was evaluated as a gas removal efficiency using a gas detection tube (GV-110S). Results and Discussion: As the content of the binder increased in the paper manufacturing process, it was confirmed that the specific surface area of ​​the prepared filter decreased by up to 39.5% compared to the activated carbon fiber. It is considered that the micropores were closed because the surface of the activated carbon fiber was coated with the excessive addition of the binder. The removal efficiency showed a removal rate of 90% of ammonia, and methyl mercaptan and hydrogen sulfide showed a removal rate of about 60%. This result might be due to the difference in the physical adsorption rate according to the vapor pressure of each material. Conclusions: An activated carbon fiber-based paper filter for removing of toxic gas was prepared. It was confirmed that the mixing ratio of the adsorbent and the binder was an important process parameter for determining moldability and adsorption performance. Finally, optimum condition was selected as weight ratio condition of 8:2.

In closed-house enclosures with various sensors, air quality parameters are sometimes not monitored regularly, especially during colder weather. Standard provisions are often not considered because reducing operating costs is cheaper. To produce these parameters, special efforts are needed to ensure temperature, relative humidity control, and simultaneous release of NH3 and CO2 gases. The cost of broiler chicken production reaches 70% from feed, so high feed use reduces farmer income. To help farmers reduce production costs, the Palopo Government provides equipment rocks to broiler chicken farmers as stators-tech tools, an element of wind speed in the cage. Data was collected directly from blower speed measurements produced by stators-tech and weighing body weight growth during maintenance. The results obtained by farmers using stator-tech control tools assisted by the Palopo City Government showed very significant results by getting an IP score of 505 (prime) because the effect of strong winds from blowers can be reduced by the tool, even though the mortality rate is 3.65%.

A cost-effective, simple, flexible, and disposable colorimetric film sensor was constructed for the rapid detection of gaseous ammonia. The sensor was designed to consist of three layers, namely top, middle, and bottom layers of a polymeric elastomer. The bromocresol (BCG) indicator embedded in the middle layer of the film facilitated a change in color of the sensor from yellow-orange to blue upon exposure to gaseous ammonia. The color change was visually observed by the naked eye. The sensitivity of the sensor was verified by a successful detection of gaseous ammonia at concentrations from 4 to 235 ppm within 3 min, and the corresponding visual detection of ammonia gas was at a concentration as low as 11 ppm. The sensor also achieved a selective detection of gaseous ammonia over a variety of alkaline chemicals. The color of the sensor exposed to ammonia reverted from blue to the original yellow-orange upon subsequent exposure to the fume of acetic acid or aeration for 48 h, and it showed reliable performance for the detection of gaseous ammonia even after five repeated uses. The applicability of the sensor was validated by attaching it onto a safety helmet for a simulation of an industrial ammonia gas leak. The results indicated that our colorimetric film sensor is affordable, disposable, and reproducible, and can serve as an effective alternative for simple and rapid recognition of gaseous ammonia in environmental and air quality monitoring as well as in industrial applications.

Based on micro-nano sensing technology, the structural and electronic characteristics of metal-doped boron nitride monolayer are investigated by first principles. The existing nano sensors have practical problems, such as no selectivity, too strong adsorption capacity to be recycled, too weak adsorption capacity to obtain sufficient response. We explore the use of a highly sensitive recyclable nano sensor that is best suited for sensing function. Gas adsorption properties for the toxic decomposition gases of C4F7 N are further developed. We select the N-vacancy with the highest binding energies, which are −6.34 eV when doped by Co atom. The strong interaction and suitable adsorption energy between the activated atoms of adsorbent and gases prove their unique adsorption properties. Since no new chemical bonds are formed, it is obvious that systems are in the form of physical adsorption, which proves their ideal desorption properties. In addition, the conductivity increases to different degrees due to the redistribution of electrons, which proves excellent selectivity. Hence, we propose the use of Co-BNN nanomaterial for the detection of C4F7N toxic decomposition gases. Results would serve as instructive reference for the investigation of resistive gas-sensitive sensors. [ABSTRACT FROM AUTHOR]

Gas sensors are extensively employed for monitoring and detection of hazardous gases and vapors. Many of them are produced on rigid substrates, but flexible and wearable gas sensors are needed for intriguing usage including the internet of things (IoT) and medical devices. The materials with the greatest potential for the fabrication of flexible and wearable gas sensing devices are two-dimensional (2D) semiconducting nanomaterials, which consist of graphene and its substitutes, transition metal dichalcogenides, and MXenes. These types of materials have good mechanical flexibility, high charge carrier mobility, a large area of surface, an abundance of defects and dangling bonds, and, in certain instances adequate transparency and ease of synthesis. In this review, we have addressed the different 2D nonmaterial properties for gas sensing in the context of fabrication of flexible/wearable gas sensors. We have discussed the sensing performance of flexible/wearable gas sensors in various forms such as pristine, composite and noble metal decorated. We believe that content of this review paper is greatly useful for the researchers working in the research area of fabrication of flexible/wearable gas sensors. [Display omitted] • Comprehensive review of 2D materials for gas sensing applications. • Discussing of flexible and wearable 2D gas sensors. • Explanation of gas sensing mechanism. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are used progressively in sensing areas because of their special electrical properties due to their extremely small size. This paper discusses the gas sensing features of QD-based resistive sensors. Different types of pristine, doped, composite, and noble metal decorated QDs are discussed. In particular, the review focus primarily on the sensing mechanisms suggested for these gas sensors. QDs show a high sensing performance at generally low temperatures owing to their extremely small sizes, making them promising materials for the realization of reliable and high-output gas-sensing devices.

Hydrogen sulfide (H2S) is a toxic gas produced via breakdown of organic matter. Hydrogen sulfide exposure can cause symptoms ranging in severity from mild effects (dizziness, headache, nausea) to severe lactic acidosis, respiratory failure, pulmonary edema, cardiac arrhythmias and death. Treatment modalities include oral countermeasures and 100% FiO2 with supportive therapy. However, case studies utilizing hyperbaric oxygen (HBO2) therapy have been reported with general benefit seen in severe cases of toxicity. In this report, cases of mild to moderate H2S toxicity occurred aboard a U.S. Navy ship, resulting in a mass casualty incident of more than 30 patients. Patient symptoms included dizziness, headaches, nausea, vomiting, and one patient with altered mental status. Most patients' symptoms resolved after several hours of supportive therapy, but six patients had symptoms refractory to 100% FiO2 at 1 atm. These six patients received HBO2 therapy with a USN Treatment Table 9 after consultation with the local emergency room and hyperbaric assets. Four separate chambers were utilized, including two chambers onboard USN ships and the local explosive ordnance disposal (EOD) chamber. Complete resolution of symptoms in all six patients was achieved within the first breathing period. Patients were monitored after treatment aboard the USN ship medical department. No patients required emergency department care. These cases demonstrate an expanded use of HBO2 to include moderate cases of H2S toxicity refractory to first-line therapy. [ABSTRACT FROM AUTHOR]

The adsorption property of small toxic gaseous molecules (SO2, SO3, H2S, and N2O) with metal/hexa‐vacancy defective graphene (denoted as HDG‐M, M: Fe2+, Co2+, Ni2+, Cu2+, and Zn2+) was determined by density functional theory. The results of these calculations show that the Fe2+ ion has the best and Cu2+ the worst absorption ability to capture all of the above toxic gases with selected adsorption orientation. These results can provide useful information for the application of the designed HDG‐M adsorbents in food science and ecosystem monitoring. [ABSTRACT FROM AUTHOR]

In this work, sensing behaviors and mechanisms of two crosslinked copolymers with dimethylamine and dimethylamide functional groups were compared and investigated for their ability to detect hydrogen chloride (HCl) gas. The crosslinked copolymer films were photopolymerized on quartz crystal electrodes using a micro-contact printing technique. The gas sensing behaviors were analyzed by measuring resonant frequency (Δf) of quartz crystal microbalance (QCM). The HCl binding capacity of photopolymerized films, with a mass between 4.6 and 5.9 μg, was optimized. Under optimized film mass conditions, the poly(2-dimethylaminoethyl methacrylate-co-ethylene glycol dimethacrylate) (DMAEMA-co-EGDMA), poly(DMAEMA-co-EGDMA), film, C2-DMA, showed a 13.9-fold higher binding capacity than the poly(N,N-dimethylacrylamide-co-ethylene glycol dimethacrylate, poly(DMAA-co-EGDMA), film, C0-DMA, during HCl gas adsorption. HCl gas was effectively adsorbed on the C2-DMA film because of the formation of tertiary amine salts through protonation and strong ionic bonding. Furthermore, the C2-DMA film exhibited excellent sensitivity, of 2.51 (ng/μg) (1/ppm), and selectivity coefficient (k* = 12.6 for formaldehyde and 13.5 for hydrogen fluoride) compared to the C0-DMA film. According to the experimental results, and due to its high functionality and stability, the C2-DMA film-coated QC electrode could be used as an HCl gas sensor, with low-cost and simple preparation, in future endeavors.

Adsorption of NOx and COx (x = 1, 2) molecules on T4,4,4-graphyne sheet is studied using density functional theory. The most stable adsorption configurations, adsorption energies, binding distances, charge transfers, electronic band structures and density of states are calculated. Our results show that CO, CO2, NO and NO2 molecules are weakly physisorbed on T4,4,4-graphyne sheet. T4,4,4-graphyne is a direct band gap semiconductor. The electronic properties of T4,4,4-graphyne show no sensitivity to the presence of CO and CO2 molecules, while the changes in the electronic properties are observed after NO and NO2 adsorption. The electronic properties of T4,4,4-graphyne are sensitive to the concentration of molecular adsorption. Our findings show immense potential of T4,4,4-graphyne as a highly sensitive gas sensor for NO and NO2 detection. [ABSTRACT FROM AUTHOR]

This study monitored concentrations and emissions of ammonia (NH3), hydrogen sulfide (H2S), and respirable dust for a commercial broiler and a cage-layer barn in the Canadian Prairies over a year between March 2015 and February 2016. Seasonal concentration and emission profiles were acquired by monthly measurements, while diurnal profiles were generated in different seasons. The indoor air quality was evaluated considering both the individual and the additive health effect (respiratory irritation) of the three air pollutants. In winter, both 8-h and 15-min exposure limits (threshold concentrations) of NH3 were exceeded in the broiler barn; the highest additive level was more than two times of the limit. Seasonal average emissions of NH3, H2S, and respirable dust were 57 g d−1 AU−1, 1.35 g d−1 AU−1, and 1.99 g d−1 AU−1, respectively, for the layer barn, all with higher levels in the mild and warm seasons than in the cold season. The emission data were only obtained for the worst-case scenarios (last week of the production cycle) of the broiler barn, with annual averages of 92 g d−1 AU−1 for NH3, 1.19 g d−1 AU−1 for H2S, and 4.32 g d−1 AU−1 for respirable dust, with obvious higher NH3 levels in winter. Additionally, manure removal once every 3–4 days for the layer barn reduced NH3 emissions by 62% and 90% in the cold and mild seasons, respectively. This study also found significant negative influence of outdoor T (Tout) on NH3 emissions for the broiler barn but positive impact of Tout on NH3 emissions for the layer barn. [ABSTRACT FROM AUTHOR]

Accurate and rapid toxic gas concentration prediction model plays an important role in emergency aid of sudden gas leak. However, it is difficult for existing dispersion model to achieve accuracy and efficiency requirements at the same time. Although some researchers have considered developing new forecasting models with traditional machine learning, such as back propagation (BP) neural network, support vector machine (SVM), the prediction results obtained from such models need to be improved still in terms of accuracy. Then new prediction models based on deep learning are proposed in this paper. Deep learning has obvious advantages over traditional machine learning in prediction and classification. Deep belief networks (DBNs) as well as convolution neural networks (CNNs) are used to build new dispersion models here. Both models are compared with Gaussian plume model, computation fluid dynamics (CFD) model and models based on traditional machine learning in terms of accuracy, prediction time, and computation time. The experimental results turn out that CNNs model performs better considering all evaluation indexes. [ABSTRACT FROM AUTHOR]

Summary: To enhance the performance of existing dry powders and ensure process security, a new type of dry powder based on ammonium dihydrogen phosphate (NH4H2PO4) was prepared. The prepared composite superfine dry powder was denoted as NH4H2PO4/zeolite composite in this paper. The effectiveness of commercial ABC dry powder, superfine dry powder, and the NH4H2PO4/zeolite composite in fire suppression were compared in a small‐sized fire‐extinguishing chamber. Laboratory‐scale tests showed that the NH4H2PO4/zeolite composite had considerably superior fire‐extinguishing efficiency to that of commercial ABC dry powder and superfine dry powder, along with shorter average extinguishing time and less average mass of powders consumed. In addition, the NH4H2PO4/zeolite composite also displayed much improved toxic gas suppression ability. The physical and chemical characteristics of commercial ABC dry powder, superfine dry powder, and the NH4H2PO4/zeolite composite were characterized using a range of techniques of laser particle size analysis, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Based on the analysis results, the improved fire suppression performance of the NH4H2PO4/zeolite composite can be ascribed to smaller particle size, larger surface area, and a special chemical decomposition process. [ABSTRACT FROM AUTHOR]

[Display omitted] • BGDY presents strong interaction with TM adatoms. • The favorite adsorption site for most TMs on BGDY is near the C≡C-B-C≡C corner. • Electron exchange causes the oxidation of TMs and the magnetic moment variation. • TMs-BGDY can effectively adsorb CO, NO and HCHO gases. • TMs-BGDY shows promising applications potential in gas detection or fixation. Layer materials anchored with transition-metal (TM) single atom is a typical catalyst model for many applications. Recent studies reveal that boron-graphdiyne (BGDY) has unique properties similar to grephyne e.g. two-dimensional nature, excellent electrical conductivity, and good thermal–mechanical properties. More importantly, it possesses electron-deficient boron atoms, larger molecular pore and more π bonds. These advantages motivate us to investigate TM single atom anchored BGDY and its adsorption behavior to CO, NO and HCHO. The DFT calculations reveal that BGDY can accommodate TMs at multiple sites and the favorite adsorption site is near the highly active C≡C-B-C≡C corner. The TMs adsorption is stronger than that on graphene. Overall, the adsorption energies, height and structural distortion vary regularly as moving along a d series. These phenomena are closely related to electrons exchange and TMs characteristic. The TMs of oxidation on BGDY can effectively adsorb CO, NO and HCHO. Interesting electron exchange occurs among gas, TMB/TM and the adjacent C atoms in GDY substrate. The three atom groups work synergistically which suggests tunable electron environment. The adsorption results reveal that TMs adsorption endows BGDY layer beneficial properties, and TMs-BGDY have good potential as the detection or fixation materials for CO, NO and HCHO. [ABSTRACT FROM AUTHOR]

The adsorption and sensing behavior of three typical industrial toxic gases NO, NO2 and SO2 by the Pd modified C3N monolayer were studied in this work on the basic first principles theory. Meanwhile, the feasibility of using the Pd doped C3N monolayer (Pd-C3N) as a sensor and adsorbent for industrial toxic gases was discussed. First, the binding energies of two doping systems were compared when Pd was doped in the N-vacancy and C-vacancy sites of C3N to choose the more stable doping structure. The result shows that the doping system is more stable when Pd is doped in the N-vacancy site. Then, on the basis of the more stable doping model, the adsorption process of NO, NO2 and SO2 by the Pd-C3N monolayer was simulated. Observing the three gases adsorption systems, it can be found that the gas molecules are all deformed, the adsorption energy (Ead) and charge transfer (QT) of three adsorption systems are relatively large, especially in the NO2 adsorption system. This result suggests that the adsorption of the three gases on Pd-C3N belongs to chemisorption. The above conclusions can be further confirmed by subsequent deformable charge density (DCD) and density of state (DOS) analysis. Besides, through analyzing the band structure, the change in electrical conductivity of Pd-C3N after gas adsorption was studied, and the sensing mechanism of the resistive Pd-C3N toxic gas sensor was obtained. The favorable adsorption properties and sensing mechanism indicate that the toxic gas sensor and adsorbent prepared by Pd-C3N have great application potential. Our work may provide some guidance for the application of a new resistive sensor and gas adsorbent Pd-C3N in the field of toxic gas monitoring and adsorption.

Graphical abstract Highlights • The possibility of using 2D CoOOH as a sensor for H 2 O 2 and NH 3 is investigated. • H 2 O 2 is adsorbed more strongly over 2D CoOOH than NH 3. • The Electronic band gap of 2D CoOOH increases after interaction with H 2 O 2 and NH 3. • NH 3 increases the work function of 2D CoOOH by 2% and H 2 O 2 decreases by 10%. • Higher selectivity of 2D CoOOH observed for H 2 O 2 and NH 3 than CO, CO 2 , NO and NO 2. Abstract To the chain of development of 2D materials, recently synthesized ultrathin cobalt oxy-hydroxide (CoOOH) nano sheets gain potential interest due to its structural, electronic and other properties. We have studied the interaction mechanism of two toxic gases hydrogen peroxide (H 2 O 2) and ammonia (NH 3) adsorbed over 2D CoOOH to understand the role of 2D CoOOH as a toxic gas sensor. We employ first principles based dispersion corrected density functional calculations to study the sensing behavior of 2D CoOOH towards H 2 O 2 and NH 3 by calculating adsorption energy, electronic band structure, density of states (DOS) and work function. The electronic band structure, DOS and work function of 2D CoOOH are modulated after adsorption of H 2 O 2 and NH 3 molecules. Adsorption of gas molecules confirms the sensing behavior of 2D CoOOH towards these molecules and depicts its use in a sensing device. The full phonon dispersion curves and phonon density of states reveal the dynamical stability of 2D CoOOH. The calculated adsorption energy of H 2 O 2 and NH 3 molecules is −0.532 and −0.460 eV respectively which indicates the strong physisorption of these gases over 2D CoOOH. The ultrafast recovery time of 1239 and 1203 ns respectively were found for H 2 O 2 and NH 3 on 2D CoOOH. The work function which is 6.29 eV found for 2D CoOOH, decreases to 5.63 eV for H 2 O 2 as it follows the reduction process on 2D CoOOH, and increases to 6.44 eV for NH 3 molecules as it acts as oxidation gas on CoOOH. Our study reveals that the 2D CoOOH can be a better sensor for the H 2 O 2 and NH 3 gases than some traditional two-dimensional materials. [ABSTRACT FROM AUTHOR]