Limited Air Exchange Research Articles

Physiological Effects of TolC‐Dependent Multidrug Efflux Pumps in Escherichia coli: Impact on Motility and Growth Under Stress Conditions

ABSTRACTEnterobacteriaceae possess eight TolC‐dependent multidrug efflux pumps: AcrAB‐TolC, AcrAD‐TolC, AcrEF‐TolC, MdtEF‐TolC, MdtABC‐TolC, EmrAB‐TolC, EmrYK‐TolC, and MacAB‐TolC, which efflux bile salts, antibiotics, metabolites, or other compounds. However, our understanding of their physiological roles remains limited, especially for less‐studied pumps like EmrYK‐TolC. In this study, we tested the effects on swimming motility and growth under stress conditions of Escherichia coli mutants individually deleted for each inner‐membrane transporter component of all eight TolC‐dependent pumps, a mutant deleted for the AcrB‐accessory protein AcrZ, and a mutant simultaneously deleted for all eight pumps (ΔtolC). We found that all mutants tested, except the ΔemrY and ΔacrZ mutants, displayed increased swimming motility. Additionally, the loss of each individual TolC‐dependent pump or AcrZ did not reduce growth and sometimes even enhanced it compared to the parental strain under various growth conditions: temperature (LB at 25, 30, 37, and 42°C), pH (LB at pH 6.0, 7.4, and 9.0; and LB buffered to pH 6.0, 7.4, and 8.25), LB with limited air exchange, and nutritional stress (M9‐glucose or M9‐glycerol). In contrast, the ΔtolC mutant grew significantly slower than the parental strain under all conditions tested except in LB‐TRIS pH 7.4 and LB with limited air exchange. Overall, these findings indicate that while individual TolC‐dependent pumps are generally dispensable for growth under many stress conditions in the absence of antimicrobials, possibly due to their partially overlapping substrate profiles, TolC‐dependent efflux is required for maximal growth under most conditions.

Improving the air environment of vehicle cabins

BACKGROUND: The use of an innovative irrigated nozzle for air purification in the cabins of small class tractors is justified. The use of it makes it possible to comprehensively solve the problem of the state of air environment in the case of tractors operation in conditions of limited air exchange. AIM: Reduction of the content of harmful substances in the air of small tractors’ cabins. METHODS: Physical and chemical processes -chemical processes, during which the cabin air can be purified from harmful substances in the air cooler nozzle, are taken into account. RESULTS: The irrigated nozzle developed for the air coolers of the cabins of the mentioned tractors makes it possible to clean the exhaust gases from harmful impurities. CONCLUSION: Nozzles of a regular structure, irrigated with water with sodium bicarbonate and potassium permanganate dissolved in it, make it possible to comprehensively solve the problem of improving the state of air environment in the case of small class tractors operation in conditions of limited air exchange.

Aerosol composition, air quality, and boundary layer dynamics in the urban background of Stuttgart in winter

Abstract. Aerosol distributions are of great relevance for air quality, especially for cities like Stuttgart, which has limited air exchange due to its location in a basin. We collected a comprehensive set of data from remote sensing and in situ methods including radiosondes for the urban background of downtown Stuttgart to determine the impact of boundary layer mixing processes on local air quality and to evaluate the simulation results of the high-resolution large eddy simulation (LES) model PALM-4U at 10 m grid spacing. Stagnant meteorological conditions caused accumulation of aerosols, and chemical composition analysis shows that ammonium nitrate (37 ± 9 %) and organic aerosol (OA; 34 ± 9 %) dominated during this winter study. Case studies show that clouds during previous nights can weaken temperature inversion and accelerate boundary layer mixing after sunrise by up to 3 h. This is important for ground-level aerosol dilution during the morning rush hour. Furthermore, our observations validate results of the LES model PALM-4U in terms of boundary layer heights and aerosol mixing for 48 h. The simulated aerosol concentrations follow the trend of our observations but are still underestimated by a factor of 4.5 ± 2.1 due to missing secondary aerosol formation processes and uncertainties of emissions and boundary conditions in the model. This paper firstly evaluates the PALM-4U model performance in simulating aerosol spatio-temporal distributions, which can help to improve the LES model and to better understand sources and sinks for air pollution as well as the role of horizontal and vertical transport.

Future Prediction of Close Contacts in IoT-based Contact Tracing System using a New Real-Life Dataset.

Contact tracing is an effective method for mitigating the infectious diseases spread and it played a crucial role in reducing COVID-19 outbreak. Since the pandemic, there has been an increased concern regarding people's health in hospital and office settings, as these limited air exchange spaces provide a conductive medium for virus spread. Various technologies were used to recognize close contacts autonomously, in addition, multiple machine learning attempts were carried out to determine proximity in contact tracing. This study, however, proposes a unique concept in contact tracing: forecasting future close contact prior to occurrence in order to regulate and control it rather than tracking past occurrences. For our research, we constructed a completely new real-life dataset that was collected during the pandemic in a hospital infectious ward (Alfred Hospital, Melbourne, Australia) utilizing a Bluetooth Low Energy (BLE) Internet of Things (IoT) system. Our prediction technique considers two types of environments: single transceiver environments and multiple transceivers settings, these transceivers record the nearby tags' BLE received signal strength indicator (RSSI) values. The system employs mathematical models and supervised machine learning (ML) algorithms to solve regression and classification problems for workers' pattern recognition within the environment. The output is compared using different metrics, such as efficiency, which reached more than 80%, root mean square errors and mean absolute errors which were as low as 2.4 and 1.2 respectively in some models.

Ensuring the environmental friendliness of internal combustion engines of agricultural machines in conditions of limited air exchange

The method of protection of personnel working in greenhouses, greenhouses and premises for maintenance and repair of agricultural machinery from exposure to exhaust gases in accordance with the “environmental concept”, according to which the negative impact must be reduced before the products of spent gases will enter the air of the working area of the service personnel and the driver of the machine. The problem was solved with the help of evaporative humidification of the air-fuel mixture due to its simplicity and effectiveness, confirmed during tests on a tractor.

Personal VOCs Exposure with a Sensor Network Based on Low-Cost Gas Sensor, and Machine Learning Enabled Indoor Localization

Indoor locations with limited air exchange can easily be contaminated by harmful volatile compounds. Thus, is of great interest to monitor the distribution of chemicals indoors to reduce associated risks. To this end, we introduce a monitoring system based on a Machine Learning approach that processes the information delivered by a low-cost wearable VOC sensor incorporated in a Wireless Sensor Network (WSN). The WSN includes fixed anchor nodes necessary for the localization of mobile devices. The localization of mobile sensor units is the main challenge for indoor applications. Yes. The localization of mobile devices was performed by analyzing the RSSIs with machine learning algorithms aimed at localizing the emitting source in a predefined map. Tests performed on a 120 m2 meandered indoor location showed a localization accuracy greater than 99%. The WSN, equipped with a commercial metal oxide semiconductor gas sensor, was used to map the distribution of ethanol from a point-like source. The sensor signal correlated with the actual ethanol concentration as measured by a PhotoIonization Detector (PID), demonstrating the simultaneous detection and localization of the VOC source.

Active Air Monitoring for Understanding the Ventilation and Infection Risks of SARS-CoV-2 Transmission in Public Indoor Spaces

Indoor, airborne, transmission of SARS-CoV-2 is a key infection route. We monitored fourteen different indoor spaces in order to assess the risk of SARS-CoV-2 transmission. PM2.5 and CO2 concentrations were simultaneously monitored in order to understand aerosol exposure and ventilation conditions. Average PM2.5 concentrations were highest in the underground station (261 ± 62.8 μgm−3), followed by outpatient and emergency rooms in hospitals located near major arterial roads (38.6 ± 20.4 μgm−3), the respiratory wards, medical day units and intensive care units recorded concentrations in the range of 5.9 to 1.1 μgm−3. Mean CO2 levels across all sites did not exceed 1000 ppm, the respiratory ward (788 ± 61 ppm) and the pub (bar) (744 ± 136 ppm) due to high occupancy. The estimated air change rates implied that there is sufficient ventilation in these spaces to manage increased levels of occupancy. The infection probability in the medical day unit of hospital 3, was 1.6-times and 2.2-times higher than the emergency and outpatient waiting rooms in hospitals 4 and 5, respectively. The temperature and relative humidity recorded at most sites was below 27 °C, and 40% and, in sites with high footfall and limited air exchange, such as the hospital medical day unit, indicate a high risk of airborne SARS-CoV-2 transmission.

Order and control of emissions of the fulfilled gases of diesels at the new level

The standard of the organization directed on increase of efficiency and quality of monitoring procedure of emissions of harmful substances of the fulfilled gases of diesels of the capital repaired tractors and self-propelled farm vehicles which are in operation, intended for work and working in the conditions of unlimited and limited air exchange is developed and establishes norms of emissions of harmful substances with the fulfilled gases, means of their definition, at control and bench tests of tractors and the agricultural cars. Technical characteristics of the fuel and engine oil intended for test of the diesel are defined. Modern control devices are optimized and techniques of tool control of the maintenance of CO, CH and NOx in the fulfilled gases of diesels of page are the agricultural cars.

Diesel engine adaptation system for operation in rooms with limited air exchange

Рассмотрен способ и дано техническое решение задачи снижения вредных выбросов и дымности трактора с дизельным двигателем, работающим на сжиженном углеводородном газе по газодизельному процессу, оснащенным системой нейтрализации вредных веществ в отработавших газах.

Order and control of emissions of the fulfilled gases of diesels at the new level

The standard of the organization directed on increase of efficiency and quality of monitoring procedure of emissions of harmful substances of the fulfilled gases of diesels of the capital repaired tractors and self-propelled farm vehicles which are in operation, intended for work and working in the conditions of unlimited and limited air exchange is developed — and establishes norms of emissions of harmful substances with the fulfilled gases, means of their definition, at control and bench tests of tractors and the agricultural cars. Technical characteristics of the fuel and engine oil intended for test of the diesel are defined. Modern control devices are optimized and techniques of tool control of the maintenance of CO, CH and NOx in the fulfilled gases of diesels of page are the agricultural cars.

A modification of a traditional Ethiopian maize store for solar powered ambient drying to reduce post-harvest losses

A gombisa is a traditional Ethiopian structure widely used for maize storage over several months. It lacks adequate ventilation for timely moisture removal, which promotes mold development and aflatoxin production. In this study, a traditional gombisa was compared to one modified by installing a solar powered fan to provide forced ambient air ventilation during daytime. Approximately 900 kg of moist ear maize were loaded into each structure and samples from selected locations were weighed periodically to monitor moisture loss. Temperature and relative humidity of ambient air and inside the maize bulk were continuously recorded. Significantly faster drying was achieved in the modified gombisa, where drying occurred from bottom to top. In the traditional store, drying was much faster at the surface, with drying rate declining sharply with increasing depth in the bulk due to more limited air exchange. Relative humidity in the bulk center of the traditional structure remained above 90% for more than 4 weeks while in the modified gombisa it decreased progressively from the beginning of the trial. The results are promising and the modifications simple to implement, with the potential to effectively reduce post-harvest losses of maize. Field tests in Ethiopia are recommended.

Effect of indoor air quality on the natural history of asthma in an urban population in Poland.

Background: Indoor air pollution may have an impact on asthma. Objective: To evaluate the influence of indoor air pollution on the natural history of asthma. Methods: Data collection by using the European Community Respiratory Health Survey and International Study of Asthma and Allergies in Childhood standardized questionnaire (N = 18,617) and medical examinations (N = 4783) in selected Polish regions was used. Statistical analysis was performed by using the χ² test. A value of p < 0.05 was considered statistically significant. Results: Questionnaire results demonstrated that people who used the central heating system were less likely to declare the occurrence of asthma (odds ratio [OR] 0.84) and were corroborated with clinical findings of moderate asthma (OR 0.35). Symptomatic asthma occurred more frequently in people who used a solid-fuel heating device (OR 1.36) and electric heaters (OR 1.54). The use of cooking appliances with municipal natural gas (OR 1.77) and gas storage tanks (OR 2.03) was correlated with more frequent declarations of asthma. Symptomatic asthma was more common among people who smoked for at least 1 year (OR 2.26) and those who smoked over the course of the preceding month (OR 1.60). Passive exposure to tobacco smoke provided for a 1.5-fold increase in the incidence of symptomatic asthma (OR 1.53), regardless of the time of exposure. Conclusion: Both active and passive tobacco smoke exposure as well as the use of certain types of heating and cooking appliances have a significant impact on the incidence of asthma and the intensification of its symptoms in rooms with limited air exchange. Highlights of the study included the following: (1) central heating had an amelioratory effect on asthma, (2) heating technologies used at home had a significant impact on the incidence of asthma, and (3) devices used for cooking (municipal and cylinder gas stoves) played an important role in the intensification of asthma symptoms.

A study of air pollution by exhaust gases from cars in well courtyards of Saint Petersburg

Abstract Pollution of the environment by exhaust gases while parking in enclosed well courtyards of Saint Petersburg is studied. A method for the assessment of extremely dangerous air pollution by CO, CH, NO x , and PM pollutants upon engine start-up and warm-up under conditions of limited air exchange is developed. Experiments involving 13 petrol and 2 diesel passenger cars of Euro 0, 3, 4, 5 emission standards were conducted. To measure the concentration of pollutants, the following gas analyzers were used: Testo-300 XXL (Testo, Germany), PGA-200 (ZAO R&D Enterprise Elektrostandart, Russia), DUSTTRAK 8530 (TSI Incorporated, USA). Values of CO, CH, NO x , PM emission factors for passenger cars of Euro 0 – Euro 5 emission standards were determined. It has been established that upon engine warm-up (in passenger cars of Euro 0 – Euro 4 emission standards) high air pollution with carbon monoxide, hydrocarbons and nitrogen oxide is formed in enclosed and poorly ventilated well courtyards in 5–10 minutes, their concentration being 2–5 times, 1.5–3 times and 1.5 times higher than the permissible levels for the Russian Federation, respectively (at the height of 2 m, i.e. at the breathing level).

English

Sucrose, the most commonly used carbon source in conventional in vitro culture, and limited air exchange in the culture containers are factors that affect the growth of in vitro-cultured plants. They may induce physiological disorders and decrease the survival rate of plants after transfer to ex vitro conditions. The aim of the present study was to analyze the effects of gas exchange and sucrose concentration on Billbergia zebrina plantlets during in vitro propagation. In vitro-established B. zebrina plantlets were transferred to culture media containing 0, 15, 30, 45, or 60 g L-1 sucrose. Two different culture-container sealing systems were compared: lids with a filter (permitting gas exchange) and lids with no filter (blocking fluent gas exchange). Carbohydrate and chlorophyll (Chl a+b) concentrations were analyzed in plantlets at 45-days of culture. The addition of sucrose to the medium reduced the Chl a+b concentration in the plantlets. On the other hand, additional sucrose had a positive effect on the carbohydrate stock formation of the plantlets. The results showed that a photoautotrophic system (air exchange and a sugar-free medium) improves the in vitro propagation of B. zebrina without creating physiological disorders. Key words: Bromeliad, In vitro plant, photoautotrophic growth, physiological disorders, sucrose.

Impacts of photoautotrophic and photomixotrophic conditions on in vitro propagated Billbergia zebrina (Bromeliaceae)

Micro-propagation techniques contribute to the multiplication of several bromeliad species. However, micropropagated plantlets often present low survival rate due to anatomical and physiological disorders induced by in vitro conditions. This study aimed to evaluate the sucrose and gas exchange impact on in vitro propagated Billbergia zebrina plants and to check if there is any residual effect of the in vitro conditions on micropropagated plants after acclimatization. Previously in vitro-established B. zebrina plants were transferred to culture media containing 0.0, 15.0, 30.0, 45.0 or 60.0 g L−1 sucrose. Two different culture container sealing systems were tested: lids with a filter (permitting an excellent gas exchange) and a filter covered with PVC (blocking fluent gas exchange). At 45 days in vitro growth, B. zebrina plantlets were transplanted onto plastic pots containing peat and cultivated for 80 days in greenhouse. At 45 days in vitro and 80 days of acclimatization in the greenhouse, the plants were evaluated. High sucrose levels in the in vitro media resulted in reduced growth. Plantlets exposed to aerated containers presented better rooting, being the sugar-free medium the best in vitro condition (photoautotrophic condition). Limited air exchange resulted in plantlets with anatomical and physiological disorders at the end of the in vitro period. The highest growth rate in the greenhouse was observed in plants previously propagated in unlimited gas exchange system and sugar-free medium. The use of photoautotrophic conditions induces B. zebrina plantlets without anatomical and physiological disorders and it interfere positively on ex vitro growth.

Short-term &amp;lt;sup&amp;gt;222&amp;lt;/sup&amp;gt;Rn activity concentration changes in underground spaces with limited air exchange with the atmosphere

Abstract. The authors investigated short-time changes in 222Rn activity concentration occurring yearly in two underground tourist facilities with limited air exchange with the atmosphere. One of them is Niedźwiedzia (Bear) Cave in Kletno, Poland – a natural space equipped with locks ensuring isolation from the atmosphere. The other site is Fluorite Adit in Kletno, a section of a disused uranium mine. This adit is equipped with a mechanical ventilation system, operated periodically outside the opening times (at night). Both sites are situated within the same metamorphic rock complex, at similar altitudes, about 2 km apart. The measurements conducted revealed spring and autumn occurrence of convective air movements. In Bear Cave, this process causes a reduction in 222Rn activity concentration in the daytime, i.e. when tourists, guides and other staff are present in the cave. From the point of view of radiation protection, this is the best situation. For the rest of the year, daily concentrations of 222Rn activity in the cave are very stable. In Fluorite Adit, on the other hand, significant variations in daily 222Rn activity concentrations are recorded almost all year round. These changes are determined by the periods of activity and inactivity of mechanical ventilation. Unfortunately this is inactive in the daytime, which results in the highest values of 222Rn activity concentration at the times when tourists and staff are present in the adit. Slightly lower concentrations of radon in Fluorite Adit are recorded in the winter season, when convective air movements carry a substantial amount of radon out into the atmosphere. The incorrect usage of mechanical ventilation in Fluorite Adit results in the most unfavourable conditions in terms of radiation protection. The staff working in that facility are exposed practically throughout the year to the highest 222Rn activity concentrations, both at work (in the adit) and at home (outside their working hours). Therefore, not very well considered solution for the ventilation system not only does not prevent radioactive exposure of the staff, but can even increase it. The authors have also observed comparable characteristics of the annual patterns of 222Rn activity concentration changes in underground spaces and residential buildings situated in the same or similar climatic zones.

Mobilization of phosphorus from iron ore by the bacterium Burkholderia caribensis FeGL03

The bacterium Burkholderia caribensis FeGL03, isolated from a Brazilian high-phosphorus iron ore, was used to mobilize the phosphate contained in the same ore. The phosphate-mobilizing ability of the organism was tested in shake-flask cultures containing sterilized crushed iron ore in a chemically-defined liquid culture medium containing glucose (1 g/l) as carbon source and no phosphorus source except the ore itself. Phosphate removal from the ore was determined by measuring the residual phosphate contained in the ore after the bacterial treatment. The time course of the phosphate mobilization process was determined with two different particle sizes (2.0 mm and 0.2 mm mean size) of the crushed ore under conditions of unlimited and limited air exchange. Between 5% and 20% of the phosphorus originally contained in the ore was mobilized in 21 days of treatment. Other variables such as dissolved Fe, pH and cell counts were also monitored throughout the trials. It was also found that this bacterium accumulated gluconic acid in the spent broth. Scanning electron microscopy, revealed biofilms on the ore surface as a result of the production of exopolymeric substances (EPS). Extraction of the EPS from the cultures and its analysis by Fourier transform infrared techniques revealed the presence of molecular functionalities capable of interacting with the ore surface and with the iron dissolved in the medium. It was found that dense biofilms, formed under limited air exchange, resulted in lower phosphate mobilization from the ore than under unlimited air exchange. This was found to be a consequence of a dynamic process of iron and phosphate re-precipitation within the formed biofilms.

Hydrogen fuel in automobiles and tractors

Abstract The concept is formulated of using hydrogen from a vehicle-borne hydrogen generator in automobile/tractor engines. Generalized information is presented on the results of computational—theoretical and experimental studies. Conditions for hydrogen stored onboard the vehicle in the form of the main raw material and energy carrier obtained from secondary aluminium, reduced oxides of silicon, aluminium and their compounds from by-products of thermal power stations and the aluminium—magnesium industry, are compared with cryostats, metal hydride and gas cylinder hydrogen accumulators. The efficiency of hydrogen generation is assessed in the automobile—tractor hydrogen generator, which is a small-size device with a flexible process control system. The region of predictable toxicity decrease parameters in combustion of the hydrocarbon fuel and hydrogen in the presence of steam is investigated. Prospects for the effective use of hydrogen and steam according to the gas—diesel variant are shown in solving the energy and ecology problems of tractor engines for areas of limited air exchange. Coordinated operating conditions are presented for a low-toxicity benzene-hydrogen automobile engine and a vehicle-borne hydrogen generator. The possibility of eliminating hydrogen self-ignition and reducing nitrogen oxide emission in the operation of a hydrogen generator in a microbus fitted with a vehicle-borne hydrogen generator is discussed.

Microorganisms for degrading simmondsin and related cyanogenic toxins in jojoba

Four microorganisms that metabolize simmondsin (S) and related cyanogenic toxins from jojoba (Simmondsia chinensis) were isolated by enrichment: Pseudallescheria boydii, a fungus which specifically degrades simmondsin ferulate but not S; Fusarium moniliforme; “Flavobacterium aurantiacum”; and Pseudomonas maltophilia. The latter three organisms grow on S as a sole carbon and nitrogen source in culture media, but only F. moniliforme attacks S in the complete jojoba meal. Combinations of the four microorganisms at two temperatures, and with free air or limited air exchange for up to 20 days, were tested on jojoba meal to determine an optimum detoxification method. Degradation of toxins was most rapid and complete when Pseudallescheria boydii and Fusarium moniliforme together were incubated on jojoba meal at 25°C with free air exchange for 20 days. Mice were fed fermented meals at 0, 5, 10 and 20% substitution levels to determine detoxification and nutritional quality. Average daily gains during rapid growth of weanling (1–3 weeks) and mature (4–8 weeks) mice did not differ significantly from controls for mice on all diets containing fermented meal. Diets containing fungally detoxified jojoba meal were more efficient for maintaenance of mature weight than jojoba meal detoxified with enzymes naturally present in the meal. Meal can be detoxified by ensilage for 20 days at 80% water content. Detoxification is attributed to as yet unidentified enzymes inherent in the jojoba seed.

Desorption of residual sulfuryl fluoride from structural and household commodities by headspace analysis using gas chromatography.

Sulfuryl fluoride, SO2F2, is a widely used fumigant for structural pest control (Monroe 1969, Ebeling 1975). Structural fumigation requires that the entire building be sealed or enclosed in tarpaulins to confine the gas for a predetermined concentration and time depending on the target organism, weather, and physical nature of the building. Because structural materials, furnishings, and household effects are also exposed to the fumigant, these act as sorptive matrices. Desorption of sulfuryl fluoride (SF) from some commodities may continue after the building has been reoccupied. The limited air exchange in modern, environmentally controlled buildings and the greater use of synthetic polymers in structures dictate a need to assess the levels of SF desorption from fumigated materials associated with human dwellings. In this study we analyze SF desorption levels over a 40-day period from 13 structural and household commodities at two exposure concentrations by gas chromatography of headspace.