Positive Air Research Articles

Benchmark Thermodynamic Contributors to the Growth and Decay of the Regional Extreme Surface Temperature

Abstract A thermodynamic energy budget analysis is applied to the lowest model level of the ERA5 dataset to investigate the mechanisms that drive the growth and decay of extreme positive surface air temperature (SAT) events. Regional and seasonal variation of the mechanisms are investigated. For each grid point on Earth’s surface, a separate composite analysis is performed for extreme SAT events, which are days when temperature anomaly exceeds the 95th percentile. Among the dynamical terms, horizontal temperature advection of the climatological temperature by the anomalous wind dominates SAT anomaly growth over the extratropics, while nonlinear horizontal temperature advection is a major factor over high-latitude regions and the adiabatic warming is important over major mountainous regions. During the decay period, advection of the climatological temperature by the anomalous wind sustains the warming while nonlinear advection becomes the dominant decay mechanism. Among diabatic heating processes, vertical mixing contributes to the SAT anomaly growth over most locations while longwave radiative cooling hinders SAT anomaly growth, especially over the ocean. However, over arid regions during summer, longwave heating largely contributes to SAT anomaly growth while the vertical mixing dampens the SAT anomaly growth. During the decay period, both longwave cooling and vertical mixing contribute to SAT anomaly decay with more pronounced effects over the ocean and land, respectively. These regional and seasonal characteristics of the processes that drive extreme SAT events can serve as a benchmark for understanding the future behavior of extreme weather.

Use of CPAP Ventilation in Non-ICU Wards May Influence Outcomes in Patients with Severe Respiratory COVID-19.

Background and Objectives: The COVID-19 disease has significantly burdened the healthcare system, including all units of severe patient treatment. Non-intensive care units were established to rationalize the capacity within the Intensive Care Unit (ICU) and to create a unit where patients with Acute Respiratory Distress Syndrome (ARDS) could be treated with non-invasive Continuous Positive Air Pressure (CPAP) outside the ICU. This unicentric retrospective study aimed to assess the efficacy of NIV Treatment in Patients of the fourth pandemic wave and how its application affects the frequency and mortality of ICU-treated patients at University Hospital Rijeka compared to earlier waves of the COVID-19 pandemic. Furthermore, the study showcases the effect of the Patient/Nurse ratio (P/N ratio) on overall mortality in the ICU. Materials and Methods: The study was conducted on two groups of patients with respiratory insufficiency in the second and third pandemic waves, treated in the COVID Respiratory Centre (CRC) (153 patients). We also reviewed a cohort of patients from the fourth pandemic wave who were initially hospitalized in a COVID-6 non-intensive unit from 1 October 2021 to 1 November 2022 (102 patients), and some of them escalated to CRC. Results: The introduction of the CPAP non-invasive ventilation method as a means of hypoxic respiratory failure treatment in non-intensive care units has decreased the strain, overall number of admissions, and CRC patient mortality. The overall fourth wave mortality was 29.4%, compared to the 58.2% overall mortality of the second and third waves. Conclusions: As a result, this has decreased CRC patient admissions and, by itself, overall mortality.

Increase of the Efficiency of Heat Supply Units of the CHP Plants Due to the Choice of Rational Heat Release Modes

The possibilities of increasing the efficiency of heat supply turbines of CHPPs due to the choice of rational modes of operation of network water heaters are analyzed. With the help of a software and computing complex developed at the Institute of Mechanical Engineering Problems of the National Academy of Sciences of Ukraine and adapted by the authors to the operating conditions of CHPP generating equipment with one or two network heaters, a set of calculation studies of various ways of connecting them depending on the outdoor air temperature is conducted in the paper. Areas of positive effect associated with increase in the electric power of the power plant have been established. The calculation study was carried out at typical power plant water consumption from 1000 t/h to 4500 t/h, in the range of changes in the outdoor air temperature from -11 ºС to 10 ºС (heating season) and more than 10 ºС (hot water supply). The load change of the power unit was carried out due to the consumption of fresh steam at a constant pressure and temperature at the turbine inlet. As shown by the results of the operation of the T-100/120-130 heat supply turbine in operating conditions with one or two heat supply steam selections, in the area of positive outdoor air temperatures above 2 ºС, it is advisable to use one lower selection (with the upper one turned off) for all network water consumption. At the same time, additional electric power in the area of outdoor air temperatures above 6ºС can be from 0.25 MW to 2.15 MW. However, when the outdoor air temperature is less than 2 ºС, work with one lower heating selection becomes irrational. From the point of view of choosing rational modes of operation of turbine plants, the most important are the results of determining the optimal distribution of heat load between network heaters. The gain in electrical power of the turbine can be up to 2.46 MW in the nominal mode of operation with two heaters, and up to 7.84 MW in comparison with the use of single-stage heating. The nature of the influence of the distribution of the heat load indicates that during deprivation from the instructional uniform distribution of the heat load between network heaters, it is possible to obtain additional electricity.

Formation of subaerial taliks in Larsemann hills, princess Elizabeth land, East Antarctica

This study presents a mathematical model of heat and mass transfer for modelling the formation and evolution of taliks in the upper subsurface of the Larsemann Hills in East Antarctica. Four simulation scenarios were considered. The first one showed that thawed areas cannot form under snowfields. The second and third scenarios demonstrated the taliks did not form if the snow melted immediately after set the positive air temperatures and covered the surface 20 days before the set of negative air temperatures or immediately after that. According to the last scenario, talik forms when snow cover persists even with positive air temperature, and snow falls before the air temperature becomes negative. Modelling demonstrates that taliks in the Larsemann Hills exist, but they are mostly in an unstable state.

Distance follow-up by a remote medical care centre improves adherence to CPAP in patients with obstructive sleep apnoea over the short and long term.

Adherence to continuous positive air pressure (CPAP) in patients with obstructive sleep apnoea (OSA) has remained invariably low over the last decades. Remote monitoring of the nocturnal CPAP treatment, within telemedicine (TM)-based follow-up programs, in these patients has been suggested as a potential tool to improve adherence and release the workload of sleep units. The aim of this study was therefore to assess whether a follow-up program carried out by a Remote Medical Care Centre (RMCC), outside the sleep unit, improves adherence to CPAP in the short and long term in patients with OSA. In this pilot protocol, we enrolled 37 patients starting CPAP in our Sleep Centre (SC). After three months of standard care in our SC, patients initiated a six-month remote follow-up carried out by the RMCC, functioning as an intermediary between patients and SC. Monthly reports and indication for face-to-face visits were sent to the SC for six months. After this period patients returned to usual care for one year. Results were compared with those obtained in 38 patients (controls) followed with usual care over the same time range. Mean nightly use of CPAP increased from 3.2 ± 2.4 h pre-RMCC to 5.2 ± 1.9 h post-RMCC (p < 0.0001). Nights/month of CPAP use improved from 19.8 ± 9.2 to 25.2 ± 2.5 (p < 0.05) and nights/month with CPAP use >4 h from 12.5 ± 10 to 21.03 ± 8.9 (p < 0.05). This improvement remained stable after 12 months from the return of patients to usual care. No significant changes in CPAP use were observed in controls over the time. A six-month follow-up through a remote facility can significantly improve adherence to CPAP in the short and long term. This pilot study provides a solid base for the design of multicentre randomized trials focusing on new models which are able to increase the long-term efficacy of TM programs.

One Year Weekly Size-Resolved Air Sampling of SARS-CoV-2 in Hospital Corridors and Relations to the Indoor Environment

Background. Airborne SARS-CoV-2 plays a prominent role in COVID-19 transmission. Numerous studies have sampled air from patient rooms, but airborne spread to other hospital areas such as corridors is less investigated. Methods. Size-fractionated aerosol particles were collected weekly, with 12 hours of sampling time daily, in corridors at two infectious disease wards in southern Sweden between March 2020 and May 2021. Samples were analysed with real-time reverse transcription polymerase chain reaction (RT-qPCR) for detection of SARS-CoV-2 RNA. Indoor temperature, relative humidity, and CO2 concentration were monitored during the sampling period. Results. 20 of the 784 collected samples contained SARS-CoV-2 RNA, although in low concentrations. Positive air samples were found in sizes between 0.14 and 8.1 μm, but none &gt;8.1 μm. 45% were found in submicron particles. No clear seasonal pattern was observed among the positive samples. There was no significant difference in the positivity rate of the samples between the two wards. Conclusions. SARS-CoV-2 was only detected in 2.6% of the aerosol samples, which indicates that the spread of airborne virus from patient rooms to the corridor was limited.

Resistive Self‐Sensing Controllable Fabric‐Based Actuator: A Novel Approach to Creating Anisotropy

AbstractDesigning advanced soft robots with soft sensing capabilities for real‐world applications remains challenging due to the intricate integration of actuation and sensor capabilities, which require diverse materials and complex procedures. This paper introduces a fabric‐based robotic technology featuring an “all textile‐based self‐sensing pneumatic actuator” and a low‐cost resistive strain sensor created through simple sewing techniques. The novel approach eliminates the need for additional strain‐limiting woven fabric, simplifying the manufacturing process. It also enables the development of bioinspired motions such as bending, twisting, and snake‐like movements. The electromechanical behaviors of the sensor and bending actuator are tested for their performance under positive air pressure. Through mathematical modeling, the actuator's sensing capacity is estimated accurately, providing precise feedback for pressure and position control. Different closed‐loop controller types, including On–Off and Proportional Integral Derivative (PID) control, are evaluated for their effectiveness. Furthermore, the practical application of the sensing actuator is demonstrated by integrating it into a wearable glove, showcasing its enhanced sensing capabilities for finger‐like soft wearable robotic applications. This research tackles the challenges associated with designing advanced soft robots with integrated sensing capabilities, offering a promising fabric‐based solution that can drive significant advancements in real‐world applications.

Ледовитость российских арктических морей трассы Северного морского пути в современный климатический период

The paper considers the ice cover in the Arctic seas of the Northern Sea Route (NSR): Kara, Laptev, East Siberian and Chukchi since 1946. A comparison of the long-term course of integral average annual air temperature anomalies and seasonal average ice cover anomalies allows identifying a year 2005, starting from which the sea ice cover sharply decreases in a good agreement with the increase and accumulation of positive air temperature anomalies. The researchers reveal that the average level of ice cover has decreased by 1.7 times since 2005, however, the values of the range of fluctuations and standard deviation have remained almost unchanged, i.e. ice cover fluctuates in the same range, but at a lower average level. The main shipping routes are cleared about three decades earlier. The repeatability of complete cleansing of the seas has increased to 60—90%.

Initial Learning Experience for Electromagnetic Navigation Bronchoscopy: A Surgeon’s Experience while Introducing the Navigation Technology in Pulmonary Lesion Diagnosis

Background: Diagnosing peripheral pulmonary lesions using a traditional bronchoscope is difficult. Reports on the learning experience for Veran’s SPiN electromagnetic navigation bronchoscopy (ENB) for the diagnosis of pulmonary lesions are limited. Aim: We aimed to evaluate the skills developed by trainees who underwent Veran ENB learning in a clinical setting. Methods: We retrospectively examined the data of patients who had undergone Veran ENB to guide instruments through the airways to a target lesion for biopsy or localization from November 2019 to March 2022. Results: In total, 23 patients, including 16 with solid lesions (69.6%), 4 with pure ground-glass opacity (17.4%), and 3 with mixed (13.0%) were included. The median largest diameter of the pulmonary lesions was 2.7 ± 1.8 cm, whereas the median distance from the pleural surface to the edge of the pulmonary lesion in its shortest path was 1.9 ± 1.6 cm. Most lesions in this cohort had a positive air bronchus sign (69.6%). The mean procedure time for a young thoracic surgeon was longer after 10 cases of operation (45.6 ± 13.4 vs. 33.8 ± 9.2 min, P = 0.027). There were no complications reported related to the procedure. Conclusion: ENB is a safe and less invasive method for tissue diagnosis or preoperative localization for patients with pulmonary lesions. However, a young thoracic surgeon in the learning process requires more time to perform ENB. This study provides basic information about the learning experience of trainees while performing the ENB procedure.

Thermodynamic characteristics of extreme heat waves over the middle and lower reaches of the Yangtze River Basin

In August 2022, an exceptionally long-lasting heat wave (HW) affected the middle and lower reaches of the Yangtze River basin. This study uses the JRA55 daily reanalysis datasets to elucidate the thermodynamic characteristics of the daily evolution of historical extreme HWs in this region via the heat budget equation. HWs are generally characterized by the occurrence of anticyclonic circulation anomaly throughout the troposphere and positive air temperature anomaly with the maximum amplitude in the boundary layer. The anticyclonic anomaly can induce compression heating in the entire troposphere and warm zonal advection in the boundary layer. Meanwhile, due to the reduced cloud cover, more shortwave radiation reaches the ground surface, and the sensible heat flux becomes an important source of diabatic heating before the onset of HWs. The accumulated excessive heat in the HWs is primarily damped through the emission of longwave radiation and meridional thermal advection. For the HW in August 2022, its extreme persistence is mainly caused by prolonged adiabatic heating, enhanced diabatic heating during the developing stage and weakened diabatic cooling during the decay stage. The upper-level portion of the anticyclonic circulation anomalies is linked to the strengthened South Asia High. After applying the state-of-the-art dynamic metric, i.e., local finite wave activity, we reveal that the formation of the anomalous South Asia High in August 2022 is associated with the Stokes drift flux rather than the dispersion of Rossby wave energy. This characteristic sets it apart from other extreme HWs.

Multidecadal Changes in the Flow Velocity and Mass Balance of the Hailuogou Glacier in Mount Gongga, Southeastern Tibetan Plateau

Maritime glaciers in the southeastern Tibetan Plateau (TP) have experienced important changes in mass and dynamics over the past decades, challenging the regional water supply and glacier-related hazards. However, knowledge about long-term variations in the surface velocity and mass balance of maritime glaciers remains incomplete due to the lack of representative observations in the southeastern TP. In this study, offset tracking is employed to measure spatiotemporal variation in the surface velocity of the Hailuogou Glacier (HLG) in Mount Gongga of the southeastern TP using Sentinel-1A imagery, while the time series of the HLG mass balance is reconstructed since 1950 by a physically based energy–mass balance model. Our satellite-based results find that HLG surface velocity shows significant spatial heterogeneity with a double-peak pattern along the flow line, and sustained slowdown below the icefall zone has been observed during the past nearly 40 years, although the icefall zone and the area above it have become relatively active. Our modeling indicates a persistent increase in mass loss over the last seven decades with an average rate of −0.58 m water equivalent (w.e.) year−1, which has accelerated in the past two decades. Sustained slowdown on the glacier is concomitant with pronounced negative mass balance, thereby enhancing glacier wastage in recent decades. The long-term trend in HLG mass loss is mainly driven by an increase in positive air temperature that decreases surface albedo and solid precipitation ratio and increases longwave incoming radiation, besides the influence of supraglacial debris cover. Large-scale atmospheric circulation patterns in the Eurasian region provide important implications for regional-to-local climate variability, unsustainably intensifying the trend of the negative mass balance of the HLG in the southeastern TP in the past two decades.

Invitro Evaluation of Forces Delivered by Aligners Fabricated using Positive Air Pressure versus Negative Air Pressure.

Invitro Evaluation of Forces Delivered by Aligners Fabricated using Positive Air Pressure versus Negative Air Pressure.

The Effect of PDCA Circulation on Improving The Up-to-Standard Rate of Wearing Time Length in OSAHS Patients with Non-Invasive Ventilator

Purpose: To investigate the clinical effect of PDCA（Plan-Do-Check-Act） circulation mode in patients with obstructive sleep apnea hypopnea syndrome (OSAHS) using continuous positive air way pressure (CPAP) ventilator. Methods: 83 patients with OSAHS who were treated in the department of otorhinolaryngology head and neck surgery were randomly divided into PDCA group (n = 41) and control group (n = 42). The nursing outcomes of the two groups were compared. Result: The rate of reaching the standard wearing time length of non-invasive ventilator in the PDCA group was 80.49%, which was significantly higher than that in the control group (35.71%), and the difference was statistically significant (χ2=17.005, P&lt;0.05). The compliance rate of patients in the PDCA group (90.24%) was higher than that in the control group (73.80%), and the difference was statistically significant (Z= 2.571, P&lt;0.05). The incidence of adverse reactions in the PDCA group was 19.51% lower than that in the control group (64.29%), and the difference was statistically significant (χ2=17.005, P&lt;0.05). The score of fatigue in the PDCA group (4.17 ±1.223) was significantly lower than that in the control group (6.45 ±0.803). Conclusion: PDCA circulation nursing model can effectively improve the up-to-standard rate of time length of patients wearing non-invasive ventilator, reduce the incidence of adverse reactions, improve patient compliance and reduce patient fatigue, which is worthy of clinical promotion. Key words: PDCA circulation nursing model; the up-to-standard rate of time length of non-invasive ventilator; compliance; incidence of adverse reactions; fatigue degree.

Meteorological drivers of melt at two nearby glaciers in the McMurdo Dry Valleys of Antarctica

Abstract We study the meteorological drivers of melt at two glaciers in Taylor Valley, Antarctica, using 22 years of weather station observations and surface energy fluxes. The glaciers are located only 30 km apart, but have different local climates; Taylor Glacier is generally drier and windier than Commonwealth Glacier, which receives more snowfall due to its proximity to the coast. Commonwealth Glacier shows more inter-annual melt variability, explained by variable albedo due to summer snowfall events. A significant increase in surface melt at Commonwealth Glacier is associated with a decrease in summer minimum albedo. Inter-annual variability in melt at both glaciers is linked to degree-days above freezing during föhn events, occurring more frequently at Taylor Glacier. At Taylor Glacier melt occurs most often with positive air temperatures, but föhn conditions also favour sublimation, which cools the surface and prevents melt for the majority of the positive air temperatures. At Commonwealth Glacier, most of the melt instead occurs with sub-zero air temperatures, driven by strong solar radiative heating. Future melt at Taylor Glacier will likely be more sensitive to changes in föhn events, while Commonwealth Glacier will be impacted more by changes in near coastal weather, where moisture inputs can drive cloud cover, snowfall and change albedo.

Comparing and validating air sampling methods for SARS-CoV-2 detection in HVAC ducts of student dorms

The Coronavirus disease 2019 (COVID-19) pandemic demonstrated the threat of airborne pathogenic respiratory viruses such as the airborne Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). The ability to detect circulating viruses in a workplace or dormitory setting allows an early warning system that can alert occupants to implement precautions (e.g. masking) and/or trigger individual testing to allow isolation and quarantine measures to halt contagion. This work extends and validates the first successful detection of SARS-CoV-2 virus in dormitory Heating, Ventilation, and Air Conditioning (HVAC) systems and compares different air sampling methods and media types combined with optimized quantitative Reverse-Transcription PCR (qRT-PCR) analysis. The study was performed in two environments; large dormitories of students who underwent periodic testing for COVID-19 (unknown environment) and the HVAC air from a suite with a student who had tested positive for COVID-19 (known dorm). The air sampling methods were performed using Filter Cassettes, BioSampler, AerosolSense Sampler and Button Sampler (with four media types with different pore sizes of 5 μm, 3 μm, 3 μm (gelatin), and 1.2 μm). The SARS-CoV-2 positive air samples were compared with the positive samples collected by individual student campus track tracing methods using PCR testing on saliva and nasopharyngeal samples. The results show a detection rate of 73% in the unknown environment and a 78% detection rate in the known dorm. Our data show that the virus was detectable with all the sampling methods we employed. However, the AerosolSense sampler and BioSampler performed the best at 63% and 61% detection rates, compared to 25% for the Filter Cassettes and 23% for the Button Sampler. Despite the success rate, it is not possible to definitively conclude which method is most sensitive due to the limited number of samples. These results show that with careful sampling and optimized PCR methods, pathogenic respiratory viruses can be detected in large buildings using HVAC return air.

Fact or fiction? Does the position of the end-to-end (EEA) stapler spike matter for colorectal anastomoses using a double-stapled technique?

Surgeons often have strong opinions about how to perform colorectal anastomoses with little data to support variations in technique. The aim of this study was to determine if location of the end-to-end (EEA) stapler spike relative to the rectal transection line is associated with anastomotic integrity. This study was a retrospective analysis of a quality collaborative database at a quaternary centre and regional hospitals. Patients with any left-sided colon resection with double-stapled anastomosis were included (December 2019 to August 2022). Our primary endpoint was a composite outcome including positive air insufflation test, incomplete anastomotic donut, or thin/eccentric donut. Our secondary endpoint was clinical leak. Overall, 633 patients were included and stratified by location of the stapler spike relative to the rectal transection line. Of note, 86 patients had an end-colon to anterior rectum ("reverse Baker") anastomosis with no crossing staple lines. The rates of the composite endpoint based on position of the stapler spike were 12.4% (anterior), 8.1% (through), 12.8% (posterior), 5.1% (corner), and 2.3% for the "reverse Baker" (p = 0.03). The overall rate of clinical leak was 3.8% and there were no differences between methods. In a multivariate analysis, the "reverse Baker" anastomosis was associated with decreased odds of poor anastomotic integrity when compared to anastomoses with crossing staple lines (OR 0.20, 95% CI: 0.05-0.87, p = 0.03). For anastomoses with crossing staple lines, the position of the stapler spike relative to the rectal staple line is not associated with differences in anastomotic integrity. In contrast, anastomoses with no crossing staple lines resulted in significantly lower rates of poor anastomotic integrity, but no difference in clinical leaks.

Changes in the parameters of extreme temperature events in the western part of the Russian Arctic according to ERA5 and MERRA-2 reanalyses in 1980–2022

The air temperature in the Arctic zone of Russia is increasing at a rate of 0.71 °C per decade, which is three times faster than the global average. The warming of climate is accompanied by an increase in its extremeness, which leads to an increase in the number of dangerous hydrometeorological phenomena. The most significant changes occurred in the statistics of large-scale summer heat waves in European Russia. One of the most important goals in studying current climate changes is to study the frequency of extreme hydrometeorological phenomena, in particular, heat or cold waves. In this paper, we investigate the average daily anomalies relative to the annual variation of air temperature at a height of 2 meters from the surface in the region of the western part of the Russian Arctic (60°–75° N, 30°–85° E), according to ERA5 and MERRA-2 atmospheric reanalyses for the period 1980–2022. Their root-mean-square deviations and the distribution of their average number per year are calculated. We have plotted the fields of average values and the rate of changes in the amplitude, duration and number of anomalous temperature events which exceed two standard deviations in the study region. Areas of increase and decrease in the amplitude, duration and number of extreme events, both with positive and negative temperature anomalies, are displayed. In general, it can be concluded that, on average, the amplitudes of positive extreme air temperature anomalies in the study area slightly increase. The duration of positive extreme anomalies is growing everywhere at a rate of 0.2 days per 10 years. The duration of negative extreme anomalies slightly decreases. The number of events with negative extreme anomalies has been decreasing at a rate of –0.5 to –3 events per year for 10 years, while the number of events with positive extreme anomalies has been increasing from 0.1 to 1 events per year for 10 years.The results obtained significantly expand our knowledge of the spatiotemporal features of the ongoing changes in the extreme climate of the western part of the Russian Arctic, which is of paramount importance for the analysis and forecasting of the development of natural and socio-economic systems in the region under study.

Multiphase SPH analysis of a breaking wave impact on elevated structures with vertical and inclined walls

Elevated structures are prevalent along shorelines that are susceptible to storm surge flooding to improve coastal resilience. In this work, we explore the influence of front wall inclination on the pressures and forces attracted by an elevated structure in response to extreme wave impact. Multiphase smoothed-particle hydrodynamics was used to examine a typical two-story building 6 m high and 10 m long with three different frontal wall inclinations impinged by a single breaking wave propagating landwards (from left to right). Relative to a vertical surface, both positive (clockwise) and negative (counterclockwise) inclinations of the front wall altered breaking wave pressures depending on the structure's position relative to the still-water level (SWL). When the bottom of the structure is located below the SWL (negative air gap), a positive inclination decreased breaking wave loads by up to 21 %, while a negative inclination may result in 50 % higher pressure maxima. However, for a structure elevated above the SWL (positive air gap), negative and positive inclinations witnessed reductions to the pressure maxima of 35 % and 10 %, respectively, when compared with a vertical surface.

Modern changes in climatic characteristics and minimum flow of the rivers in the basin of lake Sevan

Formulation of the problem. Studies and data on modern changes in the winter minimum average monthly flow of the rivers of the Lake Sevan basin and their climatic characteristics have acquired great practical importance and considerable interest due to the increased use of water resources for the purposes of various types of economic activities, in particular, in connection with the development of the economy, hydropower, irrigation, population growth and rising living standards. Especially relevant are the calculations of the minimum flow in relation to solving the problems of water supply for settlements, industrial enterprises. The aim of the work. Assessment of modern changes in the winter minimum average monthly runoff of rivers in the Lake Sevan basin and their climatic characteristics. Methods. The following methods were used in the work: mathematical-statistical, extrapolation, interpolation, spatial analysis, analogy, correlation and cartography. Results. A physical map has been compiled with a network of meteorological stations and hydrological posts in the Lake Sevan basin. Close correlations were obtained between the values of the winter minimum average monthly runoff and the average runoff of the winter period for a hydrological year. These dependences can be used for preliminary estimates of the minimum runoff of the winter low-water period of unstudied rivers in the territory under consideration. In the course of the research, the winter minimum average monthly discharges were calculated by months and for the entire observation period, the average value of the minimum runoff for the winter low water, and the linear trend of the climatic characteristic. Based on the obtained results, a map of the distribution of the modul of the average minimum runoff of the winter low-water period and the coefficients of the linear trend of the winter air temperature were constructed. Examples of curves of long-term changes in precipitation amounts for the autumn and winter periods, the sum of positive temperatures and the number of days with a positive average daily air temperature in the winter period for a series of meteorological stations in the study area are presented. The rivers of the Lake Sevan basin are characterized by an uneven spatio-temporal distribution of winter minimum runoff and climatic characteristics, changes in the winter average monthly minimum runoff, precipitation amounts for the autumn and winter periods are multidirectional, and air temperature changes are only an upward trend. In the area under consideration, there is mainly (by 8 out of 12 stations under study) a tendency to decrease in the values of the minimum average monthly river flow. The conducted studies lead us to the conclusion that the main factor causing changes in the low-water runoff of the rivers in the Lake Sevan basin in winter is the air temperature, or rather, its increase. It follows from this that when calculating and forecasting winter runoff, it is necessary to relate the values of runoff and air temperature.

Modelling aerosol transmission of porcine reproductive and respiratory syndrome virus between buildings using computational fluid dynamics

An integrated computational fluid dynamics (CFD) model was developed to simulate aerosol transmission of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) from a source to recipient building using a previously published experimental study as a test case. The integrated model consisted of CFD simulations of PRRSV aerosol movement in the atmosphere and within the recipient building, viral infectivity decay, and infection dose-response. Specific hours with the appropriate wind direction during two days (June 6 and 7, 2006) were simulated, based on historical weather data. For a given airborne PRRSV concentration exhausted from the source building, the model predicted the PRRSV distribution, infectivity decay, and probability of infection in the recipient building. Simulations indicated that wind affected the aerosol entry into the recipient building, with more stable and continuous aerosol entry at lower wind speed conditions on June 7. Elevated aerosol and PRRSV concentrations on June 7 resulted in pigs being exposed to higher doses of PRRSV than on June 6, but this only made a difference in probability of infection when there was a moderate level of PRRSV (500 TCID m−3) exhausted from the source building. At this level, there was a difference in exposure dose for pigs at different locations (pens). Overall, the positive PRRSV air sample on the morning of June 7 in the previously reported experimental study confirmed the adequacy of the model simulations, which predicted the aerosol transmission event that infected pigs in the recipient building was likely to have occurred on June 7, 2006.