Moisture Exchange Research Articles

Development and validation of a 3D printed antiviral ventilator filter - a comparative study

BackgroundThe current coronavirus infectious disease 2019 (COVID-19) pandemic has caused unexpected pressure on medical supplies, interrupting supply chains and increasing prices. The supply of antiviral filters which form an essential part of the ventilator circuit have been affected by these issues. Three-dimensional (3D) printing may provide a solution to some of these issues.MethodsWe designed and tested 3D printed heat and moisture exchange (HME) and antiviral casing. For each casing we tested two different filter materials derived from a sediment water filter cartridge or 1.5-μm glass fiber filter paper. A polyurethane sponge was used for the HME. Each design was tested for circuit leak, circuit compliance, peak inspiratory pressure and casing integrity using methylene blue dye.ResultsWe designed, produced, and tested two different types of antiviral filters with six different internal configurations. Overall, we tested 10 modified filter designs and compared them with the original commercial filter. Except for the combination of 1.5-μm filter paper and 5 mm sponge peak inspiratory pressure and circuit compliance of the filters produced were within the operating limits of the ventilator. All In addition, all filters passed the dye test.ConclusionsOur filter may be of particular importance to those working in low middle-income countries unable to compete with stronger economies. Our design relies on products available outside the healthcare supply chain, much of which can be purchased in grocery stores, hardware stores, or industrial and academic institutions. We hope that these HMEs and viral filters may be beneficial to clinicians who face critical supply chain issues during the COVID-19 pandemic.

How interactions between tropical depressions and western disturbances affect heavy precipitation in South Asia

AbstractInteractions over South Asia between tropical depressions (TDs) and extratropical storms known as western disturbances (WDs) are known to cause extreme precipitation events, including those responsible for the 2013 floods over northern India. In this study, existing databases of WD and TD tracks are used to identify potential WD–TD interactions from 1979–2015; these are filtered according to proximity and intensity, leaving 59 cases which form the basis of this paper. Synoptic charts, vorticity budgets, and moisture trajectory analyses are employed to identify and elucidate common interaction types among these cases. Two broad families of interaction emerge. Firstly, a dynamical coupling of the WD and TD, whereby either the upper- and lower-level vortices superpose (a vortex merger), or the TD is intensified as it passes into the entrance region of a jet streak associated with the WD (a jet-streak excitation). Secondly, a moisture exchange between the WD and TD, whereby either anomalous moisture is advected from the TD to the WD, resulting in anomalous precipitation near the WD (a TD-to-WD moisture exchange), or anomalous moisture is advected from the WD to the TD (a WD-to-TD moisture exchange). Interactions are most common in the post-monsoon period as the subtropical jet, which brings WDs to the subcontinent, returns south; there is a smaller peak in May and June, driven by monsoon onset vortices. Precipitation is heaviest in dynamically-coupled interactions, particularly jet-streak excitations. Criteria for automated identification of interaction types are proposed, and schematics for each type are presented to highlight key mechanisms.

Description of a novel technique for creation of a custom-made prosthesis to aid vocalisation following laryngectomy

There are various options to restore phonation after laryngectomy; one option involves using tracheo-oesophageal voice by placing a speaking valve through the tracheo-oesophageal wall. Some patients struggle to obtain good fixation of an adhesive base plate to the skin; this can result in air leakage and poor voice. We describe a technique using a custom-made prosthesis to provide a better base plate for fixation of the heat and moisture exchange cassette. This technique involves making an impression of the anterior neck around the laryngectomy stoma to create an anatomically fitted prosthesis, which accurately fills the void around the stoma. The custom-made prosthesis provides a more individualised fit compared to a standard base plate, helping improve vocalisation and communication.

Boundary condition and oceanic impacts on the atmospheric water balance in limited area climate model ensembles

Regional climate models (RCMs) are indispensable in climate research, albeit often characterized by biased terrestrial precipitation and water budgets. This study identifies excess oceanic evaporation, in conjunction with the RCMs’ boundary conditions, as drivers contributing to these biases in RCMs with forced sea surface temperatures in a CORDEX RCM ensemble over Europe. The RCMs are relaxed to the prescribed lateral boundary conditions originating from a global model, effectively matching the driving model's overall atmospheric moisture flux divergence. As a consequence, excess oceanic evaporation results in positive precipitation biases over land due to forced internal recycling of moisture to maintain the overall flux divergence prescribed by the boundary conditions. This systematic behaviour is shown through an analysis of long-term atmospheric water budgets and atmospheric moisture exchange between oceanic and continental areas in a multi-model ensemble.

CROPS WATER CONSUMPTION AND VERTICAL SOIL MOISTURE EXCHANGE

A various number of factors, which, in turn, also vary greatly, determines the process of water consumption. These are meteorological indicators, yield, crop properties and soil conditions. The values of the water consumption of irrigated crops (in the operational regime of irrigation in the calculation of the water balance) are recommended to be determined counting on: the indicators of heat supply of the territories, that is, the radiation balance; air humidity deficit and bioclimatic factors of water consumption, taking into account the type and phase of plants development, the physical condition and the soil moistening. The empirical method for determining the vertical moisture exchange takes into account the biological characteristics of crops, the conditions for the heat and moisture availability of the calculation periods, the power and humidity of the soil layer under study, the water-physical properties of the ground, and the depth of the groundwater. It gives reliable results and can be used in calculations of the water regime in designing and exploitation of the reclamation systems. The groundwater affects the formation of the soil water regime in the aeration zone. At shallow occurrence, they increase the humidity in the root layer, which makes it possible to reduce the irrigation rates and the number of irrigation events. This article considers the problem of reducing errors and improving existing methods of calculating water consumption by crops and vertical soil moisture exchange. The methods of (Shebeko et al., 1980), Rogotskiy (1981) and Pylenok (1985) were taken as the basis of the research. According to them and empirical formulas developed by Mazaiski (2002), the calculations of vertical moisture exchange were made. The empirical method for determining the vertical moisture exchange takes into account the biological characteristics of crops, the conditions for the heat and moisture availability of the calculation periods, the power and humidity of the soil layer under study, the water-physical properties of the ground, and the depth of the groundwater. It gives reliable results and can be used in calculations of the water regime in designing and exploitation the reclamation systems.

Performance of a new recuperative Heat and Moisture Exchange Mask

Aim of the study: The purpose of this work is to show the possibility to use a recuperative design of a heat and moisture exchange face mask (HME). Such HME are used as cold weather face masks for Arctic expeditions and conditioning of air for long-term intubated patients. Common regenerative HME have the disadvantage of increasing airway resistance and airway volume (dead space). In recuperative devices, the separation of inspired and expired airflow could reduce dead space and resistance. Materials and methods: Prototype HMEs were built using two concentric ducts of aluminium or cotton. A valve ensures that expired and inspired air are led through either the inner or the outer tube. The inner tube’s wall transmits heat and water. The HMEs were tested in a simulated Arctic environment using a breathing simulator and characterized in terms of heat and moisture exchange efficiency. The new design was also tested at room temperature in order to simulate the conditions of long-term intubation. To compare the results, the relative difference in temperature (Performance Coefficient PC) between the expired and the inspired air was calculated. Results: During the experiments, the ambient temperature was −37°C and therefore the absolute water content was about zero. The recuperative HME conditioned the air to 21°C and 10.7 mg/l water (61% relative humidity), giving a PC of 82%. At room temperature the recuperative mask showed a PC of 62%. Conclusion: The recuperative HME shows great potential. It might be of use in clinical conditions and Arctic expeditions.

Standardization of methods for sampling the distal airspace in mechanically ventilated patients using heat moisture exchange filter fluid.

Noninvasive sampling of the distal airspace in patients with acute respiratory distress syndrome (ARDS) has long eluded clinical and translational researchers. We recently reported that fluid collected from heat moisture exchange (HME) filters closely mirrors fluid directly aspirated from the distal airspace. In the current study, we sought to determine fluid yield from different HME types, optimal HME circuit dwell time, and reliability of HME fluid in reflecting the distal airspace. We studied fluid yield from four different filter types by loading increasing volumes of saline and measuring volumes of fluid recovered. We collected filters after 1, 2, and 4 h of dwell time for measurement of fluid volume and total protein from 13 subjects. After identifying 4 h as the optimal dwell time, we measured total protein and IgM in HME fluid from 42 subjects with ARDS and nine with hydrostatic pulmonary edema (HYDRO). We found that the fluid yield varies greatly by filter type. With timed sample collection, fluid recovery increased with increasing circuit dwell time with a median volume of 2.0 mL [interquartile range (IQR) 1.2-2.7] after 4 h. Total protein was higher in the 42 subjects with ARDS compared with nine with HYDRO [median 708 µg/mL (IQR 244-2017) vs. 364 µg/mL (IQR 136-578), P = 0.047], confirming that total protein concentration in HME is higher in ARDS compared with hydrostatic edema. These studies establish a standardized HME fluid collection protocol and confirm that HME fluid analysis is a novel noninvasive tool for the study of the distal airspace in ARDS.

In vitro evaluation of disposable transport ventilators with combination aerosol therapy

BackgroundThe COVID-19 pandemic has highlighted the need for alternative short-term, reliable means to aid in the treatment of patients requiring ventilatory support. Concurrent aerosol drug delivery is often prescribed to...

Research into the Long-Time Strength of Cement Stone with a Modified Structure

The problem of a time-dependent gain of a cement dispersed system’s strength remains the focus of both domestic and foreign researchers in terms of its practical significance. To study the above problem, we used non-additive sulfate-resistant Portland cement grade 400 made by Volsk city plant with a normal density of 24 %. 9 series of samples were made from fresh Portland cement. The kinetics of changes in the cement stone’s physical and mechanical properties was observed on series’ samples for 9.5 and 18 years. The paper imparts the values of the cement, water, superplasticizer consumption and compaction ration derived from compacted cement paste after forming test pieces, numerical values of properties in check dates as a result of natural moisture exchange with the environment and drying of test samples to a constant mass at 105°C, as well as the degree of its hydration at the age of 18 years, which was determined by calculation from non-evaporable, that is, chemically bound, water, taking into account that its amount in fully hydrated cement comprises 23% of the cement mass. Changing of the superplasticizer introduction procedure, even with a minimum consumption of S-3, led to a change in the yield value of the cement stone. The experiments targeting to reveal the long-time behavior of a superplasticized cement stone allow us to speak of a clear trend in the influence of SP and its introduction procedure on changes in long-time strength values. However, this is only a trend, since there are many other factors of influence than those discussed in this paper, which testifies to the necessity for a more detailed study of this problem due to its complexity considering the development and application of a new generation superplasticizer and composite binders to construction practice.

Sensitivity of an Idealized Tropical Cyclone to the Configuration of the Global Forecast System–Eddy Diffusivity Mass Flux Planetary Boundary Layer Scheme

The intensity and structure of simulated tropical cyclones (TCs) are known to be sensitive to the planetary boundary layer (PBL) parameterization in numerical weather prediction models. In this paper, we use an idealized version of the Hurricane Weather Research and Forecast system (HWRF) with constant sea-surface temperature (SST) to examine how the configuration of the PBL scheme used in the operational HWRF affects TC intensity change (including rapid intensification) and structure. The configuration changes explored in this study include disabling non-local vertical mixing, changing the coefficients in the stability functions for momentum and heat, and directly modifying the Prandtl number (Pr), which controls the ratio of momentum to heat and moisture exchange in the PBL. Relative to the control simulation, disabling non-local mixing produced a ~15% larger storm that intensified more gradually, while changing the coefficient values used in the stability functions had little effect. Varying Pr within the PBL had the greatest impact, with the largest Pr (~1.6 versus ~0.8) associated with more rapid intensification (~38 versus 29 m s−1 per day) but a 5–10 m s−1 weaker intensity after the initial period of strengthening. This seemingly paradoxical result is likely due to a decrease in the radius of maximum wind (~15 versus 20 km), but smaller enthalpy fluxes, in simulated storms with larger Pr. These results underscore the importance of measuring the vertical eddy diffusivities of momentum, heat, and moisture under high-wind, open-ocean conditions to reduce uncertainty in Pr in the TC PBL.

Impact of middle atmospheric humidity on boundary layer turbulence and clouds

An attempt is made to connect the moisture present above the boundary layer and its association with the cloud development and boundary layer turbulence using Large Eddy Simulation (LES) and aircraft observations. The dry boundary layer (BL) with shallow clouds observed during Cloud-Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) over the arid Indian peninsula is investigated in this study. The constant altitude aircraft observations at different elevations are used to verify LES derived fluxes and variances. LES simulations with the drier conditions above BL resulted in deeper, warmer and drier BL with an enhanced boundary layer turbulent kinetic energy. A dynamic feedback from dry air intrusion into the BL resulted in energetic BL eddies in the dry conditions and a doubling of moisture exchange coefficients. The liquid water content in cloud updrafts rather than in downdrafts were depleted significantly in dry conditions. LES sensitivity indicates that the middle atmospheric water vapor alone could influence the shallow to deep cumulus cloud transitions in the monsoon regime in a dramatic way, by changing the population of cumulus, congestus or deep cumulus clouds. A 30% drying above the BL could drastically reduce the liquid water path and cloud albedo by 10–15%.

GENERALIZED DEPENDENCES FOR ISOTHERMIC MASS TRANSFER IN THE “MASS-MINE AIR” SYSTEM

The paper presents the results of mathematical modelling on the БУСЭ- 70 integrator of the process of isothermal mass transfer in the system: “massmine air”. Generalized dependences are adduced which enable the determination of the mass transfer potential of the surface of workings in the course of moisture exchange. It is noted that mass exchange processes in the majority of workings take a less intensive course in comparison with heat exchange processes.

Surgical Performance Is Not Negatively Impacted by Wearing a Commercial Full-Face Mask with Ad Hoc 3D-Printed Filter Connection as a Substitute for Personal Protective Equipment during the COVID-19 Pandemic: A Randomized Controlled Cross-Over Trial.

(1) Background: During the COVID-19 pandemic, shortages in the supply of personal protective equipment (PPE) have become apparent. The idea of using commonly available full-face diving (FFD) masks as a temporary solution was quickly spread across social media. However, it was unknown whether an FFD mask would considerably impair complex surgical tasks. Thus, we aimed to assess laparoscopic surgical performance while wearing an FFD mask as PPE. (2) Methods: In a randomized-controlled cross-over trial, 40 laparoscopically naive medical students performed laparoscopic procedures while wearing an FFD mask with ad hoc 3D-printed connections to heat and moisture exchange (HME) filters vs. wearing a common surgical face mask. The performance was evaluated using global and specific Objective Structured Assessment of Technical Skills (OSATS) checklists for suturing and cholecystectomy. (3) Results: For the laparoscopic cholecystectomy, both global OSATS scores and specific OSATS scores for the quality of procedure were similar (Group 1: 25 ± 4.3 and 45.7 ± 12.9, p = 0.485, vs. Group 2: 24.1 ± 3.7 and 43.3 ± 7.6, p = 0.485). For the laparoscopic suturing task, the FFD mask group needed similar times to the surgical mask group (3009 ± 1694 s vs. 2443 ± 949 s; p = 0.200). Some participants reported impaired verbal communication while wearing the FFD mask, as it muffled the sound of speech, as well as discomfort in breathing. (4) Conclusions: FFD masks do not affect the quality of laparoscopic surgical performance, despite being uncomfortable, and may therefore be used as a substitute for conventional PPE in times of shortage—i.e., the global COVID-19 pandemic.

A crossover study assessing the protective efficacy of improvised snorkel-based improvised respirators.

This study was designed to determine whether improvised respirators based on modified full-face snorkel masks are able to pass a standard qualitative fit test. This is a prospective crossover study conducted in 16 staff. Fit-tests were conducted on masks mated to (1) an anaesthetic breathing circuit heat and moisture exchange filter and (2) a CE-marked P3 grade filter. P3 filters were mounted using both epoxy-coated and uncoated adaptors. None of the tests using anaesthetic filters passed. Only one overall pass was observed using the P3-rated filter mated to the snorkel mask. These data suggest that improvised PPE designs cannot provide reliable protection against aerosols. Failures are likely due to poor fit, but the suitability of 3D printed materials is also uncertain as fused-filament manufacturing yields parts that are not reliably gas-tight. Improvised PPE cannot be recommended as a substitute for purpose designed systems.

Experimental and statistical analysis research of the triticale grain drying process when countercurrent-direct-flow blowing of the grain layer

Experimental studies of the kinetics of the process of drying triticale grain during counter-current-direct blowing of the grain layer were carried out. In the experimental installation, a programmed change in the direction of the drying agent flow through the grain layer was carried out and the actual conditions of the drying agent supply through the supply and discharge boxes of the shaft grain dryer were emitted. Analysis of drying curves and drying rate of triticale grain showed the presence of only a period of decreasing drying rate, in which the intensity of moisture diffusion is significantly less than the intensity of moisture exchange. The organization of the experiment made it possible to fully adapt it to industrial mine grain dryers, in which the drying process is carried out in a continuous mode. Based on the results of the study, an empirical model of the drying process is proposed in the form of an exponential function, which establishes a unique functional relationship between the current moisture of the grain and the main parameters of the process: temperature, speed, moisture content of the drying agent and the thickness of the blown layer. Taking into ac-count the requirements to the process modes of grain drying, the triticale analyzes the ratio between the grain temperature and its humidity at various values of the mode parameters, which is proposed to be used as a restriction on the drying temperature mode.

Statistical modeling of sea ice concentration in the northwest region of the Antarctic Peninsula

Sea ice is one of the main components of the cryosphere that modifies the exchange of heat and moisture between the ocean and atmosphere, regulating the global climate. In this sense, it is important to identify the concentration of sea ice in different regions of Antarctica in order to measure the impact of environmental changes on the region's ecosystem. The objective of this study was to evaluate the performance of the multiple linear regression and Box-Jenkins methods for predicting the concentration of sea ice along the northwest coast of the Antarctic Peninsula. Sea ice concentration data from May to November for the period 1979-2018 were extracted from passive remote sensors including a scanning multichannel microwave radiometer, special sensor microwave imager, and special sensor microwave imager/sounder. Meteorological variables from the atmospheric reanalysis model ERA5 of the European Center for Medium-Range Weather Forecasts were used as predictor variables, and the leave-one-out cross-validation technique was used to calibrate and validate the models. It was found that both statistical models have similar performance when analyzing residual analysis results, root mean square error of cross-validation, and final accuracy and residual standard deviation, these responses being related to the regionalization of the study area and to the Box-Jenkins presents strong, homogeneous, and stable correlations in the time series modeled for each pixel.

A crossover trial investigating the atmospheric content of improvised respirators.

This study was designed to determine the respiratory safety of improvised respirators based on modified full-face snorkel masks, making comparisons with a purpose-designed mask. This is a prospective crossover study conducted on ten recruits. Volunteers wore snorkel masks mated to an anaesthetic heat and moisture exchange filter. The system was worn at rest then during exercise. Gases were sampled from the mask at 5-min intervals. The modified snorkel was satisfactory in seven participants. For three carbon dioxide concentrations were >1%. Two participants exposed to excessive CO2 also experienced oxygen concentrations <19%. All participants exposed to unsatisfactory gas mixtures were non-white. Modifying snorkel masks changes the way that gases circulate through the system. These modifications increase the risk of rebreathing in some users, which may yield an unsafe gas mixture. These improvised masks cannot be recommended as a substitute for purpose-designed equipment.

Bioactive properties and potential applications of Aloe vera gel edible coating on fresh and minimally processed fruits and vegetables: a review

Aloe vera gel provides numerous health benefits and is considered as one of the best coating materials, which is edible, safe, and biodegradable. It facilitates a barrier against moisture and gas exchange, conserves the firmness, color, and flavor of the fruits and vegetables. Besides, owing to the antimicrobial and antioxidative properties, Aloe vera coating provides reduced microbial proliferation and improved antioxidant activity of the stored produce. Hence, Aloe vera coating has been used as a noble edible coating for fresh produce. This review aims to highlight the application of Aloe vera gel coating alone or together with other functional compounds in order to extend postharvest shelf life and preservation quality of fresh and minimally processed fruits and vegetables. This study also summarizes relevant biological activities and compositional characteristics of the gel. Some challenges and future aspects of the application of Aloe vera coating have discussed as there is a growing interest in this unique edible coating. This information will help the food processors to identify the most effective Aloe vera coating concentration alone or in combination with other functional ingredients for a variety of fresh and minimally processed fruits and vegetables.

Investigating the Sensitivity of Marine Fog to Physical and Microphysical Processes Using Large-Eddy Simulation

Over the past few years large-eddy simulation (LES) has demonstrated success in modelling continental radiation fog, and several recent studies have used LES to investigate the sensitivity of fog formation to physical processes such as turbulent mixing and surface heat and moisture exchange, as well as to the parametrization of microphysical processes such as cloud droplet activation. Here we extend these sensitivity studies to marine fog. There are several important differences in the formation of marine and continental fog, however moisture availability is no longer a decisive factor, and surface temperature changes over a much longer time scale. Here LES is used to examine the sensitivity of simulated marine-fog formation and maintenance to the cloud-droplet number concentration, turbulent mixing, and air–sea temperature difference. The strength of the fog (in terms of liquid water content) is found to be highly sensitive to all three factors. Varying only the cloud-droplet number concentration, even within a range of physically realistic values for marine regions, can mean the difference between fog halving or doubling in liquid water content. The sensitivities demonstrated herein indicate the great need and challenge for constraining these parameters in numerical weather prediction. Similarities and differences to the findings for continental radiation fog are examined, and important considerations for future improvements in marine-fog forecasting are discussed.

To the justification of the calculation of the heat conduction process in the dough piece

The main process that ensures the production of bread as a marketable product is the external thermal energy supply during baking. This process is accompanied by a complex physical phenomenon - moisture exchange between the dough-bread with the external environment and the steam-air environment of the baking chamber, as well as internal heat and mass transfer in the heated dough piece. At the same time, biochemical processes associated with the transformation of starch and proteins. Taking into account that the main factor realizing the efficiency and quality indicators of baked bread is heat exchange in the dough piece, in this article, taking into account the peculiarities of the dynamics of the heat transfer phenomenon, a quantitative analysis of the course of this process is carried out. In this work, in contrast to the results obtained by other researchers in the field of calculating the processes of heat treatment of food products, a quantitative analysis of the process is proposed based on a new methodological approach to the problem of physical and mathematical substantiation of the heat transfer process in a dough piece. That can be effectively used in the simulation of innovative samples of baking equipment.