Low-flow Air Research Articles

Hyporheic exchange flows in a mountainous river catchment identified by distributed temperature sensing

AbstractElevated stream temperatures under low‐flows, exacerbated by global warming, are a stressor that affects aquatic species directly or in combination with other stressors. Stream temperatures are influenced by energy fluxes across the air–water interface as well as by hydrological exchange processes occurring at the water–riverbed interface. Small‐scale stream temperature dynamics influenced by exchange flows are still underrepresented in stream temperature research. To investigate high‐resolution temperature dynamics and hydrological exchange processes at the sediment–water interface we applied fiber‐optic distributed temperature sensing (FO‐DTS) at two sites in the mountainous Kinzig catchment combined with mapping and measurement of additional environmental conditions. Two types of temperature anomalies could be observed at one site under conditions of low flow and high air temperature. Dampening effects coincided with riverine features such as pools, vegetation roots, fine sediment, and signs of streambank seepage which indicated hyporheic exchange flows. Increased heating of the substrate during the day was identified in shallow sections where sediment was exposed to the air and shading from riparian vegetation was patchy. At another site, at which the cable could not be buried because of the sediment composition, temperature anomalies in the overlying water indicated diffuse groundwater exfiltration. The results show that small‐scale processes in the hyporheic zone, low water tables, and riparian shading influence stream temperature in mountainous streams and can be identified with FO‐DTS under suitable conditions. The results improve our understanding of stream temperatures (in the hyporheic zone) and provide important information on how to improve hydrological modeling.

Experimental and numerical studies on the air-injection drag reduction of the ship model

Experimental and numerical studies on the air-injection drag reduction (AIDR) of the ship model are conducted. For the experiments, the ship model and air-injection device are specially designed and the AIDR of the ship model is investigated considering one draft and three speeds. Then, considering two ship speeds, the AIDR of the ship model is simulated using two numerical models, namely the Euler-Euler two-fluid model and VOF model. It is found that for the surface ship there are still three drag reduction regions. Microbubble drag reduction (MBDR) is dominant for low air flow rates and air layer drag reduction (ALDR) is dominant for high air flow rates, and the transitional region exists for the medium air flow rates. For MBDR, the mechanism is related to the reduction of both effective dynamic viscosity and normal velocity gradient. Bubble size is the key influencing factor. Smaller bubbles are more favorable for drag reduction. Large millimeter bubbles can increase drag, which is owing to the extra turbulence viscosity. For ALDR, the mechanism is mainly owing to the loss of wet surface area and the key influencing factor is the air cover area. In general, ships with higher speed are more favorable for AIDR.

High-Flow Oxygen and High-Flow Air for Dyspnea in Hospitalized Patients with Cancer: A Pilot Crossover Randomized Clinical Trial.

The effect of high-flow oxygen (HFOx) and high-flow air (HFAir) on dyspnea in nonhypoxemic patients is not known. We assessed the effect of HFOx, HFAir, low-flow oxygen (LFOx), and low-flow air (LFAir) on dyspnea. This double-blind, 4×4 crossover clinical trial enrolled hospitalized patients with cancer who were dyspneic at rest and nonhypoxemic (oxygen saturation >90% on room air). Patients were randomized to 10 minutes of HFOx, HFAir, LFOx, and LFAir in different orders. The flow rate was titrated between 20-60 L/minute in the high-flow interventions and 2 L/minute in the low-flow interventions. The primary outcome was dyspnea numeric rating scale (NRS) "now" where 0 = none and 10 = worst. Seventeen patients (mean age 51 years, 58% female) completed 55 interventions in a random order. The absolute change of dyspnea NRS between 0 and 10 minutes was -1.8 (SD 1.7) for HFOx, -1.8 (2.0) for HFAir, -0.5 (0.8) for LFOx, and - 0.6 (1.2) for LFAir. In mixed model analysis, HFOx provided greater dyspnea relief than LFOx (mean difference [95% confidence interval] -0.80 [-1.45, -0.15]; p = .02) and LFAir (-1.24 [-1.90, -0.57]; p < .001). HFAir also provided significantly greater dyspnea relief than LFOx (-0.95 [-1.61, -0.30]; p = .005) and LFAir (-1.39 [-2.05, -0.73]; p < .001). HFOx was well tolerated. Seven (54%) patients who tried all interventions blindly preferred HFOx and four (31%) preferred HFAir. We found that HFOx and HFAir provided a rapid and clinically significant reduction of dyspnea at rest in hospitalized nonhypoxemic patients with cancer. Larger studies are needed to confirm these findings (Clinicaltrials.gov: NCT02932332). This double-blind, 4×4 crossover trial examined the effect of oxygen or air delivered at high- or low-flow rates on dyspnea in hospitalized nonhypoxemic patients with cancer. High-flow oxygen and high-flow air were significantly better at reducing dyspnea than low-flow oxygen/air, supporting a role for palliation beyond oxygenation.

High-Flow Nasal Cannula Therapy for Exertional Dyspnea in Patients with Cancer: A Pilot Randomized Clinical Trial.

Exertional dyspnea is common in patients with cancer and limits their function. The impact of high-flow nasal cannula on exertional dyspnea in nonhypoxemic patients is unclear. In this double-blind, parallel-group, randomized trial, we assessed the effect of flow rate (high vs. low) and gas (oxygen vs. air) on exertional dyspnea in nonhypoxemic patients with cancer. Patients with cancer with oxygen saturation >90% at rest and exertion completed incremental and constant work (80% maximal) cycle ergometry while breathing low-flow air at 2 L/minute. They were then randomized to receive high-flow oxygen, high-flow air, low-flow oxygen, or low-flow air while performing symptom-limited endurance cycle ergometry at 80% maximal. The primary outcome was modified 0-10 Borg dyspnea intensity scale at isotime. Secondary outcomes included dyspnea unpleasantness, exercise time, and adverse events. Seventy-four patients were enrolled, and 44 completed the study (mean age 63; 41% female). Compared with low-flow air at baseline, dyspnea intensity was significantly lower at isotime with high-flow oxygen (mean change, -1.1; 95% confidence interval [CI], -2.1, -0.12) and low-flow oxygen (-1.83; 95% CI, -2.7, -0.9), but not high-flow air (-0.2; 95% CI, -0.97, 0.6) or low-flow air (-0.5; 95% CI, -1.3, 0.4). Compared with low-flow air, high-flow oxygen also resulted in significantly longer exercise time (difference + 2.5 minutes, p = .009), but not low-flow oxygen (+0.39 minutes, p = .65) or high-flow air (+0.63 minutes, p = .48). The interventions were well tolerated without significant adverse effects. Our preliminary findings support that high-flow oxygen improved both exertional dyspnea and exercise duration in nonhypoxemic patients with cancer. (ClinicalTrials.gov ID: NCT02357134). In this four-arm, double-blind, randomized clinical trial examining the role of high-flow nasal cannula on exertional dyspnea in patients with cancer without hypoxemia, high-flow oxygen, but not high-flow air, resulted in significantly lower dyspnea scores and longer exercise time. High-flow oxygen delivered by high-flow nasal cannula devices may improve clinically relevant outcomes even in patients without hypoxemia.

High flow oxygen for dyspnea in hospitalized patients with cancer: A 4x4 crossover randomized clinical trial.

12077 Background: Dyspnea is common in hospitalized cancer patients and highly distressing. High flow oxygen (HFOx) is administered for oxygenation in this setting; however, its effect on dyspnea has not been well examined, particularly among non-hypoxemic patients. In this phase II trial, we assessed the effect of HFOx, high flow air (HFAir), low flow oxygen (LFOx) and low flow air (LFAir) on dyspnea. We hypothesized that HFO and HFA can alleviate dyspnea. Methods: This double-blind, 4x4 crossover clinical trial enrolled hospitalized patients with cancer who were dyspneic (NRS ≥3 at rest) and non-hypoxemic (SpO2&gt;90% on room air). Patients were randomized to 10 minutes of HFOx, HFAir, LFOx and LFAir in different orders. The flow rate was titrated between 20-60 L/min in the high flow groups and 2 L/min in the low flow groups. The primary outcome was dyspnea 0-10 numeric rating scale (NRS) “now”, where 0=none and 10=worst. Secondary outcomes included modified Borg scale dyspnea intensity and unpleasantness, adverse effects, and overall preference. We compared among the interventions with a linear mixed model adjusting for time, treatment effect, period effect and carryover effect. Results: 17 patients completed 55 interventions in a random order. Mean age 51, 58% female, mean baseline dyspnea NRS 6.3 (SD 1.7). The absolute change of dyspnea NRS between 0 and 10 minutes was -1.8 (SD 1.7) for HFOx, -1.8 (2.0) for HFAir, -0.5 (0.8) for LFOx and -0.6 (1.2) for LFAir. In mixed model analysis, HFOx group provided greater dyspnea relief than LFOx (mean difference [95% CI] -0.80 [-1.45, -0.15], P=0.02) and LFAir (-1.24 [-1.90, -0.57], P&lt;0.001). HFAir also provided a significantly greater dyspnea relief than LFOx (-0.95 [-1.61, -0.30], P=0.005) and LFAir (-1.39 [-2.05, -0.73], P&lt;0.001). No difference was found between HFOx and HFAir nor between LFOx and LFAir. There was no significant carryover effect. Dyspnea Borg scale intensity and unpleasantness showed similar changes. Oxygen saturation increased in the HFOx group (97.2% to 99.7%) and LFOx group (95.5% to 98.2%) but not HFAir nor LFAir groups. HFOx was well tolerated. At the end of the study, 7 (54%), 4 (31%), 1 (8%) and 1 (8%) patients blindly preferred HFOx, HFAir, LFOx and LFAir, respectively. Conclusions: For the first time, we found that HFOx and HFAir provided a rapid and clinically significant reduction of dyspnea at rest in hospitalized cancer patients even when they were non-hypoxemic, supporting a role for high flow devices to provide palliation beyond oxygenation. Larger studies are needed to confirm these findings. Clinical trial information: NCT02932332 .

Design and Testing of Cantilevered PVDF Energy Harvester Based on the Coanda Effect

Low-flow air has been attracted many researchers which can be transformed into electric energy by the piezoelectric materials. A flow amplifier device can be used to increase the performance of piezoelectric energy harvester excited by low-flow air. The Coanda effect theory has been analyzed based on the fast-moving air. To analyze the effect of the amplifier device and verify the feasibility of the proposed cantilevered PVDF energy harvester, we employed finite element simulation to analyze the flow distribution of the amplified flow air. Then the stress and potential distribution of PVDF film have been analyzed. A prototype of the cantilevered PVDF energy harvester is tested with different variables such as input air flow, pressure and cycle time. The test results show that the output voltage increases with increasing input air flow. The output voltage decreases slightly with increasing input cycle time. The peak voltage decreases as the distance between the prototype and the excitation source increases. Importantly, the output voltage for the amplified airflow is about three-times that of the non-amplified air flow. The maximal output voltage and power are 12.80 V and 19.89 μW at the pressure of 0.2 MPa and a flow rate of 200 L/min, respectively.

Evaluation on the Potential Use of Pulverized Natural Subbase Dust as Alternative Filler Material for Hot Mix Asphalt Design, Jimma Town

A well-designed asphalt mixture is expected to serve effectively for many years under a variety of loading and environmental conditions. Bituminous concrete is one of the highest and costliest types of flexible pavement. One of the main problems in the construction of asphalt paving mixture is obtaining a sufficient amount of filler material and high cost of the use of ordinary Portland cement, hydrated lime, or marble dust as filler material. Asphalt Institution restricted the use of a maximum limit of 2% proportion to improve the aggregates adhesion properties only, which is not sufficient quantity to achieve the grading requirements. To alleviate this problem, it is important to come across alternative filler material that can be used in more quantity. The study has investigated the potential use of natural subbase dust (MSD)as alternative filler material, and their characteristic on the effect of hot asphalt mixture was identified. This research was conducted by using Experimental Research Design. In total, 48 samples were prepared according to ASTM D1559, of which 15 of them used to calculate the OBC and the rest to find out the effects of adding different percentages of NSD to the asphalt mixture. For this purpose, five different bitumen contents were used (4%−6% with 0.5% increments). Aggregate mixtures blended without filler and with NSD filler were investigated to evaluate their Marshall properties on HMA mixtures. Four varying percentages of NSD ranging from (2% - 8% at 2% increments) were used for Marshall experiments. And for the control mix, 2% hydrated lime (HL) and 2% ordinary Portland cement used in the mixture besides, 4% Marble Dust was used as a reference. The aggregates were blended by using Job mix formula to obtain the percentage of material proportion. As a result for aggregates blended without filler G-1 (26%), G-2 (23%) and G-3 (51%) proportion were used whereas for aggregates blended with NSD filler, G-1 (26%), G-2 (22%), G-3 (46%) and G-4 (6%) was utilized. Where G-1 is Coarse Aggregate 3/4, G-2 is Intermediate Aggregate 3/8, G-3 is Fine Aggregate, and G-4 is NSD filler. Based on Marshall test results, the OBC was found 5.1% by the total asphalt mix. Furthermore, examining Marshall mixes containing different percentages of filler showed the optimum percentage of NSD was 6%. The Marshall properties of the experiments at 6% NDS filler resulted in high stability, low flow, lower VFB, low VMA & lower air voids that are consistent with the standard specifications. The investigation of NSD filler has resulted in good effects on the Marshall properties of the asphalt mixture. Furthermore, the outcome of Marshall parameters like stability, air voids, and bulk density values was consistent with the standard specifications. Therefore, NSD filler can potentially be used as an alternative filler material in HMA with optimum filler content of 6%. Besides, it is recommended to exercise the use of NSD as filler material in HMA projects in order to ensure the quality of works, save transportation costs and save time spend to import other filler materials from far away. It is also recommended combining NSD filler with other materials may produce a better outcome on the effects on the asphalt mix properties.

Effect of high flow oxygen on exertional dyspnea in cancer patients: A double-blind randomized clinical trial.

11600 Background: High flow oxygen therapy is effective for hypoxemic respiratory failure. However, its effect on dyspnea in non-hypoxemic patients is unknown. In this 2x2 factorial, double-blind randomized clinical trial, we assessed the effect of flow rate (high vs. low) and gas (oxygen vs. air) on exertional dyspnea in cancer patients. Methods: Non-hypoxemic patients with cancer completed two structured cycle ergometer exercise tests with Low Flow Air [LFAir] at 2 L/min. They were then randomized to receive High Flow Oxygen [HFOx] with up to 60 L/min, High Flow Air [HFAir], Low Flow Oxygen [LFOx] or LFAir during a constant work rate exercise test at 80% maximum. Dyspnea intensity was assessed with the modified 0-10 Borg scale. The primary outcome was difference in the slope of dyspnea intensity vs. time during the third test. Secondary outcomes included difference in exercise time, vital signs, and adverse events. We estimated that 10 patients per arm will provide 86% power to detect a 1-standard deviation main effect and 86% power to detect a 2-SD interaction effect with an alpha of 5%. A linear mixed effects model was used to assess the impact of flow rate and gas on study outcomes. Results: 45 patients were randomized and 44 completed the study (10, 11, 12, 11 patients on HFOx, HFAir, LFOx, LFAir, respectively). The mean age was 63 (range 47-77); 18 (41%) were female; 34 (44%) had lung cancer; and 20 (46%) had metastatic disease. In mixed effects model, the association between the change in dyspnea intensity over time with flow rate differed significantly between oxygen and air (P = 0.04). Specifically, HFOx (slope difference -0.20, P &lt; 0.001) and LFOx (-0.14, P = 0.01) were significantly better than LFAir, but not HFAir (+0.09, P = 0.09). Exercise time also significantly increased with HFOx (difference +2.5 min, P = 0.009) compared to LFAir, but not HFAir (+0.63 min, P = 0.48) or LFOx (+0.39 min, P = 0.65). HFOx was well tolerated without significant adverse effects. Conclusions: The combination of high flow rate and oxygen improved dyspnea and exercise duration during constant work exercise test in non-hypoxemic cancer patients. Larger trials are needed to confirm the benefits of HFOx during exercises. Clinical trial information: NCT02357134.

Evaluation of the release of dioxins and PCBs during kiln-firing of ball clay

Ball clay is known to be naturally contaminated with high levels of polychlorinated di-benzo-p-dioxins (PCDDs). This study evaluated the potential for PCDD, polychlorinated dibenzofuran (PCDF) and polychlorinated biphenyl (PCB) release during the kiln firing of ball clay in an art studio. Toxic equivalence (TEQ) were calculated using World Health Organization (WHO) 2005 toxic equivalence factors (TEF) and congener concentrations. Ten bags of commercial ball clay were found to have an average TEQ of 1370nanograms/kilogram (ngkg−1) dry weight (dw), almost exclusively due to PCDDs (99.98% of TEQ). After firing, none of the 29 dioxin-like analytes was measured above the limits of detection (LOD) in the clay samples. Air samples were taken during firings using both low-flow and high-flow air samplers. Few low-flow air samples contained measurable levels of dioxin congeners above the LOD. The mean TEQ in the high volume air samples ranged from 0.07pgm-3 to 0.21pgm-3 when firing ball clay, and was 0.11pgm-3 when no clay was fired. These concentrations are within the range measured in typical residences and well-controlled industrial settings. The congener profiles in the high-flow air samples differed from the unfired clay; the air samples had a considerable contribution to the TEQ from PCDFs and PCBs. Given that the TEQs of all air samples were very low and the profiles differed from the unfired clay, it is likely that the PCDDs in dry ball clay were destroyed during kiln firing. These results suggest that inhalation of volatilized dioxins during kiln firing of dry ball clay is an unlikely source of exposure for vocational and art ceramicists.

A randomised crossover study of low-flow air or oxygen via nasal cannulae to prevent desaturation in preterm infants

ObjectiveTo compare the efficacy of low-flow oxygen, low-flow air and sham treatment given via nasal cannulae in preventing desaturation (falls in oxygen saturation (SpO2)) in preterm infants.Study designInfants born at...

Indoor/ambient residential air toxics results in rural western Montana.

Indoor and ambient concentrations of 21 volatile organic compounds (including 14 hazardous air pollutants) were measured in the homes of nearly 80 western Montana (Missoula) high school students as part of the 'Air Toxics Under the Big Sky' program during the 2004/2005 and 2005/2006 school years. Target analytes were measured using low flow air sampling pumps and sorbent tubes, with analysis of the exposed samples by thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS). The results reported here present the findings of the first indoor/ambient air toxics monitoring program conducted in a semi-rural valley location located in the Northern Rocky Mountain/Western Montana region. Of all of the air toxics quantified in this study, toluene was found to be the most abundant compound in both the indoor and ambient environments during each of the two school years. Indoor log-transformed mean concentrations were found to be higher when compared with ambient log-transformed mean concentrations at P < 0.001 for the majority of the compounds, supporting the results of previous studies conducted in urban areas. For the air toxics consistently measured throughout this program, concentrations were approximately six times higher inside the student's homes compared to those simultaneously measured directly outside their homes. For the majority of the compounds, there were no significant correlations between indoor and ambient concentrations.

Emission factors and thermal efficiencies of cooking biofuels from five countries

The aim of the study was to compare the environmental and thermal performance of cooking biofuels from five countries. The standard water boiling test was used to determine thermal parameters. The fuels were burnt in a metal stove in a test chamber in accordance with standard protocol. Low-flow air samplers were used for particulate matter measurements, both TSP and RSP. Later, benzo(a)pyrene was determined using the high performance liquid chromatography (HPLC) technique after extraction from particulate samples in benzene. CO was measured using an electronic datalogger and HCHO using a passive sampler. The ventilation conditions during the experiments were manipulated by using different combinations of doors, windows and fans to ensure minimum stratification of pollutants in the chamber. The indirect method of deriving emission factors was used. Levels of most of the pollutants measured was found to be higher than that reported by previous studies, especially that of benzo(a)pyrene. The thermal efficiency was found to be in the range 10–15%. The emission per task of RSP was 0.27–0.77 g and that of B(a)P in RSP was 1.87–4.17 mg.

Performance of PEM Liquid-Feed Direct Methanol - Air Fuel Cells

A direct methanol-air fuel cell operating at near atmospheric pressure, low-flow rate air, and at temperatures close to 60oC would tremendously enlarge the scope of potential applications. While earlier studies have reported performance with oxygen, the present study focuses on characterizing the performance of a PEM liquid feed direct methanol-air cell consisting of components developed in house. These cells employ Pt-Ru catalyst in the anode, Pt at the cathode and Nafion 117 as the PEM. The effect of pressure, flow rate of air and temperature on cell performance has been studied. With air, the performance level is as high as 0.437 V at 300 mA/cm2 (90oC, 20 psig, and excess air flow) has been attained. Even more significant is the performance level at 60oC, 1 atm and low flow rates of air (3-5 times stoichiometric), which is 0.4 V at 150 mA/cm2. Individual electrode potentials for the methanol and air electrode have been separated and analyzed. Fuel crossover rates and the impact of fuel crossover on the performance of the air electrode have also been measured. The study identifies issues specific to the methanol-air fuel cell and provides a basis for improvement strategies.

Worker Exposure to Organic Vapors at a Liquid Chemical Waste Incinerator

The extent of employee exposure to organic vapors at a liquid/fluid chemical waste incinerator facility was assessed by means of a preliminary survey. The study was conducted at a facility owned by the Metropolitan Sewer District of Greater Cincinnati, Cincinnati, OH. The incineration unit employs a rotary kiln and a cyclone furnace (liquid injection) with a common combustion chamber. A wide variety of liquid industrial chemical wastes are accepted in tank truck quantities. Low flow air pumps were used to collect breathing zone and general area samples on standard 150-mg charcoal tubes. The samples were analyzed by a gas chromatograph equipped with a flame ionization detector. Benzene, methyl ethyl ketone (MEK), toluene and xylene, solvents common to many of the wastes accepted, were selected for determination. The data indicate that the routine operation of this liquid industrial waste incinerator facility results in worker exposure considerably less than the action level (50% of the health standard) for all compounds tested, except benzene. Some workers were at risk of overexposure to benzene if the NIOSH-recommended criteria are used, but not when the OSHA and ACGIH criteria are used. The highest exposure routine operations were cleaning pump strainers after receiving wastes and benzene distillations conducted in the laboratory. The non-routine operation of storage tank entry, which occurred once during the study, resulted in the highest potential exposure of any operation.

Worker exposure to organic vapors at a liquid chemical waste incinerator.

The extent of employee exposure to organic vapors at a liquid/fluid chemical waste incinerator facility was assessed by means of a preliminary survey. The study was conducted at a facility owned by the Metropolitan Sewer District of Greater Cincinnati, Cincinnati, OH. The incineration unit employs a rotary kiln and a cyclone furnace (liquid injection) with a common combustion chamber. A wide variety of liquid industrial chemical wastes are accepted in tank truck quantities. Low flow air pumps were used to collect breathing zone and general area samples on standard 150-mg charcoal tubes. The samples were analyzed by a gas chromatograph equipped with a flame ionization detector. Benzene, methyl ethyl ketone (MEK), toluene and xylene, solvents common to many of the wastes accepted, were selected for determination. The data indicate that the routine operation of this liquid industrial waste incinerator facility results in worker exposure considerably less than the action level (50% of the health standard) for all compounds tested, except benzene. Some workers were at risk of overexposure to benzene if the NIOSH-recommended criteria are used, but not when the OSHA and ACGIH criteria are used. The highest exposure routine operations were cleaning pump strainers after receiving wastes and benzene distillations conducted in the laboratory. The non-routine operation of storage tank entry, which occurred once during the study, resulted in the highest potential exposure of any operation.