Changes In Ventilation Rate Research Articles

Secondary Stress Response of Tilapia (Oreochromis Niloticus) in Different Doses of Hydrogen Peroxide (H2O2) During the Transport Period

Fish transportation is a crucial step in maintaining fish quality during the shipping process from one region to another. The closed-wet system, which is commonly used for fish transportation, has several obstacles in the form of fish stress and mortality. Stressed fish generate primary, secondary, and tertiary stress responses. The purpose of this study is to assess the secondary stress response of tilapia during transportation by giving different doses of hydrogen peroxide. 3% hydrogen peroxide applied to water resulting in three different doses i.e. 0.3 ml.L-1 , 0.1 ml.L-1 , 0.08 ml.L-1 and without hydrogen peroxide used as control groups. Data was obtained by measuring blood glucose levels and the ventilation rate of tilapia. The results showed an alteration in blood glucose levels and ventilation rate of tilapia during transportation. Treatment with 0.1 ml.L-1 hydrogen peroxide gave the lowest glucose levels during 10 hours of transportation. Changes in ventilation rate of tilapia were observed in the treatment with 0.1 ml.L-1 of hydrogen peroxide which indicated miled stress conditions. It can be concluded that the optimal dose of hydrogen peroxide in the transportation process is 0.1 ml.L-1 of hydrogen peroxide.

Numerical investigation of the impacts of environmental conditions and breathing rate on droplet transmission during dental service

Dental services are yet to return to a semblance of normality owing to the fear and uncertainty associated with the possible airborne transmission of diseases. The present study aims to investigate the impacts of environmental conditions [changes in ventilation location, ventilation rate, and relative humidity (RH)] and variations in dental patient's breathing rate on droplet transmission during dental service. Computational fluid dynamics simulation was performed based on our previous experimental study during ultrasonic scaling. The impacts of different factors were numerically analyzed by the final fate and proportion of emitted droplets in the dental surgery environment. The results revealed that about 85% of droplets deposited near the dental treatment region, where the patient's torso, face, and floor (dental chair) accounted for around 63%, 11%, and 8.5%, respectively. The change in the ventilation location had a small impact on the deposition of larger droplets ( > 60 μ m), and a spatial region with high droplet mass concentration would be presented near the dental professional. The change in the ventilation rate from 5 to 8 ACH led to a 1.5% increment in the fraction of escaped droplets. 50% RH in dental environments was recommended to prevent droplets' fast evaporation and potential mold. Variations in the patient's breathing rate had little effect on the final fate and proportion of emitted droplets. Overall, environmental factors are suggested to maintain 50% RH and larger ACH in dental surgery environments. The findings can give policymakers insights into the role of environmental factors on infection control.

Recording the ventilation activity of free-swimming zebrafish and its application to novel tank tests

Bioelectric signals related to ventilatory movements in fish can be detected via externally located electrodes. In this study, a technique to continuously monitor the electric ventilatory signals in free-swimming zebrafish was developed. This technique was applied to monitoring ventilation activity as a physiological measure in conjunction with various behavioral measures in a novel tank environment. It was found that in addition to ventilation rate, time domain analysis of changes in ventilation rate is useful for evaluating the emotional state of zebrafish. By integrating the physiological and behavioral measures in analyses, a 1 h novel tank test trial revealed that the habituation process involves two phases. The first phase, which lasted 10 min, involved rapid attenuation of the initial fear/anxiety response to encountering a novel environment. The second phase lasted 20 min and involved further attenuation of anxiety and an increase in exploration behavior. These data suggest that combining ventilation-related physiological measures with conventional behavioral measures enables multidimensional examination of the habituation process in a novel tank environment with more precision than is possible when relying on behavioral responses alone.

The high impulse, palm lift technique for chest compression: Prospective, experimental, pilot study.

The classic technique of high quality chest compression (HQCC) during cardiopulmonary resuscitation (CPR) is based on the International Liaison Committee on Resuscitation (ILCOR) guidelines which specify that the rescuer's hands should maintain constant contact with the chest surface but should not lean upon it, in order to provide full chest recoil. Since end-tidal CO2 (EtCO2) values have been shown to be a reliable indicator of CPR quality, we examined a method where classic HQCC was modified by a high impulse and palm lifting (HIPL) technique which merged rapid forceful compression with disconnection of the rescuer's palm from the patient's sternum during the recoil phase. The object of the study was to detect any differences in HIPL EtCO2 values in comparison with those from classic HQCC. We report a prospective pilot study in which we compared EtCO2 readings achieved during 2min of classic HQCC technique with readings after implementing 2min of the HIPL technique during out-of-hospital CPR, provided by medical emergency response teams for cases of cardiac arrest. EtCO2 values obtained from16 cases who received HQCC followed by HIPL compressions showed a significant difference (p=0.037) between the two techniques. Mean±SD EtCO2 values after 2min of each technique were: HQCC: 18±9mmHg; HIPL: 27±11mmHg; followed by a further 2min of HQCC: 19±11mmHg. Linear regression showed that the differences in EtCO2 were associated with non - significant changes in ventilation rate (p=0.493) and chest compression rate (p=0.889). The results obtained suggest that modifying HQCC with the HIPL technique led to a significant increase in EtCO2 values in comparison with classic HQCC, indicating an improvement in circulation during CPR. We think that these encouraging early results warrant a larger multi - centre study of HIPL.

Seasonal variation in airborne infection risk in schools due to changes in ventilation inferred from monitored carbon dioxide.

The year 2020 has seen the world gripped by the effects of the COVID‐19 pandemic. It is not the first time, nor will it be last, that our increasingly globalized world has been significantly affected by the emergence of a new disease. In much of the Northern Hemisphere, the academic year begins in September, and for many countries, September 2020 marked the return to full schooling after some period of enforced closure due to COVID‐19. In this paper, we focus on the airborne spread of disease and investigate the likelihood of transmission in school environments. It is crucial to understand the risk airborne infection from COVID‐19 might pose to pupils, teachers, and their wider social groups. We use monitored CO2 data from 45 classrooms in 11 different schools from within the UK to estimate the likelihood of infection occurring within classrooms regularly attended by the same staff and pupils. We determine estimates of the number of secondary infections arising via the airborne route over pre/asymptomatic periods on a rolling basis. Results show that, assuming relatively quiet desk‐based work, the number of secondary infections is likely to remain reassuringly below unity; however, it can vary widely between classrooms of the same school even when the same ventilation system is present. Crucially, the data highlight significant variation with the seasons with January being nearly twice as risky as July. We show that such seasonal variations in risk due to changes in ventilation rates are robust and our results hold for wide variations in disease parameterizations, suggesting our results may be applied to a number of different airborne diseases.

Impact of rapid versus gradual changes in arterial partial pressure of carbon dioxide on blood flow and myocardial oxygenation in an experimental anaesthetized model

Introduction Hyper- and hypocapnia have known vaso-modulatory effects in the coronary circulation. Oxygenation-sensitive cardiovascular magnetic resonance (OS-CMR) detects changes in tissue oxygenation and can provide a comprehensive assessment of the impact of systemic blood gas changes on the myocardium. The purpose of this study was to compare the physiological responses to rapid blood gas changes induced by hyperventilation followed by apnea in comparison to steady-state levels of hypocapnia and hypercapnia in an experimental animal model. Methods Eighteen anaesthetized female swine were used in this study. A blood flow probe was attached to the left descending coronary artery (LAD) after a left-sided thoracotomy. In ten animals a hemodynamically significant LAD stenosis was induced, while eight animals served as controls. In a 3 Tesla MRI, paCO2 was modulated from a pre-set baseline (paO2=100mmHg/paCO2=40mmHg) to 30mmHg and subsequently 50mmHg by minor changes in ventilation rate. Rapid changes in paCO2 were achieved by 60s of hyperventilating (30/min) from baseline followed by an apnea of up to 90 seconds. OS-CMR images, coronary blood flow (CBF) of the LAD and arterial blood gases were recorded at each state. Results Targeting stable hypocapnia of 30mmHg from baseline did not alter CBF or myocardial oxygenation. Subsequent stable hypercapnia (paCO2=50mmHg) increased CBF significantly in control (5±5%, p=0.007) and stenosed (4±6%, p=0.036) animals, and myocardial oxygenation rose in both post-stenotic territories (4.2±6.2%, p=0.036) and in control subjects (6.2±6.2%, p=0.011). Rapid hyperventilation induced a similar degree of hypocapnia (control: paCO2=25±7mmHg, stenosed: 27±3mmHg) and showed a significant decrease of CBF by -34±23% (p=0.012) in healthy animals, and a significant decrease of -10±6% (p=0.010) in stenosed animals. This had no effect on tissue oxygenation. Apnea resulted in a similar paCO2 (control: paCO2=52±9mmHg, stenosed: 47±7mmHg) compared to steady-state blood gas levels, which increased CBF significantly in controls 346±327% (p=0.008) and stenosed 82±110 (p=0.039) animals markedly. By the end of apnea, a rise in tissue oxygenation of 2.9±2.2% was observed in controls (p=0.008), -2.7±5.1 (0.125) was observed in the stenosed group (Figure). Significant difference in myocardial oxygenation responses observed between control and stenosed subject was exclusively observed with apnea (p=0.011). Discussion Rapid hyperventilation followed by apnea results in more pronounced changes in myocardial blood flow than similar steady state deflections in paCO2. Only apnea after hyperventilation induced deoxygenation in the stenotic myocardium, which is in agreement with the concept of hypercapnia induced intercoronary steal, while steady state deviation did not compromise myocardial oxygenation. Similar breathing maneuvers may be seen in the induction phase of anaesthesia, which could potentially be a harbinger of perioperative ischemic myocardial events.

Investigating impacts of and susceptibility to rail noise playback across freshwater fishes reveals counterintuitive response profiles.

While the expansion of anthropogenic noise studies in aquatic habitats has produced conservation-based results for a range of taxa, relatively little attention has been paid to the potential impacts on stream fishes. Recent work has shown responses to road noise in single species of stream fish; however, assemblage-wide effects of anthropogenic noise pollution have not yet been investigated. By examining five metrics of disturbance across four ecologically and evolutionarily disparate species of stream fishes, a series of laboratory experiments aimed to describe the effects of and species susceptibility to anthropogenic noise playback. Each species studied represented a unique combination of hearing sensitivity and water column position. Physiological and behavioral metrics were compared across the presence and absence of rail-noise noise playback in four target species. Through repeated subsampling, the temporal dynamics of cortisol secretion in response to noise in two target species were additionally described. Rail-noise playback had no statistically significant effect on blood glucose or water-borne cortisol levels, with the exception of decreased cortisol in noise-exposed largescale stoneroller (Campostoma oligolepis). Time-course cortisol experiments revealed rapid secretion and showed minimal effects of noise at most observation points. The presence of noise produced significant changes in ventilation rate and swimming parameters in a portion of the four species observed representing the most conserved responses. Overall, effects of noise were observed in species contrary to what would be hypothesized based on theoretical hearing sensitivity and water column position demonstrating that predicting susceptibility to this type of stressor cannot be accomplished based off these course considerations alone. More importantly, we show that anthropogenic noise can disrupt a variety of behavioral and physiological processes in certain taxa and should be further investigated via measures of fitness in the wild.

Improvement of endothelial function and external respiration in patients with comorbidity of hypertension and stage III chronic obstructive pulmonary disease, using nitric oxide donor — L-­arginine

Objective — to improve the efficacy of pharmacotherapy for patients with comorbidity of arterial hypertension (AH) and stage III chronic obstructive pulmonary disease (COPD) (group C), using an exogenous nitric oxide donor — L-arginine by correction of endothelial function as well as to improve pulmonary ventilation and quality of life in general.Materials and methods. This study involved 102 patients with stage 2 arterial hypertension (AH) (2-nd and 3-rd degree) including 82 patients with AH and concomitant COPD III stage, group C, and 20 patients with essential hypertension of the identical stage and degree at the age of (65.5 ± 4.12). According to the treatment 82 patients with AH and COPD were divided into two groups, homogeneous by age, sex, duration of AH and COPD. Group I — the control group (CG) — included 40 patients receiving basic therapy only, group II — the main group (MG) — included 42 patients, who received L-arginine hydrochloride in addition to basic therapy. Patients with AH were divided similar.Results and discussion. It has been observed that chronic obstructive disease burdened the course of hypertension by cardiorespiratory system rates deterioration. According to the spirogram in patients with comorbidity the forced expiratory volume in one second was (38.28 ± 1.33) % compared to patients with АH (67 ± 2.84) indicating a reverse negative correlation with the indicator of endothelin — 1 (ET 1) level in plasma(r = –0.45, р < 0.05). Thus, in patients with AH and concomitant COPD, the bronchial patency was significantly impaired due to increasing of endothelin — 1 (ET 1) level — marker of vasoconstriction and endothelial dysfunction (ED). 3 months after basic therapy with L-arginine, a number of positive effects in combination therapy was established: the decrease of endothelin — 1 (ET 1) level in plasma due to treatment, contributed to the improvement of endothelial function, increase in ventilation and gas exchange, as indicated by increased Tiffeneau index, while in the CG — significant changes in ventilation rates have not been noted, which is associated with the absence of bronchial obstruction in this patient cohort, the level of ET 1 decreased (p < 0.05) and significantly improved the endothelial function.Conclusions. The addition of L-arginine to the combined therapy of patients with hypertension accompanied by COPD, resulted in the potentiation of antihypertensive therapy, improvement of bronchial patency and endothelial function as well as to the improvement of quality of life in general.

Cabin air quality – Quantitative comparison of volatile air contaminants at different flight phases during 177 commercial flights

Quantitative assessment of human exposure to semi-volatile organic compounds (SVOC), such as tricresyl phosphates (TCP) that may originate from engine oil contamination of the cabin air, during air travel is challenging due to the technical complexity of the air supply in commercial jet aircraft. Normal flight operations involve reduced air exchange before and during takeoff, which results in increased concentrations of potential cabin air pollutants. During cruise, normal ventilation rates (>20 h− 1) are reestablished and thus lower pollutant concentrations are also reestablished. This relationship between changes in ventilation rate and associated changes in pollutant concentrations during the departure phase is first described in the present study, although this effect was found by previous studies that investigated distinct flight phases.The perception of so-called "smell events" in cabin air does not necessarily indicate the presence of harmful contaminants and TCP-containing oil mist must be clearly distinguished thereof. Thus, aldehydes, VOCs, and organophosphates such as TCP were investigated. In this paper, the occurrence of TCP contamination in a bleed air free Boeing 787 (B787) aircraft is reported for the first time. The results presented here show that there are TCP sources other than bleed air from leaky engines. Furthermore, exceptional release behavior of TCP suggests that a more detailed classification for engine oil-triggered cabin air contamination (CAC) events is necessary. This study evaluated measurement data from 177 flights that were either commissioned by the EASA or conducted as part of studies with the support of Lufthansa, Condor, and British Airways.

Concentrations and variability of organophosphate esters, halogenated flame retardants, and polybrominated diphenyl ethers in indoor and outdoor air in Stockholm, Sweden

We investigated the concentrations and temporal variability of organophospate esters (OPEs), halogenated flame retardants (HFRs) and polybrominated diphenyl ethers (PBDEs) in indoor and outdoor urban air in Stockholm, Sweden over one year (2014–2015) period. The median concentrations of the three target chemical groups (OPEs, HFRs, PBDEs) were 1–2 orders of magnitude higher in indoor air than outdoor urban air. OPEs were the most abundant target FRs with median concentrations in indoor (Σ10OPE = 340 000 pg/m3) and outdoor urban (Σ10OPEs = 3100 pg/m3) air, being 3 orders of magnitude greater than for HFRs in indoor (Σ15HFRs = 120 pg/m3) and outdoor urban (Σ15HFRs = 1.6 pg/m3) air. In indoor air, PBDE concentrations (Σ17PBDEs = 33 pg/m3) were lower than for the HFRs, but in outdoor urban air, concentrations (Σ17PBDEs = 1.1 pg/m3) were similar to HFRs. The most abundant OPEs in both the indoor and outdoor urban air were tris(2-butoxyethyl)phosphate (TBOEP), tris(chloroisopropyl)phosphate (TCIPP), tris(2-chloroethyl)phosphate (TCEP), tri-n-butyl-phosphate (TnBP), triphenyl phosphate (TPhP) and tris(1,3-dichloroisopropyl)phosphate (TDCIPP). TCIPP in indoor air was found in the highest concentrations and showed the greatest temporal variability, which ranged from 85 000 to 1 900 000 pg/m3 during the one-year sampling period. We speculate that activities in the building, e.g. floor cleaning, polishing, construction, introduction of new electronics and changes in ventilation rate could explain its variation. Some OPEs (TnBP, TCEP, TCIPP, TDCIPP and TPhP), HFRs/PBDEs (pentabromotoluene, 2, 3-dibromopropyl 2, 4, 6-tribromophenyl ether, hexabromobenzene, BDE-28, -47, and -99) in outdoor urban air showed seasonality, with increased concentrations during the warm period (p < 0.05, Pearson's r ranged from −0.45 to −0.91). The observed seasonality for OPEs was probably due to changes in primary emission, and those for the HFRs and PBDEs was likely due to re-volatilization from contaminated surfaces.

Effect of floor cleaners on oxygen consumption and respiratory rate in carassius auratus.

Pollution of the water bodies will create physiological stress on the aquatic fauna. Among various forms of pollution in water bodies, detergent pollution has an immediate and detrimental effect. The floor cleaners are household chemical cleaning compounds required in wide range for diverse purposes. In some rivers the concentrations of cleaning products is quite high. The major components of cleaning products such as Surfactants make adverse effects on the aquatic life at very low levels of exposure. Effect of floor cleaners on the consumption of dissolved oxygen by Carassius auratus were determined by using Winkler’s method. The floor cleaners used were Lizol, dettol and lemon grass oil. This study demonstrated that dissolved oxygen consumption in Carassius auratus increases in the presence of floor cleaners. This is due to the stress caused by the floor cleaners on the normal physiological activities of the fish. Effect of floor cleaners on the respiratory rate of Carassius auratus were determined by counting its gill movements. This study demonstrated that there will be changes in ventilation rates of Carassius auratus when dissolved oxygen levels change. Thus draining of domestic sewage containing detergents into water bodies adversely affect its aquatic fauna. The project is selected because of the higher pollution nowadays. The results of the project conducted shows that while adding detergent dissolved oxygen level started decreasing with higher concentrations. Results show that Lizol shows a higher range of decrease in the dissolved oxygen level in water with higher concentration. And lemon grass oil shows less effect compared to other two floor cleaners. So, it is better to use natural cleaners for floor cleaning purposes.

A Novel Method for Quantifying the Inhaled Dose of Air Pollutants Based on Heart Rate, Breathing Rate and Forced Vital Capacity.

To better understand the interaction of physical activity and air pollution exposure, it is important to quantify the change in ventilation rate incurred by activity. In this paper, we describe a method for estimating ventilation using easily-measured variables such as heart rate (HR), breathing rate (fB), and forced vital capacity (FVC). We recruited healthy adolescents to use a treadmill while we continuously measured HR, fB, and the tidal volume (VT) of each breath. Participants began at rest then walked and ran at increasing speed until HR was 160–180 beats per minute followed by a cool down period. The novel feature of this method is that minute ventilation () was normalized by FVC. We used general linear mixed models with a random effect for subject and identified nine potential predictor variables that influence either or FVC. We assessed predictive performance with a five-fold cross-validation procedure. We used a brute force selection process to identify the best performing models based on cross-validation percent error, the Akaike Information Criterion and the p-value of parameter estimates. We found a two-predictor model including HR and fB to have the best predictive performance (/FVC = -4.247+0.0595HR+0.226fB, mean percent error = 8.1±29%); however, given the ubiquity of HR measurements, a one-predictor model including HR may also be useful (/FVC = -3.859+0.101HR, mean percent error = 11.3±36%).

Modeling of Dynamic Ammonia Concentrations in Two Commercial Layer Hen Houses

Ammonia (NH3) concentrations in confined layer hen houses are the highest among buildings of different animal species and are of great concern to indoor air quality and animal welfare. However, little has been done to investigate the dynamic relationships between NH3 concentrations and the influencing factors. A Distributed Lag Non-linear Model was applied to study the dynamics of NH3 in two high-rise layer houses using a two-year dataset, compiled with hourly data, and its two subsets of summer and winter. Three major influencing factors, the ventilation rate, outdoor temperature, and outdoor relative humidity, were identified to have lagged effects on indoor NH3 concentrations in both houses. The duration of lagged effects of ventilation rate ranged from non-observable (<1 h) to a few subsequent hours. However, in winter, the changes in ventilation rates within the low operational ranges were not sufficiently high to induce NH3 concentration changes. The effects of temperature were not observable in winter. Higher outdoor relative humidity was related to elevated NH3 concentrations in winter, with a lag time of about 1 h in both houses. The lagged effects were considerably different between summer and winter for all three influencing factors.

Estimated effect of ventilation and filtration on chronic health risks in U.S. offices, schools, and retail stores.

We assessed the chronic health risks from inhalation exposure to volatile organic compounds (VOCs) and particulate matter (PM2.5) in U.S. offices, schools, grocery, and other retail stores and evaluated how chronic health risks were affected by changes in ventilation rates and air filtration efficiency. Representative concentrations of VOCs and PM2.5 were obtained from available data. Using a mass balance model, changes in exposure to VOCs and PM2.5 were predicted if ventilation rate were to increase or decrease by a factor of two, and if higher efficiency air filters were used. Indoor concentrations were compared to health guidelines to estimate percentage exceedances. The estimated chronic health risks associated with VOC and PM2.5 exposures in these buildings were low relative to the risks from exposures in homes. Chronic health risks were driven primarily by exposures to PM2.5 that were evaluated using disease incidence of mortality, chronic bronchitis, and non-fatal stroke. The leading cancer risk factor was exposure to formaldehyde. Using disability-adjusted life years (DALYs) to account for both cancer and non-cancer effects, results suggest that increasing ventilation alone is ineffective at reducing chronic health burdens. Other strategies, such as pollutant source control and the use of particle filtration, should also be considered.

Minimal effects of waterborne exposure to single-walled carbon nanotubes on behaviour and physiology of juvenile rainbow trout (Oncorhynchus mykiss)

Fish behaviours are often considered to be sensitive endpoints of waterborne contaminants, but little attention has been given to engineered nanomaterials. The present study aimed to determine the locomotor and social behaviours of rainbow trout (Oncorhynchus mykiss) during waterborne exposure to single-walled carbon nanotubes (SWCNTs), and to ascertain the physiological basis for any observed effects. Dispersed stock suspensions of SWCNTs were prepared by stirring in sodium dodecyl sulphate (SDS), an anionic surfactant, on an equal w/w basis. Trout were exposed to control (no SWCNT or SDS), 0.25mgL−1 SDS (dispersant control), or 0.25mgL−1 of SWCNT for 10 days. Video tracking analysis of spontaneous locomotion of individual fish revealed no significant effects of SWCNT on mean velocity when active, total distance moved, or the distribution of swimming speeds. Hepatic glycogen levels were also unaffected. Fish exposed to SWCNTs retained competitive fitness when compelled to compete in energetically costly aggressive interactions with fish from both control groups. Assessment of the respiratory physiology of the fish revealed no significant changes in ventilation rate or gill injuries. Haematocrit and haemoglobin concentrations in the blood were unaffected by SWCNT exposure; and the absence of changes in the red and white pulp of the spleen excluded a compensatory haematopoietic response to protect the circulation. Despite some minor histological changes in the kidneys of fish exposed to SWCNT compared to controls, plasma ion concentrations and tissue electrolytes were largely unaffected. Direct neurotoxicity of SWCNT was unlikely with the brains showing mostly normal histology, and with no effects on acetylcholinesterase or Na+/K+-ATPase activities in whole brain homogenates. The minimal effects of waterborne exposure to SWCNT observed in this study are in contrast to our previous report of SWCNT toxicity in trout, suggesting that details of the dispersion method and co-exposure concentration of the dispersing agent may alter toxicity.

도로 협곡에서 NOx와 VOCs에 대한 오존의 민감도

The sensitivity of ozone to and volatile organic compounds (VOCs) emission rates under different ventilation rates and emission ratios in a street canyon is investigated using a chemistry box model. The carbon bond mechanism IV (CBM-IV) with 36 gaseous species and 93 chemical reactions is incorporated. and VOCs emission rates considered range from 0.01 to with intervals of . Three different ventilation rates and three different emission ratios are considered. The simulation results show that the ozone concentration decreases with increasing emission rate but increases with increasing VOCs emission rate. When the emission ratio of VOCs to is smaller than about 4, the ozone concentration is lower in the street canyon than in the background. On average, the magnitude of the sensitivity of ozone to emission rate is significantly larger than that to VOCs emission rate. As the emission rate increases, the magnitude of the sensitivity of ozone to and VOCs emission rates decreases. Because the ozone concentration is lower in the street canyon than in the background, the increased ventilation rate enhances ozone inflow from the background. Therefore, the increase in ventilation rate results in the increase in ozone concentration and the decrease in the magnitude of the sensitivity of ozone to and VOCs emission rates when the emission ratio of VOCs to is smaller than about 4. On the other hand, the increase in emission ratio results in the increase in ozone concentration because the chemical ozone production due to the photolysis is enhanced. In the present experimental setup, the contribution of the change in emission ratio to the change in the sensitivity of ozone to emission rate is larger than that of the change in ventilation rate.

Odour, dust and non-methane volatile organic-compound emissions from tunnel-ventilated layer-chicken sheds: a case study of two farms

An observational study was undertaken to measure odour and dust (PM10 and PM2.5) emission rates and identify non-methane volatile organic compounds (NMVOCs) and odorants in the exhaust air from two tunnel-ventilated layer-chicken sheds that were configured with multi-tiered cages and manure belts. The study sites were located in south-eastern Queensland and the West Gippsland region of Victoria, Australia. Samples were collected in summer and winter on sequential days across the manure-belt cleaning cycle. Odour emissions ranged from 58 to 512 ou/s per 1000 birds (0.03–0.27 ou/s.kg) and dust emission rates ranged 0.014–0.184 mg/s per 1000 birds for PM10 and 0.001–0.190 mg/s per 1000 birds for PM2.5. Twenty NMVOCs were identified, including three that were also identified as odorants using thermal desorption–gas chromatography–mass spectrometry/olfactometry analysis. Odour emission rates were observed to vary with the amount of manure accumulation on the manure belts, being lowest 2–4 days after removing manure. Odour emission rates were also observed to vary with diurnal and seasonal changes in ventilation rate. Dust emissions were observed to increase with ventilation rate but not with manure accumulation. Some NMVOCs were identified at both farms and in different seasons whereas others were observed only at one farm or in one season, indicating that odorant composition was influenced by farm-specific practices and season.

Apparent oxygen utilization rates calculated from tritium and helium-3 profiles at the Bermuda Atlantic Time-series Study site

Abstract. We present three years of Apparent Oxygen Utilization Rates (AOUR) estimated from oxygen and tracer data collected over the ocean thermocline at monthly resolution between 2003 and 2006 at the Bermuda Atlantic Time-series Study (BATS) site. We estimate water ages by calculating a transit time distribution from tritium and helium-3 data. The vertically integrated AOUR over the upper 500 m, which is a regional estimate of export, during the three years is 3.1 ± 0.5 mol O2 m−2 yr−1. This is comparable to previous AOUR-based estimates of export production at the BATS site but is several times larger than export estimates derived from sediment traps or 234Th fluxes. We compare AOUR determined in this study to AOUR measured in the 1980s and show AOUR is significantly greater today than decades earlier because of changes in AOU, rather than changes in ventilation rates. The changes in AOU are likely a methodological artefact associated with problems with early oxygen measurements.

The impact of local sources and meteorological factors on nitrogen oxide and particulate matter concentrations: A case study of the Day of Atonement in Israel

Measurements of the atmospheric concentrations of NOx and particulate matter (PM) in three urban centers in Israel before, during, and after the Day of Atonement were performed for nine consecutive years (2000–08). This enabled to investigate the significance of local versus long-range sources of pollution and probe the effect of meteorological conditions (synoptic systems, ventilation rates, height of surface boundary layer, and wind speed) on level of pollution. During the Day of Atonement all traffic and most of the industrial activities cease in the Jewish populated parts of the country. We observed that in spite of this, concentrations of particulate matter (PM2.5 and PM10) are very similar in all three urban centers during the Day of Atonement to the days before and after. Moreover, PM levels during the Day of Atonement are generally higher during Red Sea trough synoptic conditions which carry air from the Saudi and Jordanian deserts in the east and southeast relative to Persian Trough synoptic conditions which bring air from the eastern Mediterranean and the Black Sea region in the north-west. In addition, 55% of the variation in PM values during the nine days of Atonement included in this study can be explained by changes in ventilation rates of the atmosphere, namely the product of the mixing depth and a representative boundary layer wind speed. Thus, long-range sources and local mixing conditions determine the concentrations of PM in the atmosphere of Israel as expected from their long residence time. On the other hand, NOx concentrations during the Day of Atonement are significantly lower than the days before and after, reflecting NOx short residence time in the atmosphere and the strong influence of local emission sources. Furthermore, the difference in concentrations of NOx in different Days of Atonement cannot be accounted for either by different synoptic conditions or by variations in ventilation rates, height of surface boundary layer, and wind speed. They are determined by the combination of local and regional sources of emission and the meteorological conditions which control their transport from these nearby sources to the sampling station.

Cardiac sympathetic nerve activity during kainic acid–induced limbic cortical seizures in rats

We sought to define changes in cardiac sympathetic nerve activity that occur during seizures. We studied kainic acid-induced limbic cortical seizures in urethane-anesthetized rats using cardiac sympathetic nerve, blood pressure, and electrocardiography (ECG) recordings. We studied changes in ventilation rate before and during seizures. Cardiac sympathetic nerve activity was increased during limbic cortical seizures. The modest increases were similar to changes induced by nitroprusside infusion. The normal relation of cardiac sympathetic nerve activity to ventilation rate was lost during seizure activity. Changes in cardiac sympathetic nerve activity caused by changes in ventilation rate became unpredictable, and could be extreme. We conclude that the modest changes in cardiac sympathetic nerve activity contribute to the predominantly parasympathetic effects on the heart during limbic cortical seizures and periods of asphyxia. Further, ventilation rate changes might be associated with large sudden increases or decreases in cardiac sympathetic outflow during seizures.