Venous air embolism during a craniofacial procedure

The possibility of venous air embolism exists whenever the craniofacial operative field is above the level of the heart. Craniotomy with the high-torque craniotome is hypothesized to have produced venous air embolism in the patient described in this report. The diagnosis of venous air embolism is determined by transesophageal Doppler probe, transesophageal echocardiogram or external echocardiogram, and end-tidal N2 and CO2 determinations. Treatment includes control of the air entry sites, aspiration of air from the right atrium via a catheter placed prior to operation, and discontinuing nitrous oxide. If these measures are unsuccessful, the operative field should be transposed below heart level and the procedure terminated. In the event of significant hemodynamic compromise, closed cardiac massage should be tried; if that fails, open cardiac massage and direct aspiration are necessary. The true incidence of venous air embolism in craniofacial operations may be much higher than previously suspected. We therefore recommend placement of appropriate monitoring equipment to detect intracardiac air in those major craniofacial procedures in which there is a potential for intravascular air ingress.     

Air quality indices: a review

National directives on air quality oblige nations to monitor and report on their air quality, allowing the public to be informed on the ambient pollution levels. The last is the reason for the always increasing interest, demonstrated by the number of publications on this topic in recent years, in air quality/pollution indices: since the concentration of individual pollutants can be confusing, concentration measurements are conveniently transformed in terms of an air quality index. In this way, complex situations are summarized in a single figure, letting comparisons in time and space be possible. In this paper we will give an overview about the Air Quality/Pollution Indices proposed in literature and/or adopted by countries, trying also to categorize them into homogeneous groups. For the classification different approaches can be followed. Since in real life exposure to mixtures of chemicals occurs, with additive, synergistic or antagonistic effects, here we will distinguish between indices that consider the conjoint effect of pollutants and indices only based on the actual most dangerous pollutant. This brief review on air pollution indices shows, on one side, the wide interest in the problem, on the other, the lack of a common strategy which allows to compare the state of the air for cities that follow different directives. The main differences between the indices will be also described.     

Photosynthesis and transpiration in the upper crown of a mature spruce in purified and ambient atmosphere in a natural stand

Summary This study addresses the question of whether gaseous air pollutants are capable of damaging spruce foliage. For this purpose, several twig pairs of an adult tree in a natural stand from the western part of the Bavarian Forest were supplied with pure and ambient air and gas exchange was monitored. With the exception of insignificant and unexplained differences during winter, the gas exchange of the twigs showed no negative deviation due to the influence of gaseous air pollutants. Because visible damage arises only in older needles, the duration of measurement is not sufficient to exclude a long-term influence of gaseous air pollutants.     

Importance of inlet air velocity in fluid bed dyring of a granulation prepared in a high shear granulator

Conclusions  This report shows that inlet air velocity can play a critical role in maintaining proper fluidization and, ultimately, uniform drying. The mechanism by which air velocity affects fluidization has been discussed by various researchers [4–5]. An indication of good fluidization is a free downward flow of the granules at the sight glass of the drying bowl, but such limited observation could be misleading. In such cases, the exhaust air temperature can be used to detect poor fluidization. If the exhaust air temperature rises more rapidly than anticipated, as seen with process 1 (Figure 1), it is an indication that fluidization is incomplete. In conclusion, a fundamental understanding of the mechanism of fluidization by inlet air will help in the development of a fluid bed drying process that produces uniformly dried granules and minimizes the number of process problems encountered.     

Thermal interaction between animal and microclimate: a comprehensive model

An equation based on heat transfer theory is developed to predict the rate of heat loss from a homeothermic vertebrate to the environment, specified by the air temperature, humidity, windspeed and radiation receipt. The analysis incorporates the animal's thermoregulatory responses--sweating ability, vasomotor action, and regulation of body-core temperature, metabolic and respiratory rate. The loss of heat and water vapour from cattle is used as an illustration, and particular attention is given to their heat balance in hot environments. The predicted rates of heat loss from cattle indoors at various air temperatures and humidities are consistent with experiments. Outdoors, intercepted solar radiation can reduce substantially heat loss through the body tissue when the air temperature is low. In contrast, at high air temperatures the heat dissipation may not be sensitive to the radiation load, although body-core temperature is. Increased rates of air movement can aggravate strain at low air temperatures, but mitigate strain in a hot environment.     

The functions of laryngeal air sacs in primates: a new hypothesis

A possible function of laryngeal air sacs in apes and gibbons was investigated by examining the relationships between air sac distribution, call rate, call duration and body weight in a phylogenetic context. The results suggest that lack of sacs in the smaller gibbons and in humans is a derived feature. Call parameters in primates, such as rate and duration, scaled to resting breathing rate (and therefore to body weight) only in species without air sacs, which appear to modify these relationships. Apes and larger gibbons may be able to produce fast extended call sequences without the risk of hyperventilating because they can re-breathe exhaled air from their air sacs. Humans may have lost air sacs during their evolutionary history because they are able to modify their speech breathing patterns and so reduce any tendency to hyperventilate.     

Hygienic characterization of atmospheric contamination with benzo(a)pyrene in a big city

It was demonstrated in the present study that the atmospheric air, soil and snow within a city are contaminated with benzo(a)pyrene (BP). The highest BP concentration was found in District Seven where a number of petro-chemical and chemical plants are situated. BP content in the air sampled between operational premises was in all cases below MPC (30% of the MPC values for working environment air). A major source of environmental contamination with BP is motor traffic. Atmospheric BP concentration was found to be directly proportional to traffic density. The obtained results may serve as a basis for health-improving measures.     

Effect of body orientation on regional lung expansion: a computed tomographic approach

The Dynamic Spatial Reconstructor (DSR) was used to study in vivo lung geometry and function. By replacing the lungs of three dogs with potato flakes and ping-pong balls of known air content and scanning these realistic phantoms in the DSR we have estimated accuracy of lung density to be within 7% and have demonstrated a high (+/- 3%) internal consistency (relative density within dogs). Change in total lung air content (y) as calculated from DSR volume imaging of anesthetized dogs matched the known inflation steps (x) to within 7% [range was 1-7% with a mean of 3 +/- 0.5% (SE)]. A gradient of decreasing percent lung air content was measured in the ventral-dorsal direction at functional residual capacity (FRC) in the supine body posture (y = 3.29% air content/cm lung height + 46.48% air content; r = 0.90). Regional lung air content change with lung inflation was greatest in the dependent lung regions. In contrast, regional lung air content at FRC was approximately uniform along the ventral-dorsal direction with the dog in the prone posture and was 66 +/- 0.6% (SE). Ventral-dorsal gradients in lung air content measured within an isogravimetric plane of the dogs in the left or right lateral body posture suggest that regional differences in lung air content cannot be explained solely on the basis of a direct gravitational effect on the lung. Evidence is presented to suggest a possible major role of the intrathoracic position of the mediastinal contents in determining these lung air content distributions.     

Ventilation of termite mounds: new results require a new model

In 1955, Lüscher proposed a ventilation mechanism forcathedral-shaped termite mounds to exchange respiratory gases. This mechanism was generally accepted, although it had neverbeen tested critically. We tested this mechanism by investigatingtemperatures, CO₂ concentrations, and air currents in and aroundtwo types of Macrotermes bellicosus mounds: cathedral-shapedmounds with many ridges and thin walls located in the savannaand dome-shaped mounds without ridges and with thick wallsin the forest. These two mound shapes have two different mechanismsof ventilation, depending on the environmental temperature.In the savanna during the day, sun heats the air in the peripheralair channels inside the ridges of the mound above the centralnest temperatures and produces a temperature gradient in theperipheral air channels with decreased temperatures at thetop of the mound. This temperature gradient leads to convectioncurrents with air rising inside the air channels of the ridgesto the top of the mound, meanwhile exchanging CO₂. In contrast,in the savanna during the night and generally in the forest,the temperatures inside the air channels are lower than thoseof the central nest, and no air currents rising upward insidethe air channels were detected. The CO₂ concentrations in theair channels of savanna mounds at night and forest mounds ingeneral were higher than during the day in the savanna. Therefore,our data do not support Lüscher's proposed mechanism.     

Wind Flow Characteristics on a Soybean Leaf Compared with a Leaf Model

The purpose of this paper is to describe momentum boundary layer flow parameters on a soybean leaf [Glycine max (L.) Merrill] at various velocities of the bulk air stream and these data are compared with similar measurements on an artificial leaf. The wind structure is measured at three different bulk air velocitìes (u_∞= 39, 148 and 271 centimeters per second) on an individual soybean leaf and is compared to structural effects on an artificial leaf (flat metal plate) in a small closed-circuit wind tunnel. The boundary layers were homogeneous for the metal plate, but only at the lower velocity for the soybean leaf. The boundary layer thicknesses decrease with increasing bulk air velocity for laminar flow regimes, whereas in the turbulent flow regime the boundary layer thickness greatly increases. The effect of turbulence on the soybean leaf boundary layer made the eddy diffusivities at least three times greater than in the laminar flow regime at the calculated roughness height above the leaf surface. The structure of the leaf boundary layer flow is comparable to that of the metal plate only at the lower bulk air velocity.     

Dolphin whistles: a functional misnomer revealed by heliox breathing

Delphinids produce tonal whistles shaped by vocal learning for acoustic communication. Unlike terrestrial mammals, delphinid sound production is driven by pressurized air within a complex nasal system. It is unclear how fundamental whistle contours can be maintained across a large range of hydrostatic pressures and air sac volumes. Two opposing hypotheses propose that tonal sounds arise either from tissue vibrations or through actual whistle production from vortices stabilized by resonating nasal air volumes. Here, we use a trained bottlenose dolphin whistling in air and in heliox to test these hypotheses. The fundamental frequency contours of stereotyped whistles were unaffected by the higher sound speed in heliox. Therefore, the term whistle is a functional misnomer as dolphins actually do not whistle, but form the fundamental frequency contour of their tonal calls by pneumatically induced tissue vibrations analogous to the operation of vocal folds in terrestrial mammals and the syrinx in birds. This form of tonal sound production by nasal tissue vibrations has probably evolved in delphinids to enable impedance matching to the water, and to maintain tonal signature contours across changes in hydrostatic pressures, air density and relative nasal air volumes during dives.     

Discharge in a Subthreshold Microwave Beam as an Effective Means for Mercaptan Decomposition

Plasma Physics Reports - A subthreshold microwave discharge in atmospheric-pressure air is used to process mixtures of mercaptans (thiols) with air and with air and methane. It is found that, at...     

Absence of a deglutitive inhibition equivalent with secondary peristalsis

This study aimed to determine the interactions between closely paired swallow-induced primary peristalsis (PP) and air injection-induced secondary peristalsis (SP). Ten subjects (7 men, 18-42 yr) were studied using a catheter, including two sleeves (upper and lower esophageal sphincters), a midesophageal infusion port, and seven esophageal and two pharyngeal recording sites. Ten iterations of PP and SP were induced by 5-ml water swallows and 20-ml intraesophageal air injections, respectively. Thereafter, the interactions between PP and SP, separated by 1- to 12-s intervals, were studied in all four possible sequences: paired swallows, swallow preceded by air injection, air injection preceded by swallow, and paired air injections. Tracings were analyzed for lower esophageal sphincter relaxation, presence and integrity of peristalsis, and event interaction. Eight subjects with success rates of both >/=90% PP and >/=80% SP were analyzed (PP 97 +/- 2%, SP 90 +/- 3%). During paired PP interactions and SP followed by PP, the first sequence was inhibited by the second with intervals < 4-6 s. However, no inhibition of the first peristaltic sequence was found in either PP followed by SP trials or SP followed by air injection. In contrast to swallowing or proximal esophageal distention, air injection into the lumen of the midesophagus does not inhibit an ongoing peristaltic event. Being that the elicitation of SP in the smooth muscle esophagus is intramurally mediated, this suggests that deglutitive inhibition is a centrally mediated phenomenon rather than an intrinsic property of peristalsis.     

Efficacy of three microbiological monitoring methods in a ventilated cage rack

The use of individually ventilated caging (IVC) to house mice presents new challenges for effective microbiological monitoring. Methods that exploit the characteristics of IVC have been developed, but to the authors' knowledge, their efficacy has not been systematically investigated. Air exhausted from the IVC rack can be monitored, using sentinels housed in cages that receive rack exhaust air as their supply air, or using filters placed on the exhaust air port. To aid laboratory animal personnel in making informed decisions about effective methods for microbiological monitoring of mice in IVC, the efficacy of air monitoring methods was compared with that of contact and soiled bedding sentinel monitoring. Mice were infected with mouse hepatitis virus (MHV), mouse parvovirus (MPV), murine rotavirus (agent of epizootic diarrhea of mice [EDIM]), Sendai virus (SV), or Helicobacter spp. All agents were detected using contact sentinels. Mouse hepatitis virus was effectively detected in air and soiled bedding sentinels, and SV was detected in air sentinels only. Mouse parvovirus and Helicobacter spp. were transmitted in soiled bedding, but the efficacy of transfer was dependent on the frequency and dilution of soiled bedding transferred. Results were similar when the IVC rack was operated under positive or negative air pressure. Filters were more effective at detecting MHV and SV than they were at detecting MPV. Exposure of sentinels or filters to exhaust air was effective at detecting several infectious agents, and use of these methods could increase the efficacy of microbiological monitoring programs, especially if used with soiled bedding sentinels. In contemporary mouse colonies, a multi-faceted approach to microbiological monitoring is recommended.     

Microbiological Evaluation of a Large-Volume Air Incinerator

Two semiportable metal air incinerators, each with a capacity of 1,000 to 2,200 standard ft(3) of air per min, were constructed to sterilize infectious aerosols created for investigative work in a microbiological laboratory. Each unit has about the same air-handling capacity as a conventional air incinerator with a brick stack but costs only about one-third as much. The units are unique in that the burner housing and combustion chamber are air-tight and utilize a portion of the contaminated air stream to support combustion of fuel oil. Operation is continuous. Aerosols of liquid and dry suspensions of Bacillus subtilis var. niger spores and dry vegetative cells of Serratia marcescens were disseminated into the two incinerators to determine the conditions required for sterilization of contaminated air. With the latter organisms (concentration 2.03 x 10(7) cells/ft(3) of air), a temperature of 525 F (274 C), measured at the firebox in front of the heat exchanger, was sufficient for sterilization. To sterilize 1.74 x 10(7) and 1.74 x 10(9) wet spores of B. subtilis per ft(3), the required temperature ranged from 525 to 675 F (274 to 357 C) and 625 to 700 F (329 to 371 C), respectively. Air-sterilization temperature varied with each incinerator. This was because of innate differences of fabrication, different spore concentrations, and use of one or two burners With dry B. subtilis spores (1.86 x 10(8)/ft(3)), a temperature of 700 F was required for sterilization. With dry spores, no difference was noted in the sterilization temperature for the two incinerators.     

Stoichiometry of diauxic growth of a xylanase-producing Bacillus strain

In this work, the establishment of material balances and stoichiometry of the growth of Bacillus sp. was undertaken. This strain produces high quantities of a xylanase suitable for use as bleach boost agent in chlorine-free bleaching sequences of paper pulp. As carbon dioxide plays an important role as a growth factor, bacterial growth in two fermentations, one fed with air and another fed with carbon-dioxide-enriched air, were compared. For this purpose, a method permitting the determination of the consumption of the two carbon sources, xylan and peptone, was proposed. The material balances revealed that in both cases, the bacteria first use peptone as their carbon source, and then xylan in the second part of the growth phase. The aerated culture showed diauxic growth on these two substrates, whereas carbon-dioxide-enriched air caused disappearance of the metabolic adaptation phase, and rendered biomass production more economic. The fermentation fed with air needed 30% more xylan than the fermentation fed with carbon-dioxide-enriched air for the same quantity of biomass produced.     

Behavioural Thermoregulation in a Small Neotropical Primate

The maintenance of body temperature in endothermic animals imposes considerable metabolic costs that vary with air temperature fluctuations. To minimise these costs, endotherms can adopt certain behaviours to adjust the pattern of heat transfer between their bodies and the environment. In this study, we evaluated whether a small Neotropical primate, the black‐fronted titi monkey (Callicebus nigrifrons), living in a seasonal environment can use behavioural mechanisms to cope with fluctuations in the air temperature. We monitored the air temperature and the titi monkeys’ behaviour over 1 yr. When the animals were inactive, we recorded the microhabitat used, the huddling between individuals and the body postures adopted. The monkeys primarily responded to air temperature fluctuations through microhabitat selection: they spent more time in sunny places and used higher strata of forest under lower temperatures. Moreover, they used sunny microhabitats during the first hour of their active period after colder nights. The monkeys did not huddle or change body postures in response to air temperature fluctuations. Huddling behaviour seemed to be primarily influenced by social interactions, and body postures were more energy conserving, regardless of temperature. Titi monkeys, however, used more energy‐conserving postures and huddling behaviour under cloudy conditions than sunny conditions, suggesting that these behaviours may be important when they are unable to thermoregulate by microhabitat selection. We concluded that fluctuations in air temperature can promote significant changes in the behaviour of titi monkeys and can impose important restrictions on mammals’ activities, even in tropical regions.     

Transurethral prostatectomies; a review of 560 cases

Spontaneous pneumoperitoneum most often occurs following ruptured peptic ulcer. In 80 to 85 per cent of cases of perforated ulcers, free intraperitoneal air is demonstrable. There have been reported three cases in which air was present without demonstrable cause, without peritoneal irritation or peritonitis. This presentation adds a fourth. Examination of a patient with acute disease of the abdomen should include not only a roentgenogram with the patient supine but films made in the left lateral decubitus position and/or upright position to demonstrate free air. The radiologist should be ready and willing to consult with the surgeon at the time of examination. Attention is called to a sign described recently by Rigler in supine films, namely, the visibility of both the inside and the outside of the intestinal lumen. Another sign in the supine film, namely the contrast of air against the peritoneal reflections, is described.     

Adaptation of industrial/commercial air conditioners for use in a thermally stressful environment

1. 1. The concept of intermittent, microclimate cooling during rest periods has been investigated due to the logistical and ergonomic problems associated with backpack cooling systems

2. 2. In an attempt to improve intermittent cooling applications, the use of industrial/commercial air conditioners (ICAC) as a source of cool air was conceived

3. 3. In the current study, a prototype of a pressurized air distribution unit (PADU) which can be incorporated into existing ICAC was designed and fabricated

4. 4. In a successful test, an ICAC circulated air and cooled it down to the set temperature, while the PADU pumped 5101/min (the specified air volume for one person) of 15°C into each air cooling vest, 4601/min to the body and 501/min to the face, through filters and 10 ft/1 in. diameter supply line

5. 5. The PADU is necessary to increase the air pressure in the system, creating the required air volume

6. 6. This promising concept adapts existing ICAC to provide adequate amounts of clean, cool air to individuals working in thermally stressful environments

7. 7. This development effectively increases the conditioned air sources available for use in decreasing heat storage and increasing personal comfort in military or civilian scenarios where work is conducted in protective garments.

Internal air current patterns depend on the ventilation method in a scaled-up culture vessel for micropropagation

Air current patterns were visualized inside a scaled-up culture vessel under natural or forced ventilation. Metaldehyde particles were used as tracers, and their patterns were recorded as video images by a high-resolution-and-contrast camera. Under natural conditions, the air currents were mainly influenced by natural convection that developed due to the lighting scheme, which caused differences in temperature among various articles in the chamber, including a sweet potato plantlet, supporting material, a multi-cell tray, and the culture vessel. Under forced ventilation, the air current pattern and air speed were affected by ventilation rates and by air-supply methods that were either parallel downward or circular upward. Uniformity of air movement could be achieved with air distribution pipes inside a modified vessel. Under forced ventilation, growth, photosynthetic rate, and transpiration of the micropropagated plantlets were enhanced around the air outlet as well as the inlet in the large-scale vessel. Those plant responses were probably induced by uniform spatial distribution of air current and gas concentrations.