Low Gas Volume Research Articles

QUALITAS: A mid-infrared spectrometer for sensitive trace gas measurements based on quantum cascade lasers in CW operation

We describe QUALITAS, a mid-infrared spectrometer with multipass absorption cell, suitable to apply lead chalcogenide and quantum cascade lasers as light sources in CW operation at cryogenic temperatures. The instrument has been designed for the measurement of trace gases such as carbon monoxide, nitrous oxide or methane in the clean atmosphere from space-restricted and experimentally challenging mobile platforms. The design involves compact optics, which fit into the space limitations of a standard aircraft borne 19in. rack (W×H×D≈48×45×40cm3). The instrument allows high sensitivity (≈5×10−7m−1Hz−1∕2 during flight; ≈1×10−7m−1Hz−1∕2 in the laboratory) in combination with a low sample gas volume (0.3L) for high time resolution (<1s, using a moderately sized pump). We employ a combination of elements already applied in former spectrometers in our laboratory and a novel arrangement of spherical mirrors. The design criteria, the optical, electronic and mechanical set-up are described in detail. The application of the instrument to measure atmospheric concentrations of carbon monoxide is discussed, using both, a lead chalcogenide as well as a DFB-structured quantum cascade laser (R3 line at 2158.3cm−1).

Effect of Measured Versus Predicted Thoracic Gas Volumes on Percent Body Fat in Wrestlers

0504 Disordered eating habits and unhealthy weight loss practices are two major problems in the sport of wrestling. Based on recommendations by the National Wrestling Coaches Association, the Delaware Interscholastic Athletic Association implemented a Weight Certification Program for all high school wrestlers. According to the program, airdisplacement plethysmography was used if percent body fat (%BF) using bio-electrical impedance analysis was appealed. PURPOSE: To determine whether the equation used predict thoracic gas volume (Vtgpred) was accurate when testing a relatively young group of wrestlers. METHODS: Thoracic gas volume was measured and predicted in 63 high school wrestlers. In addition, differences between %BF, body density (Db), and minimum wrestling weight (MWW) measurements attained using Vtgmeas and Vtgpred were also examined. RESULTS: Vtgpred (3.369 ± .043 L) and Vtg meas (3.355 ± .074 L) were not significantly different (p = 0.80). However, a Bland-Altman plot of Vtgpred and Vtg meas showed three distinct patterns for the low, medium, and high thoracic gas volumes. A t-test performed on the three groups showed that subjects with a Vtgmeas < 3.0 L (N = 16) had a significantly higher Vtgpred than Vtgmeas (p Ü 0.0001). A significant difference was also found in subjects with a Vtgmeas > 3.75 L (N = 17), but the trend was to under-predict Vtgmeas. The subjects with volumes between 3.0 – 3.75 L (N = 30) had no significant difference between Vtgpred and Vtg meas. The significant differences between the two volumes in groups outside of the 3.0 to 3.75 L range produced significant differences in Db, %BF, and MWW (p Ü 0.05). Thus, this study documents that Vtgpred under- or over-estimated Vtg meas in 52% (n = 33) of the wrestlers and accurately predicted Vtg in 48% (n = 30) of the wrestlers. CONCLUSION: The use of prediction equations to set guidelines for %BF and MWW in wrestlers should be done with the knowledge of its limitations.

Repetitive Pneumoperitoneum with Ozonized Oxygen as a Preventive in Lethal Polymicrobial Sepsis in Rats

The aim of this study was to test whether repetitive pretreatments of rats with ozonized oxygen at relatively low gas volumes into the abdomen (20 ml per rat per day) have any beneficial or detrimental effects on the course of a polymicrobial-induced lethal peritonitis. Peritonitis was induced in a surgical or a nonsurgical model by usage of fecal material from the cecum. As the biological read out we used the mortality analysis. To include possible mechanisms by which ozone might influence the septic outcome, we characterized the gene expression of the pro-inflammatory cytokines IL-1β, IL-2, and TNF-α mRNA in lymphoid organs. In both models, we found a significant beneficial influence of a dose-dependent O₂/O₃pneumoperitoneum on the survival rate when compared to control animals or to room air. The ozone-enhanced survival seems to be independent from altered cytokine expression because there were no differences noticed in the levels of bacterial-induced gene expression of IL-1β and TNF-α in septic animals pretreated with ozonized oxygen when compared to control animals.

Method for assessment of volume of trapped gas in infants during multiple-breath inert gas washout.

A breath-by-breath inert gas washout method for assessment of the volume of trapped gas in the lungs (V(TG)) in sedated sleeping infants is described. It is based on washin using a gas mixture containing 4% sulfur hexafluoride (V(TG,SF6)) and washout with air. A mass spectrometer was used for continuous gas concentration measurements, and a Fleisch no. 0 pneumotachometer for flow measurement. When equilibration of the tracer gas was achieved with tidal breathing washin, five passive inflations with a maximum positive airway pressure of 20 cm of H(2)O were performed to ensure filling of lung spaces not communicating during tidal breathing. After tidal washout of the tracer gas by air until the end-tidal concentration was 1/40th of its starting concentration, five passive inflations with air were instituted again. The V(TG,SF6) was calculated from the volume of SF(6) mobilized by these large breaths, and expressed as the corresponding volume of air. Triplets of V(TG,SF6) determination in 8 infants aged 9-31 months with varying degrees of airway obstruction showed an average volume of 13.7 mL (range, 4.7-25.0). The average SD of the triplets was 2.1 mL (range, 0.1-5.5 mL). Subjects with high V(TG,SF6)/FRC results demonstrated lower maximal expiratory flow at FRC (V'(max)FRC) results (Z-scores) and greater inhomogeneity of ventilation distribution than those with low trapped gas volumes. It is concluded that gas trapping can be assessed with acceptable precision with this washout method. Further studies are needed to establish the sensitivity and usefulness of the method in infants with various types of airway pathology.

Plasma arc thermal destruction applications: technology transfer opportunities

Plasma Arc Technology (PAT), an emerging environmental thermal treatment process, has been used to safely and efficiently meet the waste disposal needs of pyrotechnic smoke assemblies, thermal batteries, proximity fuses, contaminated soil and Asbestos Containing Material (ACM). Since 1989, the US Army Construction Engineering Research Laboratories (USACERL) have been active participants in the research and development towards establishing PAT as an efficient, economical and safe hazardous waste immobilisation tool. A plasma torch capable of generating high temperatures makes this technology a viable and powerful tool for the thermal destruction of ACMs into an innocuous ceramic material no longer requiring disposal as a hazardous waste. When pure asbestos is subjected to temperatures above 1000?C, the asbestos fibres melt and subsequently solidify into a nonhazardous, chemically inert, solid material. The resulting processed, rock-like substance meets all Environmental Protection Agency (EPA) criteria as a nonhazardous material and has value as gravel or aggregate material. In addition, research indicates that PAT is a powerful technology for the conversion of unique military hazardous waste contaminated items into inert, vitrified slag. Advantages of plasma arc technology include: the availability of high temperatures; flexibility to operate in either reducing or oxidising environments; low gas requirements, thus low effluent gas volumes; substantial waste volume reduction; the ability to treat a large variety of waste streams; and a saleable by-product. This paper will provide an overview of plasma arc technology and discuss the military's hazardous waste disposal needs.

Trends in long-period seismicity related to magmatic fluid compositions

Sound speeds and densities are calculated for three different types of fluids: gas–gas mixture; ash–gas mixture; and bubbly liquid. These fluid properties are used to calculate the impedance contrast (Z) and crack stiffness (C) in the fluid-driven crack model (Chouet: J. Geophys. Res., 91 (1986) 13,967; 101 (1988) 4375; A seismic model for the source of long-period events and harmonic tremor. In: Gasparini, P., Scarpa, R., Aki, K. (Eds.), Volcanic Seismology, IAVCEI Proceedings in Volcanology, Springer, Berlin, 3133). The fluid-driven crack model describes the far-field spectra of long-period (LP) events as modes of resonance of the crack. Results from our calculations demonstrate that ash-laden gas mixtures have fluid to solid density ratios comparable to, and fluid to solid velocity ratios lower than bubbly liquids (gas-volume fractions <10%). This difference results in synthetic far-field spectra with higher impedance contrasts and narrower spectral bandwidths for ash-laden gas mixture than spectra for bubbly liquids.Spectral characteristics are described in terms of the quality factor Q−1. Q−1 is measured by the ratio of the frequency of the dominant spectral peak to the bandwidth of the peak measured at one half of its amplitude. This factor expresses the losses of energy due to elastic radiation Qr−1 and other dissipative mechanisms Qi−1 at the source, Q−1=Qr−1+Qi−1. Spectra for LP events recorded at active volcanoes such as Galeras in Colombia and Kilauea in Hawaii, have Q−1 factors in the range of 0.1–0.002. The Qr−1 factors due to radiation loss calculated for a sphere filled with a H2O–CO2 or H2O–SO2 gas mixture, vary between 0.0015 and 0.0040 with a change in wt% H2O at 800–1600K and 10–50MPa. For gas-rich mixtures, Qr−1 has a strong dependence on resonator geometry (spherical versus rectangular). The spectra from a resonating sphere filled with gas-rich mixture yields values of Qr−1 an order of magnitude smaller than those from a rectangular crack. For a resonating crack filled with an ash–gas mixture (or pseudogas), Qr−1 varies parabolically from ∼0.006 for an ash-rich mixture, to 0.0015 or 0.0023 for a H2O-rich or CO2-rich mixture at 800K and 25MPa. For low (<20%) gas-volume fraction fluids (foams, bubbly fluids and ash-rich pseudogases), the magnitudes for Qr−1 are independent of crack geometry.Spectra associated with a foam (gas-volume fractions 10–90%) or bubbly basalt (gas-volume fractions <10%) may have a dominant spectral peak with values of Qr−1 on the order of 0.01 and 0.1, respectively. The spectra from a resonating sphere filled with a foam containing >20% gas-volume fraction yields values of Qr−1 similar to those for a rectangular crack. As with gas–gas and ash–gas mixtures, an increase in mass fraction narrows the bandwidth of the dominant mode and shifts the spectra to lower frequencies. Including energy losses due to dissipative processes in a bubbly liquid increases attenuation. Attenuation may also be higher in ash–gas mixtures and foams if the effects of momentum and mass transfer between the phases were considered in the calculations.

Hydrothermal vents near a mantle hot spot: the Lucky Strike vent field at 37°N on the Mid-Atlantic Ridge

The Lucky Strike hydrothermal field occurs in the summit basin of a large seamount that forms the shallow center of a 65 km long ridge segment near 37°N on the Mid-Atlantic Ridge. The depth and chemistry of the ridge segment are influenced by the Azores hot spot, and this hydrothermal field is the first Atlantic site found on crust that is dominated by a hot spot signature. Multiple hydrothermal vents occur over an area of at least 300 m by 700 m. Vent morphologies range from flanges and chimneys with temperatures of 200–212°C, to black smoker chimneys with temperatures up to 333°C. Cooler fluids from northern vents have higher chlorinities and lower gas volumes, while hotter, southern fluids have chlorinities 20% below seawater with higher gas volumes, suggesting phase separation has influenced their compositions. All gas volumes in fluids are higher than those at TAG and Snake Pit hydrothermal fields. Black smokers exhibit their typical mineralogy, except that barite is a major mineral, particularly at lower-temperature sites, which contrasts with previously investigated Atlantic sites. The fluid chemistry, distribution of the relict sulfide deposits on the seamount summit in the areas investigated using DSV Alvin, and contact relationships between active vent sites and surrounding basaltic and sulfide substrate suggest that the hydrothermal system has a long history and may have recently been rejuvenated. Fauna at the Lucky Strike vent sites are dominated by a new species of mussel, and include the first reported sea urchins. The Lucky Strike biological community differs considerably from other vent fauna at the species level and appears to be a new biogeographic province. The Lucky Strike field helps to constrain how variations in the basaltic substrate influence the composition of hydrothermal fluids and solids, because basalt compositions at Lucky Strike are 10–30 times enriched in incompatible elements compared to other Atlantic hydrothermal sites such as TAG, Snake Pit and Broken Spur. The incompatible element

Cellular thermogenesis in L-929 mouse fibroblasts. The influence of oxygen availability on growth, heat production and intermediary metabolism

Abstract Cellular thermogenesis in L-929 mouse fibroblasts growing in glass ampoules was monitored over 72 h in three different systems: (1) closed ampoules with 2.5 ml of control medium; (2) closed ampoules with 2.85 ml of medium and a reduced oxygen content; and (3) ampoules kept open. Thermogenesis was determined as heat production (HP) and the pH, and oxygen, glucose and lactate contents in the medium as well as the cellular growth were assessed in order to evaluate whether small gaseous volumes are sufficient to facilitate adequate oxygen supply. Oxygen deficiency resulted in lower HP, decreased growth and enhanced anaerobic rate of glycolysis. Low gas volume was associated with decreased HP after 40 h and a steady increasing rate of aerobic glycolysis similar to that shown during O 2 deficiency. In the open system a more pronounced decrease of HP was observed.

Multiloop Control of a Pilot-Scale Membrane System for Gas Separations

Membrane systems are preferred for many separations due to their low energy consumption, reduced environmental impact, cost effectiveness at low gas volumes, low maintenance costs, space and weight efficiency, and ease of operation. A multiloop control system for a pilot-scale membrane separation process is designed and evaluated. The process employs hollow fiber membrane modules and is representative of air separation systems in industry. The decentralized control system originally consists of five PID controllers which regulate feed flow rate and pressure, permeate pressure, suction pressure, and module temperature. This configuration yields poor performance as a result of interactions between the feed flow rate and feed pressure controllers. By disabling the flow rate controller and proper tuning of the remaining control loops, satisfactory control is achieved during 4 days of continuous operation.

An ionization chamber of large solid angle with integrated parallel plate avalanche counter for identification of slow heavy ions

A combination of a parallel plate avalanche counter (PPAC) and an ionization chamber (IC) of conventional type with large solid angle was designed for the identification of slow heavy ions with A ≈ 50 and E = 1−2 A MeV. An important feature of this arrangement is that both detectors operate in the same low pressure gas volume. Using extremely thin foils the passive energy loss could be kept very small allowing rather good charge number and energy resolution. The PPAC provides both the information about the in-plane scattering angle and a fast timing signal, which can be combined with a reference signal for time-of-flight measurement and mass determination. The out-of-plane angle is obtained from the electron drift time within the IC.

Pilot plant/full scale EP system design and performance on a BOF application

An ESP pilot plant study was done on emissions from a BOF process which is cyclic with very high and low gas volumes, temperature and grain loadings. Data collected were EP performance vs. gas velocity, and collection area. Also measured was particle size distribution, dust resi opacity at the EP outlet. From this data, a full size EP system was designed and installed. Recent performance tests indicate the data agrees well with the initial pilot plant study. Emissions have been reduced from 11 grs/scf (27.1 g/m 3) to less than 0.033 grs/scf (81 mg/m 3) and opacity to 20% or less.