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At least 451 records · Page 25Linked to original sources
PubMed2006

Increased crystal porosity and enhanced gas adsorption by intracolumnar gliding for broadband gas detection.

A new three-level structural approach based on anion-induced intracolumnar gliding of stacked coordinatively unsaturated units is described for design of metal-organic crystals which exhibit concentration- and gas-specific adsorption of a variety of small molecules and could be employed for multiple and rapid qualitative and quantitative broadband detection of gases or gaseous mixtures.

Journal Article↗
PubMed2002

Hg reactions in the presence of chlorine species: homogeneous gas phase and heterogeneous gas-solid phase.

The kinetics of Hg chlorination (with HCl) was studied using a flow reactor system with an online Hg analyzer, and speciation sampling using a set of impingers. Kinetic parameters, such as reaction order (alpha), overall rate constant (k'), and activation energy (Ea), were estimated based on the simple overall reaction pathway. The reaction order with respect to C(Hg), k', and Ea were found to be 1.55, 5.07 x 10(-2) exp(-1939.68/T) [(microg/m3)(-055)(s)(-1)]. and 16.13 [kJ/ mol], respectively. The effect of chlorine species (HCl, CH2Cl2) on the in situ Hg capture method previously developed (28) was also investigated. The efficiency of capture of Hg by this in situ method was higher than 98% in the presence of chlorine species. Furthermore, under certain conditions, the presence of chlorine enhanced the removal of elemental Hg by additional gas-phase oxidation.

Environmental Pollutants↗
PubMed1975

Postoperative arterial blood gas measurement in obese patients: effect of position on gas exchange.

The effect of position change on blood gas exchange was studied in 22 markedly obese, otherwise healthy, women both preoperatively and postoperatively. There was a statistically significant decrease in arterial oxygen tension and a simultaneous reduction both in the arterial carbon dioxide tension and the base excess with the assumption of the supine versus the semirecumbent position on postoperative days one and two. However, no positional difference was demonstrable in any variable by the third postoperative day. This study indicates that in obese patients during the first 48 hours after abdominal surgery, assumption and maintenance of the semirecumbent posture is a valuable therapeutic adjunct to improve arterial oxygenation.

Adult↗
PubMed1982

Identification of Abscisic Acid in Tulipa gesneriana L. by Gas-Liquid Chromatography with Electron Capture and Combined Gas-Liquid Chromatography and Mass Spectrometry.

A major growth inhibitory substance of tulip bulbs (Tulipa gesneriana L. cv Paul Richter) has been unequivocally shown to be abscisic acid (ABA). The ABA methyl ester of the free ether-soluble acid fractions of tulip organs had the identical retention time on gas-liquid chromatography with electron capture detector as authentic ABA methyl ester. In addition, the mass spectra were the same. On a unit dry matter basis, the basalplate and floral shoot contained 3.6 and 2.6 times more ABA than the fleshy scales, respectively.

Journal Article↗
PubMed1975

The influence of different environmental temperatures on pulmonary gas exchange and blood gas changes after birth.

The oxygen uptake (VO2) and respiratory exchange ratio (R) was determined during the first 20 min and at one and at 2 hours after birth in 16 healthy full-term newborn infants studied in different environmental temperatures. Arterial blood gases and acid-base balance were determined on repeated blood samples from the abdominal aorta. The infants were grouped in a "warm" group (n equal to 10) where efforts were made to avoid cooling after birth, and a "cold" group (n equal to 6) where a decrease in rectal temperature to a mean value of 35.4 degrees C at 2 hours occurred. Irrespective of environmental temperature, VO2 was approximately 10 ml/kg min during the first 8 min after birth, thereafter decreasing to about 6-7 ml/kg min. During the first 8 min the main increase in PaO2 occurred and about 2 ml/kg min of the VO2 was accounted for by changes in oxygen stores after birth. At 16-20 min and at 60 min after birth a negative relationship was found between VO2 and PaO2. During the period 8-120 min after birth a close relationship was found between VO2 and the degree of muscular activity. Within 4-16 min after birth, R values above 1.0 were regularly found simultaneously with the main decrease in PaO2. In infants kept "cold" a tendency to hyperventilate was found, probably elicited by cold stimuli. The rapid drop in deep body temperature regularly seen after birth could thus not be explained by a limited ability to increase pulmonary gas exchange. A high degree of evaporative heat loss, a relatively low "basal" metabolic rate and a limited response in "non-shivering thermogenesis" seem to be the main reasons for the heat loss after birth.

Acid-Base Equilibrium↗
PubMed2002

Noble gas-actinide compounds: complexation of the CUO molecule by Ar, Kr, and Xe atoms in noble gas matrices.

The CUO molecule, formed from the reaction of laser-ablated U atoms with CO in a noble gas, exhibits very different stretching frequencies in a solid argon matrix [804.3 and 852.5 wave numbers (cm(-1))] than in a solid neon matrix (872.2 and 1047.3 cm(-1)). Related experiments in a matrix consisting of 1% argon in neon suggest that the argon atoms are interacting directly with the CUO molecule. Relativistic density functional calculations predict that CUO can bind directly to one argon atom (U-Ar = 3.16 angstroms; binding energy = 3.2 kilocalories per mole), accompanied by a change in the ground state from a singlet to a triplet. Our experimental and theoretical results also suggest that multiple argon atoms can bind to a single CUO molecule.

Journal Article↗
PubMed1963

GAS EXCHANGE WITH MASS CULTURES OF ALGAE. II. RELIABILITY OF A PHOTOSYNTHETIC GAS EXCHANGER.

Comparisons of oxygen production and carbon dioxide absorption by an algal gas exchanger were made over a 3-month period. The data do not represent a continuous test, but they do represent results obtained when identical light intensities, CO(2) supply rates, and dilution rates with fresh culture medium had been used for more than 1 day. Steady-state conditions were thus assured, and the agreement in the data was excellent. Under the same experimental conditions, the unit was operated continuously for a 5-day period, and the daily variability in this test was less than in the results obtained from month to month. The variation between the average O(2) production during the 5-day test and the average of the tests over a several-month period was less than 3%. It is concluded, therefore, that the reliability of the algae in producing oxygen is sufficient to warrant their use in either submarine or space ship use.

Carbon Dioxide↗
PubMed1971

Gas exchange in renal failure. II. Pulmonary gas exchange during peritoneal dialysis.

Blood gas analysis studies have been made in patients undergoing peritoneal dialysis. It has been shown that oxygen tensions are reduced when fluid has been run into the peritoneal cavity and that this fall in Pao(2) is reversed after running out the dialysate. The change in Pao(2) is greater with 2-litre than with 1-litre cycles.

Carbon Dioxide↗
PubMed1999

[Genotoxicity of stack gas condensates of Bavarian waste incineration plants. I. Stack gas condensate--sample collection techniques].

Investigations into the toxicity and the chemical analytics of stack gas condensates from 21 waste incineration plants (locations in Bavaria) were undertaken in the years 1990 to 1995. A decisive prerequisite was the development of a simple, standardizable technique for sample collection. It was done by condensating stack gases at 0 to 5 degrees C in an intensive glass condensator. Certain types of compounds showed a different behaviour of separation at the temperatures which were used. Whereas bivalent ionic mercury and chlorophenols were comparatively well separated with amounts of 60 to 95% and the polychlorinated dioxins, furans and biphenyls (PCBs) were sufficiently separated with 20 to 60%, less than 10% of the chlorobenzenes and polycyclic aromatics (PAHs) were found in the condensates. Sufficiently sensitive biological test procedures must be chosen for a biomonitoring of the condensates on geno- and immunotoxic effects to keep the required quantity of the condensates within practicable limits. The concentration of organic wastes was done through a solid phase extraction for the genotoxicity testing in the period from 1990 to 1991, and uniformly through a dichloromethane extraction for the biological and the simultaneous chemical analytical investigations from 1992 to 1995.

Air Pollutants↗
PubMed2005

Enhanced sonography using carbon dioxide gas for small hepatocellular carcinoma: a comparison study between pure carbon dioxide gas and carbon dioxide microbubbles.

PURPOSE: To evaluate the feasibility of enhanced sonography using arterial injection of pure carbon dioxide gas (CO(2)) for detecting small hepatocellular carcinoma (HCC) nodules. MATERIALS AND METHODS: We performed enhanced sonography on 51 HCC nodules of 35 patients with HCC. The patients underwent enhanced sonography with two methods: injection of pure CO(2) (26 nodules), or injection of CO(2) microbubbles (25 nodules) using CO(2) and soy bean oil. We observed the enhancement effect of HCC on enhanced sonography, and measured the accumulation time of CO(2) in the nodules. RESULTS: Twenty-three nodules appeared hyperechoic on enhanced sonography, and 12 of the nodules could be found on enhanced sonography only. Sixteen of the hyperechoic nodules on baseline sonography revealed no enhancement. Multiple regression analysis with regard to the method of injection of CO(2), nodule location, and nodule size revealed that method (p<0.0001) and nodule size (p=0.02) remained significant. The accumulation time of CO(2) microbubbles in the nodules was 4.4+/-0.8 minutes, whereas pure CO(2) accumulation time was 14.7+/-1.5 minutes, significantly longer than the CO(2) microbubbles regardless of nodule size and location. CONCLUSION: Enhanced sonography of arterial injection of pure CO(2) is a feasible technique for detecting small HCC nodules.

Adult↗
PubMed1980

Gastric acid secretion (GAS) and hiatal hernia. I. Relationship between GAS and oesophageal reflux complications.

The relationship between GAS and oesophageal reflux complications in patients with hiatal hernia and incompetent antireflux mechanism is a matter of controversy. In a study of 70 patients operated upon for hiatal hernia, BAO and PAO after betazole stimulation were studied preoperatively in relation to oesophageal reflux complications, age and oesophageal motility. No correlation was found between BAO and oesophageal reflux complications. There was no association between PAO and such complications in patients with oesophageal hypomotility whereas PAO was clearly correlated to these complications in patients with normal oesophageal motility. Oesophageal reflux complications were closely correlated to oesophageal hypomotility and age.

Adult↗
PubMed2005

Application of direct thermal desorption gas chromatography and comprehensive two-dimensional gas chromatography coupled to time of flight mass spectrometry for analysis of organic compounds in ambient aerosol particles.

Semivolatile organic compounds (SVOC) associated with ambient particles smaller than 2.5 microm (PM2.5) were determined in the city of Augsburg, Germany. Daily samples were collected at a central monitoring station from late summer 2002 to spring 2005. SVOC were analysed by direct thermal desorption (DTD)-GC and comprehensive 2-D GC coupled to TOF MS (DTD-GC-TOF MS and DTD-GC x GC-TOF MS). Two hundred compounds were quantified and 'semi-quantified' on a daily basis by DTD-GC-TOF MS. n-Alkanes, n-alkan-2-ones, n-alkanoic acid methyl esters, acetic acid esters, n-alkanoic acid amides, nitriles, linear alkylbenzenes and 2-alkyl-toluenes, hopanes, PAH, alkylated PAH and oxidised PAH, and several compounds that are not-grouped in homologous rows or compound classes were determined. Changes in concentration and pattern of several target compounds as well as methodological advantages and restrictions of DTD-GC-TOF MS are briefly discussed. DTD-GC-TOF MS analysis provided data particularly suited for source receptor modelling and epidemiological time series studies on the health effects of ambient PM. GC x GC enhances chromatographic resolution of PM samples and therefore amplifies the peak identification capabilities of the TOF MS.

Aerosols↗