Presence Of Gaseous Research Articles

Will It Be Possible to Put into Practice the Mitigation of Ventilation Air Methane Emissions? Review on the State-of-the-Art and Emerging Materials and Technologies

The work refers to the important problem of methane emissions in relation to the ventilation air methane (VAM) emitted to the atmosphere. VAM is fuel that remains unused in most mines around the world due to the low content of the combustible component in the mixture (0.1–1%). The aim of this article is to present the real problems posed by released VAM in its utilization such as variability of flow, methane concentration, or possible presence of gaseous and non-gaseous pollutants. The paper presents the existing technologies that are ready to be implemented or have a reliable potential to be implemented in the industry and those whose development will have strong influence on the effective reduction in VAM emissions. The methods discussed include enrichment, thermal, and catalytic as well as photocatalytic oxidation. The catalysts dedicated to VAM oxidation were reviewed. The literature studies show that currently developed technologies enable more and more efficient oxidation of VAM. The most technologically advanced implemented solutions are based on the thermal oxidation method in TFRR. Catalytic methods are still at the laboratory research phase, but have been intensively developed and have the potential to be implemented at process scale in the future.

Hollow fiber membrane separation process in the presence of gaseous and particle impurities for post-combustion CO2 capture

ABSTRACTThe membrane separation process for CO2 capture can be interfered by the gaseous components and the fine particles in flue gas, especially in desulfurized flue gas. In this work, the pint-sized Polyimide(PI) hollow fiber membrane contactors were self-packed to investigate the membrane CO2 separation from flue gas containing fine particles and gaseous contaminants (SO2,SO3,H2O). First, the effects of SO2, SO3, water vapor, and gypsum particles on the CO2 capture were studied independently and synergistically. The results showed that the effect of SO2 on the membrane separation properties is indistinctive; however, the membrane performance was damaged seriously with the addition of SO3. The high humidity promoted the CO2 separation initially before inhibiting the PI membrane performance. Moreover, the decrease of the CO2/N2 selectivity and the permeation rate were accelerated with the coexistence of SO2. The membrane performance showed an obvious deterioration in the presence of gypsum particles, with a 21% decrease in the CO2/N2 selectivity and 51% decrease in the permeation rate. Furthermore, the gypsum particles exerted dramatic damage. Under the WFGD conditions, the combined effects of SO2, water vapor, and the gypsum particles influenced the stability of the membrane significantly. This tendency is mainly attributed to the deposition of fine particles and aerosol on the membrane surface, which occupied the effective area and enhanced the mass transfer resistance. This study of impurities’ influence could play an important role in further industrial application of membrane CO2 capture.

A linear fluorescence-quenching response in an amidine-functionalised solid-state sensor for gas-phase and aqueous CO2 detection.

An amidine-functionalised metal-organic framework (MOF) was shown to be an effective chemosensor in the presence of gaseous and aqueous phase CO2 by virtue of a quenched fluorescence response. This work demonstrates how multifunctional MOFs with high selectivity for CO2 may be exploited to develop CO2 chemosensors.

Colorimetric detection of gaseous ammonia by polyaniline nanocoating of natural cellulose substances

A sensitive and reversible colorimetric gaseous ammonia sensor was prepared by covering each nanofiber of natural cellulose substance (e.g., common commercial filter paper) with ultrathin polyaniline films via in situ polymerization of aniline molecules. The thickness of the deposited emeraldine salt state polyaniline film was ∼10nm. The natural hierarchical network of the initial filter paper was preserved at nanoprecision, and obvious color change of polyaniline from green to blue was achieved within 5min at 30°C in the presence of gaseous or aqueous ammonia. The respective detection limits by the naked eyes were 100ppm for gaseous ammonia in nitrogen and 10ppm for evaporated ammonia aqueous solution. Moreover, the obtained colorimetric sensing sheet endured reversible gaseous ammonia detection for at least 50 times. The current ultrathin polyaniline surface coating approach with natural cellulose substances as scaffolds opens a low-cost, facile, and effective route to improve sensitivity of colorimetric gaseous ammonia detectors.

Analyses of both the alkB Gene Transcriptional Start Site and alkB Promoter-Inducing Properties of Rhodococcus sp. Strain BCP1 Grown on n -Alkanes

Rhodococcus sp. strain BCP1, known for its capacity to grow on short-chain n-alkanes (C(2) to C(7)) and to cometabolize chlorinated solvents, was found to also utilize medium- and long-chain n-alkanes (C(12) to C(24)) as energy and carbon sources. To examine this feature in detail, a chromosomal region which includes the alkB gene cluster encoding a non-heme di-iron monooxygenase (alkB), two rubredoxins, and one rubredoxin reductase was cloned from the BCP1 genome. Furthermore, the activity of the alkB gene promoter (P(alkB)) was examined in the presence of gaseous, liquid, and solid n-alkanes along with intermediates of the putative n-alkane degradation pathway. A recombinant plasmid, pTP(alkB)LacZ, was constructed by inserting the lacZ gene downstream of P(alkB), and it was used to transform Rhodococcus sp. strain BCP1. Measurements of β-galactosidase activity showed that P(alkB) is induced by C(6) to C(22) n-alkanes. Conversely, C(2) to C(5) and >C(22) n-alkanes and alkenes, such as hexene, were not inducers of alkB expression. The effects on P(alkB) expression induced by alternative carbon sources along with putative products of n-hexane metabolism were also evaluated. This report highlights the great versatility of Rhodococcus sp. strain BCP1 and defines for the first time the alkB gene transcriptional start site and the alkB promoter-inducing capacities for substrates different from n-alkanes in a Rhodococcus strain.

Invited commentary

Adverse neurologic outcomes after heart surgery in general, and cardiac transplantation in particular, have serious consequences: an increased risk of mortality and a diminished quality of life among survivors. They also represent a burden on the health-care system, requiring prolonged hospitalizations and additional aftercare, and as a logical consequence, higher costs. Zierer and colleagues [1Zierer A. Melby S.J. Voeller R.K. et al.Significance of neurologic complications in the modern era of cardiac transplantation.Ann Thorac Surg. 2007; 83: 1684-1690Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar] report on a series of 200 consecutive patients who underwent orthotopic cardiac transplantation during a recent 10-year period. Despite the fact that this review was done retrospectively, specific findings were accurate: operative mortality for the entire series was 8% (17 of 200), but 15% (7 of 46) in patients suffering from neurologic complications (p = 0.074). Multivariate analysis emphasized advanced age, preoperative left ventricular assist assist device (LVAD), intraaortic balloon pump (IABP) support requirement, and prolonged cardiopulmonary bypass time as independent predictors of stroke or transient ischemic attack (TIA) for early neurologic complications. Furthermore, preoperative IABP support requirement, and postoperative renal and hepatic failure were identified as independent predictors of early neurologic complications other than stroke or TIA. Astonishingly, 5-year survival was not significantly impaired in those patients with neurologic complications (66.5 vs 78%; p = 0.149) [1Zierer A. Melby S.J. Voeller R.K. et al.Significance of neurologic complications in the modern era of cardiac transplantation.Ann Thorac Surg. 2007; 83: 1684-1690Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar]. Referring to widespread experience and published literature, 23% of all patients suffering from neurologic sequelae seem to reveal a rather high percentage, but this certainly reflects the fact that the cardiac transplant patient population has shifted to high-risk patients. We believe that a significant correlation between cardiopulmonary bypass (CPB) pressures (ie, 50 mm Hg or less) and prolonged aortic cross-clamp times were observed with development of postoperative neurologic symptoms. Unstable hemodynamic situations (both preoperatively and postoperatively) may directly cause cerebral hypoperfusion or modify patients’ cerebral autoregulation to lower pressure to adapt to the progressive systemic hypotension [2Perez-Miralles F. Sanchez-Manso J.C. Almenar-Bonet Incidence of risk factors for neurologic complications after heart transplantation.Transplant Proc. 2005; 37: 4067-4070Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar]. The presence of gaseous or particulate emboli in the CPB circuit may also represent the causes of neurologic problems. Recently a prospective study on patients undergoing cardiac surgery measuring objectively P300 auditory-evoked potentials revealed no difference between those operations whether cardiac chambers were opened or not [3Iskesen I. Yilmaz H. Yildrim F. et al.Opening the cardiac chambers does not make any difference in p300 measurement.Heart Surg Forum. 2006; 9: 770-773Crossref Scopus (4) Google Scholar]. Last, but not least, other authors stated that the number of posttransplant infections was also associated with neurologic complications [2Perez-Miralles F. Sanchez-Manso J.C. Almenar-Bonet Incidence of risk factors for neurologic complications after heart transplantation.Transplant Proc. 2005; 37: 4067-4070Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar]. Hence, according to the significant decrease of cardiac transplantations due to the broad use of long-lasting LVAD systems and cardiac resynchronization therapy (CRT), the term “bridging to transplant” has emerged with a new importance. Some investigators have speculated that there is a strong connection between infection and neurologic thromboembolic events related to devices during mechanical circulatory support. [4Holman W.L. Bourge R.C. Spruell R.D. et al.Ventricular assist devices as a bridge to cardiac transplantation.Ann Surg. 1997; 225: 695-706Crossref PubMed Scopus (26) Google Scholar] As a matter of fact, seizures are a very poor prognostic indicator and are associated with a 100% mortality in this specific patient group [5Thomas C.E. Jichici D. Petrucci R. et al.Neurologic complications of the Novacor left ventricular assist device.Ann Thorac Surg. 2001; 72: 1311-1315Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar]. In contrast, we were hardly able to find any corresponding literature and information about neurologic symptoms and CRT for the present invited commentary. As congenital cardiac procedures are also of main interest, neurologic complications after orthotopic cardiac transplantation in children and adults tend to be very similar in both incidence and type. However, peripheral neuropathies tend to occur more frequently in adults differing in types of complications in the immediate posttransplant period. [6Martin A.B. Bricker J.T. Fishman M. et al.Neurologic complications of heart transplantations in children.J Heart Lung Transplant. 1992; 11: 933-942PubMed Google Scholar] Significance of Neurologic Complications in the Modern Era of Cardiac TransplantationThe Annals of Thoracic SurgeryVol. 83Issue 5PreviewSevere neurologic complications after cardiac transplantation are devastating outcomes of this life-saving procedure. Incidence, risk factors, and morbidity of neurologic events in the modern era of cardiac transplantation are yet to be defined. Full-Text PDF

Spatially resolved spectroscopic measurements of CN, C2 and Al in graphite tube electrothermal atomizers under various operating conditions

Direct, spatially resolved, spectroscopic measurements of C2 in side-heated (spatially isothermal) and Massmann-type (spatially non-isothermal) atomizers showed that the partial pressure of gaseous carbon (pC2) is in thermodynamic, heterogeneous equilibrium for temperatures above 2970 K. No evidence for over-equilibrium excesses of C2 was obtained. The pCN exhibits a gradient, decreasing from the bottom to the top of the graphite tube, indicating the importance of air ingress through the injection hole. Further, the pCN is reduced by the presence of aqueous solutions, primarily close to the point of sample deposition, revealing the non-equilibrium distribution of CN in the atomizer, whereas C2 is only marginally affected. Spatially resolved measurements of Al also indicate the importance of O2 ingress and the sheath gas flow rate on the Al atomic absorption signals, indicating that the pO2 largely determines the degree of Al atom formation and not the presence of gaseous, carbon-containing species.

Infrared study of photooxidation of nitrogen oxides and ammonia adsorbed on alumina

Changes in the IR spectra of nitrogen oxides and ammonia adsorbed on Al2O3 caused by UV irradiation indicate that in the presence of gaseous or liquid (−196°C) O2 photooxidation takes place, resulting mostly in the formation of surface NO 3 − ions.

Space-related composite-material experiments

The preparation of composites in space depends on the immersion of reinforcements in a liquid-metal matrix and their uniform, stable dispersion in the bulk products until solidification occurs. The chief problem in achieving the composite is associated with the “wetting” of the reinforcements. A study of the theory of wetting revealed that wetting is prevented by the presence of gaseous and oxide contaminants at the interface between the pure liquid and pure solid. Experiment then confirmed that the use of a vacuum environment, cleaning of all surfaces, elevated temperature, ion bombardment, and vigorous mechanical agitation enabled the immersion and dispersion of candidate reinforcements. The technique is limited by the increased tendency for reaction if the time at elevated temperature is extended.